JP7516844B2 - Polypropylene resin multi-layer foam sheet - Google Patents

Description

The present invention provides a foamed sheet in which the foam cells have high closed cell properties during foam molding, and the cells are dense and relatively uniform in size. In particular, the present invention relates to a polypropylene resin multi-layer foamed sheet including a foam layer with a high expansion ratio of 3.0 times or more produced by the T-die method, a polypropylene (PP) filler layer containing an inorganic filler, and a surface layer, and a molded article thermoformed using the same.

One of the important molding and processing methods for polypropylene resin is foam molding. Various molded products obtained by extrusion foam molding and injection foam molding are used in a wide range of applications, taking advantage of their excellent properties such as thermal insulation, sound insulation, cushioning, and energy absorption. In particular, in recent years, from the perspective of environmental issues, weight reduction of materials and reduction of environmental burden have become important issues in technological development, and the technical fields in which foam molded products are used are expanding, and the demand for resins with high foaming performance is increasing.
Regarding foaming performance, the bubble size and the bubble shape are important factors. In particular, in the field of food packaging and containers, etc., since thermoformability, heat insulation, rigidity, and high appearance (high designability) are required, it is generally important to produce a foamed sheet with a high expansion ratio and fine, independent, and uniform bubbles.
Generally, foamed sheets obtained by extrusion foam molding are used for applications such as food foam trays and foam containers, and among the extrusion foam molding methods, there are the T-die method and the round die method. When the T-die method is used, the foamed resin is cooled with a cooling roll immediately after extrusion, which has the advantage that the surface of the foamed sheet becomes smooth, and the appearance and thermoformability are good. In addition, if the cooling roll is a mirror roll, it is also possible to produce a foamed sheet with excellent gloss. Thus, compared with the round die method described below, it has the advantage of having a relatively good appearance and smoothness, and also good thermoformability, while when the foamed resin discharged from the die is taken up with a roll, the width is regulated, and since it is a molding method that stretches more strongly than the round die foaming, the bubbles are likely to be crushed or broken, and it is difficult to obtain a sheet with high bubble independence. In particular, as the sheet becomes a high expansion ratio such as exceeding 3.0 times, the proportion of bubbles in the resin increases and the speed of foaming also increases, so that the bubbles are likely to coalesce, and it is difficult to maintain the independence of the bubbles and maintain a high appearance.
In order to improve the heat insulation, the expansion ratio needs to be increased, but the sheet rigidity decreases with the increase in the expansion ratio. In order to improve the rigidity of such a foamed sheet, a method of laminating a non-foamed filler layer (PP filler layer) in which inorganic filler is added to PP is widely known. The non-foamed layer containing inorganic filler has a higher rigidity than the foamed layer, and laminating this layer on the foamed layer provides a so-called sandwich effect, and a foamed sheet having a high rigidity in proportion to the sheet specific gravity is obtained.
Regarding materials that also have excellent extrusion foamability, materials have been developed to achieve both foaming properties and container appearance by blending a specific propylene-ethylene block copolymer polymerized with a Ziegler-Natta catalyst with a long-chain branched polypropylene base having a high melt tension suitable for foam molding (Patent Documents 1 to 3).
On the other hand, in extrusion molding represented by the T-die method, in order to increase productivity, it is common to increase the screw rotation speed of the extruder and the take-up speed of the sheet. In such an environment in which a sheet is molded at a high discharge rate and a high line speed, in addition to the factors caused by the increase in the expansion ratio described above, the shear heat of the resin also increases, making the resin temperature more likely to rise, and increasing the take-up speed causes excessive tension in the foamed sheet, making it easier for bubbles to collapse, coalesce, break, etc. Furthermore, when the above-mentioned PP filler layer is laminated, the inorganic filler contained in the PP filler layer has a larger heat capacity than PP, so cooling is slower and bubbles are more likely to break. Under such an environment, it is difficult to obtain a sheet with good appearance having a foamed layer of 3.0 times or more, especially by the T-die method, using conventional materials, and there has been a strong demand for the development of a material for obtaining a foamed sheet with good expansion properties and high appearance.

Patent No. 5624851 Patent No. 6064668 Patent No. 6089765

In view of the current state of the prior art, the object of the present invention is to provide a polypropylene resin multi-layer foam sheet that contains a PP filler layer and that can be used to obtain a polypropylene resin multi-layer foam that has uniform fine foam cells and a good appearance even when the foam layer is extruded using a T-die to obtain a foamed product with a foaming ratio of 3.0 times or more, and to provide a molded product thermoformed using the same.

As a result of intensive research conducted by the present inventors to solve the above problems, it was discovered that by using a polypropylene resin composition containing a specific blend amount of a polypropylene resin having a specific long-chain branching structure, a propylene block copolymer which is a multi-stage polymer consisting of a specific propylene (co)polymer and a propylene-ethylene copolymer, and a propylene-α-olefin random copolymer component polymerized with a specific metallocene catalyst, in the foam layer, it is possible to obtain a foam molded article having uniform fine foam cells and a good appearance, even when the foam layer is expanded to an expansion ratio of 3.0 times or more using a T-die expansion method, and thus completed the present invention.

That is, according to a first aspect of the present invention, there is provided a polypropylene-based resin multi-layer foamed sheet comprising a foam layer made of a polypropylene-based resin composition for foam molding containing 0.05 to 6.0 parts by weight of a foaming agent per 100 parts by weight of the polypropylene-based resin composition, a PP filler layer containing an inorganic filler, and a surface layer made of a thermoplastic resin composition,
The polypropylene resin composition comprises
67.5 to 2.5% by weight of polypropylene resin (X) having a long chain branched structure and having the following characteristics (X-i) to (X-iv),
2.5 to 67.5% by weight of a propylene-based block copolymer (Y) which is a multi-stage polymer consisting of a propylene (co)polymer (Y-1) and a propylene-ethylene copolymer (Y-2) and has the following characteristics (Y-i) to (Y-v), and
10 to 65% by weight of a propylene-α-olefin random copolymer (Z) having the following characteristics (Zi) to (Z-ii)
(wherein the total of (X), (Y) and (Z) is 100% by weight).
(X-i) MFR is 0.1 to 30.0 g/10 min.
(X-ii) The molecular weight distribution Mw/Mn measured by GPC is 3.0 to 10.0, and Mz/Mw is 2.5 to 10.0.
(X-iii) The melt tension (MT) (unit: g) satisfies either log(MT)≧−0.9×log(MFR)+0.7, or MT≧15.
(X-iv) The amount of paraxylene soluble components at 25° C. (CXS) is less than 5.0% by weight based on the total weight of the polypropylene resin (X).
(Y-i) The ratio of (Y-1) to (Y-2) is 50 to 99% by weight for (Y-1) and 1 to 50% by weight for (Y-2) (where the total weight of the propylene block copolymer (Y) is 100% by weight).
(Y-ii) The MFR of the propylene block copolymer (Y) is 0.1 to 200.0 g/10 min.
(Y-iii) The propylene block copolymer (Y) has a peak melting temperature of more than 155°C.
(Y-iv) The ethylene content in the propylene-ethylene copolymer (Y-2) is 11 to 60% by weight (wherein the total weight of the constituent monomers of the propylene-ethylene copolymer (Y-2) is taken as 100% by weight).
(Yv) The intrinsic viscosity of the propylene-ethylene copolymer (Y-2) in decalin at 135° C. is 5.3 dl/g or more.
(Zi) It is polymerized using a metallocene catalyst.
(Z-ii) The melting peak temperature as measured by DSC is 155° C. or lower.

According to a second aspect of the present invention, there is provided a polypropylene-based resin multi-layer foamed sheet, characterized in that the polypropylene resin (X) in the first aspect has the following property (X-v): the branching index g ^' at an absolute molecular weight Mabs of 1,000,000 is 0.30 or more and less than 0.95.

Furthermore, according to a third aspect of the present invention, there is provided the polypropylene resin multi-layer foamed sheet according to the second aspect, wherein the polypropylene resin (X) has the following property (X-vi):
(X-vi): The mm fraction of consecutive propylene units of three units determined by ¹³ C-NMR is 95% or more.

The fourth aspect of the present invention provides a molded article that is produced by thermoforming the multi-layer foamed sheet according to any one of the first to third aspects of the present invention.

According to the fifth aspect of the present invention, there is provided a molded article obtained by molding a multi-layer foamed sheet according to any one of the first to third aspects of the present invention, characterized in that the molded article is obtained by molding a foam layer made of the polypropylene-based resin composition for foam molding by any one of the following molding methods: injection molding, thermoforming, extrusion molding, blow molding, or bead foam molding.

The polypropylene-based resin multi-layer foamed sheet of the present invention, particularly the foamed sheet obtained by the T-die molding method, contains a PP filler layer and has a feature that uniform fine foam cells can be obtained even when the foamed layer has a high expansion ratio of 3.0 times or more, and has a feature that a molded product with good appearance can be obtained.
The polypropylene-based resin multi-layer foamed sheet of the present invention and the thermoformed product using the same have an excellent balance between foaming characteristics and rigidity, and can obtain uniform and fine foam cells. They are also excellent in appearance, thermoformability, impact resistance, light weight, heat resistance, heat insulation, oil resistance, etc., and therefore can be suitably used for food containers such as trays, plates, and cups, vehicle interior materials such as automobile door trims and automobile trunk mats, packaging, stationery, building materials, etc.

The following describes in detail an embodiment of the present invention. However, the description of the components described below is an example of an embodiment of the present invention, and the present invention is not limited to the contents described below as long as it does not exceed the gist of the present invention.

The polypropylene-based resin multi-layer foamed sheet of the present invention comprises a foamed layer made of a polypropylene-based resin composition for foam molding, a PP filler layer containing an inorganic filler, and a surface layer made of a thermoplastic resin composition.
The polypropylene resin composition for foam molding used in the present invention contains 0.05 to 6.0 parts by weight of a foaming agent per 100 parts by weight of the polypropylene resin composition.
The polypropylene resin composition used in the present invention (hereinafter, sometimes referred to as "resin composition used in the present invention") is characterized by containing 67.5 to 2.5% by weight of a polypropylene resin (X) having a long chain branched structure and having the following characteristics (X-i) to (X-iv), 2.5 to 67.5% by weight of a propylene block copolymer (Y) which is a multistage polymer consisting of a propylene (co)polymer (Y-1) and a propylene-ethylene copolymer (Y-2) and having the following characteristics (Y-i) to (Y-v), and 10 to 65% by weight of a propylene-α-olefin random copolymer (Z) having the following characteristics (Z-i) to (Z-ii) (the total of (X), (Y), and (Z) is 100% by weight).
The properties that the components (X), (Y), and (Z) should satisfy will be described in detail below.

I. Polypropylene resin (X) having a long chain branched structure
The polypropylene resin composition used in the present invention is characterized by using a polypropylene resin (X) having the following properties (X-i) to (X-iv) and having a structure with long chain branches.
Property (Xi): MFR is 0.1 to 30.0 g/10 min.
Property (X-ii): Molecular weight distribution Mw/Mn by GPC is 3.0 to 10.0, and Mz/Mw is 2.5 to 10.0.
Property (X-iii): Melt tension (MT) (unit: g)
log(MT)≧−0.9×log(MFR)+0.7 or MT≧15
The above conditions must be satisfied.
Property (X-iv): The amount of paraxylene solubles at 25° C. (CXS) is less than 5.0% by weight based on the total weight of the polypropylene resin (X).
The above-mentioned property requirements specified in the present invention and the method for producing the polypropylene resin (X) having a structure with long chain branches will be specifically described below.

1. Characteristics (Xi): MFR
The melt flow rate (MFR) of the polypropylene resin (X) having a long chain branch structure in the present invention must be in the range of 0.1 to 30.0 g/10 min, and preferably in the range of 0.3 to 20. If the MFR of the polypropylene resin (X) is 0.1 g/10 min or more, the flowability is insufficient, and the resin is difficult to mold in various moldings. On the other hand, if it is 30.0 g/10 min or less, the tension is sufficient and the properties as a high melt tension material are good, making it suitable.
The MFR is based on JIS K7210:1999 "Plastics - Test method for melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastics" in Appendix A, Table 1, Condition M (230°C, 2.16 kg The measurement was made in accordance with the load (g/10 min).

2. Property (X-ii): Molecular weight distribution by GPC Furthermore, the polypropylene resin (X) having a structure with long chain branches is required to have a relatively wide molecular weight distribution, and the molecular weight distribution Mw/Mn (where Mw is the weight average molecular weight and Mn is the number average molecular weight) obtained by gel permeation chromatography (GPC) is required to be 3.0 or more and 10.0 or less. The molecular weight distribution Mw/Mn of the polypropylene resin (X) having a structure with long chain branches is preferably in the range of 3.5 to 8.0, more preferably 4.1 to 6.0.
Furthermore, as a parameter that more significantly indicates the breadth of the molecular weight distribution, Mz/Mw (where Mz is the Z-average molecular weight) must be 2.5 or more and 10.0 or less. The preferred range of Mz/Mw is 2.8 to 8.0, and more preferably 3.0 to 6.0.
The wider the molecular weight distribution, the more improved the moldability, but those with Mw/Mn and Mz/Mw in this range are particularly excellent in moldability.
The definitions of Mn, Mw and Mz are described in "Basics of Polymer Chemistry" (edited by the Society of Polymer Science, Tokyo Kagaku Dojin, 1978) and the like, and can be calculated from a molecular weight distribution curve by GPC.

The specific measurement method of GPC is as follows.
Apparatus: Waters GPC (ALC/GPC 150C)
Detector: FOXBORO MIRAN 1A IR detector (measurement wavelength: 3.42 μm)
Column: Showa Denko AD806M/S (3 columns in series)
Mobile phase solvent: orthodichlorobenzene (ODCB)
・Measurement temperature: 140℃
・Flow rate: 1.0ml/min
・Injection amount: 0.2ml
Sample preparation: A 1 mg/mL solution of the sample is prepared using ODCB (containing 0.5 mg/mL BHT), and dissolved at 140° C. for approximately 1 hour.
The retention volume obtained by GPC measurement is converted to the molecular weight using a calibration curve prepared in advance using standard polystyrene (PS). The standard polystyrene used is the following brand manufactured by Tosoh Corporation.
F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000
A calibration curve was created by injecting 0.2 mL of a solution of each compound dissolved in ODCB (containing 0.5 mg/mL BHT) at 0.5 mg/mL. The calibration curve was created using a cubic equation obtained by approximating the curve using the least squares method.
The viscosity formula [η]=K×M ^α used for conversion to molecular weight uses the following values.
PS: K=1.38×10 ⁻⁴ , α=0.7
PP: K=1.03×10 ⁻⁴ , α=0.78

3. Property (X-iii): Melt tension (MT)
Furthermore, the polypropylene resin (X) having a structure with long chain branches must satisfy the following condition (1).
Condition (1)
log(MT)≧−0.9×log(MFR)+0.7
or MT≧15
At least one of the following conditions is satisfied.
Here, MT represents the melt tension measured using a Capillograph 1B manufactured by Toyo Seiki Seisakusho Co., Ltd. under the following conditions: capillary diameter 2.0 mm, length 40 mm, cylinder diameter 9.55 mm, cylinder extrusion speed 20 mm/min, take-up speed 4.0 m/min, temperature 230°C, and the unit is grams. However, when the MT of component (X) is extremely high, the resin may break at a take-up speed of 4.0 m/min. In such a case, the take-up speed is lowered, and the tension at the maximum speed at which take-up is possible is taken as MT. The measurement conditions and units of MFR are as described above.
This provision is an index for polypropylene resin (X) having a structure with long chain branches to have sufficient melt tension for foam molding. Generally, MT has a correlation with MFR, and therefore, it is described by a relational formula with MFR.
Thus, the method of defining MT by the relational equation with MFR is a common method for those skilled in the art. For example, in JP-A-2003-25425, the following relational equation is proposed as the definition of polypropylene having high melt tension.
log(MS)>-0.61×log(MFR)+0.82 (230℃)
(Here, MS has the same meaning as MT above.)
Furthermore, in Japanese Patent Application Laid-Open No. 2003-64193, the following relational formula is proposed as a definition of polypropylene having high melt tension.
11.32×MFR ^-0.7854 ≦MT (230℃)
Furthermore, in Japanese Patent Application Laid-Open No. 2003-94504, the following relational expression is proposed as a definition of polypropylene having high melt tension.
MT≧7.52×MFR ^-0.576
(MT is a value measured at 190°C, and MFR is a value measured at 230°C.)

When the polypropylene resin (X) having a structure with long chain branches satisfies the above condition (1), it can be said to be a resin with sufficiently high melt tension and is useful for foam molding. Furthermore, it is more preferable that the polypropylene resin (X) satisfies the following condition (1)', and further more preferable that the polypropylene resin (X) satisfies the following condition (1)".
...Condition (1)'
log(MT)≧−0.9×log(MFR)+0.9
or MT≧15
At least one of the following conditions is satisfied.
...Condition (1)"
log(MT)≧−0.9×log(MFR)+1.1
or MT≧15
At least one of the following conditions is satisfied.
There is no particular need to set an upper limit for MT, but when MT is 40 g or less, the take-up speed does not significantly slow down in the above measurement method, making measurement easy. In such a case, the extensibility of the resin is considered to be good, so that the upper limit is preferably 40 g or less, more preferably 35 g or less, and most preferably 30 g or less.

4. Property (X-iv): Amount of paraxylene solubles at 25°C (CXS)
The polypropylene resin (X) having a long chain branch structure used in the present invention preferably contains a small amount of low crystallinity components that cause stickiness and bleed-out when the product is made. The low crystallinity components are evaluated by the amount of soluble components in xylene at 25°C (CXS), which must be less than 5.0% by weight based on the total weight of the component (X), preferably 3.0% by weight or less, more preferably 1.0% by weight or less, and even more preferably 0.5% by weight or less. The lower limit is not particularly limited, but is usually 0.01% by weight or more, preferably 0.03% by weight or more. The details of the CXS measurement method are as follows.
2 g of the sample is dissolved in 300 ml of p-xylene (containing 0.5 mg/ml of BHT) at 130° C. to obtain a solution, which is then left to stand at 25° C. for 12 hours. The precipitated polymer is then filtered off, and p-xylene is evaporated from the filtrate. The solution is then dried under reduced pressure at 100° C. for 12 hours to recover the xylene-soluble components at room temperature. The ratio [wt %] of the weight of the recovered components to the weight of the charged sample is defined as CXS.

Additional features of the polypropylene resin (X) having a long chain branching structure used in the present invention include the following properties (X-v) to (X-vi).

5. Property (Xv): Branching index g'
A direct indicator of whether or not the polypropylene resin (X) has a long chain branching structure is the branching index g ^' . g ^' is given by the ratio of the intrinsic viscosity [η]br of the polymer having long chain branches to the intrinsic viscosity [η]lin of a linear polymer having the same molecular weight, i.e., [η]br/[η]lin, and takes a value smaller than 1 when long chain branches are present.
The definition of the branching index g′ is described, for example, in “Developments in Polymer Characterization-4” (J. V. Dawkins ed. Applied Science Publishers, 1983), and is an index known to those skilled in the art.

g ^' can be obtained as a function of absolute molecular weight Mabs, for example, by using GPC equipped with a light scattering meter and a viscometer as detectors as described below.
The polypropylene resin (X) having a structure with long chain branches used in the present invention preferably has a g' of 0.30 or more and less than 0.95, more preferably 0.55 or more and less than 0.95, still more preferably 0.75 or more and less than 0.95, and most preferably 0.78 or more and less than 0.95, when the absolute molecular weight Mabs determined by light scattering is 1,000,000.
As described in detail below, the polypropylene resin (X) having a structure with long chain branches used in the present invention is considered to produce comb chains as a molecular structure based on its polymerization mechanism, and when g' is 0.30 or more, the proportion of main chains is small and the proportion of side chains is not extremely large, and in such a case, the melt tension is improved and there is no risk of gel formation, which is preferable for foam molding. On the other hand, when g' is less than 0.95, the melt tension does not tend to become insufficient due to the presence of branches, and the resin is suitable for foam molding.

The reason why the lower limit of g' is preferably the above-mentioned value is as follows.
According to "Encyclopedia of Polymer Science and Engineering vol. 2" (John Wiley & Sons, 1985, p. 485), the g ^' value of a comb polymer is expressed by the following formula:

Here, g is the branching index defined by the ratio of the radius of gyration of the polymer, and ε is a constant determined by the shape of the branched chain and the solvent. According to Table 3 on p. 487 of the same document, a value of approximately 0.7 to 1.0 has been reported for comb-shaped chains in a good solvent. λ is the proportion of the main chain in the comb-shaped chain, and p is the average number of branches. According to this formula, for comb-shaped chains, the number of branches becomes extremely large, that is, in the limit where p is infinite, g ^' = ^gε = ^λε , and it does not become equal to or less than the value of ^λε , and generally there is a lower limit.
On the other hand, the formula of the conventionally known random branched chains which are thought to be generated in the case of electron beam irradiation or peroxide modification is given in formula (19) on page 485 of the same document, which shows that in the case of random branched chains, as the number of branching points increases, g' and the g value decrease monotonically without any particular lower limit. In other words, in the present invention, the fact that there is a lower limit for the g' value means that the polypropylene resin (X) having a structure with long chain branches used in the present invention has a structure close to a comb chain, which makes it easier to distinguish from the random branched chains generated by electron beam irradiation or peroxide modification.
Furthermore, in the case of a branched polymer having a structure similar to a comb chain in which g' falls within the above range, the degree of decrease in melt tension during repeated kneading is small, and therefore, when scraps generated in the process of industrially producing molded articles, for example, scraps generated by cutting edges during molding of sheets or films, or parts such as runners for injection molding, are used again as recycled materials for molding, the decrease in physical properties and moldability is small, which is preferable.

A specific method for calculating g' is as follows.
Alliance GPCV2000 manufactured by Waters is used as a GPC device equipped with a differential refractometer (RI) and a viscosity detector (Viscometer). A multi-angle laser light scattering detector (MALLS) manufactured by Wyatt Technology, DAWN-E is used as a light scattering detector. The detectors are connected in the order of MALLS, RI, and Viscometer. The mobile phase solvent is 1,2,4-trichlorobenzene (added with antioxidant Irganox 1076 manufactured by BASF Japan Ltd. at a concentration of 0.5 mg/mL).
The flow rate is 1 mL/min, and two Tosoh GMHHR-H(S) HT columns are connected together. The temperatures of the column, sample injection section, and each detector are 140° C. The sample concentration is 1 mg/mL, and the injection volume (sample loop volume) is 0.2175 mL.
In determining the absolute molecular weight (Mabs), the root mean square radius of gyration (Rg) obtained from MALLS, and the intrinsic viscosity ([η]) obtained from Viscometer, the data processing software ASTRA (version 4.73.04) attached to MALLS is used, and calculations are performed with reference to the following literature.
References:
1. "Developments in Polymer Characterization-4" (J.V. Dawkins ed. Applied Science Publishers, 1983. Chapter 1.)
2. Polymer, 45, 6495-6505 (2004)
3. Macromolecules, 33, 2424-2436 (2000)
4. Macromolecules, 33, 6945-6952 (2000)

[Calculation of Branching Index (g')]
The branching index (g') is calculated as the ratio ([η]br/[η]lin) of the intrinsic viscosity ([η]br) obtained by measuring a sample with the above-mentioned Viscometer to the intrinsic viscosity ([η]lin) obtained by separately measuring a linear polymer.
When a long chain branch structure is introduced into a polymer molecule, the radius of gyration becomes smaller compared to a linear polymer molecule of the same molecular weight. Since a smaller radius of gyration results in a smaller intrinsic viscosity, the ratio ([η]br/[η]lin) of the intrinsic viscosity ([η]br) of the branched polymer to the intrinsic viscosity ([η]lin) of the linear polymer of the same molecular weight becomes smaller as the long chain branch structure is introduced.
Therefore, when the branching index (g' = [η]br/[η]lin) is a value smaller than 1.0, it means that branching has been introduced. Here, as the linear polymer for obtaining [η]lin, a commercially available homopolypropylene (Novatec PP (registered trademark) manufactured by Japan Polypropylene Corporation, grade name: FY6) is used. It is known that the logarithm of [η]lin of a linear polymer has a linear relationship with the logarithm of the molecular weight as the Mark-Houwink-Sakurada equation, so that the value of [η]lin can be obtained by appropriately extrapolating to the low molecular weight side or the high molecular weight side.

6. Property (X-vi): mm fraction of propylene unit triads by ¹³ C-NMR The polypropylene resin (X) having a structure with long chain branches used in the present invention preferably has high stereoregularity. The level of stereoregularity can be evaluated by ¹³ C-NMR, and it is preferable that the mm fraction of propylene unit triads obtained by ¹³ C-NMR has a stereoregularity of 95.0% or more.
The mm fraction is the percentage of propylene unit triads in which the direction of the methyl branch in each propylene unit is the same among any propylene unit triads consisting of head-to-tail bonds in a polymer chain, and its upper limit is 100%. This mm fraction is a value indicating that the three-dimensional structure of the methyl groups in the polypropylene molecular chain is isotactically controlled, and the higher the mm fraction, the higher the degree of control. If the mm fraction is smaller than this value, the mechanical properties of the product, such as the elastic modulus, tend to decrease.
Therefore, the mm fraction is preferably 95.0% or more, more preferably 96.0% or more, and further preferably 97.0% or more. Note that both properties (X-iv) and (X-vi) are properties related to stereoregularity, and it is particularly preferable that the requirements of properties (X-iv) and (X-vi) are satisfied simultaneously.

The details of the method for measuring the mm fraction of propylene unit triads by ¹³ C-NMR are as follows.
375 mg of the sample is completely dissolved in 2.5 ml of deuterated 1,1,2,2-tetrachloroethane in an NMR sample tube (10φ), and then measured by the proton complete decoupling method at 125°C. The chemical shift is set to 74.2 ppm for the central peak of the three peaks of deuterated 1,1,2,2-tetrachloroethane. The chemical shifts of the other carbon peaks are based on this.
Flip angle: 90 degrees Pulse interval: 10 seconds Resonant frequency: 100 MHz or more Number of integrations: 10,000 or more Observation range: -20 ppm to 179 ppm
Number of data points: 32768
The mm fraction is analyzed using the ¹³ C-NMR spectrum measured under the above conditions.
Spectral assignments are made with reference to Macromolecules, (1975) vol. 8, p. 687 and Polymer, vol. 30, p. 1350 (1989).
A more specific method for determining the mm fraction is described in detail in paragraphs [0053] to [0065] of JP 2009-275207 A, and this method will also be followed in the present specification.
In the present invention, a polypropylene resin which satisfies the property (X-iii) log(MT)≧−0.9×log(MFR)+0.7 and g′<1 at Mabs of 1 million can be said to have a structure with long chain branches.

7. Properties: Amount of Polypropylene Resin (X) Having a Structure with Long Chain Branches The amount of polypropylene resin (X) having a structure with long chain branches is 67.5 to 2.5% by weight, preferably 60.0 to 10.0% by weight, more preferably 55.0 to 15.0% by weight, and even more preferably 52.5 to 17.5% by weight (the total of (X), (Y), and (Z) is 100% by weight). When the amount of polypropylene resin (X) having a structure with long chain branches is within this range, the load on the sheet due to shear heat generation and take-up tension can be reduced, particularly when the sheet is molded at high speed by the T-die method and at a high expansion ratio of more than 3.0 times, and a foamed sheet having excellent bubble independence and density and excellent appearance can be obtained. Furthermore, when the blending amount is 67.5% by weight or less, the fluidity is sufficient and there is no problem such as excessive load on the extruder for various moldings, and when the blending amount is 2.5% by weight or more, the melt tension is sufficient, the properties as a high melt tension material are excellent, and the material is suitable for foam molding.

8. Production method of polypropylene resin (X) having a structure with long chain branches The production method of polypropylene resin (X) having a structure with long chain branches is not particularly limited as long as it satisfies the above-mentioned properties (X-i) to (X-iv), and preferably (X-v) to (X-vi), but as described above, a preferred production method for satisfying all of the conditions such as high stereoregularity, low content of low crystalline components, relatively wide molecular weight distribution, range of branching index g ^' , and high melt tension is a method using a macromer copolymerization method utilizing a combination of metallocene catalysts. An example of such a method is the method disclosed in JP-A-2009-57542.
This method is a method for producing polypropylene having a structure with long chain branches by using a catalyst that combines a catalyst component of a specific structure capable of producing macromers with a catalyst component of a specific structure capable of copolymerizing macromers at a high molecular weight. This method makes it possible to produce a polypropylene resin having a structure with long chain branches and having desired physical properties by an industrially effective method such as bulk polymerization or gas phase polymerization, particularly by single-stage polymerization under practical pressure and temperature conditions, using hydrogen as a molecular weight modifier.
Furthermore, in the past, it was necessary to increase the branching efficiency by lowering the crystallinity using a polypropylene component with low stereoregularity. However, the above-mentioned method makes it possible to introduce a polypropylene component with sufficiently high stereoregularity into a side chain in a simple manner, and is suitable for satisfying the properties (X-vi) and (X-iv) related to high stereoregularity and a low amount of low crystallinity component, which are preferable for the polypropylene resin (X) used in the present invention.
Furthermore, the above-mentioned method is preferable because it is possible to broaden the molecular weight distribution by using two types of catalysts having significantly different polymerization characteristics, and it is possible to simultaneously satisfy the properties (X-i) to (X-iii) required for the polypropylene resin (X) having long chain branches used in the present invention.

Therefore, a preferred method for producing the polypropylene resin (X) having a structure with long chain branches used in the present invention will be described in detail below.
A preferred method for producing the polypropylene resin (X) having a structure with long chain branches is a method for producing a propylene polymer using the following catalyst components (A), (B) and (C) as a propylene polymerization catalyst.
(A): Two or more transition metal compounds of Group 4 of the periodic table selected from at least one type of component [A-1], which is a compound represented by the following general formula (a1), and at least one type of component [A-2], which is a compound represented by the following general formula (a2):
Component [A-1]: Compound represented by general formula (a1) Component [A-2]: Compound represented by general formula (a2) (B): Ion-exchangeable layered silicate (C): Organoaluminum compound

The catalyst components (A), (B) and (C) will be described in detail below.
(1) Catalyst component (A)
(i) Component [A-1]: a compound represented by general formula (a1)

In general formula (a1), R ¹¹ and R ¹² each independently represent a heterocyclic group containing nitrogen, oxygen, or sulfur and having 4 to 16 carbon atoms. R ¹³ and R ¹⁴ each independently represent an aryl group having 6 to 16 carbon atoms, which may contain halogen, silicon, oxygen, sulfur, nitrogen, boron, phosphorus, or a plurality of hetero elements selected therefrom, or a heterocyclic group containing nitrogen, oxygen, or sulfur and having 6 to 16 carbon atoms. X ¹¹ and Y ¹¹ each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing hydrocarbon group having 1 to 20 carbon atoms, a halogenated hydrocarbon group having 1 to 20 carbon atoms, an oxygen-containing hydrocarbon group having 1 to 20 carbon atoms, an amino group, or a nitrogen-containing hydrocarbon group having 1 to 20 carbon atoms, and Q ¹¹ represents a divalent hydrocarbon group having 1 to 20 carbon atoms, a silylene group or a germylene group which may have a hydrocarbon group having 1 to 20 carbon atoms.

The above-mentioned nitrogen-, oxygen- or sulfur-containing heterocyclic group having 4 to 16 carbon atoms for R ¹¹ and R ¹² is preferably a 2-furyl group, a substituted 2-furyl group, a substituted 2-thienyl group or a substituted 2-furfuryl group, more preferably a substituted 2-furyl group.
In addition, examples of the substituent of the substituted 2-furyl group, the substituted 2-thienyl group, and the substituted 2-furfuryl group include alkyl groups having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, and a propyl group, halogen atoms, such as a fluorine atom and a chlorine atom, alkoxy groups having 1 to 6 carbon atoms, such as a methoxy group and an ethoxy group, and trialkylsilyl groups. Among these, a methyl group and a trimethylsilyl group are preferred, and a methyl group is particularly preferred.
Furthermore, R ¹¹ and R ¹² are particularly preferably a 2-(5-methyl)-furyl group. It is also preferable that R ¹¹ and R ¹² are the same as each other.
The aryl group having 6 to 16 carbon atoms for R ¹³ and R ¹⁴ , which may contain halogen, silicon, oxygen, sulfur, nitrogen, boron, phosphorus, or a plurality of hetero elements selected therefrom, may have one or more hydrocarbon groups having 1 to 6 carbon atoms, silicon-containing hydrocarbon groups having 1 to 6 carbon atoms, or halogen-containing hydrocarbon groups having 1 to 6 carbon atoms on the aryl ring skeleton as substituents within the range of 6 to 16 carbon atoms.

At least one of R ¹³ and R ¹⁴ is preferably a phenyl group, a 4-methylphenyl group, a 4-i-propylphenyl group, a 4-t-butylphenyl group, a 4-trimethylsilylphenyl group, a 2,3-dimethylphenyl group, a 3,5-di-t-butylphenyl group, a 4-phenyl-phenyl group, a chlorophenyl group, a naphthyl group, or a phenanthryl group, and more preferably a phenyl group, a 4-i-propylphenyl group, a 4-t-butylphenyl group, a 4-trimethylsilylphenyl group, or a 4-chlorophenyl group. It is also preferable that R ¹³ and R ¹⁴ are the same as each other.

In the general formula (a1), ^X11 and ^Y11 are auxiliary ligands, which react with the cocatalyst of the catalyst component (B) to produce an active metallocene having olefin polymerization ability. Therefore, as long as this purpose is achieved, the type of ligand for ^X11 and ^Y11 is not limited, and each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing hydrocarbon group having 1 to 20 carbon atoms, a halogenated hydrocarbon group having 1 to 20 carbon atoms, an oxygen-containing hydrocarbon group having 1 to 20 carbon atoms, an amino group or a nitrogen-containing hydrocarbon group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylamide group having 1 to 20 carbon atoms, a trifluoromethanesulfonic acid group, or a phosphorus-containing hydrocarbon group having 1 to 20 carbon atoms.

In general formula (a1), ^Q11 represents a divalent hydrocarbon group having 1 to 20 carbon atoms, or a silylene group or germylene group which may have a hydrocarbon group having 1 to 20 carbon atoms, linking two five-membered rings. When two hydrocarbon groups are present on the silylene group or germylene group, they may be linked to each other to form a ring structure.
Specific examples of ^Q11 include alkylene groups such as methylene, methylmethylene, dimethylmethylene, and 1,2-ethylene; aryl alkylene groups such as diphenylmethylene; silylene groups; alkyl silylene groups such as methylsilylene, dimethylsilylene, diethylsilylene, di(n-propyl)silylene, di(i-propyl)silylene, and di(cyclohexyl)silylene; (alkyl)(aryl)silylene groups such as methyl(phenyl)silylene; aryl silylene groups such as diphenylsilylene; alkyl oligosilylene groups such as tetramethyldisilylene; germylene groups; alkylgermylene groups in which the silicon of the silylene group having the above divalent hydrocarbon group having 1 to 20 carbon atoms is replaced with germanium; (alkyl)(aryl)germylene groups; and arylgermylene groups. Among these, a silylene group having a hydrocarbon group of 1 to 20 carbon atoms or a germylene group having a hydrocarbon group of 1 to 20 carbon atoms is preferred, with an alkylsilylene group and an alkylgermylene group being particularly preferred.

Among the compounds represented by the above general formula (a1), preferred compounds are specifically exemplified below.
dichloro[1,1'-dimethylsilylenebis{2-(2-furyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(2-thienyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-diphenylsilylenebis{2-(5-methyl-2-furyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylgermylene bis{2-(5-methyl-2-furyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylgermylenebis{2-(5-methyl-2-thienyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-t-butyl-2-furyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-trimethylsilyl-2-furyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylene bis{2-(5-phenyl-2-furyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(4,5-dimethyl-2-furyl)-4-phenyl-indenyl}]hafnium dichloride, dichloro[1,1'-dimethylsilylenebis{2-(2-benzofuryl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-methylphenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-methylphenyl)-indenyl}]hafnium 1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-ipropylphenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-trimethylsilylphenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(2-furfuryl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-chlorophenyl)-indenyl}]hafnium , dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-fluorophenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-trifluoromethylphenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-t-butylphenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(2-furyl)-4-(1 -naphthyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(2-furyl)-4-(2-naphthyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(2-furyl)-4-(2-phenanthryl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(2-furyl)-4-(9-phenanthryl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(1-naphthyl)-indenyl}]hafnium )-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(2-naphthyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(2-phenanthryl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(9-phenanthryl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-t-butyl-2 dichloro[1,1'-dimethylsilylenebis{2-(5-t-butyl-2-furyl)-4-(2-naphthyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-t-butyl-2-furyl)-4-(2-phenanthryl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-t-butyl-2-furyl)-4-(9-phenanthryl)-indenyl}]hafnium, and the like.

Among these, more preferred are dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-methylphenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-ipropylphenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl- dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-trimethylsilylphenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-chlorophenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(2-naphthyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-t-butylphenyl)-indenyl}]hafnium.
Particularly preferred are dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-phenyl-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-ipropylphenyl)-indenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-trimethylsilylphenyl)-indenyl}]hafnium, and dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-t-butylphenyl)-indenyl}]hafnium.

(ii) Component [A-2]: Compound represented by general formula (a2)

In general formula (a2), R ²¹ and R ²² are each independently a hydrocarbon group having 1 to 6 carbon atoms, R ²³ and R ²⁴ are each independently an aryl group having 6 to 16 carbon atoms which may contain halogen, silicon, oxygen, sulfur, nitrogen, boron, phosphorus, or a plurality of hetero elements selected therefrom. X ²¹ and Y ²¹ are each independently a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing hydrocarbon group having 1 to 20 carbon atoms, a halogenated hydrocarbon group having 1 to 20 carbon atoms, an oxygen-containing hydrocarbon group having 1 to 20 carbon atoms, an amino group, or a nitrogen-containing hydrocarbon group having 1 to 20 carbon atoms, and Q ²¹ is a divalent hydrocarbon group having 1 to 20 carbon atoms, a silylene group or a germylene group which may have a hydrocarbon group having 1 to 20 carbon atoms. M ²¹ is zirconium or hafnium.

The above R ²¹ and R ²² are each independently a hydrocarbon group having 1 to 6 carbon atoms, preferably an alkyl group, and more preferably an alkyl group having 1 to 4 carbon atoms. Specific examples include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, n-pentyl, i-pentyl, n-hexyl, and the like, and are preferably methyl, ethyl, or n-propyl.

Moreover, the above R ²³ and R ²⁴ are each independently an aryl group having 6 to 16 carbon atoms, preferably 6 to 12 carbon atoms, which may contain halogen, silicon, or a plurality of hetero elements selected therefrom. Preferred examples include phenyl, 3-chlorophenyl, 4-chlorophenyl, 3-fluorophenyl, 4-fluorophenyl, 4-methylphenyl, 4-i-propylphenyl, 4-t-butylphenyl, 4-trimethylsilylphenyl, 4-(2-fluoro-4-biphenylyl), 4-(2-chloro-4-biphenylyl), 1-naphthyl, 2-naphthyl, 4-chloro-2-naphthyl, 3-methyl-4-trimethylsilylphenyl, 3,5-dimethyl-4-t-butylphenyl, 3,5-dimethyl-4-trimethylsilylphenyl, 3,5-dichloro-4-trimethylsilylphenyl, and the like.

Moreover, the above X ²¹ and Y ²¹ are auxiliary ligands, which react with the cocatalyst of the catalyst component (B) to produce an active metallocene having olefin polymerization ability. Therefore, as long as this purpose is achieved, the type of ligand for X ²¹ and Y ²¹ is not limited, and each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing hydrocarbon group having 1 to 20 carbon atoms, a halogenated hydrocarbon group having 1 to 20 carbon atoms, an oxygen-containing hydrocarbon group having 1 to 20 carbon atoms, an amino group or a nitrogen-containing hydrocarbon group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylamide group having 1 to 20 carbon atoms, a trifluoromethanesulfonic acid group, or a phosphorus-containing hydrocarbon group having 1 to 20 carbon atoms.

Furthermore, the above ^Q21 is a bonding group that crosslinks two conjugated five-membered ring ligands, and is a divalent hydrocarbon group having 1 to 20 carbon atoms, a silylene group which may have a hydrocarbon group having 1 to 20 carbon atoms, or a germylene group having a hydrocarbon group having 1 to 20 carbon atoms, and is preferably a substituted silylene group or a substituted germylene group.

The substituent bonded to silicon or germanium is preferably a hydrocarbon group having 1 to 12 carbon atoms, and two substituents may be linked together. Specific examples include methylene, dimethylmethylene, ethylene-1,2-diyl, dimethylsilylene, diethylsilylene, diphenylsilylene, methylphenylsilylene, 9-silafluorene-9,9-diyl, dimethylsilylene, diethylsilylene, diphenylsilylene, methylphenylsilylene, 9-silafluorene-9,9-diyl, dimethylgermylene, diethylgermylene, diphenylgermylene, methylphenylgermylene, etc.

Furthermore, the above ^M21 is zirconium or hafnium, and is preferably hafnium.

Non-limiting examples of the metallocene compound represented by the above general formula (a2) include the following.
However, the following describes only representative exemplary compounds to avoid a large number of complicated examples, and the present invention is not limited to these compounds, and it is obvious that various ligands, cross-linking groups, or auxiliary ligands can be used arbitrarily. Also, although compounds in which the central metal is hafnium have been described, compounds in which zirconium is substituted are also treated as being disclosed in the present specification.

Dichloro{1,1'-dimethylsilylenebis(2-methyl-4-phenyl-4-hydroazulenyl)}hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(4-chlorophenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(4-t-butylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2- dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(3-chloro-4-t-butylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(3-methyl-4-t-butylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(3-methyl-4-t-butylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis {2-methyl-4-(3-chloro-4-trimethylsilylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(3-methyl-4-trimethylsilylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(1-naphthyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(1-naphthyl)-4-hydroazulenyl}]hafnium dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(2-naphthyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(4-chloro-2-naphthyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(2-fluoro-4-biphenylyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(2 dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(9-phenanthryl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-ethyl-4-(4-chlorophenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-n-propyl-4-(3-chloro-4-trimethyl- dichloro[1,1'-dimethylsilylenebis{2-ethyl-4-(3-chloro-4-t-butylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-ethyl-4-(3-methyl-4-trimethylsilylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-t-butylphenyl)-4-hydroazulenyl}]hafnium, -(2-fluoro-4-biphenylyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylgermylenebis{2-methyl-4-(4-t-butylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-(9-silafluorene-9,9-diyl)bis{2-ethyl-4-(4-chlorophenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-ethyl -4-(4-chloro-2-naphthyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-ethyl-4-(2-fluoro-4-biphenylyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-(9-silafluorene-9,9-diyl)bis{2-ethyl-4-(3,5-dichloro-4-trimethylsilylphenyl)-4-hydroazulenyl}]hafnium, etc.

Among these, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(4-chlorophenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(3-chloro-4-trimethylsilylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-ethyl-4-(2-fluoro-4-biphenylyl)-4-hydroazulenyl}]hafnium, dichloro[1, 1'-dimethylsilylenebis{2-ethyl-4-(4-chloro-2-naphthyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-ethyl-4-(3-methyl-4-trimethylsilylphenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-(9-silafluorene-9,9-diyl)bis{2-ethyl-4-(3,5-dichloro-4-trimethylsilylphenyl)-4-hydroazulenyl}]hafnium.

Particularly preferred are dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(4-chlorophenyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-ethyl-4-(2-fluoro-4-biphenylyl)-4-hydroazulenyl}]hafnium, dichloro[1,1'-dimethylsilylenebis{2-ethyl-4-(3-methyl-4-trimethylsilylphenyl)-4-hydroazulenyl}]hafnium, and dichloro[1,1'-(9-silafluorene-9,9-diyl)bis{2-ethyl-4-(3,5-dichloro-4-trimethylsilylphenyl)-4-hydroazulenyl}]hafnium.

(2) Catalyst component (B)
The catalyst component (B) preferably used for producing the polypropylene resin (X) is an ion-exchangeable layered silicate.
(i) Types of ion-exchangeable layered silicates Ion-exchangeable layered silicates (hereinafter sometimes simply referred to as silicates) are layers of silicates in which the planes formed by ionic bonds are stacked in parallel with each other through bonding forces. It is a silicate compound that has a crystal structure and contains exchangeable ions. Most silicates are naturally produced as the main component of clay minerals, so they have no ion exchange properties. Impurities other than layered silicates (quartz, cristobalite, etc.) are often included, but they may be included. Depending on the type, amount, particle size, crystallinity, and dispersion state of these impurities, they may be more than pure silicates. Such a complex is also included in the catalyst component (B).
The silicate used in the present invention is not limited to naturally occurring silicates, but may be synthetic artificial products or may contain such products.

Specific examples of silicates include the following layered silicates described in "Clay Mineralogy" by Haruo Shiramizu, Asakura Publishing (1995).
That is, smectite group such as montmorillonite, sauconite, beidellite, nontronite, saponite, hectorite, stevensite, etc., vermiculite group such as vermiculite, mica group such as mica, illite, sericite, glauconite, etc., attapulgite, sepiolite, palygorskite, bentonite, pyrophyllite, talc, chlorite group, etc.
The silicate is preferably a silicate having a 2:1 type structure as a main component, more preferably a smectite group, and particularly preferably montmorillonite. The type of interlayer cation is not particularly limited, but from the viewpoint of being relatively easy and inexpensively available as an industrial raw material, silicates having an alkali metal or alkaline earth metal as a main component of the interlayer cation are preferred.

(ii) Chemical treatment of ion-exchanged layered silicate The ion-exchanged layered silicate of the catalyst component (B) according to the present invention can be used as it is without any particular treatment, but it is preferable to subject it to a chemical treatment. Here, the chemical treatment of the ion-exchanged layered silicate can be either a surface treatment for removing impurities adhering to the surface or a treatment that affects the structure of the clay, and specific examples thereof include an acid treatment, an alkali treatment, a salt treatment, and an organic matter treatment.

<Acid treatment>:
The acid treatment not only removes surface impurities, but also partially or entirely dissolves cations such as Al, Fe, Mg, etc. in the crystal structure.
The acid used in the acid treatment is preferably selected from hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, and oxalic acid.
The salts (described in the next section) and acids used in the treatment may be two or more kinds. The conditions for the treatment with the salts and acids are not particularly limited, but it is generally preferable to select the following conditions: salt and acid concentrations of 0.1 to 50% by weight, treatment temperature of room temperature to boiling point, and treatment time of 5 minutes to 24 hours, so that at least a part of the substance constituting at least one compound selected from the group consisting of ion-exchangeable layered silicates is eluted. The salts and acids are generally used in the form of aqueous solutions.
The treatment agent may be a combination of the following acids and salts.

<Salt treatment>:
It is preferable to ion-exchange at least 40%, preferably at least 60%, of the exchangeable cations of a metal of Group 1 of the Periodic Table contained in the ion-exchangeable layered silicate before the treatment with a salt with cations dissociated from the salts shown below.
The salts used in such salt treatment for the purpose of ion exchange are compounds consisting of a cation containing at least one atom selected from the group consisting of atoms in Groups 1 to 14 of the Periodic Table, and at least one anion selected from the group consisting of halogen atoms, inorganic acids, and organic acids, and more preferably a cation containing at least one atom selected from the group consisting of atoms in Groups 2 to 14 of the Periodic Table, and Cl, Br, I, F, _PO4 , _SO4 , _NO3 , _CO3 , _C2O4 , _{ClO4 , OOCCH3 ,} CH3COCHCOCH3 _, OCl2, O( _NO3 ) ₂ , O( _ClO4 ) ₂ , O _{( SO4} ), OH, _{O2Cl2 , OCl3} , OOCH, _{OOCCH2CH3 , C2H4O4 , and C5H5O .} and at least one anion selected from the group consisting of _:

Specific examples of such salts include LiF, LiCl, LiBr, LiI, _Li2SO4 , Li _{( CH3COO} ), _LiCO3 , Li( _C6H5O7 ), LiCHO2, _{LiC2O4 , LiClO4, Li3PO4, CaCl2, CaSO4, CaC2O4 , Ca ( NO3 ) 2 , Ca3 ( C6H5O7 ) 2} , _MgCl2 , _{MgBr2 , MgSO4, Mg(PO4)2, Mg(ClO4)2 , MgC2O4 , Mg ( NO3 ) 2 , and Mg ( OOCCH3} ) _{. 2} , MgC ₄ H ₄ O ₄ , etc.

In addition, Ti(OOCCH ₃ ) ₄ , Ti(CO ₃ ) ₂ , Ti(NO ₃ ) ₄ , Ti(SO ₄ ) ₂ , TiF ₄ , TiCl ₄ , Zr(OOCCH ₃ ) ₄ , Zr(CO ₃ ) ₂ , Ｚｒ（ＮＯ _３ ） _４ 、Ｚｒ（ＳＯ _４ ） _２ 、ＺｒＦ _４ 、ＺｒＣｌ _４ 、ＺｒＯＣｌ _２ 、ＺｒＯ（ＮＯ _３ ） _２ 、ＺｒＯ（ＣｌＯ _４ ） _２ 、ＺｒＯ（ＳＯ _４ ）、ＨＦ（ＯＯＣＣＨ _３ ） _４ 、 HF( _CO3 ) ₂ , HF( _NO3 ) ₄ , HF( _SO4 ) ₂ , _HFOCl2 , _HFF4 , HFCl ₄ , V( _CH3COCHCOCH3 ) ₃ , _VOSO4 , _VOCl3 , _VCl3 , _VCl4 , _{VBr3 ,} etc.

Also, Cr(CH ₃ COCHCOCH ₃ ) ₃ , Cr(OOCCH ₃ ) ₂ OH, Cr(NO ₃ ) ₃ , Cr(ClO ₄ ) ₃ , CrPO ₄ , Cr ₂ (SO ₄ ) ₃ , CrO ₂ Cl ₂ , CrF ₃ , _{CrCl3 , CrBr3 , CrI3, Mn(OOCCH3)2, Mn(CH3COCHCOCH3)2, MnCO3, Mn(NO3)2 , MnO , Mn ( ClO4 ) 2 , MnF2} , MnCl ₂ , Fe( _OOCCH3 ) ₂ , Fe _{( CH3COCHCOCH3} ) ₃ , FeCO ₃ , Fe( _NO3 ) ₃ , Fe( _ClO4 ) ₃ , _FePO4 , _FeSO4 , _Fe2 ( _{SO4 ) 3} , FeF3, _FeCl3 , _FeC6H5O7 , _etc.

Other examples include Co( _OOCCH3 ) ₂ , Co( _CH3COCHCOCH3 ) ₃ , _CoCO3 , Co( _NO3 ) ₂ , _CoC2O4 , Co( _ClO4 ) ₂ , _Co3 ( _{PO4 ) 2} , _CoSO4 , _{CoF2 ,} CoCl2 _{, NiCO3} , Ni( _NO3 ) ₂ , _{NiC2O4 ,} Ni( _ClO4 ) ₂ , _NiSO4 , _NiCl2 , and _NiBr2 .
Further examples _include Zn( _OOCCH3 ) ₂ , Zn( _CH3COCHCOCH3 ) ₂ , _ZnCO3 , Zn( _NO3 ) ₂ , Zn( _ClO4 ) ₂ , _Zn3 ( _PO4 ) _{2 , ZnSO4} , _ZnF2 , _{ZnCl2 ,} AlF3, _AlCl3 , _{AlBr3 ,} AlI3, _Al2 ( _SO4 ) ₃ , _Al2 ( _C2O4 ) ₃ , Al( _CH3COCHCOCH3 ) ₃ , Al( _NO3 ) ₃ , _AlPO4 , _GeCl4 , _GeBr4 , _{GeI4 ,} etc.

<Alkaline treatment>:
In addition to the acid and salt treatments, the following alkali treatment or organic treatment may be performed as necessary. Examples of treatment agents used in the alkali treatment include LiOH, NaOH, KOH, Mg(OH) ₂ , Ca(OH) ₂ , Sr(OH) ₂ , and Ba(OH) ₂ .

<Organic matter treatment>:
Examples of the organic treating agent used for treating organic matter include trimethylammonium, triethylammonium, N,N-dimethylanilinium, and triphenylphosphonium.
In addition, examples of the anions constituting the organic treatment agent include, in addition to the anions exemplified as the anions constituting the salt treatment agent, for example, hexafluorophosphate, tetrafluoroborate, tetraphenylborate, etc., but are not limited to these.

These treatment agents may be used alone or in combination of two or more. These combinations may be used in combination for treatment agents added at the start of treatment or in combination for treatment agents added during treatment. Chemical treatment may also be carried out multiple times using the same or different treatment agents.
These ion-exchangeable layered silicates usually contain adsorbed water and interlayer water, and in the present invention, it is preferred to remove the adsorbed water and interlayer water before use as catalyst component (B).

There are no particular limitations on the method of heat treatment of the adsorbed water and interlayer water of the ion-exchangeable layered silicate, but it is necessary to select conditions so that no interlayer water remains and so that structural destruction does not occur. The heating time is 0.5 hours or more, preferably 1 hour or more. In this case, it is preferable that the moisture content of the catalyst component (B) after removal is 3% by weight or less, preferably 1% by weight or less, assuming that the moisture content when dehydrated for 2 hours under conditions of a temperature of 200°C and a pressure of 1 mmHg (133 Pa) is 0% by weight.

As described above, in the present invention, the particularly preferred catalyst component (B) is an ion-exchangeable layered silicate obtained by salt treatment and/or acid treatment and having a moisture content of 3% by weight or less.

Before forming the catalyst or using it as a catalyst, the ion-exchange layered silicate can be preferably treated with catalytic component (C) of an organoaluminum compound described later. There is no limit to the amount of catalytic component (C) used per gram of ion-exchange layered silicate, but it is usually 20 mmol or less, and preferably 0.5 mmol or more and 10 mmol or less. There are no limits to the treatment temperature or time, and the treatment temperature is usually 0°C or more and 70°C or less, and the treatment time is 10 minutes or more and 3 hours or less. It is also possible and preferable to wash the ion-exchange layered silicate after the treatment. The solvent used is a hydrocarbon solvent similar to the solvent used in the prepolymerization method and slurry polymerization method described later.

The catalyst component (B) is preferably spherical particles having an average particle size of 5 μm or more. Natural or commercially available products may be used as long as the particles are spherical, or the shape and particle size of the particles may be controlled by granulation, sizing, fractionation, or the like.
The granulation method used here includes, for example, stirring granulation method and spray granulation method, but commercially available products can also be used.
During granulation, organic substances, inorganic solvents, inorganic salts, and various binders may be used.
The spherical particles obtained as described above preferably have a compressive fracture strength of 0.2 MPa or more, particularly preferably 0.5 MPa or more, in order to suppress crushing or generation of fine powder during the polymerization step. With such particle strength, the effect of improving particle properties is effectively exhibited, particularly when prepolymerization is performed.

(3) Catalyst component (C)
The catalyst component (C) is an organoaluminum compound. The organoaluminum compound used as the catalyst component (C) is suitably a compound represented by the general formula: (AlR ³¹ _q Z _3-q ) _p .
In the present invention, it goes without saying that the compounds represented by this formula can be used alone, in combination, or in combination. In this formula, R ³¹ is a hydrocarbon group having 1 to 20 carbon atoms. Z represents a halogen atom, a hydrogen atom, an alkoxy group, or an amino group, q represents an integer of 1 to 3, and p represents an integer of 1 to 2. R ³¹ is preferably an alkyl group, and Z is preferably In the case of a halogen, chlorine is preferred; in the case of an alkoxy group, an alkoxy group having 1 to 8 carbon atoms is preferred; in the case of an amino group, an amino group having 1 to 8 carbon atoms is preferred.

Specific examples of the organoaluminum compound include trimethylaluminum, triethylaluminum, tri-normal propylaluminum, tri-normal butylaluminum, triisobutylaluminum, tri-normal hexylaluminum, tri-normal octylaluminum, tri-normal decylaluminum, diethylaluminum chloride, diethylaluminum sesquichloride, diethylaluminum hydride, diethylaluminum ethoxide, diethylaluminum dimethylamide, diisobutylaluminum hydride, and diisobutylaluminum chloride.
Of these, preferred are trialkylaluminums where p = 1 and q = 3 and dialkylaluminum hydrides where p = 1 and q = 2. More preferred are trialkylaluminums where R ³¹ has 1 to 8 carbon atoms.

(4) Formation and Preliminary Polymerization of Catalyst The catalyst can be formed by contacting the above-mentioned catalyst components (A) to (C) simultaneously or continuously, or at one time or multiple times, in a (preliminary) polymerization vessel.
The contact of each component is usually carried out in an aliphatic or aromatic hydrocarbon solvent. The contact temperature is not particularly limited, but is preferably between -20°C and 150°C. The contact order may be any combination suitable for the purpose, but the particularly preferred order for each component is as follows:
When using catalyst component (C), it is possible to contact catalyst component (C) with catalyst component (A), or with catalyst component (B), or with both catalyst component (A) and catalyst component (B) before contacting catalyst component (A) with catalyst component (B), or to contact catalyst component (C) with catalyst component (A) and catalyst component (B) at the same time as contacting catalyst component (A) with catalyst component (B), or to contact catalyst component (C) after contacting catalyst component (A) with catalyst component (B). Preferably, catalyst component (C) is contacted with either catalyst component (A) or catalyst component (B) before contacting catalyst component (A) with catalyst component (B).
After contacting the components, the components can be washed with an aliphatic or aromatic hydrocarbon solvent.

The amounts of the catalyst components (A), (B) and (C) used are arbitrary. For example, the amount of the catalyst component (A) used relative to the catalyst component (B) is preferably in the range of 0.1 μmol to 1,000 μmol, particularly preferably 0.5 μmol to 500 μmol, relative to 1 g of the catalyst component (B). The amount of the catalyst component (C) relative to the catalyst component (A) is preferably in the range of 0.01 to 5×10 ⁶ , particularly preferably 0.1 to 1×10 ⁴ , in terms of the molar ratio of the transition metal.

The ratio of the component [A-1] (a compound represented by general formula (a1)) and the component [A-2] (a compound represented by general formula (a2)) used in the present invention is arbitrary within a range in which the above-mentioned properties of the propylene-based polymer are satisfied. However, the molar ratio of the transition metal in [A-1] to the total amount of the components [A-1] and [A-2] is preferably 0.30 or more and 0.99 or less.
By changing this ratio, it is possible to adjust the balance between melt properties and catalytic activity. That is, from component [A-1], a low molecular weight vinyl-terminated macromer is produced, and from component [A-2], a high molecular weight product in which a part of the macromer is copolymerized is produced. Therefore, by changing the ratio of component [A-1], it is possible to control the average molecular weight, molecular weight distribution, the bias of the molecular weight distribution toward the high molecular weight side, the very high molecular weight component, and the branching (amount, length, distribution) of the produced polymer, and thereby it is possible to control melt properties such as strain hardening, melt tension, and melt extensibility.

In order to produce a propylene-based polymer having higher strain hardening, the ratio is preferably 0.30 or more, more preferably 0.40 or more, and even more preferably 0.5 or more. The upper limit is preferably 0.99 or less, and in order to efficiently produce a polypropylene resin (X) with high catalytic activity, the upper limit is more preferably 0.95 or less, and even more preferably 0.90 or less.
Furthermore, by using the component [A-1] within the above range, it is possible to adjust the balance between the average molecular weight and the catalytic activity relative to the amount of hydrogen.

The catalyst according to the present invention is subjected to a preliminary polymerization treatment in which an olefin is brought into contact with the catalyst and polymerized in small amounts. By carrying out the preliminary polymerization treatment, it is possible to prevent the formation of gel when the main polymerization is carried out. This is thought to be because the long chain branches can be uniformly distributed among the polymer particles when the main polymerization is carried out, and this also improves the melt properties.

The olefin used in the prepolymerization is not particularly limited, and examples thereof include propylene, ethylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane, styrene, etc. The olefin can be fed to the reaction vessel at a constant speed or at a constant pressure, or any other method such as a combination of such methods or a method in which the olefin is fed in a stepwise manner.
The prepolymerization temperature and time are not particularly limited, but are preferably in the range of -20°C to 100°C and 5 minutes to 24 hours, respectively. The amount of prepolymerization is preferably 0.01 to 100, more preferably 0.1 to 50, in terms of weight ratio of the amount of prepolymerized polymer to the catalyst component (B). The catalyst component (C) can also be added or supplemented during the prepolymerization. Washing can also be performed after the completion of the prepolymerization.

It is also possible to use a method in which a polymer such as polyethylene or polypropylene, or a solid inorganic oxide such as silica or titania is allowed to coexist during or after the contact of the above components.

(5) Use of Catalyst/Propylene Polymerization Any polymerization mode can be adopted as long as the olefin polymerization catalyst containing the above-mentioned catalyst components (A), (B) and (C) can be efficiently contacted with a monomer.
Specifically, a slurry polymerization method using an inert solvent, a so-called bulk polymerization method using propylene as a solvent without substantially using an inert solvent, a solution polymerization method, or a gas phase polymerization method in which each monomer is kept in a gaseous state without substantially using a liquid solvent can be used. A method of carrying out continuous polymerization or batch polymerization can also be applied. In addition to single-stage polymerization, multi-stage polymerization of two or more stages is also possible.
In the case of the slurry polymerization method, a saturated aliphatic or aromatic hydrocarbon such as hexane, heptane, pentane, cyclohexane, benzene, toluene, etc., may be used alone or in mixture as a polymerization solvent.

The polymerization temperature is from 0° C. to 150° C. In particular, when a bulk polymerization method is used, the polymerization temperature is preferably 40° C. or higher, more preferably 50° C. or higher. The upper limit is preferably 80° C. or lower, more preferably 75° C. or lower.
Furthermore, when a gas phase polymerization method is used, the temperature is preferably 40° C. or higher, more preferably 50° C. or higher, and the upper limit is preferably 100° C. or lower, more preferably 90° C. or lower.
The polymerization pressure is preferably 1.0 MPa or more and 5.0 MPa or less. In particular, when bulk polymerization is used, the polymerization pressure is preferably 1.5 MPa or more, more preferably 2.0 MPa or more. The upper limit is preferably 4.0 MPa or less, more preferably 3.5 MPa or less.

Furthermore, when a gas phase polymerization method is used, the pressure is preferably 1.5 MPa or more, more preferably 1.7 MPa or more, and the upper limit is preferably 2.5 MPa or less, more preferably 2.3 MPa or less.
Furthermore, hydrogen can be used supplementarily as a molecular weight regulator and for the activity improving effect in a molar ratio relative to propylene in the range of 1.0×10 ⁻⁶ to 1.0×10 ⁻² .

Furthermore, by changing the amount of hydrogen used, it is possible to control not only the average molecular weight of the produced polymer but also the molecular weight distribution, the bias of the molecular weight distribution towards the high molecular weight side, the very high molecular weight component, and the branching (amount, length, distribution), thereby making it possible to control the melt properties that characterize polypropylene having a structure with long chain branches, such as MFR, strain hardening, melt tension MT, and melt extensibility.
Therefore, hydrogen is used in a molar ratio to propylene of 1.0×10 ⁻⁶ or more, preferably 1.0×10 ⁻⁵ or more, and more preferably 1.0×10 ⁻⁴ or more. The upper limit is 1.0×10 ⁻² or less, preferably 0.9×10 ⁻² or less, and more preferably 0.8×10 ⁻² or less.

In addition to the propylene monomer, copolymerization may be carried out using an α-olefin comonomer having 2 to 20 carbon atoms other than propylene, such as ethylene and/or 1-butene, as a comonomer depending on the application.
Therefore, in order to obtain a polypropylene resin (X) used in the present invention that has a good balance between catalytic activity and melt properties, ethylene and/or 1-butene is preferably used in an amount of 15 mol % or less, more preferably 10.0 mol % or less, and even more preferably 7.0 mol % or less, based on propylene.

When propylene is polymerized using the catalyst and polymerization method exemplified here, a special chain transfer reaction commonly known as β-methyl elimination occurs from the active species derived from catalyst component [A-1], resulting in a polymer with one end mainly exhibiting a propenyl structure, forming a so-called macromer. This macromer is capable of producing a higher molecular weight and is incorporated into the active species derived from catalyst component [A-2], which has better copolymerizability, and it is believed that the macromer copolymerization proceeds. Therefore, it is believed that the branching structure of the polypropylene resin with long chain branching structure that is produced is mainly comb-shaped chains.

8. Other Properties of Polypropylene Resin (X) Having a Structure with Long Chain Branches A further additional feature of the polypropylene resin (X) having long chain branches used in the present invention, which is produced by the above-mentioned method, is that the strain hardening degree (λmax(0.1)) measured by elongational viscosity at a strain rate of ^0.1 s is preferably 6.0 or more.
The strain hardening index (λmax(0.1)) is an index of strength when melted, and a large value of this index has the effect of improving melt tension. As a result, the closed cell ratio can be increased when foam molding is performed. When this strain hardening index is preferably 6.0 or more, the closed cell property can be maintained at a higher level, and more preferably 8.0 or more.

The method for calculating λmax(0.1) is described in detail below.
· λmax (0.1) calculation method The extensional viscosity at a temperature of 180°C and a strain rate of 0.1 s ^-1 is plotted on a double logarithmic graph with time t (seconds) on the horizontal axis and extensional viscosity _ηE (Pa·seconds) on the vertical axis. On the double logarithmic graph, the viscosity immediately before strain hardening occurs is approximated by a straight line.
Specifically, first, the slope at each time point is calculated when the extensional viscosity is plotted against time, and various averaging methods are used to calculate the slope at each time point, taking into consideration that the extensional viscosity measurement data is discrete. For example, the slope of each adjacent data point is calculated, and the moving average of several surrounding points is calculated.
In the low strain region, the extensional viscosity is a simple increasing function, gradually approaching a constant value, and coincides with the Trouton viscosity after a sufficient time has elapsed if there is no strain hardening. However, in the case of strain hardening, the extensional viscosity generally starts to increase with time from a strain (=strain rate x time) of about 1. That is, the above slope tends to decrease with time in the low strain region, but conversely tends to increase from a strain of about 1, and an inflection point exists on the curve when the extensional viscosity is plotted against time. Therefore, in the range of about 0.1 to 2.5, the point where the slope at each time obtained above is the minimum value is obtained, a tangent is drawn at that point, and the straight line is extrapolated until the strain amount becomes 4.0. The maximum value (ηmax) of the extensional viscosity η _E until the strain amount becomes 4.0 is obtained, and the viscosity on the above approximate straight line until that time is defined as ηlin. ηmax/ηlin is defined as λmax (0.1).

The polypropylene resin (X) having a long chain branched structure used in the present invention preferably has high stereoregularity as described above, which allows the production of molded articles with high rigidity. The polypropylene resin (X) may be a homopolypropylene, or a propylene-α-olefin random copolymer with a small amount of ethylene, α-olefin such as 1-butene, 1-hexene, or other comonomer, so long as it satisfies the various properties described above. When the polypropylene resin (X) is a homopolypropylene, the crystallinity is high and the melting peak temperature is high, but even when the polypropylene resin (X) is a propylene-α-olefin random copolymer, it is preferable that the melting peak temperature is high.
More specifically, the melting peak temperature obtained by differential scanning calorimetry (DSC) is preferably 145° C. or higher, and more preferably 150° C. or higher. A melting peak temperature higher than 145° C. is preferred from the viewpoint of heat resistance of the product, but the upper limit of the melting peak temperature of polypropylene resin (X) is usually 170° C. or lower.
The melting peak temperature is determined by differential scanning calorimetry (DSC), and is the temperature at the top of the endothermic peak when the temperature is first raised to 200°C to erase the thermal history, then lowered to 40°C at a temperature lowering rate of 10°C/min, and then measured again at a temperature raising rate of 10°C/min.

II. Propylene-based block copolymer (Y)
As the propylene-based block copolymer (Y) which is a component constituting the polypropylene-based resin composition used in the present invention, a propylene-based block copolymer (Y) which is a multistage polymer composed of a propylene (co)polymer (Y-1) (hereinafter also referred to as "(Y-1)") and a propylene-ethylene copolymer (Y-2) (hereinafter also referred to as "(Y-2)"), produced by a conventionally known sequential polymerization, is used.
The term block copolymer used here is a common name for a propylene-based resin composition obtained by multi-stage polymerization using a sequential polymerization method, which is commonly used by those skilled in the art, and is different from the so-called (real) block copolymer or graft copolymer in which the components polymerized in each stage are bonded together by chemical bonds. Since the components produced in each step of multi-stage polymerization are not chemically bonded, it is generally possible to separate each of the components produced in each step by using techniques such as crystallinity fractionation, molecular weight fractionation, or solubility fractionation, taking advantage of the differences in crystallinity, molecular weight, or solubility in solvents between the components.
Moreover, in this block copolymer (Y) produced by the conventionally known sequential polymerization method, the presence of a long chain branching structure due to chemical bonds as in the polypropylene resin (X) is not observed with an analytically possible accuracy.

The propylene-based block copolymer (Y) may be produced using any of the conventionally known catalysts such as Ziegler-Natta catalysts and metallocene catalysts, and the production method may be any of various combinations of conventionally known slurry polymerization methods, bulk polymerization methods, gas phase polymerization methods, and the like.
Here, the Ziegler-Natta catalyst refers to a catalyst system as outlined in, for example, Section 2.3.1 (pages 20-57) of "Polypropylene Handbook" edited by Edward P. Moore Jr., translated and supervised by Tetsuo Yasuda and Nobuo Sakuma, Kogyo Chosakai (1998), and refers to, for example, a titanium trichloride catalyst consisting of titanium trichloride and an organoaluminum halide, a magnesium-supported catalyst consisting of a solid catalyst component essentially containing magnesium chloride, titanium halide, and an electron donor compound, an organoaluminum, and an organosilicon compound, or a catalyst in which an organosilicon-treated solid catalyst component formed by contacting an organoaluminum and an organosilicon compound with a solid catalyst component is combined with an organoaluminum compound component. The metallocene catalyst has already been described in detail in the explanation of "Production method of polypropylene resin (X)" above. Among the above examples, those using component [A-2] as the catalyst component (A) are particularly preferably used for the production of the propylene block copolymer (Y).

Preferred catalysts include, for example, catalysts that combine a titanium trichloride composition obtained by reducing titanium tetrachloride with an organoaluminum compound and further treating it with various electron donors and electron acceptors with an organoaluminum compound and an aromatic carboxylic acid ester (see JP-A-56-100806, JP-A-56-120712, and JP-A-58-104907), and supported catalysts in which magnesium halide is contacted with titanium tetrachloride and various electron donors (see JP-A-57-63310, JP-A-63-43915, and JP-A-63-83116).

The propylene (co)polymer (Y-1) produced in the first stage of sequential polymerization is either a propylene homopolymer or a propylene random copolymer copolymerized with a small amount of comonomer within the scope of the present invention. As the comonomer, an α-olefin having up to about 10 carbon atoms, excluding 3, such as ethylene, 1-butene, or 1-hexene, is usually used. When a comonomer is contained, the comonomer content in the propylene (co)polymer (Y-1) can be, for example, 0.1 to 5.0% by weight (where the total weight of the monomers constituting the propylene (co)polymer (Y-1) is taken as 100% by weight).

1. Property (Y-i): Amount ratio of (Y-1) to (Y-2) In the present invention, the weight ratio of (Y-1) to (Y-2) is 50 to 99% by weight, preferably 55 to 97% by weight, more preferably 60 to 95% by weight, and correspondingly, the weight ratio of (Y-2) is 1 to 50% by weight, preferably 3 to 45% by weight, more preferably 5 to 40% by weight.
(The total weight of the propylene-based block copolymer (Y) is taken as 100% by weight.)
When the amount of (Y-2) is 1% by weight or more, the melt tension does not become too low and is suitable for foam molding, while when it is 50% by weight or less, the amount of the crystalline component (Y-1) does not become too small, so that the heat resistance and rigidity of the composition are not impaired.

2. Property (Y-ii): MFR
The MFR of the propylene-based block copolymer (Y) used in the present invention is in the range of 0.1 to 200 g/10 min, preferably 0.2 to 190 g/10 min, more preferably 0.5 to 180 g/10 min, and particularly preferably 2.1 to 170 g/10 min.
This is a commonly used range for the MFR of resins to be subjected to various moldings. When the MFR is 0.1 g/10 min or more, the load on the extruder does not become excessive and flow instability does not occur in the resin. On the other hand, when the MFR is 200 g/10 min or less, problems such as large neck-in during extrusion molding and difficulty in taking up the sheet are unlikely to occur.
The method for measuring the MFR is the same as that for the polypropylene resin (X) described above.

3. Property (Y-iii): Melting Peak Temperature From the viewpoint of maintaining the heat resistance of the sheet, the melting peak temperature of the propylene-based block copolymer (Y) used in the present invention must exceed 155° C., and is preferably 157° C. or higher. There is no particular need to limit the upper limit of the melting peak temperature, but it is practically difficult to produce one having a melting peak temperature exceeding 170° C.
The melting peak temperature is the endothermic peak top temperature measured by differential scanning calorimetry (DSC) after first raising the temperature to 200° C. to erase the thermal history, lowering the temperature to 40° C. at a temperature lowering rate of 10° C./min, and then raising the temperature again at a temperature raising rate of 10° C./min.

4. Property (Y-iv): Ethylene content in propylene-ethylene copolymer (Y-2) In the present invention, the ethylene content in the propylene-ethylene copolymer (Y-2) is required to be 11 to 60% by weight (wherein the total weight of the monomers constituting the propylene-ethylene copolymer (Y-2) is taken as 100% by weight). The preferred range of the ethylene content in the propylene-ethylene copolymer (Y-2) is 11 to 38% by weight, more preferably 16 to 36% by weight, and even more preferably 18 to 35% by weight.
When the ethylene content is within the above range, the dispersion state of (Y-2) in the polypropylene resin composition becomes good, and the foaming suitability is excellent.

5. Property (Y-v): Intrinsic Viscosity of Propylene-Ethylene Copolymer (Y-2) As a result of numerous experimental investigations, the present inventors have found that the intrinsic viscosity value, measured at 135° C. using decalin as a solvent, of the propylene-ethylene copolymer (Y-2) constituting the propylene-based block copolymer (Y) to be blended in the polypropylene resin composition must be 5.3 dl/g or more, preferably 6.0 dl/g or more, more preferably 7.0 dl/g or more, and most preferably 7.5 dl/g or more.

When the intrinsic viscosity is 5.3 dl/g or more, the melt tension is high and the foaming suitability is good.
The upper limit does not need to be particularly specified, but if it is too high, it may cause gelation, so it is 25.0 dl/g or less, preferably 20.0 dl/g or less, more preferably 18.0 dl/g or less, and most preferably 16.0 dl/g or less.
The intrinsic viscosity here is a value measured at a temperature of 135°C using decalin as a solvent with an Ubbelohde capillary viscometer. To determine the intrinsic viscosity of (Y-2), the component (Y-2) is recovered as a component soluble in paraxylene at 25°C using the same method as described above for CXS, and the intrinsic viscosity of this is measured. However, if the ethylene content of the component (Y-2) falls below 15% by weight, it becomes difficult to sufficiently separate the component (Y-2) using the CXS method. In such a case, a small amount of the component (Y-1) is sampled during the sequential polymerization after completion of the production of the propylene (co)polymer (Y-1) produced in the polymerization at the first stage of the sequential polymerization, and the intrinsic viscosity is measured. Furthermore, the intrinsic viscosity of the entire (Y) after completion of the sequential polymerization is measured, and the intrinsic viscosity is determined by the following formula.
Intrinsic viscosity of component (Y-2)=[intrinsic viscosity of the entire (Y)−{intrinsic viscosity of component (Y-1)×weight fraction of component (Y-1)/100}]/{weight fraction of component (Y-2)/100}

Here, the ratio of (Y-1) to (Y-2) in the component (Y) and the ethylene content in (Y-2) can be determined by a conventionally known analytical method such as IR or NMR, or a combination of a solubility fractionation method and an IR method.
In the present invention, various indexes of the component (Y) were determined mainly by a combination of the cross fractionation method and the FT-IR method described below.

(1) Analytical Equipment Used (i) Cross-fractionation Equipment CFC T-100 (abbreviated as CFC) manufactured by Dia Instruments
(ii) Fourier transform infrared absorption spectrum analysis FT-IR analyzer: PerkinElmer 1760X
The fixed wavelength infrared spectrophotometer attached as a CFC detector is removed and instead an FT-IR is connected and used as a detector. The transfer line from the outlet of the solution eluted from the CFC to the FT-IR is 1 m long and the temperature is maintained at 140°C throughout the measurement. The flow cell attached to the FT-IR has an optical path length of 1 mm and an optical path width of 5 mmφ, and the temperature is maintained at 140°C throughout the measurement.
(iii) Gel Permeation Chromatography (GPC)
The GPC column used after the CFC is three AD806MS columns manufactured by Showa Denko KK connected in series.

(2) CFC measurement conditions (i) Solvent: orthodichlorobenzene (ODCB)
(ii) Sample concentration: 4 mg/mL
(iii) Injection volume: 0.4mL
(iv) Crystallization: The temperature is lowered from 140° C. to 40° C. over about 40 minutes.
(v) Separation method:
The fractionation temperatures during temperature rising elution fractionation are 40, 100, and 140°C, and the sample is fractionated into a total of three fractions. The elution proportions (unit: weight %) of the components eluted at 40°C or less (fraction 1), the components eluted at 40 to 100°C (fraction 2), and the components eluted at 100 to 140°C (fraction 3) are defined as W40, W100, and W140, respectively. W40 + W100 + W140 = 100. Each fraction is automatically transported directly to an FT-IR analyzer.
(vi) Solvent flow rate during elution: 1 mL/min

(3) FT-IR Measurement Conditions After the sample solution starts to elute from the GPC downstream of CFC, FT-IR measurement is carried out under the following conditions, and GPC-IR data is collected for each of the above-mentioned fractions 1 to 3.
Conceptual diagrams of CFC-FT-IR are shown in, for example, JP-A-2018-135419 and JP-A-2017-031359.
(i) Detector: MCT
(ii) Resolution: 8cm ^-1
(iii) Measurement interval: 0.2 minutes (12 seconds)
(iv) Number of integrations per measurement: 15

(4) Post-processing and analysis of measurement results The elution amount and molecular weight distribution of the components eluted at each temperature are determined using the absorbance at 2945 cm ⁻¹ obtained by FT-IR measurement as a chromatogram. The elution amount is normalized so that the total of the elution amounts of each eluted component is 100%. The conversion from the retention volume to the molecular weight is performed using a calibration curve based on standard polystyrene prepared in advance. The specific method is the same as that described above.
The ethylene content distribution (distribution of ethylene content along the molecular weight axis) of each eluted component is calculated by converting the ratio of the absorbance at 2956 cm ⁻¹ to the absorbance at 2927 cm ⁻¹ obtained by GPC-IR into an ethylene content (wt%) according to a calibration curve prepared in advance using ethylene-propylene rubber (EPR) and mixtures thereof, the ethylene contents of which are known by ^13C -NMR measurement of polyethylene or polypropylene or the like.

(5) Propylene-Ethylene Copolymer Content The propylene-ethylene copolymer (Y-2) (hereinafter referred to as EP) content in the propylene-based block copolymer (Y) in the present invention is defined by the following formula (I) and can be determined by the following procedure.
EP content (weight%) = W40 x A40/B40 + W100 x A100/B100 + W140 x A140/B140 (I)
W40, W100, and W140 are the elution ratios (unit: weight %) in each of the above-mentioned fractions, A40, A100, and A140 are the average ethylene contents (unit: weight %) actually measured in each of the fractions corresponding to W40, W100, and W140, and B40, B100, and B140 are the ethylene contents (unit: weight %) of EP contained in each fraction.
How to determine A40, A100, A140, B40, B100, and B140 will be described later.
The meaning of formula (I) is as follows. The first term on the right side of formula (I) is a term for calculating the amount of EP contained in fraction 1 (a portion soluble at 40°C). When fraction 1 contains only EP and does not contain PP, W40 contributes directly to the EP content derived from fraction 1 in the total, but since fraction 1 also contains a small amount of PP-derived components (extremely low molecular weight components and atactic polypropylene) in addition to EP-derived components, it is necessary to correct for these components. Therefore, the amount of EP-derived components in fraction 1 is calculated by multiplying W40 by A40/B40. For example, when the average ethylene content (A40) of fraction 1 is 30% by weight and the ethylene content (B40) of the EP contained in fraction 1 is 40% by weight, 30/40=3/4 (i.e., 75% by weight) of fraction 1 is derived from EP, and the remaining 1/4 is derived from PP. Thus, the operation of multiplying A40/B40 in the first term on the right side means that the EP contribution is calculated from the weight percent (W40) of fraction 1. The same applies to the second term on the right side and onwards, and the EP content is determined by calculating and adding up the EP contribution for each fraction.

(i) As described above, the average ethylene contents corresponding to fractions 1 to 3 obtained by CFC measurement are designated as A40, A100, and A140, respectively (all units are weight %). The method for determining the average ethylene contents will be described later.
(ii) The ethylene content corresponding to the peak position in the differential molecular weight distribution curve of fraction 1 is defined as B40 (unit: weight %). As for fractions 2 and 3, it is considered that all the rubber portion is dissolved at 40°C, and it is not possible to define them by the same definition, so in the present invention, B100 = B140 = 100. B40, B100, and B140 are the ethylene contents of the EP contained in each fraction, but it is practically impossible to obtain these values analytically. This is because there is no means to completely separate and separate the PP and EP mixed in the fractions. As a result of investigations using various model samples, it was found that the improvement effect of the material properties can be well explained by using the ethylene content corresponding to the peak position of the differential molecular weight distribution curve of fraction 1 as B40. In addition, for two reasons: B100 and B140 have crystallinity derived from ethylene chains, and the amount of EP contained in these fractions is relatively small compared to the amount of EP contained in fraction 1, it is closer to reality and causes almost no error in calculations to approximate both of them as 100. Therefore, the analysis is performed assuming B100 = B140 = 100.

(iii) Calculate the EP content according to the following formula:
EP content (weight%) = W40 x A40/B40 + W100 x A100/100 + W140 x A140/100 (II)
In other words, the first term on the right side of equation (II), W40×A40/B40, represents the non-crystalline EP content (% by weight), and the sum of the second and third terms, W100×A100/100+W140×A140/100, represents the crystalline EP content (% by weight).
Here, the average ethylene contents A40, A100 and A140 of each of fractions 1 to 3 obtained by B40 and CFC measurement are determined as follows.
The molecular weight distribution curve of the fraction 1 separated based on the difference in crystal distribution is measured using a GPC column constituting a part of the CFC analyzer, and the distribution curve of the ethylene content measured corresponding to the molecular weight distribution curve using an FT-IR connected after the GPC column is obtained. The ethylene content corresponding to the peak position of the differential molecular weight distribution curve is B40.
In addition, the sum of the products of the weight percentage for each data point and the ethylene content for each data point, which are taken in as data points during measurement, is the average ethylene content A40.

The significance of setting the above three different separation temperatures is as follows.
In the CFC analysis of the present invention, 40°C is a temperature condition necessary and sufficient to separate only non-crystalline polymers (e.g., most of EP, or extremely low molecular weight and atactic components in the propylene polymer component (PP)). 100°C is a temperature necessary and sufficient to elute only components that are insoluble at 40°C but soluble at 100°C (e.g., components in EP that have crystallinity due to ethylene and/or propylene chains, and PP with low crystallinity). 140°C is a temperature necessary and sufficient to elute only components that are insoluble at 100°C but soluble at 140°C (e.g., components in PP that are particularly highly crystalline, and components in EP that have extremely high molecular weight and ethylene crystallinity), and to recover the entire amount of the propylene-based block copolymer used in the analysis. The amount of EP components contained in W140 is extremely small and can be substantially ignored.
Ethylene content in EP (wt%)=(W40×A40+W100×A100+W140×A140)/[EP] (III)
Here, [EP] is the EP content (wt %) determined above.
The ethylene content (E) (wt%) of the non-crystalline portion of EP is approximated by the value of B40 since dissolution of the rubber portion is almost completed at 40° C. or less.

However, in the above-mentioned analysis method by combining the cross fractionation method and the FT-IR method, accurate analysis becomes difficult when the ethylene content of (Y-2) is below 15% by weight, there is no significant difference in crystallinity with (Y-1), and temperature-based fractionation cannot be performed sufficiently. In such a case, it is preferable to extract the (Y-1) component after the completion of the production of the propylene (co)polymer (Y-1) produced in the polymerization in the first stage of the sequential polymerization during the sequential polymerization, measure its molecular weight (when a comonomer is copolymerized, the comonomer content is also measured), and further determine the quantitative ratio of the (Y-1) component and the (Y-2) component by calculation based on material balance, and further measure the comonomer content of the entire component (Y) at the end of the sequential polymerization, and then use the following simple weight additivity rule to determine the comonomer content of the (Y-2) component. When ethylene is used as the comonomer, the ethylene content of (Y-2) is determined by the following formula.
Ethylene content of component (Y-2)=[Ethylene content of entire (Y)−{Ethylene content of component (Y-1)×Weight fraction of component (Y-1)/100}]/{Weight fraction of component (Y-2)/100}

As for another method for determining the quantitative ratio of the (Y-1) and (Y-2) components, when producing components (Y-1) and (Y-2) whose average molecular weights differ to some extent, the ratio can be determined by measuring the entire (Y) by GPC after completion of sequential polymerization, separating the peaks of the resulting multi-peak molecular weight distribution curve using commercially available data analysis software, etc., and calculating the weight ratio.

6. Properties: Amount of Propylene Block Copolymer (Y) The amount of propylene block copolymer (Y) is 2.5 to 67.5% by weight, preferably 10.0 to 60.0% by weight, more preferably 15.0 to 55.0% by weight, and even more preferably 17.5 to 52.5% by weight (the sum of (X), (Y), and (Z) is 100% by weight). When the amount of propylene block copolymer (Y) is within this range, the load on the sheet due to shear heating and take-up tension can be reduced, particularly when the sheet is molded at high speed by the T-die method and at a high expansion ratio of more than 3.0 times, and a foamed sheet having excellent bubble independence and denseness and excellent appearance can be obtained. When the amount is 67.5% by weight or less, the flowability is sufficient and there is no problem such as excessive load on the extruder for various moldings, and when the amount is 2.5% by weight or more, the melt tension is sufficient and the material has excellent properties as a high melt tension material and is suitable for foam molding.

III. Propylene-α-olefin random copolymer (Z)
The propylene-α-olefin random copolymer (Z) is produced using a conventionally known metallocene catalyst, and the production method may be any combination of conventionally known slurry polymerization, bulk polymerization, gas phase polymerization, and the like.
The metallocene catalyst has already been described in detail in the above explanation of "Production method of polypropylene resin (X)". Among the above examples, the catalyst component (A) using the component [A-2] can be exemplified as a catalyst preferably used for the production of the propylene-α-olefin random copolymer (Z).

As the α-olefin of the propylene-α-olefin random copolymer (Z), an α-olefin having up to about 10 carbon atoms, excluding 3, such as ethylene, 1-butene, or 1-hexene, can be selected.

As a result of numerous experimental investigations, the present inventors have found that when the propylene-α-olefin random copolymer (Z) blended into the polypropylene resin composition has the following characteristics, a polypropylene-based foamed product can be obtained that has uniform and fine foam cells and has a good appearance when molded, even when the foamed layer is a multi-layer foamed sheet with a high expansion ratio of 3.0 times or more, particularly when the foamed layer contains a PP filler layer. This is described in detail below.

1. Property (Z-i): Polymerized with a metallocene catalyst The propylene-α-olefin random copolymer (Z) used in the present invention must be polymerized with a metallocene catalyst. Compared with those polymerized with a Ziegler-Natta catalyst, the propylene-α-olefin random copolymer polymerized with a metallocene catalyst can suppress the increase in the amount of oligomer components even if the amount of α-olefin increases, and can suppress the stickiness of the molded product.

2. Property (Z-ii): Melting peak temperature measured by DSC is 155° C. or less The melting peak temperature of the propylene-α-olefin random copolymer (Z) used in the present invention must be 155° C. or less in order to improve the extensibility of the resin during foam molding, and is preferably 145° C. or less, more preferably 140° C. or less, particularly preferably 135° C. or less, and most preferably 130° C. or less. The melting peak temperature is the endothermic peak top temperature measured by differential scanning calorimetry (DSC) after first raising the temperature to 200° C. to erase the thermal history, lowering the temperature to 40° C. at a temperature lowering rate of 10° C./min, and then measuring again at a temperature raising rate of 10° C./min.
The effect of maintaining the independence of the cells is exhibited when the melting peak temperature is 155° C. or less. There is no particular restriction on the lower limit of the melting peak temperature, but it is preferably 100° C. from the viewpoint of the heat deformation resistance of the molded article.

3. Properties: Amount of Propylene-α-olefin Random Copolymer (Z) The amount of the propylene-α-olefin random copolymer used in the present invention is 10 to 65% by weight, preferably 25 to 65% by weight, more preferably 25 to 60% by weight, even more preferably 25 to 55% by weight, and still more preferably 25 to 50% by weight (the total of (X), (Y), and (Z) is 100% by weight).
When the amount of the propylene-α-olefin random copolymer (Z) is within this range, even if the foam layer contains a PP filler layer and has a high expansion ratio of 3.0 times or more, the effect of preventing local solidified parts that cause poor spreading is obtained, and a foamed sheet with good foaming properties and high appearance can be obtained. When the amount is 65% by weight or less, even when the cooling is delayed due to the PP filler layer, cell breakage is unlikely to occur and foaming failure is unlikely to occur. In addition, when the amount is 65% by weight or less, the rigidity and melting peak temperature of the polypropylene resin composition do not decrease too much, and the molded product does not deform or melt when used at high temperatures.

4. Characteristics: α-Olefin Content As the α-olefin of the propylene-α-olefin random copolymer (Z), an α-olefin having a carbon number of up to about 10, excluding 3, such as ethylene, 1-butene, and 1-hexene, can be selected, and ethylene is preferable.
The α-olefin content in the propylene-α-olefin random copolymer (Z) is preferably 0.5 to 5.0% by weight, more preferably 0.8 to 4.5% by weight, and even more preferably 0.9 to 4.0% by weight. When the α-olefin content is within this range, a polypropylene-based foam having uniform fine foam cells, improved extensibility, and good appearance of the molded product can be obtained, even if the foam layer contains a PP filler layer and has a high expansion ratio of 3.0 times or more. In addition, when the α-olefin content is 0.5% by weight or more, the propylene-α-olefin random copolymer (Z) has excellent extensibility, and when the α-olefin content is 5.0% by weight or less, the propylene-α-olefin random copolymer (Z) has improved rigidity and melting peak temperature, and the molded product does not deform or melt when used at high temperatures.

5. Properties: Melt Flow Rate The melt flow rate (MFR) of the propylene-α-olefin random copolymer (Z) is preferably in the range of 0.1 to 100.0 g/10 min, more preferably 1.0 to 80.0 g/10 min, even more preferably 5.0 to 70.0 g/10 min, even more preferably 10.0 to 60.0 g/10 min, particularly preferably 15.0 to 55.0 g/10 min, and most preferably 21.0 to 50.0 g/10 min. When the MFR of the propylene-α-olefin random copolymer (Z) is within this range, a polypropylene-based foam having uniform fine foam cells, improved extensibility, and good appearance of the molded product can be obtained. In addition, when the melt flow rate is 0.1 g/10 min or more, orientation-induced crystallization is unlikely to occur during molding, and the molded product has excellent appearance without destruction of the cell walls during extrusion sheet molding, particularly in the T-die molding method. When the melt flow rate is 100.0 g/10 min or less, the melt tension is high, which is suitable for foaming.
The method for measuring the MFR is the same as that for the polypropylene resin (X) described above.

IV. Constituents, preparation method, and uses of polypropylene-based resin composition 1. Constituents of polypropylene-based resin composition In the present invention, the polypropylene-based resin composition contains the above-mentioned polypropylene resin (X), propylene-based block copolymer (Y), and propylene-α-olefin random copolymer (Z), and the polypropylene-based resin composition further containing a foaming agent is referred to as a polypropylene-based resin composition for foam molding.
The components of the polypropylene resin composition suitable for foam molding will be described in detail below.

(1) Foaming Agent It is preferable to further blend a foaming agent in the polypropylene resin composition used in the present invention.
The foaming agent can be any known foaming agent used for plastics, rubber, etc. Conventional foaming agents such as physical foaming agents, decomposable foaming agents (chemical foaming agents), and microcapsules containing a thermal expansion agent can be used.
Examples of physical blowing agents include aliphatic hydrocarbons such as propane, butane, pentane, and hexane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; halogenated hydrocarbons such as chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, dichlorodifluoromethane, chloromethane, dichloromethane, chloroethane, dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, chloropentafluoroethane, and perfluorocyclobutane; and inorganic gases such as water, carbon dioxide, and nitrogen, either alone or in combination of two or more thereof.
Among these, aliphatic hydrocarbons such as propane, butane, and pentane, and carbon dioxide gas are preferred because they are inexpensive and have high solubility in the polypropylene resin (X). Carbon dioxide gas becomes a supercritical state at 7.4 MPa or more and 31° C. or more, and becomes a state in which it is excellent in diffusion and solubility in the polymer.

When obtaining a polypropylene-based foam using a physical foaming agent, a foam regulator can be used as necessary. Examples of foam regulators include inorganic decomposable foaming agents such as ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, and ammonium nitrite, azo compounds such as azodicarbonamide, azobisisobutyronitrile, and diazoaminobenzene, nitroso compounds such as N,N'-dinitrosopentanmethylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide, decomposable foaming agents such as benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, p,p'-oxybisbenzenesulfonyl semicarbazide, p-toluenesulfonyl semicarbazide, trihydrazinotriazine, and barium azodicarboxylate, inorganic powders such as talc and silica, acid salts such as polycarboxylic acids, and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate, and these can be used alone or in combination.

In addition, when a polypropylene-based foam is obtained using a decomposable foaming agent (chemical foaming agent), examples of the decomposable foaming agent (chemical foaming agent) include a mixture of sodium bicarbonate and an organic acid such as citric acid, azo-based foaming agents such as azodicarbonamide and barium azodicarboxylate, nitroso-based foaming agents such as N,N'-dinitrosopentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide, sulfohydrazide-based foaming agents such as p,p'-oxybisbenzenesulfonylhydrazide and p-toluenesulfonylsemicarbazide, and trihydrazinotriazine.
The amount of the foaming agent is preferably in the range of 0.05 to 6.0 parts by weight, more preferably 0.05 to 3.0 parts by weight, even more preferably 0.5 to 2.5 parts by weight, and particularly preferably 1.0 to 2.0 parts by weight, per 100 parts by weight of the total of the components (X), (Y), and (Z).
When the amount of the foaming agent is 6.0 parts by weight or less, over-foaming is avoided and it becomes easy to make the foam cells uniform and fine. On the other hand, when the amount of the foaming agent is 0.05 parts by weight or more, a large amount of gas is generated, which is preferable.
When a bubble regulator is used, the blending amount of the bubble regulator is preferably in the range of 0.01 to 5 parts by weight in pure content per 100 parts by weight of the total of components (X), (Y), and (Z). The pure content here refers to the amount of only the bubble regulator when a master batch or the like containing a certain amount of the bubble regulator is used.

(2) Other Additives The polypropylene resin composition for foam molding used in the present invention can contain, in addition to the components (X), (Y), and (Z), a foaming agent, and, where necessary, a cell regulator, various additives such as other polymers, antioxidants, neutralizing agents, light stabilizers, UV absorbers, inorganic fillers, lubricants, antistatic agents, and metal deactivators, within limits that do not impair the object of the present invention.
Examples of other polymers include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene-based resins other than those mentioned above, propylene-α-olefin copolymers (α-olefins having 4 or more carbon atoms), polyolefins such as poly-4-methyl-1-pentene, olefin-based elastomers such as ethylene-propylene elastomers, and other monomers copolymerizable therewith, for example, copolymers of vinyl acetate, vinyl chloride, (meth)acrylic acid, (meth)acrylic acid esters, and mixtures thereof.

Examples of the antioxidant include phenol-based antioxidants, phosphite-based antioxidants, and thio-based antioxidants. Examples of the neutralizing agent include higher fatty acid salts such as calcium stearate and zinc stearate. Examples of the light stabilizer and ultraviolet absorber include hindered amines, nickel complex compounds, benzotriazoles, and benzophenones.
Examples of the inorganic filler include talc, calcium carbonate, silica, hydrotalcite, zeolite, aluminum silicate, and magnesium silicate. Examples of the lubricant include higher fatty acid amides such as stearic acid amide.
Examples of the antistatic agent include fatty acid partial esters such as glycerin fatty acid monoester, and examples of the metal deactivators include triazines, phosphones, epoxies, triazoles, hydrazides, and oxamides.

2. Method for preparing polypropylene-based resin composition The method for preparing the polypropylene-based resin composition for foam molding used in the present invention includes a method of mixing the powdered or pelletized polypropylene resin (X), the propylene-based block copolymer (Y), the propylene-α-olefin random copolymer (Z), the foaming agent, and other compounding agents used as necessary, using a dry blend, a Henschel mixer (trade name), or the like. Alternatively, the mixture may be melt-kneaded in advance using a single-screw kneader, a twin-screw kneader, a kneader, or the like. However, when a chemical foaming agent is melt-kneaded at the same time, the kneading temperature must be controlled to a temperature lower than the decomposition temperature of the chemical foaming agent.
Depending on the circumstances, only the foaming agent may be fed separately during the production of the polypropylene foam.

The polypropylene resin composition used in the present invention can be suitably used in various molding methods and applications requiring high melt tension, such as injection molding, extrusion molding, bead foam molding, extrusion foam molding, injection foam molding, blow molding, injection blow molding, foam blow molding, deep drawing molding, thermoforming, etc., and among these, it can be suitably used in the field of foam molding, where the balance between melt tension and extensibility is important.

4. Polypropylene-based resin multi-layer foamed sheet The polypropylene-based resin multi-layer foamed sheet according to the present invention comprises a foam layer made of the above-mentioned polypropylene-based resin composition for foam molding, a PP filler layer containing an inorganic filler, and a surface layer made of a thermoplastic resin composition.
The polypropylene-based resin foamed sheet according to the present invention has an average bubble diameter of 500 μm or less, more preferably 400 μm or less, and even more preferably 300 μm or less in the foamed layer. When the average bubble diameter is 500 μm or less, no defects in appearance such as holes occur in both the polypropylene-based foamed sheet and the thermoformed product obtained by further thermoforming the sheet, which is preferable.
The polypropylene resin multi-layer foamed sheet according to the present invention has a closed cell ratio of the foam layer of preferably 17% or more, more preferably 18% or more, further preferably 20% or more, and particularly preferably 25% or more. A closed cell ratio of 25% or more is preferable because the foam cells in the foam sheet are unlikely to be exposed on the container surface during thermoforming, resulting in a good container appearance.
The thickness of the polypropylene-based resin multi-layer foamed sheet according to the present invention is not particularly limited, but is preferably 0.3 mm to 10 mm, more preferably 0.5 mm to 5 mm, and most preferably 0.5 mm to 4 mm. In particular, when molding using a T-die method, if the foamed sheet has a thickness of 0.3 mm or more, there is no problem of the sheet being strongly stretched during molding and crushed, and foaming defects can be prevented, and if the thickness is 10 mm or less, there is no problem of the sheet being wrinkled, and appearance defects can be prevented.
The expansion ratio of the foam layer of the polypropylene-based multilayer resin foam sheet according to the present invention is not particularly limited, but since a higher expansion ratio generally leads to better performance as a foam, such as weight reduction and heat insulation, the expansion ratio is, for example, 2.1 times or more, preferably 2.3 times or more, more preferably 3.0 times or more, particularly preferably 3.3 times or more, and most preferably 3.5 times or more. In particular, the polypropylene-based resin foam sheet according to the present invention contains a PP filler layer containing an inorganic filler and a polypropylene-based resin composition, and can achieve uniform and fine foam cells even when the foam layer has a high expansion ratio of 3.0 times or more.

Examples of methods for obtaining the foam layer of the polypropylene-based resin multi-layer foam sheet include injection molding, thermoforming, extrusion, blow molding, and bead foam molding. For example, in the case of extrusion, a polypropylene-based resin composition is melted in an extruder and extruded from a die provided at the tip of the extruder by a known extrusion molding method. The extruder may be either a single-screw extruder or a twin-screw extruder, and may be, for example, a tandem system in which a twin-screw extruder and a single-screw extruder are combined in the front and rear stages.
In physical foaming, a physical foaming agent such as carbon dioxide gas or butane is introduced (pressurized) into the middle of the extruder cylinder. The die attached to the tip of the extruder may be a T-die or a circular die.

In order to obtain a polypropylene-based resin multi-layer foamed sheet, a method of co-extrusion molding a foamed layer made of a polypropylene-based resin composition and a non-foamed layer made of a thermoplastic resin composition can be used. The polypropylene-based multi-layer foamed sheet according to the present invention comprises a PP filler layer containing an inorganic filler and a surface layer made of a thermoplastic resin composition, and the PP filler layer and the surface layer are usually non-foamed layers.
The polypropylene resin multi-layer foamed sheet can be produced by a known co-extrusion method using a feed block or a multi-die using a plurality of extruders, an extrusion lamination method, or the like, with the co-extrusion method being preferred.

The non-foamed layer used in the polypropylene-based resin multi-layer foamed sheet may be provided on either side of the foamed layer, or may be configured to have a structure (sandwich structure) in which the foamed layer is present between two non-foamed layers. The polypropylene-based resin multi-layer foamed sheet according to the present invention may have a three-layer structure of foamed layer/PP filler layer/surface layer, or a five-layer structure of surface layer/PP filler layer/foamed layer/PP filler layer/surface layer, and is preferably configured to have three types and five layers of surface layer/PP filler layer/foamed layer/PP filler layer/surface layer.
The polypropylene-based resin multi-layer foamed sheet provided with the PP filler layer has excellent strength, and by providing a PP filler layer on the outside of the foamed layer and a surface layer made of a thermoplastic resin composition not containing inorganic filler, preferably a polypropylene-based resin composition, on the outside of the PP filler layer, the polypropylene-based resin multi-layer foamed sheet also has excellent surface smoothness and appearance. Furthermore, by using a functional thermoplastic resin for the non-foamed layer, it is possible to easily provide the polypropylene-based resin multi-layer foamed sheet with additional functions such as antibacterial properties, softness, and scratch resistance, which is also preferable.

In the polypropylene-based resin multi-layer foamed sheet according to the present invention, the PP filler layer is a layer made of a polypropylene-based resin composition containing an inorganic filler, and the surface layer is a layer made of a thermoplastic resin composition, preferably a polypropylene-based resin composition. As described above, the PP filler layer and the surface layer are usually non-foamed layers.

As the thermoplastic resin constituting the thermoplastic resin composition used in the non-foamed layer, within a range that does not impair the effects of the present invention, there can be selected high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene which may be the same as each of the components (X), (Y), and (Z), propylene-α-olefin copolymers, polyolefins such as poly-4-methyl-1-pentene, olefin-based elastomers such as ethylene-propylene elastomers, or other monomers copolymerizable therewith, for example, copolymers of vinyl acetate, vinyl chloride, (meth)acrylic acid, (meth)acrylic acid esters, and mixtures thereof.
Among these, polypropylene-based resin compositions containing polypropylene, propylene-α-olefin copolymer, etc. are preferred from the standpoints of recyclability, adhesiveness, heat resistance, oil resistance, rigidity, etc. Examples of propylene-α-olefin copolymers include multistage polymers commonly known as impact-resistant polypropylene or propylene block copolymers, which are obtained by multistage polymerization of a propylene (co)polymer and an ethylene-propylene random copolymer using multiple or a single polymerization tank.

In addition, the polypropylene resin composition used in the PP filler layer desirably contains 50 parts by weight or less of inorganic filler per 100 parts by weight of the polypropylene resin contained in the resin composition. If the amount of inorganic filler is 50 parts by weight or less, there is no problem such as the generation of resin at the die outlet, and deterioration of the appearance of the sheet can be prevented.
The inorganic filler is not particularly limited, but examples thereof include talc, calcium carbonate, silica, hydrotalcite, zeolite, aluminum silicate, and magnesium silicate.

The total thickness of the non-foamed layers in the polypropylene-based resin multi-layer foamed sheet according to the present invention is desirably 1 to 50%, more desirably 5 to 20%, of the total thickness of the resulting polypropylene-based resin multi-layer foamed sheet. If the thickness of the non-foamed layers is 50% or less, the growth of bubbles in the foamed layer is not hindered.

The polypropylene resin multi-layer foam sheet according to the present invention may be subjected to surface treatment such as corona discharge treatment, flame treatment, plasma treatment, etc. for the purpose of improving printability, paintability, etc.

The polypropylene resin multi-layer foamed sheet according to the present invention and the molded product (thermoformed product) obtained by thermoforming the multi-layer foamed sheet have uniform and fine foam cells and are excellent in appearance, thermoformability, impact resistance, light weight, rigidity, heat resistance, heat insulation, oil resistance, etc., and therefore can be suitably used for food containers such as trays, plates, cups, etc., vehicle interior materials such as automobile door trims and automobile trunk mats, packaging, stationery, building materials, etc.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.
In the examples and comparative examples, the physical properties of the polypropylene resin composition, the polypropylene resin multi-layer foamed sheet and the components thereof were measured and evaluated according to the following evaluation methods, and the resins used were as follows.

1. Evaluation Method (1) Melt Flow Rate MFR:
Measurement was performed in accordance with JIS K7210:1999, Appendix A, Table 1, Condition M (230°C, 2.16 kg load). The die shape was 2.095 mm in diameter and 8.000 mm in length. The unit is g/10 min.
(2) Melt tension MT:
Measurement was carried out under the following conditions using a Capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd.
Capillary: diameter 2.0 mm, length 40 mm
Cylinder diameter: 9.55 mm
Cylinder extrusion speed: 20 mm/min. Take-up speed: 4.0 m/min. Temperature: 230° C.
When MT is extremely high, the resin may break at a take-off speed of 4.0 m/min, in which case the take-off speed is reduced, and the tension at the maximum possible take-off speed is taken as MT. The unit is grams.
(3) Molecular weight distributions Mw/Mn and Mz/Mn:
It was determined by GPC measurement according to the method described above.
(4) Amount of paraxylene solubles at 25° C. (CXS):
The measurement was performed according to the method described in the specification.
(5) mm fraction:
The measurement was performed using a GSX-400 FT-NMR spectrometer manufactured by JEOL Ltd., according to the method described in paragraphs [0053] to [0065] of JP-A-2009-275207, as described above.
The unit is %.

(6) Branching index g ^' :
As described above, the measurement was performed by GPC equipped with a differential refractometer (RI), a viscosity detector (Viscometer), and a light scattering detector (MALLS) as detectors.
(7) Strain hardening degree λmax:
The extensional viscosity measurement was carried out under the following conditions.
Apparatus: Ares manufactured by Rheometoris
Fixture: Extension Viscosity Fixture manufactured by TA Instruments
・Measurement temperature: 180℃
Distortion rate: 0.1/sec
Preparation of test specimen: A sheet of 18 mm x 10 mm and 0.7 mm thick is prepared by press molding.
The details of the calculation method of λmax are as described above.
(8) Melting peak temperature:
Using a differential scanning calorimeter (DSC), the temperature was once raised to 200°C to erase the thermal history, and then the temperature was lowered to 40°C at a temperature drop rate of 10°C/min. Then, the temperature was again raised at a temperature rise rate of 10°C/min. The temperature at the top of the endothermic peak was recorded as the melting peak temperature.
(9) Ratio of (Y-1) and (Y-2), and ethylene content in (Y-2):
This was determined by a combination of the cross fractionation method and FT-IR method described in the specification.
(10) Intrinsic viscosity of component (Y-2):
The intrinsic viscosity of the CXS component of the propylene-based block copolymer (Y) was measured using an Ubbelohde capillary viscometer at a temperature of 135° C., using decalin as a solvent. However, for (Y-2) having an ethylene content of less than 15% by weight, the intrinsic viscosity of the component (Y-1) and the entire component (Y) was measured, and the intrinsic viscosity was calculated according to the calculation formula described in the specification.

(11) Foam Density:
A test piece was cut out from each of the polypropylene resin multi-layer foamed sheets (foams) obtained in the Examples and Comparative Examples, and the weight (g) of the test piece was divided by the volume (cm ³ ) determined from the outer dimensions of the test piece. The density of the foam was determined according to JIS K7222.
(12) Foam layer magnification:
The cross section of the foamed sheet was observed using an optical microscope, and the thicknesses of the surface layer, the PP filler layer, and the foamed layer were measured. The density of the foamed layer of the multi-layer foamed sheet was calculated from the densities of the multi-layer foamed sheet, the surface layer, and the PP filler layer, and the thicknesses of the surface layer, the PP filler layer, and the foamed layer according to an "empirical formula called the additivity rule of physical properties." The density of the polypropylene resin used in the surface layer, the PP filler layer, and the foamed layer was 0.91 g/ ^cm3 , and the density of the PP filler layer used in this example was 1.15 g/ ^cm3 .
Further, the density of the polypropylene resin (0.91 g/cm ^{3 )} divided by the density of the foamed layer was defined as the foamed layer magnification.
(13) Closed cell ratio of foam layer:
Test pieces were cut out from the polypropylene resin multi-layer foamed sheets obtained in the Examples and Comparative Examples, and the closed cell ratio of the foamed layer of the multi-layer foamed sheet was calculated using an air pycnometer (Tokyo Science Co., Ltd.) according to the method described in ASTM D2856. The density of the polypropylene resin used in the surface layer, PP filler layer, and foamed layer was 0.91 g/ ^cm3 , and the density of the PP filler layer used in the Examples was 1.15 g/ ^cm3 .
(14) Seat appearance evaluation:
The appearance of the polypropylene resin multi-layer foamed sheets obtained in the Examples and Comparative Examples was evaluated according to the following criteria.
◯: The air bubbles are highly independent, the foam sheet surface is smooth, and the appearance is beautiful.
Δ: The surface of the foamed sheet is smooth, but the air bubbles are not well separated, and the appearance is poor.
×: Wrinkles and blisters occurred on the sheet, and the appearance was extremely poor.
(15) Container formability:
The container moldability was evaluated using a multipurpose thermoforming machine manufactured by Asano Laboratory Co., Ltd. as follows.
A test piece measuring 530 mm x 530 mm was cut out from the polypropylene resin multi-layer foamed sheet obtained in the examples and comparative examples and fixed to a clamp frame. After heating both sides of the foamed sheet with upper and lower heaters, the sheet was vacuum-pressure molded using a circular container mold with an upper inner diameter of 22 cm and a depth of 3.8 cm, and the molded container was visually evaluated according to the following criteria. In addition, when molding each sample into a container, the heating time and mold position were changed to produce a container that was as clean as possible.
◯: No wrinkles or crushing were observed in the container after thermoforming, and a good container with little unevenness in thickness was formed.
Δ: Slight wrinkles and crushing were observed in the container after thermoforming, but the container was successfully formed.
×: Significant crushing and wrinkles were observed in the container after thermoforming, and there were some places where air bubbles were exposed on the surface, and a good container could not be formed.

2. Materials used (1) Polypropylene resin having a long chain branched structure (X)
The polymer (PP-1) produced in the following Production Example 1 and the polymer (PP-2) produced in the following Production Example 2 were used.

[Production Example 1 (Production of PP-1)]
<Synthesis Example 1 of Catalyst Component (A)>
Dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indenyl}]hafnium (synthesis of component [A-1] (complex 1)) was synthesized by the following procedure.
(i) Synthesis of 4-(4-i-propylphenyl)indene To a 500 ml glass reaction vessel, 15 g (91 mmol) of 4-i-propylphenylboronic acid, 200 ml of dimethoxyethane (DME), a solution of 90 g (0.28 mol) of cesium carbonate and 100 ml of water were added, and then 13 g (67 mmol) of 4-bromoindene and 5 g (4 mmol) of tetrakistriphenylphosphinopalladium were added in that order, followed by heating at 80° C. for 6 hours.
After cooling, the reaction mixture was poured into 500 ml of distilled water, transferred to a separatory funnel, and extracted with diisopropyl ether. The ether layer was washed with saturated saline and dried over sodium sulfate. The sodium sulfate was filtered, the solvent was distilled off under reduced pressure, and the product was purified using a silica gel column to obtain 15.4 g (yield 99%) of a colorless liquid of 4-(4-i-propylphenyl)indene.

(ii) Synthesis of 2-bromo-4-(4-i-propylphenyl)indene 15.4g (67mmol) of 4-(4-i-propylphenyl)indene, 7.2ml of distilled water, and 200ml of DMSO were added to a 500ml glass reaction vessel, and 17g (93mmol) of N-bromosuccinimide was gradually added thereto. The mixture was stirred at room temperature for 2 hours, and the reaction mixture was poured into 500ml of ice water and extracted three times with 100ml of toluene. The toluene layer was washed with saturated saline, 2g (11mmol) of p-toluenesulfonic acid was added, and the mixture was heated under reflux for 3 hours while removing moisture. The reaction mixture was allowed to cool, washed with saturated saline, and dried with sodium sulfate. The sodium sulfate was filtered, the solvent was distilled off under reduced pressure, and the mixture was purified with a silica gel column to obtain 19.8g (yield 96%) of a yellow liquid of 2-bromo-4-(4-i-propylphenyl)indene.

(iii) Synthesis of 2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indene 6.7 g (82 mmol) of 2-methylfuran and 100 ml of DME were added to a 500 ml glass reaction vessel, and the vessel was cooled to -70°C in a dry ice-methanol bath. 51 ml (81 mmol) of a 1.59 mol/L n-butyllithium-n-hexane solution was added dropwise thereto, and the vessel was stirred for 3 hours. The vessel was cooled to -70°C, and a solution of 20 ml (87 mmol) of triisopropyl borate and 50 ml of DME was added dropwise thereto. After the addition, the vessel was stirred overnight while gradually returning to room temperature.
50 ml of distilled water was added to the reaction mixture for hydrolysis, and then a solution of 223 g of potassium carbonate and 100 ml of water and 19.8 g (63 mmol) of 2-bromo-4-(4-i-propylphenyl)indene were added in that order, and the mixture was heated at 80° C. and reacted for 3 hours while removing low boiling points.
After cooling, the reaction mixture was poured into 300 ml of distilled water, transferred to a separatory funnel, and extracted three times with diisopropyl ether. The ether layer was washed with saturated saline and dried over sodium sulfate. The sodium sulfate was filtered off, the solvent was distilled off under reduced pressure, and the mixture was purified using a silica gel column to obtain 19.6 g (yield 99%) of a colorless liquid of 2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indene.

(iv) Synthesis of dimethylbis(2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indenyl)silane 9.1 g (29 mmol) of 2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indene and 200 ml of THF were added to a 500 ml glass reaction vessel, and the vessel was cooled to −70° C. in a dry ice-methanol bath. 17 ml (28 mmol) of a 1.66 mol/L n-butyllithium-n-hexane solution was added dropwise thereto, and the vessel was stirred for 3 hours. The vessel was cooled to −70° C., and 0.1 ml (2 mmol) of 1-methylimidazole and 1.8 g (14 mmol) of dimethyldichlorosilane were added in that order, and the vessel was stirred overnight while gradually returning to room temperature. Distilled water was added to the reaction mixture, which was then transferred to a separatory funnel and washed with saline until neutral, and sodium sulfate was added to dry the reaction mixture. The sodium sulfate was filtered off, the solvent was distilled off under reduced pressure, and the residue was purified using a silica gel column to obtain 8.6 g (yield 88%) of a pale yellow solid of dimethylbis(2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indenyl)silane.

(v) Synthesis of dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indenyl}]hafnium 8.6 g (13 mmol) of dimethylbis(2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indenyl)silane and 300 ml of diethyl ether were added to a 500 ml glass reaction vessel, and the vessel was cooled to -70°C in a dry ice-methanol bath. 15 ml (25 mmol) of a 1.66 mol/L n-butyllithium-n-hexane solution was added dropwise thereto, and the vessel was stirred for 3 hours. The solvent in the reaction mixture was distilled off under reduced pressure, and 400 ml of toluene and 40 ml of diethyl ether were added thereto, and the vessel was cooled to -70°C in a dry ice-methanol bath. 4.0 g (13 mmol) of hafnium tetrachloride was added thereto. The vessel was then gradually returned to room temperature and stirred overnight.
The solvent was distilled off under reduced pressure, and recrystallization was carried out from dichloromethane-hexane to obtain 7.6 g (yield 65%) of racemic dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indenyl}]hafnium as yellow crystals.
The identity of the obtained racemic mixture by ¹ H-NMR is shown below.
¹ H-NMR (C ₆ D ₆ ) identification results Racemic body: δ0.95 (s, 6H), δ1.10 (d, 12H), δ2.08 (s, 6H), δ2.67 (m, 2H), δ5.80 (d, 2H), δ6.37 (d, 2H), δ6.74 (dd, 2H), δ7.07 (d, 2H) , δ7.13 (d, 4H), δ7.28 (s, 2H), δ7.30 (d, 2H), δ7.83 (d, 4H).

<Synthesis Example 2 of Catalyst Component (A)>
Synthesis of rac-dichloro[1,1′-dimethylsilylenebis{2-methyl-4-(4-chlorophenyl)-4-hydroazulenyl}]hafnium: (Synthesis of component [A-2] (complex 2)):
The synthesis of rac-dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(4-chlorophenyl)-4-hydroazulenyl}]hafnium was carried out in the same manner as described in Example 1 of JP-A-11-240909.

<Catalyst Synthesis Example 1>
(i) Chemical Treatment of Ion-Exchanged Layered Silicate In a separable flask, 96% sulfuric acid (668 g) was added to 2,264 g of distilled water, and then 400 g of montmorillonite (Benclair SL, average particle size 19 μm, manufactured by Mizusawa Chemical Industries, Ltd.) was added as a layered silicate. This slurry was heated at 90° C. for 210 minutes. After adding 4,000 g of distilled water to this reaction slurry, the mixture was filtered to obtain 810 g of a cake-like solid.
Next, 432 g of lithium sulfate and 1,924 g of distilled water were added to a separable flask to prepare an aqueous lithium sulfate solution, and the entire cake-like solid was added thereto. This slurry was reacted at room temperature for 120 minutes. After 4 L of distilled water was added to the slurry, the slurry was filtered, and the pH was adjusted to 5-6 with distilled water. After further filtration, 760 g of cake-like solid was obtained.
The obtained solid was pre-dried overnight at 100° C. in a nitrogen stream, after which coarse particles having a diameter of 53 μm or more were removed, and the solid was further dried under reduced pressure at 200° C. for 2 hours to obtain 220 g of chemically treated smectite.
The composition of this chemically treated smectite was Al: 6.45 wt %, Si: 38.30 wt %, Mg: 0.98 wt %, Fe: 1.88 wt %, Li: 0.16 wt %, and Al/Si=0.175 [mol/mol].

(ii) Catalyst preparation and preliminary polymerization 20 g of the chemically treated smectite obtained above was placed in a three-neck flask (volume 1 L), and heptane (132 mL) was added to form a slurry. Triisobutylaluminum (25 mmol: 68.0 mL of a heptane solution with a concentration of 143 mg/mL) was added thereto and stirred for 1 hour, followed by washing with heptane until the residual liquid rate was 1/100 or less, and then heptane was added so that the total liquid volume became 100 mL.
In another flask (volume 200 mL), rac-dichloro[1,1'-dimethylsilylenebis{2-(5-methyl-2-furyl)-4-(4-i-propylphenyl)indenyl}]hafnium (210 μmol) prepared in Synthesis Example 1 of Catalyst Component (A) was dissolved in toluene (42 mL) (solution 1). Furthermore, in another flask (volume 200 mL), rac-dichloro[1,1'-dimethylsilylenebis{2-methyl-4-(4-chlorophenyl)-4-hydroazulenyl}]hafnium (90 μmol) prepared in Synthesis Example 2 of Catalyst Component (A) was dissolved in toluene (18 mL) (solution 2).
Triisobutylaluminum (0.84 mmol: 1.2 mL of a heptane solution with a concentration of 143 mg/mL) was added to the 1 L flask containing the chemically treated smectite, and then the above solution 1 was added and stirred at room temperature for 20 minutes. After that, triisobutylaluminum (0.36 mmol: 0.50 mL of a heptane solution with a concentration of 143 mg/mL) was further added, and then the above solution 2 was added and stirred at room temperature for 1 hour.
Then, 338 mL of heptane was added, and the slurry was introduced into a 1 L autoclave.
After the internal temperature of the autoclave was set to 40°C, propylene was fed at a rate of 10 g/hour, and prepolymerization was carried out while maintaining the temperature at 40°C for 4 hours. Thereafter, the propylene feed was stopped, and residual polymerization was carried out for 1 hour. After removing the supernatant of the obtained catalyst slurry by decantation, triisobutylaluminum (6 mmol: 17.0 mL of a heptane solution with a concentration of 143 mg/mL) was added to the remaining portion and stirred for 5 minutes.
The solid was dried under reduced pressure for 1 hour to obtain 52.8 g of a dry prepolymerized catalyst. The prepolymerization ratio (amount of prepolymerized polymer divided by amount of solid catalyst) was 1.64.
Hereinafter, this is referred to as "prepolymerization catalyst 1."

<Polymerization>
After the inside of a 200-liter stirred autoclave was fully replaced with propylene, 40 kg of fully dehydrated liquefied propylene was introduced. 9.5 liters of hydrogen (as the volume under standard conditions) and 470 ml (0.12 mol) of triisobutylaluminum-n-heptane solution were added thereto, and the internal temperature was raised to 70° C. Next, 1.9 g (weight excluding the prepolymerized polymer) of prepolymerization catalyst 1 was injected with argon to initiate polymerization, and the internal temperature was maintained at 70° C. After 2 hours, 100 ml of ethanol was injected to purge unreacted propylene and replace the inside of the autoclave with nitrogen to terminate the polymerization.
The resulting polymer was dried at 90° C. under a nitrogen stream for 1 hour to obtain 18.4 kg of a polymer (hereinafter referred to as “PP-1”).
The catalytic activity was 9200 (g-PP/g-cat), and the MFR was 9.3 g/10 min.

[Production Example 2 (Production of PP-2)]
The same procedure as in Production Example 1 was repeated except that 4.8 liters of hydrogen was added and 2.3 g (weight excluding the prepolymer) of prepolymerization catalyst 1 was used. 16.1 kg of a polymer (hereinafter referred to as "PP-2") was obtained.
The catalytic activity was 6980 (g-PP/g-cat), and the MFR was 1.9 g/10 min.

[Production of pellets (X1) to (X2) of PP-1 to PP-2]
100 parts by weight of the polymers (PP-1 to PP-2) produced in Production Examples 1 and 2 were blended with 0.125 parts by weight of tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane (product name: IRGANOX1010, manufactured by BASF Japan Ltd.), which is a phenol-based antioxidant, and 0.125 parts by weight of tris(2,4-di-t-butylphenyl)phosphite (product name: IRGAFOS 168, manufactured by BASF Japan Ltd.), which is a phosphite-based antioxidant, and mixed for 3 minutes at room temperature using a high-speed stirring mixer (Henschel mixer, product name), and then melt-kneaded using a twin-screw extruder to obtain pellets (X1) to (X2) of polypropylene resin (X).
The twin-screw extruder used was a Technobel KZW-25, with a screw rotation speed of 400 RPM and kneading temperatures set at 80, 160, 210, and 230° C. from the bottom of the hopper (the same temperature was maintained from then until the die exit).
The pellets (X1) and (X2) thus obtained were evaluated for MFR, CXS, ¹³ C-NMR, GPC, branching index, MT, and extensional viscosity. The evaluation results are shown in Table 1.

(2) Propylene-Based Block Copolymer (Y)
The propylene-based block copolymer (Y1) produced in Production Example 3 below was used.

[Production Example 3: Production of Propylene-Based Block Copolymer (Y1)]
<Catalyst analysis method>
The catalyst components, solid catalysts and prepolymerized catalysts were analyzed by the following methods.
Ti content (wt%): The sample was accurately weighed, hydrolyzed, and measured by colorimetry. For samples after prepolymerization, the content was calculated using the weight excluding the prepolymerized polymer.
Silicon compound content (wt%)
The sample was accurately weighed and decomposed with methanol. The concentration of silicon compounds in the resulting methanol solution was determined by comparison with a standard sample using gas chromatography. The content of silicon compounds in the sample was calculated from the concentration of silicon compounds in methanol and the weight of the sample. For samples after prepolymerization, the content was calculated using the weight excluding the prepolymerized polymer.

<Preparation of prepolymerization catalyst B1>
(1) Preparation of solid component B1 A 10L autoclave equipped with a stirrer was fully replaced with nitrogen, and 2L of purified toluene was introduced. Here, 200g of Mg(OEt) ₂ was added at room temperature, and _1L of TiCl4 was slowly added. The temperature was gradually raised to 90°C, and 50ml of di-n-butyl phthalate was introduced. Then, the temperature was raised to 110°C and the reaction was carried out for 3 hours. The reaction mixture was thoroughly washed with purified toluene. Next, purified toluene was introduced to adjust the total liquid volume to 2L. _1L of TiCl4 was added at room temperature, and the temperature was raised to 110°C and the reaction was carried out for 2 hours. The reaction mixture was thoroughly washed with purified toluene. Next, purified toluene was introduced to adjust the total liquid volume to 2L. _1L of TiCl4 was added at room temperature, and the temperature was raised to 110°C and the reaction was carried out for 2 hours. The reaction mixture was thoroughly washed with purified toluene. Further, the toluene was replaced with n-heptane using refined n-heptane to obtain a slurry of solid component B1. A part of this slurry was sampled and dried. Analysis revealed that the Ti content of solid component B1 was 2.7 wt%.

(2) Preparation of solid catalyst B1 Next, a 20 L autoclave equipped with a stirrer was fully purged with nitrogen, and 100 g of the slurry of the solid component B1 was introduced as a solid component. Purified n-heptane was introduced to adjust the concentration of the solid component to 25 g/L. ₅₀ ml of SiCl4 was added, and the reaction was carried out at 90°C for 1 hr. The reaction mixture was thoroughly washed with purified n-heptane.
Thereafter, refined n-heptane was introduced to adjust the liquid level to 4 L. 30 ml of dimethyldivinylsilane, 30 ml of t-BuMeSi(OMe) ₂ , and 80 g of n-heptane diluted solution of _Et3Al as _Et3Al were added thereto, and the reaction was carried out at 40°C for 2 hours. The reaction mixture was thoroughly washed with refined n-heptane, and solid component B1 was treated with organosilicon to obtain solid catalyst B1. A part of the obtained slurry of solid catalyst B1 was sampled, dried, and analyzed. Solid catalyst B1 contained 1.2 wt% Ti and 8.9 wt% t-BuMeSi(OMe) ₂ .

(3) Prepolymerization Prepolymerization was carried out by the following procedure using the solid catalyst B1 obtained above. Purified n-heptane was introduced into the above slurry to adjust the concentration of the solid catalyst to 20 g/L. After cooling the slurry to 10°C, 10 g of n-heptane diluted solution of Et ₃ Al was added as Et ₃ Al, and 280 g of propylene was fed over 4 hours. After the propylene feed was completed, the reaction was continued for another 30 min. Next, the gas phase was fully replaced with nitrogen, and the reaction mixture was thoroughly washed with purified n-heptane. The obtained slurry was extracted from the autoclave and vacuum dried to obtain a prepolymerized catalyst B1. This prepolymerized catalyst B1 contained 2.5 g of polypropylene per 1 g of solid catalyst. When analyzed, the portion of this prepolymerized catalyst B1 excluding polypropylene contained 1.0 wt% Ti and 8.3 wt% t-BuMeSi(OMe) ₂ .

The polymerization was carried out using a two-vessel gas-phase polymerization reactor. The first polymerization vessel, which carried out the first step of the sequential polymerization, and the second polymerization vessel, which carried out the second step, were both fluidized bed reactors with an internal volume of 230 liters. The raw gas used was sufficiently purified.

(First step: Production of propylene polymer)
As for the gas composition of the first polymerization tank, propylene and nitrogen were continuously supplied so that the partial pressure of propylene was 1.8 MPaA and the total pressure of the polymerization tank was 3.0 MPaG. In addition, hydrogen as a molecular weight control agent was continuously supplied so that the hydrogen/propylene molar ratio was 0.020. The polymerization temperature was controlled to be 60°C. Et ₃ Al was supplied to this first polymerization tank at 4.0 g/h, and further, the above prepolymerization catalyst B1 was continuously supplied so that the production rate of the propylene polymer in the first polymerization tank was 17.5 kg/h, and a propylene homopolymer was produced. The powder (propylene polymer) produced in the first polymerization tank was continuously extracted so that the powder holding amount in the polymerization tank was 40 kg, and was continuously transferred to the second polymerization tank. A part of the powder transferred from the first polymerization tank to the second polymerization tank was sampled and analyzed, and the MFR was 20.0 g/10 min. In measuring the MFR, tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane (trade name: IRGANOX1010, manufactured by BASF Japan Ltd.), tris(2,4-di-t-butylphenyl)phosphite (trade name: IRGAFOS 168, manufactured by BASF Japan Ltd.), and calcium stearate were each added in appropriate amounts (about 500 wtppm) to the propylene polymer sample, and these were placed in a plastic bag and the bag was shaken up and down and left and right by hand to thoroughly stir the contents to mix (dry blend) before the measurement.
Furthermore, MPaG is a gauge pressure based on atmospheric pressure, and has a relationship with MPaA (absolute pressure) based on vacuum pressure: XX [MPaG] = XX + 0.10133 [MPaA].

(Second step: Production of propylene-ethylene copolymer)
As for the gas composition of the second polymerization tank, propylene, ethylene, and nitrogen were continuously supplied so that the partial pressure of propylene was 1.15 MPaA, the partial pressure of ethylene was 0.35 MPaA, and the total pressure of the polymerization tank was 2.5 MPaG. In addition, hydrogen as a molecular weight control agent was continuously supplied so that the molar ratio of hydrogen/(propylene+ethylene) was 260 ppm. The polymerization temperature was controlled to be 70°C. Furthermore, ethanol was continuously supplied as a polymerization inhibitor so that the rate was 2.0 g/h, and a propylene-ethylene copolymer was produced. The powder (propylene-based block copolymer, which is a multistage polymer composed of a propylene polymer and a propylene-ethylene copolymer) produced in the second polymerization tank was continuously extracted into a vessel so that the powder amount in the polymerization tank was 60 kg. Nitrogen gas containing moisture was supplied to this vessel to stop the reaction, and a propylene-based block copolymer (Y1) was obtained.

[Production of propylene-based block copolymer (Y) pellets]
100 parts by weight of the propylene-based block copolymer (Y1) obtained in Production Example 3 was mixed with 0.05 parts by weight of 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate (trade name: Cyanox 1790, manufactured by Nippon Cytec Industries Co., Ltd.), 0.10 parts by weight of tris(2,4-di-t-butylphenyl)phosphite (trade name: IRGAFOS 168, manufactured by BASF Japan Co., Ltd.), and 0.05 parts by weight of calcium stearate, and mixed for 3 minutes at room temperature using a high-speed stirring mixer (Henschel mixer, trade name). Thereafter, the mixture was melt-kneaded and extruded using a twin-screw extruder, passed through a cold water bath, and then cut into strands using a strand cutter to obtain pellets.
The twin-screw extruder used was a KZW-25 manufactured by Technobel Co., Ltd. The screw rotation speed was 300 RPM, and the kneading temperatures were set to 80, 160, 180, 200, 200, 200, 210, 210, and 210° C. (die outlet) from the bottom of the hopper.
The pellets of the obtained propylene-based block copolymer (Y1) were analyzed, and as a result, the MFR was 1.2 g/10 min, the content of the propylene-ethylene copolymer (Y-2) in the propylene-based block copolymer (Y) was 28.0 wt %, the ethylene content in the propylene-ethylene copolymer (Y-2) was 26.0 wt %, the melting peak temperature of the propylene-based block copolymer (Y) was 160.0° C., and the intrinsic viscosity of the propylene-ethylene copolymer (Y-2) was 9.4 dl/g.
The pellets of the propylene-based block copolymer (Y1) are also referred to as pellets (Y1) of the component (Y).

(3) Propylene-α-olefin random copolymer (Z)
The propylene-α-olefin random copolymer (Z) may be a commercially available grade.
(Z1) Wintech WMG03 (product name, manufactured by Japan Polypropylene Corporation), catalyst: metallocene catalyst, melting peak temperature: 142°C, MFR: 30g/10min, ethylene content: 0.9% by weight
(Z2) Wintech WSX03 (product name, manufactured by Japan Polypropylene Corporation), catalyst: metallocene catalyst, melting peak temperature: 125°C, MFR: 25g/10min, ethylene content: 3.4% by weight

(4) Propylene homopolymer (H1) Novatec PP MA1B (trade name, manufactured by Japan Polypropylene Corporation), catalyst: Ziegler-Natta catalyst, melting peak temperature: 158°C, MFR: 20g/10min

(5) Inorganic filler-containing resin composition for PP filler layer (PPF-1) TX1447MBN (product name, manufactured by Japan Polypropylene Corporation), talc masterbatch

(6) Resin composition for non-foamed layer (PP-3) Novatec PP BC3BRFA (product name, manufactured by Japan Polypropylene Corporation), MFR: 13 g/10 min)

[Example 1]
To obtain a foamed layer, 100 parts by weight of a mixture of pellets (X1) of component (X), pellets (Y1) of component (Y), and pellets (Z1) of component (Z) in a weight ratio of 49:21:30 and 1.25 parts by weight of a chemical foaming agent (product name: Hydrocerol CF40E-J, manufactured by Clariant Japan K.K.) as a cell regulator were uniformly stirred and mixed in a ribbon blender, and the mixture was charged into an extruder with a screw diameter of 65 mmΦ having a barrel hole in the middle of the barrel for injecting a physical foaming agent.
The cylinder temperature of the extruder was set to 240°C and the screw rotation speed was set to 75 rpm to heat, melt, and plasticize the resin while decomposing the cell regulator. Carbon dioxide was then pressurized and kneaded as a physical foaming agent at a ratio of 0.48 parts by weight relative to the resin discharged amount of the foam layer per 100 parts by weight of the mixture to obtain a polypropylene resin composition for foam molding.
The temperature of the rear stage of the extruder was set to 180° C., and the polypropylene resin composition for foam molding was cooled.
In addition, to obtain a PP filler layer, the resin composition PPF-1 for the PP filler layer and the resin composition PP-3 for the non-foamed layer were mixed and stirred in a ribbon blender so that the weight ratio was 50:50, and then the mixture was charged into an extruder with a screw diameter of 65 mmΦ, heated and melted at 230°C, and then cooled by setting the temperature of the extruder cylinder to 180°C.
To obtain a surface layer, the resin composition for non-foamed layer PP-3 was put into an extruder having a screw diameter of 40 mm, heated and melted at 230°C, and then cooled by setting the temperature of the extruder cylinder to 200°C.
The foam layer, PP filler layer and surface layer were co-extruded through a feed block and a T-die (gap = 0.4 mm) into the atmosphere at a throughput of 105 kg/hr in a three-type, five-layer structure consisting of surface layer/PP filler layer/foam layer/PP filler layer/surface layer to form a multi-layer foam. The foam was cooled with a cooling roll and taken up with a pinch roll to adjust the thickness, thereby obtaining a polypropylene-based resin multi-layer foamed sheet having a thickness of 0.81 mm.
The resulting multi-layer foamed sheet had a layer structure of surface layer:PP filler layer:foam layer:PP filler layer:surface layer in a thickness ratio of 8:80:634:80:8, a foam density of 0.379 g/ ^cm3 , a foam layer closed cell ratio of 50%, and a good appearance. The evaluation results of the foamed sheet are shown in Table 2.

[Examples 2 to 6]
Pellets of component (X), component (Y) and component (Z) in the types and weight ratios shown in Table 2 were mixed with 1.25 parts by weight of the chemical foaming agent described in Example 1 as a cell regulator to obtain a multi-layer foamed sheet in the same manner as described in Example 1. The evaluation results of the obtained foamed sheet are shown in Table 2.

[Comparative Example 1]
A multi-layer foamed sheet was obtained in the same manner as in Example 1, except that only pellets (X1) of component (X) and pellets (Y1) of component (Y) were used in a weight ratio of 70:30 to obtain a foamed layer. The foamed sheet had a low closed cell content and was poor in appearance and moldability. The evaluation results of the obtained foamed sheet are shown in Table 2.

[Comparative Example 2]
A multi-layer foamed sheet was obtained in the same manner as in Example 1, except that only pellets (X2) of component (X) and pellets (Y1) of component (Y) were used in a weight ratio of 70:30 to obtain a foamed layer. The foamed sheet had a low closed cell content and was poor in appearance and moldability. The evaluation results of the obtained foamed sheet are shown in Table 2.

[Comparative Example 3]
A foamed sheet was obtained in the same manner as in Example 1, except that pellets (X1) of component (X), pellets (Y1) of component (Y), and pellets (H1) of a polypropylene homopolymer outside the scope of the claims of the present application were used in a weight ratio of 35:15:50 to obtain a foamed layer. The foamed sheet had a low closed cell content and was poor in the appearance of the sheet and in the moldability for containers. The evaluation results of the obtained foamed sheet are shown in Table 2.

[Comparative Example 4]
A foamed sheet was obtained in the same manner as described in Example 1, except that pellets (X1) of component (X), pellets (Y1) of component (Y), and pellets (Z2) of component (Z) were used in a weight ratio of 17.5:7.5:80, which is outside the scope of the claims of the present application, to obtain a foamed layer. The foamed sheet had a low closed cell content and was poor in the appearance of the sheet and in the moldability for containers. The evaluation results of the obtained foamed sheet are shown in Table 2.

[Comparative Example 5]
A foamed sheet was obtained in the same manner as in Example 1, except that pellets (X2) of component (X), pellets (Y1) of component (Y), and pellets (Z2) of component (Z) were used in a weight ratio of 17.5:7.5:80, which is outside the scope of the claims of the present application, to obtain a foamed layer. The foamed sheet had a low closed cell content and was poor in the appearance of the sheet and in the moldability for containers. The evaluation results of the obtained foamed sheet are shown in Table 2.

[Examples 7 to 10]
In the same manner as in Example 1, a multi-layer foamed sheet was obtained having the thickness of each layer, foam density, foam layer magnification and foam layer closed cell ratio shown in Table 3. Here, the types and weight ratios of component (X), component (Y) and component (Z) were changed to those shown in Table 3. The evaluation results of the obtained foamed sheet are shown in Table 3.

The polypropylene resin multi-layer foamed sheet of the present invention and the thermoformed product using said foamed sheet have uniform fine foam cells and are excellent in appearance, thermoformability, impact resistance, light weight, rigidity, heat resistance, heat insulation, oil resistance, etc., and can be suitably used for food containers such as trays, plates, and cups, vehicle interior materials such as automobile door trims and automobile trunk mats, packaging, stationery, building materials, etc., and are of extremely high industrial value.

Claims (4)

A polypropylene-based resin multi-layer foamed sheet comprising a foam layer derived from a polypropylene-based resin composition for foam molding, the foam layer containing 0.05 to 6.0 parts by weight of a foaming agent per 100 parts by weight of the polypropylene-based resin composition, a PP filler layer containing an inorganic filler, and a surface layer made of a thermoplastic resin composition,
The polypropylene resin composition comprises
67.5 to 2.5% by weight of polypropylene resin (X) having a long chain branched structure and having the following characteristics (X-i) to (X-iv),
2.5 to 67.5% by weight of a propylene -based block copolymer (Y) having the following characteristics (Y-i) to (Y-v) and consisting of a propylene (co)polymer (Y-1) and a propylene-ethylene copolymer (Y-2), and 10 to 65% by weight of a propylene-α-olefin random copolymer (Z) having the following characteristics (Z-i) to (Z-ii).
( wherein the total of (X), (Y), and (Z) is 100% by weight) ,
The propylene-based block copolymer (Y) is polymerized using a Ziegler-Natta catalyst,
The propylene (co)polymer (Y-1) is a propylene homopolymer or a propylene random copolymer having a comonomer content of 0.1 to 5.0% by weight .
(X-i) MFR is 0.1 to 30.0 g/10 min.
(X-ii) The molecular weight distribution Mw/Mn measured by GPC is 3.0 to 10.0, and Mz/Mw is 2.5 to 10.0.
(X-iii) Melt tension (MT) (unit: g)
log(MT)≧−0.9×log(MFR)+0.7, or MT≧15
The above conditions must be satisfied.
(X-iv) The amount of paraxylene soluble components at 25° C. (CXS) is less than 5.0% by weight based on the total weight of the polypropylene resin (X).
(Y-i) The ratio of (Y-1) to (Y-2) is 50 to 99% by weight for (Y-1) and 1 to 50% by weight for (Y-2) (where the total weight of the propylene block copolymer (Y) is 100% by weight).
(Y-ii) The MFR of the propylene block copolymer (Y) is 0.1 to 200.0 g/10 min.
(Y-iii) The propylene block copolymer (Y) has a peak melting temperature of more than 155°C.
(Y-iv) The ethylene content in the propylene-ethylene copolymer (Y-2) is 11 to 60% by weight (wherein the total weight of the constituent monomers of the propylene-ethylene copolymer (Y-2) is taken as 100% by weight).
(Yv) The intrinsic viscosity of the propylene-ethylene copolymer (Y-2) in decalin at 135° C. is 5.3 dl/g or more.
(Zi) It is polymerized using a metallocene catalyst.
(Z-ii) The melting peak temperature measured by DSC is 155° C. or lower. The polypropylene resin multi-layer foamed sheet according to claim 1, characterized in that the polypropylene resin (X) has the following property (X-v):
(Xv): The branching index g ^' at an absolute molecular weight Mabs of 1 million is 0.30 or more and less than 0.95. The polypropylene resin multi-layer foamed sheet according to claim 2, wherein the polypropylene resin (X) has the following property (X-vi):
(X-vi): The mm fraction of consecutive propylene units of three units determined by ¹³ C-NMR is 95% or more. A molded article obtained by thermoforming the multi-layer foamed sheet according to any one of claims 1 to 3.