JP5292230B2 - Linear polypropylene resin composition, injection-foamed molded article, and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a straight-chain polypropylene-based resin composition excellent in surface appearance, injection foam moldability, and impact strength, allowing significant weight reduction, and also excellent in recyclability and environmental compatibility, and an injection foam molded article. <P>SOLUTION: The straight-chain polypropylene-based resin composition contains a polypropylene-based resin (A) comprising a straight-chain propylene-ethylene block copolymer (A-1) having properties (i) to (vi) and a propylene-based polymer (A-2), an elastomer (component B), and a foaming agent (component C). Property (i): A MFR (melt flow rate) of a straight-chain propylene polymer moiety is 150 g/10 min or more. Property (ii): A ratio of a straight-chain random copolymer moiety to the component (A-1) is 2-50 wt.%. Property (iii): Intrinsic viscosity [&eta;] of the straight-chain random copolymer moiety is 5.3-10.0 dL/g. Property (iv): The MFR is more than 100 g/10 min. Property (v): A die swell ratio is 1.2-2.5. Property (vi): Strain-hardening properties are shown at an elongational viscosity measurement at 180&deg;C. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a linear polypropylene-based resin composition, an injection foam molded article, and a method for producing the same, and more specifically, has excellent surface appearance, good injection foam moldability and impact strength, and can be significantly reduced in weight. The present invention relates to a linear polypropylene resin composition, an injection-foamed molded article, and a method for producing the same.

Conventionally, polypropylene-based resins have good physical properties and moldability, and their use range is rapidly expanding as environmentally friendly materials. In particular, for automobile parts and the like, a lightweight and excellent polypropylene resin product is provided, and one of such products is an injection foam molded product of a polypropylene resin. In the injection molding of polypropylene-based resins, so-called injection foam molding has been conventionally performed in which foaming is performed for the purpose of weight reduction, cost reduction, and prevention of warping and sink marks of the molded body (see, for example, Patent Document 1).
Further, in recent years, in the automobile field, further weight reduction has been achieved in order to improve fuel efficiency (reduction of CO ₂ emissions), and it has been necessary to significantly reduce the thickness, for example, to form a product having a thin portion of about 1 to 2 mm. It is. However, polypropylene resin has a low melt tension (melting tension), and bubbles are easily broken. As a result, voids were easily generated inside, and it was difficult to increase the expansion ratio. In addition, since the bubbles were non-uniform and large, the resulting molded article had insufficient rigidity. Here, the term “void” refers to a coarse bubble that is generated when internal bubbles communicate with each other and substantially has a diameter exceeding 1.0 mm.

As a method for improving the foaming property of polypropylene, for example, a method of producing a foam while adding a foaming agent and a crosslinking aid to polypropylene and crosslinking the molecules thereof has been proposed (for example, see Patent Document 2). .
However, even with this method, the melt tension of polypropylene is insufficiently improved, and odor is a problem as a result of remaining a crosslinking aid that does not crosslink in such polypropylene.

By introducing long-chain branching by radiation irradiation, the melt tension is higher than that of ordinary linear polypropylene resin, and the viscosity increases as the stretch distortion of the melt increases. The resin is commercially available from Sun Allomer as HMS-PP (High Melt Strength Polypropylene) (see Patent Document 3).
It is known that a foam molded article can be obtained by using such HMS-PP as a base resin for injection foam molding (see Patent Document 4). Usually, in order to achieve significant weight reduction while maintaining rigidity, the mold cavity clearance thickness (thickness before foaming) at the time of injection filling is significantly reduced compared to the non-foamed injection molded body before weight reduction. It is necessary to make it highly foamed.
However, the HMS-PP used here has a melt flow rate of only about 4 g / 10 min and low fluidity at the time of melting, so it has a significant thickness reduction, for example, a thickness of about 1 to 2 mm. In molding, there is a problem that a short shot tends to occur.
In addition, thermoplastic resins having a crosslinked structure tend to be difficult to be melt-processed again, and there are problems in terms of the cost of foam, the amount of waste, and the recycling of resources.

  Also, good foam cell control and high appearance are achieved by using a thermoplastic resin or ethylene-α-olefin copolymer that does not have a cross-linked structure that defines melt index (MI) and capillary swell ratio. (For example, refer to Patent Documents 5 and 6.) As the molded body becomes larger, more complicated, and thinner, the injection has maintained a good cell form when foaming is performed by reducing the thickness before foaming and increasing the thickness before foaming. It was difficult to obtain a foamed molded product or an injection foamed molded product with good impact strength.

  Further, a propylene-based multistage polymer, a polypropylene-based resin composition, in which the intrinsic viscosity of a propylene homopolymer component or a copolymer component, further a melt index (MI), a melt flow rate (MFR), and a melt tension (MT) are defined, By using a polypropylene resin composition containing at least one resin component selected from the group consisting of an ethylene homopolymer and a vinyl aromatic compound-containing rubber, an injection foam molded article excellent in foam moldability and appearance can be obtained. However, as the molded body becomes larger, more complicated, and thinner, it tends to become a short shot and the appearance and impact strength are often insufficient (see, for example, Patent Documents 7 and 8). .

  On the other hand, as a manufacturing method for obtaining a foamed molded article having a good surface appearance, various methods have been conventionally proposed. For example, after forming a skin layer by injecting and filling a polypropylene resin into a narrow mold cavity while reversing the movable mold at a pressure equal to or higher than the foaming pressure, the movable mold is further retracted after the filling is completed. With the manufacturing method for foaming, a foamed molded article having a good surface appearance can be obtained without a special device (see, for example, Patent Document 9). However, all of the foamed molded products obtained by these methods have a low foaming ratio of less than 2 times, and those having a high foaming ratio are not exemplified.

In addition, using a material composed of a linear polypropylene resin, a modified polypropylene resin exhibiting strain hardening obtained by melt-kneading a radical polymerization initiator and a conjugated diene compound, and a foaming agent, the mold is a fixed mold. A step of injecting and filling the molten mixture into a cavity having a clearance (t ₀ ) smaller than the thickness (t ₁ ) of the molded body before foaming, which is composed of a movable mold capable of moving forward and backward, and then retracting the movable mold And a step of completing injection filling up to a clearance corresponding to the thickness (t ₁ ) of the molded body before foaming, and a step of foaming the polypropylene resin by retracting the movable mold. Proposed, injection-foaming moldability and surface appearance are excellent, and an injection-foamed molded article having a high expansion ratio can be obtained (see, for example, Patent Document 10).
However, as the molded body becomes larger, more complicated, and thinner, it tends to be a short shot, and the appearance, expansion ratio, and recyclability are often insufficient.

  Under these circumstances, the problems of conventional polypropylene resin compositions have been solved, and injection foam molded products that are relatively large, complicated in design, and thinned, especially injection foam molded products for automobile parts, especially trim. It is the performance necessary for obtaining injection foam moldings for automobile interior parts such as ceilings, trunks, etc., excellent surface appearance, good injection foam molding properties and impact strength, and can be significantly reduced in weight. There is a need for research and development on polypropylene resin compositions, injection-foamed molded articles, and methods for producing the same, which are excellent in recyclability.

JP-A-6-198668 Japanese Examined Patent Publication No. 45-40420 Japanese Patent Laid-Open No. 62-121704 (Japanese Patent Publication No. 7-45551) JP 2001-26032 A JP-A-8-231816 JP 2004-307665 A International Publication No. WO2005 / 097842 JP 2006-152271 A JP 2003-11190 A JP 2005-224963 A

In view of the above-mentioned problems of the prior art, the object of the present invention is excellent in surface appearance when used in an injection foam molded article, good in injection foam moldability and impact strength, can be significantly reduced in weight, and recycled. Another object of the present invention is to provide a linear polypropylene resin composition having excellent properties, an injection foam molded article, and a method for producing the same.
By the way, being excellent in surface appearance means exhibiting a good appearance in which the occurrence of silver streak is suppressed, and being good in injection foam moldability means that the surface tension is good, and foaming is performed according to the set expansion ratio. The cell form means that the cell diameter is uniform. In addition, the surface tension represents the uniformity of the surface on the surface of the molded body, and that the surface tension is good means that the entire surface of the molded body has no unevenness, and there is no partial dent or swelling. Is to show.

As a result of intensive studies to solve the above problems, the present inventors have found that a linear chain having a specific property / performance comprising a linear propylene polymer portion and a linear ethylene / propylene random copolymer portion. Propylene / ethylene block copolymer (component A-1) 30 to 100% by weight, other propylene polymer (component A-2) 0 to 70% by weight polypropylene resin (component A), elastomer ( When component B) and foaming agent (component C) were blended and the content ratio of each component was optimized, the specific properties and performance such as exhibiting strain-hardening properties even in the case of straight chain, etc. A polypropylene-based resin comprising 30 to 100% by weight of a linear propylene / ethylene block copolymer (component A-1) having 0 to 70% by weight and another propylene polymer (component A-2) When (Component A) is blended with an elastomer (component B) of a specific type and properties and a foaming agent (component C) to form a resin composition for injection foam molding, the surface appearance is excellent, and injection foam moldability and impact It was found that a linear polypropylene resin composition and an injection-foamed molded article thereof having good strength, significant weight reduction, and excellent recyclability can be obtained. It came to be completed.

That is, according to the first invention of the present invention, a linear chain comprising a linear propylene polymer portion and a linear ethylene / propylene random copolymer portion and having the following characteristics (i) to (vi): Polypropylene resin (component A) composed of 30 to 100% by weight of a propylene / ethylene block copolymer (component A-1) and other propylene polymer (component A-2), and melt Ethylene elastomer with a flow rate (230 ° C., 2.16 kg load) of 2.0 g / 10 min or more and / or styrene elastomer with a melt flow rate (230 ° C., 2.16 kg load) of 0.5 g / 10 min or more an elastomer (component B) consisting of the method of injection foam molded article comprising the linear polypropylene-based resin composition containing a foaming agent (component C) There,
The mold is composed of a fixed mold and a movable mold capable of moving forward and backward, and has a mold cavity clearance (T ₀ ) smaller than the mold cavity clearance (T ₁ ) corresponding to the shape position of the final product. An injection process in which a linear or polypropylene resin composition in a molten or semi-molten state is injected and filled into a mold cavity, and the movable mold is retracted to the mold cavity clearance (T ₁ ). A mold-opening injection molding method comprising a foaming step for filling a void in a mold cavity, and a method for producing an injection foamed molded product, and in the injection step for injection-filling a linear polypropylene resin composition, before foaming manufacturing methods provide of the injection foam molded injection rate for molding-filled volume 100%, characterized in that the molding 20% / sec or more conditions That.
Characteristic (i): The melt flow rate (230 ° C., 2.16 kg load) of the linear propylene polymer portion is 150 g / 10 min or more.
Characteristic (ii): The ratio of the linear ethylene / propylene random copolymer portion to the entire linear propylene / ethylene block copolymer (component A-1) is 2 to 50% by weight.
Characteristics (iii): The intrinsic viscosity _{[eta] copoly} of linear ethylene-propylene random copolymer portion is 5.3~10.0dl / g.
Characteristic (iv): Melt flow rate (230 ° C., 2.16 kg load) exceeds 100 g / 10 min.
Characteristic (v): The die swell ratio is 1.2 to 2.5.
Characteristic (vi): Shows strain hardening in 180 ° C. extensional viscosity measurement.

According to the second invention of the present invention, in the first invention, the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the entire linear propylene / ethylene block copolymer (component A-1). the ratio of the (Q value: Mw / Mn) method for producing injection foam molded article is characterized in that 7 to 13 is provided.

Furthermore, according to the third invention of the present invention, in the first or second invention, the linear ethylene / propylene random copolymer in the linear propylene / ethylene block copolymer (component A-1). the ethylene content of the portion, to linear ethylene-propylene random copolymer the total amount, the production method of the injection foam molded article, which is a 15 to 80% by weight is provided.

According to the fourth invention of the present invention, in any one of the first to third inventions, 1 to 50 parts by weight of elastomer (component B) with respect to 100 parts by weight of polypropylene resin (component A). The manufacturing method of the injection foaming molding characterized by containing is provided.
Further, according to the fifth invention of the present invention, in the fourth invention, the styrene elastomer in the elastomer (component B) is selected from hydrogenated styrene-butadiene elastomer or styrene-ethylene-butylene-styrene block copolymer. There is provided a method for producing an injection-foamed molded article characterized by being at least one kind.

As described above, the present invention relates to a method for producing an injection foam molded article , and preferred embodiments thereof include the following.
(1) In the first invention, the foaming agent (component C) is (i) sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, ammonium nitrite, azodicarbonamide (ADCA), N, N′-di A chemical blowing agent selected from nitrosopentamethylenetetramine, benzenesulfonylhydrazide or 4,4'-diphenyldisulfonyl azide; (ii) a physical blowing agent selected from carbon dioxide, nitrogen, argon, helium or air; or (iii) a blowing agent. A method for producing an injection-foamed molded article, which is a microcapsule containing (expansion agent).
(2) In the invention of (1), the blending amount of the foaming agent (component C) is 0.001 to 10 parts by weight with respect to 100 parts by weight of the polypropylene resin (component A) in the case of a chemical foaming agent. In the case of a physical foaming agent, the method for producing an injection-foamed molded article characterized in that the amount is a supercritical state.
(3) In the first invention, the linear propylene polymer portion of the linear propylene / ethylene block copolymer (component A-1) is polymerized by a multistage polymerization method, preferably a two-stage polymerization method. A method for producing an injection-foamed molded article, wherein
(4) In the first invention, the linear propylene / ethylene block copolymer (component A-1) has strain hardening in 180 ° C. extensional viscosity measurement, and in 180 ° C extensional viscosity measurement, the strain rate is A method for producing an injection-foamed molded article, wherein the value of strain hardening (λmax) at 1.0 / sec is 2.0 or more.
(5) In 1st invention, it has a foaming layer whose average bubble diameter is 500 micrometers or less, and a non-foaming layer whose thickness is 10-1000 micrometers , The manufacturing method of the injection-foaming molding characterized by the above-mentioned.
(6) In the first invention, a method of manufacturing an injection foam molding body, wherein the expansion ratio is 2.0 to 10 times.

The linear polypropylene resin composition and injection-foamed molded article of the present invention have excellent surface appearance, good injection-foaming moldability and impact strength (including a low-temperature atmosphere), even though no crosslinking modification is performed. It is possible to significantly reduce the weight and to exhibit a remarkable effect of being excellent in recyclability. In particular, molding is possible in the region where the absolute molding wall thickness before foaming is less than 2 mm, especially 1.5 mm or less, which has been difficult in the past, and it is possible to significantly reduce the weight by expressing a uniform high foaming ratio. Become.
In addition, since cross-linking modification is not performed, it is excellent in recyclability and environmental adaptability. Therefore, it can be suitably used for injection molded parts including automobile interior parts such as trims, ceiling materials, and trunks.

The present invention includes 30 to 100% by weight of a linear propylene / ethylene block copolymer (component A-1, hereinafter also simply referred to as component A-1) and other propylene polymers (component A-2, hereinafter). Simply referred to as Component A-2) Polypropylene resin (Component A, hereinafter also referred to simply as Component A) consisting of 0 to 70% by weight, melt flow rate (230 ° C., 2.16 kg load) is 2.0 g / 10. An elastomer (component B, hereinafter, also simply referred to as component B) composed of a styrene-based elastomer having an ethylene elastomer of at least minutes and / or a melt flow rate (230 ° C., 2.16 kg load) of at least 0.5 g / 10 minutes. A linear polypropylene-based resin composition and an injection-foamed molded article comprising each component of a foaming agent (component C, hereinafter also simply referred to as component C)
Hereinafter, each component of the linear polypropylene resin composition, the production of the linear polypropylene resin composition, the production of the injection-foamed molded article, and the like will be described in detail.

[I] Constituent Components of Linear Polypropylene Resin Composition Polypropylene resin (component A)
The polypropylene resin (component A) used in the linear polypropylene resin composition of the present invention is 30 to 100% by weight, preferably a linear propylene / ethylene block copolymer (component A-1) described below. 40 to 100% by weight, particularly preferably 50 to 100% by weight, and other propylene polymer (component A-2) 0 to 70% by weight, preferably 0 to 60% by weight, particularly preferably 0 to 50% by weight. %.
Here, when the component A-1 is less than 30% by weight, the surface appearance and the injection foam moldability of the linear polypropylene resin composition of the present invention and the injection foam molded article thereof are deteriorated.
In addition, the blending ratio of each component in the linear polypropylene resin composition of the present invention is based on the blending ratio of Component A of 100 parts by weight unless otherwise specified.

1-1. Linear propylene / ethylene block copolymer (component A-1)
The linear propylene / ethylene block copolymer (component A-1) used in the linear polypropylene resin composition of the present invention is composed of a linear propylene polymer portion and a linear ethylene / propylene random copolymer. It is a linear propylene / ethylene block copolymer composed of a combined portion.
Component A-1 has the following characteristics (i) to (vi), and in a linear polypropylene resin composition, has excellent surface appearance and high injection foam moldability (surface tension, expansion ratio, cell form) ).
Characteristic (i): Melt flow rate (hereinafter referred to as MFR) (230 ° C., 2.16 kg load) of the linear propylene polymer portion is 150 g / 10 min or more.
Characteristic (ii): The ratio of the linear ethylene / propylene random copolymer portion to the whole component A-1 is 2 to 50% by weight.
Characteristics (iii): The intrinsic viscosity _{[eta] copoly} of linear ethylene-propylene random copolymer portion is 5.3~10.0dl / g.
Characteristic (iv): MFR (230 ° C., 2.16 kg load) exceeds 100 g / 10 min.
Characteristic (v): The die swell ratio is 1.2 to 2.5.
Characteristic (vi): Shows strain hardening in 180 ° C. extensional viscosity measurement.

Here, the “linear” in the linear propylene polymer portion, the linear ethylene / propylene random copolymer portion or the linear propylene / ethylene block copolymer (component A-1) is methyl branched. This means that there are very few branched structures other than the structure, and this is a structure often found in ordinary polypropylene resins.
For example, it can be confirmed by ¹³ C-NMR analysis that no peak is observed at 31.5 to 31.7 ppm based on branched carbon (see Macromol. Chem. Phys. 2003, Vol. 204, page 1738).

  As described above, component A-1 exhibits strain hardening despite the linear structure. This strain hardening property is usually said to be caused by molecular entanglement. In order to develop the strain hardening property, for example, the molecular weight of the linear propylene polymer portion and the linear propylene / ethylene random copolymer weight are used. Examples of the method include increasing the difference in molecular weight of the combined portion, and increasing the compatibility between the linear propylene polymer portion and the linear propylene / ethylene random copolymer portion.

Component A-1 not only satisfies these requirements, but also has a unique dispersion structure of the linear ethylene / propylene random copolymer portion in the linear propylene polymer portion, that is, general propylene / ethylene. Unlike the case of a block copolymer (in this case, when subjected to shearing, the ethylene / propylene random copolymer portion is rejected and aggregated at the interface of the propylene polymer portion and dispersed individually), It exhibits a kind of network-like state (that is, the linear ethylene / propylene random copolymer portion penetrates into the linear propylene polymer portion in a network shape), so that the strain hardening property is improved. It is considered to show.
In addition, by exhibiting a state that approximates a kind of network, the compatibility between the linear propylene polymer portion and the linear ethylene / propylene random copolymer portion is further enhanced, Has been considered.

  The effect of exhibiting the strain hardening property is attributed to foam breakage at the molten resin flow front end (flow front) at the time of injection foam molding in the linear polypropylene resin composition and injection foam molded article of the present invention. Silver streak is unlikely to occur, the surface appearance is likely to be beautiful, and an injection foam molded article having uniform fine bubbles at a high magnification is likely to be obtained.

(1) Production The production method of the linear propylene / ethylene block copolymer (component A-1) used in the linear polypropylene resin composition of the present invention has the above characteristics (i) to (vi). As long as it is, it will not specifically limit and it selects suitably from well-known methods and conditions.
As the propylene polymerization catalyst, a highly stereoregular catalyst is usually used. For example, a catalyst comprising a combination of a titanium trichloride composition obtained by reducing titanium tetrachloride with an organoaluminum compound and further treating with various electron donors and electron acceptors, an organoaluminum compound and an aromatic carboxylic acid ester ( (See JP-A-56-100806, JP-A-56-120712, JP-A-58-104907), and support in which titanium tetrachloride and various electron donors are brought into contact with magnesium halide. And the like (see JP-A-57-63310, JP-A-63-43915, and JP-A-63-83116).

  In the presence of the catalyst, it is obtained by polymerizing propylene by applying a production process such as a gas phase polymerization method, a liquid phase bulk polymerization method, or a slurry polymerization method, followed by random polymerization of propylene and ethylene. In order to obtain a propylene / ethylene block copolymer having the above-described melting characteristics (MFR), it is preferable to perform multistage polymerization by a slurry method or a gas phase fluidized bed method.

The polymerization of the linear propylene polymer portion may be a one-stage polymerization of propylene or a multi-stage polymerization, but it is more preferably obtained by a multi-stage polymerization in order to exhibit the above characteristics.
Examples of the multistage polymerization method for the linear propylene polymer portion include a two-stage polymerization method by the following step (1) and step (2).
Step (1): Propylene is polymerized in the presence of hydrogen as a molecular weight regulator. This is to suppress the formation of a polymer having a too high molecular weight. Hydrogen is added so that the MFR of the linear propylene polymer portion is 150 g / 10 min or more. The hydrogen concentration is usually selected from the range of 0.1 to 40 mol% with respect to the total monomer amount. The polymerization temperature is usually selected from the range of 40 to 90 ° C., and the pressure is usually selected from the range of 0.1 to 5 MPa. The amount of the polymer obtained in this step (1) is usually adjusted to be 80 to 99% by weight of the total polymerization amount. When the amount of the polymer produced in the step (1) is less than 80% by weight, the amount of the high molecular weight propylene polymer produced in the step (2) is excessively increased and the moldability is impaired.

  Step (2): Compared with the linear propylene polymer portion produced in Step (1), in order to polymerize a high-molecular-weight propylene polymer, the hydrogen atmosphere is as low as possible or is substantially free of hydrogen. It is preferable to polymerize with. The polymerization is subsequently carried out in the presence of the propylene polymer produced in step (1) and a catalyst. The polymerization temperature is usually selected from the range of 40 to 90 ° C., and the pressure is usually selected from the range of 0.1 to 5 MPa. The amount of the polymer obtained in this step (2) is usually adjusted to be 1 to 20% by weight of the total polymerization amount. Any combination may be adopted as long as the physical property value of the whole polymer obtained by combining the step (1) and the step (2) can be adjusted to the above-described range.

  The linear propylene polymer portion is preferably a homopolymer of propylene in order to increase the rigidity of the linear polypropylene resin composition of the present invention, but for the purpose of further improving moldability and the like, As long as the properties are not significantly impaired, a copolymer with a small amount of a comonomer can also be used. Specifically, for example, α-olefins other than propylene such as ethylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 4-methyl 1-pentene, styrene, vinylcyclopentene, vinyl A comonomer unit corresponding to one or more comonomers selected from the group consisting of vinyl compounds such as cyclohexane and vinyl norbornane, etc., can be contained preferably in a content of 5% by weight or less. Two or more of these comonomers may be copolymerized. The comonomer is preferably ethylene and / or 1-butene, most preferably ethylene. Here, the content of the comonomer unit is a value determined by infrared spectroscopy (IR).

Following the polymerization of the linear propylene polymer portion, the linear ethylene / propylene random copolymer portion is polymerized. The linear ethylene / propylene random copolymer portion is preferably a high molecular weight linear ethylene / propylene random copolymer in order to adjust the die swell ratio and molecular weight distribution (Q value) to predetermined values.
The polymerization of the linear ethylene / propylene random copolymer portion is preferably performed in a hydrogen atmosphere as low as possible or in a state substantially free of hydrogen in order to polymerize a high molecular weight polymer. The polymerization is carried out successively in the presence of the propylene polymer produced in the linear propylene polymer partial polymerization step and a catalyst. The polymerization temperature is usually selected from the range of 40 to 90 ° C., and the pressure is usually selected from the range of 0.1 to 5 MPa.

(2) Physical property (i):
The MFR (230 ° C., 2.16 kg load) of the linear propylene polymer portion in Component A-1 used in the linear polypropylene resin composition of the present invention is 150 g / 10 min or more, preferably 250 to 3000 g / 10 min, more preferably 550 to 2000 g / 10 min. When the MFR is less than 150 g / 10 min, the surface appearance and the injection foam moldability of the linear polypropylene resin composition and the injection foam molded article are deteriorated.
The MFR is the MFR when the polymerization of the linear propylene polymer portion is completed, and when performing the multistage polymerization, the MFR is the MFR of the linear propylene polymer portion taken out from the final polymerization tank.

Characteristic (ii):
The composition ratio of the linear ethylene / propylene random copolymer portion in the component A-1 used in the linear polypropylene resin composition of the present invention to the entire component A-1 is 2 to 50% by weight, Preferably it is 5 to 40 weight%, More preferably, it is 7 to 20 weight%.
That is, the ratio of the linear propylene polymer portion to the whole component A-1 is 50 to 98% by weight, preferably 60 to 95% by weight, more preferably 80 to 93% by weight. When the linear ethylene / propylene random copolymer part is less than 2% by weight (that is, the linear propylene polymer part exceeds 98% by weight), the linear polypropylene resin composition and the injection-foamed molded article The injection foaming moldability and impact strength are deteriorated. On the other hand, if the proportion of the linear ethylene / propylene random copolymer portion exceeds 50% by weight (that is, the linear propylene polymer portion is less than 50% by weight), the surface appearance, injection foam moldability and rigidity Gets worse.

Characteristic (iii):
The intrinsic viscosity _{[eta] copoly} of linear ethylene-propylene random copolymer portion in the component A-1 used in the linear polypropylene-based resin composition of the present invention, 5.3~10.0dl / g, Preferably it is 6.0-10.0 dl / g, More preferably, it is 6.5-9.5 dl / g. When the intrinsic viscosity _{[eta] copoly} is less than 5.3 dl / g, the injection foam molding of the linear polypropylene-based resin composition and injection foam molded article is deteriorated. On the other hand, when the intrinsic viscosity [η] _copolymer exceeds 10.0 dl / g, the surface appearance and impact strength deteriorate.

Characteristic (iv):
The total MFR (230 ° C., 2.16 kg load) of Component A-1 used in the linear polypropylene resin composition of the present invention needs to exceed 100 g / 10 minutes, preferably 105 g / 10 minutes or more, More preferably, it is 135-500 g / 10min, More preferably, it is 140-300g / 10min. When the MFR is 100 g / 10 min or less, the surface appearance and the injection foam moldability of the polypropylene resin composition and the injection foam molded article are deteriorated. In molding having a portion, there may occur a case where short shot occurs and stable molding cannot be performed.

Characteristic (v):
The die swell ratio of the whole component A-1 used in the linear polypropylene resin composition of the present invention is 1.2 to 2.5, preferably 1.3 to 2.4, more preferably 1.4. ~ 2.3. When the die swell ratio is less than 1.2, the linear propylene-based resin composition cannot maintain a good cell shape at a high magnification, and the injection foam moldability deteriorates. On the other hand, those having a die swell ratio exceeding 2.5 are less practical because they are difficult to manufacture industrially.

Characteristic (vi):
Component A-1 used in the linear polypropylene resin composition of the present invention exhibits strain hardening in 180 ° C. extensional viscosity measurement. In the linear polypropylene resin composition of the present invention, the effect of showing strain-hardening properties in this 180 ° C. extensional viscosity measurement is due to foam breakage at the molten resin flow front (flow front) during injection molding. This makes it difficult to produce a silver streak, makes the surface appearance easy to be beautiful, and makes it easy to obtain a foamed molded article having uniform and fine bubbles at a high magnification.
The term “strain hardenability” as used herein means that the elongational viscosity gradually increases as the amount of stretch strain of the melt increases. It is a case of increasing.

  Here, as to the method for evaluating strain hardening, any method can be used in principle as long as the uniaxial elongation viscosity can be measured. For example, details of the measuring method and measuring instrument are known: Polymer 42 (2001) 8663 is described as a preferred measuring method, but as a measuring device, Rheometrics Ales (Jig: Extensive Visibility Fixture manufactured by TEA Instruments), Toyo Seiki Co., Ltd., Melten The method using Rheometer is mentioned.

  The degree of strain hardening is 2.0 or more, more preferably 2.5 or more, particularly preferably 3.0 or more, further preferably 5 in the 180 ° C. extensional viscosity measurement (strain rate: 1.0 / sec). It preferably has a strain hardening degree (λmax) of 0.0 or more. When the strain hardening degree (λmax) is less than 2.0, in the linear polypropylene resin composition and the injection foam molded article of the present invention, silver streaks are likely to occur during injection foam molding, and the surface appearance is deteriorated. In some cases, an injection-foamed molded article having uniform fine bubbles cannot be obtained.

Other characteristics:
The ratio (Q value: Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) representing the molecular weight distribution of the entire component A-1 used in the linear polypropylene resin composition of the present invention is 7 to 13 is preferable, and 8 to 12 is more preferable. If the Q value is less than 7, the linear polypropylene-based resin composition cannot maintain a good cell form, and there is a tendency that a high-magnification foam molded article cannot be obtained. On the other hand, a Q value exceeding 13 is not preferable because the production becomes extremely difficult.

  The ethylene content of the linear ethylene / propylene random copolymer portion in Component A-1 used in the linear polypropylene resin composition of the present invention is based on the total amount of the linear ethylene / propylene random copolymer. , Preferably 15 to 80% by weight, more preferably 20 to 70% by weight, still more preferably 25 to 45% by weight. When the ethylene content is less than 15% by weight, the injection-foaming moldability and the surface appearance of the linear polypropylene resin composition and the injection-foamed molded article are liable to be lowered. On the other hand, when the ethylene content exceeds 80% by weight, The impact strength tends to decrease.

  The weight average molecular weight (Mw) of the linear ethylene / propylene random copolymer portion in Component A-1 used in the linear polypropylene resin composition of the present invention is preferably 1,000,000 or more, more preferably 110. It is 10,000 to 8 million, more preferably 1.2 to 7 million, particularly preferably 1.5 to 4 million. If the weight average molecular weight (Mw) of the linear ethylene / propylene random copolymer portion is lower than 1,000,000, the effect of improving the injection foam moldability of the linear polypropylene resin composition tends to be insufficient.

MFR, die swell ratio, Mw, Q value, linear ethylene / propylene random copolymer portion content and ethylene content were measured using MFR meter, cross fractionator, Fourier transform infrared absorption spectrum analysis, gel permeation chromatography ( GPC). Intrinsic viscosity [η] _copy is measured using an Ubbelohde viscometer, and strain hardening in 180 ° C extensional viscosity measurement is measured using an extensional viscosity meter. The measurement conditions of main items are described in the examples.

(3) Blending ratio The blending ratio of Component A-1 in the linear polypropylene resin composition of the present invention is 30 to 100% by weight, preferably 40 to 100% by weight, especially 100% by weight, based on Component A. Preferably it is 50 to 100% by weight. When the component A-1 is less than 30% by weight, the surface appearance and injection foam moldability of the linear polypropylene resin composition of the present invention and the injection foam molded article thereof are lowered.

1-2. Other propylene polymers (component A-2)
Other propylene polymers (component A-2) used in the linear polypropylene resin composition of the present invention include propylene homopolymers, propylene / ethylene random copolymers, propylene / ethylene block copolymers, and the like. Copolymer of propylene and α-olefin excluding propylene, copolymer of propylene and vinyl compound, copolymer of propylene and vinyl ester, copolymer of propylene and unsaturated organic acid or derivative thereof, propylene And conjugated dienes, copolymers of propylene and non-conjugated polyenes, and mixtures thereof. Of these, a copolymer of propylene and ethylene is preferable, and a propylene / ethylene block copolymer is particularly preferable.
Component A-2 contributes to maintaining and improving the physical properties such as surface appearance, injection foam moldability, rigidity, impact strength, productivity and economy in the linear polypropylene resin composition of the present invention. Has characteristics.

(1) Production The production method of Component A-2 used in the linear polypropylene resin composition of the present invention is not particularly limited, and is appropriately selected from known methods and conditions.
As the polymerization catalyst for propylene, a highly stereoregular catalyst is usually used, and examples thereof include a Ziegler catalyst and a metallocene catalyst.
In the presence of the catalyst, it is obtained by applying a production process such as a gas phase polymerization method, a liquid phase bulk polymerization method, or a slurry polymerization method.
Examples of the α-olefin in the propylene / α-olefin copolymer include α-olefins having 2 to 20 carbon atoms excluding propylene, and examples thereof include ethylene, butene-1, hexene-1, and octene-1. Examples of the vinyl compound in the copolymer of propylene and a vinyl compound include styrene, vinylcyclopentene, and vinylcyclohexane. Examples of the vinyl ester in the copolymer of propylene and vinyl ester include vinyl acetate. Examples of the unsaturated organic acid or derivative thereof in a copolymer of propylene and an unsaturated organic acid or derivative thereof include maleic anhydride.
One kind or two or more kinds of the α-olefin copolymerized with propylene and the vinyl compound may be used. Of these, ethylene and butene-1 are preferred.

(2) Physical properties The MFR (230 ° C., 2.16 kg load) of the entire component A-2 used in the linear polypropylene resin composition of the present invention is preferably 0.1 to 300 g / 10 minutes, more preferably It is 3 to 200 g / 10 minutes, more preferably 10 to 100 g / 10 minutes, and particularly preferably 20 to 60 g / 10 minutes. If the MFR is less than 0.1 g / 10 min, the surface appearance and injection foam moldability of the linear polypropylene resin composition and the injection foamed molded product tend to deteriorate, for example, a mold cavity before foaming In molding having a thin portion with a clearance of about 1 to 2 mm, a short shot may occur and stable molding cannot be performed.

(3) Blending ratio The blending ratio of Component A-2 used in the linear polypropylene resin composition of the present invention is 0 to 70% by weight, preferably 0 to 60% by weight, based on 100% by weight of Component A. Particularly preferred is 0 to 50% by weight. When component A-2 exceeds 70% by weight, the surface appearance and injection foam moldability of the linear polypropylene resin composition of the present invention and the injection foamed molded product thereof are lowered.

2. Elastomer (component B)
The elastomer (component B) used in the linear polypropylene resin composition of the present invention is an ethylene elastomer and / or MFR (230 ° C.) having an MFR (230 ° C., 2.16 kg load) of 2.0 g / 10 min or more. , 2.16 kg load) is a styrene-based elastomer of 0.5 g / 10 min or more, and in a linear polypropylene resin composition and an injection-foamed molded article, in addition to imparting high impact strength, excellent dimensional stability, Used for the purpose of developing injection foaming moldability and surface appearance.

(1) Kinds Examples of the ethylene elastomer in Component B include, for example, ethylene / propylene copolymer elastomer (ethylene propylene rubber; EPR), ethylene / butene copolymer elastomer (EBR), and ethylene / hexene copolymer elastomer (EHR). ), Ethylene / α-olefin copolymer elastomers such as ethylene / octene copolymer elastomer (EOR); ethylene / propylene / ethylidenenorbornene copolymer, ethylene / propylene / butadiene copolymer, ethylene / propylene / isoprene copolymer Examples thereof include ethylene / α-olefin / diene terpolymer elastomer (EPDM) such as coalescence; ethylene-ethylene / butylene / ethylene block copolymer elastomer (CEBC).
Examples of the styrene elastomer include hydrogenated styrene / butadiene elastomer (hydrogenated styrene / butadiene rubber; HSBR), styrene-ethylene / butylene / styrene block copolymer elastomer (SEBS), and styrene / ethylene / butylene / ethylene block copolymer. Polymer elastomer (SEBC), Styrene / butadiene / styrene block copolymer elastomer (SBS), Styrene / isoprene / styrene block copolymer elastomer (SIS), Styrene-ethylene / propylene-styrene block copolymer elastomer (SEPS) And styrene-ethylene / ethylene / propylene / styrene block copolymer elastomer (SEEPS).
Component B may be, for example, a ternary or multi-component copolymer elastomer such that two or more types of α-olefins in an ethylene / α-olefin copolymer elastomer are copolymerized.
For example, commercially available products that can be used as Component B of the present invention include ethylene / α-olefin copolymer elastomer and ethylene / α-olefin / diene terpolymer elastomer as EP series manufactured by JSR Corporation, Mitsui Chemicals, Inc. Toughmer P series, A series and H series, Engage EG series / Affinity series (Plastomer) made by Dow Chemical Japan, Dynalon series (CEBC) made by JSR, etc. Examples include Shell Japan's Clayton series, JSR's Dynalon series, Kuraray's Septon series, and Asahi Kasei's Tuftec series.

  Among these, ethylene-based elastomers having MFR (230 ° C., 2.16 kg load) of 2.0 g / 10 min or more include ethylene-butene copolymer elastomer (EBR) and ethylene-hexene copolymer elastomer (EHR). , Ethylene / octene copolymer elastomer (EOR) is preferable in that it exhibits high impact strength, injection foam moldability, surface appearance and the like in the linear polypropylene resin composition and injection foam molded article of the present invention, Styrenic elastomers with MFR (230 ° C., 2.16 kg load) of 0.5 g / 10 min or more include hydrogenated styrene / butadiene elastomer (hydrogenated styrene / butadiene rubber; HSBR), styrene-ethylene / butylene / styrene block. Copolymer elastomer (SEBS), styrene-ethylene Propylene - styrene block copolymer elastomer (SEPS) are preferable for the same reason. Furthermore, in particular, similarly, ethylene / butene copolymer elastomer (EBR), ethylene / octene copolymer elastomer (EOR), hydrogenated styrene / butadiene elastomer (hydrogenated styrene / butadiene rubber; HSBR), styrene-ethylene / butylene. -Styrene block copolymer elastomers (SEBS) are preferred.

Component B is not limited to one type, and may be a mixture of two or more types having different MFR and density.
For example, when an ethylene elastomer having an MFR (230 ° C., 2.16 kg load) of 2.0 g / 10 min or more and a styrene elastomer having an MFR (230 ° C., 2.16 kg load) of 0.5 g / 10 min or more are used in combination. The linear polypropylene-based resin composition of the present invention and the injection foam molded article are preferable because the balance of physical properties such as impact strength and rigidity, injection foam moldability and surface appearance can be expressed at a high level. An ethylene / butene copolymer elastomer (EBR) and / or an ethylene / octene copolymer elastomer (EOR) having an MFR (230 ° C., 2.16 kg load) of a majority weight of 2.0 g / 10 min or more with respect to the whole component B ) And a hydrogenated styrene-butadiene elastomer having an MFR (230 ° C., 2.16 kg load) of 0.5 g / 10 min or more. When tomer (hydrogenated styrene / butadiene rubber; HSBR) and / or styrene / ethylene / butylene / styrene block copolymer elastomer (SEBS) is used in combination, physical properties balance such as impact strength and rigidity, economy, injection foam molding and This is more preferable because the effect of improving the surface appearance is even greater.

(2) Production Among component B, for example, ethylene / α-olefin copolymer elastomer of ethylene-based elastomer or ethylene / α-olefin / diene terpolymer elastomer is polymerized in the presence of a catalyst. It is manufactured by doing. Examples of the catalyst include so-called Ziegler-type catalysts such as titanium compounds such as titanium halides, organoaluminum-magnesium complexes such as alkylaluminum-magnesium complexes, alkylaluminums, or alkylaluminum chlorides, and WO-91 / 04257. The metallocene compound catalyst described in the above and the like can be used. As the polymerization method, polymerization can be performed by applying a production process such as a gas phase fluidized bed method, a solution method, a slurry method, or a high-pressure bulk polymerization method. Preferred polymerization methods include a solution method and a high-pressure bulk polymerization method.

On the other hand, a styrene-based elastomer or an ethylene-ethylene / butylene-ethylene block copolymer elastomer (CEBC) can be generally produced by a normal anion living polymerization method or the like. For example, after a styrene, butadiene, and styrene are successively polymerized to produce a triblock body, a styrene-ethylene-butylene-styrene block copolymer elastomer (SEBS) is produced by hydrogenation. There is also a method in which a styrene-butadiene diblock copolymer is first produced, then converted into a triblock body using a coupling agent, and then hydrogenated.
Moreover, a styrene-ethylene-propylene-styrene block copolymer elastomer (SEPS) can be similarly produced by using isoprene instead of butadiene.

(3) Physical Properties MFR (230 ° C., 2.16 kg load) of Component B is a high balance level of impact strength, injection foam moldability and surface appearance in the linear polypropylene resin composition of the present invention and injection foam molded article. Therefore, in the ethylene-based elastomer, 2.0 g / 10 min or more is necessary, 5.0 g / 10 min or more is preferable, and 20.0 g / 10 min or more is particularly preferable. When the MFR (230 ° C., 2.16 kg load) of the ethylene elastomer is less than 2.0 g / 10 minutes, the impact strength and injection foam moldability of the linear polypropylene resin composition and the injection foam molded article of the present invention And the balance level of the surface appearance decreases.
Moreover, in a styrene-type elastomer, 0.5 g / 10min or more is required, 1.0 g / 10min or more is preferable, and 2.0 g / 10min or more is especially preferable. When the MFR (230 ° C., 2.16 kg load) of the styrene-based elastomer is less than 0.5 g / 10 minutes, the balance level of the impact strength, the injection foam moldability and the surface appearance is lowered.

The density of Component B is preferably 0.85~0.92g / cm ^3, more preferably 0.86~0.90g / cm ^3. When the density is less than 0.85 g / cm ³ , the surface appearance of the linear polypropylene resin composition and the injection-foamed molded article of the present invention tends to be lowered. When the density exceeds 0.92 g / cm ³ , the impact There is a tendency for strength to decrease. The density is a value measured according to JIS K7112.

Among component B, the ethylene-based elastomer, for example, the ethylene / α-olefin copolymer elastomer or the α-olefin content in the ethylene / α-olefin / diene terpolymer elastomer is not particularly limited. % By weight is preferred, 25 to 45% by weight is more preferred, and 30 to 43% by weight is particularly preferred. If the α-olefin content is outside these ranges, the balance level of impact strength, injection foam moldability and surface appearance in the linear polypropylene resin composition and injection foam molded article of the present invention tends to decrease. is there.
The styrene content in the styrene elastomer is not particularly limited, but is preferably 5 to 40% by weight, more preferably 6 to 35% by weight, and particularly preferably 8 to 25% by weight. If the styrene content is outside these ranges, the balance level of impact strength, injection foam moldability and surface appearance of the linear polypropylene resin composition and injection foam molded article of the present invention tends to be lowered. The α-olefin and styrene contents are values determined by infrared spectroscopy (IR) or NMR.

(4) Blending ratio The blending ratio of Component B used in the linear polypropylene resin composition of the present invention is preferably 1 to 50 parts by weight, more preferably 5 to 45 parts by weight with respect to 100 parts by weight of Component A. Parts, more preferably 10 to 43 parts by weight, particularly preferably 15 to 40 parts by weight. When the blending ratio of component B is less than 1 part by weight, the impact strength and dimensional stability of the linear polypropylene resin composition and the injection-foamed molded product tend to be reduced. On the other hand, when it exceeds 50 parts by weight, There is a tendency for the surface appearance and rigidity to decrease.

3. Foaming agent (component C)
The foaming agent (component C) used in the linear polypropylene resin composition of the present invention is a chemical foaming agent, a physical foaming agent, a microcapsule, or the like. It is used for the purpose of developing moldability (surface tension, expansion ratio, cell form).

(1) Types, functions, etc. The types of foaming agents include chemical foaming agents, physical foaming agents and microcapsules, and can be used without particular limitation as long as they can be normally used for injection foam molding. These foaming agents can be used alone or in admixture of two or more.
Examples of the chemical foaming agent include inorganic chemical foaming agents such as sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, and ammonium nitrite, azodicarbonamide (ADCA), and N, N′-dinitrosopentamethylenetetramine. And organic chemical blowing agents such as benzenesulfonyl hydrazide and 4,4′-diphenyldisulfonyl azide.
These foaming agents include organic acids such as citric acid and sodium citrate that promote the generation of gas as necessary to stably and uniformly make the bubbles in the foamed molded product. Metal salts and the like can be used and added together, and nucleating agents such as inorganic fine particles such as talc and lithium carbonate can be added.

As the chemical foaming agent, an inorganic type is preferable from the viewpoint that a normal injection molding machine can be used safely and uniform fine bubbles are easily obtained in the molded body.
As described above, various chemical foaming agents such as inorganic and organic can be mentioned, and preferable examples include sodium bicarbonate, citric acid, sodium citrate, and a mixture of two or more of these. Examples include sodium bicarbonate, a combination of sodium bicarbonate and sodium citrate, and a combination of sodium bicarbonate and citric acid.

These chemical foaming agents are processed into particles having an average particle diameter of 1 to 100 μm, for example, and are supplied to an injection molding machine or the like after being applied to and mixed with the component A at the time of injection foam molding or injection molding. In some cases, it is injected from the middle of the cylinder of the injection molding machine and decomposes in the cylinder to generate a gas such as carbon dioxide.
Moreover, a chemical foaming agent can also be used after granulating as a masterbatch which used the polyolefin resin as the base material from points, such as a handleability, storage stability, and the dispersibility to a polypropylene resin. Thereby, contamination of the hopper of the molding machine and adhesion of powder to the surface of the molded body can be suppressed. In this case, it is preferably used as a master batch of polyolefin resin having a concentration of 10 to 50% by weight.
Alternatively, the chemical foaming agent may be added once, and the chemical foaming agent may be decomposed by pelletization, or the chemical foaming agent having a high concentration may be decomposed in advance and the residue may be added. The chemical foaming agent is decomposed in the cylinder of the injection molding machine, and the foaming residue can be a foam nucleating agent.

Examples of the physical foaming agent include an inert gas, a low boiling point organic solvent vapor, a halogen-based inert solvent vapor, carbon dioxide gas, and air.
Examples of the inert gas include nitrogen, argon, helium, neon, and astatine. Examples of the low-boiling organic solvent vapor include methanol, ethanol, propane, butane, and pentane. Examples of the active solvent vapor include dichloromethane, chloroform, carbon tetrachloride, Freon, and nitrogen trifluoride. Among these, since it is not necessary to use steam, it is inexpensive, environmental pollution, and the risk of fire is extremely low, it is preferable to use inert gas, carbon dioxide gas, and air, especially carbon dioxide gas, nitrogen, Argon and helium are preferable, and carbon dioxide and nitrogen are particularly preferable.
Furthermore, the physical foaming agent is preferably in a supercritical state, which has the advantage of facilitating gas melting into the resin.
The physical foaming agent is injected as a gaseous or supercritical fluid into the component A or the like in the cylinder of an injection molding machine, and is dispersed or dissolved. By injecting into the mold, the pressure is released. It functions as a foaming agent.

Microcapsules are obtained by encapsulating foaming agents (swelling agents) in shells made of various thermoplastic resins. Examples of the blowing agent (swelling agent) include specific freons such as trichlorofluoromethane, dichlorofluoromethane, and dichlorofluoroethane, alternative freons, hydrocarbons such as n-pentane, isopentane, isobutane, and petroleum ether, Examples thereof include chlorinated hydrocarbons such as methyl chloride, methylene chloride, and dichloroethylene. The average particle size of the microcapsule foaming agent is usually 2 to 50 μm.
These microcapsules are usually supplied to an injection molding machine or the like after being previously mixed with the component A or the like.

  These foaming agents are used in combination with a chemical foaming agent and a physical foaming agent in order to obtain more uniform and fine bubbles in a linear polypropylene resin composition and an injection foamed molded article and to increase the expansion ratio. In particular, it is preferable to use an inorganic chemical foaming agent in combination with carbon dioxide or nitrogen as a physical foaming agent.

(2) Blending Ratio The blending ratio of Component C in the linear polypropylene resin composition of the present invention may be appropriately set in view of the type of foaming agent, foaming ratio, injection foam molding conditions, and the like.
For example, when using a chemical foaming agent, 0.001-10 weight part is preferable per 100 weight part of component A, More preferably, it is 0.01-8 weight part, Especially preferably, it is 0.1-5 weight part. The blending ratio in this case is a substantial concentration of the foaming agent. For example, when a masterbatch of the foaming agent and the polyolefin resin is used, it is calculated based on the concentration of the foaming agent contained in the masterbatch. When the blending ratio of Component C is less than 0.001 part by weight, the linear polypropylene resin composition does not sufficiently foam, whereas when it exceeds 10 parts by weight, the linear polypropylene resin composition and The mechanical strength such as impact strength of the injection-foamed molded product is reduced, or secondary foaming phenomenon (the phenomenon that the surface of the injection-foamed molded product swells in a blistering state due to excessive remaining foaming gas) is caused economically. Also tend to be disadvantageous.
Moreover, when using a physical foaming agent, it sets suitably by adjusting the injection pressure of the gas to be used, for example. If the gas injection pressure is insufficient or excessive, the linear polypropylene resin composition does not sufficiently foam as in the case of the chemical foaming agent described above, or the mechanical strength of the injection foamed molded article. Tends to decrease.

4). Optional addition component (component D)
In the linear propylene-based resin composition of the present invention, in addition to the above component A, component B, and component C, if necessary, for example, the effects of the present invention can be further improved within a range that does not significantly impair the effects of the present invention. In order to impart other effects, an optional additive component (component D) can be blended.
Specifically, fillers such as talc, light stabilizers such as hindered amines, UV absorbers such as benzotriazoles, nucleating agents such as sorbitols, colorants such as pigments, phenolic and phosphorus antioxidants Agent, nonionic antistatic agent, inorganic compound neutralizing agent, thiazole antibacterial and antifungal agent, halogen compound and other flame retardant, process oil (compounded oil), plasticizer, nonionic Antistatic agents, dispersants such as organic metal salts, lubricants such as fatty acid amides, metal deactivators such as nitrogen compounds, nonionic surfactants, polypropylene other than the above component A to component C, etc. Polyolefins, thermoplastic resins such as polyamide and polyester, and elastomers (rubbers). These components may be used in combination of two or more, may be added to the composition, may be added to each component, or may be used in combination in each component.

As fillers, for example, inorganic fillers and organic fillers are effective for imparting and improving physical properties such as rigidity of linear polypropylene resin compositions and injection-foamed molded articles, heat resistance, dimensional stability and environmental adaptability. is there.
Specific examples include, for example, inorganic fillers such as silica, diatomaceous earth, barium ferrite, beryllium oxide, pumice, pumice balun and other oxides, aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate and other hydroxides, carbonic acid Carbonates such as calcium, magnesium carbonate, dolomite, dosonite, sulfates or sulfites such as calcium sulfate, barium sulfate, ammonium sulfate, calcium sulfite, talc, clay, mica, glass fiber, glass balloon, glass beads, calcium silicate, Silicates such as wollastonite, montmorillonite, bentonite, carbons such as carbon black, graphite, carbon fiber, carbon hollow sphere, molybdenum sulfide, boron fiber, zinc borate, barium metaborate, calcium borate, boric acid Na Potassium, basic magnesium sulfate fibers (magnesium oxysulfate), it may be mentioned potassium titanate fibers, aluminum borate fibers, calcium silicate fibers, calcium fibers carbonate, various metal fibers and the like.
On the other hand, examples of the organic filler include shell fibers such as fir shells, wood powder, cotton, jute, paper strips, cellophane pieces, polyamide fibers, cellulose fibers, polyester fibers, polypropylene fibers, and thermosetting resin powders. be able to.

  As light stabilizers and ultraviolet absorbers, for example, hindered amine compounds, benzotriazoles, benzophenones and salicylates are used to impart and improve the weather resistance and durability of linear polypropylene resin compositions and injection-foamed molded articles. It is valid. Specific examples of the hindered amine compound include a condensate of dimethyl succinate and 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine; poly [[6- (1, 1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidyl) imino] hexamethylene [(2 , 2,6,6-tetramethyl-4-piperidyl) imino]]; tetrakis (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate; tetrakis ( 1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate; bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebake Bis-2,2,6,6-tetramethyl-4-piperidyl sebacate and the like, and examples of the benzotriazole type include 2- (2′-hydroxy-3 ′, 5′-di-t-butyl) Phenyl) -5-chlorobenzotriazole; 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole and the like. -Methoxybenzophenone; 2-hydroxy-4-n-octoxybenzophenone and the like. Examples of salicylates include 4-t-butylphenyl salicylate; 2,4-di-t-butylphenyl-3 ', 5'- Examples include di-t-butyl-4′-hydroxybenzoate.

  Examples of nucleating agents include inorganic, sorbitol, carboxylic acid metal salt, and organic phosphate, such as linear polypropylene resin composition and injection foam molding, rigidity, heat resistance and hardness, injection foaming It is effective for imparting and improving moldability. Specific examples include talc as an inorganic system; silica and the like, and 1,3: 2,4-dibenzylidene-sorbitol as a sorbitol system; 1,3: 2,4-di- (p-methyl-benzylidene). Sorbitol; 1,3: 2,4-di- (p-ethylbenzylidene) sorbitol; 1,3: 2,4-bis- (2 ′, 4′-dimethylbenzylidene) sorbitol; 1,3-p-chlorobenzylidene -2,4-p-methylbenzylidene-sorbitol; 1,3: 2,4-di- (p-propylbenzylidene) sorbitol and the like, and as the carboxylic acid metal salt system, aluminum-hydroxy-di-pt -Butyl benzoate; sodium benzoate; calcium montanate and the like, and as an organic phosphate system, sodium bis (4-t-butyl Ruphenyl) phosphate; sodium-2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate; lithium-2,2′-methylene-bis (4,6-di-t-butyl) Phenyl) phosphate and the like.

  As a colorant, for example, an inorganic or organic pigment is added to the linear polypropylene resin composition and the injection-foamed molded article, such as a colored appearance, appearance, texture, commercial value, weather resistance and durability. It is effective for improvement. Specific examples of inorganic pigments include titanium oxide; iron oxide (eg, bengara); chromic acid (eg, galvanized lead); molybdic acid; selenide sulfide; ferrocyanide and carbon black. Insoluble azo chelates; insoluble azo chelates; condensable azo chelates; other azo chelates such as azo chelates; phthalocyanine blue; phthalocyanine pigments such as phthalocyanine green; anthraquinones; perinones; perylene; Dye lake; quinacridone type; dioxazine type; isoindolinone type. Moreover, in order to make a metallic tone or a pearl tone, an aluminum flake; a pearl pigment can be contained. Moreover, dye can also be contained.

Examples of antioxidants include phenolic, phosphorus and sulfur antioxidants, such as heat resistance stability, processing stability, and heat aging resistance of linear polypropylene resin compositions and injection-foamed molded articles. It is effective for granting and improving.
Examples of phenolic antioxidants include 2,6-di-t-butyl-4-methylphenol; tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl). Propionate] -methane; tris (3,5-di-t-butyl-4-hydroxyphenyl) isocyanurate and the like.
Examples of phosphorus antioxidants include distearyl pentaerythritol diphosphite; tris (2,4-di-t-butylphenyl) phosphite; tris (2-t-butyl-4-methylphenyl) phosphite Is mentioned.
Moreover, as a sulfur type antioxidant, distearyl thiodipropionate etc. are mentioned, for example.

  As the antistatic agent, for example, nonionic or cationic antistatic agents are effective for imparting and improving the antistatic property of the linear polypropylene resin composition and the injection foamed molded article. Specific examples include polyoxyethylene alkylamines; polyoxyethylene alkylamides; polyoxyethylene alkylphenyl ethers; stearic acid monoglycerides; alkyldiethanolamines; alkyldiethanolamides; alkyldiethanolamine fatty acid monoesters;

[II] Method for Producing Linear Polypropylene Resin Composition, Method for Producing Injection Foam Molded Article, and Uses As a method for producing the linear polypropylene resin composition of the present invention, Component A, Component B and Component C are used. In addition, if necessary, component D is blended in the above blending ratio, and then dry blending such as dusting or hand blending, various blenders such as V blenders and tumbler mixers, blending methods using a mixer, etc., uniaxial A method of kneading and granulating using an ordinary kneader such as an extruder, a twin screw extruder, a Banbury mixer, a roll mixer, a Brabender-plastograph, a kneader, and the above components individually (or partially blended) For example, a method of directly supplying to an injection molding machine as it is.

When selecting a kneading / granulating method, it is usually preferable to knead / granulate using a twin screw extruder. In this kneading and granulation, the above components A to D may be kneaded at the same time, and each component is divided in order to improve performance, for example, first, part or all of component A and component B Can be kneaded, and then the remaining components can be kneaded and granulated.
When all or part of component C is mixed and kneaded in the injection foam molding stage, kneading and granulating is performed only with the component excluding all or part of component C.

The injection foam molding method for producing the injection foam molding in the present invention is not particularly limited, and usually includes a foam molding method using an injection molding machine, an injection compression molding machine, or the like.
As an injection foam molding method, for example, a linear polypropylene resin composition containing at least part of component C in a mold cavity is injected and filled while reversing the movable mold at a pressure equal to or higher than the foaming pressure. There is a method in which after the formation of the layer, the core layer is foamed by further retracting the movable mold after completion of the filling.

  In addition, for example, a linear polypropylene resin composition composed of components excluding all or part of component C is supplied to an injection molding machine, and component C such as the physical foaming agent is also compressed gas or super There is a method of directly injecting into a mold in addition to a molding machine in a critical state to mold an injection foam molded article. That is, a linear polypropylene resin composition containing a chemical foaming agent is supplied to an injection molding machine, and at the same time, a physical foaming agent is directly controlled and introduced into the molding machine for molding. This method can also be used in a molding method in which the skin layer is formed by injection filling while retracting the movable mold, and then the core layer is foamed by retracting the movable mold.

Further, for example, the mold is composed of a fixed mold and a movable mold capable of moving forward and backward, and an initial mold cavity clearance smaller than the mold cavity clearance (T ₁ ) corresponding to the shape position of the final product. An injection step of injecting and filling a linear or polypropylene-based resin composition in a molten or semi-molten state into a mold cavity having (T ₀ ), and retracting the movable mold to the mold cavity clearance (T ₁ ) (core And a mold opening injection foaming method including a foaming step of filling the voids of the mold cavity with an expansion pressure by a foaming agent. This molding method is preferable because the surface appearance of the linear polypropylene resin composition and the injection-foamed molded article and the injection-foaming moldability can be expressed at a high level.
Among these, in the molding method, it is preferable that the injection rate with respect to 100% of the pre-foaming filling volume in the injection step of injecting and filling the linear polypropylene resin composition is preferably 20% / second or more. 50% / second or more is more preferable, 100% / second or more is more preferable, and 200% / second or more is particularly preferable.
The molding method under these conditions can exhibit the above-described injection foam moldability and surface appearance at a higher level.

  The injection-foamed molded article of the present invention preferably has an average cell diameter of 500 μm or less, more preferably 200 μm or less, and a thickness formed on the surface of at least one side of the foam layer, preferably 10 μm or more and 1000 μm or less. Preferably, it has a non-foamed layer of 100 μm or more and 500 μm or less. When the average cell diameter of the foam layer exceeds 500 μm, excellent rigidity tends not to be obtained. If the thickness of the non-foamed layer is less than 10 μm, the surface does not have a beautiful appearance and the rigidity tends to decrease, and if it exceeds 1000 μm, it is difficult to obtain light weight.

  Further, the expansion ratio of the injection-foamed molded article in the present invention is preferably 2.0 times or more and 10.0 times or less, more preferably 2.5 times or more and 6.0 times or less, and more preferably 3.0 times or more and 6.0 times. The following are particularly preferred: If the expansion ratio is less than 2.0 times, the lightness tends to be difficult to obtain, whereas if it exceeds 10.0 times, the rigidity tends to decrease significantly. The expansion ratio refers to the ratio of the specific gravity of the foamed molded product and the non-foamed molded product that was injection-molded under the same conditions except that the foaming agent was not added to the linear polypropylene resin composition of the present invention, and the thickness of the foamed molded product. And the value obtained from the ratio of the initial wall thickness.

  Applications of the linear polypropylene resin composition and the injection-foamed molded article of the present invention include automotive parts, household appliances such as televisions, industrial parts including electronic parts, etc., building material parts, preferably automobile parts, especially trim. Automobile interior parts such as roofing, ceiling material, trunk area, instrument panel and pillar.

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
The evaluation methods, analysis methods and materials used in the examples are as follows.

1. Evaluation method, analysis method (1) Surface appearance:
(A) Silver streak:
The degree of occurrence of silver streaks in the foamed molded product was evaluated in the following four stages in comparison with a separately produced non-foamed molded product.
Exhibits exactly the same level as non-foamed molded products and has a moist gloss.
Same level as non-foamed molded products ...
Slight silver streaks on the surface of the molded body
The molded product has a lot of silver streaks on the entire surface ...
In this case, ◎, ○, and Δ are levels that are judged to have practicality.

(2) Injection foaming moldability:
(A) Surface tension:
The degree of surface tension of the foamed molded product was evaluated in the following three stages in comparison with a separately produced non-foamed molded product.
Same level as non-foamed molded product
Some irregularities on the surface of the molded body
The molded product has many irregularities on the entire surface ...
In this case, ◯ and Δ are levels that are judged to have practicality.

(B) Foaming ratio:
It calculated | required by the plate | board thickness / initial stage thickness of the foaming molding. The thickness of the obtained molded product was evaluated under the condition of cavity clearance after core back / initial cavity clearance = 2.7 times the core back amount.
However, the initial cavity clearance = 1.3 mm. Therefore, the cavity clearance after the core back is 3.5 mm.
The thickness of the entire molded body is exactly the same as the cavity clearance after the core back ...
There are some places where the thickness of the molded body is partially thinner than the cavity clearance after the core back ... △
The thickness of the molded body is generally thinner than the cavity clearance after the core back.
In this case, ◯ and Δ are levels that are judged to have practicality.

(C) Cell form:
A micrograph of a cross section obtained by cutting the foam molded body in the thickness direction was visually observed and evaluated.
The cell diameter is fine and uniform throughout.
Cell diameter is small and partly non-uniform.
Cell diameter is non-uniform throughout or completely peeled
In this case, ◯ and Δ are levels that are judged to have practicality.

(3) DuPont impact strength:
(A) Test apparatus: DuPont impact tester (b) Stroke tip diameter: 12.7 mm
(C) Falling weight: 0.3 kg (constant)
(D) Test piece: 80 mm × 80 mm × 3.5 mmt ... Cut piece from the foamed molded product (e) Test temperature: -15 ° C. (immersion in ethanol solution adjusted with dry ice for 15 minutes)
(F) Height interval: 5-10 cm
(G) Calculation of impact strength (50% fracture energy):
The 50% fracture energy was calculated from the following formula.
E = [{HS (T / 100-1 / 2)} * W] /10.2
In the formula, E: impact strength (fracture energy (J)), H: height at the time of total fracture (cm), S: height interval (cm), T:% of fracture (no fracture to total fracture), W: The weight load (kg).

(4) MFR:
Conforms to JIS K7210. Test temperature: 230 ° C., load: 2.16 kg.

(5) Content of linear ethylene / propylene random copolymer portion and ethylene content:
(A) Analytical device to be used (a-1) Cross sorter CFC T-100 (abbreviated as CFC) manufactured by Dia Instruments Co., Ltd.
(A-2) Fourier transform infrared absorption spectrum analysis FT-IR, Perkin-Elmer 1760X
A fixed wavelength infrared spectrophotometer attached as a CFC detector is removed and an FT-IR is connected instead, and this FT-IR is 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.
(A-3) Gel permeation chromatography (GPC)
The GPC column in the latter part of the CFC is used by connecting three AD806MS manufactured by Showa Denko KK in series.

(B) CFC measurement conditions (b-1) Solvent: orthodichlorobenzene (ODCB)
(B-2) Sample concentration: 4 mg / mL
(B-3) Injection amount: 0.4 mL
(B-4) Crystallization: The temperature is lowered from 140 ° C. to 40 ° C. over about 40 minutes.
(B-5) Sorting method:
The fractionation temperature at the time of temperature-raising elution fractionation is 40, 100, and 140 ° C., and the fractions are separated into a total of three fractions. In addition, the elution ratio (unit:% by weight) of the component eluting at 40 ° C. or lower (fraction 1), the component eluting at 40 to 100 ° C. (fraction 2), and the component eluting at 100 to 140 ° C. (fraction 3), respectively W ₄₀ , W ₁₀₀ , and W ₁₄₀ are defined. W ₄₀ + W ₁₀₀ + W ₁₄₀ = 100. Moreover, each fractionated fraction is automatically transported to the FT-IR analyzer as it is.
(B-6) Solvent flow rate during elution: 1 mL / min

(C) Measurement conditions of FT-IR After elution of the sample solution from GPC at the latter stage of the CFC starts, FT-IR measurement is performed under the following conditions, and GPC-IR data is collected for each of the above-described fractions 1 to 3. .
(C-1) Detector: MCT
(C-2) Resolution: 8 cm ⁻¹
(C-3) Measurement interval: 0.2 minutes (12 seconds)
(C-4) Number of integrations per measurement: 15 times

(D) Post-processing and analysis of measurement results The elution amount and molecular weight distribution of components eluted at each temperature are determined using the absorbance at 2945 cm ⁻¹ obtained by FT-IR as a chromatogram. The elution amount is normalized so that the total elution amount of each elution component is 100%. Conversion from the retention volume to the molecular weight is performed using a calibration curve prepared in advance with standard polystyrene.
The standard polystyrenes used are all the following brands manufactured by Tosoh Corporation.
F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000.
A calibration curve is created by injecting 0.4 mL of a solution dissolved in ODCB (containing 0.5 mg / mL BHT) so that each is 0.5 mg / mL. The calibration curve uses a cubic equation obtained by approximation by the least square method. Conversion to molecular weight uses a general calibration curve with reference to “Size Exclusion Chromatography” written by Sadao Mori (Kyoritsu Shuppan). The following numerical values are used for the viscosity equation ([η] = K × M ^α ) used at that time.
(D-1) At the time of creating a calibration curve using standard polystyrene K = 0.000138, α = 0.70
(D-2) Sample measurement of component A-1 K = 0.000103, α = 0.78
The ethylene content distribution (distribution of ethylene content along the molecular weight axis) of each eluted component is a ratio of the absorbance of 2956 cm ⁻¹ and the absorbance of 2927 cm ⁻¹ obtained by FT-IR, and is obtained by using polyethylene, polypropylene, or ¹³ Converted to ethylene content (% by weight) using a calibration curve prepared in advance using ethylene-propylene rubber (EPR) and mixtures thereof whose ethylene content is known by C-NMR measurement, etc. Ask.

(E) Content of linear ethylene / propylene random copolymer portion:
The content (Wc) of the ethylene / propylene random copolymer portion in Component A-1 used in the present invention is theoretically defined by the following formula (I), and is determined by the following procedure.
Wc (% by weight) = W ₄₀ × A ₄₀ / B ₄₀ + W ₁₀₀ × A ₁₀₀ / B ₁₀₀ (I)
In the formula (I), W ₄₀ and W ₁₀₀ are elution ratios (unit:% by weight) in each of the above-described fractions, and A ₄₀ and A ₁₀₀ are actual values in the respective fractions corresponding to W ₄₀ and W _100. The measured average ethylene content (unit: wt%), and B ₄₀ and B ₁₀₀ are the ethylene content (unit: wt%) of the linear ethylene / propylene random copolymer portion contained in each fraction. . A method for _obtaining A ₄₀ , A ₁₀₀ , B ₄₀ , and B ₁₀₀ will be described later.

The meaning of the formula (I) is as follows.
That is, the first term on the right side of the formula (I) is a term for calculating the amount of the linear ethylene / propylene random copolymer portion contained in the fraction 1 (portion soluble at 40 ° C.). When fraction 1 contains only a linear ethylene / propylene random copolymer and no linear propylene polymer, W ₄₀ is the linear ethylene / propylene random derived from fraction 1 as it is Fraction 1 contributes to the copolymer partial content, but in addition to the component derived from the linear ethylene / propylene random copolymer, a small amount of components derived from the linear propylene polymer (components with extremely low molecular weight and Since atactic polypropylene) is also included, it is necessary to correct that portion. Therefore, by multiplying W ₄₀ by A ₄₀ / B ₄₀ , the amount derived from the linear ethylene / propylene random copolymer portion in fraction 1 is calculated. For example, when the average ethylene content A ₄₀ of the fraction 1 is 30% by weight and the ethylene content B _{40 of the} linear ethylene / propylene random copolymer contained in the fraction 1 is 40% by weight, 30/40 = 3/4 (that is, 75% by weight) is derived from a linear ethylene / propylene random copolymer, and 1/4 is derived from a linear propylene polymer. Thus, the operation of multiplying A ₄₀ / B ₄₀ by the first term on the right side means that the contribution of the linear ethylene / propylene random copolymer is calculated from the weight% W _{40 of} fraction 1. The same applies to the second term on the right side. For each fraction, the linear ethylene / propylene random copolymer partial content is calculated by adding the contribution of the linear ethylene / propylene random copolymer. .

(E-1) As described above, the average ethylene contents corresponding to fractions 1 and 2 obtained by CFC measurement are A ₄₀ and A ₁₀₀ , respectively (unit is weight%). A method for obtaining the average ethylene content will be described later.

(E-2) The ethylene content corresponding to the peak position in the differential molecular weight distribution curve of fraction 1 is defined as B ₄₀ (unit is% by weight). Fraction 2 is considered to be substantially defined as B ₁₀₀ = 100 in the present invention because it is considered that the rubber part is completely eluted at 40 ° C. and cannot be defined with the same definition. B ₄₀ and B ₁₀₀ are the ethylene content of the linear ethylene / propylene random copolymer portion contained in each fraction, but it is practically impossible to obtain this value analytically. This is because there is no means for completely separating and fractionating the linear propylene polymer and the linear ethylene / propylene random copolymer mixed in the fraction.
Results of investigations using various models sample, B _40, when using ethylene content corresponding to the peak position of the differential molecular weight distribution curve of fraction 1, it can be well explained the effect of improving the material properties I understood. Further, B ₁₀₀ has crystallinity derived from an ethylene chain, and the amount of the linear ethylene / propylene random copolymer contained in these fractions includes the linear ethylene / propylene random copolymer contained in the fraction 1. Due to the two reasons that it is relatively small compared to the amount of polymer, the approximation to 100 is closer to the actual situation and causes almost no error in calculation. Therefore, the analysis is performed with B ₁₀₀ = 100.

(E-3) For the above reason, the content (Wc) of the linear ethylene / propylene random copolymer portion is determined according to the following formula.
Wc _{(wt%) = W 40 × A 40} / B 40 + W 100 × A 100/100 ... (II)
That is, W ₄₀ × A ₄₀ / B ₄₀ which is the first term on the right side of the formula (II) indicates the content (wt%) of the linear ethylene / propylene random copolymer having no crystallinity, and the second term W ₁₀₀ × A _100/100 is a linear ethylene / propylene random copolymer partial content (% by weight) having crystallinity.
_Here, the average ethylene content _A 40 of _{B 40} and each of the fractions obtained by the CFC measurement 1 and _{2, A 100} is determined as follows.
Ethylene content corresponding to the peak position of the differential molecular weight distribution curve is B _40. In addition, the sum of the products of the weight ratio for each data point and the ethylene content for each data point, which is captured as data points at the time of measurement, is the average ethylene content A _{40 of} fraction 1. The average ethylene content A _{100 of} fraction 2 is determined in the same manner.

The significance of setting the three types of fractionation temperatures is as follows. In the CFC analysis of the present invention, 40 ° C. means that the polymer having no crystallinity (for example, most of the linear ethylene / propylene random copolymer or extremely high molecular weight in the linear propylene polymer portion). It has the significance that the temperature condition is necessary and sufficient to fractionate only low and atactic components). 100 ° C. means a component that is insoluble at 40 ° C. but becomes soluble at 100 ° C. (for example, a component having crystallinity due to a chain of ethylene and / or propylene in a linear ethylene / propylene random copolymer) , And a linear propylene polymer having low crystallinity). 140 ° C. means a component that is insoluble at 100 ° C. but becomes soluble at 140 ° C. (for example, a component having particularly high crystallinity in a linear propylene polymer and a linear ethylene / propylene random copolymer) The temperature is necessary and sufficient to elute only the component having extremely high molecular weight and extremely high ethylene crystallinity and recover the entire amount of propylene / ethylene block copolymer used for analysis. W ₁₄₀ does not contain any linear ethylene / propylene random copolymer portion, or even if it is present, it is extremely small and can be substantially ignored. It is excluded from the calculation of the content of the polymer and the ethylene content of the linear ethylene / propylene random copolymer.

(F) Ethylene content of linear ethylene / propylene random copolymer portion:
The ethylene content of the linear ethylene / propylene random copolymer portion in Component A-1 used in the present invention is determined from the following formula using the values described above.
Ethylene content (% by weight) of linear ethylene / propylene random copolymer portion = (W ₄₀ × A ₄₀ + W ₁₀₀ × A ₁₀₀ ) / Wc
(Wc is the ratio (% by weight) of the linear ethylene / propylene random copolymer portion determined previously.)

(6) Intrinsic viscosity [η] _{copy of the} linear ethylene / propylene random copolymer portion:
The intrinsic viscosity [eta] _copoly of linear ethylene-propylene random copolymer portion in the component A-1 used in the present invention is determined as follows.
First, after completion of the polymerization of the linear propylene polymer part, a part is sampled from the polymerization tank, and the intrinsic viscosity [η] _{homo of the part} is measured. Next, after polymerizing the linear propylene polymer portion, the intrinsic viscosity [η] _F of the final polymer (F) obtained by polymerizing the linear ethylene / propylene random copolymer portion is measured. This measurement is performed at a temperature of 135 ° C. using decalin as a solvent using an Ubbelohde viscometer. [Η] _copy is obtained from the following relationship.
[Η] _F = (100−Wc) / 100 × [η] _homo + Wc / 100 × [η] _copy

(7) Die swell ratio:
The die swell ratio of component A-1 used in the present invention is a value determined by the following method.
Set the in-cylinder temperature of the MFR meter to 190 ° C. The orifice has a length of 8.00 mm, a diameter of 1.00 mmφ, and L / D = 8. Also, place a graduated cylinder with ethyl alcohol directly under the orifice (the distance between the orifice and the ethyl alcohol liquid surface is 20 ± 2 mm). In this state, the sample is put into the cylinder, and the load is adjusted so that the extrusion amount per minute becomes 0.10 ± 0.03 g. The extrudate after 6 to 7 minutes is dropped into ethanol and solidified before being collected. The maximum and minimum values of the diameter of the strand-shaped sample of the collected extrudate were measured at 3 locations, 1 cm from the top, 1 cm from the bottom, and the center. Ratio.
The die swell ratio of component A-1 is determined by, for example, performing polymerization in a hydrogen atmosphere of as low a concentration as possible or in a state substantially free of hydrogen at the time of polymerization of the constituent linear ethylene / propylene random copolymer portion. It can be adjusted by controlling the molecular weight high.

(8) Strain hardenability:
The strain hardening property of Component A-1 used in the present invention is measured by the following method.
(A) Apparatus: Ales manufactured by Rheometrics
(B) Jig: EXTENSIONAL VISUALITY FIXTURE, manufactured by TA Instruments
(C) Test temperature: 180 ° C
(D) Strain rate: 1.0 / sec
(E) Sample test piece: 15 mm × 10 mm press-formed sheet having a thickness of 0.5 mm (f) Determination of the presence or absence of strain hardening:
The elongational viscosity at a strain rate of 1.0 / sec is plotted as a logarithmic graph of the amount of strain on the horizontal axis and the elongational viscosity ηE (Pa · s) on the vertical axis. As the amount of strain increases, the extensional viscosity gradually increases, and when the rate of increase in the extensional viscosity increases abruptly from a certain amount of strain, this is a case where strain hardening is exhibited. The case was made “strain hard”. On the other hand, the case where the above-mentioned phenomenon was not substantially recognized was set as “no strain”.
(G) Calculation method of strain hardening degree (λmax):
On the above logarithmic graph, the viscosity immediately before the strain hardening is approximated by a straight line, and the maximum value (ηmax) of the elongational viscosity η _E until the strain amount becomes 4.0 is obtained. Let ηlin be the viscosity on the approximate straight line. ηmax / ηlin is defined as λmax.
The strain rate can be measured in the range of 0.001 / sec to 10.0 / sec, and the strain hardening degree varies depending on the difference in strain rate.

(9) Q value (Mw / Mn):
The Q value of component A-1 used in the present invention is the total molecular weight of component A-1 prepared by synthesizing the molecular weight distribution curves of fractions 1 to 3 measured by gel permeation chromatography in the above-described cross fractionation apparatus. Obtained from the distribution curve. A method for calculating the weight average molecular weight (Mw) and the number average molecular weight (Mn) from this molecular weight distribution curve is in accordance with a known method, and Mw / Mn is used as the Q value.

2. Material (1) Component A
(A-1a): Polymerized with Ziegler catalyst, MFR (230 ° C., 2.16 kg load) of the linear propylene polymer portion is 300 g / 10 min, component of the linear ethylene / propylene random copolymer portion ratio is 7.4 wt% to the whole a-1, the intrinsic viscosity _{[eta] copoly} of linear ethylene-propylene random copolymer portion is 7.2dl / g, component a-1 overall MFR (230 ℃, 2 .16 kg load) is 105 g / 10 min, the die swell ratio of the entire component A-1 is 1.6, and shows strain hardening in 180 ° C. elongational viscosity measurement (strain hardening “Yes”). The degree (λmax) is 3.73, the Q value of the whole component A-1 is 8.1, and the ethylene content of the linear ethylene / propylene random copolymer portion is 35% by weight (measured by a cross fractionation method), Straight chain Ten thousand Mw of the ethylene-propylene random copolymer portion 124 (cross fractionation GPC measurement), linear propylene-ethylene block copolymer (antioxidant-neutralizing agent, added already pellets).
(A-1b): Polymerized with a Ziegler catalyst, MFR (230 ° C., 2.16 kg load) of the linear propylene polymer portion is 270 g / 10 min, component of the linear ethylene / propylene random copolymer portion ratio is 20.3 wt% for the entire a-1, the intrinsic viscosity _{[eta] copoly} of linear ethylene-propylene random copolymer portion is 2.7 dl / g, component a-1 overall MFR (230 ℃, 2 .16 kg load) is 103 g / 10 min, the die swell ratio of the entire component A-1 is 1.0, and shows strain hardening in 180 ° C. elongational viscosity measurement (strain hardening “Yes”). The degree (λmax) is 1.16, the Q value of the whole component A-1 is 5.6, the ethylene content of the linear ethylene / propylene random copolymer portion is 39% by weight (measured by a cross fractionation method), straight Jo ethylene-propylene random copolymer portion having Mw of 350,000 (cross fractionation GPC measurement), linear propylene-ethylene block copolymer (antioxidant-neutralizing agent, added already pellets).

(A-2a): Polymerized with a Ziegler catalyst, MFR (230 ° C., 2.16 kg load) of the entire component A-2 is 30 g / 10 minutes, relative to the entire component A-2 of the ethylene / propylene random copolymer portion A propylene / ethylene block copolymer (oxidized) having a proportion of 15.7% by weight and an ethylene content of the ethylene / propylene random copolymer portion of 54% by weight (measured by the cross fractionation method ... measured by the same method as component A-1). Inhibitor, neutralizer, added pellets).

(2) Component B
(B-1): Ethylene / octene copolymer elastomer (manufactured by Dow Chemical Japan, MFR (230 ° C., 2.16 kg load) 59 g / 10 min, density 0.87 g / cm ³ , octene content 39 wt%) .
(B-2): Hydrogenated styrene-butadiene elastomer ((HSBR) manufactured by JSR Corporation, MFR (230 ° C., 2.16 kg load) 3.5 g / 10 min, density 0.89 g / cm ³ , styrene content 10 weight%).
(B-3): Ethylene / octene copolymer elastomer (Dow Chemical Japan, MFR (230 ° C., 2.16 kg load) 1.0 g / 10 min, density 0.87 g / cm ³ , octene content 39 weight %).

(3) Component C
(C-1): Chemical foaming agent master batch (Polyslen EE25C manufactured by Eiwa Kasei Co., Ltd., foaming agent concentration 20%, amount of generated gas 75 to 90 ml / 2.5 g (220 ° C. under constant temperature × 20 min)). Acid-based, low-density polyethylene base.

[Examples 1 to 6]
Components A to C were blended and blended in the proportions shown in Table 1, and performance evaluation was performed on those molded under the following conditions. The evaluation results are shown in Table 2.
1. Injection molding machine: “α-300” manufactured by FANUC.
2. Mold: 400 mm long × 200 mm wide, having a flat plate-shaped cavity with variable thickness by adjusting the position of the movable mold, and its initial cavity clearance (T ₀ ) is 1.3 mm.
3. Molding conditions: cylinder temperature 210 ° C., mold temperature 40 ° C., injection speed 220 mm / second, cooling time 30 seconds.
4). Molding method: mold-opening injection foaming in which the initial cavity clearance (T ₀ ) is 1.3 mm and the post-core-back cavity clearance (T ₁ ) is 3.5 mm.

[Comparative Examples 1-4]
Components A to C were blended and blended in the proportions shown in Table 1, and performance evaluation was performed on those molded under the same conditions as in Examples 1 to 6. The evaluation results are shown in Table 2.

  As shown in Tables 1 and 2, the linear polypropylene resin compositions and injection-foamed molded articles having the compositions shown in Examples 1 to 6 that satisfy the respective requirements in the essential constituent elements of the present invention are all good. It has excellent surface appearance, injection foaming moldability, impact strength, can be significantly reduced in weight, and is excellent in recyclability and environmental adaptability. Automotive parts, home appliances such as TV, electronic product parts, etc. It has become clear that it has a performance suitable for automobile interior parts such as industrial parts, building material parts, preferably automobile parts, especially trims, ceiling materials, trunks, instrument panels, pillars and the like.

On the other hand, the linear polypropylene resin compositions and injection-foamed molded articles having the compositions shown in Comparative Examples 1 to 4 are inferior due to their poor performance balance.
For example, in Comparative Example 1 containing no component B, although the surface appearance and injection foam moldability were the same as in Example 1, there was a significant difference in impact strength. This indicates that the impact strength is significantly improved by Component B, and it is essential that Component B satisfies the scope of the present invention.
Further, in Comparative Example 2 using (A-1b) as Component A, the surface appearance was at a level having practicality, but the injection foam moldability was significantly different from Example 5. This indicates that the component A is remarkably improved in injection foam moldability, and it is essential that component A satisfies the scope of the present invention.
Further, in Comparative Example 3 using (B-3) as Component B, the surface appearance was at a level having practicality, but a remarkable difference was produced in Example 2 and Example 4 in injection foam moldability. This indicates that the improvement in injection foaming moldability by component B is remarkable, and it is essential that component B satisfies the scope of the present invention.
In addition, as Comparative Example 4 in which 85% by weight of (A-2a) and 15% by weight of (A-1a) are used as Component A, the amount of Component B and the molding conditions are as in Example 3 and Example 3. Despite being the same as Example 6, there was a significant difference from Example 3 and Example 6 in surface appearance and injection foam moldability.
This shows that the effect of improving the surface appearance and injection foam moldability is remarkably different due to the difference in component A, and it is essential that component A satisfies the requirements of the present invention.

  From the results of the examples and comparative examples described above, the rationality and significance of the configuration and requirements of the present invention are verified, and the superiority of the present invention over the prior art is also apparent.

  The linear polypropylene-based resin composition and injection-foamed molded article of the present invention have a good surface appearance, injection-foaming moldability and impact strength, can be significantly reduced in weight, and are recyclable and environmentally compatible. In addition, automobile parts, home appliances such as television, industrial parts including electronic parts, etc., building material parts, preferably automobile parts, especially automobiles such as trims, ceiling materials, trunks, instrument panels, pillars, etc. It has performance suitable for interior parts.

Claims (5)

A linear propylene / ethylene block copolymer (component A-1) comprising a linear propylene polymer portion and a linear ethylene / propylene random copolymer portion and having the following characteristics (i) to (vi): ) A polypropylene resin (component A) composed of 30 to 100% by weight and other propylene polymer (component A-2) 0 to 70% by weight, and a melt flow rate (230 ° C., 2.16 kg load) of 2 An elastomer (component B) composed of an ethylene-based elastomer of 0.0 g / 10 min or more and / or a styrene-based elastomer having a melt flow rate (230 ° C., 2.16 kg load) of 0.5 g / 10 min or more, and a foaming agent (component C) and a method for producing an injection-foamed molded article comprising a linear polypropylene-based resin composition comprising:
The mold is composed of a fixed mold and a movable mold capable of moving forward and backward, and has a mold cavity clearance (T ₀ ) smaller than the mold cavity clearance (T ₁ ) corresponding to the shape position of the final product. An injection process in which a linear or polypropylene resin composition in a molten or semi-molten state is injected and filled into a mold cavity, and the movable mold is retracted to the mold cavity clearance (T ₁ ). A mold-opening injection molding method comprising a foaming step for filling a void in a mold cavity, and a method for producing an injection foamed molded product, and in the injection step for injection-filling a linear polypropylene resin composition, before foaming A method for producing an injection-foamed molded article, wherein molding is performed under a condition that an injection rate with respect to a molded article filling volume of 100% is 20% / second or more .
Characteristic (i): The melt flow rate (230 ° C., 2.16 kg load) of the linear propylene polymer portion is 150 g / 10 min or more.
Characteristic (ii): The ratio of the linear ethylene / propylene random copolymer portion to the entire linear propylene / ethylene block copolymer (component A-1) is 2 to 50% by weight.
Characteristics (iii): The intrinsic viscosity _{[eta] copoly} of linear ethylene-propylene random copolymer portion is 5.3~10.0dl / g.
Characteristic (iv): Melt flow rate (230 ° C., 2.16 kg load) exceeds 100 g / 10 min.
Characteristic (v): The die swell ratio is 1.2 to 2.5.
Characteristic (vi): Shows strain hardening in 180 ° C. extensional viscosity measurement. The ratio (Q value: Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the entire linear propylene / ethylene block copolymer (component A-1) is 7 to 13. The method for producing an injection-foamed molded article according to claim 1. The ethylene content of the linear ethylene / propylene random copolymer portion in the linear propylene / ethylene block copolymer (component A-1) is 15 to 15% with respect to the total amount of the linear ethylene / propylene random copolymer. It is 80 weight%, The manufacturing method of the injection foaming molding of Claim 1 or 2 characterized by the above-mentioned. The method for producing an injection-foamed molded article according to any one of claims 1 to 3, wherein the elastomer (component B) is contained in an amount of 1 to 50 parts by weight with respect to 100 parts by weight of the polypropylene resin (component A). . The injection foam molding according to claim 4, wherein the styrene elastomer in the elastomer (component B) is at least one selected from hydrogenated styrene-butadiene elastomer or styrene-ethylene-butylene-styrene block copolymer. Body manufacturing method .