JP2007270116A - Styrene-modified polyolefin resin particles, expandable resin particles, pre-expanded particles, and expanded molded articles - Google Patents

Abstract

An object of the present invention is to provide styrene-modified polyolefin resin particles capable of providing a foamed molded article having improved physical properties such as fusion rate, rigidity, impact resistance, and chemical resistance.
SOLUTION: A styrene-modified polyolefin resin particle containing 20 to 600 parts by weight of a styrene resin with respect to 100 parts by weight of a polyolefin resin, wherein the polyolefin resin is an ethylene homopolymer or ethylene and carbon number. A copolymer with 3 or more olefins, a density of 0.940 g / cm ³ or more, a shrinkage factor (g ′ value) of less than 1.0 and 0.4 or more, and 0.15 to 20 g / 10/2. It has a melt flow rate with a load of 16 kg and satisfies the relationship of the formula: MS> 110-100 × log (MFR) (where MS is the melt tension (mN) at 160 ° C., MFR is the melt flow rate). The above problem is solved by styrene-modified polyolefin resin particles characterized by the following.
[Selection] Figure 1

Description

  The present invention relates to styrene-modified polyolefin resin particles, expandable resin particles, pre-expanded particles, and a foam-molded product.

  Conventionally, foamed molded articles obtained by filling pre-expanded particles made of polystyrene resin into a mold and then foaming by heating are excellent in rigidity, heat insulation, light weight, water resistance and foam moldability. It is known that Therefore, this foaming molding is widely used as a buffer material or a heat insulating material for building materials. However, the foamed molded body made of polystyrene resin has a problem of poor chemical resistance and impact resistance.

  On the other hand, it is known that a foam molded article made of a polyolefin resin such as polyethylene or polypropylene is excellent in chemical resistance and impact resistance. Therefore, this foaming molding is used for automobile-related parts. However, since polyolefin-based resins have poor foaming agent retention properties, it is necessary to precisely control foam molding conditions. Therefore, there is a problem that the manufacturing cost is high. In addition, the foam molded body has a problem that the rigidity is inferior to that of a foam molded body made of polystyrene resin.

  In order to solve the problem of the foamed molded article composed of the polystyrene resin and the polyolefin resin, a foamed molded article obtained from particles obtained by mixing a polystyrene resin and a polyolefin resin has been reported. This foam molded article combines the excellent rigidity and foam moldability of polystyrene-based resins with the excellent chemical resistance and impact resistance of polyolefin-based resins.

  By the way, automobile-related parts may come into contact with chemicals such as plasticizers such as gasoline, kerosene, brake oil, and vinyl chloride, and may receive a strong impact. Therefore, high chemical resistance and impact resistance are required for the foam molded article used in this application, but the above foam molded article is insufficient.

Therefore, as a method for satisfying the above requirements, an ethylene-vinyl acetate copolymer (EVA), branched low-density polyethylene (LDPE), or linear low-density polyethylene (LLDPE) particles are added to a polyolefin-based resin with a polystyrene-based resin. A method of modifying and obtaining a foamed molded product from the modified particles has been proposed (Japanese Patent Laid-Open No. 2005-97555: Patent Document 1).
JP-A-2005-97555

  In the method described in the above publication, a foamed molded article having high chemical resistance and impact resistance can be obtained. However, for applications under more severe conditions such as exposure to high temperatures, it has been desired to provide a foamed molded article with further improved heat resistance and heat dimensional stability.

  The inventors of the present invention have reviewed the raw material of the foamed molded product in order to further improve the heat resistance and heating dimensional stability, and as a result, if a polyolefin-based resin having specific properties is used, the heat resistance and heating dimension are improved. The inventors have found that the stability can be further improved and have reached the present invention.

Thus, according to the present invention, styrene-modified polyolefin resin particles containing 20 to 600 parts by weight of styrene resin with respect to 100 parts by weight of polyolefin resin, wherein the polyolefin resin is an ethylene homopolymer or ethylene And a olefin having 3 or more carbon atoms, a density of 0.940 g / cm ³ or more, a shrinkage factor (g ′ value) of less than 1.0 and 0.4 or more, and 0.15 to 20 g / 10 minutes The relationship of the formula: MS> 110-100 × log (MFR) (where MS is the melt tension (mN) at 160 ° C., MFR is the melt flow rate) Styrene-modified polyolefin resin particles characterized by satisfying the above are provided.

Furthermore, according to the present invention, there is provided expandable resin particles comprising 100 parts by weight of the styrene-modified polyolefin resin particles and 5 to 25 parts by weight of a volatile foaming agent.
The present invention also provides pre-expanded particles having a bulk density of 0.01 to 0.2 g / cm ³ obtained by pre-expanding the styrene-modified polyolefin-based expandable resin particles.
Furthermore, a foamed molded article having a density of 0.01 to 0.2 g / cm ³ obtained by in-mold foam molding of the pre-expanded particles is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the foaming molding by which heat resistance and heating dimensional stability were further improved can be obtained with the styrene modified polyolefin resin particle using the polyolefin resin which has a specific property.

(Styrene modified polyolefin resin particles)
First, the polyolefin resin in the styrene modified polyolefin resin particles (hereinafter referred to as modified resin particles) of the present invention has the following properties (1) ethylene homopolymer or ethylene and an olefin having 3 or more carbon atoms. A copolymer,
(2) Density of 0.940 g / cm ³ or more (3) Contraction factor (g ′ value) of less than 1.0 and 0.4 or more
(4) Melt flow rate at a load of 2.16 kg from 0.15 to 20 g / 10/10 (5) Formula: MS> 110-100 × log (MFR) (where MS is the melt tension at 160 ° C. (mN ), MFR is a resin having a relationship of melt flow rate).

(1) The polyolefin resin is composed of an ethylene homopolymer or a copolymer of ethylene and an olefin having 3 or more carbon atoms.
Examples of the olefin having 3 or more carbon atoms include propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane (for example, vinylcyclopentane, Vinylcyclohexane), cyclic olefins (eg, norbornene, norbornadiene), dienes (eg, butadiene, 1,4-hexadiene) and the like. The proportion of the component derived from an olefin having 3 or more carbon atoms in the polyolefin-based resin is not particularly limited, but is preferably 50% by weight or less, and more preferably 20% by weight or less.
Styrene may be copolymerized with ethylene as long as the invention is not impaired.

(2) When the density is less than 0.940 g / cm ³ , the heat resistance of the foam is insufficient, which is not preferable. Density is preferably 0.944~0.964g / cm ^3, more preferably 0.950~0.960g / cm ^3.
Regarding (3) The shrinkage factor is a parameter that represents the degree of long-chain branching in the resin. The intrinsic viscosity at an absolute molecular weight three times the weight average molecular weight (Mw) and the same absolute molecular weight of a high-density polyethylene having no branching. The ratio to the intrinsic viscosity in When the shrinkage factor is 1.0, the foamability becomes poor, which is not preferable. When the shrinkage factor is less than 0.4, the expansion ratio decreases, which is not preferable. The contraction factor is more preferably 0.80 to 0.95.

Regarding (4) Next, when the MFR under 2.16 kg load is less than 0.15 g / 10 min and greater than 20 g / 10 min, it is difficult to perform foam molding, and the foam molded product has uniform cells. Is not preferable because it may not be obtained. The MFR is preferably 0.2 to 18 g / 10 minutes, and more preferably 2 to 10 g / 10 minutes.

About (5) Moreover, when the relationship of formula: MS> 110-100 * log (MFR) is not satisfy | filled, since the retention strength of a bubble may fall, it is unpreferable. As a result, it is difficult to increase the expansion ratio, and a foamed molded article having uniform bubbles may not be obtained. Here, FIG. 1 shows a graph in which MS of various polyethylene resins used in Examples is plotted on the vertical axis and MFR is plotted on the horizontal axis. In the figure, the solid line means MS = 110-100 × log (MFR). In the figure, ■ is a resin (HDPE) satisfying the relationship and density of MS> 110-100 × log (MFR), ● is a resin (HDPE) satisfying the density but not satisfying the relationship, and ▲ is the relationship A resin (LDPE) that satisfies the above but does not satisfy the density. Resins satisfying the relationship of MS> 110-100 × log (MFR) have good air bubble retention, uniform air bubbles, heat resistance and stable heating dimensions, as shown in the examples. A foam having further improved properties can be obtained. The above relationship is more preferably MS> 130-100 × log (MFR). Moreover, x is resin (HDPE) which does not satisfy only MFR of (4).

The upper limit of MS is preferably 240, and more preferably 180. If it exceeds 240, the expansion ratio may decrease, which is not preferable.
Furthermore, the polyolefin resin used in the present invention preferably has a weight average molecular weight (Mw) of 40,000 to 120,000 in terms of linear polyethylene. When Mw is less than 40000, the strength of the foamed molded product may be low, which is not preferable. When it is larger than 120,000, the viscosity of the polyolefin resin becomes high and foam molding may be difficult, which is not preferable.

  Moreover, it is preferable that ratio (Mw / Mn) of Mw and a number average molecular weight (Mn) is 3.5-10. By being in this range, the molecular weight distribution of the polyolefin-based resin can be narrowed, so that a foamed molded product with little variation in properties can be obtained. In addition, Mn means the value of linear polyethylene conversion.

  The polyolefin resin may or may not be crosslinked. When not crosslinked, there is an advantage that recycling is easy. The presence or absence of crosslinking can be determined by measuring the gel fraction. When the value is large, the crosslinking is large, and when the value is small, the crosslinking is small.

The polyolefin resin is not particularly limited as long as it has the above properties, and various resins can be used. For example, as the polyolefin resin, a resin obtained by the following method can be used.
That is, the polyolefin resin is preferably a resin obtained by polymerizing an olefin in the presence of a macromonomer.

  Here, the macromonomer is a homopolymer of ethylene having a vinyl group at the terminal or a copolymer of ethylene having a vinyl group at the terminal and an olefin having 3 or more carbon atoms, Mn of 2000 or more, and 2 to 5 It is preferable to have Mw / Mn. Examples of the olefin having 3 or more carbon atoms include propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane (for example, vinylcyclopentane, vinyl Cyclohexane) and the like. These olefins may be used alone or in combination of two or more.

  The Mn of the macromonomer is more preferably 5000 or more, and further preferably 10,000 or more. The upper limit is preferably 100,000. Further, Mw / Mn is more preferably 2 to 4, and further preferably 2 to 3.5.

Furthermore, when the number of vinyl ends per 1000 methylene carbons as the main chain of the macromonomer is X and the number of saturated ends per 1000 methylene carbons as the main chain of the macromonomer is Y, the formula Z = X / [(( X represented by (X + Y) × 2] is preferably 0.5 to 1. Z is more preferably 0.25 to 1. It is well known to those skilled in the art that the number of vinyl ends and saturated ends can be measured by ¹ H-NMR, ¹³ C-NMR or FT-IR. For example, in the case of ¹³ C-NMR, vinyl ends have peaks at 114 ppm and 139 ppm, and saturated ends have peaks at 32.3 ppm, 22.9 ppm, and 14.1 ppm, and the number can be measured from these peaks.

By copolymerizing the macromonomer and the olefin, a polyolefin resin suitable for use in the present invention can be obtained. Here, the ratio of the new resin other than the macromonomer to the total resin is preferably 1 to 99% by weight, more preferably 5 to 90% by weight, and still more preferably 30 to 80% by weight. The ratio of the new resin can be measured by comparing the GPC chart of the resin with the GPC chart of the macromonomer. Specifically, a peak derived from a new resin is determined by comparing both charts, and the ratio of the area of the peak to the area of all peaks corresponds to the ratio of the new resin.
More specifically, the polyolefin resin can be produced in accordance with, for example, the methods described in JP-A Nos. 2004-346304 and 2006-248013.

  An outline of the above method is described below. First, ethylene is polymerized in the presence of a catalyst comprising a crosslinked biscyclopentadienyl zirconium complex in which two cyclopentadienyl groups are crosslinked by a crosslinking group and a clay mineral treated with an organic compound, or ethylene And a olefin having 3 or more carbon atoms are copolymerized to produce a macromonomer. Examples of the complex include dimethylsilanediylbis (cyclopentadienyl) zirconium dichloride, diethylsilanediylbis (cyclopentadienyl) zirconium dichloride, diphenylsilanediylbis (cyclopentadienyl) zirconium dichloride, and the like.

Moreover, hectorite can be normally used as a clay mineral. Furthermore, examples of the organic compound include amine compounds such as N, N-dimethyl-octadecylamine and N, N-dioleylmethylamine.
Next, a polyolefin-based resin can be obtained by copolymerizing a macromonomer and an olefin in the presence of a crosslinked (cyclopentadienyl) (fluorenyl) zirconium complex. Examples of the complex include diphenylmethylene (1-cyclopentadienyl) (2,7-di-tert-butyl-9-fluorenyl) zirconium dichloride, diphenylmethylene (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride. Etc.

  As the olefin copolymerized with the macromonomer, an olefin having 2 or more carbon atoms can be used. Specifically, ethylene, propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane (for example, vinylcyclopentane, vinylcyclohexane) Etc. These olefins may be used alone or in combination of two or more.

The polyolefin resin may contain other resins without departing from the object of the present invention. As other resins, other polyolefin resins not having at least one of the above properties (1) to (5) are preferable. Examples of other polyolefin-based resins include α-olefin homopolymers and copolymers having 2 to 20 carbon atoms. Specifically, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, poly 1-butene, poly (4-methyl-1-pentene), poly 1-pentene, ethylene / propylene copolymer, Ethylene / 1-butene copolymer, propylene / 1-butene copolymer, ethylene / propylene / 1-butene copolymer, 4-methyl-1-pentene / ethylene copolymer, ethylene / propylene / polyene copolymer And various propylene block copolymers and propylene random copolymers.
The blending ratio of these other resins is preferably 50% by weight or less, and more preferably 5 to 30% by weight with respect to the total amount of polyolefin resin.

  For polyolefin resins, colorants, stabilizers, fillers (reinforcing materials), higher fatty acid metal salts, flame retardants, antistatic agents, lubricants, natural or synthetic oils, waxes, UV absorbers, weather resistance, as necessary. Additives such as stabilizers, anti-fogging agents, anti-blocking agents, slip agents, coating agents, and neutron shielding agents may be included. Among these, as the colorant, both inorganic and organic colorants (pigments or dyes) can be used. In particular, inorganic colorants such as iron oxide and carbon black are preferred.

Examples of the iron oxide include α-FeOOH (hydrous crystal) as a yellow type, α-Fe ₂ O ₃ as a red type, and (FeO) x (Fe ₂ O ₃ ) y as a black type. . In these iron oxides, part of Fe may be replaced with other metals such as Zn and Mg. Further, these iron oxides may be mixed and used in order to obtain a desired color. Among them, the black line _{(FeO) x (Fe 2 O} 3) is preferably Fe ₃ O ₄ contained to y.

  The iron oxide preferably has an average particle size of 0.1 to 1 μm, and more preferably 0.2 to 0.8 μm. The average particle size can be measured with a laser diffraction particle size distribution meter (Rodos manufactured by JEOL Ltd.).

  The iron oxide is preferably contained in the range of 1.5 to 70% by weight in the polyolefin resin, more preferably in the range of 5 to 40% by weight, and still more preferably in the range of 10 to 30% by weight. If it is less than 1.5% by weight, the polyolefin-based resin may not be sufficiently colored, which is not preferable. When the amount is more than 70% by weight, it is difficult to mix in the polyolefin resin, which is not preferable. In addition, since the specific gravity of iron oxide is larger than that of the polyolefin resin, the polyolefin resin particles become heavy, and it is difficult to uniformly impregnate the styrene monomer, which is not preferable.

Examples of carbon black include furnace black, channel black, thermal black, acetylene black, graphite, and carbon fiber.
Carbon black is preferably contained in the range of 1 to 50% by weight in the polyolefin resin, and more preferably in the range of 2 to 30% by weight. If it is less than 1% by weight, the polyolefin-based resin may not be sufficiently colored, which is not preferable. When it is more than 50% by weight, it is difficult to mix it in the polyolefin resin, which is not preferable.

A stabilizer plays the role which prevents oxidation deterioration, thermal deterioration, etc., and can use all well-known things. For example, a phenol type stabilizer, an organic phosphite type stabilizer, a thioether type stabilizer, a binderd amine type stabilizer, etc. are mentioned.
Examples of the filler include talc and glass, and the shape is not particularly limited, such as a spherical shape, a plate shape, or a fiber shape.

  Examples of higher aliphatic metal salts include salts of higher fatty acids such as stearic acid, oleic acid, and lauric acid with alkaline earth metals (magnesium, calcium, barium, etc.) and alkali metals (sodium, potassium, lithium, etc.). It is done.

  Examples of the styrene resin include resins derived from styrene monomers such as styrene, α-methylstyrene, p-methylstyrene, and t-butylstyrene. Further, the styrene resin may be a component composed of a copolymer of a styrene monomer and another monomer copolymerizable with the styrene monomer. Examples of other monomers include polyfunctional monomers such as divinylbenzene, and (meth) acrylic acid alkyl esters that do not contain a benzene ring in the structure such as butyl (meth) acrylate. You may use these other monomers in the range which does not exceed 5 weight% with respect to a styrene resin.

  The amount of the styrene resin is 20 to 600 parts by weight, preferably 100 to 550 parts by weight, and more preferably 130 to 500 parts by weight with respect to 100 parts by weight of the polyolefin resin. Moreover, when it exceeds 600 weight part, since the chemical resistance and impact resistance of a foaming molding fall, it is unpreferable. When it is less than 20 parts by weight, the rigidity of the foamed molded product is lowered, which is not preferable.

The modified resin particles have a cylindrical shape, a substantially spherical shape or a spherical shape having an L / D of 0.6 to 1.6 when the particle length is L and the average diameter is D, and the average particle size is 0.00. It is preferable that it is 3-3.0 mm.
When L / D is smaller than 0.6 or larger than 1.6 and the flatness is large, the mold is filled with the pre-foamed particles obtained from the modified resin particles to obtain a foamed molded product. This is not preferable because the filling property of the resin becomes worse.
Further, the shape is more preferably approximately spherical or spherical in order to improve the filling property.

  When the average particle size is less than 0.3 mm, when used for expandable resin particles, the retention of the foaming agent is lowered, and it is difficult to reduce the density, which is not preferable. If it exceeds 3.0 mm, the filling property tends to be poor, and it is difficult to make the foamed molded product thinner, which is not preferable.

(Expandable resin particles)
Expandable resin particles are particles obtained by impregnating the modified resin particles with a foaming agent.
Examples of the foaming agent include volatile foaming agents such as propane, n-butane, isobutane, pentane, isopentane, cyclopentane, hexane, and dimethyl ether. These foaming agents can be used alone or in admixture of two or more.

The content of the foaming agent is preferably 5 to 25 parts by weight with respect to 100 parts by weight of the modified resin particles.
The L / D and average particle diameter of the expandable resin particles can be set to the same level as the modified resin particles. Further, the shape is more preferably approximately spherical or spherical in order to improve the filling property.

(Pre-expanded particles)
Pre-expanded particles are particles obtained by pre-expanding the expandable resin particles.
The pre-expanded particles have a bulk density of 0.01 to 0.2 g / cm ³ . A preferred bulk density is 0.014 to 0.15 g / cm ³ . When the bulk density is less than 0.01 g / cm ³ , the closed cell ratio is reduced when foamed, and the strength of the foamed molded product obtained from the pre-expanded particles is not preferable. On the other hand, when it is larger than 0.2 g / cm ³ , the weight of the obtained foamed molded article increases, which is not preferable. The method for measuring the bulk density is described in the column of Examples.

(Foamed molded product)
The foam molded article is a molded article obtained by subjecting the above pre-expanded particles to in-mold foam molding.
The foamed molded product has a density of 0.01 to 0.2 g / cm ³ . A preferred density is 0.014 to 0.15 g / cm ³ . When the bulk density is less than 0.01 g / cm ³ , the closed cell ratio increases, which is not preferable because the strength decreases. On the other hand, when it is larger than 0.2 g / cm ³ , the weight increases, which is not preferable. The method for measuring the density is described in the column of Examples.

In addition to excellent chemical resistance, impact strength, and rigidity, the foamed molded article has further improved heat resistance and heat dimensional stability.
The foamed molded product of the present invention can be used for various applications, but can be used for various applications such as bumper core materials, vehicle cushioning materials such as door interior cushioning materials, electronic parts, various industrial materials, food transport containers, etc. . In particular, it can be suitably used for a vehicle cushioning material.

(Modified resin particles, expandable resin particles, pre-expanded particles, and foamed molded body production method)
First, the modified resin particles can be produced, for example, as follows.
That is, 100 parts by weight of the polyolefin resin particles, 20 to 600 parts by weight of a styrene monomer, and a polymerization initiator are dispersed in an aqueous suspension. A styrene monomer and a polymerization initiator may be mixed and used in advance.

  The polyolefin resin particles can be obtained by a known method. For example, a polyolefin resin is melt-kneaded in an extruder together with an inorganic nucleating agent and additives as necessary to obtain a strand, and the obtained strand is cut in air, cut in water, The method of granulating by cutting while heating is mentioned.

  The polyolefin resin particles are cylindrical, substantially spherical or spherical with L / D of 0.6 to 1.6, where L is the particle length and D is the average diameter, and the average particle size is 0. It is preferable that it is 2-1.5 mm. When L / D is smaller than 0.6 or larger than 1.6 and the flatness is large, pre-foaming is performed as expandable resin particles, and filling the mold to obtain a foamed molded product, filling the mold It is not preferable because the properties tend to deteriorate. Further, the shape is more preferably approximately spherical or spherical in order to improve the filling property. When the average particle size is less than 0.2 mm, the retention of the foaming agent is lowered, and it is difficult to reduce the density, which is not preferable. When it exceeds 1.5 mm, not only is the filling property worsened, but it is also difficult to make the foamed molded product thinner, which is not preferable.

Examples of the inorganic nucleating agent include talc, silicon dioxide, mica, clay, zeolite, calcium carbonate and the like.
The amount of the inorganic nucleating agent used is preferably 2 parts by weight or less, more preferably 0.2 to 1.5 parts by weight with respect to 100 parts by weight of the polyolefin resin.
Examples of the aqueous medium constituting the aqueous suspension include water and a mixed medium of water and a water-soluble solvent (for example, lower alcohol).

  As the polymerization initiator, those generally used as an initiator for suspension polymerization of a styrene monomer can be used. For example, benzoyl peroxide, di-t-butyl peroxide, t-butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butylperoxy- Organic peroxides such as 3,5,5-trimethylhexanoate and t-butyl-peroxy-2-ethylhexyl carbonate. These polymerization initiators may be used alone or in combination of two or more.

  0.1-0.9 weight part is preferable with respect to 100 weight part of styrene-type monomers, and, as for the usage-amount of a polymerization initiator, 0.2-0.5 weight part is more preferable. If it is less than 0.1 part by weight, polymerization of the styrene monomer may take too much time, which is not preferable. Use of a polymerization initiator exceeding 0.9 parts by weight is not preferable because the molecular weight of the styrene resin may be lowered.

  A dispersant may be added to the aqueous suspension as necessary. The dispersant is not particularly limited, and any known dispersant can be used. Specific examples include hardly soluble inorganic substances such as calcium phosphate, magnesium pyrophosphate, sodium pyrophosphate, magnesium oxide. Further, a surfactant such as sodium dodecylbenzenesulfonate may be used.

Next, the obtained dispersion is heated to a temperature at which the styrene monomer is not substantially polymerized to impregnate the polyolefin resin particles with the styrene monomer.
The time for impregnating the polyolefin resin particles with the styrene monomer is suitably from 30 minutes to 2 hours. This is because if the polymerization proceeds before sufficient impregnation, a polymer powder of styrene resin is produced. The higher the temperature at which the monomer is not substantially polymerized, the more advantageous is to increase the impregnation rate, but it is necessary to determine it in consideration of the decomposition temperature of the polymerization initiator.

Next, the styrene monomer is polymerized. Although superposition | polymerization is not specifically limited, It is preferable to carry out at 115-140 degreeC for 1.5 to 5 hours. The polymerization is usually carried out in an airtight container that can be pressurized.
The impregnation and polymerization of the styrene monomer may be performed in a plurality of times. By dividing into multiple times, the generation of polystyrene polymer powder can be minimized.
The modified resin particles can be obtained by the above process.

  Next, the expandable resin particles can be obtained by impregnating the modified resin particles during or after the polymerization with a foaming agent. This impregnation can be performed by a method known per se. For example, the impregnation during the polymerization can be performed by performing the polymerization reaction in a sealed container and press-fitting a foaming agent into the container. The impregnation after the completion of the polymerization is performed by press-fitting a foaming agent in a sealed container.

Further, the pre-expanded particles can be obtained by pre-expanding the expandable resin particles to a predetermined bulk density by a known method.
Further, the foam molded body can be obtained by filling the foamed particles with heat while fusing the pre-foamed particles by filling the pre-foamed particles into a mold of a foam molding machine and heating the foamed pre-foamed particles again. Water vapor can be suitably used as the heating medium.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, the density of polyolefin resin in the following examples, shrinkage factor, MS, MFR, Mn and Mw, the number of vinyl terminals and the number of saturated terminals of the macromonomer, the bulk density, the density of the foamed molded product, the fusion rate, the heating dimension The method for measuring the rate of change and chemical resistance is described below.

(Polyolefin resin density)
The density of the polyolefin resin is measured by the density gradient tube method in accordance with JIS K6922-1: 1998.

(Shrink factor)
The shrinkage factor was obtained by dividing [η] at an absolute molecular weight three times Mw obtained by the method of measuring [η] of a polyolefin resin fractionated by GPC by [η] at the same molecular weight of HDPE having no branching. Value. The GPC apparatus used for the measurement was HLC-8121GPC / HT manufactured by Tosoh Corporation, TSKgel GMHhr-H (20) HT manufactured by Tosoh Corporation was used as the column, the column temperature was set at 45 ° C., and 1,2 as the eluent. , 4-trichlorobenzene is used. The measurement sample is adjusted to a concentration of 2.0 mg / ml, and the amount injected into the GPC device is 0.3 ml. As a viscometer, a capillary differential pressure viscometer 210R + manufactured by Viscotek is used.

(MS)
MS is equipped with a capillary viscometer (capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a barrel diameter of 9.55 mm and a die with a length (L) of 8 mm, a diameter (D) of 2.095 mm, and an inflow angle of 90 °. Measure with The sample temperature is set to 160 ° C., the piston lowering speed is set to 10 mm / min, the stretch ratio is set to 47, and the load (mN) required for taking-up under this setting is MS.

(MFR)
MFR is measured at 190 ° C. and a 2.16 kg load in accordance with JIS K6922-1: 1998.

(Mn and Mw)
The GPC apparatus used for the measurement was HLC-8121GPC / HT manufactured by Tosoh Corporation, TSKgel GMHhr-H (20) HT manufactured by Tosoh Corporation was used as the column, the column temperature was set to 140 ° C., and 1,2 as the eluent. , 4-trichlorobenzene is used. The measurement sample is adjusted to a concentration of 1.0 mg / ml, and the amount injected into the GPC device is 0.3 ml. The calibration curve for each molecular weight is calibrated using a polyethylene sample with a known molecular weight. Mn and Mw are determined as linear polyethylene equivalent values.

(Number of vinyl ends and saturated ends of macromonomer)
The terminal structure of the macromonomer is confirmed by ¹³ C-NMR using a JNM-ECA400 nuclear magnetic resonance apparatus manufactured by JEOL. The solvent used tetrachloroethane -d _2. The number of vinyl ends (X) is determined from the average value of the peaks at 114 ppm and 139 ppm as the number per 1000 main chain methylene carbons (chemical shift: 30 ppm). On the other hand, the number of saturated terminals (Y) is determined from the average values of 32.3 ppm, 22.9 ppm, and 14.1 ppm peaks, similarly to the number of vinyl terminal groups. From the obtained vinyl terminal number X and saturated terminal number Y, Z is determined by the formula Z = X / [(X + Y) × 2].

(Crystallinity)
The crystallinity is determined by DSC measurement. Specifically, a polyolefin resin sample is held at 50 ° C. for 1 minute. Next, the temperature is raised to 180 ° C. at a rate of 200 ° C./min and held at 180 ° C. for 5 minutes. Further, the temperature is lowered to 50 ° C. at 10 ° C./min, and held at 50 ° C. for 5 minutes. Thereafter, the temperature is raised to 180 ° C. at 10 ° C./min. In the melting curve obtained at that time, a baseline is drawn from 60 ° C to 145 ° C. The melting enthalpy (ΔH (J / g)) is calculated from this baseline and the melting curve. The crystallinity X (%) is calculated by substituting the melting enthalpy into the following equation.
X = ΔH × 100/293

(The bulk density)
The bulk density of the pre-expanded particles is measured as follows.
First, pre-expanded particles are filled in a measuring cylinder to a scale of 500 cm ³ . However, the graduated cylinder is visually observed from the horizontal direction, and if at least one pre-expanded particle reaches the scale of 500 cm ³ , the filling is finished. Next, the weight of the pre-expanded particles filled in the graduated cylinder is weighed with two significant figures after the decimal point, and the weight is defined as W (g). The bulk density of the pre-expanded particles is calculated by the following formula.
Bulk density (g / cm ³ ) = W / 500

(Density of foam molding)
The density of the foamed molded product is measured by the method described in JIS A 9511: 1995 “Foamed plastic heat insulating plate”.

(Fusion rate)
The upper surface of 400 mm long × 300 mm wide has a rectangular parallelepiped shaped foam molded body with a thickness of 30 mm. A cutting line with a length of 300 mm and a depth of about 5 mm is put along the horizontal direction with a cutter. Then divide the foamed molded product into two parts. And about the expanded particle of the fractured surface of the divided foamed product, the number of expanded particles broken in the expanded particle (a) and the number of expanded particles broken at the interface between the expanded particles (b) Measure and calculate the fusing rate based on the following formula.
Fusing rate (%) = 100 × (a) / [(a) + (b)]

(Heating dimensional change rate)
The heating dimensional change rate is measured by the B method described in JIS K6767: 1999 “Foamed Plastics—Polyethylene Test Method”. A test piece having a top surface of 150 mm in length and 150 mm in width and having a thickness of 50 mm is cut out from the foam molded article. Three straight lines are written in the center of the upper surface of the test piece in parallel with each other along the vertical and horizontal directions so as to have an interval of 50 mm. Then, the test piece is placed in a 90 ° C hot air circulating dryer for 22 hours and then taken out and left in a standard state (20 ± 2 ° C, humidity 65 ± 5%) for 1 hour, then the vertical and horizontal line dimensions. Measure. The average value of the length of the straight line before heating is L1, the average value of the length of the straight line after heating is L0, and the heating dimensional change rate is calculated based on the following formula.
Heating dimensional change rate S = 100 × (L1-L0) / L0
The evaluation of the heating dimensional change rate was as follows: ○: 0 ≦ S <3; the dimensional change rate was low, and the dimensional stability was good.
Δ: 3 ≦ S <7; Although a dimensional change was observed, it was practically usable.
X: S ≧ 7; dimensional change was remarkably seen, and practical use was impossible.

(chemical resistance)
A flat rectangular plate-shaped test piece having a length of 100 mm, a width of 100 mm, and a thickness of 20 mm is cut out from the foamed molded article and left to stand at 23 ° C. and a humidity of 50% for 24 hours. In addition, a test piece is cut out from a foaming molding so that the upper surface whole surface of a test piece may be formed from the surface of a foaming molding.
Next, 1 g of gasoline is uniformly applied to the upper surface of the test piece, and left for 60 minutes under the conditions of 23 ° C. and 50% humidity. Then, the chemical | medical agent is wiped off from the upper surface of a test piece, the upper surface of a test piece is visually observed, and it judges based on the following reference | standard.
○: Good No change △: Slightly bad Surface softening ×: Bad Surface depression (shrinkage)

Production Examples Production examples of resins A to K used in Examples and Comparative Examples are described below. The following production examples were performed under an inert gas atmosphere. Moreover, the raw material and solvent which were used for each manufacture example used what was refine | purified previously, dried, and deoxygenated by the well-known method. As component a and component c, those synthesized by a known method were used. Moreover, the Tosoh Finechem company make was used for the hexane solution (0.714M) of triisobutylaluminum.

Production Example 1
[Preparation of clay mineral (component b) treated with organic compound]
To 3 liters of water, 3 liters of ethanol and 250 ml of 37% concentrated hydrochloric acid were added. After adding 330 g (1.1 mol) of N, N-dimethyl-octadecylamine to the resulting solution, the solution was heated to 60 ° C. By this heating, the amine was converted into hydrochloric acid. A suspension was obtained by adding 1 kg of hectorite to the obtained solution. The suspension was stirred at 60 ° C. for 3 hours, and after removing the supernatant, it was washed with 5 liters of water at 60 ° C. Furthermore, the modified hectorite (component b) having an average particle diameter of 4.5 μm could be obtained by drying at 60 ° C. and 10 ⁻³ torr (about 0.13 Pa) for 24 hours and pulverizing with a jet mill.

[Adjustment of macromonomer production catalyst]
6.97 g (20 mmol) of dimethylsilanediylbis (cyclopentadienyl) zirconium dichloride (component a) was suspended in 2.07 liters of hexane. A contact product of component a and triisobutylaluminum was obtained by adding 2.93 liters of a hexane solution (0.714M) of triisobutylaluminum to the obtained suspension. 500 g of the modified hectorite (component b) was added to the solution containing the contact product. The resulting solution was stirred at 60 ° C. for 3 hours, then allowed to stand, then the supernatant was removed, and the residue was washed with a heptane solution of triisobutylaluminum (0.03M). Further, a hexane solution (0.15 M) of triethylaluminum was added to the washed product to obtain a catalyst slurry (100 g / liter).

[Manufacture of macromonomer]
After putting 30 liters of hexane and 25 ml of a hexane solution of triisobutylaluminum (0.714 mol / liter) into a 50 liter autoclave, the internal temperature of the autoclave was raised to 90 ° C. 125 ml of the catalyst slurry was added to the autoclave, ethylene was introduced until the partial pressure reached 1.2 MPa, and then polymerization was started. During the polymerization, ethylene was continuously introduced so that the partial pressure of ethylene was maintained at 1.2 MPa. The polymerization temperature was 90 ° C.

Sixteen minutes after the start of polymerization, the internal temperature was lowered to 50 ° C., the internal pressure of the autoclave was depressurized to 0.1 MPa, and then nitrogen was introduced until the internal pressure reached 0.6 MPa. This operation was repeated 5 times to obtain a macromonomer.
The Mn of the macromonomer was 9000 and Mw / Mn was 2.3. When the terminal structure of the macromonomer was analyzed by NMR, Z was 0.57.

[Manufacture of polyolefin resin]
After introducing 25 mL of a hexane solution of triisobutylaluminum (0.714 mol / liter) into a 50 liter autoclave containing the macromonomer, the internal temperature of the autoclave was raised to 85 ° C. After stirring for 30 minutes while maintaining this temperature, the autoclave was charged with diphenylmethylene (1-cyclopentadienyl) (2,7-di-tert-butyl-9-fluorenyl) zirconium dichloride (component c) 0.25 mmol. 0.5 liter of toluene solution was added. After the addition, the mixture was stirred for 1 hour while maintaining the temperature.

  Next, ethylene was introduced into the autoclave until the partial pressure reached 0.1 MPa to initiate polymerization. During the polymerization, ethylene was continuously introduced so that the partial pressure was maintained at 0.1 MPa. The polymerization temperature was maintained at 85 ° C. 180 minutes after the start of polymerization, the internal pressure of the autoclave was released. The contents were removed by suction filtration, and the resulting loaf was dried to obtain 3.3 kg of high-density polyethylene resin D.

  Mw of the obtained resin was 133000, Mw / Mn was 10.9, and the ratio of the newly produced resin amount to the total resin amount was 28% by weight. Further, MFR, density, crystallinity, MS, 110-100 × log MFR and shrinkage factor of the obtained resin were measured, and the results are shown in Table 1.

Production Example 2
[Manufacture of macromonomer]
A 50 liter autoclave was charged with 30 liters of hexane, 120 g of butene-1 and 25 ml of a hexane solution of triisobutylaluminum (0.714 mol / liter), and then the internal temperature of the autoclave was raised to 90 ° C. 125 ml of the catalyst slurry was added to the autoclave and a hydrogen / ethylene mixed gas (0.63 mmol / mo1) was introduced until the partial pressure reached 1.2 MPa, and then polymerization was started. During the polymerization, a hydrogen / ethylene mixed gas was continuously introduced so that the partial pressure of ethylene was maintained at 1.2 MPa. The polymerization temperature was 90 ° C.

25 minutes after the start of polymerization, the internal temperature was lowered to 50 ° C., the internal pressure of the autoclave was depressurized to 0.1 MPa, and then nitrogen was introduced until the internal pressure reached 0.6 MPa. This operation was repeated 5 times to obtain a macromonomer.
The Mn of the macromonomer was 8500 and Mw / Mn was 2.2. When the terminal structure of the macromonomer was analyzed by NMR, Z was 0.60.

[Manufacture of polyolefin resin]
After introducing 25 mL of a hexane solution of triisobutylaluminum (0.714 mol / L) into a 50 liter autoclave containing the macromonomer, the internal temperature of the autoclave was raised to 85 ° C. After stirring for 30 minutes while maintaining this temperature, the autoclave was charged with diphenylmethylene (1-cyclopentadienyl) (2,7-di-tert-butyl-9-fluorenyl) zirconium dichloride (component c) 0.25 mmol. 0.5 liter of toluene solution was added. After the addition, the mixture was stirred for 1 hour while maintaining the temperature.

  Next, 10 g of butene-1 was added to the autoclave, and a hydrogen / ethylene mixed gas (0.63 mmol / mo1) was introduced until the partial pressure reached 0.1 MPa to initiate polymerization. During the polymerization, a hydrogen / ethylene mixed gas was continuously introduced so that the partial pressure was maintained at 0.1 MPa. The polymerization temperature was maintained at 85 ° C. 180 minutes after the start of polymerization, the internal pressure of the autoclave was released. The contents were removed by suction filtration, and the resulting loaf was dried to obtain 4.2 kg of high-density polyethylene resin C.

  Mw of the obtained resin was 64000, Mw / Mn was 6.8, and the ratio of the newly generated resin amount to the total resin amount was 11% by weight. Further, MFR, density, crystallinity, MS, 110-100 × log MFR and shrinkage factor of the obtained resin were measured, and the results are shown in Table 1.

Production Example 3
A macromonomer was obtained in the same manner as in Production Example 1 except that the pressure was released 35 minutes after the initiation of polymerization. The Mn of the macromonomer was 9000 and Mw / Mn was 2.3. When the terminal structure of the macromonomer was analyzed by NMR, Z was 0.57.
4.5 kg by polymerizing in the same manner as in Production Example 1 except that the above macromonomer was used and diphenylmethylene (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride (component c) was used. High density polyethylene resin E was obtained.

  Mw of the obtained resin was 63000, Mw / Mn was 6.3, and the ratio of the newly generated resin amount to the total resin amount was 14% by weight. Further, MFR, density, crystallinity, MS, 110-100 × log MFR and shrinkage factor of the obtained resin were measured, and the results are shown in Table 1.

Production Example 4
A macromonomer was prepared in the same manner as in Production Example 3, except that 135 g of butene-1 was used, the polymerization temperature was 75 ° C., a hydrogen / ethylene mixed gas of 0.68 mmol / mol was used, and the pressure was released 90 minutes after the start of polymerization. Got. The Mn of the macromonomer was 8300 and Mw / Mn was 2.2. When the terminal structure of the macromonomer was analyzed by NMR, Z was 0.62.

A high density of 4.7 kg is obtained by performing polymerization in the same manner as in Production Example 2 except that 11 g of butene-1 is used and a hydrogen / ethylene mixed gas of 0.68 mmol / mo1 is used. Polyethylene resin G was obtained.
Mw of the obtained resin was 75000, Mw / Mn was 6.1, and the ratio of the newly generated resin amount to the total resin amount was 20% by weight. Further, MFR, density, crystallinity, MS, 110-100 × log MFR and shrinkage factor of the obtained resin were measured, and the results are shown in Table 1.

Production Example 5
A macromonomer was prepared in the same manner as in Production Example 2, except that 290 g of butene-1 was used, the polymerization temperature was 75 ° C., a hydrogen / ethylene mixed gas of 0.65 mmol / mol was used, and the pressure was released 90 minutes after the start of polymerization. Got. The Mn of the macromonomer was 8000, and Mw / Mn was 2.1. When the terminal structure of the macromonomer was analyzed by NMR, Z was 0.70.

A high density of 4.2 kg is obtained by performing polymerization in the same manner as in Production Example 2 except that the above macromonomer is used, 25 g of butene-1 is used, and a hydrogen / ethylene mixed gas of 0.65 mmol / mo1 is used. Polyethylene resin A was obtained.
Mw of the obtained resin was 88000, Mw / Mn was 5.0, and the ratio of the newly generated resin amount to the total resin amount was 23% by weight. Further, MFR, density, crystallinity, MS, 110-100 × log MFR and shrinkage factor of the obtained resin were measured, and the results are shown in Table 1.

Production Example 6
A macromonomer was prepared in the same manner as in Production Example 3, except that 135 g of butene-1 was used, the polymerization temperature was 75 ° C., a hydrogen / ethylene mixed gas of 0.48 mmol / mol was used, and the pressure was released 90 minutes after the start of polymerization. Got. The Mn of the macromonomer was 8500 and Mw / Mn was 2.2. When the terminal structure of the macromonomer was analyzed by NMR, Z was 0.60.

A high density of 4.7 kg is obtained by performing polymerization in the same manner as in Production Example 2 except that 11 g of butene-1 is used and a hydrogen / ethylene mixed gas of 0.48 mmol / mo1 is used. Polyethylene resin H was obtained.
Mw of the obtained resin was 97000, Mw / Mn was 5.6, and the ratio of the newly generated resin amount to the total resin amount was 25% by weight. Further, MFR, density, crystallinity, MS, 110-100 × log MFR and shrinkage factor of the obtained resin were measured, and the results are shown in Table 1.

Production Example 7
A macromonomer was obtained in the same manner as in Production Example 1 except that the polymerization temperature was 70 ° C. and the pressure was released 90 minutes after the start of polymerization. The Mn of the macromonomer was 9000 and Mw / Mn was 2.3. When the terminal structure of the macromonomer was analyzed by NMR, Z was 0.57.

Polymerization was conducted in the same manner as in Production Example 1 except that the above macromonomer was used to obtain 4.7 kg of high-density polyethylene resin I.
Mw of the obtained resin was 94000, Mw / Mn was 5.5, and the ratio of the newly generated resin amount to the total resin amount was 27% by weight. Further, MFR, density, crystallinity, MS, 110-100 × log MFR and shrinkage factor of the obtained resin were measured, and the results are shown in Table 1.

  In the table, resin type B is LDPE (Tosoh Petrocene 225), and resin types F, J, and K are HDPE, which are Tosoh Nipolon Hard 2300, 2400, and 8500, respectively.

Example 1
100 parts by weight of high-density polyethylene resin A was supplied to an extruder, melted and kneaded, and granulated by an underwater cutting method to obtain elliptical (egg-like) high-density polyethylene resin particles. The average weight of the resin particles was 0.6 mg.
Next, 10 g of magnesium pyrophosphate and 0.5 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water in a 5 liter autoclave equipped with a stirrer to obtain a dispersion medium.

600 g of the above high-density polyethylene resin particles were dispersed in a dispersion medium at 30 ° C. and held for 10 minutes, and then heated to 60 ° C. to obtain a suspension.
Further, 0.26 kg of a styrene monomer in which 0.5 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to this suspension over 30 minutes. After dropping, the styrene monomer was impregnated in the high density polyethylene resin particles by holding for 30 minutes. After impregnation, the temperature was raised to 140 ° C., and polymerization was carried out at this temperature for 2 hours (first polymerization).

  Next, 1.14 kg of a styrene monomer in which 4 g of dicumyl peroxide was dissolved was dropped into the suspension lowered to 125 ° C. over 4 hours. After dropping, the high-density polyethylene resin particles were impregnated with a styrene monomer by holding at 125 ° C. for 1 hour. After impregnation, the temperature was raised to 140 ° C., and this temperature was maintained for 2 hours and 30 minutes for polymerization (second polymerization). As a result of this polymerization, modified resin particles could be obtained.

  Subsequently, it cooled to normal temperature (about 23 degreeC), and took out the modified resin particle from the autoclave. 2 kg of modified resin particles and 2 liters of water were placed in a 5 liter autoclave with a stirrer. Furthermore, 10 g of diisobutyl adipate as a plasticizer and 520 ml (300 g) of butane as a foaming agent were placed in an autoclave. Thereafter, the temperature was raised to 70 ° C. and the stirring was continued for 4 hours to obtain expandable resin particles.

Thereafter, the mixture was cooled to room temperature, and the expandable resin particles were taken out from the autoclave and dehydrated and dried.
Next, pre-expanded particles were obtained by pre-expanding the obtained expandable resin particles to a bulk density of 0.025 g / cm ³ . The obtained pre-expanded particles were allowed to stand at room temperature (23 ° C.) for 1 day, and then placed in a molding die having a size of 400 mm × 300 mm × 30 mm. Thereafter, 0.2 MPa of water vapor is introduced for 50 seconds and heated, and then cooled until the maximum surface pressure of the foamed molded product is reduced to 0.001 MPa, whereby a foamed molded product having a density of 0.025 g / cm ³ is obtained. Obtained. Both the appearance and fusion of the obtained foamed molded article were good. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 2.

Example 2
1000 g of high density polyethylene resin A is used, 0.8 g of dicumyl peroxide and 0.43 kg of styrene monomer are used in the first polymerization, and 3 g of dicumyl peroxide and 0. Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that 57 kg was used and the dropping time was 3 hours.

Next, pre-expanded particles were obtained by pre-expanding the obtained expandable resin particles to a bulk density of 0.033 g / cm ³ . Further, a foamed molded article having a density of 0.033 g / cm ³ was obtained in the same manner as in Example 1. Both the appearance and fusion of the obtained foamed molded article were good. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 2.

Example 3
In the first polymerization, 340 g of high-density polyethylene resin A was used, 0.3 g of dicumyl peroxide and 0.15 kg of styrene monomer were used, and in the second polymerization, 5 g of dicumyl peroxide and 1. Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that 51 kg was used and the dropping time was 5 hours.

Next, pre-expanded particles were obtained by pre-expanding the obtained expandable resin particles to a bulk density of 0.020 g / cm ³ . Further, a foamed molded product having a density of 0.020 g / cm ³ was obtained in the same manner as in Example 1. Both the appearance and fusion of the obtained foamed molded article were good. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 2.

Example 4
1400 g of high density polyethylene resin A is used, 0.4 g of dicumyl peroxide and 0.20 kg of styrene monomer are used in the first polymerization, and 2 g of dicumyl peroxide and 0.2 g of styrene monomer are used in the second polymerization. Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that 50 kg was used and the dropping time was 2.5 hours.

Next, the foamable resin particles obtained were prefoamed to a bulk density of 0.050 g / cm ³ to obtain prefoamed particles. Further, a foamed molded article having a density of 0.050 g / cm ³ was obtained in the same manner as in Example 1. Both the appearance and fusion of the obtained foamed molded article were good. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 2.

Example 5
Modified resin particles, expandable resin particles, pre-expanded particles (bulk density 0.025 g / cm ³ ), as in Example 1, except that high-density polyethylene resin C is used instead of high-density polyethylene resin A A foamed molded product (density 0.025 g / cm ³ ) was obtained. Both the appearance and fusion of the obtained foamed molded article were good. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 2.

Example 6
Modified resin particles, expandable resin particles, pre-expanded particles (bulk density 0.1 g / cm ³ ), as in Example 1, except that high-density polyethylene resin D is used instead of high-density polyethylene resin A A foamed molded product (density 0.1 g / cm ³ ) was obtained. Both the appearance and fusion of the obtained foamed molded article were good. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 2.

Example 7
Modified resin particles, expandable resin particles, pre-expanded particles (bulk density 0.12 g / cm ³ ), as in Example 1, except that high-density polyethylene resin E is used instead of high-density polyethylene resin A A foamed molded product (density 0.12 g / cm ³ ) was obtained. Both the appearance and fusion of the obtained foamed molded article were good. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 2.

Example 8
Modified resin particles, expandable resin particles, pre-expanded particles (bulk density 0.033 g / cm ³ ), as in Example 1, except that high-density polyethylene resin I is used instead of high-density polyethylene resin A A foamed molded article (density 0.033 g / cm ³ ) was obtained. Both the appearance and fusion of the obtained foamed molded article were good. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 2.

Comparative Example 1
Modified resin particles, expandable resin particles, pre-expanded particles (bulk density 0.025 g / cm ³ ), as in Example 1, except that low-density polyethylene resin B is used instead of high-density polyethylene resin A A foamed molded product (density 0.025 g / cm ³ ) was obtained. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 3.

Comparative Example 2
Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that high-density polyethylene resin F was used instead of high-density polyethylene resin A. The obtained expandable resin particles were pre-expanded, but hardly expanded, and no expandable pre-expanded particles were obtained.

Comparative Example 3
250 g of high-density polyethylene resin A is used, 0.2 g of dicumyl peroxide and 0.1 kg of styrene monomer are used in the first polymerization, and 5 g of dicumyl peroxide and 1. g of styrene monomer are used in the second polymerization. Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that 65 kg was used and the dropping time was 5 hours.

Next, pre-expanded particles were obtained by pre-expanding the obtained expandable resin particles to a bulk density of 0.020 g / cm ³ . Further, a foamed molded product having a density of 0.020 g / cm ³ was obtained in the same manner as in Example 1. Both the appearance and fusion of the obtained foamed molded article were good. The fusion molding rate, heating dimensional change rate, and chemical resistance of the obtained foamed molded product were measured. The results are shown in Table 3.

Comparative Example 4
1750 g of high density polyethylene resin A is used, 0.1 g of dicumyl peroxide and 0.06 kg of styrene monomer are used in the first polymerization, and 1 g of dicumyl peroxide and 0.1 g of styrene monomer are used in the second polymerization. Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that 2 kg was used and the dropping time was 1.5 hours. The obtained expandable resin particles were pre-expanded, but hardly expanded, and no expandable pre-expanded particles were obtained.

Comparative Example 5
Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that high-density polyethylene resin G was used instead of high-density polyethylene resin A. The obtained expandable resin particles were pre-expanded, but hardly expanded, and no expandable pre-expanded particles were obtained.

Comparative Example 6
Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that high-density polyethylene resin H was used instead of high-density polyethylene resin A. The obtained expandable resin particles were pre-expanded, but hardly expanded, and no expandable pre-expanded particles were obtained.

Comparative Example 7
Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that high-density polyethylene resin J was used instead of high-density polyethylene resin A. The obtained expandable resin particles were pre-expanded, but hardly expanded, and no expandable pre-expanded particles were obtained.

Comparative Example 8
Modified resin particles and expandable resin particles were obtained in the same manner as in Example 1 except that high-density polyethylene resin K was used instead of high-density polyethylene resin A. The obtained expandable resin particles were pre-expanded, but hardly expanded, and no expandable pre-expanded particles were obtained.

Tables 2 and 3 show the following.
It can be seen from Example 1 and Comparative Example 1 that if a high-density polyethylene resin having specific properties is used, a foamed molded article having an improved heating dimensional change rate can be obtained.
It can be seen from Examples 1 to 8 that a foamed molded article excellent in both the heating dimensional change rate and the chemical resistance can be obtained when the shrinkage factor is in a specific range. It can be seen from Comparative Examples 7 and 8 that when the shrinkage factor is outside a specific range, it is difficult to obtain the foamed molded product itself.

  By Examples 1-8, it turns out that the foaming molding which was excellent in both the heating dimensional change rate and chemical-resistance can be obtained because MFR is a specific range. From Comparative Examples 5 and 6, it can be seen that it is difficult to obtain a foamed molded product itself when the MFR is outside a specific range.

  It can be seen from Examples 1 to 8 that a foamed molded article excellent in both the heating dimensional change rate and the chemical resistance can be obtained by having a relationship of MS> 110-100 × log (MFR). From Comparative Examples 2, 7, and 8, it is found that it is difficult to obtain a foamed molded product itself when it has a relationship of MS ≦ 110-100 × log (MFR).

  From Examples 1 to 8 and Comparative Examples 3 and 4, it can be seen that a foamed molded article excellent in both the heating dimensional change rate and chemical resistance can be obtained when the amount of the styrene resin used is in a specific range. .

  FIG. 1 shows a graph in which MS of various polyethylene resins used in Examples and Comparative Examples is plotted on the vertical axis and MFR is plotted on the horizontal axis. In this graph, Comparative Examples 2, 7, and 8 use known high-density polyethylene-based resins, and it can be seen that the plot has a relationship of approximately MS = 110-100 × log (MFR). Moreover, it turns out that all the high density polyethylene-type resin used for the Example has the relationship of MS> 110-100 * log (MFR). Further, Comparative Examples 5 and 6 are examples showing that the characteristics are not excellent if the MFR is out of the range of the present invention even if the relationship of MS> 110-100 × log (MFR) is satisfied. .

It is the graph which plotted MS of various polyethylene resin used by the Example and the comparative example on the vertical axis | shaft, and MFR on the horizontal axis.

Claims (6)

Styrene-modified polyolefin resin particles containing 20 to 600 parts by weight of styrene resin with respect to 100 parts by weight of polyolefin resin, wherein the polyolefin resin is an ethylene homopolymer or ethylene and an olefin having 3 or more carbon atoms With a density of 0.940 g / cm ³ or more, a shrinkage factor (g ′ value) of less than 1.0 and 0.4 or more, and a load of 2.16 kg for 0.15 to 20 g / 10/10 It has a melt flow rate and satisfies the relationship of the formula: MS> 110-100 × log (MFR) (where MS is the melt tension (mN) at 160 ° C. and MFR is the melt flow rate). Styrene-modified polyolefin resin particles.   The styrene-modified polyolefin resin particles are obtained by polymerizing a polyolefin resin particle that gives the polyolefin resin while impregnating a styrene monomer in an aqueous medium in the presence of a polymerization initiator. The styrene-modified polyolefin resin particles described in 1.   The polyolefin resin is obtained by copolymerizing an ethylene homopolymer having a vinyl group at a terminal or a macromonomer composed of a copolymer of ethylene and an olefin having 3 or more carbon atoms with an olefin having 2 or more carbon atoms. The styrene-modified polyolefin resin particles according to claim 1 or 2 obtained.   A foamable resin particle comprising 100 parts by weight of the styrene-modified polyolefin resin particles according to any one of claims 1 to 3 and 5 to 25 parts by weight of a volatile foaming agent. Pre-expanded particles having a bulk density of 0.01 to 0.2 g / cm ³ obtained by pre-expanding the styrene-modified polyolefin-based expandable resin particles according to claim 4. A foam molded article having a density of 0.01 to 0.2 g / cm ³ obtained by in-mold foam molding of the pre-expanded particles according to claim 5.

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