JP6709650B2 - Cross-linkable expandable polystyrene resin particles, pre-expanded particles thereof and foam - Google Patents

Description

TECHNICAL FIELD The present invention relates to crosslinkable expandable polystyrene resin particles, pre-expanded particles thereof and a foam.

The expandable polystyrene-based resin particles are relatively inexpensive, can be foam-molded with steam without using a special method, and have high buffering/insulating effects, and are therefore socially useful materials.

The expandable polystyrene-based resin particles are obtained by, for example, adding a foaming agent to polystyrene-based resin particles (that is, an easily volatile aliphatic hydrocarbon that only swells the particles slightly, such as butane and pentane) in an aqueous suspension. It is manufactured by the method of impregnation. The expandable polystyrene-based resin particles produced in this manner are used as a raw material for producing a foamed polystyrene-based resin molded body.

As a method for industrially and economically producing a foamed polystyrene resin molded article, expandable polystyrene resin particles are made into pre-expanded particles by steam or the like, and the pre-expanded particles are provided with a large number of small holes on a wall having a desired shape. Is filled in a closed mold, and a heating medium such as water vapor is jetted through a small hole in the mold to heat it to a temperature equal to or higher than the softening point of the pre-expanded particles, and after they are fused, they are cooled. There is a method of producing a foamed polystyrene resin molded body having a desired shape by taking it out from the mold through steps.

Therefore, in order to form the expandable polystyrene-based resin particles into a molded body, a large amount of steam is required, but due to the growing concern about environmental problems in recent years, there is an increasing demand for energy saving, and pre-foaming and There is a demand for a resin that can be foamed with a small amount of steam by reducing the temperature during in-mold molding. At the same time, in order to improve productivity, it is required to shorten the cooling time which accounts for about 50% of the molding time.

Conventionally, as a method of shortening the cooling time, a chemical that causes cracks on the surface of expandable polystyrene resin particles (aliphatic alcohol ester of higher fatty acid, particularly fatty acid triester such as hardened beef tallow oil or castor hardened oil at room temperature). Glycerin ester) was coated on the resin particles to accelerate the dissipation of the gas component contained in the resin particles to reduce the foaming power after molding (Patent Document 1, Patent Document 2, and Patent Document 3). ).

However, in the method of promoting the dissipation of gas components inside the resin by adding a chemical that causes a crack on the particle surface, the amount of the chemical that causes a crack to be more efficiently promoted to promote the dissipation of the blowing agent is added. When the amount is increased, there is a problem that pinholes are likely to occur on the surface of the molded body and fusion between particles is reduced.

Further, in Patent Document 4 and Patent Document 5, expandable polystyrene-based resin particles are proposed in which a cross-linking agent is added to a styrene-based monomer and a large amount of the cross-linking component is present on the surface or inside thereof to improve bending strength. Has been done.

However, this method has room for improvement in that the appearance of the surface of the molded product is impaired in the molded product molded at a low temperature because the surface has many crosslinking components and does not contain acrylic acid ester. Alternatively, since the cross-linking component is large inside and does not contain an acrylate ester, melting of the surface of the molded body tends to occur when highly foamed, and there was room for improvement in terms of appearance of the molded body. ..

Further, in Patent Document 6, a styrene-based monomer and an acrylic acid ester monomer are contained as a resin composition, and by containing the acrylic acid ester monomer, antistatic performance is improved by foaming. Polystyrene particles have been proposed.

However, in this method, since the crosslinking agent was not included, the cooling time was not shortened.

JP, 57-16037, A JP-B-58-56568 Japanese Patent Publication No. 4-7341 JP2012-201825A JP2012-193242A JP, 2014-193937, A

In view of the situation as described above, the object of the present invention is suitable for improving productivity by obtaining a molded product having good fusion properties and surface properties, and shortening the cooling time during molding. Another object is to provide expandable polystyrene resin particles.

The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and found that the monomer composition is a polyfunctional vinyl having two or more vinyl groups in a styrene-based monomer or an acrylate-based monomer. By containing a system monomer, to give an elastic force to the entire resin, found to obtain expandable polystyrene resin particles having the above characteristics by suppressing the tertiary foaming when taken out from the mold during molding, The present invention has been completed.

That is, the first aspect of the present invention is that the monomer composition is 90 parts by weight or more and 99 parts by weight or less of the styrene-based monomer, 1 part by weight or more and 10 parts by weight or less of the acrylate monomer (styrene-based monomer). And the total amount of acrylic acid ester-based monomer is 100 parts by weight), and a polyfunctional vinyl-based monomer having two or more vinyl groups is added to 100 parts by weight of the polymerizable monomer composition. The content of 0.005 parts by weight or more and 5.000 parts by weight or less, and the ratio (Mw1/Mw2) of the internal weight average molecular weight Mw1 and the overall weight average molecular weight Mw2 measured by gel permeation chromatography is 0.85 or more 1. Infrared absorption spectrum of polystyrene resin pre-expanded particle surface measured by ATR-FTIR, in which the weight average molecular weight (Mw1) inside the expandable polystyrene resin particles is 170,000 or more and 600,000 or less. from the absorbance ratio at 1600 cm ^-1 and 1730 cm ^-1 obtained α _(a 1730 _/ a ₁₆₀₀₎ is the absorbance ratio obtained from the infrared absorption spectrum of the polystyrene-based resin pre-expanded particles center β of _(a 1730 _/ a ₁₆₀₀₎ The present invention relates to expandable polystyrene-based resin particles, which are 1.0 times or more and 10 times or less.

A second aspect of the present invention relates to the expandable polystyrene resin particle according to the first aspect, wherein the polyfunctional vinyl monomer having two or more vinyl groups is divinylbenzene.

A third aspect of the present invention is that the ratio (Mz1/Mz2) of the internal Z-average molecular weight Mz1 and the overall Z-average molecular weight Mz2 obtained from the gel permeation chromatography measurement of the expandable polystyrene resin particles is 0.85 or more 1 0.05 or less, and Z average molecular weight (Mz1) inside the expandable polystyrene resin particles is 700,000 or more and 2,000,000 or less, according to any one of the first or second inventions. It relates to expandable polystyrene resin particles.

A fourth aspect of the present invention relates to the expandable polystyrene resin particles according to any one of the first to third aspects, wherein the acrylic acid ester-based monomer is butyl acrylate.

A fifth aspect of the present invention is characterized in that the amount of the foaming agent is contained in an amount of 3.0 parts by weight or more and 8.0 parts by weight or less with respect to 100 parts by weight of the expandable polystyrene resin particles, any one of the first to fourth inventions. The expandable polystyrene-based resin particles according to claim 1.

A sixth aspect of the present invention relates to polystyrene resin pre-expanded particles, which is obtained by expanding the expandable polystyrene resin particles according to any one of the first to fifth aspects.

A seventh aspect of the present invention relates to a polystyrene resin foam, which is obtained by in-mold molding of the polystyrene resin pre-expanded particles according to the sixth aspect.

An eighth aspect of the present invention is a substrate resin comprising the polystyrene-based resin according to any one of the first to fifth aspects of the invention, which is obtained by adding a vinyl-based cross-linking agent in a range of a polymerization conversion rate of less than 85 wt% from the initial stage of polymerization. And a method for producing expandable polystyrene resin particles.

A ninth aspect of the present invention relates to a method for producing pre-expanded polystyrene-based resin particles, which is obtained by expanding the expandable polystyrene-based resin particles according to any one of the first to fifth inventions.

A tenth aspect of the present invention relates to a method for producing a polystyrene-based resin foam, which is characterized in that the polystyrene-based resin pre-expanded particles according to the sixth aspect are molded in a mold.

According to the present invention, it is possible to obtain expandable polystyrene resin particles suitable for shortening the cooling time at the time of molding as compared with the conventional one, while obtaining a molded product having good fusion property and surface property.

The base resin constituting the expandable polystyrene-based resin particles of the present invention includes 90 parts by weight or more and 99 parts by weight or less of styrene-based monomer, 1 part by weight or more and 10 parts by weight or less (styrene-based monomer). The total amount of the monomer and the acrylic acid ester-based monomer is 100 parts by weight), and the polyfunctional vinyl-based single amount having two or more vinyl groups per 100 parts by weight of the polymerizable monomer composition. The body contains 0.005 parts by weight or more and 5.000 parts by weight or less, and the ratio (Mw1/Mw2) of the internal weight average molecular weight Mw1 to the entire weight average molecular weight Mw2 measured by gel permeation chromatography is 0.85. 1 or more and 1.05 or less, and the weight average molecular weight (Mw1) inside the expandable polystyrene-based resin particles is 170,000 or more and less than 600,000, and infrared rays on the surface of the polystyrene-based resin pre-expanded particles measured by ATR-FTIR absorbance ratio at 1600 cm ^-1 and 1730 cm ^-1 obtained from the absorption spectrum α _(a 1730 _/ a ₁₆₀₀₎ is the absorbance ratio obtained from the infrared absorption spectrum of the polystyrene-based resin pre-expanded particles center β _(a 1730 _/ a ₁₆₀₀ ) 1.0 times or more and 10 times or less.

Examples of the styrene-based monomer constituting the expandable polystyrene-based resin particles of the present invention include styrene, α-methylstyrene, dimethylstyrene, paramethylstyrene, ethylstyrene, isopropylstyrene, t-butylstyrene, chlorostyrene, Examples include styrene-based derivatives such as bromostyrene. These styrene-based monomers may be used alone or in combination of two or more.

Examples of the acrylic acid ester-based monomer constituting the expandable polystyrene-based resin particles of the present invention include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-dimethylaminoethyl acrylate, Examples thereof include alkyl acrylates such as 2-hydroxyethyl acrylate. These acrylic acid ester-based monomers may be used alone or in combination of two or more.

Of these, butyl acrylate is preferable because it is easily copolymerized with the styrene-based monomer and has good moldability.

The monomer composition of the base resin constituting the expandable polystyrene resin particles in the present invention is 90 parts by weight or more and 99 parts by weight or less of styrene monomer, 1 part by weight or more and 10 parts by weight of acrylate monomer. Below (total amount of styrene-based monomer and acrylic ester-based monomer is 100 parts by weight). More preferably, the amount of the styrene-based monomer is 94 parts by weight or more and 96 parts by weight or less, and the acrylate ester is 4 parts by weight or more and 6 parts by weight or less.

In the monomer composition of the base resin, when the amount of the acrylic acid ester-based monomer exceeds 10 parts by weight, the molded product is likely to contract, especially when it is highly foamed, and the appearance of the molded product looks good. Tends to get worse. Further, if the amount of the acrylic acid ester-based monomer is less than 1 part by weight, it becomes difficult to foam at a low temperature (the heating temperature, surface property, and fusion property required for obtaining pre-expanded particles having an intended expansion ratio). The molding temperature required to obtain a molded article having excellent heat resistance tends to increase.

Examples of the polyfunctional vinyl-based monomer having two or more vinyl groups constituting the expandable polystyrene-based resin particles of the present invention include divinylbenzene, hexamethylene diacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, Examples thereof include polyfunctional vinyl-based monomers having two or more vinyl groups such as trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, ditrimethylolpropane tetraacrylate, and dipentaerythritol hexaacrylate. These acrylic acid ester-based monomers may be used alone or in combination of two or more.

Of these, divinylbenzene is preferable because it is easily copolymerized with the styrene-based monomer.

The base resin that constitutes the expandable polystyrene resin particles in the present invention contains 0.005 parts by weight or more and 5.000 parts by weight or less of a polyfunctional vinyl-based monomer having two or more vinyl groups. More preferably, it is 0.010 parts by weight or more and 1.000 parts by weight or less of a polyfunctional vinyl-based monomer having two or more vinyl groups.

In the monomer composition of the base resin, if the multifunctional vinyl-based monomer having two or more vinyl groups is more than 5.000 parts by weight, the resin is less likely to foam, especially during molding, and the surface property is improved. , And it tends to be difficult to obtain a molded product having excellent fusion bondability. Further, when the amount of the polyfunctional vinyl-based monomer having two or more vinyl groups is less than 0.005 part by weight, it tends to be difficult to shorten the cooling time.
Regarding the monomer composition in the base resin, when the seed suspension polymerization method is carried out as the polymerization method, the monomer composition in the resin particles to be the seed is also reflected in the monomer composition.

The ratio (Mw1/Mw2) of the weight average molecular weight Mw1 inside the expandable polystyrene-based resin particles to the entire weight average molecular weight Mw2 in the present invention is preferably 0.85 or more and 1.05 or less. It is more preferably 0.90 or more and 1.05 or less. When Mw1/Mw2 is less than 0.85, the amount of cross-linking components on the surface increases, so that the foamability decreases and the surface property deteriorates. Further, when Mw1/Mw2 is more than 1.05, the internal cross-linking component increases, so that the molded body needs to be sufficiently cooled during molding, and it tends to be difficult to shorten the cooling time.

The weight average molecular weight Mw1 inside the expandable polystyrene resin particles in the present invention is 170,000 or more and 600,000 or less. It is preferably 300,000 or more and 600,000 or less. When the weight average molecular weight Mw1 inside the expandable polystyrene-based resin particles is less than 170,000, not only the strength of the foamed molded product becomes low, but also the surface of the molded product tends to melt and the appearance tends to be impaired. If it exceeds 10,000, the foamability will be low and the moldability will deteriorate (the heating temperature required to obtain pre-expanded particles having the target expansion ratio, and the molding temperature required to obtain a molded article with excellent fusion properties are Tend to be higher).

The weight average molecular weight Mw is a combination of the amount of the initiator used for polymerizing the polystyrene resin particles and the polymerization temperature, or the amount of the polyfunctional vinyl monomer having two or more vinyl groups, and the timing of the addition. Can be controlled by. For example, the Mw can be lowered by increasing the amount of the initiator used and/or decreasing the amount of the crosslinking agent used and/or increasing the polymerization temperature.

The ratio (Mz1/Mz2) of the Z average molecular weight Mz1 inside the expandable polystyrene-based resin particles and the total Z average molecular weight Mz2 in the present invention is preferably 0.85 or more and 1.05 or less. It is more preferably 0.90 or more and 1.05 or less. If Mz1/Mz2 is less than 0.85, the amount of cross-linking components on the surface increases, so that the foamability decreases and the surface property deteriorates. Further, when Mz1/Mz2 is more than 1.05, the internal cross-linking component increases, so that the molded body needs to be sufficiently cooled during molding, and it tends to be difficult to shorten the cooling time.

The Z average molecular weight Mz1 inside the expandable polystyrene resin particles in the present invention is preferably 700,000 or more and 2,000,000 or less. More preferably, it is 900,000 or more and 1.9 million or less. When the Z average molecular weight Mz1 inside the expandable polystyrene-based resin particles is less than 700,000, not only the strength of the foamed molded product becomes low, but also the surface of the molded product tends to melt and the appearance tends to be impaired. If it exceeds 10,000, the foamability will be low and the moldability will deteriorate (the heating temperature required to obtain pre-expanded particles having the target expansion ratio, and the molding temperature required to obtain a molded article with excellent fusion properties are Tend to be higher).

The Z-average molecular weight Mz is a combination of the amount of the initiator used for polymerizing the polystyrene resin particles and the polymerization temperature, or the amount of the polyfunctional vinyl monomer having two or more vinyl groups, and the timing of the addition. Can be controlled by. For example, Mz can be decreased by increasing the amount of the initiator used and/or decreasing the amount of the crosslinking agent used and/or increasing the polymerization temperature.

Here, the weight average molecular weight Mw and the Z average molecular weight Mz of the expandable polystyrene resin particles in the present invention are determined by using a gel permeation chromatograph (hereinafter, sometimes abbreviated as “GPC”) under the conditions described below. It is the value measured by Since it is difficult to measure the molecular weight inside the expandable polystyrene-based resin particles from the particles themselves, in the present specification, the surface of the pre-expanded particles obtained from the particles is cut out by 1 mm, and the remaining inner portion is expanded polystyrene. The average molecular weight inside the resin particles. The measuring method of the average molecular weight is described in the section of Examples. According to this measuring method, the average molecular weight obtained by removing the surface layer in the region of about 50% of the radius from the surface of the particle is measured. ..

Expandable polystyrene resin particles of the present invention, the absorbance ratio at 1600 cm ^-1 and 1730 cm ^-1 obtained from an infrared absorption spectrum of the measured polystyrene resin pre-expanded particle surface by _{ATR-FTIR α (A 1730 /} A 1600 ) Is 1.0 times or more and 10 times or less, preferably 1.0 times or more and 5.0 times the absorbance ratio β(A ₁₇₃₀ /A ₁₆₀₀ ) obtained from the infrared absorption spectrum of the polystyrene resin pre-expanded particles. It is less than twice.

When the ratio α/β of the absorbance ratio between the surface and the central portion is higher than 10, the ratio of acrylic acid ester on the surface of the particle becomes higher than that inside the particle, especially when molding at a high vapor pressure (high mold temperature). Surface melting tends to occur and the surface appearance tends to be impaired. When the ratio α/β of the absorbance ratio is less than 1.0, the ratio of acrylic acid ester on the particle surface becomes low, making molding at low vapor pressure (low mold temperature) difficult and deteriorating the surface appearance. In addition, the heating temperature at the time of pre-foaming tends to be high.

Examples of the foaming agent used in the present invention include aliphatic hydrocarbons such as propane, butane, and pentane, cyclobutane, alicyclic hydrocarbons such as cyclopentane, methyl chloride, dichlorodifluoromethane, and dichlorotetrafluoroethane. And other halogenated hydrocarbons. These foaming agents may be used alone or in combination of two or more. Of these foaming agents, butane is preferable because it has a good foaming power.

The foaming agent contained in the expandable polystyrene resin particles in the present invention is preferably 3.0 parts by weight or more and 8.0 parts by weight or less, preferably 4.0 parts by weight, when the expandable polystyrene resin particles are 100 parts by weight. More preferably, it is not less than 6.0 parts by weight and not more than 6.0 parts by weight. When the content of the foaming agent is less than 3.0 parts by weight, the prefoaming time tends to be long and the fusion rate at the time of molding tends to be low. If the content of the foaming agent exceeds 8.0 parts by weight, the molded product tends to shrink and the appearance of the molded product tends to be impaired.

In the present invention, the timing of adding the polyfunctional vinyl-based monomer having two or more vinyl groups is preferably within the range of the polymerization conversion rate of less than 85 wt% from the initial stage of the polymerization. More preferably, the conversion rate is in the range of 50 wt% from the initial stage of polymerization.

When the polymerization conversion rate is less than 85 wt% at the timing of adding the polyfunctional vinyl-based monomer having two or more vinyl groups, the polyfunctional vinyl-based monomer having two or more vinyl groups in the entire resin is used. Therefore, it is possible to obtain a molded product having good fusion-bonding property and surface property and to shorten the cooling time at the time of molding.

The method for producing expandable polystyrene-based resin particles of the present invention includes a method of impregnating a foaming agent into particles obtained by a suspension polymerization method in an aqueous medium, and a pellet produced by bulk polymerization or the like in an aqueous medium. It can be obtained by any method of impregnating with a foaming agent.

Among these, since spherical resin particles can be obtained, and further, the expandable polystyrene resin particles can be obtained by consistently performing the polymerization step and the foaming agent impregnation step, the suspension weight with good industrial productivity is also obtained. It is preferably manufactured by a legal method. More preferably, the seed particles are used to absorb the monomer mixture, and the polymerization of the monomer mixture is carried out after or while being absorbed to obtain resin particles. It is a suspension polymerization method in which resin particles are obtained by suspension polymerization in the presence of an agent. That is, as a method for producing expandable polystyrene-based resin particles, a styrene-based monomer, an acrylic ester-based monomer, and a polyfunctional vinyl-based monomer having two or more vinyl groups are used as a suspending agent and polymerization is initiated. A method in which the polymerization reaction is started in the presence of an agent and, if necessary, other additives, and a foaming agent is added during suspension polymerization, or a foaming agent is impregnated after the polymerization is preferable.

The total amount of the solvent and the plasticizer contained in the expandable polystyrene resin particles of the present invention is less than 0.1 part by weight when the total amount of the solvent and the plasticizer contained in the base resin is 100 parts by weight. Preferably. The solvent used in the present invention has a boiling point of 50° C. or higher in order to distinguish it from the foaming agent.

Examples of the solvent in the present invention include C6 or more aliphatic hydrocarbons such as hexane and heptane, and C6 or more alicyclic hydrocarbons such as cyclohexane and cyclooctane. Examples of the plasticizer in the present invention include diisobutyl adipate, dioctyl adipate, dibutyl sebacate, glycerin tristearate, glycerin tricaprylate, coconut oil, palm oil, and rapeseed oil.

These solvents and plasticizers serve to retain the internal pressure required for foam molding by softening the resin by the plasticizing effect and further evaporating and expanding in the heating step of in-mold molding. However, since the molecules are large and remain in the foam body even after the heating process is completed, the internal pressure is maintained even in the cooling process, and a long cooling time is inevitable. If the cooling is terminated while the internal pressure is maintained and the foam is released from the mold, the internal pressure cannot maintain the desired shape, resulting in a defective product. Therefore, these solvents and plasticizers hinder the shortening of the cooling time, so that it is preferable to use less than 0.1 parts by weight in order to improve the productivity.

Also, with regard to a plasticizer that does not vaporize in the pre-foaming step and the heating step of in-mold molding, the amount used is less than 0.1 parts by weight because it reduces the strength of the molded body or softens the resin and causes shrinkage. It is preferable that

The unreacted monomer component contained in the expandable polystyrene resin particles of the present invention is preferably less than 0.3 parts by weight. The unreacted monomer component contained tends to volatilize from the foamed molded product obtained by foaming the expandable polystyrene-based resin particles, and particularly when the contained monomer component is 0.3 parts by weight or more. It is not preferable in the medical field or in the field of packaging materials that come into direct contact with foods, or in automobiles and construction materials, and it tends to hinder the shortening of the cooling time in the cooling process.

The amount of unreacted monomer component contained can be controlled by the combination of the amount of the initiator used for polymerizing the polystyrene resin particles and the polymerization temperature. For example, the unreacted monomer component can be reduced by increasing the amount of the initiator used and increasing the polymerization temperature.

Examples of the suspending agent used in the suspension polymerization method of the present invention include polyvinyl alcohol, methyl cellulose, polyacrylamide, water-soluble polymers such as polyvinylpyrrolidone and tricalcium phosphate, and sparingly soluble inorganic substances such as magnesium borophosphate, Etc. When a sparingly soluble inorganic substance is used, the suspension stabilizing effect can be increased by using an anion surfactant such as sodium dodecylbenzene sulfonate or sodium dodecyl diphenyl ether disulfonate together. Further, the combined use of a water-soluble polymer and a poorly soluble inorganic substance is also effective.

As the polymerization initiator used in the suspension polymerization method of the present invention, a radical-generating type polymerization initiator generally used for producing a thermoplastic polymer can be used. Typical examples of the polymerization initiator include azo compounds such as azobisisobutyronitrile, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, lauroyl peroxide-t-butyl. Peroxyisopropyl carbonate, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-amylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butyl) Peroxy)-3,3,5-trimethylcyclohexane, t-butylperoxybenzoate, t-butylperoxy-2-ethylhexyl carbonate and the like peroxides. These polymerization initiators may be used alone or in combination of two or more.

As an additive that can be added during the suspension polymerization of the present invention, an external additive, a flame retardant, a flame retardant aid, etc. may be used within a range that does not impair the effects of the present invention.

As the flame retardant and flame retardant aid used in the present invention, known and conventional ones can be used.
Specific examples of the flame retardant include halogenated aliphatic hydrocarbon compounds such as hexabromocyclododecane, tetrabromobutane, hexabromocyclohexane, tetrabromobisphenol A, tetrabromobisphenol F, 2,4,6-triene. Brominated phenols such as bromophenol, tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A- Examples thereof include brominated phenol derivatives such as diglycidyl ether and 2,2-bis[4′(2″,3″-dibromoalkoxy)-3′,5′-dibromophenyl]-propane. These may be used alone or in combination of two or more.

As a specific example of the flame retardant aid, for example, an initiator such as cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane may be used. ..

As the external additives and adjuncts used in the present invention, known and conventional ones can be used.

Specific examples of external additives and adjuncts include, for example, lauric acid triglyceride, stearic acid triglyceride, fatty acid triglycerides such as linoleic acid triglyceride, lauric acid diglyceride, stearic acid diglyceride, fatty acid diglycerides such as linoleic acid diglyceride, lauric acid monoglyceride, Fatty acid monoglycerides such as stearic acid monoglyceride and linoleic acid monoglyceride, zinc stearate, calcium stearate, magnesium stearate, aluminum stearate, zinc laurate, fatty acid metal salts such as calcium laurate, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether , Nonionic surfactants such as polyoxyethylene stearyl ether, polyoxyethylene laurate, polyoxyethylene palmitate, polyoxyethylene stearate, polyoxyethylene oleate, polysiloxanes such as polydimethylsiloxane, polymethylphenylsiloxane And so on. These external additives and adjuncts may be used alone or in combination of two or more. Further, these external additives and adjuncts may be added to the water system at the time of impregnating the foaming agent, or may be added after dehydration or after drying and coated, regardless of the coating method. A preferred coating method is a method of coating after drying and mixing and stirring.

The expandable polystyrene-based resin particles of the present invention are pre-expanded and then heat-expanded to obtain an expanded molded article.

As the pre-foaming method, for example, a normal method such as using a cylindrical pre-foaming apparatus to heat with steam or the like to foam can be employed.

The expansion ratio of the pre-expanded particles obtained from the expandable polystyrene-based resin particles of the present invention is not particularly limited, but a bulk ratio generally used in the field of construction materials/civil engineering is preferably 10 times or more and 90 times or less.

As a method for foam-molding the pre-expanded particles, for example, a so-called in-mold foam molding method, which is a so-called in-mold foam molding method, in which a pre-expanded particle is filled in a mold, and a method of heating by blowing steam or the like is used. The method can be adopted.

The blowing vapor pressure at the time of in-mold molding is usually about 0.07 to 0.09 MPa, but in the present invention, molding is possible even at about 0.03 to 0.08 MPa.

Examples and comparative examples will be given below, but the present invention is not limited thereto.

The measurement evaluation method was carried out as follows.

<Conversion rate calculation method>
The calculation method of the polymerization conversion rate was calculated by the following calculation formula.

Polymerization conversion rate [wt%]=resin weight excluding volatile components/resin weight containing volatile components*100
The volatile component-free resin was prepared by adding a polymerization inhibitor to the sampled resin and placing it in an oven at 150° C. for 30 minutes.

<GPC measurement>
After dissolving 0.02 g of the expandable polystyrene-based resin particles in 20 ml of tetrahydrofuran (hereinafter, sometimes abbreviated as "THF") with respect to the obtained expandable polystyrene-based resin particles, gel permeation chromatography GPC was measured using (GPC) under the following conditions to obtain a GPC measurement chart, and a weight average molecular weight (Mw) and a Z average molecular weight (Mz). The obtained value is a polystyrene-converted relative value.
Measuring device: Tosoh Corporation, high-speed GPC device HLC-8220
Column used: Tosoh Corporation, SuperHZM-H x 2, SuperH-RC x 2
Column temperature: 40°C, mobile phase: THF (tetrahydrofuran)
Flow rate: 0.35 ml/min, injection volume: 10 μl
Detector: RI.

Here, the weight average molecular weight (Mw) and the Z average molecular weight (Mz) inside the expandable polystyrene-based resin particles means that the surface layer of the polystyrene-based pre-expanded particles pre-expanded to about 4 mm is cut out by 1 mm and the remaining inside Refers to the part.

<Measurement of absorbance ratio (A ₁₇₃₀ /A ₁₆₀₀ )>
Regarding the absorbance ratio of the obtained expandable polystyrene resin particles, 10 pre-expanded particles were sampled arbitrarily, and the surface and center of the pre-expanded particles were subjected to the ATR infrared spectroscopic analysis under the following conditions. Then, the infrared absorption spectrum was obtained.
Device: FTIR [Shimadzu Corporation, FTIR-8400S] connected to a single reflection type total reflection (ATR) measuring device [PIKE, MIRacle] ATR prism (high refractive index crystal species): zinc selenide (ZnSe)
Incident angle: 45°
Measurement area: 4000 cm ^{−1 to} 600 cm ⁻¹
Detector: DLATGS
Crawl depth: 1.66
Number of reflections: 1 time Resolution: 4 cm ^-1
Number of times of integration: 20 times Others: The infrared absorption spectrum measured without being brought into contact with the sample was used as a background, and a treatment not related to the measurement spectrum was performed.

In the ATR method, since the intensity of the infrared absorption spectrum obtained by the measurement changes depending on the degree of adhesion between the sample and the high refractive index crystal, the absorbance at ₆₉₆ cm ⁻¹ (A ₆₉₆ ) is 0.08 to 0.12. In addition, the degree of adhesion between the sample and the high refractive index crystal is adjusted and measured.

Here, when measuring the surface of the pre-expanded particles, the particle surface was directly adhered to the ATR prism for measurement. When measuring the center of the pre-expanded particles, a razor was used to divide the pre-expanded particles into two parts so as to pass through the center of the pre-expanded particles.

Here, the central portion means an area within 200 μm from the central portion of the cross section when the polystyrene resin pre-expanded particles are divided into two so as to pass through the center thereof.

From the infrared absorption spectrum obtained as described above, determine the absorbance of 1600cm ^-1 _{(A 1600)} and the absorbance of the 1730 cm ^-1 absorbance ratio of _{(A 1730) (A 1730 /} A 1600). In the present invention, the ATR-FTIR measurement is performed on the surface and the central portion of any 10 pre-expanded particles, and the minimum absorbance ratio and the maximum absorbance ratio are excluded. Then, the arithmetic average of the absorbance ratios of the eight remaining residues was defined as the absorbance ratio ((A ₁₇₃₀ /A ₁₆₀₀ ). The obtained surface absorbance ratio α (A ₁₇₃₀ /A ₁₆₀₀ ) and the central absorbance ratio β( A ₁₇₃₀ /A ₁₆₀₀ ), the absorbance ratio between the surface and the central portion was calculated by the following formula.
The ratio of the absorbance ratio between the surface and the central part=α (surface)/β (central part).

Note that the absorbance at 1730 cm ⁻¹ obtained from the infrared absorption spectrum is an absorption spectrum due to stretching vibration between C═O of a carbonyl group, which was defined as absorbance (A ₁₇₃₀ ). The absorbance at 1600 cm ⁻¹ obtained from the infrared absorption spectrum is the absorption spectrum of in-plane vibration of the aromatic benzene ring, and was defined as the absorbance (A ₁₆₀₀ ).

The ratio α/β of the absorbance ratio between the surface and the central portion of the polystyrene resin pre-expanded particles can be adjusted by changing the timing of adding the acrylate ester during the polymerization of the polystyrene resin particles.

Here, the central portion includes the central portion of the cross section when the two parts are divided so as to pass through the center of the polystyrene-based resin pre-expanded particles, and a region within 200 μm from the central portion.

The ATR-FTIR in the present invention is an FTIR that uses an ATR (Attenuated Total Reflection) method. The ATR method is a method in which a crystal with a high refractive index is pressure-bonded to the sample surface, the sample surface can be measured with high sensitivity using total internal reflection conditions, and a spectrum similar to the transmission method can be easily obtained. It is widely used for analysis of general industrial materials such as polymer thick film, resin, coating film, paper, thread, etc.

Generally, light is not reflected at the interface between the sample and the high-refractive-index crystal, but is totally reflected after entering a certain depth into the sample. At this time, the light is totally reflected in the wave number region where the sample is not absorbed, but 100 parts is not totally reflected in the region where the sample is absorbed, but the intensity of the totally reflected light is reduced depending on the intensity of the absorption. A total reflection spectrum is obtained by measuring this reflected energy.

However, the depth of light entrapment (measurement depth) varies greatly depending on the refractive index of the high-refractive-index crystal used, the refractive index of the sample, the incident angle of the measurement light, and the wave number of the measurement light, so these parameters are not specified. , The measurement results cannot be compared. The measurement depth in the ATR method has wave number dependence, and the lower the wave number, the deeper the measurement depth and the larger the absorption intensity. Therefore, correction is required in the case of comparison with the transmission spectrum.

<Pre-expansion and molding evaluation>
The expandable polystyrene resin particles obtained after drying and dehydration are sieved to collect the expandable polystyrene resin particles having a particle diameter of 0.6 mm to 1.2 mm, put them in a polyethylene bag and close the bag. After being stored in a stainless steel can with a lid at 20° C. or lower for 3 days, pre-foaming was performed. After pre-foaming, the composition was left standing at room temperature for 1 day to be cured and dried, and then subjected to molding evaluation.

When the bead life is evaluated, expandable polystyrene resin particles sieved with a particle size of 0.6 mm to 1.2 mm are put in a bag, and the bag mouth is opened for 1 week in a dryer set at 35°C. After the storage, pre-foaming was performed, and the mixture was allowed to stand at room temperature for 1 day to be cured and dried, and then a molding evaluation was performed.

<Moldability evaluation>
Using a molding machine [manufactured by Daisen, KR-57], the mixture was filled in a box-shaped mold having a bottom thickness of 30 mm and a side thickness of 25 mm, a length of 550 mm×a width of 350 mm×a height of 120 mm, and a blowing vapor pressure of 0. In-mold molding was performed under molding conditions changed within the range of 03 to 0.08 MPa to obtain a box-shaped foam-molded article.

The polystyrene-based resin foam thus obtained was dried at room temperature for 24 hours and then evaluated as follows. As for the cooling time, the cooling time was measured at the lowest vapor pressure in the vapor pressure range in which molding was possible, and 49 seconds or less was passed from the viewpoint of productivity. In addition, Table 1 shows the evaluation results of the fusion property and the surface property at a blowing vapor pressure of 0.045 MPa.

(1) Fusing property evaluation The obtained polystyrene-based resin foam was ruptured, the fracture surface was observed, and the ratio at which the particles were fractured, not at the particle interface, was determined, and fusion was performed according to the following criteria. The sex was judged.
A: The rate of particle breakage is 90 parts or more.
◯: The rate of particle breakage is 80 parts or more and less than 90 parts.
Δ: The rate of particle breakage is 70 parts or more and less than 80 parts.
X: The rate of particle breakage is less than 70 parts.

(2) Surface property evaluation The surface condition of the obtained polystyrene resin foam was visually observed, and the surface property was evaluated according to the following criteria.
⊚: Very beautiful with no surface melting and no intergranularity.
◯: Beautiful with little surface melting and intergranularity.
Δ: The surface is melted and there are particles, and the appearance is slightly poor.
X: The surface is melted, there are many intergranular particles, and the appearance is poor.

(Example 1) <Production of expandable polystyrene resin particles>
In a 6-liter autoclave attached to the stirrer, 100 parts by weight of pure water, 0.15 parts by weight of tricalcium phosphate, 0.01 part by weight of sodium dodecylbenzenesulfonate, 0.04 part by weight of polyethylene wax, and benzoyl as an initiator. 0.17 parts by weight of peroxide and 0.2 parts by weight of 1,1-bis(t-butylperoxy)cyclohexane were charged. Subsequently, 98 parts by weight of styrene monomer, 2 parts by weight of butyl acrylate monomer, and 0.01 parts by weight of divinylbenzene monomer were charged with stirring at 250 rpm, and the temperature was raised to 98°C. After 1 hour and 30 minutes, 0.05 part by weight of tricalcium phosphate was added. Subsequently, it was held at 98° C. for 2 hours and 30 minutes to obtain polystyrene resin particles.

Then, a total of 7 parts by weight of normal rich butane as a foaming agent was pressed into the autoclave, and the temperature was raised to 120°C again. Then, after keeping the temperature at 120° C. for 2 hours, it was cooled to room temperature and the polymerized slurry was taken out from the autoclave. The polymerized slurry taken out was dehydrated, washed and dried to obtain expandable polystyrene resin particles.

<Production of pre-expanded particles> The obtained expandable polystyrene resin particles were sieved to collect expandable polystyrene resin particles having a particle diameter of 0.6 mm to 1.2 mm.

The expandable polystyrene resin particles thus obtained were pre-expanded at a bulk ratio of 65 times using a pressure type pre-expanding machine [BHP, manufactured by Daikai Industry Co., Ltd.] under the condition of a steam pressure of 0.08 MPa. At this time, air was blown into the blown steam to adjust the blown steam temperature. Then, it was left at room temperature for 1 day to be cured and dried.

<Manufacture of in-mold foam molding>
Using the molding machine [Daisen, KR-57], the obtained polystyrene-based resin pre-expanded particles were box-shaped gold having a bottom thickness of 30 mm and a side thickness of 25 mm and a length of 550 mm×width of 350 mm×height of 120 mm. It was filled in a mold and was molded in the mold under a molding condition of a blowing vapor pressure of 0.045 MPa to obtain a box-shaped foam molded body.

The expandable polystyrene resin particles and the foamed molded product thus obtained were evaluated, and the results are shown in Table 1. (Example 2)

In <Production of expandable polystyrene-based resin particles>, the expandability was the same as in Example 1 except that the addition number of styrene monomer was changed to 95 parts by weight and the addition number of butyl acrylate monomer was changed to 5 parts by weight. Polystyrene-based resin particles, pre-expanded particles, and in-mold expanded molded article were obtained. The evaluation results are shown in Table 1.

(Example 3)
In <Production of expandable polystyrene resin particles>, except that the addition number of styrene monomer is changed to 95 parts by weight, the addition number of butyl acrylate monomer is changed to 5 parts by weight, and the addition number of divinylbenzene monomer is changed to 0.05 part by weight. In the same manner as in Example 1, expandable polystyrene-based resin particles, pre-expanded particles, and in-mold expanded molded article were obtained. The evaluation results are shown in Table 1.

(Example 4)
In <Production of expandable polystyrene resin particles>, the addition number of styrene monomer was changed to 95 parts by weight, the addition number of butyl acrylate monomer was changed to 5 parts by weight, and the addition number of divinylbenzene monomer was changed to 0.05 part by weight. Expandable polystyrene resin particles, pre-expanded particles, in-mold expansion molding were performed in the same manner as in Example 1 except that the timing of addition of the divinylbenzene monomer was changed to a polymerization conversion rate of styrene and butyl acrylate of 60 wt %. Got the body The evaluation results are shown in Table 1.

(Example 5)
In <Production of expandable polystyrene-based resin particles>, the expandability was the same as in Example 1 except that the addition number of styrene monomer was changed to 92 parts by weight and the addition number of butyl acrylate monomer was changed to 8 parts by weight. Polystyrene-based resin particles, pre-expanded particles, and in-mold expanded molded article were obtained. The evaluation results are shown in Table 1.

(Example 6)
In <Production of expandable polystyrene-based resin particles>, the addition number of styrene monomer was changed to 92 parts by weight, the addition number of butyl acrylate monomer was changed to 8 parts by weight, and the addition number of divinylbenzene monomer was changed to 0.05 part by weight. In the same manner as in Example 1, expandable polystyrene-based resin particles, pre-expanded particles, and in-mold expanded molded article were obtained. The evaluation results are shown in Table 1.

(Example 7)
In <Production of expandable polystyrene-based resin particles>, 0.20 parts by weight of tricalcium phosphate is added, 92 parts by weight of styrene monomer is added, 8 parts by weight of butyl acrylate monomer is added, and divinylbenzene is added. Expandable polystyrene resin particles, pre-expanded particles, and in-mold expanded molded article were obtained in the same manner as in Example 1 except that the added amount of the monomer was changed to 3.00 parts by weight. The evaluation results are shown in Table 1.

(Example 8)
In <Production of expandable polystyrene-based resin particles>, a polyfunctional vinyl-based monomer having 95 parts by weight of a styrene monomer, 5 parts by weight of a butyl acrylate monomer, and 2 or more vinyl groups is used. In the same manner as in Example 1 except that a certain divinylbenzene monomer was changed to a hexamethylene diacrylate monomer and the addition amount was changed to 0.05 parts by weight, expandable polystyrene resin particles, pre-expanded particles, and in-mold A foamed molded product was obtained. The evaluation results are shown in Table 1.

(Example 9)
In <Production of expandable polystyrene-based resin particles>, the addition number of styrene monomer was changed to 95 parts by weight, and the butyl acrylate monomer that was an acrylate ester monomer was changed to methyl acrylate monomer, and the addition number was changed to 5 parts by weight. The expandable polystyrene resin particles, the pre-expanded particles, and the in-mold expanded molded article were obtained in the same manner as in Example 1 except that the addition number of the divinylbenzene monomer was changed to 0.05 part by weight. The evaluation results are shown in Table 1.

(Comparative Example 1)
In <Production of expandable polystyrene-based resin particles>, the addition number of styrene monomer was changed to 100 parts by weight, the addition number of butyl acrylate monomer was changed to 0 part by weight, and the addition number of divinylbenzene monomer was changed to 0 part by weight. By the same operation as in Example 1, expandable polystyrene resin particles, pre-expanded particles, and in-mold expanded molded article were obtained. The evaluation results are shown in Table 1.

(Comparative example 2)
In <Production of expandable polystyrene-based resin particles>, the expandable polystyrene-based resin particles, pre-expanded particles, and in-mold were prepared in the same manner as in Example 1, except that the addition number of the divinylbenzene monomer was changed to 0 part by weight. A foamed molded product was obtained. The evaluation results are shown in Table 1.

(Comparative example 3)
In <Production of expandable polystyrene-based resin particles>, the addition number of styrene monomer was changed to 95 parts by weight, the addition number of butyl acrylate monomer was changed to 5 parts by weight, and the addition number of divinylbenzene monomer was changed to 0 part by weight. By the same operation as in Example 1, expandable polystyrene resin particles, pre-expanded particles, and in-mold expanded molded article were obtained. The evaluation results are shown in Table 1.

(Comparative example 4)
In <Production of expandable polystyrene-based resin particles>, the addition number of styrene monomer was changed to 100 parts by weight, the addition number of butyl acrylate monomer was changed to 0 part by weight, and the addition number of divinylbenzene monomer was changed to 0.05 part by weight. In the same manner as in Example 1, expandable polystyrene-based resin particles, pre-expanded particles, and in-mold expanded molded article were obtained. The evaluation results are shown in Table 1.

(Comparative example 5)
<Production of expandable polystyrene-based resin particles> In 0.25 part by weight of tricalcium phosphate added, 95 parts by weight of styrene monomer added, 5 parts by weight of butyl acrylate monomer added, divinylbenzene Expandable polystyrene resin particles were produced by the same operation as in Example 1 except that the addition amount of the monomer was changed to 10.00 parts by weight. However, evaluation was made because abnormal polymerization occurred at the stage of 1 hour of polymerization. Did not reach

(Comparative example 6)
In <Production of expandable polystyrene resin particles>, the addition number of styrene monomer was changed to 95 parts by weight, the addition number of butyl acrylate monomer was changed to 5 parts by weight, and the addition number of divinylbenzene monomer was changed to 0.05 part by weight. Expandable polystyrene resin particles were obtained in the same manner as in Example 1 except that the timing of addition of the divinylbenzene monomer was 90% by weight of the conversion of styrene and butyl acrylate and the holding time was changed to 5 hours. Thus, pre-expanded particles and an in-mold expanded molded article were obtained. The evaluation results are shown in Table 1.

(Comparative Example 7)
In <Production of expandable polystyrene-based resin particles>, the addition number of styrene monomer was changed to 85 parts by weight, the addition number of butyl acrylate monomer was changed to 15 parts by weight, and the addition number of divinylbenzene monomer was changed to 0.05 part by weight. In the same manner as in Example 1, expandable polystyrene-based resin particles, pre-expanded particles, and in-mold expanded molded article were obtained. The evaluation results are shown in Table 1.

(Comparative Example 8)
In <Production of expandable polystyrene-based resin particles>, the number of parts of styrene monomer added was changed to 100 parts by weight, the number of parts of butyl acrylate monomer added was changed to 0 part by weight, and a multifunctional vinyl-based single unit having two or more vinyl groups was used. The procedure of Example 1 was repeated except that the divinylbenzene monomer, which is a monomer, was changed to hexamethylene diacrylate monomer, and the amount of hexamethylene diacrylate was changed to 0.05 part by weight. Foamed particles and an in-mold foam molding were obtained. The evaluation results are shown in Table 1.

(Comparative Example 9)
<Production of expandable polystyrene resin particles>
In a 6-liter autoclave attached to a stirrer, 100 parts by weight of pure water, 0.15 parts by weight of tricalcium phosphate, 0.01 parts by weight of sodium dodecylbenzenesulfonate, 0.04 parts by weight of polyethylene wax, and as an initiator 0.16 parts by weight of benzoyl peroxide and 0.2 part by weight of 1,1-bis(t-butylperoxy)cyclohexane were charged. Subsequently, with stirring at 250 rpm, 90 parts by weight of styrene monomer and 0.045 parts by weight of divinylbenzene monomer were charged, and then the temperature was raised to 98°C. Then, it hold|maintained at 98 degreeC for 4 hours. Furthermore, while maintaining 98° C. and stirring, 5 parts by weight of a styrene monomer, 5 parts by weight of butyl acrylate, 0.005 parts by weight of a divinylbenzene monomer, and 0.02 parts by weight of benzoyl peroxide were added to the reaction system over 1 hour. After dropping and polymerizing, it was kept at 98° C. for 1 hour to obtain polystyrene resin particles.
Then, the operations after impregnation with the foaming agent were the same as in Example 1 to obtain expandable polystyrene resin particles.

Claims (11)

The monomer composition is 90 parts by weight or more and 99 parts by weight or less of styrene-based monomer, 1 part by weight or more and 10 parts by weight or less of acrylate-based monomer (of styrene-based monomer and acrylate-based monomer). The total amount is 100 parts by weight),
0.005 parts by weight or more and 5.000 parts by weight or less of a polyfunctional vinyl-based monomer having two or more vinyl groups per 100 parts by weight of the polymerizable monomer composition,
The ratio (Mw1/Mw2) of the internal weight average molecular weight Mw1 to the entire weight average molecular weight Mw2 measured by gel permeation chromatography is 0.85 or more and 1.05 or less, and the inside of the expandable polystyrene resin particles Has a weight average molecular weight (Mw1) of 170,000 or more and 600,000 or less,
Absorbance ratio at 1600 cm ^-1 and 1730 cm ^-1 obtained from an infrared absorption spectrum of the measured polystyrene resin pre-expanded particle surface by _{ATR-FTIR α (A 1730 /} A 1600) is a polystyrene-based resin pre-expanded particles center 1.0 times more than 10 times der following infrared absorption spectrum absorbance ratio obtained from β _(a 1730 _/ a ₁₆₀₀₎ of is,
Expandable polystyrene resin particles of gel permeation chromatography of the entire obtained from the measurement Z average molecular weight Mz2 is characterized der Rukoto 800,000 or more, expandable polystyrene resin particles. The monomer composition is 90 parts by weight or more and 99 parts by weight or less of styrene-based monomer, 1 part by weight or more and 10 parts by weight or less of acrylate-based monomer (of styrene-based monomer and acrylate-based monomer). The total amount is 100 parts by weight),
0.005 parts by weight or more and 5.000 parts by weight or less of a polyfunctional vinyl-based monomer having two or more vinyl groups per 100 parts by weight of the polymerizable monomer composition,
The ratio (Mw1/Mw2) of the internal weight average molecular weight Mw1 to the entire weight average molecular weight Mw2 measured by gel permeation chromatography is 0.85 or more and 1.05 or less, and the inside of the expandable polystyrene resin particles Has a weight average molecular weight (Mw1) of 170,000 or more and 600,000 or less,
1600 cm obtained from the infrared absorption spectrum of the surface of pre-expanded polystyrene resin particles measured by ATR-FTIR ^-1 And 1730 cm ^-1 Absorbance ratio at α(A ₁₇₃₀ /A ₁₆₀₀ ) Is the absorbance ratio β(A ₁₇₃₀ /A ₁₆₀₀ ) Is 1.0 times or more and 10 times or less,
The ratio (Mz1/Mz2) of the internal Z-average molecular weight Mz1 and the overall Z-average molecular weight Mz2 obtained from the gel permeation chromatography measurement of the expandable polystyrene resin particles is 0.85 or more and 1.05 or less, and The expandable polystyrene resin particles have a Z-average molecular weight (Mz1) of 700,000 or more and 2,000,000 or less inside the expandable polystyrene resin particles. The expandable polystyrene resin particles according to claim 1 or 2 , wherein the polyfunctional vinyl monomer having two or more vinyl groups is divinylbenzene. The ratio (Mz1/Mz2) of the internal Z-average molecular weight Mz1 and the overall Z-average molecular weight Mz2 obtained from the gel permeation chromatography measurement of the expandable polystyrene resin particles is 0.85 or more and 1.05 or less, and The expandable polystyrene resin particles according to claim 1 or 3 , wherein a Z average molecular weight (Mz1) inside the expandable polystyrene resin particles is 700,000 or more and 2,000,000 or less. Wherein the acrylic acid ester monomer is butyl acrylate, expandable polystyrene resin particles according to any one of claims 1-4. To expandable polystyrene resin particles 100 parts by weight and wherein the amount blowing agent is included less 8.0 parts by weight or more 3.0 parts by weight, expandable polystyrene resin according to any one of claims 1 to 5 particle. Pre-expanded polystyrene resin particles, wherein the expandable polystyrene resin particle according to any one of claims 1 to 7 is expanded. A polystyrene-based resin foam, which is obtained by in-mold molding of the polystyrene-based resin pre-expanded particles according to claim 7 . Obtained by adding a range of vinyl crosslinking agent from the polymerization initial under polymerization conversion 85 wt%, a polystyrene-based resin according to any one of claims 1 to 6 in the expandable polystyrene resin particles to the base resin Production method. A method for producing pre-expanded polystyrene-based resin particles, which comprises expanding the expandable polystyrene-based resin particles according to any one of claims 1 to 7 . A method for producing a polystyrene-based resin foam, which comprises molding the pre-expanded polystyrene-based resin particles according to claim 7 in a mold.