JP5824263B2 - Expandable thermoplastic resin particles - Google Patents

Description

  The present invention relates to expandable thermoplastic resin particles suitable for pre-expansion and in-mold molding at low temperatures.

  Expandable thermoplastic resin particles are a relatively useful material, and can be foam-molded with steam or the like without using a special method, so that a high buffering and heat insulation effect can be obtained. However, due to increasing interest in environmental issues in recent years, there has been a growing demand for energy saving. By reducing the temperature during pre-foaming and in-mold molding, a resin that can be foamed with a small amount of steam is required. It has been.

  The foamed molded article is manufactured by a method in which foamable thermoplastic resin particles are heated with steam or the like, pre-foamed to a desired bulk density, subjected to an aging step, filled in a molding die, and heated and foamed again. However, when the temperature at the time of foaming is lowered, there is a problem that not only pre-foaming to a desired bulk density but also the appearance of the obtained foamed molded product is remarkably deteriorated. In particular, when used in the food packaging material field or the medical field, it is desired that the monomer component remaining in the resin is less than 0.3%, but if the monomer component having plasticity is lowered, There was a problem that foaming and moldability at low temperatures deteriorated.

  In order to solve this problem, in Patent Document 1, for the purpose of producing a foamable styrenic resin using butanes as a foaming agent for the purpose different from that of the present invention, a styrene is copolymerized in an amount of 17% or less. A resin obtained by polymerizing a monomer, having a secondary transition temperature lower by 2 to 14 ° C. than that of a styrene resin, and a residual monomer content of 0.3% or less. Expandable styrenic resin particles excellent in the above have been proposed.

  In Patent Document 2, a styrene monomer and an acrylate monomer are copolymerized in an aqueous suspension, or a styrene monomer and an acrylate monomer are copolymerized in the presence of styrene polymer seed particles. A method for improving the foamability of styrenic polymer particles has been proposed.

  However, in the methods of Patent Documents 1 and 2, the foaming force is increased by lowering the secondary transition temperature, but the molecular weight has not been studied, and a satisfactory effect cannot be obtained with low temperature moldability.

  Moreover, in patent document 3, at least 1 type of acrylic resin selected from the group which consists of a butyl acrylate polymer, a cetyl methacrylate polymer, and a butyl acrylate-methacrylic acid acrylate copolymer is used for a styrene-type monomer. There has been proposed a method for producing expandable styrene resin particles, wherein 0.1 to 6.0% by weight is dissolved in the resin component of the expandable styrene resin particles obtained. However, in Patent Document 3, in order to dissolve the acrylic resin in the styrene monomer in the initial stage, it becomes a styrene-acrylate block copolymer, but the styrene-acrylate block copolymer is thermally stable. In particular, the surface of the molded body is likely to melt when it is made highly foamed, and there is room for improvement in terms of the appearance of the molded body.

  Patent Document 4 proposes foamable thermoplastic resin particles obtained by impregnating a foaming agent into thermoplastic resin particles obtained by polymerizing a styrene monomer, diallyl phthalate, and acrylic acid ester or methacrylic acid ester. Yes. However, when a crosslinking agent such as diallyl phthalate is added to increase the molecular weight, there is room for improvement in that the moldability is deteriorated and the appearance of the surface of the molded article is impaired.

  In patent document 5, although it is a foaming method different from the present invention, styrene resin particles having a weight average molecular weight of 150,000 to 500,000 are used, and a fatty acid hydrocarbon having 5 or less carbon atoms having a side chain is obtained. Expandable styrene resin particles containing 3 to 10% by weight of a foaming agent as a main component, having a foaming start temperature of 50 to 70 ° C. and a maximum foaming temperature of 80 to 110 ° C., and a method for producing the same are proposed. However, it is copolymerized with butyl acrylate in order to improve foamability at low temperature, but because the amount of butyl acrylate used relative to the styrenic monomer is large, melting of the molded body surface tends to occur, There is a problem that the appearance of the molded body is remarkably deteriorated.

Japanese Examined Patent Publication No. 46-42236 Japanese Patent Laid-Open No. 6-322038 Japanese Patent No. 1217232 Japanese Patent No. 1340620 JP-A-11-228727

  In view of the situation as described above, an object of the present invention is to provide expandable thermoplastic resin particles suitable for pre-expansion and in-mold molding at low temperatures.

  As a result of diligent studies to solve the above problems, the inventors found that the monomer composition was more than 95% by weight of styrene and 99% by weight or less, and 1% by weight or more and less than 5% by weight of acrylate (total of both). In a foamable thermoplastic resin particle comprising a thermoplastic resin (the amount is 100% by weight), a gel permeation chromatography (hereinafter abbreviated as “GPC”) measurement chart of the foamable thermoplastic resin particle. The value of the top peak of the GPC curve obtained from the above is less than 100,000 and less than 130,000, a line drawn from the point on the GPC curve having a height of ½ of the top peak on the high molecular weight side to the top peak to the top peak The area ratio surrounded by the GPC curve is less than 5.1% of the total area, the weight average molecular weight (Mw) is 200,000 to less than 320,000, the weight average molecular weight (Mw) and the number average molecular weight (M ) Ratio Mw / Mn is 2.7 or more and less than 3.4, and 4 parts by weight or more and less than 10 parts by weight of a readily volatile foaming agent with respect to 100 parts by weight of the foamable thermoplastic resin. 2 parts by weight or more and less than 2.0 parts by weight, and by making the monomer component contained in the foamable thermoplastic resin particles less than 0.3% by weight, the foamable thermoplastic resin having the above characteristics The inventors have found that particles can be obtained and have reached the present invention.

That is,
In the first aspect of the present invention, the monomer composition is more than 95% by weight of styrene monomer and 99% by weight or less, and 1% by weight or more and less than 5% by weight of acrylate monomer (the total amount of both is 100% by weight). %), The top peak value of the GPC curve obtained from the GPC measurement chart of the foamable thermoplastic resin particles is 100,000 or more and less than 130,000, The area ratio surrounded by a line drawn from the point on the GPC curve having a height of ½ of the top peak on the high molecular weight side to the top peak to the top peak and the GPC curve is less than 5.1% of the total area, The weight average molecular weight (Mw) is 200,000 to less than 320,000, the ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2.7 to less than 3.4, and the foaming heat 100 weight plastic resin 4 parts by weight or more and less than 10 parts by weight of a readily volatile foaming agent and 0.2 part by weight or more and less than 2.0 parts by weight of a plasticizer, and contained in the foamable thermoplastic resin particles. The present invention relates to expandable thermoplastic resin particles, wherein the monomer component is less than 0.3% by weight.
A second aspect of the present invention relates to the expandable thermoplastic resin particles according to the first aspect, wherein the acrylate is butyl acrylate.
A third aspect of the present invention relates to the expandable thermoplastic resin particle according to the first or second aspect, which is produced by a suspension polymerization method in an aqueous medium.
4th of this invention is related with the thermoplastic resin pre-expanded particle characterized by making the foamable thermoplastic resin particle of any one of the 1st-3rd invention foam.
5th of this invention is related with the thermoplastic resin foam characterized by carrying out the shaping | molding of the thermoplastic pre-expanded particle of 4th invention.

  In the present invention, the monomer composition is 95% by weight to 99% by weight or less of the styrene monomer, 1% by weight or more and less than 5% by weight of the acrylate monomer (the total amount of both is 100% by weight). ) In the expandable thermoplastic resin particles comprising the thermoplastic resin, the top peak value of the GPC curve obtained from the GPC measurement chart of the expandable thermoplastic resin particles is 100,000 or more and less than 130,000, which is higher than the top peak. On the molecular weight side, the area ratio surrounded by a line drawn from the point on the GPC curve at half the height of the top peak to the top peak and the GPC curve is less than 5.1% of the total area, and the weight average molecular weight (Mw ) Is 200,000 or more and less than 320,000, the ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 2.7 or more and less than 3.4, and 100 parts by weight of the foamable thermoplastic resin, Easily volatile 4 parts by weight or more and less than 10 parts by weight, plasticizer 0.2 parts by weight or more and less than 2.0 parts by weight, and 0.3% by weight of the monomer component contained in the foamable thermoplastic resin particles By being less than this, expandable thermoplastic resin particles suitable for pre-foaming at low temperature and in-mold molding can be obtained.

FIG. 1 shows a GPC measurement chart of expandable thermoplastic resin particles.

  The foamable thermoplastic resin particles of the present invention have a monomer composition of more than 95% by weight of styrene monomer and 99% by weight or less of styrene monomer, 1% by weight or more and less than 5% by weight (total of both). The foamable thermoplastic resin particles comprising a thermoplastic resin in which the amount is 100% by weight), the top peak value of the GPC curve obtained from the GPC measurement chart of the foamable thermoplastic resin particles is 100,000 or more Less than 130,000, the ratio of the area surrounded by a line drawn from the point on the GPC curve having a height of ½ of the top peak on the high molecular weight side to the top peak to the top peak and the GPC curve is 5. Less than 1%, a weight average molecular weight (Mw) of 200,000 to less than 320,000, a ratio Mw / Mn of a weight average molecular weight (Mw) to a number average molecular weight (Mn) of 2.7 to less than 3.4, and Foaming heat 4 parts by weight or more and less than 10 parts by weight of a readily volatile foaming agent and 0.2 part by weight or more and less than 2.0 parts by weight of a plasticizer with respect to 100 parts by weight of the plastic resin, in the foamable thermoplastic resin particles By making the monomer component contained in less than 0.3% by weight, expandable thermoplastic resin particles suitable for pre-expansion at low temperature and in-mold molding can be obtained.

  Examples of the styrene monomer constituting the expandable thermoplastic resin particles of the present invention include styrene derivatives such as styrene, α-methyl styrene, paramethyl styrene, t-butyl styrene, and chlorostyrene. These may be used alone or in combination of two or more.

  Examples of the acrylate monomer constituting the foamable thermoplastic resin particles of the present invention include, for example, alkyl acrylates such as methyl acrylate and butyl acrylate, methyl methacrylate, ethyl methacrylate, and cetyl methacrylate. And methacrylic acid alkyl esters. These monomers may be used independently and may be used in mixture of 2 or more types. Of these, butyl acrylate is preferred because it is easy to copolymerize with the styrene monomer and has good moldability.

The monomer composition constituting the expandable thermoplastic resin particles in the present invention is such that the monomer composition is more than 95% by weight and less than 99% by weight of the styrene monomer with respect to the total weight of 100% by weight of the charged monomers. The acrylate monomer is 1% by weight or more and less than 5% by weight, more preferably 97% by weight or more and 99% by weight or less of the styrene monomer, and 1% by weight or more and 3% by weight or less of the acrylate ester. .
In the monomer composition, when the acrylate monomer is 5% by weight or more, particularly when the foam is made highly foamed, the molded product tends to shrink, and the appearance of the molded product tends to deteriorate. is there. Moreover, when the amount of the acrylate monomer is less than 1% by weight, foaming at low temperature becomes difficult (molding with excellent heating temperature and fusing property necessary for obtaining pre-expanded particles having a desired expansion ratio. The molding temperature required to obtain the body tends to increase).

  The foamable thermoplastic resin particles in the present invention are obtained by gel permeation chromatography (hereinafter abbreviated as “GPC measurement”), the molecular weight at the top peak, the area ratio, the weight average molecular weight Mw, and the weight average. The ratio Mw / Mn between the molecular weight Mw and the number average molecular weight Mn needs to be in a specific range.

  Here, GPC measurement is performed by injecting 10 μl of a solution for measurement in which 0.02 g of expandable thermoplastic resin particles are dissolved in 20 ml of tetrahydrofuran (THF) into GPC, and measuring at a flow rate of 0.35 ml / min. A GPC measurement chart, a weight average molecular weight (Mw) and a number average molecular weight (Mn) were obtained.

  In addition, the top peak T is a point with the highest detection intensity in the GPC curve of the obtained GPC measurement chart (molecular weight vs. detection intensity) as shown in FIG.

The area ratio is a value calculated from the obtained GPC chart as follows.
As shown in FIG. 1, a straight line TH connecting the top peak T and a point H having a detection intensity of ½ of the top peak intensity on the high molecular weight side of the top peak T on the GPC curve is drawn. Let A be the area of a region surrounded by straight lines TH and GPC curves. On the other hand, let B be the area of the region surrounded by the GPC curve and the baseline.
The area ratio is calculated by the formula of area ratio (%) = A / B × 100.

The molecular weight of the top peak in the GPC curve of the expandable thermoplastic resin particles in the present invention is preferably 100,000 or more and less than 130,000.
If the molecular weight of the top peak in the GPC curve of the expandable thermoplastic resin particles is less than 100,000, the bottom split strength when foamed molded products tend to be low, and if it exceeds 130,000, the foamability is low, There is a tendency that the moldability is deteriorated (the heating temperature necessary for obtaining the pre-expanded particles having the desired expansion ratio and the molding temperature necessary for obtaining a molded article having excellent fusion property).

  The molecular weight of the top peak of the GPC curve can be controlled by a combination of the amount of initiator used for polymerizing the thermoplastic resin particles and the polymerization temperature. For example, the molecular weight can be increased by reducing the amount of initiator used and / or lowering the polymerization temperature.

In the present invention, the area ratio of the expandable thermoplastic resin particles on the GPC curve is preferably less than 5.1% of the total area, and more preferably 4.5% or less.
When the area ratio exceeds 5.1%, foamability tends to be low, and moldability tends to deteriorate.

  The area ratio on the GPC curve can be controlled by a combination of the amount of initiator used and the polymerization temperature when polymerizing the thermoplastic resin particles. For example, the area ratio can be lowered by increasing the amount of initiator used and / or increasing the polymerization temperature.

As a weight average molecular weight (Mw) of the expandable thermoplastic resin particle in this invention, 200,000 or more and less than 320,000 are preferable, and 220,000 or more and less than 280,000 are more preferable.
If the weight average molecular weight Mw of the expandable styrene resin particles is less than 200,000, the bottom split strength tends to be low when it is formed into a foamed molded product, and if it exceeds 320,000, the foamability is low and the moldability is low. Tends to deteriorate (the heating temperature necessary for obtaining pre-expanded particles having the desired expansion ratio and the molding temperature necessary for obtaining a molded article having excellent fusing properties).

  The weight average molecular weight Mw is controlled by a combination of the amount of the initiator used for polymerizing the thermoplastic resin particles and the polymerization temperature. For example, Mw can be lowered by increasing the amount of initiator used and / or increasing the polymerization temperature.

In the expandable styrene resin particles of the present invention, the ratio Mw / Mn between the weight average molecular weight (Mw) and the number average molecular weight (Mn) is preferably 2.7 or more and less than 3.4. More preferably, it is less than 3.2.
When Mw / Mn is less than 2.7, there is no molten particle on the surface, and there is a tendency that the molding temperature at which a good-looking molded product can be obtained tends to be low. Therefore, the moldability tends to be deteriorated (the heating temperature necessary for obtaining the pre-expanded particles having the desired expansion ratio and the molding temperature necessary for obtaining a molded article having excellent fusing property).

  The Mw / Mn ratio is controlled by a combination of the amount of initiator used when polymerizing thermoplastic resin particles and the polymerization temperature. For example, Mw / Mn can be lowered by increasing the amount of initiator used and / or increasing the polymerization temperature.

Examples of the blowing agent used in the present invention include aliphatic hydrocarbons such as propane, butane, pentane and hexane, alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane, methyl chloride, dichlorodifluoromethane, and dichloro. Halogenated hydrocarbons such as tetrafluoroethane are mentioned. These foaming agents may be used alone or in combination of two or more.
Among these, butane is preferable from the viewpoint of good foaming power.

The amount of the foaming agent used in the present invention is preferably 4 parts by weight or more and less than 10 parts by weight, and more preferably 5 parts by weight or more and less than 9 parts by weight with respect to 100 parts by weight of the thermoplastic resin.
When the amount of the foaming agent used is less than 4 parts by weight, the pre-foaming time becomes long and the fusion rate at the time of molding tends to decrease, resulting in an increase in production cost and economical disadvantage. When the amount of the foaming agent used is 10 parts by weight or more, the molded product tends to shrink and the appearance tends to be impaired.

Examples of the plasticizer used in the present invention include diisobutyl adipate, dioctyl adipate, dibutyl sebacate, glycerin tristearate, glycerin tricaprylate, coconut oil, palm oil, and rapeseed oil.
Among these, when used for the medical field or the packaging material field that comes into direct contact with food, edible oil is preferable, and palm oil, palm oil, and rapeseed oil are more preferable.
In the present invention, the plasticizer may be added in a step of polymerizing thermoplastic resin particles, a step of impregnating a foaming agent, or the like.

  The amount of the plasticizer used in the present invention is preferably 0.2 parts by weight or more and less than 2.0 parts by weight, more preferably 0.4 parts by weight or more and less than 1.6 parts by weight with respect to 100 parts by weight of the thermoplastic resin. . If the amount of the plasticizer used is less than 0.2 parts by weight, the secondary transition temperature does not decrease, which tends to be disadvantageous for pre-foaming and molding at low temperatures. It tends to be easy to do and spoil the appearance.

The monomer component contained in the expandable thermoplastic resin particles of the present invention is less than 0.3% by weight.
The contained monomer component tends to volatilize from the foamed molded product obtained by foaming the expandable thermoplastic resin particles. Particularly, when the contained monomer component is 0.3% by weight or more, the medical field Or it is unpreferable for the field of the packaging material which contacts a foodstuff directly, or for members of a car or a building.

Here, the amount of the remaining monomer component was determined by dissolving 1.0 g of expandable thermoplastic resin particles in 20 ml of dichloromethane, adding 0.005 g of an internal standard solution (cyclopentanol), and then performing gas chromatography (GC). It is a value measured under the following conditions.
GC: Shimadzu Corporation GC-14B
Column: PEG-20M 25%
Chromosorb W 60/80 (3.0 m × 3.0 mm ID)
Column temperature: 110 ° C
Detector (FID) temperature: 170 ° C

  The amount of the residual monomer component is controlled by a combination of the amount of initiator used when polymerizing the thermoplastic resin particles and the polymerization temperature. For example, the residual monomer component can be lowered by increasing the amount of initiator used and / or increasing the polymerization temperature.

The method for producing expandable thermoplastic resin particles of the present invention is preferably produced by suspension polymerization in an aqueous medium. For example, it can also be obtained by impregnating a pellet produced by bulk polymerization with a foaming agent, but the resulting foamed thermoplastic resin particle is difficult to be a true sphere, and thus pre-expanded particles. There is a tendency to affect the filling property in the mold.
Accordingly, spherical resin particles can be obtained, and furthermore, the foaming thermoplastic resin particles can be obtained by consistently performing the polymerization step and the foaming agent impregnation step. It is preferable.

  That is, as a method for producing expandable thermoplastic resin particles, a styrene monomer and an acrylate monomer are suspended, a polymerization reaction is initiated in the presence of a polymerization initiator and other additives, A method of adding a foaming agent during suspension polymerization or impregnating the foaming agent after polymerization is preferred.

  As the polymerization initiator of the monomer in the present invention, a radical generating polymerization initiator generally used for producing a thermoplastic polymer can be used. Typical polymerization initiators include, for example, 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-butyl peroxybenzoate, and other peroxides. These may be used alone or in combination of two or more.

The amount of the polymerization initiator used in the present invention is preferably 0.01 parts by weight or more and less than 3 parts by weight with respect to 100 parts by weight of the total weight of the charged monomers.
If the amount of the polymerization initiator used is less than 0.01 parts by weight, the polymerization rate tends to be slow, whereas if it exceeds 3 parts by weight, the polymerization reaction tends to be fast and difficult to control.

  Examples of the suspending agent used in the present invention include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic substances such as tricalcium phosphate and magnesium pyrophosphate. When a hardly soluble inorganic substance is used, the suspension stabilizing effect can be increased by using an anion surfactant such as sodium dodecylbenzenesulfonate. Moreover, the combined use of a water-soluble polymer and a hardly soluble inorganic substance is also effective.

  In the present invention, in addition to the above-mentioned raw materials, materials generally used for the production of expandable thermoplastic polymer particles such as nucleating agents and flame retardants are used in combination unless the present invention is inhibited. May be.

  Examples of the nucleating agent used in the present invention include methyl methacrylate copolymer, polyethylene wax, talc, fatty acid bisamide, ethylene-vinyl acetate copolymer resin, and the like. Specific examples of the fatty acid bisamide include methylene bisstearyl amide, ethylene bisstearyl amide (hereinafter abbreviated as EBS), hexamethylene bispalmitic acid amide, ethylene bisoleic acid amide and the like.

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, for example, halogenated aliphatic hydrocarbon compounds such as hexabromocyclododecane, tetrabromobutane, hexabromocyclohexane, tetrabromobisphenol A, tetrabromobisphenol F, 2,4,6-tri 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.
Specific examples of flame retardant aids include initiators such as cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and the like. .

  The foamable thermoplastic resin particles of the present invention are pre-foamed and then heated and foamed to obtain a foamed molded product.

  As the pre-foaming method, for example, an ordinary method such as foaming by heating with steam or the like using a cylindrical pre-foaming apparatus can be employed.

  The heating temperature at the time of preliminary foaming (temperature in the can) is appropriately adjusted depending on the blowing vapor pressure and the air amount, and is usually about 101 to 105 ° C, but in the present invention, it is about 97 to 100 ° C. Pre-foaming is possible even at low temperatures.

  As a method for foam-molding the pre-expanded particles, for example, a normal method such as filling the pre-expanded particles in a mold and blowing a vapor or the like to obtain a foam-molded body can be employed. .

The blown vapor pressure at the time of molding in the mold is usually about 0.6 to 1.0 kgf / cm ² , but in the present invention, molding is possible even at about 0.3 to 0.8 kgf / cm ^2. .

  The mold temperature at the time of in-mold molding is appropriately adjusted by the blown vapor pressure, but is usually about 113 to 115 ° C., but in the present invention, molding is also performed at a lower temperature of about 109 to 115 ° C. Is possible.

  As described above, the foamable thermoplastic resin particles of the present invention can be carried out at a lower temperature than in the prior art both at the time of preliminary foaming and in-mold foam molding, and are more suitable for energy saving. is there.

  Examples and Comparative Examples are given below, but the present invention is not limited thereby. The measurement evaluation method was performed as follows.

<Quantification of the amount of monomer components contained>
The amount of the monomer component contained in the obtained expandable thermoplastic resin particles was obtained by dissolving 1.0 g of expandable thermoplastic resin particles in 20 ml of dichloromethane and adding 0.005 g of an internal standard solution (cyclopentanol). Then, it measured on condition of the following using gas chromatography (GC).
GC: Shimadzu Corporation GC-14B
Column: PEG-20M 25%
Chromosorb W 60/80 (3.0 m × 3.0 mm ID)
Column temperature: 110 ° C
Detector (FID) temperature: 170 ° C

<GPC measurement>
After 0.02 g of expandable thermoplastic resin particles are dissolved in 20 ml of tetrahydrofuran (THF) with respect to the obtained expandable thermoplastic resin particles, using gel permeation chromatograph (GPC), the following GPC measurement was performed under the conditions, and a GPC measurement chart, a weight average molecular weight (Mw), and a number average molecular weight (Mn) were obtained.
Measuring device: manufactured by 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
Molecular Weight at Top Peak: As shown in FIG. 1, in the obtained GPC measurement chart (molecular weight vs. detected intensity), the point corresponding to the highest detected intensity on the GPC curve was taken as the top peak, and the corresponding molecular weight was derived.
Area ratio calculation: As shown in FIG. 1, on the high molecular weight side of the top peak T, a straight line TH connecting the point H on the GPC curve having a height of ½ of the top peak intensity and the top peak T The area A surrounded by the GPC curve and the area B (total area) surrounded by the GPC curve and the base line were calculated and calculated by the following equation.
Area ratio (%) = A / B × 100

<In-can temperature measurement during pre-foaming>
A thermometer was inserted from the side of the cylindrical pre-foaming machine, and the temperature inside the can during pre-foaming was measured.

<Formability evaluation>
Using a molding machine [manufactured by Daisen, KR-57], a box-shaped mold having a thickness of 30 mm, a length of 550 mm, a width of 350 mm, and a height of 120 mm is filled, and the blowing vapor pressure is 0.3 to 0.8 kgf. In-mold molding was performed under molding conditions varied within the range of / cm ² to obtain a box-shaped foam molded product.
After the obtained thermoplastic resin foam was dried at room temperature for 24 hours, the surface property and the fusing property between the foamed particles described below both passed, and the lowest water vapor pressure was determined. It was set as a vapor pressure range in which molding was possible. Further, the mold temperature at the lowest blowing water vapor pressure and the highest blowing water vapor pressure was determined.
(1) Evaluation of fusing property The obtained thermoplastic resin foam is broken, the fractured surface is observed, the ratio of the broken particles rather than the particle interface is obtained, and the fusion is performed according to the following criteria. Sex was judged.
Pass: The rate of particle breakage is 80% or more. Fail: The rate of particle breakage is less than 80%. (2) Surface property evaluation The surface state of the obtained thermoplastic resin foam is visually observed, and the surface property is determined according to the following criteria. Evaluated.
Pass: Melting of the surface, less intergranularity, and beautiful rejection: Poor appearance due to surface melting, intergranularity <Measurement of bottom split strength of molded product>
Four sides of the obtained box-shaped molded body were fixed, the center of the bottom of the box-shaped molded body was pressed using a 100 mmφ cylindrical jig, and the maximum load when the bottom was broken was measured.

Example 1
<Manufacture of expandable styrene resin particles>
In a 6 liter autoclave attached to a stirrer, 100 parts by weight of pure water, 0.2 part by weight of tricalcium phosphate, 0.01 part by weight of sodium dodecylbenzenesulfonate, 0.3 part by weight of benzoyl peroxide as an initiator, and 0.21 part by weight of 1,1-bis (t-butylperoxy) cyclohexane was charged. Subsequently, 99 parts by weight of styrene monomer, 1 part by weight of butyl acrylate monomer and 1% by weight of coconut oil were charged while stirring at 250 rpm, and the temperature was raised to 98 ° C. Then, it hold | maintained at 98 degreeC for 4 hours, and obtained the thermoplastic resin particle.
Next, 2 parts by weight of cyclohexane and 6 parts by weight of butane were injected into the autoclave as a blowing agent, and the temperature was raised to 120 ° C. again. Thereafter, the mixture was kept at 120 ° C. for 2 hours, then cooled to room temperature, and the polymerization slurry was taken out from the autoclave. The taken-out polymerization slurry was dehydrated, washed and dried to obtain expandable thermoplastic resin particles.
<Pre-foaming and manufacturing of molded products>
The obtained expandable styrene resin particles were sieved to a particle diameter of 0.6 mm to 1.2 mm. The foamable styrene-based resin particles thus screened were prefoamed at a bulk magnification of 65 times under the condition of a blowing vapor pressure of 0.8 kgf / cm ² using a pressure prefoaming machine (manufactured by Daikai Kogyo Co., Ltd., BHP). . At this time, air was blown into the blown steam to adjust the blown steam temperature. As a result, the pressure heating time was 70 seconds, and the can internal temperature was 98 ° C. Then, it was left to stand at room temperature for 1 day, and curing drying was performed.
Next, the obtained thermoplastic resin pre-expanded particles are placed in a box-shaped mold having a thickness of 30 mm, a length of 550 mm, a width of 350 mm, and a height of 120 mm, using a molding machine [manufactured by Daisen, KR-57]. Filling and in-mold molding were performed under the molding conditions of a blowing vapor pressure of 0.3 to 0.8 kgf / cm ² to obtain a box-shaped foam molded product.
The moldable vapor pressure range was 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time was 109 to 115 ° C.
Evaluation was performed using the obtained foamable thermoplastic resin particles and foamed molded article, and the results are shown in Table 1.

(Example 2)
<Manufacture of expandable styrene resin particles>
Expandable thermoplastic resin particles were obtained in the same manner as in Example 1, except that the monomer composition at the start of polymerization was changed to 98 parts by weight of styrene monomer and 2 parts by weight of butyl acrylate monomer.
<Pre-foaming and manufacturing of molded products>
When obtaining pre-expanded particles having a bulk magnification of 65 times, the pressure heating time at the time of pre-expansion was 63 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time is 109 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Example 3)
<Manufacture of expandable styrene resin particles>
Expandable thermoplastic resin particles were obtained in the same manner as in Example 1, except that the monomer composition at the start of polymerization was changed to 97 parts by weight of styrene monomer and 3 parts by weight of butyl acrylate monomer.
<Pre-foaming and manufacturing of molded products>
When pre-expanded particles having a bulk magnification of 65 times were obtained, the pressure heating time at the time of pre-expansion was 55 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time is 109 to 115 ° C. It was. The evaluation results are shown in Table 1.

Example 4
<Manufacture of expandable styrene resin particles>
In the production of expandable thermoplastic resin particles, expandable thermoplastic resin particles were obtained in the same manner as in Example 2, except that 2 parts by weight of cyclohexane and 3 parts by weight of butane were used as the foaming agent.
<Pre-foaming and manufacturing of molded products>
When pre-expanded particles having a bulk magnification of 65 times were obtained, the pressure heating time at the time of pre-expansion was 120 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time is 109 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Example 5)
<Manufacture of expandable styrene resin particles>
In the polymerization of thermoplastic resin particles, expandable thermoplastic resin particles were obtained by the same operation as in Example 2 except that the amount of coconut oil used was changed from 1 part by weight to 1.5 parts by weight at the start of polymerization. .
<Pre-foaming and manufacturing of molded products>
When obtaining pre-expanded particles having a bulk magnification of 65 times, the pressure heating time at the time of pre-expansion was 60 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time is 109 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Example 6)
<Manufacture of expandable styrene resin particles>
In the polymerization of the thermoplastic resin particles, expandable thermoplastic resin particles were obtained in the same manner as in Example 2, except that 0.3 parts by weight of benzoyl peroxide was changed to 0.2 parts by weight at the start of polymerization.
<Pre-foaming and manufacturing of molded products>
When pre-expanded particles having a bulk magnification of 65 times were obtained, the pressure heating time during pre-expansion was 80 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time is 109 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Example 7)
<Manufacture of expandable styrene resin particles>
In the polymerization of the thermoplastic resin particles, except that 0.2 parts by weight of 1,1-bis (t-butylperoxy) cyclohexane was changed to 0.25 parts by weight at the start of polymerization, the same operation as in Example 2 was performed. Expandable thermoplastic resin particles were obtained.
<Pre-foaming and manufacturing of molded products>
When pre-foamed particles having a bulk magnification of 65 times were obtained, the pressure heating time at the time of pre-foaming was 75 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time is 109 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 1)
<Manufacture of expandable styrene resin particles>
In the polymerization of the thermoplastic resin particles, the foaming thermoplasticity was changed by the same operation as in Example 1 except that the monomer composition was changed to 100 parts by weight of the styrene monomer without using the butyl acrylate monomer at the start of the polymerization. Resin particles were obtained.
<Pre-foaming and manufacturing of molded products>
To obtain a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressurizing and heating time is 97 seconds, the temperature in the reactor Was 103 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding as in Example 1 is 0.6 to 0.8 kgf / cm ² , and the mold temperature at that time is 113 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 2)
<Manufacture of expandable styrene resin particles>
Expandable thermoplastic resin particles were obtained in the same manner as in Example 1, except that the monomer composition at the start of polymerization was changed to 95 parts by weight of styrene monomer and 5 parts by weight of butyl acrylate monomer.
<Pre-foaming and manufacturing of molded products>
When obtaining pre-expanded particles having a bulk magnification of 65 times, the pressure heating time at the time of pre-expansion was 34 seconds, and the temperature in the can was 97 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.4 kgf / cm ² , and the mold temperature at that time is 109 to 110 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 3)
<Manufacture of expandable styrene resin particles>
In the production of expandable thermoplastic resin particles, expandable thermoplastic resin particles were obtained in the same manner as in Example 2, except that cyclohexane was not used as the foaming agent and butane was changed to 2 parts by weight.
<Pre-foaming and manufacturing of molded products>
Although the blowing vapor pressure at the time of preliminary foaming was changed from 0.8 kgf / cm ² to 1.0 kgf / cm ² , it was not foamed to the target magnification and evaluation was impossible.

(Comparative Example 4)
<Manufacture of expandable styrene resin particles>
In the production of expandable thermoplastic resin particles, expandable thermoplastic resin particles were obtained in the same manner as in Example 2 except that the foaming agent was changed to 3 parts by weight of cyclohexane and 9 parts by weight of butane.
<Pre-foaming and manufacturing of molded products>
When pre-expanded particles having a bulk magnification of 65 times were obtained, the pressure heating time at the time of pre-expansion was 42 seconds, and the temperature in the can was 97 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.4 kgf / cm ² , and the mold temperature at that time is 109 to 110 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 5)
<Manufacture of expandable styrene resin particles>
In the polymerization of thermoplastic resin particles, expandable thermoplastic resin particles were obtained by the same operation as in Example 2 except that the amount of coconut oil used was changed from 1 part by weight at the start of polymerization.
<Pre-foaming and manufacturing of molded products>
To obtain a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressing and heating time is 80 seconds, the temperature in the reactor Was 103 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding as in Example 1 is 0.6 to 0.8 kgf / cm ² , and the mold temperature at that time is 113 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 6)
<Manufacture of expandable styrene resin particles>
In the polymerization of thermoplastic resin particles, expandable thermoplastic resin particles are obtained by the same operation as in Example 2 except that the amount of coconut oil used at the start of polymerization is changed from 1 part by weight to 2.1 parts by weight. It was.
<Pre-foaming and manufacturing of molded products>
When pre-expanded particles having a bulk magnification of 65 times were obtained, the pressure heating time at the time of pre-expansion was 38 seconds, and the temperature in the can was 97 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.4 kgf / cm ² , and the mold temperature at that time is 109 to 110 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 7)
<Manufacture of expandable styrene resin particles>
In polymerization of thermoplastic resin particles, Example 2 was changed except that 0.30 part by weight of benzoyl peroxide was changed to 0.35 part by weight at the start of polymerization and the heat retention time at 98 ° C. was changed from 4 hours to 3 hours. Expandable thermoplastic resin particles were obtained by the same operation as in. The molecular weight of the top peak on the GPC chart of the obtained expandable resin particles was 90,000.
<Pre-foaming and manufacturing of molded products>
When obtaining pre-expanded particles with a bulk magnification of 65 times, the pressure heating time at the time of pre-expansion was 33 seconds, and the temperature in the can was 97 ° C.
Next, the vapor pressure range in which molding is possible is 0.3 to 0.6 kgf / cm ² in the same way as in Example 1, and the mold temperature at that time is 109 to 113 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 8)
<Manufacture of expandable styrene resin particles>
In polymerization of thermoplastic resin particles, 0.30 part by weight of benzoyl peroxide is 0.15 part by weight and 0.20 part by weight of 1,1-bis (t-butylperoxy) cyclohexane is 0.25 part by weight at the start of polymerization. Changed to Further, the polymerization temperature was changed from 98 ° C. to 102 ° C., and further kept at 102 ° C. for 3 hours, and then heated to 120 ° C. over 30 minutes. Subsequently, the mixture was kept at 120 ° C. for 1 hour to obtain styrene resin particles, cooled to 95 ° C., and 2 wt% cyclohexane and 6 wt% butane were injected into the autoclave as a blowing agent, and the temperature was raised again to 120 ° C. Allowed to warm. Thereafter, expandable thermoplastic resin particles were obtained in the same manner as in Example 2 except that the temperature was kept at 120 ° C. for 1 hour. The molecular weight at the top peak of the obtained expandable resin particles on the GPC chart was 130,000.
<Pre-foaming and manufacturing of molded products>
To obtain a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressurizing and heating time is 68 seconds, the temperature in the reactor Was 103 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding as in Example 1 is 0.6 to 0.8 kgf / cm ² , and the mold temperature at that time is 113 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 9)
<Manufacture of expandable styrene resin particles>
At the start of polymerization, 0.30 parts by weight of benzoyl peroxide was changed to 0.20 parts by weight, and the mixture was kept at 98 ° C. for 3 hours and 30 minutes, and then heated to 120 ° C. over 30 minutes. Subsequently, the mixture was kept at 120 ° C. for 1 hour to obtain styrene resin particles, then cooled to 95 ° C., and 2 parts by weight of cyclohexane and 6 parts by weight of butane as a foaming agent were pressed into the autoclave and again raised to 120 ° C. Allowed to warm. Thereafter, expandable thermoplastic resin particles were obtained in the same manner as in Example 2 except that the temperature was kept at 120 ° C. for 1 hour. The area ratio of the GPC chart of the obtained expandable resin particles was 5.1%.
<Pre-foaming and manufacturing of molded products>
To obtain a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressurizing and heating time is 63 seconds, the temperature in the reactor Was 103 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding as in Example 1 is 0.6 to 0.8 kgf / cm ² , and the mold temperature at that time is 113 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 10)
<Manufacture of expandable styrene resin particles>
Expandable thermoplastic resin particles were obtained in the same manner as in Example 2, except that 0.30 parts by weight of benzoyl peroxide was changed to 0.35 parts by weight at the start of polymerization. The resulting foamable resin particles had a weight average molecular weight of 190,000.
<Pre-foaming and manufacturing of molded products>
When pre-expanded particles having a bulk magnification of 65 times were obtained, the pressure heating time during pre-expansion was 31 seconds, and the temperature in the can was 97 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.4 kgf / cm ² , and the mold temperature at that time is 109 to 110 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 11 )
<Manufacture of expandable styrene resin particles>
In the polymerization of the thermoplastic resin particles, expandable thermoplastic resin particles were obtained in the same manner as in Example 2 except that 0.3 parts by weight of benzoyl peroxide was changed to 0.32 parts by weight at the start of polymerization. Mw / Mn of the obtained expandable resin particles was 2.5.
<Pre-foaming and manufacturing of molded products>
To obtain a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressurizing and heating time is 36 seconds, the temperature in the reactor Was 100 ° C.
Next, the vapor pressure range in which molding is possible is 0.3 to 0.6 kgf / cm ² in the same way as in Example 1, and the mold temperature at that time is 109 to 113 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 12 )
<Manufacture of expandable styrene resin particles>
In the polymerization of the thermoplastic resin particles, 0.3 parts by weight of benzoyl peroxide was changed to 0.2 parts by weight at the start of polymerization, and 0.20 part by weight of 1,1-bis (t-butylperoxy) cyclohexane was changed to 0. Expandable thermoplastic resin particles were obtained by the same operation as in Example 2 except that the amount was changed to 15 parts by weight. Mw / Mn of the obtained expandable resin particles was 3.5.
<Pre-foaming and manufacturing of molded products>
In obtaining a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressurizing and heating time is 112 seconds, the temperature in the reactor Was 105 ° C.
Next, the lowest vapor pressure that can be molded when performing in-mold molding as in Example 1 was 0.8 kgf / cm ² , and the mold temperature at that time was 115 ° C. The evaluation results are shown in Table 1.

The top peak on the T GPC curve H The point on the GPC curve where the detection intensity is 1/2 of the top peak on the higher molecular weight side than the top peak
A Area surrounded by straight line connecting TP and HP and GPC curve

Claims (5)

Heat having a monomer composition of more than 95% by weight of styrene monomer and 99% by weight or less, and 1% by weight or more and less than 5% by weight of acrylate monomer (the total amount of both is 100% by weight) In the foamable thermoplastic resin particles comprising a plastic resin,
Obtained from gel permeation chromatography measurement of the foamable thermoplastic resin particles,
The molecular weight at the top peak on the GPC curve is 100,000 or more and less than 130,000,
The area ratio of the line surrounded by the GPC curve from the point on the GPC curve at a higher molecular weight than the top peak and ½ the height of the top peak is 5.1% of the total area. Less than,
The weight average molecular weight (Mw) is 200,000 or more and less than 320,000, the ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 2.7 or more and less than 3.4,
And it contains 4 parts by weight or more and less than 10 parts by weight of a volatile foaming agent and 0.2 parts by weight or more and less than 2.0 parts by weight of a plasticizer with respect to 100 parts by weight of the foamable thermoplastic resin. Expandable thermoplastic resin particles characterized in that the monomer component contained in the expandable thermoplastic resin particles is less than 0.3% by weight.   2. The expandable thermoplastic resin particles according to claim 1, wherein the acrylate is butyl acrylate.   The expandable thermoplastic resin particles according to claim 1 or 2, which are produced by a suspension polymerization method in an aqueous medium.   Thermoplastic resin pre-expanded particles obtained by foaming the expandable thermoplastic resin particles according to any one of claims 1 to 3.   A thermoplastic resin foam obtained by molding the thermoplastic pre-expanded particles according to claim 4 in a mold.