JP7041578B2 - Thermoplastic resin foam - Google Patents

Description

The present invention relates to a thermoplastic resin foam, and more particularly to a thermoplastic resin foam that can be suitably used as a heat insulating material for walls, floors, roofs, etc. of buildings.

Polystyrene resin extruded foam has excellent heat insulating properties and mechanical strength, and is therefore widely used as a heat insulating material molded into a plate shape. In such a polystyrene resin extruded foam, generally, a foamable resin melt obtained by melt-kneading a thermoplastic resin and a physical foaming agent in an extruder is obtained from a die having a slit shape or the like attached to the tip of the extruder. It is manufactured by extruding into a low pressure region to foam it, and if desired, molding it with a shaping tool or the like connected to a die outlet.

In the above-mentioned polystyrene resin extruded foam, as a method for obtaining higher heat insulating properties for a long period of time, a method of using a gas having a low thermal conductivity as a foaming agent, a method of using a resin having a high gas barrier property, and a method of using a resin having a high gas barrier property are used. Various methods such as a method of reducing the bubble diameter have been proposed.

For example, in Patent Document 1, in a thermoplastic resin extruded foam insulation plate containing a non-halogen organic physical foaming agent, the thermoplastic resin is a polystyrene resin and a polyester resin having a specific blending ratio of less than 5 J / g of heat of fusion. A thermoplastic resin extruded foam insulation plate, which is a mixture, has been proposed. Further, even when a physical foaming agent such as a hydrocarbon is used, it is possible to provide a thermoplastic resin extruded foamed heat insulating plate which can suppress the dissipation of the foaming agent from the foam, has a low thermal conductivity, and has excellent heat insulating properties for a long period of time. It is supposed to be.

Japanese Unexamined Patent Publication No. 2011-219631

The thermoplastic resin extruded foamed heat insulating plate described in Patent Document 1 is excellent in that the dissipation of the foaming agent from the foamed heat insulating plate is suppressed and excellent heat insulating properties can be maintained for a long period of time. There was room for development in terms of achieving long-term heat insulation, well-balanced and excellent flame retardancy and mechanical strength.

The thermoplastic resin foam of the present invention was made to solve the above-mentioned problems, and has a small change in thermal conductivity with time, is excellent in heat insulating property for a long period of time, and is excellent in flame retardancy and mechanical strength. An object of the present invention is to provide a thermoplastic resin foam.

The present invention provides the thermoplastic resin foams described below.
<1> A thermoplastic resin foam having a thermoplastic resin as a base resin and containing a hydrocarbon having 3 to 5 carbon atoms and a flame retardant.
The thermoplastic resin is a mixed resin of a polystyrene resin, a styrene- (meth) acrylic acid alkyl ester copolymer, and an amorphous polyester resin.
The content of the amorphous polyester resin in a total of 100 parts by mass of the polystyrene resin and the styrene- (meth) acrylic acid alkyl ester copolymer is 10 to 100 parts by mass.
A thermoplastic resin characterized in that the content of the (meth) acrylic acid alkyl ester component derived from the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin is 0.5 to 6% by mass. Foam.
<2> The thermoplastic resin foam according to <1>, wherein the content of the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin is 1 to 20% by mass.
<3> The heat according to <2>, wherein the content of the (meth) acrylic acid alkyl ester component in the styrene- (meth) acrylic acid alkyl ester copolymer is 10 to 70% by mass. Plastic resin foam.
<4> The amorphous polyester resin is selected from 1 or 1,4-cyclohexanedimethanol-modified polyethylene terephthalate resin, spiroglycol-modified polyethylene terephthalate resin, dioxane glycol-modified polyethylene terephthalate resin, neopentyl glycol-modified polyethylene terephthalate resin, and 1,4-cyclohexanedimethanol-modified polyethylene terephthalate resin. The thermoplastic resin foam according to any one of <1> to <3>, which is characterized by having 2 or more.
<5> The mixed resin is characterized in that the content of the (meth) acrylic acid alkyl ester component derived from the styrene- (meth) acrylic acid alkyl ester copolymer is less than 0.5 to 4% by mass. The thermoplastic resin foam according to any one of <1> to <4>.
<6> The thermoplastic resin foam according to any one of <1> to <5>, wherein the thermoplastic resin foam has an apparent density of 20 to 50 kg / m ³ .

The thermoplastic resin foam according to the present invention is a mixed resin in which the base resin is a polystyrene resin, a styrene- (meth) acrylic acid alkyl ester copolymer, and an amorphous polyester resin, and the polystyrene resin and the styrene are used. -The content of the amorphous polyester resin with respect to the total with the (meth) acrylic acid alkyl ester copolymer is a specific amount, and is derived from the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin. By setting the content of the (meth) acrylic acid alkyl ester component to a specific ratio, a thermoplastic resin foam having a small change in thermal conductivity over time and excellent mechanical strength such as flame retardancy and bending fracture bending can be obtained. ..

It is sectional drawing of the cell membrane in the thermoplastic resin extruded foam plate of Example 1. FIG. It is a cross-sectional photograph of a bubble film in the thermoplastic resin extruded foam plate of Comparative Example 1. It is a cross-sectional photograph of a bubble film in the thermoplastic resin extruded foam plate of Comparative Example 3.

The thermoplastic resin foam of the present invention will be described below.

The thermoplastic resin foam of the present invention is a thermoplastic resin foam containing a thermoplastic resin as a base resin and containing a hydrocarbon having 3 to 5 carbon atoms and a flame retardant, and the thermoplastic resin of the base resin is polystyrene. It is a mixed resin of a resin, a styrene- (meth) acrylic acid alkyl ester copolymer, and an amorphous polyester resin, and the amorphous polyester resin is the polystyrene resin and the styrene- (meth) acrylic acid alkyl ester. Heat that is contained in a specific amount with respect to the copolymer and also contains the (meth) acrylic acid alkyl ester component derived from the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin in a specific ratio. It is a thermoplastic resin foam.

The thermoplastic resin foam of the present invention contains a (meth) acrylic acid alkyl ester component derived from a styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin in a specific ratio, whereby it is conventional. , A thermoplastic resin that has a smaller change in thermal conductivity over time and is excellent in flame retardancy and mechanical strength as compared with a thermoplastic resin foam that uses a mixed resin of a polystyrene resin and an amorphous polyester resin as a base resin. It becomes a foam. The reason is considered as follows.

FIG. 1 shows a cross-sectional photograph of the bubble membrane of the thermoplastic resin foam of the present invention. From FIG. 1, in the cross section of the bubble film portion of the thermoplastic resin foam, a sea-island structure in which the polystyrene resin forms a continuous phase and the amorphous polyester resin forms a dispersed phase is formed, and further, the amorphous in the mixed resin. It can be seen that the polystyrene resin is finely dispersed and stretched. That is, in the bubble film of the thermoplastic resin foam of the present invention, since the morphology in which the gas barrier property of the amorphous polyester resin is easily exhibited is formed, it is considered that the long-term heat insulating property is more excellent. Further, it is considered that the thermoplastic resin foam has excellent mechanical strength because the amorphous polyester resin is finely dispersed and stretched in the mixed resin.

The reason why such morphology is formed in the bubble film of the thermoplastic resin foam of the present invention is not clear, but it is derived from the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin (meth). It is considered that this is because the amorphous polyester resin is more easily dispersed and easily stretched in the mixed resin by containing the acrylic acid alkyl ester component in a specific ratio.

The content of the (meth) acrylic acid alkyl ester component derived from the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin is 0.5 to 6% by mass. When the (meth) acrylic acid alkyl ester component in the mixed resin is within the above range, it is considered that the amorphous polyester resin is more finely dispersed and easily stretched in the mixed resin. It becomes a thermoplastic resin foam having a more excellent effect of suppressing changes. Further, it is a foam that sufficiently satisfies the combustibility standard required as a building material and has excellent mechanical strength. From the above viewpoint, the content of the (meth) acrylic acid alkyl ester component in the mixed resin is preferably 0.5% by mass or more and less than 4% by mass, more preferably 0.5 to 3% by mass.

Examples of the polystyrene resin used in the present invention include copolymers of styrene and other monomers excluding polystyrene (GPPS) and styrene- (meth) acrylic acid alkyl ester copolymers. Examples of the copolymer include a styrene- (meth) acrylic acid copolymer, a styrene-maleic anhydride copolymer, a styrene-poniferylene ether copolymer, a styrene-acrylonitrile copolymer, and an acrylonitrile-styrene-butadiene copolymer. Combined, acrylonitrile-styrene acrylate copolymer, styrene-butadiene copolymer, styrene-methylstyrene copolymer, styrene-dimethylstyrene copolymer, styrene-ethylstyrene copolymer, styrene-diethylstyrene copolymer, resistant Impact-sensitive polystyrene (HIPS) and the like are exemplified. The content of the styrene component in these styrene-based copolymers is preferably 50% by mass or more, more preferably 80% by mass or more. In addition, these polystyrene resins can be used alone or in admixture of two or more. In addition, these polystyrene resins may contain a component derived from a branching agent such as a polyfunctional monomer such as divinylbenzene.

Among the above polystyrene resins, polystyrene (GPPS), styrene- (meth) acrylic acid copolymer, styrene-maleic anhydride copolymer, styrene-acrylonitrile copolymer, and styrene-methylstyrene copolymer are preferable. Among them, polystyrene (GPPS) can be particularly preferably used.

When the thermoplastic resin foam of the present invention is produced by extrusion foaming, the melt viscosity (η) of the polystyrene resin under the conditions of a temperature of 200 ° C. and a shear rate of 100 sec ^-1 is in the range of 500 to 8000 Pa · s. Is preferable. By setting the melt viscosity (η) of the polystyrene resin within the above range, the extrudability when producing the thermoplastic resin foam is excellent, and the obtained thermoplastic resin foam is excellent in mechanical strength. .. From the above viewpoint, the melt viscosity of the polystyrene resin is more preferably in the range of 700 to 6000 Pa · s, further preferably in the range of 1000 to 5000 Pa · s.

The melt viscosity of the polystyrene resin is measured by Capillograph 1D or the like manufactured by Toyo Seiki Seisakusho Co., Ltd. A capillary having a hole diameter of 1.0 mm and a length of 10.0 mm is used.

In the styrene- (meth) acrylic acid alkyl ester copolymer used in the present invention, (meth) acrylic acid means acrylic acid and / or methacrylic acid. The alkyl group of the (meth) acrylic acid alkyl ester is preferably an alkyl group having 1 to 4 carbon atoms. Specifically, the (meth) acrylic acid ester is methyl acrylate, ethyl acrylate, or propyl acrylate. , Butyl acrylate (n-butyl), methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate (n-butyl) and the like can be exemplified. Further, among the styrene- (meth) acrylic acid alkyl ester copolymers, a styrene-methyl methacrylate copolymer can be particularly preferably used. These styrene- (meth) acrylic acid alkyl ester copolymers can be used alone or in admixture of two or more.

The content of the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin is preferably in the range of 1 to 20% by mass. By setting the content of the styrene- (meth) acrylic acid alkyl ester copolymer in the above range, the thermoplastic resin foam becomes excellent in the balance of long-term heat insulating property, flame retardancy and mechanical strength. From the above viewpoint, the content of the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin is preferably 2.5 to 18% by mass, more preferably 5 to 15% by mass.

The content of the (meth) acrylic acid alkyl ester component in the styrene- (meth) acrylic acid alkyl ester copolymer is preferably in the range of 10 to 70% by mass. By setting the content of the (meth) acrylic acid alkyl ester component in the styrene- (meth) acrylic acid alkyl ester copolymer to the above range, the long-term heat insulating property, flame retardancy and mechanical strength of the thermoplastic resin foam can be determined. The balance will be even better. From the above viewpoint, the content of the (meth) acrylic acid alkyl ester copolymer in the styrene- (meth) acrylic acid alkyl ester copolymer is preferably 15 to 65% by mass, more preferably 20 to 60% by mass.

The content of the (meth) acrylic acid alkyl ester component in the styrene- (meth) acrylic acid alkyl ester copolymer and the content of the (meth) acrylic acid alkyl ester component in the mixed resin are analyzed by thermal decomposition gas chromatograph analysis. It can be obtained by a known method such as.

The amorphous polyester resin used in the present invention includes, for example, an amorphous polyethylene terephthalate co-weight in which a part of the ethylene glycol component unit is changed to a diol component having a higher bulk than the ethylene glycol component in order to prevent the crystallization of polyethylene terephthalate. Coalescence is exemplified. As the diol component, aliphatic diols, aromatic diols (including divalent phenol) and the like can be used. Examples of the diol component unit in the amorphous polyester resin include aliphatic diols such as 1,4-butanediol and 2,2-dimethyl-1,3-propanediol (hereinafter referred to as neopentyl glycol), 1,4-. Alicyclic diols such as cyclohexanedimethanol, aromatic diols such as bisphenol A, or 3,9-bis (1,1-dimethyl-2-hydroxyethyl) 2,4,8,10-tetraoxaspiro [5. 5] Undecane (hereinafter referred to as spiroglycol), 2- (5-ethyl-5-hydroxymethyl-1,3-dioxane-2-yl) -2-methylpropane-1-ol (hereinafter referred to as dioxaneglycol), etc. Can be mentioned as a diol having a cyclic ether skeleton of. These diol components may be used alone or in combination of two or more.

As the polyethylene terephthalate resin modified with the above diol component, spiroglycol-modified polyethylene terephthalate resin, dioxane glycol-modified polyethylene terephthalate resin, neopentyl glycol-modified polyethylene terephthalate resin, and 1,4-cyclohexanedimethanol-modified polyethylene terephthalate resin are particularly preferable. Can be used for.

The amorphous polyester resin used in the present invention conforms to JIS K7122 (1987) and is 23 ° C to 300 ° C at a heating rate of 2 ° C / min by a heat flux differential scanning calorimetry device (DSC device). It is preferable that the heat absorption peak calorific value associated with melting of the polyester resin based on the DSC curve obtained by heating up to is less than 5 J / g (including 0). The heat absorption peak calorific value of the polyester resin is preferably less than 2 J / g (including 0) from the viewpoint of foaming suitability of the mixture of the polystyrene resin and the amorphous polyester resin.

In order to finely disperse the amorphous polyester resin in the bubble film of the thermoplastic resin foam in the present invention, the melt viscosity (η) of the amorphous polyester resin under the conditions of a temperature of 200 ° C. and a shear rate of 100 sec ^-1 . Is preferably in the range of 500 to 10000 Pa · s, more preferably 700 to 8000 Pa · s, and particularly preferably 1000 to 5000 Pa · s. The melt viscosity of the amorphous polyester resin can be measured by the same method as the above-mentioned measurement of the melt viscosity of the polystyrene resin. However, as a measurement sample, a polyester resin having a water content adjusted to 500 ppm or less is used.

The midpoint glass transition temperature of the amorphous polyester resin is preferably 70 to 110 ° C., more preferably 75 to 105 ° C. from the viewpoint of extrusion stability.

The midpoint glass transition temperature of the amorphous polyester resin conforms to JIS K7121 (1987) and is heated from 23 ° C to 300 ° C by a heat flux differential scanning calorimetry device (DSC device) at a heating rate of 10 ° C / min. It can be measured based on the DSC curve obtained in the above. The mass of the sample piece is 10 mg, and the condition is adjusted by 3. The "case of measuring the glass transition temperature after performing a certain heat treatment" described in (3) is adopted.

By blending the amorphous polyester resin with the polystyrene resin, it is possible to stably produce a thermoplastic resin foam having a high foaming ratio without causing deterioration of the foaming suitability. It is considered that the amorphous polyester resin is easily dispersed finely in the mixed resin and is easily stretched along the bubble film, so that the dissipation of the foaming agent from the foam and the inflow of air into the foam are suppressed. It is considered that a high gas barrier property can be exhibited.

The content of the amorphous polyester resin is 10 to 100 parts by mass with respect to 100 parts by mass of the total of the polystyrene resin and the styrene- (meth) acrylic acid alkyl ester copolymer. If the content of the amorphous polyester resin is too small, the gas barrier property of the amorphous polyester resin is not sufficiently exhibited in the mixed resin, and the effect of suppressing the change in the thermal conductivity of the thermoplastic resin foam with time is obtained. It may become smaller. On the other hand, if the amount of the amorphous polyester resin is too large, the amount of the flame retardant required to maintain the flame retardancy may increase. From the above viewpoint, the content of the amorphous polyester resin is more preferably 20 to 90 parts by mass, more preferably 25 to 80 parts by mass with respect to 100 parts by mass of the total of the polystyrene resin and the styrene- (meth) acrylic acid alkyl ester copolymer. Parts by mass are more preferred.

Examples of the hydrocarbon having 3 to 5 carbon atoms used as a foaming agent in the present invention include saturated aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane and neopentane, and alicyclic type such as cyclobutane and cyclopentane. Hydrocarbons can be mentioned. Among these, isobutane can be particularly preferably used because a thermoplastic resin foam having a slow gas permeation rate and a low apparent density can be easily obtained. The above hydrocarbons may be used alone or in combination of two or more.

Further, as hydrocarbons having 3 to 5 carbon atoms, trans-1,3,3,3-tetrafluoropropene (trans HFO-1234ze) and cis-1,3,3,3-tetrafluoropropene (cis HFO-) 1234ze), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1-chloro-3,3,3-trifluoropropene (HFO-1233zd), 1,1,1,4,4,4 Examples thereof include halogenated unsaturated hydrocarbons such as -hexafluoro-2-butene (HFO-1336 mzz).

The above-mentioned halogenated unsaturated hydrocarbon is a foaming agent having a low ozone depletion potential and a very small global warming potential, and therefore has a low burden on the environment. Further, since the halogenated unsaturated hydrocarbon has a property of being hard to burn, the amount of the hydrocarbon used can be reduced by using it in combination with the above hydrocarbon, and the thermoplastic resin can be used even if the amount of the flame retardant added is small. It is possible to impart a high degree of flame retardancy to the foam.

Further, the halogenated unsaturated hydrocarbon is a foaming agent having a low thermal conductivity in a gaseous state. As described above, in the thermoplastic resin foam of the present invention, the amorphous polyester resin is used in the cross section of the bubble film portion because the dispersibility and stretchability of the amorphous polyester resin in the mixed resin are satisfactorily improved. It is considered that the sea-island structure is dispersed in layers in the mixed resin, and the dissipation of the foaming agent from the foam can be satisfactorily suppressed. Therefore, when the above-mentioned halogenated unsaturated hydrocarbon is used as the foaming agent, it is possible to suppress the dissipation of the halogenated unsaturated hydrocarbon from the thermoplastic resin foam and further improve the long-term heat insulating property.

From the viewpoint that the upper limit of the content of the hydrocarbon having 3 to 5 carbon atoms satisfies the thermal conductivity standard specified in 4.2 of JIS A9511: 2006R, the lower limit of the content is thermoplastic resin foaming. It is preferably 0.4 mol, more preferably 0.45 mol, and even more preferably 0.5 mol per 1 kg of body. On the other hand, the upper limit of the content of the hydrocarbon having 3 to 5 carbon atoms is preferably 1.0 mol, more preferably 0.9 mol, and 0.8 mol per 1 kg of the thermoplastic resin foam. It is more preferable to have. Further, when a saturated aliphatic hydrocarbon or an alicyclic hydrocarbon which is a flammable foaming agent is used as the hydrocarbon having 3 to 5 carbon atoms, the “measurement method” specified in 5.13.1 of JIS A9511: 2006R is used. From the viewpoint of satisfying high flame retardancy such as the flammability standard for the extruded polystyrene foam heat insulating plate described in "A", the upper limit of the content is 0.8 mol per 1 kg of thermoplastic resin foam. Is preferable.

Further, in order to obtain a thermoplastic resin foam having a lower apparent density, it is preferable to use a foaming agent having a gas permeation rate from the thermoplastic resin foam of the present invention faster than that of the above hydrocarbon. Examples of the foaming agent having a high gas permeation rate include alkyl chlorides, alcohols, ethers, ketones, carboxylic acid alkyl esters, carbon dioxide, water and the like. Among these foaming agents, alkyl chloride having 1 to 3 carbon atoms, aliphatic alcohol having 1 to 4 carbon atoms, ethers having 1 to 3 carbon atoms in the alkyl chain, and carboxylic acid having 1 to 5 carbon atoms in the alkyl chain. Alkyl esters, carbon dioxide, water and the like are preferred.

Examples of the alkyl chloride having 1 to 3 carbon atoms include methyl chloride and ethyl chloride. Examples of the aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, propyl alcohol, isopropyl alcohol, butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, aryl alcohol, crotyl alcohol, propagyl alcohol and the like. Be done. Examples of ethers having 1 to 3 carbon atoms in the alkyl chain include dimethyl ether, ethyl methyl ether, diethyl ether, methylene dimethyl ether and the like. Examples of the carboxylic acid alkyl ester having 1 to 5 carbon atoms in the alkyl chain include methyl formic acid, ethyl formic acid, propyl formic acid, butyl formic acid, amyl formic acid, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate and methyl propionate. , Ethyl propionate and the like. Among these, ethanol, dimethyl ether, methyl formic acid, carbon dioxide, and water are particularly preferable because of their high gas permeability and excellent handleability.

The aliphatic alcohol having 1 to 4 carbon atoms has a property of plasticizing an amorphous polyester resin. Therefore, in the present invention, when the alcohol having 1 to 4 carbon atoms is used as the foaming agent, the viscosity of the amorphous polyester resin with respect to the polystyrene resin is relatively lowered, so that the amorphous polyester resin is streaked. It is considered that the dispersed phase can be more easily formed.

The amount of the foaming agent used is appropriately selected in relation to the desired foaming ratio. For example, in the case of obtaining a thermoplastic resin foam having an apparent density of 20 to 50 kg / cm ³ , it is usually preferable to add 0.5 to 3 mol as a foaming agent per 1 kg of the thermoplastic resin, and further 0. It is preferable to add 1.6 to 2.5 mol.

Further, the thermoplastic resin foam of the present invention contains a flame retardant. As a specific flame retardant, a brominated flame retardant can be preferably used. Examples of the bromine-based flame retardant include tetrabromobisphenol A, tetrabromobisphenol-A-bis (2,3-dibromopropyl ether), tetrabromobisphenol-A-bis (2-bromoethyl ether), and tetrabromobisphenol-A-. Bis (allyl ether), tetrabromobisphenol-A-bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol S, tetrabromobisphenol-S-bis (2,3-dibromopropyl ether), hexa Of bromocyclododecane, tetrabromocyclooctane, tris (2,3-dibromopropyl) isocyanurate, tribromophenol, decabromodiphenyloxide, tris (tribromoneopentyl) phosphate, brominated polystyrene, styrene-butadiene copolymer Bromide and the like can be mentioned. These compounds can be used alone or in combination of two or more. Among the above brominated flame retardants, tetrabromobisphenol-A-bis (2,3-dibromopropyl ether) and tetrabromobisphenol-A-bis (2,3) are particularly effective from the viewpoint of high thermal stability and high flame retardancy. -Dibromo-2-methylpropyl ether), tris (2,3-dibromopropyl) isocyanurate, styrene-butadiene copolymer bromide is preferred. These compounds may be used alone or in admixture of two or more.

The blending amount of the flame retardant in the present invention is highly difficult as in the flammability standard for the extruded polystyrene foam heat insulating plate described in "Measuring method A" specified in 5.13.1 of JIS A9511: 2006R. From the viewpoint of satisfying the flammability, the lower limit of the blending amount of the flame retardant is preferably 1 part by mass with respect to 100 parts by mass of the thermoplastic resin, and more preferably 1.5 parts by mass. Further, from the viewpoint of minimizing the decrease in foamability during extrusion and the decrease in mechanical properties of the thermoplastic resin foam, the upper limit of the amount of the flame retardant compounded is 10 parts by mass with respect to 100 parts by mass of the thermoplastic resin. 7 parts by mass is preferable, and 7 parts by mass is more preferable.

Further, in the present invention, a flame retardant aid can be blended in combination with the flame retardant for the purpose of further improving the flame retardancy of the thermoplastic resin foam. As flame-retardant aids, 2,3-dimethyl-2,3-diphenylbutane, 2,3-diethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, 3,4- Diphenylalkanes such as diethyl-3,4-diphenylhexane, 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-ethyl-1-pentene, diphenylalkene, triphenylphosphate, cresyldi 2 , 6-xylenyl phosphate, antimony trioxide, diantimone pentoxide, ammonium sulfate, zinc tin acid, cyanuric acid, isocyanuric acid, triallyl isocyanurate, melamine cyanurate, melamine, melam, melem and other nitrogen-containing cyclic compounds, Examples thereof include silicone compounds, inorganic compounds such as boron oxide, zinc borate and zinc sulfide, and phosphorus compounds such as red phosphorus, ammonium polyphosphate and phosphazene. These compounds may be used alone or in combination of two or more.

As a method of blending the flame retardant into the thermoplastic resin, a predetermined ratio of the flame retardant is supplied together with the thermoplastic resin to a raw material supply unit provided in the upstream portion of the extruder, and the thermoplastic resin is added in the extruder. A method of kneading with a resin can be mentioned. In addition, the flame retardant can be supplied into the thermoplastic resin melt from the flame retardant supply unit provided in the extruder. When supplying the flame retardant to the extruder, a method of supplying a dry blend of the flame retardant and a thermoplastic resin to the extruder, a method of supplying a liquid flame retardant previously heated and melted to the extruder, or a method of supplying the flame retardant to the extruder. A method can be adopted in which a master batch containing a flame retardant and a thermoplastic resin as a base resin is prepared and supplied to an extruder. In particular, from the viewpoint of dispersibility, it is preferable to adopt a method of preparing a masterbatch containing a flame retardant and supplying it to an extruder. The method for blending the flame retardant aid is the same as the above method.

Further, in the present invention, a heat insulating property improving agent can be added as an additive to the thermoplastic resin to further improve the heat insulating property. Examples of the heat insulating property improving agent include metal oxides such as titanium oxide, metals such as aluminum, ceramics, carbon black, fine powders such as graphite, infrared shielding pigments, hydrotalcites and the like. These can be used alone or in combination of two or more. The amount of the heat insulating improver added is preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the thermoplastic resin.

Further, in the present invention, if necessary, various additives such as bubble modifiers, pigments, colorants such as dyes, heat stabilizers, and other fillers are added to the thermoplastic resin as other compounding components. Can be added as appropriate. Examples of the bubble adjusting agent include inorganic powders such as talc, kaolin, mica, silica, calcium carbonate, barium sulfate, titanium oxide, aluminum oxide, clay, bentonite, and diatomaceous earth. Among these, talc can be preferably used because it is easy to adjust the bubble diameter without impairing flame retardancy.

As a method for producing a thermoplastic resin foam of the present invention, for example, a foamable resin melt containing the above-mentioned thermoplastic resin and a physical foaming agent is extruded and foamed through a die attached to the outlet of an extruder to form a plate. A method of manufacturing a thermoplastic resin extruded foam plate by shaping is exemplified. Specifically, the mixed resin and additives added as needed are supplied to the extruder, a physical foaming agent is supplied from a physical foaming agent supply port, and these are melt-kneaded. It is manufactured by extruding an object from the die lip at the tip of an extruder under atmospheric pressure and then molding it into a predetermined shape (plate shape) with a shaper (guider or the like). As the shaper, for example, a shaper composed of a pair of upper and lower plates made of polytetrafluoroethylene can be used.

The thermoplastic resin foam of the present invention is not limited to the thermoplastic resin extruded foam plate manufactured by the above manufacturing method, and the tubular foam extruded from the circular die is cut open into a sheet shape. Alternatively, it includes an extruded foam produced by fusing the inner surface of a tubular foam, a foamed particle molded body produced by in-mold molding, and the like.

Hereinafter, various physical properties of the thermoplastic resin foam of the present invention will be described in detail.
[Apparent density]
The lower limit of the apparent density of the thermoplastic resin foam of the present invention is preferably 20 kg / m ³ and more preferably 22 kg / m ³ from the viewpoint of improving the manufacturing stability and mechanical strength of the foam. .. Further, from the viewpoint of improving the heat insulating property and ensuring the light weight, the upper limit of the apparent density is preferably 50 kg / m ³ , and more preferably 45 kg / m ³ .

[Thickness]
The thickness of the thermoplastic resin foam is appropriately set according to the purpose of use and is not particularly limited, but in the case of an extruded foam plate, it is 10 to 150 mm from the viewpoint of being used as a heat insulating material. It is preferably present, and more preferably 15 to 120 mm.

[Average bubble diameter]
In the case of the extruded foam plate, the average cell diameter in the thickness direction of the extruded foam plate is preferably 0.05 to 2 mm, more preferably 0.06 to 0.7 mm, still more preferably 0.07 to 0. It is 3 mm. When the average cell diameter is within the above range, the thermoplastic resin extruded foam plate has higher heat insulating properties and more excellent mechanical strength.

The method for measuring the average bubble diameter in the present specification is as follows.
The average bubble diameter ( _DT : mm) in the thickness direction and the average bubble diameter (D _W : mm) in the width direction are determined at a total of three locations near the center and both ends of the widthwise vertical cross section of the thermoplastic resin extruded foam plate. , Obtain an enlarged photograph in which the magnification is adjusted in the range of about 50 to 200 times so that the number of cells in the photograph is about 200 to 500, and on each photograph, image processing software manufactured by Nanosystem Co., Ltd. It can be obtained by measuring the maximum diameter in the thickness direction and the maximum diameter in the width direction of each bubble using NS2K-prо and arithmetically averaging these values.

The average bubble diameter ( _DL : mm) in the extrusion direction is the position perpendicular to the extrusion direction obtained by cutting the thermoplastic resin extrusion foam plate in the extrusion direction at a position that divides the width direction of the thermoplastic resin extrusion foam plate into two equal parts. Microscopic magnified photographs of any three points on the cross section were obtained, and the maximum diameter of each bubble in the extrusion direction was measured on each photograph using the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd. Each value can be calculated by arithmetically averaging.
Further, the horizontal average cell diameter _DH of the thermoplastic resin extruded foam plate shall be the arithmetic mean value of D _W and _DL .

[Bubble deformation rate]
Further, in the thermoplastic resin extruded foam plate, the bubble deformation rate is preferably 0.7 to 2.0. The bubble deformation rate is a value ( _DT / _DH ) calculated by dividing _DT obtained by the above measurement method by _DH , and the smaller the bubble deformation rate is, the flatter the bubble is. The larger it is, the longer it is. When the bubble deformation rate is within the above range, the thermoplastic resin extruded foam plate has excellent mechanical strength and higher heat insulating properties. The lower limit of the bubble deformation rate is more preferably 0.8 from the viewpoint of the compressive strength and dimensional stability of the foam plate. Further, the upper limit of the bubble deformation rate is more preferably 1.5 and even more preferably 1.0 from the viewpoint of the effect of improving the heat insulating property.

[Closed cell ratio]
From the viewpoint of long-term heat insulating properties, the closed cell ratio of the thermoplastic resin foam is preferably 85% or more, more preferably 90% or more, still more preferably 92% or more.

In the present specification, the closed cell ratio of the thermoplastic resin foam is determined by cutting out a cut sample from a total of 5 randomly selected places of the thermoplastic resin foam and using it as a measurement sample, and determining the closed cell ratio for each measurement sample. The arithmetic average value of the closed cell ratio at 5 points is adopted. The cut sample is a sample that is cut from a thermoplastic resin foam into a size of 45 mm in length × 20 mm in width × 25 mm in thickness and has no epidermis. For example, two samples (cut samples) cut into a size of 45 mm in length × 20 mm in width × 12.5 mm in thickness are stacked and measured. Further, for the closed cell ratio S (%), an air comparative hydrometer (for example, manufactured by Toshiba Beckman Co., Ltd., air comparative hydrometer, model: 930 type) is used according to the procedure C of ASTM-D2856-70. Calculated by the following formula (1) using the true volume Vx of the thermoplastic resin foam measured in the above.

S (%) = (Vx-W / ρ) x 100 / (VA-W / ρ) (1)
Vx: True volume of cut sample determined by measurement with an air comparative hydrometer (cm ³ ) (sum of the volume of the resin constituting the cut sample of the foam and the total volume of bubbles in the closed cell portion in the cut sample. Corresponds to.)
VA: Apparent volume of cut sample calculated from the outer dimensions of the cut sample used for measurement (cm ³ )
W: Total weight of cut sample used for measurement (g)
ρ: Density of the base resin constituting the thermoplastic resin foam (g / cm ³ )

[Thermal conductivity]
The thermal conductivity one day after the production of the thermoplastic resin foam of the present invention is preferably 0.0280 W / (m · K) or less, and preferably 0.0270 W / (m · K) or less. It is more preferably 0.0260 W / (m · K) or less, and even more preferably 0.0260 W / (m · K) or less.

Further, the thermoplastic resin foam of the present invention preferably has a thermal conductivity of 0.0280 W / (m · K) or less, and 0.0270 W / (m · K) or less, even after 100 days have passed since the production. It is more preferably present, and further preferably 0.0260 W / (m · K) or less. Further, from the viewpoint of long-term heat insulating properties of the thermoplastic resin foam, it is preferable that the difference between the thermal conductivity 100 days after production and the thermal conductivity 1 day after production is small.

For the thermal conductivity, a test piece having a length of 200 mm, a width of 200 mm, and an arbitrary thickness was cut out from the thermoplastic resin foam immediately after production and stored in an atmosphere of a temperature of 23 ° C. and a humidity of 50% for one day. The test piece and the test piece stored for 100 days are based on the flat plate heat flow meter method described in JIS A 1412-2 (1999) (two heat flow meters, high temperature side 38 ° C, low temperature side 8 ° C, average temperature 23 ° C). Is measured.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples.
The mixed resin, flame retardant, air bubble adjusting agent, and physical foaming agent used in this example and comparative example are shown below.

<Mixed resin>
(Polystyrene resin) (PS raw material)
Polystyrene: (DIC Corporation HP600ANJ), melt viscosity 1400 Pa · s
(Amorphous polyester resin) (PET raw material)
(Spiroglycol) modified PET: (Mitsubishi Gas Chemical Co., Ltd. S3012), endothermic peak calorific value 0 J / g, melt viscosity 2000 Pa · s
(Styrene- (meth) acrylic acid alkyl ester copolymer) (MS raw material) (hereinafter, the (meth) acrylic acid alkyl ester component derived from the styrene- (meth) acrylic acid alkyl ester copolymer is referred to as M component. May)
MS1: Styrene-methyl methacrylate copolymer, manufactured by Nippon Steel Chemical Co., Ltd., MS600 (methyl methacrylate component (M component) content 60% by mass), melt viscosity 2800 Pa · s
MS2: Styrene-methyl methacrylate copolymer, manufactured by Nippon Steel Chemical Co., Ltd., MS200 (methyl methacrylate component (M component) content 20% by mass), melt viscosity 1700 Pa · s

The melt viscosity of the resin was measured by the following method using Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. A capillary with a hole diameter of 1.0 mm and a length of 10.0 mm is attached to the tip of a cylinder with a cylinder diameter of 9.55 mm and a length of 350 mm. ) Was filled and sufficiently melted by preheating for 4 minutes, and the melt viscosity of the resin was measured under the condition of a shear rate of 100 sec ^-1 .

<Flame retardant>
(I) Tetrabromobisphenol-A-bis (2,3-dibromo-2-methylpropyl ether) (SR130 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and (ii) Tetrabromobisphenol-A-bis (2,3-) A flame retardant mixed with dibromopropyl ether (SR720 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) at a mass ratio of 3: 2 was used.
<Bubble adjuster>
A talc masterbatch containing 60% by mass of talc (manufactured by Matsumura Sangyo Co., Ltd., trade name: high filler # 12) using polystyrene resin as a base resin was used.
<Physical foaming agent>
Foaming agent 1: Isobutane (i-Bu)
Foaming agent 2: Ethanol (EtOH)
Foaming agent 3: Hydrofluoroolefin (HFO): Trans-1,3,3,3-tetrafluoropropene (HFO-1234ze)
Foaming agent 4: Water

Each of the above mixed resin, flame retardant agent, and bubble adjusting agent is blended in the blending ratios shown in Tables 1 and 2 below (however, the total blending amount of the PS raw material, the PET raw material, and the MS raw material is 100% by mass). It is supplied to the extruder, and the above physical foaming agent is further supplied from the physical foaming agent supply port, melt-kneaded, and the melt-kneaded product is subjected to atmospheric pressure from the die lip at the tip of the extruder under the conditions shown in Tables 1 and 2. After being extruded into a predetermined shape (plate shape) by a shaping device (guider), the plate-like heat of Examples 1 to 6 and Comparative Examples 1 to 6 having a width of 280 mm, a length of 2000 mm and a thickness of 28 mm is formed. A plastic extruded foam board was manufactured.

The manufacturing stability of the manufactured thermoplastic resin extruded foam plate was evaluated by the following method.
<Manufacturing stability>
The foamed state of the manufactured thermoplastic resin extruded foam plate was observed according to the following criteria, and the manufacturing stability was evaluated.
⊚: The foaming state is extremely good.
◯: The foaming state is good, but there are irregularities on a part of the surface.
X: The foaming state is poor, and many irregularities occur on the surface.

In addition, the apparent density, closed cell ratio, and bubble structure (cell diameter in the thickness direction, bubble deformation rate) of the manufactured thermoplastic resin extruded foam plate were measured by the following methods.
<Apparent density>
The apparent density was measured in accordance with JIS K 6767 (1999). A rectangular parallelepiped sample with a total thickness was cut out from a total of three locations near the center of each thermoplastic resin extruded foam plate in the width direction and both ends in the width direction, and the apparent density was measured for each sample, and the measured values at the three locations were measured. The arithmetic mean value was taken as the apparent density.

<Close cell ratio>
Cut samples were cut out from a total of 5 locations near the center of the thermoplastic resin extruded foam plate and used as measurement samples. The closed cell ratio was measured for each measurement sample, and the arithmetic mean value of the closed cell ratio at the 5 locations was adopted. As the cut sample, a sample having no epidermis cut from a thermoplastic resin extruded foam plate into a size of 45 mm in length × 20 mm in width × 25 mm in thickness was prepared.
The closed cell ratio of the sample was measured by the procedure C of ASTM-D2856-70 using an air comparative hydrometer (model: 930 type manufactured by Toshiba Beckman Co., Ltd.) and obtained from the above formula (1). The arithmetic mean value of was taken as the closed cell ratio.

<Bubble structure>
(Bubble diameter in the thickness direction)
The thickness direction average cell diameter ( _DT ) and the width direction average cell diameter (D _W ) are set to 100 at a total of three locations near the center and both ends of the width direction vertical cross section of the thermoplastic resin extruded foam plate. Obtained a double-adjusted enlarged photograph, and measured the maximum diameter in the thickness direction and the maximum diameter in the width direction of each bubble using the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd. on each photograph. It was obtained by arithmetically averaging each of these values.
The average bubble diameter ( _DL ) in the extrusion direction is the vertical cross section in the extrusion direction obtained by cutting the thermoplastic resin extrusion foam plate in the extrusion direction at a position that divides the width direction of the thermoplastic resin extrusion foam plate into two equal parts. , Obtain magnified microscopic photographs of any three locations, measure the maximum diameter of each bubble in the extrusion direction using the image processing software NS2K-pro manufactured by Nanosystem Co., Ltd. on each photograph, and measure those values. Each was calculated by arithmetically averaging. Further, the horizontal average cell diameter D _H of the thermoplastic resin extruded foam plate was obtained as the arithmetic mean value of the above D _W and _DL .

(Bubble deformation rate)
The bubble deformation rate was calculated as ( _DT / _DH ) by dividing the _DT obtained by the above method for measuring the bubble diameter in the thickness direction by _DH .
Tables 3 and 4 show the measurement results of the apparent density, closed cell ratio, and bubble structure (cell diameter in the thickness direction, bubble deformation rate) of the thermoplastic resin extruded foam plate measured by the above method.

In addition, the physical properties of the manufactured thermoplastic resin extruded foam plate for flame retardancy, bending fracture bending, and thermal conductivity (1 day, 100 days, 100 days, -1 day) were evaluated and measured by the following methods.
<Flame retardance evaluation>
The burnability test of the measuring method A of 5.13.1 was carried out on the thermoplastic resin extruded foam plate 7 days after the production in accordance with JIS A9511 (2006R) 5.13.1. For the measurement, five test pieces were cut out from one extruded foam plate, and the flame retardancy was evaluated according to the following criteria.
◯: In all the test pieces, the flame is extinguished within 3 seconds, there is no residual dust, and the combustion does not exceed the combustion limit line.
X: The average burning time of 5 test pieces exceeds 3 seconds.

<Bending fracture bending>
From the thermoplastic resin extruded foam plate 7 days after production, a test piece having a length of 280 mm, a width of 75 mm, and a thickness of 25 mm and having no skin is taken so that the length direction is along the width direction of the thermoplastic resin extruded foam plate. And, the midpoint in the width direction was cut out so as to be the center of the length. Using this test piece, bending fracture bending was determined under the conditions of a pressure wedge, a radius of the tip of the support base of 10 mm, a distance between fulcrums of 200 mm, and a test speed of 10 mm / min. The bending fracture deflection means the bending fracture when the test piece is fractured.

<Thermal conductivity>
From the thermoplastic resin extruded foam plate immediately after production, a test piece having a length of 200 mm, a width of 200 mm, and a thickness of 25 mm without a skin was cut out and stored in an atmosphere of a temperature of 23 ° C. and a humidity of 50% for 1 day and stored for 100 days. The thermal conductivity of each of the test pieces was measured based on the JIS A1412-2 (1999) flat plate heat flow meter method (two heat flow meters, high temperature side 38 ° C, low temperature side 8 ° C, average temperature 23 ° C). ..
Tables 3 and 4 show the above-mentioned evaluation of flame retardancy and measurement results of bending fracture bending and thermal conductivity.

<Taking a cross-sectional photograph of the bubble membrane>
Further, for the thermoplastic resin extruded foam plates of Example 1, Comparative Example 1 and Comparative Example 3, cross-sectional photographs of the bubble membrane were taken by the following method.
A sample obtained by cutting out the central portion of the thermoplastic resin extruded foam plate to an appropriate size was placed in an epoxy resin and embedded. After embedding, a surface perpendicular to the thickness direction was cut out with a glass knife, and an ultrathin section of foam having a thickness of about 0.1 μm was cut out from the cross section with a diamond knife. The cut-out sample was placed on a Cu mesh, placed in a petri dish together with several ml of a 2% _OsO4 aqueous solution, sealed at room temperature, exposed to _OsO4 vapor, and stained for 30 minutes.
Next, the sample was placed in a petri dish together with a mixture of several ml of an aqueous NaClO solution and one small spatula of RuCl ₃ crystals immediately before use, sealed at room temperature, exposed to the generated RuO ₄ vapor, and stained for 30 minutes. Ultra-thin sections of the dyed foam plate were photographed using a transmission electron microscope (JEOL-1010, a transmission electron microscope manufactured by JEOL Ltd.) under the conditions of an acceleration voltage of 100 kV and a magnification of 20000 times. The bubble membrane portion to be observed above was a portion other than the association portion where three or more bubble membranes (cell membranes) were associated in the cross section of the foam plate. The bubble film portion was defined as a portion from the thinnest portion of the bubble membrane to 1.3 times the film thickness.
The photograph of Example 1 taken is shown in FIG. 1, the photograph of Comparative Example 1 is shown in FIG. 2, and the photograph of Comparative Example 3 is shown in FIG. The above photographs were taken in the vertical cross section in the extrusion direction (MD plane) and the vertical cross section in the width direction (TD plane), respectively.

<Evaluation result>
From the evaluation and measurement results of the physical properties shown in Tables 3 and 4, the extruded foam plates of Examples 1 to 6 show good flame retardancy and bending fracture bending, and maintain low thermal conductivity for a long period of time. Was confirmed.

In Examples 1 and 4, the ratio of the (meth) acrylic acid alkyl ester component was suppressed while adjusting the amount of the styrene- (meth) acrylic acid alkyl ester copolymer added to Example 1. And, in Example 4, bending fracture bending is improved as compared with Example 1. In particular, in Example 4 using two types of (meth) acrylic acid alkyl ester components having different component ratios, the difference in thermal conductivity is smaller. It is considered that this is because the compatibility between the polystyrene resin and the amorphous polyester resin is further improved and the dispersibility is improved.

Further, in Example 3 in which a large amount of the styrene- (meth) acrylic acid alkyl ester copolymer having a low ratio of the (meth) acrylic acid alkyl ester component was added to Example 1 and the same amount of M component was obtained, the bending was performed. Both the fracture deflection and the difference in thermal conductivity were the same as in Example 1. Further, Examples 5 and 6 in which the compounding ratio of the amorphous polyester resin is increased with respect to Example 1 are high while maintaining the thermal conductivity equal to or higher than that of Example 1 for a long period of time. Bending fracture bending was shown.

On the other hand, the thermoplastic resin extruded foam plates of Comparative Example 1 and Comparative Example 4 to which the styrene- (meth) acrylic acid alkyl ester copolymer was not added were flame-retardant and had bending fracture deflection as in Example 1. Although it was equal to or higher than that, the difference in thermal conductivity was large. In particular, the difference in thermal conductivity of Comparative Example 4 to which the amorphous polyester resin was not added was extremely large.

Further, Comparative Example 2 in which the blending ratio of the styrene- (meth) acrylic acid alkyl ester copolymer was increased and Comparative Example 3 in which the blending ratio was extremely increased were inferior in flame retardancy and bending fracture bending as compared with Examples. rice field. Further, in Comparative Examples 5 and 6 to which the amorphous polyester resin was not added, the thermal conductivity could not be maintained for a long period of time, and in particular, a large amount of the styrene- (meth) acrylic acid alkyl ester copolymer was added. Comparative Example 6 was inferior in both mechanical strength and flame retardancy.

Further, from the cross-sectional photograph (morphology) of the bubble film of Example 1 shown in FIG. 1, in the bubble film of Example 1, the amorphous polyester resin is finely dispersed in the polystyrene resin and stretched along the bubble film. You can see that there is. It is considered that this is because the dispersibility and stretchability of the amorphous polyester resin are improved by adding a specified amount of the (meth) acrylic acid alkyl ester component.

On the other hand, in the photograph of Comparative Example 1 shown in FIG. 2, the amorphous polyester resin was not finely dispersed because the styrene- (meth) acrylic acid alkyl ester copolymer was not added, and it was sufficiently sufficient. Since it was not stretched, it is probable that the gas barrier property was lowered and the difference in thermal conductivity over a long period of time became large. On the other hand, in the photograph of Comparative Example 3 shown in FIG. 3, the amorphous polyester resin was dispersed more finely by adding a large amount of the styrene- (meth) acrylic acid alkyl ester copolymer, and the gas barrier property was improved. , The content of the styrene- (meth) acrylic acid alkyl ester copolymer was too high, so that the flame retardancy and bending fracture bending were extremely reduced.

From these results, the thermoplastic resin foam of the present invention is a mixed resin in which the base resin is a polystyrene resin, a styrene- (meth) acrylic acid alkyl ester copolymer, and an amorphous polyester resin, and is mixed. By setting the content of the (meth) acrylic acid alkyl ester component derived from the styrene- (meth) acrylic acid alkyl ester copolymer in the resin to a specific ratio, the amorphous polyester resin can be finely divided in the base resin. It was confirmed that the thermoplastic resin foam is excellent in flame retardancy and mechanical strength by being dispersed and stretched, and has an effect of suppressing a change in thermal conductivity with time.

Claims (6)

A thermoplastic resin foam containing a hydrocarbon having 3 to 5 carbon atoms and a flame retardant, using a thermoplastic resin as a base resin.
The thermoplastic resin conforms to a polystyrene resin, a styrene- (meth) acrylic acid alkyl ester copolymer, and JIS K7122 (1987), and has a heating rate of 2 ° C./ A mixed resin with an amorphous polyester resin having a heat absorption peak heat of less than 5 J / g (including 0) due to melting of the polyester resin based on the DSC curve obtained by heating from 23 ° C to 300 ° C under the condition of minutes. can be,
The content of the amorphous polyester resin in a total of 100 parts by mass of the polystyrene resin and the styrene- (meth) acrylic acid alkyl ester copolymer is 10 to 100 parts by mass.
A thermoplastic resin characterized in that the content of the (meth) acrylic acid alkyl ester component derived from the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin is 0.5 to 6% by mass. Foam. The thermoplastic resin foam according to claim 1, wherein the content of the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin is 1 to 20% by mass. The thermoplastic resin foaming according to claim 2, wherein the content of the (meth) acrylic acid alkyl ester component in the styrene- (meth) acrylic acid alkyl ester copolymer is 10 to 70% by mass. body. The amorphous polyester resin is one or more selected from a spiroglycol-modified polyethylene terephthalate resin, a dioxane glycol-modified polyethylene terephthalate resin, a neopentyl glycol-modified polyethylene terephthalate resin, and a 1,4-cyclohexanedimethanol-modified polyethylene terephthalate resin. The thermoplastic resin foam according to any one of claims 1 to 3, characterized in that it is present. The content of the (meth) acrylic acid alkyl ester component derived from the styrene- (meth) acrylic acid alkyl ester copolymer in the mixed resin is 0.5% by mass or more and less than 4% by mass. The thermoplastic resin foam according to any one of claims 1 to 4. The thermoplastic resin foam according to any one of claims 1 to 5, wherein the apparent density of the thermoplastic resin foam is 20 to 50 kg / m ³ .

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