JP6930422B2 - Styrene-based resin composition, biaxially stretched styrene-based resin sheet and molded product - Google Patents

Description

The present invention relates to a specific styrene-based resin composition containing inorganic fine particles, and more specifically, the strength can be improved without impairing the transparency of a molded product obtained from the styrene-based resin composition, and heat resistance can be improved. The present invention relates to a styrene-based resin composition having excellent properties and capable of contributing to thinning of a molded product, a sheet obtained by biaxially stretching the styrene resin composition, and a molded product obtained from the styrene resin composition.

Sheets obtained from polystyrene are mainly used as food packaging containers because of their excellent transparency and rigidity. However, although the sheet container obtained from this polystyrene is suitable as a general food packaging container, it has insufficient surface impact resistance, so that the sheet can be used to reduce the volume of the packaging material or improve the moldability. Or, when trying to thin the secondary molded product, it is difficult to maintain the suitability as a packaging material at a practical level, that is, the trade-off between strength and moldability cannot be eliminated, and this solution Is required.

Recently, the usage method of heating a food packaging container with a microwave oven containing the contents is increasing. However, depending on the conditions of use, the container may be deformed due to insufficient heat resistance, and further improvement in heat resistance is required for food packaging containers.

As a means for improving impact resistance, for example, a method of mixing a small amount of fine particles with a styrene resin is provided (see, for example, Patent Document 1). The molded product of the styrene resin composition substantially provided in this document is an injection-molded product, which improves impact strength in practical use in the injection-molded product, but is processed into a sheet. There is no description as to whether or not even the impact strength at the time of this is improved.

On the other hand, in order to improve the anisotropy when processed into a film, it has been proposed to add specific fine particles to the styrene resin (see, for example, Patent Document 2). In this document, although the effect of improving anisotropy when used as an inflation film is shown, it is shown that the tensile strength in the MD direction (film winding direction) is rather lower when fine particles are added. It is clear that the aim is not to improve the mechanical strength by blending fine particles with the styrene resin.

Further, for the purpose of improving the impact strength while maintaining the transparency, a molded product obtained by mixing a small amount of fine particles with a styrene resin and stretching the molded product has been proposed (see, for example, Patent Document 3). In this document, although the effect of improving the impact strength is shown, there is no description about heat resistance.

Japanese Unexamined Patent Publication No. 07-228737 Japanese Unexamined Patent Publication No. 2000-044745 Japanese Unexamined Patent Publication No. 07-323474

In view of these circumstances, the problem to be solved by the present invention is to improve the surface impact strength and heat resistance without impairing the transparency, and thus the styrene resin which can be thinned and has good secondary moldability. It is an object of the present invention to provide a composition, a biaxially stretched styrene-based sheet obtained by using the composition, and a molded product thereof.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by using a specific styrene resin composition containing a specific amount of inorganic fine particles, and the present invention has been found. Has been completed.

That is, the present invention comprises a styrene-based resin (A) having a styrene-based monomer (a1) -derived structure and a methacrylic acid (a2) -derived structure, and inorganic fine particles (B) having an average particle size of 0.1 to 10 μm. , A resin composition containing rubber-modified polystyrene (C) as an essential component, characterized in that the blending ratio of the inorganic fine particles (B) in the composition is in the range of 0.01 to 1.0% by mass. A styrene-based resin composition, a sheet obtained by biaxially stretching the styrene resin composition, and a molded product are provided.

The styrene-based resin composition of the present invention improves the heat resistance of the composition by copolymerizing a specific monomer, and by blending specific fine particles and further using rubber-modified polystyrene in combination, in particular. It is possible to improve the surface impact strength when processed into a sheet shape. Therefore, the heat resistance and impact strength of the molded product are improved, the wall thickness can be reduced, the secondary moldability is improved, and whitening during molding does not occur without impairing the original transparency of the styrene resin. It can be suitably used as a packaging material for food applications and the like.

It is a chromatograph which measured the molecular weight by GPC-MALLS. It is a simplified apparatus diagram for continuous bulk polymerization of a styrene resin.

The composition of the present invention will be described in detail below.
[Styrene-based resin composition]
The styrene-based resin composition used in the present invention contains a styrene-based resin (A) having a styrene-based monomer (a1) -derived structure and a methacrylic acid (a2) -derived structure, and an inorganic substance having an average particle size of 0.1 to 10 μm. It is a resin composition containing fine particles (B) and rubber-modified polystyrene (C) as essential components, and the blending ratio of the inorganic fine particles (B) in the composition is in the range of 0.01 to 1.0% by mass. It is characterized by that.

The styrene-based resin (A) has a styrene-based monomer (a2) -derived structure and a methacrylic acid (a3) -derived structure, and the derived structure is styrene-based monomer (a2) or methacrylic acid (a3). ) In which the polymerizable group (vinyl group) has become a single bond by the reaction. That is, the styrene resin (A) is preferably a copolymer of monomers containing a styrene monomer (a1) and methacrylic acid (a2) as essential components.

Examples of the styrene-based monomer (a1) include the following. Styrene and its derivatives; for example alkyl styrene such as styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, octyl styrene, fluoro styrene, chloro styrene. , Bromostyrene, dibromostyrene, halogenated styrene such as iodostyrene, nitrostyrene, acetylstyrene, methoxystyrene and the like, and these can be used alone or in combination of two or more. Further, together with the styrene-based monomer (a1), a compound copolymerizable with the styrene-based monomer (a1), for example, a vinyl monomer such as an ester derivative such as acrylonitrile, methacrylonitrile, methyl methacrylate, or butyl acrylate, and further anhydrous. Maleic anhydride, maleimide, nuclear-substituted maleimide and the like may be used in combination.

Furthermore, in addition to the styrene-based monomer (a1) and methacrylic acid (a2), a multi-branched macromonomer (a3) having a plurality of branches and having a plurality of polymerizable double bonds is contained as an essential component. It may be a copolymer of the monomers to be used. Alternatively, this multi-branched copolymer may be mixed with the copolymer described above.

When a copolymer of a styrene-based monomer (a1) and methacrylic acid (a2) is used, a sheet having excellent heat resistance can be obtained. Therefore, a molded product that can be used as a food packaging material using a microwave oven or the like can be obtained. Be done.

At this time, the ratio of the styrene-based monomer (a1) to the methacrylic acid (a2) is as a mass ratio represented by (a1) / (a2) from the viewpoint of heat resistance and moldability of the molded product. It is preferably in the range of 99.9 / 0.1-97.0 / 3.0% by mass.

Further, when the multi-branched macromonomer (a3) having the above-mentioned plurality of branches and a plurality of polymerizable double bonds is used in combination, the styrene resin (A) can have a higher molecular weight. As a result, the mechanical strength of the obtained molded product can be improved. As a result, it is preferable to use the sheet in combination because the sheet obtained from the resin composition and the secondary molded product thereof can be thinned.

Therefore, the styrene-based resin (A) has a plurality of branches of the styrene-based monomer (a1) and methacrylic acid (a2), and has a plurality of polymerizable double bonds (a3). ) Is essential, and the ratio of the styrene-based monomer (a1) and the methacrylic acid (a2) used at this time is represented by (a1) / (a2). The mass ratio to be obtained is more preferably in the range of 99.9 / 0.1 to 97.0 / 3.0 mass%.

The styrene-based resin (A) used in the present invention has a plurality of branches and has a plurality of polymerizable double bonds. When the multi-branched macromonomer (a3) is not used, the weight average obtained by GPC is used. The molecular weight is preferably in the range of 100,000 to 400,000, and when the multi-branched macromonomer (a3) is used in combination, the weight average molecular weight determined by the GPC-MALLS method is 150,000 to 700,000. Is preferable, and more preferably, it is in the range of 200,000 to 600,000 from the viewpoint of productivity and processability. The styrene resin (A) may be a single compound or a mixture of a plurality of copolymers, and in the case of a mixture, the molecular weight of the mixture is preferably in the above range. .. In the case of a mixture, the styrene resin (A), which is a copolymer of monomers essentialing the styrene monomer (a1) and methacrylic acid (a2), is the resin in the styrene resin composition. It is preferable that the component is contained in an amount of 85% by mass or more because the effect of the present invention is easily exhibited.

[GPC-MALLS]
When the multi-branched macromonomer (a3) is used in combination, the molecular weight of the styrene resin (A) is measured by GPC-MALLS to obtain, for example, the chromatograph shown in FIG. In FIG. 1, the peak on the low molecular weight side is P1 and the peak on the high molecular weight side is P2. It is presumed that the peak P1 contains a linear resin and a resin having a low degree of bifurcation. It is presumed that the peak P2 mainly contains a multi-branched resin having a high degree of bifurcation. The region of peak P2 includes a perpendicular line drawn from the highest point of peak P2 to a baseline (a dotted line drawn substantially parallel to the volume axis in FIG. 1), a baseline, and a molecular weight curve on the left side of the highest point. The region (1) surrounded by and the molecular weight curve formed when the region (1) is folded back to the right with the perpendicular as the axis of symmetry (in FIG. 1, a virtual line shown by a dotted line on the right of the perpendicular). It is a region formed by a region (2) surrounded by a molecular weight curve), a perpendicular line, and a baseline. The region of the peak P1 is a portion obtained by subtracting the region of the peak P1 composed of the region (1) and the region (2) from the region surrounded by the molecular weight curve and the baseline.

[Mixing ratio of resin in the peak P1 region and resin in the peak P2 region]
When the multi-branched macromonomer (a3) is used in combination, the mass ratio of the resin in the peak P1 region and the resin in the peak P2 region of the styrene resin (A) is the strength and processability of the obtained sheet. (Resin in the region of peak P2) / (resin in the region of peak P1) = 30/70 to 70/30 is preferable, and 40/60 to 60/40 is more preferable. This ratio can be adjusted for the ratio of the multibranched macromonomer (a3) to the styrene-based monomer (a1), methacrylic acid (a2), or other monomers used in combination as necessary, or for the chain transfer agent. It can be easily controlled by the type and the amount used thereof.

[Slope of log-log graph]
Further, when the multi-branched macromonomer (a3) is used in combination, the molecular weight obtained from GPC-MALLS of the styrene resin (A) is on the horizontal axis and the inertial radius is on the vertical axis, and the molecular weight in the log-log graph is 250,000 to 1000. The inclination in the ten thousand region is an index showing the degree of branching of the resin. This inclination is preferably 0.30 to 0.55 in that strength and moldability are exhibited in an excellent balance. If this slope is larger than 0.55, the physical properties are closer to those of the linear resin, and conversely, if it is smaller than 0.30, the fluidity may decrease due to the increase in molecular weight accompanying the increase in the degree of branching.

[GPC-MALLS measurement]
The above-mentioned GPC-MALS measurement is performed under the conditions of Shodex HPLC, detector Waitt Technology DAWN EOS, Shodex RI-101, column Shodex KF-806L × 2, solvent THF, and flow rate 1.0 ml / min. be. The measurement of GPC-MALLS was analyzed by Wyatt's analysis software ASTRA, and the weight average molecular weight of the styrene resin was calculated. The molecular weight of the resin obtained from GPC-MALLS was the horizontal axis, and the inertial radius was the vertical axis. Slope in the region of molecular weight 250,000 to 10 million in the log-log graph with the axis (slope of the approximate straight line automatically calculated by the software based on the measured value of only the linear part obtained in the molecular weight range) ).

[Multibranched macromonomer (a3)]
As the multi-branched macromonomer (a3) having a plurality of branches and having a plurality of polymerizable double bonds that can be used in the present invention, from the viewpoint of suppressing gel formation and ensuring fluidity. , The weight average molecular weight (Mw) of the multi-branched macromonomer (a3) is preferably in the range of 1,000 to 15,000, more preferably 3,000 to 8,000.

[GPC measurement]
The molecular weight of the multi-branched macromonomer (a1) is determined by gel permeation chromatography (hereinafter abbreviated as “GPC”) using “HPLC8010” manufactured by Toso Co., Ltd., column Shodex KF802 × 2 + KF803 + KF804, solvent THF, flow rate 1 It was measured under the condition of 0.0 ml / min.

The branched structure of the multi-branched macromonomer (a3) is not particularly limited, but all three bonds other than the electron-withdrawing group and the binding with the electron-withdrawing group are bonded to the carbon atom 4 Those branched by a class carbon atom and those forming a branched structure by repeating structural units having an ether bond, an ester bond or an amide bond are preferable.

When the multi-branched macromonomer (a3) forms a branched structure with the above-mentioned quaternary carbon, the electron-withdrawing group content is 2.5 × 10 per 1 g of the multi-branched macromonomer (a3). It is preferably in the range of -4 mmol to 5.0 × 10-1 mmol, more preferably in the range of 5.0 × 10-4 mmol to 5.0 × 10-2 mmol.

It is essential that the multi-branched macromonomer (a3) has two or more polymerizable double bonds per molecule. The content of the polymerizable double bond is preferably in the range of 0.1 to 5.5 mmol per 1 g of the macromonomer (a3), and more preferably in the range of 0.5 to 3.5 mmol. Further, it is preferable that the polymerizable double bond is present at the tip of the multi-branched macromonomer (a3).

The multi-branched macromonomer (a3) that can be used in the present invention includes a branched structure formed by repeating a structural unit having an ester bond, an ether bond, or an amide bond, and a polymerizable structure of two or more in one molecule at the branched end. A multi-branched macromonomer (a3-i) having a double bond can be mentioned.

The multi-branched macromonomer (a3-i-1) having a branched structure formed by repeating structural units having an ester bond has a quaternary carbon atom adjacent to the carbonyl group of the ester bond forming the molecular chain. A preferred embodiment is one in which a polymerizable double bond such as a vinyl group or an isopropenyl group is introduced into a multi-branched polyester polyol. Introducing a polymerizable double bond into a multi-branched polyester polyol can be carried out by an esterification reaction or an addition reaction.

In the polybranched polyester polyol, a substituent may be introduced into a part of the hydroxy group in advance by an ether bond or another bond, or a part of the hydroxy group may be subjected to an oxidation reaction or another reaction. It may be denatured. In addition, a part of the hydroxy group of the polybranched polyester polyol may be esterified in advance.

The multi-branched macromonomer (a3-i-1) includes, for example, a compound having one or more hydroxy groups, the carbon atom adjacent to the carboxy group is a quaternary carbon atom, and two or more hydroxy groups. It is obtained by reacting the monocarboxylic acid having it to form a multi-branched polymer, and then reacting the hydroxy group, which is the terminal group of the polymer, with an unsaturated acid such as acrylic acid or methacrylic acid, an isocyanate group-containing acrylic compound, or the like. Things can be mentioned. For the multi-branched polymer in which the structural unit having an ester bond is repeated to form a branched structure, refer to "Angew.Chem.Int.Ed.Engl.29" p138-177 (1990) by Tamaria et al. Have been described.

Examples of the compound having one or more hydroxy groups include a) aliphatic diol, alicyclic diol, or aromatic diol, b) triol, c) tetraol, d) sugar alcohol such as sorbitol and mannitol, and e) ann. Hydroenea-heptitol or dipentaerytriol, f) α-alkyl glucosides such as α-methylglycoside, g) monofunctional alcohols such as ethanol and hexanol, h) alkylene oxides having a weight average molecular weight of at most 8,000 or Examples thereof include a hydroxy group-containing polymer produced by reacting the derivative with a hydroxy group in one or more compounds selected from any of the above a) to g).

Examples of the a) aliphatic diol, alicyclic diol and aromatic diol include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1, 6-Hexenediol, polytetratetra, dimethylolpropane, neopentylpropane, 2-propyl-2-ethyl-1,3-propanediol, 1,2-propanediol, 1,3-butanediol, diethylene glycol, triethylene glycol , Polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol; cyclohexanedimethanol, 1,3-dioxane-5,5-dimethanol; 1,4-xylylenediol methanol, 1-phenyl-1,2-ethanediol. And so on. Examples of the b) triol include trimethylolpropane, trimethylolethane, trimethylolbutane, glycerol, 1,2,5-hexanetriol, 1,3,5-trihydroxybenzene and the like. Examples of the c) tetraol include pentaerythritol, ditrimethylolpropane, diglycerol, and ditrimethylolethane.

Examples of the monocarboxylic acid in which the carbon atom adjacent to the carboxyl group is a quaternary carbon atom and has two or more hydroxy groups include dimethylolpropionic acid, α, α-bis (hydroxymethyl) butyric acid, and α. , Α, α-Tris (hydroxymethyl) acetic acid, α, α-bis (hydroxymethyl) valerate, α, α-bis (hydroxymethyl) propionic acid and the like. By using the monocarboxylic acid, the ester decomposition reaction is suppressed and a multi-branched polyester polyol can be formed.

Further, it is preferable to use a catalyst when producing the multi-branched polyester polyol, and the catalyst includes, for example, dialkyltin oxide, dialkyltin halide, dialkyltin biscarboxylate, or organic tin such as stanoxane. Examples thereof include compounds, titanates such as tetrabutyl titanate, and organic sulfonic acids such as Lewis acid and paratoluene sulfonic acid.

As the multi-branched macromonomer (a3-i-2) in which a structural unit having an ether bond is repeated to form a branched structure, for example, a compound having one or more hydroxy groups or cyclic ether compounds has one hydroxy group. The cyclic ether compound described above is reacted to form a multi-branched polymer, and then an unsaturated acid such as acrylic acid or methacrylic acid, an isocyanate group-containing acrylic compound, or 4-chloromethyl is added to the hydroxy group which is the terminal group of the polymer. Examples thereof include those obtained by reacting methyl styrene halide such as styrene. Further, as a method for producing the multi-branched polymer, a compound having one or more hydroxy groups, a compound containing two or more hydroxy groups and a halogen atom, -OSO2OCH3 or -OSO2CH3, based on Williamson's ether synthesis method. A method of reacting with is also useful.

As the compound having one or more hydroxy groups, any of the compounds listed above can be used, and as the cyclic ether compound having one or more hydroxy groups, for example, 3-ethyl-3- (hydroxymethyl) Examples thereof include oxetane, 2,3-epoxy-1-propanol, 2,3-epoxy-1-butanol, and 3,4-epoxy-1-butanol. The compound having one or more hydroxy groups used in the ether synthesis method of Williamson may be the above-mentioned compound, but an aromatic compound having two or more hydroxy groups bonded to an aromatic ring is preferable. Examples of the compound include 1,3,5-trihydroxybenzene, 1,4-xylylene dimethanol, 1-phenyl-1,2-ethanediol and the like. Examples of the compound containing two or more hydroxy groups and a halogen atom, -OSO2OCH3 or -OSO2CH3, include 5- (bromomethyl) -1,3-dihydroxybenzene and 2-ethyl-2- (bromomethyl) -1. , 3-Propanediol, 2-methyl-2- (bromomethyl) -1,3-propanediol, 2- (bromomethyl) -2- (hydroxymethyl) -1,3-propanediol and the like. When producing the multi-branched polymer, it is usually preferable to use a catalyst, and examples of the catalyst include BF3 diethyl ether, FSO3H, ClSO3H, and HClO4.

Further, as the multi-branched macromonomer (a3-i-3) in which a structural unit having an amide bond is repeated to form a branched structure, for example, a multi-branched macromonomer (a3-i-3) having an amide bond in the molecule via a nitrogen atom in the repeating structure is used. Yes, Generation 2.0 (PAMAM dent trimmer) manufactured by Dentoritech is a typical example.

[Method of polymerizing multibranched macromonomer (a3) with styrene-based monomer (a1) and methacrylic acid (a2)]
When the multi-branched macromonomer (a3), the styrene-based monomer (a1), and the methacrylic acid (a2) are copolymerized with other monomers used in combination as necessary, the multi-branched resin and the polymerization conditions are obtained. A resin mixture which is a mixture of the linear resin and the low-branch resin which are simultaneously produced is obtained. At this time, the above-mentioned multi-branched macromonomer (a3) is preferably used at a ratio of 50 ppm to 1%, more preferably 100 ppm to 3000 ppm (mass basis) with respect to the total amount of the other monomers. The branched resin can be easily produced, and the styrene-based resin (A) used in the present invention can be easily produced.

Various general-purpose polymerization methods of styrene-based monomers can be applied to the polymerization reaction. The polymerization method is not particularly limited, but bulk polymerization, suspension polymerization, or solution polymerization is preferable. Among them, continuous bulk polymerization is particularly preferable in terms of production efficiency. For example, by performing continuous bulk polymerization incorporating one or more stirring reactors and a tubular reactor in which a plurality of mixing elements having no moving parts are fixed inside. , Excellent resin can be obtained. Although thermal polymerization can be carried out without using a polymerization initiator, it is preferable to use various radical polymerization initiators. Further, as the polymerization aid such as a suspending agent or an emulsifier required for polymerization, those used for ordinary polystyrene production can be used.

An organic solvent may be added to the reaction system in order to reduce the viscosity of the reaction product in the polymerization reaction, and examples of the organic solvent include toluene, ethylbenzene, xylene, acetonitrile, benzene, chlorobenzene, dichlorobenzene and anisole. , Cyanbenzene, dimethylformamide, N, N-dimethylacetamide, methylethylketone and the like. In particular, when it is desired to increase the amount of the multi-branched macromonomer added, it is preferable to use an organic solvent from the viewpoint of suppressing gelation. As a result, the amount of the multi-branched macromonomer (a3) added can be dramatically increased to introduce a large number of branched structures, and gelation is less likely to occur.

The radical polymerization initiator is not particularly limited, and is, for example, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis (t-butylperoxy) butane, and 2,2-bis (4). , 4-Di-Butylperoxycyclohexyl) Peroxyketals such as propane, Kumenhydroperoxide, Hydroperoxides such as t-butylhydroperoxide, Di-t-butylperoxide, Dicumyl peroxide, Di Dialkyl peroxides such as -t-hexyl peroxide, diacyl peroxides such as benzoyl peroxide and discinamoyl peroxide, t-butyl peroxybenzoate, di-t-butyl peroxyisobutyrate, t-butyl peroxide. Peroxyesters such as oxyisipropyl monocarbonate, N, N'-azobisisobutylnitrile, N, N'-azobis (cyclohexane-1-carbonitrile), N, N'-azobis (2-methylbutyronitrile) ), N, N'-azobis (2,4-dimethylvaleronitrile), N, N'-azobis [2- (hydroxymethyl) propionitrile], etc., and one or more of these may be combined. Can be used.

Further, a chain transfer agent may be added so that the molecular weight of the obtained resin does not become excessively large. As the chain transfer agent, either a monofunctional chain transfer agent having one chain transfer group or a polyfunctional chain transfer agent having a plurality of chain transfer groups can be used. Examples of the monofunctional chain transfer agent include alkyl mercaptans and thioglycolic acid esters. Examples of the polyfunctional chain transfer agent include thioglycolic acid or 3-mercaptopropionic acid as a hydroxy group in a polyhydric alcohol such as ethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, and sorbitol. Examples thereof include those esterified with.

Further, long-chain alcohols, polyoxyethylene alkyl ethers, polyoxyethylene lauryl ethers, polyoxyoleyl ethers, polyoxyethylene alkenyl ethers and the like can also be used to suppress gel generation of the obtained resin.

Further, a lubricant, an antistatic agent, an antioxidant, a heat stabilizer, an ultraviolet absorber, a dye, a plasticizer and the like can be used as long as the physical properties of the obtained resin and the sheet are not impaired.

<Polymerization process>
In the polymerization step, a styrene-based monomer (a1), methacrylic acid (a2), other monomers used in combination, and a multi-branched macromonomer (a3) are used as monomers, and by copolymerizing these, a styrene-based resin ( A) can be obtained. FIG. 2 shows an example of the reaction vessel of the polymerization apparatus for obtaining the resin (A) in the present invention. That is, the reaction solution is sent to the stirring reactor (I) by the pump (1), then to the circulation polymerization line (II) by the pump (2), and is sent to the circulation polymerization line (II) by the pump (3). It circulates, and after circulation, it is sent to the non-circulating polymerization line (III). Here, the cyclic polymerization line (II) is composed of three reactors consisting of (4) to (6), and the non-circular polymerization line (III) is composed of three reactors consisting of (7) to (9). Will be done.

If necessary, a monomer or solvent is added between the stirring reactor (I) and the circulating polymerization line (II), or between the circulating polymerization line (II) and the non-circulating polymerization line (III). It can also be added.

<Devolatile process>
After the polymerization step, the devolatilization tank 1 and the devolatilization tank 2 for volatilizing the unreacted monomer and the solvent component are connected. The devolatilization tank 1 and the devolatilization tank 2 are preferably adjusted to a reduced pressure state of 4.0 kPa and 1.3 kPa, respectively, and are pelletized after passing through the devolatilization tank 1 and the devolatilization tank 2 in the present invention. The styrene resin (A) to be used can be obtained.

<Inorganic fine particles (B)>
The present invention is characterized in that the inorganic fine particles (B) are used in the composition in the range of 0.01 to 1.0% by mass with respect to the above-mentioned styrene resin (A).

It is essential that the average particle size of the inorganic fine particles (B) is in the range of 0.1 to 10 μm. In the present invention, the average particle size is a value obtained by a laser diffraction method, and is the average value of the longest portion of the primary particles when the particles are not completely spherical.

When the average particle size in the above is less than 0.1 μm, the surface impact strength of the sheet obtained by using this composition does not reach a practical level, and when it exceeds 10 μm, the obtained molded product is obtained. Lack of transparency in.

Examples of the inorganic fine particles (B) include barium sulfate, talc, calcium phosphate and the like. In particular, barium sulfate does not impair the transparency of the molded product and contributes to the improvement of mechanical strength. It can be preferably used.

Further, the inorganic fine particles (B) are more preferably those having an average particle size of 0.5 to 8 μm, and the shape thereof is preferably plate-like. Examples of commercially available inorganic fine particles having such an average particle size include plate-shaped barium sulfate A manufactured by Sakai Chemical Industry Co., Ltd.

Further, the usage ratio must be in the range of 0.01 to 1.0% by mass from the viewpoint of excellent balance between the surface impact strength and the transparency of the obtained molded product, and in particular, 0.05 to 0.05 to 1.0% by mass. It is preferably in the range of 0.3% by mass.

<Rubber-modified polystyrene (C)>
The present invention is characterized in that rubber-modified polystyrene (C) is used in combination in order to further increase the impact strength without impairing the transparency of the molded product.

The rubber-modified polystyrene (C) used in the present invention may be a polystyrene-based resin containing a component such as rubber. For example, the rubber-like polymer is graft-polymerized into a continuous phase composed of a polymer of styrene alone to form particles. As the dispersed resin, a generally available resin can be used as it is. Examples of the rubber component contained in the rubber-modified polystyrene (C) include polybutadiene, styrene-butadiene copolymer, polyisoprene, and butadiene-isoprene copolymer. In particular, it is preferably contained as a polybutadiene or styrene-butadiene copolymer. Further, the average particle size of the particles is preferably in the range of 0.8 to 3.0 μm. The average particle size can be measured by a laser diffraction type particle size distribution measuring device.

The fluidity of the rubber-modified polystyrene (C) used in the present invention is 1 to 10 g / 10 min. It is preferable that it is in the range of.

The content of the rubber-like polymer contained in the rubber-modified polystyrene (C) is 1.5 to 15.0% by mass from the viewpoint of achieving both impact strength and processing characteristics during stretch molding. Is preferable. As the rubber-modified polystyrene (C) having such characteristics, a commercially available product may be used as it is as described above, but ordinary polystyrene is mixed with a resin having a high content of rubber component to obtain a rubber component. The content rate and fluidity may be adjusted to a suitable range before use.

Further, in the present invention, the blending ratio of the rubber-modified polystyrene (C) is 0.1 in the composition from the viewpoints of the formability of the obtained sheet, the impact strength of the molded product obtained after the secondary molding, and the prevention of whitening. It is preferably in the range of ~ 5.0 parts by mass.

<Preparation method of styrene resin composition>
The styrene resin composition in the present invention can be produced by the following method. A styrene-based monomer (a1), methacrylic acid (a2), a monomer copolymerizable with a styrene-based monomer used in combination if necessary, and inorganic fine particles (B) are uniformly mixed in advance, and after the mixed solution is polymerized, the mixture solution is polymerized. A method of mixing rubber-modified polystyrene (C), or a method of adding inorganic fine particles (B) to a polymerization solution of a styrene-based resin (A) and further mixing the rubber-modified polystyrene (C), or a styrene-based resin (A). ), Inorganic fine particles (B) and rubber-modified polystyrene (C) may be added to the melt. When inorganic fine particles (B) and rubber-modified polystyrene (C) are added to the melt of the styrene resin (A), it can be produced by melt-kneading with a twin-screw extruder or the like, but the styrene resin (A) is previously prepared. It is also possible to prepare a masterbatch by melt-kneading so that the inorganic fine particles (B) have a high concentration, and then melt-knead with a styrene resin (A) and rubber-modified polystyrene (C) to dilute to a specified concentration.

The styrene resin composition of the present invention may be blended with other resins, various additives and the like as long as the effects of the present invention are not impaired. Examples of other resins that can be used in combination include styrene-based thermoplastic elastomers such as styrene-butadiene block copolymers and hydrogenated products thereof, and styrene-isoprene block copolymers and hydrogenated products thereof. The content of the diene component of these elastomers is not particularly limited, but from the viewpoint of the strength improving effect, the content of the diene component is preferably 20% by mass or more with respect to all the monomer components constituting the elastomer. From the viewpoint of the balance between strength and transparency, the ratio of these used is 0.1 to 3 with respect to the total amount of the styrene resin (A), the inorganic fine particles (B), and the rubber-modified polystyrene (C). It is preferably used in the range of mass%.

In addition, examples of the additive include a plasticizer, an antistatic agent, an antioxidant, an ultraviolet absorber, a lubricant, an antiblocking agent, a heat stabilizer and the like.

<Unstretched sheet>
The non-stretched sheet can be produced by melt-extruding the pellets of the styrene-based resin composition obtained above with an extruder, melt-extruding the pellets into a sheet with a T-die, and then cooling with a cooling roll or the like. The cooling temperature is preferably 70 to 90 ° C.

<Biaxial stretching sheet>
The biaxially stretched sheet is obtained by melt extrusion with an extruder and then stretching in both vertical and horizontal axes with a stretching machine. For example, first, a heat-resistant styrene resin composition is supplied to an extruder, and melt-extruded into a sheet from a T-die. At that time, casting is performed so that the sheet before stretching has a predetermined thickness. Then, the sheet is cooled to a temperature at which biaxial stretching is possible, for example, 110 to 150 ° C., and stretched in the vertical direction (flow direction) and the horizontal direction (cross direction with respect to the flow direction).

As a stretching method, the styrene resin composition can be melt-extruded into a sheet and then simultaneously biaxially stretched or sequentially biaxially stretched. In the case of sequential biaxial stretching, it is common to first perform longitudinal stretching treatment and then lateral stretching. In particular, in the biaxially stretched styrene-based sheet, after longitudinal stretching using a roll, lateral stretching using a tenter is performed. The tenter method has the advantage of producing a wide range of products and high productivity.

Vertical stretching methods using rolls include a method in which a low-speed roll and a high-speed roll are rotated in the same direction to pass the resin flat and stretched, and a method in which the low-speed roll and the high-speed roll are rotated in the reverse direction to pass the resin through the cloth. There is a method of paper and stretching, and any combination of one-stage or multi-stage, flat or cloth can be used.

As a specific stretching condition, the stretching ratio varies depending on the purpose, but is usually 1.5 to 15 times, more preferably 4 to 10 times in terms of surface magnification. In the case of sequential stretching, the draw ratio in the flow direction is 1.2 to 5 times, preferably 1.5 to 3.0 times, and the draw ratio in the cross direction with respect to the flow direction is 1.2 to 5 times. , Preferably 1.5 to 3.0 times. The draw ratio in each direction of simultaneous biaxial stretching is 1.5 to 5 times. Further, the temperature condition at this time is preferably set so that the orientation relaxation stress measured in accordance with ASTMD-1504 is 0.2 to 2.0 MPa, more preferably 0.4 to 1.0 MPa. If the orientation relaxation stress is less than 0.2 MPa, the impact resistance of the sheet tends to be insufficient, and if it exceeds 2.0 MPa, the sheet is likely to be stretched and the secondary formability may be poor. Because there is. On the other hand, when the range is in the range of 0.4 to 1.0 MPa, not only the foldability of the obtained sheet is good, but also the moldability of the sheet itself is extremely good, which is more preferable.

Further, at this time, for example, the raw sheet before stretching is stretched in the longitudinal direction at a stretching temperature of 110 to 150 ° C. at the above magnification, and then crossed in the longitudinal direction at a stretching temperature of 110 to 150 ° C. Stretching is performed in the direction at the above magnification.

The thickness of the biaxially stretched sheet made of the styrene resin composition is preferably 0.1 to 0.5 mm. If necessary, the biaxially stretched sheet may be laminated with the same or different types of thermoplastic resins by coextrusion or dry laminating. Further, an anti-fog agent or the like may be applied to the biaxially stretched sheet, if necessary.

The obtained biaxially stretched sheet can be easily obtained as a desired container, lid material, etc. by air-molding with a mold having a predetermined shape under the same conditions as the conventional biaxially stretched polystyrene sheet.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention should not be limited to the scope of these examples. Hereinafter, "part" and "%" are based on mass unless otherwise specified.

[GPC-MALLS measurement]
GPC-MALS measurement of the styrene resin composition was carried out under the conditions of Shodex HPLC, detector Waitt Technology DAWN EOS, Shodex RI-101, column Shodex KF-806L × 2, solvent THF, and flow rate 1.0 ml / min. .. Further, the analysis of the measurement of GPC-MALLS was performed by the analysis software ASTRA of Wyatt Co., Ltd., and the weight average molecular weight of the styrene resin composition was obtained. In addition, the molecular weight of the resin composition obtained from GPC-MALLS is shown on the horizontal axis. Slope in a region with a molecular weight of 250,000 to 10 million in a log-log graph with the radius of inertia as the vertical axis (calculated automatically by the software based on the measured values of only the linear portion obtained in the molecular weight range) The slope of the approximate straight line) was calculated.

[Melt mass flow rate measurement method]
Measured according to JIS K7210. The measurement conditions are 200 ° C. and 5.0 kg.

[Measurement method of Vicat softening temperature]
Measured according to JIS K7206.

[Melting and kneading and sheeting of styrene resin and inorganic fine particles]
The styrene resin (A) and the inorganic fine particles (B) were mixed in advance at a mass ratio of 99.0 / 1.0 and melt-kneaded at 230 ° C. using a twin-screw extruder to prepare a masterbatch. Next, the styrene resin (A), the masterbatch, and the rubber-modified polystyrene (C) are mixed, and the extrusion temperature is 230 ° C., the roll temperature is 85 ° C., and the take-up speed is 0.8 to 0.9 m using a 40 mm single-screw extruder. A sheet having a thickness of 1.0 mm was formed at / min.

[Sheet stretching process]
The obtained sheet was cut into 8 × 8 cm and stretched 2.5 times at a stretching temperature of 130 ° C. using a single-shot stretching machine to obtain a stretched sheet.

[Evaluation of impact strength of sheet]
After preparing a stretched sheet using a styrene resin composition, the impact strength was measured using a dirt impact tester manufactured by Toyo Seiki Co., Ltd.

[Sheet transparency evaluation]
Haze (turbidity) was measured according to JIS K7105.

[Evaluation of sheet moldability]
The sheet was molded using a mold having a drawing ratio of 0.3 in a hot plate compressed air molding machine, and the presence or absence of molding whitening was evaluated. If whitening was not found at the corners of the molded product, it was marked with ◯, and if whitening was found, it was marked with x.

[Evaluation of heat resistance of sheet]
The molded product molded using the hot plate compressed air molding machine was heated in a high temp oven at 100 ° C. for 15 minutes, and the deformation after heating was observed. If there was no deformation, it was marked as ◯, and if it was deformed, it was marked as x.

As the rubber-modified polystyrene (C), impact-resistant polystyrene having a melt mass flow rate of 2.5 g / 10 min and a rubber particle diameter of 2.5 μm was used.

(Reference Example 1) Synthesis of multi-branched macromonomer (Mm-1) <Synthesis of multi-branched polyether polyol 1>
To a 2 liter flask equipped with a stirrer, a thermometer, a dropping funnel and a condenser, 50.5 g of pentaerythritol ethoxylated (pentaerythritol with 5 mol-ethylene oxide) and 1 g of BF3 diethyl ether solution (50%) were added at room temperature, and 110 Heated to ° C. To this, 450 g of 3-ethyl-3- (hydroxymethyl) oxetane was slowly added over 25 minutes while controlling the exotherm caused by the reaction. When the exotherm subsided, the reaction mixture was further stirred at 120 ° C. for 3 hours and then cooled to room temperature. The weight average molecular weight of the obtained multi-branched polyether polyol was 3,000, and the hydroxyl value was 530.

<Synthesis of multi-branched polyether 1 having a methacryloyl group and an acetyl group>
Dean-Stark decanter equipped with a stirrer, thermometer, condenser and reactor equipped with a gas introduction tube, 50 g of the multi-branched polyether polyol obtained by the above-mentioned <Synthesis of multi-branched polyether polyol 1>, and methacrylic acid 13 Add 0.8 g, 150 g of toluene, 0.06 g of hydroquinone, and 1 g of paratoluenesulfonic acid, and stir under normal pressure while blowing 7% oxygen-containing nitrogen (v / v) into the mixed solution at a rate of 3 ml / min. It was heated. The heating amount was adjusted so that the amount of the distillate in the decanter was 30 g per hour, and heating was continued until the dehydrated amount reached 2.9 g. After completion of the reaction, the mixture was cooled once, 36 g of acetic anhydride and 5.7 g of sulfamic acid were added, and the mixture was stirred at 60 ° C. for 10 hours. Then, in order to remove the remaining acetic acid and hydroquinone, the cells were washed 4 times with 50 g of a 5% aqueous sodium hydroxide solution, once with 50 g of a 1% aqueous sulfuric acid solution, and twice with 50 g of water. 0.02 g of methoquinone was added to the obtained organic layer, and the solvent was distilled off while introducing 7% oxygen-containing nitrogen (v / v) under reduced pressure to obtain 60 g of a multi-branched polyether having an isopropenyl group and an acetyl group. Obtained. The weight average molecular weight of the obtained multi-branched polyether was 3,900, and the introduction rates of isopropenyl groups and acetyl groups into the multi-branched polyether polyol were 30 mol% and 62 mol%, respectively.

(Reference Example 2) Synthesis of multi-branched macromonomer (Mm-2) <Synthesis of multi-branched polyether polyol 2>
1.24 g (8.7 mmol) of boron trifluoride diethyl ether complex was dried and removed peroxide in a 1000 mL three-necked flask connected with nitrogen, an air reflux condenser, a magnetic stir bar, and a thermometer. Diluted with 273 g of methyl-t-butyl ether. In a separate container, 140 g (1.21 mol) of 3-hydroxymethyl-3-ethyloxetane and 70.0 g (1.21 mol) of propylene oxide are mixed, and placed in the above three-necked flask over 5.5 hours with a metering pump. Dropped. At this time, cooling was performed in an ice bath at any time so as to keep the temperature in the system at 20 ° C. After completion of the dropwise addition, 63.0 g (1.08 mol) of propylene oxide was further added dropwise over 3 hours while maintaining the temperature in the system at 20 ° C., and the mixture was further stirred for 4 hours. Here, 0.620 g (4.4 mmol) of boron trifluoride diethyl ether complex was added, and the mixture was further stirred at 20 ° C. for 6 hours. The reaction mixture was adsorbed and removed by adding hydrotalcite having a weight 10 times that of the boron trifluoride diethyl ether complex used in the reaction and refluxing the mixture for 1 hour. After hydrotalcite was filtered off, methyl-t-butyl ether was removed to obtain 267 g of a transparent, highly viscous multibranched polyether polyol. This multi-branched polyether polyol has Mn = 2,876 g / mol, Mw = 7,171 g / mol, hydroxyl value = 253 mg · KOH / g, and 3-hydroxymethyl-3-ethyl on a molar basis from proton NMR. Oxetane: propylene oxide = 1: 1.9.

<Synthesis of multi-branched polyether 2 having acryloyl group>
In a 500 mL four-necked flask equipped with a Dean Stark tube, a nitrogen and air introduction tube, a stirrer, and a thermometer, the multi-branched polyether polyol obtained by the above-mentioned <Synthesis of multi-branched polyether polyol 2> is placed. 155 g, 51 g of acrylic acid, 200 g of cyclohexane, 0.21 g of hydroquinone monomethyl ether, and 4 g (12.3 mmol) of dodecylbenzenesulfonic acid as a catalyst were charged, and the temperature was raised to 82 ° C. under a mixed gas flow of 2: 1 nitrogen and air. .. The reflux of cyclohexane began and the outflow of water began gradually. Then, when the temperature was raised to 85 ° C. and the reaction was carried out for 18 hours, 60% of the theoretical dehydration amount was reached, so cooling was started. After cooling to around 30 ° C., a 5% aqueous sodium hydroxide solution and a 15% aqueous NaCl solution were added for washing. The obtained polymerizable unsaturated group-containing multi-branched polyether had a hydroxyl value of 70 mg · KOH / g, and the acrylic group introduction rate of all the hydroxyl groups was 60%.

(Reference Example 3) Synthesis of multi-branched macromonomer (Mm-3) <Synthesis of multi-branched polyether 1 having a styryl group and an acetyl group>
In a reactor equipped with a stirrer, a condenser equipped with a drying tube, a dropping funnel and a thermometer, 50 g of the multi-branched polyether polyol obtained in the above <Synthesis of the multi-branched polyether polyol 1>, 100 g of tetrahydrofuran and sodium hydride were added. 4.3 g was added, and the mixture was stirred at room temperature. To this, 26.7 g of 4-chloromethylstyrene was added dropwise over 1 hour, and the obtained reaction mixture was stirred at 50 ° C. for another 4 hours. After completion of the reaction, the mixture was cooled once, acetic anhydride (34 g) and sulfamic acid (5.4 g) were added, and the mixture was stirred at 60 ° C. for 10 hours. Then, tetrahydrofuran is distilled off under reduced pressure, the obtained mixture is dissolved in 150 g of toluene, washed four times with 50 g of a 5% aqueous sodium hydroxide solution to remove the remaining acetic acid, and further 50 g of a 1% aqueous sulfuric acid solution. It was washed once with water and twice with 50 g of water. The solvent was distilled off from the obtained organic layer under reduced pressure to obtain 70 g of a multi-branched polyether having a styryl group and an acetyl group. The mass average molecular weight of the obtained multi-branched polyether was 4,800, and the introduction rates of styryl groups and acetyl groups into the multi-branched polyether polyol were 38 mol% and 57 mol%, respectively.

(Reference Example 4) Synthesis of multi-branched macromonomer (Mm-4) <Synthesis of multi-branched macromonomer having methacryloyl group and acetyl group>
A stirrer, a pressure gauge, a cooler and a saucer were attached to the four-necked flask, and 308.9 g of pentaerythritol ethoxylated and 0.46 g of sulfuric acid were added thereto. Then, it was heated to 140 degreeC, and 460.5 g of 2,2-di (hydroxymethyl) propionic acid was added in 10 minutes. After the 2,2-di (hydroxymethyl) propionic acid is completely dissolved to form a transparent solution, the pressure is reduced to 30-40 mmHg, and the reaction is carried out for 4 hours with stirring until the acid value reaches 7.0 mgKOH / g. I let you. Then, 921 g of 2,2-di (hydroxymethyl) propionic acid and 0.92 g of sulfuric acid were added to this reaction solution over 15 minutes to form a transparent solution, the pressure was reduced to 30-40 mmHg, and the mixture was stirred. The reaction was carried out for a time to obtain a polyester polyol. In a reaction vessel equipped with a 7% oxygen introduction tube, a thermometer, a Dean-Stark decanter equipped with a condenser, and a stirrer, 10 g of the polyester polyol produced above, 1.25 g of dibutyltin oxide, and 100 g of methyl methacrylate having an isopropenyl group. , And 0.05 g of hydroquinone were added and heated under stirring while blowing 7% oxygen into the mixed solution at a rate of 3 ml / min. Adjust the heating amount so that the amount of distillate in the decanter is 15 to 20 g per hour, take out the distillate in the decanter every hour, and add the corresponding amount of methyl methacrylate for 4 hours. It was reacted. After completion of the reaction, methyl methacrylate was distilled off under reduced pressure, 10 g of acetic anhydride and 2 g of sulfamic acid were added to cap the remaining hydroxy groups, and the mixture was stirred at room temperature for 10 hours. After removing sulfamic acid by filtration and distilling acetic anhydride and acetic acid under reduced pressure, the residue was dissolved in 70 g of ethyl acetate and washed 4 times with 20 g of 5% aqueous sodium hydroxide solution to remove hydroquinone. Further, it was washed twice with 20 g of a 7% aqueous sulfuric acid solution and twice with 20 g of water. 0.0045 g of methoquinone was added to the obtained organic layer, and the solvent was distilled off while introducing 7% oxygen under reduced pressure to obtain 11 g of a multi-branched macromonomer (Mm-3) having an isopropenyl group and an acetyl group. rice field. The obtained multi-branched macromonomer (Mm-3) has a weight average molecular weight of 3,000, a number average molecular weight of 2,100, a double bond introduction amount of 2.00 mmol / g, and an isopropenyl group and an acetyl group. The introduction rates were 55 mol% and 36 mol%, respectively.

(Reference Example 5) Synthesis of multi-branched macromonomer (Mm-5) <Synthesis of PAMAM dendrimer having styryl group>
Add 50 g of a methanol solution (20%) of PAMAM dendrimer (Generation 2.0: manufactured by Dentric) to a reactor equipped with a stirrer, a condenser equipped with a drying tube, a dropping funnel and a thermometer, and stir under reduced pressure. Methanol was distilled off. Subsequently, 50 g of tetrahydrofuran and 3.0 g of pulverized potassium hydroxide were added, and the mixture was stirred at room temperature. 7.0 g of 4-chloromethylstyrene was added dropwise thereto over 10 minutes, and the obtained reaction mixture was stirred at 50 ° C. for a further 3 hours. After completion of the reaction, the mixture was cooled and the solid was filtered, and then tetrahydrofuran was distilled off under reduced pressure to obtain 13 g of a PAMAM dendrimer having a styryl group. The styryl group content of the obtained dendrimer was 2.7 mmol / gram.

(Reference Example 6) Synthesis of multi-branched macromonomer (Mm-6) <Multi-branched polyether polyol 2 having a styryl group and an acetyl group>
In a light-shielding reaction vessel equipped with a stirrer, condenser, light-shielding dropping funnel and thermometer, which can be sealed with nitrogen, under a nitrogen stream, 0.5 g of anhydrous 1,3,5-trihydroxybenzene, 29 g of potassium carbonate, 18-crown -6 2.7 g and 180 g of acetone were added, and a solution consisting of 21.7 g of 5- (bromomethyl) -1,3-dihydroxybenzene and 180 g of acetone was added dropwise over 2 hours with stirring. Then, the mixture was heated and refluxed with stirring until 5- (bromomethyl) -1,3-dihydroxybenzene disappeared. Then, 9.0 g of 4-chloromethylstyrene was added, and the mixture was further heated and refluxed with stirring until it disappeared. Then, 4 g of acetic anhydride and 0.6 g of sulfamic acid were added to the reaction mixture, and the mixture was stirred overnight at room temperature. After cooling, the solid in the reaction mixture was removed by filtration and the solvent was evaporated under reduced pressure. The resulting mixture was dissolved in dichloromethane, washed 3 times with water, and then the dichloromethane solution was added dropwise to hexane to precipitate the multi-branched polyether. This was filtered and dried to obtain 12 g of a multi-branched polyether polyol having a styryl group and an acetyl group. The mass average molecular weight was 3,200 and the styryl group content was 3.5 mmol / gram.

(Reference Example 7) Synthesis of multi-branched macromonomer (M-m7) <Synthesis of multi-branched polyester polyol having methacryloyl group and acetyl group>
A reaction vessel equipped with a 7% oxygen introduction tube, a thermometer, a Dean-Stark decanter equipped with a condenser, and a stirrer has 10 g of "Voltron H20", 1.25 g of dibutyltin oxide, and an isopropenyl group as a functional group (B). 100 g of methyl methacrylate and 0.05 g of hydroquinone were added, and the mixture was heated under stirring while blowing 7% oxygen into the mixed solution at a rate of 3 ml / min. Adjust the heating amount so that the amount of distillate in the decanter is 15 to 20 g per hour, take out the distillate in the decanter every hour, and add the corresponding amount of methyl methacrylate for 6 hours. It was reacted.

After completion of the reaction, methyl methacrylate was distilled off under reduced pressure, 10 g of acetic anhydride and 2 g of sulfamic acid were added to cap the remaining hydroxy groups, and the mixture was stirred at room temperature for 10 hours. After removing sulfamic acid by filtration and distilling acetic anhydride and acetic acid under reduced pressure, the residue was dissolved in 70 g of ethyl acetate and washed 4 times with 20 g of 5% aqueous sodium hydroxide solution to remove hydroquinone. Further, it was washed twice with 20 g of a 7% aqueous sulfuric acid solution and twice with 20 g of water. 0.0045 g of methquinone was added to the obtained organic layer, and the solvent was distilled off under reduced pressure while introducing 7% oxygen to obtain 12 g of a multi-branched polyester having an isopropenyl group and an acetyl group. The obtained multi-branched polyester had a mass average molecular weight of 2860 and a number average molecular weight of 3770, and the introduction rates of isopropenyl groups and acetyl groups into the multi-branched polyester polyol (A) were 55% and 40%, respectively.

Example 1
A mixed solution consisting of 98 parts of styrene monomer, 2 parts of methacrylic acid and 12 parts of toluene was prepared, and 2,2-bis (4,5-di-t-butylperoxycyclohexyl) propane was added as an organic peroxide. 750 ppm was added to the total amount of styrene monomer and methacrylic acid, and bulk polymerization was carried out continuously under the following conditions using the apparatus shown in FIG. The temperature of the stirring reactor (I) was 110 to 130 ° C., and the temperature of the circulating polymerization line (II) and the non-circulating polymerization line (III) was 120 to 160 ° C., respectively. From the reaction solution, the unreacted monomer and the solvent component are recovered in the devolatilization tank 1 and the devolatilization tank 2 installed after the non-circulating polymerization line (III) which is the final reactor. The temperature of the devolatilization tank 1 and the devolatilization tank 2 was 240 to 280 ° C. After that, it passed through a single tube and was stranded and pelletized with a pelletizer to obtain a styrene resin (A-1).

The obtained styrene resin and plate-shaped barium sulfate having an average particle diameter of 7 μm were melt-kneaded to prepare a masterbatch of 2.0% by mass of barium sulfate, and then styrene resin / masterbatch / rubber-modified polystyrene = 94 /. After mixing in advance with a composition of 5/1 parts by mass, melt extrusion was performed to obtain a sheet containing 0.1% by mass of barium sulfate and 1.0% by mass of rubber-modified polystyrene. The obtained sheet was stretched 2.5 times with a single-shot stretching machine to obtain a stretched sheet.

Example 2
A stretched sheet was obtained in the same manner as in Example 1 except that barium sulfate was used as a plate-shaped barium sulfate having a thickness of 4 μm.

Example 3
A stretched sheet was obtained in the same manner as in Example 1 except that barium sulfate was used as a plate-shaped barium sulfate having a thickness of 2 μm.

Example 4
The composition at the time of sheet preparation is styrene resin / masterbatch / rubber-modified polystyrene = 95.5 / 2.5 / 2 parts by mass, and contains 0.05% by mass of barium sulfate and 2.0% by mass of rubber-modified polystyrene. A stretched sheet was obtained in the same manner as in Example 1 except that a sheet was obtained.

Example 5
Prepare a mixed solution consisting of 98 parts of styrene monomer, 2 parts of methacrylic acid, 500 ppm of the multi-branched macromonomer (Mm-1) obtained in Reference Example 1 with respect to the total amount of styrene monomer and methacrylic acid, and 11 parts of toluene. Further, 300 ppm of t-butylperoxybenzoate as an organic peroxide was added to the total amount of the styrene monomer and the methacrylic acid monomer, and bulk polymerization was carried out continuously under the following conditions using the apparatus shown in FIG. The temperature of the stirring reactor (I) was 110 to 130 ° C., and the temperature of the circulating polymerization line (II) and the non-circulating polymerization line (III) was 120 to 160 ° C., respectively. From the reaction solution, the unreacted monomer and the solvent component are recovered in the devolatilization tank 1 and the devolatilization tank 2 installed after the non-circulating polymerization line (III) which is the final reactor. The temperature of the devolatilization tank 1 and the devolatilization tank 2 was 240 to 280 ° C. After that, it passed through a single tube and was stranded and pelletized with a pelletizer to obtain a styrene resin (A-2). A stretched sheet was obtained in the same manner as in Example 1 except for the method of obtaining the styrene resin (A-2).

Example 6
A stretched sheet was obtained in the same manner as in Example 5 except that the macromonomer was changed to Mm-2 obtained in Reference Example 2 to obtain a styrene resin (A-3).

Example 7
A stretched sheet was obtained in the same manner as in Example 5 except that the macromonomer was changed to Mm-3 obtained in Reference Example 2 to obtain a styrene resin (A-4).

Example 8
A stretched sheet was obtained in the same manner as in Example 5 except that the macromonomer was changed to Mm-4 obtained in Reference Example 2 to obtain a styrene resin (A-5).

Example 9
A stretched sheet was obtained in the same manner as in Example 5 except that the macromonomer was changed to Mm-5 obtained in Reference Example 2 to obtain a styrene resin (A-6).

Example 10
A stretched sheet was obtained in the same manner as in Example 5 except that the macromonomer was changed to Mm-6 obtained in Reference Example 2 to obtain a styrene resin (A-7).

Example 11
A stretched sheet was obtained in the same manner as in Example 5 except that the macromonomer was changed to Mm-7 obtained in Reference Example 2 to obtain a styrene resin (A-8).

Example 12
The composition at the time of sheet preparation is styrene resin / masterbatch / rubber-modified polystyrene = 95.5 / 2.5 / 2 parts by mass, and contains 0.05% by mass of barium sulfate and 2.0% by mass of rubber-modified polystyrene. A stretched sheet was obtained in the same manner as in Example 11 except that the sheet was obtained.

Comparative Example 1
A stretched sheet was obtained in the same manner as in Example 1 except that the content of methacrylic acid was set to 0% by mass.

Comparative Example 2
A stretched sheet was obtained in the same manner as in Example 1 except that barium sulfate was used as a plate-shaped barium sulfate having a thickness of 15 μm.

Comparative Example 3
A sheet containing 1.5% by mass of barium sulfate and 1.0% by mass of rubber-modified polystyrene was obtained by setting the composition at the time of sheet preparation as styrene resin / masterbatch / rubber-modified polystyrene = 24/75/1 parts by mass. A stretched sheet was obtained in the same manner as in Example 1 except for the above.

Comparative Example 4
A stretched sheet was obtained in the same manner as in Example 1 except that barium sulfate and rubber-modified polystyrene were not added.

The evaluation results of the stretched sheet obtained above are shown below.

Claims (8)

A styrene resin (A) having a styrene monomer (a1) -derived structure and a methacrylic acid (a2) -derived structure, inorganic fine particles (B) having an average particle size of 0.1 to 10 μm, and rubber-modified polystyrene (C). ) Is an essential component of the resin composition.
The blending ratio of the inorganic fine particles (B) in the composition is in the range of 0.01 to 1.0% by mass.
The polystyrene-based resin (A) requires a multi-branched macromonomer (a3) having a plurality of branches and a plurality of polymerizable double bonds, a styrene-based monomer (a1), and methacrylic acid (a2). It is a copolymer of monomers contained as a component, and is
The ratio of the styrene-based monomer (a1) to the methacrylic acid (a2) used is 99.9 / 0.1-97.0 / 3.0 as the mass ratio represented by (a1) / (a2). Range,
A styrene-based resin composition, wherein the inorganic fine particles (B) are plate-shaped barium sulfate. The styrene-based resin (A) is a multi-branched resin having a styrene-based monomer (a1) -derived structure and a methacrylic acid (a2) -derived structure, and (1) weight average obtained by the GPC-MALS method. It has a molecular weight of 150,000 to 700,000 and has a molecular weight of 150,000 to 700,000.
(2) The claim that the slope in the region of the molecular weight of 250,000 to 10 million is 0.30 to 0.55 in the log-log graph with the molecular weight obtained by the GPC-MALS method on the horizontal axis and the radius of inertia on the vertical axis. The styrene-based resin composition according to 1. The styrene-based resin composition according to claim 1 or 2, wherein the rubber-modified polystyrene (C) is a resin in which a rubber-like polymer is dispersed as a graft polymer in a continuous phase composed of a polymer of styrene alone. The styrene-based resin composition according to any one of claims 1 to 3 , wherein the blending ratio of the inorganic fine particles (B) in the composition is in the range of 0.1 to 0.5% by mass. A biaxially stretched styrene resin sheet, which is obtained by biaxially stretching the styrene resin composition according to any one of claims 1 to 4. The biaxially stretched styrene resin sheet according to claim 5 , wherein the thickness of the sheet is in the range of 0.1 to 0.5 mm. A molded product obtained by molding the biaxially stretched styrene resin sheet according to claim 5 or 6. The molded product according to claim 7, which is used as a packaging material for food.

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