Styrenic resin composition, extruded sheet and container

Abstract

To provide: a styrene-based resin composition that is excellent in transparency and hot oil resistance without deteriorating heat resistance and impact resistance; an extruded sheet based thereon; and a container and lid material formed by post molding of the extruded sheet.SOLUTION: A styrene-based resin composition contains: 50-98 mass% of a styrene-unsaturated carboxylic acid based resin (A) comprising styrene-based monomer units (1) and unsaturated carboxylic acid-based monomer units (a1); and 2-50 mass% of a (meth)acryl-based resin (B) having unsaturated carboxylic acid-based monomer units (b1).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a styrene-based resin composition, non-foamed and foamed extruded sheets formed using the styrene-based resin composition, and lunch box container lids formed by secondary molding of the extruded sheets. [Background technology]

[0002] Styrene-unsaturated carboxylic acid resins, such as styrene-methacrylic acid copolymer resins, are excellent in heat resistance, transparency, rigidity, and appearance, and are inexpensive, and therefore are widely used as packaging materials for food containers such as boxed lunches and prepared foods, foam boards for insulating housing, diffusion plates for liquid crystal televisions containing a diffusion agent, etc. In particular, with the recent widespread use of high-power microwave ovens for commercial use in convenience stores and the like, styrene-unsaturated carboxylic acid resins are being used as materials for containers that can withstand the temperatures used during cooking in high-power microwave ovens, and for lids that seal or cover these containers. For example, Patent Document 1 describes a technique for improving appearance, impact resistance, and heat resistance by using an alloy of a styrene-methacrylic acid copolymer, a methyl methacrylate-butyl acrylate copolymer, and a graft copolymer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-111649 A Summary of the Invention [Problem to be solved by the invention]

[0004] The technology of the above-mentioned Patent Document 1 considers heat resistance, impact resistance, and appearance, but the transparency and hot oil resistance are insufficient. In particular, for transparent containers that are intended to come into direct contact with food, conventional styrene-unsaturated carboxylic acid resins are corroded by high-temperature oil from food heated in a microwave oven, causing cracking and whitening of the transparent container, so resistance to edible oil is required. Therefore, the problem to be solved by the present invention is to provide a styrene-based resin composition used for a molded article having excellent transparency and heat oil resistance without deteriorating heat resistance, appearance and mechanical strength. Another problem to be solved by the present invention is to provide a biaxially oriented sheet or extruded sheet containing a styrene-based resin composition having excellent transparency and heat oil resistance without deteriorating heat resistance, appearance and mechanical strength, and a container and a lid material obtained by secondary molding of the biaxially oriented sheet or the extruded sheet. [Means for solving the problem]

[0005] The present inventors have conducted intensive research in view of the above problems, and as a result, have succeeded in realizing a styrene-based resin composition excellent in transparency and heat oil resistance without deteriorating heat resistance, appearance and mechanical strength by containing a predetermined amount of each of a styrene-unsaturated carboxylic acid-based resin (A) and a (meth)acrylic-based resin (B), an extruded sheet using the same, and further a container and a lid material obtained by secondary molding of the extruded sheet, thereby completing the present invention. That is, the present disclosure is as follows.

[0006] [1] The present disclosure relates to a styrene-unsaturated carboxylic acid-based resin (A) having a styrene-based monomer unit (1) and an unsaturated carboxylic acid-based monomer unit (a1), in an amount of 50 to 98% by mass; The styrene-based resin composition contains 2 to 50 mass % of a (meth)acrylic resin (B) having an unsaturated carboxylic acid monomer unit (b1).

[0007] [2] In this embodiment, the content of high molecular weight components having molecular weights of 1,000,000 or more in the entire styrene-based resin composition is preferably 1.0 mass % or less based on the total amount of the styrene-based resin composition.

[0008] [3] In the present embodiment, the styrene-based monomer unit (1) is preferably contained in an amount of 60 to 85 mass % based on the total amount of the styrene-based resin composition.

[0009] [4] In this embodiment, the unsaturated carboxylic acid monomer unit (a1) is preferably at least one selected from the group consisting of the (meth)acrylic acid monomer unit (a1-1) and the (meth)acrylic acid ester monomer unit (a1-2).

[0010] [5] In this embodiment, the unsaturated carboxylic acid monomer units (a1) contain, as essential components, the (meth)acrylic acid monomer units (a1-2) and the (meth)acrylic acid ester monomer units (a2-2), and preferably contain 2 to 30 mass% of the (meth)acrylic acid monomer units (a1-1) and 1 to 20 mass% of the (meth)acrylic acid ester monomer units (a1-2) relative to the entire styrene-unsaturated carboxylic acid resin (A).

[0011] [6] In this embodiment, the (meth)acrylic resin (B) is preferably contained in an amount of 10 to 40 mass % based on the total amount of the styrene-based resin composition.

[0012] [7] In this embodiment, the unsaturated carboxylic acid monomer unit (a1) contains a (meth)acrylic acid ester monomer unit (a1-2), and the unsaturated carboxylic acid monomer unit (b1) contains a (meth)acrylic acid ester monomer unit (b1-2), The total content of the (meth)acrylic acid ester monomer units (a1-2) and the (meth)acrylic acid ester monomer units (b1-2) is preferably 15 to 40 mass % based on the total amount of the styrene-based resin composition.

[0013] [8] In this embodiment, the (meth)acrylic resin (B) is a methyl methacrylate-methyl acrylate copolymer, and preferably contains 0.1 to 15 mass % of the methyl acrylate based on the total amount of the copolymer.

[0014] [9] In this embodiment, the styrene-based composition preferably contains 0.01 to 1.0 part by mass of an alcohol (C) having 10 or more carbon atoms relative to the total amount (100 parts by mass).

[0015]

[10] In this embodiment, the rubber-modified styrene-based resin (D) is preferably contained in an amount of 0.1 to 15 mass % relative to the total amount (100 mass %) of the styrene-based resin composition.

[0016]

[11] In this embodiment, the content of the methyl acrylate monomer unit is preferably 0.01 to 5.0% by mass based on the total amount of the styrene-based resin composition.

[0017]

[12] In the present embodiment, in the Z-average molecular weight of the styrene-based resin composition according to claim 1 or 2, measured using gel permeation chromatography (GPC) in terms of standard polystyrene, when the value measured using a differential refractometer (RI detector) is Mz(RI) and the value measured using an ultraviolet absorption detector (UV detector) is Mz(UV), It is preferable that the value of Mz(RI)-Mz(UV) is 500,000 or less.

[0018]

[13] It is preferable that a 2 mm-thick plate-shaped test piece formed by injection molding of the styrene-based resin composition of this embodiment has a haze value of less than 10%.

[0019]

[14] One aspect of this embodiment is a non-foamable or foamable extruded sheet having a styrenic resin composition.

[0020]

[15] One aspect of this embodiment is a container formed by molding the styrene-based resin composition. Effect of the Invention

[0021] According to the present disclosure, it is possible to provide a styrene-based resin composition for use in molded articles having excellent transparency and heat oil resistance without deteriorating heat resistance, appearance, and mechanical strength. According to the present disclosure, it is possible to provide a biaxially oriented sheet, a foamed extruded sheet, a non-foamed extruded sheet, and a lid material for a lunch box container that can be cooked in a microwave oven, which have excellent transparency and heat and oil resistance without compromising heat resistance, appearance, and mechanical strength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment, and can be modified in various ways within the scope of the gist of the present invention.

[0023] [Styrene-based resin composition] The styrene-based resin composition in this embodiment (hereinafter, sometimes simply referred to as a resin composition) contains a styrene-unsaturated carboxylic acid-based resin (A) having a styrene-based monomer unit (1) and an unsaturated carboxylic acid-based monomer unit (a1), and a (meth)acrylic resin (B) having an unsaturated carboxylic acid-based monomer unit (b1), and the content of the styrene-unsaturated carboxylic acid-based resin (A) is 50 to 98 mass%, and the content of the (meth)acrylic resin (B) is 2 to 50 mass%, relative to the total amount (100 mass%) of the styrene-based resin composition. Furthermore, the styrene-based resin composition in the present embodiment may contain, as necessary, one or more selected from the group consisting of alcohols (C) having 10 or more carbon atoms and rubber-modified styrene-based resins (D). This makes it possible to provide a styrene-based resin composition having excellent transparency and heat and oil resistance without reducing heat resistance and rigidity. In the styrene-based resin composition of the present embodiment, the content of high molecular weight components having a molecular weight of 1,000,000 or more is preferably 1.0 mass % or less based on the total amount of the styrene-based resin composition. The high molecular weight component having a molecular weight of 1 million or more can be a styrene-unsaturated carboxylic acid resin (A) and / or a (meth)acrylic resin (B). Therefore, the proportion of the high molecular weight component having a molecular weight of 1 million or more in the styrene resin composition is small.

[0024] "Styrene-unsaturated carboxylic acid resin (A)" The styrene-unsaturated carboxylic acid resin (A) in this embodiment is a copolymer resin (hereinafter also simply referred to as resin (A)) consisting essentially of styrene monomer units (1) and unsaturated carboxylic acid monomer units (a1), and contributes to improving the heat resistance of the entire styrene resin composition. In addition, the styrene-unsaturated carboxylic acid resin (A) may further contain other monomer units (a2) other than the essential components of the styrene monomer units (1) and unsaturated carboxylic acid monomer units (a1), if necessary. The content of the styrene-unsaturated carboxylic acid resin (A) is 50 to 98% by mass relative to the total amount (100% by mass) of the styrene-based resin composition, with the upper limit being 97% by mass or less, 96% by mass or less, 97% by mass or less, 96% by mass or less, 95% by mass or less, 94% by mass or less, 93% by mass or less, 92% by mass or less, 91% by mass or less, 90% by mass or less, 89% by mass or less, 88% by mass or less, and 87% by mass or less being preferred in this order, and the lower limit being 51% by mass or more, 52% by mass or more, 53% by mass or more, 54% by mass or more, 55% by mass or more, 56% by mass or more, 57% by mass or more, 58% by mass or more, 59% by mass or more, 60% by mass or more, 62% by mass or more, 64% by mass or more, 66% by mass or more, 68% by mass or more, 70% by mass or more, 72% by mass or more, and 74% by mass or more being preferred in this order. Styrene-unsaturated carboxylic acid resin The content of (A) can be within the range between the upper and lower limits described above. By making the content of styrene-unsaturated carboxylic acid resin (A) 50% by mass or more, the effect of imparting heat resistance can be sufficiently obtained, and by making it 98% by mass or less, the effect of improving hot oil resistance can be sufficiently obtained.

[0025] <Styrene-based monomers (1)> In the styrene-unsaturated carboxylic acid resin (A) of this embodiment, the content of the styrene-based monomer unit (1) is 60 to 98 mass%, preferably 70 to 97 mass%, more preferably 80 to 96 mass%, and even more preferably 82 to 95 mass%, based on the total amount of the styrene-unsaturated carboxylic acid resin (A). If the content of the styrene-based monomer unit (1) is less than 60 mass%, the flowability is reduced, and if it is more than 98 mass%, it becomes difficult to contain a desired amount of the unsaturated carboxylic acid monomer unit (a1) described below, and the effect of improving heat resistance by the unsaturated carboxylic acid monomer unit (a1) (especially, the (meth)acrylic acid monomer unit (a1-1)) is not sufficiently obtained. In the styrene-based resin composition of the present embodiment, the styrene-based monomer unit (1) is preferably contained in an amount of 50 to 85 mass%, more preferably 52 to 82 mass%, more preferably 54 to 79 mass%, and even more preferably 56 to 77 mass%, based on the total amount of the styrene-based resin composition. When the content of the styrene-based monomer (1) in the entire composition is within the above range, the effect of improving oil resistance can be sufficiently obtained.

[0026] In this embodiment, the styrene-based monomer (1) is not particularly limited, but examples thereof include styrene, α-methylstyrene, β-methylstyrene, paramethylstyrene, orthomethylstyrene, metamethylstyrene, chlorostyrene, bromostyrene, etc. From an industrial viewpoint, styrene and α-methylstyrene are particularly preferred, and styrene is more preferred. As the styrene-based monomer (1), these may be used alone or in combination of two or more. In this specification, the term "styrene monomer unit (1)" refers to a repeating unit constituting a polymer obtained by polymerizing a styrene monomer (1), and is a repeating unit (or structural unit) in which the carbon-carbon double bond in the styrene monomer (1) becomes a single bond (-CC-) through a polymerization reaction or crosslinking reaction of the styrene monomer (1). Other monomer units in this specification have the same meaning.

[0027] <Unsaturated carboxylic acid monomer (a1)> In the styrene-unsaturated carboxylic acid resin (A) of this embodiment, the unsaturated carboxylic acid monomer unit (a1) plays a role in improving oil resistance and compatibility with the (meth)acrylic resin (B) described below. The content of the unsaturated carboxylic acid monomer unit (a1) is 2 to 40 mass%, preferably 3 to 35 mass%, more preferably 5 to 30 mass%, even more preferably 8 to 25 mass%, and even more preferably 10 to 20 mass%, based on the total amount of the styrene-unsaturated carboxylic acid resin (A). If the content of the unsaturated carboxylic acid monomer unit (a1) is less than 2 mass%, the effect of improving heat resistance is insufficient. In addition, if the content of the unsaturated carboxylic acid monomer unit (a1) exceeds 40 mass%, it is not preferable because the processability is reduced due to an increase in resin viscosity, bubbles are generated during molding due to an increase in water absorption, and the viscosity becomes too high during production. In particular, by adjusting the content of the unsaturated carboxylic acid monomer unit (a1) to 10 to 20 mass %, good compatibility with the (meth)acrylic resin (B) can be obtained, and a composition with excellent transparency can be obtained. The unsaturated carboxylic acid monomer unit (a1) in this embodiment includes an unsaturated carboxylic acid and its ester, and specifically includes a (meth)acrylic acid monomer unit (a1-1) and a (meth)acrylic acid ester monomer unit (a1-2).

[0028] -(Meth)acrylic acid monomer unit (a1-1)- In this embodiment, the (meth)acrylic acid monomer unit (a1-1) has oil resistance and heat resistance. The (meth)acrylic acid monomer (a1-1) can be acrylic acid or methacrylic acid. From an industrial viewpoint, the (meth)acrylic acid monomer unit (a1-1) may be used alone or in combination of two or more. As the (meth)acrylic acid monomer unit (a1-1), methacrylic acid, which has a large effect of improving heat resistance, is particularly preferred. In this embodiment, the content of the (meth)acrylic acid monomer unit (a1-1) is preferably in the range of 2 to 40 mass%, more preferably 3 to 20 mass%, even more preferably 4 to 17 mass%, and even more preferably 8 to 14 mass% relative to the total amount of the styrene-unsaturated carboxylic acid resin (A). By making the content of the (meth)acrylic acid monomer unit (a1-1) 2 mass% or more, it is possible to obtain an effect of improving heat resistance, and by making the content 40 mass% or less, it is possible to suppress an excessive increase in viscosity. In particular, by making the content in the range of 8 to 13 mass%, it is possible to obtain a styrene-unsaturated carboxylic acid resin (A) that achieves both a high effect of improving heat resistance and suppressing gel generation to a level applicable to transparent sheet applications.

[0029] -(Meth)acrylic acid ester monomer (a1-2)- In this embodiment, the (meth)acrylic acid ester monomer (a1-2) serves to improve oil resistance and strength. As the (meth)acrylic acid ester monomer unit (a1-2), a (meth)acrylic acid ester monomer unit represented by the following general formula (1) [ka] (In the above general formula (1), R 1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R 2 represents an ester substituent, specifically, represents an alkyl group having 1 to 12 carbon atoms. In this embodiment, the ester substituent of the (meth)acrylic acid ester monomer unit (a1-2) (R 2 The number of carbon atoms in the alkyl group is preferably 10 or less, more preferably 8 or less, and even more preferably 4 or less. If the number exceeds 10, the effect of lowering heat resistance is significant, which is not preferred.

[0030] Examples of the (meth)acrylic acid ester monomer (a1-2) in this embodiment include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and decyl (meth)acrylate. These can be used alone or in combination. As the (meth)acrylic acid ester monomer (a1-2), methyl (meth)acrylate or butyl (meth)acrylate is preferred from the viewpoint of industrial availability, and methyl methacrylate is particularly preferred from the viewpoint of suppressing a decrease in heat resistance. In this embodiment, the content of the (meth)acrylic acid ester monomer unit (a1-2) relative to the total amount of the styrene-unsaturated carboxylic acid resin (A) is, for example, preferably in the range of 0 to 50 mass%, more preferably 1 to 20 mass%, even more preferably 2 to 17 mass%, still more preferably 3 to 12 mass%, and even more preferably 4 to 10 mass%.

[0031] <Preferable form of styrene-unsaturated carboxylic acid resin (A)> The styrene-unsaturated carboxylic acid resin (A) of this embodiment may be a multicomponent polymer containing (meth)acrylic acid monomer units (a1-1) and (meth)acrylic acid ester monomer units (a1-2). That is, the styrene-unsaturated carboxylic acid resin (A) of this embodiment may be a binary copolymer of the styrene monomer (1) and the (meth)acrylic acid monomer units (a1-1), or a ternary copolymer in which the styrene monomer (1), the (meth)acrylic acid monomer units (a1-1), and the (meth)acrylic acid ester monomer units (a1-2) are copolymerized. This further improves the compatibility with the (meth)acrylic resin (B), improves the surface hardness, or improves the mechanical strength. In particular, when emphasis is placed on improving heat resistance and surface hardness, the styrene-unsaturated carboxylic acid resin (A) preferably contains a (meth)acrylic acid monomer unit (a1-1). In particular, when emphasis is placed on improving appearance and mechanical strength, the styrene-unsaturated carboxylic acid resin (A) preferably contains a (meth)acrylic acid ester monomer unit (a1-2). Furthermore, when emphasis is placed on improving compatibility with the (meth)acrylic resin (B) and on high transparency in a mixture with the resin (B), the styrene-unsaturated carboxylic acid resin (A) is preferably a ternary copolymer in which a styrene monomer (1), a (meth)acrylic acid monomer unit (a1-1), and a (meth)acrylic acid ester monomer unit (a1-2) are copolymerized. In addition, when an unsaturated carboxylic acid ester monomer unit such as a (meth)acrylic acid ester monomer unit (a1-2) is arranged adjacent to an unsaturated carboxylic acid monomer unit such as a (meth)acrylic acid unit (a1-1) in a polymer chain, an effect such as suppressing a crosslinking reaction between unsaturated carboxylic acids can be obtained. In the case where the styrene-unsaturated carboxylic acid resin (A) in this embodiment has a styrene monomer unit (1), a (meth)acrylic acid monomer unit (a1-1), and a (meth)acrylic acid ester monomer unit (a1-2), it is preferable that the content of the (meth)acrylic acid monomer unit (a1-1) is 2 to 30 mass% and the content of the (meth)acrylic acid ester monomer unit (a1-2) is 0 to 20 mass% relative to the total amount of the styrene-unsaturated carboxylic acid resin (A), and more preferably, the content of the (meth)acrylic acid monomer unit (a1-2) is 0 to 20 mass%. The content of (meth)acrylic acid ester monomer unit (a1-1) is 2 to 30 mass%, and the content of (meth)acrylic acid ester monomer unit (a1-2) is 1 to 20 mass%, more preferably, the content of (meth)acrylic acid ester monomer unit (a1-1) is 2 to 25 mass%, and the content of (meth)acrylic acid ester monomer unit (a1-2) is 1.5 to 15 mass%, and even more preferably, the content of (meth)acrylic acid ester monomer unit (a1-1) is 2 to 20 mass%, and the content of (meth)acrylic acid ester monomer unit (a1-2) is 2 to 13 mass%. By suppressing the content of (meth)acrylic acid ester monomer unit (a1-2) to 20 mass% or less, a composition having excellent fluidity during molding processing can be obtained.

[0032] <Other monomers (a2)> The styrene-unsaturated carboxylic acid resin (A) in this embodiment may further have other monomer units (a2) other than the above-mentioned styrene monomer units (1) and unsaturated carboxylic acid monomer units (a1) (including (meth)acrylic acid monomer units (a1-1) and / or (meth)acrylic acid ester monomer units (a1-2)). That is, in this embodiment, the other monomer unit (a2) may be copolymerized with a monomer other than the two monomers shown above, without any particular limitation, as long as it is copolymerizable with the styrene-based monomer (1) and the unsaturated carboxylic acid-based monomer unit (a1) (including the (meth)acrylic acid monomer unit (a1-1) and / or the (meth)acrylic acid ester monomer unit (a1-2)), within the scope not impairing the effects of the invention. For example, examples of the other monomers (a2) other than the three monomers shown above include maleic anhydride, maleic acid, fumaric acid, itaconic acid, (meth)acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleimide, and nucleus-substituted maleimide. In the present embodiment, when the styrene-unsaturated carboxylic acid resin (A) contains the other monomer (a2), the content of the other monomer (a2) relative to the total amount of the styrene-unsaturated carboxylic acid resin (A) is preferably 0 to 12 mass%, more preferably 0 to 5 mass%, and further preferably 2 mass% or less.

[0033] <Characteristics of styrene-unsaturated carboxylic acid resin (A)> In the styrene-unsaturated carboxylic acid resin (A) in this embodiment, the contents of the styrene-based monomer units (1), the unsaturated carboxylic acid-based monomer units (a1) (including the (meth)acrylic acid monomer units (a1-1) and the (meth)acrylic acid ester monomer units (a1-2)) and the other monomer units (a2) can be quantified using a calibration curve prepared by using a resin in which each monomer unit is known, using pyrolysis GC / MS. The melt flow rate of the styrene-unsaturated carboxylic acid resin (A) in this embodiment at 200°C may be preferably 0.3 to 3.0, more preferably 0.4 to 2.5, and even more preferably 0.4 to 2.0. When the melt flow rate is 0.3 or more, it is preferable from the viewpoint of fluidity, and when it is 3.0 or less, it is preferable from the viewpoint of mechanical strength of the resin. In the present disclosure, the melt flow rate is a value measured at 200°C under a load of 49N in accordance with ISO 1133.

[0034] The weight average molecular weight (Mw) of the styrene-unsaturated carboxylic acid resin (A) in this embodiment is preferably 100,000 to 400,000, more preferably 120,000 to 320,000. When the weight average molecular weight is 100,000 to 350,000, a resin having excellent practical balance between impact strength and fluidity can be obtained. The weight average molecular weight and number average molecular weight can be measured by gel permeation chromatography in terms of standard polystyrene. The number average molecular weight (Mn) of the styrene-unsaturated carboxylic acid resin (A) is preferably 40,000 to 150,000, more preferably 50,000 to 120,000.

[0035] The Vicat softening temperature of the styrene-unsaturated carboxylic acid resin (A) in this embodiment is preferably 105 to 140° C., more preferably 107 to 135° C., even more preferably 108 to 130° C., and even more preferably 115 to 125° C. By making the Vicat softening temperature of the styrene-unsaturated carboxylic acid resin (A) 105° C. or higher, the heat resistance of the composition can be improved, and by making it 140° C. or lower, it becomes easy to knead with the (meth)acrylic resin (B). The Vicat softening temperature in this specification is measured in accordance with ISO 306.

[0036] <Method for producing styrene-unsaturated carboxylic acid resin (A)> The method for producing the styrene-unsaturated carboxylic acid resin (A) of this embodiment will be described below. The method for producing the styrene-unsaturated carboxylic acid resin (A) of the present embodiment preferably includes a step of mixing a styrene monomer (1), an unsaturated carboxylic acid monomer (a1) ((meth)acrylic acid monomer unit (a1-1) and / or (meth)acrylic acid ester monomer unit (a1-2)), and a solvent to prepare a mixed solution, a polymerization step of polymerizing the mixed solution to produce a reaction product, and a step of recovering the reaction product. The polymerization method for the styrene-unsaturated carboxylic acid resin (A) is not particularly limited, but for example, a radical polymerization method, among which a bulk polymerization method or a solution polymerization method can be preferably used. Specifically, the polymerization method mainly comprises a polymerization step of polymerizing polymerization raw materials (monomer components) and a devolatilization step of removing volatile matters such as unreacted monomers and polymerization solvent from the polymerization product.

[0037] In this embodiment, when the polymerization raw materials are polymerized to obtain the styrene-unsaturated carboxylic acid resin (A), a polymerization initiator is typically contained in the polymerization raw material composition. Examples of the polymerization initiator include organic peroxides, such as 2,2-bis(t-butylperoxy)butane, Examples of the peroxyketals include 1,1-bis(t-butylperoxy)cyclohexane and n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide and dicumyl peroxide, diacyl peroxides such as acetyl peroxide and isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyesters such as t-butyl peroxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. Among them, 1,1-bis(t-butylperoxy)cyclohexane is preferred from the viewpoints of decomposition rate and polymerization rate.

[0038] In this embodiment, a chain transfer agent may be used as necessary during polymerization of the styrene-unsaturated carboxylic acid resin (A). Examples of the chain transfer agent include α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan.

[0039] As the polymerization method of the styrene-unsaturated carboxylic acid resin (A), solution polymerization using a polymerization solvent can be adopted. As the polymerization solvent, aromatic solvents such as toluene, ethylbenzene, propylbenzene, butylbenzene, etc. are preferable, and a solvent system in which the solubility of the styrene-unsaturated carboxylic acid resin (A) is adjusted by combining polar solvents such as alcohols or ketones as necessary may be used. In this embodiment, the polymerization solvent is preferably used in the range of 3 to 35 parts by mass, more preferably 5 to 30 parts by mass, relative to 100 parts by mass of the total monomers constituting the styrene-unsaturated carboxylic acid resin (A). If the polymerization solvent exceeds 35 parts by mass relative to 100 parts by mass of the total monomers, the polymerization rate decreases and the molecular weight of the resulting resin also decreases, so that the mechanical strength of the resin tends to decrease. In addition, if the polymerization solvent is less than 3 parts by mass, it may be difficult to control the heat removal during polymerization. It is preferable to add the polymerization solvent in a ratio of 3 to 35 parts by mass relative to 100 parts by mass of the total monomers, because this makes it easier to uniformize the quality and also in terms of controlling the polymerization temperature. Furthermore, when the monohydric alcohol (C) having 10 or more carbon atoms, which is an optional component of the styrene-based resin composition of this embodiment, is added from the polymerization system, it is preferable to add the (C) component in a proportion of 1 to 10 mass % relative to 100 mass % of the total polymerization solvent.

[0040] The apparatus used in the polymerization step for obtaining the styrene-unsaturated carboxylic acid resin (A) in this embodiment is not particularly limited, and may be appropriately selected according to a general polymerization method for styrene-based resins. For example, in the case of bulk polymerization, a polymerization apparatus having one or more completely mixed reactors connected thereto can be used. The devolatilization step is also not particularly limited, and in the case of bulk polymerization, polymerization is continued until the unreacted monomer is finally reduced to preferably 50% by mass or less, more preferably 40% by mass or less, and devolatilization treatment is performed by a known method in order to remove volatile matters such as the unreacted monomer. For example, a normal devolatilization apparatus such as a flash drum, a twin-screw devolatilizer, a thin film evaporator, or an extruder can be used, but a devolatilization apparatus with a small retention portion is preferred. The temperature of the devolatilization treatment is usually about 190 to 280° C., and more preferably 190 to 260° C. from the viewpoint of suppressing decomposition. The pressure of the devolatilization treatment is usually about 0.13 to 4.0 kPa, preferably 0.13 to 3.0 kPa, and more preferably 0.13 to 2.0 kPa. As a method for removing volatile matters, for example, a method of removing volatile matters under reduced pressure while heating, or a method of removing volatile matters through an extruder or the like designed for the purpose of removing volatile matters is preferable.

[0041] "(Meth)acrylic resin (B)" The styrene-based resin composition in this embodiment contains 2 to 50 mass % of (meth)acrylic resin (B) (also simply referred to as resin (B)) based on the total amount of the styrene-based resin composition. The (meth)acrylic resin (B) has an unsaturated carboxylic acid monomer unit (b1). By containing a predetermined amount of (meth)acrylic resin (B), It contributes to improving the transparency and mechanical strength of the entire composition. In this specification, the (meth)acrylic resin (B) is a general term for synthetic resins containing 51% by mass or more of unsaturated carboxylic acid monomer units (b1). In the present invention, the number average molecular weight (Mn), weight average molecular weight (Mw), and Z average molecular weight (Mz) of the (meth)acrylic resin (B), and the proportion of high molecular weight components having a molecular weight of 1,000,000 or more in the styrene resin composition are values ​​measured using gel permeation chromatography (GPC), as described in the Examples section below.

[0042] The content of the (meth)acrylic resin (B) relative to the total amount (100 mass%) of the styrene-based resin composition is 2 to 50 mass%, and the upper limit is preferably 48 mass%, 46 mass%, 44 mass%, 42 mass%, 40 mass%, 38 mass%, 36 mass%, 34 mass%, 32 mass%, 30 mass%, 28 mass%, 26 mass%, 24 mass%, 22 mass%, and 21 mass%, in that order, and the lower limit is preferably 3 mass%, 4 mass%, 5 mass%, 6 mass%, 7 mass%, 8 mass%, 9 mass%, 10 mass%, 11 mass%, 12 mass%, 13 mass%, 14 mass%, 15 mass%, 16 mass%, 17 mass%, 18 mass%, and 19 mass%, in that order. In particular, by adjusting the content of the (meth)acrylic resin (B) to 10% by mass or more and 40% by mass or less, it is possible to prevent the deterioration of the heat resistance improved by the styrene-unsaturated carboxylic acid resin (A) from decreasing. The unsaturated carboxylic acid monomer unit (b1) constituting the (meth)acrylic resin (B) of this embodiment is preferably at least one repeating unit selected from the group consisting of (meth)acrylic acid monomer units (b1-1) and (meth)acrylic acid ester monomer units (b1-2), and more preferably two or more repeating units selected from the group consisting of (meth)acrylic acid ester monomer units (b1-2).

[0043] -(Meth)acrylic acid monomer (b1-1)- In this embodiment, the (meth)acrylic acid monomer (b1-1) may be acrylic acid or methacrylic acid.

[0044] -(Meth)acrylic acid ester monomer (b1-2)- The (meth)acrylic acid ester monomer unit (b1) constituting the (meth)acrylic resin (B) of this embodiment includes a methacrylic acid ester monomer unit and an acrylic acid ester monomer unit. In addition, the (meth)acrylic acid ester monomer (b1) includes methyl acrylate, ethyl acrylate, (n-butyl) acrylate, (2-ethylhexyl) acrylate, (n-octyl) acrylate, benzyl acrylate, methyl methacrylate, butyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, (2-ethylhexyl) methacrylate, (n-octyl) methacrylate, benzyl methacrylate, etc., and methyl acrylate, (n-butyl) acrylate, and methyl methacrylate are preferred from the viewpoint of industrial availability and low cost. The (meth)acrylic acid ester monomers (b1-2) can be used alone or in combination, and it is preferable to use two kinds of (meth)acrylic acid ester monomers in combination. As a combination of monomer units constituting the (meth)acrylic resin (B) of the present embodiment, from the viewpoint of achieving both heat resistance and thermal decomposition property, among the monomer units listed above, a copolymer of a methacrylic acid ester species and an acrylic acid ester species is preferable, and a methyl methacrylate-methyl acrylate copolymer is more preferable. In this embodiment, the upper limit of the content of the (meth)acrylic acid ester monomer unit (b1-2) relative to the total amount of the (meth)acrylic resin (B) is preferably 100% by mass or less, 99% by mass or less, 99.5% by mass or less, 98% by mass or less, 80% by mass or less, 74% by mass or less, 64% by mass or less, and 54% by mass or less in that order. The lower limit of the content is preferably 0% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, and 40% by mass or more in that order. (Meth)acrylic acid ester The content of the (meth)acrylic acid ester monomer unit (b1-2) can be any combination of the above upper limit and lower limit. The content of the (meth)acrylic acid ester monomer unit (b1-2) is, for example, preferably 0 to 100 mass%, more preferably 2 to 99 mass%, even more preferably 2 to 98 mass%, still more preferably 4 to 98 mass%, even more preferably 5 to 98 mass%, and particularly preferably 6 to 98 mass%.

[0045] <Preferable form of (meth)acrylic resin (B)> A preferred (meth)acrylic resin (B) of this embodiment is preferably a binary or ternary copolymer, and is a methacrylic acid ester-acrylic acid ester copolymer obtained by copolymerizing a methacrylic acid ester species (methacrylic acid ester monomer unit) and an acrylic acid ester species (acrylic acid ester monomer unit). The upper limit of the content of the acrylic acid ester species relative to the total amount of the methacrylic acid ester-acrylic acid ester copolymer is preferably 20% by mass or less, 18% by mass or less, 16% by mass or less, 14% by mass or less, 12% by mass or less, 10% by mass or less, 8% by mass or less, 6% by mass or less, 4% by mass or less, 3% by mass or less, and 2.5% by mass or less, in that order, and the lower limit is preferably 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 0.9% by mass or more, 1.1% by mass or more, 1.3% by mass or more, 1.5% by mass or more, and 1.7% by mass or more. The content of the acrylic ester species relative to the total amount of the methacrylic acid ester-acrylic acid ester copolymer can be any combination of the upper limit and the lower limit. In particular, by setting the content of the acrylic ester species in the range of 0.5 mass% or more and 8 mass% or less, a styrene-based resin composition having the best balance between heat resistance and oil resistance can be obtained. In addition, the (meth)acrylic resin (B) of this embodiment is preferably a methyl methacrylate-methyl acrylate copolymer, and is a copolymer containing 0.1 to 15 mass% of methyl acrylate relative to the total amount of the copolymer. More preferably, it is in the range of 0.2 to 13 mass%, even more preferably 0.3 to 11 mass%, even more preferably 0.4 to 9 mass%, and most preferably 0.5 to 7 mass%. This makes it possible to more effectively suppress the decrease in heat resistance improved by the styrene-unsaturated carboxylic acid resin (A).

[0046] In the (meth)acrylic resin (B) of this embodiment, the content of the (meth)acrylic acid ester monomer unit (b1-2) in the (meth)acrylic resin (B) is preferably 60.0 to 100 mass% based on the total amount of the (meth)acrylic resin (B), more preferably 60.0 to 99.5 mass%, even more preferably 70.0 to 98.5 mass%, and even more preferably 85 to 98.0 mass%. By setting the content of the methacrylic acid ester monomer (b1-2) in the range of 60.0 to 100 mass%, it becomes possible to withstand kneading extrusion and molding with other resins at 300°C or less. Therefore, it is possible to suppress a significant decrease in heat resistance when the styrene-unsaturated carboxylic acid resin (A) and the (meth)acrylic resin (B) are mixed. As the type of (meth)acrylic acid ester monomer (b1-2), methyl acrylate or methyl methacrylate is preferable because of its heat resistance, industrial availability, and low cost.

[0047] <Other monomers (b2)> The (meth)acrylic resin (B) of this embodiment may further have other monomer units (b2) other than the above-mentioned (meth)acrylic acid monomer (b1-1) and (meth)acrylic acid ester monomer units (b1-2). That is, the other monomer units (b2) may be copolymerized with the unsaturated carboxylic acid monomer units (b1) (including the (meth)acrylic acid monomer (b1-1) and / or the (meth)acrylic acid ester monomer (b1-2)) without any particular limitation, as long as the effect of the invention is not impaired. For example, examples of the monomer (b2) other than the above-mentioned monomers include styrene, maleic anhydride, maleic acid, fumaric acid, itaconic acid, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleimide, and nucleus-substituted maleimide. etc. In this embodiment, the content of the other monomer unit (b2) is preferably 0 to 30 mass%, more preferably 0 to 20 mass%, and further preferably 0 to 15 mass%, based on the total amount of the (meth)acrylic resin (B).

[0048] The weight average molecular weight (Mw) of the (meth)acrylic resin (B) is preferably 50,000 to 1,000,000, more preferably 60,000 to 900,000, even more preferably 70,000 to 300,000, and even more preferably 80,000 to 200,000. By making the weight average molecular weight (Mw) of the (meth)acrylic resin (B) 50,000 or more, strength can be imparted when kneaded with the styrene-unsaturated carboxylic acid resin (A), and by making it 1,000,000 or less, the viscosity difference with the styrene-unsaturated carboxylic acid resin (A) can be suppressed, the (meth)acrylic resin (B) can be well dispersed in the styrene resin composition, and the generation of unmelted matter derived from the (meth)acrylic resin (B) can be suppressed, and an extruded sheet with good appearance can be obtained using the composition.

[0049] The (meth)acrylic resin (B) of this embodiment may contain a high molecular weight component of 1 million or more. When the (meth)acrylic resin (B) contains a high molecular weight component of 1 million or more, the decrease in heat resistance and rigidity is further suppressed, and the heat oil resistance is further improved. In addition, the high molecular weight component of 1 million or more has an unsaturated carboxylic acid monomer (b1), and the proportion of the (meth)acrylic resin (B) of the high molecular weight component of 1 million or more among the (meth)acrylic resin (B) contained in the styrene-based resin composition is preferably 1.0 mass% or less with respect to the total amount of the styrene-based resin composition. In addition, as a method for controlling the content of high molecular weight components of 1 million or more in the (meth)acrylic resin (B) to 1.0 mass % or less, when radically polymerizing the unsaturated carboxylic acid monomer (b1), control can be performed by adjusting the type and amount of the unsaturated carboxylic acid monomer (b1), the type and amount of the chain transfer agent, the reaction temperature, the residence time, the type and amount of the polymerization initiator, the type and amount of the polymerization solvent, etc. As described above, the (meth)acrylic resin (B) of the present embodiment contains a high molecular weight component having a molecular weight of 1,000,000 or more in an amount of 0.0 mass % or more and 1.0 mass % or less based on the total amount of the styrene-based resin composition, and the weight average molecular weight (Mw) of the (meth)acrylic resin (B) as a whole is more preferably 70,000 to 300,000.

[0050] <(Meth)acrylic acid monomer or (meth)acrylic acid ester monomer in styrene-based resin composition> In this embodiment, the content of all (meth)acrylic acid monomer units contained in the styrene-based resin composition is preferably 0 to 20 mass%, more preferably 3 to 15 mass%, and more preferably 6 to 10 mass%, based on the total amount (100 mass%) of the styrene-based resin composition. When the content of (meth)acrylic acid monomers in the entire composition is within the above range, a sufficient effect of improving heat resistance can be obtained. The total (meth)acrylic acid monomer content indicates the total amount of (meth)acrylic acid monomer units present in the styrene-based resin composition, and therefore each content of (meth)acrylic acid monomer units in resin (A), resin (B) and resin (D) is also converted.

[0051] In this embodiment, the content of all (meth)acrylic acid ester monomer units contained in the styrene-based resin composition is preferably in the order of upper limit of 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 28% by mass or less, 27% by mass or less, 26% by mass or less, 25% by mass or less, and 24% by mass or less, relative to the total amount (100% by mass) of the styrene-based resin composition, and lower limit of 6.0% by mass or more, 8.0% by mass or more, 10.0% by mass or more, 12.0% by mass or more, 12.5% ​​by mass or more, 13.0% by mass or more, 13.5% by mass or more, 14.0% by mass or more, 14.5% by mass or more, 15.0% by mass or more, 15.5% by mass or more, 16.0% by mass or more, 16.5% by mass or more, 17.0% by mass or more, % by mass or more, and 17.5% by mass or more are preferred in that order. The content of the (meth)acrylic acid ester monomer unit can be any combination of the above upper limit and the above lower limit with respect to the total amount (100% by mass) of the styrene-based resin composition. When the content of the (meth)acrylic acid ester monomer in the entire composition is within the above range, the effect of improving heat resistance, oil resistance, and strength can be sufficiently obtained. In particular, by controlling the content range of the (meth)acrylic acid ester monomer unit to 13.5% by mass or more and 35% by mass or less, a styrene-based resin composition with the best balance between heat resistance and oil resistance can be obtained. The total (meth)acrylic acid ester monomer content indicates the total amount of (meth)acrylic acid ester monomer units present in the styrene-based resin composition, and therefore each content of (meth)acrylic acid ester monomer units in resin (A), resin (B) and resin (D) is also converted.

[0052] In a particularly preferred embodiment of the present invention, all (meth)acrylic acid ester monomer units contained in the styrene-based resin composition contain methyl acrylate, and the content thereof is, relative to the total amount (100 mass%) of the styrene-based resin composition, preferably in the following order: upper limit of 10.0 mass% or less, 8.0 mass% or less, 7 mass% or less, 6.0 mass% or less, 5.0 mass% or less, 4.0 mass% or less, 3.0 mass% or less, 2.5 mass% or less, 2.0 mass% or less, 1.5 mass% or less, and lower limit of 0.01 mass% or more, 0.05 mass% or more, 0.10 mass% or more, 0.15 mass% or more, 0.20 mass% or more, 0.25 mass% or more, 0.30 mass% or more, 0.35 mass% or more, 0.40 mass% or more, 0.45 mass% or more, 0.50 mass% or more. The content of the methyl acrylate monomer unit can be any combination of the upper limit and the lower limit with respect to the total amount (100 mass%) of the styrene-based resin composition. In particular, by setting the content range of the methyl acrylate monomer unit to 0.05 mass% or more and 0.45 mass% or less, a styrene-based resin composition having an excellent balance between heat resistance and mechanical strength and an excellent appearance can be obtained.

[0053] By controlling the content of all (meth)acrylic acid monomer units and all (meth)acrylic acid ester monomer units contained in the styrene-based resin composition within the above range, the effect of improving heat resistance due to the (meth)acrylic acid monomer units and the effect of improving oil resistance due to the (meth)acrylic acid ester monomer units can be obtained simultaneously and efficiently, and as a result, a styrene-based resin composition having excellent heat and oil resistance and a sheet molded therefrom can be obtained.

[0054] <Method for producing (meth)acrylic resin (B)> The method for producing the (meth)acrylic resin (B) of the present embodiment is not particularly limited, and the (meth)acrylic resin (B) can be produced by a process such as bulk polymerization in which a (meth)acrylic acid ester monomer and, as necessary, other monomers are polymerized, solution polymerization in which a solvent is added, or suspension polymerization in which an organic layer is dispersed in water using a suspending agent.

[0055] "Monohydric alcohol (C) with 10 or more carbon atoms" In the present embodiment, the monohydric alcohol (C) having 10 or more carbon atoms (hereinafter also simply referred to as alcohol (C)) is an optional component, which suppresses gelation of the styrene-unsaturated carboxylic acid-based resin (A) during molding, and contributes to improving the appearance of the styrene-based resin composition having a good appearance and the molded article made of the styrene-based resin composition. The content of the monohydric alcohol (C) having 10 or more carbon atoms is 0.01 to 1.0 part by mass, preferably 0.03 to 0.8 parts by mass, more preferably 0.05 to 0.6 parts by mass, and even more preferably 0.07 to 0.5 parts by mass, relative to the total amount (100 parts by mass) of the styrene-based resin composition. By making the content of the monohydric alcohol (C) having 10 or more carbon atoms 0.01 part by mass or more, gelation of the styrene-unsaturated carboxylic acid-based resin (A) during molding processing can be suppressed, and by making it 1.0 part by mass or less, deterioration of heat resistance and generation of odor can be suppressed. By controlling the content of the monohydric alcohol (C) having 10 or more carbon atoms to 0.07 to 0.5 parts by mass, the heat resistance in particular is reduced. Therefore, sufficient gel suppression effect can be obtained.

[0056] The monohydric alcohol (C) having 10 or more carbon atoms is an alcohol having 10 or more carbon atoms and containing one hydroxyl group, and may contain a heteroatom such as oxygen or nitrogen in the carbon chain constituting the alcohol (C), and may contain a bond other than a single bond, such as a double bond, a triple bond, an ester bond, or an amide bond in the carbon chain. The number of carbon atoms is preferably 16 or more, more preferably 17 or more, and even more preferably 18 to 50. The monohydric alcohol (C) having 10 or more carbon atoms may be contained in a styrene-based resin composition or a molded article made of a styrene-based resin composition. Therefore, the monohydric alcohol (C) having 10 or more carbon atoms may be present (or added) in a polymerization solution used for polymerizing the styrene-unsaturated carboxylic acid-based resin (A) or the (meth)acrylic resin (B), so that the monohydric alcohol (C) remains in the resin composition, which is the final product, or may be added when the styrene-unsaturated carboxylic acid-based resin (A) and the (meth)acrylic resin (B) are kneaded and mixed in an extruder to contain the monohydric alcohol (C).

[0057] In this embodiment, the boiling point of the monohydric alcohol (C) having 10 or more carbon atoms is preferably 260° C. or higher, more preferably 270° C. or higher, and even more preferably 290° C. or higher. If the boiling point of the alcohol is lower than 260° C., it becomes highly volatile and tends to generate an unpleasant odor during molding, etc.

[0058] The monohydric alcohol (C) having 10 or more carbon atoms is not particularly limited, but examples thereof include 1-hexadecanol, isohexadecanol, 1-octadecanol, 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)-1-octanol, isooctadecanol, 1-isoisoeicosanol, 8-methyl-2-(4-methylhexyl)-1-decanol, 2-heptyl-1-undecanol, 2-heptyl-4-methyl-1-decanol, 2-(1,5-dimethylhexyl)-(5,9-dimethyl)-1-decanol, and polyoxyethylene alkyl ethers.

[0059] The polyoxyethylene alkyl ether is preferably a compound represented by the following general formula (2). [ka] (In the above general formula (2), R is an alkyl group having 12 to 20 carbon atoms, and X represents the average number of ethylene oxides added and is an integer of 1 to 15.)

[0060] Specific product names of preferred alcohols (C) include "Fine Oxocol 180" manufactured by Nissan Chemical Industries, Ltd. and "Emulgen 109P" manufactured by Kao Corporation.

[0061] <Rubber-modified styrene-based resin (D)> In a preferred embodiment of the present invention, the styrene resin composition preferably contains a rubber-modified styrene resin (D) (also simply referred to as resin (D)). By containing an appropriate amount of the rubber-modified styrene resin (D) in the styrene resin composition, a styrene resin composition having excellent strength and a molded article obtained by molding the composition can be obtained. The rubber-modified styrene-based resin (D) of this embodiment can be obtained by dispersing rubber-like polymer particles (=rubber-like polymer particles) in a polymer matrix of a resin consisting of a styrene-based monomer (2) and, if necessary, other monomers (d1), and polymerizing the styrene-based monomer (2) in the presence of the rubber-like polymer.

[0062] The content of the rubber-modified styrene-based resin (D) in the styrene-based composition of the present embodiment is preferably 0.1 to 15 mass%, more preferably 0.6 to 10 mass%, and even more preferably 0.7 to 8 mass%, based on the total amount of the styrene-based resin composition. By setting the content of the rubber-modified styrene-based resin (D) in the range of 0.1 to 15 mass%, a composition excellent in transparency and strength can be obtained. In addition, since the styrene-based monomer (2) in this embodiment is similar to the above-mentioned styrene-based monomer (1), the contents of the description thereof are incorporated herein by reference.

[0063] -Rubber-like polymer particles- In this embodiment, the rubber-like polymer constituting the rubber-like polymer particles in the rubber-modified styrene-based resin (D) may be polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, etc., but from an industrial viewpoint, polybutadiene and styrene-butadiene copolymer are preferred. As the polybutadiene, high-cis polybutadiene having a high cis content, low-cis polybutadiene having a low cis content, or both of these may be used, but low-cis polybutadiene is preferred from the viewpoint of industrial ease of handling. The structure of the styrene-butadiene copolymer may be a random structure, a block structure, or a combination of these. These rubber-like polymers may be used alone or in combination of two or more. Saturated rubber obtained by hydrogenating butadiene rubber may also be used. The rubbery polymer particles in this embodiment preferably contain styrene-based monomer units (2) or a polymer containing the styrene-based monomer units (2) in dispersed particles of the rubbery polymer (rubber-like polymer particles). The form of the inclusion may be a core-shell type dispersed particle having a polymer containing the styrene-based monomer units (2) as a core and a rubbery polymer as a shell, or a so-called salami structure type dispersed particle in which a rubbery polymer contains a plurality of domain phases of a polymer containing the styrene-based monomer units (2). -Other monomers (d1)- Examples of the other monomer (unit) (d1), which is an optional component of the rubber-modified styrene-based resin (D) of this embodiment, include (meth)acrylic acid ester monomers such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isopropyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, and isopropyl methacrylate. Of these, n-butyl acrylate and methyl methacrylate are preferred from the viewpoint of industrial availability. In this embodiment, the content of the other monomer (unit) (d1) in the rubber-modified styrene-based resin (D) is preferably 0 to 50 mass %, more preferably 0 to 20 mass %, based on the total amount of the rubber-modified styrene-based resin (D).

[0064] <Conjugated diene monomer unit content> In this embodiment, the rubber-like polymer particles are preferably formed from a conjugated diene monomer. In this specification, the conjugated diene monomer unit refers to a diolefin having a pair of conjugated double bonds among the monomer units constituting the rubber-like polymer particles, and examples thereof include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. The content of the conjugated diene monomer unit in the rubber-modified styrene-based resin (E) and the styrene-based resin composition can be measured by the procedure described in the Examples section below or a method equivalent thereto.

[0065] In this embodiment, the content of the conjugated diene monomer unit in the rubber-modified styrene-based resin (D) is preferably 0.5 to 15.0 mass%, more preferably 1.0 to 13.0 mass%, and even more preferably 2.0 to 12.0 mass%, based on the total amount of the rubber-modified styrene-based resin (D).

[0066] <Average particle size of rubber polymer particles> The rubber-like polymer, which is the rubber component in the rubber-modified styrene-based resin (D) in this embodiment, exists as rubber-like polymer particles in the styrene-based resin composition. In this case, the average particle size of the rubber-like polymer particles is preferably 0.3 to 5.0 μm, more preferably 0.5 to 4.0 μm, and even more preferably 0.7 to 3.0 μm. The rubber-modified styrene-based resin (D) is obtained by polymerizing the styrene-based monomer (3) in a reactor equipped with a stirrer in the presence of the rubber-like polymer particles, and the average particle size of the rubber-like polymer particles can be adjusted by the number of revolutions of the stirrer, the molecular weight of the rubber-like polymer used, and the like. In the present disclosure, the average particle size of the rubber-like polymer particles is a value measured from a cross-sectional observation image by a transmission electron microscope. The above-mentioned rubber-like polymer particles are stretched by the stretching ratio in the biaxially stretched sheet described later, and the particle size increases by about 400% at the maximum.

[0067] In this embodiment, the melt flow rate of the rubber-modified styrene-based resin (D) at 200°C is preferably 1.0 to 10.0 g / 10 min, more preferably 2.0 to 8.0 g / 10 min, and even more preferably 2.5 to 7.0 g / 10 min. If the melt flow rate is in the range of 1.0 to 10.0 g / 10 min, the mixture with the styrene-unsaturated carboxylic acid-based resin (A) and the styrene-unsaturated nitrile-based resin (B) is good, and the mechanical strength is also good. In the present disclosure, the melt flow rate is a value measured at 200°C and a load of 49 N in accordance with ISO 1133.

[0068] <Production method of rubber modified styrene resin (D)> The method for producing the rubber-modified styrene-based resin (D) is not particularly limited, but it can be produced by bulk polymerization (or solution polymerization) in which a styrene-based monomer (2) and, if necessary, other monomers (d1) and a solvent are polymerized in the presence of a rubber-like polymer, bulk-suspension polymerization that transitions to suspension polymerization during the reaction, or emulsion graft polymerization in which a styrene-based monomer (3) is polymerized in the presence of latex particles that are a rubber-like polymer. In bulk polymerization, the rubber-like polymer can be produced by continuously supplying a mixed solution containing a rubber-like polymer, a styrene-based monomer, and, if necessary, other monomers, an organic solvent, an organic peroxide, and / or a chain transfer agent to a polymerization apparatus configured by connecting a complete mixing reactor or a tank reactor in series with a plurality of tank reactors.

[0069] "Optional addition ingredients" In addition to the above components, the styrene-based resin composition of the present embodiment may be made into a styrene-based resin composition by adding optional components such as various additives generally used in styrene-based resins in order to achieve known effects. Examples of the optional components include stabilizers, higher fatty acid surfactants, antioxidants, ultraviolet absorbers, lubricants, release agents, plasticizers, antiblocking agents, antistatic agents, antifogging agents, and mineral oils. In addition, elastomers such as styrene-maleic anhydride copolymers, methyl methacrylate-butyl acrylate block copolymers, methyl methacrylate-(2-ethylhexyl) acrylate block copolymers, and styrene-butadiene block copolymers, and reinforcing materials such as MBS resins may also be added to the extent that the physical properties are not impaired. There are no particular restrictions on the method of blending, but examples include a method of adding the additives during polymerization and polymerizing them, or a method of mixing the additives in advance in a blender before melt-kneading after polymerization, and then melt-kneading them in an extruder or Banbury mixer.

[0070] In this embodiment, as described above, optional additive components can be added to the styrene-based resin composition. The total content of the styrene-unsaturated carboxylic acid-based resin (A) and the rubber-modified styrene-based resin (D) in the styrene-based resin composition is, although not particularly limited, preferably 95% by mass or more, more preferably 97% by mass, and even more preferably 99% by mass. That's all. As a preferred aspect of this embodiment, the styrene resin composition preferably contains a higher fatty acid surfactant. The addition of a higher fatty acid surfactant not only prevents blocking of the sheet, but also contributes to reducing the torque between pellets when kneading the resin composition by adding an appropriate amount. Therefore, the content of the higher fatty acid surfactant is preferably in the range of 0.002 to 0.1 parts by mass relative to the total amount of the styrene resin composition. The above effect can be obtained, and by making the content 0.1 parts by mass or less, it is possible to prevent the surfactant from contributing as a gelling agent for the styrene-unsaturated carboxylic acid resin (A). The higher fatty acid surfactant may be added during polymerization of each resin, or may be additionally kneaded when the styrene-unsaturated carboxylic acid resin (A) and the (meth)acrylic resin (B) are kneaded together.

[0071] The higher fatty acid surfactant is not particularly limited, but examples thereof include stearic acid, calcium stearate, calcium stearate, and ethylene bisstearamide, with ethylene bisstearamide being preferred.

[0072] [Physical properties of styrene-based resin composition] The physical properties of the styrene-based resin composition in this embodiment will be described below. <Vicat softening temperature> In this embodiment, the Vicat softening temperature of the styrene-based resin composition is preferably 105° C. or higher, more preferably 110° C. or higher, and even more preferably 115° C. or higher. By setting the Vicat softening temperature at 105° C. or higher, a sheet or container that can be used for cooking in a general microwave oven of about 500 W can be obtained, and by setting the Vicat softening temperature at 115° C. or higher, the sheet or container can withstand cooking in a high-power commercial microwave oven of 1000 W or higher that is installed in a convenience store or the like. The Vicat softening temperature can be measured in accordance with ISO306 under conditions of a load of 50 N and a heating rate of 50° C. / h.

[0073] <Melt mass flow rate> In this embodiment, the melt flow rate of the styrene-based resin composition at 200° C. is preferably in the range of 0.1 to 2.0 g / 10 min, more preferably 0.2 to 1.5 g / 10 min, and even more preferably 0.3 to 1.0 g / 10 min. By making the melt flow rate 0.2 g / 10 min or more, good moldability can be obtained, and by making it 2.0 g / 10 min or less, a resin with excellent strength can be obtained.

[0074] <Conjugated diene monomer unit content> In the present embodiment, the content of the conjugated diene monomer unit derived from the rubber-modified styrene-based resin (E) contained in the styrene-based resin composition is preferably 0.03 to 0.50 mass%, more preferably 0.06 to 0.40 mass%, and even more preferably 0.09 to 0.30 mass%, based on the entire styrene-based resin composition. By setting the content of the conjugated diene monomer unit in the range of 0.03 to 0.50 mass%, a composition having an excellent balance between transparency and strength can be obtained.

[0075] "Amount of styrene component and amount of unsaturated carboxylic acid component in styrene-based resin composition" The styrene-based resin composition in this embodiment contains a styrene component and an unsaturated carboxylic acid-based component. The styrene component referred to here is a general term for styrene-based monomers (units) that may be contained as the styrene-based monomer (unit) (1) and the styrene-based monomer (unit) (2). On the other hand, the unsaturated carboxylic acid-based component is a general term for the unsaturated carboxylic acid-based monomer (unit) (a1) and the unsaturated carboxylic acid-based monomer (unit) (b2), in other words, the (meth)acrylic acid monomer (unit) (a1-1), the (meth)acrylic acid ester monomer (unit) (a1-2), the (meth)acrylic acid monomer (unit) (b1-1), and the (meth)acrylic acid monomer (unit) (b1-2). This refers to the general term for (b1-2). In the styrene resin composition of the present embodiment, the content of the styrene component is preferably 50 to 85 mass%, more preferably 55 to 83 mass%, and further preferably 58 to 80 mass%, based on the total amount (100 mass%) of the styrene resin composition. If the content is in the range of 50 to 85, a styrene resin composition having an excellent balance between moldability and heat oil resistance can be obtained. In the styrene resin composition of the present embodiment, the content of the unsaturated carboxylic acid component is preferably 17 to 50% by mass, more preferably 20 to 48% by mass, and even more preferably 25 to 45% by mass, based on the total amount (100% by mass) of the styrene resin composition. When the content of the unsaturated carboxylic acid component is in the range of 17 to 50% by mass, a styrene resin composition having an excellent balance of heat resistance, oil resistance, and strength can be obtained. In particular, by making it 25% by mass or more, resistance to oil exceeding 90°C can be obtained.

[0076] "High molecular weight components of over 1 million" The styrene-based resin composition of this embodiment has the resin (A) and the resin (B), and may contain one or more selected from the group consisting of a rubber-modified styrene-based resin (D), an alcohol (C) having 10 or more carbon atoms, and an optional additive component, which are blended as necessary. The styrene-based resin composition of this embodiment essentially contains the resin (A) and the resin (B), and has a matrix polymer portion soluble in an organic solvent that contains the optional component, a polymer matrix of the rubber-modified styrene-based resin (D), an alcohol (C) having 10 or more carbon atoms, and an optional additive component. In other words, the styrene-based resin composition of this embodiment contains a matrix polymer portion. The matrix polymer portion essentially contains the resin (A) and the resin (B), and optionally contains one or more selected from the group consisting of a polymer matrix of the rubber-modified styrene-based resin (D), an alcohol (C) having 10 or more carbon atoms, and an optional additive component. In the matrix polymer portion of this embodiment, when the matrix polymer portion is divided into a high molecular weight component of 1 million or more and a molecular weight component of less than 1 million, the high molecular weight component of 1 million or more is preferably 1.0 mass% or less, 0.9 mass% or less, 0.8 mass% or less, 0.7 mass% or less, 0.6 mass% or less, 0.5 mass% or less, 0.4 mass% or less, 0.3 mass% or less, or 0.2 mass% or less, based on the total amount of the matrix polymer portion soluble in an organic solvent. The content of the high molecular weight component of 1 million or more can be arbitrarily combined with the above upper and lower limits. Therefore, the amount of the high molecular weight component of 1 million or more (=the matrix polymer portion) in the entire styrene-based resin composition of this embodiment is preferably 1 mass % or less based on the total amount of the styrene-based resin composition. By making the amount of the high molecular weight component of 1 million or more 1.0 mass % or less, the occurrence of unmelted defects is reduced, and a composition having an excellent balance of thin-wall moldability, strength, and appearance can be obtained. In addition, the occupancy rate of the resin (B) in the high molecular weight component of 1 million or more in the styrene-based resin composition is preferably 40 to 100 mass %. It is preferable that the high molecular weight component of 1 million or more contained in the styrene-based resin composition is substantially derived from the (meth)acrylic resin (B). As will be described later in the Examples section, the high molecular weight component of 100 or more refers to the weight percentage of molecular weights of 1 million or more calculated from slice data of differential molecular weight distribution in terms of standard polystyrene measured with a differential refractometer (RI detector) before calculating various average molecular weights determined by gel permeation chromatography (GPC).

[0077] "The difference in Z-average molecular weight determined by the RI detector and the UV detector (Mz(RI)-Mz(UV))" In this embodiment, the Z-average molecular weight of the entire styrene-based resin composition of this embodiment (=matrix polymer portion) is measured using a gel permeation chromatography (GPC) equipped with a differential refractometer (RI detector), and the value is Mz (RI ), and assuming that the Z-average molecular weight of the entire styrene-based resin composition of this embodiment (=matrix polymer portion) is measured by a gel permeation chromatography (GPC) equipped with an ultraviolet absorption detector (UV detector) and that the value is Mz(UV) using the ultraviolet absorption detector (UV detector), it is preferable that the value of Mz(RI)-Mz(UV) is 500,000 or less. This optimizes the molecular weight difference between resin (A) and resin (B), and makes it possible to obtain a styrene-based resin composition that is excellent in processability and does not generate unmelted material when melted. The difference "Mz(RI)-Mz(UV)" between the measured value of the differential refractometer (RI detector) and the measured value of the ultraviolet spectrometer (UV detector) of the Z-average molecular weight obtained by gel permeation chromatography (GPC) of the matrix polymer portion of this embodiment is a value reflecting the Z-average molecular weight difference between the resin (A) and the resin (B), and is preferably 500,000 or less from the viewpoint of processability when melted, and more preferably 450,000 or less, 400,000 or less, 350,000 or less, 300,000 or less, 250,000 or less, 200,000 or less, 150,000 or less, 130,000 or less, 110,000 or less, 90,000 or less, 70,000 or less, 50,000 or less, 30,000 or less, and 10,000 or less in that order. In particular, by making it 250,000 or less, the molecular weight difference between the resin (A) and the resin (B) is optimal, and a styrene-based resin composition having excellent processability and no generation of unmelted matter when melted can be obtained.

[0078] "The quotient of the Z-average molecular weight determined by the RI detector and the UV detector (Mz(RI) / Mz(UV))" The quotient "Mz(RI) / Mz(UV)" of the Z-average molecular weight of the matrix polymer portion of this embodiment obtained by gel permeation chromatography (GPC) measured by a differential refractometer (RI detector) and measured by an ultraviolet spectrometer (UV detector) is a value reflecting the Z-average molecular weight ratio of resin (A) and resin (B), and is preferably 6 or less from the viewpoint of processability when melted, and more preferably 5 or less, 4.5 or less, 40,000 or less, 3.8 or less, 3.6 or less, 3.4 or less, 3.2 or less, 3.0 or less, 2.8 or less, 2.6 or less, 2.4 or less, 2.2 or less, 2.0 or less, 1.8 or less, 1.6 or less, 1.4 or less, and 1.2 or less in that order. In particular, by making it 2.0 or less, the molecular weight ratio of resin (A) and resin (B) becomes optimal, and a styrene-based resin composition having excellent processability and no generation of unmelted matter when melted can be obtained.

[0079] In the styrene-based resin composition of the present embodiment, the total content of the styrene-unsaturated carboxylic acid-based resin (A) and the (meth)acrylic resin (B) is preferably 60 to 100 mass%, more preferably 65 to 90 mass%, and even more preferably 70 to 85 mass%, based on the entire styrene-based resin composition. In the styrene-based resin composition of the present embodiment, the total content of the styrene-based resin-unsaturated carboxylic acid-based resin (A), the (meth)acrylic resin (B), and the alcohol (C) having 10 or more carbon atoms preferably accounts for 60 to 100 mass%, more preferably 65 to 90 mass%, and even more preferably 70 to 85 mass%, based on the entire styrene-based resin composition. In the styrene-based resin composition of the present embodiment, the total content of the styrene-based resin-unsaturated carboxylic acid-based resin (A), the (meth)acrylic resin (B), the alcohol having 10 or more carbon atoms (C), and the rubber-modified styrene-based resin (D) preferably accounts for 60 to 100 mass%, and more preferably 70 to 90 mass%, of the entire styrene-based resin composition. In the styrene-based resin composition of the present embodiment, the total content of the styrene-based resin-unsaturated carboxylic acid-based resin (A), the (meth)acrylic resin (B), the rubber-modified styrene-based resin (D), and any optional added components is preferably 60 to 100 mass%, more preferably 65 to 90 mass%, and even more preferably 70 to 85 mass%, based on the entire styrene-based resin composition. In the styrene-based resin composition of the present embodiment, the total content of the styrene-based resin-unsaturated carboxylic acid-based resin (A), the (meth)acrylic resin (B), the alcohol having 10 or more carbon atoms (C), and any optional added components may preferably be 60 to 100 mass%, more preferably 65 to 90 mass%, and even more preferably 70 to 85 mass%, based on the entire styrene-based resin composition. In the styrene-based resin composition of the present embodiment, the total content of the styrene-based resin-unsaturated carboxylic acid-based resin (A), the (meth)acrylic resin (B), the alcohol having 10 or more carbon atoms (C), the rubber-modified styrene-based resin (D), and any optional additional components preferably accounts for 60 to 100 mass%, more preferably 65 to 90 mass%, and even more preferably 70 to 85 mass%, of the entire styrene-based resin composition.

[0080] "2mm Plate Haze" In this embodiment, the haze (cloudiness) of a 2 mm plate, which is a test piece formed from the styrene-based resin composition, is preferably 20% or less, more preferably 15%, even more preferably 10% or less, and most preferably 8% or less. By making it 10% or less in particular, a molded product with very excellent transparency can be obtained when molded into a sheet or container. In this embodiment, as described in the Examples below, the 2 mm plate is produced by injection molding a styrene-based resin composition into a 2 mm plate under the following conditions. Molding machine: Toshiba Machine EC60N Cylinder temperature: 220-240-220-200℃ Measurement: 45mm Holding pressure switching: 10mm Injection time: 10 seconds Cooling time: 15 seconds Injection speed: 23mm / sec Holding pressure speed: 23mm / sec Pressure retention time: 10 seconds Mold temperature: 45℃

[0081] [Extruded sheet] Another aspect of the present disclosure provides an extruded sheet formed using the above-mentioned styrene-based resin composition of the present invention. The extruded sheet may be either non-foamed or foamed. A commonly known method can be used as a method for producing an extruded sheet. A method for producing a non-foamed extruded sheet can be a method using a single-axis or twin-axis extruder equipped with a T-die and a device for taking up a sheet with a single-axis or twin-axis stretching machine, and a method for producing a foamed extruded sheet can be a method using an extrusion foaming machine equipped with a T-die or circular die.

[0082] -Foam extrusion sheet- In this embodiment, when forming a foamed extruded sheet, materials that are commonly used for foaming agents and foam nucleating agents during extrusion foaming can be used. Butane, pentane, fluorocarbons, carbon dioxide, water, etc. can be used as the foaming agent, and butane is preferred. Talc, etc. can be used as the foam nucleating agent.

[0083] In this embodiment, the foamed extruded sheet preferably has a thickness of 0.5 mm to 5.0 mm, an apparent density of 50 g / L to 300 g / L, and a basis weight of 80 g / m 2 ~300g / m 2 The foamed extruded sheet of the present invention may be multi-layered, for example, by further laminating a film. The type of film used may be any type commonly used for polystyrene.

[0084] -Non-foam extruded sheet- In the present embodiment, the thickness of the non-foamed sheet is preferably, for example, about 0.1 to 1.0 mm in terms of rigidity and thermoforming cycle. The uniaxial sheet may be formed only by ordinary low-magnification roll stretching, and the biaxially oriented sheet may be formed by stretching about 1.3 to 7 times in the machine direction (MD) with a roll and then stretching about 1.3 to 7 times in the transverse direction (TD) with a tenter. It is preferable in terms of strength to stretch the non-foamed sheet. The non-foamed sheet may be multi-layered with a styrene-based resin other than the styrene-based resin composition, such as a polystyrene resin. The non-foamed sheet may be multi-layered with a resin other than the styrene-based resin. Examples of the resin other than the styrene-based resin include PET resin and nylon resin.

[0085] <Biaxially oriented sheet> Another aspect of the present disclosure is a biaxially stretched sheet formed using the styrene-based resin composition of the present disclosure described above. A commonly known method can be used as a method for producing a biaxially stretched sheet. The biaxially stretched sheet can be produced by stretching in the machine direction (MD) with a roll and then stretching in the transverse direction (TD) with a tenter, or it can be produced by sequentially or simultaneously biaxially stretching a styrene-based resin composition molded into a plate shape in a state where the composition is heated to a Vicat softening temperature of the composition +10 to 40°C.

[0086] In terms of strength, the biaxially stretched sheet of the present embodiment is preferably stretched at a ratio of about 1.3 to 7.0 in the MD direction and about 1.3 to 7.0 in the TD direction.

[0087] The average thickness of the biaxially oriented sheet of the present embodiment is preferably 0.1 mm or more, more preferably 0.15 mm or more, and even more preferably 0.2 mm or more in order to ensure the strength, particularly the rigidity, of the sheet and the container, while from the viewpoint of economy, it is preferably 0.7 mm or less, more preferably 0.6 mm or less, and even more preferably 0.5 mm or less.

[0088] The orientation relaxation stress in the machine direction and the cross direction of the biaxially stretched sheet of this embodiment is preferably in the range of 0.4 to 1.3 MPa. By adjusting the orientation relaxation stress within this range, the strength of the molded product of the biaxially stretched sheet can be maintained.

[0089] When the biaxially stretched sheet of the present embodiment is used as a food packaging container, a known anti-fogging agent may be applied to at least one side of the biaxially stretched sheet in order to prevent fogging due to moisture volatilizing from food. Examples of the anti-fogging agent include nonionic surfactants such as sucrose fatty acid esters and polyglycerin fatty acid esters, polyether-modified silicone oils, etc. The method for applying the antifogging agent to the biaxially stretched sheet of the present embodiment is not particularly limited, and examples of the method include a method of applying the agent using a roll coater, a knife coater, a gravure roll coater, etc. Spraying, immersion, etc. may also be used. Furthermore, the antifogging agent may be applied after improving the wettability of the biaxially stretched sheet surface by performing a surface treatment such as a corona treatment, an ozone treatment, or a primer treatment before application.

[0090] [Secondary molded product] Another aspect of the present invention provides a molded product formed using the above-mentioned extruded sheet. The biaxially oriented sheet or a multilayer body containing the same can be molded, for example, by vacuum forming to produce a lid for a lunch box or a container for storing side dishes. In particular, a transparent lid for a food packaging container compatible with microwave cooking is preferred because the features of the present invention can be fully utilized. EXAMPLES

[0091] The present invention will now be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The resins and extruded sheets in the examples and comparative examples were analyzed and evaluated as follows.

[0092] [Evaluation of properties of each resin and resin composition] (1) Measurement of average molecular weights (Mn, Mw, Mz) and high molecular weight components of 1 million or more The polymer matrix soluble in organic solvents of each resin and resin composition produced in the examples and comparative examples The average molecular weights (Mn, Mw, Mz) of each copolymer and the high molecular weight components of 1 million or more were measured using gel permeation chromatography (GPC) under the following conditions. Measuring equipment: Tosoh HLC-8220 Separation column: Two Tosoh TSK gel Super HZM-H (inner diameter 4.6 mm) connected in series Guard column: Tosoh TSK guard column Super HZ-H Measurement solvent: tetrahydrofuran (THF) Sample concentration: 10 mg of sample is dissolved in 10 mL of solvent. Sample pretreatment: The sample was filtered through a 0.45 μm membrane filter to remove foreign matter such as dust and components that are not necessary for the organic solvent, such as rubber-like polymer particles contained in the rubber-modified styrene-based resin (D). Injection volume: 10μL Measurement temperature: 40℃ Flow rate: 0.35mL / min Detector: Differential refractometer (RI detector) and ultraviolet spectrophotometer (UV detector) To create the calibration curve, 11 types of TSK standard polystyrenes (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) manufactured by Tosoh were used. The calibration curve was created using a linear approximation equation, and the molecular weights calculated in terms of the standard polystyrenes were measured. Unless otherwise specified, the molecular weights described in this specification are values ​​measured by a differential refractometer (RI detector). In this specification, the component (%) having a molecular weight of 1 million or more is a value calculated from the differential molecular weight distribution of the measured value by a differential refractometer (RI detector).

[0093] (2) Measurement of Melt Mass Flow Rate (MFR) The melt mass flow rate (g / 10 min) of each of the resins and resin compositions produced in the Examples and Comparative Examples was measured at 200° C. and a load of 49 N in accordance with ISO1133.

[0094] (3) Measurement of Vicat softening temperature The Vicat softening temperature of each resin and resin composition produced in the examples and comparative examples was measured in accordance with ISO 306. The load was 50 N, and the heating rate was 50°C / h. Those with a Vicat softening temperature of over 105°C had excellent dimensional stability at temperatures assumed when heating sheet molded products and container molded products in a microwave oven, and those with a Vicat softening temperature of over 115°C in particular tended to show almost no dimensional change at practical temperatures.

[0095] (4) Measurement of the content of monohydric alcohol (C) having 10 or more carbon atoms in a styrene-based resin composition The content of the monohydric alcohol (C) having 10 or more carbon atoms in the entire styrene-based resin composition was measured by gas chromatography under the following conditions. Sample preparation: 1.0 g of resin was dissolved in 5 mL of methyl ethyl ketone, and then 5 mL of hexane containing 200 μg / g of p-diethylbenzene as a standard substance was added to reprecipitate the polymer component, and the supernatant was collected and used as the measurement solution. Measurement equipment: Agilent 6850 series GC system Detector: FID Column: DB-WAX Length: 60m Film thickness: 0.50μm Diameter: 0.320mmφ Injection volume: 1μL Split ratio: 50:1 Column temperature: Hold at 100°C for 5 minutes → Raise to 130°C at 10°C / min → Raise to 180°C at 10°C / min → Hold at 180°C for 10 minutes → Raise to 220°C at 20°C / min → Hold at 220°C for 10 minutes Inlet temperature: 230℃ Detector temperature: 300℃ Carrier gas: Helium In addition, when detecting the peak of the monohydric alcohol (C) having 10 or more carbon atoms, in order to avoid overlapping with other peaks or saturation of the peak intensity, pretreatment such as the dilution rate of the sample, the column to be used, and the detection conditions may be appropriately adjusted.

[0096] (5) Measurement of the content of each monomer unit The content of each monomer unit contained in the resin compositions prepared in the Examples and Comparative Examples was measured by pyrolysis GC / MS under the following conditions. Sample preparation: The resin compositions prepared in the examples and comparative examples were formed into a film by heat pressing at 220° C., and the sample was weighed on a precision balance. Measurement conditions Pyrolysis Unit Equipment: Frontier Labs PY-3030D Furnace temperature: 600℃ GC Equipment: Shimadzu GCMS-GP2020NX Column: Ultra Alloy-5 (Length 30m, film thickness 0.25μm, diameter 0.250mmφ) Column temperature: held at 50°C for 5 minutes, heated at 10°C / min, heated from 100°C at 7°C / min, and held at 300°C for 10 minutes. Inlet temperature: 300℃ Detector temperature: 300℃ Split ratio: 1 / 300 Carrier gas: Helium Detection method: Mass spectrometer (MSD) Sample size: 20-100μg In addition, when detecting each monomer peak, in order to avoid peak overlap or saturation of peak intensity, the measurement mode may be changed as appropriate, such as SCAN mode or SIM mode, pretreatment such as sample dilution rate may be performed, the column used may be changed depending on the polarity of the chemical species to be detected, or the sample amount, split ratio, and other conditions may be adjusted to prevent saturation peaks by varying the strength of the detection signal.

[0097] (6) Average particle size of rubber-like polymer particles in rubber-modified styrene-based resin (D) The average particle size (μm) of the rubber-like polymer particles in the rubber-modified styrene-based resin (D) (so-called HIPS resin) was determined by observing the cross-sections of 200 rubber-like polymer particles using a transmission electron microscope, using the following formula (3): Average particle diameter=Σ(ni×Di4 ) / Σ(ni×Di 3 ) {In the above formula (3), ni is the number of rubber-like polymer particles having a particle diameter Di, and Di is the average value of the major axis and minor axis of the rubber-like polymer particles.} It was calculated by:

[0098] (7) Haze measurement of 2 mm plate Each resin composition produced in the Examples and Comparative Examples was molded into a 2 mm plate by injection molding, and after conditioning for 48 hours or more in a temperature-controlled room at 23°C and a humidity of 50%, the haze was measured using a color difference turbidity meter (COH-300A) manufactured by Nippon Denshoku Industries Co., Ltd., and the n3 average was recorded as the value.

[0099] (8) Evaluation of heat resistance Each of the resin compositions produced in the Examples and Comparative Examples was molded into a 2.5 mm plate by injection molding, and the styrene-based resin composition plate was immersed in coconut oil (manufactured by Wako Pure Chemical Industries, Ltd.) at 110°C for 15 minutes. After that, the haze was measured using a haze meter (NDH-2000) manufactured by Nippon Denshoku Industries Co., Ltd., and the change in haze (Δhaze) before and after immersion was calculated using the following formula, and the heat oil resistance was evaluated according to the following evaluation criteria. ΔHaze = Haze after test (%) - Haze before test (%) Evaluation criteria ◎ Δ haze is 3% or less △ Δ haze is greater than 3% and less than 7% △··ΔHaze is greater than 7% and less than 10% × Δ haze is greater than 10%

[0100] [Characteristics evaluation of non-foamed extruded sheet (biaxially oriented sheet)] (9) Measurement of the heat-resistant oil temperature of biaxially oriented sheets The biaxially stretched sheets molded using each of the resin compositions prepared in the Examples and Comparative Examples were cut into 10 cm x 1.5 cm strips, which were then wrapped circumferentially around a cylinder with a diameter of 7.5 cm. MCT oil was applied to the center of the strip to a diameter of 1 cm, and the strip was then heated for 15 minutes in a constant temperature bath heated to a specified temperature. The maximum temperature at which no cracking or whitening was observed was determined as the heat-resistant oil temperature.

[0101] (10) Strength measurement of biaxially stretched sheets The biaxially stretched sheets molded using each of the resin compositions prepared in the Examples and Comparative Examples were cut into 8 cm x 8 cm pieces, and the film impact was measured using a Toyo Seiki Film Impact Tester (No. 195), and the n8 average value was recorded.

[0102] (11) Measurement of heat resistance of biaxially oriented sheet The biaxially oriented sheets molded using each of the resin compositions prepared in the Examples and Comparative Examples were cut into strips of 10 cm x 1.5 cm and placed in an oven set at 110°C for 60 minutes. The deformation of the biaxially oriented sheets was then visually observed, and the heat resistance was evaluated based on the thermal deformation as follows. Specifically, the above-mentioned dimensional change was measured by measuring the amount of change in a 10 cm length before and after thermal deformation according to the following formula (4). Equation (4): Dimensional change (%) = (MD length of biaxially oriented sheet after 60 minutes in oven - MD length of biaxially oriented sheet before oven) / MD length of biaxially oriented sheet before oven ○: Dimensional change is 1% or less △: Dimensional change between 1% and 3% ×: Dimensional deformation 3% or more

[0103] (12) Measurement of Internal Haze of Biaxially Stretched Sheet The biaxially stretched sheets molded using each of the resin compositions prepared in the Examples and Comparative Examples were cut into 3 cm x 5 cm pieces, and in order to reduce the effects of surface roughness, the biaxially stretched sheets were immersed in liquid paraffin and the haze was measured using a Nippon Denshoku Industries Co., Ltd. haze meter (NDH-2000) and the n3 average value was recorded.

[0104] (13) Appearance assessment of non-foamed extruded sheets Using each resin composition prepared in the Examples and Comparative Examples, a sheet of the resin composition was extruded continuously for 30 minutes using a 30 mmφ short-axis sheet extruder, and then five sheets measuring 10 cm x 20 cm were cut out from the 0.3 mm thick sheet. The number of gel particles and air bubbles, which are foreign matter with an average diameter of 0.5 mm or more, was counted and the appearance was judged using the following method. ○: Gel or bubbles count is 2 or less △: Gel, number of bubbles: 3 to 9 points ×: Gel, 10 or more bubbles

[0105] [Evaluation of properties of foam extrusion sheets] (14) Heat and oil resistance measurement of foam sheet The composition was molded into a foamed extruded sheet, and coconut oil (Wako Pure Chemical Industries, Ltd.) was applied in a circle with a diameter of about 1 cm. After heating in an oven at 90°C for 10 minutes, the appearance of the coconut oil-applied area was visually evaluated. 〇: No change △: The applied part is deformed in size, but not torn. ×: The applied part was torn.

[0106] [Evaluation of properties of molded products obtained by secondary molding of biaxially oriented sheets] The resin compositions prepared in the Examples and Comparative Examples were used to form biaxially oriented sheets, which were then molded into lids measuring 160 mm in length, 140 mm in width, and 40 mm in height using a hot plate molding machine at a hot plate temperature of 145°C and a heating time of 2.0 seconds. The lids were then subjected to the following evaluations. (15) Oil resistance when heated in a microwave oven MCT oil was applied to the center of the lid in a circular shape with a diameter of approximately 5 mm, moistened with a spray bottle, and covered with polyvinylidene chloride film to prevent the moisture from evaporating.The lid was then heated in a 1500W microwave for 90 seconds, after which the condition of the area with the MCT oil attached was visually evaluated. 〇: No change △: Whitening, no tears ×: Whitening and tearing of applied area

[0107] (16) Transparency (after molding) The haze of the molded product was measured using a Nippon Denshoku Industries Co., Ltd. haze meter (NDH-2000), and the n3 average value was measured and evaluated according to the following criteria. 〇: Haze 2.0% or less △: Haze over 2.0% to 5.0% ×: Haze exceeds 5.0%

[0108] (17) Molded product strength A test piece measuring 80 mm long x 80 mm wide was cut out from the center of the lid, and the film impact was measured using a Toyo Seiki Film Impact Tester (No. 195). The n8 average was used as the value, and the film impact was evaluated from the following perspectives. 〇: 5.0kgf or more ×: Less than 5.0kgf Containers with a strength of less than 5.0 kgf resulted in cracking during transportation.

[0109] [Preparation of each resin and production examples of styrene-based resin composition] The preparation of each resin and a specific method for producing the styrene-based resin composition will be described below.

[0110] <Production Example of Styrene-Unsaturated Carboxylic Acid Resin (A)> -Preparation of resin a-1- Polymerization raw materials consisting of 65.5 parts by mass of styrene, 3.3 parts by mass of methyl methacrylate, 5.8 parts by mass of methacrylic acid, 22.9 parts by mass of ethylbenzene, 2.5 parts by mass of 2-ethyl-1-hexanol, and 0.027 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane The composition liquid was fed to a complete mixing reactor with a capacity of 3.6 liters at a rate of 0.8 liters / hour, and then continuously fed to a volatilizing device connected to a single screw extruder for removing volatile components such as unreacted monomers and polymerization solvents. The polymerization temperature of the complete mixing reactor was set to 130°C. The temperature of the single screw extruder was set to 210-230°C, and the pressure was set to 10 torr, to volatilize volatile components such as unreacted monomers and polymerization solvents. The volatilized volatile components were condensed in a condenser through which a refrigerant of -5°C was passed, and were recovered as an unreacted liquid, and the styrene-based resin was recovered as resin pellets. The physical properties of resin a-1 obtained by the above-mentioned analytical methods are shown in Table 1 below.

[0111] -Preparation of resins a-2, a-3, and a-4- The feed amount of each monomer and the polymerization conditions were adjusted, and resins a-2, a-3, and a-4 were prepared in the same manner as for resin a-1. The compositions and physical properties of the obtained resins a-1 to a-4 are shown in Table 1.

[0112] -Preparation of resin a-5- Using only styrene as a monomer, a styrene homopolymer a-5 having the composition and physical properties shown in Table 1 was obtained in the same manner as above.

[0113] [Table 1]

[0114] <Production Example of (Meth)acrylic Resin (B)> -Preparation of resin b-1- 2 kg of water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were added to a 5 L container equipped with an agitator, and the mixture was mixed and stirred to prepare a suspension. Next, 26 kg of water was added to a 60 L reactor, and the temperature was raised to 80°C to prepare for suspension polymerization. After confirming that the temperature had reached 80°C and was in a constant temperature state, 1.52 kg of methyl methacrylate, 0.20 kg of methyl acrylate, 0.99 g of lauroyl peroxide, 4.93 g of n-octyl mercaptan, and the above suspension were added as polymerization raw materials. Then, the suspension polymerization was carried out while maintaining the temperature at about 80°C, and after observing the exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min and the temperature was maintained at 92°C for 60 minutes. Then, after cooling to 50°C, 20% by mass of sulfuric acid was added to dissolve the suspension. The polymerization reaction solution was then removed from the 60 L reactor and passed through a sieve with a mesh size of 1.7 mm to remove large aggregates, after which the aqueous layer and solid matter were separated in a Buchner funnel to obtain a bead-like polymer. The bead-like polymer was washed and dehydrated five times with about 20 L of distilled water on the Buchner funnel, then dried and pelletized using a single-screw extruder to obtain resin b-1 as a pellet-like resin.

[0115] -Preparation of resins b-2, b-3, and b-4- The feed amount of each monomer and the polymerization conditions were adjusted, and resins b-2, b-3, and b-4 were prepared in the same manner as for resin b-1. The compositions and physical properties of the obtained resins b-1 to b-4 are shown in Table 2.

[0116] [Table 2]

[0117] <<Monohydric alcohol (C) having 10 or more carbon atoms used in the examples>> In the examples of this specification, the following alcohol species were used as the monohydric alcohol (C) having 10 or more carbon atoms. As the monohydric alcohol (C-1), Fine Oxocol 180 (5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)-1-octanol) manufactured by Nissan Chemical Industries, Ltd. was used. As the monohydric alcohol (C-2), Emulgen 109P (polyoxyethylene (9) lauryl ether monoalcohol) manufactured by Kao Corporation was used.

[0118] <Production Example of Rubber-Modified Styrene-Based Resin (D)> - Preparation of resin d-1 - A rubber-modified styrene-based resin d-1 (hereinafter referred to as resin d-1) was produced using a polymerization apparatus in which three laminar flow reactors (1.5 liters) equipped with a stirrer were connected in series and followed by a two-stage vented extruder. 83.5 parts by mass of styrene, 7.9 parts by mass of methyl methacrylate, 10.0 parts by mass of ethylbenzene, 6.5 parts by mass of Asahi Kasei's low-cis butadiene rubber diene 35AE as a rubber component, and 0.02 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane were charged into a raw material tank equipped with a stirrer, and after dissolving the rubber component with a stirrer, this raw material solution was supplied to the reactor at a volume of 0.75 liters / hr, and polymerization was performed at a temperature of 110 to 120 ° C. in the first stage reactor, 120 to 130 ° C. in the second stage reactor, and 140 to 150 ° C. in the third stage reactor. The extruder temperature was 210-240°C, the degree of vacuum was 3 kPa, and the total solid content in the polymerization liquid discharged from the final reactor was 70.5% by mass. The rubber particle size was controlled by adjusting the rotation speed of the agitator of the first-stage laminar flow reactor to 150 rpm. The composition and properties of the obtained resin d-1 are shown in Table 3.

[0119] -Preparation of resin d-2- Using styrene and (n-butyl) acrylate as monomers and Asahi Kasei Corporation's Asaprene 625A, a styrene-butadiene copolymer, as the rubber component, resin d-2 was obtained using the same procedure as above, with a styrene-(n-butyl) acrylate copolymer as the matrix component, with the composition and physical properties shown in Table 3.

[0120] [Table 3]

[0121] <Production Example of Styrene-Based Resin Composition> The detailed method for producing the styrene-based resin composition will be described below. Example 1 91.6 parts by mass of resin a-1 in Table 1 as styrene-unsaturated carboxylic acid resin (A), 6.9 parts by mass of resin b-1 in Table 2 as (meth)acrylic resin (B), 0.1 parts by mass of Fine Oxocol 180 as monohydric alcohol (C) having 10 or more carbon atoms, and 1.5 parts by mass of rubber-modified styrene resin d-1 in Table 3 were dry-blended, and the mixture was kneaded, extruded, and pelletized using a twin-screw extruder TEM26SS manufactured by Shibaura Machine Co., Ltd. to obtain a styrene resin composition as a pellet-shaped resin. The screw rotation speed was 150 rpm, the cylinder temperature was 180 to 230 ° C, and the feed rate was 10 kg / h. The resin temperature was 250 to 260 ° C. The pellets obtained were then processed into a plate of 10 cm x 10 cm x 1.2 mm by press molding. The plate was set to a chuck distance of 85 mm in a batch biaxial stretching machine EX6-S1 manufactured by Toyo Seiki, and after 10 minutes of preheating at the Vicat softening temperature of the styrene-based resin composition + 20 ° C., it was stretched at 250 mm / min to an X-axis magnification of 2.4 and a Y-axis magnification of 2.4 to obtain a biaxially stretched sheet of about 0.2 mm in thickness. The evaluation results of the obtained composition and biaxially stretched sheet, and the evaluation results of the molded product are shown in Table 4.

[0122] --Examples 2 to 24-- A resin composition and a biaxially stretched sheet were obtained in the same manner as in Example 1, except that the formulation was changed as shown in the following Table 4. The evaluation results of the composition and the biaxially stretched sheet, and the evaluation results of the molded product are shown in Table 4. As shown in Table 4, one or both of (meth)acrylic resin (B)_I and (meth)acrylic resin (B)_II were used as the (meth)acrylic resin (B).

[0123] [Table 4]

[0124] -Comparative Examples 1 to 3- A resin composition and a biaxially stretched sheet were obtained in the same manner as in Example 1, except that the formulation was changed as shown in the following Table 5. The evaluation results of the composition and the biaxially stretched sheet, and the evaluation results of the molded product are shown in Table 5. As shown in Table 5, one or both of (meth)acrylic resin (B)_I and (meth)acrylic resin (B)_II were used as the (meth)acrylic resin (B).

[0125] [Table 5] [Industrial Applicability]

[0126] The styrene-based resin composition obtained by the present invention is excellent in heat resistance, transparency, rigidity, heat oil resistance, and appearance. Therefore, the styrene-based resin composition of the present invention can be widely used for non-foamed or foamed sheets by extrusion molding, food packaging containers using them, or molded products by injection molding (electrical product parts, toys, daily necessities, various industrial parts), etc., and is particularly useful as a packaging material for refrigerated transport, and plays a major role in the industrial world.

Claims

1. 62 to 98% by mass of a styrene-unsaturated carboxylic acid-based resin (A) which is a binary or ternary copolymer composed only of a styrene-based monomer unit (1) and an unsaturated carboxylic acid-based monomer unit (a1); A styrene-based resin composition comprising: 2 to 38 mass% of a (meth)acrylic resin (B) having an unsaturated carboxylic acid monomer unit (b1); The unsaturated carboxylic acid monomer unit (a1) is one or two selected from the group consisting of (meth)acrylic acid monomer units (a1-1) and (meth)acrylic acid ester monomer units (a1-2), the (meth)acrylic resin (B) is a polymer constituted only of the unsaturated carboxylic acid monomer unit (b1) or a polymer constituted only of the unsaturated carboxylic acid monomer unit (b1) and another monomer (b2), and the other monomer (b2) is at least one selected from maleic anhydride, maleic acid, fumaric acid, itaconic acid, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleimide, and nucleus-substituted maleimide; The styrene-based monomer unit (1) is contained in an amount of 52 to 85 mass% based on the total amount of the styrene-based resin composition, the unsaturated carboxylic acid monomer unit (b1) is at least one repeating unit selected from the group consisting of (meth)acrylic acid monomer units (b1-1) and (meth)acrylic acid ester monomer units (b1-2), and the (meth)acrylic resin (B) contains the (meth)acrylic acid ester monomer units (b1-2) in an amount of 56% by mass to 100% by mass based on the total amount of the (meth)acrylic resin (B); a ratio of a high molecular weight component having a molecular weight of 1,000,000 or more in the (meth)acrylic resin (B) is 1.0 mass% or less based on a total amount of the (meth)acrylic resin composition.

2. 2. The styrene-based resin composition according to claim 1, wherein a high molecular weight component having a molecular weight of 1,000,000 or more in the entire styrene-based resin composition is 1.0 mass% or less based on the total amount of the styrene-based resin composition.

3. The styrene-based resin composition according to claim 1 or 2, wherein the styrene-based monomer unit (1) is contained in an amount of 60 to 85 mass% based on the total amount of the styrene-based resin composition.

4. The styrene-based resin composition according to claim 1 or 2, wherein the (meth)acrylic resin (B) has a weight average molecular weight (Mw) of 60,000 to 900,000.

5. The unsaturated carboxylic acid monomer unit (a1) contains two essential components, namely, a (meth)acrylic acid monomer unit (a1-1) and a (meth)acrylic acid ester monomer unit (a1-2), The styrene-based resin composition according to claim 1 or 2, comprising 2 to 30 mass% of the (meth)acrylic acid monomer unit (a1-1) and 1 to 20 mass% of the (meth)acrylic acid ester monomer unit (a1-2) relative to the total amount of the styrene-unsaturated carboxylic acid-based resin (A).

6. The styrene-based resin composition according to claim 1 or 2, wherein the (meth)acrylic resin (B) is contained in an amount of 10 to 32 mass% based on the total amount of the styrene-based resin composition.

7. the unsaturated carboxylic acid monomer unit (a1) contains a (meth)acrylic acid ester monomer unit (a1-2), and the unsaturated carboxylic acid monomer unit (b1) contains a (meth)acrylic acid ester monomer unit (b1-2), The styrene-based resin composition according to claim 1 or 2, wherein a total content of the (meth)acrylic acid ester monomer units (a1-2) and the (meth)acrylic acid ester monomer units (b1-2) is 15 to 40 mass% based on a total amount of the styrene-based resin composition.

8. The styrene-based resin composition according to claim 1 or 2, wherein the (meth)acrylic resin (B) is a methyl methacrylate-methyl acrylate copolymer, and contains 0.1 to 15 mass% of the methyl acrylate based on the total amount of the copolymer.

9. The styrene-based resin composition according to claim 1 or 2, comprising 0.01 to 1.0 part by mass of an alcohol (C) having 10 or more carbon atoms relative to the total amount (100 parts by mass) of the styrene-based resin composition.

10. 3. The styrene-based resin composition according to claim 1, comprising a rubber-modified styrene-based resin (D) in an amount of 0.1 to 15 mass% based on the total amount of the styrene-based resin composition.

11. 3. The styrene-based resin composition according to claim 1, wherein the content of the methyl acrylate monomer unit is 0.01 to 5.0 mass % based on the total amount of the styrene-based resin composition.

12. The Z-average molecular weight of the styrene-based resin composition according to claim 1 or 2, measured by gel permeation chromatography (GPC) in terms of standard polystyrene, When the value measured by a differential refractometer (RI detector) is Mz(RI) and the value measured by an ultraviolet absorption detector (UV detector) is Mz(UV), The styrene-based resin composition according to claim 1 or 2, wherein the value of Mz(RI)-Mz(UV) is 500,000 or less.

13. 3. The styrene-based resin composition according to claim 1, wherein a haze value of a 2 mm-thick plate-shaped test piece prepared by injection molding the styrene-based resin composition according to claim 1 or 2 is less than 10%.

14. A non-foamable or foamable extruded sheet comprising the styrene-based resin composition according to claim 1 or 2.

15. A container obtained by molding the styrene-based resin composition according to claim 1 or 2.

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