JP7702979B2 - Styrenic resin composition, extruded sheet, injection molded article, and container - Google Patents

Description

The present disclosure relates to a styrene-based resin composition, an extruded sheet molded using the styrene-based resin composition, an injection molded article, and a container obtained by secondary molding of the extruded sheet.

Styrene-unsaturated carboxylic acid resins, such as styrene-methacrylic acid copolymer resins, are excellent in heat resistance, transparency, rigidity, and appearance, are inexpensive, and can be easily reused by thermal decomposition into styrene monomers, and have excellent chemical recycling properties, and therefore are widely used as packaging materials for food containers such as lunch boxes and side dishes, foam boards for insulating materials in houses, and diffusion plates for liquid crystal televisions containing a diffusion agent. In particular, with the recent spread of high-power microwave ovens for commercial use in convenience stores and the like, styrene-unsaturated carboxylic acid resins are 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 the containers. However, the strength of these resins is inferior to that of general-purpose styrene resins, which is an issue.
For example, Patent Document 1 describes a technique for improving toughness while maintaining practical heat resistance by using a mixture of a styrene-methacrylic acid copolymer, impact-resistant polystyrene, and a methyl methacrylate-butadiene-styrene copolymer (hereinafter also referred to as MBS resin).

JP 2018-44086 A

The technology of the above Patent Document 1 was insufficient in improving mechanical strength. Furthermore, in containers intended to come into direct contact with food, the resin of a conventional styrene-unsaturated carboxylic acid resin is corroded by high-temperature oil from food heated in a microwave oven, causing cracking and a decrease in strength of the container, and therefore 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 heat resistance, mechanical strength, and hot oil resistance. Another problem to be solved by the present invention is to provide a molded article, an extruded sheet containing a styrene-based resin composition, and a food container obtained by secondary molding of the extruded sheet, all of which are excellent in heat resistance, mechanical strength, and hot oil resistance.

As a result of intensive research conducted by the inventors in consideration of the above problems, they have succeeded in realizing a styrene-based resin composition that is excellent in heat resistance, mechanical strength, and heat oil resistance by containing a predetermined amount of each of styrene-(meth)acrylic acid-based resin (A) and (meth)acrylic resin (B), as well as an extruded sheet and injection molded article using the same, and a container obtained by secondary molding of the extruded sheet, thereby completing the present invention. That is, the present disclosure is as follows.

[1] The present disclosure relates to a polymerizable composition comprising a styrene-(meth)acrylic acid-based resin (A) having 40 to 99% by mass of a styrene-(meth)acrylic acid-based resin (A) having a styrene-based monomer unit (a1) and a (meth)acrylic acid monomer unit (a2-1);
The styrene-based resin composition comprises: 1 to 60 mass % of a (meth)acrylic resin (B) having a (meth)acrylic acid ester monomer unit (b1).

[2] In this embodiment, it is preferable that the high molecular weight component having a molecular weight of 1 million or more is 1.0 mass% or less of the total amount of the styrene-based resin composition.

[3] In this embodiment, the styrene-(meth)acrylic acid-based resin (A) preferably contains the styrene-based monomer unit (a1), the (meth)acrylic acid monomer unit (a2-1), and the (meth)acrylic acid ester monomer unit (a2-2).

[4] The styrene-(meth)acrylic acid-based resin (A) contains the (meth)acrylic acid monomer unit (a2-1) and the (meth)acrylic acid ester monomer unit (a2-2) as essential components, and contains 2 to 30% by mass of the (meth)acrylic acid monomer unit (a2-1) and 1 to 20% by mass of the (meth)acrylic acid ester monomer unit (a2-2) relative to the entire styrene-(meth)acrylic acid-based resin (A). A styrene-based resin composition according to any one of [1] to [3].

[5] A styrene-based resin composition according to any one of [1] to [4], in which the total content of (meth)acrylic acid ester monomer units contained in the styrene-based resin composition is 15 to 50 mass% based on the total amount of the styrene-based resin composition.

[6] The styrene-based resin composition according to any one of [1] to [5], wherein the (meth)acrylic resin (B) is a methyl methacrylate-methyl acrylate copolymer and contains 0.5 to 15 mass% of methyl acrylate monomer units relative to the total amount of the copolymer.

[7] A styrene-based resin composition according to any one of [1] to [6], further comprising one or more selected from the group consisting of a (meth)acrylonitrile-diene-styrene-based resin (C) containing a styrene-based monomer unit (c1), a conjugated diene-based monomer unit (c2), and a (meth)acrylonitrile-based monomer unit (c3), a core-shell type rubber-like polymer particle (D) containing a butadiene-based monomer unit (d1) and a (meth)acrylic acid ester monomer unit (d2), an impact-resistant styrene-based resin (E) containing a styrene-based monomer unit (e1) and a butadiene-based monomer unit (e2), a styrene-based elastomer (F), and an acrylic elastomer (G).

[8] A styrene-based resin composition according to any one of [1] to [7], further comprising a (meth)acrylonitrile-diene-styrene-based resin (C) containing a styrene-based monomer unit (c1), a conjugated diene-based monomer unit (c2), and a (meth)acrylonitrile-based monomer unit (c3), and an acrylic elastomer (G).

[9] A styrene-based resin composition according to any one of [1] to [8], further comprising core-shell type rubber-like polymer particles (D) containing (meth)acrylic acid ester monomer units (d1) and conjugated diene monomer units (d2).

[10] A styrene-based resin composition according to any one of [1] to [9], further comprising 0.05 to 3.0 mass% of inorganic particles (H) relative to the total amount of the styrene-based resin composition.

[11] One aspect of this embodiment is an extruded sheet formed from a styrene-based resin composition according to any one of [1] to [10].

[12] One aspect of this embodiment is a molded article obtained by injection molding a styrene-based resin composition according to any one of [1] to [10].

[13] One aspect of this embodiment is a container formed by secondary molding of the extruded sheet described in [11] above.

According to the present disclosure, there is provided a styrene-based resin composition for use in a molded article having excellent heat resistance, mechanical strength, and hot oil resistance.
According to the present disclosure, it is possible to provide a foamed extruded sheet having excellent heat resistance, mechanical strength, and heat oil resistance, and a foamed container that can be used for microwave cooking.

FIG. 1 is a diagram showing a method for measuring stiffness of a tray container in an embodiment.

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 various modifications can be made within the scope of the gist of the present invention.
[Styrene-based resin composition]
The styrene-based resin composition in this embodiment (hereinafter, sometimes simply referred to as a resin composition) contains a styrene-(meth)acrylic acid-based resin (A) having a styrene-based monomer unit (a1) and a (meth)acrylic acid monomer unit (a2-1), and a (meth)acrylic resin (B) having a (meth)acrylic acid ester monomer unit (b1), and the content of the styrene-(meth)acrylic acid-based resin (A) is 40 to 99 mass%, and the content of the (meth)acrylic resin (B) is 1 to 60 mass%, relative to the total amount (100 mass%) of the styrene-based resin composition.
In addition, the styrene-based resin composition in the present embodiment may contain, as necessary, one or more selected from the group consisting of (meth)acrylonitrile-diene-styrene-based resin (C), core-shell type rubbery polymer particles (D), impact resistant styrene-based resin (E), styrene-based elastomer (F), acrylic elastomer (G) and inorganic particles (H).
This makes it possible to provide a styrene-based resin composition having excellent heat resistance, mechanical strength and heat oil resistance.
The styrene-based resin composition in this embodiment is preferably divided into a high molecular weight component of 1 million or more and a molecular weight component of less than 1 million, and the high molecular weight component of 1 million or more is 1.0 mass% or less with respect to the total amount of the styrene-based resin composition. The high molecular weight component of 1 million or more may include a styrene-(meth)acrylic acid resin (A) and/or a (meth)acrylic resin (B). The high molecular weight component of 1 million or more contained in the styrene-based resin composition of this embodiment may include a styrene-(meth)acrylic acid resin (A) and/or a (meth)acrylic resin (B) and one or more resins selected from the group consisting of a (meth)acrylonitrile-diene-styrene resin (C), a core-shell type rubber-like polymer particle (D), an impact-resistant styrene resin (E), a styrene-based elastomer (F), and an acrylic elastomer (G), which are blended as necessary.
Therefore, the proportion of high molecular weight components having molecular weights of 1,000,000 or more in the styrene-based resin composition is small.

"Styrene-(meth)acrylic acid resin (A)"
The styrene-(meth)acrylic acid resin (A) in this embodiment is a copolymer resin (hereinafter also simply referred to as resin (A)) consisting essentially of a styrene-based monomer unit (a1) and a (meth)acrylic acid monomer unit (a2-1), and contributes to improving the heat resistance of the entire styrene-based resin composition. In addition, the styrene-(meth)acrylic acid resin (A) may further contain, as necessary, a (meth)acrylic acid ester monomer (a2-2) and/or other monomer unit (a3) in addition to the essential components of the styrene-based monomer unit (a1) and the (meth)acrylic acid monomer unit (a2-1). The content of the styrene-(meth)acrylic acid resin (A) is 40 to 99% by mass, preferably 45 to 98% by mass, more preferably 50 to 97% by mass, and even more preferably 55 to 95% by mass, based on the total amount (100% by mass) of the styrene-based resin composition. By making the content of the styrene-(meth)acrylic acid-based resin (A) 40% by mass or more, the effect of imparting heat resistance can be sufficiently obtained, and by making it 99% by mass or less, the effect of improving oil resistance, which is necessary for improving heat oil resistance by the (meth)acrylic resin (B) described later, can be sufficiently obtained.
The styrene-(meth)acrylic acid-based resin (A) of the present embodiment is preferably a random copolymer or an alternating copolymer.

<Styrene-based monomer (a1)>
In the styrene-(meth)acrylic acid resin (A) of this embodiment, the content of the styrene-based monomer unit (a1) 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-(meth)acrylic acid resin (A). If the content of the styrene-based monomer unit (a1) 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 (meth)acrylic acid monomer unit (a2-1) described below, and in particular, the effect of improving heat resistance by the (meth)acrylic acid monomer unit (a2-1) is not sufficiently obtained.
In the styrene-based resin composition of the present embodiment, the styrene-based monomer unit (a1) is preferably contained in an amount of 45 to 85 mass%, more preferably 48 to 82 mass%, more preferably 52 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 (a1) in the entire composition is within the above range, the effect of improving oil resistance can be sufficiently obtained.

In this embodiment, the styrene-based monomer (a1) 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 (a1), these may be used alone or in combination of two or more.
In this specification, the term "styrene monomer unit (a1)" means a repeating unit constituting a polymer obtained by polymerizing a styrene monomer (a1), and is a repeating unit (or structural unit) in which a carbon-carbon double bond in the styrene monomer (a1) becomes a single bond (-C-C-) through a polymerization reaction or crosslinking reaction of the styrene monomer (a1). Other monomer units in this specification have the same meaning.

<(Meth)acrylic acid monomer (a2-1)>
In the styrene-(meth)acrylic acid resin (A) of this embodiment, the unsaturated carboxylic acid monomer unit such as the (meth)acrylic acid monomer unit (a2-1) plays a role in improving oil resistance and compatibility with the (meth)acrylic resin (B) described below. The content of the (meth)acrylic acid monomer unit (a2-1) is preferably 2 to 40 mass%, more preferably 3 to 35 mass%, more preferably 5 to 30 mass%, even more preferably 8 to 25 mass%, and most preferably 10 to 20 mass%, based on the total amount of the styrene-(meth)acrylic acid resin (A). In another embodiment, the content of the (meth)acrylic acid monomer unit (a2-1) is preferably 3 to 20 mass%, more preferably 4 to 17 mass%, and even more preferably 8 to 14 mass%. If the content of the (meth)acrylic acid monomer unit (a2-1) is less than 2 mass%, the effect of improving heat resistance is insufficient. In addition, if the content of the (meth)acrylic acid monomer unit (a2-1) exceeds 40% by mass, the resin viscosity increases, which leads to a decrease in processability, and the water absorption rate increases, which leads to bubbles during molding, and the viscosity becomes too high during production, which is not preferable. By making the content of the (meth)acrylic acid monomer unit (a2-1) 2% by mass or more, it is possible to obtain an effect of improving heat resistance, and by making the content 40% by mass or less, it is possible to prevent the viscosity from increasing too much. In particular, by making the content of the (meth)acrylic acid monomer unit (a2-1) 8 to 25% by mass, it is possible to obtain good compatibility with the (meth)acrylic resin (B), and it is possible to efficiently obtain the effect of improving the strength during kneading with the (meth)acrylic resin (B).

In this embodiment, the (meth)acrylic acid monomer unit (a2-1) plays a role in improving oil resistance and heat resistance. Examples of the (meth)acrylic acid monomer (a2-1) include acrylic acid and methacrylic acid. From an industrial viewpoint, the (meth)acrylic acid monomer unit (a2-1) may be used alone or in combination of two or more. As the (meth)acrylic acid monomer unit (a2-1), methacrylic acid, which has a large effect of improving heat resistance, is particularly preferred.

（上記一般式（１）中、Ｒ^１は、水素原子又は炭素原子数１～３のアルキル基を表し、Ｒ^２はエステル置換基を表し、具体的には、炭素原子数１～１２のアルキル基を表す。）で表されることが好ましい。
本実施形態において、（メタ）アクリル酸エステル単量体単位（ａ２－２）のエステル置換基（上記一般式（１）中のＲ^２）の炭素原子数としては、１０以下が好ましく、より好ましくは８以下、より更に好ましくは４以下である。エステル置換基の炭素原子数が１０を上回ると耐熱性低下の効果が大きく、好ましくない。 -(Meth)acrylic acid ester monomer (a2-2)-
In this embodiment, the styrene-(meth)acrylic acid-based resin (A) may further contain a (meth)acrylic acid ester monomer (a2-2). The (meth)acrylic acid ester monomer (a2-2) plays a role in improving oil resistance and strength. The (meth)acrylic acid ester monomer (a2-2) is a monomer represented by the following general formula (1):

(In the above general formula (1), R ¹ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ² represents an ester substituent, specifically, an alkyl group having 1 to 12 carbon atoms.)
In this embodiment, the number of carbon atoms in the ester substituent (R ² in the above general formula (1)) of the (meth)acrylic acid ester monomer unit (a2-2) is preferably 10 or less, more preferably 8 or less, and even more preferably 4 or less. If the number of carbon atoms in the ester substituent exceeds 10, the effect of reducing heat resistance is significant, which is not preferred.

Examples of the (meth)acrylic acid ester monomer (a2-2) 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 may be used alone or in combination. As the (meth)acrylic acid ester monomer (a2-2), 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 the present embodiment, the content of the (meth)acrylic acid ester monomer unit (a2-2) relative to the total amount of the styrene-(meth)acrylic acid-based resin (A) is, for example, preferably in the range of 2 to 40 mass%, more preferably 3 to 32 mass%, more preferably 3 to 20 mass%, even more preferably 3 to 17 mass%, still more preferably 3 to 12 mass%, and still more preferably 4 to 10 mass%.

<Preferable form of styrene-(meth)acrylic acid based resin (A)>
The styrene-(meth)acrylic acid resin (A) of this embodiment may be a multicomponent polymer containing a (meth)acrylic acid monomer unit (a2-1) and a (meth)acrylic acid ester monomer unit (a2-2). That is, the styrene-(meth)acrylic acid resin (A) of this embodiment may be a binary copolymer of a styrene monomer unit (a1) and a (meth)acrylic acid monomer unit (a2-1), a ternary copolymer in which a styrene monomer (a1), a (meth)acrylic acid monomer (a2-1), and a (meth)acrylic acid ester monomer (a2-2) are copolymerized, or a ternary copolymer containing a styrene monomer unit (a1) and two kinds of (meth)acrylic acid monomer units (a2-1). 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-(meth)acrylic acid resin (A) preferably contains a (meth)acrylic acid monomer unit (a2-1). In particular, when emphasis is placed on improving appearance and mechanical strength, the styrene-(meth)acrylic acid resin (A) preferably contains a (meth)acrylic acid ester monomer unit (a2-2). 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-(meth)acrylic acid resin (A) is preferably a ternary copolymer in which a styrene monomer unit (a1), a (meth)acrylic acid monomer unit (a2-1), and a (meth)acrylic acid ester monomer unit (a2-2) are copolymerized.
In addition, when an unsaturated carboxylic acid ester monomer unit such as a (meth)acrylic acid ester monomer unit (a2-2) is arranged adjacent to an unsaturated carboxylic acid monomer unit such as a (meth)acrylic acid unit (a2-1) in a polymer chain, an effect such as suppressing a crosslinking reaction between unsaturated carboxylic acids can be obtained.
In the present embodiment, when the styrene-(meth)acrylic acid-based resin (A) has a styrene-based monomer unit (a1), a (meth)acrylic acid monomer unit (a2-1), and a (meth)acrylic acid ester monomer unit (a2-2), the content of the (meth)acrylic acid monomer unit (a2-1) is preferably 2 to 30 mass% and the content of the (meth)acrylic acid ester monomer unit (a2-2) is preferably 0 to 20 mass%, more preferably 1 to 20 mass%, based on the total amount of the styrene-(meth)acrylic acid-based resin (A). The content of the units (a2-1) is 2 to 30% by mass, and the content of the (meth)acrylic acid ester monomer units (a2-2) is 1 to 20% by mass, more preferably, the content of the (meth)acrylic acid monomer units (a2-1) is 2 to 25% by mass, and the content of the (meth)acrylic acid ester monomer units (a2-2) is 1.5 to 15% by mass, and even more preferably, the content of the (meth)acrylic acid monomer units (a2-1) is 2 to 20% by mass, and the content of the (meth)acrylic acid ester monomer units (a2-2) is 2 to 13% by mass. By suppressing the content of the (meth)acrylic acid ester monomer units (a2-2) to 20% by mass or less, a composition having excellent fluidity during molding can be obtained.

<Other Monomers (a3)>
The styrene-(meth)acrylic acid resin (A) in this embodiment may further have other monomer units (a3) other than the above-mentioned styrene monomer units (a1) and (meth)acrylic acid monomer units (a2-1) and/or (meth)acrylic acid ester monomer units (a2-2).
That is, in the present embodiment, the other monomer unit (a3) may be copolymerized with a monomer other than the two monomers shown above without any particular limitation, so long as the other monomer unit (a3) is copolymerizable with the styrene-based monomer unit (a1), the (meth)acrylic acid monomer unit (a2-1) and/or the (meth)acrylic acid ester monomer unit (a2-2), within a range that does not impair the effects of the invention.
For example, examples of the other monomer (a3) 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-(meth)acrylic acid-based resin (A) contains the other monomer (a3), the content of the other monomer (a3) relative to the total amount of the styrene-(meth)acrylic acid-based resin (A) is preferably 0 to 12 mass%, more preferably 0 to 5 mass%, and even more preferably 2 mass% or less.

<Characteristics of styrene-(meth)acrylic acid resin (A)>
The contents of the styrene-based monomer unit (a1), the (meth)acrylic acid monomer unit (a2-1), the (meth)acrylic acid ester monomer unit (a2-2) and the other monomer unit (a3) in the styrene-(meth)acrylic acid-based resin (A) in this embodiment can be quantified using a calibration curve prepared using a resin in which each monomer unit is known, using pyrolysis GC/MS.
The melt flow rate of the styrene-(meth)acrylic acid-based 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 and a load of 49N in accordance with ISO 1133.

The weight average molecular weight (Mw) of the styrene-(meth)acrylic acid-based resin (A) in this embodiment is preferably 100,000 to 400,000, and more preferably 120,000 to 320,000. When the weight average molecular weight is 100,000 to 350,000, a resin having an excellent practical balance between impact strength and fluidity can be obtained.
On the other hand, the number average molecular weight (Mn) of the styrene-(meth)acrylic acid-based resin (A) is preferably in the range of 40,000 to 150,000, more preferably 50,000 to 120,000, and even more preferably 60,000 to 110,000. The weight average molecular weight and the number average molecular weight can be measured by gel permeation chromatography in terms of polystyrene standard.

In this embodiment, the Vicat softening temperature of the styrene-(meth)acrylic acid resin (A) 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-(meth)acrylic 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 easier to knead with the (meth)acrylic resin (B). The Vicat softening temperature in this specification is measured in accordance with ISO 306.

<Method for producing styrene-(meth)acrylic acid-based resin (A)>
The method for producing the styrene-(meth)acrylic acid-based resin (A) of this embodiment will be described below.
The method for producing the styrene-(meth)acrylic acid-based resin (A) of the present embodiment preferably includes a step of mixing a styrene-based monomer (a1), a (meth)acrylic acid monomer (a2-1) and/or a (meth)acrylic acid ester monomer (a2-2) with 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-(meth)acrylic acid-based 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.

In this embodiment, when the polymerization raw materials are polymerized to obtain the styrene-(meth)acrylic acid resin (A), a polymerization initiator is typically contained in the polymerization raw material composition. Examples of the polymerization initiator include organic peroxides, for example, peroxyketals such as 2,2-bis(t-butylperoxy)butane, 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-butylperoxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. From the viewpoint of decomposition rate and polymerization rate, 1,1-bis(t-butylperoxy)cyclohexane is preferred.

In this embodiment, a chain transfer agent can be used as necessary during polymerization of the styrene-(meth)acrylic acid resin (A). Examples of chain transfer agents include α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan.

As a polymerization method for the styrene-(meth)acrylic acid-based 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-(meth)acrylic acid-based resin (A) is adjusted by combining a polar solvent such as an alcohol or a ketone, 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-(meth)acrylic acid-based 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. Adding the polymerization solvent at a ratio of 3 to 35 parts by mass relative to 100 parts by mass of the total monomers is preferable in terms of making the quality uniform and controlling the polymerization temperature.
Furthermore, when the monohydric alcohol having 10 or more carbon atoms, which is an optional component of the styrene-based resin composition of the present embodiment, is added from the polymerization system, it is preferable to add the monohydric alcohol having 10 or more carbon atoms in a ratio of 1 to 10 mass% relative to 100 mass% of the total polymerization solvent.

The apparatus used in the polymerization step for obtaining the styrene-(meth)acrylic 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 together can be used. There is also no particular limitation on the devolatilization step. In the case of bulk polymerization, the polymerization is continued until the unreacted monomer is preferably 50% by mass or less, more preferably 40% by mass or less, and the devolatilization treatment is performed by a known method to remove the volatile matter 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 from the viewpoint of suppressing decomposition, 190 to 260°C is more preferred. The pressure for the devolatilization process 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. Desirable devolatilization methods include, for example, a method of removing volatiles by reducing pressure under heating, and a method of removing volatiles through an extruder or the like designed for the purpose of removing volatiles.

"(Meth)acrylic resin (B)"
The styrene-based resin composition in this embodiment contains 2 to 50 mass% of a (meth)acrylic resin (B) (also simply referred to as resin (B)) relative to the total amount of the styrene-based resin composition. The (meth)acrylic resin (B) has a (meth)acrylic acid ester monomer unit (b1). The inclusion of a predetermined amount of the (meth)acrylic resin (B) contributes to improving the transparency and mechanical strength of the entire styrene-based resin composition.
In this specification, the (meth)acrylic resin (B) is a general term for synthetic resins containing more than 40 mass % of (meth)acrylic acid ester 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.

The content of the (meth)acrylic resin (B) is 1 to 60 mass%, more preferably 6 to 46 mass%, further preferably 10 to 42 mass%, further more preferably 14 to 38 mass%, and most preferably 16 to 35 mass%, based on the total amount (100 mass%) of the styrene-based resin composition. By making the content of the (meth)acrylic resin (B) 10 mass% or more and 40 mass% or less, it is possible to suppress a decrease in the heat resistance improved by the styrene-(meth)acrylic acid-based resin (A).
The unsaturated carboxylic acid monomer unit constituting the (meth)acrylic resin (B) of this embodiment contains a (meth)acrylic acid ester monomer unit (b1), and is preferably a repeating unit containing a (meth)acrylic acid monomer unit (b2) and a (meth)acrylic acid ester monomer unit (b1), or a repeating unit containing two or more types of (meth)acrylic acid ester monomer units (b1), and more preferably contains two or more types of (meth)acrylic acid ester monomer units (b1).
In this embodiment, the upper limit of the total content of the (meth)acrylic acid ester monomer unit (b1) and the (meth)acrylic acid monomer unit (b2) relative to the total amount of the (meth)acrylic resin (B) is preferably 100% by mass or less, 99% by mass or less, 98% by mass or less, 80% by mass or less, 75% by mass or less, and 65% 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, and 10% by mass or more in that order. The total content of the (meth)acrylic acid ester monomer unit (b1) and the (meth)acrylic acid monomer unit (b2) can be arbitrarily combined with the upper limit and the lower limit.
The (meth)acrylic acid ester monomer unit (b1) and the (meth)acrylic acid monomer unit (b2) of this embodiment will be described below.

-(Meth)acrylic acid ester monomer (b1)-
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. Examples of the (meth)acrylic acid ester monomer (b1) include 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, and benzyl methacrylate. Methyl acrylate, n-butyl acrylate, and methyl methacrylate are preferred from the viewpoints of industrial availability and low cost. The (meth)acrylic acid ester monomers (b1) can be used alone or in combination, and it is preferred to use two kinds of (meth)acrylic acid ester monomers in combination.
As a preferred embodiment of the unsaturated carboxylic acid monomer unit 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, it is preferred to contain two kinds of (meth)acrylic acid ester monomers (b1), more preferred is a combination in which a methacrylic acid ester species and an acrylic acid ester species are copolymerized, and even more preferred is a methyl methacrylate-methyl acrylate copolymer.
In this embodiment, the upper limit of the content of the (meth)acrylic acid ester monomer unit (b1) is preferably 100% by mass or less, 99% by mass or less, 98% by mass or less, 80% by mass or less, 75% by mass or less, and 65% by mass or less, in this order, with respect to the total amount of the (meth)acrylic resin (B). 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, and 10% by mass or more, in this order. The content of the (meth)acrylic acid ester monomer unit (b1) can be arbitrarily combined with the above upper limit and the above lower limit. The range of the content of the (meth)acrylic acid ester monomer unit (b1) is, for example, preferably 0 to 100% by mass, more preferably 2 to 99% by mass, even more preferably 3 to 98% by mass, even more preferably 4 to 98% by mass, even more preferably 5 to 98% by mass, and particularly preferably 6 to 98% by mass.

-(Meth)acrylic acid monomer (b2)-
In this embodiment, the (meth)acrylic acid monomer (b2) may be acrylic acid or methacrylic acid.
In this embodiment, the upper limit of the content of the (meth)acrylic acid monomer unit (b2) relative to the total amount of the (meth)acrylic resin (B) is preferably less than 60% by mass, 58% by mass or less, 45% by mass or less, 35% by mass or less, and 25% by mass or less. The lower limit of the content is preferably 0% by mass or more, more than 0% by mass, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 5% by mass or more, and 10% by mass or more. The content of the (meth)acrylic acid monomer unit (b2) can be arbitrarily combined with the above upper limit and the above lower limit.

<Preferred form of (meth)acrylic resin (B)>
A preferred (meth)acrylic resin (B) of this embodiment is preferably a binary or ternary copolymer, and is preferably a methacrylic acid ester-acrylic acid ester copolymer obtained by copolymerizing a methacrylic acid ester species (methacrylic acid ester monomer unit) with an acrylic acid ester species (acrylic acid ester monomer unit), and is preferably a copolymer containing 0.5 to 20% by mass of an acrylic acid ester species relative to the total amount of the methacrylic acid ester-acrylic acid ester copolymer, more preferably a copolymer containing 1.0 to 15% by mass of an acrylic acid ester species, and even more preferably a copolymer containing 1.5 to 14% by mass of an acrylic acid ester species. In addition, the (meth)acrylic resin (B) of this embodiment is more preferably a methyl methacrylate-methyl acrylate copolymer, and is even more preferably a copolymer containing 0.5 to 14% by mass of methyl acrylate relative to the total amount of the copolymer. This makes it possible to more effectively suppress the decrease in heat resistance improved by the styrene-(meth)acrylic acid resin (A).

In the (meth)acrylic resin (B) of this embodiment, the content of the (meth)acrylic acid ester monomer unit (b1) in the (meth)acrylic resin (B) is preferably 40.0 to 100 mass% relative to the total amount of the (meth)acrylic resin (B), more preferably 50.0 to 99.5 mass%, even more preferably 60.0 to 98.5 mass%, and even more preferably 70 to 98.0 mass%. By setting the content of the (meth)acrylic acid ester monomer (b1) in the range of 40.0 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-(meth)acrylic acid resin (A) and the (meth)acrylic resin (B) are mixed. As the type of (meth)acrylic acid ester monomer (b1), methyl acrylate or methyl methacrylate is preferable because of its heat resistance, industrial ease of availability, and low cost.

<Other Monomers (b3)>
The (meth)acrylic resin (B) of this embodiment may further have other monomer units (b3) other than the above-mentioned (meth)acrylic acid monomer units (b2) and (meth)acrylic acid ester monomer units (b1). That is, the other monomers (b3) may be copolymerized with monomers other than the above-mentioned monomers without any particular limitation as long as they are copolymerizable with the (meth)acrylic acid monomer (b2) and/or the (meth)acrylic acid ester monomer (b1) within a range that does not impair the effects of the invention. For example, examples of the other monomers (b3) 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.
In the present embodiment, the content of the other monomer unit (b3) is preferably 0 to 60 mass%, more preferably 0 to 50 mass%, and even more preferably 0 to 40 mass%, relative to the total amount of the (meth)acrylic resin (B).

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, it is possible to impart strength when kneaded with the styrene-(meth)acrylic acid resin (A), and by making the weight average molecular weight (Mw) 1,000,000 or less, it is possible to suppress the viscosity difference with the styrene-(meth)acrylic acid resin (A), to allow the (meth)acrylic resin (B) to be well dispersed in the styrene resin composition, and to suppress the generation of unmelted matter derived from the (meth)acrylic resin (B), and it is possible to obtain molded articles such as foam extrusion sheets with good appearance using the composition.

The styrene-based resin composition of the present embodiment may contain a high molecular weight component of 1 million or more. When the high molecular weight component of 1 million or more is contained, the decrease in heat resistance and rigidity is further suppressed, and the heat oil resistance is further improved. The proportion of the high molecular weight component of 1 million or more 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 having a molecular weight of 1,000,000 or more to 1.0 mass % or less, when radically polymerizing the (meth)acrylic acid ester monomer (b1), control can be performed by adjusting the type and amount of the (meth)acrylic acid ester 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, and the like.
As described above, it is more preferable that the styrene-based resin composition contains a high molecular weight component having a molecular weight of 1,000,000 or more in an amount of 0.0% by mass or more and 1.0% by mass or less based on the total amount of the styrene-based resin composition.

<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 the (meth)acrylic acid ester monomer (b1) 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.

<(Meth)acrylonitrile-diene-styrene resin (C)>
As a preferred aspect of this embodiment, the styrene-based resin composition of this embodiment preferably further contains a (meth)acrylonitrile-diene-styrene-based resin (C) (also simply referred to as resin (C)) containing (meth)acrylonitrile-based monomer units (c3), conjugated diene-based monomer units (c2), and styrene-based monomer units (c1).
When the styrene-based resin composition contains an appropriate amount of the (meth)acrylonitrile-diene-styrene-based resin (C), a styrene-based resin composition capable of forming molded articles having excellent strength can be obtained.
The (meth)acrylonitrile-diene-styrene-based resin (C) in this embodiment refers to a resin obtained by dispersing rubber-like polymer particles (=rubber-like polymer particles (C-2)) mainly composed of conjugated diene-based monomer units (c2) in a polymer matrix (C-1) containing a copolymer obtained by polymerizing (meth)acrylonitrile-based monomer units (c3), a styrene-based monomer (c1), and other monomer components as necessary, and other resins blended as necessary, and may be, for example, a so-called ABS resin.
In other words, the (meth)acrylonitrile-diene-styrene resin (C) of this embodiment contains a polymer matrix (C-1) and rubber-like polymer particles (C-2). The polymer matrix (C-1) contains a copolymer obtained by polymerizing (meth)acrylonitrile-based monomer units (c3), a styrene-based monomer (c1), and other monomer components blended as necessary, and other resins blended as necessary. The rubber-like polymer particles (C-2) are particles of a rubber-like polymer mainly composed of conjugated diene-based monomer units (c2).
In this specification, "mainly composed" means occupying 50% by mass or more of the total. Therefore, for example, a rubber-like polymer particle mainly composed of conjugated diene monomer units (c2) (e.g., butadiene monomer units) means that the conjugated diene monomer units (c2) (e.g., butadiene monomer units) account for 50% by mass or more of the total rubber-like polymer particles (C-2).

Examples of styrene-based monomers (c1) include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, ethylstyrene, p-t-butylstyrene, and vinylnaphthalene. Among these, styrene is preferred from the viewpoint of versatility. The styrene-based monomers (c1) may be used alone or in combination of two or more kinds.

The conjugated diene monomer unit (c2) of this embodiment may be, for example, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, etc., with 1,3-butadiene being preferred from an industrial viewpoint. The conjugated diene monomer unit (c2) may be used alone or in combination of two or more types.

Examples of the (meth)acrylonitrile-based monomer unit (c3) include acrylonitrile units and methacrylonitrile units. Among these, from an industrial viewpoint, acrylonitrile units are preferred. The (meth)acrylonitrile-based monomer unit (c3) may be used alone or in combination of two or more types.

The mass ratio of the (meth)acrylonitrile-based monomer unit (c3) to the styrene-based monomer unit (c1) in the polymer matrix (C-1) constituting the (meth)acrylonitrile-diene-styrene-based resin (C) is preferably (meth)acrylonitrile-based monomer unit (c3)/styrene-based monomer unit (c1) = 5/95 to 40/60, more preferably 10/90 to 35/65, more preferably 15/85 to 30/70, and most preferably 20/80 to 25/75. In particular, by setting the mass ratio in the range of 20/80 to 30/70, the compatibility with the (meth)acrylic resin (B) is excellent, and the mechanical strength improving effect is increased when added to a styrene-based resin composition.

The content of the rubber-like polymer particles (C-2) mainly composed of the conjugated diene monomer unit (c2) constituting the (meth)acrylonitrile-diene-styrene resin (C) is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, and even more preferably 15 to 30% by mass, based on the total amount of the (meth)acrylonitrile-diene-styrene resin (C). By setting the content of the rubber-like polymer particles (C-2) in the range of 5 to 40% by mass, an excellent balance between rigidity and impact resistance is achieved when added to a styrene resin composition.

The average particle size of the rubber-like polymer particles (C-2) of the (meth)acrylonitrile-diene-styrene-based resin (C) is preferably in the range of 0.10 to 1.00 μm, more preferably 0.13 to 0.90 μm, even more preferably 0.16 to 0.70 μm, and even more preferably 0.20 to 0.50 μm. In particular, by making the average particle size in the range of 0.20 to 0.50 μm, the styrene-based resin composition is excellent in the effect of improving the impact resistance.
In the present disclosure, the average particle size is measured from a cross-sectional observation image taken with a transmission electron microscope, as described later in the Examples section.
In addition, a preferred embodiment of the rubber-like polymer particle (C-2) may have a structure in which a solid rubber-like particle having conjugated diene monomer units (c2) as a constituent component is used as a core, and the core is coated with a polymer containing styrene monomer units (c1) and (meth)acrylonitrile monomer units (c3) so as to cover the core.

The (meth)acrylonitrile-diene-styrene resin (C) can be produced by polymerizing and compounding a resin that is the main component of the polymer matrix (C-1), which has been prepared in advance by radical bulk polymerization or solution polymerization, with ABS rubber-like polymer particles (C-2), which have been prepared by graft polymerization with rubber latex, or by simultaneously preparing the rubber-like polymer particles (C-2) and the polymer matrix (C-1), as in the case of the impact-resistant styrene resin (E) described below. The most suitable method can be selected according to need.

The polymer matrix (C-1) of the (meth)acrylonitrile-diene-styrene resin (C) may contain, in addition to the copolymer mainly composed of (meth)acrylonitrile monomer units (c3) and styrene monomers (c1), other polymers in an amount of 25% by mass or less based on the total amount of the (meth)acrylonitrile-diene-styrene resin (C). For example, the heat resistance of the (meth)acrylonitrile-diene-styrene resin (C) may be improved by adding a styrene-acrylonitrile-N-phenylmaleimide copolymer.

In this embodiment, the melt flow rate of the (meth)acrylonitrile-diene-styrene resin (C) at 200°C is preferably 0.2 to 7.0 g/10 min, more preferably 0.3 to 6.0 g/10 min, and even more preferably 0.4 to 5.0 g/10 min. If the melt flow rate is in the range of 0.2 to 7.0 g/10 min, the resin has good mixability with the styrene-(meth)acrylic acid resin (A) and the (meth)acrylic resin (B), and also has good mechanical strength. In this disclosure, the melt flow rate is a value measured at 200°C and a load of 49 N in accordance with ISO 1133.

<Core-shell type rubber polymer particles (D)>
As a preferred aspect of this embodiment, the styrene-based resin composition of this embodiment preferably further contains core-shell type rubbery polymer particles (D) (also simply referred to as core-shell particles (D)) obtained by grafting a copolymer mainly composed of (meth)acrylic acid ester monomer units (d2) to rubbery particles containing conjugated diene monomer units (d1).
The core-shell type rubbery polymer particles (D) of this embodiment have a structure in which a rubbery particle containing a conjugated diene monomer unit (d1) serves as a core, and the core is at least partially coated with a copolymer mainly composed of a (meth)acrylic acid ester monomer unit (d2).

The content of the core-shell type rubbery polymer particles (D) is preferably 1 to 45 mass% based on the total amount of the styrene-based resin composition, more preferably 2 to 40 mass%, even more preferably 3 to 35 mass%, still more preferably 4 to 30 mass%, and most preferably 5 to 25 mass%. By making it 1 mass% or more, it is possible to improve the mechanical strength and low-temperature impact resistance, and by making it 25 mass% or less, it is possible to prevent a decrease in heat resistance and rigidity.
The conjugated diene monomer (d1) constituting the core-shell type rubber-like polymer particles (D) is a diolefin having a pair of conjugated double bonds, 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 (meth)acrylic acid ester monomer unit (d2) constituting the core-shell type rubber-like polymer particle (D) includes a methacrylic acid ester monomer unit and an acrylic acid ester monomer unit. Examples of the (meth)acrylic acid ester monomer unit include 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), and benzyl methacrylate. Of these, methyl acrylate, (n-butyl acrylate), and methyl methacrylate are preferred from the viewpoints of industrial availability and low cost.

The content of the conjugated diene monomer unit (d1) in the core-shell type rubbery polymer particle (D) is preferably 30 to 90% by mass, more preferably 40 to 85% by mass, even more preferably 50 to 80% by mass, and even more preferably 55 to 75% by mass. The higher the content of the conjugated diene monomer unit (d1), the greater the improvement in mechanical strength with a small amount added, which is preferable. On the other hand, if the content of the conjugated diene monomer unit (d1) is too high, the content of the graft copolymer mainly composed of (meth)acrylic acid ester monomer unit (d2) decreases, and the compatibility with the styrene-(meth)acrylic acid resin (A) decreases, causing a decrease in the effect of improving the mechanical strength.

The content of the (meth)acrylic acid ester monomer unit (d2) in the core-shell type rubbery polymer particle (D) is preferably 10 to 40% by mass, more preferably 12 to 35% by mass, and even more preferably 15 to 25% by mass. By making the content of the (meth)acrylic acid methyl monomer (d1) in the range of 20 to 70% by mass, it is possible to ensure compatibility with the matrix polymer portion constituting the styrene-based resin composition of this embodiment, and the effect of improving the mechanical strength can be efficiently obtained. The matrix polymer portion essentially contains the resin (A) and the resin (B), and contains one or more optional components selected from the group consisting of the polymer matrix (C-1), the polymer matrix (E-1), the styrene-based elastomer (F), the acrylic elastomer (G), the monohydric alcohol having 10 or more carbon atoms, and the optional added component. In other words, the matrix polymer portion refers to components other than the various rubbery polymer particles and the inorganic particles (H) contained in the styrene-based resin composition.
The various rubber-like polymer particles include rubber-like polymer particles (C-2), core-shell type rubber-like polymer particles (D) and rubber-like polymer particles (E-2).

<Particle size of core-shell type rubber polymer particles (D)>
The average particle size of the core-shell type rubbery polymer particles (D) is preferably 0.05 to 0.35 μm, more preferably 0.080 to 0.30 μm, even more preferably 0.10 to 0.25 μm, and still more preferably 0.15 to 0.23 μm. In particular, by making the particle size within the range of 0.15 to 23 μm, the effect of imparting strength to the styrene-based resin composition is excellent.
In the present disclosure, the average particle size is measured from a cross-sectional observation image taken with a transmission electron microscope, as described later in the Examples section.

<Method for producing core-shell type rubbery polymer particles (D)>
As a method for producing the core-shell type rubber-like polymer particles (D), an emulsion polymerization method is preferred in which conjugated diene rubber latex (e.g., butadiene rubber latex) particles are produced and then copolymerized with a (meth)acrylic acid ester monomer (d2).

<Impact-resistant styrene-based resin (E)>
In a preferred embodiment of the present invention, the styrene resin composition preferably contains an impact-resistant styrene resin (E) (also simply referred to as resin (E)). By containing an appropriate amount of the rubber-modified styrene resin (E), a styrene resin composition capable of producing a molded article having excellent strength can be obtained.
The rubber-modified styrene-based resin (E) of this embodiment may be a so-called high impact polystyrene resin (HIPS resin) obtained by dispersing particles of a rubber-like polymer (E-2) (=rubber-like polymer particles (E-2)) in a polymer matrix (E-1) of a resin consisting of a styrene-based monomer (e1) and, if necessary, other monomers (e3), and polymerizing the styrene-based monomer (e1) in the presence of the rubber-like polymer (E-2). In other words, the impact-resistant styrene-based resin (E) of this embodiment contains a polymer matrix (E-1) and rubber-like polymer particles (E-2). The polymer matrix (E-1) contains a polymer obtained by polymerizing the styrene-based monomer (e1) and, if necessary, other monomers (e3) blended. The rubber-like polymer particles (E-2) are particles of a rubber-like polymer (E-2) mainly composed of conjugated diene monomer units (e2), and the surfaces of the particles may be grafted with a polymer containing styrene monomer units (e1) as necessary.

The content of the impact-resistant styrene resin (E) in the styrene composition of this embodiment is preferably 0.5 to 30 mass %, more preferably 2 to 20 mass %, and even more preferably 3 to 15 mass %, based on the total amount of the styrene resin composition. By setting the content of the impact-resistant styrene resin (E) in the range of 3 to 15 mass %, a styrene resin composition with superior strength can be obtained.

-Rubber polymer particles (E-2)-
In this embodiment, the rubber-like polymer (E-2) constituting the rubber-like polymer particles (E-2) in the impact-resistant styrene-based resin (E) is preferably formed from a conjugated diene-based monomer (e2), and more preferably is a polymer having a conjugated diene-based monomer unit (e2). Specific examples of the rubber-like polymer (E-2) include polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, and acrylonitrile-butadiene copolymer, but from an industrial point of view, 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 can be used. 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 can also be used.
In the present specification, the term "conjugated diene monomer" is a general term for the above-mentioned conjugated diene monomer (c2), conjugated diene monomer (d1), conjugated diene monomer (e2) and conjugated diene monomer (f2). In addition, in the present specification, the term "rubber-like polymer particles" is a general term for the rubber-like polymer particles (C-2), rubber-like polymer particles (D) and rubber-like polymer particles (E-2).
The conjugated diene monomer is 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.
In the present embodiment, the rubber-like polymer particles (E-2) preferably contain a polymer containing a styrene-based monomer unit (e1) or a polymer containing the styrene-based monomer unit (e1) and another monomer (e3) in the dispersed particles of the rubber-like polymer (E-2). The form of the inclusion is preferably a so-called salami structure type dispersed particle in which a plurality of domain phases of a polymer having a styrene-based monomer unit (e1) are contained in the rubber-like polymer (E-2). Furthermore, a polymer containing a styrene-based monomer unit (e1) or a polymer containing the styrene-based monomer unit (e1) and another monomer (e3) may be grafted to the surface of the rubber-like polymer particle (E-2).

-Other monomers (e3)-
Examples of the other monomer (unit) (e3) which is an optional component of the impact resistant styrene-based resin (E) 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) (e3) in the impact resistant styrene-based resin (E) is preferably 70 mass% or less, and more preferably 60 mass% or less, based on the total amount of the impact resistant styrene-based resin (E).

<Content of conjugated diene monomer unit (e2)>
In this embodiment, the content of the conjugated diene monomer unit (e2) in the impact resistant styrene resin (E) 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 impact resistant styrene resin (E). The content of the conjugated diene monomer unit (e2) in the impact resistant styrene resin (E) and the styrene resin composition can be measured by the procedure described in the Examples section below, or a method equivalent thereto.

<Average particle size of rubber-like polymer particles (E-2)>
The rubber-like polymer (E-2) which is the rubber component in the impact-resistant styrene-based resin (E) in this embodiment is present as particles of the rubber-like polymer (E-2) (=rubber-like polymer particles (E-2)) in the styrene-based resin composition. In this case, the average particle size of the rubber-like polymer particles (E-2) 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 impact-resistant styrene-based resin (E) is obtained by polymerizing a styrene-based monomer (e1) in a reactor equipped with a stirrer in the presence of the rubber-like polymer particles (E-2), and the average particle size of the rubber-like polymer particles (E-2) can be adjusted by the number of revolutions of the stirrer, the molecular weight of the rubber-like polymer (E-2) used, and the like. In the present disclosure, the average particle size of the rubber-like polymer particles (E-2) is a value measured from a cross-sectional observation image by a transmission electron microscope, as shown in the Examples section described later. The rubber-like polymer particles (E-2) are stretched during foaming in the foamed sheet described below, and the particle size increases by about 150 to 400%.

In this embodiment, the melt flow rate of the impact resistant styrene resin (E) at 200°C is preferably 0.5 to 10.0 g/10 min, more preferably 0.7 to 8.0 g/10 min, and even more preferably 1.0 to 7.0 g/10 min. If the melt flow rate is in the range of 0.5 to 10.0 g/10 min, the resin has good mixability with the styrene-(meth)acrylic acid resin (A) and the (meth)acrylic resin (B), and also has good mechanical strength. In this disclosure, the melt flow rate is a value measured at 200°C and a load of 49 N in accordance with ISO 1133.

<Method for producing impact resistant styrene-based resin (E)>
The method for producing the impact-resistant styrene-based resin (E) is not particularly limited, but it can be produced by bulk polymerization (or solution polymerization) in which a styrene-based monomer (e1) and, if necessary, other monomers (e3) and a solvent are polymerized in the presence of a rubber-like polymer (E-2), bulk-suspension polymerization that transitions to suspension polymerization during the reaction, or emulsion graft polymerization in which a styrene-based monomer (e1) is polymerized in the presence of latex particles that are a rubber-like polymer (E-2). In bulk polymerization, the rubber-like polymer (E-2), the styrene-based monomer (e1), and, if necessary, other monomers (e3), an organic solvent, an organic peroxide, and/or a chain transfer agent are added to a mixed solution, which can be produced by continuously supplying a completely mixed reactor or a tank reactor and a polymerization apparatus configured by connecting multiple tank reactors in series.

<Styrene-based elastomer (F)>
In a preferred embodiment of this embodiment, the styrene-based resin composition further contains a styrene-based elastomer (F) (also simply referred to as elastomer (F)). The styrene-based elastomer (F) used in the styrene-based resin composition of the present invention is a block copolymer having a hard block of a styrene-based monomer (unit) (f1) and a soft block of a conjugated diene-based monomer (unit) (f2). As the elastomer (F), a block copolymer having a hard block of a styrene-based monomer (unit) (f1) and a soft block of a butadiene monomer unit is more preferred.
The styrene monomer (f1) may be the same as the styrene monomer (a1) described above. The conjugated diene monomer (f2) may be the same as the conjugated diene monomer (c2) described above.

The chain structure of the block copolymer of the styrene-based elastomer (F) includes a styrene-based monomer (f1)-butadiene diblock type, a styrene-based monomer (f1)-butadiene-styrene-based monomer (f1) triblock type, and a butadiene-styrene-based monomer (f1)-butadiene triblock type, among others. From the viewpoint of improving mechanical strength, the styrene-based monomer (f1)-butadiene-styrene-based monomer (f1) triblock type is preferred.

Regarding the contents of the styrene monomer units (f1) and the conjugated diene monomer units (f2) constituting the styrene elastomer (F), the content of the styrene monomer units (f1) is preferably 30 to 70 mass%, more preferably the content of the styrene monomer units (f1) is 35 to 65 mass%, and the content of the conjugated diene monomer units (f2) is the remainder of 100 mass%. If the content of the styrene monomer units (f1) is 35 to 65%, the dispersibility in the styrene-(meth)acrylic acid resin (A) is appropriately improved, and a product excellent in mechanical strength and appearance can be obtained.
The styrene-based elastomer (F) such as a styrene-butadiene elastomer may be produced by a radical polymerization method, an anionic polymerization method, or a polymer reaction method, with the anionic polymerization method being preferred from an industrial viewpoint.

When the content of the conjugated diene monomer (f2) in the styrene-based elastomer (F) exceeds 50% by mass, the content of the styrene-based elastomer (F) in the styrene-based composition of this embodiment is preferably 0.5 to 15% by mass, more preferably 1 to 12% by mass, and even more preferably 2 to 7% by mass, based on the total amount of the styrene-based resin composition. On the other hand, when the content of the conjugated diene monomer unit (f2) in the styrene-based elastomer (F) is 50% by mass or less, the content of the styrene-based elastomer (F) in the styrene-based composition is preferably 3 to 30% by mass, more preferably 5 to 20% by mass, and even more preferably 7 to 15% by mass, based on the total amount of the styrene-based resin composition. By setting it in the above range, it is possible to suppress the decrease in heat resistance and improve mechanical strength when added to a styrene-based resin composition.

<Acrylic Elastomer (G)>
In a preferred embodiment of this embodiment, the styrene-based resin composition preferably contains an acrylic elastomer (G) (also simply referred to as elastomer (G)). The acrylic elastomer (G) used in the resin composition of the present invention is a block copolymer having a hard block of methyl methacrylate monomer units (g1) and a soft block of acrylic ester monomer units (g2). As the acrylic elastomer (G), a block copolymer having a hard block of methyl methacrylate monomer (unit) and a soft block of acrylic ester monomer units (g2) is more preferred.
Thus, the acrylic elastomer (G) is a block copolymer, whereas the (meth)acrylic resin (B) is a random polymer or an alternating polymer, and thus the two are different from each other.
Examples of the acrylic acid ester monomer (g2) include the same monomers as the acrylic acid ester monomer units of the (meth)acrylic acid ester monomer units (b1).

Examples of the chain structure of the block copolymer of the acrylic elastomer (G) include methyl methacrylate-acrylic acid ester (g2) block type, methyl methacrylate-acrylic acid ester (g2)-methyl methacrylate triblock type, and acrylic acid ester (g2)-methyl methacrylate-acrylic acid ester (g2) triblock type, but from the viewpoint of improving mechanical strength, the methyl methacrylate-acrylic acid ester (g2)-methyl methacrylate triblock type is preferred.

As for the content of the methyl methacrylate monomer (g1) and the acrylic acid ester monomer (g2) constituting the acrylic elastomer (G), the content of the methyl methacrylate monomer (g1) is preferably 20 to 65 mass%, more preferably 30 to 55 mass%. On the other hand, the content of the acrylic acid ester monomer (g2) is the remainder of 100 mass%. If the content of the methyl methacrylate monomer (g1) is 20 to 65%, the dispersibility in the styrene-(meth)acrylic acid resin (A) is appropriately improved, and a product with excellent mechanical strength and appearance can be obtained.

The content of the acrylic elastomer (G) in the styrene-based composition of this embodiment is preferably 0.5 to 20% by mass, more preferably 1 to 17% by mass, and even more preferably 2 to 15% by mass, relative to the total amount of the styrene-based resin composition. By setting the content in the range of 0.5 to 20% by mass, it is possible to suppress a decrease in heat resistance and improve mechanical strength when added to a styrene-based resin composition.

<Inorganic particles (H)>
In a preferred embodiment of the present invention, the styrene-based resin composition preferably contains inorganic particles (H). By adding the inorganic particles (H) to the styrene-based resin composition, the inorganic particles (H) serve as a foam nucleating agent during foam molding and contribute to improving the rigidity of a molded article including the composition and a foam sheet.

Examples of inorganic particles (H) that can be used include kaolin, mica, silica, calcium carbonate, sodium carbonate, barium carbonate, barium sulfate, calcium sulfate, titanium oxide, aluminum oxide, clay, bentonite, talc, and diatomaceous earth. Among these, talc is preferred because it has a long history of use in food packaging applications and its safety is guaranteed.

The content of the inorganic particles (H) is preferably 0.1 to 7.0 parts by mass, more preferably 0.2 to 6.0 parts by mass, and even more preferably 0.3 to 4.0 parts by mass, when the total amount of the styrene-based resin composition is taken as 100% by mass. By setting the content in the range of 0.1 to 7.0 parts by mass, a sheet with an expansion ratio suitable for a foam sheet for food packaging can be obtained.

There are no particular limitations on the method of adding the inorganic particles (H) to the styrene-based resin composition, but they may be blended directly into the styrene-based resin composition when it is extruded and kneaded, or, for ease of industrial production, a resin master batch containing a known high concentration of inorganic fine particles (H) may be prepared in advance and then added.

"Monohydric alcohol with 10 or more carbon atoms"
In this embodiment, the monohydric alcohol having 10 or more carbon atoms (hereinafter also simply referred to as alcohol) is an optional component, which suppresses gelation of the styrene-(meth)acrylic acid-based resin (A) during molding, and contributes to improving the appearance of the styrene-based resin composition and the molded article made of the styrene-based resin composition having a good appearance. The content of the monohydric alcohol having 10 or more carbon atoms is 0.01 to 1.0 mass%, preferably 0.03 to 0.8 mass%, more preferably 0.05 to 0.6 mass%, and even more preferably 0.07 to 0.5 mass%, relative to the total amount (100 mass%) of the styrene-based resin composition. By making the content of the monohydric alcohol having 10 or more carbon atoms 0.01 mass% or more, it is possible to suppress gelation of the styrene-(meth)acrylic acid-based resin (A) during molding processing, and by making it 1.0 mass% or less, it is possible to suppress the decrease in heat resistance and the generation of odor. By making the content of the monohydric alcohol having 10 or more carbon atoms 0.07 to 0.5 mass%, a sufficient gel suppression effect can be obtained without particularly decreasing heat resistance.

The monohydric alcohol having 10 or more carbon atoms is an alcohol having 10 or more carbon atoms and containing one hydroxyl group, and may contain heteroatoms such as oxygen or nitrogen in the carbon chain constituting the alcohol, and may contain bonds other than single bonds, such as double bonds, triple bonds, ester bonds, and amide bonds 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 having 10 or more carbon atoms may be contained in a styrene-based resin composition or a molded product made of a styrene-based resin composition. Therefore, by making a monohydric alcohol having 10 or more carbon atoms present (or added) in the polymerization solution used for polymerizing the styrene-(meth)acrylic acid-based resin (A) or the (meth)acrylic resin (B), the monohydric alcohol may remain in the resin composition, which is the final product, or may be added when kneading the styrene-(meth)acrylic acid-based resin (A) and the (meth)acrylic resin (B) and mixed in an extruder to contain the monohydric alcohol.

In this embodiment, the boiling point of the monohydric alcohol 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 less than 260°C, it becomes highly volatile and tends to generate an unpleasant odor during molding, etc.

The monohydric alcohol 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, polyoxyethylene alkyl ethers, etc.

（上記一般式（２）中、Ｒは炭素原子数１２～２０のアルキル基であり、Ｘはエチレンオキサイドの平均付加数を表し、１～１５の整数である。）
好ましいアルコールの具体的な製品名としては日産化学社製「ファインオキソコール１８０」や花王社製「エマルゲン１０９Ｐ」等が挙げられる。 The polyoxyethylene alkyl ether is preferably a compound represented by the following general formula (2).

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

"Liquid paraffin"
In a preferred aspect of this embodiment, the styrene resin composition further contains liquid paraffin. The styrene resin composition containing liquid paraffin exhibits an effect of improving flowability, an effect of improving the strength of the resin composition and the sheet molding, and an effect of reducing cracks during winding.
The content of liquid paraffin in the styrene-based resin composition of the present embodiment is preferably 0.05 to 1.5 parts by mass, more preferably 0.10 to 1.0 parts by mass, and even more preferably 0.30 to 0.7 parts by mass, based on 100 parts by mass of the styrene-(meth)acrylic acid-based resin (A). If it is 0.05 parts by mass or less, the effect of improving fluidity cannot be obtained, and if it is 1.5 parts by mass or more, the heat resistance is reduced.

The liquid paraffin used in the present embodiment may be called white mineral oil, mineral oil, MO, white mineral oil, etc. in addition to liquid paraffin, depending on the degree of refinement and commercial practice.
The liquid paraffin used in this embodiment is preferably one having a naphthene component ratio of 20% or more, more preferably 30% or more, as determined by the n-d-M ring analysis method, since it has excellent compatibility with the styrene-(meth)acrylic acid resin (A). The n-d-M ring analysis method is a composition test method for high-boiling petroleum fractions, and is a method (ASTM D3238) for determining the aromatic ring ratio (%Ca), naphthene ring ratio (%Cn), and paraffin chain ratio (%Cp) in the oil by determining the refractive index (n), density (d), and molecular weight (M). From the viewpoint of the color of the product, the polycyclic aromatic component in the white mineral oil must be 3% or less, and is preferably 0.5% or less. In liquid paraffin, the aromatic ring is usually 0%.

It is effective to have a small amount of low boiling point components in liquid paraffin in order to avoid problems with volatile matters during extrusion molding. It is preferable that the 5% distillation temperature is 400° C. or higher as a value converted to normal pressure from the reduced pressure distillation method or gas chromatography method of JIS K2254.
The kinetic viscosity of the liquid paraffin is preferably in a range in which the above-mentioned low boiling point components are small, the Vicat softening temperature is effectively lowered, and handling is easy. The range of 40 mm2/s to 120 ^mm2 /s at 40°C is preferably, and more preferably, 60 to 80 mm2/s.

The method of adding liquid paraffin is not particularly limited, and examples thereof include a method of adding liquid paraffin (E) in the polymerization step, a method of kneading using a known kneader such as a single screw extruder, a twin screw extruder, a Banbury mixer, etc. It is particularly preferable to add liquid paraffin during the production of styrene copolymer (A) since this improves dispersibility.
The quantity and identification of liquid paraffin in this embodiment can be easily confirmed by a person skilled in the art using a general method.
For example, a solution is prepared by dissolving a fragment of a styrene-based resin composition or a molded article of the composition in a solvent that dissolves a matrix resin, such as tetrahydrofuran. Then, while stirring this solution with a stirrer, n-hexane is added dropwise in small amounts to precipitate the matrix resin and the rubber-like polymer. Thereafter, the filtrate is filtered through a glass filter, evaporated to dryness, and then adjusted to a constant volume with n-hexane. After passing through a polytetrafluoroethylene membrane filter, the mixture is separated by liquid chromatography to calculate the content of liquid paraffin in the composition or molded article. In addition, the liquid paraffin can be analyzed by various analytical devices such as pyrolysis GC-MS, ¹ H-NMR, or ¹³ C-NMR to perform identification, quantification, and molecular weight measurement.

"Optional addition ingredients"
In addition to the above components (A) to (H) and the monohydric alcohol having 10 or more carbon atoms, the styrene-based resin composition of this embodiment may also be prepared by blending various optional components generally used in styrene-based resins to achieve known effects. Examples of the optional components of this embodiment include stabilizers, higher fatty acid surfactants, antioxidants, ultraviolet absorbers, lubricants, release agents, plasticizers, antiblocking agents, antistatic agents, antifogging agents, and mineral oils. There are no particular restrictions on the blending method, but examples include a method of adding the additives during polymerization and polymerizing them, or a method of mixing the additives in a blender before melt-kneading after polymerization, and then melt-kneading them with an extruder or Banbury mixer.

Examples of the antioxidant include hindered phenol-based antioxidants such as octadecyl-3-(3,5-tertiary-butyl-4-hydroxyphenyl)propionate and 4,6-bis(octylthiomethyl)-o-cresol (product Irganox 1076), and phosphorus-based antioxidants such as tris(2,4-di-tertiary-butylphenyl)phosphite (product Irgafos 176). These stabilizers may be used alone or in combination of two or more. There is no particular restriction on the timing of addition, and it may be during either the polymerization process or the devolatilization process. The stabilizer may also be mixed into the product using a mechanical device such as an extruder or Banbury mixer.

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 foamed sheet, but also contributes to torque reduction between pellets and metering stability during kneading of the resin composition by adding an appropriate amount of the higher fatty acid surfactant. 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 higher fatty acid surfactant from contributing as a gelling agent for the styrene-(meth)acrylic acid resin (A).
The higher fatty acid surfactant may be added during polymerization of each resin, or may be additionally kneaded when the styrene-(meth)acrylic acid resin (A) and the (meth)acrylic resin (B) are kneaded together.

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

[High molecular weight component of 1 million or more]
The styrene-based resin composition of the present embodiment contains the resin (A) and the resin (B), and may contain, as necessary, one or more selected from the group consisting of a (meth)acrylonitrile-diene-styrene-based resin (C), a core-shell type rubbery polymer particle (D), an impact-resistant styrene-based resin (E), a styrene-based elastomer (F), an acrylic elastomer (G), inorganic particles (H), a monohydric alcohol having 10 or more carbon atoms, and an optional added component. The styrene-based resin composition of the present embodiment essentially contains the resin (A) and the resin (B), and also contains a matrix polymer portion, which is an optional component, and various rubbery polymer particles. The matrix polymer portion contains one or more selected from the group consisting of a polymer matrix (C-1), a polymer matrix (E-1), a styrene-based elastomer (F), an acrylic elastomer (G), a monohydric alcohol having 10 or more carbon atoms, and an optional added component. The various rubber-like polymer particles include one or more selected from the group consisting of rubber-like polymer particles (C-2), core-shell type rubber-like polymer particles (D) and rubber-like polymer particles (E-2).
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, more preferably 0.9 mass% or less, even more preferably 0.8 mass% or less, still more preferably 0.7 mass% or less, and most preferably 0.6 mass% or less, based on the total amount of the styrene-based resin composition.
By controlling the content of the high molecular weight component having a molecular weight of 1,000,000 or more to 1.0 mass % or less, the occurrence of unmelted defects is reduced, and a composition having an excellent balance of thin-wall moldability and strength can be obtained.
As will be explained in the Examples section below, the high molecular weight component of 100 or more is the weight percentage of molecular weights of 1 million or more before calculating the various average molecular weights obtained from GPC.

The styrene-based resin composition of the present embodiment contains resin (A) and resin (B), and the total content of resin (A) and resin (B) is preferably 65 to 100 mass%, more preferably 75 to 95 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), and optional additional components, and the total content of resin (A), resin (B), and optional additional components is preferably 70 to 100 mass%, and more preferably 80 to 95 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment contains resin (A), resin (B), and resin (C), and the total content of resin (A), resin (B), and resin (C) is preferably 70 to 100 mass%, and more preferably 80 to 90 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), resin (C), and optional additional components, and the total content of resin (A), resin (B), resin (C), and optional additional components preferably accounts for 85 to 100 mass%, and more preferably 90 to 95 mass%, of the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), and rubber-like polymer particles (D), and the total content of resin (A), resin (B), and rubber-like polymer particles (D) is preferably 70 to 100 mass%, more preferably 75 to 95 mass%, and even more preferably 80 to 90 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), rubber-like polymer particles (D), and optional additional components, and the total content of resin (A), resin (B), rubber-like polymer particles (D), and optional additional components is preferably 80 to 100 mass%, more preferably 85 to 97 mass%, and even more preferably 90 to 95 mass%, based on the entire styrene-based resin composition.
In particular, when emphasis is placed on improving the Charpy impact strength of the injection-molded article, the styrene-based resin composition preferably contains 70 to 100 mass % or more of the resin (A), the resin (B), and the rubber-like polymer particles (D) relative to the styrene-based resin composition.
The styrene-based resin composition of the present embodiment contains resin (A), resin (B), and resin (E), and the total content of resin (A), resin (B), and resin (E) is preferably 70 to 100 mass%, and more preferably 80 to 90 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), resin (E), and optional additional components, and the total content of resin (A), resin (B), resin (E), and optional additional components preferably accounts for 85 to 100 mass%, and more preferably 90 to 95 mass%, of the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment contains resin (A), resin (B), and elastomer (F), and the total content of resin (A), resin (B), and elastomer (F) is preferably 70 to 100 mass%, and more preferably 80 to 90 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), elastomer (F), and optional additional components, and the total content of resin (A), resin (B), elastomer (F), and optional additional components preferably accounts for 85 to 100 mass%, and more preferably 90 to 95 mass%, of the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment contains resin (A), resin (B), and elastomer (G), and the total content of resin (A), resin (B), and elastomer (G) is preferably 70 to 100 mass%, and more preferably 80 to 90 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), elastomer (G), and optional additional components, and the total content of resin (A), resin (B), elastomer (G), and optional additional components preferably accounts for 85 to 100 mass%, and more preferably 90 to 95 mass%, of the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment contains the resin (A), the resin (B), and the inorganic particles (H), and the total content of the resin (A), the resin (B), and the inorganic particles (H) is preferably 60 to 100 mass%, and more preferably 75 to 98 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), inorganic particles (H), and optional additional components, and the total content of resin (A), resin (B), inorganic particles (H), and optional additional components is preferably 75 to 100 mass%, and more preferably 80 to 98 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment contains resin (A), resin (B), resin (E), and elastomer (F), and the total content of resin (A), resin (B), resin (E), and elastomer (F) is preferably 70 to 100 mass%, and more preferably 85 to 90 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), resin (E), elastomer (F), and optional additional components, and the total content of resin (A), resin (B), resin (E), elastomer (F), and optional additional components preferably accounts for 85 to 100 mass%, and more preferably 90 to 95 mass%, of the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment contains resin (A), resin (B), resin (C), and elastomer (G), and the total content of resin (A), resin (B), resin (C), and elastomer (G) is preferably 70 to 100 mass%, more preferably 75 to 95 mass%, and even more preferably 80 to 90 mass%, based on the entire styrene-based resin composition.
The styrene-based resin composition of the present embodiment has resin (A), resin (B), resin (C), elastomer (G), and optional additional components, and the total content of resin (A), resin (B), resin (C), elastomer (G), and optional additional components preferably accounts for 80 to 100 mass%, more preferably 85 to 97 mass%, and even more preferably 90 to 95 mass%, of the entire styrene-based resin composition.
When the styrene-based resin composition contains the resin (A), the resin (B), the resin (C), and the elastomer (G), and the total content of the resin (A), the resin (B), the resin (C), and the elastomer (G) is 70 to 100 mass% based on the entire styrene-based resin composition, it is possible to obtain a styrene-based resin composition having an excellent balance between low-temperature impact strength and rigidity.

[Physical properties and characteristics of styrene-based resin composition]
The physical properties and characteristics of the styrene-based resin composition of the present 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 109° C. or higher, and even more preferably 112° C. or higher. By setting the Vicat softening temperature at 105° C. or higher, a sheet or container applicable to cooking in a general microwave oven of about 500 W can be obtained, and by setting the Vicat softening temperature at 112° C. or higher, it can withstand cooking in a high-power commercial microwave oven of 1000 W or higher that is placed in a convenience store, etc. 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.

<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 0.4 to 1.0 g/10 min. By making the melt flow rate 0.3 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.

<Content of conjugated diene monomer units>
In this embodiment, the content of the conjugated diene monomer unit contained in the styrene-based resin composition is preferably 0 to 10 mass %, more preferably 0.3 to 5.0 mass %, even more preferably 0.5 to 4.8 mass %, and most preferably in the range of 0.6 to 4.0 mass %, based on the entire styrene-based resin composition. By setting the content of the conjugated diene monomer unit in the range of 0.6 to 4.0 mass %, it is possible to obtain a composition having an excellent balance between low-temperature impact strength and rigidity, and a molded article, sheet, or container obtained by molding the composition.
As described above, the conjugated diene monomer unit is a general term for the conjugated diene monomer (c2), the conjugated diene monomer (d1), the conjugated diene monomer (e2) and the conjugated diene monomer (f2).

<(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 2 to 20 mass%, more preferably 3 to 15 mass%, more preferably 4 to 10 mass%, and even more preferably 5 to 8 mass%, relative to 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 sum of all (meth)acrylic acid monomer units present in the styrene-based resin composition, and therefore includes the respective contents of (meth)acrylic acid monomer units in the resin (A), the resin (B) and other components (the resin (C), the rubber-like polymer particles (D), the resin (E), the elastomer (G) and any additional components).

In this embodiment, the content of all (meth)acrylic acid ester monomer units contained in the styrene-based resin composition is preferably 6 to 55 mass% relative to the total amount (100 mass%) of the styrene-based resin composition, preferably 10 to 50 mass%, more preferably 14 to 45 mass%, and even more preferably 16 to 40 mass%. When the content of the (meth)acrylic acid ester monomers in the entire composition is within the above range, the oil resistance required for improving the hot oil resistance and the effect of improving the mechanical strength can be sufficiently obtained.
The above-mentioned total (meth)acrylic acid ester monomer content indicates the total amount of all (meth)acrylic acid ester monomer units present in the styrene-based resin composition, and therefore each content of the (meth)acrylic acid ester monomer units in the resin (A), the resin (B) and other components (the resin (C), the rubber-like polymer particles (D), the resin (E), the elastomer (G) and any optional added components) is also converted into this content.

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 heat resistance improving effect of the (meth)acrylic acid monomer units and the oil resistance improving effect of the (meth)acrylic acid ester monomer units can be simultaneously and efficiently obtained, and as a result, a styrene-based resin composition with excellent heat and oil resistance and a foamed sheet and container molded from the same can be obtained.

<Content of styrene-based component in styrene-based resin composition>
The styrene-based resin composition in the present embodiment contains a styrene-based component. The styrene-based component here refers to a collective term for the styrene-based monomer (unit) (a1) and the styrene-based monomer (unit) that may be contained in other components (resin (B), resin (C), rubber-like polymer particles (D), resin (E), elastomer (F), and optional added components).
In the styrene-based resin composition in the present embodiment, the content of the styrene-based component (total styrene-based monomers (units)) relative to the total amount (100 mass%) of the styrene-based resin composition is preferably 50 to 85 mass%, more preferably 55 to 83 mass%, and even more preferably 58 to 80 mass%. When it is in the range of 50 to 85, a styrene-based resin composition having an excellent balance of moldability and heat oil resistance can be obtained.

In a preferred embodiment of the styrene-based resin composition in this embodiment, the total styrene-based monomer unit content is 50 to 85% by mass, the total (meth)acrylic acid monomer unit content is 2 to 20% by mass, and the total (meth)acrylic acid ester monomer unit content is 6 to 55% by mass, relative to the total amount (100% by mass) of the styrene-based resin composition. In another preferred embodiment, the total styrene-based monomer unit content is 50 to 70% by mass, the total (meth)acrylic acid monomer unit content is 3.5 to 10% by mass, the total (meth)acrylic acid ester monomer unit content is 17 to 45% by mass, and the total conjugated diene monomer unit content is 0.5 to 10% by mass, relative to the total amount (100% by mass) of the styrene-based resin composition.

The average particle size of all rubber-like polymer particles contained in the styrene-based resin composition of the present embodiment is preferably 0.08 to 5.0 μm, more preferably 0.10 to 4.0 μm, even more preferably 0.20 to 2.5 μm, and even more preferably 0.25 to 2.0 μm.
When the average particle size of all the rubber-like polymer particles, that is, the apparent rubber-like polymer particles, is within the above range, the effect of imparting strength to the styrene-based resin composition is maximized.
The total amount of all rubber-like polymer particles (including encapsulated resin) in the entire styrene-based resin composition of this embodiment is preferably 0.5 to 8.0 mass%, more preferably 0.6 to 6.5 mass%, even more preferably 0.7 to 5.5 mass%, and even more preferably 0.8 to 4.5 mass%, relative to the total amount (100 mass%) of the styrene-based resin composition.
When the content of all the rubber-like polymer particles contained in the styrene-based resin composition is within the above range, the effect of imparting strength to the styrene-based resin composition is maximized.
In addition, when each of the rubber-like polymer particles, i.e., the ABS rubber-like polymer particles (C-2), the core-shell type rubber-like polymer particles (D) and the rubber-like polymer particles (E-2), contains a component (polymer domain phase) other than the conjugated diene monomer unit, the component (polymer domain phase) other than the conjugated diene monomer unit is also included in the content of all the rubber-like polymer particles.
The content of the conjugated diene monomer (=rubber amount) in all rubber-like polymer particles in the entire styrene-based resin composition of this embodiment is preferably 0 to 10 mass%, more preferably 0.3 to 5.0 mass%, even more preferably 0.5 to 4.8 mass%, and most preferably 0.6 to 4.0 mass%, relative to the total amount (100 mass%) of the styrene-based resin composition. It is possible to obtain a styrene-based resin composition having an excellent balance between strength and rigidity, and a molded article, sheet, or container obtained by molding the composition.
The above-mentioned total rubber-like polymer particles include all of the rubber-like polymer particles (C-2), the core-shell type rubber-like polymer particles (D) and the rubber-like polymer particles (E-2).

[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 uniaxial or biaxial 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.

<Foam extrusion sheet>
The foamed extruded sheet of the present invention can be obtained by a conventionally known method, so-called extrusion foaming, in which the base resin and various additives, such as a foam nucleating agent (cell regulator) described below, which are added as required, are heated, melted, and kneaded using an extruder, a physical foaming agent is injected and further kneaded, and the foamable molten resin, which has been adjusted to an appropriate resin temperature, is extruded through a die under atmospheric pressure to foam.

In this embodiment, when forming a foamed extrusion sheet, a substance that is normally used as a foaming agent during extrusion foaming can be used. Normal butane, isobutane, pentane, fluorocarbons, carbon dioxide, water, diethyl ether, etc. can be used as the foaming agent, with butane, isobutane, and diethyl ether being preferred, and a combination of two or more of the above foaming agents can also be used. The amount of foaming agent added during foam molding is preferably 0.5 to 8.0 parts by mass, more preferably 1.0 to 6.0 parts by mass, even more preferably 2.0 to 5.0 parts by mass, and even more preferably 2.5 to 4.5 parts by mass, based on 100 parts by mass of the styrene-based resin composition to be foamed. In particular, by setting the amount in the range of 2.0 to 5.0 parts by mass, the resin plasticization effect and foamability are excellent.

In this embodiment, when forming a foamed extruded sheet, a substance that is normally used as a foam nucleating agent during extrusion foaming can be used. For example, talc, silica, mica, etc., listed as the inorganic particles (H) can be used. The content of the foam nucleating agent is preferably 0.1 to 7.0 parts by mass, more preferably 0.2 to 6.0 parts by mass, and even more preferably 0.3 to 4.0 parts by mass, when the total amount of the styrene-based resin composition is 100 parts by mass. By setting the content in the range of 0.1 to 7.0 parts by mass, a sheet with an expansion ratio suitable for a foamed sheet for food packaging can be obtained. The foam nucleating agent may be added directly, or a master batch may be used in which a resin pellet in which a high concentration of the foam nucleating agent has been dispersed by extrusion kneading is added.

In this embodiment, the thickness of the foamed extruded sheet is preferably 0.3 mm to 5.0 mm, and more preferably in the range of 0.5 to 3.0 mm. By setting the thickness in the range of 0.5 to 3.0 mm, it is possible to provide a foamed extruded sheet with an excellent balance between strength and productivity.

In this embodiment, the apparent density of the foamed extruded sheet is preferably 0.05 to 0.30 g/cm ³ , more preferably 0.06 to 0.20 g/cm ³ , and even more preferably 0.07 to 0.10 g/cm ^3. In particular, by setting the apparent density in the range of 0.07 to 0.10 g/cm ³ , it is possible to provide a foamed extruded sheet having an excellent balance between strength and productivity.

In this embodiment, the basis weight of the foamed extruded sheet is preferably 70 to 300 g/m ² , more preferably 75 to 250 g/m ² , even more preferably 80 to 200 g/m ² , and even more preferably 90 to 150 g/m ^2. By setting the basis weight in the range of 80 to 200 g/m ² in particular, it is possible to provide a foamed extruded sheet having an excellent balance between strength and productivity.

In this embodiment, the expansion ratio of the foamed extruded sheet is preferably 5 to 18 times, more preferably 6 to 17 times, even more preferably 7 to 16 times, and even more preferably 8 to 15 times.

In this embodiment, the closed cell ratio of the foamed extruded sheet determined in accordance with the method of JIS K7138:2006 is preferably 75% or more, more preferably 80% or more, even more preferably 83% or more, and even more preferably 86% or more. In particular, by making the closed cell ratio 80% or more, the number of fragile open cells is reduced, and a foamed sheet with excellent strength can be obtained.

In this embodiment, the average bubble diameter of the foamed extruded sheet is preferably 200 to 500 μm, and more preferably in the range of 250 to 450 μm. By setting the range to 200 to 500 μm, it is possible to provide a foamed extruded sheet with an excellent balance between strength and productivity.

The foamed extruded sheet of the present invention may be multi-layered by further laminating a film. The type of film used may be any type commonly used for polystyrene. For example, a PP (polypropylene)/PS (polystyrene) dry laminate film may be used. The thickness of the film to be laminated is preferably 5 to 200 μm, more preferably 10 to 150 μm, and even more preferably 20 to 100 μm. By setting the thickness in the range of 20 to 100 μm, a good balance of weight reduction, strength, and oil resistance reinforcement is achieved.
A preferred foam extrusion sheet of this embodiment is a laminate having a foam layer of a styrene-based resin composition, a polystyrene layer provided on at least one side of the foam layer, and a polypropylene layer provided on the cotton of the polystyrene layer. With this structure, a polypropylene layer is provided on the outermost layer that may come into contact with food, etc., so that a container with excellent oil resistance can be provided. In addition, since the foam layer of the styrene-based resin composition contains a styrene-based monomer unit, a container with excellent compatibility and adhesion with the polystyrene layer can be provided.

[Secondary molded product]
The molded product obtained by thermoforming the foamed sheet is suitable for use as a container for food heated in a microwave oven. Examples of the thermoforming method include vacuum forming and compressed air forming. Such a thermoforming method is a preferred method because it can obtain containers continuously in a short time. When the laminated sheet having the above-mentioned laminate film thermocompression-bonded thereto is thermoformed, it is preferable to mold the laminate so that the polyolefin resin film having excellent oil resistance is located on the inside of the molded product obtained.

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 methods for analyzing and evaluating the resins and extruded sheets in the examples and comparative examples are as follows.

[Evaluation of properties of each resin and resin composition]
(1) Measurement of Molecular Weight and Proportion of Molecular Weight Components of 1,000,000 or More The average molecular weight (Mn, Mw, Mz) and the proportion of high molecular weight components of 1,000,000 or more for each of the resins and resin compositions produced in the Examples and Comparative Examples were measured by gel permeation chromatography (GPC) under the following conditions using a calibration curve method using standard polystyrene, and were measured as molecular weights converted into standard polystyrene.
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: 5 mg of a measurement sample was dissolved in 10 mL of a solvent and filtered through a 0.45 μm filter.
Injection volume: 10μL
Measurement temperature: 40℃
Flow rate: 0.35 mL/min Detector: differential refractometer Eleven 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 to create the calibration curve. The calibration curve was created using a linear approximation equation. If any THF insoluble matter was present in the composition, the THF insoluble matter was removed using a membrane filter of about 0.2 to 0.4 μm before measurement.

(2) Measurement of the Content of Monohydric Alcohol Having 10 or More Carbon Atoms in the Styrene-Based Resin Composition The content of the monohydric alcohol having 10 or more carbon atoms in the entire styrene-based resin composition was measured using 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 as the measurement solution.
Measurement equipment: Agilent 6850 series GC system Detector: FID
Column: DB-WAX
Length: 60m
Film thickness: 0.50 μm
Diameter: 0.320 mm
Injection volume: 1μL
Split ratio: 50:1
Column temperature: 100°C for 5 minutes → 10°C/min to 130°C → 10°C/min to 180°C → 180°C for 10 minutes → 20°C/min to 220°C → 220°C for 10 minutes Injection port temperature: 230°C
Detector temperature: 300°C
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.

(3) Measurement of Content of Each Monomer Unit The content of the conjugated diene monomer units contained in the resin compositions prepared in the Examples and Comparative Examples was measured by pyrolysis GC/MS under the following conditions.
Sample preparation: 50 μg of the resin compositions prepared in the Examples and Comparative Examples were weighed out in a sample cup using a precision balance, and measurements were performed under the following conditions.
Measurement conditions Pyrolysis unit Equipment: Frontier Lab PY-3030D
Heating furnace temperature: 600℃
G.C.
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, and then heated from 100° C. at 7° C./min, and held at 300° C. for 10 minutes.
Inlet temperature: 300℃
Detector temperature: 300°C
Split ratio: 1/300
Carrier gas: Helium Detection method: Mass spectrometer (MSD)
In detecting each monomer peak, the amount of sample, the column to be used, and the detection conditions may be appropriately adjusted to avoid peak overlap and saturation of peak intensity.

(4) Average particle size of rubber-like polymer particles (C-2), core-shell type rubber-like polymer particles (D), and rubber-like polymer particles (E-2) in impact-resistant styrene-based resin (E) The average particle size (μm) of rubber-like polymer particles (C-2), core-shell type rubber-like polymer particles (D), and rubber-like polymer particles (E-2) in impact-resistant styrene-based resin (E) is calculated using the following formula (2): for 200 rubber-like polymer particles observed by cross-sectional observation using a transmission electron microscope:
Average particle diameter = Σ(ni×Di ⁴ )/Σ(ni×Di ³ )
{In the above formula (2), 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.}
The particle diameters were calculated by averaging the particle diameters obtained from images of five fields of view.

(5) 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 ISO 1133.

(6) 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.

(7) Evaluation of hot oil 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 105°C for 15 minutes. The dimensional change rate before and after immersion was calculated using the following formula, and the hot oil resistance was evaluated according to the following evaluation criteria.
(Dimensional change rate after immersion in hot oil)
= {(original dimension) - (dimension after immersion)} / (original dimension) x 100
Evaluation criteria ◎: No dimensional change after immersion in hot oil 〇: Dimensional change rate after immersion in hot oil is 2% or less △: Dimensional change rate after immersion in hot oil is more than 2% to 10% or less ×: Dimensional change rate after immersion in hot oil is more than 10%

(8) Evaluation of surface impact of solid sheet (kg cm)
Each resin composition produced in the Examples and Comparative Examples was dried at 80° C. for 2 hours or more, and then a solid sheet having a thickness of 0.7 mm was produced using a compression molding machine. After cutting into a size of 8×8 cm, the film impact was measured using a film impact tester (No. 195) manufactured by Toyo Seiki Seisakusho Co., Ltd., and the n8 average was recorded as the value.

(9) Low-temperature impact strength of solid sheet (-30°C)
Using the styrene-based resin compositions of the Examples and Comparative Examples, a solid sheet with a thickness of 0.7 mm was prepared by a heat press set at 220° C., cut into a size of 6 cm×6 cm, cooled for 2 hours or more in a thermostatic chamber set at −30° C., and then the drop weight impact strength was immediately measured using a DuPont impact tester (No. 451) manufactured by Toyo Seiki Co., Ltd. The radius of the tip of the impact point was 6.3 mm, the radius of the impact point receiving stand was 9.4 mm, and the drop weight impact strength was calculated as the value at 50% destruction, calculated as (mass of the falling weight in kg)×(height in cm).

(10) Tensile test, bending test and impact test (10-1) Dumbbell molding of styrene-based resin composition Each pellet-shaped resin composition produced in the examples and comparative examples was molded into a 4 mm dumbbell of type A using an EC60N manufactured by Toshiba Machine Co., Ltd. under the following conditions.
Pellet drying: 80°C for 2 hours or more Weight: 63 mm
Injection time: 20 seconds Pressure retention time: 10 seconds Cylinder temperature: 220-240-220-200°C from nozzle side to hopper side
Screw rotation speed: 100 rpm Cushion: 5.5 mm
Mold temperature: 45°C
Cooling time: 25 seconds (10-2) Dumbbell tensile test (dumbbell tensile breaking point, dumbbell SS curve area)
The dumbbell tensile test was carried out on the 4 mm-thick dumbbell obtained in the previous section (10-1) in accordance with JIS K7161 (tensile speed 5 mm/min) to measure the dumbbell tensile breaking point. The dumbbell SS curve area (N mm) was calculated from the obtained SS curve.
(10-3) Bending test (flexural modulus, maximum bending point)
A test piece of 80×10×4 mm was prepared from the dumbbell piece obtained in the previous section (10-1) using a cutting machine. A bending test was carried out at a bending speed of 2 mm/min in accordance with JIS K7171, and the bending modulus and maximum bending point were measured.
(10-4) Charpy impact test (with notch)
A test piece having a size of 80×10×4 mm and having a notch was cut from the dumbbell piece obtained in the previous section (10-1) using a cutting machine. The Charpy impact strength was measured in accordance with JIS K7111/1eA.

[Characteristics evaluation of extruded sheets]
(11) Evaluation of heat resistance of extruded sheets The extruded sheets produced in the Examples and Comparative Examples were cut into strips of 10 cm x 1.5 cm with the MD direction as the long side, and placed in an oven set at 112°C for 30 minutes, after which the deformation of the foamed extruded sheet was measured, and the heat resistance was evaluated as follows based on the thermal deformation. Specifically, the above dimensional change was measured by measuring the amount of change in 10 cm length before and after thermal deformation according to the following formula (I), and the n5 average was used as the value.
Formula (I): Dimensional change (%) = (length in MD direction of non-foamed sheet after being placed in oven for 60 minutes - length in MD direction of non-foamed sheet before being placed in oven) / length in MD direction of non-foamed sheet before being placed in oven ◎: No dimensional change ◯: Dimensional change of 0.5% or less △: Dimensional change of more than 0.5% and less than 2% ×: Dimensional deformation of more than 2%

(12) Evaluation of heat oil resistance of extruded sheets Five strips of 10 cm x 1.5 cm with the long side in the MD direction were cut out from the extruded sheets produced in the Examples and Comparative Examples, and coconut oil (manufactured by Wako Pure Chemical Industries, Ltd.) was applied to the center of the strip to a diameter of approximately 1 cm. The strips were then placed in a circular oven set at 110°C for 15 minutes, and the appearance after removal from the oven was evaluated according to the following criteria.
◎: No change in any of the five sheets. ◯: One or two sheets out of five sheets turned white. △: Three or more sheets out of five sheets turned white. ×: Three or more sheets out of five sheets turned white and the sheet cracked.

(13) Surface impact of extruded sheet The extruded sheets produced in the examples and comparative examples were cut into 8 x 8 cm pieces, and the film impact was measured using a film impact tester (No. 195) manufactured by Toyo Seiki Seisakusho Co., Ltd., and the n8 average was taken as the value. The above measurements were carried out in a thermostatic chamber maintained at 23°C.

(14) Low-temperature impact strength of extruded sheet (-30°C)
The extruded sheets produced in the Examples and Comparative Examples were cut into 6 cm x 6 cm pieces and cooled in a thermostatic chamber set at -30°C for at least 2 hours, after which the drop weight impact strength was immediately measured using a DuPont impact tester (No. 451) manufactured by Toyo Seiki Co., Ltd. The mass of the falling weight was 0.15 kg, the radius of the tip of the impact center was 6.3 mm, and the radius of the impact center receiving stand was 9.4 mm. The drop weight impact strength was calculated as the 50% destruction value, calculated as (mass of the falling weight 0.15 kg) x (height cm), and evaluated according to the following criteria.
◎: More than 2.0 kg/cm ○: More than 1.0 kg/cm and less than 2.0 kg/cm △: More than 0.1 kg/cm and less than 1.0 kg/cm ×: Less than 0.1 kg/cm

[Evaluation of properties of molded containers obtained by secondary molding of extruded sheets]
The extruded sheets produced in the Examples and Comparative Examples were molded into extruded sheet molding containers with a diameter of 200 mm and a height of 45 mm into which an internal fitting lid could be fitted, using a hot plate molding machine at a hot plate temperature of 275° C. and a heating time of 5.0 seconds, and the containers were subjected to the evaluations described in (14) and (15) below.
(15) Oil resistance of extruded sheet molded containers when heated in a microwave oven Ten samples were prepared by applying MCT oil to the center of the above extruded sheet molded container in a circle with a diameter of approximately 1 cm, moistening it with a spray bottle, and covering it with a polyvinylidene chloride film to prevent the moisture from evaporating. After heating for 30 seconds in a 1,500 W microwave oven, the area with the MCT oil attached was visually inspected for tears and evaluated according to the following criteria.
◎: No change in all 10 points. ◯: 1-2 coated parts were broken. △: 3-7 coated parts were broken. ×: 8 or more coated parts were broken. (16) Impact strength of extrusion sheet molded container (kg cm)
A test piece measuring 80 mm in length and 80 mm in width was cut out from the center of the bottom surface of the above-mentioned extrusion sheet molding container, and the film impact was measured using a Toyo Seiki Film Impact Tester (No. 195) in a direction in which an impact was applied to the outer part of the container, and the n8 average value was recorded.

[Evaluation of properties of foamed extruded sheets]
(17) Basis weight of foamed extruded sheet (g/ ^m2 )
From each of the foamed extruded sheets produced in the Examples and Comparative Examples, 20 mm portions were removed from both ends to prepare 0.10 x 0.10 m sheet slices. The mass of each slice was measured, and the mass converted to per 1.0 ^m2 was calculated as the basis weight (g/ ^m2 ).

(18) Closed Cell Ratio of Foamed Extruded Sheet The closed cell ratio of the foamed extruded sheet was measured in accordance with JIS K7138.

(19) Surface Impact of Foamed Extruded Sheet The foamed extruded sheets produced in the Examples and Comparative Examples were cut into pieces of 8 x 8 cm, and then the film impact was measured using a film impact tester (No. 195) manufactured by Toyo Seiki Seisakusho Co., Ltd., and the n8 average was recorded as the value.

(20) Measurement of heat resistance of foamed extruded sheets The foamed extruded sheets produced in the Examples and Comparative Examples were cut into strips of 10 cm x 1.5 cm with the long sides in the MD direction, and placed in an oven set at 110°C for 60 minutes. The deformation of the foamed extruded sheets was then measured, and the heat resistance was evaluated from 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 (I), and the n5 average value was taken as the value.
Formula (I): Dimensional change (%) = (MD length of foamed sheet after being placed in oven for 60 minutes - MD length of foamed extruded sheet before being placed in oven) / MD length of foamed extruded sheet before being placed in oven ◎: No dimensional change ◯: Dimensional change of 1% or less △: Dimensional change of 1% or more but not exceeding 3% ×: Dimensional deformation of 3% or more

(21) Measurement of Heat Oil Resistance of Foam Sheet Coconut oil (manufactured by Wako Pure Chemical Industries, Ltd.) was applied to five circular areas of about 1 cm diameter on foamed extruded sheets obtained by molding the styrene-based resin compositions produced in the Examples and Comparative Examples, and the sheets were heated in an oven at 80° C. for 10 minutes, after which the appearance of the coconut oil-applied areas was visually evaluated.
◯: No change △: 1-2 out of 5 places on the applied area were torn ×: 3 or more places on the applied area were torn

(22) Preparation and evaluation of laminated foam sheet by laminating polyolefin resin film and foam extrusion sheet CPP/PS laminate film (45 μm thick) of CPP 25 μm (Suntox KT) and CPS 20 μm (Oishi Sangyo SPH) laminated by dry lamination and the foam extrusion sheet produced in the examples and comparative examples were passed between a heat roll and a backup roll at 195 ° C. to pressure-laminated the film to the foam sheet to obtain a laminated foam sheet. At this time, the line speed was set to 16 m / min, and the gap between the heat roll and the backup roll was set to 0.5 mm. The heat oil resistance and surface impact of the laminated foam sheet were evaluated according to the procedures of the previous paragraphs (18) and (20).

[Evaluation of properties of molded containers obtained by secondary molding of foamed extruded sheets]
The foamed extruded sheets produced in the Examples and Comparative Examples were molded into foamed containers with a diameter of 200 mm and a height of 45 mm into which an inner fitting lid could be fitted, using a hot plate molding machine under conditions of a hot plate temperature of 285°C and a heating time of 5.0 seconds, and the foamed containers were subjected to the evaluations described in the following (22) to (24).

(23) Oil resistance of foam container during microwave heating Ten samples were prepared by applying MCT oil to the center of the foam container in a circle with a diameter of about 10 mm, moistening the container with a spray bottle, and covering the container with a polyvinylidene chloride film to prevent the moisture from evaporating. After heating the container in a 1,500 W microwave oven for 30 seconds, the part with the MCT oil attached was visually inspected for tears and evaluated according to the following criteria.
◎: No change in any of the 10 points. ◯: The coated area broke in 1-2 points. △: The coated area broke in 3-7 points. ×: The coated area broke in 8 points or more.

(24) Measurement of Rigidity of Tray Container Rigidity of the foamed container was measured by the method shown in Fig. 1. More specifically, the crosshead 2 was compressed at a compression speed of 5 mm/min in the TD direction of the foamed container, that is, the tray container 1, to measure the rigidity (N) of the tray container 1.

(25) Impact strength of foaming container A test piece of 80 mm length x 80 mm width was cut out from the center of the bottom of the foaming container, and the film impact was measured in a direction to apply an impact to the outer part of the container using a film impact tester (No. 195) manufactured by Toyo Seiki Seisakusho Co., Ltd., and the n8 average was taken as a value, and the impact strength was evaluated from the following viewpoints.
⊚: 4.0 kg or more ◯: 2.0 kg·cm or more to 4.0 kg·cm or less ×: less than 2.0 kg·cm With containers with a pressure of less than 2.0 kgf, cracks tended to occur in the transport container.

(26) Low-temperature impact strength of foam sheet (-30°C)
Each foamed sheet produced in the Examples and Comparative Examples was cooled in a thermostatic chamber set at -30°C for 2 hours or more, and then evaluated for whether the sheet would break when a 100g weight was dropped from a height of 120cm.
The number of samples in which damage was observed among the 10 samples was counted and evaluated based on the following criteria.
◎: None of the 10 pieces were broken. 〇: 1-2 pieces were broken out of 10 pieces. △: 3-4 pieces were broken out of 10 pieces. ×: 5 or more pieces were broken out of 10 pieces.

[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.
<Production Example of Styrene-(Meth)acrylic Acid Resin (A)>
-Preparation of Resin (A1)-
A polymerization raw material composition liquid 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 was supplied at a rate of 0.8 liters/hour to a complete mixing type reactor having a capacity of 3.6 liters, and then continuously supplied to a volatilization device connected to a single screw extruder for removing volatile components such as unreacted monomers and polymerization solvent. The polymerization temperature of the complete mixing reactor was 130°C. The temperature of the single screw extruder was set to 210 to 230°C, and the pressure was set to 10 torr, to volatilize volatile components such as unreacted monomers and polymerization solvent. The volatilized volatile components were condensed in a condenser through which a refrigerant of -5°C was passed, and recovered as an unreacted liquid, and the styrene-based resin was recovered as resin pellets. The physical properties of Resin (A1) obtained by the above-mentioned analytical methods are shown in Table 1 below.

-Preparation of Resin (A2) and Resin (A3)-
Resin (A2) and resin (A3) were prepared in the same manner as for preparing resin (A1) under the polymerization conditions for preparing resin (A1) using the feed amounts of each monomer shown in Table 1. The compositions and physical properties of the obtained resins (A2) and (A3) are shown in Table 1.

- Preparation of Resin (A4) -
Using only styrene as a monomer, a styrene homopolymer resin (A4) having the composition and physical properties shown in Table 1 was obtained in the same manner as above.

<Production Example of (Meth)Acrylic Resin (B)>
- Preparation of Resin (B1) -
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 having a stirrer, 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., and suspension polymerization was prepared. After confirming that the temperature had reached 80 ° C. and was in a constant temperature state, 1.52 kg of methyl methacrylate, 0.22 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. Thereafter, suspension polymerization was performed while maintaining the temperature at about 80 ° C., and after observing an 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. Subsequently, the mixture was cooled to 50 ° C., and 20% by mass 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, and then 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 (B1) as a pellet-like resin.

- Preparation of Resin (B2) to Resin (B6) -
Resins (B2) to (B6) were prepared in the same manner as for the preparation of resin (B1) under the polymerization conditions for the preparation of resin (B1) using the feed amounts of each monomer shown in Table 2. The compositions and physical properties of the obtained resins (B2) to (B6) are shown in Table 2.

<(Meth)acrylonitrile-diene-styrene resin (C) used in the examples>
The outline of the preparation method of the (meth)acrylonitrile-diene-styrene resin (C) used in this example is to first produce a resin (C-2-1) containing butadiene-styrene-acrylonitrile graft copolymer particles (rubber-like polymer particles (C-2)) at a high concentration, and then knead and dilute a separately prepared styrene-acrylonitrile copolymer (C-1-1) and the butadiene-styrene-acrylonitrile graft copolymer particles (C-2-1) (corresponding to the rubber-like polymer particles (C-2)), thereby adjusting the concentration of the rubber-like polymer particles (C-2) and the polymer matrix (C-1) to a desired value. A specific example of the preparation method will be described below.

-Preparation of Resin (C1)-
To 122 parts by mass of polybutadiene rubber latex (average particle size 0.280 μm, solid content 37% by mass), 0.1 part by mass of tertiary dodecyl mercaptan and 23 parts by mass of deionized water were added, the gas phase was replaced with nitrogen, and the temperature was raised to 55° C. Next, while raising the temperature to 70° C. over 1.5 hours, an aqueous solution obtained by dissolving 0.2 part by mass of sodium formaldehyde sulfoxylate, 0.004 part by mass of ferrous sulfate, and 0.04 part by mass of disodium salt of ethylenediaminetetraacetic acid in 50 parts by mass of deionized water was added over 4 hours to a monomer mixture consisting of 14 parts by mass of acrylonitrile, 37 parts by mass of styrene, 0.5 part by mass of tertiary dodecyl mercaptan, and 0.15 part by mass of cumene hydroperoxide. After completion of the addition, 0.02 part by mass of cumene hydroperoxide was added, and the polymerization reaction was completed for another hour while controlling the reaction tank at 70° C.
To the mixture of styrene-acrylonitrile copolymer and butadiene-styrene-acrylonitrile graft copolymer thus obtained, a silicone resin defoamer (manufactured by Momentive Performance Materials Japan, LLC, product name TSA737) and a phenol-based antioxidant emulsion (manufactured by Chukyo Yushi Co., Ltd., product name L-673) were added. Thereafter, deionized water was added to adjust the solid content concentration to 10% by mass, and the mixture was heated to 70°C. Thereafter, an aqueous aluminum sulfate solution was added to coagulate the mixture, and solid-liquid separation was performed using a screw press machine. The water content at this time was 10% by mass. This was dried to obtain a resin (C-2-1) containing butadiene-styrene-acrylonitrile graft copolymer particles at a high concentration.
As a result of composition analysis, the composition ratio of the resin (C-2-1) was 17% by mass of acrylonitrile, 45% by mass of butadiene, and 38% by mass of styrene. The butadiene-styrene-acrylonitrile graft copolymer was in the form of particles like the polybutadiene rubber latex, and the average particle size was 0.30 μm.
On the other hand, a monomer mixture consisting of 63 parts by mass of styrene, 22 parts by mass of acrylonitrile, and 15 parts by mass of ethylbenzene was continuously fed to a complete mixing reactor equipped with a stirrer, and a polymerization reaction was carried out at 150°C with a residence time of 2 hours. The obtained polymerization solvent was continuously fed to an extruder, and unreacted monomers and solvent were recovered with a devolatilizing extruder to obtain a styrene-acrylonitrile copolymer (C-1-1). As a result of composition analysis using a Fourier transform infrared spectrophotometer (FR-IR) (manufactured by JASCO Corporation), the composition of the copolymer (C-1-1) was 30% by mass of acrylonitrile and 70% by mass of styrene.
The resin (C-2-1) containing a high concentration of butadiene-styrene-acrylonitrile graft copolymer particles (rubber-like polymer particles (C-2)) obtained by the above procedure and the styrene-acrylonitrile copolymer (C-1-1) were extrusion-kneaded and pelletized in a twin-screw extruder to obtain ABS resin (C1) as a pellet-shaped ABS resin. The composition and physical properties of the obtained ABS resin (C1) are shown in Table 3.

-Preparation of ABS resin (C2)-
The feed amount of each monomer and the polymerization conditions were adjusted to prepare resin (C-2-1) in the same manner as for the above ABS resin (C1), and then 90 parts by mass of the ABS resin and 10 parts by mass of a styrene-acrylonitrile-N-phenylmaleimide copolymer were extrusion-kneaded and pelletized in a twin-screw extruder to obtain ABS resin (C2) as a pellet-shaped ABS compound resin. The composition and physical properties of the obtained ABS resin (C2) are shown in Table 3.

<Production Example of Core-Shell Type Rubber Polymer Particles (D)>
-Preparation of rubber-like polymer particles (D1)-
In a pressure vessel equipped with a stirrer, 200 parts by mass of pure water, 0.002 parts by mass of disodium salt of ethylenediaminetetraacetic acid, 0.0012 parts by mass of ferrous sulfate, 0.008 parts by mass of disodium salt of ethylenediaminetetraacetic acid, and 0.03 parts by mass of sodium polyoxyethylene alkyl ether phosphate were charged and deacidified, and then 100 parts by mass of butadiene, 0.05 parts by mass of sodium formaldehyde sulfoxylate, and 0.2 parts by mass of paramenthane hydroperoxide were added, and then 1.4 parts by mass of sodium polyoxyethylene alkyl ether phosphate was added dropwise over 6 hours. The reaction solution was then kept at pH 6.5 to 7.5 for 124 hours at 50° C. to obtain a diene rubber latex with a conversion rate of 98% by weight and an average particle size of 0.18 μm.
Next, while maintaining the above-obtained rubber latex (solid content about 71 parts) at 60 ° C., 55 parts by mass of methyl methacrylate and 5 parts by mass of (n-butyl) acrylate as monomers were added over 1 hour. Simultaneously with the addition of the above-mentioned monomers, addition of 0.09 parts by mass of t-butyl hydroperoxide and 0.1 parts by mass of sodium formaldehyde sulfoxylate was started, and then the entire amount was added over 2 hours while maintaining the pH of the reaction solution at 6.5 to 7.5 and the temperature at about 60 ° C. The reaction solution was further maintained at about 60 ° C. for 1 hour to prepare a graft copolymer latex with an average particle size of 200 nm, and after adding 1 part by mass of Irganox 1076 as an antioxidant, the mixture was coagulated with an aqueous calcium chloride solution, washed with water, dehydrated and dried to obtain rubber-like polymer particles (D1) as powder. The composition and physical properties of the rubber-like polymer particles (D1) are shown in Table 4.

-Preparation of rubber-like polymer particles (D2)-
The feed amount of each monomer and the polymerization conditions were adjusted to prepare D2 in the same manner as D1. The composition and physical properties of the obtained rubber-like polymer particles (D2) are shown in Table 4.

In addition to the composition shown in Table 4 above, the following products were used in the examples as core-shell type rubbery polymer particles (D) containing (meth)acrylic acid ester monomer units (d1) and conjugated diene monomer units (d2).
(D3) Mitsubishi Chemical Corporation's Metablen C-223A
(D4) Mitsubishi Chemical Corporation's Metablen E-875A

<Production Example of Impact Resistant Styrene-Based Resin (E)>
-Preparation of impact resistant styrene resin (E1)-
An impact-resistant styrene-based resin (E1) (hereinafter referred to as resin (E1)) was produced using a polymerization apparatus in which three laminar flow reactors (1.5 liters) equipped with stirrers were connected in series and followed by a two-stage vented extruder. 82.4 parts by mass of styrene, 9.0 parts by mass of ethylbenzene, 8.6 parts by mass of high cis butadiene rubber 13HB manufactured by Ube Industries as a rubber-like polymer (E-2), 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 the rubber components were dissolved using a stirrer. The raw material solution was then supplied to the reactor at a volume of 0.75 liters/hr, and polymerization was carried out 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 to 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 average particle size of the rubber-like polymer particles (E-2) was controlled by adjusting the rotation speed of the stirrer in the first-stage laminar flow reactor to 110 rpm. The composition and properties of the obtained resin (E1) are shown in Table 5.

-Preparation of Resin (E2)-
Resin (E2) having the composition and physical properties shown in Table 5 was obtained in the same manner as above, except that high cis butadiene rubber 15HB manufactured by Ube Industries was used as the rubber polymer (E-2).

-Preparation of Resin (E3)-
Resin (E3) having the composition and physical properties shown in Table 5 was obtained in the same manner as above, using styrene, methyl methacrylate, and butyl acrylate as monomers, and styrene-butadiene copolymer 625A manufactured by Asahi Kasei as rubber-like polymer (E-2).

<Styrene-based elastomer (F) used in the examples>
In the examples of this specification, the following two types of styrene-based elastomer (F) were used.
(F1) Styrene-butadiene block copolymer Asaflex 835 manufactured by Asahi Kasei Corporation
(F2) Styrene-butadiene block copolymer Tufprene 125 manufactured by Asahi Kasei Corporation
<Acrylic elastomer (G) used in the examples>
In the examples of this specification, the following three types of acrylic elastomer (G) were used.
(G1) Kuraray Clarity LA4285
(G2) Kuraray Clarity LA2270
(G3) Kuraray Clarity LA2250
The resins (G1) to (G3) which are all acrylic elastomers (G) are poly(methyl methacrylate-b-(n-butyl) acrylate-b-methyl methacrylate) triblock copolymers and have the properties shown in Table 6 below.

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

<<Production Examples of Styrene-Based Resin Composition and Foam Extruded Sheet>>
The detailed production method of the styrene resin composition and the foamed extruded sheet will be described below.
[Example 1]
-Production of styrene-based resin composition-
A styrene-(meth)acrylic acid resin (A) was 93.0 parts by mass of the resin (A1) shown in Table 1, a (meth)acrylic resin (B) was 7.0 parts by mass of the resin (B1) shown in Table 2, and Fine Oxocol 180 was 0.12 parts by mass. The mixture was kneaded, extruded, and pelletized using a twin-screw extruder TEM26SS manufactured by Shibaura Machine Co., Ltd. to obtain a styrene-based resin composition [1] as a pelletized 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 evaluation results of the properties and physical properties of the styrene-based resin composition [1] are shown in Table 7-1.

- Manufacturing of extruded sheets -
The styrene-based resin composition [1] obtained above was fed to an extruder capable of nitrogen purge and equipped with a vacuum vent. The maximum cylinder temperature of the extruder was set to 250°C. The resin composition extruded from the T-die was wound on a mirror-finished metal roll, and an extruded sheet [1] having a thickness of 0.25 mm was produced by adjusting the winding speed and the amount of resin discharged. The evaluation results of the obtained extruded sheet [1] are shown in Table 7-1.

- Manufacturing of foam extrusion sheets -
100 parts by mass of the styrene-based resin composition [1] obtained above and 1.0 part by mass of talc (High Filler #12 manufactured by Matsumura Sangyo Co., Ltd.) as inorganic fine particles (H) were dry-blended and fed to an extruder. The maximum cylinder temperature of the extruder was set to 250°C. 4.0 parts by mass of mixed butane with a mass ratio of isobutane/normal butane of 65/35 as a foaming agent was pressed into the melt-kneaded resin composition, and the mixture was extruded into a cylindrical shape from a circular die and foamed. The obtained cylindrical foam was cooled by blowing air onto it, and then the cylindrical foam was cut open in the extrusion direction through a cooling mandrel process to obtain a foamed extruded sheet [1].
The evaluation results of the obtained foamed extruded sheet [1] and the evaluation results of the foamed container obtained by secondary molding of the foamed extruded sheet [1] are shown in Table 7-1.

[Examples 2 to 34]
Styrenic resin compositions [2] to [34], extruded sheets [2] to [34], and foamed extruded sheets [2] to [34] were obtained in the same manner as in Example 1, except that the formulation was changed as shown in the following Table 7. Evaluation results of the obtained styrenic resin compositions [2] to [34], extruded sheets [2] to [34], foamed extruded sheets [2] to [34], containers obtained by secondary molding of the extruded sheets, and containers obtained by secondary molding of the foamed extruded sheets are shown in Tables 7-1 to 7-3.

[Examples 35 to 42]
Styrenic resin compositions [35] to [42] and extruded sheets [35] to [42] were obtained in the same manner as in Example 1, except that the formulation was changed as shown in Table 8 below. The evaluation results of the obtained styrenic resin compositions [35] to [42], the extruded sheets [35] to [42], and the containers obtained by secondary molding of the extruded sheets are shown in Table 8.

[Comparative Examples 1 to 3]
A resin composition, an extruded sheet, a foamed extruded sheet, a container molded from the extruded sheet, and a container molded from the foamed extruded sheet were obtained in the same manner as in Example 1, except that the formulation was changed as shown in the following Table 9. The evaluation results of the obtained resin composition, extruded sheet, foamed extruded sheet, and containers obtained by secondary molding of each sheet are shown in Table 9.

The styrene resin composition obtained by the present invention has excellent heat resistance, transparency, rigidity, heat oil resistance, and appearance. Therefore, the styrene 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 appliance parts, toys, daily necessities, various industrial parts), etc., and is particularly useful as a packaging material compatible with microwave cooking, and plays a major role in the industrial world.

Claims (12)

40 to 99% by mass of a styrene-(meth)acrylic acid-based resin (A) having a styrene-based monomer unit (a1) and 2% by mass or more and 17% by mass or less of a ( meth)acrylic acid monomer unit (a2-1);
1 to 60 mass% of a (meth)acrylic resin (B) having a (meth)acrylic acid ester monomer unit (b1);
A styrene-based resin composition comprising one or more particles selected from the group consisting of a (meth)acrylonitrile-diene-styrene-based resin (C) containing a styrene-based monomer unit (c1), a conjugated diene-based monomer unit (c2) and a (meth)acrylonitrile-based monomer unit (c3), and a core-shell type rubbery polymer particle (D) containing a (meth)acrylic acid ester monomer unit (d1) and a conjugated diene-based monomer unit (d2) ,
The weight average molecular weight (Mw) of the (meth)acrylic resin (B) is in the range of 50,000 to 900,000;
The styrene-based resin composition is divided into a high molecular weight component of 1 million or more and a molecular weight component of less than 1 million, and the high molecular weight component of 1 million or more is 1.0 mass% or less based on the total amount of the styrene -based resin composition. The styrene-(meth)acrylic acid-based resin (A) contains the styrene-based monomer unit (a1), the (meth)acrylic acid monomer unit (a2-1) and the (meth)acrylic acid ester monomer unit (a2-2). The styrene-based resin composition according to claim 1 . The styrene-(meth)acrylic acid-based resin (A) contains, as essential components, the styrene-based monomer unit (a1), the (meth)acrylic acid monomer unit (a2-1), and the (meth)acrylic acid ester monomer unit (a2-2),
The styrene-(meth)acrylic acid-based resin composition according to claim 1 or 2, wherein the (meth)acrylic acid monomer unit (a2-1) is contained in an amount of 2 to 30 mass% and the (meth)acrylic acid ester monomer unit (a2-2) is contained in an amount of 1 to 20 mass% based on the entire styrene-(meth)acrylic acid-based resin (A). The styrene-based resin composition according to claim 1 or 2, wherein the content of all (meth)acrylic acid ester monomer units contained in the styrene-based resin composition is 15 to 50 mass% based on the total amount of the styrene-based resin composition. 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 0.5 to 15 mass% of methyl acrylate monomer units relative to the total amount of the copolymer. 3. The styrenic resin composition according to claim 1 or 2, further comprising one or more selected from the group consisting of an impact resistant styrenic resin (E) containing a styrenic monomer unit (e1) and a conjugated diene monomer unit (e2), a styrenic elastomer (F), and an acrylic elastomer (G). The styrene-based resin composition according to claim 1 or 2, further comprising the ( meth)acrylonitrile-diene-styrene-based resin (C) and an acrylic elastomer (G). The styrene-based resin composition according to claim 1 or 2, further comprising the core-shell type rubbery polymer particles (D). The styrene-based resin composition according to claim 1 or 2, further comprising inorganic particles (H) in an amount of 0.05 to 3.0% by mass relative to the total amount of the styrene-based resin composition. An extruded sheet formed from the styrene-based resin according to claim 1 or 2. A molded article obtained by injection molding the styrene-based resin according to claim 1 or 2. A container formed by secondary molding of the extruded sheet according to claim 10.

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