JP7621311B2 - Styrenic resin composition, extruded sheet and container - Google Patents

Description

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

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

JP 2020-111649 A

In the technology of the above-mentioned Patent Document 1, although heat resistance, impact resistance, and appearance were considered, transparency and hot oil resistance were insufficient. In particular, in transparent containers that are assumed to come into direct contact with food, conventional styrene-unsaturated carboxylic acid resins are corroded by high-temperature oil derived from food heated in a microwave oven, causing cracking and whitening of the transparent container, so resistance to edible oil is required. In addition, when molding a composition containing a styrene-unsaturated carboxylic acid resin, problems occur in that it is difficult to control the thickness of the obtained molded product to a constant value, or that the molded product is prone to holes.
Therefore, the problem to be solved by the present invention is to provide a styrene-based resin composition used for a molded article having excellent transparency and heat oil resistance without deteriorating heat resistance, appearance and mechanical strength. Another problem to be solved by the present invention is to provide a biaxially oriented sheet, an extruded sheet, and a container and a lid material obtained by secondary molding the biaxially oriented sheet or the extruded sheet, which contain a styrene-based resin composition having excellent transparency and heat oil resistance without deteriorating heat resistance, secondary moldability, appearance and mechanical strength.

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

[1] The present disclosure relates to a styrene-unsaturated carboxylic acid-based resin (A) having 50 to 99.9 mass% of a styrene-unsaturated carboxylic acid-based resin (A) having a styrene-based monomer unit (1) and an unsaturated carboxylic acid-based monomer unit (a1);
and 0.1 to 50 mass % of a (meth)acrylic resin (B) having a butyl (meth)acrylate monomer unit.

[2] In this embodiment, it is preferable that the amount of high molecular weight components having a molecular weight of 1 million or more in the entire styrene-based resin composition is 0.3 to 10.0 mass% based on the total amount of the styrene-based resin composition.

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

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

[5] In this embodiment, the unsaturated carboxylic acid monomer unit (a1) contains two essential components, namely, a (meth)acrylic acid monomer unit (a1-1) and a (meth)acrylic acid ester monomer unit (a1-2),
It is preferable that the styrene- unsaturated carboxylic acid resin (A) contains 2 to 30 mass% of the (meth)acrylic acid monomer unit (a1-1) and 1 to 20 mass% of the (meth)acrylic acid ester monomer unit (a1-2) relative to the total amount of the styrene-unsaturated carboxylic acid resin (A).

[6] In this embodiment, it is preferable that the (meth)acrylic resin (B) is contained in an amount of 1 to 30 mass% based on the total amount of the styrene-based resin composition.

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

[8] In this embodiment, the (meth)acrylic resin (B) is a methyl methacrylate-butyl acrylate copolymer, or a mixture containing a methyl methacrylate-butyl acrylate copolymer and a methyl methacrylate-methyl acrylate copolymer, and preferably contains 0.1 to 20% by mass of the butyl acrylate monomer unit relative to the total amount of the (meth)acrylic resin (B).

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

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

[11] In this embodiment, the content of butyl acrylate monomer units is preferably more than 0 and not more than 3.0 mass% relative to the total amount of the styrene-based resin composition.

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

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

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

[15] One aspect of this embodiment is a container formed from a styrene-based resin composition.

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

The following describes in detail the form for carrying out the present invention (hereinafter, "the present embodiment"). Note that the present invention is not limited to the following embodiment, and can be carried out in various modifications within the scope of the gist of the 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-unsaturated carboxylic acid-based resin (A) having a styrene-based monomer unit (1) and an unsaturated carboxylic acid-based monomer unit (a1), and a (meth)acrylic resin (B) having a butyl (meth)acrylate monomer unit, and the content of the styrene-unsaturated carboxylic acid-based resin (A) is 50 to 99.9 mass%, and the content of the (meth)acrylic resin (B) is 0.1 to 50 mass%, relative to the total amount (100 mass%) of the styrene-based resin composition.
Furthermore, the styrene-based resin composition in the present embodiment may contain, as necessary, one or more selected from the group consisting of alcohols (C) having 10 or more carbon atoms and rubber-modified styrene-based resins (D).
This makes it possible to provide a styrene-based resin composition having excellent transparency and heat and oil resistance without reducing heat resistance and rigidity.
In the styrene-based resin composition of the present embodiment, the content of high molecular weight components having a molecular weight of 1,000,000 or more is preferably 0.3 to 10.0 mass % or less based on the total amount of the styrene-based resin composition.
The high molecular weight component having a molecular weight of 1,000,000 or more can be a styrene-unsaturated carboxylic acid resin (A) and/or a (meth)acrylic resin (B). Therefore, when the styrene resin composition contains a predetermined amount of the high molecular weight component having a molecular weight of 1,000,000 or more, the effects of the present invention can be more effectively exhibited.

"Styrene-unsaturated carboxylic acid resin (A)"
The styrene-unsaturated carboxylic acid resin (A) in this embodiment is a copolymer resin (hereinafter also simply referred to as resin (A)) containing a styrene monomer unit (1) and an unsaturated carboxylic acid monomer unit (a1) as essential components, and contributes to improving the heat resistance of the entire styrene resin composition. Furthermore, the styrene-unsaturated carboxylic acid resin (A) may further contain other monomer units (a2) other than the essential components of the styrene monomer unit (1) and the unsaturated carboxylic acid monomer unit (a1), as necessary. The content of the styrene-unsaturated carboxylic acid resin (A) relative to the total amount (100 mass%) of the styrene resin composition is 50 to 99.9 mass%, with the upper limit being 99.5 mass% or less, 99.0 mass% or less, 98.5 mass% or less, 98.0 mass% or less, 97.8 mass% or less, 97.6 mass% or less, 97.4 mass% or less, 97.2 mass% or less, 97.0 mass% or less, 96.8 mass% or less, 96.6 mass% or less, 97.7 mass% or less, 97.8 mass% or less, 97.9 ... The preferred order is 5.0% by mass or less, 90% by mass or less, and 84% by mass or less, and the lower limit is 51% by mass or more, 52% by mass or more, 53% by mass or more, 54% by mass or more, 55% by mass or more, 56% by mass or more, 57% by mass or more, 58% by mass or more, 59% by mass or more, 60% by mass or more, 62% by mass or more, 64% by mass or more, 66% by mass or more, 68% by mass or more, 70% by mass or more, 72% by mass or more, and 74% by mass or more. The content of the styrene-unsaturated carboxylic acid resin (A) can be within the range of the upper and lower limits described above. By making the content of the styrene-unsaturated carboxylic acid resin (A) 50% by mass or more, the effect of imparting heat resistance can be sufficiently obtained, and in particular, by making the content of the styrene-unsaturated carboxylic acid resin (A) 99.0% by mass or less, the effect of improving heat oil resistance by the (meth)acrylic resin (B) can be sufficiently obtained.

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

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

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

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

（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（ａ１－２）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。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 (a1-2)-
In this embodiment, the (meth)acrylic acid ester monomer (a1-2) plays a role in improving oil resistance and strength. The (meth)acrylic acid ester monomer unit (a1-2) is 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 (a1-2) is preferably 10 or less, more preferably 8 or less, and even more preferably 4 or less. If the number exceeds 10, the effect of lowering heat resistance is significant, which is not preferred.

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

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

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

<Characteristics of styrene-unsaturated carboxylic acid resin (A)>
In the styrene-unsaturated carboxylic acid resin (A) in this embodiment, the contents of the styrene-based monomer unit (1), the unsaturated carboxylic acid-based monomer unit (a1) (including the (meth)acrylic acid monomer unit (a1-1) and the (meth)acrylic acid ester monomer unit (a1-2)) and the other monomer unit (a2) can be quantified using a calibration curve prepared from a resin in which each monomer unit is known using pyrolysis GC/MS.
The melt flow rate of the styrene-unsaturated carboxylic acid resin (A) at 200°C in this embodiment can 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-unsaturated carboxylic acid resin (A) in this embodiment is preferably 100,000 to 400,000, more preferably 120,000 to 320,000. When the weight average molecular weight is 100,000 to 350,000, a resin having excellent practical balance between impact strength and fluidity can be obtained. The weight average molecular weight and number average molecular weight can be measured by Gelper permeation chromatography in terms of polystyrene standard. The number average molecular weight (Mn) of the styrene-unsaturated carboxylic acid resin (A) is preferably 40,000 to 150,000, more preferably 50,000 to 120,000.
In this embodiment, the Z-average molecular weight (Mz) of the styrene-unsaturated carboxylic acid resin (A) is preferably 150,000 to 550,000, more preferably 200,000 to 500,000, as measured by a differential refractometer (RI detector). On the other hand, the Z-average molecular weight (Mz) of the styrene-unsaturated carboxylic acid resin (A) is preferably 150,000 to 550,000, more preferably 200,000 to 500,000, as measured by an ultraviolet absorptiometer (UV detector).
The styrene-unsaturated carboxylic acid resin (A) of this embodiment may contain a high molecular weight component of 1 million or more. When the styrene-based resin composition contains a high molecular weight component of 1 million or more, the heat resistance and rigidity are further suppressed from decreasing, and the heat oil resistance is further improved. In addition, the high molecular weight component of 1 million or more has a styrene-based monomer unit (1) and an unsaturated carboxylic acid monomer unit (a1), and the proportion of the high molecular weight component of 1 million or more of the styrene-unsaturated carboxylic acid resin (A) contained in the styrene-based resin composition is preferably 0% by mass or more and 60% by mass or less, more preferably 0% by mass or more and 40% by mass or less, based on the total amount of the styrene-based resin composition.
In addition, as a method for controlling the high molecular weight component of 1,000,000 or more in the styrene-unsaturated carboxylic acid resin (A) to 0% by mass or more and 60% by mass or less, when radically polymerizing the styrene monomer (1) and the unsaturated carboxylic acid monomer (2), it can be controlled by the types and amounts of the styrene monomer (1) and the unsaturated carboxylic acid monomer (2) or other monomer units (a2) added arbitrarily, 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, the styrene-unsaturated carboxylic acid resin (A) of the present embodiment contains a high molecular weight component of 1,000,000 or more of the styrene-unsaturated carboxylic acid resin (A) in an amount of 0 mass% or more and 60 mass% or less based on the total amount of the styrene-based resin composition, and the weight average molecular weight (Mw) of the styrene-unsaturated carboxylic acid resin (A) as a whole is more preferably 90,000 to 400,000.

In this embodiment, the Vicat softening temperature of the styrene-unsaturated carboxylic 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-unsaturated carboxylic acid resin (A) 105°C or higher, the heat resistance of the composition can be improved, and by making it 140°C or lower, it becomes 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-unsaturated carboxylic acid resin (A)>
The method for producing the styrene-unsaturated carboxylic acid resin (A) of this embodiment will be described below.
The method for producing the styrene-unsaturated carboxylic acid resin (A) of the present embodiment preferably includes a step of mixing a styrene monomer (1), an unsaturated carboxylic acid monomer (a1) ((meth)acrylic acid monomer unit (a1-1) and/or (meth)acrylic acid ester monomer unit (a1-2)), and a solvent to prepare a mixed solution, a polymerization step of polymerizing the mixed solution to produce a reaction product, and a step of recovering the reaction product.
The polymerization method for the styrene-unsaturated carboxylic acid resin (A) is not particularly limited, but for example, a radical polymerization method, among which a bulk polymerization method or a solution polymerization method can be preferably used.
Specifically, the polymerization method mainly comprises a polymerization step of polymerizing polymerization raw materials (monomer components) and a devolatilization step of removing volatile matters such as unreacted monomers and polymerization solvent from the polymerization product.

In this embodiment, when the polymerization raw materials are polymerized to obtain the styrene-unsaturated carboxylic acid resin (A), a polymerization initiator is typically contained in the polymerization raw material composition. Examples of the polymerization initiator include organic peroxides, 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-unsaturated carboxylic 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-unsaturated carboxylic acid resin (A), solution polymerization using a polymerization solvent can be adopted. As the polymerization solvent, aromatic solvents such as toluene, ethylbenzene, propylbenzene, butylbenzene, etc. are preferable, and a solvent system in which the solubility of the styrene-unsaturated carboxylic acid resin (A) is adjusted by combining 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-unsaturated carboxylic acid resin (A). If the polymerization solvent exceeds 35 parts by mass relative to 100 parts by mass of the total monomers, the polymerization rate decreases and the molecular weight of the resulting resin also decreases, so that the mechanical strength of the resin tends to decrease. In addition, if the polymerization solvent is less than 3 parts by mass, it may be difficult to control the heat removal during polymerization. It is preferable to add the polymerization solvent at a ratio of 3 to 35 parts by mass relative to 100 parts by mass of the total monomers, because this makes it easier to uniformize the quality and also in terms of polymerization temperature control.
In addition, when the monohydric alcohol (C) 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 component (C) 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-unsaturated carboxylic acid resin (A) in this embodiment is not particularly limited, and may be appropriately selected according to a general polymerization method for styrene-based resins. For example, in the case of bulk polymerization, a polymerization apparatus having one or more completely mixed reactors connected 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 (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 butyl (meth)acrylate monomer unit. The inclusion of a predetermined amount of (meth)acrylic resin (B) essentially containing a butyl (meth)acrylate monomer unit contributes to improving the heat oil resistance, 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 having a (meth)acrylic acid ester monomer unit content of 51 mass % or more.
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 GelPermeation Chromatography (GPC), as described in the Examples section below.

The content of the (meth)acrylic resin (B) relative to the total amount (100 mass%) of the styrene-based resin composition is 0.1 to 50 mass%, with the upper limit being 43 mass%, 36 mass%, 29 mass%, 24 mass%, 22 mass%, 15 mass%, 8 mass%, 6 mass%, 4 mass%, 3.0 mass%, 2.9 mass%, 2.8 mass%, 2.7 mass%, 2.8 mass%, 2.7 mass%, 2.6 mass%, 2.5 mass%, 2.4 mass%, 2.3 mass%, 2.2 mass%, 2.1 mass%, and 2.0 mass%, and the lower limit being 0.2 mass%, 0.4 mass%, 0.6 mass%, 0.7 mass%, 0.8 mass%, 0.7 mass%, 0.9 mass%, 1.0 mass%, 1.2 mass%, and 1.4 mass%, respectively. In particular, by adjusting the content of the (meth)acrylic resin (B) to 1 mass % or more and 36 mass % or less, it is possible to suppress the deterioration of the heat resistance improved by the styrene-unsaturated carboxylic acid resin (A).

-Butyl (meth)acrylate monomer-
The (meth)acrylic resin (B) of this embodiment is required to contain a butyl (meth)acrylate monomer unit, and may contain an unsaturated carboxylic acid monomer unit (b1) other than the butyl (meth)acrylate monomer unit as necessary. The unsaturated carboxylic acid monomer unit (b1) is preferably one or more repeating units selected from the group consisting of (meth)acrylic acid monomer units (b1-1) and (meth)acrylic acid ester monomer units (b1-2).
The butyl (meth)acrylate monomer unit contained in the (meth)acrylic resin (B) of the present embodiment is preferably one or more selected from the group consisting of n-butyl (meth)acrylate, s-butyl (meth)acrylate, isobutyl (meth)acrylate, and t-butyl (meth)acrylate, more preferably n-butyl (meth)acrylate, and even more preferably n-butyl acrylate.
In this embodiment, the upper limit of the content of the butyl (meth)acrylate monomer unit in 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, 74% by mass or less, 64% by mass or less, 54% by mass or less, 44% by mass or less, 34% by mass or less, 24% by mass or less, 19% by mass or less, and 14% by mass or less, in this order, based on the total amount of the (meth)acrylic resin (B). The lower limit of the content is preferably 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, in this order. The content of the butyl (meth)acrylate monomer unit can be any combination of the above upper limit and the above lower limit. The range of the content of the butyl (meth)acrylate monomer unit is, for example, preferably 0 to 100 mass%, more preferably 2 to 99 mass%, even more preferably 2 to 98 mass%, still more preferably 4 to 98 mass%, even more preferably 5 to 98 mass%, and particularly preferably 6 to 98 mass%.

-(Meth)acrylic acid monomer (b1-1)-
The (meth)acrylic acid monomer (b1-1) optionally contained in the (meth)acrylic resin (B) of the present embodiment includes a monomer such as acrylic acid or methacrylic acid.

-(Meth)acrylic acid ester monomer (b1-2)-
The (meth)acrylic acid ester monomer unit (b1) optionally contained in 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 monomers such as methyl acrylate, ethyl 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 monomer (b1-2) may be used alone or in combination, and two or more kinds of the (meth)acrylic acid ester monomer (b1-2) may be used in combination.
As a combination of monomer units constituting the (meth)acrylic resin (B) of the present embodiment, from the viewpoint of achieving both heat resistance and thermal decomposition property, a copolymer of a methacrylic acid ester species and an acrylic acid ester species is preferable, and a methyl methacrylate-butyl acrylate copolymer is more preferable.
In this embodiment, the upper limit of the content of the (meth)acrylic acid ester monomer unit (b1-2) in 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, 74% by mass or less, 64% by mass or less, and 54% by mass or less, in this order, based on 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 (b1-2) can be any combination of the above upper limit and the above lower limit. The content of the (meth)acrylic acid ester monomer unit (b1-2) is, for example, preferably in the range of 0 to 100 mass%, more preferably 2 to 99 mass%, even more preferably 2 to 98 mass%, still more preferably 4 to 98 mass%, even more preferably 5 to 98 mass%, and particularly preferably 6 to 98 mass%.

<Preferred form of (meth)acrylic resin (B)>
A preferred (meth)acrylic resin (B) of the present embodiment is preferably a binary or ternary copolymer having a (meth)acrylate butyl monomer (unit), and is preferably a methacrylate-acrylate copolymer in which a methacrylate species (methacrylate monomer unit) and an acrylate species (acrylate monomer unit) are copolymerized, and it is preferred that the alkyl group of the ester substituent of either the methacrylate monomer unit or the acrylate monomer unit is a butyl group (n-butyl, s-butyl, isobutyl or t-butyl). In this case, the upper limit of the content of the acrylic acid ester species relative to the total amount of the methacrylic acid ester-acrylic acid ester copolymer is preferably 20% by mass or less, 19% by mass or less, 18% by mass or less, and 17% by mass or less, and the lower limit is preferably 0.1% by mass or more, 0.3% by mass or more, 0.7% by mass or more, 0.9% by mass or more, 2.0% by mass or more, 5.0% by mass or more, 7.0% by mass or more, and 10.0% by mass or more. The content of the acrylic acid ester species relative to the total amount of the methacrylic acid ester-acrylic acid ester copolymer can be any combination of the upper limit and the lower limit. In particular, by setting the content of the acrylic acid ester species in the range of 5.0% by mass or more and 20% by mass or less, a styrene-based resin composition having the best balance between improved oil resistance and fluidity can be obtained. In addition, the (meth)acrylic resin (B) of this embodiment preferably contains a methyl methacrylate-butyl acrylate copolymer. In the case where the (meth)acrylic resin (B) of the present embodiment contains a methyl methacrylate-butyl acrylate copolymer, the copolymer further preferably contains 5.0 to 20 mass % of butyl acrylate monomer units relative to the total amount of the copolymer, which reduces the viscosity difference during kneading with the styrene-unsaturated carboxylic acid resin (A) and allows a styrene-based resin composition with excellent strength to be obtained.
A preferred embodiment of the (meth)acrylic resin (B) of this embodiment is a methyl methacrylate-butyl acrylate copolymer, or a mixture containing a methyl methacrylate-butyl acrylate copolymer and a methyl methacrylate-methyl acrylate copolymer, containing 0.1 to 20 mass% of the butyl acrylate monomer unit relative to the total amount of the (meth)acrylic resin (B). A particularly preferred embodiment is a mixture containing a methyl methacrylate-butyl acrylate copolymer and a methyl methacrylate-methyl acrylate copolymer.
In this embodiment, the proportion of the methyl methacrylate-butyl acrylate copolymer relative to the entire (100% by mass) of the (meth)acrylic resin (B) is preferably 2% by mass or more and 100% by mass or less, more preferably 3% by mass or more and 80% by mass or less, even more preferably 4% by mass or more and 60% by mass or less, still more preferably 5% by mass or more and 40% by mass or less, and most preferably 6% by mass or more and 30% by mass or less. By setting the proportion of the methyl methacrylate-butyl acrylate copolymer relative to the entire (100% by mass) of the (meth)acrylic resin (B) in the above range, a styrene-based resin composition and a molded article thereof having excellent appearance can be obtained.

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

<Other Monomers (b2)>
The (meth)acrylic resin (B) of this embodiment may further have other monomer units (b2) other than the butyl (meth)acrylate monomer and the above-mentioned (meth)acrylic acid monomer (b1-1) and (meth)acrylic acid ester monomer units (b1-2) added as necessary. That is, the other monomer units (b2) may be copolymerized with monomers other than the above-mentioned monomers without any particular limitation, as long as they are copolymerizable with the butyl (meth)acrylate monomer units or the unsaturated carboxylic acid monomer units (b1) (including the (meth)acrylic acid monomer (b1-1) and/or the (meth)acrylic acid ester monomer (b1-2)) within a range that does not impair the effects of the invention. For example, examples of the monomer (b2) other than the above-mentioned monomers include styrene, maleic anhydride, maleic acid, fumaric acid, itaconic acid, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleimide, and nucleus-substituted maleimide.
In the present embodiment, the content of the other monomer unit (b2) is preferably 0 to 30 mass%, more preferably 0 to 20 mass%, and even more preferably 0 to 15 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 10,000,000, more preferably 70,000 to 7,000,000, even more preferably 80,000 to 6,000,000, and even more preferably 90,000 to 5,000,000. By making the weight average molecular weight (Mw) of the (meth)acrylic resin (B) 50,000 or more, strength can be imparted when kneaded with the styrene-unsaturated carboxylic acid resin (A), and by making it 10,000,000 or less, the viscosity difference with the styrene-unsaturated carboxylic acid resin (A) can be suppressed, the (meth)acrylic resin (B) can be well dispersed in the styrene resin composition, and the generation of unmelted matter derived from the (meth)acrylic resin (B) can be suppressed, and an extruded sheet with good appearance can be obtained using the composition.
In the present embodiment, the Z-average molecular weight (Mz) of the (meth)acrylic resin (B) is preferably 100,000 to 10,000,000, and more preferably 120,000 to 9,000,000, as measured by a differential refractometer (RI detector).
In addition, as a particularly preferred embodiment described above, when the (meth)acrylic resin (B) is a mixture containing a methyl methacrylate-butyl acrylate copolymer and a methyl methacrylate-methyl acrylate copolymer, the weight average molecular weight (Mw) of the methyl methacrylate-butyl acrylate copolymer is preferably in the range of 1 to 10,000,000, more preferably 2 to 7,000,000, even more preferably 3 to 6,000,000, and still more preferably 4 to 5,000,000, and the weight average molecular weight (Mw) of the methyl methacrylate-methyl acrylate copolymer is preferably in the range of 50 to 1,000,000, more preferably 600,000 to 900,000, even more preferably 700,000 to 800,000, even more preferably 800,000 to 600,000, and most preferably 90,000 to 300,000.

When the styrene-based resin composition of the present embodiment contains a methyl methacrylate-butyl acrylate copolymer having a weight average molecular weight of 1 million or more, when the styrene-unsaturated carboxylic acid-based resin (A) is 100 parts by mass, the content of the methyl methacrylate-butyl acrylate copolymer having a weight average molecular weight of 1 million or more is preferably 5 parts by mass or less, 4 parts by mass or less, 3 parts by mass or less, 2.9 parts by mass or less, 2.8 parts by mass or less, 2.7 parts by mass or less, 2.6 parts by mass or less, 2.5 parts by mass or less, 2.4 parts by mass or less, 2.3 parts by mass or less, 2.2 parts by mass or less, 2.1 parts by mass or less, or 2.0 parts by mass or less as the upper limit, and more than 0 parts by mass, 0.1 parts by mass or more, 0.3 parts by mass or more, 0.6 parts by mass or more, 0.9 parts by mass or more, or 1.1 parts by mass or more are preferable. By setting it to the above range, the melt tension improving effect by the methyl methacrylate-butyl acrylate copolymer having a weight average molecular weight of 1 million or more can be efficiently obtained. In particular, by using a content of from more than 0 to 3 parts by mass, the generation of unmelted polymer can be suppressed, and a styrene-based resin composition and a molded article thereof having excellent appearance can be obtained.

In addition, the (meth)acrylic resin (B) of this embodiment preferably contains a high molecular weight component of 1 million or more. When the styrene-based resin composition contains the high molecular weight component of the (meth)acrylic resin (B) of 1 million or more, the heat resistance and rigidity are further suppressed from decreasing, and the heat oil resistance is further improved. In addition, the high molecular weight component of 1 million or more has a (meth)acrylate butyl monomer unit, and the proportion of the high molecular weight component of 1 million or more of the (meth)acrylic resin (B) contained in the styrene-based resin composition is preferably 0.3 mass% or more with respect to the total amount of the styrene-based resin composition.
In addition, as a method for controlling the content of high molecular weight components of 1 million or more in the (meth)acrylic resin (B) to 0.3 mass% or more, control can be performed by the type and amount of butyl (meth)acrylate or the unsaturated carboxylic acid monomer (b1) optionally added, the type and amount of a chain transfer agent, the reaction temperature, the residence time, the type and amount of a polymerization initiator, the type and amount of a polymerization solvent, etc., when radically polymerizing butyl (meth)acrylate.
As described above, in the present embodiment, it is more preferable that the (meth)acrylic resin (B) contains a high molecular weight component of 1 million or more in an amount of 0.3 mass % or more and 1.0 mass % or less relative to the total amount of the styrene-based resin composition, and that the weight average molecular weight (Mw) of the entire (meth)acrylic resin (B) (= the sum of the high molecular weight component of 1 million or more in the (meth)acrylic resin (B) and the molecular weight component of the (meth)acrylic resin (B) less than 1 million) is 5 to 10 million.

<(Meth)acrylic acid monomer or (meth)acrylic acid ester monomer in styrene-based resin composition>
In this embodiment, the content of all (meth)acrylic acid monomer units contained in the styrene-based resin composition is preferably 0 to 20 mass%, more preferably 3 to 15 mass%, and more preferably 6 to 10 mass%, 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 total amount of (meth)acrylic acid monomer units present in the styrene-based resin composition, and therefore each of the contents of (meth)acrylic acid monomer units in resin (A), resin (B) and resin (D) is also converted.

In this embodiment, the content of all (meth)acrylic acid ester monomer units contained in the styrene-based resin composition is preferably, in order of upper limit, 15.0 mass% or less, 8.0 mass% or less, 4.0 mass% or less, 3.0 mass% or less, 1.5 mass% or less, 1.2 mass% or less, 3.0 mass% or less, 2.5 mass% or less, 2.0 mass% or less, and 1.5 mass% or less, and the content of all (meth)acrylic acid ester monomer units contained in the styrene-based resin composition is preferably, in order of lower limit, 0.01 mass% or more, 0.05 mass% or more, 0.10 mass% or more, 0.15 mass% or more, 0.20 mass% or more, 0.25 mass% or more, 0.30 mass% or more, 0.35 mass% or more, 0.40 mass% or more, 0.45 mass% or more, and 0.50 mass% or more, relative to the total amount (100 mass%) of the styrene-based resin composition. The content of the total (meth)acrylic acid ester monomer units can be arbitrarily combined with the above upper limit and the above lower limit with respect to the total amount (100 mass%) of the styrene-based resin composition. When the content of the total (meth)acrylic acid ester monomers in the entire composition is within the above range, the effect of improving heat resistance, oil resistance and strength can be sufficiently obtained. In particular, by setting the content range of the total butyl acrylate monomer units contained in the styrene-based resin composition to 0 mass% or more and 0.45 mass% or less, a styrene-based resin composition having an excellent balance between heat resistance and mechanical strength and an excellent appearance can be obtained.
The above content of all (meth)acrylic acid ester monomer units indicates the total amount of (meth)acrylic acid ester monomer units present in the styrene-based resin composition, and therefore the contents of the (meth)acrylic acid ester monomer units in resin (A), resin (B) and resin (D) are also converted. Therefore, the content of butyl (meth)acrylate monomer units, which is an essential constituent of resin (B), is also included in the above content of all (meth)acrylic acid ester monomer units.

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 efficiently obtained at the same time, and as a result, a styrene-based resin composition with excellent heat and oil resistance and a sheet molded from the same can be obtained.

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

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

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

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

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

（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。） 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 (C) include "Fine Oxocol 180" manufactured by Nissan Chemical Industries, Ltd. and "Emulgen 109P" manufactured by Kao Corporation.

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

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

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

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

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

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

In this embodiment, the melt flow rate of the rubber-modified styrene-based resin (D) at 200°C is preferably 1.0 to 10.0 g/10 min, more preferably 2.0 to 8.0 g/10 min, and even more preferably 2.5 to 7.0 g/10 min. If the melt flow rate is in the range of 1.0 to 10.0 g/10 min, the resin has good mixability with the styrene-unsaturated carboxylic acid-based resin (A) and the styrene-unsaturated nitrile-based 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 rubber-modified styrene-based resin (D)>
The method for producing the rubber-modified styrene-based resin (D) is not particularly limited, but it can be produced by bulk polymerization (or solution polymerization) in which a styrene-based monomer (2) and, if necessary, other monomers (d1) and a solvent are polymerized in the presence of a rubber-like polymer, bulk-suspension polymerization that transitions to suspension polymerization during the reaction, or emulsion graft polymerization in which a styrene-based monomer (3) is polymerized in the presence of latex particles that are a rubber-like polymer. In bulk polymerization, it can be produced by continuously supplying a mixed solution containing a rubber-like polymer, a styrene-based monomer, and, if necessary, other monomers, an organic solvent, an organic peroxide, and/or a chain transfer agent to a polymerization apparatus configured by connecting a complete mixing reactor or a tank reactor and a plurality of tank reactors in series.

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

In the present embodiment, as described above, optional additive components can be added to the styrene-based resin composition. The total content of the styrene-unsaturated carboxylic acid-based resin (A) and the rubber-modified styrene-based resin (D) in the styrene-based resin composition is not particularly limited, but is preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 99% by mass or more.
As a preferred aspect of this embodiment, the styrene resin composition preferably contains a higher fatty acid surfactant. The addition of a higher fatty acid surfactant not only prevents blocking of the sheet, but also contributes to reducing the torque between pellets when kneading the resin composition by adding an appropriate amount 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 with respect 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-unsaturated carboxylic acid resin (A).
The higher fatty acid surfactant may be added during polymerization of each resin, or may be additionally kneaded when the styrene-unsaturated carboxylic acid resin (A) and the (meth)acrylic resin (B) are kneaded together.

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.

[Physical properties of styrene-based resin composition]
The physical properties 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 110° C. or higher, and even more preferably 115° C. or higher. By setting the Vicat softening temperature at 105° C. or higher, a sheet or container applicable to cooking in a general microwave oven of about 500 W can be obtained, and by setting the Vicat softening temperature at 115° C. or higher, 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 0.3 to 1.0 g/10 min. By making the melt flow rate 0.2 g/10 min or more, good moldability can be obtained, and by making it 2.0 g/10 min or less, a resin with excellent strength can be obtained.

<Melt tension>
In this embodiment, the melt tension of the styrene-based resin composition measured at 220° C. and a winding speed of 3.1 m/min is preferably in the range of 5 to 50 gf, more preferably 10 to 40 gf, even more preferably 15 to 35 gf, and even more preferably 20 to 30 gf. By setting the melt tension in the range of 15 to 35 gf in particular, the elasticity of the melt can be maintained during molding, and thickness deviation during secondary molding can be suppressed.

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

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

"High molecular weight components of 1 million or more in the entire styrene-based resin composition"
The styrene-based resin composition of this embodiment has the resin (A) and the resin (B), and may contain one or more selected from the group consisting of a rubber-modified styrene-based resin (D), an alcohol (C) having 10 or more carbon atoms, and an optional additive component, which are blended as necessary. The styrene-based resin composition of this embodiment essentially contains the resin (A) and the resin (B), and has a matrix polymer portion soluble in an organic solvent containing the polymer matrix of the rubber-modified styrene-based resin (D), an alcohol (C) having 10 or more carbon atoms, and an optional additive component. In other words, the styrene-based resin composition of this embodiment contains a matrix polymer portion. The matrix polymer portion essentially contains the resin (A) and the resin (B), and optionally contains one or more selected from the group consisting of a polymer matrix of the rubber-modified styrene-based resin (D), an alcohol (C) having 10 or more carbon atoms, and an optional additive component.
In the matrix polymer portion of this embodiment, when the matrix polymer portion is divided into a high molecular weight component of 1 million or more and a molecular weight component of less than 1 million, the upper limit of the high molecular weight component of 1 million or more is preferably 10.0 mass% or less, 6.0 mass% or less, 4.0 mass% or less, 3.0 mass% or less, 2.9 mass% or less, 2.8 mass% or less, 2.7 mass% or less, 2.8 mass% or less, 2.7 mass% or less, 2.6 mass% or less, 2.5 mass% or less, 2.4 mass% or less, 2.3 mass% or less, 2.2 mass% or less, 2.1 mass% or less, and 2.0 mass% or less, and the lower limit is preferably 0.3 mass% or more, 0.4 mass% or more, 0.5 mass% or more, and 0.6 mass% or more, in that order, with respect to the total amount of the matrix polymer portion soluble in an organic solvent. The content of the high molecular weight component of 1 million or more can be arbitrarily combined with the above upper limit and lower limit.
Therefore, the content of the high molecular weight component of 1 million or more (=the matrix polymer portion) in the entire styrene-based resin composition of this embodiment is preferably 0.3 to 10.0 mass % based on the total amount of the styrene-based resin composition.
This makes it possible to provide a styrene-based resin composition that can be used for molded articles having excellent transparency and heat oil resistance without deteriorating heat resistance, appearance and mechanical strength.
In particular, by adjusting the content of the high molecular weight component having a molecular weight of 1 million or more to 0.3 mass % or more and 2.0 mass % or less, the occurrence of unmelted defects is suppressed, and a composition having an excellent balance of strength, appearance, and suppression of thickness deviation during secondary molding due to the improvement in melt tension by the high molecular weight component can be obtained.
Of the high molecular weight components of 1 million or more in the entire styrene-based resin composition, it is preferable that the high molecular weight components of 1 million or more derived from resin (B) are greater than the high molecular weight components of 1 million or more derived from resin (A), and it is preferable that 70 mass% or more of the high molecular weight components of 1 million or more in the entire styrene-based resin composition are high molecular weight components of 1 million or more derived from resin (B).
As will be described later in the Examples section, the term "high molecular weight component having a molecular weight of 100 or more" refers to the weight percentage of molecular weights of 1,000,000 or more calculated from slice data of differential molecular weight distribution in terms of standard polystyrene measured with a differential refractometer (RI detector) before calculating various average molecular weights determined by gel permeation chromatography (GPC).

"The difference in Z-average molecular weight determined by the RI detector and the UV detector (Mz(RI) - Mz(
U.V.))
In this embodiment, when the value obtained by measuring the Z-average molecular weight of the entire styrene-based resin composition of this embodiment (=matrix polymer portion) using a gel permeation chromatography (GPC) equipped with a differential refractometer (RI detector) is taken as Mz(RI), and the value obtained by measuring the Z-average molecular weight of the entire styrene-based resin composition of this embodiment (=matrix polymer portion) using a gel permeation chromatography (GPC) equipped with an ultraviolet absorption detector (UV detector) is taken as Mz(UV), it is preferable that the value of Mz(RI)-Mz(UV) is 500,000 or less. This makes it possible to obtain a styrene-based resin composition that is excellent in preventing the generation of unmelted material during melting and in processability.
In this embodiment, the matrix polymer portion of the Z-average molecular weight obtained by gel permeation chromatography (GPC) of the difference between the measured value of a differential refractometer (RI detector) and the measured value of an ultraviolet spectrometer (UV detector) "Mz (RI) - Mz (UV)" is a value reflecting the molecular weight difference between the resin (A) and the resin (B), and mainly from the viewpoint of processability during melting, the upper limit is preferably 3 million or less, and more preferably 2.5 million or less, 2.1 million or less, 1.6 million or less, 1.2 million or less, 800,000 or less, 540,000 or less, 440,000 or less, 400,000 or less, 340,000 or less, 300,000 or less, 240,000 or less, 200,000 or less, 160,000 or less, and 130,000 or less in that order. On the other hand, the lower limit is preferably 2,000 or more, 3,000 or more, 4,000 or more, 5,000 or more, 6,000 or more, 7,000 or more, 8,000 or more, 9,000 or more, and 10,000 or more in that order. "Mz(RI)-Mz(UV)" can be within a range that combines any of the above upper and lower limit values.
In particular, by making the molecular weight difference between resin (A) and resin (B) 10,000 or more and 1,200,000 or less, the molecular weight difference between resins (A) and (B) becomes optimal, and it is possible to obtain a styrene-based resin composition that is excellent in processability and does not generate unmelted materials when melted.

"Quotient of Z-average molecular weight determined by RI detector and UV detector (Mz(RI)/Mz(UV))"
The quotient "Mz(RI)/Mz(UV)" of the measured value of the Z-average molecular weight of the matrix polymer portion of this embodiment obtained by gel permeation chromatography (GPC) measured value of a differential refractometer (RI detector) and an ultraviolet spectrometer (UV detector) is a value reflecting the molecular weight ratio of the resin (A) and the resin (B). From the viewpoint of processability during melting, the upper limit is preferably 6 or less, more preferably 5 or less, 4.5 or less, 40,000 or less, 3.8 or less, 3.6 or less, 3.4 or less, 3.2 or less, 3.0 or less, 2.8 or less, 2.6 or less, 2.4 or less, 2.2 or less, and 2.0 or less in that order, and the lower limit is more preferably 1.1 or more, 1.2 or more, 1.3 or more, and 1.4 or more and 1.5 or more. In particular, by setting it to 1.2 or more and 2.4 or less, the molecular weight ratio of the resin (A) and the resin (B) is optimized, and a styrene-based resin composition having excellent processability including generation of unmelted matter during melting and secondary moldability can be obtained.

In the styrene-based resin composition of the present embodiment, the total content of the styrene- unsaturated carboxylic acid-based resin (A) and the (meth)acrylic resin (B) is preferably 60 to 100 mass%, more preferably 70 to 90 mass%, and further preferably 75 to 85 mass%, based on the entire styrene-based resin composition.
In the styrene-based resin composition of the present embodiment, the total content of the styrene- unsaturated carboxylic acid-based resin (A), the (meth)acrylic resin (B), and the alcohol (C) having 10 or more carbon atoms preferably accounts for 60 to 100 mass%, more preferably 70 to 90 mass%, and even more preferably 75 to 85 mass%, based on the entire styrene-based resin composition.
In the styrene-based resin composition of the present embodiment, the total content of the styrene- unsaturated carboxylic acid-based resin (A), the (meth)acrylic-based resin (B), the alcohol having 10 or more carbon atoms (C), and the rubber-modified styrene-based resin (D) is preferably 60 to 100 mass%, more preferably 70 to 90 mass%, and even more preferably 75 to 85 mass%, based on the entire styrene-based resin composition.
In the styrene-based resin composition of the present embodiment, the total content of the styrene- unsaturated carboxylic acid-based resin (A), the (meth)acrylic-based resin (B), the rubber-modified styrene-based resin (D), and the optional added components is preferably 60 to 100 mass%, more preferably 70 to 90 mass%, and even more preferably 75 to 85 mass%, based on the entire styrene-based resin composition.
In the styrene-based resin composition of the present embodiment, the total content of the styrene- unsaturated carboxylic acid-based resin (A), the (meth)acrylic resin (B), the alcohol having 10 or more carbon atoms (C), and any optional added components is preferably 60 to 100 mass%, more preferably 70 to 90 mass%, and even more preferably 75 to 85 mass%, based on the entire styrene-based resin composition.
In the styrene-based resin composition of the present embodiment, the total content of the styrene- unsaturated carboxylic acid-based resin (A), the (meth)acrylic-based resin (B), the alcohol having 10 or more carbon atoms (C), the rubber-modified styrene-based resin (D), and any optional added components is preferably 60 to 100 mass%, more preferably 70 to 90 mass%, and even more preferably 75 to 85 mass%, based on the entire styrene-based resin composition.

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

[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 molding machine equipped with a T-die or circular die.

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

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

-Non-foamed extruded sheet-
In this embodiment, the thickness of the non-foamed sheet is preferably, for example, about 0.1 to 1.0 mm in terms of rigidity and thermoforming cycle. The uniaxial sheet may be formed only by roll stretching at a normal low magnification, and the biaxially stretched sheet is preferably stretched about 1.3 to 7 times in the machine direction (MD) with a roll and then stretched about 1.3 to 7 times in the perpendicular direction (TD) with a tenter in terms of strength. The non-foamed sheet may be used in a multilayer with a styrene-based resin other than the styrene-based resin composition, such as a polystyrene resin. It may also be used in a multilayer with a resin other than the styrene-based resin. Examples of the resin other than the styrene-based resin include PET resin and nylon resin.

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

The stretch ratio of the biaxially stretched sheet in this embodiment is preferably 1.3 to 7.0 times in the MD direction and 1.3 to 7.0 times in the TD direction from the viewpoint of strength.

The average thickness of the biaxially stretched sheet of this embodiment is preferably 0.1 mm or more, more preferably 0.15 mm or more, and even more preferably 0.2 mm or more, in order to ensure the strength, particularly the rigidity, of the sheet and container. On the other hand, from the viewpoint of economy, it is preferably 0.7 mm or less, more preferably 0.6 mm or less, and even more preferably 0.5 mm or less.

The orientation relaxation stress in the longitudinal and transverse directions of the biaxially stretched sheet of this embodiment is preferably in the range of 0.4 to 1.3 MPa. By adjusting the orientation relaxation stress within this range, the strength of the molded product of the biaxially stretched sheet can be maintained.

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

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

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 each average molecular weight (Mn, Mw, Mz) and high molecular weight component of 1 million or more The average molecular weight (Mn, Mw, Mz) and high molecular weight component of 1 million or more of the polymer matrix soluble in an organic solvent of each resin and resin composition produced in the examples and comparative examples were measured using gel permeation chromatography (GPC) under the following conditions.
Measuring equipment: Tosoh HLC-8220
Separation column: Two Tosoh TSK gel Super HZM-H (inner diameter 4.6 mm) connected in series Guard column: Tosoh TSK guard column Super HZ-H
Measurement solvent: tetrahydrofuran (THF)
Sample concentration: 10 mg of the measurement sample was dissolved in 10 mL of solvent.
Sample pretreatment: Filtration is performed using a 0.45 μm membrane filter to remove foreign matter such as dust and components that are not necessary for the organic solvent, such as rubber-like polymer particles contained in the rubber-modified styrene-based resin (D).
Injection volume: 10 μL
Measurement temperature: 40°C
Flow rate: 0.35 mL/min Detector: differential refractometer (RI detector) and ultraviolet spectrometer (UV detector)
The calibration curve was prepared using 11 types of TSK standard polystyrenes (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) manufactured by Tosoh Corporation. The calibration curve was prepared using a linear approximation equation, and the molecular weights calculated in terms of the standard polystyrenes were measured.
Unless otherwise specified, the molecular weights described in this specification are values measured by a differential refractometer (RI detector).
The percentage of high molecular weight components having a molecular weight of 1,000,000 or more in this specification is a value calculated from the differential molecular weight distribution measured with a differential refractometer (RI detector).

(2) Measurement of Melt Mass Flow Rate (MFR) The melt mass flow rate (g/10 min) of each of the resins and resin compositions produced in the Examples and Comparative Examples was measured at 200° C. and a load of 49 N in accordance with ISO 1133.

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

(4) Measurement of the content of monohydric alcohol (C) having 10 or more carbon atoms in the styrene-based resin composition The content of the monohydric alcohol (C) having 10 or more carbon atoms in the entire styrene-based resin composition was measured 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 p-
5 mL of hexane in which diethylbenzene had been adjusted to 200 μg/g was added to reprecipitate the polymer component, and the supernatant was collected and used as the measurement solution.
Measurement equipment: Agilent 6850 series GC system Detector: FID
Column: DB-WAX
Length: 60m
Film thickness: 0.50 μm
Diameter: 0.320 mm
Injection volume: 1 μL
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.

(5) Measurement of Content of Each Monomer Unit The content of each monomer unit contained in the resin compositions prepared in the Examples and Comparative Examples was measured by pyrolysis GC/MS under the following conditions.
Sample preparation: The resin compositions prepared in the Examples and Comparative Examples were formed into a film by heat pressing at 220° C., and the sample was weighed on a precision balance.
Measurement conditions Pyrolysis unit Equipment: Frontier 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)
Sample amount: 20-100 μg
In addition, when detecting each monomer peak, in order to avoid peak overlap or saturation of peak intensity, the measurement mode may be changed as appropriate, such as SCAN mode or SIM mode, pretreatment such as the dilution rate of the sample may be performed, the column used may be changed depending on the polarity of the chemical species to be detected, or conditions such as the sample amount and split ratio may be adjusted to prevent saturation peaks by varying the strength of the detection signal.

(6) Average particle size of rubber-like polymer particles in rubber-modified styrene-based resin (D) The average particle size (μm) of rubber-like polymer particles in rubber-modified styrene-based resin (D) (so-called HIPS resin) was measured using 200 rubber-like polymer particles observed by cross-sectional observation using a transmission electron microscope, and the average particle size (μm) of the rubber-like polymer particles was calculated based on the following formula (3):
Average particle diameter = Σ(ni×Di ⁴ )/Σ(ni×Di ³ )
{In the above formula (3), ni is the number of rubber-like polymer particles having a particle diameter Di, and Di is the average value of the major axis and minor axis of the rubber-like polymer particles.}
It was calculated by:

(7) Haze Measurement of 2 mm Plate Each of the resin compositions produced in the Examples and Comparative Examples was molded into a 2 mm plate by injection molding, and the plate was conditioned for 48 hours or more in a thermostatic chamber at 23° C. and 50% humidity. The haze was then measured using a color difference turbidity meter (COH-300A) manufactured by Nippon Denshoku Industries Co., Ltd., and the n3 average was recorded as the haze value.

(8) Measurement of Melt Tension (gf (220° C., 3.1 m/min)) The melt tension (gf) of each of the resins and resin compositions produced in the Examples and Comparative Examples was measured under the following conditions.
Measuring equipment: Malvern Capillary Rheometer RH10
Measurement temperature: 220°C
Piston descending speed: 8.1 mm/min. Winding speed: 3.1 m/min. Capillary die: 2 mmφ×20 mmL
Drying conditions: Each resin and resin composition was dried at 80° C. for 2 hours before measurement.
Under the above measurement conditions, the average value of the measurements within the range in which the load became stable was taken as the melt tension value.

(9) Evaluation of heat 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 110°C for 15 minutes. Then, the haze was measured using a haze meter (NDH-2000) manufactured by Nippon Denshoku Industries Co., Ltd., and the change in haze (Δhaze) before and after immersion was calculated according to the following formula, and the heat oil resistance was evaluated according to the following evaluation criteria.
ΔHaze = Haze after test (%) - Haze before test (%)
Evaluation criteria: ◎: Δ haze is 3% or less; ○: Δ haze is more than 3% and less than 7%; △: Δ haze is more than 7% and less than 10%; ×: Δ haze is more than 10%.

[Evaluation of properties of non-foamed extruded sheet (biaxially stretched sheet)]
(10) Measurement of heat-resistant oil temperature of biaxially oriented sheet Biaxially oriented sheets molded using each resin composition prepared in the Examples and Comparative Examples were cut into strips of 10 cm x 1.5 cm, wrapped circumferentially around a cylinder with a diameter of 7.5 cm, and MCT oil was applied to the center of the strip to a diameter of 1 cm. After heating for 15 minutes in a thermostatic bath heated to a specified temperature, the maximum temperature at which "cracks or whitening" were not observed was recorded as the heat-resistant oil temperature.

(11) Measurement of strength of biaxially stretched sheet The biaxially stretched sheets produced in the examples and comparative examples were cut into 8 cm 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 recorded as the value.

(12) Measurement of heat resistance of biaxially oriented sheets The biaxially oriented sheets produced in the examples and comparative examples were cut into strips of 10 cm x 1.5 cm and placed in an oven set at 110°C for 60 minutes. The deformation of the biaxially oriented sheets was then visually observed, and the heat resistance was evaluated based on the thermal deformation as follows.
Specifically, the above-mentioned dimensional change was measured by measuring the amount of change in length of 10 cm before and after thermal deformation according to the following formula (4).
Equation (4): Dimensional change (%) = (length in MD direction of biaxially oriented sheet after being placed in oven for 60 minutes - length in MD direction of biaxially oriented sheet before being placed in oven) / length in MD direction of biaxially oriented sheet before being placed in oven ◯: Dimensional change of 1% or less △: Dimensional change of 1% or more but not exceeding 3% ×: Dimensional deformation of 3% or more

(13) Measurement of Internal Haze (Cloudiness) of Biaxially Stretched Sheet The biaxially stretched sheets produced in the Examples and Comparative Examples were cut into pieces of 3 cm x 5 cm, and in order to reduce the influence of surface roughness, the biaxially stretched sheets were immersed in liquid paraffin, and the haze was measured using a Nippon Denshoku Industries Co., Ltd. haze meter (NDH-2000), and the n3 average was recorded as the value.

(14) Appearance Evaluation of Non-foamed Extruded Sheet Using each of the resin compositions prepared in the Examples and Comparative Examples, sheets of the same resin composition were extruded continuously for 30 minutes using a 30 mmφ short-axis sheet extruder, and then five sheets measuring 10 cm × 20 cm were cut out from the 0.3 mm thick sheet. The number of visually confirmed unmelted objects and air bubbles, which were foreign objects with an average diameter of (major axis + minor axis)/2 of 0.5 mm or more on the surfaces of the five sheets, were counted, and the appearance was evaluated by the following method.
○: 2 or less unmelted objects or bubbles visible to the naked eye △: 3 to 9 unmelted objects or bubbles visible to the naked eye ×: 10 or more unmelted objects or bubbles visible to the naked eye (15) Secondary formability of biaxially oriented sheets The biaxially oriented sheets prepared in the examples and comparative examples were subjected to secondary molding into 100 lid-shaped molded products measuring 160 mm long x 140 mm wide x 40 mm high using a hot plate molding machine under conditions of a hot plate temperature of 170°C and a heating time of 1.5 seconds. The number of lid-shaped molded products with and without holes in the corners of the lid-shaped molded products was counted, and the secondary formability was evaluated by the following method.
◎: 0 molded products with holes. 〇: 1 to 3 or less molded products with holes. △: More than 3 to 7 or less molded products with holes. ×: 7 or more molded products with holes.

[Evaluation of properties of foamed extruded sheets]
(16) Measurement of heat oil resistance of foamed sheet Coconut oil (manufactured by Wako Pure Chemical Industries, Ltd.) was applied in a circle with a diameter of about 1 cm to a foamed extruded sheet obtained by molding the composition, and after heating in an oven at 90° C. for 10 minutes, the appearance of the part where the coconut oil was applied was visually evaluated.
◯: No change △: The coated part was deformed in size but not torn ×: The coated part was torn

[Evaluation of properties of molded products obtained by secondary molding of biaxially stretched sheets]
The biaxially stretched sheets produced in the Examples and Comparative Examples were used in a hot plate molding machine to produce lid-shaped molded products measuring 160 mm in length, 140 mm in width, and 40 mm in height under conditions of a hot plate temperature of 145°C and a heating time of 2.0 seconds, and were subjected to the following evaluations.
(17) Thickness uniformity of molded product For the above-mentioned lid-shaped molded product, the difference between the maximum (D _max ) and minimum (D _min ) thickness values measured at 42 points at 20 mm intervals was measured, D _max -D _min (mm), and evaluated according to the following criteria.
◎: Less than 0.005 ◯: 0.005 or more and 0.015 or less △: More than 0.015 and less than 0.03 ×: 0.03 or more

(18) Transparency (after molding)
The haze of the above-mentioned lid-shaped molded product was measured using a haze meter (NDH-2000) manufactured by Nippon Denshoku Industries Co., Ltd. At this time, the haze value was measured as an n3 average and evaluated according to the following criteria.
◯: Haze 2.0% or less △: Haze over 2.0% to 5.0% or less ×: Haze over 5.0%

(19) Strength of Molded Product A test piece measuring 80 mm in length and 80 mm in width was cut out from the center of the above-mentioned lid-shaped molded product, 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 used as the value and evaluated from the following viewpoints.
◯: 5.0 kgf or more ×: less than 5.0 kgf Containers with a strength of less than 5.0 kgf broke during transportation.

[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-Unsaturated Carboxylic Acid Resin (A)>
-Preparation of resin a-1-
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 the resin a-1 obtained by the above-mentioned analytical methods are shown in Table 1 below.

-Preparation of resins a-2, a-3, and a-4-
Resins a-2, a-3, and a-4 were prepared in the same manner as for Resin a-1 by adjusting the feed amount of each monomer and the polymerization conditions. The compositions and physical properties of the obtained Resins a-1 to a-4 are shown in Table 1.

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

<Production Example of (Meth)Acrylic Resin (B)>
-Preparation of resin b-1-
2 kg of water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were added to a 5 L container 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, 0.20 kg of methyl acrylate, 0.99 g of lauroyl peroxide, 4.93 g of n-octyl mercaptan, and the above suspension were added as polymerization raw materials. 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 using a Buchner funnel to obtain a bead-like polymer. The bead-like polymer was washed and dehydrated five times with about 20 L of distilled water on the Buchner funnel, then dried and pelletized using a single-screw extruder to obtain resin b-1 as a pellet-like resin.

-Preparation of Resins b-2, b-3, and b-4-
Resins b-2, b-3, and b-4 were prepared in the same manner as for Resin b-1 by adjusting the feed amount of each monomer and the polymerization conditions. The compositions and physical properties of the obtained Resins b-1 to b-4 are shown in Table 2.

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

<Production Example of Rubber-Modified Styrene-Based Resin (D)>
-Preparation of resin d-1-
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 was used to produce rubber-modified styrene-based resin d-1 (hereinafter, resin d-1). 83.5 parts by mass of styrene, 7.9 parts by mass of methyl methacrylate, 10.0 parts by mass of ethylbenzene, 6.5 parts by mass of Asahi Kasei Corporation's low-cis butadiene rubber diene 35AE as a rubber component, and 0.02 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane were charged into a raw material tank equipped with a stirrer, and the rubber component was dissolved with a stirrer. The raw material solution was then fed 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 rubber particle size was controlled by adjusting the rotation speed of the stirrer of the first-stage laminar flow reactor to 150 rpm. The composition and properties of the obtained resin d-1 are shown in Table 3.

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

<Production Example of Styrene-Based Resin Composition>
The detailed method for producing the styrene-based resin composition will be described below.
--Example 1--
91.6 parts by mass of resin a-1 shown in Table 1 as styrene-unsaturated carboxylic acid resin (A), 6.9 parts by mass of resin b-1 shown in Table 2 as (meth)acrylic resin (B), 0.1 parts by mass of Fine Oxocol 180 as monohydric alcohol (C) having 10 or more carbon atoms, and 1.5 parts by mass of rubber-modified styrene-based resin d-1 shown in Table 3 were dry-blended, and the mixture was kneaded and extruded using a twin-screw extruder TEM26SS manufactured by Shibaura Machine Co., Ltd., and pelletized to obtain a styrene-based resin composition as a pellet-shaped resin. The screw rotation speed was 150 rpm, the cylinder temperature was 180 to 230 ° C, and the feed rate was 10 kg / h. The resin temperature was 250 to 260 ° C.
The pellets were then processed by press molding into a plate of 10 cm x 10 cm x 1.2 mm. The plate was then stretched at 250 mm/min to a magnification of 2.4 in the X-axis and 2.4 in the Y-axis in a batch biaxial stretching machine EX6-S1 manufactured by Toyo Seiki Seisakusho Co., Ltd., with the chuck distance set to 85 mm, and heated for 10 minutes at a temperature of 20°C above the Vicat softening temperature of the styrene-based resin composition.
A biaxially stretched sheet having a thickness of 100 mm was obtained. The evaluation results of the obtained composition, the biaxially stretched sheet, and the molded article are shown in Table 4.

--Examples 2 to 13--
A resin composition and a biaxially stretched sheet were obtained in the same manner as in Example 1, except that the formulation was changed as shown in Table 4 below. The evaluation results of the composition and the biaxially stretched sheet, and the evaluation results of the molded product are shown in Table 4. As shown in Table 4, one or two of (meth)acrylic resin (B)_I and (meth)acrylic resin (B)_II were used as the (meth)acrylic resin (B).

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

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 product parts, toys, daily necessities, various industrial parts), etc., and is particularly useful as a packaging material for refrigerated transport, and plays a major role in the industrial world.

Claims (14)

A styrene-based resin composition comprising: a styrene-unsaturated carboxylic acid-based resin (A) having a styrene-based monomer unit (1), a (meth)acrylic acid monomer unit (a1-1) and a (meth)acrylic acid ester monomer unit (a1-2); and a (meth)acrylic resin (B) having a butyl (meth)acrylate monomer unit,
The content of the styrene-based monomer unit (1) is 84.0 to 90.0% by mass based on the styrene-unsaturated carboxylic acid-based resin (A),
a total content of the styrene-unsaturated carboxylic acid resin (A) and the (meth)acrylic resin (B) in the entire styrene-based resin composition is 75% by mass to 100% by mass,
A styrene-based resin composition, wherein the content of the styrene-unsaturated carboxylic acid-based resin (A) is 82.5 to 97.5 mass% and the content of the (meth)acrylic resin (B) is 1.0 to 7.0 mass% based on the total amount of the styrene-based resin composition. The styrene-based resin composition according to claim 1, wherein the amount of high molecular weight components of 1 million or more in the entire styrene-based resin composition is 0.3 to 10.0 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 styrene-based monomer unit (1) is contained in an amount of 60 to 85 mass% based on the total amount of the styrene-based resin composition. The styrene- based resin composition according to claim 1 or 2, comprising 2 to 30 mass% of the (meth)acrylic acid monomer unit (a1-1) and 1 to 20 mass% of the (meth)acrylic acid ester monomer unit (a1-2) relative to the total amount of the styrene-unsaturated carboxylic acid-based resin (A). The styrene-based resin composition according to claim 1 or 2, containing 3.2 to 7 mass% of the (meth)acrylic resin (B) relative to the total amount of the styrene-based resin composition. The styrene - based resin composition according to claim 1 or 2, wherein the total content of the (meth)acrylic acid ester monomer unit (a1-2) and the (meth)acrylate butyl is 15 to 40 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-butyl acrylate copolymer, or a mixture containing a methyl methacrylate-butyl acrylate copolymer and a methyl methacrylate-methyl acrylate copolymer, and contains 0.1 to 20 mass% of the butyl acrylate monomer unit relative to the total amount of the (meth)acrylic resin (B). The styrene-based resin composition according to claim 1 or 2, which contains 0.01 to 1.0 parts by mass of an alcohol (C) having 10 or more carbon atoms relative to the total amount (100 parts by mass) of the styrene-based resin composition. The styrene-based resin composition according to claim 1 or 2, containing 0.1 to 20 mass% of the rubber-modified styrene-based resin (D) based on the total amount of the styrene-based resin composition. The styrene-based resin composition according to claim 1 or 2, wherein the content of butyl acrylate monomer units is more than 0 to 3.0 mass% based on the total amount of the styrene-based resin composition. The Z-average molecular weight of the styrene-based resin composition according to claim 1 or 2, measured by gel permeation chromatography (GPC) in terms of standard polystyrene,
When the value measured by a differential refractometer (RI detector) is Mz(RI) and the value measured by an ultraviolet absorption detector (UV detector) is Mz(UV),
The styrene-based resin composition according to claim 1 or 2, wherein the value of Mz(RI)-Mz(UV) is 500,000 or less. The styrene-based resin composition according to claim 1 or 2, wherein a 2 mm thick plate-shaped test piece produced by injection molding of the styrene-based resin composition according to claim 1 or 2 has a haze value of less than 10%. A non-foamable or foamable extruded sheet having the styrene-based resin composition according to claim 1 or 2. A container formed by molding the styrene-based resin composition according to claim 1 or 2.