JP6930855B2 - Styrene-based resin composition, sheet, molded product, and method for manufacturing sheet - Google Patents

Description

The present invention relates to a styrene resin composition, a sheet, a molded product, and a method for producing the sheet.

Since the styrene resin composition is excellent in transparency, molding processability, etc., it is widely used as a molding material for home appliances, office machines, miscellaneous goods, housing equipment, and food packaging materials. In recent years, with the spread of microwave ovens in food packaging applications, high heat resistance is required to withstand heating in microwave ovens. In addition, the shape of the container has become more complicated, and further improvement in moldability is required. Further, in the foamed sheet of the styrene resin composition, a material capable of foaming at a high magnification and having excellent foaming characteristics is required.

As a method for obtaining a styrene-based resin composition having excellent heat resistance, moldability, and foaming properties, Patent Document 1 discloses a technique for a resin composition containing a copolymer of a macromonomer and styrene and a polyphenylene ether.

Japanese Unexamined Patent Publication No. 2011-246588

However, in the method described in Patent Document 1, the use of these styrene-based copolymers is not sufficient for reducing the gel-like substance, and has a drawback that the appearance of the molded product is deteriorated. In addition, although there is a description of the general range of the molecular weights of the styrene resin and the polyphenylene ether resin, the effect that the relationship between the molecular weight of the styrene resin and the molecular weight of the polyphenylene ether resin leads to the improvement of moldability is disclosed. No.

An object of the present invention is to provide a styrene resin composition having excellent heat resistance, moldability, foaming properties, and appearance.

As a result of diligent research to achieve the above object, the present inventors have determined the molecular weight of the styrene resin and the molecular weight of the polyphenylene ether resin in the composition of a specific styrene resin and the polyphenylene ether resin. By setting the ratio within a certain range, it was found that a resin composition having excellent heat resistance, moldability, foaming properties, and appearance can be obtained, and the invention has been completed.

The present invention is as shown below.
[1]
A resin composition containing a styrene resin (A) and a polyphenylene ether resin (B).
When the total amount of the styrene resin (A) and the polyphenylene ether resin (B) is 100 parts by mass, the styrene resin (A) is 50 to 95 parts by mass, and the polyphenylene ether resin (B) is Containing 5 to 50 parts by mass,
The styrene resin is characterized in that the ratio (PS_Mz / PPE_Mz) of the Z average molecular weight (PS_Mz) of the styrene resin (A) to the Z average molecular weight (PPE_Mz) of the polyphenylene ether resin (B) is 12 to 50. Composition.
[2]
The styrene resin composition according to [1], wherein the styrene resin (A) has a degree of branching of 0.70 to 1.00 and a degree of gelation of 1.40 or less.
[3]
The styrene resin composition according to [1] or [2], further containing 0.01 to 1.0 parts by mass of a stabilizer.
[4]
A non-foamed or foamed sheet containing the styrene resin composition according to any one of [1] to [3].
[5]
A molded product containing the non-foamed or foamed sheet according to [4].
[6]
The molded product according to [5], which is a food packaging container.
[7]
A method for producing a sheet, which comprises using the styrene resin composition according to any one of [1] to [4].

According to the present invention, it is possible to provide a styrene resin composition, a sheet, a molded product, and a method for producing a sheet, which are excellent in heat resistance, moldability, foaming properties, and appearance.

Hereinafter, embodiments of the present invention (hereinafter referred to as “the present embodiment”) will be described, but the present invention is not limited to the present embodiment.

[Styrene-based resin composition]
[[Styrene-based resin (A)]]
The styrene-based resin (A) of the present embodiment is obtained by polymerizing a styrene-based monomer as a main component.
Examples of the styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene and the like. These can be used alone or in combination, but styrene is preferable because it can be used industrially at low cost.
Further, in the styrene resin, a monomer other than the styrene resin or a polymer having a conjugated bond can be copolymerized as long as the desired effect is not impaired.
Examples of monomers that can be copolymerized include vinyl compounds such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate, and (meth) acrylonitrile, and Included are dimethylmaleate, dimethylfumarate, diethylfumarate, ethylfumarate, maleic anhydride, maleimide, and nuclear-substituted maleimide.
Examples of the polymer having a conjugated bond include polybutadiene and isoprene.

The content of the styrene resin (A) in the resin composition of the present embodiment is 50 to 95 when the total amount of the styrene resin (A) and the polyphenylene ether resin (B) is 100 parts by mass. It is parts by mass, preferably 60 to 90 parts by mass, and more preferably 70 to 85 parts by mass.

In the styrene resin (A) of the present embodiment, the weight average molecular weight (Mw) is preferably 150,000 to 500,000, more preferably 200,000 to 450,000, and further preferably 250,000 to 400,000. ..
The Z average molecular weight (Mz) is preferably 150,000 to 2.5 million, more preferably 500,000 to 2 million, and even more preferably 750,000 to 1.5 million.
The ratio (Mw / Mz) of the weight average molecular weight (Mw) of the styrene resin (A) of the present embodiment to the Z average molecular weight (Mz) is preferably 1.8 to 5.0, more preferably. It is 2.0 to 4.8, more preferably 2.1 to 4.7.
By setting the Mw of the styrene resin (A) to 150,000 to 500,000 and setting the ratio of Mz to Mw (Mw / Mz) to the range of 1.8 to 5.0, the moldability and fluidity can be improved. An excellent styrene resin (A) can be obtained.
The molecular weight and the molecular weight distribution can be measured by GPC.

In the present embodiment, the residual amount of the styrene-based monomer for the styrene-based resin (A) is preferably 1000 mass ppm or less, more preferably 700 mass ppm or less, still more preferably 500 mass ppm or less. The odor around the die outlet at the time of sheet extrusion and the color tone of the copolymer resin are improved.
The residual amount of the styrene-based monomer can be measured by gas chromatography.

In the present embodiment, a styrene dimer or trimer is produced during the polymerization of the styrene resin, which is the raw material of the styrene resin. The amount of styrene dimer or trimer produced differs depending on the method of initiating polymerization. That is, the amount of organic peroxide or azo-based polymerization initiator produced differs between the case where an organic peroxide or an azo-based polymerization initiator is used and the case where only heat initiation is used. The amount of styrene dimer or trimer produced is lowest when organic peroxide is used and highest when only heat initiation is used. Styrene dimers and trimers may cause problems due to deterioration of heat resistance, adhesion to the eyes and eyes at the die outlet during extrusion with an extruder, and adhesion to the eyes and eyes during injection molding. be. Therefore, as a polymerization initiation method, it is preferable to use an organic peroxide as a polymerization initiator.

Specifically, the dimers and trimers of styrene include 1,3-diphenylpropane, 2,4-diphenyl-1butene, 1,2-diphenylcyclobutane, 1-phenyltetralin, 2,4,6. -Triphenyl-1-hexene, 1-phenyl-4- (1'-phenylethyl) tetralin and the like can be mentioned.

Regarding the styrene resin (A), the total amount of the styrene dimer and trimer in 100% by mass of the styrene resin (A) is preferably as low as possible, but more preferably 0.7% by mass or less, and further. It is preferably 0.6% by mass or less.
The residual amounts of the styrene dimer and trimer can be measured by gas chromatography.

Regarding the degree of branching and the degree of gelation of the styrene resin (A) of the present embodiment, it is preferable that the degree of branching is 0.70 to 1.00 and the degree of gelation is 1.40 or less.
The degree of bifurcation is more preferably 0.8 to 0.97 or less, still more preferably 0.8 to 0.95 or less. The degree of gelation is more preferably 1.25 or less, and even more preferably 1.10 or less.
If the degree of branching and the degree of gelation of the styrene resin (A) are within this range, styrene-derived lumps are unlikely to occur, and a good appearance can be obtained when molded into a sheet or container.
The degree of bifurcation and the degree of gelation can be measured by the method described in Examples described later.

Examples of the polymerization method of the styrene resin (A) of the present embodiment include known styrene polymerization methods such as a massive polymerization method, a solution polymerization method, and a suspension polymerization method. These polymerization methods may be a batch polymerization method or a continuous polymerization method, and are preferably continuous polymerization methods from the viewpoint of productivity.
Examples of the continuous polymerization method include monomers by adding and mixing a styrene-based monomer, a conjugated divinyl compound having a conjugated vinyl group, a solvent, a polymerization catalyst, a chain transfer agent, and the like, if necessary. Prepare the raw material solution. The above raw materials are provided in equipment equipped with two or more reactors arranged alone or in series and / or in parallel, and a devolatilizer for a volatilization step of removing volatile components such as unreacted monomers. Examples thereof include a method in which the solution is continuously fed and the polymerization proceeds step by step.

Examples of the reactor include a completely mixed reactor, a laminar reactor, and a loop reactor that extracts a part of the polymerization solution while advancing the polymerization. The order of arrangement of these reactors is not particularly limited.

The molecular weight and molecular weight distribution of the styrene resin of the present embodiment are the types of the reaction temperature, the residence time, the polymerization initiator, the chain transfer agent, and the molecular weight adjusting agent having two conjugated functional groups when radically polymerizing styrene. It can be controlled by the amount of addition, the type and amount of the solvent used at the time of polymerization, and the like.

When polymerizing the styrene resin of the present embodiment, a polymerization solvent, a polymerization initiator such as an organic peroxide, and a chain transfer agent can be used, if necessary, from the viewpoint of controlling the polymerization reaction. ..
The polymerization solvent is generally used for adjusting the polymerization rate, molecular weight, etc. in continuous bulk polymerization or continuous solution polymerization. The polymerization solvent is not particularly limited, and examples thereof include alkylbenzenes such as benzene, toluene, ethylbenzene, and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane.
The amount of the polymerization solvent used is not particularly limited, but is usually based on 100% by mass of the entire polymerization solution in the polymerization reactor from the viewpoints of controlling gelation, improving productivity, increasing the molecular weight, and the like. It is preferably 1 to 50% by mass, more preferably 3 to 20% by mass.

When the polymerization raw material is polymerized in order to obtain the styrene-based copolymer of the present embodiment, the polymerization initiator and the chain transfer agent can be contained in the polymerization raw material composition.
The polymerization initiator is not particularly limited, but is an organic peroxide, for example, 2,2-bis (t-butylperoxy) butane, 1,1-bis (t-butylperoxy) cyclohexane, and n-butyl-. Peroxyketals such as 4,4-bis (t-butylperoxy) valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, acetyl peroxide, isobutyryl peroxide, etc. Diacyl peroxides, peroxydicarbonates such as diisopropylperoxydicarbonate, peroxyesters such as t-butylperoxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butylhydroperoxide. Can be done.
The polymerization initiator is preferably used in an amount of 0.005 to 0.08% by mass based on the styrene-based monomer.
The chain transfer agent is not particularly limited, and examples thereof include α-methylstyrene dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan.
The chain transfer agent is preferably used in an amount of 0.01 to 0.50% by mass based on the styrene-based monomer.

As the volatilization device, for example, a normal volatilization device such as a flash drum, a twin-screw volatilizer, a thin film evaporator, or an extruder can be used, and generally, a vacuum volatilization tank equipped with a heater or a devolatilizer can be used. A volatile extruder or the like is used. As the arrangement of the devolatilizer, for example, a vacuum devastation tank with a heater is used in only one stage, a vacuum devastation tank with a heater is connected in two stages in series, and a vacuum devastation tank with a heater is connected. An example is one in which a volatilization tank and a devolatilization extruder are connected in series. In order to reduce the volatile components as much as possible, it is preferable that a vacuum devastation tank with a heater is connected in two stages in series, or a vacuum devolatilization tank with a heater and a devolatilization extruder are connected in series. ..

The conditions of the devolatilization step are not particularly limited. For example, when the polymerization of the monovinyl-based monomer is carried out by bulk polymerization, the unreacted monovinyl-based single weight is preferably used in the styrene-based copolymer. The polymerization can proceed until it becomes 50% by mass, more preferably 40% by mass or less. By the devolatile treatment, unreacted substances (monovinyl-based single weight bodies) and / or volatile components such as solvents can be removed.

The temperature of the devolatile treatment is usually about 190 to 280 ° C. The pressure of the devolatilization treatment is preferably 0.1 to 50 kPa, more preferably 0.13 to 13 kPa, still more preferably 0.13 to 7 kPa, and particularly preferably 0.13 to 1.3 kPa.

As the volatilization method, for example, it is desirable to volatilize by reducing the pressure under heating, or through an extruder designed to remove volatile components.

［式中、Ｒ¹、Ｒ²、Ｒ³、及びＲ⁴は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１〜７の第１級又は第２級のアルキル基、フェニル基、ハロアルキル基、アミノアルキル基、炭化水素オキシ基、少なくとも２個の炭素原子がハロゲン原子と酸素原子とを隔てているハロ炭化水素オキシ基からなる群から選択されるものである。］ [[Polyphenylene ether (B)]]
The polyphenylene ether-based resin (B) used in the present embodiment is a homopolymer and / or a copolymer having a repeating unit structure represented by the following formula.

[In the formula, R ¹ , R ² , R ³ , and R ⁴ are independently hydrogen atom, halogen atom, primary or secondary alkyl group having 1 to 7 carbon atoms, phenyl group, and haloalkyl. It is selected from the group consisting of a group, an aminoalkyl group, a hydrocarbon oxy group, and a halohydrocarbon oxy group in which at least two carbon atoms separate a halogen atom and an oxygen atom. ]

The reduced viscosity is preferably in the range of 0.25 to 1.00, more preferably in the range of 0.30 to 0.70, and even more preferably in the range of 0.35 to 0.6. If the reduced viscosity is less than 0.20, the strength is inferior, and if it exceeds 1.00, the fluidity is deteriorated.
The reduced viscosity can be measured using a 0.5 g / dL chloroform solution under the condition of a temperature of 30 ° C. using an Ubbelohde type viscosity tube.

The polyphenylene ether-based resin that can be used in the present embodiment is not particularly limited, and known ones may be used, for example, poly (2,6-dimethyl-1,4-phenylene ether) and poly (2-). Methyl-6-ethyl-1,4-phenylene ether), poly (2-methyl-6-phenyl-1,4-phenylene ether), poly (2,6-dichloro-1,4-phenylene ether) and the like. Further, polyphenylene ether copolymers such as 2,6-dimethylphenol and other phenols (for example, 2,3,6-trimethylphenol and 2-methyl-6-butylphenol) can also be used. Among them, poly (2,6-dimethyl-1,4-phenylene ether), a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol is preferable, and poly is more preferable. (2,6-dimethyl-1,4-phenylene ether).

The method for producing the polyphenylene ether-based resin is not particularly limited, and conventionally known ones can be used. For example, it can be easily produced by using the complex of cuprous salt and amine described in US Pat. No. 3,306,874 as a catalyst and oxidatively polymerizing, for example, 2,6-xylenol. Alternatively, US Pat. No. 3,306,875, US Pat. No. 3,257,357, US Pat. No. 3,257,358, Japanese Patent Application Laid-Open No. 52-17880, Japanese Patent Application Laid-Open No. 50-51197, Japanese Patent Application Laid-Open No. 63-152628. It can be manufactured by the method described in the publication or the like.

Polyphenylene ether-based resins are produced by oxidative coupling of phenolic compounds. The oxidation-coupling reaction catalyst of the polyphenylene ether-based resin is not particularly limited, but at least one heavy metal compound such as copper, manganese, and cobalt is used (US Pat. No. 4,042,056, No. 3,306). , 874, No. 3,306,875, etc.).
Specific examples of phenolic compounds include phenol, o-, m-, p-cresol, 2,6-, 2,5-, 2,4- or 3,5-dimethylphenol, 2-methyl-6-phenylphenol. , 2,6-diphenylphenol, 2,6-diethylphenol, 2-methyl-6-t-butylphenol and the like. Two or more kinds of the above phenol compounds may be copolymerized, and two or more kinds of the obtained homopolymers or copolymers may be mixed and used. Among the above phenol compounds, 2,6-dimethylphenol is particularly preferable, and therefore, in the present embodiment, the poly (2,6-dimethyl-1,4-phenylene) ether obtained by polymerizing this is a good result. give.

The content of the polyphenylene ether-based resin (B) in the resin composition of the present embodiment is 5 to 5 when the total amount of the styrene-based resin (A) and the polyphenylene ether-based resin (B) is 100 parts by mass. It is 50 parts by mass, preferably 10 to 40 parts by mass, and more preferably 15 to 30 parts by mass.

The Z average molecular weight of the polyphenylene ether resin (B) in the present embodiment is preferably 20,000 to 120,000, more preferably 30,000 to 100,000, and even more preferably 40,000 to 70,000. When the Z average molecular weight is 20,000 or less, the strength is insufficient, and when the Z average molecular weight is larger than 120,000, the fluidity deteriorates.
The Z average molecular weight can be adjusted by conditions such as atmosphere, solvent type, catalyst type, reaction temperature, reaction time, etc. at the time of oxidation coupling polymerization, particularly by appropriately selecting the catalyst type.
The Z average molecular weight can be measured by GPC as a polystyrene-equivalent molecular weight.

In the present embodiment, the ratio (PS_Mz / PPE_Mz) of the Z average molecular weight (PS_Mz) of the styrene resin to the Z average molecular weight (PPE_Mz) of the polyphenylene ether resin in the resin composition is preferably 12 to 50, and more. It is preferably 16 to 40, more preferably 20 to 30. If PS_Mz / PPE_Mz is smaller than 12, a sufficient rise in extensional viscosity cannot be obtained, and if it is larger than 50, kneadability is deteriorated and poor appearance occurs.

The total content of the styrene resin (A) and the polyphenylene ether resin (B) in the styrene resin composition of the present embodiment is 100% by mass, preferably 90 to 100% by mass, based on the resin composition. Yes, more preferably 95-99.8% by mass.

In the styrene-based resin composition of the present embodiment, the styrene-based resin (A) and the polyphenylene ether-based resin (B) can be separated by the following methods, and their respective molecular weights can be measured. As a specific separation method, the styrene resin composition is dissolved in chloroform so as to have a content of 5% by mass, three times the amount of methanol is added to reprecipitate the composition, and then the polymer is filtered and dried to recover the polymer component. Next, the recovered polymer is dissolved in dichloromethane at 50 ° C. to 5% by mass, and then left at −30 ° C. for 24 hours. After standing, the polymer component precipitates, which is filtered and dried to separate and recover the polyphenylene ether-based resin (B). Further, 3 times the amount of methanol is added to the remaining dichloromethane solution for reprecipitation, and then the styrene resin (A) is separated and recovered by filtration and drying.

In addition to the styrene resin (A) and the polyphenylene ether resin (B), various additives commonly used in the resin composition may be appropriately added to the styrene resin composition of the present embodiment. Examples of such additives include stabilizers, antioxidants, UV absorbers, lubricants, mold release agents, plasticizers, antiblocking agents, antistatic agents, antifog agents, mineral oils and the like. Further, a reinforcing material such as a styrene-butadiene block copolymer or MBS resin may be added to the styrene resin composition of the present embodiment as long as the physical properties are not impaired.
The method of blending these is not particularly specified, but for example, when a method of adding and polymerizing at the time of polymerization or a resin composition is obtained, the additives are mixed in advance with a blender and melt-mixed with an extruder, a Banbury mixer or the like. Examples include a method of refining.

In the present embodiment, the residual amount of the styrene-based monomer in the resin composition is preferably 1000 mass ppm or less, more preferably 500 mass ppm or less, still more preferably 300 mass ppm or less. The odor around the die outlet at the time of sheet extrusion and the color tone of the copolymer resin are improved.
The residual amount of the styrene-based monomer can be measured by gas chromatography.

In the resin composition, the total amount of the dimer and trimer of styrene in 100% by mass of the resin composition is preferably as low as possible, but preferably 0.6% by mass, more preferably 0.3% by mass. More preferably, it is 0.15% by mass or less.
The residual amounts of the styrene dimer and trimer can be measured by gas chromatography.

[[Stabilizer]]
Examples of the stabilizer include 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate (trade name: Sumilyzer GM, manufactured by Sumitomo Chemical Co., Ltd.). 2- [1- (2-Hydroxy-3,5-di-t-phenylpentyl) ethyl] -4,6-di-t-phenylpentyl acrylate (trade name: Sumilyzer GS, manufactured by Sumitomo Chemical Co., Ltd.), 6- tert-Butyl-4- [3-[(2,4,8,10-tetra-tert-butyldibenzo [d, f] [1,3,2] dioxaphosphepine-6-yl) oxy] propyl ] -2-Methylphenol (trade name: Sumilyzer GP, manufactured by Sumitomo Chemical Co., Ltd.) can be mentioned.
The content of the stabilizer in the styrene resin composition of the present embodiment is preferably 0.01 to 0.5% by mass, more preferably 0.02 to 0.3% by mass, based on the styrene resin composition. , More preferably 0.03 to 0.2% by mass.
The method of adding the stabilizer is not particularly limited, but it may be added at the time of melt-kneading the styrene resin and the polyphenylene ether, or may be added in advance at the time of producing the styrene resin and / or the polyphenylene ether. By adding a predetermined amount of stabilizer, a resin composition having excellent moldability can be obtained.

Hereinafter, the characteristics of the styrene resin composition of the present embodiment will be described.

In the present embodiment, the Vicat softening temperature of the styrene resin composition is preferably 105 ° C. or higher, more preferably 110 ° C. or higher, still more preferably 115 ° C. or higher, from the viewpoint of the environment in which it is used in a microwave oven. In addition, there is no particular upper limit to the Vicat softening temperature.
The Vicat softening temperature can be measured according to ISO306.

As the melt viscous property of the styrene resin composition of the present embodiment, the maximum rising ratio of the measured extensional viscosity is preferably 1.2 to 4.0, more preferably 1.6 to 3.5, and even more preferably. Is 2.0 to 3.0.
In the present specification, the "maximum rise ratio" is an index showing the degree of strain hardening at the maximum rise strain, and is defined by (extensional viscosity in the non-linear region of the maximum rise strain / extensional viscosity in the linear region of the maximum rise strain). Will be done. The "maximum rising strain" means the henky strain when the extensional viscosity is maximized. The larger the maximum rise ratio, the greater the degree of strain hardening and the better the moldability.
If the maximum rise ratio is less than 1.2, the moldability tends to be poor, and if it is larger than 4.0, the extensional viscosity tends to increase and the productivity tends to decrease.

Since the styrene resin composition of the present embodiment has excellent molding processability and a small amount of gel-like substance, a product having an excellent appearance can be obtained.
As a molding method, it can be suitably used for injection molding, extrusion molding, vacuum molding, pressure molding, extrusion foam molding, calendar molding, blow molding and the like, and various molded products can be obtained in a wider range of applications than before.

[Sheet]
The sheet of the present embodiment contains the styrene-based resin composition of the present embodiment, and may be a sheet produced by using the above-mentioned resin composition. The sheet may be either non-foamed or foamed.
As a method for producing the sheet, a commonly known method can be used. For the non-foamed sheet, a method of using a device that extrudes with a single-screw or twin-screw extruder equipped with a T-die or a circular die and then takes out the sheet with a uniaxial or biaxial stretching machine can be used. As a method for producing the foam sheet, a method using an extrusion foam molding machine equipped with a T die or a circular die can be used.

The non-foamed sheet preferably has a thickness of, for example, about 0.1 to 3.0 mm from the viewpoint of rigidity and thermoforming cycle.
Further, the sheet may be formed only by ordinary low-magnification roll stretching, or may be stretched by a roll about 1.3 to 7 times and then by a tenter about 1.3 to 7 times.
Further, the styrene-based resin composition of the present embodiment may be used in a multi-layered manner with a styrene-based resin such as a polystyrene resin, or may be used in a multi-layered manner with a resin other than the styrene-based resin such as PET resin and nylon resin. ..

The foamed sheet preferably has a thickness of 0.5 to 5.0 mm, an apparent density of 50 to 300 g / L, and a basis weight of 80 to 300 g / m ^2. ..
The foamed sheet of the present embodiment may be multi-layered, for example, by further laminating a film. The type of film used may be general polystyrene, polypropylene, polypropylene / polystyrene laminated film, or the like.
When forming a foamed sheet, commonly used substances can be used as the foaming agent and the foaming nucleating agent at the time of extrusion foaming. As the foaming agent, butane, pentane, chlorofluorocarbon, carbon dioxide, water and the like can be used, and butane is preferable. Further, talc or the like can be used as the effervescent nucleating agent.
Further, after foam extrusion, the sheet may be stretched about 1.3 to 7 times with a roll while heating, and then stretched about 1.3 to 7 times with a tenter.

[Molding]
The molded product of the present embodiment includes the non-foamed or foamed sheet of the present embodiment, and may be a molded product molded using the above-mentioned sheet.
From the sheet, for example, it is possible to manufacture a food packaging container which is formed by vacuum forming to contain a lid material for a lunch box, a prepared food, and the like.
Further, for example, by performing secondary molding by a conventionally known method such as vacuum forming, pressure forming, vacuum pressure forming, double-sided vacuum forming, press forming, etc., the sheet can be used as a secondary for trays, cups, bowl containers, natto containers, etc. Molded products can be formed.
As an example of the secondary molded product of the present embodiment, the extruded foam sheet of the present embodiment is used as a molding material, and a vacuum molding machine is used to make the lateral direction the extrusion direction, 5.5 to 21 cm in length and 6.5 to 36 cm in width. , Food tray containers with a depth of 1.1 to 3.4 cm. The temperature condition for vacuum forming is not limited to the following, but is usually preferably 120 to 150 ° C.

The resin composition of the present embodiment can be molded by other molding methods according to the purpose, such as injection molding and compression molding.

Hereinafter, embodiments of the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

The measurement and evaluation methods are as follows.

(1) Measurement of Vicat softening temperature The measurement was performed in accordance with ISO306. The load was 49 N and the heating rate was 50 ° C./h.

(2) Measurement of Molecular Weight The weight average molecular weight (Mw) and Z average molecular weight (Mz) of the styrene resin, and the Z average molecular weight (Mz) and ratio (PS_Mz / PPE_Mz) of the polyphenylene ether resin are gel permeation chromatography. Measurement was performed under the following conditions using graphics (GPC).
-Sample preparation: Dissolve 5 mg of the measurement sample in 10 mL of solvent-Measurement conditions Equipment: HLC-8220 manufactured by Tosoh
Sorting column: Tosoh TSK gel Super HZM-H
Guard column: Tosoh TSK guard volume Super HZ-H
Measuring solvent: tetrahydrofuran (THF)
Injection volume: 10 μL
Measurement temperature: 40 ° C
Flow velocity: 0.35 mL / min To prepare the calibration curve, 11 types of TSK standard polystyrene manufactured by Toso (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) were used. A calibration curve was created using an approximate expression of a linear straight line.

(3) Degree of branching / degree of gelation The absolute molecular weight of the styrene resin was measured using a multi-angle scattering detector (MALS) (hereinafter referred to as the MALS method), and the degree of branching / gelation was determined by the following method. ..
-Sample preparation: Dissolve 10 mg of the measurement sample in 10 mL of solvent and filter with a 0.45 μm filter.
Sorting column: Two Shodex KF806-L connected in series Guard column: Tosoh TSK guard volume Super HZ-H
Measuring solvent: tetrahydrofuran (THF)
Injection volume: 100 μL
Measurement temperature: 40 ° C
Flow velocity: 1.00 mL / min Detector: Differential refractometer MALS detector: Viscotek SEC-MALS 20 manufactured by Malvern
MALS detection angles: 12 °, 20 °, 28 °, 36 °, 44 °, 52 °, 60 °, 68 °, 76 °, 84 °, 90 °, 100 °, 108 °, 116 °, 124 °, 132 °, 140 °, 148 °, 156 °, 164 °
MALS detector temperature: 35 ° C
PS105K was used as a standard sample, and the analysis software OmniSEC 5.1 was used to analyze the absolute molecular weight and inertial radius of the styrene resin.
First, linear polystyrene (NBS706) is measured, and a graph of log (Molecular weight) is created on the horizontal axis and log (radius of gyration) is created on the vertical axis. A linear approximation straight line with respect to the log (radius of gyration) was created in the range of the log (Molecular weight) value of NBS706 in the range of 5.0 to 6.0, and this was used as a reference straight line.
The log (radius of gyration) values when the log (Molecular weight) values of the styrene resin obtained from MALS are 6.0 and 6.5 are defined as <Rg6.0> and <Rg6.5>, respectively. Then, <Rg6.0> and <Rg6.5> of NBS706 were defined as <Rg6.0> _{NBS and <Rg6.5> NBS, respectively.} The <Rg6.5> _NBS was calculated from the extrapolated value of the approximate straight line.
The degree of bifurcation was defined as the ratio of the radius of gyration <Rg6.5> of the linear polystyrene NBS706 to the radius of _{gyration <Rg6.5> of the chillene resin to NBS.} Bifurcation = <Rg6.5> / <Rg6.5> _NBS
It means how small the radius of gyration <Rg6.5> of the styrene resin is with respect to the radius of gyration <Rg6.5> _{NBS of} NBS706, and the smaller the degree of branching, the more branched the polymer. Represents.
Further, the degree of gelation = (<Rg6.0> / <Rg6.0> _NBS ) / (<Rg6.5> / <Rg6.5> _NBS ) was defined.
^{The degree of gelation indicates the rate of change in the radius of gyration of the polymer from 10 6.0} = 1 million to 10 ^6.5 = 3.16 million in absolute molecular weight, that is, the rate of branching increasing with respect to the increase in molecular weight, that is, the larger the degree of gelation, the higher the degree of gelation. It means that the number of branches increases as the molecular weight increases.

(5) Measurement of Residual Amount of Styrene Monomer, Dimer and Trimer The residual amount (mass%) of styrene monomer, dimer and trimer in the resin pellet is determined under the following conditions. It was measured by the procedure and procedure.
-Sample preparation: After 2.0 g of the resin composition was dissolved in 20 mL of chloroform, 5 mL of methanol containing a standard substance (triphenylmethane) was further added to reprecipitate the polymer component, and the supernatant was collected and used as a measurement solution.
-Measurement conditions Equipment: Agilent 6850 series GC system detector: FID
Column: HP-1 (100% dimethylpolysiloxane) 30 m, film thickness 0.25 μm, 0.32 mmφ
Injection volume: 1 μL (splitless)
Column temperature: Hold at 40 ° C for 2 minutes → Raise to 320 ° C at 20 ° C / min → Hold at 320 ° C for 15 minutes Injection temperature: 250 ° C
Detector temperature: 280 ° C
Carrier gas: helium

(6) Measurement of extensional viscosity, measurement of rising start strain, maximum rising strain, and maximum rising ratio The rising start strain, maximum rising strain, and maximum rising ratio of the styrene-based copolymer are measured under the following measurement conditions. rice field.
Device name: Viscoelasticity measuring device ARES-G2 (manufactured by TA Instruments)
Measurement system: ARES-EVF
Specimen dimensions: length 20 mm, thickness 0.7 mm, width 10 mm
Elongation strain rate: 0.01 / sec Measurement temperature: Vicat softening temperature + 40 ° C of styrene resin composition
Measurement atmosphere: In a nitrogen stream Preheating time: 1 minute Preliminary extension strain rate: 0.05 / sec,
Preliminary extension length: 0.295 mm
Relaxation time after pre-stretching: 1 minute The extensional viscosity was measured by attaching the test piece to the roller of the measuring jig of the ARES-EVF system and preheating after the temperature became stable. After the preheating was completed, it was pre-stretched. After the pre-stretching, the mixture was allowed to stand for 1 minute to relieve the stress generated by the pre-stretching and measured.
The maximum rising strain refers to the henky strain when the extensional viscosity is maximized in the above-mentioned extensional viscosity measurement. The rising start strain was calculated by the following method. From the results obtained by the above extensional viscosity measurement, a bilateral logarithmic graph was created in which the Henky strain was plotted on the horizontal axis and the extensional viscosity was plotted on the vertical axis, and the Henky strain was in the linear region in the range of 0.2 to 0.5. (It corresponds to the power approximation curve when the horizontal axis is Henky strain and the extensional viscosity is the vertical axis). When strain hardening occurred, a region where the measured extensional viscosity was larger than the approximate straight line extrapolating this linear region was observed, and this was designated as a non-linear region. Further, when the extensional viscosity of the non-linear region and the extensional viscosity obtained from the linear region straight (this is referred to as “linear linear elongation viscosity)” in the same Henky strain, the extensional viscosity of the non-linear region is the extensional viscosity of the linear straight. The Henky strain when it became 3% or more was defined as the rising strain. The maximum rising ratio was calculated by (extensional viscosity in the non-linear region of the maximum rising strain / extensional viscosity in the linear region of the maximum rising strain).

(7) Evaluation of Deep Drawing Formability of Non-Effervescent Sheet A styrene resin composition was extruded using a 30 mmφ sheet extruder (manufactured by Soken Co., Ltd.) to prepare a sheet having a thickness of 0.5 mm. The obtained sheet is cut into a size of 250 mm in length × 250 mm in width, and the sheet is sandwiched between the fixed frames of this sheet molding machine using a sheet container molding machine (manufactured by Soken Co., Ltd.) to measure the average temperature of the heater. The temperature was set to 220 ° C. and the atmospheric temperature was set to 110 ° C., and the mixture was heated for 20 seconds. Next, vacuum molding was performed by sliding the fixed frame together with a mold (temperature 40 ° C.) of a bowl container having a diameter of 10 cm and a depth of 10 cm, and 20 molded bodies were molded at a time. It was visually confirmed whether or not tearing occurred on the side surface of the molded body, and the number of molded bodies that could be molded without tearing was used as an index of deep drawing formability.
Judgment was made when the number of tears was 0 to 1, "◎ (excellent)", 2 to 3 was "○ (good)", and 4 or more was "x (impossible)".

(8) Appearance evaluation of sheet A styrene resin composition was extruded using a 30 mmφ sheet extruder (manufactured by Soken Co., Ltd.) to prepare a 0.5 mm sheet. Twenty test pieces were cut out from the obtained sheet to a size of 100 mm in length × 100 mm in width, and defects and charring with an average diameter of (major diameter + minor diameter) / 2 of 2.0 mm or more were visually measured. The appearance was judged by the evaluation criteria of.
Judgment is when the number of gel-like defects is 0 to 2 as "◎ (excellent)", 3 to 10 as "○ (good)", 10 to 19 as "△ (possible)", and 20 or more. Was set to "x (impossible)".

(9) Evaluation of Deep Drawing Formability of Foam Sheet With respect to 100 parts by mass of the styrene resin composition, 0.15 parts by mass of talc (average particle size 1.3 μm) as a foaming nucleating agent and 4 parts of liquefied butane as a foaming agent. A styrene-based resin composition was obtained by adding parts by mass.
The styrene resin composition was extruded and foamed using an extrusion foaming machine equipped with a circular die having a diameter of 150 mm. The temperature of the resin melting zone of the extruder was adjusted to 210 to 240 ° C., the rotary cooler temperature was adjusted to 140 to 180 ° C., and the die temperature was adjusted to 155 ° C. The foam immediately after extrusion foaming was cooled with a cooling mandrel and cut with a cutter at one point on the circumference to obtain an extrusion foam sheet having a sheet thickness of 1.4 mm and a width of 1000 mm. The extruded foam sheet was left at 23 ± 3 ° C. and a relative humidity of 50 ± 5% for 20 days.
Then, using a sheet container molding machine manufactured by Soken, the foamed sheet was sandwiched between the fixed frames of the sheet molding machine, the average temperature of the heater was set to 200 ° C., the atmospheric temperature was set to 130 ° C., and the mixture was heated for 15 seconds. Next, vacuum molding was performed by sliding the fixed frame together with a cup-shaped mold (temperature 40 ° C.) having a diameter of 10 cm and a depth of 3 cm or 6 cm, and 100 molded bodies were molded at a time.
It was visually confirmed whether or not tearing occurred on the side surface of the molded body, and the number of molded bodies that could be molded without tearing was used as an index of deep drawing formability.
Judgment was made when the number of tears was 0 to 5, "◎ (excellent)", 6 to 10 was "○ (good)", and when 11 or more was "x (impossible)".

The resin and the resin composition were produced as follows.

<Styrene resin (A)>
<Manufacturing of resin A>
82 parts by mass of styrene monomer, 18 parts by mass of ethylbenzene, 0.025 of 2,2-bis (4,5-di-t-butylperoxycyclohexyl) propane [manufactured by Nichiyu Co., Ltd .: Pertetra A] as a polymerization initiator The raw material solution was prepared by adding parts by mass. The prepared raw material solution was continuously supplied at 0.6 L / hour to a completely mixed first reactor having an internal volume of 5.4 L maintained at a temperature of 114 ° C.
Raw material by adding 83 parts by mass of styrene monomer, 17 parts by mass of ethylbenzene, and 0.023 parts by mass of 1,1-di- (t-butylperoxy) cyclohexane [manufactured by Nichiyu Co., Ltd .: Perhexa C] as a polymerization initiator. The solution was prepared. The prepared raw material solution was heated to 108-112 ° C. A plug-flow type second reactor having an internal volume of 1.5 L was continuously supplied at 0.17 L / hour.
Next, the polymerization solutions from the first reactor and the second reactor were merged and supplied to a plug-flow type third reactor having an internal volume of 3 L heated to 137 to 166 ° C. The polymerization solution from the third reactor was supplied to a vacuum degassing tank heated to a temperature of 240 ° C., and volatile components such as unreacted monomers and solvents were removed to obtain a styrene resin A.
The properties of the obtained resin are shown in Table 1.

<Manufacturing of resin B>
82 parts by mass of styrene monomer, 18 parts by mass of ethylbenzene, 0.038 parts by mass of pertetra A as a polymerization initiator, and 0.12 of polybutadiene-terminated diacrylate [manufactured by Osaka Organic Chemical Industry Co., Ltd .: BAC-45] as a molecular weight adjuster. The raw material solution was prepared by adding parts by mass. It was continuously supplied at 0.6 L / hour to a fully mixed first reactor having an internal volume of 5.4 L maintained at a temperature of 100 ° C.
The raw material solution was prepared by adding 65 parts by mass of styrene monomer, 35 parts by mass of ethylbenzene, 0.07 parts by mass of perhexa C as a polymerization initiator, and 0.15 parts by mass of α-methylstyrene dimer as a chain transfer agent. The prepared raw material solution was heated to 110 to 115 ° C. A plug-flow type second reactor having an internal volume of 1.5 L was continuously supplied at 0.17 L / hour.
Next, the polymerization solutions from the first reactor and the second reactor were merged and supplied to a plug-flow type third reactor having an internal volume of 3 L heated to 120 to 133 ° C. Further, 0.03 parts by mass of Perhexa C was added to the third reactor with respect to the supply amount after the merging of the first reactor and the second reactor. The polymerization solution from the third reactor was supplied to a vacuum degassing tank heated to a temperature of 240 ° C., and volatile components such as unreacted monomers and solvents were removed to obtain a styrene resin B.
The properties of the obtained resin are shown in Table 1.

<Manufacturing of resin C>
82 parts by mass of styrene monomer, 18 parts by mass of ethylbenzene, 0.038 parts by mass of pertetra A as a polymerization initiator, 0.22 parts of polybutadiene terminal diacrylate [manufactured by Osaka Organic Chemical Industry Co., Ltd .: BAC-45] as a molecular weight adjuster. The raw material solution was prepared by adding parts by mass. A fully mixed first reactor having an internal volume of 5.4 L maintained at a temperature of 102 ° C. was continuously supplied at 0.6 L / hour.
The raw material solution was prepared by adding 65 parts by mass of styrene monomer, 35 parts by mass of ethylbenzene, 0.07 parts by mass of perhexa C as a polymerization initiator, and 0.15 parts by mass of α-methylstyrene dimer as a chain transfer agent. The prepared raw material solution was heated to 110 to 115 ° C. A plug-flow type second reactor having an internal volume of 1.5 L was continuously supplied at 0.17 L / hour.
Next, the polymerization solutions from the first reactor and the second reactor were merged and supplied to a plug-flow type third reactor having an internal volume of 3 L heated to 120 to 133 ° C. Further, 0.03 parts by mass of Perhexa C was added to the third reactor with respect to the supply amount after the merging of the first reactor and the second reactor. The polymerization solution from the third reactor was supplied to a vacuum degassing tank heated to a temperature of 240 ° C., and volatile components such as unreacted monomers and solvents were removed to obtain a styrene resin C.
The properties of the obtained resin are shown in Table 1.

<Synthesis of multi-branched macromonomer>
To a 2 liter flask equipped with a stirrer, a thermometer, a dropping funnel and a condenser, 50.5 g of pentaerythritol ethoxylated (pentaerythritol with 5 mol-ethylene oxide _{) and 1 g of BF 3} diethyl ether solution (50%) were added at room temperature. It was heated to 110 ° C. To this, 450 g of 3-ethyl-3- (hydroxymethyl) oxetane was slowly added over 25 minutes while controlling the exotherm caused by the reaction. When the exotherm subsided, the reaction mixture was further stirred at 120 ° C. for 3 hours and then cooled to room temperature. The weight average molecular weight of the obtained multi-branched polyether polyol was 3,000, and the hydroxyl value was 530.
50 g of the obtained multi-branched polyether polyol, 13.8 g of methacrylic acid, 150 g of toluene, 0.06 g of hydroquinone, and 1 g of paratoluenesulfonic acid were mixed with a stirrer, a thermometer, a Dean-Stark decanter equipped with a condenser, and a gas introduction tube. In addition to the reactor, 7% oxygen-containing nitrogen (v / v) was blown into the mixed solution at a rate of 3 ml / min while stirring under normal pressure and heating. The heating amount was adjusted so that the amount of the distillate in the decanter was 30 g per hour, and heating was continued until the dehydrated amount reached 2.9 g. After completion of the reaction, the mixture was cooled once, 36 g of acetic anhydride and 5.7 g of sulfamic acid were added, and the mixture was stirred at 60 ° C. for 10 hours. Then, in order to remove the remaining acetic acid and hydroquinone, the cells were washed 4 times with 50 g of a 5% aqueous sodium hydroxide solution, once with 50 g of a 1% aqueous sulfuric acid solution, and twice with 50 g of water. 0.02 g of methquinone was added to the obtained organic layer, and the solvent was distilled off while introducing 7% oxygen-containing nitrogen (v / v) under reduced pressure to obtain 60 g of a multi-branched polyether having an isopropenyl group and an acetyl group. Obtained.
The mass average molecular weight of the obtained multi-branched polyether was 3,900, and the introduction rates of isopropenyl groups and acetyl groups into the multi-branched polyether polyol were 30 mol% and 62 mol%, respectively.

<Manufacturing of resin D>
A mixed solution consisting of 90 parts by mass of the styrene monomer, 500 parts by mass of the multi-branched macromonomer obtained as described above with respect to the styrene monomer, and 10 parts by mass of toluene was prepared, and further, with respect to the styrene monomer as an organic peroxide. A reaction solution was prepared by adding 300 mass ppm of t-butylperoxybenzoate. A loop reactor (B) containing a static mixing element is connected in series after the stirring reactor (A), and then a line reactor (C) containing a static mixing element is connected. The mixed solution was continuously supplied to the reactors at a rate of 9 L / h. The temperature at each reactor and the reflux ratio of the loop reactor were set as follows.
Reaction temperature of stirring reactor (A): 120 ° C.
Reaction temperature of loop reactor (B): 120 ° C.
Reaction temperature of line reactor (C): 130-150 ° C
Reflux ratio: R = F1 / F2 = 6
However, F1 indicates the flow rate of the mixed solution refluxing in the loop reactor, and F2 indicates the flow rate of the mixed solution flowing out to the non-circulating polymerization line.
The polymerization solution from the reactor was supplied to a vacuum degassing tank heated to a temperature of 240 ° C., and volatile components such as unreacted monomers and solvents were removed to obtain a styrene resin D.
The properties of the obtained resin are shown in Table 1.

<Manufacturing of resin E>
82 parts by mass of styrene monomer, 18 parts by mass of ethylbenzene, 0.038 parts by mass of pertetra A as a polymerization initiator, 0.16 parts of NK ester A-GLY-20E [manufactured by Shin-Nakamura Chemical Industry Co., Ltd.] as a molecular weight adjuster. The raw material solution was prepared by adding parts by mass. It was continuously supplied at 0.6 L / hour to a fully mixed first reactor having an internal volume of 5.4 L maintained at a temperature of 100 ° C.
The raw material solution was prepared by adding 65 parts by mass of styrene monomer, 35 parts by mass of ethylbenzene, 0.07 parts by mass of perhexa C as a polymerization initiator, and 0.15 parts by mass of α-methylstyrene dimer as a chain transfer agent. The prepared raw material solution was heated to 110 to 115 ° C. A plug-flow type second reactor having an internal volume of 1.5 L was continuously supplied at 0.17 L / hour.
Next, the polymerization solutions from the first reactor and the second reactor were merged and supplied to a plug-flow type third reactor having an internal volume of 3 L heated to 120 to 133 ° C. Further, 0.03 parts by mass of Perhexa C was added to the third reactor with respect to the supply amount after the merging of the first reactor and the second reactor. The polymerization solution from the third reactor was supplied to a vacuum degassing tank heated to a temperature of 240 ° C., and volatile components such as unreacted monomers and solvents were removed to obtain a styrene resin E.
The properties of the obtained resin are shown in Table 1.

<Polyphenylene ether resin (B)>
The following polyphenylene ethers were used.
· Xyron S201A [Asahi Kasei Corporation] (z-average molecular weight 8.0 × 10 ⁴⁾
· Xyron S202A [Asahi Kasei Corporation] (z-average molecular weight 6.0 × 10 ⁴⁾
· Xyron S203A [Asahi Kasei Corporation] (z-average molecular weight 4.0 × 10 ⁴⁾
* The figures in parentheses are the results of Mz molecular weight measured by GPC.

<Stabilizer>
・ Sumilyzer GS [manufactured by Sumitomo Chemical Co., Ltd.]

<Example 1>
A resin composition was obtained by kneading resin A in 80 parts by mass and polyphenylene ether Zylon S203A in 20 parts by mass at 230 to 280 ° C. and 100 rpm with a twin-screw extruder [TEM26 manufactured by Toshiba Machine Co., Ltd.]. The physical characteristics of Example 1 are shown in Table 2.

<Examples 2 to 7>
Under the same conditions as in Example 1, a styrene resin, a polyphenylene ether, and a stabilizer were added and kneaded so as to have the types and proportions shown in Table 2, and a resin composition was prepared. The physical characteristics of Examples 2 to 7 are shown in Table 2.

<Comparative example 1>
Under the same conditions as in Example 1, 75 parts by mass of the styrene resin (A) and 25 parts by mass of the polyphenylene ether S202A were kneaded to obtain a resin composition. Table 2 shows the physical characteristics of Comparative Example 1.
Since the obtained resin composition had a small PS_Mz / PPE_Mz, the extensional viscosity did not rise and the moldability was also inferior.

<Comparative example 2>
Under the same conditions as in Example 1, 75 parts by mass of the styrene resin (E) and 25 parts by mass of the polyphenylene ether S202A were kneaded to obtain a resin composition. Table 2 shows the physical characteristics of Comparative Example 2.
The obtained resin composition had a high PS_Mz / PPE_Mz, and it was confirmed that the appearance was deteriorated due to poor kneading. In addition, many gel-like substances derived from the styrene resin (E) were confirmed to have a poor appearance.

According to the present invention, it is possible to provide a styrene resin composition, a sheet, a molded product, and a method for producing a sheet, which are excellent in heat resistance, moldability, foaming properties, and appearance.
Since the styrene-based resin composition according to the present invention has excellent molding processability and few gel-like substances, it can be widely used as a molding material for home appliances, office machine products, miscellaneous goods, housing equipment, etc., a food packaging material, and the like. ..

Claims (8)

A resin composition containing a styrene resin (A) and a polyphenylene ether resin (B).
When the total amount of the styrene resin (A) and the polyphenylene ether resin (B) is 100 parts by mass, the styrene resin (A) is 50 to 95 parts by mass, and the polyphenylene ether resin (B) is Containing 5 to 50 parts by mass,
In 100% by mass of the styrene resin (A), a total amount of 0.7% by mass or less of a styrene dimer and a styrene trimer is contained.
The styrene resin is characterized in that the ratio (PS_Mz / PPE_Mz) of the Z average molecular weight (PS_Mz) of the styrene resin (A) to the Z average molecular weight (PPE_Mz) of the polyphenylene ether resin (B) is 12 to 50. Composition. The styrene resin composition according to claim 1, wherein the styrene resin (A) has a degree of branching of 0.70 to 1.00 and a degree of gelation of 1.40 or less. The styrene resin composition according to claim 1 or 2, further comprising 0.01 to 1.0 parts by mass of a stabilizer. The styrene resin composition according to any one of claims 1 to 3, wherein the weight average molecular weight (Mw) of the styrene resin (A) is 350,000 or more. A non-foamed or foamed sheet containing the styrene resin composition according to any one of claims 1 to 4. A molded product containing the non-foamed or foamed sheet according to claim 5. The molded product according to claim 6 , which is a food packaging container. A method for producing a sheet, which comprises using the styrene resin composition according to any one of claims 1 to 4.