Method for manufacturing molded product of styrene-based resin composition using mold

Abstract

To suppress appearance defects, particularly flow marks, in styrene-based resin composition containing polyester-based resin such as polylactic acid.SOLUTION: An injection molding machine used in the present invention for producing a molded product of a styrene-based resin composition containing a styrene-based resin (A) and an incompatible resin (B) that is incompatible with the styrene-based resin (A) comprises an injection part used for producing the molded product and a mold in fluid communication with the injection part. A method for manufacturing the molded product includes an injection molding step of injecting the styrene-based resin composition from the injection part into a mold under conditions that satisfy 200≤X≤240, 210≤Y≤250, and Y-X=0 to 20, where X°C is a temperature of the injection part and Y°C is the temperature of the mold during molding of the molded product.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a molded article of a styrene-based resin composition using a mold. [Background technology]

[0002] Taking advantage of their properties, styrene resins are used in a wide range of fields, including office automation equipment such as personal computers, printers, and copiers, as well as home appliances such as TVs and audio equipment. On the other hand, polyester resins are excellent in mechanical properties and are therefore widely used in various industrial applications such as films, sheets, tableware, and packaging containers.

[0003] In recent years, there has been a demand for reducing carbon dioxide emissions due to the problem of global warming, and polylactic acid has attracted attention as one of the "carbon-neutral" polyester resins that apparently emit no carbon dioxide. However, because polylactic acid is not very practical for use as a durable consumer product, polymer alloys with styrene-based resins and other materials have been investigated in recent years.

[0004] Polymer alloys of styrene resins and polylactic acid are usually produced by extrusion molding, during which time a scum is generated at the die outlet of the extruder due to resin decomposition products, undispersed additives, etc. The scum that is generated is entrained in the strand and remains attached to the pellets after pelletization, which is problematic not only because it causes a poor appearance of the pellets themselves but also because it remains as colored dots on the surface of the molded product after molding processes such as injection molding, resulting in a poor appearance.

[0005] On the other hand, as a method for suppressing the buildup, a method of adding a higher fatty acid amide or a higher fatty acid alkali metal salt to a styrene-based resin composition containing polyphenylene ether has been exemplified (Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-41502 Summary of the Invention [Problem to be solved by the invention]

[0007] However, this method has not been sufficient in suppressing poor appearance, particularly flow marks, in styrene-based resin compositions containing polyester-based resins such as polylactic acid. [Means for solving the problem]

[0008] The present inventors have been researching the prevention of flow marks in molded articles of styrene-based resin compositions, and have discovered that flow marks in molded articles of styrene-based resin compositions can be prevented without additives by injection molding using a mold under specific temperature conditions, thereby completing the present invention.

[0009] [1] The object of the present invention is to A method for producing a molded article of a styrene-based resin composition, comprising: The styrene-based resin composition comprises a styrene-based resin (A); an incompatible resin (B) that is incompatible with the styrene-based resin (A); Contains The injection molding machine used to manufacture the molded product is Injection section and a mold in fluid communication with the injection section; Equipped with A method for producing a molded article of a styrene-based resin composition, comprising an injection molding step of injecting the styrene-based resin composition from the injection part into the mold to form the molded article under conditions that satisfy 200≦X≦240, 210≦Y≦250, and YX=0 to 20, where X°C is the temperature of the injection part and Y°C is the temperature of the mold during molding. The purpose is to provide

[0010] By producing a molded article based on this method, flow marks in the molded article can be suppressed.

[0011] [2] In the method for producing a molded article of a styrene-based resin composition according to [1], the incompatible resin (B) may be a polyester resin.

[0012] [3] In the method for producing a molded article from a styrene-based resin composition according to [1] or [2], the incompatible resin (B) may be a polylactic acid resin (PLA).

[0013] [4] In the method for producing a molded article of a styrene-based resin composition according to any one of [1] to [3], the styrene-based resin composition may contain the styrene-based resin (A) and the incompatible resin (B) in a mass ratio of 80:20 to 40:60.

[0014] [5] In the method for producing a molded article of a styrene-based resin composition according to any one of [1] to [4], the average injection speed of the styrene-based resin composition from the injection part into the mold may be 30 mm / sec or less.

[0015] [6] In the method for producing a molded article of a styrene-based resin composition according to any one of [1] to [5], the injection dwell time of the styrene-based resin composition in the mold may be 4 seconds or more. DETAILED DESCRIPTION OF THE INVENTION

[0016] definition For convenience, certain terms used in this application are collected here. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0017] Although the numerical ranges and parameters set forth in the present invention are approximate, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in each test measurement. Also, as used herein, the term "about" generally means within 10%, 5%, 1%, or 0.5% of a given value or range. Alternatively, the term "about" means within an acceptable standard error as considered by one of ordinary skill in the art.

[0018] Hereinafter, embodiments of the present invention will be described. The following embodiments are merely examples, and the scope of the present invention is not limited to those shown in the following embodiments. Note that, to avoid repetition, explanations of similar content will be omitted as appropriate.

[0019] Manufacturing method The method for producing a molded article of a styrene-based resin composition according to the present embodiment is a method for producing a molded article of a styrene-based resin composition containing a styrene-based resin (A) and an incompatible resin (B) that is incompatible with the styrene-based resin (A). The molded article is produced by an injection molding machine.

[0020] injection molding machine The injection molding machine according to this embodiment is a so-called hot runner type injection molding machine that includes an injection section and a mold in fluid communication with the injection section and injects a molten styrene-based resin composition, which is a thermoplastic composition, into a molding mold. The injection section of the injection molding machine can inject the molten styrene-based resin composition into a mold cavity without solidifying the molten styrene-based resin composition, and the mold has a cavity that molds the styrene-based resin composition into a desired shape and an intermediate flow path that defines a flow path from the injection section to the cavity.

[0021] In one embodiment, the injection section includes an injection section heater that heats the injection section. In one embodiment, the injection section includes a cylinder for temporarily storing the styrene-based resin composition and a nozzle that injects the styrene-based resin composition stored in the cylinder into the mold. In one embodiment, the mold includes a mold heater that heats the mold. In one embodiment, the injection molding machine includes an injection section temperature sensor that measures the temperature of the injection section, a mold temperature sensor that measures the temperature of an intermediate flow path in the mold (hereinafter simply referred to as the "mold temperature"), and a control unit that independently controls the temperature settings of the injection section heater and the mold heater based on the temperature information from the injection section temperature sensor and the mold temperature sensor. In one embodiment, the injection section includes an injection section water jacket, and the mold includes a mold water jacket. Each water jacket may be water-cooled or oil-cooled. In one embodiment, the control unit can control the water flow in each water jacket.

[0022] The injection section may be equipped with a shutoff needle that opens and closes fluid communication between the injection section and the mold. The injection section equipped with the shutoff needle can close the mold cavity during the injection molding process described below, and also prevents the melt of the styrene-based resin composition from exiting the injection section when the mold is opened. The shutoff needle also enables the production of molded articles with smooth surfaces at the injection point.

[0023] injection molding process The manufacturing method includes an injection molding step. In the injection molding step, the styrene resin composition is injected from the injection section into the mold under specific conditions to form the molded article. The specific conditions in this embodiment are 200≦X≦240, 210≦Y≦250, and YX=0 to 20, where X°C is the temperature of the injection section of the injection molding machine during molding, and Y°C is the temperature of the mold. In one embodiment, YX under the specific conditions is 0, 1, 2, 3, 4, or 5 or more and 15, 16, 17, 18, 19, or 20 or less. In certain embodiments, X under certain conditions is between any two points selected from the group consisting of 200, 205, 210, 215, 220, 225, 230, 235, and 240, and Y under certain conditions is between any two points selected from the group consisting of 210, 215, 220, 225, 230, 235, 240, 245, and 250, and YX under certain conditions is 0, 1, 2, 3, 4, or 5 or more and 15, 16, 17, 18, 19, or 20 or less.

[0024] In one embodiment, the average injection speed of the styrene-based resin composition from the injection section into the mold is 30 mm / sec or less (e.g., 20 mm / sec or less, 15 mm / sec or less), and the injection pressure holding time of the styrene-based resin composition in the mold is 4 seconds or more (e.g., 5 seconds or more, 6 seconds or more, 7 seconds or more, and 8 seconds or more).

[0025] The injection molding process will now be described in detail. In one embodiment, the injection molding step includes a first maintaining step of maintaining the temperature of an injection section containing the styrene-based resin composition at X°C. The first maintaining step is performed by heating the injection section with an injection section heater. In the first maintaining step, the temperature of the styrene-based resin composition is maintained at X°C. By maintaining the temperature of the cylinder for temporarily storing the styrene-based resin composition at X°C, the temperature of the styrene-based resin composition injected from the nozzle becomes uniform.

[0026] In one embodiment, the injection molding step includes a heating step of heating the temperature of the mold to Y°C. In another embodiment, the injection molding step includes a second maintaining step of maintaining the temperature of the mold at Y°C before and / or while the styrene-based resin composition is injected from the injection zone. The heating step and the second maintaining step are carried out by heating the mold with a mold heater.

[0027] In one embodiment, the injection molding step includes an injection step of injecting the styrene-based resin composition into a mold, in which the styrene-based resin composition moves from a cylinder to a nozzle while being maintained at a temperature of X°C, and is then injected from the nozzle into the mold.

[0028] In one embodiment, the injection molding step includes a dwelling step of applying a dwell pressure to the mold for an injection dwell time after injecting the styrene-based resin composition into the mold (after the injection step). In one embodiment, the injection molding step may include a cooling step of curing the styrene-based resin composition after applying a dwell pressure to the mold for an injection dwell time (after the dwelling step). The cooling step may be performed by air cooling or by cooling using a water jacket. In one embodiment, the injection molding step includes a removal step of removing a molded article of the cured styrene-based resin composition from the mold.

[0029] Styrene-based resin (A) The styrene-based resin (A) according to this embodiment is a resin obtained by polymerizing an aromatic vinyl compound-based monomer. Examples of the aromatic vinyl compound-based monomer include known monomers such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and 2,4-dimethylstyrene, with styrene being preferred. The styrene-based resin (A) may be a resin obtained by polymerizing any of the above monomers alone, or may be a resin obtained by polymerizing a combination of the above monomers. The styrene-based resin (A) may also contain monomers copolymerizable with these monomers, such as acrylonitrile, (meth)acrylic acid, (meth)acrylic acid esters, and maleic anhydride, to the extent that the performance of the styrene-based resin (A) is not impaired.

[0030] The styrene resin (A) may be rubber-modified by adding a conjugated diene rubber-like polymer as needed. Examples of the conjugated diene rubber-like polymer used for rubber modification include polybutadiene, styrene-butadiene random or block copolymers, polyisoprene, polychloroprene, styrene-isoprene random, block or graft copolymers, ethylene-propylene rubber, and ethylene-propylene-diene rubber. Polybutadiene and styrene-butadiene random, block or graft copolymers are particularly preferred. These may also be partially hydrogenated.

[0031] Examples of such styrene-based resins (A) include polystyrene (GPPS), rubber-modified polystyrene (HIPS), ABS resin (acrylonitrile-butadiene-styrene copolymer), AS resin (acrylonitrile-styrene copolymer), MS resin (methyl methacrylate-styrene copolymer), AAS resin (acrylonitrile-acrylic rubber-styrene copolymer), AES resin (acrylonitrile-ethylene propylene-styrene copolymer), etc. Among these, HIPS is particularly preferred because it can increase the impact resistance of the resin composition.

[0032] There are no particular restrictions on the molecular weight of the matrix portion of HIPS, but a reduced viscosity (ηsp / C) of 0.5 or more and 1.0 or less is preferred. A reduced viscosity of 0.5 or more is preferred because it makes it difficult for the molten strands of resin to break, which is advantageous for stable production. A reduced viscosity of 1.0 or less is also preferred because it ensures the fluidity of the molten resin.

[0033] The content of the rubbery polymer in the HIPS is not particularly limited, but is preferably 3% by mass or more and 10% by mass or less, since a molded article having a rubbery polymer content in this range has a good balance between impact resistance and rigidity, which is preferred.

[0034] Styrene-based resin (A) and incompatible resin (B) The incompatible resin (B) according to this embodiment is a resin that is incompatible with the styrene-based resin (A). The incompatible resin (B) may be a polyester resin. Polyester resin is a general term for polymers having ester bonds obtained by polymerizing a polycarboxylic acid and a polyalcohol.

[0035] Polyester resins can be obtained, for example, by polymerization of dicarboxylic acids and diols. Examples of such polyester resins include polyethylene terephthalate (PET), polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, polyhexamethylene terephthalate, and polyhexamethylene naphthalate, but the present invention is not limited to these.

[0036] Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, and 4,4'-diphenylsulfonedicarboxylic acid. Other examples include aliphatic dicarboxylic acids such as adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, and cyclohexanedicarboxylic acid, as well as ester derivatives thereof. These carboxylic acid components may be used alone or in combination, and may further include partial copolymerization with oxyacids such as hydroxybenzoic acid.

[0037] Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbate, and spiroglycol.

[0038] Polyester resins can also be obtained by polymerizing a monomer having both a carboxylic acid and an alcohol in a single compound, and examples of such polyester resins include polylactic acid (PLA).

[0039] Of the polyester resins listed above, polylactic acid is preferred from the viewpoint of carbon neutrality.

[0040] As the polylactic acid, poly(L-lactic acid) is used. From the viewpoint of reducing carbon dioxide emissions, plant-derived raw materials are preferred.

[0041] In the case of poly(L-lactic acid), the crystallization rate varies depending on the proportion of D-lactic acid contained as a monomer component. Considering the heat resistance and moldability of the resin composition of the present invention, poly(L-lactic acid) composed only of L-lactic acid is preferred, and if D-lactic acid is contained, its proportion is preferably 5.0 mol% or less, and particularly preferably 1.5 mol% or less. The molecular weight of polylactic acid is preferably in the range of weight average molecular weight (Mw) of 50,000 or more and 400,000 or less, and particularly preferably in the range of 100,000 or more and 300,000 or less.

[0042] The ratio of the styrene-based resin (A) to the incompatible resin (B) is not particularly limited, but the styrene-based resin composition may contain the styrene-based resin (A) to the incompatible resin (B) in a mass ratio of 80:20 to 40:60 (for example, a range between two mass ratios selected from the mass ratios of 80:20, 70:30, 60:40, 50:50, and 40:60).

[0043] Other ingredients The styrene-based resin composition according to the present embodiment may contain components other than the styrene-based resin (A) and the incompatible resin (B) to the extent that the performance of the styrene-based resin composition is not impaired, such as an acrylic resin, a polyolefin wax, and additives.

[0044] acrylic resin The acrylic resin refers to a polymer obtained by polymerization of acrylic monomers, etc. The acrylic resin has excellent compatibility with the incompatible resin (B) and can reduce friction between the resin composition and the die outlet, etc.

[0045] The content of the acrylic resin is 0.1 to 2 parts by mass per 100 parts by mass of the total of the styrene resin (A) and the incompatible resin (B). If the content of the acrylic resin exceeds 2 parts by mass, the acrylic resin will bleed out onto the strand surface during extrusion production, and the acrylic resin transferred and adhered to the die outlet will itself become a source of scum, which is unsuitable.

[0046] The type of acrylic monomer constituting the acrylic resin is not particularly limited as long as it does not impair the effects of the present invention. For example, homopolymers of acrylate monomers such as methyl acrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, cyclohexyl acrylate, phenyl acrylate, and chloroethyl acrylate, and methacrylate monomers such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and chloroethyl methacrylate, and copolymers obtained by copolymerizing two or more of these monomers can be used.

[0047] The acrylic resin may be one obtained by adding and polymerizing, in addition to these acrylic monomers, a vinyl monomer copolymerizable therewith, as long as the effects of the present invention are not impaired. For example, the acrylic resin may be one obtained by adding and polymerizing a monomer such as an α-olefin, a vinyl aromatic compound, an unsaturated nitrile, an unsaturated carboxylic acid or an ester thereof, or a polyunsaturated compound such as ethylene glycol di(meth)acrylate.

[0048] The acrylic resin is preferably a high molecular weight material. Specifically, the weight average molecular weight Mw of the acrylic resin measured by GPC in terms of polystyrene is preferably 50,000 or more and 400,000 or less, more preferably 100,000 or more and 300,000 or less.

[0049] The acrylic resin is preferably one with higher lubricant performance, i.e., a copolymer composed of acrylic monomers having a chemical structure capable of further reducing friction with the die outlet and other portions and a monomer copolymerizable therewith.

[0050] More specifically, the acrylic monomer having a chemical structure capable of reducing friction is a monomer having an alkyl group having 1 to 20 carbon atoms, and is preferably an alkyl methacrylate or alkyl acrylate. Examples of such monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, and cyclohexyl acrylate, and it is preferable to use at least one of these.

[0051] Polyolefin wax The styrene-based resin composition may contain a polyolefin-based wax, such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, or an aliphatic hydrocarbon wax such as paraffin wax.

[0052] The content of the polyolefin wax may be 0.1 parts by mass or more and 1.5 parts by mass or less relative to 100 parts by mass of the total of the styrene resin (A) and the incompatible resin (B).

[0053] additives Examples of additives include plasticizers, spreading agents, solvents, ultraviolet absorbers, antioxidants, antiaging agents, light stabilizers, stabilizers, antistatic agents, colorants, dyes and pigments, fillers, color inhibitors, reinforcing agents, compatibilizers, crystallization accelerators, flame retardants, and flame retardant assistants.

[0054] In particular, MBS as a reinforcing agent, talc as a crystallization accelerator, and liquid paraffin as a spreading agent can be preferably added. MBS is a copolymer of methyl methacrylate, butadiene, and styrene, and is compatible with all of the styrene-based resin (A), the incompatible resin (B), and the acrylic resin, and is preferred because it can efficiently reinforce the impact resistance of the styrene-based resin composition. Talc is preferred because it can promote the crystallization of the incompatible resin (B) in the present invention and improve the mechanical strength of the resin composition. Liquid paraffin is a saturated hydrocarbon purified by removing impurities such as aromatic hydrocarbons and sulfur compounds contained in petroleum lubricating oil fractions with sulfuric anhydride or fuming sulfuric acid. When mixing the styrene-based resin composition, it can suppress classification between resins with different specific gravities, and therefore, it is preferred because it can suppress quality variation of the styrene-based resin composition during extrusion production.

[0055] The method for adding the additives is not particularly limited, and they may be added by a known method. For example, they may be added in the step of charging raw materials, the step of polymerization, or the step of finishing when producing the styrene-based resin (A) or the immiscible resin (B), or in the step of mixing the resin composition using an extruder or a molding machine.

[0056] Method for producing styrene-based resin composition The method for producing the styrene-based resin composition according to this embodiment is not particularly limited, and known mixing techniques can be applied. For example, a homogeneous resin composition can be produced by premixing various raw materials using a mixing device such as a mixer, V-blender, or tumbler mixer, and then melt-kneading the mixture. The melt-kneading device is also not particularly limited, and examples include a Banbury mixer, kneader, roll, single-screw extruder, special single-screw extruder, and twin-screw extruder. Furthermore, there is also a method in which other additives are separately added midway through the melt-kneading device such as an extruder. [Example]

[0057] The materials used in the examples and comparative examples are as follows. 〔material〕 (A) Styrene-based resin Rubber-modified impact-resistant polystyrene resin (rubber-like polymer is polybutadiene rubber, reduced viscosity of matrix part is 0.70 dl / g, rubber-like polymer content is 9.6% by mass) (B) Incompatible resin Polylactic acid: "REVODE190" manufactured by Zhejiang Hisun Biomaterials Co., Ltd. (D-lactic acid content: 0.5 mol%, weight-average molecular weight (Mw) 200,000) PET: Eastman "PET-G GN001"

[0058] [Method for measuring rubber polymer content] A styrene resin was dissolved in chloroform, a certain amount of iodine monochloride / glacial acetic acid solution was added, and the mixture was left in a dark place for approximately 30 minutes. After that, a 15% by mass potassium iodide solution and 50 ml of pure water were added, and the excess iodine monochloride was titrated with 0.1 N sodium thiosulfate solution, and the concentration was calculated from the amount of iodine monochloride added.

[0059] [Evaluation method] The molded article of the resin composition was judged by visual observation. Of the following criteria, "A" and "B" were considered to be acceptable, and "C" and "-" were considered to be unacceptable. A: No flow marks occurred. B: A small amount of flow marks occurred. C: Clear flow marks were observed. -: Discoloration occurred.

[0060] [Flow marks and discoloration] Flow marks and discoloration are molding defects that deteriorate the appearance of molded products. Flow marks are circular irregularities, and discoloration is a black or brown discoloration caused by carbonization or decomposition of an overheated resin composition.

[0061] (Examples 1 to 9, Comparative Examples 1 to 6) The (A) styrene-based resin and (B) incompatible resin listed in the [Materials] section above were premixed in the amounts (parts by mass) shown in Tables 1 and 2 in a Henschel mixer (Mitsui Miike Chemical Co., Ltd., "FM20B"). The mixture was fed into a twin-screw extruder (Toshiba Machine Co., Ltd., "TEM26SS") to form strands, which were then water-cooled and fed into a pelletizer to form pellets. Each pelletized resin composition was molded into 180 mm (3 mm thick) square plates using an injection molding machine (Japan Steel Works, Ltd., J110AD) under the conditions shown in Table 1 and at a mold cavity temperature of 50°C. A gate was located at the center of each square plate. During the above process, the occurrence of flow marks was observed using the evaluation method described above. The results are shown in Tables 1 and 2.

[0062] [Table 1]

[0063] [Table 2]

[0064] Molded articles (Examples 1 to 9) produced under the conditions of 210°C≦X≦230°C, 230°C≦Y≦250°C, and YX=0 to 20°C were judged as passing (no flow marks or slight flow marks occurred). Molded articles (Comparative Examples 1 to 6) that did not satisfy the above conditions were judged as failing (clear flow marks or discoloration occurred).

Claims

1. A method for producing a molded article of a styrene-based resin composition, comprising: The styrene-based resin composition comprises a styrene-based resin (A); an incompatible resin (B) that is incompatible with the styrene-based resin (A); Contains The injection molding machine used to manufacture the molded product is Injection section and a mold in fluid communication with the injection section; Equipped with A method for producing a molded article of a styrene-based resin composition, comprising an injection molding step of injecting the styrene-based resin composition from the injection part into the mold to mold the molded article under conditions that satisfy 200≦X≦240, 210≦Y≦250, and Y−X=0 to 20, where X°C is the temperature of the injection part and Y°C is the temperature of the mold during molding.

2. 2. The method for producing a molded article of a styrene-based resin composition according to claim 1, wherein the incompatible resin (B) is a polyester resin.

3. 2. The method for producing a molded article of a styrene-based resin composition according to claim 1, wherein the incompatible resin (B) is a polylactic acid resin (PLA).

4. The method for producing a molded article of a styrene-based resin composition according to claim 1, characterized in that the styrene-based resin composition contains the styrene-based resin (A) and the incompatible resin (B) in a mass ratio of 80:20 to 40:

60.

5. 2. The method for producing a molded article of a styrene-based resin composition according to claim 1, wherein an average injection speed of the styrene-based resin composition from the injection part into the mold is 30 mm / sec or less.

6. 6. The method for producing a molded article of a styrene-based resin composition according to claim 1, wherein the injection pressure dwell time of the styrene-based resin composition in the mold is 4 seconds or more.

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