Resin composition

Abstract

To provide a polystyrene-based resin composition that allows realization of a molded article having resistance to cracking.SOLUTION: A resin composition contains (A) a polystyrene having a syndiotactic structure and (B) a polymer-type antistatic agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polystyrene resin composition and a molded article. [Background technology]

[0002] Polystyrene is widely used, primarily in everyday items, because it is inexpensive and easy to injection mold, but because it is a resin that is generally prone to static buildup, antistatic agents are sometimes added when used in electrical appliances, precision instruments, and the like (see, for example, Patent Document 1). However, there is a concern that the addition of antistatic agents may result in a deterioration in the mechanical properties of the resulting molded articles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2011-184655 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a polystyrene resin composition that can produce a molded article that is less likely to break. [Means for solving the problem]

[0005] As a result of extensive research, the present inventors have found that by combining polystyrene having a syndiotactic structure with a polymeric antistatic agent, the mechanical properties, particularly the susceptibility to cracking, of the resulting molded article can be improved, and a molded article that is less susceptible to cracking than one in which no antistatic agent is added can be realized, thereby completing the present invention. According to the present invention, the following resin compositions and the like are provided. 1. (A) Polystyrene having a syndiotactic structure, and (B) Polymer-type antistatic agent A resin composition comprising: 2. The resin composition according to 1, wherein the content of the polymeric antistatic agent (B) is 0.1 to 30% by mass based on the total mass of the resin composition. 3. The resin composition according to 1 or 2, wherein the polymeric antistatic agent (B) is a polyether polyolefin copolymer. 4. The resin composition according to any one of 1 to 3, further comprising (D) an antioxidant. 5. The resin composition according to 4, wherein the content of the (D) antioxidant is 0.001 to 5% by mass based on the total mass of the resin composition. 6. The resin composition according to 4 or 5, wherein the (D) antioxidant is at least one selected from the group consisting of phenol-based antioxidants and phosphorus-based antioxidants. 7. The resin composition according to any one of 1 to 6, which contains (C) a compatibilizer. 8. The resin composition according to 7, wherein the content of the compatibilizer (C) is 0.1 to 20 mass % based on the total amount of the resin composition or the components (A) to (C). 9. The resin composition according to 7 or 8, wherein the compatibilizer (C) is a block copolymer containing structural units derived from styrene and structural units derived from olefin. 10. A molded article obtained from the resin composition according to any one of 1 to 9. [Effects of the Invention]

[0006] According to the present invention, a polystyrene resin composition capable of realizing a molded article that is resistant to cracking can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0007] The resin composition of the present invention will be described in detail below. In this specification, "x to y" represents a numerical range of "greater than or equal to x and less than or equal to y." The upper and lower limits of the numerical ranges can be combined in any manner. Furthermore, a combination of two or more of the individual embodiments of the present invention described below is also an embodiment of the present invention. Furthermore, a numerical range of "greater than x" implies "greater than x," and a numerical range of "less than or equal to y" implies "less than y."

[0008] [Resin composition] A resin composition according to one embodiment of the present invention comprises the following components (A) and (B): Hereinafter, these components may also be simply referred to as "component (A)" and "component (B)". (A) Polystyrene with a syndiotactic structure (B) Polymer-type antistatic agent Each component will be explained below.

[0009] ((A) Polystyrene with syndiotactic structure) Polystyrene having a syndiotactic structure (hereinafter simply referred to as "syndiotactic polystyrene" or "SPS") is a crystalline styrene-based resin with a highly syndiotactic structure. "Syndiotactic" means that the phenyl rings of adjacent styrene units are highly arranged alternately with respect to the plane formed by the main chain of the polymer block (hereinafter referred to as syndiotacticity).

[0010] Tacticity is measured by nuclear magnetic resonance (NMR) using carbon isotopes. 13 Quantitative identification can be performed using the C-NMR method. 13 By C-NMR, the proportion of consecutive structural units, for example, two consecutive monomer units as a diad, three consecutive monomer units as a triad, and five consecutive monomer units as a pentad, can be quantified.

[0011] The term "styrene resin having a highly syndiotactic structure" refers to a styrene polymer such as polystyrene, poly(hydrocarbon-substituted styrene), poly(halogenated styrene), poly(halogenated alkylstyrene), poly(alkoxystyrene), or poly(vinyl benzoate ester), having a syndiotacticity of typically 75 mol % or more, preferably 85 mol % or more in racemic diad (r), or typically 30 mol % or more, preferably 50 mol % or more in racemic pentad (rrrr), hydrogenated polymers or mixtures of these, or copolymers containing these as the main component.

[0012] Examples of poly(hydrocarbon-substituted styrenes) include poly(methylstyrene), poly(ethylstyrene), poly(isopropylstyrene), poly(tert-butylstyrene), poly(phenylstyrene), poly(vinylnaphthalene), and poly(vinylstyrene). Examples of poly(halogenated styrenes) include poly(chlorostyrene), poly(bromostyrene), and poly(fluorostyrene). Examples of poly(halogenated alkylstyrenes) include poly(chloromethylstyrene). Examples of poly(alkoxystyrenes) include poly(methoxystyrene) and poly(ethoxystyrene).

[0013] Examples of comonomer components of copolymers containing the above structural units include, in addition to the monomers of the above styrene-based polymers, olefin monomers such as ethylene, propylene, butene, hexene, and octene; diene monomers such as butadiene and isoprene; and polar vinyl monomers such as cyclic olefin monomers, cyclic diene monomers, methyl methacrylate, maleic anhydride, and acrylonitrile. Suitable copolymers include a copolymer of styrene and p-methylstyrene, a copolymer of styrene and p-tert-butylstyrene, a copolymer of styrene and divinylbenzene, and the like, with a copolymer of styrene and p-methylstyrene being preferred.

[0014] Among syndiotactic polystyrenes, one or more selected from polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly(p-tert-butylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluorostyrene), and copolymers of styrene and p-methylstyrene are preferred, one or more selected from polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), and copolymers of styrene and p-methylstyrene are more preferred, polystyrene and copolymers of styrene and p-methylstyrene are even more preferred, and polystyrene is most preferred.

[0015] The melt flow rate (MFR) of the syndiotactic polystyrene is preferably 1 g / 10 min or more, more preferably 2 g / 10 min or more, even more preferably 3 g / 10 min or more, 4 g / 10 min or more, 5 g / 10 min or more, or 7 g / 10 min or more. It is also preferably 40 g / 10 min or less, more preferably 25 g / 10 min or less, and even more preferably 18 g / 10 min or less. If the MFR is 1 g / 10 min or more, there is no problem with the fluidity of the resin during extrusion molding. If the MFR is 40 g / 10 min or less, preferably 20 g / 10 min or less, a molded product having sufficient strength can be obtained. The MFR measurement of syndiotactic polystyrene is carried out under conditions of a temperature of 300°C and a load of 1.2 kg.

[0016] The weight-average molecular weight of the syndiotactic polystyrene is, for example, 100,000 or more, 110,000 or more, 130,000 or more, or 150,000 or more. Within these ranges, excellent film-forming properties and strength are achieved. There is no particular upper limit to the weight-average molecular weight of the syndiotactic polystyrene, but it is, for example, 500,000 or less, 350,000 or less, 300,000 or less, 250,000 or less, or 200,000 or less. Within these ranges, the fluidity of the resin during extrusion molding can be ensured. The weight average molecular weight of syndiotactic polystyrene is a value measured by gel permeation chromatography at 145°C using 1,2,4-trichlorobenzene as a solvent, and converted using a calibration curve of standard polystyrene.

[0017] Syndiotactic polystyrene can be produced by known methods, for example, by polymerizing a styrene monomer in an inert hydrocarbon solvent or in the absence of a solvent using a condensation product of a titanium compound, water, and trialkylaluminum as a catalyst.

[0018] In one embodiment, the resin composition is primarily composed of polystyrene having a syndiotactic structure. "To be primarily composed of polystyrene having a syndiotactic structure" means that more than 50% by mass of the resin composition is syndiotactic polystyrene. By using syndiotactic polystyrene as the primary component, excellent heat resistance and chemical resistance can be achieved when a molded article is formed. The content of component (A) in the resin composition according to one aspect of the present invention is, for example, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, or 80% by mass or more, based on the entire resin composition or the total amount of components (A) to (C). There is no particular upper limit, but it is, for example, 99% by mass or less, or 95% by mass or less, based on the entire resin composition or the total amount of components (A) to (C). The content of component (A) in the resin composition according to one embodiment of the present invention is, for example, more than 50% by mass and not more than 99% by mass, 60% by mass or more and not more than 95% by mass, or 70% by mass or more and not more than 95% by mass, relative to the entire resin composition or the total amount of components (A) to (C).

[0019] ((B) Polymer-type antistatic agent) The resin composition according to one embodiment of the present invention contains (B) a polymeric antistatic agent, which makes the resulting molded article less likely to crack. Conventionally, adding an antistatic agent to polystyrene has the disadvantage of reducing mechanical properties, but combining (A) SPS with (B) a polymeric antistatic agent can sometimes improve mechanical properties compared to SPS alone, particularly reducing cracking. Furthermore, low-molecular-weight antistatic agents have the disadvantage that the antistatic agent bleeds out onto the surface of the molded article and contaminates the mold or post-processing equipment, and their performance varies depending on temperature and humidity conditions, resulting in poor stability. However, (B) high-molecular-weight antistatic agents have almost no such concerns.

[0020] Antistatic agents are additives used to prevent static electricity from accumulating in low-conductivity materials such as resins. Polymeric antistatic agents have at least two repeating units and typically have a weight-average molecular weight of 1,000 or more. The weight-average molecular weight of polymeric antistatic agents is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene. The low molecular weight antistatic agent is a non-polymer type antistatic agent, and typically has a weight average molecular weight of less than 1,000. Examples of the low molecular weight antistatic agent include nonionic, anionic, cationic, and amphoteric surfactants.

[0021] Examples of polymeric antistatic agents include copolymers having polyether units, such as polyetheresteramide copolymers, polyetherpolyolefin copolymers, polyetherester copolymers, and polyethermethacrylate copolymers, as well as sulfonated polystyrene and polyacrylates (containing quaternary ammonium salt groups). These copolymers may contain metal salts, such as alkali metal salts and alkaline earth metal salts, and ionic liquids. Among these, polyether polyolefin copolymers (for example, polyether polyolefin block copolymers or polyether polyolefin random copolymers) are preferred from the viewpoint of realizing higher antistatic properties.

[0022] The polyether polyolefin copolymer is a copolymer comprising units of both polyether moieties and polyolefin moieties, and exhibits antistatic properties due to the ionic conductivity of the polyether moieties. Examples of commercially available polyether polyolefin copolymers include those manufactured by Sanyo Chemical Industries, Ltd. under the product names "Pelestat 300," "Pelestat 230," "Pelestat PVH," "Pelestat PVL," "Pelestat 201," and "Pelestat UC," as well as those manufactured by Sanko Chemical Industries, Ltd. under the product name "Sankonol TBX-310."

[0023] The melt flow rate (MFR) of component (B) is, for example, 1 g / 10 min or more, 3 g / 10 min or more, 5 g / 10 min or more, or 10 g / 10 min or more. There is no upper limit, but it is, for example, 50 g / 10 min or less, 45 g / 10 min or less, 40 g / 10 min or less, 35 g / 10 min or less, 30 g / 10 min or less, 25 g / 10 min or less, or 20 g / 10 min or less. The MFR of component (B) is measured at 190°C and 21.18N in accordance with ASTM D1238.

[0024] The content of component (B) in the resin composition according to one aspect of the present invention is, for example, 0.1 mass% or more, 0.5 mass% or more, 1 mass% or more, or 3 mass% or more relative to the entire resin composition or the total amount of components (A) to (C). There is no particular upper limit, but it is, for example, 30 mass% or less, 25 mass% or less, or 20 mass% or less relative to the entire resin composition or the total amount of components (A) to (C). The content of component (B) in the resin composition according to one embodiment of the present invention is, for example, 0.1 to 30 mass%, 0.5 to 25 mass%, 1 to 20 mass%, or 3 to 20 mass% relative to the entire resin composition or the total amount of components (A) to (C). The component (B) may be any of the above-mentioned compounds, or a combination of two or more of them, and the above content is the total amount of the component (B).

[0025] ((C) Compatibilizer) The resin composition according to one embodiment of the present invention may or may not contain a compatibilizer (hereinafter, also simply referred to as "component (C)").

[0026] Examples of the compatibilizer include (C1) a copolymer of an α,β-unsaturated carboxylic acid or its acid anhydride or its ester with an olefin; (C2) a copolymer of an α,β-unsaturated carboxylic acid or its acid anhydride or its ester with styrene; (C3) a block copolymer consisting of styrene and an olefin; (C4) a copolymer of an α,β-unsaturated carboxylic acid or its acid anhydride or its ester with styrene and an olefin; and (C5) acid-modified polyphenylene ether (acid-modified PPE).

[0027] Specific examples of (C1) α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, and the like, as well as their acid anhydrides, methyl esters, ethyl esters, and the like. Examples of the olefin unit in the copolymer of an α,β-unsaturated carboxylic acid, an anhydride thereof, or an ester thereof with an olefin include ethylene, propylene, and butene units, with ethylene units being preferred. Examples of the copolymer include an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, an ethylene-methyl methacrylate copolymer, and an ethylene-maleic anhydride copolymer.

[0028] (C2) Examples of polystyrene containing an α,β-unsaturated carboxylic acid or an ester thereof include methacrylic acid-styrene copolymers and methyl methacrylate-styrene copolymers (MS resins).

[0029] (C3) As a block copolymer containing a structural unit derived from styrene and a structural unit derived from an olefin, a terblock copolymer is preferable, and specific examples thereof include hydrogenated styrene-butadiene-styrene block copolymer (SEBS) and hydrogenated styrene-isoprene-styrene block copolymer (SEPS).

[0030] As for (C4) a copolymer of an α,β-unsaturated carboxylic acid or an acid anhydride or an ester thereof with styrene and an olefin, (C3) the block copolymer contains an α,β-unsaturated carboxylic acid or an acid anhydride or an ester thereof.

[0031] (C5) Acid-modified polyphenylene ether (acid-modified PPE) includes polyphenylene ether (PPE, also called PPO (polyphenylene oxide)) modified with an acid such as maleic acid or fumaric acid.

[0032] In one embodiment, as component (C), from the viewpoints of compatibility and thermal stability, a block copolymer (C3) containing structural units derived from styrene and structural units derived from olefin is used.

[0033] When the resin composition according to an embodiment of the present invention contains component (C), the content of component (C) in the resin composition is, for example, 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more relative to the entire resin composition or the total amount of components (A) to (C). There is no particular upper limit, but it is, for example, 20% by mass or less, 15% by mass or less, or 10% by mass or less relative to the entire resin composition or the total amount of components (A) to (C). The content of component (C) in the resin composition according to one embodiment of the present invention is, for example, 0.1 to 20 mass%, 0.5 to 15 mass%, or 1 to 10 mass% relative to the entire resin composition or the total amount of components (A) to (C). The component (C) may be any of the above-mentioned compounds, or a combination of two or more of them, and the above content is the total amount of the component (C).

[0034] ((D) Antioxidants) The resin composition according to one embodiment of the present invention may or may not contain an antioxidant (hereinafter also simply referred to as "component (D)"), but preferably contains an antioxidant. By containing an antioxidant, the obtained molded article becomes less likely to crack (improved crack resistance) and the antistatic performance of the molded article can be further improved.

[0035] As the antioxidant, known materials such as phosphorus-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants can be used. Specific examples of phosphorus-based antioxidants include distearyl pentaerythritol diphosphite; dioctyl pentaerythritol diphosphite; diphenyl pentaerythritol diphosphite; bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite; bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite; and dicyclohexyl pentaerythritol diphosphite.

[0036] Specific examples of phenolic antioxidants include 2,6-di-tert-butyl-4-methylphenol; 2,6-diphenyl-4-methoxyphenol; 2,2'-methylenebis(6-tert-butyl-4-methylphenol); 2,2'-methylenebis(6-tert-butyl-4-methylphenol); 2,2'-methylenebis[4-methyl-6-(α-methylcyclohexyl)phenol]; 1,1-bis(5-tert-butyl-4-hydroxy-2-methyl 2,2'-Methylenebis(4-methyl-6-cyclohexylphenol);2,2'-Methylenebis(4-methyl-6-nonylphenol);1,1,3-Tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane;2,2-Bis(5-tert-butyl-4-hydroxy-2-methylphenyl)-4-n-dodecylmercaptobutane;Ethylene glycol-bis[3,3-bis(3-tert-butyl-4-hydroxy phenyl) butyrate];1,1-bis(3,5-dimethyl-2-hydroxyphenyl)-3-(n-dodecylthio)-butane;4,4'-thiobis(6-tert-butyl-3-methylphenol);1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene;2,2-bis(3,5-di-tert-butyl-4-hydroxybenzyl)malonic acid dioctadecyl ester;n-Octadecyl-3-(4- hydroxy-3,5-di-tert-butylphenyl)propionate; tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, and the like.

[0037] Specific examples of sulfur-based antioxidants include 2,2-bis[[3-(dodecylthio)-1-oxopropyloxy]methyl]-1,3-propanediyl bis[3-(dodecylthio)propionic acid].

[0038] When the resin composition according to an embodiment of the present invention contains component (D), the content of component (D) in the resin composition is, for example, 0.001 parts by mass or more, 0.01 parts by mass or more, 0.05 parts by mass or more, or 0.1 parts by mass or more, relative to 100 parts by mass of the entire resin composition or the total of components (A) to (C). There is no particular upper limit, but it is, for example, 5 parts by mass or less, 1 part by mass or less, or 0.5 parts by mass or less, relative to 100 parts by mass of the entire resin composition or the total of components (A) to (C). The content of component (D) in the resin composition according to one embodiment of the present invention is, for example, 0.001 to 5 parts by mass, 0.05 to 1 part by mass, or 0.1 to 0.5 parts by mass, relative to 100 parts by mass of the entire resin composition or the sum of components (A) to (C). The component (D) may be any of the above-mentioned compounds, or a combination of two or more of them, and the above content is the total amount of the component (D).

[0039] ((E): Other additives and resins) The resin composition according to one embodiment of the present invention may or may not contain resin components (e.g., thermoplastic resins) other than the above-mentioned components (A) to (D) and various additives, as long as the effects of the present invention are not impaired. Hereinafter, these components will also be referred to simply as "component (E)." In addition, by definition, any substance that falls under any of the above-mentioned components (A) to (D) is treated as any of the components (A) to (D).

[0040] The thermoplastic resin can be arbitrarily selected from known thermoplastic resins, such as linear high-density polyethylene, linear low-density polyethylene, high-pressure low-density polyethylene, isotactic polypropylene, syndiotactic polypropylene, block polypropylene, random polypropylene, polybutene, 1,2-polybutadiene, cyclic polyolefin, and poly-4-methylpentene; polystyrene resins such as polystyrene, HIPS, ABS, and AS; polyester resins such as polycarbonate, polyethylene terephthalate, and polybutylene terephthalate; polyamide resins such as polyamide 6 and polyamide 6,6; acrylic polymers such as polyphenylene ether, polyphenylene sulfide, and (meth)acrylic acid alkyl esters; and styrene-containing elastomers such as styrene-ethylene-butylene-styrene. The thermoplastic resins can be used singly or in combination.

[0041] The additives that can be blended include, for example, nucleating agents, plasticizers, mold release agents, flame retardants, flame retardant assistants, pigments, carbon black, antiblocking agents, reinforcing materials, and the like.

[0042] The nucleating agent can be arbitrarily selected from known agents such as metal salts of carboxylic acids such as aluminum di(pt-butylbenzoate), metal salts of phosphoric acids such as sodium methylenebis(2,4-di-t-butylphenol) acid phosphate, talc, phthalocyanine derivatives, etc. These nucleating agents can be used singly or in combination of two or more.

[0043] The plasticizer can be arbitrarily selected from known plasticizers such as polyethylene glycol, polyamide oligomer, ethylene bisstearamide, phthalate ester, polystyrene oligomer, polyethylene wax, mineral oil, silicone oil, etc. These plasticizers can be used alone or in combination of two or more.

[0044] The release agent can be arbitrarily selected from known agents such as polyethylene wax, silicone compounds (e.g., silicone oil and ultra-high molecular weight silicone), long-chain carboxylic acids, long-chain carboxylate salts, etc. These release agents can be used alone or in combination of two or more.

[0045] The flame retardant can be arbitrarily selected from known compounds such as brominated polymers including brominated polystyrene, brominated syndiotactic polystyrene, and brominated polyphenylene ether, and brominated aromatic compounds such as brominated diphenylalkane and brominated diphenyl ether. The flame retardant synergist can be arbitrarily selected from antimony compounds including antimony trioxide and others, and can be used singly or in combination of two or more.

[0046] Known materials can be used for the pigment, carbon black, antiblocking agent, and reinforcing material (for example, glass fiber, carbon fiber, and inorganic filler).

[0047] (Resin composition) The resin composition according to one embodiment of the present invention may contain, for example, 80% by mass or more, 85% by mass or more, 87% by mass or more, 90% by mass or more, 95% by mass or more, 98% by mass or more, 99% by mass or more, 99.9% by mass or more, or 100% by mass of Component (A) and component (B); Component (A), component (B), and component (C); Component (A), component (B), and component (D); or Component (A), component (B), component (C), and component (D) may be.

[0048] [Molded objects, applications, etc.] The resin composition according to one embodiment of the present invention can be effectively used to produce various molded articles (molded products), for example, various molded articles by injection molding; sheets, films, etc. by extrusion molding; containers, trays, etc. by extrusion molding and thermoforming; uniaxially or biaxially stretched films, sheets, etc. by extrusion molding and stretching; fibrous molded articles by spinning; and various molded articles by foaming. Specific uses include, for example, packaging materials such as vegetable packaging, twist packaging, pharmaceutical packaging, reagent containers (packaging, flexible containers), food containers, food container surface base materials, food container lids, heat-resistant cooking film, instant noodle container surface materials, adhesive labels, and simple adhesive tape; as well as industrial materials such as masking film, labels, magazine tape, release film, insulating film, chemical-resistant film, paper laminate, printed circuit board base material, film for film capacitors, component trays, nonwoven fabrics, packaging materials for household holdings, agricultural materials, and battery-related materials. [Example]

[0049] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0050] [Ingredients used] The materials used in the following examples and comparative examples are as follows. ((A) Polystyrene with syndiotactic structure) SPS1: Syndiotactic polystyrene, manufactured by Idemitsu Kosan Co., Ltd.; MFR: 14.0 g / 10 min (300°C, 1.2 kg load); Weight-average molecular weight: 170,000 (measured by gel permeation chromatography at 145°C using 1,2,4-trichlorobenzene as a solvent); Melting point: 246°C (measured by DSC) 13 C-NMR measurements confirmed that SPS1 was a polystyrene with a syndiotactic structure.

[0051] ((A') Polystyrene not corresponding to component (A)) aPS1: Polystyrene with atactic structure, "680" manufactured by PS Japan Co., Ltd., MFR: 7.0 g / 10 min (temperature 200°C, load 5 kg)

[0052] ((B) Polymer-type antistatic agent) AS1: Polyether-polyolefin block copolymer, "Pelectron PVL" manufactured by Sanyo Chemical Industries, Ltd., MFR: 15 g / 10 min (measured at 190 °C and 21.18 N in accordance with ASTM D1238)

[0053] ((C) Compatibilizer) SEPS1: Hydrogenated styrene-based thermoplastic elastomer (styrene-ethylene-propylene-styrene (SEPS)), "Septon 2104" manufactured by Kuraray Co., Ltd.

[0054] ((D) Antioxidants) AO1: Pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (BASF Japan Ltd. "Irganox 1010") AO2: Bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite (ADEKA Corporation "PEP-36")

[0055] Example 1 The components shown in Table 1 were dry-blended in a Henschel mixer in the composition (% by mass) shown in Table 1, and then melt-kneaded in a twin-screw extruder to obtain pellets (resin compositions). The compositions in Table 1 show the content (% by mass) of each component relative to the total of components (A) to (C), and the content (parts by mass) of component (D) relative to 100 parts by mass of the total of components (A) to (C). The resulting resin composition was evaluated as follows, and the results are shown in Table 1.

[0056] (crack resistance) The obtained resin composition was heat-pressed for 1 minute at 290°C and 5 kgf using a heat press. The preheating time was 3 minutes. The resin composition was then cooled for 1 minute between cooling plates running 20°C cooling water, yielding a resin sheet with a thickness of approximately 100 μm. This resin sheet was cut into a size of 10 mm wide x 50 mm long to prepare a test piece. The obtained test piece was slowly bent by hand, and it was observed whether or not a crack occurred in at least a part of the test piece before the same surface of the bent part came into contact. This test was repeated five times (n=5) and evaluated according to the following criteria. ◯: None of the five test pieces were broken. △: 1 to 4 of the 5 test pieces were broken. ×: All five test pieces were cracked. In Table 1, the numbers in parentheses indicate the number of broken test pieces out of the five test pieces.

[0057] (Surface specific resistivity) The resin pellets (resin composition) obtained by melt-kneading the composition (mass%) shown in Table 1 in a twin-screw extruder were fed into a 30mm diameter gear pump-equipped extruder and extruded at a set temperature of 280°C. The gear pump attached to the tip of the extruder was adjusted to a film thickness of 35µm, and the extruded film was extruded into a film shape through a die set at 280°C. The film was then cooled and solidified on a take-up roll at 85°C to prepare a test film. Test specimens measuring 100mm x 100mm x 50µm were conditioned at 23±2°C and 50±5% RH, and the surface resistivity was measured according to JIS-K6911. "OR" indicates over-range (insulator).

[0058] Examples 2 to 5, Comparative Examples 1 to 2 Pellets (resin compositions) were produced and evaluated in the same manner as in Example 1, except that the composition was changed as shown in Table 1. The results are shown in Table 1.

[0059] [Table 1]

[0060] A comparison of Examples 1 to 5 with Comparative Example 1 reveals that combining SPS with a polymeric antistatic agent improves the crack resistance of the resulting molded article, and that the effect is particularly pronounced when an antioxidant is used in combination. On the other hand, with polystyrene having a general atactic structure, a molded article that is less likely to crack could not be obtained even when a polymeric antistatic agent and an antioxidant were used in combination (Comparative Example 2). Furthermore, Example 5 shows that even if a polymeric antistatic agent is added, the desired surface resistivity may not be achieved unless an antioxidant is also used. Although the reason for this is unclear, it is thought that while SPS's excellent heat resistance allows for high-temperature molding, the performance of the polymeric antistatic agent deteriorates during molding at such high temperatures. In other words, it is clear that the combined use of a polymeric antistatic agent and an antioxidant in an SPS-based resin composition makes it possible to produce molded articles that are less likely to crack and exhibit better antistatic performance.

Claims

1. (A) polystyrene having a syndiotactic structure, and (B) Polymer-type antistatic agent A resin composition comprising:

2. 2. The resin composition according to claim 1, wherein the content of the polymeric antistatic agent (B) is 0.1 to 30 mass % based on the total mass of the resin composition.

3. 3. The resin composition according to claim 1, wherein the polymeric antistatic agent (B) is a polyether polyolefin copolymer.

4. The resin composition according to any one of claims 1 to 3, further comprising (D) an antioxidant.

5. The resin composition according to claim 4, wherein the content of the (D) antioxidant is 0.001 to 5 mass% with respect to the entire resin composition.

6. 6. The resin composition according to claim 4, wherein the antioxidant (D) is at least one selected from the group consisting of phenol-based antioxidants and phosphorus-based antioxidants.

7. The resin composition according to any one of claims 1 to 6, further comprising (C) a compatibilizer.

8. The resin composition according to claim 7, wherein the content of the compatibilizer (C) is 0.1 to 20 mass% based on the total amount of the resin composition or the components (A) to (C).

9. The resin composition according to claim 7 or 8, wherein the compatibilizer (C) is a block copolymer containing a structural unit derived from styrene and a structural unit derived from an olefin.

10. A molded article obtained from the resin composition according to any one of claims 1 to 9.

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