Styrenic resin composition, styrenic resin sheet, and food packaging container

Abstract

To provide a styrenic resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance and processability.SOLUTION: A styrenic resin composition contains a styrenic resin, an olefinic resin containing high density polyethylene, and a styrenic thermoplastic elastomer, wherein a used amount of the styrenic resin is within the range of 50-90 mass% in the total of the styrenic resin, the olefinic resin and the styrenic thermoplastic elastomer, a used amount of the olefinic resin is within the range of 5-40 mass% in the total of the styrenic resin, the olefinic resin and the styrenic thermoplastic elastomer, a used amount of the styrenic thermoplastic elastomer is within the range of 1-10 mass% in the total of the styrenic resin, the olefinic resin and the styrenic thermoplastic elastomer, and a styrene content of the styrenic thermoplastic elastomer is 45 mass% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a styrene-based resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance and processability, a styrene-based resin composition comprising the styrene-based resin composition, and a food packaging container comprising a styrene-based resin sheet. [Background technology]

[0002] In recent years, styrene-based thermoplastic resin sheets have been widely used as food packaging containers due to their excellent moldability and dimensional stability. The properties required for such thermoplastic resin sheets include impact resistance, rigidity, strength, heat resistance, oil resistance, processability, etc. at levels sufficient for use as food packaging containers.

[0003] Conventionally, known thermoplastic resin sheets include those containing a mixed resin layer containing 60 to 95 mass % of at least one styrene-based resin selected from polystyrene and high-impact polystyrene, 1 to 30 mass % of an olefin-based resin, 1 to 10 mass % of a styrene-based thermoplastic elastomer, and 1 to 20 mass % of talc having an average particle size of 2 to 20 μm (see, for example, Patent Document 1 below). However, these do not satisfy the increasingly high required properties and are insufficient for meeting current market demands.

[0004] Therefore, there has been a demand for materials that have even better impact resistance, rigidity, strength, heat resistance, oil resistance and processability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-075210 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a styrene-based resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance and processability, a styrene-based resin sheet made from the styrene-based resin composition, and a food packaging container made from the styrene-based resin sheet. [Means for solving the problem]

[0007] As a result of intensive investigations to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a styrene-based resin composition containing a specific amount of a styrene-based resin, a specific amount of an olefin-based resin, and a specific amount of a styrene-based thermoplastic elastomer, and have thus completed the present invention.

[0008] That is, the present invention relates to a styrene-based resin composition containing a styrene-based resin (A), an olefin-based resin (B) including high-density polyethylene, and a styrene-based thermoplastic elastomer (C), wherein the amount of the styrene-based resin (A) used is in the range of 50 to 90 mass% based on the total of the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C), the amount of the olefin-based resin (B) used is in the range of 5 to 40 mass% based on the total of the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C), the amount of the styrene-based thermoplastic elastomer (C) used is in the range of 1 to 10 mass% based on the total of the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C), and the styrene content in the styrene-based thermoplastic elastomer (C) is 45 mass% or more, a styrene-based resin sheet made of the styrene-based resin composition, and a food packaging container made of the styrene-based resin sheet. [Effects of the Invention]

[0009] The styrene-based resin composition of the present invention has impact resistance, rigidity, strength, heat resistance, oil resistance, and processability, and therefore can be suitably used for food packaging containers. In the present invention, "processability" refers to the film-formability (primary processability) when a sheet is produced from a molten resin, and the shape reproducibility and deep drawability (secondary processability) when a container is formed from the sheet by vacuum forming. DETAILED DESCRIPTION OF THE INVENTION

[0010] The styrene resin composition of the present invention is characterized by containing a styrene resin (A), an olefin resin (B), and a styrene thermoplastic elastomer (C).

[0011] The styrene-based resin (A) used contains an impact-resistant styrene-based resin (a1) and polystyrene (a2).

[0012] The impact-resistant styrene-based resin (a1) may be a polystyrene-based resin containing a component such as rubber, and for example, a commonly available resin formed by graft-polymerizing a rubber-like polymer onto a continuous phase of a styrene homopolymer and dispersing the particles therein can be used as is. Examples of the rubber component contained in the impact-resistant styrene-based resin (a1) include polybutadiene, styrene-butadiene copolymer, polyisoprene, butadiene-isoprene copolymer, etc. In particular, it is preferably contained as polybutadiene or styrene-butadiene copolymer.

[0013] The fluidity of the impact-resistant styrene-based resin (a1) used in the present invention is preferably in the range of 1 to 10 g / 10 min, since this gives a styrene-based resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance and processability.

[0014] The content of the rubber polymer contained in the impact-resistant styrene-based resin (a1) is preferably in the range of 1.5 to 15.0 mass %, since a styrene-based resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance and processability can be obtained. As the impact-resistant styrene-based resin (a1), a commercially available product may be used as is, but it is also possible to use a resin having a high rubber component content by mixing ordinary polystyrene with it, and then adjusting the rubber component content and fluidity within a suitable range.

[0015] The content of the impact-resistant styrene-based resin (a1) in the styrene-based resin (A) is 50% by mass or more, preferably in the range of 55 to 80% by mass, since a styrene-based resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance and processability can be obtained.

[0016] The polystyrene (a2) may be a styrene homopolymer generally referred to as "general-purpose polystyrene (GPPS)." Alternatively, the polystyrene (a2) may be a copolymer containing 50% by mass or more of styrene, or a hyperbranched polystyrene.

[0017] Examples of the copolymer containing 50% by mass or more of styrene include a styrene-(meth)acrylic acid copolymer, a styrene-(meth)acrylic acid ester copolymer, a styrene-acrylonitrile copolymer, and a styrene-maleic anhydride copolymer.

[0018] Examples of the hyperbranched polystyrene include those obtained by polymerizing styrene in the presence of a multifunctional polyester (meth)acrylate having multiple double bonds at the molecular end, a multifunctional polyether (meth)acrylate, a multifunctional polyurethane (meth)acrylate, etc. The hyperbranched polystyrene may also be a copolymer with other copolymerizable monomers.

[0019] These polystyrenes (a2) can be used alone or in combination of two or more kinds.

[0020] The amount of the styrene-based resin (A) used is in the range of 50 to 90 mass %, preferably 60 to 70 mass %, of the total amount of the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C), since a styrene-based resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance, and processability can be obtained.

[0021] The olefin resin (B) includes high density polyethylene (hereinafter sometimes referred to as "HDPE").

[0022] Furthermore, as the olefin resin (B), olefin resins other than HDPE (hereinafter abbreviated as "other olefin resins") can also be used, if necessary.

[0023] Examples of the other olefin resins include homopolymers and copolymers of olefins having 2 to 8 carbon atoms, such as ethylene, propylene, isobutylene, 1-butene, 4-methyl-1-pentene, hexene, and vinylcyclohexane, and copolymers of the above-mentioned olefins having 2 to 8 carbon atoms with other monomers. Specific examples include polyethylenes such as low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) resins, polypropylene, polyisobutylene, poly(1-butene), poly(4-methyl-1-pentene), polyvinylcyclohexane, α-olefin copolymers such as ethylene-propylene block copolymers, ethylene-propylene random copolymers, ethylene-1-butene copolymers, ethylene-4-methyl-1-pentene copolymers, and ethylene-hexene copolymers, ethylene-methyl methacrylate copolymers, propylene-1-butene copolymers, and cyclic polyolefins, which are homopolymers of monocyclic olefin monomers such as cyclopentene and polycyclic olefin monomers such as norbornene, or copolymers with other olefin monomers. These olefin resins can be used alone or in combination of two or more.

[0024] The high-density polyethylene may be derived from biomass, where "biomass-derived" refers to a polyethylene with a bio-based content of 80% or more as measured in accordance with ASTM D6866.

[0025] The amount of the olefin resin (B) used is in the range of 5 to 40 mass %, preferably 15 to 35 mass %, of the total amount of the styrene resin (A), the olefin resin (B), and the styrene thermoplastic elastomer (C), since a styrene resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance, and processability can be obtained.

[0026] Examples of the styrene-based thermoplastic elastomer (C) include styrene-butadiene copolymers and hydrogenated products thereof, styrene-isoprene copolymers and hydrogenated products thereof, and methyl methacrylate-butadiene-styrene copolymers.

[0027] The amount of the styrene-based thermoplastic elastomer (C) used is in the range of 1 to 10 mass %, preferably 4 to 8 mass %, of the total amount of the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C), since a styrene-based resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance, and processability can be obtained.

[0028] The styrene content in the styrene-based thermoplastic elastomer (C) is 45% by mass or more, preferably in the range of 60 to 80% by mass, since a styrene-based resin composition having excellent impact resistance, rigidity, strength, heat resistance, oil resistance and processability can be obtained.

[0029] The method for producing the styrene-based resin composition of the present invention is not particularly limited, and any method may be used, such as a method in which the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C) are dry-blended in a drum tumbler or the like, and then melt-kneaded in a twin-screw extruder or the like to form pellets.

[0030] The styrene-based resin composition of the present invention may contain other components in addition to the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C), as necessary. The content of the other components in the styrene-based resin composition of the present invention is preferably 10% by mass or less.

[0031] Examples of the other components include plasticizers such as liquid paraffin, paraffin wax, and polyethylene wax; inorganic fillers such as talc, silica, clay, titanium oxide, and calcium carbonate; lubricants such as stearic acid, lauric acid, metal salts of higher fatty acids, and ethylenebisfatty acid amides; crystal nucleating agents such as metal salts of carboxylic acids, metal salts of phosphate esters, dibenzylidene sorbitol, and di-alkyl-benzylidene sorbitol; dyes, antistatic agents, antioxidants, flame retardants, dispersants, additives such as wood flour, and resins.

[0032] Examples of the dye include anthraquinone dyes, disazo dyes, isoindolinone dyes, heterocyclic dyes, quinacridone dyes, dioxazine dyes, phthalocyanine dyes, monoazo dyes, etc. These dyes can be used alone or in combination of two or more.

[0033] Examples of the antistatic agent include fatty acid esters such as glycerin fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, and polyglycerin fatty acid esters, polyoxyalkylene alkyl ethers, polyoxyethylene alkylphenyl ethers, N,N-bis(2-hydroxyethyl)alkylamines, polyoxyethylene alkylamines, alkyl sulfonates, alkyl benzene sulfonates, alkyl phosphates, tetraalkylammonium salts, trialkylbenzylammonium salts, alkyl betaines, and alkyl imidazolium betaines. These antistatic agents can be used alone or in combination of two or more.

[0034] Examples of the antioxidant include p-methoxyphenol, p-methoxycresol, 4-methoxy-1-naphthol, 4,4'-dialkoxy-2,2'-bi-1-naphthol, 3-(N-salicyloyl)amino-1,2,4-triazole, N'1,N'12-bis(2-hydroxybenzoyl)dodecane dihydrazide, styrenated phenol, N-isopropyl-N'-phenylbenzene-1,4-diamine, 6-ethoxy-2,2,4-trimethyl- Phenol compounds such as 1,2-dihydroquinoline, quinone compounds such as hydroquinone, methylhydroquinone, p-benzoquinone, methyl-p-benzoquinone, 2,5-diphenylbenzoquinone, 2-hydroxy-1,4-naphthoquinone, anthraquinone, and diphenoquinone, melamine, p-phenylenediamine, 4-aminodiphenylamine, N,N'-diphenyl-p-phenylenediamine, Ni-propyl-N'-phenyl-p-phenylenediamine, N-(1,2-dimethyl-2,3-diphenyl-4-phenylenediamine), and methyl-p-benzoquinone.Amine compounds such as 3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, diphenylamine, 4,4'-dicumyl-diphenylamine, 4,4'-dioctyl-diphenylamine, poly(2,2,4-trimethyl-1,2-dihydroquinoline), styrenated diphenylamine, reaction products of styrenated diphenylamine with 2,4,4-trimethylpentene, and reaction products of diphenylamine with 2,4,4-trimethylpentene, phenothiazine, distearyl thiodipropionate, 2,2-bis({[3-(dodecyl) thioether compounds such as N-nitrosodiphenylamine, N-nitrosophenylnaphthylamine, p-nitrosophenol, nitrosobenzene, p-nitrosodiphenylamine, α-nitroso-β-naphthol, N,N-dimethyl p-nitrosoaniline, p-nitrosodiphenylamine, p-nitrosodimethylamine, p-nitroso-β-naphthol, N,N-dimethyl p-nitrosoaniline, p-nitrosodiphenylamine, p-nitrosodimethylamine, p-nitroso-β-naphthol, N,N-dimethyl p-nitrosoaniline, p-nitrosodiphenylamine, p-nitroso-β-naphthol, N,N-dimethyl p-nitrosoaniline ... -N,N-diethylamine, N-nitrosoethanolamine, N-nitrosodi-n-butylamine, N-nitroso-Nn-butyl-4-butanolamine, N-nitroso-diisopropanolamine, N-nitroso-N-ethyl-4-butanolamine, 5-nitroso-8-hydroxyquinoline, N-nitrosomorpholine, N-nitroso-N-phenylhydroxylamine ammonium salt, nitrosobenzene, N-nitroso-N-methyl-p-toluenesulfonamide, N-nitroso-N-ethylurethane, N-nitroso-Nn -Propyl urethane, 1-nitroso-2-naphthol, 2-nitroso-1-naphthol, sodium 1-nitroso-2-naphthol-3,6-sulfonate, sodium 2-nitroso-1-naphthol-4-sulfonate, 2-nitroso-5-methylaminophenol hydrochloride, 2-nitroso-5-methylaminophenol hydrochloride and other nitroso compounds, esters of phosphoric acid and octadecan-1-ol, triphenyl phosphite, 3,9-dioctadecan-1-yl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]Undecane, trisnonylphenyl phosphite, phosphorous acid-(1-methylethylidene)-di-4,1-phenylenetetra-C12-15-alkyl ester, 2-ethylhexyl diphenyl phosphite, diphenyl isodecyl phosphite, triisodecyl phosphite, phosphite compounds such as tris(2,4-di-tert-butylphenyl) phosphite, bis(dimethyldithiocarbamato-κ(2)S,S')zinc, zinc diethyldithiocarbamate Examples of polymerization inhibitors include zinc compounds such as zinc dibutyl dithiocarbamate, nickel compounds such as bis(N,N-dibutylcarbamodithioato-S,S')nickel, and sulfur compounds such as 1,3-dihydro-2H-benzimidazole-2-thione, 4,6-bis(octylthiomethyl)-o-cresol, 2-methyl-4,6-bis[(octan-1-ylsulfanyl)methyl]phenol, dilauryl thiodipropionate, and distearyl 3,3'-thiodipropionate. These polymerization inhibitors can be used alone or in combination.

[0035] Examples of the flame retardant include inorganic phosphorus compounds such as red phosphorus, ammonium phosphates such as monoammonium phosphate, diammonium phosphate, triammonium phosphate, and ammonium polyphosphate, and phosphoric acid amides; phosphoric acid ester compounds, phosphonic acid compounds, phosphinic acid compounds, phosphine oxide compounds, phosphorane compounds, organic nitrogen-containing phosphorus compounds, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxy Examples of suitable flame retardants include organic phosphorus compounds such as cyclic organic phosphorus compounds such as 10-(2,7-dihydroxynaphthyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide and derivatives thereof obtained by reacting them with compounds such as epoxy resins and phenolic resins; nitrogen-based flame retardants such as triazine compounds, cyanuric acid compounds, isocyanuric acid compounds, and phenothiazine; silicone-based flame retardants such as silicone oil, silicone rubber, and silicone resin; and inorganic flame retardants such as metal hydroxides, metal oxides, metal carbonate compounds, metal powders, boron compounds, and low-melting-point glass. These flame retardants can be used alone or in combination of two or more.

[0036] Examples of the dispersant include polyglycerin fatty acid esters, glycerin fatty acid ester monoglycerides, sorbitan fatty acid esters, higher alcohol fatty acid esters, special fatty acid esters, higher fatty acid metal salts, etc. These dispersants can be used alone or in combination of two or more.

[0037] Examples of the wood flour include those made from thinned wood such as Japanese cypress, Sakhalin fir, larch, cedar, etc. These wood flours can be used alone or in combination of two or more kinds.

[0038] Examples of the resin include polylactic acid, polybutylene succinate, polyhydroxybutyric acid, polymethyl methacrylate, methyl methacrylate-styrene copolymer, acrylonitrile-styrene copolymer, polyethylene terephthalate, polyvinyl alcohol, polyphenylene ether, polycarbonate, polybutylene terephthalate, polyphenylene sulfide, cellulose acetate, cellulose nitrate, cellulose propionate, ethyl cellulose, hemicellulose, lignin, starch-based polymers, etc. These resins can be used alone or in combination of two or more.

[0039] The styrene resin sheet of the present invention can be produced by melt-extruding pellets of the styrene resin composition of the present invention using an extruder, melt-extruding them into a sheet using a T-die, and then cooling them using a cooling roll or the like. The cooling temperature is preferably 70 to 90°C. After melt-extrusion using the extruder, the extruded material may be biaxially stretched lengthwise and widthwise using a stretching machine to form a biaxially stretched sheet, or may be laminated with other styrene resins using techniques such as coextrusion or dry lamination to form a multilayer sheet. Furthermore, silicone oil or the like may be applied as needed.

[0040] The food packaging container of the present invention is obtained by subjecting the styrene resin sheet to secondary forming by a method such as vacuum forming or pressure forming. [Example]

[0041] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the examples given below.

[0042] The following was used as the impact-resistant styrene-based resin (a1). (a1-1): Impact-resistant styrene resin with a melt mass flow rate of 2.0 g / 10 min and a Charpy impact strength of 14 kJ / m2. (a1-2): Impact-resistant styrene resin with a melt mass flow rate of 3.3 g / 10 min and a Charpy impact strength of 12 kJ / m2.

[0043] The following polystyrene (a2) was used: (a2-1): Polystyrene with a melt mass flow rate of 1.5 g / 10 min. (a2-2): Hyperbranched polystyrene with a melt mass flow rate of 1.2 g / 10 min. (a2-3): Hyperbranched polystyrene with a melt mass flow rate of 1.5 g / 10 min and a styrene / butyl acrylate ratio of 97 / 3. (a2-4): Hyperbranched polystyrene with a melt mass flow rate of 2.2 g / 10 min and a styrene / methacrylic acid ratio of 97 / 3.

[0044] The following olefin resins (B) were used: (B-1): High-density polyethylene, Braskem Green PE "SGF4950" (96% biomass content) (B-2): Linear low-density polyethylene, Braskem Green PE "SLH218" (biomass content 84%)

[0045] The following styrene-based thermoplastic elastomer (C) was used. (C-1): Styrene-ethylene-butylene-styrene block copolymer resin ("Tuftec H1043" manufactured by Asahi Kasei Corporation, styrene content 67% by mass) (C-2): Styrene-ethylene-propylene-styrene block copolymer resin ("Septon 2104" manufactured by Kuraray Co., Ltd., styrene content 65% by mass) (C-3): Styrene-butylene-butadiene-styrene block copolymer resin ("Tuftec P2000" manufactured by Asahi Kasei Corporation, styrene content 67% by mass) (C-4): Styrene-butylene-butadiene-styrene block copolymer resin ("Tuftec P5051" manufactured by Asahi Kasei Corporation, styrene content 45% by mass) (C-5): Styrene-ethylene-butylene-styrene block copolymer resin ("Tuftec H1041" manufactured by Asahi Kasei Corporation, styrene content 30% by mass) (C-6): Styrene-ethylene-propylene-styrene block copolymer resin ("Septon 2004F" manufactured by Kuraray Co., Ltd., styrene content 18% by mass)

[0046] (Example 1: Preparation of styrene-based resin composition (1)) The raw materials shown in Table 1 were melt-kneaded in a twin-screw extruder and pelletized. The resulting pellets were used in an injection molding machine to make dumbbells in accordance with JIS K7152-1, and, if necessary, were cut into shapes according to the evaluation items to prepare samples.

[0047] (Examples 2 to 23: Preparation of styrene-based resin compositions (2) to (22)) Using the compositions and blending ratios shown in Table 1, styrene-based resin compositions (2) to (22) were obtained in the same manner as in Example 1.

[0048] (Comparative Examples 1 to 11: Preparation of styrene-based resin compositions (R1) to (R11)) Using the compositions and blending ratios shown in Table 2, styrene-based resin compositions (R1) to (R11) were obtained in the same manner as in Example 1.

[0049] The styrene resin compositions (1) to (22) and (R1) to (R11) obtained in the above examples and comparative examples were evaluated as follows.

[0050] [Impact resistance evaluation method] The Charpy impact strength (notched) of the styrene-based resin compositions obtained in each of the Examples and Comparative Examples was measured in accordance with JIS K7111-1 and evaluated according to the following criteria.

[0051] A: Charpy impact strength is 12kJ / m 2 End B: Charpy impact strength is 10kJ / m 2 More than 12kJ / m 2 less than C: Charpy impact strength is 8kJ / m 2 More than 10kJ / m 2 less than D: Charpy impact strength is 8kJ / m 2less than

[0052] [Rigidity evaluation method] The flexural modulus of the styrene-based resin compositions obtained in each of the Examples and Comparative Examples was measured in accordance with JIS K7171 and evaluated according to the following criteria.

[0053] A: Flexural modulus is 2100 MPa or more B: Flexural modulus is 1800 MPa or more and less than 2100 MPa C: Flexural modulus is 1400 MPa or more and less than 1800 MPa D: Flexural modulus less than 1400 MPa

[0054] [Strength evaluation method] The flexural strength of the styrene-based resin compositions obtained in each of the Examples and Comparative Examples was measured in accordance with JIS K7171 and evaluated according to the following criteria.

[0055] A: Bending strength is 53 MPa or more B: Bending strength is 48 MPa or more and less than 53 MPa C: Bending strength is 42 MPa or more and less than 48 MPa D: Bending strength less than 42 MPa

[0056] [Heat resistance evaluation method] The styrene-based resin compositions obtained in each of the Examples and Comparative Examples were measured for Vicat softening temperature in accordance with JIS K7206 and evaluated according to the following criteria.

[0057] A: Vicat softening temperature is 93°C or higher B: Vicat softening temperature is 87℃ or more and less than 93℃ C: Vicat softening temperature is 80℃ or more and less than 87℃ D: Vicat softening temperature is less than 80°C

[0058] [Oil resistance evaluation method] Dumbbells of the styrene resin compositions obtained in each of the Examples and Comparative Examples were fixed to a jig with a curvature of 0.5% and, in this state, subjected to stress strain, MCT oil was applied, and the properties were evaluated according to the following criteria.

[0059] A: No change B: Minor cracks C: Large crack D: Break

[0060] [Evaluation method for primary processability] The MFR of the styrene-based resin compositions obtained in each Example and Comparative Example was measured in accordance with JIS K7210-1, and the ease of sheet production was evaluated from the MFR value according to the following criteria. MFR measurements were performed at 200°C and 5 kg. High fluidity during melting makes the composition more susceptible to drawdown, resulting in poor film-forming properties.

[0061] A: MFR is less than 2.5g / 10min B: MFR is 2.5g / 10min or more and less than 3.5g / 10min C: MFR is 3.5g / 10min or more and less than 5.0g / 10min D: MFR is 5.0g / 10min or more

[0062] [Evaluation method for secondary processability] The styrene resin compositions obtained in each of the Examples and Comparative Examples were prepared into 0.5 mm sheets, which were then vacuum-formed into cup containers. The resulting containers were evaluated according to the following criteria.

[0063] A: Wide molding range, good mold reproducibility and deep drawability B: Wide molding range and good mold reproducibility C: The molding range is narrow, but the mold reproducibility is good. D: Poor mold reproducibility

[0064] The compositions and evaluation results of the styrene-based resin compositions (1) to (22) prepared in Examples 1 to 22 and the styrene-based resin compositions (R1) to (R11) prepared in Comparative Examples 1 to 11 are shown in Tables 1 to 3.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] Examples 1 to 22 shown in Tables 1 and 2 are examples of styrene-based resin compositions of the present invention. It was confirmed that these styrene-based resin compositions have excellent impact resistance, rigidity, strength, heat resistance, oil resistance, and processability, and combine various performances.

[0069] On the other hand, Comparative Examples 1 and 2 are examples of styrene-based resin compositions that do not use the styrene-based thermoplastic elastomer (C). It was confirmed that these styrene-based resin compositions were significantly insufficient in impact resistance, oil resistance, and secondary processability.

[0070] Comparative Example 3 is an example of a styrene-based resin composition that does not use high-density polyethylene as the olefin-based resin (B). It was confirmed that this styrene-based resin composition was significantly insufficient in impact resistance, oil resistance, and secondary processability.

[0071] Comparative Example 4 is an example of a styrene-based resin composition that does not use the olefin-based resin (B). It was confirmed that this styrene-based resin composition had significantly insufficient oil resistance.

[0072] Comparative Examples 5 to 7 are examples in which the amount of olefin resin (B) used in the total of the styrene resin (A), the olefin resin (B), and the styrene thermoplastic elastomer (C) is outside the range of 5 to 40 mass %. It was confirmed that these styrene resin compositions were significantly insufficient in rigidity and strength.

[0073] Comparative Examples 8 to 10 are examples in which the styrene content in the styrene-based thermoplastic elastomer (C) is less than 45 mass %. It was confirmed that these styrene-based resin compositions were significantly insufficient in impact resistance.

[0074] Comparative Example 11 is an example in which the amount of the styrene-based thermoplastic elastomer (C) used in the total of the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C) is outside the range of 1 to 10 mass %. It was confirmed that this styrene-based resin composition was significantly insufficient in rigidity, strength, and heat resistance.

Claims

1. a styrene-based resin (A); an olefin-based resin (B) containing high-density polyethylene; a styrene-based resin composition containing a styrene-based thermoplastic elastomer (C), the amount of the styrene-based resin (A) used is in the range of 50 to 90 mass% of the total of the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C), the amount of the olefin-based resin (B) used is in the range of 5 to 40 mass% based on the total amount of the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C), the amount of the styrene-based thermoplastic elastomer (C) used is in the range of 1 to 10 mass% based on the total amount of the styrene-based resin (A), the olefin-based resin (B), and the styrene-based thermoplastic elastomer (C), the styrene content in the styrene-based thermoplastic elastomer (C) is 45% by mass or more, the styrene-based resin (A) comprises an impact-resistant styrene-based resin (a1) and polystyrene (a2); the polystyrene (a2) comprises hyperbranched polystyrene, The compound corresponding to the styrene-based thermoplastic elastomer (C) is excluded from the styrene-based resin (A). A styrene-based resin composition characterized by:

2. 2. The styrene-based resin composition according to claim 1, wherein the content of the impact-resistant styrene-based resin (a1) in the styrene-based resin (A) is 50% by mass or more.

3. 3. The styrene-based resin composition according to claim 1, wherein the high-density polyethylene is derived from biomass.

4. A styrene-based resin sheet comprising the styrene-based resin composition according to any one of claims 1 to 3.

5. A food packaging container comprising the thermoplastic resin sheet according to claim 4.

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