Styrenic resin composition and molded articles, films and foams thereof

Abstract

To provide a resin composition that has excellent hue and heat resistance, and contains starch as biomass material, resulting in reduced environmental load, and a molding, a film, and a foam obtained from the resin composition.SOLUTION: A styrenic resin composition contains styrenic resin A of 45-95 pts.mass and starch B of 5-55 pts.mass when the total of the styrenic resin A and the starch B is 100 pts.mass. The starch B has a 5% weight loss temperature of 285-350°C as measured by TG-DTA.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition that is composited with biomass and has excellent color and heat resistance, and to a molded article, film, and foam obtained from the resin composition. [Background technology]

[0002] In recent years, there has been a demand for reducing carbon dioxide emissions due to the issue of global warming, and biomass-derived materials have been attracting attention as "carbon-neutral" materials that do not emit carbon dioxide. For example, by combining biomass such as seashells, bamboo powder, and starch with resin, it is possible to reduce the amount of petroleum-derived raw materials used.

[0003] However, biomass such as shells, bamboo powder, and starch has poor dispersibility in resins, which leads to poor processability and physical properties. Therefore, in recent years, efforts have been made to improve dispersibility and processability by adding antioxidants and surfactants. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 04-173868 [Patent Document 2] Patent Publication No. 2009-120648 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a resin composition that is excellent in color and heat resistance and has a low environmental impact because it contains starch as a biomass raw material, and to provide a molded article, film, and foam obtained from the resin composition. [Means for solving the problem]

[0006] (1) A styrene-based resin composition containing 45 to 95 parts by mass of styrene-based resin A and 5 to 55 parts by mass of starch B, where the total of styrene-based resin A and starch B is 100 parts by mass, wherein the 5% weight loss temperature of the starch B measured by TG-DTA is 285 to 350°C. (2) The styrene-based resin composition according to (1), wherein the styrene-based resin A is a rubber-containing styrene-based resin. (3) The styrene-based resin composition according to any one of (1) to (2), wherein the starch B has an average particle size D of 15 to 50 μm as measured in a toluene solvent. (4) The styrene-based resin composition according to any one of (1) to (3), characterized in that the content of biomass contained in 100 parts by mass of the styrene-based resin composition is 5 parts by mass or more. (5) A molded article made of the styrene resin composition according to any one of (1) to (4). (6) A film made of the styrene-based resin composition according to any one of (1) to (4). (7) A foamed product made of the styrene-based resin composition according to any one of (1) to (4). [Effects of the Invention]

[0007] The resin composition of the present invention and the molded articles, films, and foams made therefrom have a low environmental impact and are excellent in color and heat resistance, and can therefore be advantageously used in applications such as food containers and packaging, office automation equipment, home appliance parts, and miscellaneous goods. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following describes embodiments of the present invention. The features of the embodiments described below can be combined with each other. Each feature can also be an invention independently.

[0009] 1. Styrene-based resin composition A styrene-based resin composition according to one embodiment of the present invention contains a styrene-based resin (A) and starch (B). When the total of the styrene resin (A) and the starch (B) is 100 parts by mass, the content of the styrene resin (A) is 45 to 95 parts by mass, preferably 45 to 90 parts by mass. Specifically, for example, it may be within the range of any two of the following values: 45, 50, 55, 60, 70, 80, 90, and 95 parts by mass. When the styrene resin (A) is used in combination, the amount of the styrene resin (A) used refers to the total amount of the styrene resin (A) used in combination. When the total amount of the styrene-based resin (A) and the starch (B) is 100 parts by mass, the content of the starch (B) is 5 to 55 parts by mass, preferably 10 to 55 parts by mass. Specifically, for example, it may be within the range of any two of the following values: 5, 10, 20, 30, 40, 45, 50, and 55 parts by mass. When starch (B) is used in combination, the amount of starch (B) used refers to the total amount of the starch (B) used in combination.

[0010] <Styrene-based resin (A)> The styrene-based resin (A) is obtained by radical polymerization of an aromatic vinyl compound-based monomer (a1), and may be rubber-modified by adding a conjugated diene-based rubber-like polymer, if necessary. The polymerization method can be a known method, such as bulk polymerization, two-stage bulk / suspension polymerization, or solution polymerization. The aromatic vinyl compound-based monomer is a monocyclic or polycyclic aromatic vinyl-based monomer, such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, p-tert-butylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene, isopropenylbenzene (α-methylstyrene), isopropenyltoluene, isopropenylethylbenzene, isopropenylmethylbenzene, methylstyrene ... The styrene-based resin composition may contain, alone or in mixtures of two or more thereof, such as phenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, and isopropenyloctylbenzene. Preferred examples include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, and p-tert-butylstyrene. Styrene-based resin compositions may also contain, within the limits that do not impair the performance of the styrene-based resin composition, monomers copolymerizable with these aromatic vinyl compound-based monomers, such as acrylonitrile, (meth)acrylic acid, and (meth)acrylic acid esters. Furthermore, in the present invention, a crosslinking agent such as divinylbenzene may be added to the styrene-based monomer and then polymerized.

[0011] Conjugated diene rubbery polymers used for rubber modification of the styrene-based resin (A) of the present invention include polybutadiene, styrene-butadiene random or block copolymers, polyisoprene, polychloroprene, styrene-isoprene random, block or graft copolymers, ethylene-propylene rubber, ethylene-propylene-diene rubber, etc., with polybutadiene and styrene-butadiene random, block or graft copolymers being particularly preferred. These may be partially hydrogenated and may be used alone or in combination of two or more.

[0012] The content of the rubbery polymer in 100 parts by mass of the styrene-based resin (A) according to this embodiment is preferably 1.0 to 25.0 parts by mass, more preferably 5.0 to 20.0 parts by mass, from the viewpoint of strength and moldability. The content of the rubbery polymer may be within the range of any two of the following values: 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, and 25.0 parts by mass. When a rubbery polymer is used in combination, the amount of the rubbery polymer used refers to the total amount of the rubbery polymers used in combination.

[0013] The content of the rubbery polymer can be measured, for example, as follows. The sample is dissolved in chloroform, a certain amount of iodine monochloride / carbon tetrachloride solution is added, and the mixture is left in a dark place for approximately 1 hour. After that, 15% by mass potassium iodide solution and 50 ml of pure water are added, and the excess iodine monochloride is titrated with 0.1 N sodium thiosulfate / ethanol aqueous solution, and the amount of iodine monochloride added is calculated.

[0014] The volume average particle diameter of the rubbery polymer in the styrene-based resin (A) is preferably 2.0 to 8.0 μm, particularly preferably 2.3 to 7.0 μm, from the viewpoint of strength and rigidity. This volume average particle diameter may be within the range of any two of the following values: 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.5, 6.0, 6.5, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, and 8.0. When a rubbery polymer is used in combination, the volume average particle diameter of the rubbery polymer refers to the volume average particle diameter of the entire rubbery polymer used in combination.

[0015] The volume average particle size of the rubber-like polymer can be measured, for example, as follows. The sample is dissolved in dimethylformamide and measured using a laser diffraction particle size distribution analyzer (Beckman Coulter Laser Diffraction Particle Analyzer "LS-230").

[0016] The molecular weight of the styrene-based resin (A) is preferably 10,000 to 500,000, more preferably 30,000 to 400,000, in terms of weight average molecular weight (Mw). Specifically, for example, it may be 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 500,000, and may be within a range between any two of the values ​​exemplified here. By adjusting the molecular weight within this range, a styrene-based resin composition with an excellent balance between fluidity and heat resistance can be obtained. The weight average molecular weight of the styrene-based resin (A) can be controlled by the reaction temperature and residence time in the polymerization step, the type and amount of polymerization initiator, the type and amount of chain transfer agent, the type and amount of solvent used during polymerization, and the like.

[0017] The weight average molecular weight can be measured using gel permeation chromatography (GPC) under the following conditions. GPC model: Showa Denko Shodex GPC-101 Column: Polymer Laboratories PLgel 10 μm MIXED-B Mobile phase: tetrahydrofuran Sample concentration: 0.2% by mass Temperature: Oven 40℃, injection port 35℃, detector 35℃ Detector: differential refractometer The molecular weight in the present invention is calculated as a polystyrene-equivalent molecular weight by calculating the molecular weight at each elution time from the elution curve of monodisperse polystyrene.

[0018] Among styrene resins (A), rubber-modified styrene resins have rubber-like dispersed particles dispersed in the matrix phase of polystyrene resin, and the molecular weight refers to the molecular weight of the matrix phase. Therefore, the sample used for molecular weight measurement is prepared by dissolving styrene resin (A) in a 50% methyl ethyl ketone / 50% acetone mixed solution, removing the rubber-like dispersed particles using a centrifuge (Kokusan H-2000B (rotor: H)), and reprecipitating the polymer in methanol. GPC model: Showa Denko Shodex GPC-101 Column: Polymer Laboratories PLgel 5 μm MIXED-C Mobile phase: tetrahydrofuran Sample concentration: 0.2% by mass Temperature: Oven 40℃, injection port 35℃, detector 35℃ Detector: differential refractometer The molecular weight in the present invention is calculated as a polystyrene-equivalent molecular weight by calculating the molecular weight at each elution time from the elution curve of monodisperse polystyrene.

[0019] The polymerization method for the styrene-based resin (A) includes known styrene polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. From the viewpoints of quality and productivity, bulk polymerization and solution polymerization are preferred, and continuous polymerization is preferable. As the solvent, for example, alkylbenzenes such as benzene, toluene, ethylbenzene, and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane can be used.

[0020] In the case of continuous polymerization, first, in the polymerization step, a known complete mixing tank type agitator tank or tower reactor is used, and the polymerization reaction is controlled by adjusting the polymerization temperature, etc., so as to achieve the target molecular weight, molecular weight distribution, and reaction conversion rate. The polymerization solution containing the polymer that has left the polymerization step is transferred to the devolatilization step, where unreacted monomers and polymerization solvent are removed. The devolatilization step is composed of a vacuum devolatilization tank equipped with a heater or a devolatilization extruder equipped with a vent. The molten polymer that has left the devolatilization step is transferred to the granulation step. In the granulation step, the molten resin is extruded in the form of strands through a multi-hole die and processed into pellets using the cold cut method, the in-air hot cut method, or the underwater hot cut method.

[0021] During the polymerization of the styrene-based resin (A), a polymerization initiator and a chain transfer agent can be used as necessary. As the polymerization initiator, a radical polymerization initiator is preferred, and known and commonly used examples thereof include peroxyketals such as 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 2,2-di(4,4-di-t-butylperoxycyclohexyl)propane, and 1,1-di(t-amylperoxy)cyclohexane, hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide, alkyl peroxides such as t-butyl peroxyacetate and t-amyl peroxyisononanoate, t-butylcumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, and di-t-hexyl peroxide. Examples of suitable peroxides include dialkyl peroxides such as t-butyl peroxyacetate, t-butyl peroxybenzoate, and t-butylperoxyisopropyl monocarbonate; peroxyesters such as t-butylperoxyisopropyl carbonate and polyether tetrakis(t-butylperoxycarbonate); and peroxycarbonates such as N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methylbutyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), and N,N'-azobis[2-(hydroxymethyl)propionitrile]. These may be used alone or in combination. Examples of suitable chain transfer agents include aliphatic mercaptans, aromatic mercaptans, pentaphenylethane, α-methylstyrene dimer, and terpinolene.

[0022] <Starch (B)> The starch (B) according to this embodiment is a branched carbohydrate polymer having repeating units of amylose and amylopectin. Such starch is well known as a storage polysaccharide in plants, i.e., a natural high molecular weight polysaccharide, and examples thereof include unprocessed starch obtained from potatoes, sweet potatoes, and other roots, rice, wheat, and other grains, corn, tapioca, and the like.

[0023] The starch (B) may be chemically or physically modified, and may be a chemically decomposed modified starch, an enzymatically modified starch, a physically modified starch, or the like.

[0024] Specific examples of the above-mentioned starches classified according to the raw material or processing step include unmodified starches obtained by separation from natural polymers, such as corn starch, bracken starch, arrowroot starch, potato starch, wheat starch, barley starch, rice starch, cassava starch, sago starch, tapioca starch, sorghum starch, soybean starch, lotus starch, water chestnut starch, and sweet potato starch.

[0025] Examples of chemically decomposed modified starches include allyl etherified starch, carboxymethyl etherified starch, hydroxymethyl etherified starch, hydroxypropyl etherified starch, methyl etherified starch, phosphate cross-linked starch, formaldehyde cross-linked starch, epichlorohydrin cross-linked starch, acrolein cross-linked starch, acetoacetate esterified starch, acetate esterified starch, succinate acetate esterified starch, xanthogen acetate esterified starch, nitrate esterified starch, urea phosphate esterified starch, phosphate esterified starch, chemically decomposed modified starch derivatives thereof, dialdehyde starch, acid-treated starch, and hypochlorite oxidized starch.

[0026] Examples of enzyme-modified starches include hydrolyzed dextrin, enzymatically decomposed dextrin, and amylose.

[0027] Physically modified starches include α-starch, fractionated amylose, and heat-moisture treated starch.

[0028] 5% weight loss temperature T of starch (B) d5is 285°C to 350°C, preferably 290°C to 325°C. Specifically, for example, it is 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 305, 310, 315, 320, 325, 330, 335, 340, 345, or 350°C, and may be within a range between any two of the values ​​exemplified here. By setting it in such a range, a styrene-based resin composition having an excellent balance between heat resistance and dispersibility can be obtained. The 5% weight loss temperature T of starch (B) d5 It can be controlled by the difference in raw materials, chemical or physical denaturation, and conditions for chemical decomposition denaturation, enzymatic denaturation, and physical denaturation.

[0029] 5% weight loss temperature T of starch (B) d5 It can be determined by thermogravimetric analysis (TGA). The dried raw material is heated from room temperature in a nitrogen atmosphere at a rate of 20°C / min. The temperature at which the weight loss is 5% of the weight of the dried raw material is determined as T. d5 Let's say.

[0030] The average particle size D of starch (B) is preferably 15 to 50 μm, and is 20 to 35 μm. Specifically, for example, it may be 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 45, or 50 μm, and may be within a range between any two of the values ​​exemplified here. By adjusting the range in this way, a styrene-based resin composition with an excellent balance between strength and dispersibility can be obtained. The average particle size D of starch (B) can be controlled by differences in raw materials, chemical or physical modification, and conditions for chemical decomposition modification, enzymatic modification, and physical modification.

[0031] The average particle diameter D of the starch (B) can be determined by dissolving the starch in toluene and measuring the particle size distribution using a laser diffraction particle size analyzer (Laser Diffraction Particle Analyzer LS-230 manufactured by Coulter).

[0032] Other additives, such as plasticizers, spreaders, solvents, ultraviolet absorbers, light stabilizers, stabilizers, antistatic agents, colorants, dyes and pigments, organic fillers, color inhibitors, reinforcing agents, compatibilizers, crystallization accelerators, flame retardants, and flame retardant assistants, may be added within the scope of the present invention, and naturally occurring materials other than starch may also be included as biomass.

[0033] In this embodiment, biomass refers to renewable, biologically derived organic resources, excluding fossil resources. The biomass in this embodiment is not particularly limited, but examples include wood flour, bamboo flour, paper flour, charcoal, rice stalks, tea stalks, used rice flour, rice bran, bran, soy pulp, sake, shochu, beer, wine, and soy sauce pomace, starch, konnyaku by-products, fruit peels or pomace, grasses including rice, wheat, and buckwheat, seaweed or algae, cotton fiber, palm fiber, and mixtures thereof. From the viewpoint of dispersibility, starch, bamboo flour, and wood flour are preferred.

[0034] The method for adding these is not particularly limited, and they may be added by a known method, such as a method of adding them in a raw material charging step, polymerization step, or finishing step during the production of the styrene-based resin (A) or starch (B), or a method of adding them in a step of mixing the resin composition using an extruder or molding machine.

[0035] In one embodiment, the resin composition according to the present invention does not contain natural antioxidants or equivalent synthetic compounds. Examples of natural antioxidants or equivalent synthetic compounds include tocopherols (vitamin E compounds) such as α-, β-, γ-, and δ-tocopherol and their dimers; flavone derivatives such as catechin, gallocatechin gallate, and flavonol; caffeic acid derivatives such as caffeic acid, ferulic acid, and oryzanol; amino acids and derivatives thereof; B vitamins such as B1, B2, and B6 and derivatives thereof; L-ascorbic acid (vitamin C) and stearic acid esters of L-ascorbic acid; K vitamins such as K1 to K7 and derivatives thereof; and unsaturated terpene alcohols, gossypol, sezamol, eugenol, camphene, thymol, shogaol, and cinnamaldehyde.

[0036] In one embodiment, the resin composition according to the present invention does not contain a peracid compound, such as a compound represented by the general formula YR-COOOH (wherein R represents an aliphatic hydrocarbon or an aromatic hydrocarbon, and Y represents a functional group such as a carboxyl group or an aldehyde group capable of reacting with a hydroxyl group on the surface of starch).

[0037] In one embodiment, the resin composition according to the present invention does not contain oxidized oils, such as oxidized animal oils or vegetable oils, specifically rapeseed oil, corn oil, sunflower oil, and safflower oil.

[0038] In one embodiment, the resin composition according to the present invention may contain an inorganic filler. Examples of the inorganic filler include barite powder, precipitated barium sulfate, barium carbonate, lime carbonate powder, precipitated calcium carbonate, gypsum, asbestos, clay, silica powder, finely powdered silicic acid, diatomaceous earth, talc, basic magnesium carbonate, alumina white, gloss white, satin white, zinc oxide, white lead, basic lead sulfate, littobon, zinc sulfide, titanium oxide, antimony oxide, carbon black, acetylene black, lamp black, bone black, graphite, iron black, mineral black, aniline black, cyanine black BX, yellow lead, zinc yellow, barium chromate, cadmium yellow, and yellow oxide. Examples of inorganic fillers include iron, ochre, titanium yellow, lead cyanamide, calcium plumbate, red chrome chrome, chrome vermilion, iron oxide, umber, red iron oxide, red lead, vermilion, cadmium red, cadmium mercury red, antimony vermilion, cobalt purple, manganese purple, ultramarine, Prussian blue, cobalt blue, cerulean blue, gosu, chrome green, zinc green, chromium oxide, viridian, emerald green, cobalt green, zinc sulfide, zinc silicate, zinc cadmium sulfide, calcium sulfide, strontium sulfide, calcium tungstate, aluminum powder, bronze powder, copper powder, tin powder, lead powder, and zinc powder. The content of the inorganic filler is preferably less than 1 part by mass, and more preferably less than 0.5 parts by mass, per 100 parts by mass of the resin composition.

[0039] In one embodiment, the resin composition according to the present invention does not contain a nonionic surfactant. Examples of the low-melting point additive include glycerol monostearate and polyoxyethylene sorbitol tetraoleate. In one embodiment, the resin composition according to the present invention does not contain an anionic surfactant. Examples of low-melting point additives include Pelex OT-P (trade name, manufactured by Kao Corporation).

[0040] Next, a method for producing the resin composition of the present invention will be described.

[0041] The method for mixing the resin composition of the present invention 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-type mixer, a V-type blender, or a tumbler-type mixer, and then melt-kneading the mixture. The melt-kneading device is also not particularly limited, and examples include a Banbury mixer, a kneader, a roll, a single-screw extruder, a special single-screw extruder, and a twin-screw extruder. Furthermore, other additives can be added separately midway through the melt-kneading device such as an extruder.

[0042] There are no particular limitations on the molding method for obtaining a molded article from the resin composition of the present invention, and known molding methods can be suitably used, such as extrusion molding methods such as calendar molding, blow molding, extrusion foam molding, profile extrusion molding, lamination molding, inflation molding, T-die film molding, sheet molding, vacuum forming, and pressure molding, and injection molding methods such as injection molding, RIM molding, and injection foam molding, but injection molding or sheet molding is preferred. [Example]

[0043] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0044] The materials used in the examples and comparative examples are as follows.

[0045] [Styrene-based resin (A)] (A) HIPS (polystyrene resin modified with polybutadiene rubber, molecular weight (Mw) 220,000, rubber polymer content 10% by mass in 100% by mass of resin, volume average particle diameter 2.9 μm)

[0046] [Starch (B)] (B-1) Cornstarch (manufactured by Nihon Shokuhin Kako Co., Ltd.) 5% weight loss temperature T d5 298℃, average particle size D23μm (B-2) Modified starch 5% weight loss temperature T d5 297℃, average particle size D28μm (B-3) Modified starch 5% weight loss temperature T d5 284℃, average particle size D14μm

[0047] (Examples 1 to 5, Comparative Examples 1 to 5) The components were premixed in a Henschel mixer (FM20B, manufactured by Mitsui Miike Chemical Co., Ltd.) in the amounts shown in Tables 1 and 2, and fed into a twin-screw extruder (TEM26SS, manufactured by Toshiba Machine Co., Ltd.) to form strands at a cylinder temperature of 200°C and a feed rate of 25 kg / h. After water cooling, the strands were fed into a pelletizer and pelletized. The resulting pellets were injection molded, and the properties were evaluated. The results are shown in Tables 1 and 2.

[0048] [Biomass content] Biomass content was calculated using the following formula: Biomass content (%) = X / A × 100 X: Total content of starch (B) and biomass components other than starch (% by mass) A: Total content (parts by mass) of starch (B), biomass components other than starch, and styrene-based resin (A)

[0049] [Extrusion Stability] The extrusion stability was evaluated based on the following criteria. ×: Strands cannot be fed to the pelletizer and cannot be pelletized ○: Strands can be fed intermittently to the pelletizer ◎: Strands can be continuously supplied to the pelletizer

[0050] [Pellet color] The pellet color was evaluated based on the following criteria. ×: Yellowing observed compared to pellets made from 100 parts by mass of styrene-based resin (Comparative Example 1) ◯: No yellowing compared to pellets made from 100 parts by mass of styrene-based resin (Comparative Example 1)

[0051] [Charpy impact strength] Test pieces were prepared using an injection molding machine and measured according to JIS K7111.

[0052] [Measurement of Vicat softening temperature] Test pieces were prepared using an injection molding machine, and measurements were made under the condition of a 50N load in accordance with JIS K7206.

[0053] [Table 1]

[0054] [Table 2]

[0055] It can be seen from the Examples in Table 1 that the resin compositions of the present invention are excellent in biomass content and pellet color, and have a high Vicat softening temperature. On the other hand, it can be seen from the Comparative Examples in Table 2 that resin compositions that do not satisfy the specifications of the present invention are inferior in biomass content and pellet color, and have a low Vicat softening temperature. [Industrial Applicability]

[0056] The styrene-based resin composition according to the present invention, which contains a styrene-based resin and starch, has a low environmental impact, an excellent color, and excellent heat resistance. The styrene-based resin composition according to the present invention can be suitably used as a molded product, a film, or a foam, and has industrial applicability.

Claims

1. A styrene-based resin composition containing 45 to 95 parts by mass of a styrene-based resin A and 5 to 55 parts by mass of a starch B, where the total of the styrene-based resin A and the starch B is 100 parts by mass, wherein the 5% weight loss temperature of the starch B measured by TG-DTA is 285 to 350°C.

2. The styrene-based resin composition according to claim 1, wherein the styrene-based resin A is a rubber-containing styrene-based resin.

3. 3. The styrene-based resin composition according to claim 1, wherein the starch B has an average particle size D of 15 to 50 μm as measured in a toluene solvent.

4. The styrene-based resin composition according to any one of claims 1 to 3, wherein the content of biomass contained in 100 parts by mass of the styrene-based resin composition is 5 parts by mass or more.

5. A molded article made of the styrene-based resin composition according to any one of claims 1 to 4.

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

7. A foamed product made from the styrene-based resin composition according to any one of claims 1 to 4.

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