Styrene-based resin composition, molded article, and tableware

Abstract

To provide a styrene-based resin composition that exhibits superior moldability, rigidity, and antibacterial properties.SOLUTION: According to the present invention, a styrene-based resin composition comprises a styrene-based resin and bamboo powder. When the total amount of the styrene-based resin and the bamboo powder is 100 pts.mass, the content of the bamboo powder is 10 to 60 pts.mass. The melt mass flow rate of the styrene-based resin composition is 0.8 g / 10 min or more as measured at 200°C under 49 N.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a styrene resin composition, a molded article, and tableware.

Background Art

[0002] In recent years, due to the problem of global warming, reduction of carbon dioxide has been demanded, and biomass-derived materials have attracted attention as "carbon neutral" materials that do not emit carbon dioxide. For example, by compounding biomass such as starch with a resin (Patent Document 1), the amount of use of petroleum-derived raw materials can be reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, while carbon dioxide reduction is possible, the moldability, rigidity, and antibacterial properties required for molded articles for specific applications such as tableware represented by resin spoons, forks, or knives have not been obtained.

[0005] The present invention has been made in view of the above circumstances, and provides a styrene resin composition excellent in moldability, rigidity, and antibacterial properties.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that by containing a styrene resin and bamboo powder in a predetermined amount and having a melt mass flow rate within a predetermined range, the above problems can be solved, and the present invention has been completed.

[0007] According to the present invention, the following inventions are provided. [1] A styrene resin composition containing a styrene resin and bamboo powder, wherein when the total of the styrene resin and the bamboo powder is 100 parts by mass, the bamboo powder is contained in an amount of 10 to 60 parts by mass, and the melt mass flow rate of the styrene resin composition measured at 200 ° C. and 49 N is 0.8 g / 10 min or more. [2] The styrene resin composition according to [1], wherein the bamboo powder contains 30 to 50% by mass of lignin in 100% by mass of the bamboo powder. [3] A molded article made of the styrene resin composition according to [1] or [2]. [4] Tableware made of the styrene resin composition according to [1] or [2].

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described. Various characteristic matters shown in the following embodiments can be combined with each other. In addition, the invention can be established independently for each characteristic matter.

[0009] 1. Styrene resin composition The styrene resin composition according to one embodiment of the present invention contains a styrene resin and bamboo powder.

[0010] When the total of the styrene resin and the bamboo powder in the styrene resin composition is 100 parts by mass, the bamboo powder is contained in an amount of 10 to 60 parts by mass, preferably 20 to 40 parts by mass. When such a range is satisfied, the moldability, rigidity, and antibacterial property are excellent. The content of the bamboo powder is specifically, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 parts by mass when the total of the styrene resin and the bamboo powder is 100 parts by mass, and it may be within the range between any two of the numerical values exemplified here. When two or more kinds of bamboo powder are used in combination, the content (or content rate) of the bamboo powder is based on the total amount of the bamboo powder used in combination.

[0011] When the total of the styrene resin and bamboo powder is 100 parts by mass, the styrene resin composition contains 40 to 90 parts by mass of bamboo powder, preferably 60 to 80 parts by mass. When such a range is satisfied, it is excellent in moldability, rigidity, and antibacterial property. The content of the styrene resin is specifically, for example, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 parts by mass when the total of the styrene resin and bamboo powder is 100 parts by mass, and it may be within the range between any two of the numerical values exemplified here. When two or more kinds of styrene resins are used in combination, the content (or content rate) of the styrene resin is based on the total amount of the styrene resins used in combination.

[0012] The styrene resin composition can contain 10 to 60% by mass of bamboo powder. The content rate of bamboo powder is specifically, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60% by mass, and it may be within the range between any two of the numerical values exemplified here. Also, the styrene resin composition can contain 40 to 90% by mass of the styrene resin. The content rate of the styrene resin is specifically, for example, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90% by mass, and it may be within the range between any two of the numerical values exemplified here.

[0013] The melt mass flow rate (MFR) of the styrene resin composition measured at 200 °C and 49 N is 0.8 g / 10 min or more, preferably 0.8 to 10.0 g / 10 min. When such a range is satisfied, the moldability is excellent. The MFR is specifically, for example, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 8.0, 9.0, 10.0 g / 10 min, and it may be within the range between any two of the numerical values exemplified here. The MFR can be measured based on JIS K 7210.

[0014] The styrene resin composition has a flexural modulus measured in accordance with JIS K-7171 of, for example, 1800 or more, preferably 2200 to 6500 MPa. Specifically, the flexural modulus is, for example, 1800, 2020, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900, 5000, 5100, 5200, 5300, 5400, 5500, 5600, 5700, 5800, 5900, 6000, 6100, 6200, 6300, 6400, 6500 MPa, and may be within the range between any two of the values exemplified herein. The detailed measurement method of the flexural modulus is described in the examples.

[0015] The styrene resin composition has a flexural strength measured in accordance with JIS K-7171 of, for example, 40 MPa or more. The upper limit of the flexural strength is not particularly limited, and may be, for example, 80 MPa or less. Specifically, the flexural strength is, for example, 40, 45, 50, 55, 60, 65, 70, 75, 80 MPa, and may be within the range between any two of the values exemplified herein. The detailed measurement method of the flexural strength is described in the examples.

[0016] The surface resistance of the styrene resin composition measured in an environment of 23°C and 50% RH (relative humidity) in accordance with JIS K 6911 is, for example, less than 1×10 14 Ω / □. The detailed measurement method of the surface resistance is described in the examples.

[0017] <Styrene resin> Styrene resins are obtained by radical polymerization of aromatic vinyl compound monomers (a1). Styrene resins may be rubber-modified by adding a conjugated diene rubber-like polymer as necessary and may be rubber-containing styrene resins. As the polymerization method, known methods such as bulk polymerization, bulk / suspension two-stage polymerization, solution polymerization, etc. can be used for production. The aromatic vinyl compound monomers are monocyclic or polycyclic aromatic vinyl monomers, for example, 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, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene, etc., alone or as a mixture of two or more. Preferably, they are 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, alone or as a mixture of two or more, and more preferably styrene. Also, monomers such as acrylonitrile, (meth)acrylic acid, (meth)acrylic acid esters, etc., which are copolymerizable with these aromatic vinyl compound monomers, may be contained within a range that does not impair the performance of the styrene resin composition. Furthermore, in the present invention, it may be a polymer obtained by adding a crosslinking agent such as divinylbenzene to the styrene monomer and polymerizing it.

[0018] Examples of the conjugated diene rubber-like polymer used for rubber-modifying the styrene resin of the present invention include polybutadiene, random or block copolymers of styrene-butadiene, polyisoprene, polychloroprene, random, block or graft copolymers of styrene-isoprene, ethylene-propylene rubber, ethylene-propylene-diene rubber, etc. Among them, polybutadiene, random, block or graft copolymers of styrene-butadiene are particularly preferred. These may be partially hydrogenated and may be used alone or in combination of two or more kinds.

[0019] From the viewpoints of strength and moldability, the content of the rubber-like polymer in 100 parts by mass of the styrene resin according to the present embodiment is preferably 1.0 to 25.0 parts by mass, more preferably 5.0 to 20.0 parts by mass. The content of the rubber-like polymer is 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, 25.0 parts by mass in 100 parts by mass of the styrene resin, and may be within the range between any two of the values exemplified here. When the rubber-like polymers are used in combination, the amount of the rubber-like polymers used means the total amount of the rubber-like polymers used in combination.

[0020] The content of the rubber-like polymer can be measured, for example, as follows. Dissolve the sample in chloroform, add a certain amount of iodine monochloride / carbon tetrachloride solution, leave it in the dark for about 1 hour, then add 50 mL of 15 mass% potassium iodide solution and pure water, and titrate the excess iodine monochloride with 0.1N sodium thiosulfate / ethanol aqueous solution, and calculate from the amount of iodine monochloride added.

[0021] The volume median particle diameter (median diameter) of the rubber-like polymer in the styrene resin is preferably 0.5 to 8.0 μm, particularly preferably 0.7 to 7.0 μm, from the viewpoints of strength and rigidity. The volume median particle diameter is 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, 8.0 μm, and may be within the range between any two of the values exemplified herein. When using the rubber-like polymer in combination, the volume median particle diameter of the rubber-like polymer means the volume median particle diameter of the entire combined rubber-like polymer.

[0022] The volume median particle diameter of the rubber-like polymer can be measured, for example, as follows. Dissolve the sample in dimethylformamide and measure it with a laser diffraction / scattering particle size distribution analyzer (LA-960 manufactured by Horiba, Ltd.: relative refractive index 120A000I).

[0023] The molecular weight of the styrene resin is preferably 10,000 to 500,000 in terms of weight average molecular weight (Mw), more preferably 30,000 to 400,000. Specifically, for example, it is 10,000, 20,000, 30,000, 40,000, 50,000, 100,000, 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, and may be within the range between any two of the values exemplified herein. By setting such a range, a styrene resin composition excellent in the balance between fluidity and heat resistance can be obtained. The weight average molecular weight of the styrene resin can be controlled by the reaction temperature, residence time, type and addition amount of the polymerization initiator, type and addition amount of the chain transfer agent, type and amount of the solvent used during polymerization, etc.

[0024] The weight average molecular weight can be measured using gel permeation chromatography (GPC) under the following conditions. GPC model: Shodex GPC-101 manufactured by Showa Denko K.K. Column: PLgel 10μm MIXED-B manufactured by Polymer Laboratories Mobile phase: Tetrahydrofuran Sample concentration: 0.2 mass% Temperature: Oven 40°C, injection port 35°C, detector 35°C Detector: Differential refractometer The molecular weight of the present invention is calculated from the elution curve of monodisperse polystyrene to obtain the molecular weight at each elution time, and is calculated as the molecular weight in terms of polystyrene.

[0025] Among styrenic resins, for rubber-modified styrenic resins, rubbery dispersed particles are dispersed in the matrix phase of the polystyrene resin, and the molecular weight means the molecular weight of the matrix phase. Therefore, as the sample used for molecular weight measurement, a styrenic resin is dissolved in a 50% methyl ethyl ketone / 50% acetone mixed solution, rubbery dispersed particles are removed with a centrifuge (H-2000B manufactured by Kokusan Co., Ltd. (rotor: H)), and a polymer reprecipitated in methanol is used. GPC model: Shodex GPC-101 manufactured by Showa Denko KK Column: PLgel 5μm MIXED-C manufactured by Polymer Laboratories Mobile phase: Tetrahydrofuran Sample concentration: 0.2 mass% Temperature: Oven 40°C, injection port 35°C, detector 35°C Detector: Differential refractometer The molecular weight of the present invention is calculated from the elution curve of monodisperse polystyrene to obtain the molecular weight at each elution time, and is calculated as the molecular weight in terms of polystyrene.

[0026] Examples of the polymerization method of styrenic resins include known styrene polymerization methods such as bulk polymerization method, solution polymerization method, suspension polymerization method, and emulsion polymerization method. In terms of quality and productivity, the bulk polymerization method and the solution polymerization method are preferred, and continuous polymerization is preferred. 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.

[0027] In the case of continuous polymerization, first, in the polymerization step, a known completely mixed tank type stirring tank, a tower type reactor, etc. are used, and the polymerization reaction is controlled by adjusting the polymerization temperature or the like so as to achieve the target molecular weight, molecular weight distribution, and reaction conversion rate. The polymerization solution containing the polymer that has exited the polymerization step is transferred to the devolatilization step, and unreacted monomers and the polymerization solvent are removed. The devolatilization step is composed of a vacuum devolatilization tank with a heater, a devolatilization extruder with a vent, etc. The polymer in the molten state that has exited the devolatilization step is transferred to the granulation step. In the granulation step, the molten resin is extruded in a strand shape from a porous die and processed into a pellet shape by a cold cut method, an air hot cut method, or a water hot cut method.

[0028] When polymerizing styrene resins, a polymerization initiator and a chain transfer agent can be used as necessary. As the polymerization initiator, a radical polymerization initiator is preferred. Known and commonly used examples 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, 1,1-di(t-amylperoxy)cyclohexane; hydroperoxides such as cumene hydroperoxide, t-butyl hydroperoxide; alkyl peroxides such as t-butyl peroxyacetate, t-amyl peroxyisononanoate; dialkyl peroxides such as t-butyl cumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, di-t-hexyl peroxide; peroxy esters such as t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyisopropyl monocarbonate; peroxy carbonates such as t-butyl peroxyisopropyl carbonate, polyether tetrakis(t-butyl peroxycarbonate); azo compounds such as N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methylbutyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), N,N'-azobis[2-(hydroxymethyl)propionitrile]. These can be used alone or in combination of two or more. As the chain transfer agent, aliphatic mercaptans, aromatic mercaptans, pentaphenylethane, α-methylstyrene dimer, terpinolene, etc. can be mentioned.

[0029] <Bamboo powder> Bamboo powder is obtained by pulverizing bamboo (for example, Moso bamboo, true bamboo, tortoise shell bamboo, cloud pattern bamboo, light bamboo, etc.) into powder by powdering processes such as grinding or crushing.

[0030] The bamboo powder preferably contains 30 to 50% by mass of lignin, more preferably 35 to 45% by mass of lignin in 100% by mass of the bamboo powder. By satisfying such a range, it is excellent in antistatic property and rigidity. The content rate of lignin in 100% by mass of the bamboo powder is specifically, for example, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50% by mass, and it may be within the range between any two of the numerical values exemplified here.

[0031] The bamboo powder preferably contains 20 to 50% by mass of cellulose, more preferably 25 to 40% by mass of cellulose in 100% by mass of the bamboo powder. Further, the bamboo powder preferably contains 15 to 30% by mass of hemicellulose in 100% by mass of the bamboo powder.

[0032] The volume median particle diameter of the bamboo powder is preferably 5 to 500 μm. When it is less than 5 μm, it is not preferable because it is easy to classify during mixing with the styrene resin. When it is more than 500 μm, it is not preferable because the surface state of the molded product deteriorates. The volume median particle diameter of the bamboo powder can be controlled by the conditions of the pulverization treatment.

[0033] The volume median particle diameter of the bamboo powder can be determined by dispersing the sample in water and measuring it with a laser diffraction / scattering particle size distribution measuring device (LA-960 manufactured by Horiba, Ltd.: refractive index of bamboo powder 1.610, refractive index of water 1.333).

[0034] <Other additives> The styrene resin composition can add other additives, such as plasticizers, spreading agents, solvents, ultraviolet absorbers, light stabilizers, stabilizers, colorants, dyes and pigments, organic fillers, anti-coloring agents, reinforcing agents, compatibilizers, crystallization accelerators, flame retardants, flame retardant aids, etc. within the range that does not impair the object of the present invention, and may also contain natural-derived materials other than bamboo powder as biomass.

[0035] Biomass means renewable organic and inorganic resources derived from living organisms, excluding fossil resources. Biomass includes organic biomass and / or inorganic biomass. Organic biomass is biomass mainly composed of solid components derived from plants and / or solid components derived from algae. Inorganic biomass is biomass mainly composed of solid components derived from aggregates of inorganic substances (such as calcium carbonate) in living organisms. "Biomass mainly composed of solid components" means biomass with a moisture content of 30, 25, 20, 15, 10, 5 or 1 mass% or less. The organic biomass in this embodiment is not particularly limited, but for example, wood powder, paper powder, charcoal, rice bran, tea bran, old rice powder, rice bran, okara, bran, lees of sake, shochu, beer, wine, soy sauce, starch, konjac by-products, squeezed lees of fruit tree peels or fruits, grasses including rice, wheat, buckwheat, seaweeds or algae, cotton fibers, palm fibers, or mixtures thereof can be preferably used. Also, cellulose, hemicellulose, lignin, etc. derived from plants can be used as biomass. From the viewpoint of dispersibility, wood powder is preferred other than bamboo powder. The inorganic biomass in this embodiment is not particularly limited, but for example, bones, eggshells, and shells can be preferably used.

[0036] In one embodiment, biomass other than bamboo powder may be contained in the styrene resin composition in an amount of 25, 20, 15, 10, 5 or 1 mass% or less. In another embodiment, the styrene resin composition according to the present invention does not contain biomass other than bamboo powder.

[0037] These addition methods are not particularly limited, and they may be added by known methods. Methods of adding during the raw material charging step, polymerization step, and finishing step in the production of styrene resin or bamboo powder, or methods of adding during the step of mixing the resin composition using an extruder or a molding machine can be applied.

[0038] In one embodiment, the styrenic resin composition may contain an inorganic filler. Examples of the inorganic filler include barite powder, precipitated barium sulfate, barium carbonate, calcium carbonate powder, precipitated calcium carbonate, gypsum, asbestos, clay, silica powder, fine silica, diatomaceous earth, talc, basic magnesium carbonate, alumina white, gloss white, satin white, zinc white, lead white, basic lead sulfate, lithopone, 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, yellow iron oxide, loess, titanium yellow, lead cyanamide, calcium plumbate, red mouth yellow lead, chrome vermilion, iron oxide, amber, red iron oxide, red lead, cinnabar, cadmium red, cadmium mercury red, antimony red, cobalt violet, manganese violet, ultramarine, dark blue, cobalt blue, cerulean blue, indigo, chrome green, zinc green, chromium oxide, viridian, emerald green, cobalt green, zinc sulfide, zinc silicate, cadmium zinc sulfide, calcium sulfide, strontium sulfide, calcium tungstate, aluminum powder, bronze powder, copper powder, tin powder, lead powder, zinc dust. The content of the inorganic filler is preferably less than 1 part by mass, more preferably less than 0.5 part by mass, based on 100 parts by mass of the styrenic resin composition.

[0039] <Method for producing styrenic resin composition>

[0040] The styrene resin composition can be obtained, for example, by mixing raw materials such as styrene resin and bamboo powder. The mixing method is not particularly limited, and known mixing techniques can be applied. For example, using a mixing device such as a mixer-type mixer, V-type blender, and tumbler-type mixer, various raw materials are pre-mixed, and a uniform resin composition can be produced by melt-kneading the mixture. The melt-kneading device is also not particularly limited, and examples include a Banbury mixer, kneader, roll, single-screw extruder, special single-screw extruder, and twin-screw extruder. Furthermore, there is also a method of separately adding other additives from the middle of a melt-kneading device such as an extruder.

[0041] <Molded article> The molded article according to an embodiment of the present invention is a molded article made of the above styrene resin composition. The molded article is, for example, a film, sheet, foam, and appliance. As the appliance, for example, it is an appliance used for eating, and more specifically, tableware and cutlery. The cutlery is, for example, resin spoons, forks, knives, etc. provided at convenience stores, restaurants, etc. These plastic molded articles may require antistatic properties from the viewpoint of preventing adhesion of dust, dirt, etc.

[0042] The molded article can be obtained by various molding methods. The molding method is not particularly limited, and known molding methods such as extrusion molding methods such as calender molding, blow molding, extrusion foam molding, profile extrusion molding, lamination molding, inflation molding, T-die film molding, sheet molding, vacuum molding, and pressure air molding, and injection molding methods such as injection molding, RIM molding, and injection foam molding can be preferably used, but injection molding or sheet molding is preferred.

Examples

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

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

[0045] [Styrenic Resin (A)] (A-1) HIPS (Polystyrene resin modified with polybutadiene rubber, MFR 8 g / 10 min, content of rubber-like polymer in 100% by mass of resin 10% by mass, volume median particle diameter of rubber-like polymer 5.5 μm) (A-2) HIPS (Polystyrene resin modified with polybutadiene rubber, MFR 4 g / 10 min, content of rubber-like polymer in 100% by mass of resin 9% by mass, volume median particle diameter of rubber-like polymer 4.5 μm)

[0046] [Biomass (B)] (B-1) Bamboo powder 1 (manufactured by Bamboo Techno Co., Ltd., volume median particle diameter 60 μm) (B-2) Bamboo powder 2 (completely dried bamboo powder, manufactured by Nippon Aim Co., Ltd., volume median particle diameter 75 μm) (B-3) Wood powder (ARBCEL C100, manufactured by Rettenmaier Japan Co., Ltd., volume median particle diameter 140 μm) (B-4) Cellulose fiber (FIBRA-CEL SW-10, manufactured by Celite Corporation, volume median particle diameter 150 μm) (B-5) Lignin (Lignin(Dealkaline), manufactured by Tokyo Chemical Industry Co., Ltd., volume median particle diameter 40 μm) The content rates of lignin, cellulose, and hemicellulose of each biomass are shown in Table 1. These content rates are the contents when the alcohol-soluble components and benzene-soluble components (alcohol-benzene-soluble components) other than lignin, cellulose, and hemicellulose are combined to be 100% by mass. However, for cellulose fiber and lignin, since the alcohol-benzene-soluble components were unknown, the total of lignin, cellulose, and hemicellulose was set to 100% by mass.

[0047] [Table 1]

[0048] (Examples 1 to 5, Comparative Examples 1 to 6) Each component was premixed in a Henschel mixer (manufactured by Mitsui Miike Chemical Co., Ltd., FM20B) at the compounding amounts shown in Table 2, and then supplied to a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd., TEM26SS). Under the conditions of a cylinder temperature of 200 °C and a supply rate of 15 kg / h, it was formed into strands, cooled with water, and then led to a pelletizer to be pelletized. The resulting pellets were injection-molded, and the results of various measurements and property evaluations are shown in Table 2.

[0049] <Measurement> [Flexural strength, flexural modulus] For the pellets, the MFR (melt mass flow rate) was measured based on JIS K 7210 under the conditions of 200 °C and a load of 49 N.

[0050] [Flexural strength, flexural modulus] After the pellets were heated and dried at 80 °C for 3 hours, using an injection molding machine (manufactured by Nippon Steel Works, Ltd., J100E-P), under the conditions of a cylinder temperature of 200 °C and a mold temperature of 50 °C, a Type A test piece (dumbbell) described in JIS K-7139 was molded. Using the test piece cut out from the central part of the above dumbbell piece, the flexural strength and flexural modulus were measured respectively in accordance with JIS K-7171.

[0051] [Surface resistance] After the pellets were heated and dried at 80 °C for 3 hours, using an injection molding machine (manufactured by Nippon Steel Works, Ltd., J100E-P), under the conditions of a cylinder temperature of 200 °C and a mold temperature of 50 °C, a 90 mm × 90 mm × 2 mm thick plate was molded as a test piece. The surface resistivity was measured using a super insulation meter R-503 manufactured by Kawaguchi Electric Works Co., Ltd. in an environment of 23 °C and 50% RH (relative humidity) in accordance with JIS K 6911, with the diameter of the main electrode being 50 mm, the inner diameter of the ring electrode being 70 mm, the outer diameter being 80 mm, and the applied voltage being 100 V.

[0052] <Evaluation> [Moldability] After heating and drying the pellets at 80°C for 3 hours, using an injection molding machine (manufactured by Japan Steel Works, Ltd., J100E-P), 10 plates with a thickness of 2 mm, a length of 90 mm, and a width of 50 mm were molded at a cylinder temperature of 180°C and a mold temperature of 45°C. The moldability was evaluated according to the following evaluation criteria. ○: All 10 can be molded (no short shots) △: 1 to 5 out of 10 are short shots ×: 6 or more out of 10 are short shots

[0053] 〔Rigidity〕 The rigidity was evaluated based on the following evaluation criteria. ○: Flexural modulus is 2200 MPa or more △: Flexural modulus is 1800 MPa or more and less than 2200 MPa ×: Flexural modulus is less than 1800 MPa

[0054] 〔Antibacterial property〕 After heating and drying the pellets at 80°C for 3 hours, using an injection molding machine (manufactured by Japan Steel Works, Ltd., J100E-P), a plate with a thickness of 2 mm, a length of 90 mm, and a width of 90 mm was molded at a cylinder temperature of 200°C and a mold temperature of 50°C. The obtained plate was divided into 4 pieces to obtain test pieces with a size of 45 mm × 45 mm × 2 mm. For the antibacterial property, in accordance with JIS Z 2810, after sterilizing the surface of the test piece with ethanol, a bacterial solution of Staphylococcus aureus (4×10 5 cells / mL) was dropped at 0.23 mL, and a 30 mm × 30 mm polyethylene film was closely attached thereon. The test piece was transferred to a sterilized petri dish and cultured at 35°C for 24 hours. Then, the bacteria on the test piece were washed out, and the number of viable bacteria in the washed-out solution was measured. The antibacterial activity value (R) was calculated from the following formula. R = U - A U: Logarithmic value of the number of viable bacteria of the unprocessed test piece (polyethylene film) after 24 hours A: Logarithmic value of the number of viable bacteria of the test piece after 24 hours The antibacterial property was evaluated based on the following evaluation criteria. ○: Antibacterial activity value (R) is 2.0 or more ×: Antibacterial activity value (R) is less than 2.0

[0055] [Antistatic property] The antistatic property was evaluated based on the following evaluation criteria. ○: Surface resistivity is less than 1×10 14 Ω / □ ×: Surface resistivity is 1×10 14 Ω / □ or more

[0056]

Table 2

Claims

1. A styrene-based resin composition comprising a styrene-based resin and bamboo powder, The bamboo powder is contained in an amount of 10 to 60 parts by mass when the total amount of the styrene-based resin and the bamboo powder is 100 parts by mass, The styrene-based resin composition has a melt mass flow rate of 0.8 g / 10 min or more, measured at 200° C. and 49 N.

2. The styrene-based resin composition according to claim 1, wherein the bamboo powder contains 30 to 50 mass% of lignin per 100 mass% of the bamboo powder.

3. A molded article comprising the styrene-based resin composition according to claim 1 or 2.

4. 3. An eating tool comprising the styrene-based resin composition according to claim 1 or 2.

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