Resin composition and molded article

Abstract

The present invention provides a resin composition that allows for the production of molded articles with high fluidity during molding, a good appearance, and sufficient toughness. [Solution] The resin composition contains a thermoplastic resin and an inorganic powder in a mass ratio of 71:29 to 95:5. The thermoplastic resin contains 90% or more by mass of impact-resistant polystyrene resin relative to the total mass of the thermoplastic resin. The melt mass flow rate (MFR) of the impact-resistant polystyrene resin, measured at 200°C and under a load of 5 kg according to JIS K7210-1:2014 (ISO 1133-1:2011), is 6 g / 10 min to 13 g / 10 min, and the Charpy impact strength according to JIS K7111-1:2012 is 9 kJ / m 2 More than 13kJ / m 2 The following applies:

Description

[Technical Field]

[0001] This invention relates to resin compositions and molded articles. [Background technology]

[0002] Thermoplastic resins are widely used as molding materials for various molded products. Furthermore, to reduce the amount of resin used and to improve the rigidity and design of molded products, the use of inorganic powders as fillers in thermoplastic resins is being considered (see, for example, Patent Documents 1-3). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-160900 [Patent Document 2] Japanese Patent Application Publication No. 7-52227 [Patent Document 3] Japanese Patent Publication No. 2010-106270 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, resin compositions in which inorganic powder is filled into a thermoplastic resin tend to have lower fluidity during molding, such as injection molding, and lower toughness in the molded product, compared to resin compositions without inorganic powder filling. According to the inventors' studies, the decrease in fluidity and toughness due to the filling of inorganic powder is particularly pronounced in resin compositions based on polystyrene resin.

[0005] If the fluidity of the resin composition during molding is low, not only will the production efficiency during molding decrease, but thin-wall molding will become difficult, limiting the range of designs. Furthermore, if the toughness of the molded product is low, it may break or crack during assembly or use, or cause poor fitting. Therefore, it is desirable to improve the fluidity during molding and the toughness of the molded product.

[0006] Furthermore, molded products containing thermoplastic resins are prone to sink marks. To obtain molded products with a good appearance, it is desirable to be able to suppress such sink marks.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a resin composition that has high fluidity during molding and can produce a molded article having a good appearance and sufficient toughness, and a molded article containing the resin composition. [Means for solving the problem]

[0008] The present invention relates to the following resin compositions and molded articles. [1] Contains a thermoplastic resin and an inorganic powder, wherein the ratio of the mass of the inorganic powder to the total mass of the thermoplastic resin and the inorganic powder is 5% by mass or more and less than 30% by mass, the thermoplastic resin contains 90% by mass or more of impact-resistant polystyrene resin relative to the total mass of the thermoplastic resin, the melt mass flow rate (MFR) of the impact-resistant polystyrene resin measured at 200°C and a load of 5 kg according to JIS K7210-1:2014 (ISO1133-1:2011) is 6 g / 10 min or more and 13 g / 10 min or less, and the Charpy impact strength according to JIS K7111-1:2012 is 9 kJ / m 2 More than 13kJ / m 2 The following is the resin composition. [2] The resin composition of [1], wherein the content of the impact-resistant polystyrene resin is 95% by mass or more relative to the total mass of the thermoplastic resin. [3] The resin composition of [1] or [2], wherein the ratio of the mass of the inorganic powder to the total mass of the thermoplastic resin and the inorganic powder is 5% by mass or more and less than 20% by mass. [4] The resin composition according to [2] or [3], wherein the thermoplastic resin comprises 95% by mass or more and 99% by mass or less of the impact-resistant polystyrene resin and 1% by mass or more and 5% by mass or less of the polystyrene resin, based on the total mass of the thermoplastic resin. [5] The resin composition according to [1], wherein the inorganic powder comprises calcium carbonate powder. [6] The resin composition according to [5], wherein the calcium carbonate powder comprises heavy calcium carbonate powder. [7] The resin composition according to [6], wherein the median diameter D50 of the heavy calcium carbonate powder is 0.7 μm or more and 6.0 μm or less. A molded article comprising the resin composition described in any of [8][1] to [7]. [9] The molded article is an injection molded article, as described in [8]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a resin composition that has high fluidity during molding and can produce a molded article having a good appearance and sufficient toughness, as well as a molded article containing the resin composition. [Modes for carrying out the invention]

[0010] As a result of diligent research, the present inventors have found that in a resin composition containing a thermoplastic resin and an inorganic powder, by setting the ratio of the mass of the inorganic powder to the total mass of the thermoplastic resin and the inorganic powder to 5% by mass or more and less than 30% by mass, and by including a large amount of a specific impact-resistant polystyrene resin as the thermoplastic resin, it is possible to suppress the occurrence of sink marks in molded products while increasing the fluidity during molding (especially during injection molding), thereby increasing the toughness of the molded products.

[0011] The reason for this is not clear, but it can be considered as follows: The higher the proportion of inorganic powder relative to the total amount of thermoplastic resin, the lower the proportion of thermoplastic resin becomes, making shrinkage less likely. On the other hand, the fluidity during molding and the toughness of the molded product tend to decrease. In contrast, by moderately reducing the proportion of inorganic powder as described above, and by incorporating a specific impact-resistant polystyrene with high fluidity, it is possible to suppress shrinkage while sufficiently improving fluidity during molding and the toughness of the molded product.

[0012] Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to this embodiment. Also, in this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0013] 1. Resin composition The resin composition of this embodiment contains a thermoplastic resin and an inorganic powder. The ratio of the mass of the inorganic powder to the total mass of the thermoplastic resin and the inorganic powder is 5% by mass or more and less than 30% by mass, preferably 5% by mass or more and less than 20% by mass. When the ratio of the mass of the inorganic powder is 5% by mass or more, sink marks on the molded product can be suppressed, and the appearance can be improved. Also, an appropriate matte feeling can be imparted to the surface of the molded product. When the ratio of the mass of the inorganic powder is less than 30% by mass, the fluidity of the resin composition can be increased, and the toughness of the molded product can be increased.

[0014] 1-1. Thermoplastic resin The thermoplastic resin includes an impact-resistant polystyrene resin (HIPS), and may further include a polystyrene resin (GPPS) or other resins as needed.

[0015] 1-1-1. Impact-resistant polystyrene resin (HIPS) The melt mass flow rate (MFR, 200 °C, 5 kg) of the impact-resistant polystyrene resin according to JIS K7210-1:2014 (ISO1133-1:2011) is 6 g / 10 min or more and 13 g / 10 min or less. When the MFR of the impact-resistant polystyrene resin is 6 g / 10 min or more, the fluidity of the resin composition and the toughness of the molded product can be sufficiently increased. When the MFR of the impact-resistant polystyrene resin is 13 g / 10 min or less, the tensile strength of the molded product is less likely to be impaired. From the same perspective, the MFR of the impact-resistant polystyrene resin is preferably 7 g / 10 min or more and 12 g / 10 min or less.

[0016] The Charpy impact strength of the impact-resistant polystyrene resin according to JIS K7111-1:2012 is 9 kJ / m 2 or more and 13 kJ / m 2The following is true: The Charpy impact strength of the impact-resistant polystyrene resin is 9 kJ / m². 2 The above-mentioned Charpy impact strength of the impact-resistant polystyrene resin is 13 kJ / m². 2 The tensile strength of the molded product is less likely to be impaired if the following conditions are met. From a similar perspective, the Charpy impact strength of the impact-resistant polystyrene resin is 10 kJ / m². 2 More than 12kJ / m 2 The following is preferable:

[0017] The MFR and Charpy impact strength of impact-resistant polystyrene resins can be adjusted by any method, such as the amount of rubber modification (content of structural units derived from rubbery polymers). For example, increasing the content of structural units derived from rubbery polymers in impact-resistant polystyrene resins tends to increase both the MFR and Charpy impact strength of the impact-resistant polystyrene resin.

[0018] Impact-resistant polystyrene resins are not particularly limited as long as they satisfy the above-mentioned MFR and Charpy impact strength requirements. For example, an impact-resistant polystyrene resin may be an aromatic vinyl polymer containing structural units derived from an aromatic vinyl compound, which has been rubber-modified with a conjugated diene rubber-like polymer.

[0019] Examples of aromatic vinyl compounds include known ones such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, and p-methylstyrene. Among these, styrene is preferred.

[0020] Aromatic vinyl polymers may further contain structural units derived from other monomers copolymerizable with aromatic vinyl compounds. Examples of other monomers include acrylonitrile, (meth)acrylic acid, and (meth)acrylic acid esters.

[0021] Examples of conjugated diene rubber-like polymers used for rubber modification 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, acrylic rubber, and acrylonitrile butadiene rubber. Among these, polybutadiene and random, block or graft copolymers of styrene-butadiene are preferred. These may also be partially hydrogenated.

[0022] The content of structural units derived from conjugated diene rubbery polymers in the impact-resistant polystyrene resin is set so that the MFR and Charpy impact strength of the impact-resistant polystyrene resin fall within the above range. The content of structural units derived from conjugated diene rubbery polymers in the impact-resistant polystyrene resin may be, for example, 3 to 15% by mass.

[0023] Examples of impact-resistant polystyrene resins include the NORYL® series from sabic and the DIC styrene HIPS series from DIC.

[0024] In the resin composition, the content of impact-resistant polystyrene resin relative to the total mass of the thermoplastic resin is 90% by mass or more. When the above content of impact-resistant polystyrene resin is 90% by mass or more, the fluidity of the resin composition during molding can be increased, and the toughness of the molded product can be increased. From a similar viewpoint, it is more preferable that the above content of impact-resistant polystyrene resin is 95% by mass or more. The upper limit of the above content of impact-resistant polystyrene resin is not particularly limited and may be 100% by mass or 99% by mass or less.

[0025] 1-1-2. Polystyrene resin (GPPS) The thermoplastic resin may further contain polystyrene resins other than impact-resistant polystyrene resin (general-purpose polystyrene resins) to the extent that it does not impair the effects of the present invention.

[0026] Polystyrene resin is a styrenic polymer that does not contain structural units derived from rubber components, and is preferably a homopolymer of styrene. The polystyrene resin has a Charpy impact strength according to JIS K7111-1:2012 of at least 9 kJ / m 2 lower than that. By further containing an appropriate amount of polystyrene resin, the toughness of the molded product can be increased while moderately increasing the tensile strength.

[0027] When the resin composition contains polystyrene resin, the content of polystyrene resin relative to the total mass of the thermoplastic resin is not particularly limited, but is, for example, 1% by mass or more and 10% by mass or less, preferably 1% by mass or more and 5% by mass or less. When the above content of polystyrene resin is 10% by mass or less, the content of the impact-resistant polystyrene resin can be set to a predetermined value or more, so that the fluidity of the resin composition can be increased and the toughness of the molded product can be increased. On the other hand, when the above content of polystyrene resin is 1% by mass or more, the toughness of the molded product can be increased while moderately increasing the tensile strength.

[0028] 1-1-3. Other Resins The thermoplastic resin may further contain other resins other than those described above. Examples of other resins include acrylic resins, polyvinyl acetate, polyacrylonitrile, polycarbonate, polyamide, polyvinyl alcohol, petroleum hydrocarbon resins, and the like.

[0029] The content of the thermoplastic resin in the resin composition is not particularly limited as long as the mass of the inorganic powder relative to the total mass of the thermoplastic resin and the inorganic powder satisfies the above range. For example, the content of the thermoplastic resin in the resin composition is preferably 65% by mass or more and 95% by mass or less, more preferably 75% by mass or more and 95% by mass or less, based on the total mass of the resin composition. When the content of the thermoplastic resin is at least the lower limit value, the fluidity during molding of the resin composition and the toughness of the molded product can be further increased. When the content of the thermoplastic resin is at most the upper limit value, sink marks on the molded product can be further suppressed and the appearance can be made better.

[0030] 1-2. Inorganic Powder Inorganic powders are powders of inorganic substances. Examples of inorganic substances include carbonates, sulfates, silicates, phosphates, borates, oxides, or hydrates of calcium, magnesium, aluminum, titanium, zinc, silicon, barium, molybdenum, sodium, and potassium. Examples of inorganic substances also include inorganic carbon compounds.

[0031] Specific examples of inorganic substances include calcium carbonate, magnesium carbonate, zinc oxide, titanium dioxide, silica, alumina, clay (e.g., talc and kaolin), aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, carbon black, zeolite, molybdenum, diatomaceous earth, sericite, shirasu, calcium sulfite, sodium sulfate, potassium titanate, bentonite, wollastonite, dolomite, graphite, etc. These may be synthetic or derived from natural minerals. The inorganic powder may consist of only one type or two or more types.

[0032] Preferred examples of inorganic powders include calcium carbonate, magnesium carbonate, dolomite, zinc oxide, titanium oxide, silica, alumina, clay, talc, kaolin, aluminum hydroxide, and magnesium hydroxide powders, with calcium carbonate powder being particularly preferred.

[0033] The calcium carbonate powder may be prepared by a synthetic method, so-called light calcium carbonate powder, or it may be obtained by mechanically crushing and classifying natural raw materials such as limestone that mainly consist of CaCO3, so-called heavy calcium carbonate powder. The light calcium carbonate powder may also be powder made from raw materials such as concrete sludge, steel slag, carbide slag, waste concrete, coal ash, biomass ash, incinerator ash, waste gypsum, alkaline wastewater, etc.

[0034] The shape of the inorganic powder is not particularly limited and may be particulate, flake, granular, fibrous, or any other form. In the case of particulate powder, it may be spherical, as is generally the case with synthesis methods, or it may be irregularly shaped, as is the case with natural minerals that have been collected and crushed.

[0035] Inorganic powders may be surface-modified or unmodified. Examples of surface modification methods for inorganic powders include physical modification methods such as plasma treatment, and chemical modification methods using coupling agents or surfactants. Examples of coupling agents that can be used in chemical modification methods include silane coupling agents and titanium coupling agents. Any type of surfactant can be used, including anionic, cationic, nonionic, and amphoteric surfactants, and examples include higher fatty acids, higher fatty acid esters, higher fatty acid amides, and higher fatty acid salts.

[0036] The 50% particle size (median diameter D50) in the volume-based particle size distribution of inorganic powder is not particularly limited, but is preferably 0.7 μm or more and 6.0 μm or less, and more preferably 1.0 μm or more and 5.0 μm or less. When the median diameter D50 of the inorganic powder is 6.0 μm or less, the inorganic powder is less likely to fall off the molded product. When the average particle size of the inorganic powder is 0.7 μm or more, it is easier to adjust the viscosity to a desired range when kneading with thermoplastic resin. The median diameter D50 can be measured using a laser diffraction particle size distribution analyzer.

[0037] The inorganic powder content in the resin composition is not particularly limited, as long as the mass of the inorganic powder relative to the total mass of the thermoplastic resin and inorganic powder satisfies the above range. For example, the inorganic powder content in the resin composition is preferably 2% by mass or more and less than 30% by mass, and more preferably 4% by mass or more and 20% by mass or less, based on the total mass of the resin composition. If the inorganic powder content is above the lower limit, shrinkage in the molded product can be reduced and the appearance can be improved. If the inorganic powder content is below the upper limit, the fluidity during molding and the toughness of the molded product can be improved.

[0038] 1-3. Other ingredients The resin composition may further contain components other than those mentioned above, as long as they do not impair the effects of the present invention. Examples of components other than those mentioned above include polyethylene wax, paraffin oil, lubricants, plasticizers, colorants, antioxidants, flame retardants, foaming agents, flow regulators, and the like.

[0039] (Polyethylene-based wax) The resin composition may further contain a polyethylene-based wax. The polyethylene-based wax may be any wax mainly composed of polyethylene, and may contain more than 50% by mass of polyethylene, but it is preferable that it contains 80% by mass or more of polyethylene, and more preferably 90% by mass or more.

[0040] The melting point of polyethylene-based wax is not particularly limited, but it is preferably between 70°C and 150°C, and more preferably between 80°C and 130°C. A melting point within this range of polyethylene-based wax can further enhance the fluidity of the resin composition. The melting point is measured in accordance with JIS K7121:2012.

[0041] Polyethylene-based waxes can be commercially available products, including the POLYWAX series from NuCera Solutions, the Hiwax series and Excellex series from Mitsui Chemicals, the Sunwax series from Sanyo Chemical Industries, and Q-112 from Qingdao Sinoplas Hi-New Materia.

[0042] The polyethylene-based wax content in the resin composition is preferably 0.01% to 0.9% by mass, and more preferably 0.1% to 0.7% by mass, relative to the total mass of the resin composition. When the amount of polyethylene-based wax is 0.01% by mass or more, the fluidity of the resin composition can be further increased. On the other hand, when the polyethylene-based wax content is 0.9% by mass or less, bleed-out from the molded product can be further suppressed.

[0043] (Paraffin oil) The paraffin oil is not particularly limited as long as it is liquid at 23°C, and any known paraffin oil can be used. The paraffin oil is, for example, a linear or branched hydrocarbon with 14 to 30 carbon atoms, but it may also contain some cyclic hydrocarbons (naphthenes) or aromatic hydrocarbons.

[0044] The paraffin oil content in the resin composition is preferably 0.01% by mass or more and 0.9% by mass or less, and more preferably 0.1% by mass or more and 0.7% by mass or less, relative to the total mass of the resin composition. When the paraffin oil content is 0.01% by mass or more, the fluidity of the resin composition can be further increased. On the other hand, when the paraffin oil content is 0.9% by mass or less, bleed-out from the molded product can be further suppressed.

[0045] (Lubricant) Examples of lubricants include fatty acids such as stearic acid, hydroxystearic acid, complex stearic acid, and oleic acid; aliphatic alcohols; aliphatic amides such as stearamide, oxystearamide, oleylamide, erucylamide, ricinolamide, behenamide, methylolamide, methylenebisstearoamide, methylenebisstearobehenamide, bisamic acid of higher fatty acids, and complex amides; aliphatic esters such as n-butyl stearate, methyl hydroxystearate, polyhydric alcohol fatty acid esters, saturated fatty acid esters, and ester waxes; and fatty acid metal soaps such as zinc stearate and magnesium stearate.

[0046] The lubricant content in the resin composition is preferably, for example, 0.001% by mass or more and 0.50% by mass or less relative to the total mass of the resin composition. If the lubricant content is 0.001% by mass or more, the fluidity of the resin composition can be further improved. If the lubricant content is 0.5% by mass or less, bleed-out from the molded product can be further suppressed.

[0047] (Plasticizer) Examples of plasticizers include, for example, triethyl citrate, acetyl triethyl citrate, dibutyl phthalate, diaryl phthalate, dimethyl phthalate, diethyl phthalate, dioctyl phthalate, di(2-ethylhexyl) phthalate, di-2-methoxyethyl phthalate, dibutyl tartrate, o-benzoyl benzoate, diacetin, epoxidized soybean oil, etc. The resin composition may contain one of these individually or two or more of them.

[0048] (Colorants) The colorant may be any known organic pigment, inorganic pigment, or dye. Specific examples of colorants include organic pigments such as azo, anthraquinone, phthalocyanine, quinacridone, isoindolinone, diosadin, perinone, quinophthalone, and perylene pigments, as well as inorganic pigments such as ultramarine, titanium dioxide, titanium yellow, iron oxide (red iron oxide), chromium oxide, zinc oxide, and carbon black. The resin composition may contain one of these individually or two or more.

[0049] (Antioxidant) Examples of antioxidants include phosphorus-based antioxidants, phenol-based antioxidants, and pentaerythritol-based antioxidants. The resin composition may contain one or more of these. Phosphorus-based antioxidant stabilizers, more specifically phosphorus-based phosphate esters and phosphoric acid esters, are preferably used. Examples of phosphorus-based phosphate esters include, for example, triphenyl phosphite, trisnonylphenyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, and other triesters, diesters, monoesters, etc. of phosphorus-based phosphates.

[0050] Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl) phosphate, and 2-ethylphenyldiphenyl phosphate.

[0051] Examples of phenolic antioxidants include α-tocopherol, butylhydroxytoluene, cinapyl alcohol, vitamin E, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-t-butyl-6-(3'-t-butyl-5'-methyl-2'-hydroxybenzyl)-4-methylphenyl acrylate, 2,6-di-t-butyl-4-(N,N-dimethylaminomethyl)phenol, 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester, and tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxymethyl]methane.

[0052] (Flame retardant) The flame retardant is not particularly limited, but for example, halogen-based flame retardants or non-phosphorus halogen-based flame retardants such as phosphorus-based flame retardants or metal hydrates can be used. The resin composition may contain one of these alone or two or more of them.

[0053] Examples of halogenated flame retardants include halogenated bisphenol compounds such as halogenated bisphenylalkanes, halogenated bisphenyl ethers, halogenated bisphenyl thioethers, and halogenated bisphenylsulfones, as well as bisphenol-bis(alkyl ether) compounds such as brominated bisphenol A, brominated bisphenol S, chlorinated bisphenol A, and chlorinated bisphenol S. Examples of phosphorus-based flame retardants include aluminum tris(diethylphosphinate), bisphenol A bis(diphenyl phosphate), triarylisopropyl phosphate, cresyl di2,6-xylenyl phosphate, and aromatic condensed phosphate esters. Examples of metal hydrates include aluminum trihydrate, magnesium dihydrate, or combinations thereof.

[0054] Furthermore, the above-mentioned flame retardants may be combined with flame retardant additives. Examples of flame retardant additives include antimony oxides such as antimony trioxide and antimony pentoxide, and other known flame retardant additives.

[0055] (Foaming agent) The blowing agent is not particularly limited as long as it is a compound capable of generating bubbles when mixed with or injected under pressure into a composition that is in a molten state in a melting and mixing machine. Examples of blowing agents include those that change phase from solid to gas to generate bubbles, those that change phase from liquid to gas to generate bubbles, or the gas itself.

[0056] Examples of blowing agents include aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; halogenated hydrocarbons such as chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, dichloromethane, dichlorodifluoromethane, chloromethane, chloroethane, chloroethane, dichlorotrifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, and perfluorocyclobutane; inorganic gases such as carbon dioxide, nitrogen, and air; and water.

[0057] The foaming agent may contain the active ingredient of the foaming agent together with the carrier resin. Examples of carrier resins include crystalline olefin resins such as crystalline propylene. Examples of active ingredients include bicarbonates. Of these, bicarbonates are preferred. Preferably, the foaming agent concentrate contains crystalline polypropylene resin as the carrier resin and bicarbonate as a thermal decomposition type foaming agent.

[0058] (Flow modifier) Known fluidity modifiers can also be used. Examples of fluidity modifiers include peroxides such as dialkyl peroxides, for example, 1,4-bis[(t-butylperoxy)isopropyl]benzene.

[0059] (Antistatic agent) Examples of antistatic agents include fatty acid diethanolamides such as lauryl diethanolamide and stearyl diethanolamide; and hydroxyl group-containing compounds, including alcoholamine compounds. Alcoholamines, such as monoethanolamine, diethanolamine, and triethanolamine, are particularly preferred. Two or more antistatic agents can also be used in combination. These antistatic agents may be supported on calcium silicate or calcium carbonate. Furthermore, a range of 8 to 22 carbon atoms in the acyl group of fatty acid diethanolamide is preferred from the viewpoint of exhibiting sufficient antistatic effect.

[0060] The total amount of other components in the resin composition (excluding polyethylene-based wax, paraffin oil, and lubricant) is not particularly limited, but can be, for example, 2% by mass or less of the total mass of the resin composition.

[0061] 2. Method for producing resin compositions The resin composition can be manufactured by a process of mixing the above-mentioned thermoplastic resin, inorganic powder, and other components as needed.

[0062] The mixing method is not particularly limited, but may be, for example, by melt-mixing. All components may be mixed before melt-mixing, or some components may be melt-mixed first and the remaining components mixed afterward. The apparatus for melt-mixing is not particularly limited, and general extruders, kneaders, Banbury mixers, etc., can be used. In particular, from the viewpoint of obtaining a resin composition with a uniform composition, mixing with a twin-screw kneader is preferable.

[0063] 3. Molded articles and methods for manufacturing the same By molding the resin composition described above, a molded article containing the resin composition can be obtained.

[0064] The molding method is not particularly limited as long as it can be molded into the desired shape, and examples include extrusion molding, injection molding, vacuum forming, blow molding, and calendering. Among these, injection molding is preferred because it is easy to mold into a variety of shapes. In other words, the molded product is preferably an injection molded product. Note that injection molding includes not only conventional injection molding but also injection foam molding, multi-color molding, and the like.

[0065] The shape of the molded product is not particularly limited and may be in the form of a sheet or a three-dimensional shape. The use of the molded product is also not particularly limited and may include various sheets, toys, daily necessities such as brushes and shoehorns, housings for remote controls and telephones, and food containers. In particular, the above resin composition is suitable for toys, housings, and daily necessities because it has high fluidity during molding, making it easy to mold into various shapes with thin or uneven thickness sections, it has little shrinkage, resulting in molded products with a good appearance, and the molded product has high toughness, making it less likely to break or crack even when force is applied during assembly or use. In particular, molded products of the above resin composition are suitable for assembly toys such as models (including plastic models).

[0066] Assembly toys are manufactured or used by fitting together multiple parts that have interlocking protrusions and recesses. Furthermore, assembly toys modeled after people, animals, robots, etc., may include various joints and movable parts that are made up of multiple interlocking parts in order to enable movements and posing that closely resemble those of people, animals, or robots.

[0067] In contrast, molded articles of the above resin composition have a moderately low inorganic powder content, so even when multiple parts are fitted together or moved while fitted, the inorganic powder is less likely to fall off the surface of the parts, and they are less prone to wear. Furthermore, the molded articles have high toughness, making them less prone to breakage or cracking. In addition, the above resin composition has high fluidity during molding and is less prone to shrinkage, so even when there are thin-walled or unevenly thickened sections, it is possible to mold parts with high shape accuracy and a good appearance.

[0068] The wall thickness of the molded product is not particularly limited, but can be, for example, 40 μm to 40 mm, preferably 50 μm to 30 mm. [Examples]

[0069] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0070] 1. Preparation of materials The following examples and comparative examples use the following materials.

[0071] 1-1.Thermoplastic resin (Impact-resistant polystyrene resin) • HIPS-1: High-impact polystyrene (H800 manufactured by Toyo Styrene Co., Ltd., MFR: 8.2g / 10min, Charpy impact strength 11kJ / m²) 2 ) • HIPS-2: High-impact polystyrene (DIC Corporation, GH-6300-3, MFR: 7.2g / 10min, Charpy impact strength: 13kJ / m²) 2 ) • HIPS-3: High-impact polystyrene (DIC Corporation, MH-6100-2, MFR: 6.0g / 10min, Charpy impact strength: 12kJ / m²) 2 ) • HIPS-4: High-impact polystyrene (DIC Corporation, MH-6800-1, MFR: 15g / 10min, Charpy impact strength: 10kJ / m²) 2 ) • HIPS-5: High-impact polystyrene (DIC Corporation, GH-9600-2, MFR: 3.3g / 10min, Charpy impact strength: 12kJ / m²) 2 ) • HIPS-6: High-impact polystyrene (H350, manufactured by Toyo Styrene Co., Ltd., MFR: 8.0g / 10min, Charpy impact strength 8kJ / m²) 2 ) The above-mentioned MFR is a value measured at 200°C and 5kg according to JIS K7210-1:2014 (ISO1133-1:2011). Furthermore, the Charpy impact strength mentioned above is a value measured according to JIS K7111-1:2012.

[0072] (Polystyrene resin) GPPS: Polystyrene resin (G200C manufactured by Toyo Styrene Co., Ltd., MFR: 9g / 10min according to JIS K7210-1:2014 (ISO1133-1:2011), Charpy impact strength: 1.4kJ / m according to JIS K7111-1:2012) 2 )

[0073] (Styrene-based thermoplastic elastomer) • SEBS: Styrene-ethylene-butadiene-styrene block copolymer (manufactured by Asahi Kasei Corporation, Toughprene® 126S, MFR: 4.5g / 10min according to JIS K7210-1:2014 (ISO 1133-1:2011))

[0074] 1-2.Inorganic powder Calcium carbonate powder 1: Heavy calcium carbonate powder (manufactured by Takehara Chemical Industry Co., Ltd., WS-2200, median diameter D50: 1.3 μm) Calcium carbonate powder 2: Light calcium carbonate powder (calcium carbonate powder made from steel slag, median diameter D50: 4.8 μm) Talc powder: Median diameter D50: 6 μm The median diameter D50 mentioned above was measured using a laser diffraction particle size distribution analyzer.

[0075] 1-3. Others • Paraffin-based oils • Polyethylene-based wax (Q-112, manufactured by Qingdao Sinoplas Hi-New Materia) • Zinc stearate (manufactured by Sunace Co., Ltd., SAK-ZS-TB, lubricant) • Stearic acid (manufactured by Kao Corporation, lubricant)

[0076] 2. Preparation of resin composition and production of molded articles 2-1. Preparation of resin compositions 1 to 19 Thermoplastic resin, inorganic powder, and other components (polyethylene wax, paraffin oil, zinc stearate, stearic acid) were fed into a Parker HK-25D co-rotating twin-screw compounding extruder (φ25mm, L / D=41) in the mass ratios shown in Tables 1 and 2. The mixture was then melt-kneaded at a cylinder temperature of 200-220°C and extruded into strands. After the extruded resin composition was cooled, it was cut to obtain resin pellets.

[0077] 2-2. Evaluation The tensile properties, bending properties, fluidity, and fit of the obtained resin composition were evaluated by the following method.

[0078] (Tensile properties) The obtained pellets were fed into an injection molding machine to produce dumbbell-shaped (Type 1A) test specimens according to JIS K 7161-2:2014. Using this test specimen, the tensile strength and elongation at the breaking point were measured in accordance with JIS K 7161-2:2014 under conditions of 23°C and 50% RH using an Autograph AG-100kNXplus (Shimadzu Corporation). The elongation rate was 5 mm / min.

[0079] The tensile strength was then evaluated based on the following criteria. A: The tensile strength is 20 MPa or more. B: Tensile strength is 16 MPa or more and less than 20 MPa. C: Tensile strength is 12 MPa or more and less than 16 MPa. D: Tensile strength is less than 12 MPa

[0080] The elongation at the fracture point was evaluated according to the following criteria. A: The elongation at the time of cutting is more than 50%. B: The elongation at the time of cutting is between 30% and 50%. C: The elongation at the time of cutting is between 10% and 30%. D: Elongation at break is 10% or less. The elongation at the time of cutting can be calculated using the following formula. Elongation = (Distance between gauge marks after the test - Distance between gauge marks before the test) / Distance between gauge marks before the test × 100

[0081] (Bending properties) The obtained pellets were fed into an injection molding machine to produce test specimens conforming to JIS K7171:2016, with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. Using this test specimen, the bending strength and bending modulus were measured in accordance with JIS K7171:2016, under conditions of 23°C and 50%RH, using an Autograph AG-100kNXplus (Shimadzu Corporation) at a speed of 2 mm / min.

[0082] The bending strength was then evaluated based on the following criteria. A: The bending strength is 30 MPa or more. B: Bending strength is 25 MPa or more and less than 30 MPa. C: Bending strength is 20 MPa or more and less than 25 MPa. D: Bending strength is less than 20 MPa

[0083] The flexural modulus was evaluated based on the following criteria. A: The flexural modulus is less than 1700 MPa. B: The flexural modulus is between 1700 MPa and 1800 MPa. C: The flexural modulus is between 1800 MPa and 1900 MPa. D: The flexural modulus is 1900 MPa or higher.

[0084] (Liquidity) The obtained pellets were fed into an injection molding machine to produce dumbbell-shaped (Type 1A) test specimens according to JIS K 7161-2:2014. The molding conditions were a nozzle temperature of 210°C, and the maximum peak pressure (filling peak pressure) during injection was measured. The fluidity was then evaluated based on the following criteria. ◎: The peak filling pressure is less than 100 MPa. ○: The peak filling pressure is between 100 MPa and 110 MPa. ×: The peak filling pressure is 110 MPa or higher.

[0085] (exterior) The appearance of the obtained molded products was visually observed and evaluated according to the following criteria. ◎: No shrinkage marks, and the appearance is good. ○: Slight shrinkage occurs, but it has almost no effect on the appearance. ×: There are many sink marks, which is a practical problem.

[0086] (Matching ability) A first molded member having a convex portion and a second molded member having a concave portion were manufactured by injection molding. The fit of the convex portion of the first molded member into the concave portion of the second molded member was then evaluated according to the following criteria. ◎: It can be fitted without significant resistance, and no abnormalities occur in the fitting area. ○: There is some resistance, but it is possible to fit the parts together, and no abnormalities occur in the fitting area. ×: The resistance is high, and attempting to force the mating together will cause damage to the mating surface.

[0087] Table 1 shows the evaluation results for resin compositions 1 to 10, and Table 2 shows the evaluation results for resin compositions 11 to 19. A composition was judged to have good toughness if the tensile elongation at break, flexural modulus, and flexural strength were all C or higher, and was judged to be poor if even one of them was D.

[0088] [Table 1]

[0089] [Table 2]

[0090] As shown in Table 2, resin compositions 13, 14, and 16, in which the ratio of inorganic powder to the total mass of thermoplastic resin and inorganic powder is 30% by mass or more, exhibit low elongation at break and bending properties, and low toughness. Furthermore, mating tests show that the inorganic powder detaches, resulting in reduced mating performance. In addition, the filling peak pressure during injection molding is high, and the fluidity is low. On the other hand, resin composition 15, in which the ratio of inorganic powder to the total mass of thermoplastic resin and inorganic powder is less than 5% by mass, exhibits good elongation at break and bending properties, but sink marks occur, resulting in poor appearance. Furthermore, resin composition 17 using HIPS-5 with an MFR lower than 6 g / 10 min exhibits low elongation at fracture, poor bending properties, low toughness, and inferior interlocking properties. On the other hand, resin composition 18 using HIPS-4 with an MFR higher than 13 g / 10 min exhibits inferior tensile strength and appearance (sink marks). Additionally, the Charpy impact strength is 9 kJ / m². 2 In resin composition 19 using a lower HIPS-6, it can be seen that the elongation at fracture and flexural stiffness are inferior.

[0091] In contrast, as shown in Table 1, resin compositions 1 to 12, which contain predetermined HIPS with a ratio of inorganic powder mass to the total mass of thermoplastic resin and inorganic powder of 5% by mass or more and less than 30% by mass, and an MFR of 6 g / 10 min or more and 13 g / 10 min or less, exhibit high elongation at fracture, high bending properties, and high toughness while suppressing shrinkage. Furthermore, they exhibit low filling peak pressure and high fluidity during injection molding.

[0092] In particular, it can be seen that by further including GPPS as a thermoplastic resin, the tensile strength can be increased while maintaining the bending properties (comparison of resin compositions 1 and 3).

[0093] Furthermore, it can be seen that the fluidity during injection is further enhanced by including polyethylene wax and paraffin-based oil (comparison of resin compositions 1, 3, 11, and 12). [Industrial applicability]

[0094] According to the resin composition of the present invention, it is possible to obtain molded articles that have high fluidity during molding, a good appearance, and sufficient toughness. Therefore, this resin composition is suitable for various molded articles, especially injection molded articles having thin-walled or unevenly thickened sections.

Claims

1. It contains thermoplastic resin and inorganic powder, The ratio of the mass of the inorganic powder to the total mass of the thermoplastic resin and the inorganic powder is 5% by mass or more and less than 30% by mass. The thermoplastic resin contains 90% by mass or more of impact-resistant polystyrene resin relative to the total mass of the thermoplastic resin. The aforementioned impact-resistant polystyrene resin has a melt mass flow rate (MFR) of 6 g / 10 min or more and 13 g / 10 min or less, measured at 200°C and under a load of 5 kg according to JIS K7210-1:2014 (ISO 1133-1:2011), and a Charpy impact strength of 9 kJ / m² according to JIS K7111-1:2012. ２ More than 13kJ / m ２ The following is: Resin composition.

2. The content of the impact-resistant polystyrene resin is 95% by mass or more relative to the total mass of the thermoplastic resin. The resin composition according to claim 1.

3. The ratio of the mass of the inorganic powder to the total mass of the thermoplastic resin and the inorganic powder is 5% by mass or more and less than 20% by mass. The resin composition according to claim 1.

4. The thermoplastic resin is, with respect to the total mass of the thermoplastic resin The impact-resistant polystyrene resin comprising 95% by mass or more and 99% by mass or less, Polystyrene resin in an amount of 1% to 5% by mass, including, The resin composition according to claim 2 or 3.

5. The inorganic powder includes calcium carbonate powder. The resin composition according to claim 1.

6. The calcium carbonate powder includes heavy calcium carbonate powder. The resin composition according to claim 5.

7. The median diameter D50 of the heavy calcium carbonate powder is 0.7 μm or more and 6.0 μm or less. The resin composition according to claim 6.

8. A resin composition comprising the resin composition according to any one of claims 1 to 7, Molded products.

9. The aforementioned molded product is an injection-molded product. The molded article according to claim 8.

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