Thermoplastic resin composition and molded article

Abstract

To provide a thermoplastic resin composition for obtaining a molded article which has good balance among flowability, impact resistance and heat resistance, and has good matte appearance.SOLUTION: A thermoplastic resin composition contains a polycarbonate resin (A), a graft copolymer (B) and a hard copolymer (C), and satisfies the following conditions (1) to (4). (1) Content of the polycarbonate resin (A) is 40-70 mass% in 100 mass% of the total of the (A), (B) and (C). (2) Graft copolymer (B) is obtained by graft polymerization of more than 75 mass% and 100 mass% or less of an aromatic vinyl-based monomer (b-2), less than 25 mass% of a (meth)acrylate-based monomer (b-3), and less than 10 mass% of another monomer (b-4) with a rubbery polymer (b-1) (total of monomers to be grafted is 100 mass%). (3) Content of the graft copolymer (B) is 10-30 mass% in 100 mass% of the total of the (A), (B) and (C). (4) The hard copolymer (C) is obtained by polymerizing a monomer including an aromatic vinyl-based monomer and a vinyl cyanide-based monomer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition for producing molded articles having an excellent balance of flowability, impact resistance, and heat resistance and a matte appearance. [Background technology]

[0002] Compositions consisting of polycarbonate resin and rubber-reinforced styrene resin (hereinafter referred to as PC alloy resin) have excellent impact resistance, heat resistance, and moldability, and are therefore used in a variety of applications, including automotive parts, home appliance parts, and office equipment parts. In particular, vehicle parts tend to become larger and have more complex designs. Furthermore, to reduce vehicle weight, molded parts tend to be designed with thinner walls, which requires materials with excellent moldability, impact resistance, heat resistance, and other properties.

[0003] In addition, in recent years, there has been a trend toward a luxurious feel in the fields of automobile parts, home appliance parts, etc., and there is a demand for resin materials that have been imparted with a matte finish to reduce the gloss of the part surface in order to obtain a subdued matte texture. Conventionally, methods for obtaining such matte parts with reduced gloss have been used, such as applying a embossing finish to the mold surface, using a matte coating, or compounding an inorganic filler such as talc or a rubber component.

[0004] For example, Patent Document 1 discloses a thermoplastic resin composition that achieves a good matte appearance by utilizing the difference between the content of vinyl cyanide monomer units in the graft chains and the content of vinyl cyanide monomer units in the vinyl copolymer. However, the balance between heat resistance and impact resistance required for large, thin-walled vehicle parts and the like is still not satisfactory.

[0005] Patent Document 2 proposes a thermoplastic resin composition that is endowed with heat resistance and matte finish by using a cross-linked rubber-containing imidized copolymer. However, as the amount of the copolymer added increases, the fluidity and impact resistance tend to decrease, and there are problems such as poor moldability, which can easily result in poor appearance after molding. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-308551

[0007] [Patent Document 2] Japanese Patent Application Publication No. 9-316278 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a thermoplastic resin composition that has an excellent balance of flowability, impact resistance, and heat resistance and that can be used to obtain molded articles having a good matte appearance. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using specific amounts of a polycarbonate resin, a graft copolymer, and a rigid copolymer, and by adjusting the contents of the aromatic vinyl monomer, the (meth)acrylic acid ester monomer, and other monomers in the graft side chains to fall within specific ranges, thereby completing the present invention.

[0010] That is, the present invention comprises the following [1] to [3]. [1] A thermoplastic resin composition comprising a polycarbonate resin (A), a graft copolymer (B), and a rigid copolymer (C), and satisfying the following conditions (1) to (4): (1) The content of the polycarbonate resin (A) is 40 to 70% by mass in a total of 100% by mass of (A), (B), and (C). (2) The graft copolymer (B) is obtained by graft polymerizing more than 75% by mass but not more than 100% by mass of an aromatic vinyl monomer (b-2), less than 25% by mass of a (meth)acrylic acid ester monomer (b-3), and less than 10% by mass of other monomers (b-4) onto a rubbery polymer (b-1) (the total of the grafted monomers is taken as 100% by mass). (3) The content of the graft copolymer (B) is 10 to 30% by mass based on 100% by mass of the total of (A), (B), and (C). (4) The rigid copolymer (C) is obtained by polymerizing monomers including an aromatic vinyl monomer and a vinyl cyanide monomer. [2] The thermoplastic resin composition according to [1], which satisfies the following condition (5): (5) The 60-degree specular gloss value of a molded article obtained by injection molding the thermoplastic resin composition is less than 70. [3] A molded article having a matte appearance obtained by molding the thermoplastic resin composition according to any one of [1] and [2]. [Effects of the Invention]

[0011] The present invention can provide a thermoplastic resin composition that has an excellent balance of flowability, impact resistance, and heat resistance and that can be used to obtain molded articles having a good matte appearance. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below.

[0013] The thermoplastic resin composition of the present invention contains a polycarbonate resin (A), a graft copolymer (B), and a rigid copolymer (C).

[0014] The polycarbonate resin (A) is a polymer obtained by the phosgene method in which various dihydroxydiaryl compounds are reacted with phosgene, or by the transesterification method in which a dihydroxydiaryl compound is reacted with a carbonate ester such as diphenyl carbonate, and a representative example is a polycarbonate resin produced from 2,2-bis(4-hydroxyphenyl)propane, or "bisphenol A."

[0015] Examples of the dihydroxydiaryl compound include, in addition to bisphenol A, bis(hydroxyaryl)alkanes such as bis(4-hydroxydiphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)diphenylmethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 1,1-bis(4-hydroxy-3-tert-butylphenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, and 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane; dihydroxydiphenyl ethers such as 4,4'-dihydroxydiphenyl ether and 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether; dihydroxydiaryl sulfides such as 4,4'-dihydroxydiphenyl sulfide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; dihydroxydiaryl sulfoxides such as 4,4'-dihydroxydiphenyl sulfoxide; and dihydroxydiaryl sulfones such as 4,4'-dihydroxydiphenyl sulfone and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone.

[0016] These may be used alone or in combination of two or more kinds, and other compounds such as piperazine, dipiperidylhydroquinone, resorcinol, and 4,4'-dihydroxydiphenyls may also be mixed.

[0017] Furthermore, the dihydroxydiaryl compound may be mixed with a trivalent or higher phenol compound such as those shown below. Examples of trivalent or higher phenols include phloroglucinol, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptene, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane, 1,3,5-tri-(4-hydroxyphenyl)benzene, 1,1,1-tri-(4-hydroxyphenyl)ethane, and 2,2-bis-[4,4-bis(4-hydroxyphenyl)cyclohexyl]propane. When producing these polycarbonate resins, the weight-average molecular weight of the polycarbonate resin is typically 10,000 to 80,000, preferably 15,000 to 60,000. A molecular weight modifier, catalyst, etc. may be used as needed. The weight-average molecular weight can be measured by gel permeation chromatography (GPC) using polystyrene as a standard.

[0018] The graft copolymer (B) is obtained by graft polymerizing more than 75 mass % but not more than 100 mass % of an aromatic vinyl monomer (b-2), less than 25 mass % of a (meth)acrylic acid ester monomer (b-3), and less than 10 mass % of other monomers (b-4) onto a rubbery polymer (b-1) (the total of the grafted monomers is taken as 100 mass %).

[0019] The rubbery polymer (b-1) constituting the graft copolymer (B) is not particularly limited, and can be obtained by known polymerization methods, such as polybutadiene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), etc., conjugated diene rubber, ethylene-propylene rubber, ethylene-propylene-non-conjugated diene (ethylidene norbornene, dicyclopentadiene, etc.) rubber, acrylic rubber, such as polybutyl acrylate rubber, silicone rubber, or one or more of these can be used, and can also be used as a rubbery polymer having a multilayer structure combining these. Among them, it is preferable to use conjugated diene rubber from the viewpoint of impact resistance.

[0020] The mass average particle size of the rubbery polymer (b-1) is not particularly limited, but from the viewpoints of impact resistance and fluidity, it is preferably 0.1 to 2.0 μm, more preferably 0.15 to 1.0 μm. It can also be adjusted by aggregating and enlarging a rubbery polymer having a mass average particle size of 0.05 to 0.3 μm.

[0021] Examples of the aromatic vinyl monomer (b-2) include styrene, α-methylstyrene, paramethylstyrene, and bromostyrene, and one or more of these can be used.

[0022] The content of the aromatic vinyl monomer (b-2) must be more than 75% by mass but not more than 100% by mass, preferably 77 to 100% by mass, and more preferably 80 to 100% by mass (the total amount of the grafted monomers being 100% by mass). By adjusting it to the above range, the matte appearance can be improved.

[0023] Examples of the (meth)acrylic acid ester monomer (b-3) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl acrylate, phenyl (meth)acrylate, 4-t-butylphenyl (meth)acrylate, (di)bromophenyl (meth)acrylate, and chlorophenyl (meth)acrylate, and one or more of these can be used.

[0024] The content of the (meth)acrylic acid ester monomer (b-3) must be less than 25% by mass, preferably 23% by mass or less, and more preferably 20% by mass or less (the total amount of the grafted monomers being 100% by mass). By adjusting it to the above range, the matte appearance can be improved.

[0025] Examples of the other monomer (b-4) include vinyl cyanide monomers, maleimide monomers, amide monomers, unsaturated carboxylic acid monomers, and polyfunctional monomers, and one or more of these can be used.

[0026] Examples of vinyl cyanide monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, and fumaronitrile.

[0027] Examples of the maleimide monomer include N-phenylmaleimide and N-cyclohexylmaleimide.

[0028] Examples of the amide monomer include acrylamide and methacrylamide.

[0029] Examples of the unsaturated carboxylic acid monomer include (meth)acrylic acid, 2-ethylacrylic acid, maleic acid, fumaric acid, itaconic acid, and crotonic acid.

[0030] Examples of polyfunctional monomers include divinylbenzene, allyl (meth)acrylate, ethylene glycol di(meth)acrylate, diallyl phthalate, dicyclopentadiene di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, triallyl cyanurate, and triallyl isocyanurate.

[0031] The content of the other monomer (b-4) must be less than 10% by mass, preferably 7% by mass or less, and more preferably 5% by mass or less (the total amount of the grafted monomers being 100% by mass). By adjusting it to the above range, the matte appearance can be improved.

[0032] The content of the rubber polymer (b-1) in the graft copolymer (B) is not particularly limited, but in view of the balance of physical properties such as impact resistance and fluidity, it is preferably 20 to 80 mass %, more preferably 40 to 70 mass %.

[0033] The graft ratio of the graft copolymer (B) and the reduced viscosity of the acetone soluble matter are not particularly limited, but from the viewpoint of the balance of physical properties such as impact resistance and fluidity, the graft ratio is preferably 20 to 150%, more preferably 30 to 100%, and particularly preferably 36 to 75%. The reduced viscosity of the acetone soluble matter is preferably 0.2 to 1.5 dL / g, more preferably 0.3 to 1.0 dL / g.

[0034] The graft ratio and the reduced viscosity of the acetone soluble matter can be determined as follows.

[0035] Separation method Approximately 2 g of graft copolymer (B) and 60 ml of acetone were placed in an Erlenmeyer flask and left to soak for 24 hours. The mixture was then centrifuged at 15,000 rpm for 30 minutes to separate the soluble and insoluble fractions. The insoluble fraction was obtained by drying overnight at room temperature using a vacuum dryer. The soluble fraction was obtained by precipitating the acetone-soluble fraction in methanol and then drying overnight at room temperature using a vacuum dryer. Grafting rate Graft rate (%) = (X-Y) / Y x 100 X: Amount of acetone insoluble matter after vacuum drying (g) Y: Amount of rubber polymer in the graft copolymer (g) Reduced viscosity of acetone soluble matter (dl / g) The acetone soluble portion is dissolved in N,N-dimethylformamide to give a solution with a concentration of 0.4 g / 100 ml, and the reduced viscosity is determined from the flow time measured at 30°C using a Cannon-Fenske viscometer.

[0036] The graft copolymer (B) obtained as described above usually mainly contains a grafted polymer (B1 component) in which a monomer component is grafted onto the rubber polymer (b-1), and also contains a copolymer (referred to as B2 component) in which a monomer component not grafted onto the rubber polymer (b-1) is copolymerized. Therefore, in the present invention, when the B2 component contained in the graft copolymer (B) satisfies the monomer component constituting the rigid copolymer (C), it means that the graft copolymer (B) contains the rigid copolymer (C).

[0037] The rigid copolymer (C) is obtained by polymerizing a monomer component containing an aromatic vinyl monomer and a vinyl cyanide monomer.

[0038] Examples of aromatic vinyl monomers constituting the rigid copolymer (C) include styrene, α-methylstyrene, paramethylstyrene, bromostyrene, etc., and one or more of these can be used.

[0039] Examples of vinyl cyanide monomers constituting the rigid copolymer (C) include acrylonitrile, methacrylonitrile, ethacrylonitrile, fumaronitrile, etc., and one or more of these can be used.

[0040] Furthermore, the rigid copolymer (C) may contain other monomers copolymerizable with the aromatic vinyl monomer and the vinyl cyanide monomer, such as (meth)acrylic acid ester monomers, maleimide monomers, amide monomers, unsaturated carboxylic acid monomers, and polyfunctional monomers, and one or more of the same monomers as those described above in (b-3) and (b-4) can be used.

[0041] The composition ratio of the monomers constituting the rigid copolymer (C) is not particularly limited, but examples thereof include a composition ratio of 50 to 90 mass% aromatic vinyl monomer, 10 to 50 mass% vinyl cyanide monomer, and 0 to 40 mass% other copolymerizable monomer. In particular, it is preferable that the content of the vinyl cyanide monomer constituting the rigid copolymer (C) is 25 to 40 mass% in terms of the balance of physical properties such as impact resistance and fluidity.

[0042] The reduced viscosity of the rigid copolymer (C) is not particularly limited, but from the viewpoint of the balance of physical properties such as impact resistance and fluidity, it is preferably 0.2 to 1.5 dl / g, more preferably 0.3 to 1.0 dl / g.

[0043] The reduced viscosity can be calculated by the following formula.

[0044] The rigid copolymer (C) is dissolved in N,N-dimethylformamide to give a solution with a concentration of 0.4 g / 100 ml, and the reduced viscosity is determined from the flow time measured at 30° C. using a Cannon-Fenske viscometer.

[0045] The polymerization method for the graft copolymer (B) and the rigid copolymer (C) constituting the thermoplastic resin composition is not particularly limited, and they can be produced by, for example, emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, or a combination of these methods.

[0046] The content of polycarbonate resin (A) constituting the thermoplastic resin composition of the present invention must be 40 to 70 mass%, preferably 42 to 68 mass%, and more preferably 45 to 65 mass% (the total of (A) + (B) + (C) being 100 mass%). By adjusting it within the above range, the balance of impact resistance, fluidity, and heat resistance can be improved.

[0047] The content of the graft copolymer (B) must be 10 to 30% by mass, preferably 12 to 28% by mass, and more preferably 14 to 26% by mass (the total of (A) + (B) + (C) being 100% by mass). By adjusting the content within the above range, impact resistance and a matte appearance can be improved.

[0048] The thermoplastic resin composition of the present invention has a good matte appearance, and the 60° specular gloss value of a molded article obtained by molding the thermoplastic resin composition is preferably less than 70, more preferably less than 65, and even more preferably less than 60. The 60° specular gloss value can be measured by the method described in the examples below, and can be adjusted, for example, by the composition of the monomers polymerized into the rubber polymer (b-1) of the graft copolymer (B) referred to in the present invention.

[0049] The thermoplastic resin composition of the present invention may contain other thermoplastic resins as long as the effects of the present invention are not impaired. Examples of such other thermoplastic resins include acrylic resins such as polymethyl methacrylate, polyolefin resins such as polyethylene and polypropylene, polyester resins such as polybutylene terephthalate resin, polyethylene terephthalate resin, and polylactic acid resin, polyamide resins, and polyimide resins.

[0050] Furthermore, the thermoplastic resin composition of the present invention may contain, within the scope of the present invention, hindered amine light stabilizers; antioxidants such as hindered phenols, sulfur-containing organic compounds, and phosphorus-containing organic compounds; heat stabilizers such as phenols and acrylates; UV absorbers such as benzoates, benzotriazoles, benzophenones, and salicylates; lubricants such as organonickels and higher fatty acid amides; flame retardants and flame retardant aids such as polybromophenyl ethers, tetrabromobisphenol-A, brominated epoxy oligomers, brominated halogen-containing compounds, phosphorus-containing compounds, and antimony trioxide; odor masking agents; pigments such as carbon black and titanium oxide; dyes; and reinforcing agents and fillers such as talc, calcium carbonate, aluminum hydroxide, glass fiber, glass flakes, glass beads, glass wool, carbon fiber, and metal fiber.

[0051] The thermoplastic resin composition of the present invention can be obtained by melt-kneading the above-mentioned components using a known kneading machine such as a roll, a Banbury mixer, a single-screw extruder, a multi-screw extruder, or a kneader.

[0052] The thermoplastic resin composition thus obtained can be molded by injection molding, extrusion molding, compression molding, injection compression molding, blow molding, or the like to obtain a molded product having a good matte appearance. [Example]

[0053] The present invention will be described in detail below using examples, but the present invention is not limited by these examples. In the examples, parts and percentages are based on mass. In addition, various physical properties in each example and comparative example were measured by the following methods.

[0054] Charpy impact strength (NC) Using the pellets obtained in each example and comparative example, various test pieces were molded in accordance with ISO test method 294, and the notched Charpy impact values ​​of 4 mm thick test pieces were measured in accordance with ISO test method 179. Unit: kJ / m2

[0055] Melt Volume Flow Rate (MVR) The pellets obtained in each of the Examples and Comparative Examples were used to measure the melt volume-flow rate at 220°C and a load of 98.07 N in accordance with ISO test method 1133. Unit: cm 3 / 10 minutes

[0056] Heat deflection temperature (HDT) Using the pellets obtained in each example and comparative example, various test pieces were molded in accordance with ISO test method 294, and the deflection temperature under load of 1.8 MPa was measured in accordance with ISO 75. Unit: °C

[0057] Specular gloss value The pellets obtained in each example and comparative example were injection molded using a 1.0 oz. injection molding machine. A 55 mm x 90 mm x 2.5 mm thick flat mold for gloss measurement, with the mold surface polished to a mirror finish with a #1,500 grit, was used as the molding mold. Molding was performed under molding conditions of a cylinder temperature of 250°C, a mold temperature of 60°C, and an injection pressure of 4 MPa. The gloss of the flat mirror surface was measured at an incident angle of 60° using a gloss meter VG-7000 manufactured by Nippon Denshoku Industries Co., Ltd. The lower the specular gloss value, the better the matte appearance.

[0058] Polycarbonate resin (A) A polycarbonate resin made from phosgene and bisphenol A with a viscosity average molecular weight of 20,200.

[0059] Preparation of graft copolymer (B-1) A glass reactor was charged with 70 parts by weight of coagulated, agglomerated styrene-butadiene rubber latex (5% styrene, 95% butadiene, mass average particle diameter 315 nm) in solids, stirring was initiated, and nitrogen purge was performed. After nitrogen purge, the temperature inside the reactor was raised to 60°C, and an aqueous solution containing 0.008 parts by weight of ethylenediaminetetraacetic acid tetrasodium salt, 0.2 parts by weight of sodium formaldehyde sulfoxylate, and 0.002 parts by weight of ferrous sulfate dissolved in 13 parts by weight of deionized water was added. Subsequently, an aqueous solution containing 30 parts by weight of styrene and 0.15 parts by weight of t-butyl hydroperoxide (solids equivalent) dissolved in 20 parts by weight of deionized water was added dropwise continuously over 3.5 hours. After the dropwise addition, the mixture was held for 2 hours to obtain a graft copolymer latex. The mixture was then salted out, dehydrated, and dried to obtain a powder of graft copolymer (B-1). The graft ratio of the resulting graft copolymer (B-1) was 34%. The mass average particle size of the aggregated and thickened styrene-butadiene rubber latex was determined as follows. The samples were stained with osmium tetroxide (OsO4), dried, and then photographed using a transmission electron microscope. The area of ​​800 rubber particles was measured using an image analysis processor (IP-1000PC, manufactured by Asahi Kasei Corporation), and their equivalent circle diameters (diameters) were calculated to calculate the mass-average particle diameter.

[0060] Preparation of graft copolymer (B-2) Graft copolymer (B-2) powder was obtained in the same manner as in the production of graft copolymer (B-1), except that 30 parts by mass of styrene was replaced with 27 parts by mass of styrene and 3 parts by mass of methyl methacrylate. The graft ratio of the obtained graft copolymer (B-2) was 36%.

[0061] Preparation of graft copolymer (B-3) Graft copolymer (B-3) powder was obtained in the same manner as in the production of graft copolymer (B-1), except that 30 parts by mass of styrene was changed to 24 parts by mass of styrene and 6 parts by mass of methyl methacrylate. The graft ratio of the obtained graft copolymer (B-3) was 30%.

[0062] Preparation of graft copolymer (B-4) Graft copolymer (B-4) powder was obtained in the same manner as in the production of graft copolymer (B-1), except that 30 parts by mass of styrene was changed to 21 parts by mass of styrene and 9 parts by mass of methyl methacrylate. The graft ratio of the obtained graft copolymer (B-4) was 31%.

[0063] Preparation of graft copolymer (B-5) Graft copolymer (B-5) powder was obtained in the same manner as in the production of graft copolymer (B-1), except that 30 parts by mass of styrene was changed to 9 parts by mass of styrene and 21 parts by mass of methyl methacrylate. The graft ratio of the obtained graft copolymer (B-5) was 35%.

[0064] Preparation of graft copolymer (B-6) Graft copolymer (B-6) powder was obtained in the same manner as in the production of graft copolymer (B-1), except that 30 parts by mass of styrene was replaced with 30 parts by mass of methyl methacrylate. The graft ratio of the obtained graft copolymer (B-6) was 33%.

[0065] Preparation of graft copolymer (B-7) A glass reactor was charged with 60 parts by weight of coagulated and agglomerated styrene-butadiene rubber latex (5% by weight styrene, 95% by weight butadiene, mass average particle diameter 440 nm) in terms of solids, stirring was initiated, and nitrogen substitution was performed. After nitrogen substitution, the temperature inside the reactor was raised to 65°C. When it reached 65°C, an aqueous solution containing 0.06 parts by weight of glucose, 0.03 parts by weight of anhydrous sodium pyrophosphate, and 0.001 parts by weight of ferrous sulfate dissolved in 10 parts by weight of deionized water was added, and the temperature was then raised to 70°C. Subsequently, a mixture of 10 parts by weight of acrylonitrile, 30 parts by weight of styrene, 0.3 parts by weight of tertiary dodecyl mercaptan, and 0.1 parts by weight of t-butyl hydroperoxide and an emulsifier aqueous solution containing 1.0 parts by weight of potassium oleate (solids equivalent) dissolved in 20 parts by weight of deionized water were continuously added dropwise over 4 hours. After the dropwise addition, the mixture was maintained for 3 hours to obtain a graft copolymer latex. The mixture was then salted out, dehydrated, and dried to obtain a powder of graft copolymer (B-7).The graft rate of the obtained graft copolymer (B-7) was 42%.

[0066] Preparation of rigid copolymer (C) A copolymer (C) consisting of 75 parts by mass of styrene and 25 parts by mass of acrylonitrile was obtained by a known bulk polymerization method. The copolymer (C) obtained by the above method had a reduced viscosity of 0.50 dL / g.

[0067] Examples 1 to 3 and Comparative Examples 1 to 4 Polycarbonate resin (A), graft copolymers (B-1) to (B-7), and rigid copolymer (C) were mixed in the proportions shown in Table 1, and then melt-kneaded and pelletized in a 26 mm diameter twin-screw extruder with a cylinder temperature of 250°C and a main screw rotation speed of 400 rpm and a discharge rate of 20 kg / hr. These pellets were then molded in an injection molding machine (cylinder temperature 250°C, mold temperature 60°C) to produce test pieces for measuring physical properties and flat plates for measuring gloss. The test pieces and flat plates were then used to measure physical properties and specular gloss. The results are shown in Table 1.

[0068] The abbreviations in Table 1 represent the following components. (monomer) STY: Styrene ACN: Acrylonitrile MMA: methyl methacrylate

[0069] [Table 1]

[0070] As is clear from Table 1, in Examples 1 to 3, which used the thermoplastic resin composition of the present invention, molded articles were obtained that were excellent in balance between impact resistance, fluidity, and heat resistance and had a good matte appearance. In Comparative Examples 1 to 3, the content of the aromatic vinyl monomer (b-2) grafted to the rubber polymer (b-1) of the graft copolymer (B) was below the lower limit of the range specified in the present application, and therefore the specular gloss value was high and the matte appearance was poor. In Comparative Example 4, the content of the other monomer (b-4) grafted to the rubber polymer (b-1) of the graft copolymer (B) exceeded the upper limit of the range specified in the present application, and therefore the specular gloss value was high and the matte appearance was poor. [Industrial Applicability]

[0071] As described above, the thermoplastic resin composition of the present invention has an excellent balance of impact resistance, fluidity, and heat resistance, and can give molded articles with a good matte appearance. Therefore, the composition can be used in a variety of applications, such as vehicle interior parts, vehicle exterior parts, and home appliance parts.

Claims

1. A thermoplastic resin composition comprising a polycarbonate resin (A), a graft copolymer (B), and a rigid copolymer (C), and satisfying the following conditions (1) to (4): (1) The content of the polycarbonate resin (A) is 40 to 70% by mass in a total of 100% by mass of (A), (B) and (C). (2) The graft copolymer (B) is obtained by graft polymerizing more than 75% by mass but not more than 90% by mass of an aromatic vinyl monomer (b-2), 10% by mass or more but not more than 25% by mass of a (meth)acrylic acid ester monomer (b-3), and less than 10% by mass of other monomers (b-4) onto a rubber polymer (b-1) (the total of the grafted monomers is taken as 100% by mass). (3) The content of the graft copolymer (B) is 10 to 30% by mass based on 100% by mass of the total of (A), (B), and (C). (4) The rigid copolymer (C) is obtained by polymerizing monomers including an aromatic vinyl monomer and a vinyl cyanide monomer.

2. 2. The thermoplastic resin composition according to claim 1, which satisfies the following condition (5): (5) The 60-degree specular gloss value of a molded article obtained by injection molding the thermoplastic resin composition is less than 70.

3. A molded article having a matte appearance, obtained by molding the thermoplastic resin composition according to any one of claims 1 and 2.

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