JP7628044B2 - Thermoplastic resin composition and method for producing same - Google Patents

Description

The present invention relates to a thermoplastic resin composition that has an excellent balance of impact resistance, fluidity, heat resistance, and surface appearance, and a method for producing the same.

Rubber-reinforced styrene resins, such as ABS resin, are excellent in impact resistance, moldability, and surface appearance, and are used in various fields such as vehicle parts and electrical products. In rubber-reinforced styrene resins, graft polymers formed by graft polymerization of styrene monomers are dispersed in rubber polymers, and it is known that the state of dispersion affects impact resistance and surface appearance. In order to improve productivity, economy, and the degree of freedom in component design of the final composition containing rubber-reinforced styrene resins, there is a tendency to increase the proportion of rubber polymers in the graft polymers. However, if the proportion of rubber polymers in the graft polymers is increased, the dispersibility of the rubber polymers decreases when melt-kneaded with other resins, resulting in decreased impact resistance and surface appearance. Therefore, Patent Document 1 proposes that the problem can be improved by using the melt viscosity a (Pa·s) of the graft polymer (A), the melt viscosity b (Pa·s) of the polymer (B), and the content ratio x (wt%) of the rubber polymer in the graft polymer (A) to satisfy (Formula 1) a/(b·x)≦0.7 in a thermoplastic resin composition consisting of a graft polymer (A) and a polymer (B). However, when the content ratio x of the rubber polymer in the graft polymer (A) is increased, the melt viscosity a of the graft polymer (A) inevitably increases, and in order to satisfy (Formula 1), it is necessary to increase the melt viscosity b of the polymer (B). This leads to a decrease in the fluidity of the thermoplastic resin composition consisting of the graft polymer (A) and the polymer (B). Therefore, when the content ratio of the rubber polymer in the graft polymer is increased, the dispersibility of the rubber polymer and the fluidity of the thermoplastic resin composition are in a trade-off relationship, and the material that combines both of these is still not satisfactory.

Japanese Patent Application Publication No. 10-273578

The present invention aims to provide a thermoplastic resin composition that has an excellent balance of impact resistance, fluidity, heat resistance, and surface appearance, and a method for producing the same.

As a result of intensive research, the present inventors have found that for a thermoplastic resin composition containing a rubber-reinforced styrene-based resin powder having a melt volume rate (220°C, 10 kg) of 20 ( ^cm3 /10 min) or more, the above-mentioned problems can be solved by adding a specific amount of lubricant to the rubber-reinforced styrene-based resin powder, and have thus completed the present invention.

That is, the present invention comprises the following [1] to [4].
[1] A thermoplastic resin composition containing a rubber-reinforced styrene-based resin powder, which satisfies the following conditions (1) and (2):
(1) The rubber-reinforced styrene-based resin powder contains 0.2 parts by mass or more of a lubricant per 100 parts by mass of the rubber-reinforced styrene-based resin component.
(2) The melt volume rate (220° C., 10 kg) of the thermoplastic resin composition is 20 (cm ³ /10 min) or more.
[2] The thermoplastic resin composition according to claim 1, further satisfying the following condition (3):
(3) The following formula (i) is satisfied:
5≦X/Y≦250... Formula (i)
X: Melt volume rate of thermoplastic resin composition (220°C, 10 kg)
Y: Lubricant content of rubber-reinforced styrene-based resin powder
[3] A method for producing a thermoplastic resin composition having a melt volume rate (220°C, 10 kg) of 20 (cm3/10 min) or more, which is obtained by mixing 0.2 parts by mass or more (solid content equivalent) of an emulsion-state lubricant with 100 parts by mass (solid content equivalent) of a rubber-reinforced styrene-based resin ^latex , and then melt-kneading the resulting compound containing the powdered rubber-reinforced styrene-based resin powder.
[4] The method for producing a thermoplastic resin composition according to claim 3, further comprising satisfying the following formula (i):
5≦X/Y≦250... Formula (i)
X: Melt volume rate of thermoplastic resin composition (220°C, 10 kg)
Y: Lubricant content of rubber-reinforced styrene-based resin powder

The present invention provides a thermoplastic resin composition that has an excellent balance of impact resistance, fluidity, heat resistance, and surface appearance, and a method for producing the same.

The present invention will be described in detail below.

The thermoplastic resin composition of the present invention contains a rubber-reinforced styrene-based resin powder.

The rubber-reinforced styrene-based resin powder of the present invention is obtained by powdering a rubber-reinforced styrene-based resin latex containing a latex of a graft copolymer (A) containing a styrene-based monomer component obtained by an emulsion polymerization method, or a latex mixture of a latex of a graft copolymer (A) and a polymer (B) containing a vinyl-based monomer component obtained by an emulsion polymerization method.

The graft copolymer (A) is obtained by graft polymerization of a rubber polymer and a monomer containing a styrene-based monomer.

The rubbery polymer constituting the graft copolymer (A) is not particularly limited, and examples thereof include conjugated diene rubbers such as polybutadiene rubber, styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR); ethylene-propylene rubbers such as ethylene-propylene rubber and ethylene-propylene-non-conjugated diene (ethylidene norbornene, dicyclopentadiene, etc.) rubber; acrylic rubbers such as polybutyl acrylate rubber; and silicone rubbers. One or more of these may be used, and these may also be combined to form a rubbery polymer having a multilayer structure. Among these, it is preferable to include a conjugated diene rubber from the viewpoint of impact resistance.

In addition, there are no particular restrictions on the mass average particle size of the rubber polymer, but it is preferably 50 to 1000 nm, more preferably 200 to 800 nm, and even more preferably 300 to 500 nm. By adjusting it to the above range, there is a tendency for the balance between mechanical strength and surface appearance to be excellent.

The monomers that can be graft polymerized onto the rubber polymer of the graft copolymer (A) essentially include styrene-based monomers such as styrene and α-methylstyrene, and further include vinyl cyanide-based monomers, (meth)acrylic acid ester-based monomers, maleimide-based monomers, amide-based monomers, unsaturated carboxylic acid-based monomers, and polyfunctional monomers, and one or more of these can be used.

Examples of vinyl cyanide monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, fumaronitrile, etc.

Examples of (meth)acrylic acid ester monomers 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.

Examples of maleimide monomers include N-phenylmaleimide and N-cyclohexylmaleimide.

Examples of amide monomers include acrylamide and methacrylamide.

Examples of unsaturated carboxylic acid monomers include (meth)acrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, and crotonic acid.

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.

There are no particular restrictions on the content of the rubber polymer in the graft copolymer (A), but it is preferably 20 to 80% by mass, and more preferably 40 to 70% by mass. By adjusting it to the above range, there is a tendency for the balance between mechanical strength and surface appearance to be excellent.

The graft ratio of the graft copolymer (A) and the reduced viscosity of the acetone soluble portion are not particularly limited, but the graft ratio is preferably 20 to 150%, more preferably 30 to 100%, and even more preferably 36 to 75%. The reduced viscosity of the acetone soluble portion is preferably 0.2 to 1.5 dl/g, and more preferably 0.3 to 1.0 dl/g. Adjusting the ratio within the above ranges tends to provide an excellent balance between mechanical strength and fluidity.

The above graft ratio and reduced viscosity of the acetone soluble portion can be calculated as follows:

Fractionation method : Approximately 2 g of graft copolymer (A) and 60 ml of acetone were placed in an Erlenmeyer flask and soaked for 24 hours. The mixture was then centrifuged at 15,000 rpm for 30 minutes using a centrifuge to separate the soluble and insoluble portions. The insoluble portion was obtained by drying overnight at room temperature using vacuum drying. The soluble portion was obtained by precipitating the acetone-soluble portion in methanol and drying overnight at room temperature using vacuum drying.
Grafting rate
Graft ratio (%)=(X−Y)/Y×100
X: Amount of acetone insoluble matter after vacuum drying (g)
Y: Amount of rubber polymer in graft copolymer (A) (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.

Polymer (B) is a polymer formed by polymerization of monomers including a vinyl monomer.

The vinyl monomer may be one or more of styrene monomers, vinyl cyanide monomers, (meth)acrylic acid ester monomers, maleimide monomers, amide monomers, unsaturated carboxylic acid monomers, polyfunctional monomers, etc. The above-mentioned monomers may be used as each monomer.

The reduced viscosity of polymer (B) is not particularly limited, but is preferably 0.2 to 1.5 dl/g, and more preferably 0.3 to 1.0 dl/g. By adjusting it to the above range, there is a tendency for the balance between mechanical strength and fluidity to be excellent.

The reduced viscosity can be calculated using the following formula:

Polymer (B) is dissolved in N,N-dimethylformamide to give a solution with a concentration of 0.4 g/100 ml, and the reduced viscosity is calculated from the flow time measured at 30°C using a Cannon-Fenske viscometer.

The above rubber polymer, graft copolymer (A) and polymer (B) can be obtained by a known emulsion polymerization method.

Examples of emulsifiers used in emulsion polymerization include aliphatic carboxylates such as potassium oleate, dipotassium alkenyl succinate, and sodium rosinate; alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate; aliphatic sulfonates such as sodium lauryl sulfate; alkyl diphenyl ether disulfonates; sulfate ester salts of higher alcohols; formalin condensates of naphthalene sulfonic acid; anionic surfactants such as sulfate ester salts of nonionic surfactants; and nonionic surfactants such as alkyl ester type, alkyl phenyl ether type, and alkyl ether type of polyethylene glycol. One or more of these can be used.

Examples of initiators used in emulsion polymerization include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, and redox-type initiators using sodium sulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate, ascorbic acid, ferrous sulfate, etc. as reducing agents and potassium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, acetyl peroxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, etc. as oxidizing agents.

The rubber polymer content of the rubber-reinforced styrene-based resin powder of the present invention is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. By adjusting it to the above range, the degree of freedom in component design of the final composition containing the rubber-reinforced styrene-based resin powder can be improved.

The rubber polymer content of the rubber-reinforced styrene-based resin powder can be adjusted by adjusting the content of the rubber polymer constituting the graft copolymer (A) or by mixing the graft copolymer (A) and the polymer (B) in a latex state.

The rubber-reinforced styrene-based resin powder of the present invention is obtained by powdering a rubber-reinforced styrene-based resin latex that contains a latex of graft copolymer (A) or a latex mixture of the latex of graft copolymer (A) and the latex of polymer (B).

Methods for powdering include, for example, the spray-drying method and the wet method in which a coagulant is added to coagulate into a slurry.

The coagulants used in the wet method include inorganic acids such as hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid, organic acids such as formic acid and acetic acid, and inorganic acid metal salts such as magnesium sulfate, calcium chloride, and aluminum sulfate. These can be used alone or in combination.

After solidification, the mixture is washed with water, dehydrated, and dried to obtain rubber-reinforced styrene-based resin powder.

The rubber-reinforced styrene-based resin powder of the present invention contains 0.2 parts by mass or more, and preferably 0.3 parts by mass or more, of a lubricant per 100 parts by mass of the rubber-reinforced styrene-based resin component (graft copolymer (A), or graft copolymer (A) and polymer (B)). By adjusting the amount of the lubricant within the above range, the surface appearance tends to be excellent.
The content of the lubricant refers to the amount added before the rubber-reinforced styrene-based resin is powdered, and does not include, for example, the amount of the lubricant added during melt-kneading.

Examples of lubricants include hydrocarbon-based lubricants such as low molecular weight wax, paraffin wax, polyethylene wax, chlorinated hydrocarbons, and fluorocarbons; natural wax-based lubricants such as carnauba wax and candy wax; fatty acid-based lubricants such as higher fatty acids such as lauric acid, stearic acid, and behenic acid, or oxyfatty acids such as hydroxystearic acid; fatty amide-based lubricants such as stearylamide, laurylamide, and oleylamide; and alkylene bis-fatty amide compounds such as methylene bis-stearylamide and ethylene bis-stearic acid amide; ester compounds of fatty acids and monohydric alcohols such as stearyl stearate, butyl stearate, and distearyl phthalate; and glycerin tristearate, sorbitan tristearate, pentaerythritol, and the like. Examples of the lubricants include fatty acid alcohol ester lubricants such as ester compounds of fatty acids and polyhydric alcohols, such as erythritol tetrastearate, dipentaerythritol hexastearate, polyglycerol polyricinoleate, and hardened castor oil, and complex ester compounds of monovalent fatty acids and polybasic organic acids and polyhydric alcohols, such as dipentaerythritol adipic acid-stearic acid ester, fatty acid alcohol lubricants such as stearyl alcohol, lauryl alcohol, and palmityl alcohol, metal soaps of fatty alcohols and metals, such as alkaline earth metals, titanium, zirconium, iron, cobalt, nickel, copper, zinc, and aluminum, montanic acid lubricants such as partially saponified montanic acid esters, acrylic lubricants, and silicone oils, and these can be used alone or in combination of two or more.

It is preferable to add the lubricant in an emulsion state when producing the rubber-reinforced styrene-based resin powder, as this allows the lubricant to be uniformly dispersed in the powder.

There are no particular limitations on the timing of adding the emulsion-state lubricant, and examples of the method include (1) mixing it with the rubber-reinforced styrene-based resin latex before it is powdered, or (2) adding it to a slurry of the rubber-reinforced styrene-based resin latex that has been solidified. Among these, method (1) is preferred from the viewpoint of surface appearance.

The thermoplastic resin composition of the present invention may contain, in addition to the rubber-reinforced styrene-based resin powder, one or more of the following resins in combination: acrylic resins such as polymethyl methacrylate; polyolefin-based resins such as polyethylene and polypropylene; polycarbonate resins; polyester-based resins such as polybutylene terephthalate resin, polyethylene terephthalate resin, and polylactic acid resin; polyamide resins; and polyimide-based resins.

Furthermore, within the scope of the present invention, it is also possible to add hindered amine-based light stabilizers; antioxidants such as hindered phenol-based, sulfur-containing organic compound-based, and phosphorus-containing organic compound-based; heat stabilizers such as phenol-based and acrylate-based; ultraviolet absorbers such as benzoates, benzotriazoles, benzophenones, and salicylates; lubricants such as organic nickel-based and higher fatty acid amides; plasticizers such as phosphate esters; flame retardants and flame retardant assistants such as polybromophenyl ether, tetrabromobisphenol-A, brominated epoxy oligomers, halogen-containing compounds such as brominated compounds, phosphorus-based compounds, and antimony trioxide; odor masking agents; pigments such as carbon black and titanium oxide; dyes, etc. Furthermore, it is also possible to add reinforcing agents and fillers such as talc, calcium carbonate, aluminum hydroxide, glass fiber, glass flakes, glass beads, glass wool, carbon fiber, and metal fiber.

The thermoplastic resin composition of the present invention must have a melt volume rate (220°C, 10 kg) of 20 ( ^cm3 /10 min) or more, preferably 35 ( ^cm3 /10 min) or more, and more preferably 45 ( ^cm3 /10 min) or more. Also, it is preferably 80 ( ^cm3 /10 min) or less, and more preferably 70 ( ^cm3 /10 min) or less. By adjusting it to the above range, the balance of impact resistance, fluidity, and heat resistance tends to be excellent.

Furthermore, the thermoplastic resin composition of the present invention preferably satisfies the following formula (i).
5≦X/Y≦250... Formula (i)
X: Melt volume rate of thermoplastic resin composition (220°C, 10 kg)
Y: The lower limit of the lubricant content of the rubber-reinforced styrene-based resin powder is more preferably 10 or more, and even more preferably 50 or more. The upper limit is more preferably 200 or less, even more preferably 150 or less, and most preferably 130 or less. By adjusting the content within the above range, the balance of impact resistance, fluidity, heat resistance, and surface appearance tends to be excellent.
X/Y indicates that there is a correlation between the melt volume rate of the thermoplastic resin composition and the lubricant content of the rubber-reinforced styrene-based resin powder. For example, when the melt volume rate of the thermoplastic resin composition is designed to be high, the rubber-reinforced styrene-based resin powder must contain a large amount of lubricant.

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

The present invention will be described in detail below using examples and comparative examples, but the present invention is not limited thereto. Note that parts and percentages shown in the examples and comparative examples are based on mass.
In each of the examples and comparative examples, various physical properties were measured by the following methods.

[Impact resistance]
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 value (NC) was measured at a thickness of 4 mm in accordance with ISO test method 179. Unit: kJ/m2

[Liquidity]
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 under conditions of 220° C. and a load of 10 kg in accordance with ISO test method 1133. Unit: cm ³ /10 min.

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

[Surface appearance evaluation]
40 g of the pellets obtained in each of the Examples and Comparative Examples were used and subjected to a hot press at 230° C. to prepare a film test piece having a thickness of 0.1 mm or less.
Three circles with a diameter of 9 mm were drawn at random locations on the obtained test piece, and the number of bumps with a diameter of 50 μm or more within each circle was counted using an optical microscope and the average value was calculated.The number of bumps was then converted into the number equivalent to a circle with a diameter of 10 cm, and the surface appearance was evaluated according to the following criteria.

Good: The number of bumps larger than 50 μm is less than 550.
△: The number of bumps of 50 μm or more is 550 or more and less than 800.
×: The number of bumps larger than 50 μm is 800 or more.

<Production of Graft Copolymer Latex>
A glass reactor was charged with 65 parts by mass of coagulated and thickened styrene-butadiene rubber latex (styrene 5% by mass, butadiene 95% by mass, mass average particle size 440 nm) in terms of solid content, stirring was started, and nitrogen replacement was performed. After nitrogen replacement, the temperature in the tank was raised to 65 ° C., and an aqueous solution in which 0.06 parts by mass of glucose, 0.03 parts by mass of anhydrous sodium pyrophosphate, and 0.001 parts by mass of ferrous sulfate were dissolved in 10 parts by mass of deionized water was added, and the temperature was raised to 70 ° C. Thereafter, a mixture of 10 parts by mass of acrylonitrile, 25 parts by mass of styrene, 0.3 parts by mass of tertiary decyl mercaptan, and 0.1 parts by mass of t-butyl hydroperoxide and an emulsifier aqueous solution in which 1.0 parts by mass of potassium oleate (solid content equivalent) was dissolved in 20 parts by mass of deionized water were continuously dropped over 4 hours. After dropping, the mixture was held for 3 hours to obtain a graft copolymer latex.
The graft ratio of the resulting graft copolymer latex was 42%, and the reduced viscosity of the acetone soluble portion was 0.28 dl/g.
The mass average particle size of the aggregated and thickened styrene-butadiene rubber latex was determined as follows.
The rubber particles were stained with osmium tetroxide (OsO4), dried, and then photographed with a transmission electron microscope. The areas of 800 rubber particles were measured using an image analysis processing device (device name: Asahi Kasei Corporation IP-1000PC), and their circle-equivalent diameters (diameters) were calculated to calculate the mass-average particle diameter.
<Production of rubber-reinforced styrene-based resin powder (A-1)>
An emulsion of ethylene bisstearic acid amide was used as the lubricant.
(Step 1)
0.39 parts by mass of an emulsion of ethylene bisstearic acid amide (solid content equivalent) was added to 100 parts by mass (solid content equivalent) of the above graft copolymer latex, and mixed.
(Step 2)
A stirring tank was charged with deionized water so that the final slurry concentration was 25%, and 5 parts by mass of magnesium sulfate was further added. Stirring was started and the temperature inside the tank was raised to 75°C.
(Step 3)
After the temperature in the tank reached 75° C., the entire amount of the mixture obtained in (Step 1) was added.
(Step 4)
Thereafter, the obtained coagulated slurry was dehydrated and dried to obtain a rubber-reinforced styrene-based resin powder (A-1).

<Production of rubber-reinforced styrene-based resin powder (A-2)>
The rubber-reinforced styrene-based resin powder (A-1) was produced in the same manner as in the production of the rubber-reinforced styrene-based resin powder (A-1), except that the amount of ethylene bisstearic acid amide emulsion (solid content equivalent) added in (step 1) was changed from 0.39 parts by mass to 0.48 parts by mass.
<Production of rubber-reinforced styrene-based resin powder (A-3)>
The rubber-reinforced styrene-based resin powder (A-1) was produced in the same manner as in the production of the rubber-reinforced styrene-based resin powder (A-1), except that the amount of ethylene bisstearic acid amide emulsion (solid content equivalent) added in (step 1) was changed from 0.39 parts by mass to 0.67 parts by mass.
<Production of rubber-reinforced styrene-based resin powder (A-4)>
The rubber-reinforced styrene-based resin powder (A-1) was produced in the same manner as in the production of the rubber-reinforced styrene-based resin powder (A-1), except that the amount of ethylene bisstearic acid amide emulsion (solid content equivalent) added in (step 1) was changed from 0.39 parts by mass to 0.95 parts by mass.
<Production of rubber-reinforced styrene-based resin powder (A-5)>
The rubber-reinforced styrene-based resin powder (A-1) was produced in the same manner as in the production of the rubber-reinforced styrene-based resin powder (A-1), except that the amount of ethylene bisstearic acid amide emulsion (solid content equivalent) added in (step 1) was changed from 0.39 parts by mass to 10.00 parts by mass.
<Production of rubber-reinforced styrene-based resin powder (A-6)>
The rubber-reinforced styrene-based resin powder (A-1) was produced in the same manner as in the production of the rubber-reinforced styrene-based resin powder (A-1), except that the amount of ethylene bisstearic acid amide emulsion (solid content equivalent) added in (step 1) was changed from 0.39 parts by mass to 20.00 parts by mass.
<Production of rubber-reinforced styrene-based resin powder (A-7)>
The rubber-reinforced styrene-based resin powder (A-1) was produced in the same manner as in the production of the rubber-reinforced styrene-based resin powder (A-1), except that the amount of ethylene bisstearic acid amide emulsion (solid content equivalent) added in (step 1) was changed from 0.39 parts by mass to 0 parts by mass.
<Production of rubber-reinforced styrene-based resin powder (A-8)>
The rubber-reinforced styrene-based resin powder (A-1) was produced in the same manner as in the production of the rubber-reinforced styrene-based resin powder (A-1), except that the amount of ethylene bisstearic acid amide emulsion (solid content equivalent) added in (step 1) was changed from 0.39 parts by mass to 0.19 parts by mass.

<Production of Polymer (B-1)>
A polymer (B-1) consisting of 75 parts by mass of styrene and 25 parts by mass of acrylonitrile was obtained by a known bulk polymerization method. The reduced viscosity of the polymer (B-1) obtained by the above method was 0.44 dl/g.
<Production of Polymer (B-2)>
A polymer (B-2) consisting of 75 parts by mass of styrene and 25 parts by mass of acrylonitrile was obtained by a known bulk polymerization method. The reduced viscosity of the polymer (B-2) obtained by the above method was 0.62 dl/g.
<Production of Polymer (B-3)>
A polymer (B-3) consisting of 75 parts by mass of styrene and 25 parts by mass of acrylonitrile was obtained by a known emulsion polymerization method. The reduced viscosity of the polymer (B-3) obtained by the above method was 1.20 dl/g.

<Other additives>
Ethylenebisstearic acid amide (EBS): Kao Wax EB-P manufactured by Kao Corporation

Examples 1 to 6 and Comparative Examples 1 to 5
The rubber-reinforced styrene-based resin powder (A), the polymer (B) and other additives were mixed in the proportions shown in Table 1, and then melt-kneaded and pelletized in a φ26 mm twin-screw extruder set at a cylinder temperature of 230° C., a main screw rotation speed of 300 rpm, and a discharge rate of 25 kg/hr. The pellets obtained were used to carry out various evaluations. The results are shown in Table 1.

As is apparent from Table 1, the thermoplastic resin composition of the present invention had an excellent balance of impact resistance, flowability, heat resistance and surface appearance.
Comparative Examples 1 and 2 were good in impact resistance, heat resistance and surface appearance, but had poor fluidity with an MVR of less than 20 (cm ³ /10 min).
Comparative Examples 3 to 5 had good impact resistance and heat resistance, and had good fluidity with an MVR of 20 (cm ³ /10 min) or more, but the lubricant content of the rubber-reinforced styrene-based resin powder was less than 0.2 parts by mass, and the surface appearance was poor.

As described above, the thermoplastic resin composition of the present invention has an excellent balance of impact resistance, fluidity, heat resistance, and surface appearance, and can be used for a wide variety of applications, such as vehicle parts, electronic and electrical parts, and housing equipment parts, and is particularly suitable as a material for large molded parts.

Claims (4)

A thermoplastic resin composition containing a rubber-reinforced styrene-based resin powder, which satisfies the following conditions (1) and (2):
(1) The rubber-reinforced styrene-based resin powder contains 0.2 parts by mass or more of a lubricant per 100 parts by mass of the rubber-reinforced styrene-based resin component.
(2) The melt volume rate (220° C., 10 kg) of the thermoplastic resin composition is 20 (cm ³ /10 min) or more. 2. The thermoplastic resin composition according to claim 1, further satisfying the following condition (3):
(3) The following formula (i) is satisfied:
5≦X/Y≦250... Formula (i)
X: Melt volume rate of thermoplastic resin composition (220°C, 10 kg)
Y: Lubricant content of rubber-reinforced styrene-based resin powder A method for producing a thermoplastic resin composition having a melt volume rate (220°C, 10 kg) of 20 (cm3/10 min) or more, the composition being obtained by mixing 0.2 parts by mass or more (in terms of solid content) of an emulsion-state lubricant with ¹⁰⁰ parts by mass (in terms of solid content) of a rubber-reinforced styrene-based resin latex and then melt-kneading the resulting compound containing the powdered rubber-reinforced styrene-based resin powder. The method for producing a thermoplastic resin composition according to claim 3, further comprising satisfying the following formula (i):
5≦X/Y≦250... Formula (i)
X: Melt volume rate of thermoplastic resin composition (220°C, 10 kg)
Y: Lubricant content of rubber-reinforced styrene-based resin powder