THERMOPLASTIC RESIN COMPOSITION AND MOLDED ARTICLE THEREOF

Abstract

A thermoplastic resin composition of the present invention comprises: a graft copolymer (A) obtained by polymerizing a vinyl-based monomer mixture (m1) composed of one or more types of vinyl-based monomers, in the presence of a rubber-like polymer (a) having a volume average particle size of 80 to 250 nm; and a vinyl-based copolymer (B) composed of 31 to 50% by mass of a vinyl cyanide-based monomer unit, 50 to 69% by mass of an aromatic vinyl-based monomer unit, and 0 to 30% by mass of another vinyl-based monomer unit, wherein proportions of the graft copolymer (A) and the vinyl-based copolymer (B) are 30 to 70% by mass and 30 to 70% by mass, respectively, with respect to a total of 100% by mass of the graft copolymer (A) and the vinyl-based copolymer (B).

Claims

1. A thermoplastic resin composition comprising: a graft copolymer (A) obtained by polymerizing a vinyl-based monomer mixture (m1) composed of one or more types of vinyl-based monomers, in the presence of a rubber-like polymer (a) having a volume average particle size of 80 to 250 nm; and a vinyl-based copolymer (B) composed of 31 to 50% by mass of a vinyl cyanide-based monomer unit, 50 to 69% by mass of an aromatic vinyl-based monomer unit, and 0 to 30% by mass of another vinyl-based monomer unit, wherein proportions of said graft copolymer (A) and said vinyl-based copolymer (B) are 30 to 70% by mass and 30 to 70% by mass, respectively, with respect to a total of 100% by mass of said graft copolymer (A) and said vinyl-based copolymer (B).

2. The thermoplastic resin composition according to claim 1, wherein said vinyl-based copolymer (B) is composed of 31 to 43% by mass of said vinyl cyanide-based monomer unit, 57 to 69% by mass of said aromatic vinyl-based monomer unit, and 0 to 30% by mass of said another vinyl-based monomer unit.

3. The thermoplastic resin composition according to claim 1, wherein said vinyl-based copolymer (B) has a weight average molecular weight of 80,000 to 120,000.

4. The thermoplastic resin composition according to claim 1, wherein a proportion of all rubber-like polymer components contained in said thermoplastic resin composition with respect to a total mass of said thermoplastic resin composition is from 15 to 35% by mass.

5. A molded article using the thermoplastic resin composition according to claim 1.

Description

EXAMPLES

[0082] Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to these examples.

[0083] Hereinafter, the units parts and % refer to parts by mass and % by mass, respectively.

Measurement and Evaluation

Volume Average Particle Size

[0084] Using a dynamic light scattering type particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.), a volume-based particle size distribution of a polymer in a latex was measured by a dynamic light scattering method, and the volume average particle size was determined from the particle size distribution.

Weight Average Molecular Weight of Vinyl-Based Copolymer (B)

[0085] Using a solution obtained by dissolving a vinyl-based copolymer (B) in tetrahydrofuran as a measurement sample, a weight average molecular weight was measured by gel permeation chromatography (GPC) (manufactured by Tosoh Corporation) and calculated by a standard polystyrene conversion method.

Impact Resistance

[0086] A test piece (type A, notched) (molded article) was produced from a pelletized thermoplastic resin composition, using an injection molding machine (IS55FP-1.5A manufactured by Toshiba Machine Co., Ltd.) in accordance with ISO 3167. The Charpy impact strength of the test piece was measured in accordance with ISO 179 under an atmosphere of 20 C. The higher the Charpy impact strength, the better the impact resistance.

Color Developability

[0087] A plate-shaped test piece (molded article) having a length of 100 mm, a width of 100 mm and a thickness of 2 mm was produced from a pelletized thermoplastic resin composition under conditions of a cylinder set temperature of 260 C., a mold temperature of 60 C., and an injection rate of 20 g/sec, by using a 4-ounce injection molding machine (manufactured by The Japan Steel Works, Ltd.), and lightness (L* value) was measured by a colorimeter CM-508d (manufactured by Konica Minolta, Inc.). The smaller the L* value, the better the color developability.

Fluidity

[0088] The melt volume flow rate (MVR) of the pelletized thermoplastic resin composition was measured using a melt indexer (F-F01 manufactured by Toyo Seiki Seisaku-sho, Ltd.) in accordance with ISO 1133 at a cylinder temperature of 220 C. and a load of 10 kg. The larger the MVR value, the better the fluidity.

Production Example 1: Production of Graft Copolymer (A-1)

[0089] 240 parts of ion-exchanged water (hereinafter, simply referred to as water), 0.7 parts of dipotassium alkenyl succinate (LATEMUL ASK, manufactured by Kao Corporation), 50 parts of n-butyl acrylate, 0.15 parts of allyl methacrylate, 0.05 parts of 1,3-butanediol dimethacrylate and 0.1 parts of t-butyl hydroperoxide were charged into a reactor with stirring, and following replacement of the air inside of the reactor with nitrogen, the temperature of the contents was raised. An aqueous solution composed of 0.2 parts of sodium formaldehyde sulfoxylate, 0.00015 parts of ferrous sulfate heptahydrate, 0.00045 parts of disodium ethylenediaminetetraacetate, and 10 parts of water was added thereto at an internal temperature of 55 C. to initiate the polymerization. Following confirmation of heat generation from the polymerization, the jacket temperature was set to 75 C. and the polymerization was continued until heat generated by the polymerization reaction could no longer be detected, and the state was further maintained for 1 hour to obtain a latex of an acrylic rubber-like polymer (al) having a volume average particle size of 100 nm.

[0090] The internal temperature was continuously controlled at 70 C., and an aqueous solution composed of 0.2 parts of dipotassium alkenyl succinate (LATEMUL ASK, manufactured by Kao Corporation), 0.3 parts of sodium formaldehyde sulfoxylate, 0.001 parts of ferrous sulfate heptahydrate, 0.003 parts of disodium ethylenediaminetetraacetate and 10 parts of water was added. Then, the temperature was raised to 80 C. while adding dropwise a mixed solution composed of 12 parts of acrylonitrile, 28 parts of styrene, and 0.2 parts of t-butyl hydroperoxide over 80 minutes. After completion of the dropwise addition, the resulting mixture was held at a temperature of 80 C. for 30 minutes, and then cooled to 75 C., and a mixed solution composed of 3 parts of acrylonitrile, 7 parts of styrene, 0.02 parts of normal octyl mercaptan, and 0.05 parts of t-butyl hydroperoxide was added dropwise over 20 minutes. After completion of the dropwise addition, the resulting mixture was held at 75 C. for 60 minutes and then cooled to obtain a graft copolymer (A-1) latex. Then, 100 parts of a 2.0% aqueous solution of sulfuric acid was heated to 40 C., 100 parts of the graft copolymer (A-1) latex was gradually added dropwise to the aqueous solution while stirring the aqueous solution to solidify the graft copolymer (A-1), and the temperature was further raised to 95 C. and held for 10 minutes. Subsequently, the solidified product was dehydrated, washed and dried to obtain the graft copolymer (A-1) in the form of a powder.

Production Example 2: Production of Graft Copolymer (A-2)

[0091] 150 parts of water, 100 parts of 1,3-butadiene, 3.0 parts of a hardened fatty acid potassium soap, 0.3 parts of organic sodium sulfonate, 0.2 parts of tertiary dodecyl mercaptan, 0.3 parts of potassium persulfate having a 10-hour half-life temperature of 71 C. and 0.14 parts of potassium hydroxide were charged into a pressure resistant container, and the temperature was raised to 60 C. with stirring under a nitrogen atmosphere to initiate the polymerization. 5 parts of water in which 0.1 parts of potassium persulfate was dissolved was added to the pressure resistant container when the polymerization rate was 65% to raise the polymerization temperature to 70 C., and the polymerization was completed at a reaction time of 13 hours and a polymerization conversion rate of 90%. Then, 0.1 parts of sodium formaldehyde sulfoxylate was added to the pressure resistant container to obtain a butadiene-based rubber-like polymer having a volume average particle size of 80 nm. Subsequently, 1.25 parts of acetic acid was added thereto for enlargement, thereby obtaining a latex of a butadiene-based rubber-like polymer (a2) having a volume average particle size of 200 nm.

[0092] 40 parts of the obtained latex of the butadiene-based rubber-like polymer (a2) in terms of solid content, 170 parts of water, 0.3 parts of disproportionated potassium rosinate, 0.01 parts of ferrous sulfate heptahydrate, 0.2 parts of sodium pyrophosphate and 0.5 parts of crystalline glucose were charged into a reactor. The was raised to 60 C. while stirring the contents, and a mixture composed of 16 parts of acrylonitrile, 44 parts of styrene, 0.4 parts of cumene hydroperoxide, and 0.2 parts of t-dodecyl mercaptan was added dropwise over 100 minutes for polymerization. After completion of the dropwise addition, the temperature was raised to 75 C., and the resulting mixture was further stirred and held for 1 hour to complete the graft polymerization reaction. An antioxidant was added to the polymer obtained by the above reaction to obtain a latex of the graft copolymer (A-2). Subsequently, the obtained latex of the graft copolymer (A-2) was charged into a dilute aqueous solution of sulfuric acid having a liquid temperature of 80 C., and then heated to 90 C. over 30 minutes for coagulation, followed by dehydration, washing and drying, thereby obtaining the graft copolymer (A-2) in the form of a powder.

Production Example 3: Production of Graft Copolymer (A-3)

Production of Acid Group-Containing Copolymer Latex (K):

[0093] 200 parts of water, 2 parts of potassium oleate, 4 parts of sodium dioctyl sulfosuccinate, 0.003 parts of ferrous sulfate heptahydrate, 0.009 parts of disodium ethylenediaminetetraacetate, and 0.3 parts of sodium formaldehyde sulfoxylate were charged into a reactor under a nitrogen atmosphere, and the temperature was raised to 60 C. From the point at which the temperature reached 60 C., a mixture composed of 82 parts of n-butyl acrylate, 18 parts of methacrylic acid and 0.5 parts of cumene hydroperoxide was added dropwise in a continuous manner over 120 minutes. After completion of the dropwise addition, aging was further carried out for 2 hours while maintaining the temperature at 60 C. to obtain an acid group-containing copolymer latex (K) having a volume average particle size of 150 nm.

[0094] 310 parts of water, 1 part of dipotassium alkenyl succinate (LATEMUL ASK, manufactured by Kao Corporation), 80 parts of n-butyl acrylate, 0.48 parts of allyl methacrylate, 0.42 parts of triallyl isocyanurate, and 0.2 parts of t-butyl hydroperoxide were charged into a reactor with stirring, and following replacement of the air inside of the reactor with nitrogen, the temperature of the contents was raised. An aqueous solution composed of 0.3 parts of sodium formaldehyde sulfoxylate, 0.0001 parts of ferrous sulfate heptahydrate, 0.0003 parts of disodium ethylenediaminetetraacetate, and 10 parts of water was added thereto at an internal temperature of 55 C. to initiate the polymerization. Following confirmation of heat generation from the polymerization, the jacket temperature was set to 75 C. and the polymerization was continued until heat generated by the polymerization reaction could no longer be detected, and the state was further maintained for 1 hour to obtain an acrylic rubber-like polymer having a volume average particle size of 100 nm. Then, 1 part of a 5% sodium pyrophosphate aqueous solution was added as a solid, and the jacket temperature was controlled so that the internal temperature was 70 C. 3 parts of the acid group-containing copolymer latex (K) was added thereto as a solid at an internal temperature of 70 C., and the resulting mixture was stirred for 30 minutes while maintaining the internal temperature of 70 C. for enlargement to obtain an acrylic rubber-like polymer having a volume average particle size of 420 nm. Furthermore, an aqueous solution composed of 0.03 parts of sodium formaldehyde sulfoxylate, 0.002 parts of ferrous sulfate heptahydrate, 0.006 parts of disodium ethylenediaminetetraacetate, and 80 parts of water was added at an internal temperature of 70 C., and then a mixed solution composed of 20 parts of n-butyl acrylate, 0.12 parts of allyl methacrylate, 0.1 parts of triallyl isocyanurate and 0.02 parts of t-butyl hydroperoxide was added dropwise over 1 hour. After completion of the dropwise addition, the resulting mixture was held at a temperature of 70 C. for 1 hour and then cooled to obtain a latex of an acrylic rubber-like polymer (a3) having a volume average particle size of 450 nm.

[0095] 50 parts of the obtained latex of the acrylic rubber-like polymer (a3) in terms of solid content, 230 parts of water, 0.5 parts of dipotassium alkenyl succinate (LATEMUL ASK, manufactured by Kao Corporation), and 0.3 parts of sodium formaldehyde sulfoxylate were charged into a reactor, and following thorough replacement of the air inside of the reactor with nitrogen, the internal temperature was raised to 70 C. with stirring. Subsequently, the temperature was raised to 80 C. while adding dropwise a mixed solution composed of 15 parts of acrylonitrile, 35 parts of styrene and 0.5 parts of t-butyl hydroperoxide over 100 minutes. After completion of the dropwise addition, the resulting mixture was held at a temperature of 80 C. for 30 minutes and then cooled to obtain a graft copolymer (A-3) latex. Subsequently, 100 parts of a 1.5% aqueous solution of sulfuric acid was heated to 80 C., and 100 parts of the graft copolymer (A-3) latex was gradually added dropwise to the aqueous solution while stirring the aqueous solution to solidify the graft copolymer (A-3), and the temperature was further raised to 95 C. and held for 10 minutes. Then, the solidified product was dehydrated, washed and dried to obtain the graft copolymer (A-3) in the form of a powder.

[0096] The volume average particle sizes of the rubber-like polymers used for the graft copolymers (A-1) to (A-3), the types of rubber-like polymers, and the rubber contents and production methods of the graft copolymers (A-1) to (A-3) are listed in Table 1.

TABLE-US-00001 TABLE 1 Volume average particle size Graft of rubber-like Rubber-like Rubber Production copolymer polymer (nm) polymer content method (A-1) 100 Acrylic 50% Emulsion polymerization (A-2) 200 Diene-based 40% Emulsion polymerization (A-3) 450 Acrylic 50% Emulsion polymerization

Production Example 4: Production of Vinyl-Based Copolymer (B-1)

[0097] 34 parts of acrylonitrile and 66 parts of styrene were polymerized by a known suspension polymerization method to obtain an acrylonitrile-styrene copolymer having a reduced viscosity of 0.62 dl/g as measured at 25 C. from an N,N-dimethylformamide solution. This copolymer was used as a vinyl-based copolymer (B-1).

Production Example 5: Production of Vinyl-Based Copolymer (B-2)

[0098] 35 parts of acrylonitrile and 65 parts of styrene were polymerized by a known suspension polymerization method to obtain an acrylonitrile-styrene copolymer having a reduced viscosity of 0.78 dl/g as measured at 25 C. from an N,N-dimethylformamide solution. This copolymer was used as a vinyl-based copolymer (B-2).

Production Example 6: Production of Vinyl-Based Copolymer (B-3)

[0099] 42 parts of acrylonitrile and 58 parts of styrene were polymerized by a known suspension polymerization method to obtain an acrylonitrile-styrene copolymer having a reduced viscosity of 0.49 dug as measured at 25 C. from an N,N-dimethylformamide solution. This copolymer was used as a vinyl-based copolymer (B-3).

Production Example 7: Production of Vinyl-Based Copolymer (B-4)

[0100] 47 parts of acrylonitrile and 53 parts of styrene were polymerized by a known suspension polymerization method to obtain an acrylonitrile-styrene copolymer having a reduced viscosity of 0.71 dl/g as measured at 25 C. from an N,N-dimethylformamide solution. This copolymer was used as a vinyl-based copolymer (B-4).

Production Example 8: Production of Vinyl-Based Copolymer (B-5)

[0101] 27 parts of acrylonitrile and 73 parts of styrene were polymerized by a known suspension polymerization method to obtain an acrylonitrile-styrene copolymer having a reduced viscosity of 0.62 dl/g as measured at 25 C. from an N,N-dimethylformamide solution. This copolymer was used as a vinyl-based copolymer (B-5).

[0102] The vinyl cyanide-based monomer ratios (%), weight average molecular weights (Mw) and production methods of the vinyl-based copolymers (B-1) to (B-5) are listed in Table 2. The vinyl cyanide-based monomer ratio is a ratio of the vinyl cyanide-based monomer with respect to the total of all vinyl-based monomers.

TABLE-US-00002 TABLE 2 Vinyl Weight Vinyl- cyanide-based average based monomer molecular copolymer ratio (%) weight Production method (B-1) 34 90,000 Suspension polymerization (B-2) 35 150,000 Suspension polymerization (B-3) 42 55,000 Suspension polymerization (B-4) 47 115,000 Suspension polymerization (B-5) 27 110,000 Suspension polymerization

Production of Thermoplastic Resin Compositions and Molded Articles

Examples 1 to 5, Comparative Examples 1 to 3

[0103] The graft copolymer (A) and the vinyl-based copolymer (B) in amounts (parts) shown in Table 3, and 0.5 parts of ethylenebisstearylamide ALFLOW H50S, 1 part of an antioxidant ADK STAB AO-50 (manufactured by ADEKA Corporation), 1 part of a light stabilizer ADK STAB LA-77Y (manufactured by ADEKA Corporation), 0.5 parts of an ultraviolet absorber ADK STAB LA-31 (manufactured by ADEKA Corporation), 0.1 parts of magnesium oxide KYOWAMAG 150 (manufactured by Kyowa Chemical Industry Co., Ltd.) and 1 part of carbon black #966B (manufactured by Mitsubishi Chemical Corporation) were mixed using a Henschel mixer. The obtained mixture was melt-kneaded at 250 C. using a screw type extruder (TEX-30 type twin screw extruder manufactured by The Japan Steel Works, Ltd.), and then pelletized by a pelletizer to obtain a thermoplastic resin composition. The MVR values of the thermoplastic resin compositions are shown in Table 3. It should be noted that a blank column in Table 3 indicates that the corresponding component is not blended.

[0104] A test piece (molded article) was produced using the obtained pelletized thermoplastic resin composition. The Charpy impact strength (20 C.) and the color developability of the obtained molded article were evaluated. The results are shown in Table 3.

TABLE-US-00003 TABLE 3 Examples Comparative Examples 1 2 3 4 5 1 2 3 Thermoplastic Graft (A-1) 48 48 48 48 48 resin copolymer (A) (A-2) 60 60 composition (A-3) 48 (parts) Vinyl-based (B-1) 52 40 52 copolymer (B) (B-2) 52 (B-3) 52 (B-4) 52 (B-5) 52 40 Ratio of all rubber-like polymer components % 24 24 24 24 24 24 24 24 Charpy impact strength 20 C. kJ/m.sup.2 6 5 5 5 6 3 4.5 4 Color developability L* 6.5 4.4 7.8 6.4 7.2 6.9 4 14.8 MVR cm.sup.3/10 min 7 7 4 16 3 8 9 7

[0105] The thermoplastic resin compositions of Examples 1 to 5 exhibited favorable fluidity. In addition, the molded articles obtained by molding these thermoplastic resin compositions exhibited excellent impact resistance in a low temperature environment and excellent color developability.

[0106] On the other hand, in the thermoplastic resin compositions of Comparative Examples 1 and 2, since the vinyl cyanide-based monomer ratios of the vinyl-based copolymers (B) were less than 31% by mass, the obtained molded articles were inferior in impact resistance in a low temperature environment.

[0107] In the thermoplastic resin composition of Comparative Example 3, since the rubber-like polymer (a) had a volume average particle size of more than 250 nm, the obtained molded article was inferior in color developability.

INDUSTRIAL APPLICABILITY

[0108] The molded article using the thermoplastic resin composition of the present invention is useful as an automotive exterior part, an automotive interior part, office automation (OA) equipment, a home appliance part, or the like, and is particularly useful as an automotive exterior part.