Thermoplastic resin composition, resin molded article, and plated article

Abstract

The thermoplastic resin composition is a melt-kneaded product of a rubber-containing graft copolymer (A) obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubbery polymer and a copolymer (B) obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, independent of the rubber-containing graft copolymer (A). The calcium content relative to the total mass of the thermoplastic resin composition is 0.3 mass% or less.

Description

Thermoplastic resin compositions, resin molded products, and plated products

[0001] The present invention relates to a thermoplastic resin composition, a resin molded article, and a plated article. This application claims priority to Japanese Patent Application No. 2024-003220, filed on January 12, 2024, the contents of which are incorporated herein by reference.

[0002] Molded articles made of ABS resins have excellent impact resistance, mechanical strength, and chemical resistance, and are therefore used in a wide range of fields, including office equipment, information and communication equipment, electronic and electrical equipment, home appliances, automobiles, and construction. Furthermore, when plated, molded articles made of ABS resins have excellent plating appearance, high plating film adhesion strength, and excellent thermal cycle properties, and are therefore used in a wide variety of plastic plating applications. For example, in the automotive field, efforts are being made to expand their use to plating radiator grille parts, emblem parts, and the like.

[0003] Plating characteristics are easily affected by factors such as the properties of the resin composition forming the molded product and molding conditions. Therefore, even when a resin composition containing ABS resin is used, poor plating appearance may occur. Poor molding conditions can cause poor appearance phenomena such as peeling or lifting of the plating film, significantly reducing the commercial value of the final product. Therefore, a thermoplastic resin composition containing a graft copolymer with a different rubber particle size and a specific copolymer other than the graft copolymer in a specified ratio has been proposed as a thermoplastic resin composition that provides high plating film adhesion strength and does not cause swelling or cracking of the plating film even during thermal cycling (Patent Document 1).

[0004] Japanese Patent No. 6218347

[0005] However, when the thermoplastic resin composition of Patent Document 1 is plated, adhesion of the plating is obtained and a certain degree of effectiveness is exhibited in a thermal cycle test (also called a "heat cycle test" or "cooling cycle test," which is a test in which gradual temperature changes are repeatedly applied over time). However, in a thermal shock test (a test in which rapid temperature changes are repeatedly applied over time), the plating film is likely to become swollen or peel off, which can impair the decorative properties of the product or impair its function as a part.

[0006] The present invention aims to provide a thermoplastic resin composition that has excellent impact resistance and flowability during molding, and is also excellent in plating adhesion strength, plating appearance, and thermal cycle characteristics, and that can maintain plating adhesion even in a thermal shock test, as well as a resin molded article and a plated article (decorated part) made using the same.

[0007] The present invention encompasses the following aspects: [1] A thermoplastic resin composition which is a melt-kneaded mixture of a rubber-containing graft copolymer (A) obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubber polymer, and a copolymer (B) which is independent of the rubber-containing graft copolymer (A) and is obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, wherein 20 to 60 parts by mass of the rubber-containing graft copolymer (A) and 40 to 80 parts by mass of the copolymer (B) are mixed relative to 100 parts by mass of the rubber-containing graft copolymer (A) and the copolymer (B), and when the molecular weights of all polymers in the copolymer (B) are measured in terms of standard polystyrene by a GPC method, the proportion of polymers having a molecular weight of less than 50,000 is 20% by mass or less relative to the total mass of all polymers, and the total content of the rubber-containing graft copolymer (A) and the copolymer (B) is 75 to 100% by mass relative to the total mass of the thermoplastic resin composition, A thermoplastic resin composition, wherein the calcium content in the thermoplastic resin composition is 0.30% by mass or less relative to the total mass of the thermoplastic resin composition. [2] The thermoplastic resin composition according to [1], wherein, among all polymers of the copolymer (B), the proportion of polymers in which the proportion of repeating units derived from a vinyl cyanide compound is 10 to 30% by mass of all repeating units is 85 to 100% by mass relative to the total mass of all polymers. [3] The thermoplastic resin composition according to [1] or [2], wherein the copolymer (B) is a mixture of multiple copolymers (B), and when the mass average molecular weight of each copolymer (B) is measured in terms of standard polystyrene by a GPC method, the mixing proportion of the copolymers (B) having a mass average molecular weight of 50,000 to 300,000 relative to the total mass of the mixture is 85 to 100% by mass.[4] The copolymer (B) is a mixture of copolymer (BI) and copolymer (BII), the copolymer (BI) is a copolymer obtained by polymerization of a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, the content of the vinyl cyanide compound relative to the total mass of the monomer mixture is 10 to 30 mass%, and the mass average molecular weight of the copolymer (BI) is 50,000 to 150,000 as measured by a standard polystyrene method using a GPC method; and the copolymer (BII) is a copolymer obtained by polymerization of a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, the content of the vinyl cyanide compound relative to the total mass of the monomer mixture is 10 to 30 mass%, and the mass average molecular weight of the copolymer (BII) is more than 150,000 to 300,000 as measured by a standard polystyrene method using a GPC method. The thermoplastic resin composition according to any one of [1] to [3]. [5] The thermoplastic resin composition according to any one of [1] to [4], wherein the calcium content in the thermoplastic resin composition is 0.20 mass% or less relative to the total mass of the thermoplastic resin composition. [6] A resin molded article made of the thermoplastic resin composition according to any one of [1] to [5]. [7] A plated article having a plating film on at least a portion of the surface of the resin molded article according to [6].

[0008] The present invention provides a thermoplastic resin composition that is excellent in impact resistance and fluidity during molding, and that is also excellent in plating adhesion strength, plating appearance, and thermal cycle characteristics, and that can maintain plating adhesion even in a thermal shock test. Furthermore, it is possible to provide a resin molded product and a plated product (decorated part) using the same.

[0009] The following definitions of terms apply throughout the present specification and claims. A "resin molded article" is one obtained by molding the thermoplastic resin composition of the present invention. A "plated article" is one obtained by plating a resin molded article, and has a plating film on at least a portion of the surface of the resin molded article. "Thermal cycle characteristics" refer to the property of little change in the plating film of a plated article in a test in which gradual temperature changes are repeated cyclically over time. "Thermal shock characteristics" refer to the property of little change in the plating film of a plated article in a test in which rapid temperature changes are repeated cyclically over time. "(Meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. "(Meth)acrylate" is a general term for acrylate and methacrylate. The "to" symbol indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] Hereinafter, the rubber-containing graft copolymer (A), copolymer (B), and other components, which are materials for the thermoplastic resin composition of the present invention, will be described, and then the thermoplastic resin composition of the present invention will be described.

[0011] <Rubber-Containing Graft Copolymer (A)> The rubber-containing graft copolymer (A) is a copolymer in which a monomer component (a) is graft-polymerized onto a rubbery polymer. It is not easy to identify how the monomer component (a) is polymerized onto the rubbery polymer in the rubber-containing graft copolymer (A). That is, there are circumstances in which it is impossible or practical to directly identify the graft copolymer (A) based on its structure or properties (impossible or impractical circumstances). Therefore, it is more appropriate to define the graft copolymer (A) as "a rubbery polymer in which a monomer component is graft-polymerized."

[0012] (Rubber Polymer) Examples of the rubber polymer constituting the rubber-containing graft copolymer (A) include butadiene-based rubbers such as polybutadiene, styrene-butadiene copolymer, and acrylate-butadiene copolymer; conjugated diene-based rubbers such as styrene-isoprene copolymer; acrylic rubbers such as polybutyl acrylate; olefin-based rubbers such as ethylene-propylene copolymer; and silicone-based rubbers such as polyorganosiloxane. These rubber polymers can be used in the form of a monomer. The rubber polymer may have a composite rubber structure or a core / shell structure. As the rubber polymer, butadiene-based rubber is preferred because of its good balance of plating properties (plating adhesion strength and plating appearance) and color tone and impact resistance. These rubber polymers may be used alone or in combination of two or more.

[0013] The volume average particle diameter of the rubber polymer is preferably 200 to 500 nm, more preferably 250 to 440 nm, and even more preferably 280 to 380 nm. When the volume average particle diameter of the rubber polymer is equal to or greater than the lower limit, the thermal shock properties of the plated product are further improved. When the average particle diameter of the rubber polymer is equal to or less than the upper limit, the plating adhesion strength of the plated product is further increased. In addition, the flowability of the thermoplastic resin composition is improved.

[0014] The method for producing the rubber polymer is not particularly limited, but emulsion polymerization is preferred because it is easy to control the particle size. Known methods can be used for emulsion polymerization, and there are no particular limitations on the catalysts, emulsifiers, etc. that can be used, and various types can be used.

[0015] The rubber polymer may be an enlarged rubber. Furthermore, the average particle size, particle distribution, etc. can be adjusted by the enlargement procedure. Examples of enlargement methods include mechanical coagulation, chemical coagulation, and coagulation using an acid group-containing copolymer. Examples of chemical coagulation include adding an acidic substance to a rubber polymer latex to destabilize the emulsion stability and cause coagulation. Once the target particle size is reached, an alkaline substance is added to re-stabilize the rubber polymer latex. Examples of acidic substances include acetic acid, acetic anhydride, sulfuric acid, and phosphoric acid. Examples of alkaline substances include potassium hydroxide and sodium hydroxide. Examples of coagulation methods using an acid group-containing copolymer include mixing a rubber polymer latex with an acid group-containing copolymer latex to obtain an enlarged rubber latex. Examples of the acid group-containing copolymer latex include a latex of an acid group-containing copolymer obtained by polymerizing, in water, a monomer component including an acid group-containing monomer (e.g., a carboxy group-containing monomer such as (meth)acrylic acid), an alkyl (meth)acrylate monomer, and, if necessary, other monomers copolymerizable therewith.

[0016] The volume average particle diameter of the rubber polymer can be measured using a measuring instrument such as that used in the Examples described below. The volume average particle diameter of the rubber polymer can be controlled by adjusting the polymerization conditions (temperature, time, etc.) during the production of the rubber polymer, and the type and blending ratio of the monomers. Such rubber polymers are commercially available as rubber latexes. Furthermore, rubber polymer latexes with different volume average particle diameters can be mixed, and in this case, the volume average particle diameter can be adjusted within a preferred range.

[0017] (Monomer Component (a)) The monomer component (a) constituting the rubber-containing graft copolymer (A) contains an aromatic vinyl compound (a1), a vinyl cyanide compound (a2), and, if necessary, another vinyl compound (a3). Examples of the aromatic vinyl compound (a1) include styrene, α-methylstyrene, vinyltoluenes (e.g., p-methylstyrene, etc.), halogenated styrenes (e.g., p-bromostyrene, p-chlorostyrene, etc.), p-tert-butylstyrene, dimethylstyrene, and vinylnaphthalene. Among these, styrene and α-methylstyrene are preferred. These aromatic vinyl compounds (a1) may be used alone or in combination of two or more.

[0018] Examples of the vinyl cyanide compound (a2) include acrylonitrile and methacrylonitrile. Among these, acrylonitrile is preferred. These vinyl cyanide compounds (a2) may be used alone or in combination of two or more.

[0019] The other vinyl compound (a3) ​​may be a vinyl compound copolymerizable with the aromatic vinyl compound (a1) and the vinyl cyanide compound (a2). Examples of such vinyl compounds include alkyl methacrylates such as methyl methacrylate or ethyl methacrylate; alkyl acrylates such as methyl acrylate, ethyl acrylate, or butyl acrylate; maleimide compounds such as N-phenylmaleimide or N-cyclohexylmaleimide; and unsaturated carboxylic acid compounds such as (meth)acrylic acid, itaconic acid, or fumaric acid. These other vinyl compounds (a3) ​​may be used alone or in combination of two or more.

[0020] The proportions of each vinyl compound in the monomer component (a) are preferably such that, relative to the total mass of the monomer component (a), the aromatic vinyl compound (a1) is preferably 60 to 80 mass%, the vinyl cyanide compound (a2) is preferably 20 to 40 mass%, and the other vinyl compound (a3) ​​is preferably 0 to 20 mass%. However, the sum of the contents of the aromatic vinyl compound (a1), the vinyl cyanide compound (a2), and the other vinyl compound (a3) ​​does not exceed 100 mass% relative to the total mass of the monomer component (a). When the proportions of each compound are within the above ranges, the performance balance of the moldability of the thermoplastic resin composition, the plating adhesion strength of plated products, the thermal cycle properties, the thermal shock properties, and the impact strength is improved.

[0021] (Rubber Content in Rubber-Containing Graft Copolymer (A)) The content of the rubbery polymer component in the rubber-containing graft copolymer (A) is preferably 30 to 70 mass% and more preferably 40 to 60 mass% relative to the total mass of the rubber-containing graft copolymer (A). Therefore, the content of the monomer component (a) constituting the rubber-containing graft copolymer (A) is preferably 30 to 70 mass% and more preferably 40 to 60 mass% relative to the total mass of the rubber-containing graft copolymer (A), while maintaining the proportion of each vinyl compound in the monomer component (a) within the above-mentioned range. However, the sum of the contents of the rubbery polymer component and the monomer component (a) does not exceed 100 mass% relative to the total mass of the rubber-containing graft copolymer (A). When the content of the rubbery polymer-derived component in the rubber-containing graft copolymer (A) is within this range, the adhesion strength characteristics, thermal cycle characteristics, thermal shock characteristics, impact resistance, or fluidity in the plating process are more excellent.

[0022] The rubber-containing graft copolymer (A) is obtained by copolymerizing a monomer mixture (a) containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubber polymer. The polymerization method is not particularly limited, but emulsion polymerization is preferred because it allows for stable reaction control. Specifically, examples include a method in which the monomer mixture is charged all at once to a rubber polymer latex and then polymerized; a method in which a portion of the monomer mixture is first charged to a rubber polymer latex and polymerized as needed, while the remainder is added dropwise to the polymerization system; and a method in which the entire amount of the monomer mixture is added dropwise to a rubber polymer latex and polymerized as needed. These methods can be carried out in one or more stages. When carried out in two or more stages, it is also possible to vary the type and composition ratio of the monomers constituting the monomer mixture in each stage. The rubber-containing graft copolymer (A) obtained by emulsion polymerization is usually in the form of a latex.

[0023] Emulsion polymerization typically uses a radical polymerization initiator and an emulsifier. Examples of radical polymerization initiators include peroxides, azo initiators, and redox initiators that combine an oxidizing agent and a reducing agent. Among these, redox initiators are preferred, and sulfoxylate initiators that combine ferrous sulfate, ethylenediaminetetraacetic acid disodium salt, sodium formaldehyde sulfoxylate, and hydroperoxide are particularly preferred. The emulsifier is not particularly limited, but carboxylic acid salts such as sodium sarcosinate, potassium fatty acid, sodium fatty acid, dipotassium alkenyl succinate, and rosin acid soap are preferred because they provide excellent latex stability during radical polymerization and can increase the polymerization rate. Among these, dipotassium alkenyl succinate is preferred because it can suppress gas generation when the resulting rubber-containing graft copolymer and a thermoplastic resin composition containing the copolymer are molded at high temperatures. Specific examples of dipotassium alkenylsuccinate include dipotassium octadecenylsuccinate, dipotassium heptadecenylsuccinate, dipotassium hexadecenylsuccinate, etc. These emulsifiers may be used alone or in combination of two or more.

[0024] During polymerization, various known chain transfer agents may be added to control the molecular weight and graft ratio of the resulting rubber-containing graft copolymer (A). Polymerization conditions may be, for example, 30 to 95°C for 1 to 10 hours. The rubber-containing graft copolymer (A) is usually obtained in the form of a latex. Methods for recovering the rubber-containing graft copolymer (A) from its latex include, for example, a wet method in which the latex of the rubber-containing graft copolymer (A) is coagulated into a slurry by pouring it into hot water containing a coagulant; and a spray-drying method in which the rubber-containing graft copolymer (A) is semi-directly recovered by spraying the latex of the rubber-containing graft copolymer (A) into a heated atmosphere. Examples of coagulants used in the wet method include inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid; and metal salts such as calcium chloride, calcium acetate, and aluminum sulfate. The coagulant is selected depending on the emulsifier used in the polymerization. For example, when only a carboxylic acid soap such as a fatty acid soap or a rosin acid soap is used as the emulsifier, one or more of the coagulants described above can be used. When an emulsifier that exhibits stable emulsifying power even in the acidic range, such as sodium alkylbenzene sulfonate, is used as the emulsifier, a metal salt is preferred as the coagulant. Using a wet method, a rubber-containing graft copolymer (A) in a slurry form can be obtained. Methods for obtaining a dry rubber-containing graft copolymer (A) from this slurry rubber-containing graft copolymer (A) include first dissolving the remaining emulsifier residue in water and washing, then dehydrating the slurry using a centrifuge or a press dehydrator, and then drying using a flash dryer, etc.; or simultaneously dehydrating and drying using a squeeze dehydrator or extruder, etc. This method can obtain a dried rubber-containing graft copolymer (A) in a powder or particle form. While the washing conditions are not particularly limited, it is preferable to wash under conditions such that the amount of emulsifier residue contained in 100% by mass of the rubber-containing graft copolymer (A) after drying is 2% by mass or less.

[0025] (Graft Ratio) The graft ratio is the percentage ((Wa / Wd) × 100) of the mass (Wa) of the vinyl monomer mixture graft-polymerized onto the rubbery polymer relative to the mass (Wd) of the rubbery polymer. Generally, the graft ratio can be calculated from the acetone-insoluble portion of the rubber-containing graft copolymer (A) obtained after graft polymerization as follows: Acetone is added to the rubber-containing graft copolymer (A) and the mixture is shaken at 25°C for 2 hours to extract the acetone-soluble portion. The acetone-insoluble portion is then filtered and dried, and its mass is measured, and the graft ratio is calculated using the following formula (1). In the formula (1), "m" is the mass (g) of the rubber-containing graft copolymer (A) before extraction, "n" is the mass (g) of the acetone-insoluble portion, and "L" is the rubber content of the rubber-containing graft copolymer (A), i.e., the mass (% by mass) of the rubbery polymer. The rubber content of the rubber-containing graft copolymer (A) can be calculated from the polymerization recipe and polymerization addition rate, or determined from infrared absorption spectroscopy, etc. Graft ratio (%) = {(n-m x L) / (m x L)} x 100 (1)

[0026] The graft ratio of the rubber-containing graft copolymer (A) is not particularly limited, but is preferably 30 to 120% by mass, more preferably 35 to 100% by mass, even more preferably 40 to 80% by mass, particularly preferably 50 to 80% by mass, and most preferably 60 to 80% by mass. If the graft ratio of the rubber-containing graft copolymer (A) is within the above range, the impact resistance of the resin molded article is further improved, and from the viewpoint of plating processing, adhesion strength is easily exhibited.

[0027] (Mass Average Molecular Weight and Molecular Weight Distribution of Acetone-Soluble Fraction of Rubber-Containing Graft Copolymer (A)) The acetone-soluble fraction of the rubber-containing graft copolymer (A) is a non-grafted copolymer in the rubber-containing graft copolymer (A), and its composition falls within the range of the blending ratio of the monomer component (a). The mass average molecular weight (Mw) of the acetone-soluble fraction of the rubber-containing graft copolymer (A) is preferably 50,000 to 500,000, more preferably 60,000 to 300,000, and even more preferably 80,000 to 150,000. The molecular weight distribution (Mw / Mn) is preferably 2.0 to 5.0, more preferably 2.3 to 4.0, and even more preferably 2.6 to 3.5. When the mass average molecular weight (Mw) and molecular weight distribution (Mw / Mn) are within the above ranges, the resulting thermoplastic resin composition has better fluidity and impact resistance, and the plated product has an improved balance of plating adhesion strength, thermal cycle characteristics, and thermal shock characteristics. The mass average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the ungrafted copolymer (acetone solubles) can be measured as polystyrene equivalent values ​​by GPC. Details are as described in the Examples section below. The content of acetone solubles in the rubber-containing graft copolymer (A) having a molecular weight of less than 50,000 is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the acetone solubles.

[0028] The rubber-containing graft copolymer (A) may be a single type or a mixture of multiple types, such as those having different volume average particle sizes of rubber polymers, different monomer composition ratios or mass average molecular weights of acetone soluble components, or those produced by different methods.

[0029] <Copolymer (B)> Copolymer (B) is a copolymer obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the absence of a rubbery polymer. When the molecular weight of all polymers of copolymer (B) melt-kneaded as a material for the thermoplastic resin composition of the present invention is measured by GPC in terms of standard polystyrene, the proportion of polymers having a molecular weight of less than 50,000 is 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 6.5% by mass or less, relative to the total mass of all polymers. The lower limit of this proportion may be 0% by mass. By keeping it within this range, impact resistance and thermal shock properties are more excellent.

[0030] The proportion of molecular weights of less than 50,000 in copolymer (B) is measured using gel permeation chromatography (GPC). From the measurement results (dissolution chart with the vertical axis representing the elution amount and the horizontal axis representing the retention time or elution volume) of the entire polymer of copolymer (B) as a sample, an elution peak showing the molecular weight distribution of the eluted polymer is drawn. The content of polymers with a molecular weight of less than 50,000 among all polymers in the sample can be calculated from the proportion of the area of ​​the molecular weight in the elution peak. Here, this molecular weight corresponds to the mass molecular weight. Note that this value is converted from standard polystyrene of known molecular weight.

[0031] Of all the polymers in copolymer (B) melt-kneaded as materials for the thermoplastic resin composition of the present invention, the proportion of polymers containing 10 to 30% by mass of repeating units derived from a vinyl cyanide compound (out of 100% by mass of all repeating units) is preferably 85 to 100% by mass relative to the total mass of all polymers. By keeping the proportion within this range, impact resistance, thermal shock properties, and the like are improved. Here, the proportion of repeating units derived from a vinyl cyanide compound relative to all repeating units is preferably 10 to 30% by mass, more preferably 15 to 29% by mass, and even more preferably 20 to 28% by mass. The proportion of repeating units derived from a vinyl cyanide compound relative to all repeating units reflects the content of the vinyl cyanide compound relative to the total mass of the monomer mixture during copolymerization, and is equivalent to that content.

[0032] The copolymer (B) may further contain repeating units derived from other copolymerizable compounds other than the aromatic vinyl compound and the vinyl cyanide compound, as necessary. Preferred examples of the aromatic vinyl compound, the vinyl cyanide compound, and the other copolymerizable compound used as needed as monomers of the copolymer (B) include the compounds (a1), (a2), and (a3) ​​listed above for the rubber-containing graft copolymer (A), respectively.

[0033] The copolymer (B) to be melt-kneaded as a material for the thermoplastic resin composition of the present invention is a material independent of the rubber-containing graft copolymer (A), and may be a single type polymerized alone or a mixture of multiple types polymerized individually.

[0034] [Mixture of Copolymers (B)] When the copolymer (B) melt-kneaded as a material for the thermoplastic resin composition of the present invention is a mixture of multiple copolymers (B), the mass average molecular weight of each copolymer (B) before mixing can be measured individually using GPC in terms of standard polystyrene. After this measurement, the blending ratio Z of copolymers (B) having a mass average molecular weight of 50,000 to 300,000 relative to the total mass of the mixture is preferably 85 to 100 mass%. This range can further improve the impact resistance, thermal shock properties, etc., of the present invention. For example, in a mixture of 10 parts by mass of copolymer (B) having a mass average molecular weight of 40,000 and 40 parts by mass of copolymer (B) having a mass average molecular weight of 100,000, the blending ratio Z is calculated to be 80 mass% (40 parts by mass / 50 parts by mass × 100%).

[0035] The mixture of copolymer (B) is preferably a mixture of specific copolymer (BI) and copolymer (BII).

[0036] The copolymer (BI) is a copolymer obtained by polymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, in which the content of the vinyl cyanide compound (i.e., the repeating units derived from the vinyl cyanide compound in the copolymer (BI)) relative to the total mass of the monomer mixture is 10 to 30 mass%, and the mass average molecular weight of the copolymer (BI) is 50,000 to 150,000 as calculated using standard polystyrene standards by GPC.

[0037] The content of repeating units derived from a vinyl cyanide compound in all repeating units constituting copolymer (BI) is preferably 12 to 28 mass%, more preferably 15 to 26 mass%, and even more preferably 20 to 25 mass%, in which range the thermoplastic resin composition according to the present invention has an improved performance balance among the flowability, plating adhesion strength of plated products, thermal cycle properties, and thermal shock properties.

[0038] The mass average molecular weight of the copolymer (BI) is preferably 60,000 to 140,000, more preferably 70,000 to 130,000, and even more preferably 80,000 to 120,000. When the mass average molecular weight of the copolymer (BI) is within this range, the fluidity of the thermoplastic resin composition according to the present invention and the balance of performances of the plating adhesion strength, thermal cycle characteristics, thermal shock characteristics, and impact strength of the plated product are improved.

[0039] Copolymer (BII) is a copolymer obtained by polymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, in which the content of the vinyl cyanide compound (i.e., repeating units derived from the vinyl cyanide compound in copolymer (BII)) relative to the total mass of the monomer mixture is 10 to 30 mass%, and the mass average molecular weight of copolymer (BII) is greater than 150,000 and less than 300,000, as calculated using standard polystyrene standards by GPC.

[0040] The content of the vinyl cyanide compound in all repeating units constituting copolymer (BII) is preferably 20 to 30 mass%, more preferably 24 to 29.5 mass%, and even more preferably 26 to 29 mass%, in this range, which improves the fluidity of the thermoplastic resin composition according to the present invention and the balance of performance among the plating adhesion strength, thermal cycle properties, thermal shock properties, and impact strength of plated products.

[0041] The mass average molecular weight of copolymer (BII) is preferably 155,000 to 290,000, more preferably 160,000 to 270,000, and even more preferably 165,000 to 250,000. When the mass average molecular weight of copolymer (BII) is within this range, the fluidity of the thermoplastic resin composition according to the present invention and the balance of performance among the plating adhesion strength, thermal cycle properties, thermal shock properties, and impact strength of plated products are improved.

[0042] When copolymer (BI) and copolymer (BII) are mixed as copolymer (B) to be melt-kneaded as a material for the thermoplastic resin composition of the present invention, the mixing ratio of copolymer (BI) / copolymer (BII) is preferably 95 to 40% by mass / 5 to 60% by mass, more preferably 90 to 50% by mass / 10 to 50% by mass, and even more preferably 80 to 70% by mass / 20 to 30% by mass, when the total of copolymer (BI) and copolymer (BII) is 100% by mass. By having the mixing ratio of copolymer (BI) and copolymer (BII) in this range, the thermal shock properties are further improved.

[0043] Various copolymers (B) (e.g., copolymer (BI)) can be produced by copolymerizing an aromatic vinyl compound, a vinyl cyanide compound, and, if necessary, other copolymerizable compounds. As the polymerization method, any of known polymerization methods such as emulsion polymerization, suspension polymerization, bulk polymerization, or a combination thereof can be applied.

[0044] When copolymer (BI), copolymer (BII), and copolymer (BV) which does not fall under copolymer (BI) or copolymer (BII) are mixed as copolymer (B) to be melt-kneaded as a material for the thermoplastic resin composition of the present invention, the mixing ratio of copolymer (BV) to the total mass of copolymer (B) is preferably 0 to 15 masses.

[0045] When the molecular weight of all polymers of copolymer (B) melt-kneaded as a material for the thermoplastic resin composition of the present invention is measured by GPC in terms of standard polystyrene, the mass average molecular weight is preferably 50,000 to 300,000, more preferably 60,000 to 280,000, even more preferably 80,000 to 250,000, and most preferably 90,000 to 200,000. In another aspect, the mass average molecular weight may be 85,000 to 200,000, 100,000 to 150,000, or 110,000 to 150,000. Having the mass average molecular weight of all polymers of copolymer (B) within this range improves the balance of plating adhesion strength, thermal cycle properties, and thermal shock properties of plated products made from the thermoplastic resin composition of the present invention.

[0046] <Other Components> Examples of other components include various additives and other resins. Examples of additives include known antioxidants, light stabilizers, UV absorbers, lubricants, plasticizers, stabilizers, transesterification reaction inhibitors, hydrolysis inhibitors, release agents, antistatic agents, colorants (e.g., pigments, dyes, etc.), fillers such as carbon fiber, glass fiber, wollastonite, calcium carbonate, silica, and talc, flame retardants such as bromine-based flame retardants and phosphorus-based flame retardants, flame retardant assistants such as antimony trioxide, anti-drip agents such as fluororesins, antibacterial agents, antifungal agents, silicone oils, and coupling agents. These additives may be used alone or in combination of two or more. Other resins include rubber-reinforced styrene resins such as HIPS resin, ABS resin, ASA resin, AES resin, and SAS resin, AS resin, polystyrene resin, nylon resin, methacrylic resin, polyvinyl chloride resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene ether resin, and polycarbonate resin, etc. Blends of two or more of these resins may also be used, or these resins may be modified with a compatibilizer, functional group, or the like.

[0047] Any of the essential components and optional components used in the present invention may be products recovered from processes such as polymerization processes, processing processes, and molding processes, or recycled products recovered from the market, provided that there is no problem with quality.

[0048] <<Thermoplastic Resin Composition>> The thermoplastic resin composition of the present invention is a melt-kneaded mixture of a rubber-containing graft copolymer (A) and a copolymer (B). The rubber-containing graft copolymer (A) is obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubbery polymer. The copolymer (B) is obtained, independently of the rubber-containing graft copolymer (A), by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the absence of a rubbery polymer.

[0049] The thermoplastic resin composition of the present invention may further contain other components in addition to the rubber-containing graft copolymer (A) and copolymer (B), as needed, within a range that does not impair the effects of the present invention. The content of the other components is preferably 0 to 25 parts by mass, more preferably 0 to 10 parts by mass, relative to 100 parts by mass of the total mass of the rubber-containing graft copolymer (A) and copolymer (B).

[0050] From the viewpoint of ensuring that the thermoplastic resin composition of the present invention fully exhibits the above-mentioned effects, the total content of the rubber-containing graft copolymer (A) and the copolymer (B) relative to the total mass of the thermoplastic resin composition is preferably 75 to 100 mass%, more preferably 85 to 100 mass%, and even more preferably 95 to 100 mass%.

[0051] In the thermoplastic resin composition of the present invention, when the total mass of the rubber-containing graft copolymer (A) and copolymer (B) is taken as 100 parts by mass, the content of the rubber-containing graft copolymer (A) is preferably 20 to 60 parts by mass and the content of copolymer (B) is 40 to 80 parts by mass, the content of the rubber-containing graft copolymer (A) is preferably 25 to 55 parts by mass and the content of copolymer (B) is 45 to 75 parts by mass, and the content of the rubber-containing graft copolymer (A) is more preferably 30 to 50 parts by mass and the content of copolymer (B) is 50 to 70 parts by mass. When the contents of the rubber-containing graft copolymer (A) and copolymer (B) are within these ranges, the adhesion strength characteristics, thermal cycle characteristics, thermal shock characteristics, impact resistance, and fluidity in the plating process are excellent.

[0052] The calcium content of the thermoplastic resin composition of the present invention relative to the total mass is 0.30 mass% or less, more preferably 0.20 mass% or less, even more preferably 0.10 mass% or less, most preferably 0.05 mass% or less, and may be 0 mass% or less, which is below the detection limit. By being in this range, the plating appearance is excellent, and further, the thermal cycle characteristics and thermal shock characteristics are also excellent.

[0053] In the thermoplastic resin composition of the present invention, when the total mass of the rubber-containing graft copolymer (A) and the copolymer (B) is taken as 100 parts by mass, the content of the rubber polymer is preferably in the range of 10 to 30 parts by mass, more preferably 12 to 28 parts by mass, even more preferably 15 to 25 parts by mass, and most preferably 16 to 20 parts by mass. By being within this range, impact resistance, flowability, adhesion strength properties in a plating process, thermal cycle properties, and thermal shock properties are more excellent.

[0054] The rubber-containing graft copolymer (A) used as a material for the thermoplastic resin composition of the present invention may contain a component (non-graft component) that is not grafted to the rubbery polymer. This non-graft component is not polymerized as an independent copolymer (B) in the absence of the rubbery polymer, and is therefore not considered to be copolymer (B). However, when the thermoplastic resin composition of the present invention is dissolved in a solvent such as THF and the soluble fraction is used as sample Z for measuring molecular weight by GPC, it may be difficult to distinguish between copolymer (B) and the non-graft component contained in sample Z. Therefore, for convenience, it is preferable to measure all of these polymers without distinguishing between copolymer (B) and the non-graft component contained in sample Z and calculate the molecular weight in polystyrene equivalent by GPC. When the molecular weights of all polymers contained in sample Z are measured in standard polystyrene equivalent by GPC, the content of polymers having a molecular weight of less than 50,000 is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, and most preferably 4.5% by mass or less, based on the total mass of all polymers. By setting the content within this range, the thermoplastic resin composition of the present invention will have better impact resistance and thermal shock properties.

[0055] <Method for producing thermoplastic resin composition> The thermoplastic resin composition of the present invention is produced by mixing and melt-kneading the rubber-containing graft copolymer (A), the copolymer (B), and other components used as needed. There are no particular limitations on the method for mixing and kneading the components of the thermoplastic resin composition, and any common mixing and kneading method can be used. For example, a method in which the mixture is kneaded using an extruder, a Banbury mixer, or a kneading roll, and then cut and pelletized using a pelletizer, etc., can be mentioned. The thermoplastic resin composition of the present invention is molded into a resin molded product.

[0056] The thermoplastic resin composition of the present invention contains a rubber-containing graft copolymer (A) and a copolymer (B), and when the total mass of the rubber-containing graft copolymer (A) and the copolymer (B) is taken as 100 parts by mass, the content of the rubber-containing graft copolymer (A) is 20 to 60 parts by mass and the content of the copolymer (B) is 40 to 80 parts by mass. This allows the composition to exhibit excellent plating adhesion strength, and in thermal cycle characteristics and thermal shock characteristics, the plating appearance is less likely to change, and a resin molded product with excellent impact resistance can be obtained. The composition also has excellent fluidity during molding.

[0057] <<Resin Molded Article>> The resin molded article of the present invention is made of the thermoplastic resin composition of the present invention described above. The resin molded article of the present invention can be obtained by molding the thermoplastic resin composition of the present invention. The molding method is not particularly limited. Examples of molding methods include injection molding, extrusion molding, compression molding, insert molding, vacuum molding, and blow molding.

[0058] <Plated Product> The plated product of the present invention comprises the resin molded product of the present invention described above and a plating film formed on at least a portion of the surface of the resin molded product. The plated product of the present invention is obtained by subjecting the resin molded product of the present invention to a plating treatment. The plating method is not limited in any way. Examples of the plating method include an electroless plating method, a direct plating method, and a non-chromium plating method.

[0059] Since the plated product of the present invention uses the resin molded product of the present invention, the adhesive strength between the resin molded product and the plating film is excellent, the plating appearance is less likely to change during thermal cycle and thermal shock, and the impact resistance is also excellent.

[0060] The plated product of the present invention can be suitably used in a wide variety of applications including office automation (OA) equipment, information and communication equipment, electronic and electrical equipment, home appliances, automobiles, and architecture.

[0061] The present invention will be described in more detail below with reference to synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples as long as the gist of the invention is not exceeded. In the following, "parts" means "parts by mass" and "%" means % by mass.

[0062] [Measurement and Evaluation Methods] <Volume Average Particle Diameter of Rubber Polymer> A water-diluted solution of the rubber polymer latex used in the synthesis of the rubber-containing graft copolymer (A) was measured for its volume average particle diameter using a nanoparticle particle size distribution analyzer (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) based on the principle of dynamic scattering theory.

[0063] <Composition Ratio of Copolymer (B)> The composition ratio of copolymer (B) (ratio of repeating units derived from monomers) was determined by quantifying the amount of remaining monomer after completion of the reaction using a gas chromatograph (manufactured by Shimadzu Corporation, "GC-2014") and calculating backward from this value to determine the fixed amount (amount incorporated into the copolymer as monomer units).

[0064] <Weight average molecular weight (Mw) and number average molecular weight (Mn) of copolymer (B)> A solution obtained by dissolving copolymer (B) in tetrahydrofuran (THF) was used as a measurement sample, and the retention time or elution volume of copolymer (B) was measured using a GPC apparatus (manufactured by Tosoh Corporation, "TOSOH EcoSEC HLC-8320GPC"). Based on the measurement results, the weight average molecular weight and number average molecular weight of copolymer (B) were calculated using a standard polystyrene conversion method.

[0065] The GPC measurement conditions were as follows: [Measurement conditions] Eluent: THF, flow rate: 0.35 ml / min, injection volume: 10 μl [Set temperatures] Pump oven: 40°C, column oven: 40°C [Columns used] TSKgel Supermultipore HZ-M / TSKgel guard column SuperMPHZ-M were used in series connection. [Standard product information] PStQuick MP-M Part No. 0021913 manufactured by Tosoh Corporation

[0066] In addition, when calculating the mass average molecular weight in copolymer (B), the content ratio of polymers having a molecular weight of less than 50,000 among all polymers in copolymer (B) was calculated from the area ratio of polymers having a molecular weight of less than 50,000 among the total area of ​​peaks showing the elution of all polymers (elution curve related to the mass average molecular weight) by chart and data analysis of the GPC measurement results.

[0067] When the copolymer (B) to be blended into the thermoplastic resin composition and melt-kneaded is a mixture of multiple types of copolymers (B) that have been synthesized individually, the mixture was dissolved in THF, and the resulting solution was used as a measurement sample, and measurement was performed using the above-mentioned GPC apparatus to calculate "the content ratio of polymers having a molecular weight of less than 50,000 among all polymers of all copolymers (B) blended into the thermoplastic resin composition."

[0068] When the copolymer (B) to be blended into the thermoplastic resin composition and melt-kneaded is a mixture of multiple copolymers (B) synthesized individually, the mixture is dissolved in THF, and the resulting solution is used as a measurement sample. The solution is measured using the above-mentioned GPC apparatus to calculate the "mass average molecular weight of all copolymers (B) blended into the thermoplastic resin composition." <Mass average molecular weight (Mw) and number average molecular weight (Mn) of acetone-soluble fraction of rubber-containing graft polymer (A)> In the method for measuring the mass average molecular weight (Mw) and number average molecular weight (Mn) of copolymer (B), the "copolymer (B)" is replaced with the "acetone-soluble fraction of rubber-containing graft polymer (A)," and the mass average molecular weight (Mw) and number average molecular weight (Mn) of the acetone-soluble fraction of rubber-containing graft polymer (A) were measured.

[0069] [Synthesis Examples of Rubber-Containing Graft Copolymer (A)] <Synthesis Example 1: Production of Rubber-Containing Graft Copolymer (A-1)> A nitrogen-purged reactor was charged with 125 parts of pure water, 0.5 parts of glucose, 0.5 parts of sodium pyrophosphate, 0.005 parts of ferrous sulfate, 32 parts (solids equivalent) of a polybutadiene (BR) latex having a volume average particle size of 300 nm, and 8 parts (solids equivalent) of a polybutadiene (BR) latex having a volume average particle size of 600 nm (volume average particle size of mixed BR: 360 nm), and the temperature inside the reactor was raised to 65°C with stirring. Polymerization was initiated when the internal temperature reached 65°C, and 43.2 parts of styrene (ST), 16.8 parts of acrylonitrile (AN), and 0.2 parts of a chain transfer agent t-dodecyl mercaptan mixture were continuously added over 5 hours. Simultaneously, an aqueous solution of polymerization initiators, cumene hydroperoxide (0.2 parts) and disproportionated rosin acid sodium salt (0.4 parts), was continuously added over 7 hours to complete the reaction. To the resulting latex, 1 part of 2,2'-methylenebis(4-methyl-6-t-butylphenol) was added per 100 parts of latex solids. Subsequently, this latex (100 parts of polymer component) was coagulated using 5% sulfuric acid to give a ratio of 2 parts of coagulant, followed by washing, filtration, and drying to obtain a powdery rubber-containing graft copolymer (A-1). This rubber-containing graft copolymer (A-1) had a rubber content of 40.1% and a graft ratio of 62%. Furthermore, the acetone-soluble portion contained 27.2% vinyl cyanide monomer, a mass-average molecular weight (Mw) of 122,000, and a molecular weight distribution (Mw / Mn) of 2.9.

[0070] Synthesis Example 2: Production of Rubber-Containing Graft Copolymer (A-2) A nitrogen-purged reactor was charged with 125 parts of pure water, 0.5 parts of glucose, 0.5 parts of sodium pyrophosphate, 0.005 parts of ferrous sulfate, and 50 parts (solids content equivalent) of polybutadiene (BR) latex having a volume average particle size of 300 nm, and the temperature inside the reactor was raised to 65°C with stirring. Polymerization was initiated when the internal temperature reached 65°C. Using 36 parts of styrene (ST) and 14 parts of acrylonitrile (AN), a mixture of this and chain transfer agents (0.12 parts of terpinolene, 0.13 parts of α-methylstyrene dimer) was continuously added over 5 hours. Simultaneously, an aqueous solution of cumene hydroperoxide (0.2 parts), a polymerization initiator, and disproportionated rosin acid sodium salt (0.4 parts) was continuously added over 7 hours to complete the reaction. To the obtained latex, 1 part of 2,2'-methylenebis(4-methyl-6-t-butylphenol) was added per 100 parts of latex solids. Subsequently, this latex (100 parts of polymer component) was coagulated using 5% sulfuric acid to give a ratio of 2 parts of coagulant, followed by washing, filtration, and drying to obtain a powdery rubber-containing graft copolymer (A-2). This rubber-containing graft copolymer (A-2) had a rubber content of 49.8% and a graft ratio of 60%. Furthermore, with regard to the acetone solubles, the vinyl cyanide monomer component was 27.2%, the mass average molecular weight (Mw) was 280,000, and the molecular weight distribution (Mw / Mn) was 4.9.

[0071] Synthesis Example 3: Production of Rubber-Containing Graft Copolymer (A-3) A nitrogen-purged reactor was charged with 125 parts of pure water, 0.5 parts of glucose, 0.5 parts of sodium pyrophosphate, 0.005 parts of ferrous sulfate, and 40 parts (solids content equivalent) of polybutadiene (BR) latex having a volume average particle size of 200 nm, and the temperature inside the reactor was raised to 65°C with stirring. Polymerization was initiated when the internal temperature reached 65°C. Using 44.4 parts of styrene (ST) and 15.6 parts of acrylonitrile (AN), this and 0.22 parts of a t-dodecyl mercaptan mixture as a chain transfer agent were continuously added over 5 hours. Simultaneously, an aqueous solution of cumene hydroperoxide (0.2 parts) and disproportionated rosin acid sodium salt (0.4 parts), which served as a polymerization initiator, was continuously added over 7 hours to complete the reaction. To the obtained latex, 1 part of 2,2'-methylenebis(4-methyl-6-t-butylphenol) was added per 100 parts of latex solids. Subsequently, this latex (100 parts of polymer component) was coagulated using 5% sulfuric acid to give a ratio of 2 parts of coagulant, followed by washing, filtration, and drying to obtain a powdery rubber-containing graft copolymer (A-3). This rubber-containing graft copolymer (A-3) had a rubber content of 40.2% and a graft ratio of 80%. Furthermore, with regard to the acetone solubles, the vinyl cyanide monomer component was 27.2%, the mass average molecular weight (Mw) was 90,000, and the molecular weight distribution (Mw / Mn) was 2.5.

[0072] Synthesis Example 4: Production of Rubber-Containing Graft Copolymer (A-4) A nitrogen-purged reactor was charged with 125 parts of pure water, 0.5 parts of glucose, 0.5 parts of sodium pyrophosphate, 0.005 parts of ferrous sulfate, and 65 parts (solids content equivalent) of polybutadiene (BR) latex having a volume average particle size of 300 nm, and the temperature inside the reactor was raised to 65°C with stirring. Polymerization was initiated when the internal temperature reached 65°C. Using 24.5 parts of styrene (ST) and 10.5 parts of acrylonitrile (AN), this and 0.19 parts of a t-dodecyl mercaptan mixture as a chain transfer agent were continuously added over 5 hours. Simultaneously, an aqueous solution of cumene hydroperoxide (0.18 parts) and disproportionated rosin acid sodium salt (0.4 parts), which served as a polymerization initiator, was continuously added over 7 hours to complete the reaction. To the obtained latex, 1 part of 2,2'-methylenebis(4-methyl-6-t-butylphenol) was added per 100 parts of latex solids. Subsequently, this latex (100 parts of polymer component) was coagulated using 5% sulfuric acid to give a ratio of 2 parts of coagulant, followed by washing, filtration, and drying to obtain a powdery rubber-containing graft copolymer (A-4). This rubber-containing graft copolymer (A-4) had a rubber content of 64.9% and a graft ratio of 39%. Furthermore, with regard to the acetone solubles, the vinyl cyanide monomer component was 27.2%, the mass average molecular weight (Mw) was 115,000, and the molecular weight distribution (Mw / Mn) was 3.9.

[0073] [Synthesis Example of Copolymer (B)] <Synthesis Example 5: Copolymer (BI-1)> After purging the atmosphere in a stainless steel autoclave equipped with ribbon blades with nitrogen, 76.5 parts by mass of styrene, 23.5 parts by mass of acrylonitrile, and 20 parts by mass of toluene were continuously added to the reaction vessel. A solution of 0.26 parts by mass of tert-dodecyl mercaptan and 5 parts by mass of toluene as a molecular weight modifier, and a solution of 0.1 parts by mass of 1,1'-azobis(cyclohexane-1-carbonitrile) and 5 parts by mass of toluene as a polymerization initiator were continuously fed. The temperature was controlled at 110°C for polymerization. After the polymerization conversion reached 75%, the resulting copolymer solution was directly subjected to devolatilization of unreacted monomers and solvent using a twin-screw, three-stage vented extruder to obtain Copolymer (BI-1). The resulting copolymer had a mass average molecular weight of 95,000 and a vinyl cyanide compound content of 23.5%.

[0074] Synthesis Example 6 Copolymer (BI-2) Except for using 0.47 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier, copolymer (BI-2) was obtained in the same manner as in Synthesis Example 5. The mass average molecular weight of the obtained copolymer was 55,000, and the content of vinyl cyanide compound was 23.5%.

[0075] Synthesis Example 7 Copolymer (BI-3) Copolymer (BI-3) was obtained in the same manner as in Synthesis Example 5, except that 86.0 parts by mass of styrene, 14.0 parts by mass of acrylonitrile, and 0.50 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier were used. The mass average molecular weight of the obtained copolymer was 40,000, and the content of vinyl cyanide compound was 14.0%.

[0076] Synthesis Example 8: Copolymer (BI-4) Except for using 0.36 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier, copolymer (BI-4) was obtained in the same manner as in Synthesis Example 7. The mass average molecular weight of the obtained copolymer was 75,000, and the content of vinyl cyanide compound was 14.0%.

[0077] Synthesis Example 9 Copolymer (BI-5) Copolymer (BI-6) was obtained in the same manner as in Synthesis Example 5, except that 81.0 parts by mass of styrene, 19.0 parts by mass of acrylonitrile, and 0.20 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier were used. The mass average molecular weight of the obtained copolymer was 120,000, and the content of vinyl cyanide compound was 19.0%.

[0078] Synthesis Example 10: Copolymer (BI-6) A reactor was charged with 125 parts of water, 0.5 parts of calcium phosphate (TCP), 0.003 parts of potassium alkenyl succinate, 0.05 parts of 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 0.04 parts of 1,1-di(t-hexylperoxy)cyclohexane, 0.04 parts of t-butylperoxy-2-ethylhexyl carbonate, 0.38 parts of t-dodecyl mercaptan, 76.5 parts of styrene, and a monomer mixture consisting of 23.5 parts of acrylonitrile. The reaction was heated from a reaction start temperature of 65 ° C. for 6.5 hours, and then allowed to reach 125 ° C. After further reaction at 125 ° C. for 1 hour, a copolymer slurry was obtained. After cooling, the slurry was centrifuged and washed with 200 parts of water to obtain copolymer (BI-6). The copolymer thus obtained had a mass average molecular weight of 95,000, a vinyl cyanide compound content of 23.5%, and a residual Ca content derived from TCP of 0.05%.

[0079] Synthesis Example 11: Copolymer (BI-7) A copolymer slurry was obtained in the same manner as in Synthesis Example 10, except that calcium phosphate (TCP) was used in an amount of 0.8 parts. After cooling, the slurry was centrifuged and dehydrated while being washed with 100 parts of water, to obtain copolymer (BI-7). The polymer composition of the obtained copolymer was the same as that of copolymer (BI-6), and the residual Ca content derived from TCP was 0.3%.

[0080] Synthesis Example 12: Copolymer (BI-8) A copolymer slurry was obtained in the same manner as in Synthesis Example 11. After cooling, the slurry was centrifuged and washed with 45 parts of water to obtain copolymer (BI-8). The polymer composition of the obtained copolymer was the same as that of copolymer (BI-8), and the residual amount of Ca derived from TCP was 0.6%.

[0081] Synthesis Example 13: Copolymer (BII-1) After purging the air in a stainless steel autoclave equipped with ribbon blades with nitrogen, 72.5 parts by mass of styrene, 27.5 parts by mass of acrylonitrile, and 20 parts by mass of toluene were continuously added to the reaction vessel. A solution of 0.19 parts by mass of tert-dodecyl mercaptan and 5 parts by mass of toluene as a molecular weight modifier, and a solution of 0.1 parts by mass of 1,1'-azobis(cyclohexane-1-carbonitrile) and 5 parts by mass of toluene as a polymerization initiator were continuously fed. The temperature was controlled at 110°C to carry out polymerization. After the polymerization conversion reached 75%, the resulting copolymer solution was directly subjected to devolatilization of unreacted monomers and solvent using a twin-screw, three-stage vented extruder to obtain Copolymer (BII-1). The resulting copolymer had a mass average molecular weight of 185,000 and a vinyl cyanide compound content of 27.5%.

[0082] Synthesis Example 14: Copolymer (BII-2) A copolymer (BII-2) was obtained in the same manner as in Synthesis Example 13, except that 81.0 parts by mass of styrene, 19.0 parts by mass of acrylonitrile, and 0.20 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier were used. The mass average molecular weight of the obtained copolymer was 175,000, and the content of vinyl cyanide compound was 19.0%.

[0083] Synthesis Example 15: Copolymer (BII-3) A copolymer (BII-3) was obtained in the same manner as in Synthesis Example 13, except that 65.0 parts by mass of styrene, 35.0 parts by mass of acrylonitrile, and 0.18 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier were used. The mass average molecular weight of the obtained copolymer was 185,000, and the content of vinyl cyanide compound was 35.0%.

[0084] Synthesis Example 16: Copolymer (BII-4) A reactor was charged with 125 parts of water, 0.5 parts of calcium phosphate (TCP), 0.003 parts of potassium alkenyl succinate, 0.05 parts of 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 0.04 parts of 1,1-di(t-hexylperoxy)cyclohexane, 0.04 parts of t-butylperoxy-2-ethylhexyl carbonate, 0.18 parts of t-dodecyl mercaptan, 73.5 parts of styrene, and 27.5 parts of a monomer mixture of acrylonitrile. The reaction was heated from a reaction start temperature of 65 ° C. for 6.5 hours, and then allowed to reach 125 ° C. Further, after reacting at 125 ° C. for 1 hour, a copolymer slurry was obtained. After cooling, the slurry was centrifuged and washed with 200 parts of water to obtain a copolymer (BII-4). The copolymer thus obtained had a mass average molecular weight of 185,000, a vinyl cyanide compound content of 27.5%, and a residual Ca content derived from TCP of 0.05%.

[0085] Examples 1 to 13, Comparative Examples 1 to 4 (Production of Thermoplastic Resin Compositions) The rubber-containing graft copolymer (A), copolymers (BI) and (BII), and 0.5 parts of "Kaowax EB-G (trade name)" (ethylene bisstearamide) manufactured by Kao Corporation were mixed in the proportions shown in Table 1 and melt-kneaded to prepare thermoplastic resin compositions. The mixture of materials was melt-kneaded at 200°C using a 30 mm twin-screw extruder ("TEX30α" manufactured by The Japan Steel Works, Ltd.) and pelletized to obtain pellets of the thermoplastic resin composition. The thermoplastic resin composition of each example was evaluated as follows. The results are shown in Table 1.

[0086] <Calcium (Ca) Content> The thermoplastic resin composition was burned in an electric furnace to turn it into ashed material, and the Ca content was calculated using an X-ray fluorescence analyzer (HITACHI Hi-Tech Science, Model: EA6000VX).

[0087] <Proportion of polymers with a molecular weight of less than 50,000 contained in thermoplastic resin composition> A solution of soluble components obtained by dissolving a thermoplastic resin composition in tetrahydrofuran (THF) was used as a measurement sample, and the retention time or elution volume of the eluted polymer was measured using a GPC apparatus (manufactured by Tosoh Corporation, "TOSOH EcoSEC HLC-8320GPC") under the same measurement conditions as for copolymer (B). Based on the measurement results, the molecular weight of the eluted polymer was calculated using the standard polystyrene conversion method. The content of polymers with a molecular weight of less than 50,000 among all the eluted polymers was calculated by data analysis (slice data) of the GPC measurement results, as the proportion corresponding to the area occupied by polymers with a molecular weight of less than 50,000 among the total area of ​​the peak showing the elution of the polymer (elution curve for mass average molecular weight).

[0088] <Ratio of copolymers (B) having a mass average molecular weight of 50,000 to 300,000 among multiple copolymers (B) polymerized individually and blended into a thermoplastic resin composition> As shown in Table 1, any of the individually polymerized copolymers (BI) and (BII) was combined and blended into a thermoplastic resin composition. The content ratio of the copolymers (B) having a mass average molecular weight of 50,000 to 300,000 relative to the total mass of all the blended copolymers (B) was calculated.

[0089] <Proportion of polymers containing 10 to 30 mass% of repeating units derived from a vinyl cyanide compound in all copolymers (B) blended in a thermoplastic resin composition> For each of (BI) and (BII) blended as copolymers (B), the proportion was calculated from the monomer composition blended during polymerization. In all examples, all of the blended copolymers (B) were polymers containing 10 to 30 mass% of repeating units derived from a vinyl cyanide compound, relative to 100 mass% of all repeating units. In other words, the proportion of the polymer was 100 mass% in all examples.

[0090] (Evaluation of Plating Adhesion Strength) Pellets of the thermoplastic resin composition were injection molded using an 80-ton injection molding machine (J80ADS-110U manufactured by The Japan Steel Works, Ltd.) to obtain test specimens. The injection molding was carried out using a mold for evaluating plating adhesion strength (90 mm long x 50 mm wide x 3 mm thick) at a cylinder temperature of 250°C, a mold temperature of 60°C, and a medium injection speed (15 mm / sec). The obtained test specimens were plated, and the plating film was peeled off in the vertical direction on a load measuring device to measure its strength, and the plating adhesion strength was evaluated according to the following criteria: ◎: The plating adhesion strength was 12 N / cm or more, which was very excellent. ○: The plating adhesion strength was 10 N / cm or more but less than 12 N / cm, which presented no problems in practical use. △: The plating adhesion strength was 8 N / cm or more but less than 10 N / cm, which could be used if the application was limited. ×: The plating adhesion strength was less than 8 N / cm, which could not be used.

[0091] In the evaluation of plating adhesion strength, plating was performed in the following steps (1) to (15): (1) Degreasing process [5 minutes at 50°C] → (2) Water washing → (3) Etching treatment (CrO ３ : 400 g / l, sulfuric acid: 200 cc / l >> [65°C for 15 minutes] ⇒ (4) Water washing ⇒ (5) Acid treatment [23°C for 1 minute] ⇒ (6) Water washing ⇒ (7) Catalysis treatment [30°C for 3 minutes] ⇒ (8) Water washing ⇒ (9) Activation treatment [40°C for 3 minutes] ⇒ (10) Water washing ⇒ (11) Chemical Ni plating [40°C for 5 minutes] ⇒ (12) Water washing ⇒ (13) Copper electroplating [film thickness: 35 μm, 20°C for 60 minutes] ⇒ (14) Water washing ⇒ (15) Drying [80°C for 2 hours]

[0092] (Evaluation of Thermal Cycle Properties) Pellets of the thermoplastic resin composition were injection molded using an 80-ton injection molding machine ("J80ADS-110U" manufactured by The Japan Steel Works, Ltd.) to obtain test pieces. The injection molding was performed using a thermal cycle evaluation mold (length 100 mm × width 100 mm × thickness 3 mm) under the conditions of a cylinder temperature of 230°C, a mold temperature of 60°C, and an injection speed of 50 mm / sec. The obtained test pieces were plated, and a thermal cycle test was performed using a Hitachi Global Life Solutions, Inc., Model EC-86MTPE thermal cycle tester. The temperature was lowered from 23°C to -30°C over 30 minutes, held at -30°C for 1 hour, then raised to 23°C over 30 minutes and held at 23°C for 15 minutes. The temperature was then raised to 80°C over 30 minutes and held at 80°C for 1 hour. The temperature was then lowered to 23°C over 30 minutes and held at 23°C for 15 minutes. This cycle constituted one cycle, and 20 cycles were performed. The condition of the plating film on the product was then visually observed, and the thermal cycle characteristics were evaluated according to the following criteria: ◎: No change in the plating film, very excellent; ○: Some swelling in the plating film, but no practical problems; △: Changes such as swelling in the plating film, usable if used for limited purposes; ×: Significant changes such as swelling in the plating film, not practical.

[0093] In the evaluation of thermal cycle characteristics, plating was performed in the following steps (1) to (17): (1) Degreasing process [5 minutes at 50°C] → (2) Water washing → (3) Etching treatment (CrO ３ : 400 g / l, sulfuric acid: 200 cc / l >> [65°C for 20 minutes] ⇒ (4) Water washing ⇒ (5) Acid treatment [23°C for 1 minute] ⇒ (6) Water washing ⇒ (7) Catalysis treatment [30°C for 3 minutes] ⇒ (8) Water washing ⇒ (9) Activation treatment [40°C for 3 minutes] ⇒ (10) Water washing ⇒ (11) Chemical Ni plating [40°C for 5 minutes] ⇒ (12) Water washing ⇒ (13) Copper electroplating [film thickness: 20 μm, 20 minutes at 20°C] ⇒ (14) Water washing ⇒ (15) Ni electroplating [film thickness: 10 μm, 55°C for 15 minutes] ⇒ (16) Water washing ⇒ (17) Cr electroplating [film thickness: 0.3 μm, 45°C for 2 minutes]

[0094] (Evaluation of Thermal Shock Properties) Using the same plated products as those used in the evaluation of thermal cycle properties, a Hitachi Global Life Solutions, Inc., Model ES-306L thermal shock tester was used. The products were held in a bath cooled to -30°C for one hour, then heated to 80°C within 10 minutes, held at 80°C for one hour, cooled to -30°C within 10 minutes, held at -30°C for one hour, and then heated again to 80°C and held at 80°C for one hour. This cycle was repeated, and after the 20th cycle, the products were held at 80°C for one hour, allowed to cool, and the samples were removed. The condition of the plating film on the products was visually observed to evaluate the thermal shock properties. ⊚: No change in the plating film, very excellent. ◯: Some swelling in the plating film, but no practical problems. △: Changes such as swelling in the plating film, usable if used for limited purposes. ×: Significant changes such as swelling in the plating film, not practical.

[0095] (Evaluation of Charpy Impact Strength) Pellets of the thermoplastic resin composition were injection molded using a 100-ton injection molding machine (FANUC ROBOSHOT α-S100iB, manufactured by FANUC Corporation) to obtain test pieces (length 80 mm, width 10 mm, thickness 4 mm). Injection molding was performed under conditions of a molding temperature of 235°C and a mold temperature of 60°C. The Charpy impact strength (notched) of the obtained test pieces was measured in accordance with ISO 179 at a measurement temperature of 23°C, and the impact resistance was evaluated according to the following criteria. ⊚: Charpy impact strength of 20 kJ / m ２ ◯: Charpy impact strength is 15 kJ / m or more, which is very excellent. ２ 20kJ / m or more ２ △: Charpy impact strength is less than 15 kJ / m, and there is no problem in practical use. ２ This is less than practical level.

[0096] (Evaluation of fluidity (spiral flow)) Using a spiral flow mold (width 15 mm x thickness 2 mm), pellets of the thermoplastic resin composition were injection molded from an 85-ton injection molding machine ("J85AD-110H" manufactured by The Japan Steel Works, Ltd.) under conditions of a cylinder temperature of 270°C, a mold temperature of 60°C, and an injection pressure of 100 MPa. The spiral flow length (mm) of the obtained molded product was measured, and the fluidity (spiral flow) was evaluated according to the following criteria: ◎: The spiral flow length was 470 mm or more, indicating excellent material properties. ○: The spiral flow length was 450 mm or more and less than 470 mm, indicating no practical problems. △: The spiral flow length was 430 mm or more and less than 450 mm, indicating usable use if the application was limited. ×: The spiral flow length was less than 430 mm, indicating that the product was not at a practical level.

[0097] (Appearance of molded product) The entire surface of the test piece (length 90 mm x width 50 mm x thickness 3 mm) before plating, which was molded to measure plating adhesion strength, was visually observed. ○: 0 to 2 bumps, excellent appearance. △: 3 to 4 bumps, inferior appearance compared to "○". ×: 5 or more bumps, extremely inferior appearance compared to "○".

[0098] (Plating Appearance) The entire surface of the test piece (length 90 mm x width 50 mm x thickness 3 mm) after plating, which was formed to measure plating adhesion strength, was visually observed. ○: 0 to 2 bumps, excellent appearance. △: 3 to 4 bumps, inferior appearance compared to "○". ×: 5 or more bumps, extremely inferior appearance compared to "○".

[0099]

[0100]

[0101]

[0102]

[0103] It can be seen that the thermoplastic resin compositions of Examples 1 to 13 provide resin molded articles excellent in plating adhesion strength, thermal cycle properties, thermal shock properties, impact resistance, fluidity, molding appearance, and plating appearance. The plating appearance of Example 11 was inferior to that of the other Examples. This is thought to be due to the slightly high Ca content in the thermoplastic resin composition. The thermal shock properties of Example 12 were inferior to that of the other Examples. This is thought to be due to the absence of (BII) in copolymer (B). The plating adhesion strength and thermal cycle properties of Example 13 were inferior to that of the other Examples. This is thought to be due to the slightly low mass average molecular weight of copolymer (B) and the absence of (BII).

[0104] The thermoplastic resin composition of Comparative Example 1 had a high Ca content and was therefore poor in thermal cycle properties, thermal shock properties, molded appearance, and plating appearance.The thermoplastic resin compositions of Comparative Examples 2 to 4 had a high content of polymers having a molecular weight of less than 50,000 in the total copolymer (B) blended therein and were therefore poor in impact resistance and plating adhesion strength, as well as in thermal cycle properties and thermal shock properties.

[0105] According to the present invention, it is possible to provide a thermoplastic resin composition capable of producing a resin molded article having excellent adhesion strength, thermal cycle properties, thermal shock properties, impact resistance, fluidity, and appearance in a plating process, and a resin molded article and a plated article obtained by molding the thermoplastic resin composition. Therefore, the present invention is extremely important from an industrial viewpoint.

Claims

1. A thermoplastic resin composition which is a melt-kneaded product of a rubber-containing graft copolymer (A) obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubbery polymer, and a copolymer (B) obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound independently of the rubber-containing graft copolymer (A), wherein the rubber-containing graft copolymer (A) and the copolymer (B) are mixed in a ratio of 20 to 60 parts by mass of the rubber-containing graft copolymer (A) and 40 to 80 parts by mass of the copolymer (B) with respect to a total of 100 parts by mass of the rubber-containing graft copolymer (A) and the copolymer (B); when the molecular weight of the total polymer of the copolymer (B) is measured by GPC method in terms of standard polystyrene conversion, the proportion of the polymer having a molecular weight of less than 50,000 is 20% by mass or less with respect to the total mass of the total polymer; the total content of the rubber-containing graft copolymer (A) and the copolymer (B) with respect to the total mass of the thermoplastic resin composition is 75 to 100% by mass; and the calcium content in the thermoplastic resin composition with respect to the total mass of the thermoplastic resin composition is 0.30% by mass or less.

2. The thermoplastic resin composition according to claim 1, wherein the proportion of the polymer in which the proportion of the repeating unit derived from the vinyl cyanide compound in the total polymer of the copolymer (B) is 10 to 30% by mass of the total repeating units is 85 to 100% by mass with respect to the total mass of the total polymer.

3. The thermoplastic resin composition according to claim 2, wherein the copolymer (B) is a mixture of a plurality of copolymers (B), and when the mass average molecular weight of each copolymer (B) is measured by GPC method in terms of standard polystyrene conversion, the mixing ratio of the copolymer (B) having a mass average molecular weight of 50,000 to 300,000 with respect to the total mass of the mixture is 85 to 100% by mass.

4. The copolymer (B) is a mixture of a copolymer (BI) and a copolymer (BII). The copolymer (BI) is a copolymer formed by polymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound. The content of the vinyl cyanide compound relative to the total mass of the monomer mixture is 10 to 30% by mass, and the mass average molecular weight of the copolymer (BI) in terms of standard polystyrene by the GPC method is 50,000 to 150,000. The copolymer (BII) is a copolymer formed by polymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound. The content of the vinyl cyanide compound relative to the total mass of the monomer mixture is 10 to 30% by mass, and the mass average molecular weight of the copolymer (BII) in terms of standard polystyrene by the GPC method is more than 150,000 to 300,000. The thermoplastic resin composition according to claim 1.

5. The thermoplastic resin composition according to claim 1, wherein the calcium content in the thermoplastic resin composition relative to the total mass of the thermoplastic resin composition is 0.20% by mass or less.

6. A resin molded article comprising the thermoplastic resin composition according to any one of claims 1 to 5.

7. A plated article having a plating film on at least a part of the surface of the resin molded article according to claim 6.

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