JP7733504B2 - Resin composition for plating and plated molded product - Google Patents

Description

The present invention relates to a resin composition for plating and a plated molded article. More specifically, the present invention relates to a resin composition for plating and a plated molded article obtained by plating a molded article made from the resin composition for plating.

Styrenic resins, typified by ABS resin, have excellent moldability and a balance of mechanical properties, as well as excellent paintability and electrical insulation properties, and are therefore used in a wide range of fields, including vehicle interior and exterior parts, building materials, home appliances, electrical and electronic devices, office equipment parts, and office automation equipment.

Molded products made from ABS resin are often required to have a decorative appearance. For example, when ABS resin is used as a substitute for metal to reduce weight, it is often used after being plated with a metallic decorative coating. Resin compositions using ABS resin for plating are disclosed, for example, in Patent Documents 1 and 2.

JP 2009-292921 A International Publication No. 2018/008669

In recent years, resin compositions for plating that use graft copolymers, such as ABS resin, formed by graft polymerization of a rubbery polymer with a monomer component containing an aromatic vinyl monomer, are required to have even better adhesion strength to the plating of molded articles. One possible way to improve this adhesion strength is to increase the blending ratio of the rubbery polymer. However, this approach results in problems such as reduced fluidity of the resin composition, which makes it less moldable.

The thermoplastic resin composition in Patent Document 1 is said to improve the melt fluidity of ABS resin without impairing its plating ability. However, when the specific copolymer used to improve melt fluidity in Patent Document 1 is blended, the adhesion strength of the molded article to the plating decreases. For this reason, there is a demand for a resin composition for plating that uses the above graft copolymer and that has excellent adhesion strength to the plating of molded articles without reducing the fluidity of the resin composition.

Therefore, an object of the present invention is to provide a resin composition for plating that uses a graft copolymer containing a rubbery polymer and has excellent fluidity and adhesion strength to plating on molded articles.

As a result of extensive research to achieve the above objective, the inventors have discovered that by blending a specific ratio of an acrylic block copolymer with a graft copolymer containing a rubber polymer, a resin composition for plating can be obtained that exhibits excellent fluidity and adhesive strength for plating on molded articles. The present disclosure relates to a product that was completed based on these findings.

That is, the present invention provides a composition comprising a graft copolymer (A) obtained by graft polymerization of a rubber polymer with a monomer component containing an aromatic vinyl monomer, and an acrylic block copolymer (B), and may further comprise another thermoplastic resin (C),
Provided is a resin composition for plating, in which the total content of the graft copolymer (A) and the other thermoplastic resin (C) is 51 to 99.5 mass%, and the content of the acrylic block copolymer (B) is 0.5 to 49 mass%, relative to 100 mass% of the total of the graft copolymer (A), the acrylic block copolymer (B), and the other thermoplastic resin (C).

The rubbery polymer preferably contains a conjugated diene rubber.

It is preferable that the above monomer component further contains a vinyl cyanide monomer.

The content of the rubbery polymer is preferably 7 to 20% by mass, relative to 100% by mass of the total of the graft copolymer (A), acrylic block copolymer (B), and other thermoplastic resin (C).

The Shore hardness (Type A) of the acrylic block copolymer (B) is preferably 10 to 99.

The melt flow rate of the acrylic block copolymer (B) at 230°C is preferably 30 g/10 min or more.

The acrylic block copolymer (B) is preferably a block copolymer of an acrylic acid ester polymer block and a methacrylic acid ester polymer block.

The above-mentioned plating resin composition preferably contains an aromatic vinyl-vinyl cyanide copolymer and/or a polycarbonate resin as the other thermoplastic resin (C).

The present invention also provides a plated molded article obtained by plating a molded article made from the above-mentioned resin composition for plating.

The plating resin composition of the present invention uses a graft copolymer containing a rubber polymer, and has excellent fluidity and excellent adhesion strength to the plating of molded articles. Furthermore, using the above plating resin composition, molded articles with excellent impact resistance can be obtained.

The plating resin composition of the present invention contains at least a graft copolymer (A) formed by graft polymerization of a rubber polymer with a monomer component containing an aromatic vinyl monomer, and an acrylic block copolymer (B). The plating resin composition of the present invention may also contain a thermoplastic resin (C) other than the graft copolymer (A) and the acrylic block copolymer (B).

The plating resin composition of the present invention is a resin composition used in applications where a metallic surface treatment (plating) is applied to the surface of a molded article.

(Graft polymer (A))
The graft copolymer (A) is obtained by graft polymerization of a rubber polymer and a monomer component containing an aromatic vinyl monomer. Only one type of graft polymer (A) may be used, or two or more types may be used.

The rubbery polymer is not particularly limited, and examples include those obtained by known or conventional polymerization methods. Examples of the rubbery polymer include conjugated diene rubbers such as polybutadiene rubber, styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR); ethylene-propylene rubbers such as ethylene-propylene rubber and ethylene-propylene-non-conjugated diene (ethylidene norbornene, dicyclopentadiene, etc.) rubber; acrylic rubbers such as polybutyl acrylate rubber; and silicone rubbers. One or more of the above rubbery polymers may be used.

The acrylic rubber also includes rubbers with a core-shell structure. Examples of rubbers with a core-shell structure (referred to as core/shell) include conjugated diene rubber/acrylic rubber, silicone rubber/acrylic rubber, and hard polymer (polymer with a glass transition temperature of 20°C or higher)/acrylic rubber. Examples of the hard polymer include polymers containing structural units derived from monomers containing one or more selected from the group consisting of aromatic vinyl monomers, vinyl cyanide monomers, and (meth)acrylic acid ester monomers. The glass transition temperature of the hard polymer can be calculated using the FOX formula.

Of the rubbery polymers mentioned above, polybutadiene rubber, styrene-butadiene rubber, ethylene-propylene-non-conjugated diene rubber, and acrylic rubber are preferred. Among the acrylic rubbers mentioned above, rubbers with a core-shell structure are preferred, and more preferred are conjugated diene rubber/acrylic rubber, silicone rubber/acrylic rubber, and hard polymer/acrylic rubber (referred to as core/shell).

There are no particular restrictions on the mass average particle diameter of the rubber polymer, but from the viewpoint of achieving excellent impact resistance in the molded article, a value of 0.1 to 2.0 μm is preferred, and from the viewpoint of achieving even better adhesion strength to plating in the molded article, a value of 0.2 to 1.0 μm is more preferred. The mass average particle diameter can also be adjusted by agglomerating and enlarging a rubber polymer with a mass average particle diameter of 0.05 to 0.3 μm.

The graft copolymer (A) is obtained by graft polymerizing the above rubbery polymer with a monomer component containing an aromatic vinyl monomer.

From the viewpoint of achieving a better balance of physical properties such as flowability and the impact resistance of molded articles, the content of the rubber polymer in graft copolymer (A) is preferably 20 to 80% by mass, and more preferably 40 to 70% by mass, based on 100% by mass of the total amount of graft copolymer (A).

The aromatic vinyl monomer constituting the graft copolymer (A) may be a monomer having a styrene structure (a styrene monomer). Examples of the styrene monomer include styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, p-isobutylstyrene, p-t-butylstyrene, bromostyrene, and chloromethylstyrene. Among these, styrene and α-methylstyrene are preferred. The aromatic vinyl monomers may be used singly or in combination.

In addition to the aromatic vinyl monomer, the above-mentioned monomer component may also contain other monomers copolymerizable with the aromatic vinyl monomer. Examples of such other monomers include vinyl cyanide monomers, (meth)acrylic acid ester monomers, amide monomers, and unsaturated carboxylic acid monomers. One or more of the above-mentioned other monomers may be used.

Examples of the vinyl cyanide monomers include nitrile group-containing monomers such as acrylonitrile, methacrylonitrile, ethacrylonitrile, and fumaronitrile. Examples of the (meth)acrylic acid ester monomers include alkyl (meth)acrylates having an alkyl group that may have a substituent, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, phenyl (meth)acrylate, 4-t-butylphenyl (meth)acrylate, dibromophenyl (meth)acrylate, and chlorophenyl (meth)acrylate. Examples of the amide monomers include amide group-containing monomers such as acrylamide and methacrylamide. Examples of the unsaturated carboxylic acid monomers include carboxy group-containing monomers such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid.

The content of the aromatic vinyl monomer in the above monomer component is preferably 30 to 95% by mass, more preferably 50 to 90% by mass, and even more preferably 60 to 80% by mass, based on 100% by mass of the total amount of the above monomer component. The content of the above other monomers is preferably 5 to 70% by mass, more preferably 10 to 50% by mass, and even more preferably 20 to 40% by mass, based on 100% by mass of the total amount of the above monomer component.

The graft ratio of graft copolymer (A) is not particularly limited, but from the viewpoint of achieving a better balance of physical properties such as fluidity and impact resistance of molded articles, it is preferably 20 to 150% by mass, more preferably 30 to 100% by mass, and even more preferably 36 to 75% by mass. Furthermore, the reduced viscosity of the acetone-soluble portion of graft copolymer (A) is not particularly limited, but is preferably 0.1 to 1.5 dl/g, more preferably 0.2 to 0.6 dl/g.

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

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

When producing graft copolymer (A), it typically contains primarily a grafted polymer (component a1) in which a monomer component containing an aromatic vinyl monomer is grafted onto a rubbery polymer. However, a copolymer (component a2) may also be produced in which a monomer component containing an aromatic vinyl monomer that is not grafted onto the rubbery polymer is copolymerized. The copolymer (a2) component corresponds to the other thermoplastic resin (C).

(Acrylic Block Copolymer (B))
The acrylic block copolymer (B) is a block copolymer having a polymer block that is a soft segment and a polymer block that is a hard segment. Only one type of acrylic block copolymer (B) may be used, or two or more types may be used.

The acrylic block copolymer (B) contains an acrylic monomer (a monomer having an acryloyl group or a methacryloyl group) as a monomer component constituting at least one of the polymer blocks of the soft segment and the hard segment.

The acrylic monomer constituting the soft segment is preferably an acrylic ester. That is, the polymer block of the soft segment is preferably an acrylic ester polymer block (b1). Examples of the acrylic ester include acrylic esters having a hydrocarbon group that may have an alkoxy group (particularly, alkyl acrylates that may have an alkoxy group), such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, isobornyl acrylate, phenyl acrylate, benzyl acrylate, phenoxyethyl acrylate, and 2-methoxyethyl acrylate. The hydrocarbon group in the acrylic ester may be an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a group formed by combining two or more of these. The acrylic monomers may be used singly or in combination.

As the acrylic monomer constituting the acrylic ester polymer block (b1), from the viewpoint of achieving superior fluidity and impact resistance of molded articles, acrylic esters having a hydrocarbon group with 1 to 22 carbon atoms (preferably 1 to 10, more preferably 1 to 4 carbon atoms) are preferred. From the same viewpoint, the hydrocarbon group in the acrylic ester is preferably an aliphatic hydrocarbon. Therefore, as the acrylic ester, alkyl acrylates are particularly preferred, with n-butyl acrylate and 2-ethylhexyl acrylate being more preferred.

The acrylic monomer constituting the acrylic ester polymer block (b1) may include acrylic monomers other than the acrylic ester having a hydrocarbon group optionally containing an alkoxy group. Examples of such other acrylic monomers include acrylic esters having a crosslinkable functional group, such as 2-hydroxyethyl acrylate, glycidyl acrylate, and allyl acrylate; methacrylic esters constituting hard segments; and carboxyl group-containing monomers, such as methacrylic acid and acrylic acid. Furthermore, the monomer components constituting the soft segments may further include other monomers, such as aromatic vinyl compounds; vinyl cyanide monomers, such as acrylonitrile and methacrylonitrile; and olefins. The proportion of the acrylic ester having a hydrocarbon group optionally containing an alkoxy group in the acrylic ester polymer block (b1) is preferably 90% by mass or more, and more preferably 95% by mass or more, based on 100% by mass of the total amount of the monomer components constituting the acrylic ester polymer block (b1).

The glass transition temperature of the acrylic acid ester polymer block (b1) is not particularly limited, but is preferably -100 to 20°C, more preferably -80 to 0°C, and even more preferably -60 to -40°C.

The acrylic monomer constituting the hard segment is preferably a methacrylic acid ester. That is, the polymer block that constitutes the hard segment is preferably a methacrylic acid ester polymer block (b2). Examples of the methacrylic acid ester include methacrylic acid esters having a hydrocarbon group that may have an alkoxy group (particularly, alkyl methacrylates that may have an alkoxy group), such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, pentadecyl methacrylate, dodecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, and 2-methoxyethyl methacrylate. The hydrocarbon group in the above methacrylic acid ester may be an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a group in which two or more of these are bonded. The above acrylic monomers may be used alone or in combination.

As the acrylic monomer constituting the methacrylic acid ester polymer block (b2), from the viewpoint of achieving superior impact resistance and heat resistance of the molded article, methacrylic acid esters having a hydrocarbon group containing 1 to 22 carbon atoms (preferably 1 to 10, more preferably 1 to 4 carbon atoms) are preferred. From the same viewpoint, the hydrocarbon group in the methacrylic acid ester is preferably an aliphatic hydrocarbon. Therefore, as the methacrylic acid ester, alkyl methacrylates are particularly preferred, with methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate being more preferred, and methyl methacrylate being particularly preferred.

The acrylic monomer constituting the methacrylic acid ester polymer block (b2) may include acrylic monomers other than the methacrylic acid ester having a hydrocarbon group which may have an alkoxy group. Examples of such other acrylic monomers include methacrylic acid esters having a crosslinkable functional group, such as 2-hydroxyethyl methacrylate, glycidyl methacrylate, and allyl methacrylate; acrylic acid esters constituting soft segments; and carboxyl group-containing monomers, such as methacrylic acid and acrylic acid. The monomer components constituting the methacrylic acid ester polymer block (b2) may further include other monomers, such as aromatic vinyl compounds; vinyl cyanide monomers, such as acrylonitrile and methacrylonitrile; and olefins. The proportion of the methacrylic acid ester having a hydrocarbon group which may have an alkoxy group in the methacrylic acid ester polymer block (b2) is preferably 90% by mass or more, and more preferably 95% by mass or more, based on 100% by mass of the total amount of the monomer components constituting the methacrylic acid ester polymer block (b2).

The glass transition temperature of the methacrylic acid ester polymer block (b2) is not particularly limited, but is preferably 30 to 180°C, more preferably 60 to 160°C, and even more preferably 100 to 120°C.

The acrylic block copolymer (B) may have a polymer block (b3) other than the acrylic acid ester polymer block (b1) and the methacrylic acid ester polymer block (b2). The other polymer block is composed of a monomer component other than an acrylic acid ester or a methacrylic acid ester. Examples of monomers that may constitute the other polymer block include α-olefins such as ethylene, propylene, 1-butene, isobutylene, and 1-octene; conjugated dienes such as butadiene, isoprene, and myrcene; aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, and m-methylstyrene; vinyl acetate, vinylpyridine, acrylonitrile, methacrylonitrile, vinyl ketone, vinyl chloride, vinylidene chloride, vinylidene fluoride, acrylamide, methacrylamide, ε-caprolactone, and valerolactone.

The bonding form of each polymer block constituting the acrylic block copolymer (B) is not particularly limited, but examples include linear, branched, radial, etc. Examples of such bonding forms include linear structures such as the {(b1)-(b2)}n structure, {(b1)-(b2)}n-(b1) structure, (b2)-{(b1)-(b2)}n structure, (b2)-{(b1)-(b2)}n-(b3) structure, and (b3)-(b2)-{(b1)-(b2)}n-(b3) structure; and the {(b1)-(b2)}nZ structure (where n is a natural number and Z represents a coupling agent residue). From the viewpoint of achieving better dispersibility of the graft copolymer (A) and other thermoplastic resins (C) in the resin composition for plating, a linear structure is preferred, and it is more preferable to use a triblock copolymer in which methacrylic acid ester polymer blocks (b2) are bonded to both ends of an acrylic acid ester polymer block (b1).

The weight-average molecular weight of the acrylic block copolymer (B) is preferably 10,000 to 200,000, and more preferably 15,000 to 150,000. When the weight-average molecular weight of the acrylic block copolymer (B) is 10,000 or more, the melt viscosity is appropriate, the melt-kneadability with the graft copolymer (A) and other thermoplastic resins (C) is good, and the dispersibility of the thermoplastic resin in the molded article is improved. When the weight-average molecular weight is 200,000 or less, high melt viscosity is suppressed, melt fracture during melt molding is prevented, and the appearance of the molded article can be improved. The weight-average molecular weight of both the acrylic acid ester polymer block (b1) and the methacrylic acid polymer block (b2) in the acrylic block copolymer (B) is preferably 2,000 to 100,000, and more preferably 5,000 to 80,000.

The total content of the acrylic acid ester polymer blocks (b1) in the acrylic block copolymer (B) is preferably 35 to 85% by mass, more preferably 40 to 80% by mass, and even more preferably 45 to 75% by mass, based on 100% by mass of the total amount of the acrylic block copolymer (B). A content of 35% by mass or more improves the flowability and flexibility of the molded product. A content of 85% by mass or less makes it possible to further reduce the occurrence of sticking in the plating resin composition. From the same perspective, the total content of the methacrylic acid ester polymer blocks (b2) in the acrylic block copolymer (B) is preferably 15 to 65% by mass, more preferably 20 to 60% by mass, and even more preferably 25 to 55% by mass, based on 100% by mass of the total amount of the acrylic block copolymer (B).

The total content of the acrylic acid ester polymer block (b1) and the methacrylic acid ester polymer block (b2) in the acrylic block copolymer (B) is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on 100% by mass of the total amount of the acrylic block copolymer (B).

The molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the acrylic block copolymer (B) is preferably 1.01 or more and less than 1.50, more preferably 1.01 to 1.35, and even more preferably 1.01 to 1.20. When the molecular weight distribution is within the above range, the molding processability of the plating resin composition during melt molding is more stable.

The Shore hardness (Type A) of the acrylic block copolymer (B) is preferably 10 to 99, more preferably 20 to 98, and even more preferably 40 to 97. The Shore hardness (Type D) of the acrylic block copolymer (B) is preferably 60 or less (e.g., greater than 0 and less than 60), more preferably 5 to 55, and even more preferably 10 to 50. When the Shore hardness is within the above range, the fluidity of the plating resin composition is superior. The Shore hardness is a value measured in accordance with ISO 7619-1.

The melt flow rate (MFR) of the acrylic block copolymer (B) at 190°C is preferably 1 to 50 g/10 min, more preferably 1.5 to 40 g/10 min, and even more preferably 10 to 30 g/10 min. The MFR of the acrylic block copolymer (B) at 230°C is preferably 30 g/10 min or higher (e.g., 30 to 600 g/10 min), more preferably 100 g/10 min or higher (e.g., 100 to 500 g/10 min), and even more preferably 200 g/10 min or higher (e.g., 200 to 400 g/10 min). When the MFR is within the above range, the resin composition for plating has better fluidity and the molded product has better processability. The above MFR is a value measured at a pressure of 2.16 kg in accordance with ISO 1133.

The acrylic block copolymer (B) may optionally have functional groups such as hydroxyl groups, carboxyl groups, acid anhydrides, and amino groups in the molecular chain or at the molecular chain terminals.

(Other thermoplastic resins (C))
The other thermoplastic resin (C) is not particularly limited, and known or commonly used thermoplastic resins can be used. Examples of the other thermoplastic resin (C) include aromatic vinyl resins; acrylic resins such as polymethyl methacrylate resin; polycarbonate resins; polyester resins such as polybutylene terephthalate resin and polyethylene terephthalate resin; polyamide resins; biodegradable resins such as polylactic acid resin; (modified) polyphenylene ether resins, polyoxymethylene resins, polysulfone resins, polyarylate resins, polyphenylene resins, and thermoplastic polyurethane resins, and other engineering plastics. Only one type of other thermoplastic resin (C) can be used, or two or more types can be used.

Aromatic vinyl resins and polycarbonate resins are preferred as the other thermoplastic resin (C) from the viewpoint of providing superior impact resistance to the molded article.

The aromatic vinyl resin contains structural units derived from an aromatic vinyl monomer. A styrene monomer is preferred as the aromatic vinyl monomer. That is, the aromatic vinyl resin is preferably a styrene resin. Examples of the styrene monomer include styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, p-isobutylstyrene, p-t-butylstyrene, bromostyrene, and chloromethylstyrene. Of these, styrene and α-methylstyrene are preferred. The aromatic vinyl monomers may be used alone or in combination.

The aromatic vinyl resin may contain, in addition to the aromatic vinyl monomer, structural units derived from other monomers copolymerizable with the aromatic vinyl monomer. Examples of such other monomers include those exemplified and explained above as other monomers that can constitute the graft copolymer (A). Only one type of such other monomer may be used, or two or more types may be used.

The monomer components constituting the aromatic vinyl resin preferably include a vinyl cyanide monomer as the other monomer. Examples of the vinyl cyanide monomer include those exemplified and explained as vinyl cyanide monomers that can constitute the graft copolymer (A) described above. In other words, the aromatic vinyl resin is preferably a copolymer (C1) of an aromatic vinyl monomer and a vinyl cyanide monomer (aromatic vinyl-vinyl cyanide copolymer).

The monomer components constituting copolymer (C1) may include other monomers copolymerizable with the aromatic vinyl monomer and the vinyl cyanide monomer. Examples of such other monomers include those exemplified and explained above as other monomers that can constitute graft copolymer (A). One or more of the above other monomers may be used.

The content of structural units derived from aromatic vinyl monomers in copolymer (C1) is preferably 50 to 90% by mass, and more preferably 60 to 80% by mass, based on 100% by mass of the total amount of copolymer (C1). The content of structural units derived from vinyl cyanide monomers in copolymer (C1) is preferably 10 to 50% by mass, and more preferably 20 to 40% by mass, based on 100% by mass of the total amount of copolymer (C1).

Specific examples of the aromatic vinyl resin include styrene polymer (PS resin), styrene-acrylonitrile copolymer (AS resin), α-methylstyrene-acrylonitrile copolymer (αMS-ACN resin), methyl methacrylate-styrene copolymer (MS resin), methyl methacrylate-acrylonitrile-styrene copolymer (MAS resin), styrene-N-phenylmaleimide copolymer (S-NPMI resin), and styrene-N-phenylmaleimide-acrylonitrile copolymer (S-A-NPMI resin).

The reduced viscosity of the aromatic vinyl resin is not particularly limited, but is preferably 0.2 to 1.5 dl/g, more preferably 0.3 to 1.0 dl/g, from the perspective of achieving a better balance of physical properties such as flowability and impact resistance of molded products. The reduced viscosity can be determined by dissolving the aromatic vinyl resin in N,N-dimethylformamide to prepare a solution with a concentration of 0.4 g/100 ml, and then measuring the flow time at 30°C using a Cannon-Fenske viscometer.

Polycarbonate resins include polymers obtained by the phosgene process, in which various dihydroxydiaryl compounds are reacted with phosgene, or by the transesterification process, in which dihydroxydiaryl compounds are reacted with carbonate esters such as diphenyl carbonate. Specific examples of polycarbonate resins include polycarbonate resins made from 2,2-bis(4-hydroxyphenyl)propane and bisphenol A.

The dihydroxydiaryl compounds mentioned above include, in addition to bisphenol A, bis(hydroxyaryl)alkanes such as bis(4-hydroxydiphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)diphenylmethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 1,1-bis(4-hydroxy-3-tert-butylphenyl)propane, 2,2-bis(4-hydroxy-3-bromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, and 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane; Examples of suitable dihydroxydiaryl compounds include bis(hydroxyaryl)cycloalkanes such as 1,1-bis(4-hydroxyphenyl)cyclopentane and 1,1-bis(4-hydroxyphenyl)cyclohexane, dihydroxydiaryl ethers such as 4,4'-dihydroxydiphenyl ether and 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether, dihydroxydiaryl sulfides such as 4,4'-dihydroxydiphenyl sulfide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide, dihydroxydiaryl sulfoxides such as 4,4'-dihydroxydiphenyl sulfone, and dihydroxydiaryl sulfones such as 4,4'-dihydroxydiphenyl sulfone. The dihydroxydiaryl compounds may be used singly or in combination. In addition to the dihydroxydiaryl compounds, the polycarbonate resin may also contain piperazine, dipiperidyl hydroquinone, resorcinol, 4,4'-dihydroxydiphenyls, and the like.

Furthermore, the above dihydroxydiaryl compounds may be used in combination with the following trivalent or higher phenolic compounds. Examples of trivalent or higher phenolic compounds include phloroglucin, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptene, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane, 1,3,5-tri-(4-hydroxyphenyl)benzene, 1,1,1-tri-(4-hydroxyphenyl)ethane, and 2,2-bis-[4,4-bis(4-hydroxyphenyl)cyclohexyl]propane.

The weight-average molecular weight of the polycarbonate resin is, for example, 10,000 to 80,000, and preferably 15,000 to 60,000. The weight-average molecular weight can be measured by gel permeation chromatography (GPC) using polystyrene as a standard substance.

Furthermore, the plating resin composition of the present invention may contain hindered amine light stabilizers, hindered phenols, sulfur-containing organic compounds, phosphorus-containing organic compounds, and other antioxidants; phenolic and acrylate heat stabilizers; benzoate, benzotriazole, benzophenone, and salicylate ultraviolet absorbers; lubricants such as organonickel compounds and higher fatty acid amides; plasticizers such as phosphate esters; halogen-containing compounds such as polybromophenyl ether, tetrabromobisphenol A, brominated epoxy oligomers, and brominated compounds; phosphorus-based compounds; flame retardants and flame retardant aids such as antimony trioxide; odor masking agents; pigments such as carbon black and titanium oxide; and dyes. Furthermore, reinforcing agents and fillers such as talc, calcium carbonate, aluminum hydroxide, glass fiber, glass flakes, glass beads, glass wool, carbon fiber, and metal fiber may also be added.

The total content of the graft copolymer (A) and other thermoplastic resin (C) in the resin composition for plating use of the present invention is 51 to 99.5% by mass, preferably 70 to 99% by mass, and more preferably 80 to 98.5% by mass, based on 100% by mass of the total of the graft copolymer (A), acrylic block copolymer (B), and other thermoplastic resin (C). When the resin composition for plating use of the present invention does not contain other thermoplastic resin (C), the above content refers to the content of the graft copolymer (A) based on 100% by mass of the total of the graft copolymer (A) and the acrylic block copolymer (B).

The content of the acrylic block copolymer (B) in the resin composition for plating use of the present invention is 0.5 to 49% by mass, preferably 1 to 30% by mass, and more preferably 1.5 to 20% by mass, based on 100% by mass of the total of the graft copolymer (A), the acrylic block copolymer (B), and the other thermoplastic resin (C). When the resin composition for plating use of the present invention does not contain the other thermoplastic resin (C), the above content refers to the content of the acrylic block copolymer (B) based on 100% by mass of the total of the graft copolymer (A) and the acrylic block copolymer (B).

The content of graft copolymer (A) in the resin composition for plating use of the present invention is preferably 1 to 60% by mass, more preferably 5 to 55% by mass, and even more preferably 10 to 50% by mass, relative to 100% by mass of the total amount of the resin composition for plating use of the present invention. When the content is 1% by mass or more, the effects of incorporating graft copolymer (A) are more easily obtained, and the physical properties of the molded product, such as impact resistance, are more excellent. When the content is 60% by mass or less, it is possible to incorporate a sufficient amount of other thermoplastic resin (C), and the effects of incorporating other thermoplastic resin (C) are more easily obtained.

The content of the other thermoplastic resin (C) in the resin composition for plating use of the present invention is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less, based on 100% by mass of the total amount of the resin composition for plating use of the present invention. When the content is 90% by mass or less, the effects of incorporating the graft copolymer (A) are more easily obtained, and the physical properties of the molded product, such as impact resistance, are superior. The lower limit of the content is, for example, 10% by mass, but may also be 30%, 50%, or 60% by mass.

The content of the rubber polymer in the resin composition for plating of the present invention is preferably 7 to 20% by mass, more preferably 8 to 18% by mass, even more preferably 10 to 15% by mass, and particularly preferably 11 to 14% by mass, based on 100% by mass of the total of the graft copolymer (A), acrylic block copolymer (B), and other thermoplastic resin (C). By adjusting the content within the above range, an improved balance between plating deposition performance and plating adhesion strength can be achieved.

In the resin composition for plating of the present invention, the total content of the aromatic vinyl monomer and vinyl cyanide monomer constituting the graft copolymer (A) and other thermoplastic resin (C) (e.g., copolymer (C1)) is preferably 20 to 73 mass%, more preferably 30 to 65 mass%, and even more preferably 36 to 59 mass%, based on 100 mass% of the total of the graft copolymer (A), acrylic block copolymer (B), and other thermoplastic resin (C). When the content is within the above range, the molded article will have excellent adhesion strength to the plating and excellent plating deposition.

The total content of the graft copolymer (A), acrylic block copolymer (B), and other thermoplastic resin (C) in the resin composition for plating use of the present invention is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on 100% by mass of the total amount of the resin composition for plating use of the present invention. When the content is 50% by mass or more, the effects of the present invention are further improved.

The notched Charpy impact value (test piece thickness: 4 mm, measurement temperature: 23°C) of the resin composition for plating of the present invention in accordance with ISO test method 179 is preferably 20 kJ/ ^m2 or more, more preferably 30 kJ/ ^m2 or more, and even more preferably 50 kJ/ ^m2 or more. When the Charpy impact value is 20 kJ/ ^m2 or more, the impact resistance of the molded article is superior.

The resin composition for plating use of the present invention preferably has a melt volume flow rate (MVR) of 2 to 30 cm ³ /10 min, more preferably 4 to 29 cm ³ /10 min, and even more preferably 8 to 27 cm ³ /10 min, at 220°C and a load of 98.07 N, as measured in accordance with ISO test method 1133. When the MVR is within the above range, the molded article has excellent adhesion strength to plating and excellent flowability.

The deflection temperature under load of the resin composition for plating of the present invention, measured in accordance with ISO Test Method 75 at a load of 1.8 MPa, is preferably 75°C or higher, more preferably 80°C or higher, even more preferably 82°C or higher, and particularly preferably 85°C or higher. A deflection temperature under load of 75°C or higher provides molded articles with excellent adhesion strength to plating and superior heat resistance.

The plating resin composition of the present invention is obtained by mixing and melt-kneading the various resins described above and, if necessary, additives. For the mixing, any known or conventional kneading machine typically used for mixing resins can be used, such as a roll, Banbury mixer, extruder, or kneader.

The plating resin composition obtained in this manner can be molded by injection molding, extrusion molding, compression molding, injection-compression molding, blow molding, etc. to produce a resin molded product (molded product). The surface of the molded product can be plated to obtain a plated molded product. The plating can be performed using a known plating method, for example, under conditions similar to those used for plating ordinary ABS resin.

The plating adhesion strength of the plated molded product obtained by plating the above-mentioned resin molded product, according to JIS H8630, is preferably 9 N/cm or more, more preferably 10 N/cm or more, and even more preferably 12 N/cm or more. The plating resin composition of the present invention has excellent adhesion strength to the plating of the molded product, making it possible to achieve the above-mentioned plating adhesion strength.

The plating adhesion strength can be measured, for example, by molding a resin composition for plating using an injection molding machine to produce a resin molded product 3 mm thick, subjecting the resulting resin molded product to general treatments such as degreasing, etching, adding a catalyst, and rinsing with water, followed by electroless plating (nickel plating solution mainly consisting of nickel sulfate, sodium hypophosphite, and sodium citrate, 50°C x 8 minutes), rinsing with water, and electrolytic copper plating (room temperature x 2 hours, current density 3 A/ ^dm2 , film thickness 50 μm) to obtain a plated molded product.

The present invention will be explained in detail using the following examples, but the present invention is not limited by these examples. Note that parts and percentages shown in the examples are based on mass.

Examples and Comparative Examples The various materials shown in Table 1 were mixed in the blending ratios shown in Table 1, and then melt-kneaded and pelletized in a φ26 mm twin-screw extruder set at a cylinder temperature of 250° C., with a main screw rotation speed of 400 rpm and a discharge rate of 20 kg/hr, to produce pellets (resin composition for plating use). The various materials used in the examples and comparative examples were prepared as follows.

Graft copolymer (A)
A glass reactor was charged with 60 parts by mass of coagulated and agglomerated styrene-butadiene rubber latex (styrene 5% by mass, butadiene 95% by mass, mass average particle diameter 440 nm) in terms of solids, stirring was initiated, and nitrogen substitution was performed. After nitrogen substitution, the temperature inside the vessel was raised to 65°C, and when it reached 65°C, an aqueous solution prepared by dissolving 0.06 parts by mass of glucose, 0.03 parts by mass of anhydrous sodium pyrophosphate, and 0.001 parts by mass of ferrous sulfate in 10 parts by mass of deionized water was added, and the temperature was then raised to 70°C. Thereafter, a mixture of 10 parts by mass of acrylonitrile, 30 parts by mass of styrene, 0.3 parts by mass of tertiary dodecyl mercaptan, and 0.1 parts by mass of t-butyl hydroperoxide, and an emulsifier aqueous solution prepared by dissolving 1.0 part by mass of potassium oleate (solids equivalent) in 20 parts by mass of deionized water were continuously added dropwise over 4 hours. After the dropwise addition, the mixture was maintained for 3 hours to obtain a graft copolymer latex. The resulting mixture was salted out, dehydrated, and dried to obtain a powder of graft copolymer (A). The graft ratio of the resulting graft copolymer (A) was 42% by mass, and the reduced viscosity of the acetone-soluble portion was 0.28 dl/g. The mass-average particle size of the aggregated and thickened styrene-butadiene rubber latex was determined as follows.
The samples were stained with osmium tetroxide (OsO ₄ ), dried, and then photographed with a transmission electron microscope. The areas of 800 rubber particles were measured using an image analysis processor (IP-1000PC, manufactured by Asahi Kasei Corporation), and their equivalent circle diameters were determined to calculate the mass-average particle diameter.

Acrylic Block Copolymer (B1)
Product name: "Clarity LA4285", manufactured by Kuraray Co., Ltd.

Acrylic Block Copolymer (B2)
Product name: "Clarity LA2250", manufactured by Kuraray Co., Ltd.

Copolymer (C11)
A copolymer consisting of 75 parts by mass of styrene and 25 parts by mass of acrylonitrile was obtained by a known bulk polymerization method. The copolymer obtained by the above method had a reduced viscosity of 0.50 dl/g.

Copolymer (C12)
A copolymer consisting of 75 parts by mass of styrene and 25 parts by mass of acrylonitrile was obtained by a known bulk polymerization method. The copolymer obtained by the above method had a reduced viscosity of 0.60 dl/g.

Polycarbonate resin (C21)
A polycarbonate resin made from phosgene and bisphenol A with a viscosity average molecular weight of 20,500.

Polycarbonate resin (C22)
A polycarbonate resin made from phosgene and bisphenol A with a viscosity average molecular weight of 19,000.

[Measurement and Evaluation]
The resin compositions for plating obtained in the examples and comparative examples were evaluated as follows. The results are shown in Table 1.

(1) Melt Volume Flow Rate (MVR)
Using the pellets obtained in each of the Examples and Comparative Examples, the melt volume flow rate was measured under conditions of 220°C and a load of 98.07 N in accordance with ISO test method 1133. Unit: cm ³ /10 min

(2) Charpy impact strength (NC)
Using the pellets obtained in each example and comparative example, various test pieces were molded in accordance with ISO test method 294, and the notched Charpy impact values were measured at a thickness of 4 mm in accordance with ISO test method 179. Unit: kJ/ ^m2

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

(4) Plating Adhesion Strength The pellets obtained in each Example and Comparative Example were molded into flat plate molded products for plating (55 x 90 x 3 mm) using an injection molding machine, and plated by the following method. The adhesion strength of the deposited plating film was measured in accordance with JIS H8630, and was expressed as the stress (N/cm) when cuts were made in the metal film of the plated molded product at 1 cm intervals reaching the substrate, and the metal film was peeled off in a perpendicular direction.
<Plating process>
The above-mentioned plate molded product for plating was degreased by immersion in a degreasing solution (aqueous surfactant solution) at 55°C for 3 minutes. After degreasing, the plate was rinsed with water at room temperature for 1 minute and then immersed in a surface preparation solution (aqueous sulfuric acid solution - aqueous surfactant solution) for 3 minutes for surface preparation. After surface preparation, the plate was immersed in an etching solution (400 g/L chromic anhydride, 400 g/L sulfuric acid) at 68°C for 15 minutes for etching. After etching, the plate was rinsed with water at room temperature for 1 minute and then immersed in a neutralizing solution (aqueous hydrochloric acid solution) at room temperature for 2 minutes for neutralization. After neutralization, the plate was rinsed with water at room temperature for 1 minute and then immersed in a catalyst application solution (aqueous palladium chloride - stannous chloride - hydrochloric acid solution) at 35°C for 5 minutes for catalyst application. After catalyst application, the plate was rinsed with water at room temperature for 1 minute and then immersed in an accelerator solution (aqueous hydrochloric acid solution) at 40°C for 5 minutes for activation. After activation, the plate was rinsed with room temperature water for 1 minute and then immersed in a 50°C electroless plating solution (nickel plating solution mainly composed of nickel sulfate, sodium hypophosphite, and sodium citrate) for 8 minutes to perform an electroless nickel plating treatment. The electroless nickel-plated plate was rinsed with room temperature water for 1 minute and then immersed in an electroless copper plating bath at 25°C for 2 hours with a current density of 3 A/ ^dm2 to deposit a 50 μm thick electrolytic copper plating film on the plate. After electrolytic copper plating, the plate was rinsed with room temperature water for 1 minute and then dried at room temperature. The dried plate was aged at 80°C for 2 hours and left overnight.

(5) Measurement of Graft Ratio The weight ratio of the acetone-insoluble portion of the graft copolymer (A) was determined by fractionating it with acetone, and was found to be 42% by mass.

As shown in Table 1, the plating resin composition of the present invention was evaluated as having excellent fluidity, adhesion strength to plating on molded articles, and also excellent impact resistance of molded articles (Examples). On the other hand, when the acrylic block copolymer (B) was not included (Comparative Examples 1 and 3-5), adhesion strength to plating on molded articles was poor. Furthermore, Comparative Example 1 was slightly inferior in fluidity and impact resistance of molded articles compared to Example 1, which also contained copolymer (C11). Furthermore, Comparative Example 3 was inferior in fluidity compared to Examples 2 and 3, which also contained copolymer (C11) and polycarbonate resin (C21). When the blending amount of acrylic block copolymer (B) was high (Comparative Example 2), plating could not be applied to molded articles. Furthermore, Comparative Examples 4 and 5 were significantly inferior in impact resistance of molded articles compared to Examples 4-6, which also contained copolymer (C12) and polycarbonate resin (C21).

The plating resin composition of the present invention has excellent flowability and provides molded products with excellent plating adhesion strength and impact resistance. Therefore, it can be used in a variety of applications to meet market needs, such as vehicle interior and exterior parts.

Claims (8)

The present invention relates to a thermoplastic resin composition comprising: a graft copolymer (A) obtained by graft polymerization of a rubber polymer with a monomer component containing an aromatic vinyl monomer and a vinyl cyanide monomer; an acrylic block copolymer (B) ; and another thermoplastic resin (C) ,
The other thermoplastic resin (C) includes a copolymer (C1) of an aromatic vinyl monomer and a vinyl cyanide monomer,
the total content of the aromatic vinyl monomer and the vinyl cyanide monomer constituting the graft copolymer (A) and the other thermoplastic resin (C) is 20 to 73 mass% relative to 100 mass% of the total of the graft copolymer (A), the acrylic block copolymer (B), and the other thermoplastic resin (C);
the total content of the graft copolymer (A) and the other thermoplastic resin (C) is 90 to 99.5 mass%, and the content of the acrylic block copolymer (B) is 0.5 to 10 mass%, relative to 100 mass% of the total of the graft copolymer (A), the acrylic block copolymer (B), and the other thermoplastic resin (C);
In the graft copolymer (A), the content of the vinyl cyanide monomer is 10 to 50% by mass relative to 100% by mass of the total amount of the monomer components,
the content of the structural units derived from vinyl cyanide monomers in the copolymer (C1) is 10 to 50% by mass, relative to 100% by mass of the total amount of the copolymer (C1);
A resin composition for plating use, which has a melt volume flow rate (MVR) of 2 to 30 cm ³ /10 min under conditions of 220°C and a load of 98.07 N according to ISO test method 1133 . The plating resin composition according to claim 1, wherein the rubbery polymer contains a conjugated diene rubber. 3. The resin composition for plating according to claim 1, wherein the content of the rubber polymer is 7 to 20% by mass relative to 100% by mass of the total of the graft copolymer (A), the acrylic block copolymer (B), and the other thermoplastic resin (C). 4. The resin composition for plating use according to claim 1 , wherein the acrylic block copolymer (B) has a Shore hardness (Type A) of 10 to 99. 5. The resin composition for plating use according to claim 1 , wherein the acrylic block copolymer (B) has a melt flow rate at 230° C. of 30 to 600 g/10 min. 6. The resin composition for plating use according to claim 1, wherein the acrylic block copolymer (B) is a block copolymer of an acrylic ester polymer block and a methacrylic ester polymer block. The resin composition for plating use according to any one of claims 1 to 6 , wherein the other thermoplastic resin (C) comprises a polycarbonate resin. A plated molded article obtained by plating a molded article made of the resin composition for plating use according to any one of claims 1 to 7 .