Graft copolymer, thermoplastic resin composition, molded article, and coating composition

Abstract

To provide a graft copolymer capable of imparting excellent fingerprint resistance to a molded article or a coating film and also having excellent handleability and to provide a thermoplastic resin composition, a molded article and a coating composition using the same.SOLUTION: There is provided a graft copolymer obtained by graft-polymerizing a vinyl monomer in the presence of a copolymer (A) containing a structural unit derived from a (meth)acrylate (a) having a linear or branched hydrocarbon group having 11 or more carbon atoms.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a graft copolymer, a thermoplastic resin composition, a molded article, and a paint composition.

Background Art

[0002] As interior and exterior members of automobiles and housings of electronic devices, those having a black or metallic luster appearance have become widespread. However, the black or metallic luster has a problem that fingerprints adhered to it are easily noticeable. Therefore, for maintaining a high-class and clean feeling, the need for fingerprint resistance such as the inconspicuousness of adhered fingerprints and the ease of removing adhered fingerprints is increasing.

[0003] As a method for imparting fingerprint resistance to the surface of a molded article, there is known a method in which a stain-resistant agent is applied to the surface of the molded article to form a water-repellent and lipophilic coating film, thereby improving the compatibility with sebum components and making fingerprints less noticeable even if they adhere. Patent Document 1 discloses a stain-resistant agent containing a (meth)acrylic copolymer containing a (meth)acrylate having a water-repellent group such as a long-chain alkyl group as a copolymerization component.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, a copolymer containing a (meth)acrylate having a long-chain alkyl group as a copolymerization component is produced by solution polymerization, and the obtained solution is directly blended into a stain-resistant agent. Considering the storage, transportation of the above copolymer, subsequent mixing with other thermoplastic resins, or redissolution in an organic solvent, it is desirable to make the above copolymer into a powder. However, according to the study by the present inventors, since the above copolymer contains a (meth)acrylate having a long-chain alkyl group as a copolymerization component, its glass transition temperature is low, and there is a problem that the powder particles are likely to fuse with each other and the handleability is poor.

[0006] An aspect of the present invention aims to provide a graft copolymer capable of imparting excellent fingerprint resistance to molded articles and coating films and having excellent handleability in a powder state, a thermoplastic resin composition using the same, a molded article, and a coating composition.

Means for Solving the Problems

[0007] The present invention has the following aspects. 〔1〕A graft copolymer obtained by graft polymerizing a vinyl monomer in the presence of a copolymer (A) containing a structural unit based on a (meth)acrylate having a linear or branched hydrocarbon group having 11 or more carbon atoms. 〔2〕The graft copolymer according to 〔1〕above, having a toluene-insoluble content of 50% by mass or less. 〔3〕The graft copolymer according to 〔1〕or 〔2〕above, wherein the copolymer (A) does not contain a crosslinked structure. 〔4〕The graft copolymer according to any one of 〔1〕to 〔3〕above, wherein the copolymer (A) has a polymerizable unsaturated bond at the main chain terminal. 〔5〕A thermoplastic resin composition containing the graft copolymer according to any one of 〔1〕to 〔4〕above and another thermoplastic resin. 〔6〕A molded article containing the thermoplastic resin composition according to 〔5〕above. 〔7〕A coating composition containing the graft copolymer according to any one of 〔1〕to 〔4〕above and an organic solvent.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a graft copolymer capable of imparting excellent fingerprint resistance to molded articles and coating films and having excellent handleability, a thermoplastic resin composition using the same, a molded article, and a coating composition.

Brief Description of the Drawings

[0009]

Figure 1

DETAILED DESCRIPTION OF THE INVENTION

[0010] In this specification, (meth)acrylate is a general term for acrylate and methacrylate. A vinyl monomer is a compound having one polymerizable unsaturated double bond. The toluene-insoluble content is measured by the method described in the examples below. The weight-average molecular weight is a value in terms of standard polystyrene measured by gel permeation chromatography (GPC). Specifically, it is as described in the examples below. Hereinafter, the weight-average molecular weight may be referred to as Mw. The volume-average particle diameter of dispersed particles in an aqueous dispersion such as latex is measured by dynamic light scattering. The average particle diameter of the powder is measured by a sonic vibration sieve shaker described below. The glass transition temperature is a value determined by differential scanning calorimetry (DSC). Specifically, it is the glass transition temperature observed when the temperature is raised from 35°C to 200°C at 10°C / min under a nitrogen atmosphere, then cooled to -100°C, and then raised to 200°C again. Hereinafter, the glass transition temperature may be referred to as Tg. The "~" indicating a numerical range means that the numerical values described before and after it are included as the lower limit value and the upper limit value.

[0011] 〔Graft copolymer〕 The graft copolymer according to one aspect of the present invention (hereinafter, also referred to as "graft copolymer (B)") is a copolymer in which a vinyl monomer (hereinafter, also referred to as "vinyl monomer (m)") is graft-polymerized in the presence of a copolymer (A). The graft copolymer (B) contains a copolymer (A) portion and a polymer portion obtained by polymerizing a vinyl monomer (m). It is not easy to specifically identify the structure of the graft copolymer in detail. Therefore, for the graft copolymer (B), there is a situation (impossible or impractical situation) where it is impossible to directly identify it based on its structure or properties, or it is not very practical. The copolymer (A) and the vinyl monomer (m) will be described in detail later.

[0012] The proportion of the vinyl monomer (m) relative to the total 100% by mass of the copolymer (A) and the vinyl monomer (m) is preferably 10 to 90% by mass, more preferably 20 to 80% by mass. If the proportion of the vinyl monomer (m) is at least the above lower limit, the handleability of the graft copolymer (B) is more excellent, and if it is at least the above lower limit, the effect of imparting fingerprint resistance is more excellent.

[0013] The toluene-insoluble content of the graft copolymer (B) is preferably 50% by mass or less, more preferably 10% by mass or less, and particularly preferably 0% by mass, based on 100% by mass of the graft copolymer (B). If the toluene-insoluble content of the graft copolymer (B) is at most the above upper limit, it is excellent in compatibility with the thermoplastic resin and solubility in organic solvents, and is useful for imparting fingerprint resistance to molded articles and coating films.

[0014] The Mw of the graft copolymer (B) is preferably from 1,000 to 1,000,000, more preferably from 10,000 to 500,000, and even more preferably from 20,000 to 200,000. If the Mw of the graft copolymer (B) is at least the above lower limit, the handleability is more excellent, and if it is at most the above upper limit, the effect of imparting fingerprint resistance is more excellent.

[0015] The graft copolymer (B) typically has a Tg. The graft copolymer (B) may have one Tg, but from the viewpoint of handleability, it preferably has two or more Tgs. When the graft copolymer (B) has two or more Tgs, at least one is considered to be the Tg of the copolymer (A) part, and at least one is considered to be the Tg of the polymer part obtained by polymerizing the vinyl monomer (m). When the copolymer (A) part and the polymer part obtained by polymerizing the vinyl monomer (m) each have one Tg, and when the Tg of the copolymer (A) part is equivalent to the Tg of the polymer part obtained by polymerizing the vinyl monomer (m), the Tg of the graft copolymer (B) becomes one. When the graft copolymer (B) has two or more Tgs, some of the two or more Tgs are preferably in the range of -200 to 30°C, more preferably in the range of -100 to 25°C. The remaining Tg is preferably in the range of 50 to 200°C, more preferably in the range of 80 to 150°C. The difference between the Tg in the range of -200 to 30°C and the Tg in the range of 50 to 200°C is preferably in the range of 20 to 400°C, more preferably in the range of 60 to 200°C. When obtaining the difference between the Tg in the range of -200 to 30°C and the Tg in the range of 50 to 200°C, when there are two or more Tgs in the range of -200 to 30°C, the highest value is adopted, and when there are two or more Tgs in the range of 50 to 200°C, the lowest value is adopted. When the graft copolymer (B) has one Tg, the Tg is preferably in the range of 50 to 200°C, more preferably in the range of 80 to 150°C.

[0016] <Copolymer (A)> The copolymer (A) contains a structural unit based on a (meth)acrylate (a) having a linear or branched hydrocarbon group with 11 or more carbon atoms (hereinafter, also referred to as a “(meth)acrylate (a) unit”). The copolymer (A) preferably further contains a structural unit based on a vinyl monomer other than (meth)acrylate (a) (hereinafter, also referred to as a “vinyl monomer (b)”) (hereinafter, also referred to as a “vinyl monomer (b) unit”). (Meth)acrylate (a) and vinyl monomer (b) will be described in detail later.

[0017] The proportion of the (meth)acrylate (a) unit with respect to the total 100% by mass of all the constitutional units constituting the copolymer (A) is preferably 5 to 90% by mass, more preferably 10 to 80% by mass, and still more preferably 20 to 70% by mass. If the proportion of the (meth)acrylate (a) unit is at least the above lower limit, the fingerprint resistance of the molded article or coating film containing the graft copolymer (B) is more excellent, and if it is at most the above upper limit, the handleability is improved. The total of all the constitutional units constituting the copolymer (A) is the total of the (meth)acrylate (a) unit and the vinyl monomer (b) unit.

[0018] The copolymer (A) may contain a crosslinked structure. From the viewpoint of making the toluene-insoluble content not more than the above-mentioned preferable upper limit value, it is preferable that the copolymer (A) does not contain a crosslinked structure.

[0019] Examples of the crosslinked structure include a crosslinked structure based on a crosslinking agent having two or more polymerizable unsaturated bonds. When the (meth)acrylate (a) and the vinyl monomer (b) are polymerized in the presence of a crosslinking agent, a crosslinked structure is introduced into the copolymer (A). Examples of the crosslinking agent include allyl (meth)acrylate, butylene di(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, triallyl cyanurate, triallyl isocyanurate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polybutylene glycol di(meth)acrylate, polyester di(meth)acrylate, polyurethane di(meth)acrylate, polybutadiene di(meth)acrylate, polyglycerin poly(meth)acrylate, divinylbenzene, and the like.

[0020] The amount of the crosslinking agent used is preferably as small as possible from the viewpoint of making the toluene-insoluble content of the graft copolymer (B) not more than the above-mentioned preferable upper limit value. For example, with respect to 100 parts by mass in total of the (meth)acrylate (a) and the vinyl monomer (b), 1 part by mass or less is preferable, and 0 part by mass is particularly preferable.

[0021] The copolymer (A) preferably has a polymerizable unsaturated bond at the main chain terminal. When a polymerizable unsaturated bond is present at the main chain terminal of the copolymer (A), the fingerprint resistance and the solubility of the graft copolymer (B) in an organic solvent are improved. This is presumably because the polymerizable unsaturated bond serves as a graft point and the copolymer (A) and the polymer obtained by polymerizing the vinyl monomer (b) are chemically bonded.

[0022] The copolymer (A) having a polymerizable unsaturated bond at the main chain terminal can be obtained, for example, by using α-methylstyrene dimer as a chain transfer agent when polymerizing the (meth)acrylate (a) and, if necessary, the vinyl monomer (b). By using α-methylstyrene dimer, a copolymer having a structure represented by -CH2-C(Ph)=CH2 (Ph is a phenyl group) at the main chain terminal can be obtained.

[0023] The toluene-insoluble content of the copolymer (A) is preferably 70% by mass or less, more preferably 20% by mass or less, and particularly preferably 0% by mass with respect to 100% by mass of the copolymer (A). If the toluene-insoluble content of the copolymer (A) is not more than the above upper limit value, it is easy to make the toluene-insoluble content of the graft copolymer (B) not more than the above-mentioned preferable upper limit value.

[0024] The Mw of the copolymer (A) is preferably from 1,000 to 1,000,000, more preferably from 9,000 to 400,000, and even more preferably from 15,000 to 190,000. If the Mw of the copolymer (A) is not less than the above lower limit value, the handleability is more excellent, and if it is not more than the above upper limit value, the effect of imparting fingerprint resistance is more excellent.

[0025] The copolymer (A) preferably has a Tg from the viewpoint of the effect of imparting fingerprint resistance. When the copolymer (A) has a Tg, the Tg of the copolymer (A) is preferably from -200 to 30°C, more preferably from -100 to 25°C. If the Tg of the copolymer (A) is at least the above lower limit value, the handleability is more excellent, and if it is at most the above upper limit value, the effect of imparting fingerprint resistance is more excellent.

[0026] The copolymer (A) is produced by known methods such as bulk polymerization, solution polymerization, bulk suspension polymerization, suspension polymerization, emulsion polymerization and the like. Among these, from the viewpoint of easily controlling the particle diameter of the copolymer (A) particles, emulsion polymerization is preferable. Among emulsion polymerizations, miniemulsion polymerization is preferable from the viewpoint of easily narrowing the particle diameter distribution of the copolymer (A) particles and easily synthesizing a more homogeneous copolymer (A).

[0027] As a method for producing the copolymer (A) by an emulsion polymerization method, for example, a method of mixing a vinyl monomer ((meth)acrylate (a) and, if necessary, a vinyl monomer (b)), water, an emulsifier, and, if necessary, other additives (a polymerization initiator, a chain transfer agent, a crosslinking agent), emulsifying the obtained mixture, and heating the obtained emulsion to polymerize the vinyl monomer can be mentioned. Thereby, an aqueous dispersion containing the copolymer (A) is obtained.

[0028] Examples of the emulsifier include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants and the like, and anionic surfactants are preferable. Examples of the anionic surfactant include alkali metal salts of fatty acids (for example, oleic acid, palmitic acid, stearic acid, rosin acid, etc.), alkali metal salts of alkenyl succinic acids, sodium alkylbenzenesulfonate, sodium alkylsulfosuccinate, sodium polyoxyethylene nonylphenyl ether sulfate ester, and the like. The emulsifier may be used alone or in combination of two or more. The addition amount of the emulsifier is, for example, 0.01 to 5.0 parts by mass with respect to 100 parts by mass of the vinyl monomer.

[0029] Examples of the polymerization initiator include azo compound-based polymerization initiators, organic peroxide-based polymerization initiators, inorganic peroxide-based polymerization initiators, etc. As the azo compound-based polymerization initiator, organic peroxide-based polymerization initiator, and inorganic peroxide-based polymerization initiator, known ones can be used without limitation. The polymerization initiator may be used alone or in combination of two or more. The addition amount of the polymerization initiator is, for example, 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the vinyl monomer. Examples of the chain transfer agent include mercaptans such as octyl mercaptan, n- or t-dodecyl mercaptan, n-hexadecyl mercaptan, n- or t-tetradecyl mercaptan; α-methylstyrene dimer; terpenes, etc. The addition amount of the chain transfer agent is, for example, 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the vinyl monomer.

[0030] Examples of the emulsification method include a method of treating the mixed solution with a homogenizer. Examples of the homogenizer include a pressure type homogenizer, an ultrasonic type homogenizer, etc. In the pressure type homogenizer, the monomer particles in the mixed solution are refined by colliding the mixed solution in a high-pressure state using a pump or the like against a homogenizing valve. In the pressure type homogenizer, the pressure applied to the mixed solution is not particularly limited and can be, for example, 1 to 100 MPa. In the ultrasonic type homogenizer, ultrasonic vibration is applied to the mixed solution to generate minute vacuum bubbles inside the mixed solution. The monomer particles in the mixed solution are refined by the impact generated when these vacuum bubbles burst. In the ultrasonic type homogenizer, the amplitude of the ultrasonic vibration applied to the mixed solution is not particularly limited and can be, for example, 10 to 17000 μm. As the homogenizer, usually, a continuous type homogenizer that continuously treats the mixed solution is used, but a batch type homogenizer that treats an arbitrary amount of the mixed solution one by one may also be used.

[0031] The volume average particle diameter of the dispersed particles in the emulsion is preferably 10 to 1000 nm, more preferably 50 to 500 nm. If the volume average particle diameter of the emulsion particles in the emulsion is within the above range, the volume average particle diameter of the dispersed particles in the aqueous dispersion of the obtained copolymer (A) is also likely to be within the above range. Note that a miniemulsion is an emulsion having a volume average particle diameter of the emulsion particles of 1000 nm or less. The polymerization conditions are not particularly limited, but for example, they are 50 to 80 °C for 0.5 to 24 hours.

[0032] The obtained aqueous dispersion of the copolymer (A) is usually used as it is for the production of the graft copolymer (B). The volume average particle diameter of the dispersed particles in the aqueous dispersion of the copolymer (A) is preferably 10 to 1000 nm, more preferably 50 to 500 nm. If the volume average particle diameter is at least the above lower limit value, the handleability is good, and if it is at most the above upper limit value, the stability of the emulsion is good.

[0033] “(Meth)acrylate (a)” The number of carbon atoms of the linear or branched hydrocarbon group of (meth)acrylate (a) is 11 or more, preferably 12 or more, more preferably 16 or more. The upper limit of the number of carbon atoms of the hydrocarbon group is not particularly limited, but is, for example, 50. If the number of carbon atoms of the hydrocarbon group is 11 or more, the lipophilicity of the surface of the molded article or coating film containing the graft copolymer (B) is improved, and the attached fingerprints are less noticeable. The hydrocarbon group may be linear or branched, and a linear group is preferred in terms of easy availability of raw materials. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an isoalkyl group, etc. Among these, an alkyl group is preferred from the viewpoint of the effect of imparting fingerprint resistance.

[0034] Examples of (meth)acrylate (a) include compounds represented by the following formula (1). CH2=CR 1 -C(=O)-O-R 2 ···(1) However, R 1 is a hydrogen atom or a methyl group, and R2 is a linear or branched hydrocarbon group having 11 or more carbon atoms. R 2 Examples of the hydrocarbon group of

[0035] Specific examples of the (meth)acrylate (a) include dodecyl (meth)acrylate, dodecenyl (meth)acrylate, tetradecyl (meth)acrylate, tetradecenyl (meth)acrylate, hexadecyl (meth)acrylate, hexadecenyl (meth)acrylate, octadecyl (meth)acrylate (alias: stearyl (meth)acrylate), octadecenyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, and the like. These (meth)acrylates (a) may be used alone or in combination of two or more. As the (meth)acrylate (a), stearyl (meth)acrylate is preferable from the viewpoint of the effect of imparting fingerprint resistance.

[0036] "Vinyl monomer (b)" The vinyl monomer (b) may be copolymerizable with the (meth)acrylate (a). For example, other (meth)acrylates other than the (meth)acrylate (a), aromatic vinyl compounds, vinyl cyanide compounds, maleic anhydride, maleimide compounds, (meth)acrylic acid, maleic acid, and the like can be mentioned.

[0037] Examples of the other (meth)acrylates include (meth)acrylates having one or more of a linear or branched hydrocarbon group having 1 to 10 carbon atoms, an alicyclic group, and an aromatic group. Examples of the linear or branched hydrocarbon group include an alkyl group, an alkenyl group, and an isoalkyl group. The alicyclic group may be monocyclic or polycyclic. The number of carbon atoms of the alicyclic group is, for example, 4 to 10. Examples of the aromatic group include aryl groups such as a phenyl group and aralkyl groups such as a benzyl group.

[0038] Specific examples of other (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, adamantyl (meth)acrylate, and glycidyl (meth)acrylate.

[0039] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, o-, m- or p-methylstyrene, vinylxylene, p-t-butylstyrene, and ethylstyrene. Examples of vinyl cyanide compounds include acrylonitrile and methacrylonitrile. Examples of maleimide compounds include N-alkylmaleimides such as N-methylmaleimide, N-ethylmaleimide, N-n-propylmaleimide, N-i-propylmaleimide, N-n-butylmaleimide, N-i-butylmaleimide, and N-tert-butylmaleimide; N-cycloalkylmaleimides such as N-cyclohexylmaleimide; N-arylmaleimides such as N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(4-hydroxyphenyl)maleimide, and N-chlorophenylmaleimide; and N-aralkylmaleimides. These vinyl monomers (b) may be used alone or in combination of two or more.

[0040] As the vinyl monomer (b), from the viewpoint of easy availability of raw materials, at least one selected from the group consisting of other (meth)acrylates, aromatic vinyl compounds, vinyl cyanide compounds, maleic anhydride and maleimide compounds is preferable, and at least one selected from the group consisting of (meth)acrylates having a linear or branched hydrocarbon group having 1 to 8 carbon atoms, aromatic vinyl compounds and vinyl cyanide compounds is more preferable. Among these, from the viewpoint of reactivity with the (meth)acrylate (a), (meth)acrylates having a linear or branched hydrocarbon group having 1 to 8 carbon atoms are preferable, and from the viewpoint of compatibility with the thermoplastic resin described later, aromatic vinyl compounds and vinyl cyanide compounds are preferable. When the vinyl monomer (b) consists of an aromatic vinyl compound and a vinyl cyanide compound, it is preferable that the aromatic vinyl compound is 60 to 90% by mass and the vinyl cyanide compound is 10 to 40% by mass with respect to the total mass of the vinyl monomer (b), and it is more preferable that the aromatic vinyl compound is 65 to 80% by mass and the vinyl cyanide compound is 20 to 35% by mass.

[0041] <Vinyl monomer (m)> Examples of the vinyl monomer (m) include (meth)acrylates, aromatic vinyl compounds, vinyl cyanide compounds, maleic anhydride, maleimide compounds, (meth)acrylic acid, maleic acid, and the like. Examples of the (meth)acrylate include the above-mentioned (meth)acrylate (a) and other (meth)acrylates. Specific examples of the (meth)acrylate (a), other (meth)acrylates, aromatic vinyl compounds, vinyl cyanide compounds, and maleimide compounds are the same as those described above.

[0042] As the vinyl monomer (m), from the viewpoint of handleability, vinyl monomers other than the (meth)acrylate (a) are preferable. As the vinyl monomer other than (meth)acrylate (a), from the viewpoint of easy availability of raw materials, at least one selected from the group consisting of other (meth)acrylates, aromatic vinyl compounds, vinyl cyanide compounds, maleic anhydride and maleimide compounds is preferable, and at least one selected from the group consisting of (meth)acrylates having a linear or branched hydrocarbon group having 1 to 8 carbon atoms, aromatic vinyl compounds and vinyl cyanide compounds is more preferable. Among these, when the graft copolymer (B) is mixed with the thermoplastic resin described later, it is preferable to select a composition that is easily dispersed in the thermoplastic resin. For example, when the thermoplastic resin is an ABS resin or an AS resin described later, it is advisable to select a combination of aromatic vinyl and vinyl cyanide compounds, and when the thermoplastic resin is an acrylic resin, it is advisable to select (meth)acrylate. When the vinyl monomer (m) consists of an aromatic vinyl compound and a vinyl cyanide compound, it is preferable that the aromatic vinyl compound is 60 to 90% by mass and the vinyl cyanide compound is 10 to 40% by mass with respect to the total mass of the vinyl monomer (m), and it is more preferable that the aromatic vinyl compound is 65 to 80% by mass and the vinyl cyanide compound is 20 to 35% by mass. When the copolymer (A) contains a vinyl monomer (b) unit and the vinyl monomer (m) is a vinyl monomer other than (meth)acrylate (a), the vinyl monomer (b) and the vinyl monomer (m) may be the same or different.

[0043] <Method for Producing Graft Copolymer (B)> The graft copolymer (B) is obtained by graft-polymerizing the vinyl monomer (m) in the presence of the copolymer (A). During the graft polymerization, a chain transfer agent may be added to adjust the molecular weight of the graft copolymer (B). The graft polymerization method is not particularly limited, but an emulsion polymerization method is preferable.

[0044] As a method for producing the graft copolymer (B) by the emulsion polymerization method, for example, a method of adding a vinyl monomer (m) and a polymerization initiator to an aqueous dispersion containing the copolymer (A), water, and an emulsifier, and polymerizing the vinyl monomer (m) by heating can be mentioned. Thereby, an aqueous dispersion containing the graft copolymer (B) is obtained. The aqueous dispersion of the copolymer (A) can be obtained by the production method described above. Examples of the polymerization initiator include the same ones as described above. The polymerization conditions are not particularly limited, but for example, they are 50 to 90 °C for 0.5 to 6 hours.

[0045] In the aqueous dispersion of the graft copolymer (B), the volume average particle diameter of the dispersed particles is preferably 10 to 1000 nm, more preferably 50 to 500 nm. If the volume average particle diameter is at least the above lower limit value, the handleability is good, and if it is at most the above upper limit value, the stability of the emulsion is good.

[0046] If necessary, the graft copolymer (B) may be recovered from the aqueous dispersion of the graft copolymer (B). Thereby, a powder of the graft copolymer (B) is obtained. Examples of the method for recovering the graft copolymer (B) include known methods such as a precipitation method and a spray drying method. As the precipitation method, a method of adding a precipitating agent to an aqueous dispersion, heating and stirring, then separating the precipitating agent, and washing, dehydrating, and drying the precipitated graft copolymer (B) can be mentioned. Examples of the precipitating agent include aqueous solutions such as sulfuric acid, acetic acid, calcium chloride, and magnesium sulfate.

[0047] The average particle diameter of the powder of the graft copolymer (B) is preferably 100 to 800 μm, more preferably 150 to 600 μm. If the average particle diameter is at least the above lower limit value, the dispersibility of the powder is small and it is easy to handle, and if it is at most the above upper limit value, the dispersibility in the thermoplastic resin is good.

[0048] 〔Thermoplastic resin composition〕 The thermoplastic resin composition according to one aspect of the present invention contains a graft copolymer (B) and another thermoplastic resin other than the graft copolymer (B) (hereinafter also referred to as "thermoplastic resin (C)"). The thermoplastic resin composition may contain additives as necessary within a range not significantly impairing the effects of the present invention.

[0049] The thermoplastic resin (C) is not particularly limited. For example, acrylic resin (e.g., PMMA resin), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-α-methylstyrene copolymer (αSAN resin), styrene-maleic anhydride copolymer, acrylonitrile-styrene-N-substituted maleimide terpolymer, styrene-maleic anhydride-N-substituted maleimide terpolymer, a resin obtained by graft-polymerizing at least one vinyl monomer selected from the group consisting of aromatic vinyl, vinyl cyanide, and (meth)acrylate in the presence of a rubbery polymer (e.g., polybutadiene, acrylic rubber, silicone rubber, ethylene propylene diene rubber (EPDM) or a composite rubber thereof, etc.) (e.g., ABS resin, ASA resin, SAS resin, AES resin, etc.), polycarbonate resin, polybutylene terephthalate (PBT resin), polyethylene terephthalate (PET resin), polyvinyl chloride, polyolefins such as polyethylene, polypropylene, styrene-butadiene-styrene (SBS), styrene-butadiene (SBR), hydrogenated SBS, styrene-isoprene-styrene (SIS) and other styrenic elastomers, various olefinic elastomers, various polyester elastomers, polystyrene, methyl methacrylate-styrene copolymer (MS resin), acrylonitrile-styrene-methyl methacrylate copolymer, polyacetal resin, modified polyphenylene ether (modified PPE resin), ethylene-vinyl acetate copolymer, polyphenylene sulfide (PPS resin), polyethersulfone (PES resin), polyetheretherketone (PEEK resin), polyarylate, liquid crystal polyester resin, polyamide resin (e.g., nylon), etc. These thermoplastic resins (C) may be used alone or in combination of two or more.

[0050] Examples of the additives include various stabilizers such as antioxidants and light stabilizers, lubricants, plasticizers, mold release agents, dyes, pigments (such as carbon black), antistatic agents, flame retardants, inorganic fillers, metal powders, and the like.

[0051] In the thermoplastic resin composition, the content of the graft copolymer (B) is preferably 1 to 80 parts by mass, more preferably 5 to 50 parts by mass, based on 100 parts by mass in total of the graft copolymer (B) and the thermoplastic resin (C). If the content of the graft copolymer (B) is at least the above lower limit, the fingerprint resistance of the molded article of the thermoplastic resin composition is more excellent, and if it is at most the above upper limit, the moldability is more excellent.

[0052] The content of the additive is preferably 0 to 100 parts by mass, more preferably 0 to 10 parts by mass, based on 100 parts by mass in total of the graft copolymer (B) and the thermoplastic resin (C).

[0053] The thermoplastic resin composition can be produced, for example, by mixing and dispersing the powder of the graft copolymer (B), the thermoplastic resin (C), and, if necessary, the additive with a V-type blender, a Henschel mixer, or the like, and then melt-kneading the resulting mixture using a melt-kneading machine such as a screw-type extruder, a Banbury mixer, a pressure kneader, or a mixing roll. If necessary, the obtained melt-kneaded product may be pelletized using a pelletizer or the like.

[0054] [Molded Article] The molded article according to one aspect of the present invention contains the above-described thermoplastic resin composition. The molded article of this aspect can be obtained, for example, by molding the above-described thermoplastic resin composition by a known molding method. Examples of the molding method include an injection molding method, a press molding method, an extrusion molding method, a vacuum molding method, a blow molding method, and the like.

[0055] [Coating Composition] The coating composition according to one aspect of the present invention contains a graft copolymer (B) and an organic solvent. The coating composition may contain, if necessary, other resins and additives other than the graft copolymer (B) within the range where the effects of the present invention are not significantly impaired.

[0056] The organic solvent is not particularly limited, and those that easily volatilize during the production of the coating film are preferred. For example, aromatic hydrocarbons (benzene, toluene, xylene, etc.), alcohols (methanol, ethanol, isopropanol, etc.), ketones (acetone, ethyl methyl ketone, cyclohexanone, etc.), aliphatic hydrocarbons (hexane, heptane, etc.), amides (N,N-dimethylformamide, etc.), esters (methyl acetate, etc.) can be mentioned. These organic solvents may be used alone or in combination of two or more. As the organic solvent, those capable of dissolving the copolymer (A) and the graft copolymer (B) are preferred.

[0057] The other resin may be a resin known as a coating resin, and examples thereof include polyester, polyurethane, polyisocyanate, polyurea, epoxy resin, polyolefin, polysiloxane, etc. If necessary, a monomer for synthesizing the resin may be contained, and it may be cured by ultraviolet rays or two-component curing after coating. The additive may be an additive known as a coating additive, and examples thereof include a viscosity modifier, a bright pigment, a coloring pigment, a rust inhibitor, a curing catalyst, an ultraviolet absorber, a light stabilizer, a pigment dispersant, a neutralizer, a surfactant, an antifoaming agent, a plasticizer, a preservative, etc.

[0058] In the coating composition, the content of the graft copolymer (B) is preferably 1% by mass or more, more preferably 5% by mass or more, based on 100% by mass of the solid content of the coating composition. If the content of the graft copolymer (B) is at least the above lower limit value, the fingerprint resistance of the coating film of the coating composition is more excellent. The solid content of the coating composition is the solid content (heating residue) obtained in accordance with JIS K5601 1-2:2008.

[0059] The content of the organic solvent is set according to the solid content concentration of the coating composition. The solid content concentration of the coating composition is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, based on the total mass of the coating composition. If the solid content concentration is at least the above lower limit, the drying efficiency until the formation of the coating film is good, and if it is at most the above upper limit, the coatability of the coating composition is good.

[0060] The coating composition can be produced, for example, by mixing a powder of the graft copolymer (B), an organic solvent, and, if necessary, other resins and additives.

[0061] A coating film can be formed by applying the coating composition to the surface of a substrate and drying it. The substrate is not particularly limited, and examples thereof include resin substrates, metals (such as iron), glass, and concrete. Examples of the resin of the resin substrate include the above-described thermoplastic resin (C) and cured resins cured by heat, active energy rays, or the like. The coating method and drying method of the coating composition are also not particularly limited, and known methods can be used.

Examples

[0062] The present invention will be described more specifically with reference to the following examples and comparative examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the following, "parts" means "parts by mass" and "%" means "% by mass".

[0063] The abbreviations used below are as follows. (Monomer) SMA: Stearyl methacrylate. MMA: Methyl methacrylate. MA: Methyl acrylate. ST: Styrene. AN: Acrylonitrile. (Crosslinking agent) AMA: Allyl methacrylate. (Chain transfer agent) MSD: α-Methylstyrene dimer. TDM: t-Dodecyl mercaptan. (Coincidence initiator) LPO: Lauroyl peroxide. BHP: t-Butyl hydroperoxide. (Thermoplastic resin) PMMA: Polymethyl methacrylate (「Acrypet VH5」manufactured by Mitsubishi Chemical). AS: Acrylonitrile-styrene copolymer produced by suspension polymerization method (「UMG AXS Resin S102N」manufactured by Technos UMG).

[0064] [Measurement of toluene-insoluble content of copolymer] The latex of the copolymer (copolymer (A) or graft copolymer (B)) was dried in a dryer at 60 °C for 1 day, washed with isopropanol, and dried in a vacuum dryer to recover the copolymer. 1 g (X) of the recovered copolymer was added to 20 mL of toluene, allowed to stand at room temperature (25 °C) for 3 days, and then the resulting suspension or solution was centrifuged at 14,000 rpm for 180 minutes. After centrifugation, if there was a precipitate component, the precipitate component and the supernatant solution (toluene solution) were separately collected. Then, the precipitate component was sufficiently dried by a vacuum dryer to measure its mass Y (g), and the toluene-insoluble content was calculated from the following formula. If there was no precipitate component after centrifugation, the toluene-insoluble content was set to 0 mass%. Toluene-insoluble content (mass%) = (Y / X) × 100

[0065] [Evaluation of appearance of toluene solution] The copolymer (A) or graft copolymer (B) was recovered from the latex of the copolymer (A) or graft copolymer (B) by the respective methods described below. 50 g of toluene was added to 0.5 g of the recovered copolymer (A) or graft copolymer (B), stirred with a stirrer for 6 hours, and the appearance of the resulting solution was visually observed and evaluated according to the following criteria. ◎ or ○ was regarded as passing. ◎: Transparent, no precipitate. ○: Slightly turbid, no precipitate. △: Turbid, no precipitate. ×: Turbid and with precipitate.

[0066] [Measurement of weight-average molecular weight] The copolymer (A) or the graft copolymer (B) was recovered from the latex of the copolymer (A) or the latex of the graft copolymer (B) by the respective methods described below. 0.005 g of the recovered copolymer (A) or graft copolymer (B) was dissolved in 10 g of tetrahydrofuran (THF) at room temperature (25°C), and the solution was introduced into a GPC apparatus. The molecular weight of the polymer in terms of polystyrene was measured using a calibration curve previously obtained with standard polystyrene of known molecular weight, and Mw was determined. In the case where the copolymer (A) or the graft copolymer (B) was not soluble in THF, the measurement was considered impossible.

[0067] [Measurement of volume-average particle diameter of latex] For the latex of the copolymer (A) or the latex of the graft copolymer (B), the volume-average particle diameter (nm) was determined by the dynamic light scattering method using Nanotrac UPA-EX150 manufactured by Nikkiso Co., Ltd.

[0068] [Measurement of glass transition temperature] The powder of the copolymer (A) (hereinafter also referred to as "copolymer powder") or the powder of the graft copolymer (B) (hereinafter also referred to as "graft copolymer powder") was heated from 35°C to 200°C at a heating rate of 10°C / min in a nitrogen atmosphere using differential scanning calorimetry (DSC), then cooled to -100°C, and then heated to 200°C again, and the glass transition temperature (°C) observed was determined.

[0069] [Measurement of fraction not passing through sieve #16 of powder] 10 g of the copolymer powder or the graft copolymer powder was sieved using a robot shifter (RPS-105) manufactured by Seishin Enterprise Co., Ltd. with the sieves used: 16 mesh - 28 mesh - 35 mesh - 48 mesh - 70 mesh - 100 mesh - 200 mesh, and the fraction not passing through sieve #16 (%) was determined under the classification conditions: sonic intensity 40, sonic frequency 51 Hz, classification time 3 minutes, and pulse interval 1.

[0070] [Measurement of average particle diameter of powder] The average particle diameter (μm) of the copolymer powder or graft copolymer powder was determined from the amount of residue on each mesh in the measurement of the fraction of the above powder that did not pass through sieve #16.

[0071] [Measurement of the angle of repose of the powder] For the copolymer powder or graft copolymer powder, the angle of repose (°) was determined by the following method using an A.B.D powder property measuring device (ABD-100) manufactured by Tsutsui Rikagaku Kikai Co., Ltd. under the environment of 25 °C and 50% RH. The sample put into the sample hopper was dropped onto the disc of the angle of repose sample stage through a vibrating rod, a vibrating screen, a sample discharge hopper and a sample discharge nozzle to form a pile, and the angle of the pile was measured with a protractor from three different directions. The above operation was repeated three times, and the average value was taken as the angle of repose. Also, those that did not fall even with a sample discharge nozzle having a diameter of φ10 mm were regarded as unmeasurable.

[0072] [Evaluation of the handleability of the powder] The handleability of the powder was evaluated based on the following criteria from the average particle diameter of the powder. The smaller the average particle diameter of the powder, the less likely the particles are to stick to each other, and the better the mixing and kneading with other components can be performed. ○: The average particle diameter of the powder is 1000 μm or less. ×: The average particle diameter of the powder exceeds 1000 μm.

[0073] [Measurement of the oleic acid absorption amount of the molded product] Under the environment of room temperature (25 °C), a dumbbell-shaped molded product of about 11 g was immersed in oleic acid for one week. The oleic acid absorption amount (μg) was calculated based on the mass (μg) of the test piece after immersion - the mass (μg) of the test piece before immersion.

[0074] [Measurement of the pure water contact angle of the surface of the molded product or coating film] Under the environment of 25 °C and 50% RH, 1 μL of pure water was dropped onto the surface of the horizontally placed molded product or coating film using a contact angle meter ("DMs-401" manufactured by Kyowa Interface Science Co., Ltd.), and the contact angle (pure water contact angle) was measured 1 second after the dropping. The larger the pure water contact angle, the better the lipophilicity.

[0075] [Measurement of the Oleic Acid Contact Angle on the Surface of the Molded Product or Coating Film] The contact angle (oleic acid contact angle) was measured in the same manner as the measurement of the pure water contact angle, except that oleic acid was used instead of pure water. The smaller the oleic acid contact angle, the better the lipophilicity.

[0076] [Evaluation of the Appearance of the Molded Product after Wiping off Fingerprints] The right thumb was pressed against the surface of the test piece for 10 seconds to attach fingerprints. The fingerprints on the surface of the test piece with fingerprints attached were wiped off by reciprocating a Kim towel [manufactured by Nippon Paper Crecia Co., Ltd.] in one direction once. Specifically, as shown in FIG. 1, a rod-shaped jig 10 with a hemispherical tip 11 was prepared, and the tip 11 was covered with a Kim towel [manufactured by Nippon Paper Crecia Co., Ltd.] 12. The tip 11 covered with the Kim towel 12 was brought into contact with the surface of the test piece 13 so that the rod-shaped jig 10 was perpendicular, and the tip 11 was slid in the horizontal direction (the direction of the arrow in the figure) on the surface of the test piece 13 and reciprocated once. At that time, the applied load was 500 g. After wiping, the surface of the test piece was visually observed and evaluated according to the following criteria. ◎ or 〇 was regarded as passing. ◎: No fingerprint marks are visible. 〇: Almost no fingerprint marks are visible. △: Slight fingerprint marks are prominent. ×: Fingerprint marks are prominent.

[0077] [Measurement of the Toluene Insoluble Content of the Paint Composition] After separating the paint composition X (g) with a centrifuge (14,000 rpm, 180 minutes), if there was a precipitate component, the precipitate component and the supernatant solution (toluene solution) were separately collected. Then, the precipitate component was sufficiently dried with a vacuum dryer and its mass Y (g) was measured, and the toluene insoluble content was calculated from the following formula. If there was no precipitate component after centrifugation, the toluene insoluble content was set to 0 mass%. Toluene insoluble content (mass%) = (Y / X) × 100

[0078] [Evaluation of the Appearance of the Paint Composition] The appearance of the coating composition was visually observed and evaluated according to the following criteria. ◎ or ○ was considered as passing. ◎: Transparent, no precipitate. ○: Slightly turbid, no precipitate. △: Turbid, no precipitate. ×: Turbid and with precipitate.

[0079] [Production of copolymer (A)] [Production Example A-1: Production of copolymer (A-1)] Into a container, 50 parts of stearyl methacrylate (SMA), 45 parts of methyl methacrylate (MMA), 5 parts of methyl acrylate (MA), 2 parts of α-methylstyrene dimer (MSD), and 1 part of lauroyl peroxide (LPO) were charged. To this, a mixed solution of 180 parts of distilled water and 0.1 part of dipotassium alkenyl succinate was added, and a pre-emulsion with a volume average particle diameter of 300 nm was obtained by treating it with a pressure homogenizer (manufactured by Sanmaru Kikai Kogyo Co., Ltd.) at 30 MPa for 2 Passes. The above pre-emulsion was transferred to a reactor equipped with a reagent injection container, a cooling pipe, a jacket heater, and a stirring device, and after nitrogen substitution, it was heated to 60 °C with stirring to initiate radical polymerization, and then aged at 80 °C for 5 hours to complete the polymerization. Thereby, a latex of copolymer (A-1) was obtained. The solid content of the obtained latex was 21%, the amount of coagulum was 0.03%, and the volume average particle diameter was the same as that of the pre-emulsion, 300 nm. A part of the obtained latex was coagulated with isopropanol, washed, and dried with a vacuum dryer to obtain a powder of copolymer (A-1). For the obtained powder (copolymer powder), the glass transition temperature, the fraction not passing through sieve #16, the average particle diameter, and the angle of repose were measured. The results are shown in Table 1.

[0080] [Production Examples A-2 to A-5: Production of copolymers (A-2) to (A-5)] Except that the types and amounts of (meth)acrylate (a), vinyl monomer (b), chain transfer agent, and polymerization initiator were changed as shown in Table 1, latexes and powders of copolymers (A-2) to (A-5) were obtained in the same manner as in Production Example (A-1).

[0081] Table 1 shows the evaluation results of the copolymers (A-1) to (A-5).

[0082] [Table 1]

[0083] [Production of Graft Copolymer (B)] [Production Example B-1: Production of Graft Copolymer (B-1)] Into a reactor equipped with a reagent injection vessel, a cooling pipe, a jacket heater, and a stirring device, raw materials were charged according to the following formulation. After thoroughly purging the inside of the reactor with nitrogen, the internal temperature was raised to 70 °C with stirring. [Formulation] 50 parts of copolymer (A-1) latex (in terms of solid content) 200 parts of water (including the water in the copolymer (A-1) latex) 1 part of dipotassium alkenyl succinate 0.3 part of sodium formaldehyde sulfoxylate 0.001 part of ferrous sulfate 0.003 part of disodium ethylenediaminetetraacetate

[0084] Next, while dropping a mixed solution containing methyl methacrylate (MMA), methyl acrylate (MA), and t-butyl hydroperoxide (BHP) according to the following formulation 2 over 100 minutes, the temperature was raised to 80 °C. [Formulation] 45 parts of methyl methacrylate 5 parts of methyl acrylate 0.3 part of t-butyl hydroperoxide

[0085] After completion of the dropping, the mixture was held at 80 °C for 30 minutes and then cooled to obtain a latex of graft copolymer (B-1). The solid content of the obtained latex was 33%, the amount of coagulum was 0.1%, and the volume average particle diameter was 400 nm. An aqueous solution prepared such that 9% dilute sulfuric acid was 2.5% by mass with respect to 100 parts by mass of the graft copolymer (B) was heated at 60 °C. While stirring this aqueous solution, the obtained latex was gradually dropped therein and coagulated. The obtained coagulum was separated, washed with water, and then dried to obtain a powder of the graft copolymer (B-1). For the obtained powder (graft copolymer powder), the glass transition temperature, the fraction not passing through sieve #16, the average particle diameter, and the angle of repose were measured. The results are shown in Table 2.

[0086] <Production Example: Graft Copolymers (B-2) to (B-4)> Using the latexes of copolymers (A-2) to (A-4) instead of the latex of copolymer (A-1) and changing the type and amount of the vinyl monomer (m) as shown in Table 2, powders of the graft copolymers (B-2) to (B-4) were obtained in the same manner as in Production Example B-1.

[0087] Table 2 shows the evaluation results of the graft copolymers (B-1) to (B-4).

[0088]

Table 2

[0089] [Examples 1 to 4, Comparative Examples 1 to 3] The handleability of the copolymer (A) or graft copolymer (B) shown in Table 3 was evaluated. The results are shown in Table 3. Note that Example 4 is a reference example.

[0090] <Preparation of Thermoplastic Resin Composition> According to the formulation shown in Table 3, the powder of the copolymer (A) or graft copolymer (B), the thermoplastic resin (C), and carbon black were mixed using a Henschel mixer, and this mixture was supplied to an extruder heated to 240 °C and kneaded to obtain pellets of the thermoplastic resin composition.

[0091] <Preparation and Evaluation of Test Pieces for Oleic Acid Absorption Amount Evaluation> Using the pellets of the above thermoplastic resin composition, a dumbbell-shaped molded product with a mass of about 11 g was obtained by molding with a 4-ounce injection molding machine (manufactured by Japan Steel Works, Ltd.) under the conditions of a cylinder temperature of 240 °C, a mold temperature of 60 °C, and an injection rate of 20 g / s. The obtained molded product was evaluated for the oleic acid absorption amount. The results are shown in Table 3.

[0092] <Preparation and Evaluation of Test Pieces for Contact Angle Measurement and Appearance Evaluation> Using the pellets of the above thermoplastic resin composition, a plate-shaped molded product with a length of 100 mm, a width of 100 mm, and a thickness of 3 mm was prepared by molding with a 4-ounce injection molding machine (manufactured by Japan Steel Works, Ltd.) under the conditions of a cylinder temperature of 240 °C, a mold temperature of 60 °C, and an injection rate of 20 g / s. For the obtained molded product, the measurement of the pure water contact angle, the measurement of the oleic acid contact angle, and the evaluation of the appearance after wiping off fingerprints were carried out. The results are shown in Table 3.

[0093] <Preparation and Evaluation of Paint Composition> According to the formulation shown in Table 3, the powder of the copolymer (A) or the graft copolymer (B) and toluene were mixed and stirred with a stirrer for 6 hours to obtain a paint composition. For the obtained paint composition, the measurement of the toluene-insoluble content and the evaluation of the appearance were carried out. The results are shown in Table 3.

[0094] <Formation and Evaluation of Paint Film> The obtained paint composition was applied to the surface of a plate-shaped molded product made of ABS resin using a bar coater No. 7 so that the thickness after drying was about 5 μm, and left standing for 24 hours to form a paint film. For the obtained paint film, the pure water contact angle and the oleic acid contact angle were measured. The results are shown in Table 3.

[0095]

Table 3

[0096] The powders of the graft copolymers (B-1) to (B-4) were each excellent in handleability. From the comparison of the powder properties (fraction not passing through sieve #16, average particle diameter, angle of repose) of the copolymers (A-1) to (A-4) and the graft copolymers (B-1) to (B-4), it is considered that using the copolymers (A-1) to (A-4) as the graft copolymers (B-1) to (B-4) suppresses the sticking of particles to each other. Also, the molded products of the thermoplastic resin compositions using the powders of the graft copolymers (B-1) to (B-4) had high lipophilicity, and the actual fingerprint resistance evaluation results were also good. The coating films of the coating compositions using those powders also had high lipophilicity. In particular, the coating compositions using the powders of the graft copolymers (B-1) to (B-3) with a toluene-insoluble content of 50% by mass or less were also excellent in appearance. On the other hand, the powder of the copolymer (A-1) was inferior in handleability. The copolymer (A-5) that does not contain the (meth)acrylate (a) unit had good handleability, but the molded products and coating films had low lipophilicity and were inferior in fingerprint resistance.

Industrial Applicability

[0097] According to the graft copolymer of the present invention, excellent fingerprint resistance can be imparted to the surface of the molded product and the coating film. For example, the molded products and coating films of the thermoplastic resin compositions containing the graft copolymer of the present invention are excellent in lipophilicity, so fingerprints are less likely to be noticeable when they adhere. Also, the adhered fingerprints are easy to wipe off. Furthermore, the graft copolymer of the present invention is excellent in handleability and can be well mixed with thermoplastic resins and organic solvents. According to the thermoplastic resin composition of the present invention, a molded product excellent in fingerprint resistance can be obtained. Therefore, the thermoplastic resin composition of the present invention is useful as various industrial materials for forming parts that are easily touched by human hands, such as around the car navigation and switches, and the casings of televisions, audio equipment, and electronic devices. According to the coating composition of the present invention, excellent fingerprint resistance can be imparted to the surface of the molded body. Therefore, the coating composition of the present invention is useful for coating parts that are easily touched by human hands, such as around the car navigation and switches, and the casings of televisions, audio equipment, and electronic devices.

Claims

1. A graft copolymer obtained by graft polymerizing a vinyl monomer (m) in the presence of a copolymer (A) containing a structural unit based on a (meth)acrylate (a) having a linear or branched hydrocarbon group with 11 or more carbon atoms and a vinyl monomer (b), wherein the vinyl monomer (b) is a vinyl monomer other than the (meth)acrylate (a) copolymerizable with the (meth)acrylate (a), the proportion of the (meth)acrylate (a) is 20 to 70% by mass based on 100% by mass in total of all the structural units constituting the copolymer (A), the vinyl monomer (m) is a vinyl monomer other than the (meth)acrylate (a) and is at least one selected from the group consisting of a (meth)acrylate having any one of a linear or branched hydrocarbon group with 1 to 10 carbon atoms, an alicyclic group, and an aromatic group, an aromatic vinyl compound, and a vinyl cyanide compound, the amount of the crosslinking agent used for the copolymer (A) is 1 part by mass or less based on 100 parts by mass in total of the (meth)acrylate (a) and the vinyl monomer (b), the volume average particle diameter of the copolymer (A) is 10 to 1000 nm, the proportion of the vinyl monomer (m) is 20 to 80% by mass based on 100% by mass in total of the copolymer (A) and the vinyl monomer (m), the weight average molecular weight of the graft copolymer is 20,000 to 200,000, Graft copolymer.

2. The graft copolymer according to claim 1, wherein the toluene-insoluble content is 50% by mass or less.

3. The graft copolymer according to claim 1 or 2, wherein the copolymer (A) does not contain a crosslinked structure.

4. The graft copolymer according to any one of claims 1 to 3, wherein the copolymer (A) has a polymerizable unsaturated bond at the main chain terminal.

5. A thermoplastic resin composition comprising the graft copolymer according to any one of claims 1 to 4 and another thermoplastic resin.

6. A molded article comprising the thermoplastic resin composition according to claim 5.

7. A paint composition comprising the graft copolymer according to any one of claims 1 to 4 and an organic solvent.

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