Composition and coating composition

Abstract

To provide a low-viscosity composition and a coating composition using this composition.SOLUTION: A resin composition contains an acrylic polymer (P) and a polyol (S), wherein the acrylic polymer (P) contains a structural unit derived from a hydroxyl group-containing unsaturated monomer (p1), and the molecular weight of the polyol (S) is 100 or less, thereby providing both a low-viscosity composition and a coating composition that utilizes this resin composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a composition and a coating composition.

Background Art

[0002] Conventionally, for the purpose of imparting excellent appearance, performance, etc. to the surface of a substrate, a coating composition is applied onto the surface of the substrate and cured to form a coating film. In recent years, from the viewpoint of reducing the environmental load, reduction of volatile organic compounds (VOCs) in the coating composition and reduction of air-conditioning energy during coating have been demanded. Usually, since VOCs have the role of reducing the viscosity of the paint, in order to reduce the VOCs of the paint, it is necessary to lower the viscosity of the composition.

[0003] In addition, reduction of VOCs and reduction of air-conditioning energy are also demanded for coating compositions used in the automotive field. Generally, an automobile has a metal material forming the body of the automobile and a resin material forming bumpers, etc., and a coating composition is applied using the metal material or the resin material as a substrate. In recent years, due to reasons such as improvement in the strength of resin materials, conversion to lighter resin materials has been progressing at sites where metal materials were conventionally used.

[0004] There are various coating methods for resin materials, and one of the coating methods is in-mold coating. In-mold coating is a coating method in which after molding a resin material in a mold, a coating composition is injected between the molded article and the inner wall of the mold, and after curing the coating composition, the molded article coated with the coating film is taken out of the mold. In this coating method, since coating to curing is performed in a closed system, it is required to be substantially solvent-free in order to avoid defects in the coating film due to air bubbles or the like.

[0005] Patent Document 1 proposes a curable composition capable of reducing the use of a solvent, which is a curable composition obtained by combining a specific polyol, a polymer containing a hydroxyl group, and an isocyanate, and discloses that a coating film excellent in coating film appearance during curing in a high-humidity atmosphere can be obtained.

[0006] In addition, as a composition combining a polymer and an isocyanate, Patent Document 2 discloses a coating composition for in-mold coating containing an isocyanate-reactive group-containing resin (A), a polyisocyanate compound (B), and a hydroxyl group-containing aromatic compound (C) having a number average molecular weight in the range of 100 to 1000. Further, it is described that the properties of the formulated coating composition and the coating film performance of the coated molded substrate are good by this method.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, as a result of investigations by the present inventors, in the technique described in Patent Document 1, although a polyol component is used instead of a solvent, it has been found that especially in in-mold coating, the viscosity of the paint is high and coating is difficult. In the technique described in Patent Document 2, since the polyester resin is the main component, there are concerns about weather resistance. Further, since benzyl alcohol is used as a solvent, a dandeling chain may be formed during the crosslinking reaction with isocyanate, which may reduce the toughness of the coating film. Also, when the amount of solvent used is reduced for VOC reduction, there is a problem that the viscosity of the coating liquid increases and coating becomes difficult.

[0009] An object of the present invention is to provide a low-viscosity composition and a coating composition using the composition.

Means for Solving the Problems

[0010] As a result of intensive studies by the present inventors to achieve the above object, it has been found that when a polyol component is used instead of a solvent, high molecular weight polyols have too high a viscosity to be applied to in-mold coating. As a result of further studies, it has been found that the above object can be achieved by using a composition containing an acrylic polymer having a hydroxyl group and a polyhydric alcohol having a molecular weight of 100 or less. Normally, the use of polyhydric alcohols having a molecular weight of 100 or less has been avoided due to concerns about a decrease in the toughness of the coating film. However, in the present invention, by deliberately using the polyhydric alcohol, a composition having a low viscosity can be obtained. Further, when a curing agent such as isocyanate is contained to form a coating composition, the polyhydric alcohol causes a crosslinking reaction to form a crosslinked structure, so that all of the coating composition can be used as an active ingredient, and a coating film excellent in toughness can be formed.

[0011] That is, the present invention relates to the following [1] to [8]. [1] A composition containing an acrylic polymer (P) and a polyhydric alcohol (S), wherein the acrylic polymer (P) contains a structural unit derived from a hydroxyl group-containing unsaturated monomer (p1), and the polyhydric alcohol (S) has a molecular weight of 100 or less. [2] The composition according to [1], wherein the weight average molecular weight of the acrylic polymer (P) is 2,000 or more and 8,000 or less. [3] The composition according to [1] or [2], wherein the hydroxyl value of the acrylic polymer (P) is 80 mgKOH / g or more and 170 mgKOH / g or less. [4] The composition according to any one of [1] to [3], wherein the boiling point of the polyhydric alcohol (S) is 100°C or more. [5] The composition according to any one of [1] to [4], wherein the viscosity of the polyhydric alcohol (S) at 25°C is 100 mPa·s or less. [6] The composition according to any one of [1] to [5], wherein the viscosity of the composition at 80°C is 1,200 mPa·s or less. [7] A coating composition comprising the composition according to any one of [1] to [6] and a curing agent (C). [8] The coating composition according to [7], wherein the curing agent (C) is a polyisocyanate. [9] The coating composition according to [7] or [8], which is a coating composition for in-mold coating. [Effects of the Invention]

[0012] According to the present invention, a low-viscosity composition and a coating composition using said composition are provided. When the coating composition of the present invention is used as a coating composition for in-mold coating, a coating film having excellent toughness is formed. Furthermore, since the coating composition is mainly composed of an acrylic resin, the coating film has excellent transparency and durability, and is suitable for applications requiring weather resistance, such as automobile parts. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below, but these are examples of preferred embodiments, and the present invention is not limited to these contents. In addition, in this specification, "(meth)acrylate" means acrylate or methacrylate. "(meth)acrylic acid" means acrylic acid or methacrylic acid. "(meth)acryloyl" means acryloyl or methacryloyl. "(meth)acrylamide" means acrylamide or methacrylamide. "Active ingredient" means an ingredient that forms a coating film upon curing reaction.

[0014] The composition of the present invention (hereinafter also referred to as "composition (W)") contains an acrylic polymer (P) and a polyhydric alcohol (S). Each component will be explained in turn below.

[0015] [Acrylic polymer (P)] The acrylic polymer (P) used in the present invention contains a structural unit derived from a hydroxyl group-containing unsaturated monomer (p1), and further may contain a structural unit derived from a (meth)acrylic monomer (excluding the hydroxyl group-containing unsaturated monomer (p1)), and a structural unit derived from another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing unsaturated monomer (p1) (excluding the (meth)acrylic monomer and the hydroxyl group-containing unsaturated monomer (p1)). The hydroxyl group of the hydroxyl group-containing unsaturated monomer (p1) is reactive with an isocyanate group. The hydroxyl group may be either primary or secondary, but from the viewpoint of reactivity, it is preferably rich in primary hydroxyl groups.

[0016] The acrylic polymer (P) used in the present invention can be obtained, for example, by polymerizing the above-mentioned hydroxyl group-containing unsaturated monomer (p1) and a copolymerization component (p) further containing a (meth)acrylic monomer. If necessary, the copolymerization component (p) may further contain another polymerizable unsaturated monomer having a polymerizable unsaturated group copolymerizable with the hydroxyl group-containing unsaturated monomer (p1). Also, the acrylic polymer (P) has a structural unit derived from each copolymerization component (p). In the present specification, the "polymerizable unsaturated group" means an unsaturated group capable of radical polymerization. Examples of such polymerizable unsaturated groups include (meth)acryloyl group, vinyl group, (meth)acrylamide group, vinyl ether group, allyl group, propenyl group, isopropenyl group, maleimide group, and the like.

[0017] (hydroxyl group-containing unsaturated monomer (p1)) The above-mentioned hydroxyl group-containing unsaturated monomer (p1) is a compound having at least one hydroxyl group and at least one polymerizable unsaturated group in one molecule. Examples of the hydroxyl group-containing unsaturated monomer (p1) include monoesterified products of (meth)acrylic acid and a divalent alcohol having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; ε-caprolactone-modified products of the monoesterified products of the above-mentioned (meth)acrylic acid and a divalent alcohol having 2 to 8 carbon atoms; N-hydroxymethyl (meth)acrylamide; allyl alcohol; and (meth)acrylate having a polyoxyethylene chain with a hydroxyl group at the molecular end. Among them, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred in terms of good reactivity.

[0018] ((Meth)acrylic monomer, other polymerizable unsaturated monomers copolymerizable with the hydroxyl group-containing unsaturated monomer (p1)) As the above-mentioned (meth)acrylic monomer (excluding the hydroxyl group-containing unsaturated monomer (p1)) and other polymerizable unsaturated monomers copolymerizable with the hydroxyl group-containing unsaturated monomer (p1) (excluding (meth)acrylic monomers and hydroxyl group-containing unsaturated monomers (p1)), for example, the following monomers (p2) to (p20) can be used. These polymerizable unsaturated monomers can be used alone or in combination of two or more. (p2) Alkyl or cycloalkyl (meth)acrylate: for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecanyl (meth)acrylate, etc. (p3) Polymerizable unsaturated monomer having an isobornyl group: isobornyl (meth)acrylate, etc. (p4) Polymerizable unsaturated monomer having an adamantyl group: adamantyl (meth)acrylate, etc. (p5) Polymerizable unsaturated monomer having a tricyclodecenyl group: tricyclodecenyl (meth)acrylate, etc. (p6) Aromatic ring-containing polymerizable unsaturated monomer: benzyl (meth)acrylate, styrene, α-methylstyrene, vinyltoluene, etc. (p7) Polymerizable unsaturated monomer having an alkoxysilyl group: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, etc. (p8) Polymerizable unsaturated monomer having a fluorinated alkyl group: perfluoroalkyl (meth)acrylate such as perfluorobutylethyl (meth)acrylate, perfluorooctylethyl (meth)acrylate; fluoroolefin, etc. (p9) Polymerizable unsaturated monomer having a photopolymerizable functional group such as a maleimide group. (p10) Vinyl compounds: N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, etc. (p12) Polymerizable unsaturated monomers containing a carboxyl group: (meth)acrylic acid, maleic acid, crotonic acid, β-carboxyethyl (meth)acrylate, etc. (p13) Nitrogen-containing polymerizable unsaturated monomers: (meth)acrylonitrile, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, methylenebis(meth)acrylamide, ethylenebis(meth)acrylamide, adducts of glycidyl (meth)acrylate and amine compounds, etc. (p12) Polymerizable unsaturated monomers having two or more polymerizable unsaturated groups in one molecule: allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, etc. (p13) Polymerizable unsaturated monomers containing an epoxy group: glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, allyl glycidyl ether, etc. (p14) (Meth)acrylate having a polyoxyethylene chain with an alkoxy group at the molecular terminal. (p15) Polymerizable unsaturated monomers having a sulfonic acid group: 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allyl sulfonic acid, 4-styrenesulfonic acid, etc.; sodium salts and ammonium salts of these sulfonic acids, etc. (p16) Polymerizable unsaturated monomers having a phosphate group: acid phosphooxyethyl (meth)acrylate, acid phosphooxypropyl (meth)acrylate, acid phosphooxypoly(oxyethylene) glycol (meth)acrylate, acid phosphooxypoly(oxypropylene) glycol (meth)acrylate, etc. (p17) Polymerizable unsaturated monomers having an ultraviolet absorbing functional group: 2-hydroxy-4(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2-hydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2-(2'-hydroxy-5'-methacryloyloxyethylphenyl)-2H-benzotriazole, etc. (p18) Photostable polymerizable unsaturated monomers: 4-(meth)acryloyloxy 1,2,2,6,6-pentamethylpiperidine, 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, etc. (p19) Polymerizable unsaturated monomers having a carbonyl group: acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrene, vinyl alkyl ketones having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), etc. (p20) Polymerizable unsaturated monomers having an acid anhydride group: maleic anhydride, itaconic anhydride, citraconic anhydride, etc.

[0019] Among monomers (p2) to (p20), in terms of being easily reduced in viscosity when made into a paint and having good fluidity of the paint composition, it is preferable to use (p2) alkyl or cycloalkyl (meth)acrylate. Furthermore, alkyl (meth)acrylates having 4 to 8 carbon atoms such as n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate are preferable in terms of improving the water resistance of the coating film and having good weather resistance. Furthermore, alkyl methacrylates having 4 to 8 carbon atoms are preferable, and in particular, it is preferable to contain 2-ethylhexyl methacrylate in terms of the hardness of the coating film.

[0020] The content of the structural unit derived from the hydroxyl group-containing unsaturated monomer (p1) in the acrylic polymer (P) is preferably 10 to 80% by mass, more preferably 20 to 40% by mass, based on the entire acrylic polymer (P). Within the above range, the viscosity of the resulting paint composition and the hardness of the coating film are excellent. Also, the content of the structural unit derived from the monomer (p2) in the acrylic polymer (P) is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, based on the entire acrylic polymer (P). Furthermore, the content of the structural unit derived from the alkyl acrylate having 4 to 8 carbon atoms in the structural unit (100% by mass) derived from the monomer (p2) is preferably 10 to 50% by mass, more preferably 15 to 40% by mass, and the content of the structural unit derived from the alkyl methacrylate having 4 to 8 carbon atoms is preferably 10 to 50% by mass, more preferably 15 to 40% by mass. Within the above range, the viscosity of the resulting paint composition and the hardness of the coating film are excellent.

[0021] From the viewpoints of the viscosity and curability of the resulting coating composition, the adhesion between the formed coating film and the substrate, etc., the hydroxyl value of the acrylic polymer (P) is preferably 80 to 170 mgKOH / g, more preferably 100 to 150 mgKOH / g. Note that the hydroxyl value of the acrylic polymer (P) is calculated by the method described in the examples below.

[0022] Also, from the viewpoints of viscosity suppression of the resulting coating composition, the hardness of the formed coating film, and the adhesion between the formed coating film and the substrate, etc., the weight average molecular weight of the acrylic polymer (P) is preferably 2,000 to 8,000, more preferably 3,000 to 6,000. Note that the weight average molecular weight is a value calculated by converting the value measured by gel permeation chromatography (GPC) to standard polystyrene.

[0023] Also, from the viewpoints of viscosity suppression of the resulting coating composition and the hardness of the formed coating film, etc., the glass transition temperature (Tg) of the aqueous acrylic polymer (P) is preferably -10 to 20 °C, more preferably 0 to 15 °C.

[0024] Note that in this specification, the glass transition temperature (Tg) of the acrylic polymer (P) is a value calculated by the following formula. 1 / Tg(K)=W1 / T1+W2 / T2+···+W n / T n Tg(°C)=Tg(K)-273 In the formula, W1, W2, ··· W n are the mass fractions of the respective monomers, and T1, T2 ··· T n are the glass transition temperatures Tg(K) of the homopolymers of the respective monomers. Note that the glass transition temperatures of the homopolymers of the respective monomers are values according to POLYMER HANDBOOK Fourth Edition, edited by J. Brandrup, E.h. Immergut, E.A. Grulke (1999).

[0025] The production method for obtaining the acrylic polymer (P) is not particularly limited, and it can be obtained by polymerization methods such as solution polymerization method, suspension polymerization method, bulk polymerization method, emulsion polymerization method, etc. in the presence of a conventionally known radical polymerization initiator.

[0026] In the production of the acrylic polymer (P), the thermal polymerization initiator used in radical polymerization is not particularly limited, and ordinary radical polymerization initiators such as organic peroxides and azo compounds can be used. Examples of the organic peroxide include t-butyl peroxy 2-ethylhexanoate, benzoyl peroxide, dicumyl peroxide, dibutyl peroxide, and di-t-amyl peroxide.

[0027] Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(2,4-dimethylvaleronitrile). Any one of these may be used alone, or two or more thereof may be used in combination. The amount of the thermal polymerization initiator used is appropriately determined depending on the weight average molecular weight of the target resin and the like.

[0028] From the viewpoints of the viscosity and curability of the obtained composition, the adhesion between the formed coating film and the substrate, etc., the amount of the thermal polymerization initiator used is preferably 1 to 5 parts by mass with respect to 100 parts by mass of the total monomer components. When producing using the solution polymerization method, as the solvent, in order to obtain a coating composition with an active ingredient approaching 100% by mass, it is preferable to use a polyhydric alcohol (S) having a boiling point of 100°C or higher. It is also possible to remove the solvent after manufacturing to remove the non-volatile components. In this case, any components that can dissolve and be desolvated can be used, and there are no particular limitations. For example, aromatic solvents such as toluene, xylene, and other high-boiling aromatic solvents; ester solvents such as ethyl acetate, normal butyl acetate, isobutyl acetate, ethyl acetate, propyl acetate, and cellosolve acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, diacetone alcohol, cyclohexanone, and isophorone; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, and isobutanol; hydrocarbon solvents such as cyclohexane: can be mentioned. These may be used alone or in combination of two or more.

[0029] [Other hydroxyl group-containing resins] In addition to the above acrylic polymer (P), resins having at least one hydroxyl group in one molecule can be added within a range that does not inhibit the viscosity suppression of the obtained coating composition, the hardness of the formed coating film, and the adhesion between the formed coating film and the substrate. For example, resins such as polyester resin, acrylic-modified polyester resin, polyurethane resin, polyether resin, polycarbonate resin, epoxy resin, and alkyd resin having a hydroxyl group can be mentioned.

[0030] [Polyhydric alcohol (S)] Next, the polyhydric alcohol (S) used in the present invention will be described. The polyhydric alcohol (S) is a polyhydric alcohol having a molecular weight of 100 or less. When the molecular weight of the polyhydric alcohol (S) is 100 or less, the composition (W) of the present invention has a low viscosity without using a solvent. The molecular weight of the polyhydric alcohol (S) is preferably 95 or less, particularly preferably 91 or less. The lower limit is usually 60.

[0031] The polyhydric alcohol (S) has two or more hydroxyl groups in one molecule. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol and the like. The polyhydric alcohol (S) may be used alone or in combination of two or more.

[0032] In addition, other alcohol components other than the above can be added as long as they do not inhibit the viscosity reduction of the resulting composition, the hardness of the coating film obtained by curing the composition containing a curing agent, the adhesion to the substrate, and the like. The amount of the other alcohol component used is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, based on 100 parts by mass of the polyhydric alcohol (S). The other alcohol components are not particularly limited as long as they are alcohols selected from polyhydric alcohol groups having two or more hydroxyl groups. For example, 2-methyl-1,3-propanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, neopentyl glycol hydroxypivalate, hydrogenated bisphenol A, hydrogenated bisphenol F, and divalent alcohols such as dimethylolpropionic acid; polylactone diols obtained by adding lactone compounds such as ε-caprolactone to these divalent alcohols; ester diol compounds such as bis(hydroxyethyl) terephthalate; polyether diol compounds such as alkylene oxide adducts of bisphenol A, polyethylene glycol, polypropylene glycol, and polybutylene glycol; polyhydric alcohols having three or more hydroxyl groups such as glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tris(2-hydroxyethyl) isocyanurate, sorbitol, and mannitol; polylactone polyol compounds obtained by adding lactone compounds such as ε-caprolactone to these polyhydric alcohols having three or more hydroxyl groups; fatty acid esterified products of glycerin, etc.

[0033] [Composition (W)] The composition (W) of the present invention contains the above acrylic polymer (P) and polyhydric alcohol (S). The content ratio of the acrylic polymer (P) in the entire composition (W) is preferably 50 to 95% by mass, more preferably 70 to 90% by mass, and still more preferably 75 to 85% by mass. The content of the polyhydric alcohol (S) is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass, and even more preferably 15 to 25 parts by mass with respect to 100 parts by mass of the acrylic polymer (P).

[0034] In addition to the acrylic polymer (P) and the polyhydric alcohol (S), the composition (W) of the present invention may contain other components. For example, polyhydric alcohol resins such as polycarbonate diol and polyether diol that can undergo a curing reaction with an isocyanate curing agent, a curing catalyst, a pigment, inorganic materials such as silica, and the like can be mentioned.

[0035] The viscosity of the composition (W) of the present invention is preferably 130,000 mPa·s or less, preferably 100,000 mPa·s or less, and particularly preferably 50,000 mPa·s or less at 25°C. The viscosity of the composition (W) of the present invention is preferably 1200 mPa·s or less, more preferably 200 to 1200 mPa·s, and even more preferably 300 to 1100 mPa·s at 80°C. The viscosity is a value measured by a B-type viscometer.

[0036] The hydroxyl value of the active ingredient of the composition (W) is preferably 200 to 500 mgKOH / g, and particularly preferably 300 to 400 mgKOH / g. The hydroxyl value of the active ingredient of the composition is calculated by the method described below.

[0037] [Paint Composition] The paint composition of the present invention (hereinafter, also referred to as "paint composition (T)") includes the composition (W) and a curing agent (C). That is, the paint composition (T) includes the acrylic polymer (P), the polyhydric alcohol (S), and the curing agent (C). The paint composition (T) may contain other additives as necessary.

[0038] [Curing Agent (C)] The hardener (C) may be any compound that can react with the hydroxyl group of the acrylic polymer (P), and polyisocyanates having at least two isocyanate groups in one molecule are particularly preferred. For example, aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, derivatives of the polyisocyanates, etc. are included.

[0039] Examples of the aliphatic polyisocyanates include aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methyl 2,6-diisocyanatohexanoate (common name: lysine diisocyanate); aliphatic triisocyanates such as 2-isocyanatoethyl 2,6-diisocyanatohexanoate, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane, etc.

[0040] Examples of the alicyclic polyisocyanate include alicyclic diisocyanates such as 1,3 - cyclopentene diisocyanate, 1,4 - cyclohexane diisocyanate, 1,3 - cyclohexane diisocyanate, 3 - isocyanatomethyl - 3,5,5 - trimethylcyclohexyl isocyanate (common name: isophorone diisocyanate), methyl - 2,4 - cyclohexane diisocyanate, methyl - 2,6 - cyclohexane diisocyanate, 1,3 - or 1,4 - bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or a mixture thereof, norbornane diisocyanate; alicyclic triisocyanates such as 1,3,5 - triisocyanatocyclohexane, 1,3,5 - trimethylisocyanatocyclohexane, 2 - (3 - isocyanatopropyl)-2,5 - di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 2 - (3 - isocyanatopropyl)-2,6 - di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3 - (3 - isocyanatopropyl)-2,5 - di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5 - (2 - isocyanatoethyl)-2 - isocyanatomethyl - 3 - (3 - isocyanatopropyl)-bicyclo(2.2.1)heptane, 6 - (2 - isocyanatoethyl)-2 - isocyanatomethyl - 3 - (3 - isocyanatopropyl)-bicyclo(2.2.1)heptane, 5 - (2 - isocyanatoethyl)-2 - isocyanatomethyl - 2 - (3 - isocyanatopropyl)-bicyclo(2.2.1)-heptane, 6 - (2 - isocyanatoethyl)-2 - isocyanatomethyl - 2 - (3 - isocyanatopropyl)-bicyclo(2.2.1)heptane, etc.

[0041] Examples of the aromatic aliphatic polyisocyanate include aromatic aliphatic diisocyanates such as 1,3 - or 1,4 - xylylene diisocyanate or a mixture thereof, ω,ω’ - diisocyanato - 1,4 - diethylbenzene, 1,3 - or 1,4 - bis(1 - isocyanato - 1 - methylethyl)benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof; aromatic aliphatic triisocyanates such as 1,3,5 - triisocyanatomethylbenzene, etc. Examples of the aromatic polyisocyanate include aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4'- or 4,4'-diphenylmethane diisocyanate or a mixture thereof, 2,4- or 2,6-tolylene diisocyanate or a mixture thereof, 4,4'-toluidine diisocyanate, and 4,4'-diphenylether diisocyanate; aromatic triisocyanates such as triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, and 2,4,6-triisocyanatotoluene; and aromatic tetraisocyanates such as 4,4'-diphenylmethane-2,2',5,5'-tetraisocyanate. Examples of the polyisocyanate derivatives include dimers, trimers, biurets, allophanates, uretdione, uretoimine, isocyanurates, oxadiazinetriones, polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI), crude TDI, and the like of the above-mentioned polyisocyanate compounds. The polyisocyanates and derivatives thereof may be used alone or in combination of two or more thereof. Among these polyisocyanates, it is preferable to use aliphatic diisocyanates, alicyclic diisocyanates, and derivatives thereof alone or in combination of two or more thereof.

[0042] From the viewpoints of adhesion between the formed coating film and the substrate and releasability between the formed coating film and the mold, the polyisocyanate compound is preferably used in such a proportion that the ratio of isocyanate groups in the polyisocyanate compound to hydroxyl groups in the acrylic polymer (P) is generally within the range of 0.5 to 2.0, particularly 0.7 to 1.5.

[0043] [Pigment] Pigments can be added to the coating composition (T). Examples of the pigments include pearlescent pigments, coloring pigments, extender pigments, etc. The pigments can be used alone or in combination of two or more. Examples of the pearlescent pigments include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, glass flakes, aluminum oxide coated with at least one of aluminum oxide, titanium oxide and iron oxide, mica coated with at least one of titanium oxide and iron oxide, etc.

[0044] Examples of the coloring pigments include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, perylene pigments, dioxazine pigments, diketopyrrolopyrrole pigments, heat shielding pigments, etc. Examples of the extender pigments include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, alumina white, etc.

[0045] When the coating composition (T) of the present invention contains the above pigments, the content of the pigments is preferably 0.1 to 40% by mass, more preferably 3 to 30% by mass, and still more preferably 5 to 20% by mass based on the total amount in the coating composition (T) from the viewpoints of the adhesion between the formed coating film and the substrate, the weather resistance and hardness of the formed coating film, etc.

[0046] [Catalyst] A catalyst can be added to the coating composition (T) for curing at low temperature or in a short time. As the catalyst, those conventionally known can be used. Specific examples of the catalyst include, for example, tin octylate, dibutyltin diacetate, dibutyltin bis(2-ethylhexanoate), dibutyltin dilaurate, dioctyltin diacetate, dioctyltin bis(2-ethylhexanoate), dioctyltin dineodecanoate, dibutyltin oxide, dibutyltin sulfide, dioctyltin oxide, dibutyltin fatty acid salts, lead 2-ethylhexanoate, zinc octylate, zinc naphthenate, zinc fatty acids, bismuth octanoate, bismuth 2-ethylhexanoate, bismuth oleate, bismuth neodecanoate, bismuth versatate, bismuth naphthenate, cobalt naphthenate, calcium octylate, copper naphthenate, tetra(2-ethylhexyl) titanate and other organometallic compounds; tertiary amines and the like. These can be used alone or in combination of two or more thereof.

[0047] When the coating composition (T) of the present invention contains the above catalyst, from the viewpoints of the adhesion between the formed coating film and the substrate, the mold release property between the formed coating film and the mold, and the hardness of the formed coating film, etc., the blending amount of the catalyst is preferably 0.005 to 2% by mass, more preferably 0.01 to 1% by mass based on the total amount of the coating composition (T).

[0048] Further, when the coating composition (T) of the present invention contains the above catalyst, from the viewpoints of storage stability, curability, etc., the coating composition (T) of the present invention may contain organic acids such as acetic acid, propionic acid, butyric acid, isopentanoic acid, hexanoic acid, 2-ethylbutyric acid, naphthenic acid, octylic acid, nonanoic acid, decanoic acid, 2-ethylhexanoic acid, isooctylic acid, isononanoic acid, lauric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, neodecanoic acid, versatic acid, isobutyric anhydride, itaconic anhydride, acetic anhydride, citraconic anhydride, propionic anhydride, maleic anhydride, butyric anhydride, citric anhydride, trimellitic anhydride, pyromellitic anhydride, phthalic anhydride; inorganic acids such as hydrochloric acid, phosphoric acid; metal coordinating compounds such as acetylacetone, imidazole-based compounds and the like. <L

[0049] [Method for forming a coating film with a coating composition] For example, after forming an uncured coating film by applying the coating composition (T) of the present invention onto a substrate and then heating and curing it, a target coating film can be formed. The material of the above substrate is particularly suitable for a resin material formed by injection molding. That is, the coating composition (T) of the present invention is particularly useful as a coating composition for in-mold coating. In addition, the coating composition (T) of the present invention can also be used for resin materials for other applications. The coating composition (T) of the present invention can be suitably used as a coating composition applied to a substrate containing a resin material.

[0050] Examples of the above resin material include acrylic resins such as polymethyl methacrylate, polyester resins such as polyethylene terephthalate, polyethylene naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, polyethylene-1,2-diphenoxyethane-4,4'-dicarboxylate, polybutylene terephthalate, epoxy resins represented by commercially available products such as Epicoat (trade name: manufactured by Yuka Shell Epoxy Co., Ltd.), polycarbonate resins, polyimide resins, novolak resins, phenolic resins, acrylonitrile-butadiene-styrene (ABS) resins, acrylonitrile-ethylene-styrene (AES) resins, acrylonitrile-styrene-acrylate (ASA) resins, vinyl chloride resins, vinylidene chloride resins, polyurethane resins, cellulose ester resins (e.g., triacetyl cellulose, diacetyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, nitrocellulose), polyamide resins, polystyrene resins (e.g., syndiotactic polystyrene), polyolefin resins (e.g., polypropylene, polyethylene, polymethylpentene), polysulfone resins, polyethersulfone resins, polyarylate resins, polyetherimide resins, polyetherketone resins, various fiber reinforced plastic materials (Fiber Reinforced Plastics: hereinafter may be abbreviated as FRP materials or simply FRP).

[0051] Furthermore, the applications of the substrates to which the coating composition (T) of the present invention is applied are not particularly limited, and examples thereof include outer panels of automobile bodies such as passenger cars, trucks, motorcycles, and buses; interior and exterior automobile parts such as bumpers, center pillars, mirrors, door handles, instrument panels, door trims, and center consoles; furniture and building materials such as chairs, vanity mirrors, window frames, and gates; and outer panels of household electrical appliances such as mobile phones and audio equipment.

[0052] [heating] Heating is preferably carried out to the extent possible so that the substrate does not melt in the mold. From the viewpoints of productivity, workability, and thermal stability of the substrate, the heating temperature is preferably 60 to 120° C., more preferably 80 to 100° C. The heating time is preferably within a range of 20 seconds to 60 minutes, more preferably 1 to 10 minutes. [Example]

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following, "parts" means "parts by mass."

[0054] [Ingredients used] The components used in the following examples are as follows: [Raw materials for acrylic polymer (P)] (Hydroxyl group-containing unsaturated monomer (p1)) HEMA: 2-hydroxyethyl methacrylate (Mitsubishi Chemical Corporation) (Other polymerizable unsaturated monomers) MMA: Methyl methacrylate (Mitsubishi Chemical Corporation) St: Styrene (manufactured by Taishin Chemical Co., Ltd.) 2-EHA: 2-ethylhexyl acrylate (Mitsubishi Chemical Corporation) EHMA: 2-ethylhexyl methacrylate (Mitsubishi Chemical Corporation) n-BMA: normal butyl methacrylate (manufactured by Mitsubishi Chemical Corporation) MAA: Methacrylic acid (manufactured by Mitsubishi Chemical Corporation) (Thermal polymerization initiator) Luperox DTA: Di-t-amyl peroxide (manufactured by Arkema Kishima Co., Ltd.) Perbutyl O: t-Butyl 2-ethylhexanoate (manufactured by NOF Corporation) AMBN: 2,2’-Azobis(2-methylbutyronitrile) (manufactured by Otsuka Chemical Co., Ltd.) AIBN: 2,2’-Azobisisobutyronitrile (manufactured by Otsuka Chemical Co., Ltd.) (Polyhydric alcohol (S)) 1,4BD: 1,4-Butanediol (molecular weight: 90.1, manufactured by Mitsubishi Chemical Corporation) (Other polyhydric alcohols) NL1010DB: Polycarbonate diol (molecular weight: 110, manufactured by Mitsubishi Chemical Corporation) (Hardener (C)) TPA-100: Isocyanurate of hexamethylene diisocyanate (trade name “Duránate TPA-100” manufactured by Asahi Kasei Corporation) (Optional component) BYK-333: Silicone leveling agent (manufactured by BYK-Chemie Japan Co., Ltd.)

[0055] [Hydroxyl value of acrylic polymer (P)] The hydroxyl value of acrylic polymer (P) was calculated by the following formula (I) from the mass ratio (%) of the hydroxyl group-containing unsaturated monomer used. Hydroxyl value (unit: mgKOH / g) = (mass ratio (%) of the hydroxyl group-containing unsaturated monomer used in the polymer / molecular weight of the hydroxyl group-containing unsaturated monomer) × 56.1 × 10 ··· (I)

[0056] [Acid value of acrylic polymer (P)] The acid value of acrylic polymer (P) was calculated by the following formula (II) from the mass ratio (%) of the hydroxyl group-containing unsaturated monomer used. Acid value (unit: mgKOH / g) = (mass ratio (%) of the acid group-containing unsaturated monomer used in the polymer / molecular weight of the acid group-containing unsaturated monomer) × 56.1 × 10 ··· (II)

[0057] [Weight-average molecular weight of acrylic polymer (P)] The weight-average molecular weight of acrylic polymer (P) was measured using gel permeation chromatography (GPC) ("HLC-8320" manufactured by Tosoh Corporation). After preparing a tetrahydrofuran solution (0.2% by mass) of acrylic polymer (P), 10 μL of the solution was injected into an apparatus equipped with columns manufactured by Tosoh Corporation (TSKgel SuperHZM-M (inner diameter 4.6 mm, length 15 cm), HZM-M (inner diameter 4.6 mm, length 15 cm), HZ-2000 (inner diameter 4.6 mm, length 15 cm), TSKguardcolumn SuperHZ-L (inner diameter 4.6 mm, length 3.5 cm)), and measurement was carried out under the conditions of a flow rate of 0.35 mL / min, an eluent of tetrahydrofuran (stabilizer BHT), and a column temperature of 40°C. The weight-average molecular weight (Mw) was calculated in terms of standard polystyrene conversion.

[0058] [Glass transition temperature of acrylic polymer (P)] The glass transition temperature of acrylic polymer (P) was calculated by the following formula. 1 / Tg (K) = W1 / T1 + W2 / T2 + ··· W n / T n Tg (°C) = Tg (K) - 273 In the formula, W1, W2, ··· W n are the mass fractions of the respective monomers, and T1, T2 ··· T n are the glass transition temperatures Tg (K) of the homopolymers of the respective monomers. Note that the glass transition temperatures of the homopolymers of the respective monomers were values according to POLYMER HANDBOOK Fourth Edition, edited by J. Brandrup, E. h. Immergut, E. A. Grulke (1999).

[0059] [Measurement of B-type viscosity] The viscosities of the composition were measured at 25°C and 80°C respectively using a B-type viscometer.

[0060] [Hydroxyl value of the active ingredient of the composition] The hydroxyl value of the active ingredient of the composition was calculated by adding the hydroxyl value of the polyhydric alcohol (S) to the hydroxyl value of the aforementioned acrylic polymer (P).

[0061] <Production of Acrylic Polymer (P)> [Example 1] 15.5 parts of 1,4 - butanediol was charged into a reaction vessel equipped with a thermometer, a temperature adjuster, a stirrer, a reflux condenser, a nitrogen gas introduction tube and a dropping device. The inside of the polymerization apparatus was purged with nitrogen and heated to 165°C. A monomer-containing mixture of 20 parts of styrene, 34.8 parts of 2 - hydroxyethyl methacrylate, 21 parts of 2 - ethylhexyl acrylate, 23.2 parts of 2 - ethylhexyl methacrylate, 1 part of methacrylic acid and 4 parts of di - t - amyl peroxide was dropped therein over 2 hours. After completion of the dropping, 2 parts of 1,4 - butanediol was rapidly dropped, and then the internal temperature was cooled to 120°C in 30 minutes. Thereafter, a mixture of 5 parts of 1,4 - butanediol and 0.2 part of t - butyl 2 - ethylhexanoate was dropped over 30 minutes. After completion of the dropping, it was aged for 1 hour. Thereafter, 2 more parts of 1,4 - butanediol was added to obtain a composition (W - 1) containing an acrylic polymer (P - 1). The hydroxyl value of the obtained acrylic polymer (P - 1) was 150 mgKOH / g, the glass transition temperature was 13°C, and the weight average molecular weight was 5,000. The hydroxyl value of the composition (W - 1) was 366 mgKOH / g.

[0062] [Examples 2 - 4] In Example 1, except that the composition of the monomer-containing mixture to be dropped was changed as shown in Table 1, in the same manner as in Example 1, compositions (W - 2) - (W - 4) containing acrylic polymers (P - 2) - (P - 4) were obtained.

[0063] [Comparative Example 1] A reaction vessel equipped with a thermometer, a temperature adjuster, a stirrer, a reflux condenser, a nitrogen gas inlet pipe, and a dropping device was charged with 25 parts of paste-like NL1010DB. 43 parts of butyl acetate was charged to obtain fluidity and mixed until uniform. Then, the inside of the polymerization apparatus was purged with nitrogen and heated to 120 °C. A monomer-containing mixture of 38.85 parts of methyl methacrylate, 21.75 parts of normal butyl methacrylate, 14.22 parts of 2-hydroxyethyl methacrylate, 0.18 part of methacrylic acid, 2.63 parts of AMBN, and 1.5 parts of butyl acetate was added dropwise over 4 hours. After the addition was complete, 2.1 parts of butyl acetate was rapidly added dropwise. Then, the internal temperature was cooled to 110 °C over 30 minutes. Thereafter, a mixture of 3.5 parts of butyl acetate, 0.2 part of AMBN, and 0.02 part of AIBN was added dropwise over 60 minutes. After the addition was complete, it was aged for 1 hour. Thereafter, 31.5 parts of ethyl acetate was further added to obtain a composition (W-5) containing an acrylic polymer (P-5). The hydroxyl value of the obtained acrylic polymer (P-5) was 81 mgKOH / g, the glass transition temperature was 66 °C, and the weight average molecular weight was 8,000. The hydroxyl value of the composition (W-5) was 106 mgKOH / g.

[0064] [Preparation of Paint Composition] To simply confirm the physical properties of the obtained composition (W), a paint composition was prepared with the following formulation. 50 g of acrylic polymer (P-1), 0.05 g of BYK-333, and 59.3 g of TPA-100 were blended in a 500 cc cup to obtain a paint composition (T-1).

[0065] [Confirmation of Coating Film Physical Properties] The obtained paint composition (T-1) was applied to a glass plate with a 200 μm applicator, pre-dried at room temperature for 10 minutes, and then dried in a dryer at 120 °C for 30 minutes to obtain a coating film for physical property evaluation.

[0066] [Toughness: Measurement of Martens Hardness] The hardness of the obtained coating film was measured with a microhardness tester (manufactured by Fisher Instruments, product name: HM2000). The measurement conditions were F (test force) = 50 mN / 10 s and C (maximum load creep time) = 10 s. The martensite hardness was measured at five different locations on the same coating film, and the average value thereof was taken as the hardness of the coating film.

[0067] The criteria for hardness determination are as follows. (Determination criteria) ◎: Hardness is 100 N / mm 2 or more 〇: Hardness is 50 N / mm 2 or more and less than 100 N / mm 2 △: Hardness is 35 N / mm 2 or more and less than 50 N / mm 2 ×: Hardness is less than 35 N / mm 2

[0068]

Table 1

[0069] As shown in Table 1, the compositions of Examples 1 to 4 had fluidity even in an atmosphere at 25°C, and the viscosity further decreased when heated to 80°C, making them suitable for use in in-mold coating and the like. On the other hand, in Comparative Example 1 where the molecular weight of the polyhydric alcohol was high, dilution with a solvent was necessary at the initial stage of polymerization due to the high viscosity of the polyhydric alcohol, and the proportion of the active ingredient could not be increased. Further, the obtained composition was turbid and separation occurred, and fluidity could not be obtained.​​​

Claims

1. A composition containing an acrylic polymer (P) and a polyhydric alcohol (S), wherein the acrylic polymer (P) contains a structural unit derived from a hydroxyl group-containing unsaturated monomer (p1), and the polyhydric alcohol (S) has a molecular weight of 100 or less.

2. The composition according to Claim 1, wherein the acrylic polymer (P) has a weight average molecular weight of 2,000 or more and 8,000 or less.

3. The composition according to Claim 1, wherein the acrylic polymer (P) has a hydroxyl value of 80 mgKOH / g or more and 170 mgKOH / g or less.

4. The composition according to Claim 1 or 2, wherein the polyhydric alcohol (S) has a boiling point of 100°C or higher.

5. The composition according to Claim 1 or 2, wherein the polyhydric alcohol (S) has a viscosity at 25°C of 100 mPa·s or less.

6. The composition according to Claim 1 or 2, wherein the viscosity of the composition at 80°C is 1,200 mPa·s or less.

7. A coating composition comprising the composition according to Claim 1 or 2 and a curing agent (C).

8. The coating composition according to Claim 7, wherein the curing agent (C) is a polyisocyanate.

9. The coating composition according to Claim 7, which is a coating composition for in-mold coating.

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