JP2010285459A - Coating composition and method for forming coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating composition that can form a cured coating film excellent in all of scratch resistance, acid resistance and finished appearances. <P>SOLUTION: The coating composition comprises a hydroxy group-containing resin (A) having a hydroxy value of 80-200 mg-KOH/g and a weight-average molecular weight of 2,500-40,000, a polyisocyanate compound (B), and a hydroxy group-containing reaction product (C) having a hydroxy value of 30-150 mg-KOH/g and a number-average molecular weight of 1,000-12,000, obtained by an addition reaction of a carboxy group-containing reaction product (c-1) having an acid value of 10-120 mg-KOH/g and a number-average molecular weight of 400-2,500, obtained by a half-esterification reaction of a polycarbonate diol obtained by allowing a carbonylation reagent to react with a 2-10C diol, with an acid anhydride, with a polyepoxy compound (c-2). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a novel coating composition having excellent scratch resistance and acid resistance.

  A paint to be applied to an object such as an automobile body is required to have excellent coating film performance such as scratch resistance, acid resistance, stain resistance, and finished appearance.

  Conventionally, a melamine cross-linking coating material has been widely used as the coating material for the object. The melamine cross-linking paint is a paint containing a hydroxyl group-containing resin and a melamine resin as a cross-linking agent, has a high cross-linking density at the time of heat curing, and is excellent in coating film performance such as scratch resistance and finish. However, this paint has a problem that the melamine cross-linking is easily hydrolyzed by acid rain, and the acid resistance of the coating film is poor.

  As a composition excellent in scratch resistance, a paint composition (resin coating agent) in which a polycarbonate diol (polyol) is applied to a urethane crosslinking system using a hydroxyl group-containing resin such as an acrylic resin as a base resin and a polyisocyanate compound as a crosslinking agent (For example, Patent Document 1, Patent Document 2, and Patent Document 3).

  However, generally, the polycarbonate diol (polyol) has a problem that the compatibility with the base resin is not good and defects in the finished appearance are likely to occur.

  For example, when used as a clear coating in a 2-coat, 1-bake coating consisting of a metallic base coating and a clear coating, which is widely used in automotive top coating, especially low molecular weight polycarbonate diol (polyol) is used. As a result, there is a problem that the finished appearance such as metallic finish is insufficient due to the mixed layer of the base coating layer and the clear coating layer when the clear coating is applied onto the uncured base coating.

JP 2006-182904 A JP 2007-16231 A WO2007 / 119305

  The objective of this invention is providing the coating composition which can form the cured coating film which is excellent in all of abrasion resistance, acid resistance, and finished appearance.

  As a result of intensive studies to solve the above problems, the present inventors have found that a hydroxyl group-containing resin (A), a polyisocyanate compound (B) having a hydroxyl value and a weight average molecular weight within a specific range, and a specific polycarbonate diol, Specificity obtained by addition reaction of a reaction product (c-1) having a specific range of acid value and number average molecular weight having a carboxyl group obtained by reaction with an acid anhydride, and a polyepoxy compound (c-2) The inventors have found that the above object can be achieved by a coating composition containing a hydroxyl group-containing reaction product (C) having a hydroxyl value and a number average molecular weight in the range, and have completed the present invention.

  That is, in the present invention, a carbonylating agent is reacted with a hydroxyl group-containing resin (A) having a hydroxyl value of 80 to 200 mg KOH / g and a weight average molecular weight of 2500 to 40000, a polyisocyanate compound (B), and a diol having 2 to 10 carbon atoms. A carboxyl group-containing reaction product (c-1) having an acid value of 10 to 120 mgKOH / g and a number average molecular weight of 400 to 2500, obtained by half-esterifying a polycarbonate diol and an acid anhydride obtained by A coating composition containing a hydroxyl group-containing reaction product (C) having a hydroxyl value of 30 to 150 mgKOH / g and a number average molecular weight of 1000 to 12000 obtained by addition reaction with an epoxy compound (c-2) is provided. .

  The present invention also relates to a method of forming a multilayer coating film by coating at least one layer of a colored base coat paint and at least one layer of a clear coat paint on an object to be coated. The above-mentioned coating composition is applied, and a method for forming an overcoat multilayer coating film is provided.

  The coating composition of the present invention comprises a hydroxyl group-containing resin (A), a polyisocyanate compound (B), and a specific range of acid values and number average molecular weights having a carboxyl group obtained by a reaction between a specific polycarbonate diol and an acid anhydride. A hydroxyl group-containing reaction product (C) having a hydroxyl value and a number average molecular weight in a specific range obtained by addition reaction of the reaction product (c-1) with the polyepoxy compound (c-2). It is characterized by.

  According to the coating composition of the present invention, film properties such as mechanical strength can be improved by the carbonate bond derived from the polycarbonate diol of the hydroxyl group-containing reaction product (C), and the hydroxyl group-containing resin (A) and the hydroxyl group can be improved. Since the urethane bond by the reaction of the hydroxyl group of the contained reaction product (C) and the isocyanate group of the polyisocyanate compound (B) and the carbonate bond are excellent in hydrolysis resistance, it can be either scratch-resistant or acid-resistant. Can also form excellent cured coatings.

  Further, the use of the polycarbonate diol as it is does not cause a decrease in the finished appearance due to poor compatibility with the base resin and the cross-linking agent, and the above base when used as a clear paint in 2-coat 1-bake coating Since there is no deterioration in the finished appearance such as a metallic finish feeling due to the mixed layer of the coating film layer and the clear coating film layer, there is an effect that a coating film having a good finished appearance can be obtained.

  Hereinafter, the coating composition of the present invention (hereinafter sometimes referred to as “the present coating”) and the method for forming a multilayer coating film will be described in detail.

The coating composition of the present invention comprises a hydroxyl group-containing resin (A) having a hydroxyl value and a weight average molecular weight within a specific range, a polyisocyanate compound (B), and a carboxyl group obtained by a reaction between a specific polycarbonate diol and an acid anhydride. Hydroxyl group having a specific range of hydroxyl value and number average molecular weight obtained by addition reaction of a reaction product (c-1) having a specific range of acid value and number average molecular weight with a polyepoxy compound (c-2) It is a coating composition characterized by containing a contained reaction product (C).
Hydroxyl-containing resin (A)
The hydroxyl group-containing resin (A) of the coating composition of the present invention is a hydroxyl group-containing resin having a hydroxyl value of 80 to 200 mgKOH / g and a weight average molecular weight of 2500 to 40000.

  The hydroxyl group-containing resin (A) is not particularly limited as long as the hydroxyl value is in the range of 80 to 200 mgKOH / g and the weight average molecular weight is in the range of 2500 to 40000. Specifically, for example, an acrylic resin, a polyester resin, A polyether resin, a polyurethane resin, etc. can be mention | raise | lifted, A hydroxyl-containing acrylic resin, a hydroxyl-containing polyester resin, and a hydroxyl-containing polyurethane resin can be mention | raise | lifted as a preferable thing.

  The hydroxyl group-containing acrylic resin can be produced by copolymerizing a hydroxyl group-containing unsaturated monomer (M-1) and another copolymerizable unsaturated monomer (M-2) by a conventional method.

  The hydroxyl group-containing unsaturated monomer (M-1) is a compound having one hydroxyl group and one unsaturated bond in one molecule, and this hydroxyl group mainly functions as a functional group that reacts with a crosslinking agent. . As the monomer, specifically, monoesterified products of acrylic acid or methacrylic acid and a dihydric alcohol having 2 to 10 carbon atoms are suitable. For example, 2-hydroxyethyl (meth) acrylate, 2- Examples thereof include hydroxyalkyl (meth) acrylates such as hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Furthermore, examples of the monomer include a ring-opening polymerization adduct of the hydroxyalkyl (meth) acrylate and a lactone such as ε-caprolactone. Specifically, for example, “Plaxel FA-1”, “Plaxel FA-2”, “Plaxel FA-3”, “Plaxel FA-4”, “Plaxel FA-5”, “Plaxel FM-1”, “ “Placcel FM-2”, “Placcel FM-3”, “Placcel FM-4”, “Placcel FM-5” (all are trade names, manufactured by Daicel Chemical Industries, Ltd.) and the like.

  Among the above, the hydroxyl group-containing unsaturated monomer (1a) having a hydroxyl group-containing hydrocarbon group having 4 or more carbon atoms can be suitably used from the viewpoint of improving the scratch resistance of the coating film. By using the monomer (1a) as a constituent component, it is possible to increase the crosslinking density of the obtained coating film, and thus the effect of improving the scratch resistance of the coating film can be obtained.

As the hydroxyl group-containing unsaturated monomer having a hydroxyl group-containing hydrocarbon group having 4 or more carbon atoms,
For example, ε-caprolactone is ring-opened to a monoesterified product of acrylic acid or methacrylic acid and a dihydric alcohol having 4 to 10 carbon atoms, or to a monoesterified product of acrylic acid or methacrylic acid and a dihydric alcohol having 2 to 10 carbon atoms. Examples include polymerized compounds.

Specific examples of the monoesterified product of acrylic acid or methacrylic acid and a dihydric alcohol having 4 to 10 carbon atoms include 4-hydroxybutyl (meth) acrylate among those described above.

  Specific examples of the compound obtained by ring-opening polymerization of ε-caprolactone to a monoesterified product of acrylic acid or methacrylic acid and a dihydric alcohol having 2 to 10 carbon atoms include “Placcel FA-2”, “ Plaxel FM-3 "(all of which are trade names, manufactured by Daicel Chemical Industries, Ltd.).

  In addition, from the viewpoint of improving the scratch resistance without lowering the acid resistance of the coating film, an unsaturated monomer having both a cyclohexyl ring and a hydroxyl group can be preferably used. Specifically, CHDMMA (manufactured by Nippon Kasei Co., Ltd., 1,4-cyclohexanedimethanol monoacrylate) and the like.

  As an unsaturated monomer having both a cyclohexyl ring and a hydroxyl group, for example, a polyester oligomer having a hydroxycyclohexyl group or a methylolcyclohexyl group at both molecular ends, a (isocyanate) reaction product of a diisocyanate compound and a hydroxyl group-containing (meth) acrylate, The macromonomer etc. which are obtained by reacting can also be used. Examples of the polyester oligomer include flexo reds 148 and flexo reds 188 (both trade names, manufactured by King Industries, USA).

  The acrylic resin having both a cyclohexyl ring and a hydroxyl group obtained by using an unsaturated monomer having both a cyclohexyl ring and a hydroxyl group as a copolymerization component has, for example, an acrylic resin having a hydroxyl group and a cyclohexyl ring. An acid anhydride (for example, hexahydrophthalic anhydride) is subjected to an addition reaction, and a compound having both an epoxy group and a hydroxyl group (for example, glycidol) is added to the carboxylic acid produced by the addition reaction by an acid / epoxy reaction. Thus, it can also be obtained by a method of forming a terminal hydroxyl group.

  The mixing ratio of the hydroxyl group-containing unsaturated monomer (M-1) is preferably 20 to 50% by mass, particularly preferably 25 to 45% by mass based on the total amount of the monomer mixture.

  If the blending ratio of the hydroxyl group-containing unsaturated monomer (M-1) is less than 20% by mass, the cured coating film may be insufficiently cross-linked, making it difficult to obtain the predetermined scratch resistance. On the other hand, when it exceeds 50% by mass, the compatibility with other copolymerizable unsaturated monomer (M-2) and the copolymerization reactivity are lowered, and other components of the obtained hydroxyl group-containing acrylic resin ( When the compatibility with the polyisocyanate compound (B) and the hydroxyl group-containing reaction product (C) is lowered, the finished appearance of the coating film may be lowered.

  In the present specification, “(meth) acrylate” means “acrylate or methacrylate”.

  The other copolymerizable unsaturated monomer (M-2) is a compound having one unsaturated bond in one molecule other than the hydroxyl group-containing unsaturated monomer (M-1). Specific examples are listed below in (1) to (8).

  (1) Acid group-containing unsaturated monomer: a compound having one or more acid groups and one unsaturated bond in one molecule, such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic Carboxyl group-containing unsaturated monomers such as acid and maleic anhydride; sulfonic acid group-containing unsaturated monomers such as vinyl sulfonic acid and sulfoethyl (meth) acrylate; 2- (meth) acryloyloxyethyl acid phosphate; Examples include acidic phosphate ester unsaturated monomers such as 2- (meth) acryloyloxypropyl acid phosphate, 2- (meth) acryloyloxy-3-chloropropyl acid phosphate, and 2-methacryloyloxyethylphenyl phosphate. be able to. These can be used alone or in combination of two or more. The acid group-containing unsaturated monomer can also act as an internal catalyst when the component (A) undergoes a crosslinking reaction with the crosslinking agent, and the amount used thereof is the total amount of the monomer mixture constituting the hydroxyl group-containing acrylic resin. Is preferably used in the range of 0 to 5% by mass, particularly 0.1 to 3% by mass.

  (2) Monoesterified product of acrylic acid or methacrylic acid and monohydric alcohol having 1 to 20 carbon atoms: for example, methyl (meth) acrylate, ethyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (Meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, isostearyl acrylate (Osaka Organic Chemical Industry) Product name, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, adamantyl (meth) acrylate, 3,5-dimethyla Mantyl (meth) acrylate, 3-tetracyclododecyl methacrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, 4-methylcyclohexylmethyl (meth) acrylate, 4-ethylcyclohexylmethyl (meth) acrylate, 4-methoxycyclohexyl Methyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclododecyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate and the like.

  Among the above, unsaturated monomers having a bridged alicyclic hydrocarbon group having 10 to 20 carbon atoms and / or unsaturated monomers having an alicyclic hydrocarbon group having 3 to 12 carbon atoms ( 2a) can be preferably used from the viewpoint of improving the stain resistance of the coating film. By using the monomer (2a) as a constituent component, the Tg of the resulting resin increases and the polarity decreases, so the effect of improving the finish by smoothing the surface and improving the water resistance and stain resistance Can be obtained. Typical examples of the bridged alicyclic hydrocarbon group having 10 to 20 carbon atoms include isobornyl group, tricyclodecanyl group and adamantyl group.

  Specific examples of the unsaturated monomer having a bridged alicyclic hydrocarbon group having 10 to 20 carbon atoms include, for example, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, Examples thereof include adamantyl (meth) acrylate, 3,5-dimethyladamantyl (meth) acrylate, and 3-tetracyclododecyl methacrylate.

  Specific examples of the unsaturated monomer having an alicyclic hydrocarbon group having 3 to 12 carbon atoms include, for example, cyclohexyl (meth) acrylate, 4-methylcyclohexylmethyl (meth) acrylate, 4 -Ethylcyclohexylmethyl (meth) acrylate, 4-methoxycyclohexylmethyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclododecyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, etc. Can give.

  When the monomer (2a) is used as a constituent component, the blending ratio is preferably 3 to 50% by mass, particularly 10 to 40% by mass based on the total amount of the monomer mixture.

  Moreover, among the above, the unsaturated monomer (2b) which has a C8 or more hydrocarbon group which has a branched structure can be used conveniently from a viewpoint of improving the abrasion resistance of a coating film. By using the monomer (2b) as a constituent component, the Tg and polarity of the resulting resin are reduced, so the effect of improving the scratch resistance of the coating film by imparting flexibility and the improvement of finishing by smoothing the surface. Can be obtained. In addition, since it has a branched structure, it suppresses a decrease in the Tg of the coating film as compared with a case where a unsaturated monomer having a linear hydrocarbon group having 8 or more carbon atoms is used as a constituent component. Therefore, it is advantageous from the viewpoint of improving acid resistance.

  Specific examples of the unsaturated monomer having a branched hydrocarbon group having 8 or more carbon atoms include, for example, 2-ethylhexyl acrylate, isooctyl (meth) acrylate, and isomyristyl (meth) acrylate. , Isostearyl acrylate (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.).

  When the monomer (2b) is used as a constituent component, the blending ratio is preferably 3 to 50% by mass, particularly 10 to 40% by mass based on the total amount of the monomer mixture.

  (3) Alkoxysilyl group-containing unsaturated monomer: for example, vinyltrimethoxysilane, vinyltriethoxysilane, acryloxyethyltrimethoxysilane, methacryloxyethyltrimethoxysilane, acryloxypropyltrimethoxysilane, methacryloxypropyltri Methoxysilane, acryloxypropyltriethoxysilane, methacryloxypropyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, and the like. Among these, preferable alkoxysilane group-containing unsaturated monomers include vinyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like.

  By using an alkoxysilyl group-containing unsaturated monomer as a constituent component, in addition to the crosslinking bond between a hydroxyl group and an isocyanate group, a condensation reaction between alkoxysilyl groups and a crosslinking bond caused by a reaction between an alkoxysilyl group and a hydroxyl group are generated. Can do. Thereby, since the crosslinking density of the coating film obtained improves, the improvement effect of acid resistance and stain resistance can be acquired.

  When an alkoxysilyl group-containing unsaturated monomer is used as a constituent component, the blending ratio is preferably 3 to 50% by mass, particularly preferably 5 to 35% by mass based on the total amount of the monomer mixture. .

  (4) Aromatic unsaturated monomers: for example, styrene, α-methylstyrene, vinyltoluene and the like.

  By using an aromatic unsaturated monomer as a constituent component, the Tg of the resulting resin is increased, and a hydrophobic coating film with a high refractive index can be obtained. The effect of improving the property, improving the water resistance and acid resistance can be obtained.

  When an aromatic unsaturated monomer is used as the constituent component, the blending ratio is preferably 3 to 50% by mass, particularly 5 to 40% by mass based on the total amount of the monomer mixture.

  (5) Glycidyl group-containing unsaturated monomer: a compound having one glycidyl group and one unsaturated bond in a molecule, specifically, glycidyl acrylate, glycidyl methacrylate, and the like.

  (6) Nitrogen-containing unsaturated monomer: For example, (meth) acrylamide, dimethylacrylamide, N, N-dimethylpropylacrylamide, N-butoxymethylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetoneacrylamide, N, N-dimethylaminoethyl (meth) acrylate, vinylpyridine, vinylimidazole and the like.

  (7) Other vinyl compounds: For example, vinyl acetate, vinyl propionate, vinyl chloride, versatic acid vinyl ester Veova 9, Veova 10 (Japan Epoxy Resin) and the like.

  (8) Unsaturated bond-containing nitrile compounds: for example, acrylonitrile, methacrylonitrile and the like.

  These other vinyl monomers (M-2) can use 1 type (s) or 2 or more types.

  A monomer mixture comprising the monomers (M-1) and (M-2) can be copolymerized to obtain a hydroxyl group-containing acrylic resin.

  A monomer (M-1) having the following composition is used as a hydroxyl group-containing acrylic resin for making a coating composition excellent in both scratch resistance, acid resistance and stain resistance coating film performance and coating finish performance. ) And (M-2), a hydroxyl group-containing acrylic resin obtained by copolymerization of a monomer mixture is particularly preferred.

  1. (A) 3-40% by weight of an unsaturated monomer having an aromatic unsaturated monomer and / or an alicyclic hydrocarbon group having 3 to 12 carbon atoms, (B) having 10 to 20 carbon atoms 3-40% by weight of unsaturated monomer having a bridged alicyclic hydrocarbon group, (c) 20-50% by weight of unsaturated monomer having a hydroxyl group, (d) Other unsaturated monomer capable of copolymerization The monomer mixture consisting of 0 to 60% by mass of the body is copolymerized, and the total mass of the components (a) and (b) is 20 to 70 masses based on 100 parts by mass of the monomer mixture. Part of a hydroxyl group-containing acrylic resin (α).

  2. (B) 3 to 40% by mass of an unsaturated monomer having an aromatic unsaturated monomer and / or an alicyclic hydrocarbon group having 3 to 12 carbon atoms, and (b) the number of carbon atoms having a branched structure. 3 to 40% by mass of an unsaturated monomer having 8 or more hydrocarbon groups, (c) 3 to 50% by mass of a hydroxyl group-containing unsaturated monomer having a hydroxyl group-containing hydrocarbon group having 4 or more carbon atoms, ) A monomer mixture comprising 0 to 77% by weight of other copolymerizable unsaturated monomers is copolymerized, and the total mass of the components (a) and (b) is the monomer mixture. Hydroxyl group-containing acrylic resin (β) that is 20 to 70 parts by mass based on 100 parts by mass.

  The copolymerization method for copolymerizing the monomer mixture to obtain a hydroxyl group-containing acrylic resin is not particularly limited, and a known copolymerization method can be used. A solution polymerization method in which polymerization is carried out in the presence of a polymerization initiator can be preferably used.

  Examples of the organic solvent used in the solution polymerization method include aromatic solvents such as toluene, xylene, and swazole 1000 (trade name, high-boiling petroleum solvent) manufactured by Cosmo Oil; ethyl acetate, 3-methoxybutyl Ester solvents such as acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, propyl propionate, butyl propionate, ethoxy ethyl propionate, etc. Can be mentioned.

  These organic solvents can be used alone or in combination of two or more. However, since the hydroxyl group-containing acrylic resin used in the coating material has a high hydroxyl value, it has a high boiling point in terms of the solubility of the resin. It is preferable to use an ester solvent or a ketone solvent. In addition, aromatic solvents having higher boiling points can be suitably used in combination.

  Examples of the polymerization initiator that can be used for copolymerization of the hydroxyl group-containing acrylic resin include 2,2′-azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, di-t-amyl peroxide, Mention may be made of radical polymerization initiators known per se, such as t-butyl peroctoate and 2,2′-azobis (2-methylbutyronitrile).

  The hydroxyl value of the hydroxyl group-containing acrylic resin is in the range of 80 to 200 mgKOH / g, more preferably in the range of 100 to 170 mgKOH / g. When the hydroxyl value is less than 80 mgKOH / g, the scratch resistance may be insufficient due to the low crosslinking density. On the other hand, if it exceeds 200 mgKOH / g, the water resistance of the coating film may decrease.

  The weight average molecular weight of the hydroxyl group-containing acrylic resin is in the range of 2500 to 40000, more preferably in the range of 5000 to 30000. When the weight average molecular weight is less than 2500, the coating performance such as acid resistance may be deteriorated, and when it exceeds 40000, the smoothness of the coating film is deteriorated, so that the finish may be deteriorated.

  In the present specification, the average molecular weight is a value calculated based on the molecular weight of standard polystyrene from a chromatogram measured by gel permeation chromatography. As the gel permeation chromatograph, “HLC8120GPC” (manufactured by Tosoh Corporation) was used. As the columns, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name) were used, Mobile phase: Tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, detector: RI

  The glass transition temperature of the hydroxyl group-containing acrylic resin is preferably -40 ° C to 85 ° C, and particularly preferably -30 ° C to 80 ° C. When the glass transition temperature is less than −40 ° C., the coating film hardness may be insufficient, and when it exceeds 85 ° C., the coated surface smoothness of the coating film may be deteriorated.

  In this specification, the glass transition temperature is a value measured by DSC (Differential Scanning Calorimeter) at a heating rate of 10 ° C./min based on JISK7121 (Plastic transition temperature measurement method). The measurement in the following production examples, etc., was performed by using “SSC5200” (trade name, manufactured by Seiko Denshi Kogyo Co., Ltd.) as a DSC, weighing a predetermined amount in a sample dish, and drying at 130 ° C. for 3 hours. I did it.

  The hydroxyl group-containing polyester resin that can be used as the hydroxyl group-containing resin (A) can be produced by a conventional method, for example, by an esterification reaction between a polybasic acid and a polyhydric alcohol. The polybasic acid is a compound having two or more carboxyl groups in one molecule. For example, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexa And hydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid and their anhydrides. The polyhydric alcohol contains two or more hydroxyl groups in one molecule. For example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-1,3 -Propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, hydroxy Diols such as valinic acid neopentyl glycol ester, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethylpentanediol, hydrogenated bisphenol A, etc. , And trivalent or higher polyol components such as trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, and the like, and 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylol Examples thereof include hydroxycarboxylic acids such as pentanoic acid, 2,2-dimethylolhexanoic acid, and 2,2-dimethyloloctanoic acid.

  In addition, α-olefin epoxides such as propylene oxide and butylene oxide, monoepoxy compounds such as Cardura E10 (manufactured by Japan Epoxy Resin Co., Ltd., trade name, glycidyl ester of synthetic hyperbranched saturated fatty acid) and the like are reacted with acids, A compound may be introduced into the polyester resin.

  When introducing a carboxyl group into a polyester resin, for example, it can be introduced by adding an acid anhydride to a hydroxyl group-containing polyester and half-esterifying it.

  The hydroxyl value of the hydroxyl group-containing polyester resin is in the range of 80 to 200 mgKOH / g, more preferably in the range of 100 to 170 mgKOH / g. When the hydroxyl value is less than 80 mgKOH / g, the scratch resistance may be insufficient, and when it exceeds 200 mgKOH / g, the water resistance of the coating film may be lowered.

  The weight average molecular weight of the hydroxyl group-containing polyester resin is in the range of 2500 to 40000, more preferably in the range of 5000 to 30000. When the weight average molecular weight is less than 2500, the coating performance such as acid resistance may be deteriorated, and when it exceeds 40000, the coating surface smoothness of the coating may be deteriorated.

The glass transition temperature of the hydroxyl group-containing polyester resin is preferably in the range of −40 ° C. to 85 ° C., particularly in the range of −30 ° C. to 80 ° C. When the glass transition temperature is less than −40 ° C., the coating film hardness may be insufficient, and when it exceeds 85 ° C., the coated surface smoothness of the coating film may be deteriorated.
The hydroxyl group-containing resin (A) also includes so-called urethane-modified acrylic resins and urethane-modified polyester resins.

  Examples of the hydroxyl group-containing polyurethane resin include a hydroxyl group-containing polyurethane resin obtained by reacting a polyol and a polyisocyanate.

  Examples of the polyol include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, and hexamethylene glycol, and trihydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol. Can do. Examples of the high molecular weight material include polyether polyol, polyester polyol, acrylic polyol, and epoxy polyol. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Examples of the polyester polyol include alcohols such as the above divalent alcohols, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol, and dibasic acids such as adipic acid, azelaic acid, and sebacic acid. Lactone-based ring-opening polymer polyol such as polycaprolactone, polycarbonate diol, and the like. Moreover, for example, carboxyl group-containing polyols such as 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid can also be used.

  Examples of the polyisocyanate to be reacted with the above polyol include aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate; and burette type addition of these polyisocyanates. Product, isocyanurate cycloadduct; isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4- (or-2,6-) diisocyanate, 1,3- (or 1,4-) Alicyclic diisocyanates such as di (isocyanatomethyl) cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate And burette type adducts, isocyanurate cycloadducts of these polyisocyanates; xylylene diisocyanate, metaxylylene diisocyanate, tetramethyl xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5- Naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 4,4-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, (m- or p-) phenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethyl- Aromatic diisos such as 4,4'-biphenylene diisocyanate, bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenylisocyanate) And burette-type adducts, isocyanurate cycloadducts of these polyisocyanates; triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2, Polyisocyanates having three or more isocyanate groups in one molecule such as 4,6-triisocyanatotoluene, 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate; and And polyisocyanate burette type adducts, isocyanurate ring adducts, and the like.

  The hydroxyl value of the hydroxyl group-containing polyurethane resin is in the range of 80 to 200 mgKOH / g, more preferably in the range of 100 to 170 mgKOH / g. When the hydroxyl value is less than 80 mgKOH / g, the scratch resistance may be insufficient, and when it exceeds 200 mgKOH / g, the water resistance of the coating film may be lowered.

  The weight average molecular weight of the hydroxyl group-containing polyurethane resin is in the range of 2500 to 40000, more preferably in the range of 5000 to 30000. When the weight average molecular weight is less than 2500, the coating performance such as acid resistance may be deteriorated, and when it exceeds 40000, the coating surface smoothness of the coating may be deteriorated.

  The glass transition temperature of the hydroxyl group-containing polyurethane resin is preferably in the range of -40 ° C to 85 ° C, particularly -30 ° C to 80 ° C. When the glass transition temperature is less than −40 ° C., the coating film hardness may be insufficient, and when it exceeds 85 ° C., the coated surface smoothness of the coating film may be deteriorated.

The hydroxyl group-containing resin (A) can be used alone or in combination of two or more. As the hydroxyl group-containing resin (A), a hydroxyl group-containing acrylic resin or a hydroxyl group-containing polyester resin can be suitably used.
Polyisocyanate compound (B)
The polyisocyanate compound (B) of the coating composition of the present invention is a compound having two or more free isocyanate groups in one molecule, and those conventionally used in the production of polyurethane can be used. Examples thereof include aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of these polyisocyanates.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3- Aliphatic diisocyanates such as butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, such as lysine ester triisocyanate, 1,4,8- Triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2 5,7 and aliphatic triisocyanates such as trimethyl-1,8-diisocyanato-5-isocyanatomethyl octane and the like.

  Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: Isophorone diisocyanate), 4,4'-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,3- or 1,4-bis (isocyanatomethyl) cyclohexane ( Common name: hydrogenated xylylene diisocyanate) or mixtures thereof, alicyclic diisocyanates such as norbornane diisocyanate, for example 1,3,5-triisocyanatocyclohexane, 1, , 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-isocyanate Natomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyana Propyl) -bicyclo (2.2.1) -heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, etc. And alicyclic triisocyanate.

  Examples of the araliphatic polyisocyanate include 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 an aromatic aliphatic diisocyanate such as a mixture thereof, for example, an araliphatic triisocyanate such as 1,3,5-triisocyanatomethylbenzene Etc.

  Examples of the aromatic polyisocyanate include 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 mixtures thereof, aromatic diisocyanates such as 4,4′-toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate, for example, triphenylmethane-4,4 ′, 4 Aromatic triisocyanates such as '' '-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, such as 4,4'-diphenylmethane-2,2', 5 , 5'- Or the like can be mentioned aromatic tetracarboxylic isocyanates such as tiger isocyanate.

  Examples of the polyisocyanate derivative include dimer, trimer, biuret, allophanate, carbodiimide, uretdione, uretoimine, isocyanurate, oxadiazine trione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric). MDI) and Crude TDI.

  These polyisocyanate compounds may be used alone or in combination of two or more. Of these polyisocyanate compounds, aliphatic diisocyanates and derivatives thereof can be suitably used from the viewpoint of scratch resistance, weather resistance, and the like.

  Moreover, the blocked polyisocyanate compound which is the compound which blocked the isocyanate group of the polyisocyanate compound which has a 2 or more free isocyanate group in 1 molecule mentioned above with the blocking agent as a polyisocyanate compound can also be used.

  The blocking agent blocks free isocyanate groups. When the blocked polyisocyanate compound is heated to, for example, 100 ° C. or higher, preferably 130 ° C. or higher, the isocyanate group is regenerated and can easily react with the hydroxyl group. Examples of the blocking agent include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and hydroxybenzoic acid methyl; ε-caprolactam, δ-valerolactam, Lactams such as γ-butyrolactam and β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, lauryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether Ethers such as propylene glycol monomethyl ether and methoxymethanol; benzyl alcohol; glycolic acid; glycolic acid esters such as methyl glycolate, ethyl glycolate and butyl glycolate; lactic acid esters such as lactic acid, methyl lactate, ethyl lactate and butyl lactate; Alcohols such as methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; oximes such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime System: Dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone Which active methylene series; mercaptans such as butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol; Acid amides such as amides, acetic acid amides, stearic acid amides, benzamides; imides such as succinimides, phthalic acid imides, maleic acid imides; Amines such as butylamine, dibutylamine and butylphenylamine; imidazo such as imidazole and 2-ethylimidazole Pyrazoles such as 3,5-dimethylpyrazole; Ureas such as urea, thiourea, ethyleneurea, ethylenethiourea and diphenylurea; Carbamate esters such as phenyl N-phenylcarbamate; Ethyleneimine and propyleneimine And the like, and blocking agents such as sulfites such as sodium bisulfite and potassium bisulfite.

  When blocking (reacting the blocking agent), a solvent can be added as necessary. As the solvent used for the blocking reaction, those not reactive to isocyanate groups are preferable. For example, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and solvents such as N-methylpyrrolidone (NMP). Can give.

A polyisocyanate compound (B) can be used individually or in combination of 2 or more types.
Hydroxyl group-containing reaction product (C)
The hydroxyl group-containing reaction product (C) of the coating composition of the present invention is obtained by half-esterifying a polycarbonate diol obtained by reacting a carbonylating agent with a diol having 2 to 10 carbon atoms and an acid anhydride. , A hydroxyl group value of 30 to 150 mgKOH obtained by addition reaction of a carboxyl group-containing reaction product (c-1) having an acid value of 10 to 120 mgKOH / g and a number average molecular weight of 400 to 2500 and a polyepoxy compound (c-2). / G, a hydroxyl group-containing reaction product having a number average molecular weight of 1,000 to 12,000.
Carboxyl group-containing reaction product (c-1)
The carboxyl group-containing reaction product (c-1) is obtained by half-esterifying a polycarbonate diol obtained by reacting a carbonylating agent with a diol having 2 to 10 carbon atoms and an acid anhydride.

  The polycarbonate diol which is a synthetic intermediate of the reaction product (c-1) is usually a compound obtained by polycondensation reaction of a diol and a carbonylating agent.

  The polycarbonate diol compound can be synthesized by transesterifying the diol compound and the carbonylating agent in the presence or absence of a transesterification catalyst.

  The diol used for the production of the polycarbonate diol is a dihydric alcohol having 2 to 10 carbon atoms, preferably 4 to 8 carbon atoms. Specifically, for example, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1 , 7-heptanediol, 1,8-octanediol, 2-ethyl-1,6-hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, etc. Aliphatic diols; 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and other alicyclic diols; p-xylenediol, p-tetrachloroxylenediol and other aromatics Diols such as ether diols such as diethylene glycol and dipropylene glycolThese diols can be used alone or in combination of two or more.

  The diol used for the production of the polycarbonate diol is 1,6-hexanediol from the viewpoint of excellent durability and hardness of the coating film of the coating composition containing the hydroxyl group-containing reaction product (C) obtained by using the diol. And 1 or 2 or more diols other than these are preferably used in combination, and consists of 1,6-hexanediol, 1,5-pentanediol, 1,4-butanediol and 1,4-cyclohexanedimethanol. It is more preferable to use a mixture of at least one selected from the group. Specific combinations include, for example, a combination of 1,6-hexanediol and 1,5-pentanediol, a combination of 1,6-hexanediol and 1,4-butanediol, 1,6-hexanediol and 1,1. A combination of 4-cyclohexanedimethanol and the like can be given.

  A well-known thing can be used as a carbonylating agent. Specific examples include alkylene carbonate, dialkyl carbonate, diallyl carbonate, phosgene, and the like, and one of these can be used or a combination of two or more can be used. Of these, preferred are ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, diphenyl carbonate and the like.

  As the polycarbonate diol which is a synthetic intermediate of the reaction product (c-1), it is preferable to use a polycarbonate diol having a viscosity at 50 ° C. of about 10,000 mPa · s or less. When the viscosity at 50 ° C. exceeds 10,000 mPa · s, handling may be difficult.

  The viscosity of the polycarbonate diol used for the synthesis of the reaction product (c-1) is more preferably about 10 to 10000 mPa · s, more preferably 10 to 8000 mPa · s at 50 ° C. It is particularly preferably about 5000 mPa · s.

  The viscosity was measured using a B-type viscometer (Brookfield viscometer) at 50 ° C. and 6 rpm.

  The number average molecular weight of the polycarbonate diol used for the synthesis of the reaction product (c-1) is about 300 to 2000 from the viewpoint that the coating film of the finally obtained coating composition is excellent in acid resistance and scratch resistance. Is more preferable, about 500 to 1800 is more preferable, and about 700 to 1500 is particularly preferable.

  A commercial item can be used as polycarbonate diol which is a synthetic intermediate of reaction product (c-1). Examples of commercially available products include “T-5650J” (trade name, diol components: 1,6-hexanediol and 1,5-pentanediol) manufactured by Asahi Kasei Chemicals Corporation, and “T-4671” (trade name, diol component). : 1,6-hexanediol and 1,4-butanediol); “UM-CARB90” (trade name, diol components: 1,6-hexanediol and 1,4-cyclohexanedimethanol) manufactured by Ube Industries, Ltd. I can give you.

  Examples of the acid anhydride used for the synthesis of the reaction product (c-1) include phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, succinic acid, glutaric acid, pimelic acid, and naphthalene dicarboxylic acid. Polyvalent carboxylic acids such as acid, 4,4-diphenyl ether dicarboxylic acid, diphenylmethane-4,4′-dicarboxylic acid, het acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, hexahydrotrimellitic acid, pyromellitic acid Examples include acid anhydrides of acids. These acid anhydrides can be used individually by 1 type or in combination of 2 or more types.

  Of these, succinic anhydride, hexahydrophthalic anhydride, and trimellitic anhydride can be suitably used because they are excellent in acid resistance and scratch resistance of the coating film.

  The reaction product (c-1) is usually a compound having a structure in which the terminal hydroxyl group of the polycarbonate diol is converted to a carboxyl group by half esterification without polycondensation of the polycarbonate diol and the acid anhydride. Synthesized under conditions. However, as a reaction product (c-1), as long as an acid value and a number average molecular weight exist in a specific range, it may contain the unreacted product which has not been half-esterified.

  The optimum temperature for the half esterification reaction varies mainly depending on the melting point of the acid anhydride used. For example, when hexahydrophthalic anhydride is used as the acid anhydride, the temperature is about 100 to 180 ° C. In general, when the temperature exceeds about 200 ° C., a polycondensation reaction tends to occur.

  In the reaction product (c-1), the polycarbonate diol and the acid anhydride are half-esterified at a molar ratio of 0.15 to 0.95 (acid anhydride group / polycarbonate diol hydroxyl group). preferable. The molar ratio is more preferably about 0.4 to 0.9 from the viewpoint of controlling the molecular weight of the hydroxyl group-containing reaction product (C) obtained by addition reaction with the polyepoxy compound (c-2). More preferably, it is about 0.6 to 0.85.

  In the reaction product (c-1), the lower the molar ratio is, the higher the production ratio of the compound having a structure in which only one end of the polycarbonate diol is modified with a carboxyl group, and the higher the corresponding ratio, the both ends of the polycarbonate diol. The proportion of the compound having a structure in which is modified with a carboxyl group increases.

  The lower the equivalent ratio, the more unreacted polycarbonate diol remains in the reaction product (c-1). In this case, in the present invention, the hydroxyl group of the polycarbonate diol can also react with the epoxy group of the polyepoxy group compound or the isocyanate group of the polyisocyanate compound. Therefore, usually, the reaction product (c-1) containing the remaining polycarbonate diol can be used as it is without separating the unreacted polycarbonate diol.

  The acid value of the reaction product (c-1) is 10 to 120 mgKOH / g, from the viewpoint of controlling the molecular weight of the hydroxyl group-containing reaction product (C) obtained by the addition reaction with the polyepoxy compound (c-2). 30 to 110 mgKOH / g, preferably about 50 to 100 mgKOH / g.

  The number average molecular weight of the reaction product (c-1) is 400 to 2500, and is preferably about 500 to 2000, more preferably about 700 to 1500 from the viewpoint of the finished appearance.

  The hydroxyl value of the reaction product (c-1) is preferably about 10 to 65 mgKOH / g, more preferably about 15 to 50 mgKOH / g from the viewpoint of scratch resistance.

In the present invention, the acid value, number average molecular weight, and hydroxyl value of the reaction product (c-1) mean the value of the entire reaction product including the unreacted residual polycarbonate diol.
Polyepoxy compound (c-2)
The polyepoxy compound is a compound having two or more epoxy groups in one molecule, specifically, ethylene glycol diglycidyl ether, hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerin diglycidyl ether, Polyglycidyl ether of polyhydric alcohol or polyhydric phenol such as glycerin triglycidyl ether, diglycerin triglycidyl ether, sorbitol polyglycidyl ether, hydrogenated bisphenol A diglycidyl ether or bisphenol A diglycidyl ether; glycidyl of p-oxybenzoic acid Esters, glycidyl esters such as glycidyl ether, glycidyl etherified products; diglycidyl phthalate or diglycidyl hexahydrophthalate A polyglycidyl ester of a polyvalent carboxylic acid such as an ester; a polyepoxy compound containing a nitrogen-containing heterocycle such as a hydantoin ring; a compound having two or more epoxy groups in one molecule and a polyhydric alcohol, polyphenol or poly Examples include epoxy resins that are adducts with basic acids; modified epoxy resins such as fatty acid-modified epoxy resins and amine-modified epoxy resins.

  A commercially available product can be used as the polyepoxy compound. Examples of commercially available products include Denacol series epoxy compounds manufactured by Nagase ChemteX Corporation. As a trade name, as a bifunctional polyepoxy compound, Denacol EX-201 (resorcinol diglycidyl ether), Denacol EX-211 (neopentyl glycol diglycidyl ether), Denacol EX-212 (1,6-hexanediol di) Glycidyl ether), Denacol EX-252 (hydrogenated bisphenol A diglycidyl ether), Denacol EX-810, Denacol EX-811, Denacol EX-850, Denacol EX-851, Denacol EX-821, Denacol EX-830, Denacol EX -832, Denacol EX-841, Denacol EX-861 (all of the 800 series are diglycidyl ethers of ethylene or polyethylene glycol), Denacol EX-911, Denacol X-941, Denacol EX-920, Denacol EX-931 can be mentioned (these are both 900s ones of propylene or polypropylene glycol diglycidyl ether) and the like. Examples of the tri- or higher functional polyepoxy compound include Denacol EX-611, Denacol EX-612, Denacol EX-614, Denacol EX-614B, Denacol EX-622 (all of these 600 series products are sorbitol polyglycidyl ether), Denacol EX-512, Denacol EX-521 (all those in the 500 series are polyglycerol polyglycidyl ether), Denacol EX-411 (pentaerythritol polyglycidyl ether), Denacol EX-421 (diglycerol polyglycidyl ether), Denacol EX -313, Denacol EX-314 (all those in the 310 series are glycerol polyglycidyl ether), Denacol EX-321 (Trimethylolpropane polyglycidyl) Ether), and the like.

  As the polyepoxy compound (c-2), it is preferable to use a bifunctional polyepoxy compound from the viewpoint of the finished appearance and the compatibility with the acrylic resin.

  The molecular weight of the polyepoxy compound (c-2) is preferably about 50 to 2000, and more preferably about 100 to 1000, from the viewpoint of scratch resistance and compatibility with the acrylic resin.

  Specifically, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, and the like can be preferably used.

  As the Denacol series epoxy compound manufactured by Nagase ChemteX Corporation, Denacol EX-212, Denacol EX-252, Denacol EX-931 and the like can be suitably used.

  The hydroxyl group-containing reaction product (C) can be obtained by addition reaction of the carboxyl group-containing reaction product (c-1) and the polyepoxy compound (c-2).

  The reaction product (c-1) can be used as it contains residual polycarbonate diol.

  This addition reaction proceeds by a reaction between the carboxyl group of (c-1) and the epoxy group of (c-2).

  The addition reaction can be performed by mixing the reaction product (c-1) and the polyepoxy compound (c-2) and reacting at a temperature of about 130 to 165 ° C. for about 3 to 15 hours.

  The above reaction can be carried out by further adding an organic solvent, if necessary. As an organic solvent, what was mentioned by the hydroxyl-containing acrylic resin of the said hydroxyl-containing resin (A) can be used similarly.

  Moreover, in the said addition reaction, a catalyst can be used as needed. Specifically, quaternary compounds such as tetraethylammonium bromide, tetrabutylammonium bromide, tetraethylammonium chloride, tetrabutylphosphonium bromide, and triphenylbenzylphosphonium chloride are effective catalysts for the reaction between a carboxyl group and an epoxy group. Salt catalysts; amines such as triethylamine and tributylamine can be exemplified. Of these, quaternary salt catalysts can be preferably used.

  In the reaction between the reaction product (c-1) and the polyepoxy compound (c-2), the reaction ratio between (c-1) and (c-2) is equimolar or the reaction between the carboxyl group and the epoxy group. From the viewpoints of properties and storage properties, an excess of carboxyl groups is preferred. The molar ratio of the carboxyl group in (c-1) to the epoxy group in (c-2) is preferably about 0.7 to 1.0 (epoxy group / carboxyl group), and 0.8 to 1 More preferably, it is about 0.0.

  The hydroxyl group-containing reaction product (C) may contain unreacted substances as long as the hydroxyl value and the number average molecular weight are within a specific range. Usually, it can use as it is as a hydroxyl-containing reaction product (C), without isolate | separating an unreacted substance.

  The hydroxyl value of the hydroxyl group-containing reaction product (C) is 30 to 150 mgKOH / g from the viewpoint of the curability of the finally obtained coating composition and the coating performance such as scratch resistance and water resistance of the resulting coating. Preferably, it is about 45-120 mgKOH / g, More preferably, it is about 60-110 mgKOH / g.

  The acid value of the hydroxyl group-containing reaction product (C) is determined by determining the appropriate reaction ratio between the above (c-1) and (c-2), the molecular weight of the coating composition finally obtained, and the water resistance of the resulting coating film. In view of the above, it is preferably about 0 to 25 mgKOH / g, more preferably about 0 to 15 mgKOH / g.

  The epoxy group content of the hydroxyl group-containing reaction product (C) is 0 to 0.2 mmol / g from the viewpoint of the appropriate reaction ratio, water resistance, and storage stability of the above (c-1) and (c-2). It is preferably about 0, more preferably about 0 to 0.1 mmol / g.

  The number average molecular weight of the hydroxyl group-containing reaction product (C) is 1000 to 1000 from the viewpoint of the curability of the coating composition finally obtained and the finished appearance of the obtained coating film, the scratch resistance, the water resistance and the like. 12000, preferably 1500 to 7000, more preferably 2000 to 5000.

  In the present invention, the hydroxyl value, number average molecular weight, acid value, and epoxy group content of the hydroxyl group-containing reaction product (C) mean the values of the entire reaction product including unreacted products such as residual polycarbonate diol. .

  In the coating composition of the present invention, the hydroxyl group of the hydroxyl group-containing resin (A) and the hydroxyl group-containing reaction product (C) and the isocyanate group of the polyisocyanate compound (B) from the viewpoint of the curability of the coating film and the scratch resistance. The equivalent ratio (NCO / OH) is preferably in the range of 0.5 to 2.0, more preferably 0.8 to 1.5.

The amount of the hydroxyl group-containing resin (A), the polyisocyanate compound (B) and the hydroxyl group-containing reaction product (C) in the coating composition of the present invention is the solid content of the component (A), the component (B) and the component (C). Based on the total amount of 100 parts by mass, the non-volatile content of the hydroxyl group-containing resin (A) is 30 to 75% by mass, preferably 40 to 65% by mass, and the polyisocyanate compound (B) is 20 to 65% by mass, preferably 30. It is suitable that ˜55% by mass and the hydroxyl group-containing reaction product (C) is in the range of 3 to 30% by mass, preferably 5 to 25% by mass, more preferably 10 to 20% by mass.
Other Components Known pigments such as color pigments, extender pigments, glitter pigments, and rust preventive pigments can be blended in the coating composition of the present invention as necessary.

  Examples of the coloring pigment include titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, selenium pigment, Examples include perylene pigments. Examples of extender pigments include talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, and alumina white. Examples of the bright pigment include aluminum powder, mica powder, and mica powder coated with titanium oxide.

  Various resins such as an acrylic resin, a polyester resin, an alkyd resin, a silicon resin, and a fluororesin can be added to the coating composition of the present invention as necessary. It is also possible to use a small amount of a crosslinking agent such as a melamine resin or a blocked polyisocyanate compound. Moreover, it is also possible to use polycarbonate diol together. Furthermore, if necessary, general paint additives such as a curing catalyst, an ultraviolet absorber, a light stabilizer, an antioxidant, a surface conditioner, and an antifoaming agent can be blended.

  Examples of the curing catalyst include tin octylate, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dioctyltin diacetate, dibutyltin dilaurate, dibutyltin oxide, and dioctyltin. Examples thereof include oxides, organometallic catalysts such as lead 2-ethylhexanoate, and tertiary amines.

  These compounds described above as the curing catalyst may be used alone or as a mixture of two or more. The amount of the curing catalyst varies depending on the type, but is usually 0 to 5 parts by mass, preferably 0.1 to 4 parts per 100 parts by mass of the total solids of the component (A), the component (B) and the component (C). About mass parts.

  Known ultraviolet absorbers can be used, and examples thereof include ultraviolet absorbers such as benzotriazole absorbers, triazine absorbers, salicylic acid derivative absorbers, and benzophenone absorbers. By blending the ultraviolet absorber, the weather resistance, yellowing resistance and the like of the coating film can be improved.

  As content in the coating composition of a ultraviolet absorber, it is about 0-10 mass parts normally with respect to 100 mass parts of resin solid content total measurement. Moreover, it is preferable that content of a ultraviolet absorber is about 0.2-5 mass parts, and it is more preferable that it is about 0.3-2 mass parts.

  A conventionally well-known thing can be used as a light stabilizer, For example, a hindered amine light stabilizer can be mention | raise | lifted. By blending a light stabilizer, the weather resistance, yellowing resistance and the like of the coating film can be improved.

  As content in the coating composition of a light stabilizer, it is about 0-10 mass parts normally with respect to 100 mass parts of resin solid content total measurement. Further, the content of the light stabilizer is preferably about 0.2 to 5 parts by mass, and more preferably about 0.3 to 2 parts by mass.

Although the form of the coating composition of the present invention is not particularly limited, it is usually used as an organic solvent type coating composition. As the organic solvent used in this case, various organic solvents for paints such as aromatic or aliphatic hydrocarbon solvents; alcohol solvents; ester solvents; ketone solvents; ether solvents and the like can be used. As the organic solvent to be used, those used at the preparation of the component (A), the component (C) and the like may be used as they are, or may be added as appropriate.
Preparation Method of Coating Composition The coating composition of the present invention comprises a hydroxyl group-containing resin (A), a polyisocyanate compound (B), a hydroxyl group-containing reaction product (C), and a curing catalyst, pigment, It can be prepared by mixing a resin, an ultraviolet absorber, a light stabilizer, an organic solvent, and the like by a known method.

  When the isocyanate group of the polyisocyanate compound as the component (B) is not blocked, the coating composition of the present invention has a hydroxyl group-containing resin (A) and a hydroxyl group-containing reaction product (from the storage stability). C) and the polyisocyanate compound (B) are separated from each other, and it is preferable to use a mixture of the two immediately before use.

  The solid content concentration of the coating composition of the present invention is preferably about 30 to 70% by mass, and more preferably about 40 to 60% by mass.

Coating Method The coating composition of the present invention can be suitably used in various coating methods shown below.

Examples of the object to be coated include bodies such as automobiles and motorcycles, or parts thereof. Also, cold rolled steel sheets, galvanized steel sheets, zinc alloy plated steel sheets, stainless steel sheets, tin plated steel sheets, etc., metal base materials such as aluminum plates and aluminum alloy plates; various plastic base materials, etc. May be.

  Moreover, as a to-be-coated article, the metal surface of the said vehicle body, components, and a metal base material may be subjected to chemical conversion treatment such as phosphate treatment, chromate treatment, and complex oxide treatment. Furthermore, as the object to be coated, an undercoat film and / or an intermediate coat film such as various electrodeposition paints may be formed on the vehicle body, metal base material, or the like.

  Furthermore, examples of the object to be coated include industrial machines, home appliances, kitchen appliances, roofs, walls, and shutters.

Coating and curing method The coating method of the coating composition of the present invention is not particularly limited. For example, wet coating may be performed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, or roll coat coating. A film can be formed. In air spray coating, airless spray coating, and rotary atomization coating, electrostatic application may be performed as necessary. Of these, air spray coating and rotary atomization coating are particularly preferred. In general, the coating film thickness is preferably about 10 to 50 μm as the cured film thickness.

  In the case of air spray coating, airless spray coating, and rotary atomization coating, the viscosity of the coating is adjusted to a viscosity range suitable for the coating, usually Ford Cup #No. In a 4-viscosity meter, it is preferable to adjust appropriately using a solvent such as an organic solvent so that the viscosity is within a range of about 15 to 60 seconds at 20 ° C.

  The wet coating film is cured by heating. Heating can be performed by a known heating means. For example, a drying furnace such as a hot air furnace, an electric furnace, or an infrared induction heating furnace can be applied.

  The heating temperature is usually about 100 to 180 ° C, preferably about 120 to 160 ° C. The heating time is usually in the range of about 5 to 60 minutes.

Multilayer coating film forming method According to the coating composition of the present invention, a coating film having excellent coating performance such as scratch resistance, acid resistance, and finished appearance can be formed. In the coating film forming method to be used, it is preferably used as a clear coating composition for forming a top clear coat.

  Moreover, the coating composition of this invention can be conveniently used also as a top-coat coloring coating composition by containing an organic pigment or an inorganic pigment, for example.

  The multi-layer coating film forming method of the present invention is a coating film forming method in which at least one colored base coat and at least one clear coat are sequentially formed on an object to be coated, and the uppermost clear coat is formed. As the coating composition, the coating composition of the present invention is used.

  As an object to which the multilayer coating film forming method of the present invention is applied, an automobile body and its parts are particularly preferable.

  More specifically, examples of the method for forming a multilayer coating film include a method of using the coating composition of the present invention for forming a top clear coat in the multilayer coating film forming method of the following methods a to c. Can do.

  Method a: A method of forming a top coat multilayer coating film in which a colored base coat and a top clear coat are sequentially formed on an object to be coated.

  Method b: A method of forming a top coat multilayer coating film in which a colored base coat, a clear coat, and a top clear coat are sequentially formed on an object to be coated.

  Method c: A three-coating multi-layer coating film forming method in which a first colored base coat, a second colored base coat, and a top clear coat are sequentially formed on an object to be coated.

  Each top coat film forming step of these methods a, b and c will be described in detail.

  In each method, as a method for applying the colored base coating composition and the clear coating composition, a coating method such as airless spray, air spray, or rotary atomization coating can be employed. In these coating methods, electrostatic application may be performed as necessary.

In the method a, as the coating composition for forming the colored base coat, a known colored coating composition can be used.
As the colored base coating composition, it is preferable to use a coating composition that is used when painting an automobile body or the like.

  The colored base coating composition is an organic solvent-type or aqueous coating composition containing a base resin, a crosslinking agent, a colored pigment, a metallic pigment, a light interference pigment, an extender pigment and the like.

  As the base resin, for example, at least one of acrylic resin, vinyl resin, polyester resin, alkyd resin, urethane resin, and the like can be used. The base resin has, for example, a crosslinkable functional group such as a hydroxyl group, an epoxy group, a carboxyl group, or an alkoxysilyl group. As the crosslinking agent, for example, at least one of alkyl etherified melamine resin, urea resin, guanamine resin, polyisocyanate compound, blocked polyisocyanate compound, epoxy compound, carboxyl group-containing compound and the like can be used. The base resin and the crosslinking agent are preferably used in a proportion of 50 to 90% by weight of the base resin and 50 to 10% by weight of the crosslinking agent based on the total amount of both components.

  In method a, the colored base coating composition is applied to an object to be coated so that the cured film thickness is about 10 to 50 μm. The coated base coating composition is cured by heating at about 100-180 ° C., preferably about 120-160 ° C. for about 10-40 minutes, or left at room temperature for several minutes without curing after coating, or about 40 Preheat at ~ 100 ° C for about 1-20 minutes.

  Next, as a coating material for forming the top clear coat, the coating composition of the present invention is applied so that the film thickness is about 10 to 70 μm as a cured film thickness, and heated to form a cured multilayer coating film. Can be formed. The heating is performed at about 100 to 180 ° C., preferably about 120 to 160 ° C. for about 10 to 40 minutes.

  In the above-mentioned two-coat system, the base paint composition is applied and the clear paint composition is applied without being heated and cured, and when these two-layer coating films are cured simultaneously, the two-coat one-bake system is used. When the composition is applied and cured by heating, and then the clear coating composition is applied and the clear coating film is cured, the 2-coat 2-bake method is used.

  As the colored base coating composition in method b, the same colored base coating composition as described in the section of method a can be used. Further, the first clear paint composition for forming the clear coat may be a paint for forming a transparent coating film, for example, a paint composition that does not contain most or all of the pigment in the above-mentioned known colored base paint composition. Things can be used. And the coating composition of this invention is used as a 2nd clear coating composition which forms a top clear coat. Further, as the first clear paint composition, the clear coat and the top clear coat formed from the paint composition of the present invention may be formed using the paint composition of the present invention.

  In method b, in the same manner as in method a, the colored base coating composition is applied to the object to be coated and heat-cured, or left to stand at room temperature for several minutes or pre-heated without being cured, and then the colored base coating composition is coated. The first clear coating composition is applied onto the film so that the film thickness is about 10 to 50 μm as a cured film thickness, and is about 100 to 180 ° C., preferably about 120 to 160 ° C., for about 10 to 40 minutes. Heat to cure or leave or preheat at room temperature for several minutes without curing.

  Next, as the second clear coating composition, the coating composition of the present invention is applied so that the film thickness is about 10 to 50 μm as a cured film thickness, and heated to form a cured multilayer coating film. Can be formed. The heating conditions are the same as in method a.

  Without applying and curing the base coating composition, the first clear coating composition is applied, the second clear coating composition is applied without curing, and the three-layer coating film is simultaneously cured. In this case, the 3-coat 1-bake method is used. When the first clear paint composition is applied without applying the base paint composition and heat-curing, these coating films are simultaneously heat-cured, and the second clear paint composition is applied and cured. Is a 3-coat 2-bake system. In addition, when a base coating composition is applied and heated and cured, a first clear coating composition is applied, this is cured, a second clear coating composition is applied, and this is cured, a 3 coat 3 bake system It is.

  In the method c, as the first colored base coating composition, the same colored base coating composition as described in the method a can be used.

  In the method c, in the same manner as in the method a, the first colored base coating composition is applied to the object to be coated and heat-cured, or left to stand for several minutes at room temperature without being cured or pre-heated. On the colored base coating film, the second colored base coating composition is applied so that the film thickness is about 10 to 50 μm as a cured film thickness, and about 100 to 180 ° C., preferably about 120 to 160 ° C. Heat for 10 to 40 minutes to cure, or leave or preheat at room temperature for several minutes without curing.

  Next, as the coating composition for forming the top clear coat, the coating composition of the present invention is applied so that the film thickness is about 10 to 50 μm in terms of the cured film thickness, and heated to cure the multilayer. A coating film can be formed. The heating conditions are the same as in method a.

  Without applying the first base coating composition and curing by heating, the second base coating composition is applied, and without being cured, the clear coating composition is applied, and these three-layer coating films are simultaneously cured. In this case, the 3-coat 1-bake method is used. In addition, when the first base coating composition is applied and heated and cured, the second base coating composition is applied, the clear coating composition is applied without curing, and these coating films are simultaneously cured. This is a 3-coat 2-bake method. When the first base coating composition is applied and heat-cured, the second base coating composition is applied, this is cured, and the clear coating composition is applied and cured. It is.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples. In the following, “part” and “%” are both based on mass, and the film thickness of the coating film is based on the cured coating film.

Production examples of carboxyl group-containing reaction product (c-1) Production examples 1 to 9
A four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet was charged with the amount (part by mass) of polycarbonate diol shown in Table 1 below, and the temperature was raised to 130 ° C. in a nitrogen atmosphere. After reaching 130 ° C., an amount of acid anhydride (part by mass) shown in Table 1 below was added and reacted for 2 hours to obtain a carboxyl group-containing reaction product (c-1). No. of each reaction product (c-1) obtained. The special values of 1 to 9 are also shown in Table 1 below.

  Hereinafter, (* 1) to (* 12) in each table have the following meanings, respectively, and the viscosity of the polycarbonate diol is a value measured at 50 ° C. under a condition of 6 rpm using a B-type viscometer. .

  (* 1) T-5650J: manufactured by Asahi Kasei Chemicals, polycarbonate diol having 1,6-hexanediol and 1,5-pentanediol as diol components, number average molecular weight 800, viscosity 860 mPa · s, hydroxyl value 140 mgKOH / g, 100% solids.

  (* 2) T-4671: manufactured by Asahi Kasei Chemicals, polycarbonate diol containing 1,6-hexanediol and 1,4-butanediol as diol components, number average molecular weight 1000, viscosity 2400 mPa · s, hydroxyl value 112 mgKOH / g, 100% solids.

  (* 3) UM-CARB90: manufactured by Ube Industries, Ltd., polycarbonate diol having 1,6-hexanediol and 1,4-cyclohexanedimethanol as diol components, number average molecular weight 900, viscosity 7000 mPa · s, hydroxyl value 124 mgKOH / g , 100% solids.

  (* 4) T-4672: manufactured by Asahi Kasei Corporation, polycarbonate diol having 1,6-hexanediol and 1,4-butanediol as diol components, number average molecular weight 2000, viscosity 20000 mPa · s, hydroxyl value 112 mgKOH / g, solid 100% min.

Production Examples of Hydroxyl-Containing Reaction Product (C) Production Examples 10 to 21
In a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, the amount (parts by mass) of the carboxyl group-containing reaction product (c-1) and polyepoxy compound (c-) shown in Table 2 below 2) Methoxypropyl acetate and tetrabutylammonium bromide were charged, heated to 140 ° C. in a nitrogen atmosphere, and reacted for 7 hours to obtain each hydroxyl group-containing reaction product (C). No. of each reaction product (C) obtained. The special values of 1 to 10 are also shown in Table 2 below. Production Examples 20 and 21 are resins for comparative examples.

(* 5) Denacol EX-212: trade name, manufactured by Nagase ChemteX Corporation, 1,6-hexanediol diglycidyl ether, epoxy equivalent (WPE) 151
(* 6) Denacol EX-252: Trade name, manufactured by Nagase ChemteX Corporation, hydrogenated bisphenol A diglycidyl ether, epoxy equivalent (WPE) 213
(* 7) Denacol EX-920: trade name, manufactured by Nagase ChemteX Corporation, polyoxypropylene glycol diglycidyl ether, epoxy equivalent (WPE) 176
(* 8) Denacol EX-931: trade name, manufactured by Nagase ChemteX Corporation, polyoxypropylene glycol diglycidyl ether, epoxy equivalent (WPE) 471

Production Examples of Hydroxyl Group Resin (A) (Hydroxyl Group Acrylic Resin) Production Examples 22-30
A four-necked flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet is charged with 310 parts of Swazol 1000 (Cosmo Oil Co., Ltd., hydrocarbon solvent), and the temperatures shown in Table 3 below under a nitrogen atmosphere The mixture consisting of the monomer and the initiator in the amount (parts by mass) shown in Table 3 below was added dropwise over 4 hours. Next, after aging for 30 minutes while ventilating nitrogen gas, a mixture of 320 parts of Swazol 1000 and 5 parts of 2,2′-azobisisobutyronitrile was added dropwise over 1 hour. Then, the solution of each hydroxyl-containing resin (A) (hydroxyl group-containing acrylic resin) was obtained by further aging for 1 hour. No. of each hydroxyl-containing resin (A) obtained. The special values of 1 to 5 are shown together in Table 3 below. In addition, Production Examples 27 to 30 are resins for comparative examples.

Production Examples 1 to 16 of Coating Composition and Comparative Examples 1 to 11
Using the hydroxyl group-containing resin (A) and hydroxyl group-containing reaction product (C) obtained in the above production example, and the polyisocyanate compound (B) and raw materials listed in Table 3 below, the formulation (mass) shown in Table 4 below Part)) using a rotary blade type stirrer and mixing to obtain each coating composition No. 1-27 were obtained. In addition, the compounding quantity in Table 4 is a solid content (mass part).

  Moreover, the coating compositions 17-27 are coating compositions for comparative examples.

(* 9) N3300: trade name, manufactured by Bayer, HMDI isocyanurate (* 10) UV1164: trade name, manufactured by Ciba Geigy, ultraviolet absorber.

  (* 11) HALS292: trade name, manufactured by Ciba Geigy Corp., light stabilizer.

  (* 12) BYK-300: trade name, manufactured by Big Chemie, surface conditioner.

  Each coating composition No. Nos. 1-27 added Ford Cup #No. 4 was used to adjust the viscosity to 25 seconds at 20 ° C.

Preparation of test plate Each coating composition No. 1 to 27 were used to prepare test plates as follows.

(Coating)
ELECRON GT-10 (trade name, manufactured by Kansai Paint Co., Ltd., thermosetting epoxy resin-based cationic electrodeposition coating) is formed on a 0.8 mm-thick dull steel sheet that has been subjected to zinc phosphate conversion treatment so as to have a film thickness of 20 μm. Electrodeposited and heated at 170 ° C. for 30 minutes to cure, and on the electrodeposited surface, Amirac TP-65-2 (trade name, manufactured by Kansai Paint Co., Ltd., polyester / melamine resin-based automotive intermediate coating, gray coating The intermediate coating plate was coated with air spray so that the film thickness was 35 μm, and was cured by heating at 140 ° C. for 30 minutes.

(Creation of silver paint test plate)
A water-based metallic base coat WBC713T # 1F7 (manufactured by Kansai Paint Co., Ltd., acrylic / melamine resin-based top coat paint for automobiles, silver coating color) was applied on the substrate to a thickness of 15 μm. After standing at room temperature for 5 minutes and preheating at 80 ° C. for 10 minutes, each coating composition No. 1-27 was coated to a film thickness of 35 μm. Then, after leaving to stand at room temperature for 10 minutes, it heated at 140 degreeC for 20 minutes, and each coating film was obtained by hardening both coating films together.

(Creation of black paint test plate)
In the preparation of the above-mentioned silver coating color test plate, an aqueous metallic base coat WBC713T # 202 (manufactured by Kansai Paint Co., Ltd., acrylic / melamine resin-based automotive top coat base coat, black paint color) is used instead of the aqueous metallic base coat WBC713T # 1F7. Each black coating color test board was obtained by painting similarly to preparation of a silver coating color test board except that.
(Preparation of white test plate for stain resistance)
On the 0.8 mm-thick dull steel sheet that has been subjected to zinc phosphate chemical conversion treatment, Eleklon GT-10 (trade name, manufactured by Kansai Paint Co., Ltd., thermosetting epoxy resin cationic electrodeposition paint) has a thickness of 20 μm. Electrodeposited and heated at 170 ° C. for 30 minutes to cure, and on top of that, Amirac TP-65-2 (manufactured by Kansai Paint Co., Ltd., trade name, polyester / melamine resin-based automotive intermediate coating, white coating color) A coated plate, which was air spray coated to a film thickness of 35 μm and heat-cured at 140 ° C. for 30 minutes, was used as an object to be coated, and each coating composition No. 1 to 27 were coated to a film thickness of 35 μm, allowed to stand at room temperature for 10 minutes, and then heated and cured at 140 ° C. for 20 minutes to obtain each white test plate obtained.

Each of the obtained test plates was allowed to stand at room temperature for 7 days and then subjected to the following coating film performance test.
Performance Test Results Metallic Appearance: The metallic appearance of the silver paint test plate was evaluated by IV value. The IV value is measured using a laser-type metallic feel measuring device (ALCOLM LMR-200 (manufactured by Kansai Paint Co., Ltd.)). Among the reflections of laser light irradiated at an incident angle of 45 degrees, the minimum light intensity in the regular reflection region. The signal output at the light receiving angle was measured. The IV value is obtained by quantifying the whiteness of the metallic coating film, and the whiter the metallic pigment is, the more the metallic pigment is uniformly oriented in parallel to the coating surface.

  Scratch resistance: 20 degree specular reflectance of a test plate after a car washer was washed 15 times with a car wash machine under a condition of 20 ° C. with a black coated test plate attached to the roof with a water resistant tape manufactured by Nichiban Co., Ltd. (20 ° gloss value) was measured and evaluated by the gloss retention (%) relative to the 20 ° gloss value before the test. The higher the gloss retention, the better the scratch resistance. As the car washer, “PO20 FWRC” manufactured by Yasui Industry Co., Ltd. was used.

  Acid resistance: 0.4 cc of 40% sulfuric acid was dropped on the coating surface of each black coating test plate, heated for 15 minutes on a hot plate heated to 60 ° C., and then washed with water. The etching depth (μm) of the sulfuric acid dropping portion was cut off using a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., surface roughness profile measuring machine “Surfcom 570A”) with a cutoff of 0.8 mm (scanning speed: 0.3 mm / sec, The acid resistance was evaluated by measurement under the condition of 5000 times magnification. The smaller the etching depth value, the better the acid resistance.

  Contamination resistance: Each white test plate was tested for 600 hours under the conditions of JIS K5400 in a sunshine weatherometer (manufactured by Suga Test Instruments Co., Ltd., accelerated rust resistance test machine), and then composed of a mixture of mud, carbon black, mineral oil and clay. Contaminants were adhered to the flanks and rubbed lightly on the test plate. This was left for 24 hours in a constant temperature and humidity chamber at 20 ° C. and 75% RH, then the coated surface was washed with running water, and the degree of contamination of the coated film was evaluated according to the following criteria based on the lightness difference (ΔL) of the coated plate. The smaller the ΔL value, the better the stain resistance. ΔL was determined by the following equation.

ΔL = (L value before stain resistance test) − (L value after stain resistance test)
The L value was measured using CR400 manufactured by Konica Minolta (tristimulus value direct-reading color meter D65 light source 2 ° visual field diffuse illumination vertical light reception (d / 0)). The L value is a value based on the CIE 1976 L ^* a ^* b ^* color system.
A: ΔL <0.2, O: 0.2 ≦ ΔL <0.5, OΔ: 0.5 ≦ ΔL <1, Δ: 1 ≦ ΔL <2, X: 2 ≦ ΔL.

  Finishability (20 ° gloss): The 20-degree specular reflectance (20 ° gloss value) of each black-coated test plate was measured using HG-268 (manufactured by Handy Gloss Meter Suga Test Instruments Co., Ltd.).

  The performance test results are also shown in Table 3.

Claims (7)

  Polycarbonate diol obtained by reacting a carbonylating agent to a hydroxyl group-containing resin (A) having a hydroxyl value of 80 to 200 mgKOH / g and a weight average molecular weight of 2500 to 40000, a polyisocyanate compound (B), and a diol having 2 to 10 carbon atoms. And a carboxyl group-containing reaction product (c-1) having an acid value of 10 to 120 mg KOH / g and a number average molecular weight of 400 to 2500, obtained by half-esterification reaction of the acid and an acid anhydride, and a polyepoxy compound (c-2) A coating composition containing a hydroxyl group-containing reaction product (C) having a hydroxyl value of 30 to 150 mgKOH / g and a number average molecular weight of 1000 to 12000, which is obtained by addition reaction.   The coating composition according to claim 1, wherein the polycarbonate diol compound (C) uses 1,6-hexanediol as a diol component.   The coating composition according to claim 1 or 2, wherein the hydroxyl group-containing resin (A) is a hydroxyl group-containing acrylic resin.   The hydroxyl group-containing acrylic resin is a hydroxyl group-containing acrylic resin obtained by copolymerizing a monomer mixture containing a hydroxyl group-containing unsaturated monomer having a hydroxyl group-containing hydrocarbon group having 4 or more carbon atoms. The coating composition as described.   Unsaturated monomer having hydroxyl group-containing acrylic resin having an unsaturated monomer having a bridged alicyclic hydrocarbon group having 10 to 20 carbon atoms and / or an alicyclic hydrocarbon group having 3 to 12 carbon atoms The coating composition according to claim 3 or 4, which is a hydroxyl group-containing acrylic resin obtained by copolymerizing a monomer mixture containing a body.   The hydroxyl group-containing acrylic resin is a hydroxyl group-containing acrylic resin obtained by copolymerizing a monomer mixture containing an unsaturated monomer having a hydrocarbon group having 8 or more carbon atoms having a branched structure. 5. The coating composition according to 4.   A method for forming a multi-layer coating film by sequentially coating at least one layer of a colored base coat paint and at least one layer of a clear coat paint on an object to be coated, wherein the clear coat paint is the uppermost layer. A method for forming a multilayer coating film, comprising coating the coating composition according to any one of the above.