JP2010100748A - Coating composition and method for forming coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating composition forming a cured coating film excellent in all of scratch resistance, acid resistance, stain resistance and finished properties. <P>SOLUTION: The coating composition comprises: a hydroxy group-containing resin (A) having a hydroxyl value of 80-200 mgKOH/g and a weight-average molecular weight of 2,500-40,000; a polyisocyanate compound (B); and a reaction product (C) having a hydroxyl value of 40-180 mgKOH/g and a number-average molecular weight of 1,000-5,000, which is obtained by adding a hydroxy acid to a carbodiimide group in a reaction product (a) obtained by urethanization reaction of a polycarbonate diol and a carbodiimide compound having isocyanate groups at both ends under conditions of excessive hydroxy groups. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

A coating material to be coated on an object such as an automobile body is required to have excellent coating film properties such as scratch resistance, acid resistance, stain resistance, and finish.
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.

  Japanese Patent Application Laid-Open No. 6-220397 discloses a two-component urethane cross-linking coating composition comprising a hydroxyl group-containing acrylic resin, a hydroxyl group-containing oligoester and an isocyanate prepolymer. This paint is excellent in acid resistance of the coating film because urethane crosslinks are hardly hydrolyzed. However, the scratch resistance of the coating film is insufficient.

Japanese Patent Laid-Open No. 6-220397

  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, stain resistance, and finish.

As a result of intensive studies to solve the above problems, the present inventors have obtained a hydroxyl group-containing resin and a polyisocyanate compound having a specific hydroxyl value and an average molecular weight, and a polycarbonate diol and a carbodiimide compound having an isocyanate group at both ends. A reaction product (C) having a hydroxyl value and a number average molecular weight in a specific range obtained by addition reaction of a hydroxy acid to a carbodiimide group of a reaction product (a) obtained by urethanation under hydroxyl excess conditions. It has been found that the above object can be achieved by a coating composition characterized by containing the present invention, and the present invention has been completed.

  That is, the present invention relates 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 polycarbonate diol and a carbodiimide having isocyanate groups at both ends. It has a hydroxyl value of 40 to 180 mgKOH / g and a number average molecular weight of 1,000 to 5,000 obtained by addition reaction of a hydroxy acid with a carbodiimide group in a reaction product (a) obtained by urethanation of a compound with hydroxyl group-excess conditions. The present invention provides a coating composition containing the reaction product (C).

  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 present invention provides a method for forming a multilayer coating film characterized by coating the coating composition described above.

Specific hydroxyl group-containing resin and polyisocyanate compound, and a specific polycarbonate diol and a carbodiimide group of the reaction product (a) obtained by urethanizing a carbodiimide compound having an isocyanate group at both ends under hydroxyl excess conditions According to the coating composition of the present invention containing the reaction product (C) obtained by the addition reaction, the reaction product (C) has good compatibility with the hydroxyl group-containing resin and the polyisocyanate compound. Therefore, a coating film with good finish can be obtained.
Further, the physical properties of the coating such as mechanical strength can be improved by the reaction product (C), and urethane cross-linking by reaction of the hydroxyl group-containing resin and the polyisocyanate compound or the reaction product (C) and the polyisocyanate compound. In addition, since the carbonate bond of the reaction product (C) is excellent in hydrolysis resistance by acid, a cured coating film excellent in any of scratch resistance, acid resistance, stain resistance, etc. can be formed. There is an effect.

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 of 80 to 200 mgKOH / g and a weight average molecular weight of 2500 to 40000, a polyisocyanate compound (B), and a polycarbonate diol and isocyanate groups at both ends. The hydroxyl value obtained by urethanating a carbodiimide compound having hydroxyl group-excess conditions to synthesize a reaction product (a), and adding a hydroxy acid to the carbodiimide group in the obtained reaction product (a). It is a coating composition characterized by containing the reaction product (C) of 40-180 mgKOH / g and a number average molecular weight 1000-5000.
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, hydroxypropyl Examples include acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate. In addition, examples of monoesterified products of polyhydric alcohols and acrylic acid or methacrylic acid include compounds obtained by ring-opening condensation of ε-caprolactone, such as “Placcel FA-1”, “Placcel FA-2”, “Placcel”. FA-3, Plaxel FA-4, Plaxel FA-5, Plaxel FM-1, Plaxel FM-2, Plaxel FM-3, Plaxel FM-4, Plaxel FM -5 "(all are trade names manufactured by Daicel Chemical Industries, Ltd.).
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 thereof include condensed 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.

As a compound obtained by ring-opening condensation of ε-caprolactone to a monoesterified product of acrylic acid or methacrylic acid and a dihydric alcohol having 2 to 10 carbon atoms, specifically, among those described above, “Placcel FA-2”, “Placcel FM-3” (all of which are trade names, manufactured by Daicel Chemical Industries, Ltd.) can be used.
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 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) alkoxysilane 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 alkoxysilane group-containing unsaturated monomer as a constituent component, in addition to the crosslinking bond between the hydroxyl group and the isocyanate group, a condensation reaction between the alkoxysilane groups and a crosslinking bond caused by the reaction between the alkoxysilane group and the hydroxyl group are generated. Can do. Thereby, since the crosslinking density of the obtained coating film improves, the effect of an improvement in acid resistance and stain resistance can be obtained.
When an alkoxysilane group-containing unsaturated monomer is used as a constituent component, the blending ratio is preferably in the range of 3 to 50% by weight, particularly 5 to 35% by weight, 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 addition, in this specification, a weight average molecular weight is the value which converted the weight average molecular weight measured with the gel permeation chromatograph (The Tosoh company make, "HLC8120GPC") on the basis of the weight average molecular weight of polystyrene. Columns are “TSKgel G-4000H × L”, “TSKgel G-3000H × L”, “TSKgel G-2500H × L”, “TSKgel G-2000H × L” (both manufactured by Tosoh Corporation, trade names) ), Mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, detector: RI. The number average molecular weight is also a value measured under the same conditions as described above.
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.
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 of 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, and these are reacted. 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 or higher alcohols such as trimethylolpropane, glycerin, pentaerythritol, and sorbitol. Etc. 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, tetramethylxylylene 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 diisocyanates such as 4,4′-biphenylene diisocyanate, bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenylisocyanate) Compounds; and burette-type adducts of these polyisocyanates, isocyanurate cycloadducts; triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2,4, Polyisocyanates having three or more isocyanate groups in one molecule such as 6-triisocyanatotoluene, 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate; and these polyisocyanates 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 '-Tet And aromatic tetra isocyanates such as isocyanate can be mentioned.

  Examples of the polyisocyanate derivative include dimer, trimer, burette, 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. For example, when heated to 100 ° C. or higher, preferably 130 ° C. or higher, isocyanate groups are regenerated and can easily react with hydroxyl groups. 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.
Reaction product (C)
The reaction product (C) of this paint is a urethanation reaction between polycarbonate diol and a carbodiimide compound having an isocyanate group at both ends under hydroxyl excess conditions to synthesize a reaction product (a), and the reaction product obtained It is a reaction product having a hydroxyl value of 40 to 180 mgKOH / g and a number average molecular weight of 1000 to 5000 obtained by addition reaction of a hydroxy acid to a carbodiimide group in the product (a).
The hydroxyl value of the reaction product (C) is compatible with the hydroxyl group-containing resin (A) and the polyisocyanate compound (B), the curability of the resulting coating composition and the scratch resistance, acid resistance, From the viewpoint of water resistance and the like, it is 40 to 180 mgKOH / g, preferably 50 to 150 mgKOH / g.
The reaction product (C) was obtained by urethanating a polycarbonate diol and a carbodiimide compound having an isocyanate group at both ends under hydroxyl-excess conditions to synthesize a reaction product (a), and the reaction product (a) thus obtained. It can be synthesized by adding a hydroxy acid to the carbodiimide group therein.
To synthesize the reaction product (C), first, the reaction product (a) is synthesized. The reaction product (a) can be synthesized by urethanizing a polycarbonate diol and a carbodiimide compound having isocyanate groups at both ends under conditions of excess hydroxyl group.
Polycarbonate diol is usually a compound obtained by polycondensation reaction between a diol and a carbonylating agent.
The diol component of the polycarbonate diol used for the synthesis of the reaction product (C) is preferably a divalent alcohol having 2 to 10 carbon atoms, particularly 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 systems such as 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and the like; aromatic systems such as p-xylenediol and p-tetrachloroxylenediol; Examples thereof include diols such as diethylene glycol and dipropylene glycol. These diols can be used alone or in combination of two or more.
As the polycarbonate diol used for the synthesis of the reaction product (C), those obtained by polycondensation of a diol component containing 1,6-hexanediol and a carbonylating agent are preferable from the viewpoint of durability and hardness.
Further, as a particularly preferred one, 1,6-hexanediol is used as an essential diol component and two or more diol components are used in combination, and a combination of 1,6-hexanediol and 1,5-pentanediol, Polycarbonate diol obtained by polycondensation of a diol component and a carbonylating agent such as a combination of 1,6-hexanediol and 1,4-butanediol, or a combination of 1,6-hexanediol and 1,4-cyclohexanedimethanol Can give.
As the carbonylating agent, for example, one or a combination of two or more commonly used alkylene carbonates, dialkyl carbonates, diallyl carbonates and phosgenes 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 used for the synthesis of the reaction product (C), those having a viscosity at 50 ° C. of 10,000 mPa · s or less are preferably used. When the viscosity at 50 ° C. exceeds 10,000 mPa · s, handling may be difficult, and the obtained reaction product (C) is compatible with the hydroxyl group-containing resin (A) and the polyisocyanate compound (B). Since it becomes inferior, the glossiness of a coating film, white turbidity, etc. arise, and the finish of a coating film may become inferior.
The viscosity of the polycarbonate diol used for the synthesis of the reaction product (C) is preferably 8000 mPa · s or less, more preferably 5000 mPa · s or less, at 50 ° C. The viscosity is a value measured at 50 ° C. using a B-type viscometer under the condition of 6 rpm.
The number average molecular weight of the polycarbonate diol used for the synthesis of the reaction product (C) is preferably from 300 to 2000, more preferably from 500 to 1800, and even more preferably from 700 to 2000, from the viewpoint of acid resistance and scratch resistance of the coating film. 1500.
In the present specification, the number average molecular weight is a value calculated based on the molecular weight of standard polystyrene from the 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

As the polycarbonate diol used for the synthesis of the reaction product (C), a commercially available product can be used. Examples of commercially available products include T-5650J (diol components: 1,6-hexanediol and 1,5-pentanediol) manufactured by Asahi Kasei Chemicals, T-4671 (diol components: 1,6-hexanediol and 1, 4-butanediol); UM-90 (diol components: 1,6-hexanediol and 1,4-cyclohexanedimethanol) manufactured by Ube Industries, Ltd. can be exemplified.
As the carbodiimide compound having an isocyanate group at both ends used for the synthesis of the reaction product (a),
For example, “Carbodilite V-01” and “Carbodilite V-05”, which are carbodiimide compounds manufactured by Nisshinbo Co., Ltd., can be mentioned.
Among these, “Carbodilite V-05” can be preferably used from the viewpoints of weather resistance, scratch resistance of the coating film, and the like.
These carbodiimide compounds having an isocyanate group at both ends can be used alone or in appropriate combination of two or more.
The reaction product (a) is usually synthesized under such conditions that the terminal isocyanate group of the carbodiimide compound having isocyanate groups at both ends reacts with the hydroxyl group of polycarbonate diol to form a urethane bond. .
The reaction can be carried out by a urethanization reaction at a temperature of 60 to 120 ° C. for about 3 to 6 hours.
The polycarbonate diol and the carbodiimide compound having an isocyanate group at both ends are synthesized by urethanizing the equivalent ratio (NCO group of the carbodiimide compound having an isocyanate group at both ends / hydroxyl group of the polycarbonate diol) under hydroxyl group-excess conditions. Can do. The relevant amount ratio is preferably 0.2 to 0.7, more preferably 0.3 to 0.6, from the viewpoint of curability when used as a coating composition, finish of the resulting coating film, acid resistance, and the like. More preferably, it is 0.4 to 0.5.
The lower the amount ratio, the more unreacted polycarbonate diol remains in the reaction product (a). In the present invention, however, the remaining polycarbonate diol was usually contained without separating the unreacted polycarbonate diol. The reaction product (a) can be used.
The reaction product (C) can be obtained by adding a hydroxy acid to the carbodiimide group in the obtained reaction product (a).
As the hydroxy acid, dimethylolbutanoic acid, dimethylolpropionic acid, 12-hydroxystearic acid and the like can be used.
Of these, 12-hydroxystearic acid can be suitably used from the viewpoint of scratch resistance of the coating film.
These hydroxy acids can be used alone or in appropriate combination of two or more as required.

In the reaction product (C), a hydroxy acid is usually added to the carbodiimide group of the reaction product (a) by addition reaction of the carboxyl group of the hydroxy acid to the carbodiimide group in the reaction product (a). The compound is synthesized under the condition that a compound having a structure is obtained.
The reaction can be carried out by addition reaction at a temperature of 60 to 140 ° C. for about 2 to 5 hours.
The reaction product (a) and the hydroxy acid can be synthesized by addition reaction with an equivalent ratio (carboxyl group of hydroxy acid / carbodiimide group in the reaction product (a)) of 0.5 to 1.0. it can. The relevant amount ratio is preferably 0.6 to 0.9, more preferably 0.65 to 0.8, from the viewpoints of curability when used as a coating composition and acid resistance and water resistance of the resulting coating film. It is.
The hydroxyl value of the reaction product (C) is 40 to 180 mgKOH / g, preferably 50 to 50 from the viewpoints of curability when used as a coating composition and scratch resistance, acid resistance, water resistance and the like of the resulting coating film. 150 mgKOH / g, more preferably 60 to 130 mgKOH / g.
The number average molecular weight of the reaction product (C) is in terms of compatibility with the hydroxyl group-containing resin (A) and the polyisocyanate compound (B), scratch resistance, hardness, weather resistance, finish, etc. of the resulting coating film. 1000-5000, preferably 1500-4500, more preferably 1800-4000.
In the present invention, the hydroxyl value and the number average molecular weight are values as a reaction product (C) including an unreacted compound (such as residual polycarbonate diol).
In the coating composition of the present invention, the equivalent ratio of the hydroxyl group of the hydroxyl group-containing resin (A) and the reaction product (C) to the isocyanate group of the polyisocyanate compound (B) from the viewpoints of the curability and scratch resistance of the coating film. (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), polyisocyanate compound (B) and reaction product (C) in the coating composition of the present invention is the total solid content of the component (A), the component (B) and the component (C). Based on 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 to 55%. It is suitable that the mass% and the reaction product (C) are in the range of 3 to 30 mass%, preferably 5 to 25 mass%, more preferably 10 to 20 mass%.
Other components The coating composition is a coating composition containing the hydroxyl group-containing resin (A), polyisocyanate compound (B) and reaction product (C) as essential components, and usually contains an organic solvent. In addition, if necessary, it may contain other additives such as curing catalysts, pigments, pigment dispersants, leveling agents, ultraviolet absorbers, light stabilizers, plasticizers and the like, which are usually used in the field of paints. it can.

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

Examples of the 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, and perylene. Color pigments (D) such as pigments; extender pigments such as talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, silica, alumina white; aluminum powder, mica powder, mica powder coated with titanium oxide, etc. Metallic pigments can be mentioned.
These pigments described above can be used alone or in combination of two or more. The pigment content varies depending on the type, but is usually 0 to 200 parts by weight, preferably 1 to 100 parts by weight, based on 100 parts by weight of the total solids of the components (A), (B) and (C) Degree.
Moreover, although content of a color pigment changes with the kinds, it is 0-150 mass parts normally with respect to 100 mass parts of total solid content of (A) component, (B) component, and (C) component, Preferably it is 1- About 100 parts by mass.
As the ultraviolet absorber, conventionally known ones can be used, and examples thereof include ultraviolet absorbers such as benzotriazole absorbers, triazine absorbers, salicylic acid derivative absorbers, and benzophenone absorbers.

  As content in the coating composition of a ultraviolet absorber, it is 0-10 mass parts normally with respect to 100 mass parts of resin solid content total measurement, especially 0.2-5 mass parts, Furthermore, especially 0.3-2 mass It is preferable from the viewpoint of weather resistance and yellowing resistance to be within the range of 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.

  The content of the light stabilizer in the coating composition is usually from 0 to 10 parts by weight, particularly from 0.2 to 5 parts by weight, more particularly from 0.3 to 2 parts by weight, based on 100 parts by weight of the total resin solid content. It is preferable from the viewpoint of weather resistance and yellowing resistance to be within the range of parts.

  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 reaction product (C) because of storage stability. And the polyisocyanate compound (B) are separated from each other, and it is preferable to use a mixture of both before use.

Coating Method of Coating Composition The coating object to which the present coating is applied is not particularly limited, but is preferably the body of various vehicles such as automobiles, motorcycles and containers. In addition, cold rolled steel sheets, galvanized steel sheets, zinc alloy plated steel sheets, stainless steel sheets, tin plated steel sheets, etc., metal substrates such as aluminum plates, aluminum alloy plates, etc .; Good.

  Moreover, as a to-be-coated object, surface treatments, such as a phosphate process, a chromate process, a complex oxide process, may be given to the metal surface of the said vehicle body or a metal base material. 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.

  The coating method of this paint is not particularly limited, and for example, the wet coating film can be formed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, or curtain coat coating. In these coating methods, electrostatic application may be performed as necessary. Of these, air spray coating is particularly preferred. In general, the coating amount of the paint is preferably set to an amount of about 10 to 50 μm as a 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.

  Curing of the wet coating film formed by applying the coating material to the object to be coated is performed by heating, and the heating can be performed by a known heating means, such as a hot air furnace, an electric furnace, an infrared induction heating furnace, etc. The drying oven can be applied. The heating temperature is suitably in the range of 60 to 180 ° C, preferably 90 to 150 ° C. The heating time is not particularly limited but is preferably in the range of 15 to 30 minutes.

  Since this paint can obtain a cured coating film excellent in any of scratch resistance, acid resistance, stain resistance and finish, it can be suitably used as a top-coat top clear coat paint. This paint can be particularly suitably used as an automobile paint.

Multi-layer coating film formation method As a top-coat top clear coat paint, as a multi-layer coating film formation method in which this paint is applied,
A method for forming a multi-layer 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 a substrate to be coated, wherein the paint composition of the present invention is used as the uppermost clear coat paint. A multilayer coating film forming method characterized by painting an object can be given.
Specifically, for example, a solvent-type or water-based base coat paint is applied on an object to which electrodeposition coating and / or intermediate coating has been applied, and the coating film is not cured, as needed. In order to promote the volatilization of the solvent in the base coat paint, for example, after preheating at 40 to 90 ° C. for about 3 to 30 minutes, the paint is applied as a clear coat paint on the uncured base coat film. Thereafter, there can be mentioned a method for forming a multi-layer coating film of a 2-coat 1-bake method in which the base coat and the clear coat are cured together.

  Further, it can also be suitably used as a top clear coat paint in the top coat of the 3-coat 2-bake method or the 3-coat 1-bake method.

  As the base coat paint used in the above, a conventionally known normal thermosetting base coat paint can be used. Specifically, for example, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin type, or the like. In addition, a coating material obtained by appropriately combining a curing agent such as an amino resin, a polyisocyanate compound, or a block polyisocyanate compound with a reactive functional group contained in the base resin can be used.

  The base coat paint is preferably a high solid type with a small amount of organic solvent used from the viewpoints of environmental problems and resource saving, and an aqueous paint or powder paint can also be used.

  In the multilayer coating film forming method, when two or more clear coats are applied, a conventionally known ordinary thermosetting clear coat paint can be used as the clear coat paint in addition to the present paint.

  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 Hydroxyl-Containing Resin (A) Production Examples 1-9
31 parts of ethoxyethyl propionate was charged into a four-necked flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet, and the temperature was raised to 155 ° C. under nitrogen gas flow. After reaching 155 ° C., the flow of nitrogen gas was stopped, and a dropping monomer mixture composed of a monomer and a polymerization initiator shown in Table 1 below was dropped over 4 hours. After aging at 155 ° C. for 2 hours while bubbling nitrogen gas, the mixture was cooled to 100 ° C. and diluted with 32.5 parts of butyl acetate to obtain a coating resin having a solid content of 60%. Table 1 below shows the mass solid content concentration (%) and the resin property values of the obtained coating resin.

In addition, the glass transition temperature (degreeC) in Table 1 was computed by the following formula.
1 / Tg (K) = (W1 / T1) + (W2 / T2) +
Tg (° C.) = Tg (K) -273
In each formula, W1, W2,... Represent the respective mass fractions of the monomers used for copolymerization, and T1, T2,... Represent the Tg (K) of the homopolymer of each monomer. T1, T2,... Are values according to Polymer Handbook (Second Edition, edited by J. Brandup, E. H. Immergut).

Production examples of reaction product (C) Production examples 10 to 17
In a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, polycarbonate diol, carbodilite V-05 (Nisshinbo Co., Ltd., trade name, carbodiimide compound) shown in Table 2 below, Swazol 1000 (Cosmo) Petroleum Company, trade name, hydrocarbon solvent) was charged, and the temperature was raised to 100 ° C. in a nitrogen atmosphere. After reaching 100 ° C., the reaction was allowed to proceed for 5 hours, and after confirming that the NCO value was 0, the hydroxy acid shown in Table 2 below was added, the temperature was raised to 120 ° C., and the reaction was allowed to proceed for 5 hours. Solution No. of product (C) 1-8 were obtained. The mass solid content concentration (%) and the characteristic value of each reaction product solution obtained are also shown in Table 2 below.
(* 1) to (* 3) in Table 2 have the following meanings, respectively, and the viscosity of the polycarbonate diol is a value measured at 50 ° C. using a B-type viscometer under the condition of 6 rpm.
(* 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) UM-90: 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.
(* 3) PC-N: 1,6-hexanediol and 3-methylpentanediol as diol components, polycarbonate diol synthesized using diphenyl carbonate as carbonylating agent, number average molecular weight 380, viscosity 120 mPa · s, hydroxyl value 260 mg KOH / g, solid content 100%.

Production Examples 1-9 and Comparative Examples 1-9 of Coating Composition
Using the hydroxyl group-containing resins obtained in the above Production Examples 1 to 17, the reaction product solution, and the raw materials listed in Table 3 below, the mixture shown in Table 3 below is stirred and mixed using a disper to form a paint. Each paint composition No. 1-18 were obtained. In addition, the mixing | blending of each coating composition shown in Table 3 is solid content mass ratio of each component, (* 4)-(* 7) has the following meaning, respectively.
(* 4) N-3300: Sumika Bayer Urethane Co., Ltd., hexamethylene diisocyanate, solid content 100%, NCO content 21.8%.
(* 5) UV1164: UV absorber manufactured by Ciba Geigy.
(* 6) HALS292: Ciba Geigy Corporation light stabilizer.
(* 7) BYK-300: trade name, manufactured by Big Chemie, surface conditioner.

  Each coating composition No. obtained in Examples 1-9 and Comparative Examples 1-9. Nos. 1 to 18 are ford cups #No. 4 was adjusted to a viscosity of 25 seconds at 20 ° C.

Preparation of test plates Each of the coating composition Nos. Obtained in Examples 1-9 and Comparative Examples 1-9. Test plates were prepared in the following manner for each of those having a viscosity of 1 to 18 adjusted.
Electron GT-10 (trade name, thermosetting epoxy resin-based cationic electrodeposition paint manufactured by Kansai Paint Co., Ltd.) has a thickness of 20 μm on a 0.8 mm-thick dull steel sheet subjected to zinc phosphate conversion treatment. Electrodeposited as above, cured by heating at 170 ° C. for 30 minutes, and then coated with Amirac TP-65-2 (trade name, polyester / melamine resin-based automotive intermediate coating) manufactured by Kansai Paint Co., Ltd. with a film thickness of 35 μm Air spray coating was performed, and the mixture was heated and cured at 140 ° C. for 30 minutes. A water-based metallic base coat WBC713T # 202 (manufactured by Kansai Paint Co., Ltd., acrylic / melamine resin-based automotive top coat paint, black paint color) is applied to the coating film so as to have a film thickness of 15 μm and left at room temperature for 5 minutes. Then, after preheating at 80 ° C. for 10 minutes, each coating composition No. prepared and viscosity-adjusted in the above Examples and Comparative Examples on the uncured coating film was prepared. 1 to 18 were coated to a film thickness of 35 μm, and allowed to stand at room temperature for 10 minutes, and then heated at 140 ° C. for 20 minutes to cure both coating films together to obtain a test plate. 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.
Results of performance test : Scratch resistance: 20 degrees of test plate after car washer was washed 15 times with car wash machine at 20 ° C ± 5 ° C under the condition of 20 ° C ± 5 ° C. The specular reflectance (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 film of each test plate, heated for 15 minutes on a hot plate heated to 60 ° C., and then the test plate was 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, the better the acid resistance.

  Finishability (gloss): The 20-degree specular reflectance (20 ° gloss value) of the test plate was measured and evaluated.

  Contamination resistance: After each test coating plate was tested for 600 hours in a sunshine weatherometer (manufactured by Suga Test Instruments Co., Ltd., accelerated weathering tester), each test coating plate was contaminated with a mixture of mud, carbon black, mineral oil and clay. The substance was adhered to the nell and rubbed lightly on the surface of each 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 CR-200 (color difference meter manufactured by Minolta Camera Co.).
A: ΔL <0.2, O: 0.2 ≦ ΔL <1, Δ: 1 ≦ ΔL <2, X: 2 ≦ ΔL.
In the contamination resistance test, Eleclon GT-10 (trade name, thermosetting epoxy resin-based cationic battery, manufactured by Kansai Paint Co., Ltd.) was applied on a 0.8 mm-thick dull steel plate subjected to zinc phosphate conversion treatment. Electrodeposition coating to a film thickness of 20 μm, and cured by heating at 170 ° C. for 30 minutes, and then amylak TP-65-2 (trade name, polyester / melamine resin system, manufactured by Kansai Paint Co., Ltd.) Each of the above-mentioned Examples and Comparative Examples was prepared and viscosity-adjusted on a coating film that was air-sprayed to a film thickness of 35 μm and cured by heating at 140 ° C. for 30 minutes. Using the test plate obtained by coating the coating composition so as to have a film thickness of 35 μm, allowing it to stand at room temperature for 10 minutes, and then heating and curing at 140 ° C. for 20 minutes, each test plate was similarly used. At room temperature It was performed stain resistance test from left to days.
The performance test results are also shown in Table 3.

Claims (6)

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 polycarbonate diol and a carbodiimide compound having an isocyanate group at both ends are allowed to have an excess of hydroxyl groups. Reaction product (C) having a hydroxyl value of 40 to 180 mgKOH / g and a number average molecular weight of 1000 to 5000, obtained by addition reaction of a hydroxy acid with a carbodiimide group in the reaction product (a) obtained by urethanation under conditions A coating composition comprising: The coating composition according to claim 1, wherein the hydroxyl group-containing resin (A) is a hydroxyl group-containing acrylic resin. The coating composition according to claim 1 or 2, which contains an aliphatic diisocyanate or a derivative thereof as the polyisocyanate compound (B). The coating composition according to any one of claims 1 to 3, wherein the hydroxy acid is 12-hydroxystearic acid. Furthermore, the coating composition of any one of Claims 1-4 containing a coloring pigment. A method for forming a multi-layer 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, 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.