WO2010122965A1 - Coating material composition and method for forming coating film - Google Patents

Abstract

Disclosed is a coating material composition which is capable of forming a urethane crosslinked clear coating film which enables the achievement of a multilayer coating film having excellent finish appearance such as metallic finish when the multilayer coating film is composed of a base coating film and a clear coating film and formed by a two-coat-one-bake coating method.

Description

Coating composition and coating film forming method

The present invention relates to a novel coating composition and a coating film forming method using the same.

A paint to be applied to an object to be coated such as an automobile body is required to have excellent coating performance such as scratch resistance, acid resistance, stain resistance, and finished appearance.
Conventionally, a melamine curable coating is widely used as a coating for the object. The melamine curable paint is a paint containing a hydroxyl group-containing resin as a base resin and a melamine resin as a crosslinking agent, and has a high crosslinking density at the time of heat curing and is excellent in finished appearance. However, this paint has a problem that the ether cross-linking formed by the reaction between the hydroxyl group of the hydroxyl group-containing resin and the melamine resin is easily hydrolyzed by acid rain, and the formed coating film is inferior in acid resistance.
For example, Patent Document 1 discloses a specific acrylic resin and a specific hydroxyl group-containing oligoester as well as an isocyanate for a hydroxyl group contained in these base resin components, as a paint having a coating performance excellent in both acid resistance and scratch resistance. A two-component urethane coating composition comprising an isocyanate prepolymer having a group ratio within a specific range is disclosed.
However, a two-coat one-bake clear coat paint for applying a base coat paint and a clear coat paint generally used for top coating of automobiles to a two-component urethane paint composition comprising the isocyanate prepolymer as described above. When used as, since the isocyanate prepolymer has a low molecular weight, when the clearcoat film is applied over the uncured basecoat film, a mixture of the basecoat film layer and the clearcoat film layer is likely to occur. In particular, when the base coat film is a metallic film containing a flaky aluminum pigment, the orientation of the flaky aluminum pigment is disturbed by the mixed layer. (Usually referred to as "modulation phenomenon"), and finishes such as a metallic finish. Appearance is lowered.

Japanese Patent Laid-Open No. 6-220397

It is an object of the present invention to obtain a multilayer coating film excellent in finished appearance such as a metallic finish when forming a two-coat one-bake multilayer coating film comprising a base coat film and a clear coat film. Another object of the present invention is to provide a coating composition capable of forming a urethane cross-linked clear coating and a method for forming a multilayer coating using the coating composition.

As a result of diligent research to solve the above problems, the present inventors have used an acrylic resin having a specific range of hydroxyl value, weight average molecular weight and solubility parameter value as a base resin, and a polyisocyanate compound. Reacting an acrylic resin having a hydroxyl value, weight average molecular weight and solubility parameter value in a specific range or a hydroxyl group-containing compound having a hydroxyl value, weight average molecular weight and solubility parameter value in a specific range at a reaction ratio in a specific range. The present inventors have found that the above-mentioned object can be achieved by using the reaction product obtained by the above as a crosslinking agent, and have completed the present invention.
Thus, the present invention
(A) an acrylic resin having a hydroxyl value in the range of 80 to 180 mg KOH / g, a weight average molecular weight in the range of 3000 to 20000, and a solubility parameter value in the range of 8.5 to 9.8, and (B) Polyisocyanate compound (b-1), having a hydroxyl value in the range of 40 to 180 mg KOH / g, a weight average molecular weight in the range of 700 to 4000, and a solubility parameter value in the range of 8.5 to 9.8 A reaction product (B-1) obtained by reacting an acrylic resin (b-2) with an NCO / OH ratio in the range of 7 to 15, or a polyisocyanate compound (b-1); A hydroxyl group-containing compound (b-3) having a hydroxyl value in the range of 450 mg KOH / g and a weight average molecular weight in the range of 250 to 3000 is reacted at an NCO / OH ratio in the range of 6 to 12. Reaction product (B-2) having a weight average molecular weight within the range of 1000 to 15000
It is intended to provide a coating composition characterized by containing.
The present invention is also characterized in that the above-mentioned coating composition is used as a clear coat paint in forming a multilayer coating film by sequentially applying a colored base coat paint and a clear coat paint to an object to be coated. The present invention provides a method for forming an overcoat multilayer coating film.

By using the coating composition of the present invention, there is no deterioration in the finished appearance due to poor compatibility between the base resin and the cross-linking agent due to the use of the polyisocyanate compound, and the coating with 2 coats and 1 bake specification is possible. Forming a multilayer coating film with a good finished appearance without causing deterioration of the finished appearance such as metallic finish due to the mixed layer of the base coat film layer and the clear coat film layer when used as a clear paint in Can do.
Moreover, since the urethane bond by reaction of an acrylic resin (A) and a reaction product (B) is excellent in a physical property and hydrolysis resistance, the coating composition of this invention is excellent in both abrasion resistance and acid resistance. Has an effect that an excellent cured coating film can be formed.

Hereinafter, the coating composition of the present invention (hereinafter sometimes referred to as “the present coating”) and the method for forming a top coating multilayer coating film will be described in more detail.
Acrylic resin (A)
The acrylic resin (A) used in the coating composition of the present invention has a hydroxyl value in the range of 80 to 180 mgKOH / g, a weight average molecular weight in the range of 3000 to 20000, and a range of 8.5 to 9.8. An acrylic resin having a solubility parameter value of
The acrylic resin (A) is obtained by, for example, copolymerizing a hydroxyl group-containing unsaturated monomer (M-1) and other copolymerizable unsaturated monomer (M-2) by a method known per se. Can be manufactured.
The hydroxyl group-containing unsaturated monomer (M-1) includes a compound having one hydroxyl group and one unsaturated bond in one molecule, and the hydroxyl group mainly reacts with the isocyanate group of the reaction product (B). It acts as a functional group.
As the hydroxyl group-containing unsaturated monomer (M-1), specifically, a monoesterified product of (meth) acrylic acid and a dihydric alcohol having 2 to 10 carbon atoms is suitable. For example, 2-hydroxy Examples include ethyl (meth) acrylate, hydroxypropyl acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate. Further, as the hydroxyl group-containing unsaturated monomer (M-1), a compound obtained by ring-opening condensation of ε-caprolactone to a monoesterified product of the above dihydric alcohol and acrylic acid or methacrylic acid, for example, “ “Plaxel FA-1,” “Plaxel FA-2,” “Plaxel FA-3,” “Plaxel FA-4,” “Plaxel FA-5,” “Plaxel FM-1,” “Plaxel FM-2,” “Plaxel” "FM-3", "Placcel FM-4", "Placcel FM-5" (all of which are trade names, manufactured by Daicel Chemical Industries, Ltd.) can also be used.
In this specification, “(meth) acrylate” means acrylate or methacrylate. “(Meth) acrylic acid” means acrylic acid or methacrylic acid. “(Meth) acrylamide” means acrylamide or methacrylamide.
The other copolymerizable unsaturated monomer (M-2) includes a compound having one unsaturated bond in one molecule other than the hydroxyl group-containing unsaturated monomer (M-1). Specific examples are listed in the following (1) to (9).
(1) Acid group-containing unsaturated monomer: includes compounds having at least one acid group and one unsaturated bond in one molecule, such as (meth) acrylic acid, crotonic acid, itaconic acid Carboxyl group-containing unsaturated monomers such as maleic 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 is generally 0 ~ based on the total amount of the hydroxyl group-containing unsaturated monomer (M-1) and the other copolymerizable unsaturated monomer (M-2). It is preferable to use within a range of 5% by mass, particularly 0.1-3% by mass.
(2) Monoesterified product of (meth) acrylic acid or methacrylic acid and a 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) Made by Organic Chemical Industry Co., Ltd., trade name), cyclohexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, adamantyl (meth) acrylate, 3,5- Dimethyladamantyl (meth) acrylate, 3-tetracyclododecyl methacrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, 4-methylcyclohexylmethyl (meth) acrylate, 4-ethylcyclohexylmethyl (meth) acrylate, 4-methoxy Cyclohexylmethyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclododecyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, methoxybutyl (meth) acrylate, methoxyethyl (meth) Acrylate, ethoxybutyl (meth) acrylate, etc.
From the viewpoint that the weather resistance of the coating film can be improved, among the above, unsaturated monomers having a bridged alicyclic hydrocarbon group having 10 to 20 carbon atoms and / or 3 to 12 carbon atoms. The unsaturated monomer (2a) having an alicyclic hydrocarbon group can be preferably used.
As representative examples of the Aribashi alicyclic hydrocarbon group, an isobornyl group, a tricyclodecanyl group, an adamantyl group, and the like can be given. Accordingly, 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, adamantyl ( Examples thereof include (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 ( Examples include meth) acrylate, 4-methoxycyclohexylmethyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, and cyclododecyl (meth) acrylate.
When the monomer (2a) is used, the proportion of use is based on the total amount of the hydroxyl group-containing unsaturated monomer (M-1) and the other copolymerizable unsaturated monomer (M-2). In general, it is preferably in the range of 3 to 50% by mass, particularly 10 to 40% by mass.
Moreover, from the viewpoint that the scratch resistance of the coating film can be improved, among the above, the unsaturated monomer (2b) having a branched hydrocarbon structure having 8 or more carbon atoms is preferably used. be able to. When the monomer (2b) is used, since the Tg and polarity of the resulting resin are lowered, the effect of improving the scratch resistance of the coating film by imparting flexibility and the effect of improving the finish by smoothing the surface can be obtained. . In addition, since it has a branched structure, it is possible to suppress a decrease in the Tg of the coating film as compared with the case of using an unsaturated monomer having a linear hydrocarbon group having 8 or more carbon atoms. Therefore, it is advantageous from the viewpoint of improving acid resistance.
Specific examples of the unsaturated monomer having a hydrocarbon group having 8 or more carbon atoms having a branched structure include, for example, 2-ethylhexyl acrylate, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, isostearyl acrylate ( And a product name of Osaka Organic Chemical Industry Co., Ltd.
When the monomer (2b) is used, the use ratio is based on the total amount of the hydroxyl group-containing unsaturated monomer (M-1) and the other copolymerizable unsaturated monomer (M-2). In general, it is preferably in the range of 3 to 50% by mass, particularly 10 to 40% by mass.
(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, vinyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane and the like can be cited as preferred alkoxysilane group-containing unsaturated monomers.
By using an alkoxysilane group-containing unsaturated monomer, in the coating film, in addition to the crosslinking bond between the hydroxyl group and the isocyanate group, the condensation reaction between the alkoxysilane groups and the crosslinking bond between the alkoxysilane group and the hydroxyl group are performed. Can be generated. Thereby, the crosslinking density of the obtained coating film is improved, and the effect of improving acid resistance and stain resistance can be obtained.
When using an alkoxysilane group-containing unsaturated monomer, the use ratio is the sum of the hydroxyl group-containing unsaturated monomer (M-1) and the other copolymerizable unsaturated monomer (M-2). In general, the content is preferably in the range of 3 to 50% by mass, particularly 5 to 35% by mass, based on the amount.
(4) Aromatic unsaturated monomer: For example, styrene, α-methylstyrene, vinyltoluene and the like.
By using an aromatic unsaturated monomer, the Tg of the resulting resin increases, and a hydrophobic film with a high refractive index can be obtained. The effect of improvement, improvement in water resistance and acid resistance can be obtained.
When an aromatic unsaturated monomer is used, the use ratio is the total amount of the hydroxyl group-containing unsaturated monomer (M-1) and the other copolymerizable unsaturated monomer (M-2). In general, it is preferably in the range of 3 to 50% by mass, particularly 5 to 40% by mass.
(5) Glycidyl group-containing unsaturated monomer: A compound having one glycidyl group and one unsaturated bond in each molecule is included, and specific examples include glycidyl acrylate and glycidyl methacrylate.
(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, N-vinylpyrrolidone, (meth) acryloylmorpholine, vinylimidazole and the like.
(7) Vinyl ethers and allyl ethers: For example, linear or branched alkyl vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, butyl vinyl ether, tert-butyl vinyl ether, pentyl vinyl ether, hexyl vinyl ether, octyl vinyl ether; Cycloalkyl vinyl ethers such as cyclopentyl vinyl ether and cyclohexyl vinyl ether; Allyl vinyl ethers such as phenyl vinyl ether and trivinyl ether; Aralkyl vinyl ethers such as benzyl vinyl ether and phenethyl vinyl ether; Allyl ethers such as allyl glycidyl ether and allyl ethyl ether.
(8) Other vinyl compounds: For example, vinyl acetate, vinyl propionate, vinyl chloride, versatic acid vinyl ester (for example, “Veoba 9” and “Veoba 10” (trade name) manufactured by Japan Epoxy Resin Co., Ltd.) Such.
(9) Unsaturated bond-containing nitrile compound: For example, acrylonitrile, methacrylonitrile and the like.
These other vinyl monomers (M-2) can be used alone or in combination of two or more.
An acrylic resin (A) can be obtained by copolymerizing a hydroxyl group-containing unsaturated monomer (M-1) and another copolymerizable unsaturated monomer (M-2).
The proportion of the hydroxyl group-containing unsaturated monomer (M-1) used is the total amount of the hydroxyl group-containing unsaturated monomer (M-1) and the other copolymerizable unsaturated monomer (M-2). In general, it is preferably in the range of 15 to 50% by mass, particularly 20 to 45% by mass. When the use ratio of the hydroxyl group-containing unsaturated monomer (M-1) is less than 15% by mass, the formed cured coating film is insufficiently crosslinked, and the scratch resistance of the coating film is insufficient. There is. On the other hand, when it exceeds 50% by mass, the compatibility with other copolymerizable unsaturated monomer (M-2) is lowered, and the reaction product (B) of the obtained acrylic resin (A) and The finished appearance of the coating film may be reduced due to a decrease in the compatibility.
The copolymerization method of the hydroxyl group-containing unsaturated monomer (M-1) and other copolymerizable unsaturated monomer (M-2) is not particularly limited, and is a copolymerization method known per se. Can be used. Among these, a solution polymerization method in which copolymerization is performed in an organic solvent in the presence of a polymerization initiator is preferable.
Examples of the organic solvent used in the solution polymerization method include aromatic solvents such as toluene, xylene, “Swazole 1000” (trade name, high-boiling petroleum solvent) manufactured by Cosmo Oil, ethyl acetate, 3- Ester solvents such as methoxybutyl 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 propio Nate etc. can be mentioned.
These organic solvents can be used alone or in combination of two or more. However, since the acrylic resin (A) has a high hydroxyl value, from the viewpoint of the solubility of the resin, a high-boiling ester solvent, ketone It is preferable to use a system solvent. In addition, aromatic solvents having higher boiling points can be used in combination.
Examples of the polymerization initiator that can be used in the copolymerization of the acrylic resin (A) include 2,2′-azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, and di-t-. Examples thereof include radical polymerization initiators known per se of azo type or peroxide type such as amyl peroxide, t-butyl peroctoate, and 2,2′-azobis (2-methylbutyronitrile).
Also, a chain transfer agent known per se can be used in combination for adjusting the molecular weight.
The acrylic resin (A) can have a hydroxyl value within the range of 80 to 180 mgKOH / g, preferably 95 to 175 mgKOH / g, and more preferably 110 to 170 mgKOH / g. When the hydroxyl value is less than 80 mgKOH / g, the formed coating film is not sufficiently crosslinked, and the scratch resistance of the coating film may be insufficient. On the contrary, if it exceeds 180 mgKOH / g, the water resistance of the formed coating film may be lowered.
The acrylic resin (A) can have a weight average molecular weight in the range of 3000 to 20000, preferably 4000 to 18000, and more preferably 5000 to 16000. When the weight average molecular weight is less than 3,000, the water resistance and scratch resistance of the formed coating film may be lowered. On the other hand, when it exceeds 20,000, the coated surface smoothness of the formed coating film may be lowered.
In the present specification, the “weight average molecular weight” is a value obtained by converting the weight average molecular weight measured with a gel permeation chromatograph (“HLC8120GPC” manufactured by Tosoh Corporation) based on the weight average molecular weight of polystyrene. The weight average molecular weights of the samples are “TSKgel G-4000H × L”, “TSKgel G-3000H × L”, “TSKgel G-2500H × L”, “TSKgel G-2000H × L” (all of which are Tosoh Corporation ), Manufactured under the trade name), and measured under the conditions of 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 acrylic resin (A) can have a solubility parameter value in the range of 8.5 to 9.8, preferably 8.6 to 9.7, and more preferably 8.7 to 9.6. When the solubility parameter value is less than 8.5 or exceeds 9.8, the compatibility with the reaction product (B) is lowered, and the curability and the finished appearance of the coating film may be lowered.
In the present specification, the “solubility parameter value” (SP value) of an acrylic resin represents a measure of the intermolecular interaction of liquid molecules, and can be calculated by the following method.
The solubility parameter value (SP value) of the acrylic resin obtained by copolymerization of at least two kinds of polymerizable monomers can be calculated by the following formula.
SP value = SP₁× f_W1+ SP₂× f_W2+ ...... SP_n× f_Wn
In the above formula, SP₁, SP₂... SP_nRepresents the SP value of the homopolymer of each polymerizable monomer, f_W1, F_W2... f_WnRepresents the weight fraction of each monomer with respect to the total amount of monomers. The SP value of the homopolymer of the polymerizable monomer is J.P. Paint Technology, vol. 42, 176 (1970).
The acrylic resin (A) also preferably has a glass transition temperature in the range of generally −30 ° C. to 90 ° C., particularly −20 ° C. to 80 ° C., more particularly −10 ° C. to 70 ° C. If the glass transition temperature of the acrylic resin (A) is less than −30 ° C., the coating film hardness may be insufficient. On the contrary, if it exceeds 90 ° C., the coated surface smoothness of the coating film may be reduced. is there.
In the present specification, the “glass transition temperature” (Tg (° C.)) of the acrylic resin can be calculated by the following formula.
1 / Tg (° K) = (W₁/ T₁) + (W₂/ T₂+ + ...
Tg (° C) = Tg (° K) -273
In each formula, W₁, W₂,... Represent the weight fraction of each polymerizable monomer used in the copolymerization with respect to the total amount of monomers, and T₁, T₂,... Represent the Tg (° K) of the homopolymer of each polymerizable monomer. T₁, T₂, ... are Polymer Handbook (4th Edition, edited by J. Brandup, E. H. Immergut), and those that are not listed in Polymer Handbook are Journal of Applied Polymer Science. It is a value as described in Applied Polymer Symposium, 45, 289-316 (1990).
Reaction product (B)
As the reaction product (B), a polyisocyanate compound (b-1), a hydroxyl value in the range of 40 to 180 mgKOH / g, a weight average molecular weight in the range of 700 to 4000, and 8.5 to 9.8 A reaction product (B-1) obtained by reacting an acrylic resin (b-2) having a solubility parameter value within a range with an NCO / OH ratio within a range of 7 to 15; and a polyisocyanate compound (B-1) and a hydroxyl group-containing compound (b-3) having a hydroxyl value in the range of 70 to 450 mgKOH / g and a weight average molecular weight in the range of 250 to 3000, an NCO in the range of 6 to 12 The reaction product (B-2) having a weight average molecular weight within the range of 1000 to 15000 obtained by reacting at a / OH ratio is included. In the coating composition of the present invention, an acrylic resin ( ) Serves as a crosslinking agent for.
Polyisocyanate compound (b-1)
The polyisocyanate compound (b-1) is a compound having at least two isocyanate groups in one molecule. As the polyisocyanate compound (b-1), those known per se for polyurethane production and the like can be used. For example, aliphatic polyisocyanate, alicyclic polyisocyanate, araliphatic polyisocyanate, aromatic polyisocyanate, and the like. Examples thereof include isocyanates 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; lysine ester triisocyanate, 1,4,8-triisocyanate Natooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5 , And the like aliphatic triisocyanate such as 7-trimethyl-1,8-diisocyanato-5-isocyanatomethyl octane.
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-bis (isocyanatomethyl) cyclohexane, 1,4-bis (Isocyanatomethyl) cycloaliphatic diisocyanates such as cyclohexane and norbornane diisocyanate; 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanate Chlohexane, 2- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 2- (3-isocyanatopropyl) -2,6-di ( Isocyanatomethyl) -bicyclo (2.2.1) heptane, 3- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 5- (2 -Isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2 1) alicyclic triisocyanates such as -heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane be able to.
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 ( Araliphatic diisocyanates such as 1-isocyanato-1-methylethyl) benzene (common name: tetramethylxylylene diisocyanate) or mixtures thereof; araliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene Can be mentioned.
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; triphenylmethane-4,4 ′, 4 ″ Aromatic triisocyanates such as '-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene; 4,4'-diphenylmethane-2,2', 5,5'- Tetraisocyanate Etc. and aromatic tetraisocyanates, such as chromatography and.
Examples of the polyisocyanate derivative include various derivatives such as dimer, trimer, biuret, allophanate, carbodiimide, uretdione, uretoimine, isocyanurate, and iminooxadiazinedione of the above polyisocyanate compounds.
These polyisocyanates can be used alone or in combination of two or more.
Among these polyisocyanates, aliphatic diisocyanates, alicyclic diisocyanates and derivatives thereof are preferable from the viewpoint of excellent scratch resistance of the cured coating film. Hexamethylene diisocyanate (HMDI), hexamethylene diisocyanate derivatives, isophorone More preferred are diisocyanate (IPDI) and isophorone diisocyanate derivatives.
Acrylic resin (b-2)
As the acrylic resin (b-2), the hydroxyl group-containing unsaturated monomer (M-1) and the other copolymerizable unsaturated monomer (M-2) described above for the acrylic resin (A) are known per se. It can manufacture by making it copolymerize by the method of.
The use ratio of the hydroxyl group-containing unsaturated monomer (M-1) is the total amount of the hydroxyl group-containing unsaturated monomer (M-1) and the other copolymerizable unsaturated monomer (M-2). In general, it is preferably in the range of 15 to 50% by mass, particularly 20 to 45% by mass. When the proportion of the hydroxyl group-containing unsaturated monomer (M-1) used is less than 15% by mass, the coating film performance such as acid resistance and scratch resistance of the formed coating film may be deteriorated. %, The compatibility with the other copolymerizable unsaturated monomer (M-2) and the copolymerization reactivity are lowered, and the polyisocyanate compound (b-1) and the acrylic resin (b- When the compatibility between the reaction product (B-1) obtained by the reaction with 2) and the acrylic resin (A) is lowered, the finished appearance of the coating film may be lowered.
An acrylic resin (b-2) can be obtained by copolymerizing the hydroxyl group-containing unsaturated monomer (M-1) and other copolymerizable unsaturated monomer (M-2).
The copolymerization of the hydroxyl group-containing unsaturated monomer (M-1) and the other copolymerizable unsaturated monomer (M-2) is not particularly limited, and the acrylic resin (A) is copolymerized. Can be performed in the same manner as described above. In the solution polymerization of the acrylic resin (b-2), it is preferable to use an ester solvent or an ether solvent from the viewpoint of solubility. Further, aromatic solvents having higher boiling points can be suitably combined and used.
As the polymerization initiator that can be used in the copolymerization of the acrylic resin (b-2), those exemplified above for the acrylic resin (A) can be used.
Moreover, a chain transfer agent can be used in the copolymerization of the acrylic resin (b-2). Examples of the chain transfer agent include alkyl mercaptans such as n-butyl mercaptan, n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, cetyl mercaptan, stearyl mercaptan; thioglycolic acid, thioglycerol And other mercaptans such as ethylenethioglycol, 2-ethylhexyl thioglycolate, 2-mercaptoethanol, mercaptoglycerin, mercaptosuccinic acid, mercaptopropionic acid; halogen compounds such as carbon tetrachloride, chloroform, trichlorobromoethane, bromoform; Disulfide, Dimethylxanthogen disulfide, Secondary alcohol, Isopropyl alcohol, Dioxane, Tet Hydrofuran, isopropyl benzol, alpha-methylstyrene dimer, 2,4-diphenyl-4-methyl-1-pentene, .gamma. such mercaptopropyltrimethoxysilane may be mentioned.
Of these, chain transfer agents having a hydroxyl group such as 2-mercaptoethanol can be suitably used. By using a chain transfer agent having a hydroxyl group, an acrylic resin having a structure in which a hydroxyl group is introduced at the end of the acrylic resin (b-2) can be obtained. Thereby, in synthesizing the reaction product (B-1), the isocyanate group of the polyisocyanate compound (b-1) easily reacts with the hydroxyl group of the acrylic resin (b-2), and the acrylic resin (b-2). ) Can be set low, the high molecular weight of the reaction product (B-1) can be suppressed, and the smoothness of the coating film formed from the coating composition of the present invention can be improved. Can do.
The amount of chain transfer agent used is not particularly limited, and for example, based on the total amount of hydroxyl group-containing unsaturated monomer (M-1) and other copolymerizable unsaturated monomer (M-2). In general, it is preferably in the range of 0.1 to 10% by mass.
The acrylic resin (b-2) has a hydroxyl value within the range of 40 to 180 mgKOH / g, preferably 50 to 170 mgKOH / g, more preferably 80 to 170 mgKOH / g, and still more preferably 100 to 170 mgKOH / g. Can do. When the hydroxyl value of the acrylic resin (b-2) is less than 40 mgKOH / g, the coating film performance such as acid resistance and scratch resistance of the formed coating film may be insufficient. On the contrary, 180 mgKOH / g If it exceeds, the finished appearance such as the smoothness of the coating surface may be deteriorated.
When the acrylic resin (b-2) is produced using a chain transfer agent, the hydroxyl value of the acrylic resin (b-2) is generally 40 to 140 mgKOH / g, particularly 50 to 130 mgKOH / g. It is preferable to be within the range.
The acrylic resin (b-2) can have a weight average molecular weight in the range of 700 to 4000, preferably 800 to 3000, and more preferably 1000 to 2000. When the weight average molecular weight of the acrylic resin (b-2) is less than 700, the coating film performance such as acid resistance and scratch resistance of the formed coating film may be insufficient. Conversely, when it exceeds 4000, The finished appearance such as the smoothness of the coating surface of the formed coating film may deteriorate.
The acrylic resin (b-2) can have a solubility parameter value in the range of 8.5 to 9.8, preferably 8.6 to 9.6, and more preferably 8.7 to 9.5. . When the solubility parameter value of the acrylic resin (b-2) is less than 8.5 or exceeds 9.8, the compatibility with the acrylic resin (A) may be lowered.
The acrylic resin (b-2) also preferably has a glass transition temperature in the range of generally −30 ° C. to 80 ° C., particularly −25 ° C. to 70 ° C., more particularly −20 ° C. to 60 ° C. If the glass transition temperature of the acrylic resin (b-2) is less than −30 ° C., the hardness of the formed coating film may be insufficient. May decrease.
Reaction product (B-1)
The reaction product (B-1) can be obtained by addition reaction of the polyisocyanate compound (b-1) and the acrylic resin (b-2) described above. This reaction proceeds by an addition reaction between the isocyanate group of the polyisocyanate compound (b-1) and the hydroxyl group of the acrylic resin (b-2).
In the above addition reaction, the polyisocyanate compound (b-1) and the acrylic resin (b-2) are usually at a temperature of about 60 to about 140 ° C., preferably about 70 to about 130 ° C., usually for about 1 to 10 hours. Preferably, the reaction can be carried out by reacting for about 2 to 8 hours. The reaction can usually be performed until the hydroxyl value of the acrylic resin (b-2) becomes 2 mgKOH / g or less.
If the reaction temperature is less than 60 ° C., a large amount of unreacted hydroxyl groups may remain. Conversely, if the reaction temperature exceeds 140 ° C., the reaction product may be decomposed.
The above reaction can be carried out by further adding an organic solvent, if necessary. As an organic solvent, what was illustrated about manufacture of the said acrylic resin (A) can be used similarly. As the solvent, those which are not reactive with an isocyanate group are preferable. Examples thereof include ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and solvents such as N-methylpyrrolidone (NMP). it can.
In the addition reaction, a catalyst can be used as necessary. Specifically, examples of the catalyst effective for the reaction between a hydroxyl group and an isocyanate group include a tin-based catalyst and a phosphoric acid-based catalyst. Of these, dibutyltin dilaurate and the like can be preferably used.
In the reaction of the polyisocyanate compound (b-1) and the acrylic resin (b-2), the ratio of the polyisocyanate compound (b-1) to the acrylic resin (b-2) is the finished appearance of the coating film and the anti-moisture resistance. In view of the above, the NCO / OH ratio can be within the range of 7 to 15, preferably 8 to 14, and more preferably 9 to 12. If the NCO / OH ratio is less than 7, the reaction product (B-1) may have a high molecular weight, which may cause problems such as deterioration of the finished appearance such as the smoothness of the coating film formed. On the contrary, when the NCO / OH ratio is greater than 15, the ratio of the unreacted polyisocyanate compound (b-1) increases, and the anti-moisture resistance of the formed coating film may decrease.
The reaction product (B-1) may contain an unreacted product and can be used as it is without separating the unreacted product.
The reaction product (B-1) generally has an NCO equivalent weight in the range of 200 to 370, preferably 210 to 350, more preferably 220 to 330, from the viewpoint of the curability of the finally obtained coating composition. Can have.
The reaction product (B-1) generally has a hydroxyl value in the range of 0 to 10 mgKOH / g, preferably 0 to 7.5 mgKOH / g, more preferably 0 to 5 mgKOH / g, from the viewpoint of storage stability. be able to.
The reaction product (B-1) is generally in the range of 0 to 15 mgKOH / g, preferably 0 to 12.5 mgKOH / g, more preferably 0 to 10 mgKOH / g, from the viewpoint of the reactivity between isocyanate and hydroxyl group. It can have an acid value.
The reaction product (B) is generally 1000 to 40000, preferably 1500 to 30000, from the viewpoint of finished appearance such as curability of the finally obtained coating composition and smoothness of the coating film obtained. More preferably, it can have a weight average molecular weight in the range of 2000 to 20000.
In this specification, the NCO equivalent, hydroxyl value, acid value, and weight average molecular weight of the reaction product (B-1) are the unreacted remaining polyisocyanate compound (b-1) and acrylic resin (b-2). ) Also means the value of the reaction product as a whole.
In the coating composition of the present invention, the equivalent ratio (NCO / OH) of the hydroxyl group in the acrylic resin (A) to the isocyanate group in the reaction product (B-1) depends on the curability of the coating composition and the coating stability. From the viewpoint, it is generally preferable to be within the range of about 0.5 to about 2.0, particularly about 0.75 to about 1.75, more particularly about 0.8 to about 1.5.
Moreover, the content of the acrylic resin (A) and the reaction product (B-1) in the coating composition of the present invention is based on the total solid content of the acrylic resin (A) and the reaction product (B-1). As the non-volatile content, the acrylic resin (A) is generally 30 to 75% by mass, preferably 35 to 70% by mass, more preferably 40 to 65% by mass, and the reaction product (B-1) is generally It can be in the range of 25 to 70% by mass, preferably 30 to 65% by mass, and more preferably 35 to 60% by mass.
Hydroxyl-containing compound (b-3)
The hydroxyl group-containing compound (b-3) is a compound having at least 2, preferably 2 to 4 hydroxyl groups in one molecule. Specifically, for example, polyether polyol, polyester polyol, polyether ester polyol , Polyalkylene polyol, polycarbonate polyol, polycaprolactone polyol, silicone polyol, polyurethane polyol and the like. These polyols may be either diol compounds or trifunctional or higher functional polyol compounds. Among the above, polyether polyol, polycarbonate polyol, and polycaprolactone polyol can be particularly preferably used.
Examples of polyether polyols include ethylene oxide, propylene glycol, glycerin, and pentaerythritol as initiators, ethylene oxide, propylene oxide, mixtures of ethylene oxide and propylene oxide, ring-opening polymers such as tetrahydrofuran, and the like. Can be mentioned.
As the polyester polyol, a direct esterification reaction between a polyhydric alcohol and an ester-forming derivative such as an ester, an anhydride, or a halide of a polyvalent carboxylic acid or an ester, anhydride, or halide in an amount less than the stoichiometric amount of the polyhydric alcohol and / or The thing obtained by transesterification can be mentioned.
Examples of the polyhydric alcohol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, and 2-butyl-2-ethyl-1,3-propane. Diol, 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2 -Methyl-2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethyleneglycol Aliphatic diols such as triethylene glycol; cycloaliphatic diols such as cyclohexanedimethanol and cyclohexanediol; trimethylolethane, trimethylolpropane, hexitols, pentitols, glycerin, pentaerythritol, tetramethylolpropane, etc. Mention may be made of trihydric or higher alcohols.
Examples of the polyvalent carboxylic acid or its ester-forming derivative include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 2-methylsuccinic acid. Acid, 2-methyladipic acid, 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid, hydrogenated dimer acid Aliphatic dicarboxylic acids such as dimer acid; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid; 1,2-cyclopentanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2 -Cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicar Cycloaliphatic dicarboxylic acids such as acid, 1,4-dicarboxylic methylenecyclohexane, nadic acid, and methyl nadic acid; polyvalent carboxylic acids such as trimellitic acid, trimesic acid, tricarboxylic acid such as castor oil fatty acid trimer; Acid anhydrides of these polycarboxylic acids, halides of the polycarboxylic acids, halides such as bromides, methyl esters, ethyl esters, propyl esters, isopropyl esters, butyl esters, isobutyl esters, amyl esters of the polyvalent carboxylic acids And lactones such as γ-caprolactone, δ-caprolactone, ε-caprolactone, dimethyl-ε-caprolactone, δ-valerolactone, γ-valerolactone, and γ-butyrolactone.
Examples of the polyether ester polyol include those obtained by reacting the above polyether polyol with a polybasic acid to form a polyester; those having both polyether and polyester segments in the molecule.
Examples of the polyalkylene polyol include polybutadiene polyol and polyisoprene polyol.
Examples of the polycarbonate polyol include compounds obtained by polycondensation reaction of a normal polyol component and a carbonylating agent.
Examples of the polyol component include diols and polyhydric alcohols such as trihydric or higher alcohols. Examples of the diol include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, , 9-nonanediol, 1,10-decanediol and the like linear diols; 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-ethyl-1 , 6-hexanediol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl-1,8-octanediol, 2,2,4 -Branched diols such as trimethyl-1,3-pentanediol and 2-ethyl-1,3-hexanediol; 1,3-cyclohexanediol, 1,4 Examples include alicyclic diols such as cyclohexanediol and 1,4-cyclohexanedimethanol; aromatic diols such as p-xylenediol and p-tetrachloroxylenediol; ether diols such as diethylene glycol and dipropylene glycol. These diols can be used alone or in combination of two or more. Examples of the trihydric or higher alcohols include glycerin, trimethylolethane, trimethylolpropane, trimethylolpropane dimer, pentaerythritol, and the like.
As the carbonylating agent, those known per se can be used, and specific examples thereof include alkylene carbonate, dialkyl carbonate, diallyl carbonate, phosgene and the like. It can be used in combination of more than one species. Of these, preferred are ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, diphenyl carbonate and the like.
Examples of the polycaprolactone polyol include ring-opening polymerization products of caprolactone such as polycaprolactone diol.
Examples of the silicone polyol include silicone oils having a hydroxyl group at the terminal having a siloxane bond in the molecule.
Examples of the polyurethane polyol include those obtained by a urethanization reaction between a polyol and a polyisocyanate in an amount less than the stoichiometric amount of the polyol. For example, a reaction product of diamine and ethylene carbonate can also be used. Can be used.
The hydroxyl group-containing compounds (b-3) described above can be used alone or in combination of two or more.
The hydroxyl group-containing compound (b-3) can have a hydroxyl value in the range of 70 to 450 mgKOH / g, preferably 80 to 425 mgKOH / g, more preferably 90 to 400 mgKOH / g. If the hydroxyl value of the hydroxyl group-containing compound (b-3) is less than 70 mgKOH / g, the resulting coating film may have insufficient coating performance such as acid resistance and scratch resistance, and conversely, 450 mgKOH / When g is exceeded, compatibility with an acrylic resin (A) may fall.
The hydroxyl group-containing compound (b-3) can have a weight average molecular weight in the range of 250 to 3000, preferably 300 to 2500, and more preferably 350 to 2000. If the weight average molecular weight of the hydroxyl group-containing compound (b-3) is less than 250, the compatibility with the acrylic resin (A) may be reduced. Conversely, if it exceeds 3000, the acid resistance of the resulting coating film will be reduced. In some cases, the film performance such as scratch resistance may be insufficient.
Reaction product (B-2)
The reaction product (B-2) can be obtained by addition reaction of the polyisocyanate compound (b-1) and the hydroxyl group-containing compound (b-3). This reaction proceeds by an addition reaction between the isocyanate group of the polyisocyanate compound (b-1) and the hydroxyl group of the hydroxyl group-containing compound (b-3).
In the addition reaction, the polyisocyanate compound (b-1) and the hydroxyl group-containing compound (b-3) are usually at a temperature of about 60 to about 140 ° C., preferably about 70 to about 130 ° C., usually for 1 to 10 hours. The reaction can be carried out for about 2 hours, preferably about 2 to 8 hours. The reaction can usually be carried out until the hydroxyl value of the hydroxyl group-containing compound (b-3) is 2 mgKOH / g or less. If the reaction temperature is less than 60 ° C., a large amount of unreacted hydroxyl groups may remain. Conversely, if the reaction temperature exceeds 140 ° C., the reaction product may be decomposed.
The above reaction can be carried out by further adding an organic solvent, if necessary. As an organic solvent, what was illustrated in the case of manufacture of an acrylic resin (A) can be used similarly. Solvents that are not reactive with isocyanate groups are preferred, and examples include ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and solvents such as N-methylpyrrolidone (NMP). .
In the addition reaction, a catalyst can be used as necessary. Specifically, examples of the catalyst effective for the reaction between the hydroxyl group and the isocyanate group include a tin-based catalyst and a phosphoric acid-based catalyst. Of these, dibutyltin dilaurate and the like can be preferably used.
In the reaction of the polyisocyanate compound (b-1) and the hydroxyl group-containing compound (b-3), the ratio of the polyisocyanate compound (b-1) to the hydroxyl group-containing compound (b-3) depends on the finished appearance and resistance of the coating film. From the viewpoint of motility, the NCO / OH ratio can be in the range of 6 to 12, preferably 6.5 to 11, and more preferably 7 to 10. When the NCO / OH ratio is less than 6, the reaction product (B-2) to be produced has a high molecular weight, which causes problems such as a decrease in the finished appearance such as the smoothness of the coating film. There is. On the other hand, when the NCO / OH ratio is larger than 12, the ratio of the unreacted polyisocyanate compound (b-1) is increased, and thus the anti-moisture resistance of the formed coating film may be lowered.
The reaction product (B-2) may contain an unreacted product and can be used as it is without separating the unreacted product.
The reaction product (B-2) generally has an NCO equivalent weight in the range of 200 to 370, preferably 210 to 350, more preferably 220 to 330, from the viewpoint of the curability of the coating composition finally obtained. Can have.
The reaction product (B-2) generally has a hydroxyl value in the range of 0 to 10 mgKOH / g, preferably 0 to 7.5 mgKOH / g, more preferably 0 to 5 mgKOH / g, from the viewpoint of storage stability. be able to.
The reaction product (B-2) is also 1000 to 15000, preferably 1250 to 14000, from the viewpoint of finished appearance such as curability of the finally obtained coating composition and smoothness of the coating film formed. More preferably, it can have a weight average molecular weight in the range of 1500 to 13000.
In the present specification, the NCO equivalent, hydroxyl value and weight average molecular weight of the reaction product (B-2) are the same as those of the polyisocyanate compound (b-1) and the hydroxyl group-containing compound (b-3) remaining unreacted. It means the value of the entire reaction product.
In the coating composition of the present invention, the equivalent ratio (NCO / OH) of the hydroxyl group in the acrylic resin (A) to the isocyanate group in the reaction product (B-2) depends on the curability of the coating composition and the coating stability. From the viewpoint, it is generally more preferable to be in the range of 0.5 to 2.0, particularly 0.65 to 1.75, and more particularly 0.8 to 1.5.
The contents of the acrylic resin (A) and the reaction product (B-2) in the coating composition of the present invention are based on the total solid content of the acrylic resin (A) and the reaction product (B-2). As the non-volatile content, the acrylic resin (A) is generally 30 to 75% by mass, preferably 35 to 70% by mass, more preferably 40 to 65% by mass, and the reaction product (B-2) is generally It can be in the range of 25 to 70% by mass, preferably 30 to 65% by mass, and more preferably 35 to 60% by mass.
Other ingredients
If necessary, the coating composition of the present invention may be blended with pigments known per se, such as colored pigments, extender pigments, glitter pigments and rust preventive pigments, to the extent that the transparency of the formed coating film is not impaired. Can do.
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.
In the coating composition of the present invention, various resins such as a polyester resin, an alkyd resin, a silicon resin, and a fluorine resin can be added as necessary. It is also possible to use a small amount of a crosslinking agent such as a melamine resin and a polyisocyanate compound in which some or all of the isocyanate groups may be blocked. 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 as the curing catalyst can be used alone or in combination of two or more. The blending amount of the curing catalyst varies depending on the type, but is usually 0 to 5 parts by mass, preferably 0.1 to 5 parts by mass based on the total solid content of 100 parts by mass of the acrylic resin (A) and the reaction product (B). It can be in the range of 4 parts by mass.
As the ultraviolet absorber, those known per se can be used, and examples thereof include ultraviolet absorbers such as benzotriazole absorbers, triazine absorbers, salicylic acid derivative absorbers, and benzophenone absorbers. it can. By blending the ultraviolet absorber, the weather resistance, yellowing resistance and the like of the coating film can be improved. The content of the ultraviolet absorber in the coating composition is usually 0 to 10 parts by mass, particularly 0.2 to 10 parts by mass, based on 100 parts by mass of the total solid content of the acrylic resin (A) and the reaction product (B). It is preferably 5 parts by mass, more preferably in the range of 0.3 to 2 parts by mass.
As the light stabilizer, those known per se can be used, and examples thereof include hindered amine light stabilizers. By blending the light stabilizer, the weather resistance, yellowing resistance and the like of the coating film can be improved. The content of the light stabilizer in the coating composition is usually 0 to 10 parts by mass, particularly 0.2 to 10 parts by mass, based on 100 parts by mass of the total solid content of the acrylic resin (A) and the reaction product (B). It is preferably 5 parts by mass, more preferably in the range of 0.3 to 2 parts by mass.
The form of the coating composition of the present invention is not particularly limited, but an organic solvent type is usually preferable. As the organic solvent used in this case, various organic solvents for paints such as aromatic or aliphatic hydrocarbon solvents; ester solvents; ketone solvents; ether solvents and the like can be used. As the organic solvent to be used, those used at the time of preparation of the acrylic resin (A) and the reaction product (B) may be used as they are, or may be added as appropriate.
Preparation of coating composition
The coating composition of the present invention comprises an acrylic resin (A), a reaction product (B), and a curing catalyst, a pigment, various resins, an ultraviolet absorber, a light stabilizer, an organic solvent, etc. It can be prepared by mixing by a method known per se.
The coating composition of the present invention is prepared as a two-component coating material in which the acrylic resin (A) and the reaction product (B) are separated because the hydroxyl group and the isocyanate group may react even at room temperature. It is preferable to use a mixture of both.
The solid content concentration of the coating composition of the present invention is generally in the range of 30 to 70% by mass, particularly 40 to 60% by mass.
Painting method
The coating composition of the present invention can be applied to an object to be coated by various coating methods shown below.
Article
Examples of articles to which the coating composition of the present invention can be applied include bodies such as automobiles and motorcycles, or parts thereof. In addition, examples of the objects to be coated include 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; A plastic substrate or the like can also be used.
Further, the object to be coated may be one in which the metal surface of the vehicle body, the part, or the metal substrate is subjected to chemical conversion treatment such as phosphate treatment, chromate treatment, or complex oxide treatment. Further, the object to be coated may be one in which an undercoat film and / or an intermediate coat film such as various electrodeposition paints are formed on the vehicle body, metal base material, or the like.
Furthermore, examples of the objects to be coated include industrial machines, home appliances, kitchen appliances, roofs, walls, shutters, and the like.
Painting and curing method
The coating method of the coating composition of the present invention is not particularly limited. For example, a wet coating film is formed by a coating method such as air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, roll coat coating, or the like. Can do. In air spray coating, airless spray coating, and rotary atomization coating, electrostatic application may be applied as necessary. Of these, air spray coating and rotary atomization coating are particularly preferred.
The coating film thickness is usually preferably within a range of 10 to 50 μm as a cured film thickness.
When the coating composition of the present invention is applied by air spray coating, airless spray coating or rotary atomization coating, the viscosity of the coating composition of the present invention 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 as to be within a viscosity range of about 15 to 60 seconds at 20 ° C.
The wet coating film can be cured by heating, and the heating can be performed using 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 used.
The heating is usually performed at a temperature in the range of about 100 to about 180 ° C., preferably about 120 to about 160 ° C., usually for about 5 to 60 minutes.
Multi-layer coating formation method
The coating composition of the present invention can form a coating film having excellent coating performance such as scratch resistance, acid resistance, and finished appearance, so that a coating for forming an overcoat multilayer coating film on an object to be coated can be formed. In the film forming method, it can be suitably used as a clear coating composition for forming a top clear coat.
Therefore, according to the present invention, when a multi-layer coating film is formed by sequentially applying a colored base coat paint and a clear coat paint to an object, the coating composition of the present invention is used as the clear coat paint. A featured topcoat multilayer coating formation method is provided.
As the article to be applied for applying the method for forming a multilayer coating film of the present invention, the above-described automobile body and its parts are particularly preferable.
As a method for applying the colored base coat paint and the clear coat paint, for example, a coating method such as airless spray, air spray, and rotary atomization coating can be adopted. You may do it.
As the colored base coat paint, a known colored paint composition can be used, and it is particularly preferable to use a paint composition that is usually used when painting an automobile body or the like.
The colored base coat paint includes an organic solvent type containing a base resin, a crosslinking agent and a colorant (for example, a color pigment, a metallic pigment, a light interference pigment, an extender pigment, etc.) and, optionally, other paint additives. Or an aqueous coating composition is included.
Examples of the base resin include at least one selected from an acrylic resin, a vinyl resin, a polyester resin, an alkyd resin, a urethane resin, and the like having a crosslinkable functional group such as a hydroxyl group, an epoxy group, a carboxyl group, and an alkoxysilyl group. Resin can be used. In addition, as the crosslinking agent, for example, at least one selected from alkyl etherified melamine resin, urea resin, guanamine resin, polyisocyanate compound, blocked polyisocyanate compound, epoxy compound, carboxyl group-containing compound, and the like is used. it can. The base resin and the cross-linking agent are usually preferably used in the range of 50 to 90% by weight of the base resin and the cross-linking agent in the range of 50 to 10% by weight based on the total amount of both components.
In the method for forming a multilayer coating film of the present invention, first, the colored base coat paint is applied to an object to be coated so that the cured film thickness is about 10 to about 50 μm. The coated base coat paint is cured by heating at a temperature of about 100 to about 180 ° C., preferably about 120 to about 160 ° C. for about 10 to about 40 minutes, or left at room temperature for several minutes without curing after coating. Alternatively, preheat at about 40 to about 100 ° C. for about 1 to about 20 minutes.
Next, as the clear coat paint, the coating composition of the present invention is applied so that the film thickness is about 10 to about 70 μm as a cured film thickness, and a cured multilayer coating film can be formed by heating. it can. The heating is preferably performed at a temperature of about 100 to about 180 ° C., preferably about 120 to about 160 ° C., for about 10 to about 40 minutes.
In the above-mentioned 2-coat method, a 2-coat 1-bake method can be used in which a clear coat paint is applied without applying a base coat paint and cured by heating, and these two-layer coating films are cured simultaneously, or a base coat paint is applied. Then, after the base coat film is heat-cured, a 2-coat 2-bake method in which a clear coat paint is applied and the clear coat film is cured may be employed.

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 of acrylic resin (A) Production examples 1 to 8
A four-necked flask equipped with a stirrer, a thermometer, a cooling tube and a nitrogen gas inlet is charged with 340 parts of “Swazol 1000” (trade name, manufactured by Cosmo Oil Co., Ltd., hydrocarbon solvent), and 125 under a nitrogen atmosphere. The temperature was raised to 0 ° C., and a mixture composed of monomers and a polymerization initiator in an amount (parts by mass) shown in Table 1 below was added dropwise over 4 hours. Next, after aging for 30 minutes while flowing nitrogen gas at 125 ° C., a mixture of 320 parts of “Swazole 1000” and 5 parts of 2,2′-azobisisobutyronitrile was added dropwise over 1 hour. Thereafter, by further aging for 1 hour, the acrylic resin (A) No. 1-No. A solution of 8 was obtained. The special values of the obtained acrylic resins (A) are shown together in Table 1 below. In addition, acrylic resin (A) No. 5 ~ No. 8 is a resin for a comparative example.

Production of acrylic resin (b-2) Production Examples 9 to 15
A four-necked flask equipped with a stirrer, a thermometer, a cooling tube and a nitrogen gas inlet is charged with 340 parts of “Swazol 1000” (trade name, manufactured by Cosmo Oil Co., Ltd., hydrocarbon solvent), and 125 under a nitrogen atmosphere. The temperature was raised to 0 ° C., and a mixture composed of an amount (parts by mass) of a monomer, a chain transfer agent and a polymerization initiator shown in Table 2 below was added dropwise over 4 hours. Next, after aging for 30 minutes while flowing nitrogen gas at 125 ° C., a mixture of 320 parts of “Swazole 1000” and 5 parts of 2,2′-azobisisobutyronitrile was added dropwise over 1 hour. Then, by further aging for 1 hour, acrylic resin (b-2) No. 1-No. A solution of 7 was obtained. The special values of the obtained acrylic resins (b-2) are shown together in Table 2 below. In addition, acrylic resin (b-2) No. 5 ~ No. 7 is a resin for a comparative example.

Production of reaction product (B-1) Production examples 16 to 25
In a four-necked flask equipped with a stirrer, a thermometer, a condenser tube and a nitrogen gas inlet, the amounts (parts by mass) of the polyisocyanate compound (b-1) and the acrylic resin (b-2) shown in Table 3 below were used. The solution was charged and heated to 130 ° C. under a nitrogen atmosphere, and then reacted for 4 hours. Thereafter, by adding isobutyl acetate and diluting to a mass solids concentration of 70%, the reaction product (B-1) No. 1-No. Ten solutions were obtained. The characteristic values of the solution of each reaction product (B-1) obtained are shown in Table 3 below. The reaction product (B-1) No. 6-No. 10 is a resin for a comparative example. Moreover, the compounding quantity in Table 3 is solid content (mass part).

(* 1) N3300: trade name, manufactured by Bayer, isocyanurate of hexamethylene diisocyanate (solid content 100%).
Preparation of coating composition Examples 1-8 and Comparative Examples 1-10
Acrylic resin (A) obtained in the above production example, reaction product (B-1), and raw materials described in Table 4 below were used in a mixing ratio (parts by mass) shown in Table 4 below using a rotary blade type agitator. By stirring and mixing, the coating composition No. 1-18 were obtained. In addition, the compounding quantity in Table 4 is solid content (mass part).
Each coating composition No. For Nos. 1-18, “Swazole 1000” was added and Ford Cup #No. 4 was used for coating after adjusting the viscosity to 25 seconds at 20 ° C. The coating was performed 10 minutes after adjusting the viscosity.
Preparation of test plate Each coating composition No. 1 to 18 were used to prepare test plates as follows.
(Preparation of coated objects)
On the 0.8 mm-thick dull steel sheet that has been subjected to zinc phosphate conversion treatment, “ELECRON GT-10” (trade name, manufactured by Kansai Paint Co., Ltd., thermosetting epoxy resin-based cationic electrodeposition paint) has a thickness of 20 μm. Electrodeposition coating was performed, and the coating was heated and cured at 170 ° C. for 30 minutes, and then “Amirac TP-65-2” (trade name, manufactured by Kansai Paint Co., Ltd., polyester / melamine resin-based automobile) The intermediate coating plate obtained by applying air spray coating to a film thickness of 35 μm and curing it by heating at 140 ° C. for 30 minutes was used as an object to be coated.
(Preparation of silver paint test plate)
A water-based metallic base coat “WBC713T # 1F7” (trade name, manufactured by Kansai Paint Co., Ltd., acrylic / melamine resin-based automotive top coat paint, silver coating color) is applied on the above-mentioned object so that the film thickness is 15 μm. After standing at room temperature for 5 minutes and preheating at 80 ° C. for 10 minutes, each coating composition No. Each silver coating test was performed by coating 1-18 so that the film thickness would be 35 μm, then let stand at room temperature for 5 minutes, and then heat at 140 ° C. for 20 minutes to cure both coatings together I got a plate.
(Preparation of black paint test plate)
In the production of the above-mentioned silver coating color test plate, “WBC713T # 1F7” (trade name, manufactured by Kansai Paint Co., Ltd., acrylic / melamine resin-based topcoat paint for automobiles, silver coating color) was used as “WBC713T # 202” (manufactured by Kansai Paint Co., Ltd.). A black-coated color test plate was obtained in the same manner except that it was changed to an acrylic / melamine resin-based automotive topcoat base paint, black color).
(Preparation of white paint test plate)
In the preparation of the above-mentioned coating object, “Amilak TP-65-2” (trade name, manufactured by Kansai Paint Co., Ltd., polyester / melamine resin-based automotive intermediate coating, gray coating color) is used instead of “Amilack TP-65-2”. (Product name, manufactured by Kansai Paint Co., Ltd., polyester / melamine resin-based automotive intermediate coating, white coating color) is processed in the same manner to produce a white coating, and the resulting white coating On top of each other, each coating composition No. A white test plate was prepared in the same manner as in the preparation of the silver-coated test plate except that 1 to 18 were applied.
The obtained test plates were allowed to stand at room temperature for 7 days and then subjected to the following coating film performance test.
Coating Film Performance Test Metallic Appearance: The metallic appearance of the silver paint color test plate was evaluated by IV value. In addition, the measurement of IV value uses a laser type metallic feeling measuring apparatus ("ALCOLM LMR-200" (trade name, manufactured by Kansai Paint Co., Ltd.)), and among the reflection of laser light irradiated at an incident angle of 45 degrees, The signal output at the light receiving angle at which the minimum light intensity is obtained in the regular reflection region was measured. The IV value is a numerical value of the whiteness of the metallic coating film, and the whiter the metallic pigment is, the more uniform the metal pigment is oriented in parallel to the coating surface, the better the metallic feeling, and the higher the IV value, the whiter the value is.
Scratch resistance: An automobile in which each black-colored test plate was attached to the roof of an automobile using a water resistant tape manufactured by Nichiban Co., Ltd. was washed 15 times with a car wash machine at 20 ° 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. “PO20 FWRC” (trade name, manufactured by Yasui Industry Co., Ltd.) was used as the car wash machine.
Acid resistance: 0.4 cc of 40% sulfuric acid was dropped on the coated surface of the black-colored test plate, heated on a hot plate heated to 60 ° C. for 15 minutes, and then the test plate was washed with water. The etching depth (μm) of the sulfuric acid dropping portion was cut off with a surface roughness meter (“Surfcom 570A”, trade name, manufactured by Tokyo Seimitsu Co., Ltd., surface roughness shape measuring machine) with a cutoff of 0.8 mm (scanning speed: 0.8 mm). The acid resistance was evaluated by measurement under the conditions of 3 mm / sec and a magnification of 5000 times. The smaller the etching depth value, the better the acid resistance.
Contamination resistance: A white paint color test plate was tested in an accelerated weather resistance tester (“Sunshine Weather Omometer”, trade name, manufactured by Suga Test Instruments Co., Ltd.) for 600 hours under the conditions of JIS K5400, and then mud A pollutant consisting of a mixture of carbon black, mineral oil and clay was deposited on the nell and rubbed lightly on the test plate. This was left for 24 hours in a constant temperature and humidity room of 75% RH at 20 ° C., then the coated surface was washed with running water, and the degree of contamination of the coating film was evaluated by the difference in lightness (ΔL) of the test plate.
ΔL was determined by the following formula.
ΔL = (L value before stain resistance test) − (L value after stain resistance test)
The L value is measured using a tristimulus value direct-reading color meter (“CR400”, trade name, manufactured by Konica Minolta Co., Ltd.) under the conditions of light source D65, visual field 2 °, diffuse illumination vertical light reception (d / 0). Performed below. This L value is a value based on the CIE 1976 L ^* a ^* b ^* color system.
The evaluation criteria for the degree of contamination of the coating film are as follows. A smaller ΔL value indicates better contamination resistance.
A: ΔL <0.2,
○: 0.2 ≦ ΔL <0.5,
○ △: 0.5 ≦ ΔL <1,
Δ: 1 ≦ ΔL <2,
X: 2 ≦ ΔL.
Finishing property (20 ° gloss): “HG-268” (trade name, manufactured by Suga Test Instruments Co., Ltd., handy gloss meter) is used as the 20-degree specular reflectance (20 ° gloss value) of each black paint test plate. Measured.
The results of the coating performance test are shown in Table 4 below.

(* 1) N3300: trade name, manufactured by Bayer, isocyanurate of hexamethylene diisocyanate (solid content 100%).
(* 2) NACURE4054: Phosphoric acid curing catalyst manufactured by King Industry.
(* 3) UV1164: trade name, manufactured by Ciba-Geigy Corporation, UV absorber.
(* 4) HALS292: trade name, manufactured by Ciba Geigy Corp., light stabilizer.
(* 5) BYK-300: trade name, manufactured by Big Chemie, surface conditioner.
Production of reaction product (B-2) Production examples 26 to 36
In a four-necked flask equipped with a stirrer, a thermometer, a cooling tube and a nitrogen gas inlet, the amount (parts by mass) of the polyisocyanate compound (b-1) and the hydroxyl group-containing compound (b-3) shown in Table 5 below In addition, isobutyl acetate was added in an amount such that the total mass concentration of the polyisocyanate compound (b-1) and the hydroxyl group-containing compound (b-3) was 70%. Then, after heating up to 120 degreeC in nitrogen atmosphere, by making it react for 4 hours, each reaction product (B-2) No. 1-No. 11 solutions were obtained. The characteristic values of the obtained reaction products (B-2) are shown in Table 5 below. The reaction product (B-2) No. 8 ~ No. 11 is a resin for a comparative example. Moreover, the compounding quantity in Table 5 is a solid content (mass part). In addition, the raw material details in Table 5 are as follows.
N3300 (* 1): Isocyanurate of hexamethylene diisocyanate (manufactured by Bayer, trade name, solid content 100%).
Hydroxyl-containing compound no. 1: “Uniol D-700” (polypropylene glycol, hydroxyl value 160.3 mg KOH / g, weight average molecular weight 700, manufactured by NOF Corporation, trade name, solid content 100%).
Hydroxyl-containing compound no. 2: “Uniol D-250” (polypropylene glycol, hydroxyl value 448.8 mgKOH / g, weight average molecular weight 250, manufactured by NOF Corporation, trade name, solid content 100%).
Hydroxyl-containing compound no. 3: “Uniol TG-2000” (polypropylene triol, hydroxyl value 84.1 mg KOH / g, weight average molecular weight 2000, manufactured by NOF Corporation, trade name, solid content 100%).
Hydroxyl-containing compound no. 4: “ETERRNACOLL UM-90” (mixture of 1 / 1,4-cyclohexanedimethanol and 1,6-hexanediol (1/1) polycarbonate diol, hydroxyl value 122.8 mgKOH / g, weight average molecular weight 900, manufactured by Ube Industries, Ltd. , Trade name, solid content 100%).
Hydroxyl-containing compound no. 5: “PLACCEL 205” (polycaprolactone diol, hydroxyl value 211.7 mg KOH / g, weight average molecular weight 530, manufactured by Daicel Chemical Industries, trade name, solid content 100%).
Hydroxyl-containing compound no. 6: Dipropylene glycol (hydroxyl value 837.3 mg KOH / g, molecular weight 134.18).
Hydroxyl-containing compound no. 7: “Uniol D-4000” (polypropylene glycol, hydroxyl value 28.1 mgKOH / g, weight average molecular weight 4000, manufactured by NOF Corporation, trade name, solid content 100%).

Preparation of coating composition Examples 9 to 18 and Comparative Examples 11 to 19
Acrylic resin (A) obtained in the above production example, reaction product (B-2), and raw materials described in Table 6 below were used in a mixing ratio (parts by mass) shown in Table 6 below using a rotary blade type agitator. By stirring and mixing, the coating composition No. 19-35 were obtained. In addition, the compounding quantity in Table 6 is a solid content (mass part).
Each coating composition No. Nos. 19 to 35 are ford cup #No. 4 was used for coating after adjusting the viscosity to 25 seconds at 20 ° C. The coating was performed 10 minutes after adjusting the viscosity.
Preparation of test plate and coating film performance test Each coating composition No. 19 to 35 were used, and test plates were prepared in the same manner as above, and the coating film performance test (metallic appearance, scratch resistance, acid resistance, stain resistance, finish (20 ° gloss) )).
The results of the coating performance test are also shown in Table 6.

(* 1) N3300: trade name, manufactured by Bayer, isocyanurate of hexamethylene diisocyanate (solid content 100%).
(* 2) NACURE 4054: trade name, manufactured by King Industry, phosphoric acid curing catalyst.
(* 3) UV1164: trade name, manufactured by Ciba-Geigy Corporation, UV absorber.
(* 4) HALS292: trade name, manufactured by Ciba Geigy Corp., light stabilizer.
(* 5) BYK-300: trade name, manufactured by Big Chemie, surface conditioner.

Claims (15)

1. (A) an acrylic resin having a hydroxyl value in the range of 80 to 180 mg KOH / g, a weight average molecular weight in the range of 3000 to 20000, and a solubility parameter value in the range of 8.5 to 9.8, and (B) Polyisocyanate compound (b-1), having a hydroxyl value in the range of 40 to 180 mg KOH / g, a weight average molecular weight in the range of 700 to 4000, and a solubility parameter value in the range of 8.5 to 9.8 A reaction product (B-1) obtained by reacting an acrylic resin (b-2) with an NCO / OH ratio in the range of 7 to 15, or a polyisocyanate compound (b-1); A hydroxyl group-containing compound (b-3) having a hydroxyl value in the range of 450 mg KOH / g and a weight average molecular weight in the range of 250 to 3000 is reacted at an NCO / OH ratio in the range of 6 to 12. Reaction product (B-2) having a weight average molecular weight within the range of 1000 to 15000
   A coating composition comprising:
2. The acrylic resin (A) has a hydroxyl value in the range of 110 to 170 mg KOH / g and / or a weight average molecular weight in the range of 5000 to 16000 and / or a solubility parameter value in the range of 8.7 to 9.6. The coating composition according to claim 1.
3. The coating composition according to claim 1, wherein the acrylic resin (A) has a glass transition temperature in the range of -30 ° C to 90 ° C.
4. The coating composition according to claim 1, wherein the polyisocyanate compound (b-1) is an aliphatic diisocyanate, an alicyclic diisocyanate, or a derivative thereof.
5. The coating composition according to claim 1, wherein the polyisocyanate compound (b-1) is hexamethylene diisocyanate (HMDI), a derivative of hexamethylene diisocyanate, isophorone diisocyanate (IPDI) or a derivative of isophorone diisocyanate.
6. The acrylic resin (b-2) has a hydroxyl value in the range of 50 to 170 mg KOH / g and / or a weight average molecular weight in the range of 800 to 3000 and / or a solubility parameter in the range of 8.6 to 9.6. The coating composition of claim 1 having a value.
7. The coating composition according to claim 1, wherein the acrylic resin (b-2) has a glass transition temperature in the range of -30 ° C to 80 ° C.
8. The reaction product (B-1) has an NCO equivalent weight in the range of 200 to 370 and / or a hydroxyl value in the range of 0 to 10 mg KOH / g and / or an acid value in the range of 0 to 15 mg KOH / g and / or The coating composition according to claim 1, having a weight average molecular weight in the range of 1000 to 40,000.
9. Based on the total solid content of acrylic resin (A) and reaction product (B-1) as a non-volatile content, 30 to 75% by mass of acrylic resin (A) and 25 to 25% of reaction product (B-1) The coating composition according to claim 1, containing 70% by mass.
10. The coating composition according to claim 1, wherein the hydroxyl group-containing compound (b-3) is a polyether polyol, a polycarbonate polyol or a polycaprolactone polyol.
11. The coating composition according to claim 1, wherein the hydroxyl group-containing compound (b-3) has a hydroxyl value in the range of 90 to 400 mgKOH / g and / or a weight average molecular weight in the range of 350 to 2000.
12. The reactant (B-2) has an NCO equivalent weight in the range of 200 to 370 and / or a hydroxyl value in the range of 0 to 10 mg KOH / g and / or a weight average molecular weight in the range of 1500 to 13,000. The coating composition as described in 1.
13. Based on the total solid content of the acrylic resin (A) and the reaction product (B-2), 30 to 75% by mass of the acrylic resin (A) and 25 to 25% of the reaction product (B-2) as a non-volatile content. The coating composition according to claim 1, containing 70% by mass.
14. The coating composition according to any one of claims 1 to 13 is used as a clear coat paint when a multi-layer coating film is formed by sequentially applying a colored base coat paint and a clear coat paint to an article to be coated. A method for forming an overcoat multilayer coating film characterized by the above.
15. Articles coated by the method according to claim 14.