JP2005126649A - Thermosetting coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosetting coating composition which is capable of forming a film excellent in acid resistance, scratch resistance and durability and which is excellent in the recoat adhesion and storage stability. <P>SOLUTION: The thermosetting coating composition contains as the essential components (A) a vinyl copolymer and (B) a blocked isocyanate compound in a molar ratio of hydroxy groups of (A) component to blocked isocyanate groups of (B) component of 1/2-2/1. The above vinyl copolymer (A) has hydroxy groups having a hydroxyl value of 20-200 mgKOH/g and carboxy groups having an acid value of 5-50 mgKOH/g. The above blocked isocyanate compound (B) comprises isocyanate compounds of (b1) an aliphatic-based polyisocyanate compound having in one molecule three or more isocyanate groups and (b2) an aromatic- and/or alicyclic-based polyisocyanate compound having in one molecule three or more isocyanate groups in a mass ratio of the solid contents of 20/80-80/20, with the isocyanate compounds being blocked with a blocking agent which consists of (b3) a heterocyclic compound and (b4) an active methylene compound in a molar ratio of 50/50-90/10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention can form a coating film excellent in acid resistance, scratch resistance and durability, and the adhesion between the formed coating film and the coating film coated on the coating film (hereinafter, The present invention relates to a thermosetting coating composition that is excellent in recoat adhesion) and can be suitably used as an automotive top coating.

In recent years, in automobile coatings, the occurrence of rain due to acid rain and the occurrence of scratches due to car wash machines and the like have been regarded as problems, and the development of paints excellent in acid resistance, scratch resistance and durability is urgently needed. In order to solve such a problem, there has been proposed a coating composition in which the acid resistance of the coating film is improved by combining the crosslinking type of the coating film forming resin and the curing agent. For example, a thermosetting composition using a blocked isocyanate blocked with an azole-based blocking agent and an amino resin as a curing agent has been proposed (Patent Document 1). However, the coating film obtained from this thermosetting coating composition is superior in acid resistance to a coating film cured with melamine resin alone, which is a kind of amino resin, but it has sufficient acid resistance because it contains melamine resin. The scratch resistance could not be obtained.
In addition, a thermosetting coating composition in which the curing agent is a combined type of blocked isocyanate and 1,3,5-triazine-2,4,6-tris-carbamic acid ester is proposed as a crosslinking type that does not contain a melamine resin. (Patent Document 2). However, the coating film obtained from this thermosetting coating composition has good acid resistance, but has insufficient scuff resistance because it contains a triazine ring.

In addition, a one-component polyurethane baking composition using a blocked polyisocyanate blocked with 1,2,4-triazole, 3,5-dimethylpyrazole and other blocking agents as a curing agent has been proposed (Patent Document 3). ). However, although the coating film obtained from this one-component polyurethane baking composition shows good baking yellowing, the deblocking reaction of 1,2,4-triazole is slower than 3,5-dimethylpyrazole, so There was a problem and recoat adhesion was insufficient.
Further, a one-component thermosetting composition containing blocked isocyanate blocked with diethyl malonate and other blocking agent, a hydrolyzable silyl group-containing polyvalent hydroxy compound, monoalcohol and / or diol has been proposed (Patent Document). 4.) This one-component thermosetting composition is excellent in low-temperature curability, adhesion, and recoatability, but has poor hydrolytic stability, and thus has poor storage stability. It was enough.

In addition, a coating film obtained from a top coating composed of a hydroxyl group-containing acrylic copolymer having an acid value of 4 or less, an aliphatic and / or alicyclic block polyisocyanate, an organic tin compound and / or an organic zinc compound has been proposed. (Patent Document 5). Although this top coat was excellent in finished appearance, weather resistance, and acid resistance, the recoat adhesion was insufficient because the acid value was 4 or less.
Moreover, the resin composition for coatings containing the polymer which has a hydroxyl group and a carboxyl group, and the blocked isocyanate blocked with the active methylene type blocking agent is proposed (patent document 6). However, this coating resin composition can form a coating film excellent in appearance, low-temperature curability, weather resistance, water resistance, solvent resistance, and repaintability, but is blocked only with an active methylene-based blocking agent. Therefore, there was a problem that the storage stability was inferior.

JP-A-9-169950 JP 2002-80781 A JP-A-7-304843 JP-A-10-251373 JP-A-9-125000 JP 2000-327993 A

The present invention can form a coating film excellent in acid resistance, scratch resistance and durability, and is excellent in recoat adhesion and storage stability, and can be suitably used as an automotive top coating. The object is to provide a coating composition.

As a result of repeating various studies to solve the above-mentioned conventional problems, the present inventors have used a vinyl copolymer having a hydroxyl group and a carboxyl group as a resin, and a specific aliphatic polyisocyanate compound as a curing agent and A coating composition using a block isocyanate obtained by blocking a mixture of a specific aromatic and / or alicyclic polyisocyanate compound with a heterocyclic compound and an active methylene compound is excellent in acid resistance, scratch resistance and durability. The present invention has been found to provide a thermosetting coating composition that can form a coated film, has excellent recoat adhesion, and can be suitably used as a top coating for automobiles. It came to complete.

That is, the present invention comprises (A) a vinyl copolymer having a hydroxyl group and a carboxyl group having a hydroxyl value of 20 to 200 mgKOH / g and an acid value of 5 to 50 mgKOH / g, and (B) a blocked isocyanate compound as essential components. And (b1) an aliphatic polyisocyanate compound having 3 or more isocyanate groups in one molecule, and a thermosetting coating composition containing (B2) A blocking agent comprising an aromatic and / or alicyclic polyisocyanate compound having three or more isocyanate groups in one molecule, and further blocking the isocyanate compound is (b3) a heterocyclic compound and (B4) an active methylene compound, which is a polyisocyanate compound (b1) The mass ratio of the solid content to (b2) is 20/80 to 80/20, the molar ratio of the blocking agent (b3) to (b4) is 50/50 to 90/10, and the component (A) The molar ratio of the hydroxyl group of the vinyl copolymer having a hydroxyl group and a carboxyl group to the blocked isocyanate group of the blocked isocyanate compound of the component (B) is 1/2 to 2/1. An adhesive coating composition is provided.

（式中、Ｘは水素原子またはメチル基である。Ｒは炭素数３〜８のアルキレン基又はシクロアルキレン基である。）で表される構造単位を含む共重合体である熱硬化性塗料組成物を提供する。 In the thermosetting coating composition, the present invention provides a vinyl copolymer having a hydroxyl group and a carboxyl group (A) having a hydroxyl value of 20 to 200 mgKOH / g and an acid value of 5 to 50 mgKOH / g. , Formula (1)

(Wherein X is a hydrogen atom or a methyl group, R is an alkylene group or a cycloalkylene group having 3 to 8 carbon atoms), and a thermosetting coating composition that is a copolymer containing a structural unit represented by Offer things.

In the thermosetting coating composition according to the present invention, the vinyl copolymer having a hydroxyl group and a carboxyl group in (A) is a lactone-modified vinyl copolymer, and the number average molecular weight of the graft chain by lactone modification is Is a thermosetting coating composition having a primary hydroxyl group at the end of the graft chain by lactone modification.
Further, the present invention provides the above thermosetting coating composition, wherein (b1) is an isocyanurate body, burette body and adduct body of an aliphatic isocyanate having 3 or more isocyanate groups in one molecule, and 2 -One or more polyisocyanate compounds selected from isocyanatoethyl-2,6-diisocyanatocaproate, wherein (b2) is an aromatic group having three or more isocyanate groups in one molecule and / or Or the thermosetting coating composition which is 1 or more types of polyisocyanate compounds chosen from the isocyanurate body of an alicyclic isocyanate, a burette body, and an adduct body is provided.
Further, the present invention provides the above thermosetting coating composition, wherein (b3) is one or more heterocyclic compounds selected from 3,5-dimethylpyrazole and 1,2,4-triazole, and (b4) Provided is a thermosetting coating composition which is one or more active methylene compounds selected from diethyl malonate and ethyl acetoacetate.

The thermosetting coating composition of the present invention can form a coating film excellent in acid resistance, scratch resistance and durability, and is excellent in recoat adhesion and storage stability.

The vinyl copolymer having a hydroxyl group and a carboxyl group having an acid value of 5 to 50 mgKOH / g and a hydroxyl value of 20 to 200 mgKOH / g used in the present invention is a hydroxyl group-containing vinyl monomer and a carboxyl group-containing vinyl. It can be obtained by copolymerizing a monomer and, if necessary, another vinyl monomer.
Specific examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and a hydroxyl group-containing vinyl monomer represented by the general formula (1). The body is mentioned.

（式中、Ｘは、それぞれ水素原子またはメチル基である。Ｒは炭素数３〜８のアルキレン基又はシクロアルキレン基である。）

(In the formula, each X is a hydrogen atom or a methyl group. R is an alkylene group or a cycloalkylene group having 3 to 8 carbon atoms.)

Specific examples of the hydroxyl group-containing vinyl monomer represented by the general formula (1) include (meth) acrylic acid, 1,4-butanediol, 1,4-hexanediol, 1,6-hexane. Examples thereof include monomers added with diols such as diols and 2,2-dimethyl-1,3-propiondiol. These hydroxyl group-containing vinyl monomers can be used alone or in combination of two or more.

When the vinyl copolymer having a hydroxyl group and a carboxyl group is a lactone-modified vinyl copolymer, the hydroxyl group-containing vinyl monomer used to produce the lactone-modified vinyl copolymer is 3- Hydroxyl-containing vinyl-based monomers such as hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate Examples include lactone-modified vinyl monomers in which lactones are ring-opened and added to the body.

Examples of the lactones include lactones such as ε-caprolactone, δ-valerolactone, γ-butyrolactone, and β-propionlactone.
The amount of lactone to be subjected to ring-opening addition can be produced by adding 1 to 5 mol per mol of the hydroxyl group-containing vinyl monomer. The number average molecular weight of the graft chain by lactone modification is preferably 100 to 600. When the number average molecular weight of the graft chain due to lactone modification is 100 or less, the scratch resistance of the cured coating film decreases, and when the number average molecular weight of the graft chain due to lactone modification is 600 or more, the solvent resistance of the coating film decreases. Lactones may be copolymerized after modifying the vinyl monomer, or modified after copolymerizing the vinyl monomer. The terminal of the graft chain by lactone modification is preferably a primary hydroxyl group that is a hydroxyl group bonded to the first carbon atom.
The hydroxyl group-containing vinyl monomer can be used alone or in combination of two or more.

Specific examples of the carboxyl group-containing vinyl monomer include acrylic acid and methacrylic acid. The carboxyl group-containing vinyl monomers can be used alone or in combination of two or more.
Other vinyl monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl- (meth) acrylate, i-propyl- (meth) acrylate, n-butyl (meth) acrylate, i- Butyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, i-pentyl (meth) acrylate, 2-methyl-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2- Methyl-pentyl (meth) acrylate, n-heptyl (meth) acrylate, 2-methyl-hexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl ( (Meth) acrylate, isoborni And alkyl esters or cycloalkyl esters having 1 to 24 carbon atoms of acrylic acid or methacrylic acid (meth) acrylate. Other styrenes such as styrene, α-methylstyrene, β-methylstyrene, alkyl styrene such as vinyl toluene, acrylonitrile, acrylamide, vinyl acetate, glycidyl (meth) acrylate, α, β-unsaturated carboxylic acid and Cardura E10 ( Trade names, shell petrochemicals) and adducts with monoepoxy compounds such as α-olefin epoxides.
Other vinyl monomers can be used singly or in combination of two or more.

As a method for polymerizing a hydroxyl group-containing vinyl monomer, a carboxyl group-containing vinyl monomer, and other vinyl monomers, a known method can be employed. For example, solution polymerization, non-aqueous dispersion Polymerization methods such as polymerization and bulk polymerization can be employed, and solution polymerization is particularly preferable.
The resin acid value of the vinyl copolymer (A) is 5 to 50 mgKOH / g, preferably 5 to 30 mgKOH / g, and more preferably 5 to 20 mgKOH / g. When the resin acid value is 5 mgKOH / g or less, the recoat adhesion is insufficient, and when the resin acid value is 50 mgKOH / g or more, the stability of the coating is lowered.

The hydroxyl value of the vinyl copolymer (A) is 20 to 200 mgKOH / g, preferably 40 to 160 mgKOH / g. When the hydroxyl value is less than 20 mgKOH / g, the solvent resistance of the cured coating film decreases, and when it exceeds 200 mgKOH / g, the weather resistance of the cured coating film decreases, which is not preferable.
The hydroxyl value of the primary hydroxyl group at the end of the graft chain by lactone modification is preferably 20 to 200 mgKOH / g, and particularly preferably 40 to 160 mgKOH / g.
In the present invention, the proportion of the various monomers used for producing the vinyl copolymer of component (A) is usually from 5 to 70% by mass, preferably 10%, of the hydroxyl group-containing vinyl monomer. -65 mass%, and the proportion of carboxyl group-containing vinyl monomer used is 0.5-7.0 mass%, preferably 0.6-3.0 mass%, and the use of other vinyl monomers. The ratio is 94.5 to 23% by mass, preferably 89.4 to 32% by mass.
In addition, as other vinyl-type monomers, C1-C20, Preferably it is 1-10, Most preferably, the ester of the methacrylic acid or acrylic acid of the alkyl alcohol of 1-7 is the total amount of all the monomers. A combination of 10 to 90% by mass, 5 to 20% by mass of the total amount of styrenes and 0 to 10% by mass of the total amount of other monomers is preferable.
(A) The weight average molecular weight of the vinyl copolymer of a component is 3000-30000, Preferably it is 4000-20000.

(B1) The aliphatic polyisocyanate compound having 3 or more isocyanate groups in one molecule, which is the blocked isocyanate compound of (B), isocyanurate of hexamethylene diisocyanate, burette of hexamethylene diisocyanate, hexa Methylene diisocyanate adducts, 2-isocyanatoethyl-2,6-diisocyanatocaproate and the like are preferred, and one or more isocyanate compounds selected from these can be used.

(B2) The aromatic polyisocyanate compound having 3 or more isocyanate groups in one molecule, which is a blocked isocyanate compound of (B), isocyanurate of tetramethylxylene diisocyanate, buret of tetramethylxylene diisocyanate An adduct of tetramethylxylene diisocyanate is preferred. Examples of the alicyclic polyisocyanate compound include isophorone diisocyanate isocyanurate, isophorone diisocyanate burette, isophorone diisocyanate adduct, 1,3-bis (isocyanatomethyl) cyclohexane isocyanurate, 1,3- Bis (isocyanatomethyl) cyclohexane burette, 1,3-bis (isocyanatomethyl) cyclohexane adduct, 1,4-bis- (isocyanatomethyl) -cyclohexane isocyanurate, 1,4-bis -(Isocyanatomethyl) -cyclohexane burette, 1,4-bis- (isocyanatomethyl) -cyclohexane adduct, bis (4-isocyanatocyclohexyl) methane isocyanurate, bis (4-isocyanate Preparative cyclohexyl) methane biuret body, bis (4-isocyanatocyclohexyl) adduct of methane and the like are preferable, it is possible to use one or more polyisocyanate compounds selected from these.

The heterocyclic compound (b3) which is a blocking agent for the blocked isocyanate compound (B) includes pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4- Pyrazole or pyrazole derivatives such as bromo-3,5-dimethylpyrazole, 3-methyl-5-phenylpyrazole, imidazole or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, 1,2,4 -Triazole and the like are preferred. The heterocyclic compound (b3) can be used alone or in combination of two or more.

As the active methylene compound of (b4) which is a blocking agent of the blocked isocyanate compound of (B), dimethyl malonate, diethyl malonate, dipropyl malonate, diisopropyl malonate, dibutyl malonate, methyl ethyl malonate, malonic acid Acetoacetic acid such as methyl propyl ester, malonic acid methyl butyl ester, malonic acid ethyl propyl ester, malonic acid ethyl butyl ester, etc., methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, isopropyl acetoacetate, butyl acetoacetate etc. Esters are preferred. The active methylene compound of (b4) can be used alone or in combination of two or more.

When the blocked isocyanate compounds (b1) and (b2) are blocked by the blocking agents (b3) and (b4), the equivalent ratio of isocyanate group to blocking agent is 0.95: 1.0. To 1.1: 1.0 to block at least 95% of the isocyanate groups of the polyisocyanate, preferably all isocyanate groups are blocked.
Usually, the blocking reaction is carried out at a temperature of 50 to 100 ° C. A catalyst can be used for the blocking reaction. Examples of the catalyst include metal alcoholates such as sodium methylate, sodium ethylate, sodium phenolate and potassium methylate, tetraalkylammonium hydroxide such as tetramethylammonium, tetraethylammonium and tetrabutylammonium, and acetates thereof. Organic weak acid salts such as octylate, myristic acid salt, benzoic acid salt, alkali metal salts of alkylcarboxylic acid such as acetic acid, caproic acid, octylic acid, myristic acid, and tin, zinc, lead of the above alkylcarboxylic acid, etc. And metal acyl salts, aminoacyl group-containing compounds such as hexamethylenedisilane, and alkali metal hydroxides such as lithium, sodium and potassium. A catalyst can also be used individually by 1 type and can also be used in combination of 2 or more type.

The mass ratio of the blocked isocyanate compounds (b1) and (b2) is preferably 20/80 to 80/20, more preferably 30/70 to 80/20, still more preferably 40/60 to 80/20. When the mass ratio of (b1) to (b2) is less than 20/80, the hardness of the coating film is insufficient, and when it is greater than 80/20, the scratch resistance of the coating film is insufficient. .
The molar ratio of (b3) to (b4), which is a blocking agent of the blocked isocyanate compound, is preferably 50/50 to 90/10, more preferably 60/40 to 90/10, and even more preferably 60/40 to 80/20. It is. When the molar ratio of (b3) to (b4) is less than 50/50, the curability and gasoline resistance of the coating film are insufficient, and when it is greater than 90/10, the recoat adhesion is insufficient. It is.

The molar ratio of the hydroxyl group of the vinyl copolymer having a hydroxyl group and a carboxyl group of the component (A) to the blocked isocyanate group of the blocked isocyanate compound of the component (B) is 1/2 to 2/1, preferably Is 1.2 / 2 to 1.9 / 1.
In addition to the above components, the thermosetting coating composition of the present invention can contain a blocked isocyanate group deblocking catalyst and an isocyanate group crosslinking reaction catalyst. For example, dibutyltin dilaurate, tin octylate, tetra-n-butyl-1,3-diacetyloxydistanoxane, dibutyltin fatty acid salts, dibutyltin bismaleic acid monoalkyl ester salts, dibutyltin diacetate, dibutyltin fatty acid salt oxides, monobutyltin Examples include fatty acid salts, bismuth-tris (2-ethylhexynol), bismuth octylate, zircon octylate, and the like. Each of the blocked isocyanate group deblocking catalyst and the isocyanate group crosslinking reaction catalyst may be used alone or in combination of two or more.

In addition to the above components, the thermosetting coating composition of the present invention includes benzotriazole-based UV absorbers, triazine-based UV absorbers, UV absorbers such as oxalic anilide-based UV absorbers, and hindered amine light stabilizers. Light stabilizers such as phenolic antioxidants, phosphite antioxidants, thioether antioxidants, antioxidants such as phosphites, organic resin fine particles, fatty acid amide waxes, polyamide waxes, polyethylenes Wax, oxidized polyethylene wax, silica, organic bentonite, viscosity modifier such as urea compound viscosity modifier, surface modifier such as silicone surface modifier, vinyl compound surface modifier, silicone antifoam, vinyl compound Antifoaming agent such as an antifoaming agent, acidic phosphoric acid ester-based curing catalyst or sulfonic acid-based curing catalyst, Additives such as metal chelating agents such as tilacetone and benzotriazole, and polyurethane resin stabilizers such as HN-130, HN-150, and HN-300P (trade name, manufactured by Nippon Hydrazine Industry Co., Ltd.) can do.

  Further, as coloring pigments, inorganic coloring pigments such as titanium oxide, zinc white, yellow iron oxide, red iron oxide, carbon black, phthalocyanine blue, selenium blue, phthalocyanine green, insoluble azo, soluble azo, perylene, quinacridone red, thio Organic coloring pigments such as indigo red, dioxazine violet, anthrapyrimidine yellow, quinophthalone yellow, benzidine yellow, etc., aluminum powder, nickel powder, pearl mica powder, colored aluminum flake pigment, metal oxide coated aluminum flake pigment, vapor deposition Aluminum flake pigment, metal oxide coated mica pigment, metal oxide coated synthetic mica pigment, metal oxide coated alumina flake pigment, metal oxide coated silica flake pigment, metal oxide coated plate iron oxide, stainless steel Lake, can be formulated metallic titanium flake pigment, a plate-like molybdenum sulfide, plate-like bismuth chloride, plate-like iron oxide, and the cholesteric liquid crystal polymer or the like. In addition, calcium carbonate, talc, precipitated barium sulfate, and the like can be blended as extender pigments. These pigments may be used alone or in combination of two or more.

  Furthermore, an organic solvent can be mix | blended with the thermosetting coating composition of this invention. Specific examples of the organic solvent include aromatics such as toluene, xylene, ethylbenzene, aromatic petroleum naphtha, Solvesso # 100 (Exxon Chemical Co., Ltd. registered trademark), Solvesso # 150 (Exxon Chemical Co., Ltd. registered trademark), and the like. Hydrocarbons, aliphatic hydrocarbons such as hexane, heptane and octane, alicyclic hydrocarbons such as cyclohexane, ethers such as dioxane and tetrahydrofuran, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, Alcohols such as 2-butanol, 2-ethylhexanol, methyl isobutyl carbinol, butyl cellosolve, 3-methoxybutanol, 3-methyl-3-methoxybutanol, methyl carbitol, carbitol, butyl carbitol, propylene glycol Ether alcohols such as methyl ether and dipropylene glycol monomethyl ether, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, propylene glycol monomethyl ether acetate, methoxybutyl acetate, n-propionic acid Esters and ether esters such as butyl and n-pentyl propionate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl n-amyl ketone, cyclohexanone, isophorone, methyl isoamyl ketone, ethyl n-butyl ketone, ethyl n-butyl ketone, ethyl n-amyl ketone , Ketones such as diisobutyl ketone, diethyl ketone, methyl propyl ketone, diisopropyl ketone, dimethyl sulfoxide, N, N-dimethylform Bromide, and the like. An organic solvent may be used individually by 1 type and may combine 2 or more types.

Further, the thermosetting coating composition of the present invention can be dispersed in water and used as an aqueous dispersion.
In the thermosetting resin composition of the present invention, the component (A), the component (B), and other components to be blended as necessary are blended at a blending ratio so as to be the blending amount, and using a usual paint mixing means. It can manufacture by mixing by a conventional method.
The thermosetting coating composition of the present invention can be used as a top coating applied to an object to be coated such as a metal material or a resin material. The thermosetting coating composition of the present invention is applied as it is as an overcoat on the object to be coated, or is applied onto the undercoat or intermediate coat. As the coating specifications, one-coat coating alone, two-coat coating in combination with a base coat, three-coat coating, or overcoat coating on a normal top coat film is possible. As the paint used for the base coat to be combined, any form of paint such as acrylic resin-based or polyester resin-based (including alkyd resin-based) solvent-based paints, solvent-based high solid paints, and water-based paints can be used. The thermosetting coating composition of the present invention can be used as a clear coating or as an enamel coating containing a pigment or a glittering material.
In addition, as a coating material used for the base coat for recoat, the same thing as the coating material used for said base coat is mentioned.

The coating film thickness is preferably about 10 to 60 μm in terms of dry film thickness, and the baking conditions for curing the coating film are preferably about 100 to 180 ° C. and time of about 10 to 120 minutes.
The thermosetting coating composition of the present invention is applied by the usual coating method, for example, air spray, airless spray, electrostatic coating, dip coating, etc. so as to have the dry film thickness, and is cured under the baking conditions. A coating film can be formed.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. Unless otherwise specified, “parts” and “%” mean “parts by mass” and “% by mass”, respectively.
Production Examples 1 to 9 (vinyl copolymers A-1 to 9 having a hydroxyl group and a carboxyl group)
A four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a dropping funnel was charged with the amounts of xylene shown in Tables 1 and 2, respectively, and the temperature was raised to 140 ° C. Subsequently, the vinyl monomer and the polymerization initiator mixture described in Tables 1 and 2 were dropped from the dropping funnel over 2 hours. After completion of dropping, the content was cooled to 100 ° C. while maintaining the reflux temperature for 1 hour. After cooling to 100 ° C., the polymerization initiators listed in Tables 1 and 2 were added dropwise over 30 minutes. Thereafter, the polymerization reaction was terminated when kept at a temperature of 100 ° C. for 3 hours, and vinyl copolymers A-1 to 9 having hydroxyl groups and carboxyl groups having the characteristics shown in Tables 1 and 2, respectively.
Solution was obtained.

* 1 PLACCEL FM-4: manufactured by Daicel Chemical Industries, Ltd. A monomer obtained by adding 4 mol of ε-caprolactone to 1 mol of hydroxyethyl methacrylate.
* 2 t-Butyl peroxybenzoate: Product name “Perbutyl Z” manufactured by NOF Corporation

Production Examples 10 to 20 (Blocked isocyanate B-1 to 5, C-1 to 6)
A reactor equipped with a thermometer, a reflux condenser, and a stirrer was charged with xylene, isocyanate, and a blocking agent described in Tables 3 and 4, and the catalysts described in Tables 3 and 4 were added in a stirred state to 100 ° C. The temperature rose. After maintaining at 100 ° C. for 3 hours and confirming the disappearance of the isocyanate group by IR, the solvent was removed while replacing toluene with Solvesso # 100, and the blocked isocyanate B- having the characteristics described in Tables 3 and 4 was used. 1 to 5 and C1 to 6 were obtained.

* 3 Death Module N3200: manufactured by Sumitomo Bayer Urethane Co., Ltd., solid content = 100%, NCO (%) = 23.0
* 4 Death Module Z4470SN: manufactured by Sumitomo Bayer Urethane Co., Ltd., solid content = 70%, NCO (%) = 11.8
* 5 3,5-dimethylpyrazole: manufactured by Wako Pure Chemical Industries, Ltd. * 6 diethyl malonate: manufactured by Wako Pure Chemical Industries, Ltd. * 7 sodium methylate: manufactured by Wako Pure Chemical Industries, Ltd.

(Examples 1-13 and Comparative Examples 1-12)
a) Creation of clear paint
Clear paints having the compositions shown in Tables 5 to 8 were prepared, and the clear paints were treated with a thinner having a composition of Solvesso # 100 / n-butanol = 90/10 (weight ratio) for 25 seconds (Ford Cup # 4/20 C.) viscosity was adjusted. This paint was applied by the following method to form a paint film, and the paint film performance was tested.

* 8 Tinuvin 384: Benzotriazole UV absorber, manufactured by Ciba Geigy * 9 Tinuvin 292: Hindered amine radical scavenger, manufactured by Ciba Geigy * 10 BYK306: Leveling agent, manufactured by Big Chemie * 11 Solvesso 100: Aromatic hydrocarbon, Exon Made by Chemical Co., Ltd.

(B) Formation of coating film As a cationic electrodeposition coating on zinc phosphate-treated mild steel sheet, “Aqua No. 4200” manufactured by NOF BASF Coatings Co., Ltd. was electrodeposited so as to have a dry film thickness of 20 μm. Baking at 175 ° C. for 25 minutes, and “Hi-Epico No. 560 sealer” manufactured by Nippon Oil & Fats BASF Coatings Co., Ltd. as an intermediate coating, air sprayed to a dry film thickness of 40 μm and baking at 140 ° C. for 30 minutes. A painted plate was obtained. On this intermediate coating plate, as an aqueous base coat paint, “Aqua BC-3 Black” manufactured by Nippon Oil & Fats BASF Coatings Co., Ltd. is air sprayed to a dry film thickness of 15 μm and flashed at 80 ° C. for 10 minutes. Each clear paint shown in a) and a) was air spray coated to a dry film thickness of 40 μm and baked at 140 ° C. for 30 minutes. The coating film performance evaluation test of each obtained test board was conducted. The results are shown in Tables 9-10.

Coating Film Performance Evaluation Method (1) Acid resistance: 0.2 ml of 40% sulfuric acid aqueous solution was spotted on a test plate, heated at 60 ° C. for 15 minutes, then washed with water and visually observed for the degree of occurrence of spot marks.
○: Almost no change is observed in the coating film.
Δ: Slight traces of water spots are seen.
X: A remarkable water spot is seen.

(2) Scratch resistance: After applying muddy water (JIS Z-8901-84, 8 types of dust / water / neutral detergent = 10/99/1 weight ratio) on the test plate by brush, car wash The car wash brush is rotated at 150 rpm for 10 seconds with a machine, and the test plate is washed with running water. After the above operation was repeated twice, the L ^* value was measured with a color difference meter (manufactured by CR-331 Minolta Camera Co., Ltd.) for the degree of abrasion on the surface of the test plate. The ΔL ^* value was calculated by the following formula, and the scratch resistance was evaluated from the value.

ΔL ^* value = after the test ^{L *} value - before the test ^{L *} value ◎: ΔL ^* value of less than 2.
○: ΔL ^* value is 2 or more and less than 3.
Δ: ΔL ^* value is 3 or more and less than 4.
X: ΔL ^* value is 4 or more.

(3) Moisture resistance: The test plate was visually observed for 120 hours after being placed in a sealed container having a temperature of 50 ± 1 ° C. and a relative humidity of 98% or more.
○: Almost no change is observed in the coating film.
Δ: Swelling (diameter 0.2 mm or more) is observed in the coating film.
X: Many blisters (diameter 0.2 mm or more) are seen in the coating film.
(4) Gasoline resistance: After immersing the test plate in regular gasoline at 20 ° C. for 7 hours, the state of the coated surface was observed.
○: No abnormality Δ: Slight swelling of the coating film is observed.
X: Swelling and discoloration peeling of the coating film are remarkable.

(5) Pencil hardness: The coating film hardness was measured by a JIS K5600 (1999) 5.4 testing method, and the coating film was evaluated for scratches.
○: HB or more ×: B or less (6) Recoat adhesion: The basecoat paint and the clearcoat paint are once again applied to the test plate obtained by applying the basecoat paint and the clearcoat paint by the above coating method. After painting and baking under conditions, JIS
According to the K-5400 (1990) 8.5 adhesion test, the peeling state of the coating film was visually observed.
○: No abnormality ×: There is peeling (7) 60 ° specular gloss: According to 60 ° specular gloss of JIS K-5600 (1999) 4.7.

(8) Accelerated weather resistance: BYK MICRO-GLOSS (manufactured by Big Chemie) is used for the 60-degree gloss after the test plate is tested for 3000 hours with a sunshine carbon arc lamp type (JIS K-5400 (1990) 9.8.1). And measured by gloss retention.
A: Gloss retention exceeds 95%.
○: Gloss retention is 90 to 95%.
X: The gloss retention is less than 90%.
(9) Storage stability: The obtained thermosetting composition was put in a 250 ml container and stored in an atmosphere of 40 ° C. for 7 days, and then the thickening seconds of the thermosetting composition were measured and evaluated according to the following criteria. .
○: Less than 3 seconds.
Δ: 3 to 8 seconds.
X: Over 8 seconds.

Examples 1 to 13 showed an automotive top coating excellent in acid resistance, scratch resistance, weather resistance, and recoat adhesion. In Comparative Examples 1 and 2, since the ratio of the vinyl copolymer having a hydroxyl group and a carboxyl group to the blocked isocyanate was not appropriate, moisture resistance, gasoline resistance and weather resistance were lowered. In Comparative Example 3, since the amount of isocyanate blocked with the active methylene compound was low, the recoat adhesion decreased. In Comparative Example 4, the gasoline resistance was lowered because the amount of isocyanate blocked with the heterocyclic compound was low. In Comparative Example 5, the pencil hardness decreased because the amount of the aliphatic polyisocyanate compound was too high. In Comparative Example 6, since the amount of the aromatic and / or alicyclic polyisocyanate compound was too high, the scratch resistance was lowered. In Comparative Example 7, since the amount of isocyanate blocked with the heterocyclic compound was too high, the recoat adhesion decreased. In Comparative Example 8, the storage stability was lowered because the amount of isocyanate blocked with active methylene was too high. In Comparative Example 9, gasoline resistance was lowered because the hydroxyl value of the vinyl copolymer having a hydroxyl group and a carboxyl group was too low. In Comparative Example 10, since the hydroxyl group of the vinyl copolymer having a hydroxyl group and a carboxyl group was too high, the weather resistance was lowered. In Comparative Example 11, since the acid value of the vinyl copolymer having a hydroxyl group and a carboxyl group was too low, the recoat adhesion decreased. In Comparative Example 12, the storage stability decreased because the acid value of the vinyl copolymer having a hydroxyl group and a carboxyl group was too high.

  The thermosetting coating composition of the present invention can be used in various coating fields such as the automotive coating field.

Claims (5)

(A) Thermosetting containing a hydroxyl group having a hydroxyl value of 20 to 200 mgKOH / g and an acid value of 5 to 50 mgKOH / g, a vinyl copolymer having a carboxyl group and a carboxyl group, and (B) a blocked isocyanate compound as essential components. A coating composition comprising:
(B) The isocyanate compound of the blocked isocyanate compound as the component is (b1) an aliphatic polyisocyanate compound having three or more isocyanate groups in one molecule, and (b2) three or more isocyanate groups in one molecule. An aromatic and / or alicyclic polyisocyanate compound, and the blocking agent for blocking the isocyanate compound is (b3) a heterocyclic compound and (b4) an active methylene compound, The mass ratio of the solid content of (b1) and (b2) is 20/80 to 80/20, and the molar ratio of the blocking agent (b3) to (b4) is 50/50 to 90/10, (A) Hydroxyl group of vinyl copolymer having hydroxyl group and carboxyl group of component and block isocyanate conversion of component (B) The molar ratio of blocked isocyanate groups of things, thermosetting coating composition which is a 1 / 2-2 / 1. A vinyl copolymer having a hydroxyl group and a carboxyl group having a hydroxyl value of (A) of 20 to 200 mgKOH / g and an acid value of 5 to 50 mgKOH / g is represented by the formula (1).

2. The copolymer according to claim 1, wherein X is a hydrogen atom or a methyl group, and R is an alkylene group or cycloalkylene group having 3 to 8 carbon atoms. Thermosetting paint composition. The vinyl copolymer having a hydroxyl group and a carboxyl group in (A) is a lactone-modified vinyl copolymer, the number average molecular weight of the graft chain by lactone modification is 100 to 600, and the primary hydroxyl group is by lactone modification. The thermosetting coating composition according to claim 1, which is present at the end of the graft chain. (B1) is an isocyanurate body, burette body and adduct body of an aliphatic isocyanate having 3 or more isocyanate groups in one molecule, and 2-isocyanatoethyl-2,6-diisocyanatocaproate And (b2) is an isocyanurate body, a burette body of an aromatic and / or alicyclic isocyanate having 3 or more isocyanate groups in one molecule, and The thermosetting coating composition according to claim 1, which is one or more polyisocyanate compounds selected from adduct bodies.
(B3) is at least one heterocyclic compound selected from 3,5-dimethylpyrazole and 1,2,4-triazole, and (b4) is at least one activity selected from diethyl malonate and ethyl acetoacetate. The thermosetting coating composition according to claim 1 or 3, which is a methylene compound.