JP6696715B2 - Paint composition - Google Patents

Description

  The present invention relates to a coating composition having excellent coating stability and capable of forming a coating film having good low temperature curability, coating film hardness, specular gloss, impact resistance, weather resistance, corrosion resistance, alkali resistance and acid resistance. ..

  Various coating compositions are used for driver's cabs and luggage racks in industrial transport vehicles such as trucks. However, when baking and drying the coating film, 1. 1. The heat capacity of the object to be coated is large, the heat of the drying oven is not sufficiently transferred to the object to be coated, and low temperature curability is required. Since it is used outdoors in a harsh environment, there are problems such as further requirements for corrosion resistance, alkali resistance and acid resistance.

  Conventionally, for example, in Patent Document 1, (A) a hydroxyl group-containing resin selected from a hydroxyl group-containing acrylic resin and a hydroxyl group-containing polyester resin, (B) an amino resin and (C) a blocked polyisocyanate compound are the main components. A thermosetting coating composition is disclosed. However, with the coating composition described in Patent Document 1, it was difficult to obtain good coating performance in low temperature baking.

  Patent Document 2 discloses a coating composition containing a hydroxyl group-containing synthetic resin (A), an amino resin (B), an active methylene blocked polyisocyanate (C) and a pigment (D). However, the coating composition described in Patent Document 2 can obtain coating film performance by baking at 140 ° C., but cannot obtain sufficient coating film performance by baking at 110 ° C. The alkalinity and acid resistance were insufficient.

JP-A-2-242867 Japanese Patent Publication No. 9-503796

  The problem to be solved by the present invention is to provide a coating composition which is excellent in coating stability and which can obtain good coating performance in low temperature baking.

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by using a coating composition containing a specific fatty acid-modified resin (A), an imino group-containing melamine resin (B) and an active methylene-blocked polyisocyanate compound (C). The inventors have found that a solution can be achieved and completed the present invention.

That is, the present invention is
A coating composition containing a fatty acid-modified resin (A) having an oil length of 1.5 to 40% by mass, an imino group-containing melamine resin (B), and an active methylene-blocked polyisocyanate compound (C), wherein 60 to 85 parts by mass of the fatty acid-modified resin (A) and 9 to 30 parts by mass of the imino group-containing melamine resin (B), based on the total mass of the solid contents of the component (A), the component (B) and the component (C). A coating composition containing 3 to 15 parts by mass of the active methylene-blocked polyisocyanate compound (C), and B component / C component = 1.0 to 3.0 (mass ratio),
Based on the total solid content of 100 parts by mass of the fatty acid-modified resin (A) having an oil length of 2.5 to 40% by mass, the imino group-containing melamine resin (B) and the active methylene-blocked polyisocyanate compound (C), The coating composition according to item 1, which contains 0.1 to 10 parts by mass of fumed silica (D),
3. 10 to 150 parts by mass of titanium dioxide having the following characteristics based on 100 parts by mass of the total solid content of the fatty acid-modified resin (A), the imino group-containing melamine resin (B) and the active methylene blocked polyisocyanate compound (C). 1. The coating composition according to 1 or 2,
Titanium dioxide: Titanium dioxide that has been subjected to at least two types of surface treatments of silicon dioxide and aluminum oxide, and 1.0 to 8.0 mass% of silicon dioxide and aluminum oxide based on the solid content of the titanium dioxide. 3. Titanium dioxide pigment surface-treated at a rate of 0 to 4.5% by mass. The coating composition according to any one of 1 to 3, wherein the fatty acid-modified resin (A) is a fatty acid-modified polyester resin,
5. On a metal plate, which may be subjected to a chemical conversion treatment, with or without a primer coating film, a coating film of the coating composition according to any one of items 1 to 4 is formed thereon. A method for forming a coating film to be formed,
6. On a metal plate, which may be subjected to a chemical conversion treatment, with or without a primer coating film, a coating film of the coating composition according to any one of items 1 to 4 is formed thereon. A method for forming a coating film, which comprises forming and further forming at least one coating film on the coating film,
A coated article obtained by the method for forming a coating film according to item 7.5 or 6.

  The coating composition of the present invention is excellent in coating stability and can obtain good coating performance in low temperature baking. Specifically, since it can be sufficiently cured by baking at 1.110 ° C. for 20 minutes, it can be applied to an object having a large heat capacity. 2. A coating film having excellent corrosion resistance, alkali resistance, and acid resistance can be formed, which is also useful for outdoor use. Furthermore, the effect of the invention is that a coating film having excellent coating film hardness, specular gloss, impact resistance and weather resistance can be provided. Specifically, it is suitable as a coating composition for metal members such as car bodies and parts.

The present invention is a coating composition containing a fatty acid-modified resin (A) having an oil length of 5 to 40% by mass, an imino group-containing melamine resin (B) and an active methylene-blocked polyisocyanate compound (C) in specific amounts. .. The details will be described below.

Fatty acid-modified resin (A) having an oil length of 5 to 40% by mass: a fatty acid-modified resin (A) (having an oil length of 5 to 40% by mass (preferably 10 to 40% by mass) in the coating composition of the present invention. Hereinafter, the fatty acid-modified resin (A) may be abbreviated) and has excellent compatibility with the imino group-containing melamine resin (B) and the active methylene-blocked polyisocyanate compound (C), and in the obtained coating film. , Is an essential component for anticorrosion, alkali resistance and acid resistance.

  Examples of the fatty acid-modified resin (A) include fatty acid-modified polyester resin, fatty acid-modified acrylic resin and fatty acid-modified epoxy resin. In particular, in order to achieve the object of the present invention, it is desirable to use a fatty acid-modified polyester resin.

  As the fatty acid-modified acrylic resin, for example, a resin obtained by copolymerizing a fatty acid-modified acrylic-based monomer and another unsaturated monomer can be used. The fatty acid-modified polyester resin will be described below.

Fatty Acid-Modified Polyester Resin As the above-mentioned fatty acid-modified polyester resin, a resin obtained by adding a fatty acid and / or a fat and oil and reacting during the preparation of the polyester resin, or after the esterification reaction or after the transesterification reaction can be used. In addition, a resin obtained by reacting with a radically polymerizable unsaturated monomer added during the preparation of the above-mentioned resin, or after the esterification reaction or after the transesterification reaction can be used, if necessary. Examples of the radically polymerizable unsaturated monomer include monomers having a vinyl group, a (meth) acryloyl group, and the like.

Polyester Resin The polyester resin can be usually produced by an esterification reaction or a transesterification reaction with a polybasic acid component and a polyhydric alcohol component. As the polybasic acid component, for example, an alicyclic polybasic acid component, an aliphatic polybasic acid component, an aromatic polybasic acid component or the like can be used.

  As the alicyclic polybasic acid component, generally, a compound having at least one alicyclic structure (mainly a 4- to 6-membered ring) and at least two carboxyl groups in one molecule, an acid anhydride of the compound And an esterified product of the compound. Examples of the alicyclic polybasic acid component include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 3- Alicyclic polycarboxylic acid such as methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid An anhydride of these alicyclic polyvalent carboxylic acids; a lower alkyl ester of these alicyclic polycarboxylic acids, and the like. The alicyclic polybasic acid components can be used alone or in combination of two or more.

  As the alicyclic polybasic acid component, particularly, 1,2-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid anhydride, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene- 1,2-dicarboxylic acid and 4-cyclohexene-1,2-dicarboxylic acid anhydride can be preferably used. Of the above, 1,2-cyclohexanedicarboxylic acid and 1,2-cyclohexanedicarboxylic anhydride can be particularly preferably used from the viewpoint of hydrolysis resistance.

  The above-mentioned aliphatic polybasic acid component is generally an aliphatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aliphatic compound, and an esterified product of the aliphatic compound. Acids, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, octadecanedioic acid, citric acid and other aliphatic polycarboxylic acids; these aliphatic polycarboxylic acids An anhydride of a carboxylic acid; a lower alkyl ester of these aliphatic polycarboxylic acids, and the like. The aliphatic polybasic acid components can be used alone or in combination of two or more.

As the aliphatic polybasic acid component, it is preferable to use a dicarboxylic acid having an alkylene chain having 4 to 18 carbon atoms. Examples of the dicarboxylic acid having an alkylene chain having 4 to 18 carbon atoms include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid and octadecanedioic acid. Among them, adipic acid can be preferably used.
The aromatic polybasic acid component is generally an aromatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aromatic compound, and a lower alkyl ester compound of the aromatic compound, For example, aromatic polyvalent carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, 4,4′-biphenyldicarboxylic acid, trimellitic acid, pyromellitic acid; anhydrides of these aromatic polyvalent carboxylic acids A lower alkyl ester compound of these aromatic polyvalent carboxylic acids and the like. The aromatic polybasic acid components can be used alone or in combination of two or more.

  As the polyhydric alcohol component, a polyhydric alcohol having two or more hydroxyl groups in one molecule can be preferably used. Examples of the polyhydric alcohol include alicyclic diols, aliphatic diols, aromatic diols, and trivalent or higher polyhydric alcohols.

  The alicyclic diol is generally a compound having at least one alicyclic structure (mainly a 4- to 6-membered ring) and two hydroxyl groups in one molecule. Examples of the alicyclic diol include dihydric alcohols such as 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, hydrogenated bisphenol A and hydrogenated bisphenol F; and divalent alcohols such as ε-caprolactone. Examples thereof include polylactone diols having a lactone compound added, and these can be used alone or in combination of two or more kinds.

  The above aliphatic diol is generally an aliphatic compound having two hydroxyl groups in one molecule. Examples of the aliphatic diol include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, and 2,3. -Butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, 1,5-pentanediol 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3 -Pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,12- Examples thereof include dodecanediol, neopentyl glycol; polyether diol compounds such as polyethylene glycol, polypropylene glycol and polybutylene glycol. These can be used alone or in combination of two or more.

  The aromatic diol is generally an aromatic compound having two hydroxyl groups in one molecule. Examples of the aromatic diol include ester diol compounds such as bis (hydroxyethyl) terephthalate; alkylene oxide adducts of bisphenol A, and the like, and these can be used alone or in combination of two or more.

  Examples of the trihydric or higher polyhydric alcohol include glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, sorbitol, and mannitol. Trihydric or higher alcohol; polylactone polyol compound obtained by adding a lactone compound such as ε-caprolactone to these trihydric or higher alcohols; tris (2-hydroxyethyl) isocyanurate, tris (2-hydroxypropyl) isocyanurate, Examples thereof include tris (hydroxyalkyl) isocyanurate such as tris (2-hydroxybutyl) isocyanurate. Of these, trimethylolpropane is particularly preferable.

The production of the polyester resin is not particularly limited and can be carried out according to a usual method. For example, an acid component containing the polybasic acid component as an essential component and a polyhydric alcohol component are reacted in a nitrogen stream at 150 to 250 ° C. for 5 to 10 hours to perform an esterification reaction or a transesterification reaction. can do.
In the esterification reaction or transesterification reaction, the acid component and the alcohol component may be added at once, or may be added in several times. Further, after synthesizing the carboxyl group-containing polyester resin first, a part of the carboxyl groups in the carboxyl group-containing polyester resin may be esterified by using the alcohol component. Further, after the polyester resin is first synthesized, the acid anhydride may be reacted to half-esterify the polyester resin.

In the esterification or transesterification reaction, a catalyst may be used to accelerate the reaction. As the catalyst, known catalysts such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate and tetraisopropyl titanate can be used.
The fatty acid-modified resin (A) is obtained by adding a fatty acid, an oil and fat, and if necessary, a radically polymerizable unsaturated monomer during the preparation of the polyester resin, or after the esterification reaction or after the transesterification reaction, and reacting them. Resins can be used.

Fatty acids As the fatty acid, for example, coconut oil fatty acid, cottonseed oil fatty acid, hempseed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, dehydration Fatty acids such as castor oil fatty acid and safflower oil fatty acid; lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid and the like can be mentioned.

Fats and Oils Examples of the fats and oils include coconut oil, cottonseed oil, hempseed oil, rice bran oil, fish oil, tall oil, soybean oil, linseed oil, tung oil, rapeseed oil, castor oil, dehydrated castor oil, safflower oil and the like. The oil length of the obtained fatty acid-modified resin (A) is required to be in the range of 10 to 40% by mass, preferably 15 to 35% by mass from the viewpoint of coating film hardness, alkali resistance and corrosion resistance. is there.

  Further, the hydroxyl value is in the range of 30 to 200 mgKOH / g, preferably 10 to 100 mgKOH / g. The acid value is 30 mgKOH / g or less, preferably 1 to 20 mgKOH / g. The number average molecular weight is 1,000 or more and 7,000 or less, preferably in the range of 1,200 or more and 4,000 or less. The above range is also desirable from the viewpoint of coating film hardness, alkali resistance and corrosion resistance.

  Here, the “number average molecular weight” in the specification is a value calculated based on the molecular weight of standard polystyrene from a chromatogram measured by gel permeation chromatography according to the method described in JIS K 0124-83. As the gel permeation chromatograph, “HLC8120GPC” (manufactured by Tosoh Corporation) was used. As the column, four columns of "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL" and "TSKgel G-2000HXL" (both manufactured by Tosoh Corporation, trade names) were used, and mobile phase: tetrahydrofuran Measurement temperature: 40 ° C., flow rate: 1 ml / min, detector: RI.

Imino group-containing melamine resin (B)
The imino group-containing melamine resin (B) is a melamine resin that essentially contains an imino group in one molecule thereof, and usually, in addition to the imino group (—NH), a methylol group (—CH ₂ OH) and / or It is a melamine resin having an alkyl ether group (—CH ₂ OR) [wherein, for example, R is an alkyl group having 1 to 7 carbon atoms].

  In the imino group-containing melamine resin (B), it is desirable that the average number of imino groups is 0.3 to 3.5, and preferably 1.0 to 3.5 in one molecule. The weight average molecular weight of the imino group-containing melamine resin (B) is preferably in the range of 200 to 4,000, preferably 250 to 3,000, from the viewpoint of curability and corrosion resistance.

Examples of commercially available imino group-containing melamine resin (B) include U-VAN 125 (manufactured by Mitsui Chemicals, Inc., trade name), U-VAN 225 (manufactured by Mitsui Chemicals, Inc., trade name), Cymel 254, Cymel 325, Cymel 327, Cymel 701, Cymel 703 (manufactured by Daicel Ornex, Inc., trade name), Mycoat 508 (manufactured by Daicel Ornex, Inc., trade name), Super Beckamine L-116, Super Beckamine ME-44P, Super Beckamine ME-609P. (These are the product names manufactured by DIC Co., Ltd.) and the like. The imino group-containing melamine resins (B) can be used alone or in combination of two or more.

Further, in order to accelerate the curing reaction involving the imino group-containing melamine resin (B), a curing catalyst can be used if necessary. Generally, a sulfonic acid compound, a neutralized product of a sulfonic acid compound, a phosphoric acid compound, or the like can be used as a curing catalyst for promoting the curing reaction.

Examples of the sulfonic acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid,
Examples thereof include dinonylnaphthalene sulfonic acid and dinonyl naphthalene disulfonic acid. Examples of the neutralizing agent in the neutralized product of the sulfonic acid compound include primary compounds such as primary amine, secondary amine, tertiary amine, ammonia, caustic soda, and caustic potash.

Active methylene-blocked polyisocyanate compound (C)
The active methylene-blocked polyisocyanate compound (C) is obtained by reacting a polyisocyanate compound (c1) having at least two or more isocyanate groups in one molecule with an active methylene compound (c2). A polyisocyanate compound partially blocked with an active methylene compound can be used.

Polyisocyanate compound (c1)
Examples of the polyisocyanate compound (c1) include diphenylmethane-4,4′-diisocyanate (MDI), 1,5-naphthalene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate, 1,4-tetramethylene diisocyanate, 2-Methyl-1,5-diisocyanate pentane (MPDI), 1,6-diisocyanate hexane (HDI), 2,2,4-trimethyl-1,6-hexamethylene diisocyanate (TMDI), lysine diisocyanate, 1-isocyanate- 3,5,5-Trimethyl-3- (isocyanatomethyl) cyclohexane (IPDI), dicyclohexylmethane-4,4'-diisocyanate (HMDI), m-tetramethylxylylene diisocyanate (TMXDI), diisocyanate norbornane, di (isocyanatomethyl) ) C4 to C25 diisocyanates such as norbornane; C6 to C30 triisocyanates such as 2- (isocyanatoethyl) -2,6-diisocyanate caproate (LTI); these di or triisocyanates Of polyfunctional hydroxyl group-containing compound or monofunctional alcohol or water; these di- or triisocyanates; or urethane structure-containing polyisocyanate, biuret structure-containing polyisocyanate, isocyanurate structure-containing derivative derived from the addition product Polyisocyanates, allophanate structure-containing polyisocyanates, uretdione structure-containing polyisocyanates, etc., having a number average molecular weight of 300 to 20,000 and an average isocyanate functional group number of 2 to 100 in one molecule; (meth) Acryloyl isocyanate, 2-isocyanatoethyl (meth) acrylate, m-isopropenyl-α, α'-dimethylbenzyl isocyanate, isocyanate group-containing vinyl type such as 1: 1 addition product of hydroxyl group-containing vinyl type monomer and the above diisocyanates The number average molecular weight is 1,000 to 20,000, which is obtained by homopolymerizing a monomer or copolymerizing the vinyl monomer containing an isocyanate group with another vinyl monomer such as a (meth) acrylic acid ester or a vinyl aromatic compound. And polyisocyanates having an average number of isocyanate functional groups in one molecule of 2 to 100; and the like, and these may be used alone or in combination of two or more.

  Among these polyisocyanate compounds (c1), isocyanurate type polyisocyanates of diisocyanates or isocyanurate type polyisocyanates of adducts of diisocyanates with polyfunctional hydroxyl group-containing compounds, monofunctional alcohols or water are particularly preferable. .. The modification with a polyfunctional hydroxyl group-containing compound, a monofunctional alcohol or water is a urethanization reaction with an isocyanate group, and can be performed either before or after the polyisocyanate isocyanurate reaction. A catalyst may be used for the isocyanurate-forming reaction.

  Examples of the catalyst include basic compounds such as metal hydroxides, metal alkoxides, metal carboxylates, metal acetylacetonates, hydroxides of onium salts, onium carboxylates, metal salts of active methylene compounds, and onium salts of active methylene compounds. Lewis acids such as organic tin compounds are preferable. As the onium salt, an ammonium salt, a phosphonium salt or a sulfonium salt is preferable.

  The amount of the above catalyst is usually 10 to 10,000 ppm, preferably 20 to 5,000 ppm relative to the isocyanate compound. The reaction can be carried out at 0 ° C to 150 ° C. If the reaction proceeds as intended, the basic compound of the catalyst may be neutralized by adding an acid to stop the reaction. Unreacted isocyanates may be removed after the completion of the isocyanurate-forming reaction.

  The polyfunctional hydroxyl group-containing compound is a polyol having a number average molecular weight of 60 to 10,000 and having two or more hydroxyl groups in one molecule, and examples thereof include ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, butane. Diol, polytetramethylene glycol, methylpropanediol, pentanediol, methylpentanediol, hexanediol, neopentylglycol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3- Propanediol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, hydroxypivalic acid-neopentyl glycol Compounds having two or more hydroxyl groups in one molecule such as ester, dimethylolpropanoic acid, dimethylolbutanoic acid, trimethylolethane, trimethylolpropane, trimethylolbutane, glycerin and pentaerythritol; these compounds, ethylene oxide and propylene At least one ring-opening adduct selected from oxides, tetrahydrofuran, lactones and cyclocarbonates; reaction product of a compound having both an amino group and a hydroxyl group in one molecule with an epoxy group-containing compound, an amino group in one molecule Examples thereof include reaction products of a compound having both hydroxyl groups and polyisocyanate, hydroxyl group-containing polyesters, hydroxyl group-containing polyurethanes, hydroxyl group-containing vinyl copolymers, epoxy resins and the like.

Active methylene compound (c2)
Examples of the active methylene compound (c2) include dimethyl malonate, diethyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, disec-butyl malonate, di-t-butyl malonate, and malon. Acid di (2-ethylhexyl), methyl isopropyl malonate, ethyl isopropyl malonate, methyl n-butyl malonate, ethyl n-butyl malonate, methyl isobutyl malonate, ethyl isobutyl malonate, methyl sec-butyl malonate, malon Malonic acid diesters such as ethyl sec-butyl acetate; acetoacetic acid esters such as methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, isobutyl acetoacetate, sec-butyl acetoacetate, t-butyl acetoacetate Examples include β-diketones such as acetylacetone, and these may be used alone or in combination of two or more. Of these, diethyl malonate and ethyl acetoacetate are particularly preferable.

  In the blocking reaction of the isocyanate group with the active methylene compound (c2), a reaction catalyst can be used if necessary. Examples of the reaction catalyst include metal hydroxides, metal alkoxides, metal carboxylates, metal acetyl acetylates, hydroxides of onium salts, onium carboxylates, metal salts of active methylene compounds, onium salts of active methylene compounds, aminosilanes. , Basic compounds such as amines and phosphines are preferable. Among these, ammonium salts, phosphonium salts and sulfonium salts are preferable as the onium salt. The amount of the catalyst is usually 10 to 10,000 ppm, preferably 20 to 5,000 ppm, based on the total amount of the isocyanate compound and the active methylene compound. The above reaction can be carried out at 0 ° C to 150 ° C, and a solvent may be used. In this case, the solvent is preferably an aprotic solvent, and particularly preferably an ester, ether, N-alkylamide, ketone or the like. If the reaction has proceeded as intended, the basic compound as a catalyst may be neutralized by adding an acid component to stop the reaction.

  The amount of the active methylene compound (c2) used is not particularly limited, but is 0.1 to 3 equivalents, preferably 0.2 to 2 equivalents relative to 1 equivalent of the isocyanate group in the polyisocyanate compound (c1). Is preferred, and the unreacted active methylene compound (c2) can be removed after completion of the block reaction.

  In addition to the above active methylene compound (c2), for example, alcohol-based, phenol-based, oxime-based, amine-based, acid amide-based, imidazole-based, pyridine-based, mercaptan-based blocking agents, etc. within a range that does not impair the low temperature curability. You may use together.

  Further, a part of the isocyanate groups in the polyisocyanate compound (c1) may be reacted with at least one selected from the above-mentioned polyfunctional hydroxyl group-containing compound, water and monofunctional alcohol, and particularly monofunctional alcohol is reacted. It is preferable from the viewpoint of compatibility with the base resin component.

  Examples of the monofunctional alcohol include propanol, butanol, pentanol, hexanol, 2-ethylhexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, hepta. Aliphatic alcohols such as decanol, octadecanol and their isomeric alcohols; mono (or oligo) s such as ethylene glycol monoalkyl ether, diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tetraethylene glycol monoalkyl ether Ethylene glycol monoalkyl ethers; propylene glycol monoalkyl ethers, dipropylene glycol monoalkyl ethers, tripropylene glycol monoalkyl ethers, tetrapropylene glycol monoalkyl ethers and other mono (or oligo) propylene glycol monoalkyl ethers; ethylene glycol monoalkyl ethers Mono (or oligo) ethylene glycol monoesters such as ester, diethylene glycol monoester, triethylene glycol monoester, tetraethylene glycol monoester; propylene glycol monoester, dipropylene glycol monoester, tripropylene glycol monoester, tetrapropylene glycol Examples thereof include mono (or oligo) propylene glycol monoesters such as monoester; and the like, and these may be used alone or in combination of two or more kinds.

  The order of the reaction between the polyisocyanate compound (c1) and the active methylene compound (c2) is that after blocking the required amount of isocyanate groups with the active methylene compound (c2), the remaining isocyanate groups are reacted with a monofunctional alcohol. Alternatively, vice versa, or the active methylene compound (c2) and the monofunctional alcohol may be simultaneously reacted with the isocyanate group. Examples of the monofunctional alcohol include propanol, butanol, hexanol, heptanol, 2-ethylhexanol, octanol, nonanol, decanol, tridecanol, stearyl alcohol and isomers thereof, mono (oligo or poly) ethylene glycol monoalkyl ethers, Examples include mono (oligo or poly) propylene glycol monoalkyl ethers. The amount of the monofunctional alcohol used is 0.6 equivalent or less, preferably 0.4 equivalent or less with respect to 1 equivalent of the isocyanate group in the polyisocyanate compound (c1), since the curability may decrease if used in large amounts. Appropriate. The polyisocyanate compound (C) is usually obtained by reacting the polyisocyanate compound (c1) with the active methylene compound (c2). The polyisocyanate compound (C) thus obtained generally has a number average molecular weight of 500 to 20,000, preferably 800 to 18,000. Examples of commercial products of the polyisocyanate compound (C) include Duranate MF-K60X and Duranate MF-K60B (all manufactured by Asahi Kasei Chemicals Corporation).

  The active methylene-blocked polyisocyanate compound (C) thus obtained has good compatibility with the fatty acid-modified resin (A) and the imino group-containing melamine resin (B) and is desirable for improving coating stability. ..

Fumed silica (D)
The coating composition of the present invention may contain fumed silica (D), if necessary. The fumed silica (D) is a dry silica that is vaporized from silicon chloride and is synthesized by a gas phase reaction in a high temperature hydrogen flame, and is an amorphous glassy, spherical, and pore-free silica. The average primary particle diameter of such fumed silica (D) is usually 5 to 100 nm, preferably 20 to 50 nm.

The average primary particle size of fumed silica (D) can be measured by observing with an electron microscope. The specific surface area of the fumed silica (D) is, 100~1,000m ² / g, preferably in the range of 100 to 200 m ² / g, preferably in terms of paint stability. The specific surface area can be measured by the BET method.

  Commercially available products of fumed silica (D) are, for example, AEROSIL 130, AEROSIL 200, AEROSIL R202, AEROSIL 300, AEROSIL 300CF, AEROSIL 380PE, AEROSIL R805, AEROSIL R811, AEROSIL R812, AEROSIL R971 and AEROSIL R972, AEROSIL R971 and AEROSIL R972, AEROSIR R971 and AEROSIL R971 and AEROSIL R972. , Both are trade names of Nippon Aerosil Co., Ltd.).

  When the fumed silica (D) is blended in the coating composition of the present invention, the blending ratios thereof are a fatty acid modified resin (A), an imino group-containing melamine resin (B) and an active methylene blocked polyisocyanate compound (C). 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the total solid content, from the viewpoint of improving paint stability, corrosion resistance, alkali resistance and acid resistance. desirable.

Titanium Dioxide The coating composition of the present invention can contain titanium dioxide, if necessary. Titanium dioxide is a pigment in which the surface of titanium dioxide particles is surface-treated with silicon dioxide and aluminum oxide, and is 1.0 to 8.0 mass% of silicon dioxide, preferably 1. The titanium dioxide pigment is preferably surface-treated in the range of 3 to 6.6% by mass, aluminum oxide 2.0 to 4.5% by mass, and preferably 2.5 to 4.4% by mass. is there. The above range is desirable in terms of weather resistance and coating stability.

  The surface treatment ratio of silicon dioxide and aluminum oxide in the titanium dioxide was determined by elemental analysis by energy dispersive X-ray analysis using EDX-700HS (manufactured by Shimadzu Corporation).

Examples of commercially available products of such titanium dioxide, for example, TI-SELECT TS-6200 ( Du Pont Co., Ltd., trade _{name, SiO 2 / Al 2 O 3} = 2.4 / 3.4 ( mass%)), TI-PURE R-960 (Du Pont Co., Ltd., trade _{name, SiO 2 / Al 2 O 3} = 6.5 / 3.5 ( mass%)), TI-PURE R902 + (Du Pont Co., Ltd., trade name , SiO ₂ / Al ₂ O ₃ = 1.4 / 4.3 (mass%)), Taipek CR-95 (manufactured by Ishihara Sangyo Co., Ltd., trade name, SiO ₂ / Al ₂ O ₃ = 3.7 / 2.6). (mass%))
And so on.

  When titanium dioxide is compounded in the coating composition of the present invention, the compounding ratio thereof is the total solid content of the fatty acid-modified resin (A), imino group-containing melamine resin (B) and active methylene blocked polyisocyanate compound (C). It is desirable that the amount is 10 to 150 parts by mass, preferably 40 to 120 parts by mass, based on 100 parts by mass, from the viewpoint of coating stability, coating film hardness and weather resistance.

Coating Composition The coating composition of the present invention is a coating composition containing a fatty acid-modified resin (A), an imino group-containing melamine resin (B) and an active methylene-blocked polyisocyanate compound (C). ) Component, the above component (B) and the above component (C) based on the total solid content of 100 parts by mass, the fatty acid-modified resin (A) 60 to 85 parts by mass, preferably 65 to 80 parts by mass, imino group-containing melamine. Resin (B) 9 to 30 parts by mass, preferably 15 to 25 parts by mass, active methylene blocked polyisocyanate compound (C) 3 to 15 parts by mass, preferably 5 to 10 parts by mass, and B component / C Component = 1.0 to 3.0 (mass ratio), preferably 2.0 to 2.9, whereby the coating has excellent coating stability and low temperature curability, corrosion resistance, alkali resistance and acid resistance. A membrane can be obtained. In addition to the components (A), (B) and (C), other components can be added to the coating composition of the present invention, if necessary.

Other Components Other components in the coating composition of the present invention include coloring pigments such as iron oxide, carbon black, quinacridone magenta and red iron oxide; extender pigments such as clay, mica and calcium carbonate; zinc oxide, silica fine powder and water. Rust preventive pigments such as bismuth oxide, basic bismuth carbonate, bismuth nitrate, bismuth silicate, zinc phosphate, aluminum phosphate, zinc molybdate, calcium molybdate; bright pigments such as aluminum powder and mica; UV absorbers, Examples thereof include light stabilizers, defoamers, pigment dispersants, surface conditioners, surfactants, curing catalysts, thickeners, preservatives, antifreezing agents, matting agents, and other resins.

  For example, examples of the curing catalyst include tin catalysts such as dibutyltin dibenzoate, dioctyltin oxide, and dibutyltin oxide; p-toluenesulfonic acid, xylenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, dinonylnaphthalene. Sulfonic acid catalysts such as disulfonic acid; phosphoric acid catalysts such as monobutyl phosphate, dibutyl phosphate, diisopropyl phosphate, monooctyl phosphate, monodecyl phosphate, didecyl phosphate, metaphosphoric acid, orthophosphoric acid, orthophosphoric acid ester; And the like can be preferably used.

Coating film formation method (1)
As the coating film forming method of the present invention, for example, on a metal plate which may be subjected to a chemical conversion treatment, with or without a primer coating film, a coating film with the coating composition of the present invention The method of forming is.

  Examples of the metal plate include cold rolled steel plate, black skin steel plate, galvannealed steel plate, galvanized steel plate, aluminum and the like. Furthermore, if necessary, shot blasting, surface adjustment, chemical conversion treatment, etc. can be performed.

  The primer coating is a primer containing a binder component such as an epoxy resin, a polyisocyanate resin and a melamine resin, a pigment component such as a color pigment, an extender pigment and a rust preventive pigment, and if necessary, a surface conditioner and a catalyst. It can be formed by applying a paint and baking and drying at 50 to 160 ° C., preferably 90 to 130 ° C. for 10 to 120 minutes, preferably 15 to 50 minutes.

  The coating film of the coating composition is a conventionally known coating method, for example, dip coating, brush coating, roll brush coating, spray coating, roll coating, spin coating, dip coating, bar coating, flow coating, electrostatic coating, An object to be coated, which is coated by airless coating, electrodeposition coating, die coating or the like so as to have a dry film thickness of 10 μm to 150 μm, preferably 30 μm to 80 μm, for example, 50 to 160 ° C., preferably 90 It can be formed by baking and drying at ˜130 ° C. for 10 to 120 minutes, preferably 15 to 50 minutes.

Coating film formation method (2)
Other examples of the method for forming a coating film of the present invention include a method of forming a coating film of the coating composition of the present invention and then forming at least one coating film on the coating film. The colored coating film or the clear coating film is obtained by dissolving or dispersing an acrylic resin, a cross-linking agent or the like in a solvent, and optionally mixing a pigment component to obtain a thermosetting coating material, and drying film 5 to It can be obtained by coating to 50 μm, preferably 15 to 40 μm, and heating and drying at a temperature of 90 to 180 ° C., preferably 110 to 150 ° C. for about 5 to 60 minutes, preferably 10 to 40 minutes. ..

  Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples and Comparative Examples, but the present invention is not limited thereto. In each example, "part" means mass part and "%" means mass%.

Fatty acid modified resin (A)
Production Example 1 Fatty acid-modified polyester resin solution No. Production of 1 In a reaction device having a heating device, a stirrer, a nitrogen introduction tube and a fractionation tower, 252 parts of soybean oil fatty acid, 222 parts of phthalic anhydride, 207 parts of dodecanedioic acid, 164 parts of trimethylolpropane, 1,6-hexane 240 parts of diol and 48 parts of 2-butyl-2-ethyl-1,3-propanediol were charged, heating was started under dry nitrogen, and the temperature was gradually raised to 230 ° C. to carry out the esterification reaction. After maintaining the temperature at 230 ° C. and performing an esterification reaction until the resin acid value becomes 2 mgKOH / g, the temperature is cooled to 170 ° C., ethylene glycol monobutyl ether is added, and fatty acid-modified polyester resin No. 80 having a resin solid content of 80% by mass is added. One solution was obtained.
Fatty acid-modified polyester resin No. The resin solid content of one solution was an acid value of 2 mgKOH / g, an oil length of 24% by mass, a hydroxyl value of 80 mgKOH / g, and a number average molecular weight of 1,750.

Production Examples 2 to 5 Fatty Acid Modified Polyester Resin Solution No. 2 to No. Production of 5 Fatty acid-modified polyester resin No. 5 was produced in the same manner as in Production Example 1 except that the content of the formulation in Table 1 was used. 2 to No. Got 5.

Comparative Production Examples 1 to 4 Fatty Acid Modified Polyester Resin Solution No. 6-No. Production of Fatty Acid-Modified Polyester Resin No. 9 in the same manner as in Production Example 1 except that the content of the formulation in Table 1 was used. 6-No. Got 9.

Production Example of Active Methylene Blocked Polyisocyanate Compound (C) Production Example 6 Polyisocyanate Compound No. Manufacturing process 1
A 2 L flask equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a dropping pump, etc. was mixed with 605 parts of Sumidule N-3300 (Note 1), 413 parts of diethyl malonate, and 181 parts of ethyl acetate, and a nitrogen stream was added. 7.0 g of 28% methanol solution of sodium methoxide was added below, and the mixture was kept at 60 ° C. for 12 hours. Then, when the NCO value was measured, the isocyanate content was 0.2%. To this, 99 parts of ethyl acetate was added to obtain a resin (A-1) solution. The number average molecular weight of the resin (A-1) was about 3,000.
(Note 1) Sumidur N-3300: manufactured by Sumika Bayer Urethane Co., Ltd., trade name, isocyanurate of hexamethylene diisocyanate, isocyanate content 21.8%
Process 2
In a 2 L flask equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a dropping pump, a simple trap for removing solvent, etc., 505 parts of the resin (A-1) solution obtained in step 1 and 450 parts of propylene glycol monopropyl ether were added. Then, the temperature was raised to 90 ° C. Under reduced pressure, the solvent was distilled off and removed over 2 hours while maintaining the system temperature at 80 to 90 ° C., and the solid content was adjusted with propylene glycol monopropyl ether to prepare an active methylene solution having a solid content of 50 mass%. Polyisocyanate compound solution No. Got 1. The removal solvent simple trap contained 42 parts of ethanol. Polyisocyanate compound No. The number average molecular weight of 1 was about 3,500.

Production Example 7 Polyisocyanate compound No. Manufacturing process 2
To a 2 L flask similar to that used in Production Example 6, 4,000 parts of hexamethylene diisocyanate and 32 parts of 2-butyl-2-ethyl-1,3-propanediol were added, and the mixture was kept at 100 ° C. for 1 hour under a nitrogen stream. Then, tetramethylammonium laurate as a catalyst for isocyanurate formation was added at 60 ° C., and when the yield reached 23.0%, dibutylphosphoric acid was added to stop the isocyanurate formation reaction. After that, unreacted hexamethylene diisocyanate was removed using a thin film distillation apparatus, and polyisocyanate having an isocyanate content of 22.8% and a number average molecular weight of about 600 was obtained.
To a 2 L flask, 605 parts of this polyisocyanate, 413 parts of diethyl malonate and 181 parts of ethyl acetate were blended, 8.0 parts of 28% methanol solution of sodium methoxide was added, and the mixture was kept at 60 ° C. for 12 hours. Then, when the NCO value was measured, the isocyanate content was 0.1%. To this, 99 parts of ethyl acetate was added to obtain a resin (A-2) solution. The number average molecular weight of the resin (A-2) was about 3,000.
Process 2
505 parts of the resin (A-2) solution obtained in step 1 and 450 parts of propylene glycol monopropyl ether were added, and the temperature was raised to 90 ° C. Under reduced pressure, the solvent was distilled off and removed over 2 hours while maintaining the system temperature at 80 to 90 ° C., the solid content was adjusted with propylene glycol monopropyl ether, and the solid content was adjusted to 50% with active methylene. Blocked polyisocyanate compound solution No. Got 2. The removal solvent simple trap contained 43 parts of ethanol. Polyisocyanate compound No. The number average molecular weight of 2 was about 3,500.

Production Example 8 Polyisocyanate compound No. 3 (caprolactam-blocked hexamethylene diisocyanate nurate) A 2 L flask similar to that of Production Example 6 was charged with 100 parts of Sumidule N-3300 (Note 1) and 72.0 parts of dehydrated diethylene glycol dimethyl ether. Warmed to ° C. Next, 67.9 parts of ε-caprolactam was added, and the mixture was heated to 130 ° C., sampled over time while maintaining the temperature, and reacted until no isocyanate group was detected by FT-IR measurement. After that, the solid content was adjusted with diethylene glycol dimethyl ether to obtain a polyisocyanate compound solution No. 50 having a solid content of 50%. Got 3.

Manufacturing Example 1 of Coating Composition Coating Composition No. Manufacture of Fatty Acid-Modified Polyester Resin Solution No. 1 part of the solution was uniformly mixed with 75 parts (solid content), Super Beckamine L-166 (note 2) 18 parts (solid content) and Duranate MF-K60B (note 6) 7 parts (solid content). Paint composition No. with a solid content of 30% by adjusting the solid content by adding a trade name, petroleum hydrocarbon solvent manufactured by Maruzen Petrochemical Co., Ltd. Got 1.

Examples 2 to 30 Coating composition No. 2 to coating composition No. Manufacture of No. 30 Coating composition No. 30 having a coating solid content of 30% was prepared in the same manner as in Example 1 except that the formulation contents shown in Tables 2 and 3 below were used. 2 to No. I got 30.

Comparative Example 1 Coating composition No. Production of 31. Fatty acid-modified polyester resin solution No. 75 parts (solid content) of 1 solution, 10 parts (solid content) of Super Beckamine L-166 (note 2), 15 parts (solid content) of Duranate MF-K60B (note 6), AEROSIL R972 (note 9) 0.5 parts and 50 parts of Ti-Pure R902 + (Note 11) are uniformly mixed, and SWAZOL 1000 is added to adjust the solid content to obtain a coating composition No. 30 having a coating solid content of 30%. I got 31.

Comparative Examples 2-16
A coating composition No. 30 having a coating solid content of 30% was prepared in the same manner as in Comparative Example 1 except that the formulation contents shown in Table 4 below were used. 32-No. I got 46.

(Note 2) Super Beckamine L-166: DIC Corporation, trade name, imino group-containing methyl etherified melamine resin (Note 3) Super Beckamine ME-609P: DIC Corporation, trade name, imino group-containing methyl Etherified melamine resin (Note 4) Super Beckamine ME-040: manufactured by DIC Corporation, trade name, imino group-containing methyl etherified melamine resin (Note 5) Cymel 303: manufactured by Daicel Ornex Co., trade name, methyl ether Melamine resin (Note 6) Cymel 235: manufactured by Daicel Ornex Co., trade name, methyl / butyl mixed etherified melamine resin (Note 7) Duranate MF-K60B: manufactured by Asahi Kasei Chemicals Corporation, trade name, blocked with active methylene Hexamethylene diisocyanate (Note 8) Duranate MF-K60X: Asahi Kasei Chemicals Corporation, trade name, hexamethylene diisocyanate (Note 9) Desmodur BL-3175: Sumika Bayer Urethane, blocked with methyl ethyl ketoxime Hexamethylene Diisocyanate Isocyanurate Formed, NCO Content 11%
(Note 10) AEROSIL R972: manufactured by Nippon Aerosil Co., Ltd., trade name, fumed silica, specific surface area 110 m ² / g
(Note 11) AEROSIL R130: manufactured by Nippon Aerosil Co., Ltd., trade name, fumed silica, specific surface area 130 m ² / g
(Note 12) Ti-Pure R902 +: manufactured by Du Pont Co., Ltd., trade name, titanium dioxide pigment (coating amount SiO ₂ / Al ₂ O ₃ = 1.4 / 4.3 mass%).
(Note 13) Ti-Pure R-960: manufactured by Du Pont Co., Ltd., trade name, titanium dioxide pigment (coating amount SiO ₂ / Al ₂ O ₃ = 6.5 / 3.5 mass%).
(Note 14) TI-SELECT TS-6200: manufactured by Du Pont, trade name, titanium dioxide pigment (coating amount SiO ₂ / Al ₂ O ₃ = 2.4 / 3.4 mass%).
(Note 15) Taipaque CR-95: manufactured by Ishihara Sangyo Co., Ltd., trade name, titanium dioxide pigment (coating amount (SiO ₂ / Al ₂ O ₃ = 3.7 / 2.6 mass%))
(Note 16) UT-771: manufactured by Ishihara Sangyo Co., Ltd., trade name, titanium dioxide pigment (coating amount SiO ₂ / Al ₂ O ₃ = 0.1 / 2.1 mass%)
(Note 17) TITON R-7E: Sakai Chemical Industry Co., Ltd., trade name, titanium dioxide pigment (coating amount SiO ₂ / Al ₂ O ₃ = 7 / 2.5 mass%)
The test plate was prepared and the performance was evaluated according to the following. The results are also shown in Tables 2-4.

Preparation of test plate (1) A cold-rolled steel plate (100 mm x 300 mm x 2.0 mm) that has been subjected to zinc phosphate chemical conversion treatment, and a primer coating (One-coat enamel # 600TG ivory, trade name, Kansai Paint Co., Ltd., one-pack type Epoxy-based primer paint) was spray-painted to a dry film thickness of 20 μm.
Each coating composition obtained in the above Examples and Comparative Examples was spray-coated on the coating film so that the dry film thickness was 50 μm. Then, using an electric hot air dryer, it was heated and dried at 110 ° C. for 20 minutes to obtain a test plate (1).

Preparation of Test Plate (2) A test plate (2) was obtained in the same manner as the test plate (1) except that the baking temperature and time of the test plate (1) were 100 ° C. and 20 minutes.

Preparation of test plate (3) A cold-rolled steel plate (100 mm x 300 mm x 2.0 mm) that has been subjected to a zinc phosphate chemical conversion treatment, and a primer coating (One-coat enamel # 600TG ivory, trade name, manufactured by Kansai Paint Co., Ltd., one-pack type Epoxy-based primer paint) was spray-painted to a dry film thickness of 20 μm. Each coating composition obtained in the above Examples and Comparative Examples was spray-coated on the coating film so that the dry film thickness was 50 μm. Then, using an electric hot air dryer, it was heated and dried at 110 ° C. for 20 minutes to obtain a cured coating film.
Further, Amilak 1026 (trade name, alkyd melamine resin-based clear coating manufactured by Kansai Paint Co., Ltd.) was spray-coated on the coating film so that the dry film thickness was 25 μm, and dried by heating at 130 ° C. for 20 minutes. A test plate (3) was obtained.

Performance evaluation (Note 18) Paint stability:
Each coating composition was placed in a 1000 mL glass container and stored in a closed container at 35 ° C. for 35 days. The subsequent state was judged according to the following criteria.
⊚ is good with no change from before storage ○: Viscosity is slightly increased, but returns to the original state by motor stirring for 1 minute or less (stirring blade with diameter 2 cm, rotation speed 300 rpm) Δ is viscosity increasing When the motor stirring for more than 1 minute and 10 minutes or less (stirring blade having a diameter of 2 cm, rotation speed 300 rpm) returns to the original state, x indicates that the layers are separated and cannot be used as a paint.

(Note 19) Low temperature curability:
A tin plate (100 mm × 150 mm × 0.3 mm) was spray coated with each coating composition obtained in Examples and Comparative Examples so that the dry film thickness was 50 μm. Then, it was heated and dried at 110 ° C. for 20 minutes using an electric hot air dryer. Then, the dried coating film was peeled off by an amalgam method, put in a 300 mesh wire net, and extracted with a solvent of acetone / methanol = 1/1 at a reflux temperature for 6 hours, and then a gel fraction was calculated according to the following formula.
Gel fraction (%) = [(coating film weight after extraction) / (coating film weight before extraction)] × 100
◎ indicates that the gel fraction is 93% or more
◯ is a gel fraction of 90% or more and less than 93%
△: gel fraction is 85% or more and less than 90%
X: Gel fraction less than 85%.

(Note 20) Coating hardness:
Using the test plate (1), according to JIS K 5600-5-4, apply a pencil lead to the coating surface of the test plate at an angle of about 45 °, and strongly test the test plate so that the lead does not break. While pressing it against the surface of the coating film, it was moved forward about 10 mm at a uniform speed. The hardness of the hardest pencil that did not break the coating film was defined as the pencil hardness.

(Note 21) Specular gloss:
Using the test plate (1), according to JIS K 5600-4-7 (1999) "60 degree specular gloss", the reflectance when the incident angle and the light receiving angle are 60 degrees respectively, the test plate (1) Was measured 10 times in the longitudinal direction at intervals of about 2.5 cm to obtain an "average value" of the specular glossiness and evaluated according to the following criteria.
⊚ has a specular gloss of 90 ° or more,
◯ indicates that the difference in specular glossiness is 85 ° or more and less than 90 °,
Δ indicates that the specular gloss difference is 75 ° or more and less than 85 °,
X indicates a difference in specular gloss of less than 75 °.

(Note 22) Impact resistance:
The test plate (1) was tested using a DuPont type impact tester under the conditions of a diameter of the impact core: 1/2 inch, a falling weight height: 50 cm, and a measurement atmosphere: 20 ° C. The parts and recesses were visually observed according to the following criteria.
◎ indicates no abnormality in both convex and concave
◯: Some small cracks are observed on the convex part
△: cracks are observed in both convex and concave
In the case of ×, cracks are observed on the entire surface that has been impacted.

(Note 23) Weather resistance:
The test plate (1) was subjected to a sunshine carbon arc lamp type light resistance and weather resistance test defined in JIS B-7533 until the irradiation time reached a maximum of 1,200 hours. The irradiation time at which the gloss retention ratio to the gloss before the test in the coating film of the test plate (1) was 80% was measured.
⊚ indicates that the gloss retention rate is 80% or more even after the irradiation time reaches 1,200 hours. ◯ indicates that the irradiation time at which the gloss retention rate is less than 80% is 1,000 hours or more and less than 1200 hours.
Δ indicates that the gloss retention rate is less than 80%, the irradiation time is 800 hours or more and less than 1,000 hours,
In the case of ×, the gloss retention rate is less than 80% and the irradiation time is less than 800 hours.

(Note 24) Anticorrosion:
The coating film of the test plate (1) was provided with a cross-cut flaw with a knife, and this was subjected to a salt water spray test for 120 hours in accordance with JISZ-2371. The rust from the knife flaw and the blister width were evaluated according to the following criteria.
◎ indicates that the maximum width of rust and blisters is less than 2 mm from the cut part (one side),
○ indicates that the maximum width of rust and blisters is 2 mm or more from the cut portion and less than 3 mm (one side),
△ indicates that the maximum width of rust and blisters is 3 mm or more and less than 4 mm (one side) from the cut portion,
× indicates that the maximum width of rust and blisters is 4 mm or more from the cut portion (one side).

(Note 25) Alkali resistance:
Using the test plate (1) or the test plate (2), the test plate (1) or the test plate (2) was immersed in a 5% sodium hydroxide aqueous solution (20 ° C.) for 24 hours, and the gloss retention of the gloss before the test was measured in the coating film of the test plate.
◎, the gloss retention rate is 90% or more,
○, the gloss retention rate is 80% or more,
Δ indicates that the gloss retention rate is 50% or more,
X indicates that the gloss retention rate is less than 50%.

(Note 26) Acid resistance (1):
Using the test plate (1) or the test plate (2), the test plate (1) or the test plate (2) was immersed in a 5% hydrochloric acid aqueous solution (20 ° C.) for 24 hours, and the gloss retention of the gloss before the test was measured in the coating film of the test plate.
◎, the gloss retention rate is 90% or more,
○, the gloss retention rate is 80% or more,
Δ indicates that the gloss retention rate is 50% or more,
X indicates that the gloss retention rate is less than 50%.

(Note 27) Acid resistance (2):
Using the test plate (3), it was immersed in a 5% hydrochloric acid aqueous solution (20 ° C.) for 48 hours, and the coating film of the test plate was measured for the gloss retention ratio with respect to the gloss before the test.
◎, the gloss retention rate is 90% or more,
○, the gloss retention rate is 80% or more,
Δ indicates that the gloss retention rate is 50% or more,
X indicates that the gloss retention rate is less than 50%.

  The coating composition of the present invention can provide a coated article having good coating film hardness, specular gloss, impact resistance, weather resistance, corrosion resistance, alkali resistance and acid resistance.

Claims (7)

A coating composition containing a fatty acid-modified resin (A) having an oil length of 5 to 40% by mass, an imino group-containing melamine resin (B), and an active methylene-blocked polyisocyanate compound (C), which comprises the above (A) 60 to 85 parts by mass of the fatty acid-modified resin (A), 9 to 30 parts by mass of the imino group-containing melamine resin (B), and the activity based on the total solid mass of the component, the above (B) component, and the above (C) component A coating composition containing 3 to 15 parts by mass of a methylene-blocked polyisocyanate compound (C), and B component / C component = 2.0 to 2.9 (mass ratio). Fumed based on a total solid content of 100 parts by mass of a fatty acid-modified resin (A) having an oil length of 5 to 40% by mass, an imino group-containing melamine resin (B) and an active methylene-blocked polyisocyanate compound (C). The coating composition according to claim 1, which contains 0.1 to 10 parts by mass of silica (D). 10 to 150 parts by mass of titanium dioxide having the following characteristics based on 100 parts by mass of the total solid content of the fatty acid-modified resin (A), the imino group-containing melamine resin (B) and the active methylene blocked polyisocyanate compound (C). The coating composition according to claim 1 or 2.
Titanium dioxide: Titanium dioxide that has been subjected to at least two types of surface treatments of silicon dioxide and aluminum oxide, and 1.0 to 8.0 mass% of silicon dioxide and aluminum oxide based on the solid content of the titanium dioxide. Titanium dioxide pigment surface-treated at a ratio of 0 to 4.5% by mass The coating composition according to any one of claims 1 to 3, wherein the fatty acid-modified resin (A) is a fatty acid-modified polyester resin. A coating film of the coating composition according to any one of claims 1 to 4 with or without a primer coating film on a metal plate which may be subjected to a chemical conversion treatment. And baking and drying at 90 to 130 ° C. to form a coating film. A coating film of the coating composition according to any one of claims 1 to 4 with or without a primer coating film on a metal plate which may be subjected to a chemical conversion treatment. And baking at 90 to 130 ° C. to form at least one coating film on the coating film. A coated article obtained by the coating film forming method according to claim 5 or 6.