JP2005074272A - Coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method capable of forming a composite layer coating film with excellent corrosion-resistance, weather-resistance and durability by a less number of coating steps for corrosion prevention and fine appearance maintenance of steel structures such as steel tower structures for power transmission and for communication, a transportation container, a vessel, a bridge and a tank. <P>SOLUTION: After a surface to be coated is coated with zinc rich coating (I) containing an epoxy resin based binder and zinc powder as main components, the surface is coated with a coating composition (III) containing an acrylic resin (A), an epoxy resin (B) having at least two epoxy groups in a molecule and an amine curing agent (C) capable of containing aminosilane. The coating film by the zinc rich coating (I) may be further coated with an epoxy resin based primer (II) before the coating film is coated with the coating composition (III). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a multilayer coating excellent in corrosion resistance, weather resistance and durability for corrosion prevention and maintenance of aesthetics of steel structures such as power transmission and communication tower structures, shipping containers, ships, bridges and tanks. The present invention relates to a coating method capable of forming a film with few coating processes.

  In steel structures such as power transmission and communication tower structures, shipping containers, ships, bridges, tanks, etc., anticorrosion coating is applied to prevent corrosion and maintain aesthetics. In the case of bridge painting, after applying zinc rich paint with excellent corrosion resistance, epoxy resin primer, and epoxy resin intermediate coating in order, various top coatings such as urethane resin paint with further excellent weather resistance are usually applied. I often paint. However, in order to maintain the target performance, at least five or more coating steps are required when the undercoat is applied a plurality of times, or the intermediate coat and the top coat are included. In particular, when painting on existing steel structures, work is done at a high place without a scaffold, and labor costs and scaffolding costs account for more than 80% of the painting cost, so the number of paintings is minimized. However, shortening the painting process has been strongly demanded from the viewpoint of safety and economy.

  For this reason, various types of anticorrosion coating methods with reduced processes have been conventionally studied (see, for example, Patent Document 1), but the required level has been increasing year by year in both anticorrosion and weather resistance, which has been insufficient.

Japanese Patent Laid-Open No. 7-8905

  The present applicant has proposed a two-component coating composition that can form a coating film excellent in both corrosion resistance and weather resistance in a single coating process (see, for example, Patent Document 2). The use of this coating composition makes it possible to shorten the coating process particularly in finish coating, but further reduction of the coating process including undercoating has been desired.

JP 2002-167546 A

  As a result of intensive studies to solve the above problems, the present inventors applied a specific zinc rich paint (I) to the surface to be coated, and an epoxy resin-based primer (II) as necessary. Applying the coating composition (III), which has the functions of intermediate coating and top coating, to form a multilayer coating film with excellent corrosion resistance, weather resistance and durability in a few steps As a result, the present invention has been completed.

  That is, in the present invention, after coating a zinc rich paint (I) mainly composed of an epoxy resin binder and zinc powder on the surface to be coated, the acrylic resin (A) has at least two epoxy groups in one molecule. It is related with the coating method characterized by coating the coating composition (III) containing the epoxy resin (B) which has silane, and the amine hardening | curing agent (C) which may contain aminosilane.

  According to the method of the present invention, it is possible to reduce the number of conventional coating steps without impairing the coating performance such as corrosion resistance, weather resistance and durability. Therefore, the method of the present invention is particularly useful for coating steel structures such as bridges, power transmission and communication tower structures, transportation containers, ships, tanks and the like.

  The zinc rich paint (I) used in the present invention contains an epoxy resin binder and zinc powder as main components.

  The epoxy resin binder includes an epoxy resin having two or more, preferably 2 to 5, epoxy groups in one molecule. Examples of the epoxy resin include glycidyl ether type epoxy resins and glycidyl esters. Type epoxy resins, other glycidyl ether type epoxy resins, alicyclic epoxy resins, modified epoxy resins obtained by modifying these epoxy resins with alkylphenols and / or fatty acids, or alkyldiphenols or alkylphenol novolac type resins and epichlorohydrin An epoxy group-introduced alkylphenol or alkylphenol novolac type resin obtained by reaction can be used.

  As the curing agent for the epoxy resin, conventionally known amine curing agents such as polyamines and modified products thereof can be used. Examples of the amine curing agents include aliphatic polyamines, alicyclic polyamines, and aromatic polyamines. , Michael adducts of these polyamines, epoxy resin adducts, Mannich adducts, and the like, as well as ketimines, polyamides, polyamidoamines, reactants of fatty acids and polyamines, and reactants of dimer acids and polyamines. . These can be used alone or in admixture of two or more. The mixing ratio of the amine curing agent is such that the active hydrogen of the amine curing agent is 0.5 to 5 equivalents, preferably 0.6 to 3 equivalents per 1 equivalent of the epoxy group in the epoxy resin. It is desirable to use it.

  In order to improve the adhesion between the steel material and the coating film, a silane coupling agent can be added to the epoxy binder, and examples of the silane coupling agent include γ- (2-aminoethyl). ) Aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, etc. Amino group-containing silane coupling agent; Glycidyl group-containing silane coupling agent such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane; Mercapto group-containing silane such as γ-mercaptopropyltrimethoxysilane A coupling agent etc. are mentioned. The content of the silane coupling agent is suitably 0.5 to 20 parts by weight, preferably 1 to 15 parts by weight with respect to 100 parts by weight of the resin solid content in the zinc rich paint (I).

  As the zinc powder, those having an average particle diameter in the range of 5 to 60 μm, preferably 10 to 45 μm can be suitably used from the viewpoint of corrosion resistance and frictional strength at the time of coating the joint. The shape may be any of a spherical shape, a rod shape, a lump shape, a needle shape, and the like, but substantially spherical particles are preferred. From the viewpoint of corrosion resistance and durability, the zinc powder is preferably contained within the range of 50 to 95% by weight, preferably 60 to 93% by weight, in the resulting dried coating film. Other metal powders such as aluminum powder and copper powder may be used in combination with the zinc powder.

  If necessary, the zinc rich paint (I) can be used in combination with ordinary extender pigments, rust preventive pigments and colored pigments so as not to impair the denseness of the coating film. Examples of extender pigments include silica powder, Examples thereof include barium sulfate, calcium carbonate, talc, kaolin, and clay. Examples of the rust preventive pigment and colored pigment include titanium oxide, iron phosphide, MIO, lead cyanamide, zinc chromate, zinc phosphate, calcium phosphate, and metaboric acid. Examples thereof include barium, zinc molybdate, aluminum molybdate, bengara, cyanine color pigments, carbon black, rutile powder, and zircon powder.

  If necessary, the zinc rich paint (I) may further contain usual paint additives such as organic solvents, anti-settling agents, anti-sagging agents, wetting agents, reaction accelerators and adhesion promoters. Also good.

  The zinc-rich paint (I) used in the present invention is preferably a paint having a sliding coefficient of 0.40 or more when the friction resistance of the joint portion of the steel structure is required. .

  The zinc rich paint (I) is applied to the surface to be coated so that the dry film thickness is 10 μm or more, preferably 20 to 400 μm. The coating can be performed by conventionally known means such as air spray, airless spray, and brush.

  The epoxy resin-based primer (II) used in the present invention is applied to the coating surface of the zinc rich paint (I) as necessary, and has an epoxy resin and an amine-based curing agent as main components. Is.

  The epoxy resin is a resin that is liquid or solid at room temperature and has 2 or more, preferably 2 to 5 average epoxy groups in one molecule. Specifically, the resin that is liquid at room temperature is a resin having a viscosity at 25 ° C. of 15000 mPa · s or less, preferably 5000 mPa · s or less.

  Examples of the epoxy resin include glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, other glycidyl ether type epoxy resins, alicyclic epoxy resins, and modified products obtained by modifying these epoxy resins with alkylphenols and / or fatty acids. An epoxy group-introduced alkylphenol or alkylphenol novolac type resin obtained by reacting an epoxy resin or an alkyldiphenol or an alkylphenol novolak type resin with epichlorohydrin can be used.

  As the epoxy resin, an epoxy group-introduced alkylphenol or alkylphenol novolac resin obtained by reacting an alkyldiphenol or alkylphenol novolac resin with epichlorohydrin as a liquid resin, or a bisphenol A epoxy resin is particularly suitable. As the resin, a bisphenol A type epoxy resin and a modified epoxy resin obtained by modifying this with an alkylphenol or / and a fatty acid are preferable from the viewpoint of the film forming property and toughness of the resulting coating film. Also, an acrylic-modified epoxy resin obtained by reacting a dibasic acid and a carboxyl group-containing acrylic resin with these epoxy resins, or a polybasic addition of dibasic acid and graft polymerization or copolymerization of a polymerizable unsaturated monomer to the epoxy resin. Acrylic-modified epoxy resins, and further modified epoxy resins that also use carboxyl group-containing phenols for the modification of these acrylic-modified epoxy resins can be suitably used when solubility in weak solvents such as mineral spirits and drying properties are required. .

  If necessary, the epoxy resin may be selected from urethane-modified epoxy resin, dimer acid-modified epoxy resin, xylene resin, toluene resin, ketone resin, coumarone resin, petroleum resin, etc. From the viewpoint of improving the drying property and the like, they can be used together as appropriate.

  The amine-based curing agent is a curing agent for the epoxy resin, and any conventionally known one can be used without particular limitation, and is preferably liquid at room temperature. The amine curing agent is generally a polyamine compound having a primary amino group equivalent in the range of about 2000 or less, preferably in the range of about 30 to about 1000, which is also generally about 5000 or less, preferably Preferably has a number average molecular weight in the range of about 60-3000.

  Examples of the polyamine compound include aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, and pentaethylenehexamine; aromatic polyamines such as metaxylylenediamine, diaminodiphenylmethane, and phenylenediamine. And alicyclic polyamines such as 1,3-bis (aminomethyl) cyclohexane and isophoronediamine.

  Further, examples of the amine curing agent include ketimine compounds in which the amino group of the polyamine compound is blocked with a dialkyl ketone. By using the ketimine compound, the epoxy resin primer (II) can be made into a one-component composition. In this case, among the polyamine compounds, a polyamine compound having no secondary amino group in the molecule, that is, only having a primary amino group that can be blocked with a carbonyl compound as an amino group having an active hydrogen atom. Is preferably used because of its good storage stability after mixing with the epoxy resin. When a ketimine compound having a secondary amino group in the molecule is used, it is desirable to use it as an adduct compound in which the secondary amino group is consumed by reacting the secondary amino group with an epoxy compound.

  Suitable dialkyl ketones used for blocking the primary amino group of the polyamine compound are, for example, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl from the viewpoint of balance between curability and storage stability. Examples thereof include ketone, methyl t-butyl ketone, methyl sec-butyl ketone, and methyl hexyl ketone.

  The mixing ratio of the amine curing agent is such that the active hydrogen in the amine curing agent is 0.5 to 3.0 equivalents, preferably 0.8 to 1.5 equivalents, relative to 1 equivalent of the epoxy group in the epoxy resin. It is desirable from the viewpoint of curability, non-adhesiveness, and corrosion resistance of the coating film.

  The epoxy resin primer (II) can be blended with pigments such as color pigments, extender pigments and rust preventive pigments, if necessary. Examples of the pigments include titanium white, yellow lead, red lead, zinc white, bengara, barium sulfate, calcium carbonate, silica balloon, silica flour, silica alumina, zinc phosphate, cuprous oxide, basic lead sulfate, hematite. , Erosyl and the like, and these may be used alone or in combination of two or more. In the epoxy resin primer (II), the pigment volume concentration of the whole pigment is 20 to 70%, preferably 30 to 60%.

  For the epoxy resin primer (II), if necessary, an organic solvent, a reactive diluent, a dehydrating agent, a modifying resin component, a thickener, a resin fine particle, a plasticizer, a dispersing agent, a dehydrating agent, etc. Additives and the like can be contained.

  As the organic solvent, conventionally known solvents such as hydrocarbon, ester, ketone, ether, alcohol and the like can be used without particular limitation. A hydrocarbon solvent ("weak solvent") selected from an aliphatic hydrocarbon solvent and a high-boiling aromatic hydrocarbon solvent depending on the lower layer coating film and the upper layer coating film as a dilution solvent when coating and / or painting. It is desirable to use an organic solvent containing 80 wt% or more, preferably 95 wt% or more, more preferably 100 wt%.

  Specific examples of the aliphatic hydrocarbon solvent and the high-boiling aromatic hydrocarbon solvent include, for example, VM & P naphtha, mineral spirit, solvent kerosene, aromatic naphtha, solvent naphtha, Solvesso 100, Solvesso 150, Solvesso 200 ["Solvesso Is a registered trademark of Esso Petroleum, Ltd.], Swazol 310, Swazol 1000, Swazol 1500 [“Swazol” is a registered trademark of Cosmo Oil Co., Ltd.] and the like, aliphatic or aromatic hydrocarbons having relatively low dissolving power; n Aliphatic hydrocarbons such as butane, n-hexane, n-heptane, n-octane, isononane, n-decane, n-dodecane, cyclopentane, cyclohexane and cyclobutane are used.

  The above-mentioned epoxy resin primer (II) is highly solidified, uses a non-aqueous dispersion resin, and contains thick coaters such as thickeners and amide waxes, especially from the viewpoint of thick film formation. It is desirable to do.

  As a method for coating the epoxy resin primer (II), general methods such as brush coating, roller coating, spray coating, and various coater coatings can be used. The coating amount is not particularly limited, but usually a dry film thickness of about 20 to 1000 μm, preferably about 30 to 300 μm is appropriate.

  On the coating film formed from the epoxy resin-based primer (II), an epoxy-based or urethane-based coating is used as necessary, for example, when the coating interval of the coating composition (III), which will be described later as a top coating, becomes long. An intermediate coating such as the above may be applied. As a coating method of the intermediate coating, general methods such as brush coating, roller coating, spray coating, and various coater coatings can be used, and the coating amount is not particularly limited, but usually a dry film The thickness is about 10 to 500 μm, preferably about 15 to 400 μm.

The coating composition (III) used in the present invention is coated on the coating surface by the zinc rich coating material (I), on the coating surface by the epoxy resin primer (II), or on the coating surface of the intermediate coating. An acrylic resin (A), an epoxy resin (B) having at least two epoxy groups in one molecule, and an amine curing agent (C) that may contain aminosilane.
As the acrylic resin (A), a conventionally known one can be used without limitation, and usually an acrylic copolymer obtained by copolymerizing a mixture of polymerizable unsaturated monomers with a radical polymerization initiator in the presence of an organic solvent. A polymer can be suitably used.

  Examples of the polymerizable unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-, i-, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth). C1-C24 alkyl ester or cycloalkyl ester of acrylic acid or methacrylic acid such as acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, and cyclododecyl (meth) acrylate An alkoxyl group-containing unsaturated monomer such as methoxymethyl acrylate and methoxyethyl acrylate; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl ) Hydroxyl group-containing unsaturated monomers such as acrylate; carboxyl group-containing unsaturated monomers such as acrylic acid and methacrylic acid; styrene, (meth) acrylamide, vinyl acetate and the like. It may be used in combination of two or more.

  In addition, as the polymerizable unsaturated monomer, a crosslinking functional group capable of reacting with the amine curing agent (C) described later is introduced to improve the corrosion resistance and weather resistance of the coating film. A monomer and / or an alkoxysilyl group-containing unsaturated monomer can be used.

  Examples of the epoxy group-containing unsaturated monomer include glycidyl (meth) acrylate, 3,4-epoxycyclohexyl (meth) acrylate, β-methylglycidyl (meth) acrylate, and allyl glycidyl ether. Or may be used in combination of two or more.

  Examples of the alkoxysilyl group-containing unsaturated monomer include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, and γ- (meth) acryloyl. An oxypropyl triethoxysilane etc. are mentioned, These may be used independently and may be used together 2 or more types.

  Furthermore, as the polymerizable unsaturated monomer, an ultraviolet-absorbing unsaturated monomer and / or an ultraviolet-stable unsaturated monomer can be used from the viewpoint of improving the weather resistance of the acrylic resin (A). .

  The UV-absorbing unsaturated monomer is a monomer containing a polymerizable unsaturated group and a site having UV-absorbing ability. It is a benzotriazole, triazine, anilide, benzophenone, oxalic anilide, cyano Specific examples include 2- [2′-hydroxy-5 ′-(methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-( Methacryloyloxyethyl) phenyl] 2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxypropyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-(methacryloyloxyhexyl) ) Phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-butyl-5'- Methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-t-butyl-3 '-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy -5 '-(methacryloyloxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2'-hydroxy-5'-(methacryloyloxyethyl) phenyl] -5-methoxy-2H-benzotriazole, 2 -[2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl] -5-cyano-2H-benzotriazole, 2- [2'-hydroxy-5'-(methacryloyloxyethyl) phenyl] -5-t- Butyl-2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) ) Phenyl] -5-nitro-2H-benzotriazole and the like. These may be used alone or in combination of two or more.

  The UV-stable unsaturated monomer is a monomer containing a polymerizable unsaturated group and a site having UV-stabilizing ability. As a specific example, for example, 4- (meth) acryloyloxy-2,2,6 , 6-tetramethylpiperidine, 4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4, -(Meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine, 4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy -2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, and the like. These may be used alone or in combination of two or more. May be.

  When an epoxy group-containing unsaturated monomer is used as the polymerizable unsaturated monomer, it is suitable that the monomer mixture contains 70 wt% or less, preferably 1 to 20 wt%. When an alkoxysilyl group-containing unsaturated monomer is used, it is suitable that it is contained in the monomer mixture in an amount of 70% by weight or less, preferably 1 to 30% by weight. Further, when an ultraviolet-absorbing unsaturated monomer is used as the polymerizable unsaturated monomer, it is preferably contained in the monomer mixture in an amount of 20% by weight or less, preferably 0.1 to 10% by weight. In the case where an ultraviolet-stable unsaturated monomer is used, it is preferable that the monomer mixture contains 20% by weight or less, preferably 0.1 to 10% by weight.

  The organic solvent at the time of copolymerization is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as butyl acetate, and alcohols such as isopropanol Examples thereof include aliphatic solvents such as system solvents, mineral spirits, n-hexane, n-octane, 2,2,2-trimethylpentane, isooctane, n-nonane, cyclohexane, and methylcyclohexane. These may be used alone or in combination. The polymerization initiator is not particularly limited, but azobisisobutyronitrile, 2,2-azobis (2-methylbutyronitrile), 2,2-azobis (2-methylpropionitrile), 2,2-azobis ( 2,4-dimethylvaleronitrile) and other azo initiators, benzoyl peroxide, t-butylperoxyoctanoate, diisobutyl peroxide, di (2-ethylhexylperoxypivalate), decanoyl peroxide Oxide systems can be used.

  The weight average molecular weight of the acrylic resin (A) obtained as described above is 1,000 to 100,000, preferably 2000 to 50,000. If it is less than 1,000, the weather resistance is insufficient. On the other hand, if it exceeds 100,000, the compatibility with the epoxy resin (B), the organosilane compound (E) and the amine curing agent (C) becomes insufficient. . In addition, in this specification, a weight average molecular weight is the value which converted the molecular weight measured by the gel permeation chromatography on the basis of the molecular weight of polystyrene.

  The solubility parameter value of the acrylic resin (A) (hereinafter sometimes abbreviated as “SP value”) is 8 to 10, preferably 8 to 9.5. If it is less than 8, the compatibility with the epoxy resin (B) is insufficient, and if it exceeds 10, the compatibility with the organosilane compound (E) decreases, which is not preferable. Here, the SP value of the acrylic resin, which is a copolymer of the monomer mixture, can be calculated by the following formula.

SP value = SP1 × fw1 + SP2 × fw2 + ......... + SPn × fwn
(In the above formula, SP1, SP2,... SPn represents the SP value of the homopolymer of each monomer, and fw1, fw2,. The SP value of the homopolymer of each monomer is described in J. Paint Technology, vol. 42 [541] 76-102 (1970).

  The epoxy resin (B) has at least two epoxy groups in one molecule. Examples of the epoxy resin include glycidyl ether type epoxy resins such as bisphenol A and bisphenol F, and hydrogenated bisphenol A type. Epoxy resins, glycidyl ester type epoxy resins, alicyclic epoxy resins, polyglycol type epoxy resins; modified epoxy resins obtained by modifying these epoxy resins with at least one modifier selected from alkylphenols and fatty acids; alkylphenols or alkylphenols Epoxy group-introduced alkylphenol or alkylphenol novolac resin obtained by reacting novolak resin with epichlorohydrin; dibasic acid-modified epoxy resin, dibasic acid and carboxyl group-containing phenol , And the like sex epoxy resin. The weight average molecular weight of the epoxy resin (B) is in the range of about 200 to about 3,000, preferably in the range of about 300 to about 1,000. When the weight average molecular weight is less than 200, the anticorrosion property is lowered, and when it exceeds 3,000, the compatibility with other resins becomes poor, which is not preferable.

  As the epoxy resin (B), specifically, “Epicoat 828”, “Epicoat 830”, “Epicoat 834”, “Epicoat 806H” (manufactured by Japan Epoxy Resin Co., Ltd.), “DER-331J” (manufactured by Dow Chemical Co., Ltd.) ), “AER260” (manufactured by Asahi Kasei Epoxy), “ST-3000”, “ST-5080” (manufactured by Tohto Kasei), “Epomic R # 140P” (manufactured by Mitsui Chemicals), “ERL-4221”, “ Commercial products such as “ERL-4229” (manufactured by Union Carbide), “Denacol EX-830” (manufactured by Nagase Kasei Kogyo Co., Ltd.), and “Haripol EP-450” (manufactured by Harima Kasei Co., Ltd.) can be used.

  When the acrylic resin (A) contains a functional group capable of reacting with an epoxy group, it can be used as an acrylic-modified epoxy resin obtained by at least partially reacting the acrylic resin (A) with the epoxy resin (B). is there. As a method for synthesizing such an acrylic-modified epoxy resin, for example, a monomer having a carboxyl group or a monomer having an amino group is copolymerized as the acrylic resin (A), and at least the epoxy group contained in the epoxy resin (B) The polymerizable unsaturated monomer that is partially or fully reacted or that forms the acrylic resin (A) on the epoxy resin (B) is graft-polymerized or copolymerized in the presence of a polymerization initiator. When such a reaction is an epoxy group-carboxyl group reaction, a reaction catalyst therefor may be used. Examples of the catalyst include tetraethylammonium bromide, tetrabutylammonium bromide, tetraethylammonium chloride, tetrabutylphosphonium bromide, tritium. Examples thereof include quaternary salt catalysts such as phenylbenzylphosphonium chloride and amines such as triethylamine and tributylamine.

  The blending ratio of the acrylic resin (A) and the epoxy resin (B) is 5 to 95% by weight, preferably 10 to 90% by weight, and (B) 5 to 5% by weight with respect to the total solid content of these resins. 95% by weight, preferably 10 to 90% by weight. When the blending ratio of the acrylic resin (A) is less than 5% by weight, the coating film tends to be cracked, and the drying property after coating is lowered. On the other hand, when it exceeds 95% by weight, the corrosion resistance and weather resistance are lowered. Absent. If the blending ratio of the epoxy resin (B) is less than 5% by weight, the anticorrosion property is lowered. Conversely, if it exceeds 95% by weight, the weather resistance is lowered, which is not preferable.

  The amine curing agent (C) used in the coating composition (III) is a curing agent that reacts with the epoxy group in the epoxy resin (B), and further when an alkoxysilyl group is introduced into the coating composition. This also serves as a reaction catalyst when water in the air undergoes hydrolysis and condensation reactions.

  The amine curing agent (C) is an amine that can contain an aminosilane, and in particular, a polyfunctional amine can be suitably used. Examples of the polyfunctional amine include aliphatic or alicyclic polyamines and epoxy resins of the polyamines. Examples thereof include adducts, polyamidoamines, aromatic amines, aliphatic or alicyclic Mannich compounds, and these may be used alone or in combination of two or more. Specifically, commercially available products such as “Sunmide J230N”, “Sunmide I518” (manufactured by Sanwa Chemical Industry Co., Ltd.), and “Ditocraal B1969” (manufactured by Daito Sangyo Co., Ltd.) can be used.

The aminosilane is usually represented by the following formula (1)
X-Si- (OY) ₃ (1)
(In the formula, X is an alkyl group, aryl group, alkoxyalkyl group or cycloalkyl group which may contain an —NH ₂ group and / or —NH— bond, and Y is an alkyl group having 1 to 6 carbon atoms. Specifically, N-β- (aminoethyl) aminopropyltrimethoxysilane, N-β- (aminoethyl) aminopropyltriethoxysilane, N-phenyl-γ-aminopropyl Examples include trimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and the like. These may be used alone or in combination of two or more. As a commercial item, "KBM-603", "KBE-903" (made by Shin-Etsu Chemical Co., Ltd.) etc. are mentioned, for example.

  As the amine curing agent (C), a ketimized amine curing agent can also be used. The ketiminated amine curing agent reacts with the epoxy group in the epoxy resin (B) when the protection of the amino group is released, and when an alkoxysilyl group is further introduced into the coating composition (III). This also serves as a reaction catalyst when water in the air undergoes hydrolysis and condensation reactions.

  The ketiminated amine curing agent can include a ketimylated aminosilane, and the above-mentioned polyfunctional amines and ketimine products of aminosilane can be used. In the ketimination of the polyfunctional amine and aminosilane, a primary amino group in these is blocked with a carbonyl compound to form a protected amino group. Examples of the carbonyl compound include ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl t-butyl ketone, diisobutyl ketone, and cyclohexanone, and aldehydes such as acetaldehyde and benzaldehyde. It may be partially aldiminated.

  The amine curing agent (C) contains the polyfunctional amine and aminosilane, or the polyfunctional amine and aminosilane ketimine compound, and may be either one of them, but it is desirable to use them in combination. It is preferable that the aminosilane is 0.1 mol or more with respect to 1 mol of the polyfunctional amine. If the aminosilane ratio is less than 0.1 mol, the weather resistance is lowered, which is not preferable.

  The compounding ratio of the amine curing agent (C) is (the number of equivalents of active hydrogen of amino group or the number of equivalents of active hydrogen of amino group from which the carbonyl compound is released) / (epoxy resin (B) and acrylic resin (A). ) The ratio of the number of equivalents of epoxy groups contained therein is in the range of 0.1 to 2.0, preferably in the range of 0.2 to 1.2. The resulting coating film has curability, corrosion resistance, and weather resistance. It is suitable from the point of property.

In the coating composition (III), an organosilane compound (D) can be contained as required from the viewpoint of the weather resistance of the coating film. The organosilane compound (D) is usually represented by the formula (2)
(R ¹ SiO _3/2 ) _m (R ² R ³ SiO _2/2 ) _n (2)
(In the formula, R ¹ , R ² and R ³ are the same or different in each repeating unit, and are a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an aryl group or an alkoxy group, and m is from 0 to 0) 134, n is within the range of 0 to 134, and m + n ≧ 2.
In particular, a linear or branched polyorganosiloxane having at least one silanol group or alkoxysilyl group at the molecular chain terminal or side chain is preferable. The weight average molecular weight is 400 to 30,000, preferably 1,000 to 10,000. In the formula ^(2), examples of the alkyl group having 1 to 6 carbon atoms in R ^1, R 2, ^{R 3} are, for example, methyl group, ethyl group, (iso) propyl group, a pentyl group, a hexyl group, a cyclohexyl group Specific examples of the aryl group for R ¹ , R ² and R ³ include a phenyl group and a tolyl group. Specific examples of the alkoxy group for R ¹ , R ² and R ³ include a methoxy group and an ethoxy group. Specific examples include phenylmethylalkoxysilicone oligomers and methylalkoxysilicone oligomers such as “DC3074”, “DC3037” (manufactured by Toray Dow Corning Silicone), “KR-9218”, “KR-212”, “ Commercial products such as “X-40-9220” (manufactured by Shin-Etsu Chemical Co., Ltd.) and “TSR165” (manufactured by Toshiba Silicone) can be used. These may be used singly or in combination of two or more, and these hydrolyzed / condensed products can also be used.

  Moreover, in order to orientate an alkoxysilyl group on the surface layer of the coating film and further improve the weather resistance, an alkylalkoxysilane and a hydrolysis / condensation product thereof can be used in combination with the organosilane compound (D). Specific examples of the alkylalkoxysilane include trimethoxymethylsilane, trimethoxyethylsilane, triethoxymethylsilane, trimethoxyisopropoxysilane, trimethoxyphenylsilane, triethoxyphenylsilane, dimethoxydimethylsilane, dimethoxydiethylsilane, and methoxytrimethylsilane. And methoxytriethylsilane. These may be used alone or in combination of two or more.

  When the organosilane compound (D) is used in the present invention, (A) is 5 to 5 with respect to the total resin solids of the acrylic resin (A), the epoxy resin (B), and the organosilane compound (D). 95% by weight, preferably 10 to 80% by weight, (B) is 5 to 95% by weight, preferably 10 to 80% by weight, and (D) is 0 to 90% by weight, preferably 10 to 80% by weight. If the proportion of the organosilane compound (D) exceeds 90% by weight, the anticorrosion property is lowered, which is not preferable.

  In the coating composition (III), it is preferable to add a curing catalyst (E) as necessary in order to promote the formation of siloxane bonds. Examples of the curing catalyst (E) include tin octylate, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dibutyltin diacetate, dioctyltin diacetate, dibutyltin dilaurate. Organic tin compounds such as dibutyltin oxide, dioctyltin oxide, dibutyltin dioctate, monobutyltin trioctate, dibutyltin fatty acid salt; tris (ethylacetoacetate) aluminum, aluminum di-isopropoxymonoethylacetoacetate, tetraisopropyl titanate, etc. Examples thereof include metal chelate compounds and metal alkoxides; boric acid compounds such as trimethyl borate, triethyl borate, and tributyl borate.

  The amount of the curing catalyst (E) is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total resin solid content in the paint.

  The coating composition (III) contains an aminosilane immediately before use in the main agent containing the acrylic resin (A), the epoxy resin (B) and, if necessary, an organosilane compound (D), a curing catalyst (E), etc. A room temperature-curable two-component coating composition obtained by mixing the obtained amine curing agent (C) can be obtained.

  The coating composition (III) in the case of using a ketiminated amine curing agent as the amine curing agent (C) may be a one-component type or a two-component type. Is preferable. In the case of a one-pack type, it is particularly desirable to add a dehydrating agent. As the dehydrating agent, known dehydrating agents can be used, and typical examples thereof include the following.

(1) Metal oxide or carbonized material rich in porosity in powder form; for example, synthetic silica, activated alumina, zeolite, activated carbon, etc.
(2) Calcium compounds having a composition such as CaSO 4, CaSO 4 .1 / 2H 2 O, CaO; for example, calcined gypsum, soluble gypsum, quick lime, etc.
(3) Metal alkoxides; for example, aluminum isopropylate, aluminum sec-butyrate, tetraisopropyl titanate, tetra n-butyl titanate, zirconium 2-propylate, zirconium n-butyrate, ethyl silicate, vinyltrimethoxysilane, etc.
(4) Organic alkoxy compounds; for example, methyl orthoformate, ethyl orthoformate, methyl orthoacetate, ethyl orthoacetate, isopropyl orthoacetate, dimethoxypropane, etc.
(5) Monofunctional isocyanates; for example, additive TI (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name).

  These dehydrating agents can be used alone or in combination of two or more. The amount of the dehydrating agent to be used varies depending on the amount of water contained in the coating composition and the absorption of the dehydrating agent, the adsorption capacity or the reactivity with water. Is suitably in the range of 0.2 to 25% by weight, preferably 0.5 to 15% by weight, based on the weight of the coating composition.

If necessary, the coating composition (III) is further improved by the following formula (3) to prevent rain stains and the like and to improve the stain resistance.
Si (OR ⁷ ) ₄ (3)
(In the formula (3), R ⁷ is the same or different and is a monovalent hydrocarbon group having 1 to 10 carbon atoms) and / or a condensate thereof is added to the coating composition. Is preferred. In formula (3), examples of R ⁷ include an alkyl group and an aryl group. The alkyl group may be either linear or branched, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl. , I-pentyl, neopentyl, n-hexyl, i-hexyl, n-octyl group and the like, among which a lower alkyl group having 1 to 4 carbon atoms is preferable. The aryl group may be monocyclic or polycyclic, and examples thereof include phenyl, toluyl, xylyl, and naphthyl groups. Among them, the phenyl group is preferable.

  Specific examples of the organosilicate include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraphenoxysilane, and dimethoxydiethoxysilane. These may be used alone or in combination of two or more.

The organosilicate condensate is a branched or linear condensate of organosilicates represented by the above general formula, and has a condensation degree of 2 to 100 from the viewpoint of stain resistance. preferable. As the organosilicate condensate, R ⁷ is a lower alkyl group having 1 to 4 carbon atoms and a condensation degree of 2 to 100 is particularly preferable. Further, two or more kinds of condensates of different organosilicates may be mixed and used.

  Further, the organosilicate and / or its condensate may be modified with a mercapto compound or boric acid compound, or modified to introduce an alkyl group having 11 or more carbon atoms into the organosilicate and / or its condensate. You may do it.

  The organosilicate and / or its condensate is suitably blended in an amount of 0.1 to 50 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the total resin solids in the paint. If the blending amount is less than 0.1 parts by weight, the stain resistance of the coating film is inferior, and if it exceeds 50 parts by weight, the coating film becomes stiff and may cause defects such as cracking and gloss reduction.

  In order to promote hydrolysis of the organosilicate and / or its condensate, a boric acid compound such as trialkyl borate, an organic tin compound, an aluminum compound, an acidic phosphate, etc. may be added as necessary. Can do.

  In order to improve the weather resistance, it is preferable to add one or both of an ultraviolet absorber and an ultraviolet stabilizer to the coating composition (III) as necessary. Examples of such ultraviolet absorbers include benzotriazole, triazine, anilide, benzophenone, oxalate anilide, and cyanoacrylate. Commercially available products include “Tinuvin 1130” and “Tinuvin 400” (above, Ciba Specialty). Chemicals), “CYASORB UV-1164L” (above, Mitsui Cytec), “SANDUVOR 3206” (above, Clariant Japan). As the UV stabilizer, a hindered amine type is suitable, and as commercially available products, “Tinuvin 123”, “Tinuvin 144” (above, manufactured by Ciba Specialty Chemicals), “Sanol LS-292” (above, manufactured by Sankyo Co., Ltd.) Can be illustrated.

  The coating composition (III) can be used as a clear coating, and can also be used as an enamel coating by blending pigments such as a color pigment, an extender pigment, and a rust preventive pigment. These pigments include titanium dioxide, carbon black, lamp black, zinc oxide, iron oxide, toluidine, benzine yellow, phthalocyanine blue, phthalocyanine green, and carbazole violet, crystalline silica, barium sulfate, magnesium silicate, calcium silicate, mica Mica-like iron oxide, calcium carbonate, zinc powder, aluminum, aluminum silicate, gypsum, feldspar and the like. These can be used alone or in combination. The blending ratio of the pigment is preferably 10 to 40 vol% in terms of pigment volume concentration (PVC). As a method for dispersing the pigment, a conventionally known method can be adopted without any particular limitation, and examples thereof include a method of dispersing by a ball mill, a sand mill or the like.

  If necessary, the coating composition (III) may further include a thickening agent, an anti-sagging agent, a leveling agent, an antifoaming agent, a dispersant, an organic solvent, and other additives for paints. An alkyd resin or the like can be blended with the main agent or the amine curing agent (C).

  As the organic solvent, conventionally known solvents such as hydrocarbon, ester, ketone, ether, alcohol and the like can be used without particular limitation. Depending on the lower layer coating film, the aliphatic hydrocarbon solvent and the high-boiling aromatic hydrocarbon solvent listed in the description of the epoxy resin primer (II) described above may be used as a dilution solvent when coating and / or painting. It is desirable to use an organic solvent containing 80% by weight or more, preferably 95% by weight or more, more preferably 100% by weight of a hydrocarbon solvent selected from

  As a coating method of the coating composition (III), general methods such as brush coating, roller coating, spray coating, and various coater coatings can be used. The coating amount is not particularly limited, but it is usually suitable that the coating thickness is about 15 to 400 μm, preferably about 25 to 300 μm, in one coating finish.

  In the method of the present invention, it is desirable from the viewpoint of rust prevention and the like that the total film thickness of the multilayer coating film in each coating process is 100 μm or more.

  Hereinafter, the present invention will be described in more detail with reference to examples. “Part” and “%” mean “part by weight” and “% by weight”, respectively, unless otherwise specified.

Manufacture example 1 of acrylic resin (A)
While charging 660 parts of xylene and 20 parts of “MOA” (trade name, manufactured by Niho Chemical Co., Ltd., active ingredient orthoacetic acid methyl ester, dehydrating agent) in the flask, stirring to 130 ° C. while ventilating nitrogen gas The temperature rose. Next, while maintaining the temperature at 130 ° C.
Methyl methacrylate 600 parts Methoxyethyl acrylate 100 parts n-butyl acrylate 300 parts t-butyl peroxy-2-ethylhexanoate 40 parts of a mixture was added dropwise over 3 hours. Thereafter, the mixture was aged for 2 hours while maintaining the temperature at 130 ° C. to obtain an almost colorless and transparent acrylic resin solution (A1) having a non-volatile content of 60%.

Production Example 2
Except having used the following compound as a mixture of a vinyl monomer and a polymerization initiator in manufacture example 1, it carried out similarly to manufacture example 1 and obtained the acrylic resin solution (A2) of 60% of non volatile matters.

Glycidyl methacrylate 100 parts Methyl methacrylate 600 parts Methoxyethyl acrylate 100 parts n-Butyl acrylate 200 parts t-Butyl peroxy-2-ethylhexanoate 40 parts

Production Example 3
Except having used the following compound as a mixture of a vinyl monomer and a polymerization initiator in manufacture example 1, it carried out similarly to manufacture example 1 and obtained the acrylic resin solution (A3) of 60% of non volatile matters.

Glycidyl methacrylate 100 parts Methyl methacrylate 500 parts Methoxyethyl acrylate 100 parts n-Butyl acrylate 200 parts γ-methacryloxypropyltrimethoxysilane 100 parts t-butylperoxy-2-ethylhexanoate 40 parts

Production Example 4
660 parts of mineral spirits and 20 parts of “MOA” (trade name, manufactured by Niho Chemical Co., Ltd., active ingredient orthoacetic acid methyl ester, dehydrating agent) are charged into the flask, and the mixture is stirred up to 130 ° C. while aeration of nitrogen gas. While raising the temperature. Next, while maintaining the temperature at 130 ° C.
Isobonyl acrylate 400 parts butyl methacrylate 200 parts butyl acrylate 200 parts 2-ethylhexyl acrylate 100 parts γ-methacryloxypropyltrimethoxysilane 100 parts t-butylperoxy-2-ethylhexanoate 40 parts of a mixture for 3 hours It was dripped at. Thereafter, the mixture was aged for 2 hours while maintaining at 130 ° C. to obtain a substantially colorless and transparent acrylic resin solution (A4) having a non-volatile content of 60%.

Production Example 5
532 parts of mineral spirits and 429 parts of "Epicoat 828" (Japan Epoxy Resin, bisphenol A type epoxy resin, epoxy equivalent 187) are heated to 140 ° C under a nitrogen stream, and a mixture of the following vinyl monomer and polymerization initiator: Was added dropwise over 3 hours, and aged for 2 hours after the addition. Next, 0.2 part of tetraethylammonium bromide was added and reacted for about 2 hours. When the resin acid value reached 0.3 mgKOH / g, 157 parts of mineral spirit was added to obtain an acrylic-modified epoxy resin solution (A5). It was. The resin solution had a nonvolatile content of 65% and an epoxy equivalent of 652.

Methacrylic acid 10 parts Styrene 250 parts Ethyl acrylate 200 parts i-Butyl methacrylate 200 parts 2-ethylhexyl acrylate 290 parts γ-methacryloxypropyltrimethoxysilane 50 parts t-butyl peroxy-2-ethylhexanoate 80 parts

Preparation examples 1-5 of coating composition (III)
In a ball mill, an epoxy resin and a pigment are blended according to the formulation shown in Table 1, and a pigment dispersion paste is prepared by dispersing for 1 hour. The main component is adjusted according to the formulation shown in Table 1, and a curing agent is mixed. Each paint was obtained. In addition, the number of Table 1 is a solid content display, and a symbol is as follows.

B1: “Epicoat 828EL”: manufactured by Japan Epoxy Resin, bisphenol A type epoxy resin, epoxy equivalent 187
B2: “ST-3000”: Toto Kasei Co., Ltd., trade name, hydrogenated bisphenol type epoxy resin epoxy equivalent 230
B3: “ST-5080”: manufactured by Tohto Kasei Co., Ltd., trade name, bisphenol type epoxy resin / hydrogenated bisphenol type epoxy resin, molecular weight 1200
D1: “KR212”: Phenylmethylalkoxysilicone oligomer produced by Toray Dow Corning Silicone Co., Ltd. C1: N-β (aminoethyl) γ-aminopropyltrimethoxysilane C2: γ-aminopropyltriethoxysilane C3: “Sunamide 390” -70 ": Sanwa Chemical Industry Co., Ltd., modified polyamidoamine C4: 3-trimethoxysilyl-N- (1,2-dimethyl-propylidene) propyl obtained by ketiminizing γ-aminopropyltrimethoxysilane with methyl isopropyl ketone Amine E1: “CAT-AC”: Shin-Etsu Silicone Co., Ltd., trade name, aluminum chelate catalyst, active ingredient 50%
E2: Tetraisopropyl titanate E3: Dibutyltin acetate F1: “Tinuvin 1130”: Ciba Specialty Chemicals, benzotriazole UV absorber G1: “Sanol LS-292”: Sankyo Co., Ltd., hindered amine UV stabilizer H1 : Trimethyl orthoacetate

Application Example 1
The organic zinc rich paint “SD Zinc 500” (trade name, manufactured by Kansai Paint Co., Ltd.) is spray-coated on a sandblasted steel plate having a size of 3.2 × 500 × 500 mm by spraying to a dry film thickness of 75 μm. After drying at (20 ° C.) for 1 day, the coating composition (III-1) was applied on the obtained coating film by spraying so that the dry film thickness was about 90 μm, and then at room temperature. After drying for 1 day, the coating composition (III-1) was applied by spraying so that the dry film thickness was about 85 μm, and dried at room temperature for 7 days to prepare a test coating plate.

Example 2
The organic zinc rich paint “SD Zinc 500HF” (trade name, manufactured by Kansai Paint Co., Ltd.) was sprayed onto a sandblasted steel plate having a size of 3.2 × 500 × 500 mm by spraying so that the dry film thickness was 75 μm. After drying at (20 ° C.) for 1 day, an epoxy resin primer “ESCO NB Safety” (trade name, weak solvent-soluble acrylic-modified epoxy resin paint manufactured by Kansai Paint Co., Ltd.) is applied on the obtained coating film. The coating was applied by spraying to a dry film thickness of about 60 μm and dried at room temperature for 1 day.
After coating the coating composition (III-3) on the coating film with a spray so that the dry film thickness is about 60 μm, the coating composition (III-3) is dried at room temperature for 1 day. A test coating plate was prepared by coating with a spray so that the dry film thickness was about 55 μm and drying at room temperature for 7 days.

Example 3
The organic zinc rich paint “SD Zinc 500HF” (trade name, manufactured by Kansai Paint Co., Ltd.) was sprayed onto a sandblasted steel plate having a size of 3.2 × 500 × 500 mm by spraying so that the dry film thickness was 75 μm. After drying at (20 ° C.) for 1 day, an epoxy resin primer “Epomarine Primer” (trade name, epoxy resin paint, manufactured by Kansai Paint Co., Ltd.) is sprayed on the obtained coating film. After coating at about 60 μm and drying at room temperature for 1 day, an epoxy resin primer “ESCO NB Safety” (trade name, weak solvent soluble acrylic modified epoxy resin paint manufactured by Kansai Paint Co., Ltd.) Was applied by spraying to a dry film thickness of about 60 μm and dried at room temperature for 1 day.
On the coating film, the coating composition (III-1) was applied by spraying so that the dry film thickness was about 55 μm, and then dried at room temperature for 7 days to prepare a test coating plate.

Example 4
The organic zinc rich paint “SD Zinc 500” (trade name, manufactured by Kansai Paint Co., Ltd.) is spray-coated on a sandblasted steel plate having a size of 3.2 × 500 × 500 mm by spraying to a dry film thickness of 75 μm. After drying at (20 ° C.) for 1 day, an epoxy resin primer “Epomarine Primer” (trade name, epoxy resin paint, manufactured by Kansai Paint Co., Ltd.) is sprayed on the obtained coating film. Was applied to a thickness of about 60 μm and dried at room temperature for 1 day. On the coating film, an intermediate coating “Seractect U Intermediate Coating” (trade name, epoxy resin coating, manufactured by Kansai Paint Co., Ltd.) is applied by spraying to a dry film thickness of 30 μm and dried at room temperature for 1 day. It was.
On the coating film, the coating composition (III-2) was applied by spraying so that the dry film thickness was about 85 μm, and dried at room temperature for 7 days to prepare a test coating plate.

Example 5
The organic zinc rich paint “SD Zinc 500” (trade name, manufactured by Kansai Paint Co., Ltd.) is spray-coated on a sandblasted steel plate having a size of 3.2 × 500 × 500 mm by spraying to a dry film thickness of 75 μm. After drying at (20 ° C.) for 1 day, an epoxy resin primer “ESCO NB Safety” (trade name, weak solvent-soluble acrylic-modified epoxy resin paint manufactured by Kansai Paint Co., Ltd.) is applied on the obtained coating film. The coating was applied by spraying to a dry film thickness of 60 μm and dried at room temperature for 1 day. On the coating film, an intermediate coating “Seractect U Mild Intermediate Coating” (trade name, weak solvent type urethane resin coating, manufactured by Kansai Paint Co., Ltd.) is sprayed to a dry film thickness of 30 μm, and at room temperature. Dried for 1 day.
On the coating film, the coating composition (III-2) was applied by spraying so that the dry film thickness was about 85 μm, and dried at room temperature for 7 days to prepare a test coating plate.

Example 6
The organic zinc rich paint “SD Zinc 500” (trade name, manufactured by Kansai Paint Co., Ltd.) is spray-coated on a sandblasted steel plate having a size of 3.2 × 500 × 500 mm by spraying to a dry film thickness of 75 μm. After drying at (20 ° C.) for 1 day, an epoxy resin primer “ESCO NB Safety” was applied on the obtained coating film by spraying to a dry film thickness of 60 μm, and at room temperature for 1 day. After drying, an intermediate coating “Serect U Mild Intermediate Coating” (trade name, weak solvent type urethane resin coating) manufactured by Kansai Paint Co., Ltd. is sprayed onto the coating film to a dry film thickness of 30 μm. And dried at room temperature for 1 day.
On the coating film, the coating composition (III-4) was applied by spraying so that the dry film thickness was about 85 μm, and dried at room temperature for 7 days to prepare a test coating plate.

Example 7
In Example 2, a test coated plate was prepared in the same manner as in Example 2 except that the coating composition (III-5) was used instead of the coating composition (III-3).

Comparative Example 1
The organic zinc rich paint “SD Zinc 500” (trade name, manufactured by Kansai Paint Co., Ltd.) is spray-coated on a sandblasted steel plate having a size of 3.2 × 500 × 500 mm by spraying to a dry film thickness of 75 μm. After drying at (20 ° C.) for 1 day, an epoxy resin primer “Epomarine Primer” (trade name, epoxy resin paint, manufactured by Kansai Paint Co., Ltd.) is sprayed on the obtained coating film. After coating at 60 μm and drying at room temperature for 1 day, an epoxy resin primer “ESCO NB Safety” (trade name, weak solvent-soluble acrylic-modified epoxy resin paint, manufactured by Kansai Paint Co., Ltd.) is applied thereon. The coating was applied by spraying to a dry film thickness of 60 and dried at room temperature for 1 day.

  On the coating film, an intermediate coating “Seractect U Intermediate Coating” (trade name, epoxy resin coating, manufactured by Kansai Paint Co., Ltd.) is applied by spraying to a dry film thickness of 30 μm and dried at room temperature for 1 day. It was. On top of the coating, a top coating “Seractect U top coating” (trade name, polyurethane resin coating, manufactured by Kansai Paint Co., Ltd.) is applied by spraying so that the dry film thickness is about 25 μm, and then dried at room temperature for 7 days. A test coated plate was prepared.

Comparative Example 2
The organic zinc rich paint “SD Zinc 500HF” (trade name, manufactured by Kansai Paint Co., Ltd.) was sprayed onto a sandblasted steel plate having a size of 3.2 × 500 × 500 mm by spraying so that the dry film thickness was 75 μm. After drying at (20 ° C.) for 1 day, an epoxy resin primer “Epomarine Primer” (trade name, epoxy resin paint, manufactured by Kansai Paint Co., Ltd.) is sprayed on the obtained coating film. After coating at 60 μm and drying at room temperature for 1 day, an epoxy resin primer “ESCO NB Safety” (trade name, weak solvent-soluble acrylic-modified epoxy resin paint, manufactured by Kansai Paint Co., Ltd.) is applied thereon. The coating was applied by spraying to a dry film thickness of 60 μm and dried at room temperature for 1 day.
On the coating film, an intermediate coating “Seractect U Mild Intermediate Coating” (trade name, weak solvent type urethane resin coating, manufactured by Kansai Paint Co., Ltd.) is sprayed to a dry film thickness of 30 μm, and at room temperature. Dried for 1 day. On the coating film, a top coating “Seractect U mild top coating” (trade name, weak solvent-soluble polyurethane resin coating made by Kansai Paint Co., Ltd.) was applied by spraying so that the dry film thickness was about 25 μm, and then room temperature was applied. And dried for 7 days to prepare a test coated plate.

Comparative Example 3
The organic zinc rich paint “SD Zinc 500” (trade name, manufactured by Kansai Paint Co., Ltd.) is spray-coated on a sandblasted steel plate having a size of 3.2 × 500 × 500 mm by spraying to a dry film thickness of 75 μm. After drying for 7 days at (20 ° C.), an epoxy resin primer “Epomarine Primer” (trade name, epoxy resin paint, manufactured by Kansai Paint Co., Ltd.) is sprayed on the resulting coating film to dry the film thickness. Was coated to 60 μm and dried at room temperature for 1 day.

  On the coating film, an intermediate coating “Seractect U Intermediate Coating” (trade name, epoxy resin coating, manufactured by Kansai Paint Co., Ltd.) is applied by spraying to a dry film thickness of 30 μm and dried at room temperature for 1 day. It was. The top coat “Epomarine HB” (trade name, thick film type epoxy resin paint, manufactured by Kansai Paint Co., Ltd.) is applied on the coating film by spraying so that the dry film thickness is about 85 μm, and dried at room temperature for 7 days. A test coated plate was made.

Test method (* 1) Whitening property: Half the area of each test coated plate is submerged for 1 hour, and after the submersion is finished, the coated plate is pulled up, and the coating state of the submerged part and the unsubmerged part is observed. Evaluation was based on criteria. The results are shown in Table 2.
○: There is no difference in color △: There is a slight difference (the submerged part is slightly whiter)
×: There is a big difference (submerged part is much whiter)
(* 2) Corrosion prevention: After each test coating plate was cut with a width of 1 mm so as to reach the substrate, a salt spray test was conducted for 500 hours in accordance with JIS K 5600 7-1, and then the coating state was observed. And evaluated according to the following criteria (◯: no abnormality, Δ: slight rusting, x: marked rusting). The results are shown in Table 2.
(* 3) Weather resistance test: Each test coated plate was tested for 300 hours using a sunshine carbon arc lamp type tester according to JIS K 5600 7-7. The glossiness of the coating film at that time was evaluated by comparing with the initial coating surface not subjected to the accelerated weather resistance test (◯: almost no change, Δ: slight decrease, ×: significant decrease). The results are shown in Table 2.

Claims (8)

After coating a zinc rich paint (I) mainly composed of an epoxy resin binder and zinc powder on the surface to be coated, an acrylic resin (A) and an epoxy resin having at least two epoxy groups in one molecule (B And a coating composition (III) containing an amine curing agent (C) that may contain aminosilane. The coating method according to claim 1, wherein after the zinc-rich paint (I) is applied, the epoxy resin primer (II) is applied, and the paint composition (III) is further applied. In the coating composition (III), the acrylic resin (A) contains a functional group capable of reacting with an epoxy group, and is an acrylic modified epoxy resin obtained by at least partially reacting the acrylic resin (A) and the epoxy resin (B). The coating method according to claim 1 or 2, wherein The coating method according to claim 1 or 2, wherein the coating composition (III) further contains an organosilane compound (D). In the coating composition (III), the blending ratio of the acrylic resin (A), the epoxy resin (B), and the organosilane compound (D) is 5 to 95% by weight in the total resin solid content (A) (B The coating method according to claim 4, wherein 5) to 95% by weight and (D) 0 to 90% by weight. The coating method according to claim 1 or 2, wherein the amine curing agent (C) of the coating composition (III) is ketiminated. The coating method according to claim 1 or 2, wherein the coating composition (III) contains a curing catalyst (E). The coating composition (III) contains 80% by weight or more of a hydrocarbon solvent selected from an aliphatic hydrocarbon solvent and a high-boiling aromatic hydrocarbon solvent as a dilution solvent at the time of coating and / or coating. The coating method according to claim 1 or 2, wherein an organic solvent is used.