JP2012066204A - Method for forming multilayer coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a multilayer coating film including a primer coating film and excellent in workability and corrosion resistance in the worked portion even when forming a cured primer coating film at a lower temperature than heretofore for energy saving.SOLUTION: There is provided a method for forming a multilayer coating film including: a step of forming a cured primer coating film by coating an aqueous primer composition comprising a carbonyl group-containing modified epoxy resin (A), a crosslinking agent (B) including hydrazide compounds and/or semicarbazide compounds and antirust pigment (C) and by drying at a lower temperature than heretofore; and a step of coating a top coating composition on the cured primer coating film to perform heat-curing.

Description

  The present invention relates to a method for forming a multilayer coating film. More specifically, the present invention relates to a multilayer coating film forming method including a step of forming a cured primer coating film at a temperature lower than conventional.

  Pre-coated steel sheets are widely used in building roofs, walls, shutters and other building materials, home appliances, and steel furniture. This pre-coated steel sheet is manufactured by applying a primer paint to a plated steel sheet, baking it at a material reaching maximum temperature of 180 ° C or higher, and then applying a top coating and baking at a temperature of 180 ° C or higher. From the viewpoint, it is desired to lower the maximum material temperature. However, when a conventional primer coating is applied and a top coating is applied onto a primer coating obtained by baking at a low temperature, for example, a material maximum temperature of less than 180 ° C., the interface between the primer coating and the top coating In addition to the deterioration of the final appearance of the finally obtained multilayer coating film, deterioration of the top coating film appearance may be promoted when used outdoors.

  On the other hand, adverse effects on the environment due to the volatilization of organic substances into the atmosphere have become a problem in recent years. From the viewpoint of environmental conservation, replacement of organic solvent-based paints with water-based paints with reduced use of organic solvents is desired. Yes. Patent Document 1 discloses a resin composition containing a carbonyl group-containing acrylic resin emulsion and a dihydrazide compound suitable for a one-component water-based paint capable of forming a cured coating film by drying at room temperature. However, when this resin composition is used as a water-based primer coating for a pre-coated steel sheet, even when baked at a material reaching maximum temperature of 180 ° C. or higher, the water resistance and corrosion resistance may be inferior.

  Patent Document 2 discloses an amide epoxy resin obtained by a reaction between an epoxy resin and a Michael adduct of an amino compound and an acrylamide compound as a technique that can apply an epoxy resin having excellent water resistance to a one-pack type paint. However, when the technique disclosed in Patent Document 2 is used as a primer coating for a pre-coated steel sheet, the reaction of the epoxy group contained in the primer coating is fast, and thus the primer coating may have poor storage stability. .

  Patent Document 3 discloses an aqueous coating composition containing an aqueous polymer having a carboxyl group as a low-temperature curable aqueous coating composition suitable for precoated steel sheet applications and an aqueous polymer having an oxazoline group as a crosslinking agent. . Although this composition was excellent in storability, the obtained coating film was sometimes inferior in water resistance and corrosion resistance.

JP-A-8-157775 Japanese Patent Laid-Open No. 7-48435 Japanese Patent Laid-Open No. 9-328656

  Accordingly, the present invention provides a multilayer coating film that can form a multilayer coating film having excellent processability and processed portion corrosion resistance even when a cured primer coating film is formed at a lower temperature than conventional for energy saving. An object is to provide a forming method.

As a result of intensive studies to achieve the above object, the inventors of the present invention have found that a carbonyl group-containing modified epoxy resin (A), a crosslinking agent (B) containing a hydrazide compound and / or a semicarbazide compound, and a rust preventive pigment (C). A step of coating a water-based primer composition containing, and drying at a lower temperature than before to form a cured primer coating, and a step of applying a top-coating composition on the cured primer coating and curing by heating. The present inventors have found that the above problems can be solved by a multilayer coating film forming method, and have completed the present invention. That is, the present invention comprises the following items.
1. A metal primer is coated with an aqueous primer composition containing a carbonyl group-containing modified epoxy resin (A), a crosslinking agent (B) containing a hydrazide compound and / or a semicarbazide compound, and a rust preventive pigment (C). Is dried in the range of 10 ° C. to less than 180 ° C. to form a cured primer coating film (1), and the top coating material is applied on the cured primer coating film obtained in step (1), and the material reaches the highest temperature. Is a method of forming a multi-layer coating film comprising a step (2) of drying in the range of 180 ° C. to 300 ° C. to form a top coat film.
2. The carbonyl group-containing modified epoxy resin (A) has at least one active hydrogen bonded to a nitrogen atom in one molecule, and has at least two amine compounds (a) having a carbonyl group and an epoxy group in one molecule. 2. The method for forming a multilayer coating film according to 1, which is produced by reacting an epoxy resin (b) having a reaction.
3. A coated article in which a multilayer coating film is formed on a metal material by the multilayer coating film forming method of 1 or 2.

  According to the method for forming a multilayer coating film of the present invention, a multilayer coating film having excellent workability and processed portion corrosion resistance can be obtained in a process that saves energy compared to the conventional method.

  Hereinafter, the multilayer coating film forming method of the present invention will be described in more detail. The multilayer coating film forming method of the present invention is an aqueous solution containing a carbonyl group-containing modified epoxy resin (A), a crosslinking agent (B) containing a hydrazide compound and / or a semicarbazide compound, and a rust preventive pigment (C) on a metal material. On the cured primer coating obtained in step (1), and applying the primer composition, drying the material reaching the maximum temperature in the range of 10 ° C. to less than 180 ° C. to form a cured primer coating, and step (1) And (2) forming a top coat film by applying a top coat paint and drying the material at a maximum temperature of 180 ° C. to 300 ° C.

  The aqueous primer composition includes a carbonyl group-containing modified epoxy resin (A), a crosslinking agent (B), and a rust preventive pigment (C).

[Carbonyl group-containing modified epoxy resin (A)]
The carbonyl group-containing modified epoxy resin (A) has at least one active hydrogen bonded to a nitrogen atom in one molecule, and at least two amine compounds (a) having a carbonyl group and an epoxy group in one molecule. It can manufacture by making it react with the epoxy resin (b) which has. The amine compound (a) can be obtained by a Michael addition reaction between diacetone acrylamide and an amine compound (c) having two or more active hydrogens bonded to a nitrogen atom in one molecule.

  The amine compound (c) may be a compound containing an oxygen atom, a sulfur atom, a nitrogen atom, etc., for example, methylamine, ethylamine, propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine. , T-butylamine, hexylamine, 2-methoxyethylamine, 2-ethoxyethylamine, 3-methoxypropylamine, 3-methylthiopropylamine, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylene Pentamine, iminobispropylamine, methyliminobispropylamine, lauryliminobispropylamine, N, N′-bisaminopropyl-1,3-propylenediamine, N, '-Bisaminopropyl-1,3-butylenediamine, 1,2-diaminopropane, bis- (3-aminopropyl) ether, bis- (3-aminopropoxy) ethane, 1,3bis- (3-aminopropoxy) C1-C16 such as -2,2-dimethylpropane, N-laurylpropylenediamine, N, N'-di-t-butylethylenediamine, N-methylethylenediamine, N-ethylethylenediamine, N, N-dimethylethylenediamine, allylamine An aliphatic compound having a carbon number of: cyclopentylamine, cyclohexylamine, cycloheptylamine, cyclooctylamine, aminomethylcyclohexane, 4-methylcyclohexylamine, 1-cyclohexylethylamine, 3,3,5-trimethylcyclohexylamine, Cycloaliphatic compounds having C1 to C16 carbon atoms such as Rondiamine and bisaminomethylcyclohexane; benzylamine, phenethylamine, 4-methylbenzylamine, N-aminopropylaniline, 2-amino-1,2-diphenylethanol 9-aminofluorene, benzhydrylamine, xylylenediamine, phenylenediamine, diaminodiphenylmethane, N-benzylethylenediamine, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2,3-diaminopyridine, 2,5 -Diaminopyridine, 2,3,6-triaminopyridine, N-aminopropylaniline, 2-amino-3-methylpyridine, 2-amino-4-methylpyridine, 2-amino-6-methylpyridine, 2-amino -3-ethylpyridine, 2- C1-C16 such as mino-3-propylpyridine, 2-amino-4,6-dimethylpyridine, 2,6-diamino-4-methylpyridine, 3-amino-6-isopropylpyridine, 2,6-diaminopyridine and the like. Aromatic compounds having carbon number; piperazine, N-aminopropylpiperazine, 2-methylpiperazine, 2,6-dimethylpiperazine, 2,5-dimethylpiperazine, 3-methylaminopiperidine, 2-aminomethylpiperazine, 3-amino Pyrrolidine, homopiperazine, N-aminopropylpiperazine, 1,4- (bisaminopropyl) piperazine, N-aminoethylpiperidine, N-aminopropylpiperidine, 2-aminomethylpiperidine, 4-aminomethylpiperidine, furfurylamine, tetrahydro Furfurylamine, 3- ( Heterocyclic compounds having C1-C16 carbon number such as methylamino) pyrrolidine, 5-methylfurfurylamine, 2- (furfurylthio) ethylamine, 2-picolylamine, 3-picolylamine, 4-picolylamine; 2-hydroxy Ethylamine, methyl (2-hydroxyethyl) amine, 1-amino-2-propanol, 3-amino-1-propanol, 2-amino-1-propanol, 1-amino-2-propanol, diethanolamine, 3-amino-1 , 2-propanediol, 2- (2-aminoethoxy) ethanol, N- (2-hydroxyethyl) ethylenediamine, compounds having one or more hydroxyl groups such as 2-amino-1,3-propanediol, and the like. it can.

  Among the amine compounds (c), an amine compound having one primary amino group in one molecule, an amine compound having one primary amino group and one secondary amino group in one molecule, and secondary amino group In view of the fact that the amine compound having two groups in one molecule and the amine compound having two primary amino groups in one molecule can increase the carbonyl group concentration of the carbonyl group-containing modified epoxy resin in the present invention, It is preferable from the viewpoint of easy adjustment of the molecular weight.

  When n-butylamine having one primary amino group in one molecule is selected as the amine compound (c), the reaction for producing the amine compound (a) by Michael addition reaction to diacetone acrylamide is represented by the following formula (1) Indicated by

  Further, when N-ethylethylenediamine, which is an amine compound having one primary amino group and one secondary amino group in each molecule, is selected as the amine compound (c), an amine by Michael addition reaction to diacetone acrylamide The reaction for producing the compound (a) is represented by the following formula (2).

  The Michael addition reaction in the present invention is usually carried out in the range of 0 to 200 ° C., preferably in the range of 50 to 120 ° C., to obtain the amine compound (a) as a desired reaction product in a short time. It is preferable from the point that it can be suppressed and a side reaction can be suppressed. Mixing so that the molar ratio of diacetone acrylamide and amine compound (c) is within the range of 1 / 0.8 to 1 / 5.0, and further within the range of 1 / 0.9 to 1 / 2.2. Thus, it is preferable to perform the Michael addition reaction from the viewpoint that unreacted diacetone acrylamide does not remain and the production of a compound that does not have active hydrogen that reacts with the epoxy group is suppressed.

  The Michael addition reaction can be carried out in the presence of water or an organic solvent, but is not particularly required. When using an organic solvent, the kind is not specifically limited, However, Well-known organic solvents, such as ester type, ether type, and alcohol type, can be used. When water or an organic solvent is used, the concentration of the reaction solution is preferably 20% or more, more preferably 50% or more. If it is more dilute than this, it is not preferable because the reaction hardly proceeds. The reaction time is usually 30 minutes to 5 hours, although it varies depending on the type of amino compound used.

  From the standpoint of corrosion resistance, the Michael addition reaction is preferably carried out with a colorless medium, but a catalyst can be used if necessary. The catalyst is not particularly limited. For example, metal alkoxides such as sodium methoxide, sodium ethoxide, and magnesium ethoxide; metal phenoxides such as sodium phenoxide; metal carbochelates such as sodium benzoate and potassium benzoate; triethylamine, Triethylenediamine, N, N-diethylaniline, N, N-dimethylaniline, N, N-dimethylbenzylamine, N-methylmorpholine, N-ethylmorpholine, N, N'-dimethylpiperazine, pyridine, picoline, 1,8 -Tertiary amines such as diazabicyclo (5,4,0) undecene-7; tetraethylammonium bromide, tetrabutylammonium bromide, benzyltriethylammonium chloride, trioctylmethylammonium chloride, cetyltrimethyl bromide Quaternary ammonium salts such as ruammonium iodide, tetrabutylammonium iodide, dodecyltrimethylammonium iodide, benzyldimethyltetradecylammonium acetate; quaternary phosphonium salts such as tetraphenylphosphonium chloride, triphenylmethylphosphonium chloride, tetramethylphosphonium bromide 2-methylimidazole, 2-ethylimidazole, 2-methyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-phenyl-4-methyl-5-hydroxymethyl Examples include basic compounds such as imidazole compounds such as imidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and 1-azine-2-methylimidazole. The catalyst is not limited to one type, and a plurality of types can be used. When using a catalyst, the usage-amount is preferable 10 mol% or less with respect to the usage-amount of an amine compound, and multiple types can also be used as needed.

  The amine compound (a) produced by the Michael addition reaction is obtained as a mixture with an unreacted amine compound (c) or a compound in which the carbonyl group in the Michael addition reaction product is ketiminated by the amine compound. There is.

  When a large amount of unreacted amino compound is contained, in the reaction between the amine compound (a) and the epoxy resin (b) described later, the carbonyl group-containing modified epoxy resin is extremely polymerized and thereby gelled. Since it may be, it is preferable to remove.

  Removal of the amine compound (c) from the mixture containing the amine compound (a) can be performed by distillation or azeotropy with water and / or an organic solvent under normal pressure or reduced pressure conditions. As the organic solvent, the solvent used in the Michael addition reaction can be used, but a known solvent such as alcohol or ether may be further added after the Michael addition reaction.

  Further, when the mixture containing the amine compound (a) contains a ketiminated compound, the viscosity of the carbonyl group-containing modified epoxy resin produced by the reaction between the mixture and the epoxy resin may increase. . Furthermore, in the aqueous primer composition containing the carbonyl group-containing modified epoxy resin, the ketiminated portion may be hydrolyzed to become a volatile organic compound. Therefore, the above problem can be solved by adding excess water to the mixture obtained by the Michael addition reaction to hydrolyze the ketiminated portion of the ketiminated compound to regenerate the carbonyl group. preferable. The amine compound produced by this hydrolysis can be removed in the same manner as the unreacted amine compound.

  The removal of the unreacted amine compound and the amine compound produced by hydrolysis of the ketiminated compound shown here can be performed simultaneously with the Michael addition reaction or after the completion of the Michael addition reaction. May be.

Diacetone acrylamide is derived from a hydrogen atom bonded to a carbon atom forming a carbon-carbon double bond (CH ₂ ═CH) at 6.19 to 6.23 ppm in ¹ H-NMR measurement using a deuterated chloroform solvent. A peak is observed. In the measurement of ¹ H-NMR using a deuterated chloroform solvent of the reaction product, no peak is observed at 6.19 to 6.23 ppm. Therefore, in the present invention, the reaction rate of the Michael addition reaction is determined by the NMR measurement. Can be watched.

  In the reaction between the amine compound (a) and the epoxy resin (b), the amine compound (a) may be used alone having at least one active hydrogen bonded to a nitrogen atom, but different numbers. These amine compounds having active hydrogen or different types of amine compounds may be used in combination.

  In the present invention, the epoxy resin (b) having two or more epoxy groups in one molecule is not particularly limited as long as it has two or more epoxy groups in the molecule. The epoxy resin (b) is obtained by reacting, for example, polyphenols such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol A / F type epoxy resin, and novolac type phenol resin with epihalohydrin such as epichlorohydrin. Epoxy resin such as aliphatic epoxy resin and cycloaliphatic epoxy resin; epoxy resin obtained by further reacting polyphenols with the resin obtained by introducing a group or this glycidyl group introduction reaction product; Examples thereof include an epoxy group-containing acrylic copolymer obtained by copolymerizing a group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer; a polybutadiene resin having an epoxy group; a polyurethane resin having an epoxy group. The epoxy resin (b) has an epoxy equivalent of 140 to 5,000, preferably 150 to 2,000 and a number average molecular weight of 200 to 50,000, preferably 160 to 10. , 000 is preferably used in view of the stability and viscosity of the modified epoxy resin aqueous dispersion.

  The compounding ratio of the amine compound (a) and the epoxy resin (b) is such that the carbonyl group concentration in the carbonyl group-containing modified epoxy resin is in the range of 0.1 to 3.5 mol / kg based on the resin solid content. It is preferable from the viewpoint of the corrosion resistance of the coating film obtained from the aqueous primer composition in the present invention, and more preferably in the range of 0.4 to 3 mol / kg.

  The carbonyl group-containing modified epoxy resin preferably has a weight average molecular weight in the range of 2,000 to 50,000, more preferably in the range of 5,000 to 20,000. When the weight average molecular weight is larger than 50,000, the viscosity becomes high and the production is difficult, and the finish of the coating film is uneasy. Further, when the weight average molecular weight is less than 5,000, sufficient water resistance may not be obtained.

  In the present specification, the number average molecular weight and weight average molecular weight of resins other than those having a cationic group introduced are the same as the retention time (retention capacity) measured using a gel permeation chromatograph (GPC). It is a value obtained by converting to the molecular weight of polystyrene based on the retention time (retention capacity) of standard polystyrene with a known molecular weight measured in (1). Specifically, “HLC8120GPC” (trade name, manufactured by Tosoh Corporation) is used as a gel permeation chromatograph, and “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL” are used as columns. ”And“ TSKgel G-2000HXL ”(trade names, all manufactured by Tosoh Corporation), a differential refractometer is used as a detector, mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: It can be measured under the condition of 1 mL / min.

  Specifically, the number average molecular weight and the weight average molecular weight of the resin into which the cationic group is introduced are “HLC-8120GPC” (trade name, manufactured by Tosoh Corporation) as a gel permeation chromatograph apparatus, and “ Using a total of three TSKgel Super-H3000 and two TSKgel Super-H2500 (trade names, both manufactured by Tosoh Corporation), a differential refractometer was used as a detector. , Mobile phase: tetrahydrofuran (containing 0.5% by weight of triethanolamine), measurement temperature; 25 ° C., flow rate: 0.6 mL / min.

  In the present invention, the reaction between the amine compound (a) and the epoxy resin (b) can be carried out in the presence of an organic solvent. Although it does not specifically limit as an organic solvent, Well-known organic solvents, such as ester type | system | group, alcohol type | system | group, ether type | system | group, and a ketone type | system | group, can be used. The solution concentration is preferably in the range of 50 to 90% by mass from the viewpoint that the reaction rate and the amount of solvent remaining when the obtained resin is dispersed with water can be reduced, more preferably 55 to 55% by mass. It is in the range of 80% by mass. Moreover, it is preferable to make reaction temperature into the range of 40-160 degreeC from the point of reaction rate or a viscosity, More preferably, it exists in the range of 60-140 degreeC.

  The molecular weight of the carbonyl group-containing modified epoxy resin can be adjusted by the mixing ratio of the amine compound (a) and the epoxy resin (b). Also, amine compounds such as isophoronediamine, 2-ethylhexylamine and cyclohexylamine having two or more active hydrogens capable of reacting with an epoxy group, compounds having a phenolic hydroxyl group and dibasic acids such as terephthalic acid and adipic acid Etc. can be added to the reaction system of the amine compound (a) and the epoxy resin (b) and reacted to adjust the molecular weight of the carbonyl group-containing modified epoxy resin.

  The amine value of the carbonyl group-containing modified epoxy resin is preferably in the range of 10 to 200 mg-KOH / g from the viewpoint of achieving both water dispersibility and water resistance when neutralized, and more preferably 20 to 200 mg-KOH / g. It is in the range of 180 mg-KOH / g. The amine value in this specification means a value measured by a titration method defined in JIS K 7237.

  The epoxy equivalent of the carbonyl group-containing modified epoxy resin in the present invention is preferably greater than 1000. When this epoxy equivalent is 1000 or less, the storage stability of the aqueous primer composition in the present invention may be lowered.

  The carbonyl group-containing modified epoxy resin is dispersed in water or a medium containing water (hereinafter sometimes referred to as an aqueous medium) and used as an aqueous dispersion in the aqueous primer composition of the present invention. In the present specification, the aqueous dispersion includes one in which a carbonyl group-containing modified epoxy resin is dissolved in an aqueous medium. Examples of the medium containing water include a mixture of water and an organic solvent such as a water-soluble organic solvent. Water dispersion can be carried out by a conventionally known method without particular limitation. For example, a carbonyl group-containing modified epoxy resin is subjected to shearing force in the presence of an emulsifier to form fine particles in water or a medium containing water to form an aqueous dispersion. A method for obtaining a water dispersion by applying shearing force to a carbonyl group-containing modified epoxy resin into which a hydrophilic group such as an anionic group, a cationic group, or a nonionic group is introduced to form fine particles in an aqueous medium, Examples thereof include a method of applying a shearing force to the carbonyl group-containing modified epoxy resin having the hydrophilic group introduced therein in the presence of an emulsifier to form fine particles in an aqueous medium to obtain an aqueous dispersion.

  The emulsifier is not particularly limited, and an anionic emulsifier, a cationic emulsifier, a nonionic emulsifier, an amphoteric emulsifier, a reactive emulsifier, and the like can be used.

  For example, alkyl benzene sulfonates such as sodium dodecylbenzene sulfonate and sodium dodecyl sulfate, fatty acid salts, rosinates, alkyl sulfates, alkyl sulfosuccinates, α-olefin sulfonates, alkyl naphthalene sulfonates, polyoxyethylenes Anionic emulsifiers such as alkyl (aryl) sulfate salts; quaternary ammonium salts such as lauryl trialkyl ammonium salts, stearyl trialkyl ammonium salts, trialkyl benzyl ammonium salts, primary to tertiary amine salts, lauryl pyridinium Salt, benzalkonium salt, benzethonium salt, or cationic surfactant such as laurylamine acetate; polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether Nonionic surfactants such as polyoxyethylene alkyl ester and polyoxyethylene sorbitan alkyl ester; amphoteric surfactants such as carboxybetaine type, sulfobetaine type, aminocarboxylic acid type, and imidazoline derivative type; Eleminol JS-2 (Sanyo Kasei) Industrial), Eleminol RS-30 (Sanyo Kasei Kogyo), Latemuru S-180A (Kao), Aqualon HS-05 (Daiichi Kogyo Seiyaku), Aqualon RN-10 (Daiichi Kogyo Seiyaku), Adekaria And reactive emulsifiers such as Soap SE-10N (Asahi Denka).

  In the present invention, the amount of the emulsifier used is based on 100 parts by mass of the solid content of the carbonyl group-containing modified epoxy resin from the viewpoint of water stability when used as a film-forming component of the aqueous dispersion or the aqueous primer composition. The content is preferably in the range of 0 to 20 parts by mass, more preferably in the range of 0 to 15 parts by mass.

  In the present invention, one or more functional groups selected from an anionic group, a cationic group, and a nonionic group may be added to the carbonyl group-containing modified epoxy resin, and then dispersed in a medium containing water.

  Examples of imparting an anionic group include the following methods for imparting a carboxyl group. To a solution of a cyclic ether such as dioxane, a dialkyl ether of an oxyethylene chain such as glyme or diglyme, an aprotic organic solvent such as acetone, a carbonyl group-containing modified epoxy resin solution is added, and carboxylic anhydride is added. A carbonyl group-containing modified epoxy resin having a carboxyl group is obtained by raising the temperature to about 90 ° C. and reacting. Furthermore, if the carboxyl group is neutralized using a basic compound and then phase-reversed in an aqueous medium, an aqueous dispersion of a carbonyl group-containing modified epoxy resin can be obtained.

  The carboxylic anhydride may be an anhydride of a compound having two or more carboxyl groups in one molecule. For example, succinic anhydride, itaconic anhydride, maleic anhydride, citraconic anhydride, phthalic anhydride, trihydric anhydride A merit acid or the like can be used. In addition, as the basic compound, amines, alkaline earth metal hydroxides and / or alkali metal hydroxides can be used.

  As an example of imparting a cationic group, a method of introducing a basic amino group into an epoxy group of a carbonyl group-containing modified epoxy resin, neutralizing with an acid, and dispersing in a medium containing water can be mentioned. Specifically, a carbonyl group-containing modified epoxy resin and an amino group-containing compound are reacted to give an amino group, and then neutralized using an acidic compound such as a carboxylic acid.

  Among the amino group-containing compounds, examples of the primary amino group-containing compound include monoethanolamine, propanolamine, hydroxyethylaminopropylamine, diethylenetriamine, 2-ethylhexylamine, cyclohexylamine, and triethylenetetramine. . Examples of secondary amino group-containing compounds include diethylamine, diisopropylamine, diethanolamine, di (2-hydroxypropyl) amine, monomethylaminoethanol, monoethylaminoethanol and the like. The above amino group-containing compounds can be used alone or in combination of two or more.

  In addition, the amine compound (a) used in the production of the carbonyl group-containing modified epoxy resin or the amino group derived from the amine compound used for adjusting the molecular weight of the resin is neutralized with an acidic compound, and then the carbonyl group The contained modified epoxy resin may be dispersed in an aqueous medium to obtain an aqueous dispersion.

  In the method in which the amino group contained in the carbonyl group-containing modified epoxy resin is neutralized with an acidic compound and dispersed in water, the acidic compound includes, for example, formic acid, acetic acid, lactic acid, phosphoric acid, and organic phosphoric acid. Can do. These acidic compounds may be mixed with a carbonyl group-containing modified epoxy resin to neutralize amino groups and then dispersed while adding an aqueous medium, or a mixture with an aqueous medium may be mixed with a carbonyl group-containing modified epoxy resin. You may neutralize and disperse | distribute, mixing.

  Specific examples of the method for imparting a nonionic group include a method of reacting an amine compound (a), an epoxy resin (b), and a polyoxyalkyleneamine compound in the production of a carbonyl group-containing modified epoxy resin. be able to. Examples of the polyoxyalkyleneamine compound include a compound represented by the following formula having an amino group capable of reacting with an epoxy group.

(Wherein R ¹ represents a hydroxyl group or an alkoxy group having 1 to 4 carbon atoms, R ² represents a hydrogen atom or a methyl group, m is an integer of 2 to 220, preferably 5 to 180, and n is 2) An integer of ˜3, preferably 2, where the m oxyalkylene units (CnH _2n O) may be the same or different from each other.)
These polyoxyalkylene compounds are preferably used in the range of 1 to 25% by mass, and more preferably 3 to 15% by mass in the solid content of the carbonyl group-containing modified epoxy resin from the viewpoint of achieving both water dispersibility and water resistance. preferable.

  As another method for imparting a nonionic group, specifically, in the production of a carbonyl group-containing modified epoxy resin, an amine compound (a), an epoxy resin (b), and a polymer having an unsaturated group capable of Michael addition reaction are used. Examples thereof include a method of reacting with an oxyalkylene unsaturated compound. Examples of the polyoxyalkylene unsaturated compound include compounds represented by the following formula.

(In the formula, R ³ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m is an integer of 2 to 220, preferably 5 to 180, and n is an integer of 2 to 3, preferably 2. And m oxyalkylene units (CnH _2n O) may be the same or different from each other). Specific examples thereof include polyethylene glycol acrylate, polypropylene glycol acrylate, methoxy polyethylene glycol acrylate, and ethoxy polyethylene glycol acrylate.

  In the present invention, after the amine compound (a) and the epoxy resin (b) are reacted to obtain a carbonyl group-containing modified epoxy resin, one or more functional groups selected from an anionic group, a cationic group and a nonionic group From the anionic group, cationic group and nonionic group by simultaneously carrying out the reaction between the amine compound (a) and the epoxy resin (b) and the reaction for imparting the functional group. A carbonyl group-containing modified epoxy resin having one or more selected functional groups may be obtained.

  Further, the concentration of the aqueous dispersion of the carbonyl group-containing modified epoxy resin is preferably in the range of 10 to 50% by mass, more preferably in the range of 20 to 45% by mass as the solid content from the viewpoint of stability and viscosity. Is within.

  In the present invention, when a nonionic group is introduced, an aqueous dispersion can be obtained in an aqueous medium as it is, but if necessary, an amino group contained in the resin is neutralized with an acidic compound. An aqueous dispersion can also be obtained in an aqueous medium.

[Crosslinking agent (B)]
The crosslinking agent (B) in the present invention contains, as an essential component, a hydrazide compound and / or a semicarbazide compound that can crosslink with the carbonyl group of the carbonyl group-containing modified epoxy resin at a relatively low temperature to form a cured coating film.

  As the hydrazide compound and / or semicarbazide compound, for example, a compound having two or more hydrazide groups and / or semicarbazide groups in one molecule can be preferably used. For example, saturated fatty acid dihydrazides having 2 to 18 carbon atoms such as succinic acid dihydrazide, malonic acid dihydrazide, glutaric acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, etc .; maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide Monoolefinically unsaturated dicarboxylic acid dihydrazide, phthalic acid, terephthalic acid or isophthalic acid dihydrazide, and pyromellitic acid dihydrazide, trihydrazide or tetrahydrazide; nitrilotrihydrazide, citric acid trihydrazide, 1,2,4-benzenetrihydrazide , Ethylenediaminetetraacetic acid tetrahydrazide, 1,4,5,8-naphthoic acid tetrahydrazide, two or more carboxylic acid lower alkyl ester groups in one molecule. A polyhydrazide compound such as polyhydrazide (see Japanese Patent Publication No. 52-22878) obtained by reacting a low polymer having hydrazine or hydrazine hydrate (hydrazine hydride); diisocyanate such as hexamethylene diisocyanate and isophorone diisocyanate; Polysemicarbazide compound obtained by reacting polyisocyanate compound derived therefrom with hydrazine or monoalkyl-substituted hydrazine, polyhydrazide obtained by reacting diisocyanate compound or polyhydrazide compound exemplified above with polyisocyanate compound containing diisocyanate Obtained from the reaction of a compound, a polyisocyanate compound and a polyether or polyol having active hydrogen such as polyethylene glycol monoalkyl ethers. Polysemicarbazide compound obtained by reacting an isocyanate group in a modified polyisocyanate compound with hydrazine or a monoalkyl-substituted hydrazine, polyhydrazide obtained by reacting the above-exemplified dihydrazide or polyhydrazide with the isocyanate group of the modified polyisocyanate compound Examples thereof include compounds, and these can be used alone or mixed together as necessary.

  The hydrazine derivative generally has a total of 0.01 to 2 mol of hydrazide group and semicarbazide group contained in the hydrazine derivative with respect to 1 mol of carbonyl group of the carbonyl group-containing modified epoxy resin (A). It is preferably from the range of 0.1 to 1.5 mol from the viewpoint of low temperature curability.

  Furthermore, the crosslinking agent (B) may react with a functional group such as a carbonyl group or a hydroxyl group of the carbonyl group-containing modified epoxy resin in order to strengthen the crosslinked structure of the cured primer coating film obtained by the method of the present invention. Other crosslinkers that can be formed may be included. Other crosslinking agents include, for example, amino resins, polyaldehyde compounds, phenol resins, epoxy compounds, isocyanate compounds, blocked isocyanate compounds, metal compounds (metal salts, metal complexes, metal oxides, metal hydroxides, etc.), silicates A compound etc. can be mentioned.

  Examples of the amino resin include methylolated amino resins obtained by reaction of amino components such as melamine, urea, benzoguanamine, acetogranamamine, sterologamine, spiroguanamine, and dicyandiamide with aldehydes. Examples of aldehydes used in the above reaction include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Moreover, what etherified the said methylolated amino resin with suitable alcohol can also be used as an amino resin. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

  The polyaldehyde compound is a compound having at least two aldehyde groups in one molecule, and specific examples thereof include glyoxal and glutaraldehyde.

  For example, the phenol resin may be obtained by heating a phenol component and an aldehyde in the presence of a reaction catalyst to cause a condensation reaction by introducing a methylol group, and a part or all of the methylol group of a methylolated phenol resin obtained by introducing an alcohol with an alcohol. Examples thereof include resol type phenol resins formed by alkyl etherification. In the production of a resol-type phenol resin, a bifunctional phenol compound, a trifunctional phenol compound, a tetrafunctional or higher functional phenol compound, or the like can be used as the phenol component as a starting material.

  Examples of the phenol compound include, for example, o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-xylenol as bifunctional phenol compounds. Examples of trifunctional phenolic compounds include coalic acid, m-cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol. Examples of tetrafunctional phenolic compounds include bisphenol A and bisphenol F. And so on. Among them, in order to improve scratch resistance, it is preferable to use a trifunctional or higher functional phenol compound, in particular, carboxylic acid and / or m-cresol. These phenol compounds may be used alone or in combination of two or more.

  Examples of the aldehydes used for the production of the phenol resin include formaldehyde, paraformaldehyde, trioxane and the like, and they can be used alone or in combination of two or more.

  As the alcohol used for alkyl etherifying a part of the methylol group of the methylolated phenol resin, a monohydric alcohol having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, can be suitably used. Suitable monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, isobutanol and the like.

  The phenolic resin has an average of 0.5 or more, preferably 0.6 to 3.0 alkoxymethyl groups per benzene nucleus from the viewpoint of reactivity with the carbonyl group-containing modified epoxy resin. Is suitable.

  The epoxy compound is a compound having at least two epoxy groups in one molecule, and typical examples thereof include ethylene glycol diglycidyl ether, hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerin. Polyhydric alcohols such as diglycidyl ether, glycerin triglycidyl ether, diglycerin triglycidyl ether, sorbitol polyglycidyl ether, hydrogenated bisphenol A diglycidyl ether, bisphenol A diglycidyl ether, phenol novolac polyglycidyl ether or cresol novolac polyglycidyl ether Or polyglycidyl ethers of polyphenols; glycidyl esters and glycidyl ethers of p-oxybenzoic acid Polyglycidyl esters of polycarboxylic acids such as phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester or (meth) acrylic acid glycidyl ester copolymer; polyepoxy compounds containing nitrogen-containing heterocycles such as hydantoin rings An epoxy resin which is an adduct of a compound having two or more epoxy groups in one molecule and a polyhydric alcohol, polyhydric phenol or polybasic acid; a modified epoxy resin such as a fatty acid-modified epoxy resin or an amine-modified epoxy resin A vinyl polymer having an epoxy group in the side chain, and the like. When the epoxy compound is blended, the amount of the epoxy group in the epoxy compound is 0.05 to 3 with respect to 1 mol in total of the carboxyl group and hydroxyl group contained in the carbonyl group-containing modified epoxy resin (A). It is desirable to adjust so that it may become in the range of mol, Preferably it is 0.1-2 mol.

  The said isocyanate compound is a compound which has two or more isocyanate groups in 1 molecule, and what is conventionally used for manufacture of a polyurethane can be used. Examples thereof include aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of these polyisocyanates.

  Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: Isophorone diisocyanate), 4,4'-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,3- or 1,4-bis (isocyanatomethyl) cyclohexane ( Common name: hydrogenated xylylene diisocyanate) or mixtures thereof, alicyclic diisocyanates such as norbornane diisocyanate, for example 1,3,5-triisocyanatocyclohexane, 1, , 5-trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 2- (3-isocyanatopropyl) -2 , 6-Di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 3- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane 5- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 6- (2-isocyanatoethyl) -2-isocyanate Natomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyana Propyl) -bicyclo (2.2.1) -heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) heptane, etc. And alicyclic triisocyanate.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3- Aliphatic diisocyanates such as butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, such as lysine ester triisocyanate, 1,4,8- Triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2 5,7 and aliphatic triisocyanates such as trimethyl-1,8-diisocyanato-5-isocyanatomethyl octane and the like.

  Examples of the araliphatic polyisocyanate include 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω′-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis ( 1-isocyanato-1-methylethyl) benzene (common name: tetramethylxylylene diisocyanate) or an aromatic aliphatic diisocyanate such as a mixture thereof, for example, an araliphatic triisocyanate such as 1,3,5-triisocyanatomethylbenzene And so on.

  Examples of the aromatic polyisocyanate include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4′- or 4,4′-diphenylmethane diisocyanate or a mixture thereof. 2,4- or 2,6-tolylene diisocyanate or mixtures thereof, aromatic diisocyanates such as 4,4′-toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate, for example, triphenylmethane-4,4 ′, 4 Aromatic triisocyanates such as '' '-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, such as 4,4'-diphenylmethane-2,2', 5 , 5'- Or the like can be mentioned aromatic tetracarboxylic isocyanates such as tiger isocyanate.

  Examples of the polyisocyanate derivative include dimer, trimer, biuret, allophanate, carbodiimide, uretdione, uretoimine, isocyanurate, oxadiazine trione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric). MDI) and a crude product of tolylene diisocyanate (crude TDI).

  As the above-mentioned isocyanate compound, a part of the isocyanate group may be modified with a compound containing 1 to 5 active hydrogens such as a hydroxyl group or an amino group as necessary.

  Said isocyanate compound may be used independently and may be used together 2 or more types.

  The blocked isocyanate compound as a crosslinking agent is a compound obtained by blocking the isocyanate group of the isocyanate compound with a blocking agent.

  The reaction between the isocyanate compound and the blocking agent can be carried out under known conditions. Moreover, it is preferable that the ratio of both components is set so that a slightly excessive amount of the blocking agent is formed with respect to all isocyanate groups in the isocyanate compound so that no isocyanate groups remain. When blocking (reacting the blocking agent), a solvent can be added as necessary. As the solvent used for the blocking reaction, those not reactive to isocyanate groups are preferable. For example, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and solvents such as N-methylpyrrolidone (NMP). Can be mentioned.

  The blocking agent is a compound that blocks the isocyanate group. When the blocked isocyanate group is heated to, for example, 100 ° C. or higher, preferably 130 ° C. or higher, the blocking agent is dissociated to regenerate the isocyanate group and can be easily reacted with a hydroxyl group or the like.

  Examples of the blocking agent include phenols such as phenol and cresol; lactams such as ε-caprolactam and δ-valerolactam; aliphatics such as methanol, ethanol, propyl alcohol, butyl alcohol and lauryl alcohol; ethylene glycol monomethyl ether Ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; benzyl alcohol; glycolic acid esters such as methyl glycolate and ethyl glycolate; lactic acid such as lactic acid, methyl lactate, ethyl lactate and butyl lactate Esters: Alcohols such as methylol urea and diacetone alcohol; Acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzoph Oximes such as enone oxime and cyclohexane oxime; active methylenes such as diethyl malonate, ethyl acetoacetate, methyl acetoacetate and acetylacetone; butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, thiophenol, ethylthiophenol Mercaptans such as acetanilide, acetanisidide, acid amides such as methacrylamide, acetic acid amide and benzamide; imides such as phthalimide and maleic imide; amines such as diphenylamine, phenylnaphthylamine, carbazole, aniline, naphthylamine and butylamine; Imidazoles such as imidazole and 2-ethylimidazole; Ureas such as urea, thiourea, ethyleneurea and diphenylurea; N Carbamate esters such as phenyl phenylcarbamate; Imines such as ethyleneimine and propyleneimine; Sulphites such as sodium bisulfite and potassium bisulfite; 3,5-dimethylpyrazole, 3-methylpyrazole, 4-nitro- Examples include pyrazole-based compounds such as 3,5-dimethylpyrazole and 4-bromo-3,5-dimethylpyrazole. The above blocking agents can be used alone or in combination of two or more.

  The blocked isocyanate compounds can be used alone or in combination of two or more. When blending the blocked isocyanate compound, the blending amount is usually 0.05 to 3 mol of the blocked isocyanate group with respect to 1 mol of the hydroxyl group contained in the carbonyl group-containing modified epoxy resin (A) in the present invention. It is desirable to adjust so that it may become in the range of 0.1-2 mol preferably.

[Anti-rust pigment (C)]
As the rust preventive pigment (C), chromate, vanadium compound, silicon-containing compound, phosphoric acid compound, phosphite pigment, calcium compound, aluminum oxide, zinc oxide, zirconic acid, zirconic acid compound, What mixed any 1 type or 2 types or more, such as a molybdate compound, can be used. Among these, non-chromium rust preventive pigments other than chromate are preferable from the viewpoint of human health and environmental protection. As the non-chromium rust preventive pigment, for example, a mixture of a rust preventive pigment containing a vanadium compound (c1), a silicon-containing compound (c2) and a phosphate compound (c3) is particularly preferable from the viewpoint of corrosion resistance.

  The vanadium compound (c1) is at least one vanadium compound selected from vanadium pentoxide, calcium vanadate, and ammonium metavanadate. In particular, vanadium pentoxide and calcium vanadate are excellent in elution of pentavalent vanadium ions into water, and the pentavalent vanadium ions released from the vanadium compound (c1) react with the material metal, It effectively works to improve corrosion resistance by reacting with ions from the rust preventive pigment mixture.

The silicon-containing compound (c2) contains at least one compound selected from metal silicate salts, silica fine particles, and metal ion exchanged silica fine particles.
The silicate metal salt is a salt made of silicon dioxide and a metal oxide, and may be any of orthosilicate, polysilicate and the like. Examples of silicates include zinc silicate, aluminum silicate, aluminum orthosilicate, hydrated aluminum silicate, calcium aluminum silicate, sodium aluminum silicate, beryllium aluminum silicate, sodium silicate, calcium orthosilicate, calcium metasilicate, sodium calcium silicate, and silicic acid. Zirconium, magnesium orthosilicate, magnesium metasilicate, magnesium calcium silicate, manganese silicate, barium silicate, olivine, garnet, tortovite, cyllite, benitoite, neptunite, nymphite, turquoise, quartzite, barracite, tosen Stones, zonotorite, talc, gyoganite, aluminosilicate, borosilicate, beryllosilicate, cholite, fluorite and the like. As the metal silicate, calcium orthosilicate and calcium metasilicate are particularly preferable.

The silica fine particles can be used without particular limitation as long as they are silica fine particles, such as silica fine powder with an untreated surface, silica fine powder with a surface treated with an organic material, calcium ion-exchanged silica fine particles, organic solvent-dispersed colloidal silica, etc. Can be mentioned. Examples of the silica fine particles whose surface is not treated or treated with an organic substance include silica fine powder having an average particle size of 0.5 to 15 μm, preferably 1 to 10 μm, and organic solvent-dispersible colloidal silica. As the fine silica powder, those having an oil absorption of 30 to 350 ml / 100 g, preferably 30 to 150 ml / 100 g can be suitably used, and as commercially available products, silicia 710, silicia 740, silicia 550, Examples include Aerosil R972 (all of which are manufactured by Fuji Silysia Chemical Co., Ltd.), Mizukacil P-73 (manufactured by Mizusawa Chemical Industry Co., Ltd.), Gasil 200DF (manufactured by Crossfield).
The organic solvent-dispersible colloidal silica is also referred to as an organosilica sol, in which silica fine particles having a particle size of about 5 to 120 nm are stably dispersed in an organic solvent such as alcohols, glycols, and ethers. In addition, examples of commercially available products include the OSCAL series (manufactured by Catalytic Chemicals Co., Ltd.) and organosols (manufactured by Nissan Chemical Co., Ltd.).

  The metal ion exchanged silica fine particles are silica fine particles in which metal ions are introduced into a fine porous silica carrier by ion exchange. Specifically, it is a silica fine particle into which calcium or magnesium is introduced. For example, as commercially available products of calcium ion exchange silica, SHIELDEX (Shielddex, registered trademark) C303, SHIELDEXAC-3, SHIELDEXC-5 (all of which are manufactured by WR Grace & Co.) and the like can be mentioned. it can.

  Examples of the phosphate compound (c3) include calcium phosphate, calcium ammonium phosphate, calcium monohydrogen phosphate, calcium dihydrogen phosphate, calcium phosphate phosphate, zinc phosphate, aluminum phosphate, magnesium phosphate, phosphorus Phosphate metal salts such as zinc oxyhydrogen, aluminum phosphate, magnesium phosphate, aluminum hydrogen phosphate, magnesium hydrogen phosphate, magnesium ammonium phosphate, aluminum dihydrogen triphosphate, phosphoric acid, organic phosphate compounds, etc. Can be mentioned. Phosphate ions released from the phosphoric acid compound (c3), metal ions such as Ca, Zn, Al or Mg effectively work to improve the corrosion resistance.

In the aqueous primer composition, the vanadium compound (c1), the silicon-containing compound (c2), and the phosphoric acid system with respect to 100 parts by mass of the total solid content of the carbonyl group-containing modified epoxy resin (A) and the crosslinking agent (B). The metal salt (c3) is preferably within the following range.
Vanadium compound (c1): 3 to 50 parts by mass, preferably 5 to 30 parts by mass,
Silicon-containing compound (c2): 3 to 50 parts by mass, preferably 5 to 30 parts by mass,
Phosphate metal salt (c3): 3 to 50 parts by mass, preferably 5 to 30 parts by mass.

  In the primer composition, the total amount of (c1), (c2) and (c3) is 10 to 10 parts by mass based on the total solid content of the carbonyl group-containing modified epoxy resin (A) and the crosslinking agent (B). 150 parts by mass, preferably 15 to 90 parts by mass is suitable from the viewpoint of corrosion resistance.

  Further, the vanadium compound (c1), the silicon-containing compound (c2) and the rust preventive pigment mixture (C) blended with respect to 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B), A mixture of phosphoric acid metal salt (c3) in an amount of parts by mass within each quantitative range was added to 10000 parts by mass of a 5% strength by weight sodium chloride aqueous solution at 25 ° C, stirred for 6 hours, and allowed to stand at 25 ° C for 48 hours. The solubility of the vanadium compound (c1), the silica fine particles (c2) and the phosphate metal salt (c3) due to moisture is such that the pH of the filtrate obtained by filtering the placed supernatant is 3 to 10, preferably 4 to 8. And it is suitable from the viewpoint of the reactivity between the solution of the anticorrosive pigment and the metal plate, and being in this range is more preferred from the viewpoint of corrosion resistance.

  That is, the above-mentioned filtrate for pH measurement has a silicon content of any one of 3 to 50 parts by mass of the vanadium compound (c1) with respect to 10000 parts by mass of a 5% by mass sodium chloride aqueous solution at 25 ° C. The amount of the compound (c2) in the range of 3 to 50 parts by mass and the amount of the phosphate metal salt (c3) in the range of 3 to 50 parts by mass added and dissolved The filtrate.

  In the aqueous primer composition, in addition to the carbonyl group-containing modified epoxy resin (A), the crosslinking agent (B), the rust preventive pigment (C), and a curing catalyst blended as necessary, coloring that can be used in the paint field Pigments, extender pigments, UV absorbers, UV stabilizers, organic solvents; additives such as anti-settling agents, antifoaming agents, coating surface modifiers, and the like can be blended as necessary.

  Examples of the colored pigment include organic colored pigments such as cyanine blue, cyanine green, organic red pigments such as azo and quinacridone; and inorganic colored pigments such as titanium white, titanium yellow, bengara, carbon black, and various fired pigments. Among them, titanium white can be preferably used.

  Examples of the extender pigment include talc, clay, silica, mica, alumina, calcium carbonate, barium sulfate and the like.

  Examples of the ultraviolet absorber include 2- (2-hydroxy-3,5-di-t-amylphenyl) -2H-benzotriazole, isooctyl-3- (3- (2H-benzotriazol-2-yl)- 5-t-butyl-4-hydroxyphenylpropionate, 2- [2-hydroxy-3,5-di (1,1-dimethylbenzidine) phenyl] -2H-benzotriazole, 2- [2-hydroxy-3- Dimethylbenzyl-5- (1,1,3,3-tetramethylbutyl) phenyl] -2H-benzotriazole, methyl-3- [3-t-butyl-5- (2H-benzotriazol-2-yl)- Benzotriazole derivatives such as condensates with 4-hydroxyphenyl] propionate / polyethylene glycol 300; 2- [4- (2-hydroxy -3-dodecyloxypropyl) oxy] -2-triazine derivatives such as 2-hydroxyphenyl-4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine; ethanediamide-N- (2-ethoxy Succinic acid anilide such as phenyl) -N ′-(2-ethylphenyl)-(oxalic amide), ethanediamide-N- (2-ethoxyphenyl) -N ′-(4-isododecylphenyl)-(oxalic amide) System derivatives and the like.

  Examples of the UV stabilizer include hindered amine compounds, hindered phenol compounds; CHIMASORB 944, TINUVIN 144, TINUVIN 292, TINUVIN 770, IRGANOX 1010, IRGANOX 1098 (all of these products are products of Ciba Specialty Chemicals) Product)).

  By blending a UV absorber or UV stabilizer into the aqueous primer composition, it is possible to suppress deterioration of the primer surface due to light passing through the upper coating film and reaching the primer coating surface. Delamination between the primer coating and the upper coating due to surface deterioration can be prevented, and excellent corrosion resistance can be maintained.

  The said organic solvent which can be mix | blended with the said aqueous primer composition is mix | blended as needed for the coating property improvement of this invention composition, etc., a carbonyl group containing modified epoxy resin (A) and a crosslinking agent (B ) Can be used. Specifically, for example, hydrocarbon solvents such as toluene, xylene, high-boiling petroleum hydrocarbons, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, Ester solvents such as ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, methanol, ethanol, isopropanol, butanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethyl It can be mentioned alcohol solvents such as glycol monobutyl ether, which may be used alone or in combination of two or more.

  Even when the aqueous primer composition is coated on a metal material and cured at a relatively low temperature, the finally formed multilayer coating film exhibits excellent workability and processed portion corrosion resistance. As a reason for this, the present inventors speculate as follows. The crosslinking agent (B) containing the hydrazide compound and / or the semicarbazide compound contained in the aqueous primer composition reacts efficiently with the carbonyl group of the carbonyl group-containing modified epoxy resin (A) even at a relatively low temperature, and the In addition to forming a cured primer coating film having a cross-linked structure, the carbonyl group-containing modified epoxy resin (A) has the inherent corrosion resistance of the epoxy resin, and a highly polar amide bond contained in the resin. We believe that the contribution of the carbonyl group to the adhesion to the metal material led to excellent corrosion resistance. Moreover, flexibility is imparted to the carbonyl group-containing modified epoxy resin (A) by incorporating the structure of the amine compound (a) having a carbonyl group next to the rigid epoxy resin skeleton, and further the amine compound (a) It is believed that the high polar amide bond and carbonyl group contained improved the cohesive strength of the resin, leading to excellent processability.

[Multilayer coating film forming method]
In the multilayer coating film forming method of the present invention, the aqueous primer composition is coated on a metal material and then a cured primer coating film is formed (1) and the cured primer coating film obtained in the step (1). A step (2) of forming a top coat film by applying a top coat on the top and then drying by heating is included.

Process (1)
The aqueous primer composition is applied onto a metal material by a known method such as a roll coating method, a curtain flow coating method, a spray method, a brush coating method, or a dipping method. The film thickness of the cured primer coating film is not particularly limited, but is usually 2 to 10 μm, preferably 3 to 6 μm. The cured primer coating film can be formed by drying the coated metal material for 15 seconds to 24 hours under the condition that the material arrival maximum temperature is 10 ° C. to less than 180 ° C., preferably 20 ° C. to 160 ° C. The drying can be performed by setting a coated metal material at room temperature or heating. When the maximum material reaching temperature is less than 10 ° C., the primer coating film may be insufficiently cured. Further, when the maximum material reaching temperature is 180 ° C. or higher, there is no problem in performance of the cured primer coating film, but the energy saving effect may be reduced. When the metal material is a metal plate, the cured primer coating film may be formed on both surfaces of the metal plate by coating the aqueous primer composition on the back surface and drying in the same manner as described above.

  Examples of the metal plate include a cold rolled steel plate, a hot dip galvanized steel plate, an electrogalvanized steel plate, an iron-zinc alloy plated steel plate (galvanyl steel plate), and an aluminum-zinc alloy plated steel plate (containing about 55% aluminum in the alloy). Galvalume steel plate "," Galfan "containing about 5% aluminum in the alloy), nickel-zinc alloy plated steel plate, stainless steel plate, aluminum plate, copper plate, copper plated steel plate, tin plated steel plate, etc., and these metal plates The surface may be subjected to chemical conversion treatment. Examples of the chemical conversion treatment include phosphate treatment such as zinc phosphate treatment and iron phosphate treatment, composite oxide film treatment, chromium phosphate treatment, and chromate treatment.

Process (2)
A top coat is applied on the cured primer coating obtained in step (1), and dried at a material maximum temperature of 180 ° C. to 300 ° C. to form a top coat. The drying time is preferably about 5 seconds to 30 minutes. The film thickness of the top coat film is not particularly limited, but the dry film thickness is preferably in the range of 3 to 30 μm. When the maximum material reaching temperature is less than 180 ° C., the top coat film may be insufficiently dried. In addition, when the maximum material reaching temperature exceeds 300 ° C., the energy saving effect may be reduced. When the metal material is a metal plate, the top coat film may be formed on the back surface of the surface on which the top coat film is formed in the same manner as described above. As the top coat, solid color paints, metallic paints, light interference color paints, clear paints and the like can be used. One or more kinds selected from these can be used to form a single layer or two or more layers of top coats. A film can be formed on the primer coating. As these top coating materials, various water-based or organic solvent-type coating materials known per se can be used.

  Hereinafter, the present invention will be described more specifically with reference to production examples and examples. The present invention is not limited to the following examples. Hereinafter, “parts” and “%” are based on mass.

Production of amine compound (a) [Production Example 1]
Air in a 1 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and 338.4 g of diacetone acrylamide, 180.2 g of deionized water, and 352.6 g of N-ethylethylenediamine were added. Then, the mixture was stirred, heated to 80 ° C. and held at 80 ° C. for 3 hours. Next, while reducing the pressure to about 100 mmHg, the temperature was maintained at 60 to 80 ° C. for 2 hours, and about 240 g of a mixture of water and unreacted N-ethylethylenediamine was removed azeotropically. Thereafter, 200 g of water was added and maintained at 80 ° C. for 1 hour, and then maintained at 60 to 80 ° C. for 1.5 hours while reducing the pressure to about 100 mmHg to remove azeotropically about 200 g of the mixture of water and N-ethylethylenediamine. Repeated twice. Then, hold at 60-80 ° C. for 1.5 hours while reducing the pressure to about 10 mmHg, remove the remaining water and N-ethylethylenediamine to remove two secondary amino groups, and further add a Michael having a carbonyl group An amine compound (a1) as a reaction product was obtained. In the ¹ H-NMR measurement of the product using a deuterated chloroform solvent, no peak of 6.19 to 6.23 ppm due to diacetone acrylamide was observed, confirming that no unreacted diacetone acrylamide remained. .

  0.1 g of the amine compound (a1) obtained in a 100 mL Erlenmeyer flask was weighed, and 30 mL of acetic acid was added and dissolved. Then, an indicator (alphazulin G 0.3 g dissolved in 100 mL of glacial acetic acid and thymol blue 1. 0.2 mL of a solution obtained by dissolving 5 g in methanol was added and titrated with 0.1N perchloric acid (acetic acid solution) until the solution changed from green to red. As a result, the amine value of the amine compound (a1) was 426 mg-KOH / g.

[Production Example 2]
The air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and 507.7 g of diacetone acrylamide, 270.3 g of water and 438.8 g of butylamine were added and stirred. The temperature was raised to 0 ° C. and kept at 80 ° C. for 2 hours. Next, the pressure was reduced to about 100 mmHg and maintained at 60 to 80 ° C. for 1.5 hours, and about 430 g of a mixture of water and unreacted butylamine was removed azeotropically. After that, an operation for attaching a moisture determination receiver to the flask, adding 270 g of water, raising the temperature to 105 ° C., holding at 103 to 105 ° C. under normal pressure for 1 hour, and azeotropically removing about 200 g of the mixture of water and butylamine twice. Repeated. Next, while maintaining the pressure at 60-80 ° C for 1.5 hours while reducing the pressure to about 10 mmHg, the remaining water and butylamine are removed to have one secondary amino group in one molecule, and further a Michael having a carbonyl group An amine compound (a2) as an addition reaction product was obtained. In the ¹ H-NMR measurement of the product using a deuterated chloroform solvent, no peak of 6.19 to 6.23 ppm due to diacetone acrylamide was observed, confirming that no unreacted diacetone acrylamide remained. . The amine value of the obtained amine compound (a2) was 230 mg-KOH / g.

[Production Example 3]
The air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and 507.7 g of diacetone acrylamide, 270.3 g of water, and 366.5 g of 2-aminoethanol were added and stirred. The temperature was raised to 80 ° C. and held at 80 ° C. for 2 hours. Next, thin film distillation was performed on a wall surface at a reduced pressure of 5 mmHg and 100 ° C. using a thin film distillation apparatus (Tokyo Rika Kikai Co., Ltd., model: MF-10A, evaporation area 0.04 m ² ), and water and unreacted 2- The aminoethanol mixture was removed. Thereafter, air in a 2 L flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet was replaced with nitrogen, and about 720 g of reaction product was obtained by removing unreacted 2-aminoethanol by thin-film distillation. 500 g of water was added, the temperature was raised to 105 ° C., and the ketimine was hydrolyzed by maintaining at normal pressure at 103 to 105 ° C. for 1 hour. Furthermore, thin film distillation is performed on a wall at 100 ° C. under reduced pressure of 5 mmHg to remove a mixture of 2-aminoethanol formed by hydrolysis of water and ketimine, so that one secondary amino group per molecule and one hydroxyl group Thus, an amine compound (a3) which is a Michael addition reaction product having one carbonyl group and a carbonyl group was obtained. In the ¹ H-NMR measurement of the product using a deuterated chloroform solvent, no peak of 6.19 to 6.23 ppm due to diacetone acrylamide was observed, confirming that no unreacted diacetone acrylamide remained. . The amine value of the obtained amine compound (a3) was 255 mg-KOH / g.

Production of carbonyl group-containing modified epoxy resin (A) and aqueous dispersion thereof [Production Example 4]
The air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and “jER828” (trade name, manufactured by Japan Epoxy Resins Co., Ltd., bisphenol A type epoxy resin) 152 0.0 g and 281.1 g of propylene glycol monomethyl ether were added and stirred, and the mixture was heated to 100 ° C. and dissolved. Thereafter, a mixture of 28.1 g of 2-ethylhexylamine and 57.5 g of “Surfonamine L-100” (trade name, manufactured by Huntsman Corporation, polyoxyalkyleneamine compound) was added and held at 100 ° C. for 2 hours. 19.3 g of a1) and 24.2 g of amine compound (a2) were added, and the temperature was raised to 120 ° C. and maintained at 120 ° C. for 7.5 hours to obtain a solution of a carbonyl group-containing modified epoxy resin (A1). Thereafter, a mixture of 15.8 g of acetic acid, 8.1 g of 85% phosphoric acid, and 100.0 g of water was added to the solution. Further, after adding 1200 g of water, about 980 g was removed while azeotropically evaporating the solvent and water under reduced pressure, diluted with water so that the heating residue was about 30%, and the carbonyl group concentration in the resin solids was reduced to 0. An aqueous dispersion (AD1) of a carbonyl group-containing modified epoxy resin (A1) of 62 mol / Kg was obtained. The amine value of this resin was 105 mg-KOH / g, and the weight average molecular weight was about 11,000.

[Production Example 5]
Air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and 152.0 g of “jER828” and 282.9 g of propylene glycol monomethyl ether were added and stirred until 100 ° C. The temperature was raised and dissolved. Thereafter, a mixture of 32.0 g of 2-ethylhexylamine and 56.0 g of “Surfonamine L-100” was added and held at 100 ° C. for 2 hours, and then 4.1 g of amine compound (a1) and 38 of amine compound (a2) were obtained. 0.8 g was added and the temperature was raised to 120 ° C. and maintained at 120 ° C. for 7.5 hours to obtain a solution of the carbonyl group-containing modified epoxy resin (A2). did. Thereafter, a mixture of 14.9 g of acetic acid, 7.6 g of 85% phosphoric acid, and 100.0 g of water was added to the solution. Further, after adding 1200 g of water, about 980 g was removed while azeotropically evaporating the solvent and water under reduced pressure, diluted with water so that the heating residue was about 30%, and the carbonyl group concentration in the resin solids was reduced to 0. An aqueous dispersion (AD2) of a carbonyl group-containing modified epoxy resin (A2) of 62 mol / Kg was obtained. The amine value of this resin was 98 mg-KOH / g, and the weight average molecular weight was about 7200.

[Production Example 6]
The air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and 145.9 g of “jER828” and 267.4 g of propylene glycol monomethyl ether were added and stirred to 100 ° C. The temperature was raised and dissolved. Thereafter, a mixture of 25.2 g of 2-ethylhexylamine and 54.4 g of “Surfonamine L-100” was added and maintained at 100 ° C. for 2 hours, and then 26.4 g of amine compound (a1) and 15 of amine compound (a2) were added. 0.5 g was added, and the temperature was raised to 120 ° C. and maintained at 120 ° C. for 7.5 hours to obtain a solution of the carbonyl group-containing modified epoxy resin (A3). Thereafter, a mixture of 15.6 g of acetic acid, 8.0 g of 85% phosphoric acid and 100.0 g of water was added to the solution. Further, after adding 1150 g of water, about 950 g is removed while azeotropically evaporating the solvent and water while reducing the pressure, and diluted with water so that the heating residue is about 30%. An aqueous dispersion (AD3) of a carbonyl group-containing modified epoxy resin (A3) of 62 mol / Kg was obtained. The amine value of this resin was 109 mg-KOH / g, and the weight average molecular weight was about 22,000.

[Production Example 7]
The air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and 152.0 g of “jER828” and 271.9 g of propylene glycol monomethyl ether were added and stirred until 100 ° C. The temperature was raised and dissolved. Thereafter, a mixture of 35.5 g of 2-ethylhexylamine and 55.0 g of “Surfonamine L-100” was added and held at 100 ° C. for 2 hours, and then 5.1 g of amine compound (a1) and 24 of amine compound (a2) were added. 0.2 g was added, and the temperature was raised to 120 ° C. and maintained at 120 ° C. for 7.5 hours to obtain a solution of a carbonyl group-containing modified epoxy resin (A4). Thereafter, a mixture of 14.1 g of acetic acid, 7.2 g of 85% phosphoric acid and 100.0 g of water was added to the solution. Further, after adding 1150 g of water, about 950 g is removed while azeotropically evaporating the solvent and water while reducing the pressure, and diluted with water so that the heating residue is about 30%. An aqueous dispersion (AD4) of a carbonyl group-containing modified epoxy resin (A4) of 45 mol / Kg was obtained. The amine value of this resin was 97 mg-KOH / g, and the weight average molecular weight was about 10,000.

[Production Example 8]
Air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, 145.9 g of “jER828” and 276.7 g of propylene glycol monomethyl ether were added, and the mixture was stirred until 100 ° C. The temperature was raised and dissolved. Thereafter, a mixture of 20.2 g of 2-ethylhexylamine and 55.2 g of “Surfonamine L-100” was added and held at 100 ° C. for 2 hours, and then 32.1 g of amine compound (a1) and 23 of amine compound (a2) were added. .3 g was added, and the temperature was raised to 120 ° C. and maintained at 120 ° C. for 7.5 hours to obtain a solution of the carbonyl group-containing modified epoxy resin (A5). Thereafter, a mixture of 16.7 g of acetic acid, 8.6 g of 85% phosphoric acid, and 100.0 g of water was added to the solution. Further, after adding 1200 g of water, about 1000 g is removed while azeotropically evaporating the solvent and water under reduced pressure, diluted with water so that the heating residue is about 30%, and the carbonyl group concentration in the resin solids is reduced to 0. An aqueous dispersion (AD5) of a carbonyl group-containing modified epoxy resin (A5) at 80 mol / Kg was obtained. The amine value of this resin was 113 mg-KOH / g, and the weight average molecular weight was about 12000.

[Production Example 9]
The air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and 152.0 g of “jER828” and 271.0 g of propylene glycol monomethyl ether were added and stirred, until 100 ° C. The temperature was raised and dissolved. Thereafter, a mixture of 22.6 g of 2-ethylhexylamine and 55.0 g of “Surfonamine L-100” was added and held at 100 ° C. for 2 hours, and then 30.9 g of amine compound (a1) and 10.5 g of diethanolamine were added. The temperature was raised to 120 ° C. and held at 120 ° C. for 7.5 hours to obtain a solution of a carbonyl group-containing modified epoxy resin (A6). Thereafter, a mixture of 17.1 g acetic acid, 8.8 g 85% phosphoric acid and 100.0 g water was added to the solution. Further, after adding 1150 g of water, about 950 g is removed while azeotropically evaporating the solvent and water while reducing the pressure, and diluted with water so that the heating residue is about 30%. An aqueous dispersion (AD6) of a carbonyl group-containing modified epoxy resin (A6) at 45 mol / Kg was obtained. The amine value of this resin was 118 mg-KOH / g, and the weight average molecular weight was about 11,000.

[Production Example 10]
The air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and 94.1 g of “jER1001” and 201.6 g of propylene glycol monomethyl ether were added and stirred to 100 ° C. The temperature was raised and dissolved. Thereafter, a mixture of 15.9 g of 2-ethylhexylamine and 52.8 g of “Surfonamine L-100” was added, and the mixture was kept at 100 ° C. for 2 hours. After the retention, 38.8 g of amine compound (a2), 56.3 g of “jER154” (trade name, manufactured by Japan Epoxy Resin Co., Ltd., phenol novolac type epoxy resin), 56.3 g of propylene glycol monomethyl ether were added at 120 ° C. The temperature was raised to 120 ° C. and maintained for 7.5 hours to obtain a solution of the carbonyl group-containing modified epoxy resin (A7). Thereafter, a mixture of 10.1 g of acetic acid, 5.2 g of 85% phosphoric acid and 100.0 g of water was added to the solution. Further, after adding 1100 g of water, about 900 g is removed while azeotropically evaporating the solvent and water while reducing the pressure, and diluted with water so that the heating residue is about 30%, and the carbonyl group concentration in the resin solids is reduced to 0. An aqueous dispersion (AD7) of a carbonyl group-containing modified epoxy resin (A7) of 62 mol / Kg was obtained. The amine value of this resin was 73 mg-KOH / g, and the weight average molecular weight was about 13,000.

[Comparative Production Example 1]
The air in a 2 L flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was replaced with nitrogen, and 152.0 g of “jER828” and 253.7 g of propylene glycol monomethyl ether were added and stirred until 100 ° C. The temperature was raised and dissolved. Thereafter, a mixture of 38.8 g of 2-ethylhexylamine, 50.0 g of “Surfonamine L-100” and 12.9 g of dibutylamine was added, the temperature was raised to 120 ° C. and held at 120 ° C. for 5 hours, and no carbonyl group was contained. A solution of a modified epoxy resin (A8) was obtained. Thereafter, a mixture of 13.5 g of acetic acid, 6.9 g of 85% phosphoric acid, and 100.0 g of water was added to the solution. Further, after adding 1100 g of water, about 900 g is removed while azeotropically evaporating the solvent and water under reduced pressure, and diluted with water so that the heating residue is about 30%, and modified epoxy resin containing no carbonyl group (A8) An aqueous dispersion (AD8) was obtained. The amine value of this resin was 100 mg-KOH / g, and the weight average molecular weight was about 11,000.

Production of aqueous primer composition, creation of multilayer coating [Example 1]
95 parts (316.7 parts as an aqueous dispersion) of the aqueous dispersion (AD1) of the carbonyl group-containing modified epoxy resin (A1) obtained in Production Example 1 as a solid content, an antirust pigment (C) [vanadium pentoxide 5 parts, calcium phosphate 5 parts, Shieldex C303 (manufactured by WR Grace & Co., trade name, calcium ion exchanged silica) 5 parts], and titanium white pigment [TS-6200 (manufactured by DuPont)] 30 Part of the mixture was mixed, and the pigment was dispersed until the nub (particle diameter of the coarse pigment particles) became 15 microns or less. Next, a cross-linking agent (B) [ADH (adipic acid dihydrazide) 5 parts] was added to this dispersion and mixed uniformly to adjust the viscosity to about 25 seconds (Ford Cup # 4/25 ° C.). Got.

  A test coating plate in which a multilayer coating film was formed using the above aqueous primer composition and the aqueous primer compositions obtained in the following other examples and comparative examples was prepared as follows.

  Aqueous primer obtained in each of the examples and comparative examples so that the dry film thickness is 5 μm on a 55% aluminum-zinc plated steel plate (galvalume steel plate, plate thickness 0.35 mm, plating AZ150) subjected to chemical conversion treatment Is applied with a bar coater, heated to reach the predetermined material temperature (hereinafter referred to as PMT) to a predetermined temperature described in Tables 1-1 and 1-2, and then baked for 30 seconds. The opposite surface was similarly painted and baked to obtain a primer-coated steel sheet. On the first painted surface, KP color 1555 brown full gloss (manufactured by Kansai Paint Co., Ltd., polyester / melamine paint, glass transition temperature 50 ° C.) is heated so that the dry film thickness is 15 μm and the PMT is 220 ° C. For 45 seconds to prepare a test coating.

[Examples 2 to 16 and Comparative Examples 1 to 5]
Each aqueous primer composition was obtained in the same manner as in Example 1 according to the blending ratio according to the solid content shown in Table 1-1 and Table 1-2 below. Note that (Note 1) to (Note 8) in the table are as follows.
(Note 1) ADH: adipic acid dihydrazide, solid content 100%
(Note 2) Hardener SC: manufactured by Asahi Kasei Chemicals, semicarbazide-based curing agent, concentration 50%
(Note 3) Cymel 701: Nippon Cytec Industry, methylated melamine, 82% solids
(Note 4) Bihijoule VPLS 2310: manufactured by Sumika Bayer Urethane Co., Ltd., blocked polyisocyanate compound with water dispersibility, solid content 38%
(Note 5) Shieldex C303: W.W. R. Grace & Co. Calcium ion exchange silica
(Note 6) Gasil 200DF: manufactured by Crossfield, silica fine powder
(Note 7) K-White G105: Phosphoric metal salt compound manufactured by Teika
(Note 8) TS6200: DuPont, titanium white pigment
performance test
Since each obtained coating plate for a test was tested according to the following conditions, the results are shown in Table 1-1 and Table 1-2.

[Machinability (4T processability)]
At a room temperature of 20 ° C., each test coating plate cut to a size of 6 cm × 12 cm was subjected to 4T bending processing (bending with the surface side of the coating plate facing outward, so that the length of the bent portion was 6 cm, Four plates having the same thickness as the coated plate were sandwiched inside, and the coated plate was processed by bending 180 degrees with a vise. The crack resistance of the coating film in the bent portion and the adhesion of the coating film in the bent portion were evaluated according to the following criteria. The adhesiveness of the coating film in the bent portion was evaluated by the degree of peeling of the coated film in the bent portion when a cellophane adhesive tape was applied to the bent portion and the tape was peeled off instantaneously.

(Draft resistance of the coating film in the bent part)
○: No cracking of the coating film is observed in the processed part, or slight cracking of the coating film is recognized in the processed part
Δ: Significant cracking of the coating is observed in the processed part
X: The crack of a coating film is recognized remarkably in a process part (The adhesiveness of the coating film of a bending process part)
○: Degree of peeling of the coating film is not recognized in the processed part, or slight peeling of the coating film is recognized in the processed part
Δ: Peeling of the coating film is considerably observed in the processed part
X: The coating film of the whole process part peels.

[Composite cycle corrosion test (CCT test)]
Conforms to JASO M609-91 (material corrosion test for automobiles, 1991). For each test, cut to a size of 6 cm x 12 cm so that the burrs at the edge of the long side of each test coating plate face the front side on the right side toward the front side and the back side on the left side. Insert a cross cut with a narrow angle of 30 degrees and a line width of 0.5 mm into the center of the surface side of the paint board using the back of the cutter knife, and seal the top edge of the paint board with anticorrosive paint. Is provided with a 4T bending portion (processing to bend with the surface side of the coated plate facing outward, sandwiching four plates of the same thickness as the painted plate inside, and bending the painted plate 180 degrees in a vise) With respect to the coated plate, one cycle of (5% saline spray at 35 ° C. for 2 hours) − (drying at 60 ° C. for 4 hours relative humidity 95%) − (50 ° C. for 2 hours relative humidity 95%) is 100 cycles ( The test was conducted for a total of 800 hours. The state of the 4T bending process part, crosscut part, and edge part of the coated board after this test was evaluated.

(4T process part) The rust part in a 4T process part was observed, and the following reference | standard evaluated.
A: Almost no occurrence of rust
○: Slight white rust is recognized
Δ: Clear white rust is observed, but not enough to cover the entire processed part
X: White rust is generated in the entire processed part, or occurrence of swelling is observed in the entire processed part (cross cut part) The corrosion state of the cross cut part was observed and evaluated according to the following criteria.
A: No white rust is observed
○: White rust is observed, but less than 20 mm
Δ: generation of white rust is 20 mm or more and less than 40 mm
X: Generation | occurrence | production of white rust 40 mm or more (edge part) The average value of the edge creep width of the left and right long sides of a coating board was calculated | required, and the following reference | standard evaluated.
◎: Corrosion progression width less than 5mm
○: Corrosion progression width of 5 mm or more and less than 10 mm
Δ: Corrosion progression width of 10 mm or more and less than 20 mm
×: Corrosion progression width 20 mm or more [Weather resistance test]
In accordance with JIS H 8602 5.12 (1992) (water spray time 12 minutes, black panel temperature 60 ° C.), a carbon arc lamp type accelerated weathering tester (Sunshine Weatherometer) is used for 750 hours test. The gloss of the test plate was measured before and after the test to determine the gloss retention and evaluated according to the following criteria.
A: 60 degree gloss retention 90% or more
○: 60 degree gloss retention 70% or more and less than 90%
Δ: 60 degree gloss retention 30% or more and less than 70%
X: 60 degree gloss retention less than 30%

Claims (3)

A metal primer is coated with an aqueous primer composition containing a carbonyl group-containing modified epoxy resin (A), a crosslinking agent (B) containing a hydrazide compound and / or a semicarbazide compound, and a rust preventive pigment (C). Is dried in the range of 10 ° C. to less than 180 ° C. to form a cured primer coating film (1), and the top coating material is applied on the cured primer coating film obtained in step (1), and the material reaches the highest temperature. Is a method of forming a multi-layer coating film comprising a step (2) of drying in the range of 180 ° C. to 300 ° C. to form a top coat film. The carbonyl group-containing modified epoxy resin (A) has at least one active hydrogen bonded to a nitrogen atom in one molecule, and has at least two amine compounds (a) having a carbonyl group and an epoxy group in one molecule. The method for forming a multilayer coating film according to claim 1, wherein the multilayer coating film is produced by reacting the epoxy resin (b). A coated article comprising a multilayer coating film formed on a metal material by the multilayer coating film forming method according to claim 1 or 2.