JPWO2015174129A1 - Water-based primer coating composition for aluminum substrate - Google Patents

Abstract

The problem to be solved by the present invention is to find an aqueous primer coating composition for an aluminum substrate which can form a coating film excellent in anticorrosion properties, particularly edge covering properties, yarn rust resistance and transparency. The present invention relates to an aqueous primer coating composition containing a hydroxyl group-containing resin (A), a crosslinking agent (B), and at least one clay mineral (C) selected from hectorites (C1) and mica (C2). An aqueous primer for an aluminum substrate containing 0.1 to 40 parts by mass of the clay mineral (C) with respect to 100 parts by mass of the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). A coating composition is provided.

Description

[Cross-reference of related applications]
This application claims priority based on Japanese Patent Application No. 2014-101062 filed on May 15, 2014, the entire disclosure of which is incorporated herein by reference.

  TECHNICAL FIELD The present invention relates to an aqueous primer coating composition for an aluminum substrate that can form a coating film having excellent coating stability and anticorrosion properties, particularly edge covering properties, yarn rust resistance and transparency.

  Aluminum base materials are widely used in automobile parts such as aluminum wheels because they are easy to machine, such as cutting and polishing, have excellent corrosion resistance, and are lightweight and improve fuel efficiency. A primer coating is applied on the aluminum wheel, and the coating film is required to have anticorrosion properties, edge covering properties and yarn rust resistance properties.

  Recent aluminum bases have increased the number of complex designs that can provide a high-class feeling, and therefore have increased sharp edges that have been cut. Accordingly, various devised paints have been developed to cover and protect the edge portion. For example, a coating film forming method characterized by applying an aqueous primer paint containing a thermosetting resin and colloidal silica to an aluminum wheel having an edge portion is disclosed (Patent Document 1).

  In addition, in the coating method in which a primer coating film is formed by a primer coating on an aluminum wheel having a cut surface and / or a cast surface, and further a top clear coating is formed thereon, the primer coating is organic It is disclosed that it is a coating composition containing bentonite (Patent Document 2).

  However, aluminum substrates, particularly aluminum wheels, may be used in severe corrosive environments such as coastal areas where sea salt particles are scattered or cold regions where snowmelt salt is scattered, and are disclosed in Patent Document 1 or Patent Document 2 above. In the coated film by the primer coating, any one of the anticorrosion, edge covering, yarn rust resistance and transparency is insufficient, and further improvement has been demanded.

JP-A-4-66172 JP 2002-239455 A

  An object of the present invention is to find an aqueous primer coating composition for an aluminum base material that can form a coating film having excellent coating stability and excellent corrosion resistance, edge covering properties, yarn rust resistance, and transparency. . Hereinafter, the “aqueous primer coating composition for an aluminum substrate” may be simply referred to as “aqueous primer coating composition”.

  As a result of intensive studies, the inventors of the present invention are aqueous primer coating compositions containing a hydroxyl group-containing resin (A), a crosslinking agent (B), and a specific clay mineral (C). Solution of the above problem is achieved by the aqueous primer coating composition for an aluminum substrate containing 0.1 to 40 parts by mass of the specific clay mineral (C) with respect to 100 parts by mass of the total solid content of the agent (B). The present inventors have found that this can be done and have completed the present invention.

That is, the present invention
“1. An aqueous primer coating composition containing a hydroxyl group-containing resin (A), a crosslinking agent (B), and at least one clay mineral (C) selected from hectorites (C1) and mica (C2). An aqueous primer coating for an aluminum substrate containing 0.1 to 40 parts by mass of the clay mineral (C) with respect to 100 parts by mass of the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). Composition,
2. The aqueous primer for an aluminum substrate according to 1, which contains 0.1 to 20 parts by mass of the phenol resin (D) with respect to 100 parts by mass of the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). Paint composition,
3. The aluminum group according to 1 or 2, wherein 0.1 to 10 parts by mass of metal ion-exchanged silica (E) is contained with respect to 100 parts by mass of the solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B) Water-based primer coating composition for materials.

4). 4. The composition according to any one of items 1 to 3, which contains 1 to 20 parts by mass of the silane coupling agent (F) with respect to 100 parts by mass of the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). An aqueous primer coating composition for an aluminum substrate,
5). The aqueous primer coating composition for an aluminum substrate according to any one of items 1 to 4, wherein the hydroxyl group-containing resin (A) is an acrylic urethane resin,
6). On the aluminum wheel which has a cutting surface, after forming the unhardened coating film by the water-based primer coating composition for aluminum base materials of any one of 1-5, and giving preheating, this coating film The present invention relates to a “coating film forming method for forming at least one top coating film”.

  The aqueous primer coating composition for an aluminum substrate of the present invention has good coating stability. The aluminum wheel obtained by applying the aqueous primer coating composition is excellent in anticorrosion, edge covering, yarn rust resistance and transparency.

  The present invention provides an aqueous solution for an aluminum substrate containing at least one clay mineral (C) selected from a hydroxyl group-containing resin (A), a crosslinking agent (B), hectorites (C1) and mica (C2). The present invention relates to a primer coating composition.

Hydroxyl-containing resin (A)
The hydroxyl group-containing resin (A) is an organic resin that can be dissolved or dispersed in water. As a method for dissolving or dispersing the organic resin in water, a conventionally known method can be used. Examples of such a hydroxyl group-containing resin (A) include epoxy resins, acrylic resins, acrylic epoxy resins, acrylic urethane resins, urethane resins, polyvinyl alcohol resins, and polyglycerin resins. Said resin can be used individually or in combination of 2 or more types.

  The acid value of the hydroxyl group-containing resin (A) is 1 to 50 mgKOH / g, particularly 5 to 40 mgKOH / g, and the hydroxyl value is 1 to 100 mgKOH / g, particularly 5 to 50 mgKOH / g. It is desirable to be within the above range from the viewpoints of paint stability, corrosion resistance, edge covering property, yarn rust resistance, transparency and the like.

  Among the hydroxyl group-containing resins (A) in the present invention, an acrylic resin and an acrylic urethane resin are preferable from the viewpoint of obtaining a coating film excellent in anticorrosion properties, edge covering properties and transparency. More preferably, an acrylic urethane resin having a core / shell type multi-layer structure including at least two layers of a core layer (acrylic resin) and a shell layer (urethane resin) is preferable for improving edge covering properties. The meaning of the acrylic urethane resin having “core / shell type multilayer structure” means that the shell part is a polymer layer present in the outermost layer of the resin composite particles, and the core part is a resin composite excluding the shell part. It means the polymer layer of the inner particle layer.

  The emulsion of the acrylic resin or acrylic urethane resin can be produced by a known method such as an emulsion polymerization method. In the polymerization, conventionally known monomers, initiators, emulsifiers, dispersants, solvents, chain transfer agents, buffers and other additives can be added. The emulsion type may be a forced emulsification type emulsion, a self-emulsification type emulsion, or a soap-free type emulsion.

  In addition, the structural ratio of the urethane resin (A1) and the acrylic resin (A2) in the acrylic urethane resin is urethane resin: acrylic resin = 5: 95-50: 50 (mass ratio), preferably 10: 90-40: 60. Is desirable.

  The urethane resin (A1) in the acrylic urethane resin is, for example, a polyisocyanate compound, a polyol, and, if necessary, a compound having both an active hydrogen-containing group and an ion-forming group. Can be synthesized.

  A polyisocyanate compound, a polyol, and a compound having both an active hydrogen-containing group and an ion-forming group are reacted in a solvent that is not reactive with an isocyanate group to produce an isocyanate group-terminated urethane prepolymer. The solvent may be a polymerizable unsaturated monomer that is not reactive with the polyisocyanate compound.

  Examples of the polyisocyanate compound include isophorone diisocyanate (IPDI), 2,4-tolylene diisocyanate (2,4-TDI), and a mixture of 2,4-TDI and 2,6-tolylene diisocyanate (2,6-TDI). 4,4'-diphenylmethane diisocyanate, 1,4-phenylene diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate (HMDI), trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, 4,4'-dicyclohexylmethane Diisocyanate, xylylene diisocyanate, tetramethyl xylylene diisocyanate and the like can be used. Further, if necessary, a trimer such as TDI, HMDI, or IPDI, or a trivalent polyisocyanate that is a reaction product with trimethylolpropane or the like can also be used.

  Examples of the polyol include the following compounds. Diol compound: ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, Neopentyl glycol, 1,6-hexane glycol, 2,5-hexanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, tricyclodecane dimethanol, 1,4-cyclohexanedimethanol etc.

  Polyether diols: alkylene oxide adducts of the above diol compounds, ring-opening (co) polymers of alkylene oxides and cyclic ethers (such as tetrahydrofuran), such as polyethylene glycol, polypropylene glycol, ethylene glycol-propylene glycol (block or random) Copolymer, glycol, polytetramethylene glycol, polyhexamethylene glycol, polyoctamethylene glycol and the like.

  Polyester diol: dicarboxylic acid (anhydride) such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid and the above-mentioned ethylene glycol, propylene glycol, 1,4-butanediol, 1 , 6-hexanediol, 1,8-octamethylenediol, neopentylglycol and other diol compounds obtained by polycondensation under conditions of excess hydroxyl group.

  Polyether ester diol: An ether group-containing diol (such as the above polyether diol or diethylene glycol) or a mixture of this with another glycol is added to (anhydrous) dicarboxylic acid as exemplified in the above polyester diol to react with an alkylene oxide. For example, polytetramethylene glycol-adipic acid condensate.

  Polycarbonate diol: General formula HO-R- (OC (O) -O-R) x-OH (wherein R is a saturated fatty acid diol residue having 1 to 12 carbon atoms, x is the number of repeating units of the molecule) And is usually an integer of 5 to 50). These include a transesterification method in which a saturated aliphatic diol and a substituted carbonate (diethyl carbonate, diphenyl carbonate, etc.) are reacted under the condition that the hydroxyl group is excessive, the saturated aliphatic diol and phosgene are reacted, or as necessary. Thereafter, it is obtained by a method of further reacting with a saturated aliphatic diol.

  Acrylic polyol: Acrylic polyol was obtained by polymerization reaction containing a carboxyl group-containing radical polymerizable unsaturated monomer, a hydroxyl group-containing radical polymerizable unsaturated monomer, and other radical polymerizable unsaturated monomers as constituent monomer components. A polyol is mentioned.

  Examples of the carboxyl group-containing radical polymerizable unsaturated monomer include monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid.

  Examples of the hydroxyl group-containing radical polymerizable unsaturated monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and the like. In addition, Plaxel FM1, Plaxel FM2, Plaxel FM3, Plaxel FA1, Plaxel FA2, Plaxel FA3 (manufactured by Daicel Chemical Industries, trade name, caprolactone-modified (meth) acrylic acid hydroxyesters) and the like can be mentioned.

  Examples of the other radical polymerizable unsaturated monomers include n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, Octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate , Methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) Acrylate, alkyl or cycloalkyl (meth) acrylates such as tricyclodecanyl (meth) acrylate. These monomers can be used alone or in combination of two or more.

  In the present specification, “alkyl or cycloalkyl (meth) acrylate” means “one kind selected from the group consisting of alkyl acrylate, cycloalkyl acrylate, alkyl methacrylate and cycloalkyl methacrylate”.

  For example, an alkyl (meth) acrylate having an alkyl group having 1 to 3 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate; ) Aromatic ring-containing polymerizable unsaturated monomers such as acrylate, styrene, α-methylstyrene, vinyltoluene; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyl Polymerizable unsaturated monomers having alkoxysilyl groups such as trimethoxysilane and γ- (meth) acryloyloxypropyltriethoxysilane; (meth) acrylonitrile, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acryl N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, nitrogen-containing polymerizable unsaturated monomers such as adducts of glycidyl (meth) acrylate and amines; glycidyl ( (Meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, allyl And epoxy group-containing polymerizable unsaturated monomers such as glycidyl ether. These monomers can be used alone or in combination of two or more.

  In this specification, “(meth) acrylate” means “acrylate or methacrylate”. “(Meth) acrylic acid” means “acrylic acid or methacrylic acid”. “(Meth) acryloyl” means “acryloyl or methacryloyl”. “(Meth) acrylamide” means “acrylamide or methacrylamide”.

  The blending ratio of these radically polymerizable unsaturated monomers is 1 to 20% by mass, preferably 4 to 10% by mass of the carboxyl group-containing radically polymerizable unsaturated monomer, based on the total amount of the radically polymerizable unsaturated monomers to be constituted. In the range of 1 to 40% by weight, preferably 5 to 30% by weight of the hydroxyl group-containing radical polymerizable unsaturated monomer, and 40 to 98% by weight, preferably 60 to 91% by weight of the other radical polymerizable unsaturated monomer. It is preferable to include. The number average molecular weight of the polyol is preferably 300 to 3,000, more preferably 500 to 2,500, from the viewpoint of coating stability.

  The weight average molecular weight or number average molecular weight in this specification is a value calculated based on the molecular weight of standard polystyrene from the chromatogram measured by gel permeation chromatograph according to the method described in JIS K 0124-83. . As the gel permeation chromatograph, “HLC8120GPC” (manufactured by Tosoh Corporation) was used. As the columns, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name) were used, Mobile phase: Tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 ml / min, detector: under the conditions of RI.

  Here, it is preferable that the said polyol is a polyester polyol, a polyether polyol, and / or an acrylic polyol from a corrosion-proof point. In this manner, an isocyanate group-terminated urethane prepolymer solution can be obtained.

  Examples of the compound having both the active hydrogen-containing group and the ion-forming group include, for example, a compound having two or more hydroxyl groups and one or more carboxyl groups in the molecule, two or more hydroxyl groups and one or more in the molecule. And compounds having a sulfonic acid group. This compound acts as an ion forming group in the urethane resin.

  Examples of the compound containing two or more hydroxyl groups and one or more carboxyl groups in the molecule include dimethylolpropionic acid, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolheptanoic acid, dimethylolnonanoic acid, 1- Examples include alkanol carboxylic acids such as carboxy-1,5-pentylenediamine, dihydroxybenzoic acid and 3,5-diaminobenzoic acid, and half ester compounds of polyoxypropylene triol with maleic anhydride and phthalic anhydride. .

  Examples of the compound containing a sulfonic acid group include 2-sulfonic acid-1,4-butanediol, 5-sulfonic acid-di-β-hydroxyethyl isophthalate, and N, N-bis (2-hydroxyethyl). Aminoethylsulfonic acid etc. can be mentioned.

  When a compound containing a carboxyl group or a sulfonic acid group is used as a compound having both an active hydrogen-containing group and an ion-forming group, trimethylamine, triethylamine, and monoethanol are used as neutralizing agents to form a salt and make it hydrophilic. Amines such as amine, diethanolamine, triethanolamine, triethylenediamine, and dimethylaminoethanol, and alkali metal compounds such as sodium hydroxide and potassium hydroxide can be used. The neutralization rate with respect to a carboxyl group or a sulfonic acid can be normally 50-100 mol%. As the neutralizing agent, triethylamine is preferable from the viewpoints of basicity and improved water resistance.

  The acrylic resin (A2) in the acrylic urethane resin is, for example, in the presence of the urethane prepolymer, with a polymerization initiator added to the radical polymerizable unsaturated monomer and stirring, for example, in the presence of an inert gas such as nitrogen. It can be obtained by holding at about 50 ° C. to about 300 ° C., preferably about 60 ° C. to 250 ° C., and carrying out a radical polymerization reaction for about 1 hour to about 24 hours, preferably about 2 hours to about 10 hours.

  Examples of the radical polymerizable unsaturated monomer include the carboxyl group-containing radical polymerizable unsaturated monomer, the hydroxyl group-containing radical polymerizable unsaturated monomer, and, if necessary, the other radical polymerizable unsaturated monomer. .

  The acrylic resin (A2) has a hydroxyl value of 1 to 150 mgKOH / g, preferably 2 to 100 mgKOH / g, an acid value of 1 to 50 mgKOH / g, preferably 2 to 20 mgKOH / g. It is preferable from the point of improvement.

  In addition, although the typical manufacturing method of an acrylic urethane resin is shown below, it is not limited to this method, The manufacturing method of a conventionally well-known acrylic urethane resin can also be used.

  The method up to the formation of the urethane prepolymer of the urethane resin is as described above. In this method, the urethane prepolymer is produced in a polymerizable unsaturated monomer ((meth) acrylic monomer) solution having no reactivity with an isocyanate group. Hereinafter, the “polymerizable unsaturated monomer having no reactivity with an isocyanate group” may be simply referred to as “polymerizable unsaturated monomer”.

  Subsequently, after adding a neutralizing agent, water is added, the oil layer and the water layer are phase-inverted and dispersed in water to obtain an aqueous dispersion. A radical polymerization initiator is added to this aqueous dispersion to carry out a polymerization reaction of the polymerizable unsaturated monomer. If necessary, a chain elongation reaction of a urethane resin (urethane prepolymer) is performed.

  As a method for obtaining the aqueous dispersion, the following methods can also be performed as necessary. When dispersing the polymerizable unsaturated monomer solution of the urethane prepolymer in water, by adding a polyoxyalkylene group-containing (meth) acrylic monomer, the dispersion in water becomes good and the water dispersion is uniform and more stable. Is obtained. The polyoxyalkylene group-containing (meth) acrylic monomer is an acrylic monomer having a polyoxyethylene group or a polyoxypropylene group, and having a hydroxy group or an alkoxy group having 1 to 3 carbon atoms at the end of the group.

  Here, as a method of dispersing the polymerizable unsaturated monomer solution of the urethane prepolymer in water, it is possible to disperse with a normal stirrer, but in order to obtain a uniform aqueous dispersion having a finer particle diameter, A homogenizer, a disper, a line mixer, etc. can be used.

  After obtaining an aqueous dispersion of the polymerizable unsaturated monomer of the urethane prepolymer as described above, the polymerization initiator is added to this to raise the temperature, and within the range of the polymerization temperature of the polymerizable unsaturated monomer, Aqueous dispersion of acrylic urethane resin composite particles composed of urethane resin and acrylic resin can be obtained by performing chain extension with water of the urethane prepolymer as necessary and polymerizing a polymerizable unsaturated monomer. .

  The polymerization reaction in the aqueous dispersion can be performed by a known radical polymerization reaction. As the polymerization initiator, either a water-soluble initiator or an oil-soluble initiator can be used. When an oil-soluble initiator is used, it is preferably added in advance to the polymerizable unsaturated monomer solution of the urethane prepolymer before making an aqueous dispersion.

  When chain extension of the urethane prepolymer is performed, a chain extender other than water can be added as necessary to react the urethane prepolymer with the chain extender. As the chain extender, a known chain extender having active hydrogen can be used. Specific examples include diamines such as ethylenediamine, hexamethylenediamine, cyclohexanediamine, cyclohexylmethanediamine, and isophoronediamine, and hydrazine.

  In the aqueous dispersion of acrylic urethane resin, the core-shell structure, urethane resin (A1) and acrylic resin (A2) are adjusted by adjusting the composition of each resin component (urethane resin (A1), acrylic resin (A2)), reaction conditions, and the like. ), An aqueous dispersion of an acrylic urethane resin having a desired form such as a form in which a part or all of) is mixed.

  The acrylic urethane resin thus obtained has an average particle size in the range of 10 to 5,000 nm, preferably 10 to 1,000 nm, and more preferably 20 to 500 nm.

  In the present specification, the average particle diameter is a value measured at 20 ° C. after diluting with deionized water by a conventional method using a submicron particle size distribution measuring apparatus. As the submicron particle size distribution measuring device, for example, “COULTER N4 type” (trade name, manufactured by Beckman Coulter, Inc.) can be used.

Cross-linking agent (B)
The crosslinking agent (B) in the aqueous primer coating composition of the present invention can be used without particular limitation as long as it can be reacted with the hydroxyl group of the hydroxyl group-containing resin (A) by heating and cured. Melamine resin, benzoguanamine resin, urea resin and blocked polyisocyanate.

  As said melamine resin, the melamine resin which etherified the methylol group of the methylol-ized melamine resin with the C1-C8 monohydric alcohol can be used, for example. The etherified melamine resin may be one in which all the methylol groups of the methylolated melamine resin are etherified, or may be partially etherified to leave a methylol group or imino group.

  Specific examples of melamine resins include fully alkyl methyl / butyl mixed etherified melamine resins, methylol group methyl / butyl mixed etherified melamine resins, imino methyl / butyl mixed etherified melamine resins, fully alkyl methylated melamine resins. And imino group-type methylated melamine resins. These melamine resins may be used alone or in combination of two or more.

  Examples of commercially available melamine resins include Cymel 232, Cymel 232S, Cymel 235, Cymel 236, Cymel 238, Cymel 266, Cymel 267, Cymel 285, and other fully alkyl methyl / butyl mixed etherified melamine resins; Cymel 272, etc. Methylol-based methyl / butyl mixed etherified melamine resins; Cymel 202, Cymel 207, Cymel 212, Cymel 253, Cymel 254 and other imino methyl / butyl mixed etherified melamine resins; Cymel 300, Cymel 301, Cymel 303, Cymel Fully alkyl type methylated melamine resin such as 350; Cymel 325, Cymel 327, Cymel 703, Cymel 712, Cymel 254, Cymel 253, Cymel 212, Cymel 1 Imino group type methylated melamine resin, such as 28 (or more, Daicel Orunekusu trade name), Uban 20SE60 (Mitsui Cytec Co., Ltd., butyl etherified melamine resins), and the like.

  Examples of the benzoguanamine resin include methylolated benzoguanamine resins obtained by reaction of benzoguanamine and aldehyde. Examples of the aldehyde include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like.

  In addition, those obtained by etherifying this methylolated benzoguanamine resin with one or more alcohols are also included in the benzoguanamine resin. Examples of the alcohol used for etherification include monohydric alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol, and 2-ethylhexanol. . Among these, a benzoguanamine resin obtained by etherifying at least a part of the methylol group of the methylolated benzoguanamine resin with a monohydric alcohol having 1 to 4 carbon atoms is preferable.

  Specific examples of the benzoguanamine resin include, for example, My Coat 102, My Coat 105, My Coat 106 (all of which are manufactured by Mitsui Cytec Co., Ltd.), Nicarak SB-201, Nicarac SB-203, Nicarac SB-301, Nicarac SB. -303, Nicalac SB-401 (all of which are manufactured by Sanwa Chemical Co., Ltd.) and other methyl etherified benzoguanamine resins; Cymel 1123 (above, manufactured by Mitsui Cytec Co., Ltd.) and other mixed etherified benzoguanamine resins of methyl ether and ethyl ether Methyl ether and butyl ether such as My Coat 136 (above, manufactured by Mitsui Cytec Co., Ltd.), Nicarak SB-255, Nicarac SB-355, Nicarac BX-37, Nicarac BX-4000 (all of which are manufactured by Sanwa Chemical Co., Ltd.) Etherified benzoguanamine resins; Mycoat 1128 (or, Mitsui Cytec Co., Ltd.) and the like butyl etherified benzoguanamine resins such as.

  The urea resin is a resin obtained by a condensation reaction of urea and formaldehyde and can be dissolved or dispersed in a solvent or water.

  The polyisocyanate compound is a compound having two or more isocyanate groups in one molecule. For example, aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate; tetramethylene diisocyanate, hexamethylene diisocyanate Aliphatic diisocyanates such as dimer acid diisocyanate and lysine diisocyanate; alicyclic diisocyanates such as methylene bis (cyclohexyl isocyanate), isophorone diisocyanate, methylcyclohexane diisocyanate, cyclohexane diisocyanate and cyclopentane diisocyanate; a biuret type adduct of the polyisocyanate, isocyanuric Ring type adduct These polyisocyanates with low molecular weight or high molecular weight polyol compound (e.g., acrylic polyols, polyester polyols, polyether polyols, etc.) and an isocyanate group excess obtained by reacting the free isocyanate group-containing prepolymer can be mentioned a.

  Furthermore, the free isocyanate groups of these polyisocyanate compounds are converted into phenol compounds, oxime compounds, active methylene compounds, lactam compounds, alcohol compounds, mercaptan compounds, acid amide compounds, imide compounds, amine compounds, imidazole compounds, urea compounds. A blocked polyisocyanate blocked with a blocking agent such as a compound, a carbamic acid compound or an imine compound can also be used.

  As a mixing ratio of the hydroxyl group-containing resin (A) and the crosslinking agent (B), the hydroxyl group-containing resin (A) is 60 to 95 parts by mass, preferably 70, based on a total solid content of 100 parts by mass. It is -90 mass parts, and a crosslinking agent (B) is 5-40 mass parts, Preferably it is 10-30 mass parts, it is excellent in coating-material stability, and anticorrosion property, edge covering property, and yarn rust resistance It is suitable from the point of obtaining a coating film excellent in.

Clay mineral (C)
The aqueous primer coating composition of the present invention contains at least one clay mineral (C) selected from hectorites (C1) and mica (C2).

  Examples of the hectorites (C1) include naturally occurring hectorites and synthetic hectorites, and both can be used. In the present invention, hectorites can also be indicated as hectorite compounds. Examples of commercially available hectorites (C1) include LAPONITE XLG, LAPONITE RD (above, trade name, hectorite, manufactured by ROCKWOOD), thermabis (trade name, hectorite, manufactured by Henkel), bee gum (bander). (Manufactured by Bilt, trade name, hectorite) and the like.

  Mica (C2) is a layered silicate mineral. Examples of commercially available products of mica (C2) include Somasif (trade name, mica manufactured by Co-op Chemical Co., Ltd.), Daimonite (trade name, mica manufactured by Topy Industries, Ltd.), and the like. In the present invention, mica can also be referred to as a mica compound.

  The clay mineral (C) can be blended in the water-based primer coating composition as it is, but preferably the clay mineral (C) is mixed with the hydroxyl group-containing resin (A) to obtain the hydroxyl group-containing resin (A). It is desirable from the viewpoint of improving the stability of the paint that it is blended in the aqueous primer paint composition as a dispersion containing.

  The blending ratio of the clay mineral (C) in the aqueous primer coating composition of the present invention is 0.1 to 40 parts by mass with respect to 100 parts by mass in total of the solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). , Preferably it is 0.5-20 mass parts, More preferably, it is the range of 1-10 mass parts. The above range is desirable for obtaining a coating film having excellent paint stability and anticorrosion properties, particularly excellent edge covering properties.

  In addition to the hydroxyl group-containing resin (A), the cross-linking agent (B), and the clay mineral (C), the aqueous primer coating composition of the present invention includes a phenol resin (D) and a metal ion-exchanged silica (if necessary). E) and at least one selected from the group consisting of silane coupling agents (F) can be contained.

Phenolic resin (D)
In the water-based primer coating composition of the present invention, the phenol resin (D) that is blended as necessary comprises a phenol compound such as phenol, cresol, bisphenol A and an aldehyde such as formaldehyde in the presence of an acidic catalyst or a basic catalyst. Of these resins, those condensed with an acidic catalyst are referred to as novolak type phenol resins, and those condensed with a basic catalyst are referred to as resol type phenol resins.

  In the aqueous primer coating composition, as the phenol resin (D), any of novolak type phenol resin and resol type phenol resin can be used. Further, a resin having a methylol group introduced therein is also included, and a phenol resin obtained by alkyl etherifying a part or all of the introduced methylol group with an alcohol having 6 or less carbon atoms can also be used.

  Commercially available products of the phenolic resin (D) include SUMILITERESIN PR-HF-3, SUMILITERESIN PR-HF-6, SUMILITERESIN PR-53194, SUMILITERESIN PR-53195, SUMILITERESIN PR-54869, SUMILITERESIN39, SUMILITERES19. , SUMILITERESIN PR-53153, SUMILITERESIN PR-53364, SUMILITERESIN PR-53365, SUMILITERESIN PR-50702 (manufactured by "Sumitomo Bakelite Co., Ltd."); PHENOLITE TD-2131, PHENOLITE TD-2106 PHENOLITE TD-2091, PHENOLITE TD-2090, PHENOLITE VH-4150, PHENOLITE VH-4170, PHENOLITE VH-4240, PHENOLITE KH-1160, PHENOLITE KH-1163, PHENOLITE KH-1163, PHENOLITE KH-1163 2090-60M, PHENOLITE LF-4711, PHENOLITE LF-6161, PHENOLITE LF-4871, PHENOLITE LA-7052, PHENOLITE LA-7705, PHENOLITE LA-7651, PHENOLITE LA-1856, PHENOLITE LA-1856 Made); Shoonol BRG-555, Shoonol BRG-556, Shoonol BRG-558, Shoonol CKM-923, Shoonol CKM-983, Shoonol BKM-2620, Shoonol BRL-2854, Shoonol BRG-5590M, Shoonol CKS -3898, Shounol CKS-3877A, Shounol CKM-937 (manufactured by Showa Polymer Co., Ltd.) and the like.

  In the aqueous primer coating composition, the proportion when the phenol resin (D) is blended is 0.1 to 20 masses per 100 mass parts of the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). Parts, preferably 0.2 to 15 parts by mass, more preferably 0.3 to 10 parts by mass. The above range is desirable for improving yarn rust resistance.

Metal ion exchange silica (E)
In the water-based primer coating composition of the present invention, the metal ion exchange silica (E) blended as necessary is a metal ion exchange silica in which the metal is at least one of calcium and magnesium. Examples include exchanged silica and magnesium ion exchanged silica. These metal ion exchange silicas (E) can be modified with phosphoric acid as necessary to obtain phosphoric acid modified metal ion exchange silica.

  The calcium ion exchanged silica is silica fine particles in which calcium ions are introduced into a fine porous silica carrier by ion exchange. Commercially available products of calcium ion exchange silica include SHIELDEX (Shielddex, registered trademark) C303, SHIELDEXAC-3, SHIELDEXC-5 (all of which are manufactured by WR Grace & Co.), Silo Mask 52 (manufactured by Fuji Silysia). ) And the like.

  The magnesium ion-exchanged silica is silica fine particles in which magnesium ions are introduced into a fine porous silica carrier by ion exchange. Examples of commercially available magnesium ion-exchanged silica include Silo Mask 52M (manufactured by Fuji Silysia) and Novinox ACE-110 (manufactured by SNCZ, France).

  When the metal ion exchange silica (E) is blended, the amount of the metal ion exchange silica (E) is 0. 0 parts by mass with respect to the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). The content of 1 to 10 parts by mass, preferably 0.2 to 8 parts by mass, and more preferably 0.3 to 7 parts by mass is desirable for improving corrosion resistance, edge covering properties and yarn rust resistance.

Silane coupling agent (F)
In the water-based primer coating composition of the present invention, the silane coupling agent (F) blended as necessary includes, for example, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, N- (β-amino) Ethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltriethoxysilane, γ-ureidopropyltri Amino group-containing silane coupling agents such as ethoxysilane, N- (β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane, γ-anilinopropyltrimethoxysilane; γ-glycidoxypropylmethyl Dimethoxysilane, γ-glycidoxypropyltriethoxyxysilane , Β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and other epoxy group-containing silane coupling agents; β-carboxylethylphenylbis (2-methoxyethoxy) silane, N-β- (N-carboxymethylaminoethyl) ) -Γ-aminopropyltrimethoxysilane and other carboxy-containing silane coupling agents, etc. These silane coupling agents (F) may be used alone or in combination of two or more.

  Commercially available silane coupling agents (F) include KBM-402, KBM-403, KBM-502, KBM-503, KBM-603, KBE-903, KBM-603, KBE-602, KBE-603 ( As mentioned above, the product name of Shin-Etsu Silicone Co., Ltd., etc. are mentioned.

  When the silane coupling agent (F) is blended, the amount of the silane coupling agent (F) is 1 to 100 parts by mass in total of the solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). The content of 20 parts by mass, preferably 2 to 15 parts by mass, and more preferably 3 to 10 parts by mass is desirable for improving corrosion resistance, edge covering properties and yarn rust resistance.

  The aqueous primer coating composition of the present invention may contain other pigments, catalysts, pigment dispersants (for example, amide-based wetting dispersants), dyes, plasticizers, anti-settling agents, ultraviolet absorbers, if necessary. An antioxidant, a surface conditioner, a surfactant, an anti-sagging agent, a thickener, an antifoaming agent, a lubricant, crosslinkable polymer particles (microgel), an organic solvent, and the like can be contained.

  Examples of the other pigment include, for example, colored pigments such as titanium white and carbon black; extender pigments such as clay, talc, barita and kaolin; rust preventive pigments such as aluminum dihydrogen phosphate and aluminum phosphomolybdate; Bismuth compounds such as bismuth oxide, bismuth hydroxide and bismuth lactate; as the catalyst, organic tin compounds such as dibutyltin oxide and dioctyltin oxide; dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dioctyltin dibenzoate And tin compounds such as aliphatic or aromatic carboxylates of dialkyltin such as dibutyltin dibenzoate.

  The aqueous primer coating composition of the present invention comprises a hydroxyl group-containing resin (A), a crosslinking agent (B), a viscous mineral (C), and, if necessary, a phenol resin (D), metal ion exchange silica (E), silane. Coupling agent (F), other anti-rust pigments, dyes, coloring pigments, extender pigments, metallic pigments, plasticizers, anti-settling agents, curing catalysts, UV absorbers, antioxidants, surface conditioners, anti-sagging agents, It is obtained by mixing a thickener, an antifoaming agent, a lubricant, crosslinkable polymer particles (microgel) and the like and diluting with deionized water.

  The aqueous primer coating composition of the present invention is applied to aluminum base materials such as automobile parts and building materials, particularly aluminum wheels. The aluminum wheel is made of an alloy containing aluminum as its main component and containing magnesium, silicon, etc., and is subjected to surface treatments such as chromate treatment (chromium chromate, chromium phosphate, etc.) and non-chromium treatment (zirconium phosphate, zirconium oxide, etc.). What has been done is desirable for corrosion resistance, edge covering properties and yarn rust resistance.

About the coating film formation method The coating film formation using the aqueous primer coating composition of this invention forms an uncured coating film by this aqueous primer coating composition on the aluminum wheel which has a process (1) cutting surface. Step (2) Preheating is performed at a temperature of 50 to 110 ° C., preferably 60 to 100 ° C., for 30 seconds to 30 minutes, preferably 1 minute to 20 minutes. Step (3) Two coats are applied by applying at least one top coat and baking and drying at a temperature of 100 to 180 ° C., preferably 110 to 150 ° C. for about 5 to 60 minutes, preferably about 10 to 40 minutes. One baking method is mentioned. The coating thickness of the aqueous primer coating composition is 5 to 25 μm, preferably 10 to 23 μm based on the cured coating film. As the top coating material, an acrylic resin-based coating material is suitable. Specifically, a thermosetting coating material obtained by dissolving or dispersing an acrylic resin, a crosslinking agent and a pigment (optional component) in an organic solvent is preferable.
Such a top coat is preferably applied by airless spray, air spray, electrostatic method or the like. The viscosity during coating is preferably 10 to 30 seconds / Ford Cup # 4/20 ° C., and the coating film thickness is preferably about 10 to 50 μm, particularly 15 to 35 μm based on the cured coating film.

  Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto.

Production Example 1 Acrylic resin no. 1. Preparation of aqueous dispersion 1 In a reaction vessel equipped with a thermometer, thermostat, stirring device and reflux condenser, 144.5 parts of deionized water and 1.2 parts of Newcol 562SF (Note 1) were charged in a nitrogen stream. The mixture was stirred and heated to 80 ° C. Then, 1 part of the following “Emulsion a” and 5.2 parts of a 3% ammonium persulfate aqueous solution were charged therein and kept at 80 ° C. for 15 minutes.

"Emulsion a"
Methyl methacrylate 70 parts Ethyl acrylate 20 parts n-Butyl methacrylate 3.5 parts 2-hydroxyethyl methacrylate 5 parts Methacrylic acid 1.5 parts Newcol 562SF (Note 1) 1.2 parts Deionized water 94.3 parts (Note 1) Newcol 562SF: manufactured by Nippon Emulsifier Co., Ltd., trade name, surfactant, 60% ammonium polyoxyethylene alkylbenzenesulfonate After that, the rest of the emulsion a was dropped into the flask over 3 hours, and after ripening for 1 hour, While gradually adding 1.5 parts of a 1.5% diethylaminoethanol aqueous solution to the flask, the mixture was cooled to 30 ° C., the solid content was adjusted, and an acrylic resin No. 2 having an average particle size (Note 2) of 100 nm and a solid content of 30% was adjusted. 1 aqueous dispersion was obtained. The acrylic resin no. The hydroxyl value of 1 was 20 mgKOH / g, the acid value was 10 mgKOH / g, and the weight average molecular weight was 6,500.

  (Note 2) Average particle diameter: diluted with deionized water using a submicron particle size distribution measuring apparatus “COULTER N4 type” (manufactured by Beckman Coulter, Inc.) and measured at 20 ° C.

Production Example 2 Acrylic resin no. Production of aqueous dispersion of No. 2 A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device was charged with 145 parts of deionized water and 1.2 parts of Newcol 562SF (Note 1) in a nitrogen stream. The mixture was stirred and mixed and heated to 80 ° C. Next, 1% of the total amount of the following emulsion (1) and 5.2 parts of a 3% aqueous solution of ammonium persulfate were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes. Then, the remaining emulsion (1) was dripped in reaction container over 3 hours, and ageing | curing | ripening was performed after completion | finish of dripping.

Thereafter, the following emulsion (2) was added dropwise over 2 hours and aged for 1 hour, and then cooled to 30 ° C. while gradually adding 1.5 parts of a 1.5% dimethylethanolamine aqueous solution to the reaction vessel. The resin was discharged while being filtered through a mesh nylon cloth, the solid content was adjusted, and an acrylic resin No. 1 having an average particle diameter of 100 nm and a solid content of 25% was obtained. An aqueous dispersion of 2 was obtained. The acrylic resin no. The hydroxyl value of 2 was 22.1 mg KOH / g, the acid value was 30.7 mg KOH / g, and the weight average molecular weight was 7,500.
(Note 1) Newcol 562SF: Nippon Emulsifier Co., Ltd., trade name, ammonium polyoxyethylene alkylbenzenesulfonate, active ingredient 60%.

"Emulsion (1)"
Emulsion (1) was obtained by mixing and stirring 94.3 parts of deionized water, 17 parts of methyl methacrylate, 80 parts of n-butyl acrylate, 3 parts of allyl methacrylate, and 1.2 parts of Newcol 562SF (Note 1).

"Emulsion (2)"
39 parts of deionized water, 154 parts of methyl methacrylate, 2.9 parts of n-butyl acrylate, 5.9 parts of hydroxyethyl acrylate, 5.1 parts of methacrylic acid and 0.5 part of Newcol 562SF were mixed and stirred to give an emulsion (2 )

Production Example 3 Acrylic urethane resin no. 1 In a reaction vessel equipped with a thermometer, thermostat, stirrer and reflux condenser, 24.3 parts of ETERNCOLLUH-100 (Note 3), 43 parts of 2-ethylhexyl acrylate, 0. 014 parts and 0.03 part of dibutyltin laurate were charged and the temperature was raised to 90 ° C., and then 5.7 parts of hydrogenated MDI was added dropwise over 30 minutes. Thereafter, the reaction was continued at 90 ° C. until the NCO value disappeared.

  Hydroxyl group diluted with acrylic monomer by adding 5 parts of n-butyl acrylate, 14 parts of methyl methacrylate, 3.5 parts of 2-hydroxyethyl methacrylate, 0.5 part of acrylic acid and 4 parts of allyl methacrylate to this reaction product Containing polyurethane resin no. One solution was obtained. The obtained hydroxyl group-containing polyurethane resin No. The hydroxyl value of urethane resin No. 1 was 10 mgKOH / g, and the weight average molecular weight was 30,000.

  After that, the following “emulsion (3)” was put in a glass beaker, stirred for 15 minutes at 2000 rpm with a disper to produce a preliminary emulsion, and then this preliminary emulsion was subjected to high pressure treatment at 100 MPa with a high pressure emulsifier. A polyurethane-containing acrylic monomer emulsion having an average particle size of dispersed particles of 290 nm was obtained.

"Emulsion (3)"
Hydroxyl-containing polyurethane resin No. 1 solution 100 parts Newcol 707SF (Note 5) 6.7 parts Deionized water 93.3 parts 200 parts of the above monomer emulsion was transferred to a flask and diluted with 28.8 parts of deionized water. While stirring, the temperature was raised to 70 ° C., and an initiator solution prepared by dissolving 0.35 part of VA-057 (Note 4) in 17.5 parts of deionized water was dropped into the flask over 30 minutes, and the temperature was maintained. The mixture was stirred for 2 hours. Further, an initiator solution prepared by dissolving 0.175 part of VA-057 (Note 4) in 8.75 parts of deionized water was added to the flask, stirred for 2 hours while maintaining the temperature, cooled, and acrylic urethane. Resin No. 1 aqueous dispersion was obtained.

The obtained acrylic urethane resin No. The aqueous dispersion of No. 1 had a solid content concentration of 40% by mass and an average particle size of 190 nm. Acrylic urethane resin No. The resin solid content of No. 1 had a hydroxyl value of 21.6 mgKOH / g and an acid value of 5.6 mgKOH / g.
(Note 3) ETERNACOLL UH-100: manufactured by Ube Industries, trade name, 1,6-hexanediol-based polycarbonate diol, weight molecular weight of about 1,000
(Note 4) VA-057: manufactured by Wako Pure Chemical Industries, Ltd., trade name, polymerization initiator for emulsion polymerization Production Example 4 Acrylic urethane resin No. 2. Preparation of aqueous dispersion of 2 In a reaction vessel equipped with a thermometer, thermostat, stirrer and reflux condenser, 24.3 parts of ETERNCOLLUH-100 (Note 3), 35 parts of 2-ethylhexyl acrylate, 0. 008 parts and 0.03 part of dibutyltin laurate were charged and the temperature was raised to 90 ° C., and then 5.7 parts of hydrogenated MDI was added dropwise over 30 minutes.

  Thereafter, the temperature was maintained at 90 ° C., and the reaction was continued until NCO disappeared. To this reaction product, 2 parts of n-butyl acrylate and 3 parts of allyl methacrylate were added. Two solutions were obtained. The obtained hydroxyl group-containing polyurethane resin No. The hydroxyl value of 2 was 10 mgKOH / g, and the weight average molecular weight was 30,000.

  Thereafter, the following components were put into a glass beaker, stirred for 15 minutes at 2,000 rpm with a disper to prepare a preliminary emulsion, and then this preliminary emulsion was subjected to high pressure treatment at 100 MPa with a high pressure emulsifier, thereby obtaining an average of dispersed particles. A polyurethane-containing acrylic monomer emulsion (4) having a particle size of 290 nm was obtained.

"Polyurethane-containing acrylic monomer emulsion (4)"
Hydroxyl-containing polyurethane resin No. 2 solution 70.0 parts Newcol 707SF (Note 5) 4.7 parts deionized water 65.3 parts (Note 5) Newcol 707SF: trade name, manufactured by Nippon Emulsifier Co., Ltd., anionic emulsifier having polyoxyethylene chain, active ingredient 30% by mass.

  140 parts of the polyurethane-containing acrylic monomer emulsion (4) was transferred to a flask and diluted with 42.5 parts of deionized water. While stirring, the temperature was raised to 70 ° C., and an initiator solution in which 0.2 part of VA-057 (Note 4) was dissolved in 10 parts of deionized water was dropped into the flask over 30 minutes, and the temperature was maintained. Stir for 2 hours.

  Thereafter, a monomer emulsion (5) having the following composition and 0.15 part of VA-057 (Note 4) dissolved in 7.5 parts of deionized water were added dropwise over 1.5 hours to maintain the temperature. After stirring for 1 hour, an initiator solution in which 0.1 part of VA-057 (Note 4) was dissolved in 5 parts of deionized water was added to the flask and stirred for 2 hours while maintaining the temperature. After cooling, acrylic urethane resin no. A two water dispersion was obtained.

Monomer emulsion (5)
2-ethylhexyl acrylate 8 parts n-butyl acrylate 3 parts methyl methacrylate 14 parts 2-hydroxyethyl methacrylate 3.5 parts acrylic acid 0.5 parts allyl methacrylate 1 part Newcol 707SF (Note 5) 2.0 parts deionized water 18 parts The obtained acrylic urethane resin No. The solid content concentration of the 2-water dispersion was 40% by mass, and the average particle size (Note 2) was 210 nm. The hydroxyl value in the acrylic resin was 21.6 mgKOH / g, and the acid value was 5.6 mgKOH / g.

Example of production of water-based primer paint Example 1 Production of acrylic resin No. 1 obtained in Production Example 1 One mixture of 70 parts (solid content) of water dispersion, 30 parts of Cymel 327 (Note 6), 1.5 parts of LAPONITE XLG (Note 8), triethylamine (0.4 equivalents), and Add deionized water, stir for 1 hour with a stirrer (7 cm diameter stirring blade, 700 rpm) and adjust with deionized water. 1 was obtained.

Examples 2 to 20 Primer paint No. 2-No. Manufacture of No. 20 The primer paint no. 2-No. 20 was obtained.

Comparative Examples 1 to 13 Primer paint No. 21-No. Production of No. 33 Primer paint No. 33 was prepared in the same manner as in Example 1 except that the content of blending shown in Table 3 below was used. 21-No. 33 was obtained.

  Using the primer paints obtained in Examples 1 to 20 and Comparative Examples 1 to 13, aluminum wheel coated articles were obtained according to the following steps.

Preparation of aluminum wheel coating article Spray coating of each primer paint to an aluminum wheel having a cutting surface subjected to non-chromic chemical conversion treatment to a dry film thickness of 25 μm, preheating at 80 ° C. for 10 minutes, Magiclon EN-2 Clear (Kansai Paint Co., Ltd., trade name, acrylic resin-based organic solvent paint) was applied to a dry film thickness of 25 μm and heated at 140 ° C. for 20 minutes to test aluminum wheels A painted article was obtained. Tables 1 to 3 show the results of evaluation using the aluminum wheel coated article according to the following test conditions.

(Note 6) Cymel 327: Nihon Cytec Industries, Inc., trade name, imino group-type methylated melamine resin (Note 7) Bihydur 3100: Sumika Bayer Urethane, trade name, hexamethylene diisocyanate polyisocyanate compound (Note 8) ) LAPONITE XLG: manufactured by ROCKWOOD, trade name, hectorite (Note 9) Bee gum: manufactured by Vanderbilt, trade name, hectorite (Note 10) Thermabis: manufactured by Henkel, trade name, hectorite (Note 11) dymonite: Topy Industries Co., Ltd., trade name, synthetic mica (Note 12) Benton 38: National Red, trade name, organic bentonite (Note 13) Shounol BKM-262: Showa Polymers, trade name, phenol resin (Note 14) ) Silo mask 52M: Product name, Ma, manufactured by Fuji Silysia Gnesium ion exchanged silica (Note 15) SHIELDEX C303: R. Grace & Co. Product name, calcium ion exchanged silica, average particle size 3μm
(Note 16) KBM-403: Shin-Etsu Chemical Co., Ltd., trade name, silane coupling agent, 3-glycidoxypropyltrimethoxysilane (Note 17) Snowtex PMT-ST: Nissan Chemical Industries, trade name, colloidal Silica (Note 18) paint stability:
Each primer coating composition (solid content 40% by mass) obtained in Examples 1 to 20 and Comparative Examples 1 to 13 was placed in a 100 mL glass container, and sealed and stored in a container at 35 ° C. for 35 days. Subsequent conditions were judged by the following criteria:
S is as good as it was before storage A is slightly increased in viscosity, but returns to its original state with stirring for 1 minute or less B is increased in viscosity and is less than 10 minutes for more than 1 minute Returning to the original state with stirring of C, layer separation is observed and it cannot be used as a paint.

(Note 19) Anticorrosion:
A cast test liquid prepared according to JIS Z 2371 (2000) is sprayed at 50 ± 2 ° C. for 120 hours on a sample in which a cut wound having a length of 10 cm is made with a cutter knife on the surface of an aluminum wheel coated article. After 24 hours, the degree of corrosion around the cut was evaluated:
S has no abnormalities such as swelling and rust on the coating film. A shows swelling or rust of less than 1 mm from the cut part. B shows swelling or rust of 1 mm or more from the cut part and less than 2 mm. C Swells or rust exceeding 2 mm from the cut part.

(Note 20) Edge corrosion resistance:
Using the aluminum wheel coated article, a salt water spray test was conducted for 168 hours in accordance with JIS Z-2371, and the rust at the edge of the aluminum wheel was evaluated according to the following criteria:
S is the number of rust generation is 0 / whole aluminum wheel A is the number of rust generation is 1 to 3 / the whole aluminum wheel B is the number of rust generation is 4 to 10 / the whole aluminum wheel C The number of rust generation is 11 or more / the entire aluminum wheel.

(Note 21) Yarn rust resistance:
Cut scratches were made on the surface of the aluminum wheel coated article, and a salt spray resistance test was conducted for 24 hours in accordance with JIS Z 2371. Then, it kept for 480 hours in the wet state (humidity 85%, 40 degreeC), and measured the rust width from a cut part. Rust and blister width from the cut part were evaluated according to the following criteria:
S is the maximum width of rust or blisters less than 2mm on one side from the cut part,
A has a maximum width of rust or blisters of 2 mm or more to less than 3 mm on one side from the cut part,
B, the maximum width of rust or blisters is 3mm or more and less than 4mm on one side from the cut part,
For C, the maximum width of rust or swelling is 4 mm or more from one side of the cut.

(Note 22) Transparency:
The transparency of the coating film is obtained by measuring and evaluating the transmission haze using a turbidimeter (NDH2000) manufactured by Nippon Denshoku Industries Co., Ltd., and follows the following evaluation criteria.

S is 2% or less of transmission haze
A exceeds 2% of transmission haze and 6% or less. B exceeds 6% of transmission haze and 10% or less. C exceeds 10% of transmission haze.

The aluminum wheel which can form the coating film excellent in anticorrosion property, especially edge covering property, yarn rust resistance, and transparency can be provided.

Claims (6)

An aqueous primer coating composition containing a hydroxyl group-containing resin (A), a crosslinking agent (B), and at least one clay mineral (C) selected from hectorites (C1) and mica (C2), An aqueous primer coating composition for an aluminum substrate containing 0.1 to 40 parts by mass of the clay mineral (C) with respect to 100 parts by mass of the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). The aqueous solution for an aluminum substrate according to claim 1, comprising 0.1 to 20 parts by mass of the phenol resin (D) with respect to 100 parts by mass of the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). Primer paint composition. The aluminum group according to claim 1 or 2, comprising 0.1 to 10 parts by mass of metal ion-exchanged silica (E) with respect to 100 parts by mass of the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). Water-based primer coating composition for materials. The silane coupling agent (F) is contained in any one of claims 1 to 3, containing 1 to 20 parts by mass of the silane coupling agent (F) based on 100 parts by mass of the total solid content of the hydroxyl group-containing resin (A) and the crosslinking agent (B). Aqueous primer coating composition for aluminum substrates. The aqueous primer coating composition for an aluminum substrate according to any one of claims 1 to 4, wherein the hydroxyl group-containing resin (A) is an acrylic urethane resin. On the aluminum wheel which has a cutting surface, after forming the uncured coating film by the water-based primer coating composition for aluminum base materials of any one of Claims 1-5, and performing preheating, this coating A coating film forming method for forming at least one overcoating film on a film.