JP2008069336A - Top coat coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a top coat coating composition which forms a coating film excellent in soil resistance against rainwater or the like both at an early stage and after the elapse of a long period of time. <P>SOLUTION: The top coat coating composition is of thermosetting type and includes a resin binder containing (A) a hydroxyl group-containing coating film forming resin and (B) an amino resin-crosslinking agent, (C) an organosilicate and/or its condensate, (D) an organic sulfonic acid and (E) a secondary or tertiary amine compound with a boiling point of 30-250°C in an amount of 1.5-30 equivalent to 1 equivalent of (D) the sulfonic acid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a top coating composition capable of forming a coating film having excellent anti-contamination resistance against rainwater and the like at the beginning and over time, particularly a top coating composition suitable for forming a top coating film on a coated metal plate, and the top coating composition. The present invention relates to a method for forming a coating film excellent in rainwater contamination resistance used, and a coated metal sheet on which a cured coating film is formed by the top coating composition.

  Conventionally, outdoor base materials (for example, buildings, display objects, guard fences, appliances, machines, etc.) have been coated with an outdoor paint excellent in weather resistance for the purpose of decoration or protection. Examples of paints used for outdoor use include polyurethane resin paints, fluororesin paints, silicone resin paints, acrylic resin paints, and polyester paints. There is a drawback that the surface of the coated material is easily soiled by the influence of powder, rain (acid rain), sunlight, etc., and the appearance of the coating film is deteriorated.

  In order to solve this problem, the applicant of the present invention is an organic solvent-based coating composition (1) containing a hydroxyl group-containing fluororesin and an amino resin crosslinking agent as a reaction-curable organic resin, or a hydroxyl group-containing fluororesin and / or a hydroxyl group-containing composition. Paint obtained by blending tetraalkylsilicate and / or condensate thereof with organic solvent-based paint composition (2) containing acrylic resin and (blocked) polyisocyanate compound crosslinking agent as reaction-curable organic resin A top coating composition excellent in stain resistance, which is a composition and has a contact angle to water of 70 ° or less on the surface of a coating film after acid treatment, has been proposed (see Patent Document 1).

  However, the top coating composition of Patent Document 1 has good contamination resistance against rain streaks and other rainwater after 3 months in outdoor use, but in the initial stage of outdoor use, it is resistant to rainwater and the like. Contamination was not sufficient.

  In order to improve this, the present applicant has proposed a coating composition in which a tetraalkyl silicate and / or a condensate thereof and a surfactant or boric acid compound exhibiting acidity are blended in the coating composition. (See Patent Document 2). However, according to the coating composition of Patent Document 2, the stain resistance becomes good after about 2 months of outdoor use and the onset of the stain resistance is slightly advanced, but the stain resistance at a further initial stage has been demanded.

  Further, as a coating composition for a precoated steel sheet excellent in stain resistance, workability and coating film appearance against rain streak contamination, (A) a polyol resin having a hydroxyl number of 5 to 300 and a number average molecular weight of 500 to 20000, (B) A thermosetting resin composition comprising an amino resin, (C) an alkoxysilane compound, and (D) a curing catalyst has been proposed. (Refer to Patent Document 3) However, the coating film obtained from this thermosetting resin composition is excellent in chemical resistance, hardness, stain resistance against long-term rain streak contamination over time, and processability. In addition, the anti-contamination property was not sufficient, and there was a problem in the coating workability during continuous coating with a roll coater.

International Publication WO94 / 06870 JP 2000-309749 A JP-A-10-67945

  The present invention can form a coating film excellent in initial stain resistance against rainwater, etc., which cannot be achieved by conventional techniques, and can also form a coating film excellent in stain resistance over time. An object of the present invention is to provide a top coating composition excellent in coating workability during continuous coating, particularly a top coating composition suitable for forming a top coating film on a coated metal plate. The present invention also provides a method for forming a coating film excellent in rainwater stain resistance using the top coating composition, and a coated metal plate on which a cured coating film is formed by the top coating composition.

  Therefore, as a result of intensive studies to solve the above-mentioned problems, the present inventors have found that an organic sulfone as a curing catalyst is added to a resin binder containing a hydroxyl group-containing coating film-forming resin and an amino resin crosslinking agent. A coating composition containing an acid, an organosilicate and / or its condensate, and a secondary or tertiary amine compound in a large excess equivalent to the above organic sulfonic acid is a coating having excellent anti-contamination property against rainwater at the initial stage. The present inventors have found that a film can be formed and a coating film excellent in anti-contamination property with time can be formed, and the present invention has been completed.

That is, the present invention provides “1. (A) a resin binder containing 60 to 95 parts by mass of a hydroxyl group-containing coating film-forming resin and (B) 5 to 40 parts by mass of an amino resin crosslinking agent, and the resin. , with respect to the sum 100 parts by weight of (C) the general _{^{formula: (R 1) n -Si- (}} oR 2) in _4-n (wherein, ^{R 1} is optionally substituted with an epoxy group or a mercapto group having a carbon An alkyl group having 1 to 18 carbon atoms or a phenyl group, R ² is an alkyl group having 1 to 6 carbon atoms, and n is 0 or 1.) 1 to 40 parts by mass, (D) 0.1 to 3.0 parts by mass of organic sulfonic acid, and (E) an organic sulfonic acid (D) having an boiling point of 30 to 30 equivalents to 1 equivalent It is a paint containing a secondary or tertiary amine compound at 250 ° C. A thermosetting top coating composition, wherein the organic sulfonic acid (D) may be neutralized with the amine compound (E),
2. The top coating composition according to item 1, wherein the hydroxyl group-containing film-forming base resin (A) is a hydroxyl group-containing polyester resin having a hydroxyl value of 7 to 180 mgKOH / g,
3. The top coating composition according to Item 1 or 2, wherein the amino resin crosslinking agent (B) is a methyl etherified melamine resin or a mixed melamine resin of a methyl etherified melamine resin and a butyl etherified melamine resin,
4). Component (C) is a condensate of an organosilicate represented by the above general formula, having a methoxy group and an alkoxy group having 2 to 6 carbon atoms as an OR ² group, and having a methoxy group / carbon atom number of 2 The top coating composition according to any one of items 1 to 3, wherein the ratio of the number of alkoxy groups to -6 is in the range of 95/5 to 30/70,
5. The top coating composition according to any one of the above items 1 to 4, wherein a reaction mixture in which the organic sulfonic acid (C) and the amine compound (E) are mixed in advance is blended in the coating. object,

6). Furthermore, the top coat composition as described in any one of said claim | item 1-5 containing the hydrolysis accelerator which is surfactant and / or a boric-acid type compound which shows acidity.

7). Furthermore, the top-coat paint composition as described in any one of said claim | item 1-6 containing a silica fine particle,
8). 8. A coating film forming method, wherein the top coating composition according to any one of the above items 1 to 7 is applied onto a metal plate through at least one primer coating film; Provided is a “coated metal plate, wherein a cured coating film is sequentially formed on the metal plate by at least one primer coating film and the top coating composition according to any one of the above items 1 to 7.” To do.

  The top coating composition of the present invention comprises a resin binder containing a hydroxyl group-containing film-forming resin and an amino resin crosslinking agent, an organic sulfonic acid, an organosilicate and / or a condensate thereof as a curing catalyst, and an organic sulfonic acid. Is a coating composition containing a secondary or tertiary amine compound in a large excess equivalent to the above, and by this coating, it is possible to form a coating film excellent in initial stain resistance against rainwater, etc. A coating film having excellent properties can be formed. In addition, the difference in curability between the paint film surface and the inside of the paint film becomes large during heat curing, and a crease pattern is formed on the paint film surface, resulting in a good matte appearance. A matte coating without problems such as film discoloration, choking, and color fading can be obtained.

  Although the reason why the present inventors can form a coating film excellent in initial stain resistance is not clear, the organosilicate and / or its condensate has a low surface tension and tends to move to the surface. Yes, when heat-curing the coating film of the top coating composition, the presence of a large excess of amine compound slows the curing inside the coating film compared to the surface, and low molecular components such as amine compounds from the coating film interior to the surface. The amine compound has a low specific gravity and is also a factor that easily moves to the surface of the coating film. As the amine compound moves, the organosilicate and / or its condensate easily move to the surface. Therefore, it is thought that it may be for forming a hydrophilic layer on the surface. Moreover, the coating film to be formed is a fine concavo-convex pattern with a shrinking pattern, and it is considered that this fine concavo-convex form is advantageous for wetting the rainwater coating surface. With the composition of the present invention, for the first time, it was possible to form a coating film having excellent anti-contamination properties in the initial stage and over time against rainwater and the like.

  The thermosetting top coating composition of the present invention contains the following hydroxyl group-containing film-forming resin (A) and amino resin crosslinking agent (B) as a resin binder.

Hydroxyl-containing film-forming resin (A)
As the hydroxyl group-containing coating film-forming resin (A), a hydroxyl group-containing coating film-forming resin that is usually used as a base resin for thermosetting paints can be used, and representative examples include a hydroxyl group-containing polyester resin, a hydroxyl group-containing acrylic resin, and a hydroxyl group. Examples include a silicon-containing polyester resin, a hydroxyl group-containing silicon-modified acrylic resin, a hydroxyl group-containing epoxy resin, a hydroxyl group-containing vinyl resin (vinyl chloride copolymer resin), and a hydroxyl group-containing fluororesin. These may be used alone or in combination. it can. The hydroxyl group-containing polyester resin includes both an oil-free polyester resin and an oil-modified polyester resin.

  Among these, a hydroxyl group-containing polyester resin, a hydroxyl group-containing acrylic resin, a hydroxyl group-containing silicon-modified polyester resin, a hydroxyl group-containing silicon-modified acrylic resin and a hydroxyl group-containing fluororesin are preferable from the viewpoints of mechanical strength, weather resistance, and the like. Of these, a hydroxyl group-containing polyester resin is particularly suitable.

  Among the hydroxyl group-containing polyester resins, the oil-free polyester resin can be produced using a known method such as a direct esterification method, a transesterification method, or a ring-opening polymerization method. Specific examples of the direct esterification method include a method of polycondensation of a polybasic acid and a polyhydric alcohol. As the polybasic acid, one or more dibasic acids selected from phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, fumaric acid, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, etc .; Tribasic acid or more polybasic acid such as trimellitic anhydride, methylcyclohexylic carboxylic acid, pyromellitic anhydride, etc. is used, and benzoic acid, crotonic acid, p-tertbutylbenzoic acid, etc. are used as the acid component as required. Monobasic acids can also be used. As the polyhydric alcohol, dihydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, butanediol, neopentyl glycol, hexanediol, and 1,6-hexanediol are mainly used. A trihydric or higher polyhydric alcohol such as methylolethane, trimethylolpropane and pentaerythritol can also be used in combination. The direct esterification reaction of these components can be performed by a known method at a compounding ratio in which the hydroxyl group is excessive with respect to the acid group.

  The oil-free polyester resin can also be produced by polycondensation by transesterification between a polybasic acid lower alkyl ester and a polyhydric alcohol. Furthermore, the oil-free polyester resin can also be produced by ring-opening polymerization of lactones such as δ-valerolactone and ε-caprolactone.

  Among the hydroxyl group-containing polyester resins, an oil-modified polyester resin is obtained by reacting an oil fatty acid with the oil-free polyester resin. Examples of the oil fatty acid include coconut oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, Flower oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid, tung oil fatty acid and the like can be mentioned. The reaction between the polyester resin and the oil fatty acid can also be carried out by a known method, and the oil length is usually 30% or less. Is preferred.

  As the hydroxyl group-containing acrylic resin, those having a hydroxyl group in its skeleton can be used and obtained by copolymerizing a polymerizable unsaturated monomer having a hydroxyl group and other monomers copolymerizable with this monomer. Can do. As the hydroxyl group-containing unsaturated monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2,3-dihydroxybutyl (meth) acrylate, 4-hydroxybutyl Monoesterified products of polyhydric alcohol and acrylic acid or methacrylic acid such as (meth) acrylate and polyethylene glycol mono (meth) acrylate; lactones are opened to monoesterified products of polyhydric alcohol and acrylic acid or methacrylic acid. Examples include a ring-polymerized compound. These can be used alone or in combination of two or more. Examples of the lactones include lactones such as ε-caprolactone, δ-valerolactone, γ-butyrolactone, and β-propionlactone. In this specification, “(meth) acrylate” means “acrylate or methacrylate”.

  Other monomers that can be copolymerized with the polymerizable unsaturated monomer having a hydroxyl group include carboxyl group-containing unsaturated monomers such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid; methyl (meth) acrylate, ethyl (meta ) Acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) ) Alkyl esters with acrylic acid or methacrylic acid such as acrylate and stearyl (meth) acrylate; styrene, vinyl toluene, vinyl acetate, acrylonitrile, acrylamide, methacrylamide, glycidyl ( Data) acrylate, allyl glycidyl ether, 3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexylmethyl methacrylate. These can be used alone or in combination of two or more.

  The hydroxyl group-containing silicon-modified polyester resin is obtained by reacting the polyester resin with a silicon intermediate. The silicon intermediate is a polysiloxane having a siloxane bond, having a functional group such as a hydroxyl group or an alkoxy group that reacts with a hydroxyl group of a polyester resin, and further having a substituent such as a methyl group, an ethyl group, or a phenyl group. Some are also used. Specific examples of these include, for example, “SH-6188” (methoxy group-containing, molecular weight 600), “SH-6018” (hydroxyl group-containing, molecular weight 1,600) (all manufactured by Toray Dow Corning Silicone Co., Ltd.) Name); “TSR-160” (hydroxyl group-containing, molecular weight 1,300), “TSR-165” (methoxy group-containing, molecular weight 650) (all of these are trade names manufactured by Toshiba Silicone Co., Ltd.), KR218 (Shin-Etsu) Commercial products such as those manufactured by Kagaku Co., Ltd. are available. The reaction between the polyester resin and the silicon intermediate (dehydration reaction or dealcoholization reaction) is a known ratio of 95 to 40% by weight of the polyester resin and 5 to 60% by weight of the silicon intermediate based on the total amount of both components. It can be done by the method.

  The hydroxyl group-containing silicon-modified acrylic resin is obtained by reacting a silicon intermediate with the acrylic resin. As the silicon intermediate, the same silicon intermediate used in the production of the hydroxyl group-containing silicon-modified polyester resin is used. The reaction between the acrylic resin and the silicon intermediate can be carried out by a known method at a ratio of 95 to 40% by weight of the acrylic resin and 5 to 60% by weight of the silicon intermediate based on the total amount of both components.

  The hydroxyl group-containing fluororesin is a resin obtained by copolymerization using a polymerizable unsaturated monomer having a fluorine atom as a part of other monomer components in the production of the hydroxyl group-containing acrylic resin. Examples of the polymerizable unsaturated monomer having a fluorine atom include fluoroolefins such as hexafluoropropene, tetrafluoroethylene, monochlorotrifluoroethylene, dichlorodifluoroethylene, perfluorocyclohexylethylene, vinylidene fluoride, and monofluoroethylene; “Biscoat 8F ”,“ Biscoat 8FM ”,“ Biscoat 3F ”,“ Biscoat 3FM ”(all manufactured by Osaka Organic Chemical Co., Ltd., (meth) acrylates having a fluorine atom in the side chain), perfluorocyclohexyl (meth) acrylate, etc. (Meth) acrylates having a fluorine atom; The copolymerization reaction can be performed based on a known polymerization reaction of a fluororesin. Examples of commercially available hydroxyl group-containing fluororesins include Lumiflon series (Asahi Glass Co., Ltd.), cefral coat series (Central Glass Co., Ltd.), Zaffle series (Daikin Kogyo Co., Ltd.), Cotax (Toray Industries, Inc.), and the like. be able to.

  The hydroxyl group-containing coating film-forming resin (A) must have a hydroxyl group that becomes a crosslinking point with the amino resin crosslinking agent that is the component (B), and the hydroxyl value of the solid component resin component (A) is cured. From the viewpoint of properties and water resistance, it is preferably 7 to 180 mgKOH / g, more preferably 7 to 100 mgKOH / g. In addition, the resin (A) preferably has a number average molecular weight of about 2,000 to 33,000, more preferably 2,500 to 30,000, from the viewpoint of the properties of the obtained coating film and coating workability. From the viewpoint of the hardness and workability of the resulting coating film, it is suitable to have a glass transition temperature of −25 to 35 ° C., preferably −20 to 25 ° C.

  In the present specification, the number average molecular weight is a value calculated based on the molecular weight of standard polystyrene from a chromatogram measured with a gel permeation chromatograph (manufactured by Tosoh Corporation, “HLC8120GPC”). The column used was “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name), and moved. Phase: Tetrahydrofuran, Measurement temperature: 40 ° C., Flow rate: 1 cc / min, Detector: Under the conditions of RI. Moreover, in this specification, glass transition temperature (Tg) is based on a differential thermal analysis (DSC).

Amino resin crosslinking agent (B)
The amino resin crosslinking agent (B) is an amino resin that undergoes a crosslinking reaction with the hydroxyl group-containing film-forming base resin (A), and includes, for example, amino components such as melamine, urea, benzoguanamine, acetoguanamine, spiroguanamine, and dicyandiamide. Mention may be made of methylolated amino resins obtained by reaction with aldehydes. Examples of the aldehyde include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Moreover, what methylated this methylolated amino resin with 1 type, or 2 or more types of alcohol can also be used, As an example of alcohol used for etherification, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n -Monohydric alcohols, such as butyl alcohol, isobutyl alcohol, 2-ethylbutanol, 2-ethylhexanol, are mentioned. Of these, methylolated melamine resins and melamine resins obtained by etherifying at least part of methylol groups of methylolated melamine resins with monohydric alcohols having 1 to 4 carbon atoms are preferred.
Examples of commercially available products of the melamine resin include Uban 20SE-60, Uban 225 (both manufactured by Mitsui Chemicals, Inc., trade name), Super Becamine G840, and G821 (both manufactured by Dainippon Ink and Chemicals, Inc.). Butyl etherified melamine resins such as: Sumimar M-100, M-40S, M-55 (both manufactured by Sumitomo Chemical Co., Ltd., trade names), Cymel 303, 325, 327, 350, 370 (above, All are methyl etherified melamine resins such as Mitsui Cytec Co., Ltd., trade name), Nicarak MS17, MS15 (both from Sanwa Chemical Co., trade name), Resimin 741 (trade name, Monsanto Co., Ltd.); Cymel 235, 202, 238, 254, 272, 1130 (all manufactured by Nippon Cytec Industries, Ltd. Name), Sumamil M66B (commercial name, manufactured by Sumitomo Chemical Co., Ltd.), etc. Mixed etherified melamine resin of methylated and isobutylated; Cymel XV805 (manufactured by Nippon Cytec Industries, Inc., commercial name), Nikarac MS95 (Sanwa Chemical) And a mixed etherified melamine resin of methylation and n-butylation, etc.

  As the amino resin cross-linking agent (B), among them, it is a methyl etherified melamine resin or a mixed melamine resin of a methyl etherified melamine resin and a butyl etherified melamine resin. It is preferable from the viewpoint of workability.

  In the thermosetting top coating composition of the present invention, the blending ratio of the hydroxyl group-containing film-forming resin (A) and the amino resin crosslinking agent (B) contains the resin (A) and the crosslinking agent (B). Based on 100 parts by mass of the solid content of the resin binder, the resin (A) is 60 to 95 parts by mass, preferably 70 to 90 parts by mass, and the crosslinking agent (B) is 5 to 40 parts by mass, preferably 10 to 30 parts by mass. It is preferable from the viewpoints of curability, mechanical strength, workability, solvent resistance, corrosion resistance, weather resistance, and the like of the resulting coating film.

  The thermosetting top coating composition of the present invention is prepared by adding the following organosilicate or a partially hydrolyzed condensate thereof to a resin binder containing the hydroxyl group-containing film-forming resin (A) and the amino resin crosslinking agent (B). C), an organic sulfonic acid (D) and an amine compound (E).

Organosilicate and / or condensate thereof (C)
As the component (C) of the present invention, the general formula: (R ¹ ) _n —Si— (OR ² ) _{4 -n} (wherein R ¹ is an optionally substituted epoxy group or mercapto group having 1 to 1 carbon atoms) 18 is an alkyl group or a phenyl group, R ² is an alkyl group having 1 to 6 carbon atoms, and n is 0 or 1.) and / or a condensate thereof. The component (C) used in the coating composition of the present invention is blended in order to efficiently exhibit a hydrophilic effect on the surface of the substrate after coating. From the viewpoint of this effect, the condensation of the above-described organosilicate. More preferred.

Specific examples of R ¹ in the above general formula include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, hexyl, heptyl, n-octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, Examples include tetradecyl, hexadecyl, octadecyl, glycidyl, methylglycidyl, mercaptomethyl, 2-mercaptoethyl, 2-mercaptopropyl, 3-mercaptopropyl, 4-mercaptobutyl, phenyl, and p-mercaptophenyl groups.
Specific examples of the organosilicate of component (C) include tetrafunctional silanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetrabutoxysilane, tetraisobutoxysilane; methyltrimethoxysilane, methyl Triethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, methyltri-n-butoxysilane, methyltriisobutoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane, phenyltriisopropoxysilane, phenyltri n-butoxysilane, phenyltriisobutoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, lauryltrimethoxysilane, lauryltrieth Shishiran, mercaptomethyl trimethoxysilane, mercaptoethyl trimethoxy silane, mercaptomethyl triethoxysilane, mercaptopropyl triethoxysilane, mercaptopropyl trimethoxysilane, include trifunctional silanes such as mercaptopropyltriethoxysilane. Examples of the condensate of the organosilicate include a condensate of one or a combination of two or more of these tetrafunctional or trifunctional silanes.
The organosilicate condensate can be produced by a conventional method. For example, MKC silicate MS51, MS56, MS57, MS56S, MS56SB5, MS58B15, MS58B30, ES40, EMS31, BTS (all of which are Mitsubishi Chemical) (Trade name), methyl silicate 51, ethyl silicate 40, ethyl silicate 40T, ethyl silicate 48 (all of which are trade names, manufactured by Colcoat Co., Ltd.), KR500, KR9218, X-41-1805, X -41-1810, X-41-1818, X-41-1053, X-41-1056 (all are trade names manufactured by Shin-Etsu Chemical Co., Ltd.) and the like. Alternatively, these organosilicate condensates can be obtained by single hydrolysis or by partial hydrolysis condensation using a combination of two or more. The organosilicate condensate is a branched or linear condensate, and the degree of condensation is preferably 2 to 100, and preferably 2 to 20. In the coating composition of the present invention, the component (C) organosilicate or organosilicate condensate may be used alone or in combination of two or more.

In the organosilicate represented by the above general formula and / or its condensate, it has a methoxy group and an alkoxy group having 2 to 6 carbon atoms as an OR ² group, and a methoxy group / an alkoxy group having 2 to 6 carbon atoms; It is preferable from the viewpoint of the pot life after the preparation of the paint that the ratio of the number is in the range of 95/5 to 30/70.

  (C) The compounding quantity of a component is 0.1-50 mass parts based on the said resin binder 100 mass parts, Preferably it is 0.5-30 mass parts, More preferably, it is 1-20 mass parts. (C) When the amount of component is in the above range, the effect of blending component (C) is exerted, the initial stain resistance of the coating film, the effect of improving the stain resistance over time, and the mechanical strength of the coating film, It is also suitable from the viewpoint of durability.

Organic sulfonic acid (D)
The organic sulfonic acid that is the component (D) in the composition of the present invention is a catalyst that accelerates the curing reaction between the hydroxyl group-containing film-forming resin (A) that is the resin binder and the amino resin crosslinking agent (B). Examples of the organic sulfonic acid (D) include dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, dinonylnaphthalenesulfonic acid, paratoluenesulfonic acid and the like, and these can be used alone or in combination of two or more. The blending amount of the organic sulfonic acid (D) is 0.1 to 3.0 parts by weight, preferably 100 parts by weight based on 100 parts by weight of the resin binder, from the viewpoint of reaction promoting effect, workability of the resulting coating film, water resistance and the like. Is preferably 0.2 to 2.5 parts by mass, more preferably 0.5 to 2.0 parts by mass.

Amine compound (E)
The amine compound as component (E) in the composition of the present invention is a secondary or tertiary amine compound having a boiling point of 30 to 250 ° C., and neutralizes the organic sulfonic acid (D) to form an amine salt. This suppresses the curing catalytic action of the organic sulfonic acid (D) during storage and contributes to the storage stability of the coating composition. During the heat curing, the amine compound evaporates to form a free sulfonic acid group. The organic sulfonic acid having the content is regenerated and acts as a curing catalyst.

  Examples of the amine compound (E) having a boiling point of 30 to 250 ° C. include diethylamine, diisopropylamine, di-n-propylamine, diallylamine, diamylamine, di-n-butylamine, diisobutylamine, di-sec-butylamine, N-ethyl- 1,2-dimethylpropylamine, N-methylhexylamine, di-n-octylamine, piperidine, 2-pipecoline, 3-pipecoline, 4-pipecoline, 2,4-, 2,6-, 3,5-lupetidine Secondary amines such as 3-piperidinemethanol; triethylamine, tributylamine, triallylamine, N-methyldiallylamine, N-methylmorpholine, N, N, N ′, N′-tetramethyl-1,2-diaminoethane, Third-part such as N-methylpiperidine, pyridine, 4-ethylpyridine Primary amines; one or a mixture of two or more of amines having secondary and tertiary amino groups such as N-methylpiperazine. Among these, dialkylamines such as diisopropylamine, di-n-propylamine, di-n-butylamine, diisobutylamine, etc. have low odor, excellent initial stain resistance, and good coating film appearance. Is preferable.

  The compounding quantity of an amine compound (E) is 1.5-30 equivalent with respect to 1 equivalent of sulfonic acids of organic sulfonic acid (D), Preferably it is 2.0-20 equivalent, More preferably, it is 5-15 equivalent. . By being within this quantitative range, the sulfonic acid curing catalyst action is delayed in the coating film, and the organosilicate and / or its condensate (C), amine compound (E), etc. from the coating film to the surface. Smooth transition makes it possible to form a matte coating with excellent scumming resistance at the initial stage and over time, and the mass transfer of these materials causes the amine compound to evaporate. The curing catalyst action of sulfonic acid is effectively exhibited inside, and a coating film with good curability can be obtained.

  In the composition of the present invention, the blending method of the organic sulfonic acid (D) and the amine compound (E) into the coating is as follows: (1) A reaction mixture of 1 equivalent of the sulfonic acid and 1.5 to 30 equivalents of the amine compound is blended. A method, (2) a method of separately blending a sulfonic acid and an amine compound having a boiling point of 30 to 250 ° C. in an amount corresponding to 1.5 to 30 equivalents relative to the sulfonic acid, (3) the above (1) and (2 ), Which is a method in which a reaction mixture of a sulfonic acid and a part of an amine compound and the remaining amine compound are separately blended, and any blending method may be used.

  The reaction mixture in the method (1) can be easily obtained by mixing 1.5 to 30 equivalents of the amine compound at room temperature with respect to 1 equivalent of the sulfonic acid, and a salt of the sulfonic acid and the amine compound; It is a mixture with an excess amount of an amine compound. The above method (2) is a method of separately blending a sulfonic acid and an amine compound at the time of making a paint, and by mixing and stirring both in the paint, a salt of the sulfonic acid and the amine compound is formed, As in the case where the reaction mixture is blended by the method (1), a salt of sulfonic acid and an amine compound and an amine compound are present in the paint. As the method (3), for example, when a commercially available organic sulfonic acid catalyst is supplied as an amine salt, a sulfonic acid amine salt that is a commercially available catalyst and an amine compound are blended separately.

  In the composition of the present invention, in addition to the components (A), (B), (C), (D), and (E) described above, hydrolysis of an acidic surfactant or boric acid compound is accelerated. Conventional paints such as additives, coloring pigments, extender pigments such as silica fine particles, organic resin powders, inorganic aggregates, pigment dispersants, UV absorbers, UV stabilizers, antifoaming agents and surface conditioners, solvents, etc. Known materials used in the above can also be used.

  The acidic surfactant or boric acid compound has an action of promoting hydrolysis of the organosilicate and / or its condensate (C). Examples of the surfactant exhibiting acidity include phosphate ester salts such as polyoxyethylene phosphate and alkyl phosphate; alkyl or alkylbenzene sulfonate such as sodium lauryl sulfonate and sodium dodecylbenzene sulfonate. Sulfonates such as alkyl naphthalene sulfonates such as sodium isopropyl naphthalene sulfonate, alkyl diphenyl ether sulfonates; sulfates such as alkyl or alkyl benzene sulfates, sulfates such as (poly) oxyethylene alkyl phenyl ether sulfates; Examples thereof include carboxylate-based surfactants such as alkylsulfosuccinates. Examples of the boric acid compound include trialkyl borate such as trimethyl borate, triethyl borate, tributyl borate; boric acid and the like. The blending amount of these hydrolysis accelerators is 30 parts by mass or less, preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the resin binder.

  Examples of the extender pigment include silica fine particles, talc, mica powder, and barita. Among these, by adding silica fine particles having an oil absorption of 100 to 280 ml / 100 g, the shrinkage pattern can be made dense and can contribute to uniform stabilization of the shrinkage pattern. The amount of the extender pigment is 0.1 to 20 parts by weight, preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the resin binder.

  The thermosetting top coat composition of the present invention can be produced by uniformly mixing the above components (A) to (E) and, if necessary, the above other components. Preferably, the pigment component can be prepared in advance by mixing and dispersing a part of the resin (A) and / or a pigment dispersant to prepare a pigment paste, and mixing this with the remaining components. The coating composition of the present invention may be a one-pack type paint, but the two-component mixture is prepared immediately before use by separating the organosilicate and / or its condensate as component (C) from other components. It can also be a mold paint. From the viewpoint of storage properties, it is preferable to use a two-component paint.

  As a method of applying the top coating composition of the present invention, the coating composition is adjusted to a desired viscosity by adding an organic solvent, if necessary, and then air spray, electrostatic air spray, roll coater, flow. Using a coater, dipping-type coating machine, brush, bar coater, applicator, etc., the coating film after drying is usually applied to a thickness of 0.5 to 300 μm, preferably 5 to 50 μm, and usually 80 to 300. Examples include a method of curing at a temperature of 5 ° C. for 5 seconds to 1 hour. Of the above methods, spray coating and roll coater coating are suitable for the coating method.

Coating Film Forming Method The coating film forming method of the present invention is a method of applying the thermosetting top coating composition of the present invention to a metal plate through at least one primer coating film.

  Examples of the metal plate to be coated in the coating film forming method of the present invention include cold rolled steel plate, hot dip galvanized steel plate, electrogalvanized steel plate, alloy galvanized steel plate (iron-zinc, aluminum-zinc, nickel-zinc, etc. Alloy galvanized steel plate), aluminum plate, stainless steel plate, copper plate, copper plated steel plate, tin plated steel plate and the like.

  When painting on metals, the metal surface, which is the material to be coated, may be painted as it is if it is not contaminated with oil or other pollutants, but it is well known for improving adhesion and corrosion resistance with the coating film. It is desirable to apply a metal surface treatment. These known surface treatment methods include phosphate surface treatment, chromate surface treatment, zirconium surface treatment and the like.

  As a primer for forming a primer coating on a metal plate, known primers used in the field of colored color steel plate coating, industrial machine coating, metal parts coating, etc. can be applied. Depending on the type, epoxy-based, polyester-based primers and their modified primers are particularly suitable, and polyester-based primers are suitable when processability is particularly required. The primer is applied by a known coating method such as roll coating or spray coating so that the primer coating thickness is 1 to 30 μm, preferably 2 to 20 μm. Usually, the primer is coated at an ambient temperature of 80 to 300 ° C. for 5 seconds to When pre-coating for 1 hour, it is preferably heat-cured for 15 seconds to 120 seconds under the condition that the maximum material reaching temperature is 140 to 250 ° C.

  The primer coating film may be a single layer or two layers in which a second primer coating film (intermediate coating film) is formed on the first primer coating film. When the primer film has two layers, the first primer film has an anticorrosion function, and the second primer film (intermediate film) has processability and chipping resistance. The primer coating can also have different functions.

  In the coating film forming method of the present invention, the thermosetting top coating composition of the present invention is applied onto the primer coating film. Examples of the coating method include curtain coating, roll coater coating, dip coating, and spray coating. Usually, the coating thickness after drying is 5 to 50 μm, preferably 8 to 25 μm. Is done.

  When the coating composition of the present invention is pre-coated, the coating method is not limited, but curtain coating and roll coater coating are recommended in view of the economy of pre-coated steel sheet coating. When roll coater coating is applied, the bottom feed method (so-called natural reverse coating or natural coating) with the usual two rolls is suitable for practical use, but the uniformity of the coating surface is best. Therefore, a top feed or bottom feed method using three rolls can be performed. The curing condition of the top coat film by the composition of the present invention is usually about 15 seconds to 30 minutes at a material maximum temperature of 120 to 260 ° C. In the field of pre-coating, which is applied by coil coating or the like, it is usually carried out at a raw material maximum temperature of 160 to 260 ° C. for a baking time of 15 to 90 seconds.

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 Example 1
A reactor equipped with a thermometer, a stirrer, a heating device and a rectifying column was charged with 1079 parts of isophthalic acid, 407 parts of adipic acid, 466 parts of neopentyl glycol, and 802 parts of trimethylolpropane, and the temperature was increased to 160 ° C. After gradually raising the temperature from ℃ to 230 ℃ over 3 hours and continuing the reaction at 230 ℃ for 30 minutes, the rectification column was replaced with a water separator, and 124 parts of xylene was added to the content part to add to the water separator. Xylene was added, water and xylene were azeotroped to remove condensed water, and the reaction was continued until the acid value reached 10 mgKOH / g, followed by cooling, 855 parts of cyclohexanone, 951 parts of Swazole 1500, ethylene glycol mono n-butyl ether. 95 parts was added to obtain a polyester resin solution B having a solid content of 55%. The obtained resin had a hydroxyl value of 184 mgKOH / g, a number average molecular weight of 2400, and a Tg point of -18 ° C.

Examples 1-19 and Comparative Examples 1-5
With the composition shown in Table 1 below, coating was performed to obtain each top coating. On the zinc phosphate-treated electrogalvanized steel sheet with a thickness of 0.5 mm, KP color 8620 primer (polyester primer for pre-coated steel sheet) manufactured by Kansai Paint Co., Ltd. was applied to a dry film thickness of 5 μm. The primer-coated steel sheet was obtained by baking at 45 ° C. for 45 seconds. Each of the top coats obtained as described above is coated on this primer-coated steel sheet with a bar coater so that the dry film thickness is about 18 μm, and baked for 60 seconds so that the maximum material temperature reaches 230 ° C. Got. Various tests were performed on the obtained coated steel sheet.

  The test results are shown in Table 1. In Table 1, the amounts of the base resin, the crosslinking agent, the organosilicate, and the organosilicate condensate are expressed by solid mass, and the amount of the curing catalyst (amine neutralization) of (Note 7) to (Note 10) is It is a display by the amount of active ingredients (sum of sulfonic acid compound and amine compound). In the preparation of the examples and comparative examples, titanium white pigment was dispersed, and cyclohexanone / swazol 1500 (manufactured by Maruzen Petroleum Co., Ltd., aromatic high-boiling solvent) = 60/40 (weight ratio) ) Was used for viscosity adjustment and the like. During coating, the viscosity of the paint was adjusted to about 100 seconds (25 ° C.) with Ford Cup # 4.

  The tests in Table 1 were conducted according to the following test methods.

Appearance of the coated surface: The appearance of the coated surface (30 cm × 30 cm) was observed with the naked eye and evaluated according to the following criteria.
A: A dense and uniform shrinkage pattern occurs on the coating surface, and no coating surface abnormality such as repellency, dents, or cloudiness is observed.
○: A shrinkage pattern occurs on the paint surface, and no paint surface abnormality such as repellency, dents, or cloudiness is observed, but the denseness or uniformity of the shrinkage pattern is slightly inferior to that of the above item ◎.
Δ: No coating surface abnormality such as repellency, dent, or cloudiness is observed, but no shrinkage pattern is generated on the coating surface.
X: Abnormalities in the paint surface such as repellency, dents and cloudiness are observed on the paint surface.

  Gloss: The gloss of the coated surface was measured according to the specular gloss (60 degrees) of JIS K5400 7.6 (1990).

  Pencil hardness: A pencil scratch test specified in JIS K5400 8.4.2 (1990) was performed, and evaluation by a tearing method was performed.

  Workability: In a room at 20 ° C., the test plate was folded 180 ° with the coating surface facing outside, and the T number at which no cracking occurred at the bent portion was displayed. T number is 0T when bending 180 ° without anything inside the bent part, 1T, 2 when a sheet of the same thickness as the test plate is folded. The number of sheets is 2T, and the number of sheets is 6T.

Outdoor exposure test: An outdoor exposure test specimen (100 x 300 x 0.5 mm) is attached to the installation table that models the eaves so that the coating film faces the north side, and the roof of Kansai Paint Co., Ltd. in Kanzaki-cho, Amagasaki City An exposure test was conducted and the stain resistance and rain streak stain resistance (rain streak-like stains) were evaluated according to the following criteria. Contamination resistance was measured by using a multi-light source spectrocolorimeter MSC-5N manufactured by Suga Test Instruments Co., Ltd., based on JIS Z8370, the color difference (ΔE) before and after exposure. The resistance to rain streak contamination was judged visually.
・ Contamination resistance after outdoor exposure test (△ E)
A: Less than 2,
○: 2 or more and less than 3
Δ: 3 or more and less than 5
X: 5 or more.
-Rain streak contamination after outdoor exposure test ◎: No trace of rain streak
○: A slight trace of rain streak is observed,
△: A lot of rain traces are recognized,
×: Rain streaks remain dark.

Resistant to carbon contamination: 1 cc of a dispersion of carbon black / water = 2/98 (weight ratio) was placed on the coating surface, left in a constant temperature room at 70 ° C. for 2 hours, washed with water, and then the dispersion was placed. The degree of discoloration of the painted surface of the part was judged visually.
◎: no trace is recognized,
〇: Slight traces are recognized,
Δ: Marks remain
X: A trace remains darkly.

  Accelerated weather resistance: 1,000 hours test was conducted with a sunshine weatherometer. The gloss retention (60 degree gloss) of the coated plate after the test with respect to the coated plate before the test was described.

Solvent resistance: A load of about 1 kg / cm ² was applied to the coated surface with a gauze soaked with methyl ethyl ketone in a room at 20 ° C., and reciprocated between about 5 cm in length. The number of reciprocations until the primer coating was visible was described. When the primer coating was not visible after 50 reciprocations, 50 <was indicated.

In addition, the wrinkles in Table 1 are as follows.
(Note 1) Byron KS-1430V: manufactured by Toyobo Co., Ltd., polyester resin, resin number average molecular weight 12000, hydroxyl value 11 mgKOH / g, Tg point 1 ° C.
(Note 2) Byron KS-1520V: manufactured by Toyobo Co., Ltd., polyester resin, number average molecular weight of resin 6400, hydroxyl value of about 42 mgKOH / g, Tg point 2 ° C.
(Note 3) Byron KS-1660V: manufactured by Toyobo Co., Ltd., polyester resin, number average molecular weight of resin 2700, hydroxyl value 98 mgKOH / g, Tg point 12 ° C.
(Note 4) Cymel 303: A low molecular weight methylated melamine resin manufactured by Nippon Cytec Industries, Ltd.
(Note 5) Nicarak MS95: A mixed etherified melamine resin made by Sanwa Chemical Co., Ltd., low-nuclear methyl ether and butyl ether.
(Note 6) Uban 20SE-60: Mitsui Chemicals, butyl etherified melamine resin.
(Note 7) DNBA-DDBSA: di-n-butylamine / dodecylbenzenesulfonic acid = 10/1 (molar ratio) neutralized product.
(Note 8) DIPA-DDBSA: diisopropylamine / dodecylbenzenesulfonic acid = 10/1 (molar ratio) neutralized product.
(Note 9) TEA-DDBSA: triethylamine / dodecylbenzenesulfonic acid = 10/1 (molar ratio) neutralized product.
(Note 10) Nature 5225: Isopropanol solution of neutralized secondary amine of dodecylbenzenesulfonic acid, manufactured by King Industries, USA. The degree of neutralization of amine / DDBSA is about 1.1 (molar ratio). The active ingredient is about 33% by weight, of which amine / DDBSA (mass ratio) is about 8/25.
(Note 11) MS58B15: trade name “MKC silicate MS58B15” manufactured by Mitsubishi Chemical Corporation, methyl / n-butyl mixed esterified silicate which is a condensate of tetraalkoxysilane, the ratio of methyl / butyl number is 85/15.
(Note 12) MS58B30: Mitsubishi Chemical Co., Ltd., trade name “MKC silicate MS58B30”, methyl / butyl mixed esterified silicate which is a condensate of tetraalkoxysilane, the ratio of methyl / butyl number is 70/30.
(Note 13) MS56S: trade name “MKC silicate MS56S” manufactured by Mitsubishi Chemical Corporation, methyl esterified silicate which is a condensate of tetramethoxysilane.
(Note 14) Ethyl silicate 40: manufactured by Colcoat, trade name, ethyl esterified silicate which is a condensate of tetraethoxysilane.
(Note 15) X-41-1805: manufactured by Shin-Etsu Chemical Co., Ltd., trade name, mercaptoalkyl group-containing trialkoxysilane condensate, mercaptoalkyl group has 18 or less carbon atoms, and alkoxy group has 6 or less carbon atoms .
(Note 16) X-41-1053: manufactured by Shin-Etsu Chemical Co., Ltd., trade name, epoxyalkyl group-containing trialkoxysilane condensate epoxyalkyl group has 18 or less carbon atoms, and alkoxy group has 6 or less carbon atoms.
(Note 17) Thyroid 161W: manufactured by GRACE GMBH, trade name, organically treated silica fine powder, oil absorption 170 ml / 100 g.

Claims (9)

(A) Hydroxyl-containing film-forming resin 60-95 parts by mass and (B) 100 parts by mass of resin binder containing 5-40 parts by mass of amino resin cross-linking agent, and 100 parts by mass of the sum of the resins, (C) General formula: (R _< ¹ _> ) _n- Si- (OR _< ² _> ) _{< 4> -n} (In formula, R _< ¹ _> is a C1-C18 alkyl group which may be substituted by the epoxy group or the mercapto group, or A phenyl group, R ² is an alkyl group having 1 to 6 carbon atoms, and n is 0 or 1.) 0.1 to 40 parts by weight of an organosilicate and / or a condensate thereof (D ) 0.1 to 3.0 parts by mass of organic sulfonic acid, and (E) secondary or tertiary boiling point of 30 to 250 ° C. in an amount of 1.5 to 30 equivalents relative to 1 equivalent of organic sulfonic acid (D) A coating composition comprising the organic sulfonic acid (D) May be neutralized with the amine compound (E), a thermosetting top coating composition. The top coating composition according to claim 1, wherein the hydroxyl group-containing film-forming substrate resin (A) is a hydroxyl group-containing polyester resin having a hydroxyl value of 7 to 180 mgKOH / g. The top coating composition according to claim 1 or 2, wherein the amino resin crosslinking agent (B) is a methyl etherified melamine resin or a mixed melamine resin of a methyl etherified melamine resin and a butyl etherified melamine resin. Component (C) is a condensate of an organosilicate represented by the above general formula, having a methoxy group and an alkoxy group having 2 to 6 carbon atoms as an OR ² group, and having a methoxy group / carbon atom number of 2 The top coating composition according to any one of claims 1 to 3, wherein a ratio of the number of alkoxy groups to -6 is within a range of 95/5 to 30/70. The top coating composition according to any one of claims 1 to 4, wherein a reaction mixture in which the organic sulfonic acid (D) and the amine compound (E) are mixed in advance is blended in the coating. object. Furthermore, the top coat composition as described in any one of Claims 1-5 containing the surfactant which shows acidity, and / or the hydrolysis accelerator which is a boric-acid type compound. The top coating composition according to any one of claims 1 to 6, further comprising silica fine particles having an oil absorption of 100 to 280 ml / 100 g. A method of forming a coating film, comprising: applying a top coating composition according to any one of claims 1 to 7 on a metal plate via at least one primer film. A coated metal plate, comprising a metal plate, and at least one primer coating film and a cured coating film formed by the top coating composition according to any one of claims 1 to 7 are sequentially formed.