JP2002285069A - Top coat coating composition, method of coating finish and coated article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition capable of providing a cured film excellent in stain resistance, stain-removing properties, weather resistance, chemical resistance, humidity resistance and appearance, and having high environmental friendliness and safety. SOLUTION: The top coat composition comprises (A) a resin component containing a fluorinated vinylidene resin and an acrylic polymer in a mass ratio of 90:10 to 70:30, (B) a polyisocyanate compound containing two or more isocyanato groups or block-isocyanato groups in a molecule, and/or a relamine formaldehyde compound, (C) at least one inorganic oxide sol selected from an aluminum oxide sol, a silicone oxide sol, a zirconium oxide sol and an antimony oxide sol, and (D) an organosilicate represented by general formula (1): R<1> m Si(OR<2> )n (wherein R<1> is a phenyl group or a 1-18C alkyl group, and R<2> is a 1-6C alkyl group) or its partially hydrolyzed condensate, and/or a silicone compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel top coating composition, a method for forming a coating film on a coated metal sheet using the same, and a coated metal sheet. More specifically, the present invention can provide a cured coating having excellent stain resistance, stain removal properties, weather resistance, chemical resistance, moisture resistance and appearance,
The present invention also relates to a top coat composition having high environmental preservation and safety, a method for forming a coated metal plate having long-term coating durability, and a coated metal plate.

[0002]

2. Description of the Related Art In recent years, oil droplets and dust contained in the air have increased due to environmental changes such as air pollution, and as a result, coatings applied to buildings and automobiles have become more contaminated than before. However, there is a problem that the stain becomes difficult to remove. Thus, the coating film has good gloss, appearance, water resistance, and chemical resistance as well as resistance to contamination, that is, stain resistance, and the ability to remove contaminants from the contaminated coating film. It has been desired to have a removability, that is, a decontamination property. Also, creation of a coating composition excellent in environmental preservation and safety has been desired as a coating. By the way, stain-resistant paints that have been used in the past have a fluorine-containing resin as a main component,
The stain resistance was due to the weather resistance of the fluorine-containing resin. The fluororesin has (1) stability due to a large bond energy between a fluorine atom and a carbon atom, and (2) a fluorine atom having a larger atomic radius than a hydrogen atom and a polarizability between fluorine molecules. Low (0.68 × 10
⁻²⁴ CC), the function is exhibited by water repellency and oil repellency resulting from low surface free energy.

[0003] Further, in order to use a fluororesin for paints, for the purpose of improving solubility in a solvent, etc.,
Copolymers of fluoroolefins with vinyl ether monomers such as cyclohexyl vinyl ether (JP-A-57-34107), and those used in the form of a resin mixture of a fluorinated copolymer and an acrylic copolymer (JP-A-61-12760). However, in these, the portion based on the fluorine-containing monomer is reduced, and at present, the high weather resistance and stain resistance inherent in the fluorine-containing resin are not sufficiently exhibited. Further, to improve the weather resistance and stain resistance of the fluorine-containing resin for coatings, a fluoroolefin, a β-methyl-substituted α-olefin, a monomer having a chemically curing reactive group, and an ester group having a side chain. (Japanese Patent Application Laid-Open No. 4-279612). However, the decontamination property is not yet sufficient.

On the other hand, painted steel sheets having a thickness of 0.3 to 0.8 mm, called pre-coated steel sheets, are used for parts requiring long-term durability such as roofs and building exteriors, electric equipment, indoor equipment, and the like.
Currently widely used for vehicle interiors. These coating films for coated steel sheets have conventionally been required to have a high degree of bending workability, but in recent years, they have been required to further have stain resistance and stain removal properties. For these requirements for paint for coated steel sheets, various types of paints of thermosetting type and thermoplastic type have been proposed.For the thermoplastic type, for example, a specific acrylic resin is blended with vinylidene fluoride resin, A method has been proposed in which the crystallization of the vinylidene fluoride resin is prevented to maintain the elongation of the coating film for a long period of time (Japanese Patent Laid-Open No. 6-299115). However, at present, no problems have been solved with respect to stain resistance and stain removal properties while maintaining the bending processability of the thermoplastic type pre-coated metal top coating composition. On the other hand, as a stain-resistant composition, a coating composition comprising a partial condensate of an organosilicon compound and specific silica fine particles has been proposed (JP-A-2-3468). However, this publication does not describe the resin component used in the coating composition in detail. Further, a composition for a topcoat composition containing an acrylic polyol resin, a binder, an inorganic organosol and a solvent has been proposed (JP-A-4-173882), but this topcoat composition has a long-term stain resistance and Although the weather (light) resistance has been improved to some extent, the decontamination property is insufficient, and furthermore, there is no description regarding initial contamination resistance. As described above, a top coat composition that gives a coating film having excellent initial stain resistance, long-term stain resistance, stain removal properties, and weather (light) resistance has not yet been found.

[0005]

SUMMARY OF THE INVENTION Under the above circumstances, the present invention has been developed under the above circumstances, in addition to chemical resistance, workability, impact resistance, initial stain resistance, long-term stain resistance, stain removal property, and weather resistance. (light)
Can give a coating film with excellent properties, moisture resistance and appearance,
Further, the present invention has been made for the purpose of providing a top coating composition having high environmental preservation and safety.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop a top coating composition having the above-mentioned properties, and as a result, they have contained a vinylidene fluoride resin and an acrylic polymer in a predetermined ratio. In addition, if necessary, a mixture containing a polyisocyanate compound containing two or more isocyanate groups or blocked isocyanate groups in one molecule and / or a mixture containing a melamine formaldehyde compound may be further specified as a specific inorganic oxide sol. It has been found that a topcoat composition containing the above-mentioned organosilicates can be suitable for the purpose, and based on this finding, the present invention has been completed.

That is, the present invention provides (A) a vinylidene fluoride resin and an acrylic polymer in a mass ratio of 90:10 to 10:10.
The resin component contained in a ratio of 70:30, (B) two isocyanate groups or blocked isocyanate groups in one molecule.
(C) aluminum oxide sol, silicon oxide sol, zirconium oxide sol and antimony oxide sol, and (D) at least one inorganic oxide sol selected from the group consisting of polyisocyanate compounds and / or melamine formaldehyde compounds, ) General formula (1) R ¹ _m Si (OR ² ) _n (1) (wherein, R ¹ is a phenyl group or an alkyl group having 1 to 18 carbon atoms, and R ² is a 1 to 6 carbon atom. An alkyl group, m is an integer of 0 to 1, n is an integer of 3 to 4, and m + n is 4.) or a partially hydrolyzed condensate thereof, and / or It contains a silicone compound having a degree of polymerization of 3 to 100 and having an organic functional group and a hydrolyzable group in one molecule, and the mass ratio of the non-volatile component of the component (A) to the component (B) is 100: 0 to 70:
The solid content of the component (C) is 1 to 60% by mass based on the total solid content, and the solid content of the component (D) is 0 based on the total solid content. .1
To 10% by mass.

[0008] The present invention also provides a top coat composition in which the component (C) is a silicon oxide sol. The present invention also provides a top coating composition, wherein the silicon oxide sol is a silicon oxide sol whose surface has been modified with a silane coupling agent. In addition, the present invention provides a top coating composition containing 0 to 300 parts by mass of a pigment excluding an inorganic oxide sol per 100 parts by mass of all the nonvolatile components (A) to (D) in the above top coating composition. To provide. Further, the present invention is to apply a primer coating composition to a metal plate, and then apply an intermediate coating composition as needed, and then cure each time of coating, and thereafter, any one of the above top coating compositions An object of the present invention is to provide a method for coating and finishing a metal plate, which is characterized in that an object is applied and cured by heating. The present invention also provides a coated article characterized by being coated by the above-mentioned coating finishing method. Hereinafter, the present invention will be described in detail.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the top coating composition of the present invention, the vinylidene fluoride resin as the component (A) has a weight average molecular weight of at least 150,000 and a melting point of 150.
~ 180 ° C is preferred. Examples of such a vinylidene fluoride resin include, for example, Kainer [trade name, manufactured by Elf Atochem Japan KK, weight average molecular weight of 35,000]
0, melting point 160-165 ° C.], NEOFLON VP-850
[Product name, manufactured by Daikin Industries, Ltd., weight average molecular weight 340]
000, melting point 160-165 ° C], Horaphron 1000
VLD [trade name, manufactured by Elf Atochem Japan Ltd., weight average molecular weight 166,000, melting point 165 to 170 ° C],
Bidart 1002X [trade name, manufactured by Solvay Co., Ltd., weight average molecular weight 190000, melting point 165 to 170 ° C], and the like. One of these vinylidene fluoride resins may be used, or two or more thereof may be used in combination.

On the other hand, the acrylic polymer in the component (A) preferably contains at least 80% by mass of polymerized units of an alkyl (meth) acrylate having 1 to 6 carbon atoms in the alkyl group. Particularly, those containing polymerized units of methyl methacrylate in an amount of 50% by mass or more are preferable. When the content of the polymerization unit of the alkyl (meth) acrylate having 1 to 6 carbon atoms in the alkyl group is less than 80% by mass,
Due to poor compatibility with the vinylidene fluoride resin, sufficient molding performance cannot be obtained. Here, the alkyl (meth) acrylate is a general term for the alkyl acrylate and the alkyl methacrylate. The alkyl group having 1 to 6 carbon atoms in the alkyl (meth) acrylate may have one or more hydroxyl groups. Examples of the monomer forming a polymerized unit of the alkyl (meth) acrylate having 1 to 6 carbon atoms in the alkyl group include methyl (meth) acrylate,
Ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid Hydroxypropyl and the like.

In the acrylic polymer, the monomer forming a polymerized unit other than the polymerized unit of the alkyl (meth) acrylate may be a monomer copolymerizable with the alkyl (meth) acrylate. Any examples are possible, and examples thereof include (meth) acrylic acid, styrene, vinyl toluene, (meth) acrylonitrile, (meth) acrylamide, and vinyl chloride. As the molecular weight of the acrylic polymer, the weight average molecular weight is 20
It is preferably in the range of 000 to 300,000. If the weight average molecular weight deviates from this range, the compatibility with the vinylidene fluoride resin is reduced, and the molding performance is poor.
In the top coating composition of the present invention, the vinylidene fluoride resin and the acrylic polymer are mixed at a mass ratio of 70:30.
It needs to be contained at a ratio of up to 90:10. If the content is out of this range, it becomes difficult to suppress crystallization of the vinylidene fluoride resin, and the object of the present invention cannot be achieved.

In the top coating composition of the present invention,
As the curing agent (B), a polyisocyanate compound containing two or more isocyanate groups or blocked isocyanate groups in one molecule and / or a melamine formaldehyde compound is used as a curing agent. 1 isocyanate group
Examples of the polyisocyanate compound containing two or more in the molecule include, for example, hexamethylene diisocyanate,
Compounds called isocyanate monomers such as isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and polyuretes such as biuret, isocyanurate, and adduct of trimethylolpropane Preferred examples include isocyanate derivatives. These polyisocyanate compounds may be used alone,
Two or more kinds may be used in combination.

Examples of the polyblocked isocyanate compound include, for example, those prepared by blocking a part or all of the isocyanate groups of the polyisocyanate compound with a blocking agent. Examples of this blocking agent include, for example, ketoxime blocking agents such as ε-caprolactam, methyl ethyl ketoxime, methyl isoamyl ketoxime, methyl isobutyl ketoxime, and phenol blocking agents such as phenol, cresol, catechol, and nitrophenol. Blocking agents such as alcohol, isopropanol and trimethylolpropane; active methylene blocking agents such as malonic acid ester and acetoacetic ester; and azole blocking agents such as 3,5-dimethylpyrazole and 1,2,4-triazole. Agents and the like. These polyblocked isocyanate compounds may be used alone or in combination of two or more. Further, as an example of the melamine formaldehyde compound, a compound obtained by adding formaldehyde to a part or all of the amino group of melamine and then modifying a part or all of the generated methylol group with an alcohol having 1 to 6 carbon atoms. And any of a mononuclear type and a condensed type can be used.

In the top coating composition of the present invention,
The acrylic polymer having two or more hydroxyl groups among the resin of the component (A) (hereinafter, the resin of the component A) may be referred to as an acrylic polyol resin. ) And the compound of the component (B) (hereinafter, sometimes referred to as a curing agent) are compounded in the following proportions:
When the component (B) is a polyisocyanate compound,
The molar ratio of the isocyanate group and / or the blocked isocyanate group in the component (B) to the hydroxyl group in the component (A) is preferably in the range of 0.6 to 1.6, particularly preferably 0.8 to 1.6. .3. When the molar ratio is less than 0.6, the amount of hydroxyl groups remaining in the resin during the crosslinking reaction between the acrylic polyol resin (A) and the polyisocyanate compound (B) becomes relatively large. The water resistance and moisture resistance of the resulting coating film are reduced, and the weather resistance of the coating film is deteriorated. On the other hand, when the molar ratio exceeds 1.6, the amount of the remaining isocyanate groups and / or blocked isocyanate groups increases, so that the water resistance and moisture resistance of the coating film also decrease in this case, and the weather resistance of the coating film also decreases. It may cause the sex to deteriorate. From the viewpoint of coating film properties, a particularly preferred molar ratio is in the range of 0.6 to 1.6.

The weight ratio of the nonvolatile components (A) and (B) is preferably in the range of 100: 0 to 70:30. Here, when the ratio of the component (B) is larger than 40, the weather resistance of the obtained coating film is reduced. In the top coating composition of the present invention, a curing reaction catalyst may be used. When the component (B) is a polyisocyanate compound in the overcoat composition of the present invention, examples of the curing reaction catalyst include metal compounds such as tin compounds and zinc compounds, and amines. Examples of the tin compound include tin chloride, tin halides such as tin bromide, dibutyltin diacetate, organic tin compounds such as dibutyltin dilaurate, and the like.
Examples thereof include zinc halides such as zinc chloride and zinc bromide, and zinc salts of organic acids such as zinc octylate and zinc laurate. Examples of the amine include primary to tertiary high boiling amines such as dimethylbenzylamine, dimethylethanolamine and dimethyllaurylamine. One of tin compounds, zinc compounds and amines as a curing reaction catalyst may be used, or two or more of them may be used in combination, or may be used in combination with another curing reaction catalyst.

In the top coating composition of the present invention,
When the component (B) is a melamine formaldehyde compound, examples of the curing reaction catalyst include sulfonic acid-based curing reaction catalysts such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalenedisulfonic acid. Further, a phosphoric acid-based curing reaction catalyst, a carboxylic acid-based curing reaction catalyst, and the like can be mentioned, and one kind may be used alone or two or more kinds may be used in combination. The curing reaction catalyst is preferably used at a ratio of 0.1 to 10% by mass based on the total solids in the topcoat composition. If this amount is less than 0.1% by mass, the effect of accelerating the curing reaction may not be sufficiently exhibited, and 10% by mass.
If the ratio exceeds the above range, the water resistance and moisture resistance of the coating film may be reduced, which may lead to a decrease in the stain resistance, stain removal property, weather resistance and the like of the coating film. From the viewpoint of the balance between the curing speed and the physical properties of the coating film, a more preferable amount of the curing reaction catalyst is
0.1 to 5% by mass based on the total solid content of the top coating composition
Range.

In the top coating composition of the present invention,
As the inorganic oxide sol of the component (C), at least one inorganic oxide sol selected from aluminum oxide sol, silicon oxide sol, zirconium oxide sol and antimony oxide sol is used. The inorganic oxide sol used as the component (C) preferably has an average particle size of 100 nm or less, and particularly preferably 50 nm or less. The lower limit of the average particle size is not particularly limited as long as an inorganic oxide sol can be formed, but is preferably 1 nm or more.
When the average particle size is larger than 100 nm, the appearance of the coating film may be impaired, and the stain resistance and stain removal properties of the coating film may be reduced. These inorganic oxide sols are often supplied as an aqueous dispersion in general, and in the case of an aqueous dispersion, if the top coating composition is aqueous, it can be used as it is, but if it is an organic solvent, And a method of phase inversion into a desired organic solvent. As a method of the phase inversion, for example, a method of adding a water-soluble organic solvent in an aqueous dispersion and repeating the operation of distilling off water to perform phase inversion into a desired organic solvent may be used. Can be.

As the silicon oxide sol, for example, Snowtex 40, Snowtex O, Snowtex C, Snowtex N, Snowtex IPA / ST, Snowtex EG / ST, Snowtex XBA / ST, Snowtex MIBK / ST (All trade names, manufactured by Nissan Chemical Industry Co., Ltd.), Cataloid S-30H, Cataloid SI-30, Cataloid SN, Cataroid SA, Oscar 1132, Oscar 1232 (All trade names, manufactured by Catalyst Chemical Industry Co., Ltd.) Adelite AT-30, Adelite AT-20N, Adelite AT-20A, Adelite AT-20Q (all trade names, Asahi Denka Kogyo Co., Ltd.)
Silica Doll 30, Silica Doll 20A, Silica Doll 20B (all trade names, Nippon Chemical Industry Co., Ltd.)
Manufactured). As the aluminum oxide sol, for example, alumina sol 100, alumina sol 20
0, alumina sol 520 (all trade names, manufactured by Nissan Chemical Industries, Ltd.), alumina clear sol, aluminum sol 1
0, aluminum sol 20, aluminum sol SV-102, aluminum sol SH-5, aluminum sol CSA-55, aluminum sol C
SA-110A (all trade names, manufactured by Kawaken Fine Chemical Co., Ltd.) and the like. Examples of zirconium oxide sol include NZS-30A and NZS-30B
(Both are trade names, manufactured by Nissan Chemical Industries, Ltd.). As antimony oxide sol, for example, A-1
550, A-2550, sun colloid ATL-130,
Sun Colloid AMT-130 (all trade names, manufactured by Nissan Chemical Industries, Ltd.) and the like. Preferred of these inorganic oxide sols are silicon oxide sols.

Further, the inorganic oxide sol is preferable since the particle surface can be modified with a silane coupling agent. Since this surface-modified inorganic oxide sol can introduce various functional groups into the particle surface, when used in the topcoat composition of the present invention, the inorganic oxide particles are used in the topcoat composition. In addition to being able to disperse more stably, it becomes possible to chemically bond to organic components such as an acrylic polyol resin, a polyisocyanate compound, and a melamine formaldehyde compound. When the inorganic oxide particles and the organic component are chemically bonded as described above, the cross-linking of the coating film becomes stronger than when the chemical components are not chemically bonded, and the stain resistance, the stain removal property, the weather resistance, and the like are improved. improves. Examples of the silane coupling agent include vinyltrimethoxysilane, phenyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane , Methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane and the like.
Preferred are methyltrimethoxysilane, dimethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane. In addition, as commercial products, A-162,
A-163 and AZ-6122 (both are trade names, manufactured by Nippon Unicar Co., Ltd.) and the like. Further, condensates of the above compounds, for example, as commercial products, KR-9218, KR
-9202 (both trade names, manufactured by Shin-Etsu Chemical Co., Ltd.)
Can also be used as the silane coupling agent. These silane coupling agents can be used alone or in combination of two or more. When the surface treatment is performed with a silane coupling agent, the amount of the silane coupling agent is preferably from 1 to 100% by mass, more preferably from 5 to 50% by mass, based on the solid content of the inorganic oxide sol.

As the inorganic oxide sol stabilized with the silane coupling agent, water contained in the aqueous inorganic oxide sol is azeotropically distilled and dehydrated with an azeotropic solvent with water, and then the inorganic oxide sol is converted into silane. It is preferable to use a solvent-dispersed inorganic oxide sol obtained by stabilizing with a coupling agent. In particular, the inorganic oxide sol is preferably a silicon oxide sol. The inorganic oxide sol obtained by this production method is improved in stain resistance, stain removal properties, weather resistance and the like, and is also liable to undergo high solid differentiation at the time of forming a top coating composition. Therefore, the range of choice of the thinner for viscosity adjustment at the time of coating is wide, and the coating film can be made thick. Examples of the azeotropic solvent include water-soluble alcohols, carboxylic esters, and cyclic ethers. Examples of water-soluble alcohols include ethanol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol,
-Butyl alcohol, sec-butyl alcohol, t-butyl alcohol, methyl cellosolve, ethyl cellosolve, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-propyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol mono Ethyl ether, diethylene glycol monobutyl ether, 3-methyl-3-
Examples include methoxybutanol, propylene glycol monomethyl ether, ethylene glycol, propylene glycol and the like. Examples of the water-soluble carboxylate include methyl acetate and butyl acetate.
Examples of the water-soluble cyclic ether include 1,4-dioxane. These azeotropic solvents can be used alone or in combination of two or more.

A solvent that is immiscible with water may be used for the purpose of increasing the efficiency of azeotropic distillation dehydration by using a solvent that is miscible with water. Examples of the solvent include benzene, toluene, xylene, cyclohexane, diphenyl ether, dibutyl ether and the like.
These solvents can be used alone or in combination of two or more. However, the amount used is limited to a range that does not cause the inorganic oxide sol to aggregate, and varies depending on the type of solvent, but is usually preferably in the range of 1 to 10% by mass. The azeotropic distillation dehydration is preferably performed while dropping an azeotropic solvent, preferably in the range of 30 to 100 ° C, and particularly preferably in the range of 40 to 80 ° C. Further, the azeotropic distillation dehydration can be performed under normal pressure or under reduced pressure, but it is particularly preferable to perform it under reduced pressure.

The stabilization of the inorganic oxide particles by the silane coupling agent is not particularly limited, but is usually from 20 to 100 ° C.
And more preferably in the range of 30 to 90 ° C. The water content in the solvent-dispersed inorganic oxide sol in which the inorganic oxide particles are stabilized by the silane coupling agent is usually preferably 1% by mass or less, particularly preferably 0.5% by mass or less. . Further, the solvent-dispersed inorganic oxide sol can be replaced with a desired solvent as needed. Examples of the solvent used for this solvent replacement include the above-mentioned alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, dimethylacetamide, dimethylformamide, ethyl acetate, butyl acetate, hexyl acetate, benzene, toluene, xylene, etc. Is mentioned. Further, this solvent substitution is preferably performed in a temperature range of 30 to 120 ° C., and particularly preferably 40 to 110 ° C., although it depends on the type of solvent used in the substitution.
It is preferred to be carried out in the temperature range of

In the top coating composition of the present invention, one kind of inorganic oxide sol may be used, or two or more kinds may be used in combination. Further, it is necessary to use the compounding amount such that the solid content of the inorganic oxide sol is 1 to 60% by mass with respect to the total solid content of the top coating composition. When the solid content of the inorganic oxide sol is less than 1% by mass based on the total solid content, the effect of adding the inorganic oxide sol is not sufficiently exhibited, and the coating film has a long-term stain resistance, stain removal property, and weather resistance. The effect of improving the properties is not recognized, and when it exceeds 60% by mass, the flexibility of the coating film tends to decrease. From the viewpoint of the balance of long-term stain resistance, stain removal property, weather resistance, flexibility, etc. of the coating film, the solid content of the inorganic oxide sol is 5 to 40 mass based on the total solid content of the top coating composition. % Is preferred.

In the top coating composition of the present invention,
The component (D) has a general formula (1) R ¹ _m Si (OR ² ) _n (1) (wherein R ¹ is a phenyl group or an alkyl group having 1 to 18 carbon atoms, and R ² is a carbon number Is an alkyl group of 1 to 6, m is an integer of 0 to 1, n is an integer of 3 to 4, and m + n is 4.) or a partially hydrolyzed condensate thereof. And / or a silicone compound having an average degree of polymerization of 3 to 100 and having an organic functional group and a hydrolyzable group in one molecule is used. The component (D) used in the top coat composition of the present invention is more preferably a non-volatile compound in order to efficiently exert an effect on the surface of the substrate after coating.

Specific examples of the organosilicate as the component (D) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetrabutoxysilane, tetraisobutoxysilane, and the like, alone or in combination. Partial hydrolysis condensates and the like can be mentioned. In addition, methyl trimethoxy silane, methyl triethoxy silane, methyl tripropoxy silane, methyl triisopropoxy silane, methyl tributoxy silane, methyl triisobutoxy silane, phenyl trimethoxy silane, phenyl triethoxy silane, phenyl tripropoxy silane, phenyl Triisopropoxysilane, phenyltributoxysilane, phenyltriisobutoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldipropoxysilane, dimethyldibutoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldipropoxysilane, diphenyl Dibutoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, methylphenyldipropoxy , Methylphenyldibutoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, lauryltrimethoxysilane, lauryltriethoxysilane, lauryltrimethoxysilane, lauryltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ- Examples thereof include methacryloyloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane and the like, and partial hydrolysis condensates of these alone or in combination.

The partially hydrolyzed condensate of an organosilicate can be produced by a conventional method.
C silicate MS51, MS56, MS57, MS56
S, MS56SB5, ES40, EMS31, BTS
(All trade names, manufactured by Mitsubishi Chemical Corporation), methyl silicate 51, ethyl silicate 40, ethyl silicate 4
OT and ethyl silicate 48 (all trade names, manufactured by Colcoat Co., Ltd.) can be used alone or in combination of two or more. The partially hydrolyzed condensate of an organosilicate is preferably a 2- to 20-mer. The silicone compound having an organic functional group and a hydrolyzable group in one molecule of the component (D) includes an epoxy group, a mercapto group, a (meth)
Obtained by subjecting a silane coupling agent having one or more organic functional groups selected from an acroyl group, a vinyl group, and a haloalkyl group to condensation polymerization with a silicon compound represented by the general formula (2) or (3). Compounds having an average degree of polymerization of 3 to 100 are preferred. _{^{R 3 Si (OR 2) 3}} (2) Si (OR 2) 3 (3) ( wherein, ^{R 3} is an organic substituent having 1 to 3 carbon atoms, ^{R 2}
Is an alkyl group having 1 to 6 carbon atoms. )

When the average degree of polymerization is less than 3, the silicone compound volatilizes or elutes during the curing process of the coating film, so that a coating film with insufficient stain resistance cannot be obtained. The average degree of polymerization is 1
If it exceeds 00, the dispersion of the silicone compound in the coating film becomes poor, and a uniform coating film cannot be obtained. Specific examples of the silicone compound having an organic functional group and a hydrolyzable group in one molecule include X-41-1805 and X-4-1053 (both are trade names, manufactured by Shin-Etsu Chemical Co., Ltd.). .
In the top coating composition of the present invention, the organosilicate and / or the silicone compound as the component (D) may be used alone or in combination of two or more. In addition, the compounding amount is such that the solid content of the component (D) is 0.1 to 10% by mass based on the total solid content of the top coating composition.
It is necessary to use it. When the solid content of the component (D) is less than 0.1% by mass relative to the total solid content,
The effect of the addition of the component (D) is not sufficiently exhibited, and the effect of improving the initial stain resistance and stain removal property of the coating film is not observed. When the amount exceeds 10% by mass, the water resistance of the coating film tends to decrease. Is seen. From the viewpoint of the balance of the initial stain resistance, stain removal property, water resistance, etc. of the coating film, the solid content of the component (D) is 0.5 to 5% by mass based on the total solid content of the top coating composition.
Is preferable.

The top coating composition of the present invention includes:
As other components, coloring pigments, extenders, solvents, additives, and the like generally used in a top coating composition can be blended. As a coloring pigment, for example, titanium oxide,
Examples include carbon black, iron oxide, lead chromate, aluminum powder, copper powder, and baked pigments such as cobalt blue and cobalt green. Examples of the extender include calcium carbonate, clay, talc, antimony trioxide, barium sulfate, kaolin and the like. Examples of the solvent include toluene, xylene, ethyl acetate, butyl acetate, cellosolve solvents, methyl isobutyl ketone, methyl ethyl ketone, diisobutyl ketone, isophorone, cyclohexanone, and the like. Examples of the additive include an antifoaming agent, a pigment dispersant, an anti-sagging agent, an ultraviolet absorber, an antioxidant, and an anti-scratch agent. In addition, for the purpose of improving the coating film hardness and other properties in the top coating composition,
Glass fiber, alumina fiber, glass beads, alumina,
Inorganic aggregates such as mica and silica and organic aggregates such as polytetrafluoroethylene, benzoguanamine, polymethyl methacrylate, polyacrylonitrile, and melamine may be blended.

Next, the method for forming a coating film on a coated steel sheet according to the present invention will be described. The plate to be used in the method of the present invention may be a metal plate such as a cold-rolled steel plate, a galvanized steel plate, an aluminum / zinc alloy-plated steel plate, a stainless steel plate, an aluminum plate, or an aluminum alloy plate. A hot-dip galvanized steel sheet, a 5% aluminum / zinc alloy-plated steel sheet, and a 55% aluminum / zinc alloy-plated steel sheet are preferable because they have excellent blistering and anticorrosion properties in the formed portion. The surface of the substrate to be coated can be subjected to a chemical conversion treatment prior to painting in consideration of the adhesion to the coating film and the like. As the chemical conversion treatment, one generally used as a coating base treatment may be used. For a hot-dip galvanized steel sheet and a 5% aluminum / zinc alloy-plated steel sheet, a zinc phosphate treatment, or a coating or reaction type chromate treatment is used. It can be preferably applied to a 55% aluminum / zinc alloy-plated steel sheet, and a coating type or reactive type chromate treatment can be preferably applied.

The undercoat paint composition used in the method of forming a coating film of the present invention is most preferably an epoxy resin-based overcoat paint composition which has been widely used for coated steel sheets, but is not limited thereto. Instead, other types of topcoat compositions, such as vinyl resin-based and acrylic resin-based topcoat compositions such as polyester resin and vinyl butyral, can be used as long as they can achieve the object of the present invention. . The coating film forming method of the present invention,
If necessary, the above-mentioned undercoating composition and the topcoating composition of the present invention are applied over the coated plate which has been subjected to the above-mentioned chemical conversion treatment. An example of the coating method is described below, but the coating method is not limited thereto. As the coating method, there is a method in which an undercoat composition is applied and cured by heating, and then the top coating composition of the present invention is applied and cured by heating. Here, the curing means curing by drying or curing by a curing agent. The thickness of the cured coating film of the undercoat is preferably from 1 to 20 μm, and the heating and curing temperature thereof is usually preferably from 160 to 250 ° C. attained plate temperature. In addition, the thickness of the cured coating film of the top coating composition is usually preferably 5 to 50 μm, and the heat curing temperature thereof is preferably 200 to 300 ° C. of the ultimate plate temperature. As the form of the topcoat composition, in addition to the solvent-type topcoat composition, a water-dispersion type topcoat composition, a non-acidic topcoat composition, a powder topcoat composition, an electrodeposition type topcoat composition, and the like are required. Can be appropriately selected according to the conditions.

[0031]

Next, 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 to these Examples. In addition, the performance of the test piece was evaluated as follows. (1) Pencil hardness The pencil hardness was determined in accordance with JIS K5400 8.4.2. (2) Adhesiveness A cross-cut (1 mm; 10 × 10 cross cut) was cut on the coated surface with a cutter knife, and this portion was extruded from the back by 6 mm with an Erichsen tester. Thereafter, a cellophane (registered trademark) was attached to the extruded portion and a peeling test was performed.
The adhesion of the coating was evaluated. ；: No peeling at all △: coating film peeling rate is 30% or less. (Fail) ×: The coating film peeling rate is 70% or more.

(3) Workability The workability of each test plate was evaluated at room temperature. 2T in the table is the same coated plate as the test piece sandwiched between two (3T-6
(T: 3 to 6 sheets are sandwiched)) The coated surface is bent 180 degrees with the painted surface facing outward. The bent tip was observed with a 10-fold loupe to show the crack-free processing level. (4) Carbon contamination The test piece was coated with a carbon black suspension, dried at 60 ° C. for 1 hour, allowed to cool to room temperature, and then gauze was applied to the surface of the test piece under running water. And washed until no dirt was removed. Thereafter, the coated surface was wiped off and dried at room temperature for 3 hours, and then the stained state of the coated surface was visually determined and evaluated as follows. ◎: No contamination ○: Almost no contamination (pass) △: Trace of contamination remains (fail) ×: No contaminants can be removed

The carbon black suspension was prepared by mixing carbon black FW-200 (manufactured by Degussa) and deionized water at a mass ratio of 5:95 and stirring thoroughly before use. After immersing the test plate in boiling water for 3 hours as a pretreatment,
Constant temperature and humidity chamber (Temperature 20 ± 1 ° C, relative humidity: 65 ± 5%)
The test was carried out on two types, one dried for 24 hours and one without pretreatment. (5) Outdoor exposure contamination resistance After exposing the test specimen outdoors for 1 month and 6 months, the L value after the test was measured with a color difference meter, and the L value before the test was subtracted from the L value after the test. The obtained value was determined as ΔL and evaluated. (6) Accelerated weathering The accelerated weathering test was conducted using the following tester and test conditions.
The test was conducted for 00 hours, and the retention of 60 ° gloss (%) (J
IS K5400 (1990) 7.6). Tester: WEL-Sunshine-DC, manufactured by Suga Test Instruments Co., Ltd. (commonly known as Du-Cycle Sunshine Weather-Ometer) Test conditions: Light source Carbon arc Black panel temperature 63 ° C

(7) Salt Sprayability The test piece subjected to 2T processing was subjected to JIS Z2371.
The test was conducted for 2,000 hours in accordance with the method described above, and the degree of rust in the processed portion was visually determined and evaluated as follows. ◎: No abnormality at all ○: Almost no abnormality (pass) △: Swelling or white rust observed (fail) ×: Abnormally abnormal (8) Moisture resistance For the test piece subjected to 2T processing, a moisture resistance tester (temperature
The test was conducted for 2000 hours using a tester at 50 ° C. and a relative humidity of 95% or more), and the degree of rust in the processed portion was visually determined and evaluated as follows. ◎: No abnormality at all ○: Almost no abnormality (pass) △: Swelling and white rust recognized (fail) ×: Obviously abnormal

(9) Acid Rain Resistance Test As an accelerated acid rain test, test pieces were immersed in a 5% by mass aqueous solution of sulfuric acid for 10 days, and the degree of the state of the coated surface was visually determined and evaluated as follows. The test was performed in a constant temperature and humidity room. ◎: No abnormality at all ○: Almost no abnormality (pass) △: Swelling and white rust recognized (fail) ×: Obviously abnormal

(Production Example 1) Synthesis of Acrylic Copolymer Resin Solution A-1 4 equipped with a thermometer, a reflux condenser, a stirrer and a dropping funnel
Solvesso # 150 (Esso Corporation)
Manufacture: 70 parts by mass of aromatic petroleum naphtha) and 60 parts by mass of isophorone were heated and maintained at 110 ° C. There,
42 parts by mass of methyl methacrylate, ethyl acrylate 18
Parts by mass 2,2'-azobis (2-methylbutyronitrile)
A mixture of 0.1 parts by mass was dropped from the dropping funnel over 4 hours. After completion of the dropwise addition, stirring was continued for 4 hours while maintaining the same temperature. A mixture of 0.1 parts by mass of 2,2′-azobis (2-methylbutyronitrile) and 10 parts by mass of isobutyl acetate was added, and the mixture was further added for 1 hour. Stirring was continued. After completion of the polymerization, an acrylic copolymer resin solution A-1 having a solid content of 30.2% by mass was obtained. The weight average molecular weight of the obtained acrylic copolymer was 67000.

(Production Example 2) Synthesis of Acrylic Copolymer Resin Solution A-2 An acrylic copolymer resin solution A-2 having the composition shown in Table 1 was obtained in the same manner as in Production Example 1. Solid content is 30.4 mass%
The molecular weight in terms of polystyrene by GPC was 83,000 in number average molecular weight, and the hydroxyl value was 56 mgKOH / g.

[0038]

[Table 1] (Note) The abbreviations in Table 1 are shown below. 1) ABMBN: 2,2'-azobis (2-methylbutyronitrile)

(Production Examples 3 and 4) Production of Inorganic Oxide Sols C-1 and C-2 as Component (C) A reaction equipped with a thermometer, a reflux condenser equipped with a Dean-Stark trap, a stirrer, and a dropping funnel. A silicon oxide sol and a silane coupling agent described in Table 2 were charged into a container,
By heating and stirring at 80 ° C. for 8 hours, the surface of the silicon oxide particles was treated, and the stabilized silicon oxide sol C-
1, C-2 was obtained.

[0040]

[Table 2] (Note) The abbreviations in Table 2 are shown below. 1) MIBK-ST: Snowtex-MIBK-S
T, trade name, manufactured by Nissan Chemical Industries, Ltd., silicon oxide sol (average particle size 10 to 15 nm, solvent: methyl isobutyl ketone), solid content 30% by mass 2) IPA-ST: Snowtex-IPA-ST,
Trade name, manufactured by Nissan Chemical Industries, Ltd., silicon oxide sol (average particle diameter 10 to 15 nm, solvent: i-propyl alcohol), solid content 30% by mass 3) SH-6040: Trade name, Dow Corning Toray Silicone 4) A-163: Trade name, manufactured by Nippon Unicar Co., Ltd., silane coupling agent

(Examples 1 to 14, Comparative Examples 1 to 7) (1) Preparation of Top Coating Composition According to the composition shown in Tables 3 to 5, a mixture of an acrylic polymer liquid, a pigment and a solvent was mixed with a sand grinder. 10μ
m or less, vinylidene fluoride resin powder was added while stirring with a dissolver, and dispersed to 30 μm or less. Thereafter, the inorganic oxide sol was uniformly dispersed and mixed while being stirred with a disper to prepare a top coat composition of the example and a top coat composition of the comparative example. Example 4
In the above, the molar ratio of the isocyanate group and / or the blocked isocyanate group in the component (B) to the hydroxyl group in the component (A) was 1.25. (2) Test plate production method Z-27 (hot-dip galvanized steel plate (basis weight 275 g / m ² )) was used as the plate to be coated. An epoxy resin-based overcoating composition "trade name; Precolor Primer F-
1. Nippon Oil & Fats BASF Coatings Co., Ltd. "was applied using a bar coater # 12 so that the cured coating thickness became 5 μm, and was cured at an ultimate plate temperature of 210 ° C. Next, each of the overcoat compositions of Examples 1 to 14 and Comparative Examples 1 to 7 was applied using a bar coater # 40 so that the thickness of the cured coating film became 20 μm. Then, each test plate was produced. The performance of each test plate prepared in this manner was evaluated. The results are shown in Tables 6 to 8. In addition,
In Comparative Example 5, since the coating workability was poor and the finished state of the coated surface was abnormal, only evaluation of pencil hardness adhesion and workability was performed.

[0042]

[Table 3]

[0043]

[Table 4]

(Note) The abbreviations in Tables 3 to 5 indicate the following. * 1) F1: Kynar 500 (trade name), manufactured by Elphatochem Japan Ltd., weight average molecular weight 350,000,
Melting point 160-165 ° C * 2) F2: Horaphron 1000 VLD (trade name), manufactured by Elphatochem Japan Ltd., weight average molecular weight 16
6000, melting point 165-170 ° C * 3) B-1: Desmodur BL3175 (trade name), Sumitomo Bayer Urethane Co., Ltd., block type hexamethylene diisocyanate polymer * 4) B-2: Cymel 303 (trade name) ), Manufactured by Mitsui Cytec Co., Ltd., fully alkylated methylated melamine resin * 5) Titanium oxide: TYPAQUE CR-97 (trade name),
* 6) Catalyst 6000: trade name, manufactured by Mitsui Cytec Co., Ltd., dodecylbenzene sulfonic acid catalyst * 7) Additive: Floren AC-300 (trade name), manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd. * 8) D-1: MKC silicate MS56 (trade name),
Condensate of organosilicate, manufactured by Mitsubishi Chemical Corporation, weight average molecular weight 1000-1500 * 9) D-2: MKC silicate MS56SB5 (trade name), condensate of organosilicate, manufactured by Mitsubishi Chemical Corporation, weight average molecular weight 1500-2000 * 10) D-3: X41-1805 (trade name), manufactured by Shin-Etsu Chemical Co., Ltd., silicone oligomer 11) D-4: NSJ8547L (trade name), manufactured by Kusumoto Kasei Co., Ltd.

[0045]

[Table 5]

[0046]

[Table 6]

[0047]

[Table 7]

[0048]

[Table 8]

As is clear from Tables 6 to 8, Comparative Example 1, which is out of the range of the present invention, does not contain the component (D), so that the initial stain resistance is insufficient. Further, Comparative Example 2 does not contain the component (C), so that the long-term stain resistance is insufficient. Further, Comparative Example 3 is insufficient in carbon contamination and outdoor exposure contamination resistance because the amounts of the components (C) and (D) are small. Comparative Example 4 with a large amount of component (C)
Is insufficient in adhesion, processability, salt sprayability and moisture resistance. Comparative Example 5, in which the ratio of vinylidene fluoride resin to acrylic resin was 95/5, was poor in coating workability and coating surface appearance. Comparative Example 6, in which the ratio of vinylidene fluoride resin to acrylic resin is 60/40, is insufficient in workability. Further, the ratio of the component (A) / the component (B) is 6
Comparative Example 7, which is 0/40, is insufficient in weather resistance and acid rain resistance. On the other hand, in Examples 1 to 14 according to the present invention, the coating workability, coating film appearance, adhesion, workability, carbon stainability, initial and long-term stain resistance in outdoor exposure, moisture resistance, etc. are all excellent. The results show that the top coating composition of the present invention is excellent.

[0050]

The metal sheet coated with the top coating composition of the present invention has the same workability, weather resistance and acid rain resistance as the conventional coated metal sheet, and is difficult with the conventional coated metal sheet. It has both the initial and long-term anti-staining and anti-staining properties, and can maintain not only the durability of the coating film but also the aesthetic appearance of the coating film.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 133/00 C09D 133/00 161/28 161/28 175/04 175/04 183/02 183/02 183 / 04 183/04 C23C 28/00 C23C 28/00 C (72) Inventor Nobuhiro Nishida 138-6-302 Setagaya-cho, Hodogaya-ku, Yokohama-shi, Kanagawa F-term (reference) 4D075 AE17 BB26Y BB26Z CA02 CA04 CA13 CA32 CA33 CA34 CA38 CA44 CB04 DA06 DB02 DB04 DB05 DB07 DC01 DC10 DC13 DC18 EA07 EA12 EB14 EB15 EB17 EB19 EB22 EB32 EB33 EB35 EB38 EB43 EB52 EB56 EC03 EC05 EC11 EC54 4J038 CD111 CG162 CH032 CH042 GA122 DG 309 DG 163 HA066 HA216 HA286 HA376 HA446 HA526 HA536 JC32 JC35 KA03 KA08 KA15 MA14 NA01 NA04 NA05 NA11 NA27 PA19 PC02 4K044 AA02 AA06 AB02 BA10 BA15 BA17 BA21 BB04 BB11 BC02 BC05 BC07 BC09 CA53 CA62

Claims (6)

[Claims] 1. A resin component containing (A) a vinylidene fluoride resin and an acrylic polymer in a mass ratio of 90:10 to 70:30, and (B) an isocyanate group or a blocked isocyanate group in one molecule. At least one inorganic oxide sol selected from the group consisting of a polyisocyanate compound and / or a melamine formaldehyde compound, (C) aluminum oxide sol, silicon oxide sol, zirconium oxide sol and antimony oxide sol, and (D) General formula (1) R ¹ _m Si (OR ² ) _n (1) (wherein, R ¹ is a phenyl group or an alkyl group having 1 to 18 carbon atoms, and R ² has 1 to 1 carbon atoms. 6 is an alkyl group, m is an integer of 0 to 1, n is an integer of 3 to 4, and m + n is 4.) or a partial hydrate thereof. A condensate and / or a silicone compound having an average degree of polymerization of 3 to 100 and having an organic functional group and a hydrolyzable group in one molecule, and a non-volatile component mass ratio of the component (A) and the component (B) Is 100: 0 to 70:
The solid content of the component (C) is 1 to 60% by mass based on the mass of the total solid content, and the solid content of the component (D) is 0% based on the mass of the total solid content. .1
A top coating composition, characterized in that the amount is from 10 to 10% by mass. 2. The top coating composition according to claim 1, wherein the component (C) is a silicon oxide sol. 3. The top coating composition according to claim 2, wherein the silicon oxide sol is a surface-modified silicon oxide sol with a silane coupling agent. 4. A total of 100 non-volatile components (A) to (D).
0 to 300 pigments excluding the inorganic oxide sol per part by mass
The top coating composition according to any one of claims 1 to 3, which is contained by mass. 5. An undercoat composition is applied to a metal plate,
Next, if necessary, the intermediate coating composition is applied and cured sequentially for each application, and thereafter, the top coating composition according to any one of claims 1 to 4 is applied and cured by heating. Paint finishing method for metal plate. 6. A coated article coated by the coating finishing method according to claim 5.