JPH07252448A - Curable composition for top coating compound - Google Patents

Abstract

PURPOSE:To obtain the subject composition suitable as a top coating compound especially for automobiles, showing excellent water resistance, scratching resis tance, appearance, thermosetting properties and extremely excellent acid resis tance. CONSTITUTION:(A) 100 pts.wt. of a vinyl-based monomer comprising a main chain composed of a vinyl-based copolymer chain and containing (i) a hydrolyzable vinyl group (380-30,000gl/mol equivalent of hydrolyzable silyl group) of the formula (R<1> is H, 1-10C alkyl group, etc.; R<2> is H, a 1-10C alkyl group, an aryl group, etc.; (a) is 0, 1 or 2) and (ii) an alcoholic hydroxyl group (400-2,000g/mol equivalent of alcoholic hydroxyl group) at an end of the main chain and/or a side chain in the molar ratio of the group (i) to the group (ii) of 0.1-3 is mixed with (B) 1-100 pts.wt. of a carboxyl group-containing acrylic copolymer (50-200 mgKOH acid value) containing 0.1-95% of a carboxyl group- containing vinyl-based monomer containing a polymerizable unsaturated double bond in the molecule and (C) 0.001-10 pts.wt. of a curing catalyst.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a curable composition for a top coat. For details, for example, automobiles, industrial machinery,
A curable composition for a top coating, which is suitably used for steel furniture, interior and exterior of buildings, home appliances, plastics, and the like, and more specifically exhibits excellent water resistance, abrasion resistance, appearance, thermosetting property, and the like. At the same time, it relates to a curable composition for an overcoating material which exhibits extremely excellent acid resistance and can be suitably used especially for an overcoating material for automobiles.

[0002]

2. Description of the Related Art Conventionally, paints mainly containing melamine resins such as alkyd melamine and acrylic melamine have been used for painting automobiles, building interiors and exteriors, industrial machinery, steel furniture, plastics, etc. A coating material mainly containing a melamine resin has a problem that a large amount of harmful formalin is generated at the time of curing and the cured coating film is inferior in acid resistance, so that it is attacked by acid rain.

In particular, the problem of acid rain caused by air pollution in recent years has become serious, and there are phenomena such as etching, whitening, and stains on the coating film.

In order to solve the above-mentioned problems, the present inventors have developed a blend system of a vinyl copolymer having a hydrolyzable silyl group and an acrylic polyol, and a vinyl monomer having a hydrolyzable silyl group. As a result of investigating the use of a copolymer of a vinyl monomer having an alcoholic hydroxyl group and the like in a coating material, a curable resin for coating having excellent acid resistance and weather resistance is obtained when these are used. It has been found that this is possible, and a patent application has been filed first (Japanese Patent Laid-Open No. 63-132977, etc.).

A blend system of a vinyl copolymer having a hydrolyzable silyl group and an acrylic polyol, and a copolymerization weight of a vinyl monomer having a hydrolyzable silyl group and a vinyl monomer having an alcoholic hydroxyl group. As a feature of the combination, the hydrolyzable silyl group and the alcoholic hydroxyl group form a stable siloxane bond or siloxy bond and cure, so that when using a paint mainly composed of melamine resin such as acrylic melamine or alkyd melamine. In comparison, it can be mentioned that a coating film having excellent acid resistance and weather resistance is formed, and the hydrolyzable silyl group has a general formula (II):

[Chemical 2] (In the formula, R ³ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, and R ⁴ is a monovalent carbon atom selected from the group consisting of a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, an aryl group and an aralkyl group. Hydrogen group, and b represents 0, 1 or 2), the silicon atom (Si) in the hydrolyzable silyl group is the main unit of the copolymer through the carbon atom (C) directly connected to the silicon atom (Si). Since it is introduced into the chain, it is possible to form a coating film having excellent acid resistance and weather resistance.

[0006]

However, although the vinyl-based copolymer having the hydrolyzable silyl group and the alcoholic hydroxyl group in the same molecule certainly exhibits excellent water resistance and acid resistance, for example, in automobiles. Adhesion between coating films (hereinafter referred to as "recoat adhesion") when repainting (recoating), which is indispensable for topcoat paints for automobiles, is not sufficiently satisfied.

[0007] In view of the above-mentioned prior art, the present inventors have therefore proposed a coating composition exhibiting excellent acid resistance, water resistance, weather resistance, scratch resistance and thermosetting property as well as excellent recoat adhesion. As a result of repeated intensive training to obtain things,
The present invention has been completed by finding out such a curable composition for coating materials.

[0008]

That is, in the curable composition for top coating composition of the present invention, (A) the main chain is substantially composed of a vinyl copolymer chain, and the main chain end and / or side chain The general formula (I), which is attached via a carbon atom (C) in the chain:

[Chemical 3] (In the formula, R ¹ is a hydrogen atom, an alkyl group or an aryl group having 1 to 10 carbon atoms, and R ² is a hydrogen atom or 1 to 1 carbon atoms.
0 is a monovalent hydrocarbon group selected from the group consisting of an alkyl group, an aryl group and an aralkyl group, a is 0, 1 or 2, and has at least one hydrolyzable silyl group represented by 100 parts by weight of vinyl-based copolymer having at least one alcoholic hydroxyl group at the main chain terminal and / or side chain and having an alcoholic hydroxyl group equivalent of 400 to 2,000 g / mol, (B) carboxyl group-containing acrylic 1 to 100 parts by weight of copolymer, (C) curing catalyst 0.0
It is a mixture of 01 to 10 parts by weight.

Component (A) The vinyl copolymer (A) used in the present invention has a hydrolyzable silyl group represented by the following general formula (I).

[0010]

[Chemical 4] (R ¹ , R ² and a are the same as above).

In the vinyl-based copolymer (A) used in the present invention, the silicon atom (Si) bonded to the hydrolyzable group is linked to the copolymer chain via the carbon atom (C) directly bonded to the silicon atom (Si). Since it is introduced into the main chain terminal and / or the side chain (Si-C bond is formed), the resulting curable composition exhibits excellent acid resistance and weather resistance. In the vinyl copolymer (A), since the alcoholic hydroxyl group is introduced into the main chain terminal and / or side chain of the copolymer chain together with the hydrolyzable silyl group, the alcoholic hydroxyl group is The resulting curable composition has excellent acid resistance as compared with the case where a vinyl-based copolymer having only a hydrolyzable silyl group and a blended system of the vinyl-based copolymer and an acrylic polyol are not used. And it is considered that they will exhibit weather resistance.

Further, in the present invention, the vinyl copolymer (A) is blended with a carboxyl group-containing acrylic copolymer (B), and the carboxyl group of the carboxyl group-containing acrylic copolymer (B) is mixed. And a hydrolyzable silyl group of the vinyl copolymer (A) and a carboxyl group react with an acrylic melamine resin base coat, an acrylic urethane resin base coat used for recoating, and exhibit excellent recoat adhesion. I think it will be.

The hydrolyzable silyl group represented by the general formula (I) contained in the vinyl copolymer (A) is, for example, a hydrolyzable silyl group-containing vinyl monomer described below as (A-1). Examples include body-based groups.

In the general formula (I), R ¹ is a hydrogen atom,
An alkyl group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, a butyl group) or an aryl group having 6 to 10 carbon atoms (for example, a phenyl group), R ² is an alkyl group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms (eg, methyl group, ethyl group, propyl group, butyl group), 6 carbon atoms
-10 aryl group (eg phenyl group) and C 7-10 aralkyl group (eg benzyl group)
It is a monovalent hydrocarbon group selected from the group consisting of

The alcoholic hydroxyl group equivalent in the vinyl copolymer (A) (the resin solid content (g) of the vinyl copolymer (A) containing 1 mol of the alcoholic hydroxyl group) is 400.
~ 2,000 g / mol, preferably 500-2,000
g / mol, more preferably 600 to 1,800 g / mol. The alcoholic hydroxyl group equivalent is 400 g /
When the amount is less than mol, the acid resistance of the coating film formed by using the obtained curable composition is lowered, and when it is more than 2,000 g / mol, the composition is thermally cured. And the scratch resistance and impact resistance of the coating film are deteriorated.

Further, the hydrolyzable silyl group equivalent in the vinyl copolymer (A) (resin solid content (g) of the vinyl copolymer (A) containing 1 mol of the hydrolyzable silyl group) is excellent. 380 to 30,000 from the viewpoint that a curable composition exhibiting thermosetting property, acid resistance, weather resistance and the like can be obtained.
g / mol, preferably 410 to 3,000 g / mol, and particularly preferably 450 to 1,500 g / mol.

Further, the molar ratio of the alcoholic hydroxyl group to the hydrolyzable silyl group in the vinyl copolymer (A) (alcoholic hydroxyl group / hydrolyzable silyl group) is excellent in thermosetting and acid resistance. From the viewpoint that a curable composition exhibiting properties, weather resistance, water resistance and the like can be obtained, it is preferably 0.1 to 3, preferably 0.5 to 2.5, and particularly preferably 0.7 to 2.

In order to make the value of the molar ratio fall within the above range, for example, the hydrolyzability described later as (A-1) is used when the vinyl copolymer (A) is obtained. Silyl group-containing vinyl-based monomer, and (A-
The amount of the alcoholic hydroxyl group-containing vinyl-based monomer described below as 2) may be adjusted.

The vinyl copolymer (A) is, for example, a hydrolyzable silyl group-containing vinyl monomer (hereinafter referred to as "monomer (A-1)") and an alcoholic hydroxyl group-containing vinyl monomer ( Hereinafter, referred to as "monomer (A-2)" and other monomers copolymerizable with these (hereinafter,
It can be produced by polymerizing a copolymerization component containing "monomer (A-3)").

The monomer (A-1) is not particularly limited, and may be, for example, a compound represented by the general formula (III):

[Chemical 5] (In the formula, R ¹ , R ² and a are the same as described above, and R ⁵ is a general formula:

[Chemical 6] (In the formula, R ⁶ represents a hydrogen atom or a methyl group) or a group containing a hydrolyzable silyl group represented by —CH ₂ —.

Examples of the monomer (A-1) include, for example,

[Chemical 7] Such as the general formula (IV):

[Chemical 8] (Wherein R ¹ , R ² , R ⁶ and a are the same as defined above).

[0022]

[Chemical 9] Such as general formula (V):

[Chemical 10] (In the formula, R ¹ , R ² and a are the same as those described above, R ⁷ is a hydrogen atom or a methyl group, and n is an integer of 1 to 12).

[0023]

[Chemical 11] Such as the general formula (VI):

[Chemical 12] (In the formula, R ¹ , R ² , R ⁷ , a and n are the same as above)
A compound represented by.

[0024]

[Chemical 13] Such as the general formula (VII):

[Chemical 14] (In the formula, R ¹ , R ² , R ⁷ and a are the same as above, and m is an integer of 1 to 8).

[0025]

[Chemical 15] (In the formula, p represents an integer of 0 to 20) and the like, the general formula (V
III):

[Chemical 16] (Wherein R ¹ , R ² , R ⁷ and a are the same as above, q is an integer of 0 to 20) and the hydrolyzable silyl group represented by the general formula (III) is urethane. Examples thereof include (meth) acrylate having a terminal via a bond or a siloxane bond.

These can be used alone or in admixture of two or more, and among them, the above-mentioned general formula (V Compounds represented by

The amount of the monomer (A-1) blended is preferably 5 to 40% by weight (hereinafter simply referred to as "%") of the total amount of the copolymerization components, and preferably 10 to 35%.
When the amount of the monomer (A-1) blended is less than 5%, the acid resistance of the coating film formed using the obtained curable composition tends to be insufficient, and 40% is required. If it exceeds, the storage stability of the curable composition tends to decrease.

Examples of the monomer (A-2) include 2-hydroxyethyl (meth) acrylate, 1-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl vinyl ether and N-methylol. (Meth) acrylamide, Aronix 5700 (Toa Gosei Chemical Industry Co., Ltd.)
Manufactured), 4-hydroxystyrene, HE-10, HE-2
0, HP-1, HP-20, etc. Acrylic ester oligomers having a hydroxyl group at the terminal (above, manufactured by Nippon Shokubai Chemical Co., Ltd.), Blemmer PP series, (polypropylene glycol methacrylate), Blemmer PE series (polyethylene glycol mono). Methacrylate),
Blemmer PEP series (polyethylene glycol polypropylene glycol methacrylate), Blemmer AP-400 (polypropylene glycol monoacrylate), Blemmer AE-350 (polyethylene glycol monoacrylate), Blemmer NKH-5050.
Compounds such as (polypropylene glycol polytrimethylene monoacrylate) and Bremmer GLM (glycerol monomethacrylate) (above, NOF Corporation)
Manufactured), and an ε-caprolactone-modified hydroxyalkylvinyl copolymerizable compound obtained by the reaction of a hydroxyl group-containing vinyl compound and ε-caprolactone.

Typical examples of the ε-caprolactone-modified hydroxyalkylvinyl copolymerizable compound include, for example, the general formula (IX):

[Chemical 17] (In the formula, R ⁸ represents a hydrogen atom or a methyl group, r represents an integer of 1 or more), for example, Placcel F
A-1 (R ⁸ represents a hydrogen atom, r represents 1), Placc
el FA-4 (R ⁸ represents a hydrogen atom, r represents 4), P
laccel FM-1 (R ⁸ is a methyl group, r is 1), Placcel FM-4 (R ⁸ is a methyl group, r
Indicates 4) (above, manufactured by Daicel Chemical Industries, Ltd.); T
ONE M-100 (R ⁸ is a hydrogen atom, r is 2), TONE M-201 (R ⁸ is a methyl group, r is 1)
(These are manufactured by UCC) and the like.

The above-mentioned monomer (A-2) can be used alone or as a mixture of two or more kinds. Among these, the acid resistance of the coating film formed by using the curable composition obtained can be used. And from the viewpoint of excellent water resistance, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and ε-caprolactone-modified hydroxyalkylvinyl copolymerizable compound are preferable, and 2-hydroxypropyl (meth) is particularly preferable. Acrylate is preferred.

The amount of the monomer (A-2) blended is preferably 5 to 50%, and more preferably 7 to 35% of the total amount of the copolymerization components. When the content of the monomer (A-2) is less than 5%, the resulting composition tends not to exhibit sufficient curability, and when it exceeds 50%, the curable composition is The water resistance and acid resistance of the coating film formed by using it tend to be reduced.

Examples of the monomer (A-3) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and stearyl ( (Meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, trifluoroethyl (meth) acrylate,
Pentafluoropropyl (meth) acrylate, perfluorocyclohexyl (meth) acrylate, (meth)
Acrylonitrile, glycidyl (meth) acrylate,
Dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) acrylamide, α-ethyl (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth)
Acrylamide, N-butoxymethyl (meth) acrylamide, macromonomers AS-6, AN-6, A
Compounds such as A-6, AB-6, AK-5 (above, manufactured by Toagosei Kagaku Kogyo Co., Ltd.), α, β-ethylenically unsaturated carboxylic acids such as hydroxyalkyl esters of (meth) acrylic acid Phosphate ester group-containing vinyl compounds such as condensation products of hydroxyalkyl esters and phosphoric acid or phosphoric acid esters, (meth) acrylic acid derivatives such as (meth) acrylate containing urethane bond or siloxane bond, and styrene , Α-Methylstyrene, chlorostyrene, styrenesulfonic acid, 4-hydroxystyrene, vinyltoluene and other aromatic hydrocarbon vinyl compounds; maleic acid, fumaric acid, itaconic acid and other unsaturated carboxylic acids, and their alkali metal salts , Ammonium salts, salts such as amine salts; acid anhydrides of unsaturated carboxylic acids such as maleic anhydride, Unsaturated carboxylic acid esters such as diesters or half-esters of these with linear or branched alcohols having 1 to 20 carbon atoms; vinyl esters such as vinyl acetate, vinyl propionate, diallyl phthalate and allyl compounds; Vinyl pyridine,
Amino group-containing vinyl compounds such as aminoethyl vinyl ether; amide group-containing vinyl compounds such as itaconic acid diamide, crotonamide, maleic acid diamide, fumaric acid diamide, N-vinylpyrrolidone; methyl vinyl ether, cyclohexyl vinyl ether, vinyl chloride, chloride Vinylidene, chloroprene, propylene, butadiene, isoprene, fluoroolefin maleimide,
Other vinyl compounds such as N-vinyl imidazole and vinyl sulfonic acid may be mentioned, and these may be used alone or in admixture of two or more by appropriately adjusting the compounding amount thereof.

In the present invention, when a polar monomer having an amine, carboxylic acid, sulfonic acid or phosphoric acid group is used among the monomers (A-3), the crosslinking reaction at the time of polymerization is suppressed. Therefore, it is desirable that the blending amount be 5% or less of the total amount of the copolymerization components.

Further, in the present invention, for the purpose of improving the weather resistance, solvent resistance, impact resistance and the like of the coating film formed by using the obtained curable composition, the obtained vinyl copolymer (A ), The segment formed by a urethane bond or a siloxane bond, or (meth)
The copolymerization component may be adjusted so that the segment derived from the monomer (A-3) other than the acrylic acid derivative is contained in the main chain of the copolymer.

The vinyl-based copolymer (A) used in the present invention includes the monomer (A-1) and the monomer (A-
2), a copolymerization component containing a monomer (A-3) and the like, for example, JP-A-54-36395 and JP-A-57.
Although it can be produced by the method described in JP-A-55954, etc., it can be produced by a solution polymerization method using an azo radical polymerization initiator such as azobisisobutyronitrile from the viewpoint of ease of synthesis. Particularly preferred.

The polymerization solvent used in the solution polymerization method is
It is not particularly limited as long as it is non-reactive, but for example, hydrocarbons such as toluene, xylene, n-hexane and cyclohexane; acetic acid esters such as ethyl acetate and butyl acetate; methanol, ethanol, isopropanol, n -Alcohols such as butanol; ethers such as ethyl cellosolve, butyl cellosolve, cellosolve acetate; methyl ethyl ketone, ethyl acetoacetate,
Ketones such as acetylacetone, diacetone alcohol, methyl isobutyl ketone, acetone and the like can be mentioned.

The above-mentioned polymerization solvent may be used alone or in combination of two or more kinds, but the total amount of the copolymerization components is 100.
If the amount of alcohols such as methanol and butanol in the composition of the polymerization solvent is less than 1 part, gelation may occur during polymerization. It is preferable to adjust so that 1 to 30 parts of alcohols are contained in 100 parts of the total amount.

In the solution polymerization, if necessary, for example, n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butyl mercaptan, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane, (CH ₃ O) ₃ Si—S—S—Si
_{(OCH 3) 3, (CH} 3 O) 3 Si-S 8 -Si (O
The molecular weight of the resulting vinyl-based copolymer (A) can be adjusted by using a chain transfer agent such as CH ₃ ) ₃ alone or in combination of two or more. In particular, when a chain transfer agent having an alkoxysilyl group such as γ-mercaptopropyltrimethoxysilane in the molecule is used, the alkoxysilyl group should be introduced at the end of the main chain of the vinyl copolymer (A). Is preferable because it can The amount of the chain transfer agent used is 0.1 to 1 of the total amount of the copolymerization components.
It is preferably about 0%.

The vinyl copolymer (A) thus obtained
Can be used alone or in combination of two or more,
Further, the number average molecular weight of the vinyl-based copolymer (A) is that the resulting curable composition has excellent thermosetting properties, and the coating film formed using the composition has excellent physical properties such as durability. To 1,000 to 30,000,
It is more preferably 2,000 to 25,000, further preferably 3,000 to 12,000.

Component (B) The carboxyl group-containing acrylic copolymer (B) used in the present invention is a component used to develop recoat adhesion, and its main chain is substantially an acrylic copolymer. Since it is composed of chains, the weather resistance, chemical resistance, water resistance and the like of the cured product are improved.

The acrylic copolymer (B) having a carboxyl group is, for example, a carboxyl group-containing vinyl monomer (B-1) which is a carboxyl group-containing monomer unit having a polymerizable unsaturated double bond in the molecule, It can be obtained by copolymerization of a derivative of acrylic acid or methacrylic acid (B-2).

In particular, the component (B) contains the carboxyl group-containing vinyl monomer (B-1) in an amount of 0.1 to 95%,
A polymer containing 1 to 30% is preferable.

When the above ratio is less than 0.1%, the effect of improving the recoat adhesion tends to be small, and 95
If it exceeds%, the storage stability tends to decrease.

The carboxyl group-containing vinyl monomer (B-1) contained as the copolymerization component is, for example,

[Chemical 18] Alternatively, among them, a dicarboxylic acid and 1 to 2 carbon atoms
Other compounds such as unsaturated carboxylic acids such as half esters with 0 straight or branched alcohols are mentioned.

Acrylic acid or methacrylic acid derivative (B
-2) is not particularly limited, and specific examples thereof include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, benzyl ( (Meth) acrylate, cyclohexyl (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, perfluorocyclohexyl (meth) acrylate, (meth) acrylonitrile, glycidyl (meth) acrylate, dimethylaminoethyl (meth) ) Acrylate, diethylaminoethyl (meth) acrylate, (meth) acrylamide, α-ethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N,
N-dimethylacrylamide, N-methylacrylamide, acryloylmorpholine, Toagosei Chemical Industry Co., Ltd.
Manufactured macromers AS-6, AN-6, AA-6,
Examples thereof include AB-6, AK-5, and (meth) acrylate having a urethane bond or a siloxane bond.

The carboxyl group-containing copolymer (B) may contain a segment formed by a urethane bond or a siloxane bond in the main chain within a range not exceeding 50%, and a (meth) acrylic acid derivative Other monomers (B
-3) The segment derived from may be included.

The monomer (B-3) is not limited,
Specific examples thereof include aromatic hydrocarbon vinyl compounds such as styrene, α-methylstyrene, chlorostyrene, styrenesulfonic acid, and vinyltoluene; vinyl esters such as vinyl acetate, vinyl propionate, and diallyl phthalate, and allyl compounds. Amino group-containing vinyl compounds such as vinyl pyridine and aminoethyl vinyl ether; amide group-containing vinyl compounds such as itaconic acid diamide, crotonamide, maleic acid diamide, fumaric acid diamide and N-vinylpyrrolidone; methyl vinyl ether, cyclohexyl vinyl ether, chloride Vinyl, vinylidene chloride, chloroprene, propylene, butadiene, isoprene, fluoroolefin maleimide, N-
Other vinyl compounds such as vinyl imidazole and vinyl sulfonic acid may be mentioned.

The acrylic resin having a carboxyl group is
It is preferably produced by a solution polymerization method using an azo radical initiator such as azobisisobutyronitrile for ease of synthesis.

In the solution polymerization, n-dodecyl mercaptan, t-dodecyl mercaptan, n-
The molecular weight can be adjusted by using a chain transfer agent such as butyl mercaptan.

Polymerization solvents used in the solution polymerization include hydrocarbons (toluene, xylene, n-hexane, cyclohexane, etc.), acetic acid esters (ethyl acetate, butyl acetate, etc.), alcohols (methanol, ethanol, etc.).
Non-reactive solvents such as isopropanol, n-butanol, etc.), ethers (ethyl cellosolve, butyl cellosolve, cellosolve acetate etc.), ketones (methyl ethyl ketone, ethyl acetoacetate, acetylacetone, diacetone alcohol, methyl isobutyl ketone, acetone etc.) So long as it is not limited.

There is no particular limitation on the molecular weight of the acrylic copolymer (B) having a carboxyl group, and any commonly used one can be used, but from the viewpoint of the physical properties of the coating film such as durability, it may be several. Average molecular weight is 1,500-40,000
Is preferred, 3,000 to 25,000 is more preferred, and 4,000 to 15,000 is more preferred.

The acid value is 30 to 500 mg KOH /
g, and more preferably 50 to 200 mgKOH / g is preferable from the viewpoint of recoat adhesion and curability.

The mixing ratio of the vinyl copolymer (A) and the carboxyl group-containing acrylic copolymer (B) is (A).
The component (B) is 1 to 100 parts, preferably 1 to 50 parts, and more preferably 2 to 30 parts with respect to 100 parts of the component, from the viewpoint of coating physical properties such as recoat adhesion, durability and water resistance. preferable.

Component (C) As the curing catalyst (C) used in the present invention, for example, dibutyltin dilaurate, dibutyltin dimaleate,
Organotin compounds such as dioctyl tin dilaurate, dioctyl tin dimaleate, tin octylate; phosphoric acid,
Phosphoric acid or phosphate such as monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monooctyl phosphate, monodecyl phosphate, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, didecyl phosphate; propylene oxide, butylene oxide, cyclohexene Oxide, glycidyl methacrylate, glycidol, acrylic glycidyl ether, γ-glycidoxypropyltrimethoxysilane, γ
-Glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, formula:

[Chemical 19] Compound represented by, Cardura E, Epikote 82
8, an addition reaction product of an epoxy compound such as Epikote 1001 (all manufactured by Yuka Shell Epoxy Co., Ltd.) with phosphoric acid and / or a monophosphate ester; isopropyltriisostearoyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, Organic titanate compounds such as bis (dioctyl pyrophosphate) oxyacetate titanate; organoaluminum compounds such as tris (ethylacetoacetate) aluminum and tris (acetylacetonato) aluminum; maleic acid, adipic acid, azelaic acid, sebacic acid, itaconic acid Saturated or unsaturated polycarboxylic acids such as citric acid, succinic acid, phthalic acid, trimellitic acid and pyromellitic acid and their acid anhydrides; dodecylbenzene sulfonic acid, paratol Acidic compounds such as Nsuruhon acid; hexylamine, di-2-ethylhexylamine,
N, N-dimethyldodecylamine, dodecylamine, D
Amines such as ABCO, DBU, morpholine, diisopropanolamine; reaction products of these amines with acidic phosphate esters or acidic compounds, eg KING
INDUSTRIES (King Industries)
NACURE 5225, NACURE 554
3, NACURE 5925; alkaline compounds such as sodium hydroxide and potassium hydroxide, organic zirconium compounds such as tetrabutyl zirconate, tetrakis (acetylacetonato) zirconium, butoxytris (acetylacetonato) zirconium, and the like,
These may be used alone or in combination of two or more.

Among the curing catalysts, organotin compounds,
Acidic phosphoric acid ester, reaction product of the acidic phosphoric acid ester and amines, saturated or unsaturated polyvalent carboxylic acid, acid anhydride of the polyvalent carboxylic acid, acidic compound, reaction product of the acidic compound and amines , Organic titanate compounds, organic aluminum compounds, organic zirconium compounds, and mixtures thereof are preferable from the viewpoint of high curing activity.

By stirring and mixing the vinyl copolymer (A), the carboxyl group-containing acrylic copolymer (B) and the curing catalyst (C) with a stirrer or the like so as to obtain a uniform composition. The curable composition for a top coating composition of the present invention can be obtained.

The mixing ratio of the vinyl copolymer (A) and the curing catalyst (C) is such that the vinyl copolymer (A) 1
0.001-10 parts of the curing catalyst (C) with respect to 00 parts,
It is preferably 0.05 to 10 parts. When the amount of such a curing catalyst is less than 0.001 part, the curability of the resulting composition is lowered, and when it exceeds 10 parts, the curable composition is formed. The appearance of the coated film is deteriorated.

In the coating composition of the present invention, in addition to the vinyl-based copolymer (A), the carboxyl group-containing acrylic copolymer (B) and the curing catalyst (C), substantially no carboxyl group is contained. It was found that by further blending the acrylic resin (D) and amino resin (E) having a hydroxyl group, the curability was increased and the effect of further improving the scratch resistance was obtained.

Component (D) The acrylic resin (D) which does not substantially contain a carboxyl group and has a hydroxyl group includes, for example, a hydroxyl group-containing vinyl monomer (D-1) and a derivative of acrylic acid or methacrylic acid (D- It can be obtained by copolymerization with 2) or the like.

The hydroxyl group-containing vinyl monomer (D-1) contained as the copolymerization component is, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl vinyl ether, N-. Methylol (meth) acrylamide, Aronix 5700 manufactured by Toagosei Kagaku Kogyo Co., Ltd.,
4-hydroxystyrene, HE-10, HE-20, HP-10 and HP-20 manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.
(Acrylic ester oligomer having a hydroxyl group at each end), NOF CORPORATION, BLEMMER PP series (polypropylene glycol methacrylate), BLEMMER PE series (polyethylene glycol monomethacrylate), BLEMMER PEP series (polyethylene glycol polypropylene glycol methacrylate) , Bremmer AP-400 (polypropylene glycol monoacrylate), Bremmer AE-350 (polyethylene glycol monoacrylate), Bremmer NKH-5050 (polypropylene glycol polytrimethylene monoacrylate) and Bremmer GLM.
(Glycerol monomethacrylate), ε-caprolactone-modified hydroxyalkyl vinyl-based monomer obtained by reacting a hydroxyl group-containing vinyl compound with ε-caprolactone, and the like.

Typical examples of the above-mentioned ε-caprolactone-modified hydroxyalkylvinyl-based monomer include those represented by the formula:

[Chemical 20] (Wherein R is H or CH ₃ , and n is an integer of 1 or more) and has a structure represented by Daicel Chemical Industries, Ltd.
Placcel FA-1 (R = H, n = 1), P
laccel FA-4 (R = H, n = 4), Plac
_{cel FM-1 (R = CH} 3, n = 1) and Pla
ccel FM-4 (R = CH ₃ , n = 4), UCC
Ltd. of TONE M-100 (R = H , n = 2) and _{TONEM201 (R = CH 3, n} = 1) , and the like. As the hydroxyl group-containing vinyl monomer, especially ε
-By using a caprolactone-modified hydroxyalkylvinyl-based monomer, impact resistance and flexibility of the coating film can be improved.

These hydroxyl group-containing vinyl monomers (D-
1) may be used alone or in combination of two or more.

The acrylic acid or methacrylic acid derivative (D-2) copolymerizable with the hydroxyl group-containing vinyl monomer is not particularly limited, and specific examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, and the like.
Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate,
Benzyl (meth) acrylate, cyclohexyl (meth) acrylate, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, perfluorocyclohexyl (meth) acrylate, (meth) acrylonitrile, glycidyl (meth) acrylate, dimethylaminoethyl (Meth) acrylate, diethylaminoethyl (meth) acrylate, (meth) acrylamide, α-ethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-
Dimethyl acrylamide, N-methyl acrylamide,
Acryloylmorpholine, N-methylol (meth) acrylamide, macromer AS-6, AN-6, AA-6, AB-6, AK- manufactured by Toagosei Kagaku Kogyo Co., Ltd.
5. Phosphate ester group-containing vinyl system which is a condensation product of hydroxyalkyl esters of α, β-ethylenically unsaturated carboxylic acids such as hydroxyalkyl esters of (meth) acrylic acid with phosphoric acid or phosphoric acid esters Compound, including urethane bond and siloxane bond (meta)
Examples thereof include acrylate.

The copolymer may contain a segment formed by a urethane bond or a siloxane bond in the main chain within a range not exceeding 50% and is derived from a monomer other than the (meth) acrylic acid derivative. The segment may be included. The monomer is not limited, and specific examples thereof include aromatic hydrocarbon vinyl compounds such as styrene, α-methylstyrene, chlorostyrene, styrenesulfonic acid and vinyltoluene; maleic acid, fumaric acid and itaconic acid. Unsaturated carboxylic acids such as, their salts (alkali metal salts, ammonium salts, amine salts, etc.),
Esters of unsaturated carboxylic acids such as their acid anhydrides (maleic anhydride, etc.) or diesters or half esters thereof with linear or branched alcohols having 1 to 20 carbon atoms; vinyl acetate, vinyl propionate, Vinyl esters and allyl compounds such as diallyl phthalate; vinyl group-containing vinyl compounds such as vinyl pyridine and aminoethyl vinyl ether; itaconic acid diamide crotonamide, maleic acid diamide, fumaric acid diamide,
Amide group-containing vinyl compounds such as N-vinylpyrrolidone; other vinyls such as methyl vinyl ether, cyclohexyl vinyl ether, vinyl chloride, vinylidene chloride, chloroprene, propylene, butadiene, isoprene, fluoroolefin maleimide, N-vinyl imidazole and vinyl sulfonic acid. System compounds and the like.

The acrylic resin (D) having a hydroxyl group is preferably produced by a solution polymerization method using an azo radical initiator such as azobisisobutyronitrile for ease of synthesis.

In solution polymerization, n-dodecyl mercaptan, t-dodecyl mercaptan, n-
The molecular weight can be adjusted by using a chain transfer agent such as butyl mercaptan.

The polymerization solvent is not particularly limited as long as it is a non-reactive solvent. The acrylic resin (D) having a hydroxyl group may be a non-aqueous dispersion type in which insoluble polymer particles are dispersed in a non-polar organic solvent such as heptane or pentane.

There is no particular limitation on the molecular weight of the acrylic resin (D) having a hydroxyl group, and any conventionally used one can be used, but the coating film physical properties such as durability (formed from the composition of the present invention From the viewpoint of the physical properties of the coating film), the number average molecular weight is preferably 1,500 to 40,000,
More preferably, it is 3,000 to 25,000.

Further, it preferably has a hydroxyl group capable of being sufficiently crosslinked, and the hydroxyl value is preferably 10 to 300 mgKOH / g, and 30 to 150 mgKOH / g from the viewpoint of coating film physical properties such as strength and durability. Is more preferable.

The acrylic resin (D) having such a hydroxyl group may be used alone or in combination of two or more. When the component (D) is used, its mixing ratio is not particularly limited, but it is preferable to mix 5 to 50 parts with respect to 100 parts of the component (A). If the blending ratio is less than 5 parts, the effect of imparting heat curability tends to be small, and if it exceeds 50 parts, the water resistance tends to be reduced.

Component (E) The amino resin (E) is obtained by reacting an amino compound such as melamine, urea or benzoguanamine with an aldehyde such as formaldehyde or paraformaldehyde. Further, those obtained by reacting these methylolated amino resins with alcohol to be etherified can be used.
As the amino resin (E), commercially available amino resins with trade names such as Cymel 235 (manufactured by Mitsui Cyanamid Co., Ltd.) and U-Van 20SE-60 (manufactured by Mitsui Toatsu Co., Ltd.) can be used.

When the above component (E) is used,
The mixing ratio is not particularly limited, but it is preferable to mix 0.5 to 20 parts with respect to 100 parts of the component (A). If the mixing ratio is less than 0.5 part, the effect of imparting the heat-curing property tends to be small, and if it exceeds 20 parts, the acid resistance tends to decrease.

[0073] Other Incidentally, when it is intended to lower the viscosity of the top coat paint for the curable composition of the present invention, tetraalkoxysilane and alkyltrialkoxysilane, and a partial hydrolyzate thereof, a vinyl copolymer It may be added in an amount of preferably 50 parts or less, more preferably 30 parts or less with respect to 100 parts of (A).

Further, the curable composition of the present invention contains an acrylic polyol, a polycarbonate diol, an acrylic polyol, a polycarbonate diol, in order to improve the thermosetting property of the composition and the impact resistance of the coating film formed by using the composition. For the hydroxyl group-containing polymer compound such as polyester diol, the molar ratio of the alcoholic hydroxyl group to the hydrolyzable silyl group (alcoholic hydroxyl group / hydrolyzable silyl group) should be in the range of 0.1 to 3. You may mix.

By adding a dehydrating agent and a solvent to the curable composition of the present invention, the storage stability of the curable composition can be further improved.

Examples of the dehydrating agent include ester compounds such as methyl orthoformate, ethyl orthoformate, methyl orthoacetate, ethyl orthoacetate, ethyl silicate and methyl silicate, and hydrolyzable ester compounds such as methyltrimethoxysilane. These may be used alone or in admixture of two or more.

The dehydrating agent may be added during the polymerization of the vinyl copolymer (A) or after the polymerization,
If the amount of such a dehydrating agent is too large, in the coating film formed using the resulting curable composition,
Since there is a tendency for defects such as armpits (foaming phenomenon) to easily occur, 70% to 100 parts of the vinyl-based copolymer (A).
Parts or less, preferably 50 parts or less, more preferably 20 parts
It is desirable that the number is not more than a part.

Examples of the solvent include alkyl alcohols having an alkyl group having 1 to 10 carbon atoms, and specific examples thereof include methyl alcohol and the like.
Examples thereof include ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoamyl alcohol, hexyl alcohol and octyl alcohol.

The above-mentioned solvents such as alkyl alcohol can be used alone or in combination of two or more kinds, and the compounding amount is not particularly limited, but when it is too much,
In a coating film formed using the obtained curable composition, defects such as cracking (foaming phenomenon) tend to occur easily, so 70 parts or less is usually added to 100 parts of the vinyl copolymer (A). The amount is preferably 50 parts or less, more preferably 20 parts or less, and when the solvent is used alone without using the dehydrating agent, it is usually 0.5.
To 70 parts, preferably 1 to 50 parts, more preferably 2 parts.
It is desirable that the content is up to 20 parts.

By adding, for example, an ultraviolet absorber and a light stabilizer to the curable composition for top coating composition of the present invention, the weather resistance thereof can be further improved, and particularly by using these in combination, the weather resistance can be further improved. It is possible to improve the sex.

Examples of the ultraviolet absorber include benzophenone-based, triazole-based, phenyl salicylate-based, diphenyl acrylate-based, and acetophenone-based ones, which may be used alone or in combination of two or more. You can

Examples of the light stabilizer include bis (2,2
2,6-tetramethyl-4-piperidyl) sebacate,
Bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (1,2-bis (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate 2,2,6,6-pentamethyl-4-piperidyl), tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, tetrakis (1, 2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate and the like can be mentioned, and these can be used alone or in combination of two or more kinds.

The amount of the ultraviolet absorber compounded is usually 0.1 to 10 parts with respect to 100 parts of the resin solid content of the curable composition,
The content of the light stabilizer is preferably 0.1 to 10 parts, and preferably 1 to 5 parts, based on 100 parts of the resin solid content of the curable composition. Preferably there is.

Further, when the curable composition for top coating composition of the present invention is used as a clear coating composition, additives such as diluents, cissing inhibitors and leveling agents; fibrin compounds such as nitrocellulose and cellulose acetate butyrate. ; Epoxy resin, melamine resin, vinyl chloride resin,
Resins such as chlorinated polypropylene, chlorinated rubber, polyvinyl butyral and the like can be appropriately blended depending on the application.

The curable composition of the present invention has low toxicity,
It is also possible to adjust to a high solid having a resin solid content concentration of 50 to 70%. The curable composition of the present invention is applied to a substrate by a method such as spray coating, brush coating, roll coating or dip coating, and then cured by heating at about 80 to 160 ° C. to obtain acid resistance. It is possible to obtain a cured coating film having excellent chemical resistance, water resistance, weather resistance, scratch resistance, and appearance.

As described above, the curable composition for a top coating composition of the present invention exhibits excellent water resistance, abrasion resistance, appearance and thermosetting property, and at the same time exhibits extremely excellent acid resistance. For example, it can be suitably used as a top coat paint used for automobiles, industrial machines, steel furniture, interior and exterior of buildings, household appliances, plastics, etc., especially a top coat paint for automobiles.

[0087]

EXAMPLES Next, the curable composition for top coating composition of the present invention will be explained in more detail based on examples, but the present invention is not limited to these examples.

Production Examples 1 to 3 (of the vinyl-based copolymer (A))
Production) 26 parts of Solvesso 100 (manufactured by Exxon Chemical Co., Ltd., petroleum-based aromatic solvent) was charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen gas introduction pipe and a dropping funnel,
After introducing nitrogen gas and raising the temperature to 110 ° C., [Table 1]
Copolymerization component having the composition shown in the above, 2.75 parts of 2,2'-azobisisobutyronitrile, Solvesso 100 (see above)
A mixture of 3.5 parts and 2 parts of methanol was added dropwise from the dropping funnel at a constant rate over 4 hours.

After the addition of the mixture was completed, 0.25 parts of 2,2'-azobisisobutyronitrile and 10 parts of xylene were added at a constant rate over 30 minutes, polymerization was carried out for 1 hour and 30 minutes, and then the mixture was cooled. Methyl orthoacetate (4 parts) and methanol (4 parts) were added, and further 100 parts of Solvesso was added to the resin solution to adjust the resin solid content concentration to 60% to obtain a solution of the vinyl copolymer (A).

The number average molecular weight and the hydrolyzable silyl group equivalent (g / mol) of the obtained vinyl copolymer (A),
The values of the alcoholic hydroxyl group equivalent (g / mol) and the molar ratio of the alcoholic hydroxyl group and the hydrolyzable silyl group (alcoholic hydroxyl group / hydrolyzable silyl group) are also shown in [Table 1]. The abbreviations of the vinyl copolymers (A) are also shown in [Table 1].

[0091]

[Table 1]

Production Examples 4 to 5 (carboxyl group-containing acrylate)
(Production of copolymer (B)) Solvesso 100 (manufactured by Exxon Chemical Co., Ltd., petroleum-based aromatic solvent) was placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen gas introducing pipe and a dropping funnel Part, n-butanol 10 parts were charged, and 100 ° C while introducing nitrogen gas.
After the temperature was raised to 2, a copolymerization component having the composition shown in [Table 2], 2,
A mixture of 4.75 parts of 2'-azobisisobutyronitrile, 13.5 parts of Solvesso 100 (see above), and 6 parts of n-butanol was added dropwise at a constant rate over 5 hours from a dropping funnel.

After the dropping of the mixture, 0.25 parts of 2,2'-azobisisobutyronitrile and 10 parts of toluene were added dropwise at a constant rate over 1 hour.

After completion of the dropping, the mixture was aged at 100 ° C. for 2 hours and then cooled, and Solvesso 100 was added to the resin solution to adjust the resin solid content concentration to 60% to obtain a carboxyl group-containing acrylic copolymer (B). Obtained. The characteristics of the obtained resin solution are shown in [Table 2].

Production Example 6 (activities containing no carboxyl group)
Production of ril copolymer (B ′)) Solvesso 100 (manufactured by Exxon Chemical Co., petroleum-based aromatic solvent) was placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen gas inlet tube and a dropping funnel. 17 parts and 10 parts of n-butanol were charged, and 100 ° C while introducing nitrogen gas.
After the temperature was raised to 2, a copolymerization component having the composition shown in [Table 2], 2,
A mixture of 4.75 parts of 2'-azobisisobutyronitrile, 13.5 parts of Solvesso 100 (see above) and 6 parts of n-butanol was added dropwise at a constant rate through a dropping funnel over 5 hours.

After the addition of the mixture was completed, 0.25 parts of 2,2'-azobisisobutyronitrile and 10 parts of toluene were added dropwise at a constant rate over 1 hour.

After completion of dropping, the mixture was aged at 100 ° C. for 2 hours and then cooled, and Solvesso 100 was added to the resin solution to adjust the resin solid content concentration to 60%, and the carboxyl group-free acrylic copolymer (B I got ´). The characteristics of the obtained resin solution are also shown in [Table 2].

Production Example 7 (acrylic resin having a hydroxyl group
(Production of (D) ) 17 parts of Solvesso 100 (manufactured by Exxon Chemical Co., petroleum-based aromatic solvent) in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen gas introducing pipe and a dropping funnel, n- Charge 10 parts butanol and introduce nitrogen gas to 100 ℃
After the temperature was raised to 2, a copolymerization component having the composition shown in [Table 2], 2,
A mixture of 4.75 parts of 2'-azobisisobutyronitrile, 13.5 parts of Solvesso 100 (see above) and 6 parts of n-butanol was added dropwise at a constant rate through a dropping funnel over 5 hours.

After the addition of the mixture was completed, 0.25 parts of 2,2'-azobisisobutyronitrile and 10 parts of toluene were added dropwise at a constant rate over 1 hour.

After the dropping was completed, the mixture was aged at 100 ° C. for 2 hours and then cooled, and Solvesso 100 was added to the resin solution to adjust the resin solid content concentration to 60% to obtain a hydroxyl group-containing acrylic resin (D). . The characteristics of the obtained resin solution are also shown in [Table 2].

[0101]

[Table 2]

Examples 1 to 7 and Comparative Examples 1 to 4 Vinyl type copolymers (A) obtained in Production Examples 1 to 6, carboxyl group-containing acrylic copolymer (B) or acrylic group containing no carboxyl group. The polymer (B '), the acrylic resin (D) having a hydroxyl group, and the amino resin (E) were blended so as to have the composition shown in [Table 3], and to 100 parts of the resin solid content of the component (A), 0.4 parts of a leveling agent (Disbaron # 1984-50, manufactured by Kusumoto Kasei Co., Ltd.),
A mixture of dodecylbenzene sulfonic acid and diisopropanolamine (equivalent ratio) as 2 parts of Tinuvin 384 (manufactured by Ciba Geigy) as an ultraviolet absorber, 1 part of Tinuvin 123 (manufactured by Ciba Geigy) as a light stabilizer, and 1 part of a curing catalyst (C). : Dodecylbenzenesulfonic acid / diisopropanolamine = 1 / 1.03) 1 part was added.

This was diluted with Solvesso 100 (Petroleum aromatic solvent manufactured by Exxon Chemical Co., Ltd.)
A clear paint for a top coat was prepared by adjusting the viscosity with a 4 Ford cup to be about 22 seconds.

[Evaluation of Thermosetting Property] Using the obtained clear coating material for top coat, the gel fraction was examined according to the following method. The results are shown in [Table 3].

(A) Gel Fraction Baking a clear paint for top coat at 140 ° C. for 30 minutes to cut a free clear film, and pre-weighed a 200-mesh stainless wire gauze (W ₀ ).
It was wrapped in and weighed (W ₁ ). This was immersed in acetone for 24 hours for extraction, then dried and precisely weighed (W ₂ ), and the gel fraction (%) was determined based on the following formula. Gel fraction _{(%) = {(W 2} -W 0) / (W 1 -W 0)}
× 100

[Evaluation of Acid Resistance, Scratch Resistance, Warm Water Resistance, and Appearance] Next, a mild steel sheet that had been degreased and phosphorylated was treated with an epoxy amide-based cationic electrodeposition primer for automobiles and an intermediate coating surfacer. The painted coated plate was used as a test piece, and an acrylic melamine resin paint (black) was applied as a base coat on the surface thereof. Next, after applying the above clear coating for top coat wet-on-wet and setting for 10 minutes, 140 ° C
And baked for 30 minutes to form a coating film. The dry film thickness of the obtained coating film was about 15 μm for the base coat and about 30 to 40 μm for the top coat clear. The obtained coating film was examined for acid resistance, scratch resistance, warm water resistance, appearance and recoat adhesion according to the following methods. The results are shown in [Table 3].

(B) Acid resistance Using a pipette, 4 drops of 40% sulfuric acid aqueous solution was dropped on the coating film and heated at 70 ° C. for 30 minutes, and then the sulfuric acid aqueous solution was washed off with water to see how the coating surface changed. It was visually observed and evaluated based on the following evaluation criteria. <Evaluation Criteria> 10 points: No change compared to before dropping 9 points: A slight change is recognized 8 points: Circular marks remain 7 points: Discoloration or swelling is slightly recognized 6 points: Gloss Is slightly observed or a discoloration is observed 5 points: A decrease in gloss or a discoloration is clearly observed 4 points: A slight shrinkage or a clear blistering is observed 3 points: A slight lifting or a sharp shrinkage or a discoloration is observed 2 Point: Lifting is clearly observed. 1 point: Dissolution of coating film is observed.

(C) Scratch resistance The test piece on which the coating film was formed was fixed horizontally, and an abrasive (JIS 8 type ROHM 1.2%, JIS 11 type ROHM 1.2%, kaolin 0) was placed on the coating film. .6%, a mixture of 1% neutral detergent and 96% water), after applying about 0.05 g / cm ²
Weight covered with kraft paper (contact surface diameter: 5 cm, load:
22 g / cm ² ) was stroked over the surface. Gloss meter (manufactured by Murakami Color Research Laboratory Co., Ltd.) to measure the 20 ° gloss on the surface of the coating film before the weight is stroked and after 20 strokes.
The gloss retention rate (%) after 20 strokes was calculated based on the following formula. Gloss retention (%) = (Gloss value after stroke / Gloss value before stroke) × 100 Note that the larger the value of the gloss retention is, the more excellent the scratch resistance is.

(D) Warm water resistance The coated plate was immersed in warm water of 40 ° C. for 240 hours and then taken out.
After washing with water, the state of the coating film was observed.

(E) Appearance Image clarity measuring instrument (ICM-1-DP type, manufactured by Suga Test Instruments Co., Ltd.,
The sharpness of the coating film was measured using a slit width of 0.5 mm). It should be noted that the larger the value of the image clarity is, the more excellent the appearance is.

[Evaluation of Recoat Adhesion] (f) Recoat Adhesion As a test piece, a mild steel sheet that had been degreased and phosphorylated was coated with an epoxyamide-based cationic electrodeposition primer for automobiles and an intermediate coat surfacer. Used,
Acrylic melamine resin paint (black) was applied as a base coat on the surface. Next, apply the clear paint for the top coat wet-on-wet to 10
After setting for 1 minute, it was baked at 160 ° C. for 30 minutes to form a coating film. The dry film thickness of the obtained coating film is about 15 μm for the base coat and about 30 for the top coat clear.
Was about 40 μm. Acrylic melamine resin paint (black) is applied as a base coat on the above-mentioned coated object, and then the clear paint for top coat is wet-coated.
After coating on wet, setting for 10 minutes, baking was performed at 120 ° C. for 30 minutes to form a coating film.
The dry film thickness of the obtained coating film is about 15 μm for the base coat,
The top coat clear was 30 to 40 μm. The coated article after baking was tested by a cross cut test method according to JIS K5400. 25/25 was evaluated as 10 points and 0/25 was evaluated as 0 points. The results are also shown in [Table 3].

[0112]

[Table 3]

From the results shown in [Table 3], Examples 1 to
It can be seen that the coating films formed by using the coating material obtained in No. 7 are excellent in acid resistance and scratch resistance, and at the same time, are extremely excellent in recoat adhesion.

[0114]

The curable composition for a top coating composition of the present invention comprises:
While exhibiting excellent acid resistance, abrasion resistance, appearance and thermosetting properties, and exhibiting extremely excellent recoat adhesion, for example, automobiles, industrial machines, steel furniture, building interiors and exteriors, household appliances, It can be suitably used for top-coat paints used for plastics and the like.

Claims (10)

[Claims] 1. A compound represented by the general formula (I) wherein the main chain (A) consists essentially of a vinyl-based copolymer chain, and the main chain ends and / or side chains are bonded via carbon atoms (C): 1] (In the formula, R ¹ is a hydrogen atom, an alkyl group or an aryl group having 1 to 10 carbon atoms, and R ² is a hydrogen atom or 1 to 1 carbon atoms.
0 is a monovalent hydrocarbon group selected from the group consisting of an alkyl group, an aryl group and an aralkyl group, a is 0, 1 or 2, and has at least one hydrolyzable silyl group represented by 100 parts by weight of a vinyl-based copolymer having at least one alcoholic hydroxyl group at the main chain terminal and / or side chain and having an alcoholic hydroxyl group equivalent of 400 to 2,000 g / mol, (B) carboxyl group-containing acrylic Copolymer 1-100
Curable composition for topcoat paint, which comprises 0.001 to 10 parts by weight of (C) curing catalyst. 2. The curable composition according to claim 1, wherein the component (A) has a hydrolyzable silyl group equivalent of 380 to 30,000 g / mol. 3. The curable composition according to claim 1, wherein the component (A) has a hydrolyzable silyl group equivalent of 410 to 3,000 g / mol. 4. The curable composition according to claim 1, wherein the component (A) has a hydrolyzable silyl group equivalent of 450 to 1,500 g / mol. 5. The curable composition according to claim 1, wherein the alcoholic hydroxyl group equivalent of the component (A) is 600 to 1,800 g / mol. 6. The component (A) has an alcoholic hydroxyl group equivalent of 600 to 1,800 g / mol, a hydrolyzable silyl group equivalent of 450 to 1,500 g / mol, and a number average molecular weight of 3,000. The curable composition according to claim 1, wherein the component (B) has an acid value of 50 to 200 mgKOH / g and a number average molecular weight of 4,000 to 15,000. 7. The value of the molar ratio of the alcoholic hydroxyl group to the hydrolyzable silyl group (alcoholic hydroxyl group / hydrolyzable silyl group) in the component (A) is 0.1 to 3. The curable composition according to any one of 1. 8. The component (B) is a polymer containing 0.1 to 95% by weight of a carboxyl group-containing monomer unit having a polymerizable unsaturated double bond in the molecule.
The curable composition according to any one of 1. 9. The component (C) is an organic tin compound, an acidic phosphoric acid ester, an acidic phosphoric acid ester or a mixture or reaction product of an acidic compound and an amine, a saturated or unsaturated polyvalent carboxylic acid, a saturated or unsaturated polycarboxylic acid. The curable composition according to claim 1, which is an acid anhydride of a polycarboxylic acid, an organic titanate compound, an organic aluminum compound, an organic zirconium compound or a mixture thereof. 10. An acrylic resin (D) containing substantially no carboxyl group but a hydroxyl group, and an amino resin (E).
The curable composition according to any one of claims 1 to 9, further comprising: