JP2001081393A - Curable composition for top-coating coating material and coated material obtained by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition having an excellent balance of physical properties of coating film by making the composition include a specific resin, a vinyl-based copolymer and specified two kinds of compounds. SOLUTION: This composition comprises (A) a resin for a coating material composed of an acrylic resin containing an acid group/hydrocxy group, an acrylic resin containing an epoxy group/hydroxy group and a blocked isocyanate compound, (B) a vinyl-based copolymer containing a carbon atom-bonded hydrolyzable silyl group of formula I (R1 is H or the like; R2 is H or a monofunctional hydrocarbon such as a 6-10C aryl or the like; a is 0-2) at a main chain end and/or a side chain and an alcoholic hydroxy group at the main chain and/or the side chain has 1,500-4,000 g/mol alcoholic hydroxy group equivalent, (C) a silicon compound (partial hydrolyzate condensate) of formula II (R3 and R4 are each H or a monofunctional hydrocarbon such as a 1-10C alkyl or the like; b is 0 or 1) and (D) an oligomer compound which is obtained by half esterifying a polyol compound with an acid anhydride compound, contains two or more carboxy groups and has <=2,000 molecular weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curable composition for a top coat which is suitably used for, for example, automobiles, industrial machines, steel furniture, interior and exterior of buildings, home appliances, plastic products and the like, and uses the same. Related to painted objects. More specifically, the present invention relates to a paint and a coated material which exhibit excellent acid resistance, abrasion resistance, appearance properties, thermosetting properties, etc., and exhibit extremely excellent stain resistance, and which can be used particularly as a topcoat paint for automobiles. is there.

[0002]

2. Description of the Related Art Conventionally, paints mainly containing melamine resins such as alkyd melamine and acrylic melamine have been used for coating automobiles, industrial machines, steel furniture, interior and exterior of buildings, home appliances, plastic products and the like. Was.

[0003] However, paints mainly containing such melamine resins have the problem that harmful formaldehyde is generated during curing, and the cured coating film is poor in acid resistance, so that it is easily attacked by acid rain. In particular, the problem of acid rain caused by air pollution in recent years has become serious, and phenomena such as etching, whitening, and spots occurring in the coating film have been observed.

In order to solve the above problems, a blend of a vinyl copolymer having a hydrolyzable silyl group and an acrylic polyol, a vinyl monomer having a hydrolyzable silyl group and a vinyl monomer having an alcoholic hydroxyl group are used. There is a disclosure that a copolymer with a monomer is used for a coating material (Japanese Patent Laid-Open No.
No. 141952).

A blend of a vinyl copolymer having a hydrolyzable silyl group and an acrylic polyol, or a copolymer of a vinyl monomer having a hydrolyzable silyl group and a vinyl monomer having an alcoholic hydroxyl group. As a feature when using a polymer, since the hydrolyzable silyl group and the alcoholic hydroxyl group form a stable siloxane bond or siloxy bond and are cured, the coating is mainly made of a melamine resin such as acrylic melamine or alkyd melamine. A coating film having excellent acid resistance and weather resistance can be formed as compared with the case where it is used.

Another coating composition having excellent acid resistance is a block composition using a blocked isocyanate compound instead of at least a part of the melamine resin as a crosslinking resin (curing agent) for a hydroxyl group-containing acrylic resin. There is a disclosure of an isocyanate-curable coating (Japanese Patent Laid-Open No. 2-24)
No. 2867). The blocked isocyanate compound is obtained by blocking an isocyanate component with a blocking agent. Specifically, a diisocyanate such as hexamethylene diisocyanate (HDI) or an isocyanurate or an adduct thereof is used as an isocyanate component, and methyl ethyl ketoxime (MEKO) is most commonly used as a blocking agent. ing.

In the above-mentioned blocked isocyanate-cured coating material, an isocyanate component serving as a cross-linking resin reacts with a hydroxyl group of an acrylic resin to form a urethane bond that is strong against an acid. Can be. Since the isocyanate group is blocked, this paint has excellent storage stability of the paint. However, such blocked isocyanate compounds have fewer crosslinking points as compared with melamine resins, and thus have a problem that physical properties such as solvent resistance are reduced. Further, in the conventional blocked isocyanate compound, the blocking agent does not dissociate unless the temperature is relatively high at 140 ° C., and thus there is a problem in curability at a low temperature of about 120 ° C.

Separately, as a coating composition having excellent acid resistance, an acid / epoxy curable coating composed of an acrylic resin containing a carboxyl group in a molecule and an acrylic resin containing an epoxy group in a molecule is also known. Have been. That is,
Also in the case of this acid / epoxy curable coating, since a relatively strong ester bond is formed in the acid, a coating film excellent in acid rain resistance can be formed. Such an acid / epoxy curable paint is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-139653. However, since such an acid / epoxy curable paint cures in a wide temperature range, for example, when used as a clear top coat on a metallic base coat composed of a melamine resin curable paint, the curing balance with the base coat is poor, As a result, there is a problem that sharpness deteriorates. In addition, this paint
Since the reaction between the epoxy group and the carboxyl group proceeds to some extent even at room temperature, there is a problem that the storage stability of the paint is lacking.

In general, there are two types of finish coatings for automobiles: metallic color finishing and solid color finishing.

[0010] Of these, in the case of metallic color finishing, a method of applying a metallic base coat, then applying a clear paint of an acrylic melamine resin paint by a wet-on-wet method, and heating and curing by a two-coat one-bake method is generally used. Is being done.

On the other hand, in the case of solid color finishing,
An alkyd melamine resin paint is used, and a method of heating and curing by a one-coat one-bake method has been generally adopted.

Recently, requirements for various properties such as finished appearance, weather resistance, acid resistance, abrasion resistance, stain resistance and the like have become strict, and an acrylic melamine resin paint has been applied on a solid color finish. Such as a paint composed of a blend of a vinyl copolymer having a hydrolyzable silyl group and an acrylic polyol, or a paint composed of a vinyl copolymer having a hydrolyzable silyl group and an alcoholic hydroxyl group in the same molecule. A method of applying clear paint has been proposed.

However, even when the above-mentioned clear paint is used, the adhered dirt is hardly removed particularly in an urban area, and the tendency is more conspicuous especially in the case of a light-colored paint.
Improvements in stain resistance are desired in terms of aesthetics, ease of cleaning, and reduction in the number of cleanings. Further, even when a clear paint is applied on the solid color finish, a product satisfying various physical properties such as acid resistance, curability, stain resistance and storage stability has not been obtained.

[0014]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide excellent acid resistance,
In addition to exhibiting curability, the present invention proposes a curable composition for a topcoat that exhibits excellent balance of physical properties of the coating film such as appearance and hardness, and also exhibits extremely excellent stain resistance, and a coated article using the same. As an issue.

[0015]

The curable composition for a top coating composition of the present invention comprises (A) an acid / hydroxyl group-containing acrylic resin having a carboxyl group and a hydroxyl group in a molecule, and an epoxy group and a hydroxyl group. 100 parts by weight of a coating resin comprising an epoxy group / hydroxyl group-containing acrylic resin contained in a molecule and a blocked isocyanate compound, (B) the main chain is substantially composed of a vinyl copolymer chain, /
Or, in the side chain, the following general formula (1): (Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ² is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. A represents an integer of 0 to 2), and has at least one hydrolyzable silyl group bonded to a carbon atom represented by the following formula: And / or having at least one alcoholic hydroxyl group in the side chain, and having an alcoholic hydroxyl equivalent of 1500 to 40.
200 g / mole vinyl copolymer 15 to 100 parts by weight of, (C) the general formula ^{(2); (R 3 O} ) 4-b -Si-R 4 b (2) ( wherein, R ³ Is a hydrogen atom or a monovalent hydrocarbon group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group and an aralkyl group, and R ⁴ is a monovalent hydrocarbon group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group and an aralkyl group. A hydrocarbon group, b is an integer of 0 or 1) and / or a partial hydrolysis condensate thereof of 5 to 10
By weight, a molecular weight containing at least two carboxyl groups in one molecule obtained by subjecting (D) a polyol compound and an acid anhydride compound to a half-esterification reaction is 2,000.
And 1 to 10 parts by weight of the following oligomer compound.

The component (C) is preferably a tetraalkyl silicate and / or a partially hydrolyzed condensate thereof.

The coated article of the present invention is a coated article obtained by applying a topcoat clear paint to a coating surface on which a paint containing a metallic powder and / or a coloring pigment has been applied. A curable composition for a topcoat material according to any one of the above items 1 and 2, which is a main component.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Each component contained in the curable composition for a top coat of the present invention will be described. The form of the component (A) includes an acid group / hydroxyl group-containing acrylic resin containing a carboxyl group and a hydroxyl group in a molecule, an epoxy group / hydroxyl group-containing acrylic resin containing an epoxy group and a hydroxyl group, and a blocked isocyanate compound. Paint composition.

The acrylic resin containing an acid group and a hydroxyl group is a vinyl copolymer containing a carboxyl group and a hydroxyl group in a molecule, and forms one resin component of an acid / epoxy curable resin, and is formed from a blocked isocyanate compound. It forms a skeletal resin for the crosslinked resin. The acid / hydroxyl-containing acrylic resin has an acrylic vinyl monomer as a main component, and a monomer including a carboxyl-containing vinyl monomer and a hydroxyl-containing vinyl monomer. It is obtained by copolymerizing the components.

Here, as the acrylic vinyl monomer, acrylic acid such as methyl acrylate, n-butyl acrylate, isobutyl acrylate, lauryl acrylate, and 2-ethylbutyl acrylate have 1-2 carbon atoms.
4 alkyl esters, methyl methacrylate, n-
Butyl methacrylate, isobutyl methacrylate, 2
-C1-C24 alkyl esters of methacrylic acid, such as -ethylhexyl methacrylate, decyl methacrylate, and stearyl methacrylate. These acrylic vinyl monomers can be used alone or in an appropriate combination of two or more. However, among these, n-
A relatively lower acrylic ester of acrylic acid or methacrylic acid, such as butyl acrylate and n-butyl methacrylate, is generally suitably used.

As the monomer containing a carboxyl group, acrylic acid or methacrylic acid is generally used, but other ethylenically unsaturated carboxylic acids such as maleic acid, fumaric acid, crotonic acid and itaconic acid are used. Can be used. These monomers can be used alone or in an appropriate combination.

Further, examples of the hydroxyl group-containing monomer include hydroxyalkyl having 2 to 24 carbon atoms of acrylic acid or methacrylic acid such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate. Esters, N-methylolacrylamide, N
-C1-C1 of acrylic acid or methacrylic acid such as methylol methacrylamide, N-hydroxyethyl acrylamide, N-dihydroxyethyl methacrylamide, etc.
And 12 hydroxyalkylamides. And, these hydroxyl group-containing vinyl monomers may be any one of them.
The species can be used alone or in combination of two or more. However, among these, 2-hydroxyethyl methacrylate and the like are the most common and can be preferably used.

In addition to these monomers, aromatic vinyl monomers such as styrene and vinyltoluene, acrylonitrile, methacrylonitrile, acrylamide,
Vinyl-based non-functional monomers such as vinyl acetate can also be used in appropriate combination. For example, the use of styrene or vinyltoluene is preferable from the viewpoint of further increasing the acid resistance of the resin coating.

The acid group / hydroxyl group-containing acrylic resin obtained by copolymerizing these monomer components preferably has an average molecular weight (number average molecular weight) of about 500 to 50,000. More preferable average molecular weight is 1500 to 1500
It is about 0. If the average molecular weight is less than 500, it becomes difficult to form a sufficiently cured coating film, and if the average molecular weight exceeds 50,000, the solubility decreases, the viscosity of the coating material increases, and the workability deteriorates.

The acid value and the hydroxyl value of the acid / hydroxyl-containing acrylic resin can be appropriately determined according to the required coating film performance and the like. Generally, the acid value is 30 to 130.
(mgKOH / g) is preferred. If the acid value is less than 30, the crosslink density with the epoxy group / hydroxyl group-containing acrylic resin tends to be insufficient, and it is difficult to obtain practically sufficient coating film performance in terms of curability. Conversely, if the acid value exceeds 130, the resin viscosity becomes high, and the compatibility with the epoxy resin / hydroxyl group-containing acrylic resin and the blocked isocyanate compound decreases, which is not preferable. More preferably 60-1
It is about 10. The same applies to the hydroxyl group,
If this is too small, it is difficult to obtain a practically sufficiently cured coating film, and if the hydroxyl value is too high,
Compatibility with other resin components tends to decrease. Therefore, the hydroxyl value is preferably in the range of 10 to 100 (mgKOH / g).

The epoxy / hydroxyl-containing acrylic resin is
A vinyl copolymer containing an epoxy group and a hydroxyl group in the molecule, which forms the acid / epoxy curable resin with the above-mentioned acid group / hydroxyl group-containing acrylic resin, and cross-links with a blocked isocyanate compound in cooperation therewith. Form a resin. The epoxy group / hydroxyl group-containing acrylic resin is similar to the acid group / hydroxyl group containing acrylic resin except that a vinyl monomer containing an epoxy group is used instead of a vinyl monomer containing a carboxyl group. It is obtained by copolymerizing a monomer component having a vinyl vinyl monomer as a main component.

Here, epoxy group-containing vinyl monomers include glycidyl methacrylate, glycidyl acrylate, 3,4-epoxycyclohexyl acrylate,
In addition to acrylic monomers such as 3,4-epoxycyclohexyl methacrylate, for example, allyl glycidyl ether and the like can be mentioned. These epoxy group-containing vinyl monomers can be used alone or in appropriate combination. Generally, glycidyl (meth) acrylate is most commonly used.

The epoxy group / hydroxyl group-containing acrylic resin obtained by copolymerizing a monomer component containing the epoxy group-containing vinyl monomer has an average molecular weight (number average molecular weight) of an acid group / hydroxyl group-containing acrylic resin. As in the case of
It is preferable to be about 00 to 50,000. More preferably, it is in the range of 1500 to 15000. Here, one of the acid group / hydroxyl group-containing acrylic resin and the epoxy group / hydroxyl group-containing acrylic resin can have a relatively large molecular weight and a relatively small molecular weight. Thereby, the compatibility between the acrylic resins can be enhanced, and the mutual crosslinking reaction can be favorably performed.

The epoxy equivalent and the hydroxyl value of the epoxy / hydroxyl-containing acrylic resin can be appropriately determined in consideration of the correspondence with the acid / hydroxyl-containing acrylic resin. Generally, the epoxy equivalent is preferably about 200 to 1,000. That is, if the epoxy equivalent is too small, the reaction with the carboxyl group becomes locally excessive, and curing distortion may occur when the coating film is cured,
Conversely, if the epoxy equivalent is too large, the crosslinking density tends to be insufficient, and it is difficult to obtain practically sufficient curability of the coating film. Therefore, the epoxy equivalent is 200 to 100
0, more preferably 250 to 500. The epoxy equivalent is represented by the mass (g) of the resin containing 1 gram equivalent of epoxy group (molecular weight of resin per epoxy group). The hydroxyl value of the acrylic resin is preferably about the same as that of the acid / hydroxyl-containing acrylic resin, and more preferably in the range of 10 to 100.

In this acid / epoxy curable coating composition, the ratio of the acid group / hydroxyl group-containing acrylic resin and the epoxy group / hydroxyl group-containing acrylic resin is such that their carboxyl groups and epoxy groups are equivalent, that is, It is blended on the basis of a ratio such that the molar ratio (number ratio) of the carboxyl group contained in the acid group / hydroxyl group-containing acrylic resin to the epoxy group contained in the epoxy group / hydroxyl group-containing acrylic resin becomes approximately 1: 1. . In other words, the acid group / hydroxyl group-containing acrylic resin and the epoxy group / hydroxyl group-containing acrylic resin have a carboxyl group-epoxy group molar ratio of 1: 2 to 2: 1.
It can be blended in such a ratio range as follows.

The isocyanate component of the blocked isocyanate compound is not particularly limited as long as it is a compound having two or more isocyanate groups in one molecule. For example, aliphatic diisocyanates such as hexamethylene diisocyanate (HDI) and trimethylhexamethylene diisocyanate (TMDI), alicyclic diisocyanates such as isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI) ), Tolylene diisocyanate (TDI), aromatic isocyanates such as 4,4-diphenylmethane diisocyanate (MDI), dimer acid diisocyanate (DDI), hydrogenated TDI (HTDI), hydrogenated XDI (H ₆ XD)
I) hydrogenated diisocyanates such as hydrogenated MDI (H ₁₂ MDI), dimers, trimers, tetramers and higher polyisocyanates thereof, and polyisocyanates such as trimethylolpropane; Examples thereof include an adduct with a polyhydric alcohol, water, or a low molecular weight polyester resin. Among them, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and tetramethylxylylene diisocyanate (TMXDI), which are relatively excellent in yellowing resistance, are preferable.

Also, the blocked isocyanate compound is
It is a compound in which an active reactive group is usually blocked with a suitable blocking agent in order to enhance the coating stability of the obtained coating composition. This blocking agent is not particularly limited. For example, oxime blocking agents such as methyl ethyl ketoxime, acetoxime, cyclohexanonoxime, acetophenone oxime, benzophenone oxime, phenol blocking agents such as m-cresol, xylenol, methanol, ethanol, butanol,
Alcohol blocking agents such as ethylhexanol, cyclohexanol and ethylene glycol monoethyl ether, lactam blocking agents such as ε-caprolactam, diethyl malonate, diketones such as acetoacetates, and mercaptan blocks such as thiophenol. Urea blocking agents such as thiourea, imidazole blocking agents, carbamic acid blocking agents, and the like. Of these, oxime-based blocking agents and diketone-based blocking agents that can be dissociated at a relatively low temperature can be suitably used. Further, the diketone blocking agent does not contain a nitrogen atom in the molecule that causes yellowing during baking and drying of the paint. Therefore, by using a diketone-based blocking agent, yellowing resistance to baking can be improved. Further, they have a low dissociation temperature and are excellent in low-temperature dissociation. Therefore, even when the baking temperature is relatively low, for example, about 120 ° C., a sufficiently cured coating film can be formed.

These blocked isocyanate compounds may be used alone or in combination of two or more.

In order to accelerate the crosslinking reaction of these blocked isocyanate compounds during baking and drying of the paint, a curing catalyst for accelerating the dissociation of the blocking agent can be used, if necessary. As such a curing catalyst, any one can be used, but it is preferable to use an organic tin compound which is a salt of an organic tin and a carboxylic acid. As the organic tin, alkyl tin such as methyl, butyl, and octyl is preferable, and dialkyl tin is more preferable. As the carboxylic acid, aliphatic monocarboxylic acids such as lauric acid, maleic acid, phthalic acid and the like are preferable. Particularly preferred organic tin compounds include, for example, di-n-butyltin dilaurate.

These blocked isocyanate compound parts have a molar ratio of the hydroxyl group of the acrylic resin to the effective isocyanate group of 1: 0 to the above-mentioned acid / hydroxyl group-containing acrylic resin and epoxy group / hydroxyl group-containing acrylic resin. .2 to 1: 2.0, preferably 1:
The composition can be in the range of 0.4 to 1: 1.2.

The reason for mixing the blocked isocyanate compound into such an acid / epoxy curable resin composition is to make up for the respective disadvantages.
For example, the block isocyanate-curing type alone has a small number of cross-linking points, resulting in an insufficient cross-linking density and a decrease in solvent resistance and the like. Can be done. In the case of the acid / epoxy curable type, the reaction proceeds even in a relatively low temperature range, so that the storage stability of the coating material is lowered. However, the storage stability of the coating material can be improved by adding a blocked isocyanate compound. As a result, this paint composition can control paint properties and paint storage stability in a well-balanced manner.

Component (B) As the form of the component (B) used in the present invention, the main chain substantially consists of a vinyl copolymer chain, and the terminal of the main chain and / or the side chain has the general formula (1) : (Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ² is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms) A is a monovalent hydrocarbon group selected from
Having at least one hydrolyzable silyl group bonded to a carbon atom represented by the following formula, and having at least one alcoholic hydroxyl group at the terminal and / or side chain of the main chain. It is a copolymer. Since the main chain of the copolymer is substantially composed of a vinyl copolymer chain, the cured coating film of the curable resin composition obtained has excellent weather resistance and chemical resistance. Further, since the hydrolyzable silyl group is bonded to the carbon atom, the coating film is excellent in water resistance, alkali resistance, acid resistance, and the like.

The component (B) may have at least one hydrolyzable silyl group represented by the above general formula (1) in the molecule, but a coating film formed using the resulting curable composition. Is preferably 2 to 10 from the viewpoint of excellent solvent resistance.

In the above formula (1), R ¹ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably a methyl group, an ethyl group, an n-propyl group, a 1-propyl group, an n-butyl group, Examples thereof include an alkyl group having 1 to 4 carbon atoms such as a t-butyl group. The alkyl group has 1 carbon atom.
If it exceeds 0, the reactivity of the hydrolyzable silyl group tends to decrease. Further, when R ¹ is a group other than an alkyl group such as a phenyl group and a benzyl group, the reactivity of the hydrolyzable silyl group is undesirably reduced.

In the above general formula (1), R ² is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and preferably has 1 carbon layer as a specific example of R ¹ .
And monovalent hydrocarbon groups selected from aryl groups having 6 to 25 carbon atoms such as alkyl groups and phenyl groups, and aralkyl groups having 7 to 12 carbon atoms such as benzyl groups. Alkyl groups are preferred in that the resulting composition has excellent curability.

The alcoholic hydroxyl group equivalent (the amount (g) of the vinylic copolymer containing 1 mol of alcoholic hydroxyl groups) in the vinyl copolymer is preferably 1500 to 4000 g / mol. When the hydroxyl equivalent is 1500
When the amount is less than g / mol, the storage stability and acid resistance of the coating film formed using the obtained curable composition are not sufficient,
On the other hand, if it exceeds 4000 g / mol, the curability of the composition tends to deteriorate, which is not preferable.

The vinyl copolymer is, for example, the following (a) to
It can be produced by polymerizing a polymerization component containing (c) and the like. (A) Hydrolyzable silyl group-containing vinyl monomer (b) Hydroxyl group-containing vinyl monomer (C) Other copolymerizable monomer As the vinyl monomer of (a), Chemical formula 8 is exemplified.

[0043]

Embedded image

[0044]

Embedded image

[0045]

Embedded image

[0046]

Embedded image

[0047]

Embedded image

[0048]

Embedded image

[0049]

Embedded image

[0050]

Embedded image

And a (meth) acrylate having a hydrolyzable silyl group represented by the above general formula 1 at a terminal via a urethane bond or a siloxane bond. These may be used alone or in combination of two or more. Among these, the compounds represented by the above general formula 5 are preferable because they are easy to handle, inexpensive, and do not generate reaction by-products.

The amount of the monomer (a) used is preferably 5 to 60% (% by weight, hereinafter the same) in the total amount of the copolymer,
0% is more preferable. When the use amount of the above monomer is less than 5%, the acid resistance of the coating film formed using the obtained curable composition is insufficient, which is not preferable. Also,
If the amount of the above-mentioned monomer is more than 60%, the storage stability of the curable composition decreases, which is not preferable.

Examples of the monomer (b) include 2-hydroxyethyl (meth) acrylate, 1-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl vinyl ether, N-methylol (Meth) acrylamide, Aronix 5700 (manufactured by Toa Gosei Chemical Industry Co., Ltd.), 4-hydroxystyrene, HE-10, HE-20, HP-
1. Acrylic ester oligomer having a hydroxyl group at the terminal such as HP-20 (the above are available from Nippon Shokubai Chemical Co., Ltd.)
), Blemmer PP series (polypropylene glycol methacrylate), Blemmer PE series (polyethylene glycol monomethacrylate), Blemmer PEP series (polyethylene glycol polypropylene glycol methacrylate), Blemmer AP-40
0 (polypropylene glycol monoacrylate), Blemmer AE-400 (polyethylene glycol monoacrylate), Blemmer NKH-5050 (polyethylene glycol polytrimethylene monoacrylate),
Blemmer GLM (glycerol monomethacrylate)
And the like, and ε-caprolactone-modified hydroxyalkylvinyl-based copolymerizable compounds obtained by reacting a hydroxyl-containing vinyl compound with ε-caprolactone.

A typical example of the ε-caprolactone-modified hydroxyalkylvinyl copolymer is a compound represented by the following formula.

[0055]

Embedded image

As a specific example, for example, Placcel FA
-1 (R ⁶ is a hydrogen atom, q is 1), Placcel FA-4
(R ⁶ is a hydrogen atom, q is 4), Placcel FM-1 (R ⁶ is a hydrogen atom, q is 1), and Placcel FM-4 (R ⁶ is a hydrogen atom, q is 4) (Daicel Chemical Industries, Ltd. Co., Ltd.), T
ONE M-100 (R ⁶ is a hydrogen atom, q is 2), TO
NEM-201 (R ⁶ is a methyl group, q is 1) (the above are manufactured by UCC) and the like.

These monomers (b) may be used alone or in combination of two or more.

Among the above monomers (b), 2-hydroxypropyl (meth) acrylate, which is excellent in acid resistance and water resistance of a coating film formed by using the obtained curable composition, 2-Hydroxyethyl (meth) acrylate and ε-caprolactone-modified hydroxyalkyl vinyl copolymerizable compound are preferred. Particularly, 2-hydroxypropyl (meth) acrylate is more preferable.

The amount of the monomer used is preferably 1 to 50%, more preferably 2 to 35% of the total amount of the copolymer components. If the amount of the monomer (b) is more than 50%, the water resistance and the acid resistance of a coating film formed using the curable composition are undesirably reduced.

Examples of the monomer (c) include methyl (meth) acrylate, ethyl (meth) acrylate,
n-butyl (meth) acrylate, isobutyl (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-methyl (meth) acrylamide, N , N-dimethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, AS-6, AN-6, AA which are macromonomers
-6, AB-6, AK-5 and the like (these are manufactured by Toa Gosei Chemical Industry Co., Ltd.), and hydroxy of α, β-ethylenically unsaturated carboxylic acids such as hydroxyalkyl esters of (meth) acrylic acid. Phosphoric ester group-containing vinyl compounds such as condensation products of alkyl esters and phosphoric acid or phosphoric esters, (meth) acrylic acid derivatives such as (meth) acrylates containing urethane bonds or siloxane bonds, styrene, α-methyl Styrene, chlorostyrene,
Aromatic hydrocarbon-based vinyl compounds such as styrene sulfonic acid, 4-hydroxystyrene, and vinyl toluene; unsaturated carboxylic acids such as maleic acid, fumaric acid, and itaconic acid; alkali metal salts, ammonium salts, and amine salts thereof; Acid anhydrides of unsaturated carboxylic acids such as maleic acid; esters of unsaturated carboxylic acids such as diesters or half esters thereof with alcohols having a linear or branched chain having 1 to 20 carbon atoms; vinyl acetate; Vinyl esters and allyl compounds such as vinyl propionate and diallyl phthalate; vinyl compounds containing an amino group such as vinyl pyridine and aminoethyl vinyl ether; itaconic diamide, crotonamide, maleic diamide, fumaric diamide, N-vinylpyrrolidone and the like Amide group-containing vinyl compound; methyl bi Ether, cyclohexyl vinyl ether, vinyl chloride, vinylidene chloride, chloroprene, propylene, butadiene, isoprene, fluoroolefin maleimide, N- vinyl imidazole, other vinyl compounds such as vinyl sulfonic acid.
These may be used alone or in combination of two or more.

When a polar monomer having an amine, carboxylic acid, sulfonic acid or phosphoric acid group is used as the monomer (c), a crosslinking reaction during polymerization is suppressed.
It is desirable that the amount used be 5% or less of the total amount of the copolymer components.

In the present invention, in order to improve the weather resistance, solvent resistance, impact resistance and the like of the coating film formed using the obtained curable composition, the content of the vinyl copolymer exceeds 50%. The segment formed by urethane bond or siloxane bond may be used as long as it is not included in the vinyl copolymer main chain.

The vinyl copolymer used in the present invention is:
It is produced from a copolymer component containing the monomers (a), (b) and (c) by a method described in, for example, JP-A-54-36395, JP-A-57-55954 and the like. However, it is preferably produced by a solution polymerization method using an azo radical polymerization initiator such as azobisisobutyronitrile from the viewpoint of ease of synthesis and the like.

The polymerization solution used in the solution polymerization method is as follows:
There is no particular limitation as long as it is non-reactive, and for example, hydrocarbons such as toluene, xylene, n-hexane and cyclohexane; acetates such as ethyl acetate and butyl acetate; methanol, ethanol, isopropanol,
alcohols such as n-butanol; ethyl cellosolve;
Ethers such as butyl cellosolve and cellosolve acetate; and ketones such as methyl ethyl ketone, ethyl acetoacetate, acetylacetone, diacetone alcohol, methyl isobutytone, and acetone.

The above-mentioned polymerization solvents may be used alone.
Two or more kinds may be used in combination, but if the amount of alcohol such as methanol or butanol in the polymerization solvent is less than 1 part based on 100 parts of the copolymerization component, gelation may occur during polymerization. Therefore, in the polymerization solvent, the copolymerization component 100
It is preferred that the alcohol be contained in a ratio of 1 to 30 parts per part.

The molecular weight of the obtained vinyl copolymer may be adjusted by using a chain transfer agent in the above solution polymerization.

Specific examples of the chain transfer agent include, for example, n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butyl mercaptan, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyl dimethoxysilane, .gamma.-mercaptopropyl methyl diethoxy _{silane, (CH 3 O) 3 Si} -S-S-Si (OCH 3) 3,
_{(CH 3 O) 3 Si-} S 8 -Si (OCH 3) 3 and the like. These may be used alone or in combination of two or more.

For example, when a chain transfer agent having a hydrolyzable silyl group such as γ-mercaptopropyltrimethoxylane in the molecule is used, the hydrolyzable silyl group is introduced into the main chain terminal of the vinyl copolymer. It is preferable because it is possible.

The use amount of such a chain transfer agent is preferably about 0.1 to 10% with respect to the copolymer component.

The amount of component (B) used is preferably 15 to 100 parts by weight, and more preferably 15 to 8 parts by weight, per 100 parts by weight of component (A).
0 parts by weight is more preferred.

When the amount of the component (B) is less than 15 parts by weight, the compatibility decreases, and when it exceeds 100 parts by weight, the storage stability decreases. (C) used in the component (C) according to the present invention the general formula is a component ^{(2); (R 3 O} ) 4-b -Si-R 4 b (2) silicon represented by the compounds and / or their partial hydrolysis The condensate is a component that improves the stain resistance of a coating film formed using the obtained curable composition.

In the general formula (2), R ³ is a hydrogen atom or a carbon atom having 1 to 10, preferably 1 to 4 carbon atoms.
Alkyl group or aryl group, preferably having 6 to 10 carbon atoms
Aryl or aralkyl group, preferably having 7 to 1 carbon atoms
It is a monovalent hydrocarbon selected from 0 aralkyl groups and alkoxy groups, preferably alkoxy groups having 1 to 10 carbon atoms. R ⁴ has 1 to 10 carbon atoms, preferably 1 carbon atom.
To 4 alkyl groups and aryl groups, preferably 6 to 6 carbon atoms
It is a monovalent hydrocarbon group selected from 10 aryl groups and aralkyl groups, preferably 7 to 10 carbon atoms. B is 0 to 2 and (R
^Although there are 4 to 2 ³ O) groups, the 4 to 2 (R ³ O) groups present in the same molecule need not be the same.

Specific examples of the silicon compound include, for example, tetramethyl silicate, tetraethyl silicate, tetra n-propyl silicate, tetra i-propyl silicate, tetra n-butyl silicate, tetra i
Tetraalkyl silicates such as -butyl silicate and tetra-t-butyl silicate; alkyl tris such as methyltrimethoxysilane, methyltriethoxysilane, octadecylethoxysilane, methylsec-octyloxysilane, methyltriisopropoxysilane and methyltributoxysilane Examples thereof include aryltrialkoxysilanes such as alkoxysilane, phenyltrimethoxysilane, and phenylethoxysilane, and alkyltriaryloxysilanes such as methyltriphenoxysilane.

Examples of the partially hydrolyzed condensate of the silicon compound include, for example, those obtained by adding water to the above tetraalkyl silicate, trialkoxysilane, triaryloxysilane, etc., and partially hydrolyzing and condensing the silicon compound. Or those hydrolyzed in the above-mentioned tetraalkylsilicate or alcohol-based solvent in the presence of an acidic substance and water.

As specific examples, for example, MSI51,
Tetraalkyl silicate partially hydrolyzed condensates such as ESI40, HAS-1, HAS-10 (all, manufactured by Colcoat Co., Ltd.), MS51, MS56, MS56S (all, manufactured by Mitsubishi Chemical Corporation) and, for example, AFP-1 (Manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

The component (C) may be added during the polymerization of the component (B).
It can be used by a method such as cold blending with the component (C), and the addition method is not particularly limited.

The above component (C) may be used alone or in combination of two or more. However, the compatibility between the component (B) and the component (D), the curability of the obtained composition and the ESI28, MS5 from the viewpoint that the hardness of the coating film formed by using the composition is high, so that the fixation of contaminants is suppressed.
1, a partial hydrolysis condensate of a tetraalkyl silicate such as MS56 and HAS-1 and / or a tetraalkyl silicate such as ESi48 is preferable.

The amount of component (C) used is 5 to 10 parts, preferably 5 to 8 parts by weight, per 100 parts by weight of component (A). When the amount of the component (C) is less than 5 parts by weight, the effect of stain resistance is not sufficient. When the amount exceeds 10 parts by weight, the compatibility is undesirably reduced. Component (D) The component (D) of the present invention is a compound obtained by subjecting a polyol compound and an acid anhydride to a half-esterification reaction and containing at least two carboxyl groups in one molecule. From the viewpoints of curability, weather resistance, acid resistance, recoat adhesion and the like of a coating film obtained from the composition, a polyol compound having 2 or more hydroxyl groups per molecule, preferably 2 to 10 hydroxyl groups, and an acid anhydride At least 2 in one molecule obtained by subjecting a compound to a half-esterification reaction.
It is preferably a compound containing two carboxyl groups (hereinafter referred to as a carboxylic acid oligomer).

As the polyol having two or more hydroxyl groups per molecule for synthesizing the carboxylic acid oligomer, ethylene glycol, 1,2- and 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, diethylene glycol, pentanediol, dimethylbutanediol, hydrogenated bisphenol A, glycerin, sorbitol, neopentyl glycol, 1,3-octanediol, 1,4
-Cyclohexanedimethanol, 2-methyl-1,3-
Propanediol, 1,2,6-hexanetriol,
1,2,4-butanthryl, trimethylolethane,
Polyhydric alcohols such as trimethylolpropane, pentaerythritol, quinitol, mannitol, trishydroxyethyl isocyanurate, dipentaerythritol, and trishydroxymethylethane; these polyhydric alcohols and lactone compounds such as γ-butyrolactone and ε-caprolactone A ring-opened adduct of the polyhydric alcohol with an isocyanate compound such as tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, or isophorodiisocyanate in excess of alcohol; Vinyl ether, polyethylene glycol divinyl ether, butanediol divinyl ether, pentanediol divinyl ether, hexanediol divinyl ether Adduct with a vinyl ether compound such as 1,4-cyclohexanedimethanol divinyl ether in excess of alcohol, and the polyhydric alcohol and an alkoxysilicol compound, for example, KR-213;
Condensates with KR-217 and KR-9218 (both trade names manufactured by Shin-Etsu Chemical Co., Ltd.) in excess of alcohol can be exemplified.

On the other hand, preferred acid anhydrides to be reacted with these polyols are hexahydrophthalic anhydride,
Examples include phthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride and trimellitic anhydride.

The hydroxyl group-containing carboxylic acid oligomer can be obtained by adjusting the ratio of the polyol to the acid anhydride to be reacted.

The molecular weight of the component (D) is 2,000 or less, preferably in the range of 100 to 1,800.

The amount of component (D) is 1 to 10 parts by weight based on 100 parts by weight of component (A). If the amount of the component (D) exceeds 10 parts by weight, the storage stability may decrease. If the amount is less than 1 part, the curability may deteriorate, which is not preferable.

(Other Components) In the curable composition of the present invention, a solvent (E) is used in addition to the above components. The solvent (E) is not particularly limited as long as it can dissolve or stably disperse any of the components (A) to (D) used in the present invention. Typical examples thereof include hydrocarbons such as toluene, xylene, cyclohexane, n-hexane and octane, methanol, ethanol, i
-Propanol, n-butanol, i-butanol, se
c-butanol, t-butanol, alcohols such as ethylene glycol monoalkyl ether, methyl acetate, ethyl acetate, ester such as butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone,
It is a solvent used when preparing a vinyl copolymer (B) such as a ketone such as cyclohexane. Among these, when a dehydrating agent is used in combination with an alcohol-based solvent, a composition having excellent stability can be obtained. As the solvent, the solvent used at the time of polymerization of the component (B) can be used as it is.

The amount of the alcohol-based solvent used is not particularly limited, but if it is too large, defects such as wrinkles (foaming phenomenon) tend to occur in the coating film formed using the obtained cured composition. Therefore, the amount is usually 70 parts by weight or less, preferably 50 parts by weight or less, more preferably 20 parts by weight or less based on 100 parts by weight of the vinyl copolymer (B). Usually 0.5 to 70 parts by weight, preferably 1
５０50 parts by weight, more preferably 2-20 parts by weight.

The storage stability of the curable composition can be further improved by adding a dehydrating agent or a specific solvent.

Examples of the above dehydrating agent include methyl orthoformate, ethyl orthoformate, methyl orthoacetate, ethyl orthoacetate, methyl orthobutyrate, ethyl orthobutyrate, methyl orthopropionate, ethyl orthopropionate and the like. These may be used alone or in combination of two or more.

The dehydrating agent may be added at the time of polymerization of the vinyl copolymer (B), or may be added after the polymerization. If the usage of such a dehydrating agent is too large,
Since there is a tendency for defects such as pinholes to occur in a coating film formed using the obtained curable composition, 70 parts by weight or less, preferably 100 parts by weight of the vinyl copolymer (B). It is used in an amount of 50 parts by weight or less, and more preferably 20 parts by weight or less.

The weatherability can be further improved by adding a weatherability improver such as an ultraviolet absorber and a light stabilizer to the curable composition for a topcoat paint of the present invention. In particular, by using these together, the weather resistance can be more effectively improved.

Examples of the ultraviolet absorber include benzophenone-based, triazole-based, phenylsulfylate-based, diphenylacrylate-based, and acetophenone-based ones. These may be used alone or in combination of two or more.

As the light stabilizer, for example, bis (2,2)
2,6-tetramethyl-4-piperi) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 2- (3,5-tert-butyl-4-hydroxybenzyl)- Bis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate 2-n-butylmalonate;
Tetrakis (1,2,2,6,6-pentamethyl-4-
Piperidyl) -1,2,3,4-butanetetracarboxylate and the like. These may be used alone or in combination of two or more.

The amount of the ultraviolet absorber used is usually 0.1 to 10 parts by weight per 100 parts by weight of the resin solid content of the curable composition.
The light stabilizer is used in an amount of usually 0.1 to 10 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the resin solid content of the curable composition. ~
5 parts by weight.

Next, an example of coating using the curable composition of the present invention will be described.

First, a coating material containing a metallic powder and / or a coloring pigment is applied to an object to be coated, and then a topcoat clear coating material containing the curable composition of the present invention as a main component is applied to the applied surface.

The paint (base coat) containing the metallic powder and / or the coloring pigment is not particularly limited. For example, amino alkyd resin, oil-free alkyd resin, thermosetting acrylic resin, thermosetting urethane resin, nitrified cotton lacquer, modified acrylic lacquer, slate acrylic lacquer, room temperature curing urethane resin, acrylic enamel resin, oxidative curing alkyd resin, oxidative curing modification ( CAB, etc.)
Alkyd resin, room-temperature or heat-curable fluororesin, hydrolyzable silyl group-containing resin, curable composition of the present invention and those containing a mixture thereof as a main component, those containing a metallic powder or a coloring pigment, etc. Can be used.

The coating containing the metallic powder and / or the coloring pigment may be any of a solution-type coating using an organic solvent as a medium, a non-aqueous dispersion coating, a multi-liquid coating, a powder coating, a slurry coating, an aqueous coating and the like. It may be a type of paint.

The metallic powder and coloring pigment are not particularly limited, and those conventionally used can be used. Specific examples of the metallic powder include, for example, aluminum powder, copper powder, mica powder and the like, and specific examples of the coloring pigment include, for example, phthalocyanine blue,
Organic pigments such as toluidine red and benzidine yellow, and inorganic pigments such as titanium oxide, carbon black and red bengal are exemplified. These metallic powders and color pigments may be used alone or in combination of two or more.

If the above-mentioned ultraviolet absorber and light stabilizer are added to the base coat, the weather resistance of the coated product can be further improved.

The coated article of the present invention is obtained by further applying a top coat clear coating on the coated surface to which the base coat has been applied. For example, a coating containing the above-mentioned metallic powder and / or coloring pigment is applied to an object to be coated. After setting for several minutes, apply a top coat clear paint by wet-on-wet method and heat-curing, or apply a coating containing metallic powder and / or coloring pigment and heat-curing After that, a coated product can be formed by a method such as a two-coat two-bake method in which a top coat clear paint is applied and heated and cured. Topcoat clear paint application
It can be performed by various methods conventionally used, such as immersion, spraying, brush coating, a method using a roll coater or a flow coater. After that, 30 ° C or more,
Preferably, it can be cured by heating to 55 to 350 ° C.

The thickness of the coating film of the coating material cannot be specified unconditionally because it varies depending on the application. However, the thickness of the coating film containing the metallic powder and / or the coloring pigment is in the range of 10 to 30 μm from the viewpoint of concealability and the like. Is preferable, and the thickness of the top coat clear coating film is 20 to 50 μm from the viewpoint of durability and the like.
The range of m is preferred.

As described above, the curable composition for a top coating composition of the present invention exhibits excellent acid resistance, abrasion resistance, appearance, heat curability, etc. and extremely excellent stain resistance. For example, it can be suitably used as a topcoat for automobiles, industrial machines, steel furniture, building exteriors, home appliances, plastic products, etc., especially as a topcoat for automobiles.

[0102]

The present invention will be specifically described below with reference to examples.

The curable composition for a topcoat paint of the present invention and the coated product using the same will be described in more detail with reference to Examples, but the present invention is not limited to only these Examples.

(Synthesis Example 1) Synthesis of Acid- and Hydroxyl-Containing Acrylic Resin (A-1) Component In a reactor equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube and dropping funnel, n-butanol / 66 parts by weight of a mixed solvent of xylene (3/7) was added and maintained at 120 ° C. 20 parts by weight of styrene, 38 parts by weight of n-butyl methacrylate, 23 parts by weight of n-butyl acrylate, 7 parts by weight of 2-hydroxyethyl methacrylate
Azobisisobutyronitrile (A) was added to a monomer mixture (100 parts by weight in total) consisting of 12 parts by weight of acrylic acid and 12 parts by weight of acrylic acid.
The monomer mixture to which IBN (2 parts by weight) was added was added dropwise over 4 hours to cause a reaction, and then 1 hour by weight of AIBN was added evenly every 5 minutes, kept for 2 hours, and further reacted for 1 hour. The weight average molecular weight of this acrylic resin A is 120
The acid value was 94 and the hydroxyl value was 30.

Synthesis Example 2 Synthesis of Epoxy / Hydroxy Group-Containing Acrylic Resin (A-2) Component A reactor equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube and dropping funnel was charged with n-butanol / 53 parts by weight of a mixed solvent of xylene (3/7) was added and maintained at 120 ° C. In this mixed solution, 10 parts by weight of styrene, 18 parts by weight of n-butyl methacrylate, 18 parts by weight of n-butyl acrylate, 7 parts of 2-hydroxyethyl methacrylate 7
A monomer mixture obtained by adding 3 parts by weight of azobisisobutyronitrile (AIBN) to a monomer mixture consisting of 47 parts by weight of glycidyl methacrylate (total 100 parts by weight) was dropped and reacted over 4 hours. Thereafter, the mixture was kept for 2 hours while uniformly adding 1 part by weight of AIBN every 5 minutes, and further reacted for 1 hour. The weight average molecular weight of this acrylic resin A is 3000, its epoxy equivalent is 300,
The hydroxyl value was 30.

(Synthesis Example 3) Synthesis of Hydroxy Group-Containing Acrylic Resin (A-3) Component n-Butanol / xylene (3) was placed in a reactor equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube and dropping funnel. 66 parts by weight of the mixed solvent of (7)) was added and maintained at 120 ° C. In this mixed solution, 20 parts by weight of styrene, 39 parts by weight of n-butyl methacrylate, 18 parts by weight of n-butyl acrylate, and 2-hydroxyethyl methacrylate 2
Azobisisobutyronitrile (A) was added to a monomer mixture consisting of 1 part by weight and 2 parts by weight of acrylic acid (total 100 parts by weight).
The monomer mixture to which IBN (2 parts by weight) was added was added dropwise over 4 hours to cause a reaction, and then 1 hour by weight of AIBN was added evenly every 5 minutes, kept for 2 hours, and further reacted for 1 hour. The weight average molecular weight of this acrylic resin A is 120
The acid value was 90 and the hydroxyl value was 15.

(Synthesis Example 4) Synthesis of Components B-1 to B-5 The solvent of Part 2 in Table 1 was charged into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube and dropping funnel. After the temperature was raised to 115 ° C. while introducing nitrogen gas, the monomer mixture of Part 1 shown in Table 1 was dropped at a constant speed over 4 hours.

Next, the solvent shown in Part 3 of Table 1 was dropped into the reactor at a constant speed over 1 hour. After that,
After stirring at 115 ° C. for 2 hours, the mixture was cooled to room temperature. Finally, a mixed solution having the composition shown in Part 4 of Table 1 was added and stirred.

The solid content concentration of the obtained solution is shown in Table 1 together with the number average molecular weight of the copolymer (measured by gel permeation chromatography (GPC)), hydrolyzable silyl group equivalent and alcoholic hydroxyl group equivalent. .

[0110]

[Table 1]

In Table 1, A174 represents γ-trimethoxysilylpropyl methacrylate (manufactured by Nippon Unicar Co., Ltd.);
-59 is 2,2'-azobis (2-methylbutyronitrile) manufactured by Wako Pure Chemical Industries, Ltd. (Synthesis Example 5) Synthesis of carboxylic acid oligomer (D-1) component Stirrer, thermometer, reflux condenser, nitrogen The components of Part 1 in Table 2 were charged into a reaction vessel equipped with a gas inlet tube and a dropping funnel. After stirring at 120 ° C. for 15 minutes while introducing nitrogen gas, Part 2 shown in Table 2 was added over 15 minutes. Thereafter, the reaction was performed at 120 ° C. for 3 hours. It was confirmed from the infrared absorption spectrum that the absorption of the acid anhydride group (1785 cm ^-1 ) disappeared.

[0112]

[Table 2]

Blocked Isocyanate Compound Blocked isocyanate blocked with methylethylketoxime (MEKO), an adduct of polyhydric alcohol of tetramethylxylylenediisocyanate (TMXDI), as a relatively non-yellowing and excellent low-temperature dissociation blocked isocyanate (MEKO) Takenate-XB-77-M
9 Takeda Pharmaceutical Co., Ltd .: Effective NCO content 12.6
66% (solid content) was used.

(Compounding Example of Component A) (A1) Among the above, resin A-1 and resin A-2 were converted to resin A-1 / resin A-2 = 66.0 / 34.0 in terms of resin solid content.
At the ratio of That is, the molar ratio (number ratio) of the carboxyl group to the epoxy group in the acrylic resin is 1 so that the acrylic resin A-1 and the acrylic resin A-2 forming the acid / epoxy curable resin are substantially equivalent. : 1.

(A2) Among the above synthetic resins, resins A-1,
Resin A-2 and blocked isocyanate were blended in a ratio of resin A-1 / resin A-2 / blocked isocyanate = 59.2 / 30.3 / 10.5 in terms of resin solid content.
That is, the acrylic resin A-1 and the acrylic resin A-2 forming the acid / epoxy curable resin have a molar ratio (number ratio) of a carboxyl group and an epoxy group in the acrylic resin such that they are substantially equivalent. Was 1: 1. The blocked isocyanate compound was added to these acrylic resins so that the molar ratio (number ratio) of the total hydroxyl groups of the acrylic resin to the effective isocyanate groups of the blocked isocyanate was 1: 0.66.

(A3) A resin obtained by blending resin A-3 and a melamine resin among the above-mentioned synthetic products, and corresponds to a conventional melamine resin-curable coating. In particular,
The synthetic resin A-3 and the melamine resin-curable paint were blended in a ratio of resin A-3 / melamine resin = 70/30 in terms of resin solid content. Individually, as a melamine resin, Superbecamine L-117-60 (manufactured by Dainippon Ink and Chemicals, Inc.) was used.

(A4) A resin obtained by blending the resin A-3 and a blocked isocyanate compound among the above-mentioned synthesized products, and corresponds to a conventional curable coating material containing a conventional blocked isocyanate compound. Specifically, the synthetic resin A-3 and the blocked isocyanate compound were blended in a ratio of resin A-3 / blocked isocyanate compound = 65.3 / 34.7 in terms of resin solid content. Table 3 shows examples of the composition of the component A as described above.

[0118]

[Table 3]

(Examples 1 to 7) As shown in Table 4, the B component shown in the above synthesis example, based on 100 parts by weight of the coating resin of the A2 component in the formulation examples obtained as described above, Commercially available products of silicone compounds D and C were added to prepare coatings of Examples 1 to 7.

(Comparative Examples 1 to 7) The components B, C and D were added as shown in Tables 4 and 5 to 100 parts by weight of the coating resin A2 obtained as described above. Paints of Comparative Examples 1 to 7 were produced. Comparative Example 3 was produced without adding B, C, D and components.

(Comparative Examples 8 to 10) As shown in Table 5, 17 parts by weight of the B component and C based on 100 parts by weight of the coating resin of each of the components A1, A3 and A4 obtained as described above. The coating materials of Comparative Examples 8 to 10 were prepared by adding 6 parts by weight of the component and 2 parts by weight of the D component.

(Comparative Examples 11 to 13) As shown in Table 4, the components B, C and D were added to 100 parts by weight of the coating resin A1, A3 and A4 obtained as described above. The coating materials of Comparative Examples 11 to 13 were prepared without addition.

In addition to the above resin components for coatings, the clear coatings of these Examples and Comparative Examples include a benzotriazole-based ultraviolet absorber (manufactured by Tinuvin 900, Ciba Geigy) and a hindered amine-based antioxidant ( Tinuvin 440 (manufactured by Ciba Geigy) was added in an amount of 1 PHR. Further, 0.5 PHR of a silicon-based leveling agent (BYK-300, manufactured by BYK) as a surface conditioner
Was added. And a mixed solvent (toluene / solvesso 10
0 / xylene = 40/40/20) and adjusted to a viscosity of 20 seconds (room temperature) with a Ford cup (FC # 4).

(Painted Plate) Using the clear paint prepared as described above as a topcoat paint, a test painted plate was prepared under the same conditions as in the case of actual painting of an automobile body.

First, a zinc phosphate chemical conversion treatment was performed to a thickness of 0.1 mm.
8mm dull steel plate is coated with epoxy cationic electrodeposition,
This was coated with a polyester intermediate coating, dried and baked, and then polished and degreased to prepare for a top coating. The thickness of the electrodeposition coating film is about 20 μm, and the thickness of the intermediate coating film is about 35 μm.

Then, a metallic base coating material was applied to the prepared test plate so that the thickness of the dried coating film became 15 μm, and each of the clear coating materials of Examples and Comparative Examples was wet-on-wet. Each having a thickness of 35 μm, and after setting, 14
The coating film was baked and dried under heating conditions of 0 ° C. × 20 minutes.

This metallic base paint is a melamine resin-curable paint and has the following composition. Acrylic resin (Acrydic 47-712, manufactured by Dainippon Ink and Chemicals, Inc.) 27.3 parts by weight, melamine resin (Super Beckamine L-117-60) manufactured by Dainippon Ink and Chemicals, 5.7 parts by weight Part, aluminum flake pigment (Alpaste 7160NS manufactured by Toyo Aluminum Co., Ltd.)
4.5 parts by weight and 62.5 parts by weight of thinner (ethyl acetate / toluene / solvesso 100 = 40/40/20).

(Test Evaluation) Next, with respect to the coating films of the clear paints of Examples and Comparative Examples thus formed, their pencil hardness, solvent resistance, water resistance, acid resistance, appearance (sharpness), The stain resistance, the contact angle of the coating film, and the gel fraction (low-temperature curability) storage stability were tested and evaluated.

The test methods and evaluation criteria are as follows.

Pencil hardness: JIS K5400 8.4.
The pencil hardness was measured according to 2.

Solvent resistance: A xylene rubbing test was carried out, the coating was rubbed 10 times with a gauze impregnated with xylene, and the surface of the coating was observed and evaluated according to the following criteria.

◎: No abnormality, ：: Slightly scratched,
Δ: The scratch is conspicuous and the color slightly changes. X: The coating film swells and whitens.

Water resistance: 240 coated plates in warm water of 40 ° C.
The coating was immersed for a period of time, and the coating film surface was observed and evaluated according to the following criteria.

◎: No abnormality, ：: Micro blisters are generated. Δ: Blister occurs ×: Whitening,
Or shrink. Poor luster and other poor appearance.

Acid resistance: 0.5% of 10% sulfuric acid aqueous solution on the coating film
ml was dropped in the form of a spot, left at 50 ° C. for 30 minutes, washed with water, and the coating film surface was observed and evaluated according to the following criteria.

◎: No abnormality, ：: No discoloration, etc., but slight dents in spots.

Δ: Discoloration occurs, and spots are dented. X: Remarkable discoloration, dent, and etching occur.

Sharpness: The sharpness of the coating film was measured using a PGD meter (sharpness meter) and evaluated according to the following criteria.

A: The sharpness is 1.0 or more. Δ: The sharpness is 0.3 or more and less than 1.0. X: The sharpness is 0.3 or less.

Storage stability: For each clear coating, the initial viscosity was adjusted to 30 seconds (FC # 4) at room temperature 20 ° C., and then the viscosity change (increase in viscosity) when left at 40 ° C. for 240 hours was measured. Was evaluated according to the following criteria.

A: Less than +10 seconds. △: +10 seconds or more 1
Less than 5 seconds. X: 15 seconds or more.

Gel fraction (low-temperature curability): Each clear paint was applied to an aluminum plate with a clear paint single film.
After baking at 20 ° C. for 20 minutes, the clear coating film is isolated from the aluminum plate to produce a clear film. This clear film is immersed in a closed acetone bath at 20 ° C. for 24 hours, and the film weight before and after immersion is weighed with a precision balance. Then, the gel fraction is measured from the measured value by the following equation.

Gel fraction = (weight before dipping−weight after dipping) /
Weight before immersion x 100 A: + 90% or more. Δ: + 80% or more and less than 90%.
X: 80% or less.

Stain resistance: Each of the above clear paints was applied to a middle coat / water polished board which was finished with a white middle coat, and was coated at 140 ° C. ×
The test plate was prepared by baking for 20 minutes. This test plate is
Exposure to a horizontal level outdoors, measure the stain resistance over time with a color difference meter (CR-200 (manufactured by Minolta)), and compare the stain resistance with the L value showing the characteristics of the lightness value from the initial value. And measured at ΔL.

A: ΔL = 0.5 or less. Δ: ΔL = 0.
5 or more and less than 1.0. ×: ΔL = 1.0 or more.

Contact angle (hydrophilicity) of coating film: The hydrophilicity of the coating film was determined from the contact angle of water from the initial stage to the lapse of time on the same test plate evaluated for stain resistance.

◎: 40 ° or less. Δ: 40 ° or more and less than 80 °. ×: 80 ° or more. Tables 4 and 5 show the results of these test evaluations.

[0148]

[Table 4]

[0149]

[Table 5]

From the results shown in Table 4, all of the coating films formed by using the coating materials obtained in Examples 1 to 7 were cured at low temperature, acid resistance, appearance (sharpness), solvent resistance, It is clear that the coating film was excellent in stain resistance and excellent in stain resistance.

On the other hand, in Comparative Example 1, the equivalent of alcoholic hydroxyl group of the component B was less than 1500 g / mol, and the acid resistance was lowered. In Comparative Example 2, the alcoholic hydroxyl equivalent of the B component was 4000 g / mol or more, and the appearance was reduced due to the reduced compatibility. In the case of Comparative Example 3 where only the A component containing no B, C, and D components was used, the stain resistance and water resistance were reduced. When the amount of the component C in Comparative Example 4 is as small as less than 5 parts by weight, the stain resistance hydrophilicity is reduced. Comparative Example 5
Conversely, when the added amount of the C component is large, the appearance deteriorates.
In Comparative Example 6, the addition amount of the D component was less than 1 part by weight, and the curability (pencil hardness) was reduced. On the contrary, in Comparative Example 7, when the added amount is more than 10 parts by weight, the storage stability of the paint is reduced. Comparative Example 8 does not include the blocked isocyanate compound in the component A, and cannot provide the coating film performance. Comparative Example 9 is a conventional melamine resin system in which the component A does not contain an epoxy group, and has insufficient acid resistance. Comparative Example 10 is a conventional urethane-based compound containing no epoxy group, and has insufficient curability and other properties of the coating film. Comparative Examples 11, 1
Nos. 2 and 13 are the cases where the component B, the component C and the component D are not contained, and show that the required coating film performance cannot be exhibited.

Thus, it can be seen that the desired coating film characteristics can be obtained by the composition of the present invention.

[0153]

According to the present invention, the curable composition for a topcoat paint comprises:
In addition to showing excellent thermosetting properties, the formed coating film has good acid resistance and good appearance, and has a good balance of coating film properties such as stain resistance. It can be suitably used as an overcoat paint used for interior and exterior of buildings, plastics and the like. A coated article obtained by applying the curable composition for a top coating composition has excellent properties as described above.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // (C09D 175/04 183: 02) (72) Inventor Susumu Umemura 1st Toyota Town, Toyota City, Toyota City, Aichi Prefecture Toyota Inside the Automobile Co., Ltd. (72) Inventor Toshiro Nambu 3-4-2 Nakanoshima, Kita-ku, Osaka-shi Kanebuchi Kagaku Kogyo Co., Ltd. (72) Inventor Seigo Nakamura 3-4-2 Nakanoshima, Kita-ku, Osaka-bell Fuchika Kagaku Kogyo K.K. PA07 PB05 PB07

Claims (3)

[Claims] (A) an acid / hydroxyl-containing acrylic resin containing a carboxyl group and a hydroxyl group in a molecule, an epoxy / hydroxyl-containing acrylic resin containing an epoxy group and a hydroxyl group in a molecule, and a blocked isocyanate A compound;
100 parts by weight of a coating resin comprising: (B) a main chain substantially consisting of a vinyl copolymer chain, and at the main chain terminal and / or side chain, the following general formula (1): (Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ² is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. A represents an integer of 0 to 2), and has at least one hydrolyzable silyl group bonded to a carbon atom represented by the following formula: And / or having at least one alcoholic hydroxyl group in the side chain, and having an alcoholic hydroxyl equivalent of 1500 to 40.
200 g / mole vinyl copolymer 15 to 100 parts by weight of, (C) the general formula ^{(2); (R 3 O} ) 4-b -Si-R 4 b (2) ( wherein, R ³ Is a hydrogen atom or a monovalent hydrocarbon group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group and an aralkyl group, and R ⁴ is a monovalent hydrocarbon group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group and an aralkyl group. A hydrocarbon group, b is an integer of 0 or 1) and / or a partial hydrolysis condensate thereof of 5 to 10
By weight, a molecular weight containing at least two carboxyl groups in one molecule obtained by subjecting (D) a polyol compound and an acid anhydride compound to a half-esterification reaction is 2,000.
A curable composition for a topcoat comprising: 1 to 10 parts by weight of the following oligomer compound. 2. The curable composition for a top coat according to claim 1, wherein the component (C) is a tetraalkyl silicate and / or a partially hydrolyzed condensate thereof. 3. A coated article obtained by applying a topcoat clear paint on a coating surface to which a paint containing a metallic powder and / or a coloring pigment has been applied, wherein the topcoat clear paint is applied. 2. A coated article characterized by comprising the curable composition for top coating composition described in any one of 2 above as a main component.