JP2001002983A - Hardenable composition for coating material and formation of topcoat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hardenable composition for a coating material capable of providing a coated film excellent in acid resistance and scratch resistance, and further to provide a method for forming a topcoat by using the composition. SOLUTION: This composition for a coating material contains (a) a vinylic polymer having both of a carboxyl group obtained by converting an acid anhydride group into a half ester, and an alkoxysilyl group as essential components, and (b) a vinylic polymer having both of an epoxy group and hydroxy group in one molecule as the essential components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel curable composition for coatings and a method for forming a top coat using the composition.

[0002]

2. Description of the Related Art In the past, paints for overcoating such as automobile outer panels have been mainly of a type in which a hydroxyl group-containing acrylic resin is cured by heating with a melamine resin. However, in recent years, etching of a coating film and stain-like stains due to acid rain have become problems worldwide. Further, with the spread of car wash machines, abrasion caused by the car wash machines has also become a problem. for that reason,
There is a need for a topcoat paint, particularly a clear topcoat paint, which can form a coating film having both sufficient acid resistance and abrasion resistance.

[0003] The imparting of scratch resistance to a coating film is usually achieved by making the coating film highly crosslinked. On the other hand, imparting acid resistance to a coating film is achieved by introducing a crosslinking system resistant to acid. However, almost no method has been proposed so far to impart acid resistance to the coating film while also imparting scratch resistance.

[0004] For example, Japanese Patent Application Laid-Open No. 2-227553 discloses that an acrylic resin having a high hydroxyl value is baked in the presence of a monomeric melamine resin and an acid catalyst to form a highly crosslinked density coating film, and a high degree of scratch resistance can be obtained. Is described.
However, this crosslinked system has a drawback that the acid resistance is inferior due to the fact that the crosslinked coating film of the melamine resin is easily decomposed with an acid.

[0005] As a method for introducing another acid-resistant cross-linking system into the acid-sensitive melamine resin cross-linking system to achieve both acid resistance and scratch resistance of the coating film, carboxyl groups / epoxy groups / hydroxyl groups / Complex cross-linking system of melamine resin
No. 247264) and a complex crosslinking system of a hydroxyl group / alkoxysilyl group / melamine resin (JP-A-4-816383).
Nos. 1 and 2, but the improvement in acid resistance was not always sufficient due to the use of a melamine resin.

On the other hand, as a cross-linking system using no melamine resin, a cross-linking system consisting of only a carboxyl group / epoxy group or a carboxyl group / epoxy group / hydroxyl group (JP-A-62-87288, JP-A-2-4557).
No. 7, JP-A-3-287650), these systems are excellent in acid resistance of the coating film, but have insufficient scuff resistance because the cured coating does not have a high crosslinking density. There is a disadvantage that there is.

Also, a resin composition comprising a carboxyl group-containing vinyl polymer and a compound containing an epoxy group and a hydrolyzable silyl group, which is a cross-linking system combining a carboxyl group / epoxy group / hydrolyzable silyl group (particularly, Kaisho 6
No. 2,187,749) is known, but it has a drawback that, although its abrasion resistance is slightly improved, it is still at an insufficient level.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel curable composition for paints in which the above-mentioned disadvantages of the prior art have been solved and a method for forming a top coat using the composition. .

Another object of the present invention is to provide a novel curable composition for coatings capable of forming a coating film having both excellent acid resistance and abrasion resistance at the same time, and a method for forming a top coat using the composition. It is in.

The present inventor has made intensive studies to achieve the above object. As a result, the curable composition for a coating containing the specific polymer (a) and the specific polymer (b) includes:
The inventors have found that the above objects can be achieved, and based on this, have completed the present invention.

Thus, the present invention provides (a) a vinyl polymer having a carboxyl group and an alkoxysilyl group as an essential component obtained by half-esterifying an acid anhydride group in one molecule, and (b) an epoxy group in one molecule. And a curable composition for a paint characterized by containing a vinyl polymer having a hydroxyl group as an essential component.

The present invention also relates to a method for forming a top coat by sequentially forming a colored base coat and a clear top coat on a material, wherein the paint for forming the colored base coat and / or the clear top coat comprises It is intended to provide a method for forming an overcoating film, wherein the method comprises using a conductive composition as a resin component.

The present invention further provides an article coated by the above method for forming a top coat.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Each component of the curable composition for paints of the present invention will be specifically described below.

The polymer (a) used in the present invention is a vinyl polymer having a group obtained by half-esterifying an acid anhydride group and an alkoxysilyl group in one molecule.

Here, the group obtained by half-esterifying an acid anhydride group means a carboxyl group obtained by adding an aliphatic monoalcohol to the acid anhydride group to open a ring (ie, half-esterifying) and a carboxylic acid ester. Means a group consisting of Hereinafter, this group may be simply referred to as a half ester group.

The carboxyl group promotes the reaction of the alkoxysilyl group in the same molecule in the form of a catalyst. That is, the reaction between the alkoxysilyl group and the hydroxyl group in (b) and the condensation of the alkoxysilyl groups by moisture are promoted.
Further, the carboxyl group itself also reacts with the epoxy group in (b). On the other hand, some of the half ester groups are de-alcoholized by heating at about 100 ° C. to regenerate the acid anhydride groups. The acid anhydride group reacts with the hydroxyl group of (b) to generate a carboxyl group. This carboxyl group promotes the above-mentioned reaction of the alkoxysilyl group and simultaneously reacts with the epoxy group of (b).

The polymer (a) can be easily obtained by copolymerizing a vinyl monomer having a half ester group, a vinyl monomer having an alkoxysilyl group and other vinyl monomers by a conventional method. Further, it can also be easily obtained by similarly copolymerizing a vinyl monomer having an acid anhydride group instead of the vinyl monomer having a half ester group, and then half-esterifying the acid anhydride group.

Examples of the vinyl monomer having an acid anhydride group include maleic anhydride and itaconic anhydride. Examples of the vinyl monomer having a half ester group include those obtained by half esterifying the acid anhydride group of the vinyl monomer having the acid anhydride group.

As described above, the half esterification may be performed before or after the copolymerization reaction. As the aliphatic monoalcohol used for the half esterification, low molecular weight monoalcohols, for example, methanol, ethanol,
Isopropanol, tert-butanol, isobutanol, methyl cellosolve, ethyl cellosolve and the like. The half-esterification reaction can be carried out according to a usual method, usually at a temperature of about room temperature to about 100 ° C., if necessary, using a basic substance as a catalyst.

Unsaturated monomers obtained by half-esterifying an acid anhydride (such as hexahydrophthalic anhydride, succinic anhydride, tetrahydrophthalic anhydride, methyl-hexahydrophthalic anhydride) and a hydroxyl-containing polymerizable monomer are also used. It can be used as a vinyl monomer having a half ester group. Examples of the hydroxyl group-containing polymerizable monomer include 2-
Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and hydroxyalkyl (meth) acrylate obtained by reacting these with lactones; Is mentioned.

Examples of the vinyl monomer having an alkoxysilyl group include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (methoxyethoxy) silane, γ- (meth) acryloyloxypropyltriethoxysilane, γ- (meth) acryloyloxypropyl Trimethoxysilane, γ- (meth) acryloyloxypropylmethyldiethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane and the like.

Other vinyl monomers include, for example, (meth) acrylic acid; (meth) acrylates; vinyl ethers and aryl ethers; olefinic compounds and diene compounds; hydrocarbon ring-containing unsaturated monomers; And unsaturated monomers.

Here, examples of (meth) acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, and tert-acrylate.
-Butyl, hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, stearyl acrylate, lauryl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, methacryl Isopropyl acrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, etc. C 1-2 of acrylic acid or methacrylic acid
Alkyl or cycloalkyl esters of 4; methoxybutyl acrylate, methoxybutyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, ethoxybutyl acrylate, ethoxybutyl methacrylate and the like having 2 carbon atoms of acrylic acid or methacrylic acid
To 18 alkoxyalkyl esters.
Also, a hydroxyl group monomer may be copolymerized within a range that does not gel during polymerization. For example, 2-hydroxyethyl (meth)
Acrylate, hydroxypropyl (meth) acrylate
4-hydroxybutyl (meth) acrylate
Hydroxyalkyl (meth) acrylates obtained by reacting these with lactones are exemplified.

Examples of vinyl ethers and aryl ethers include linear alkyl vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, butyl vinyl ether, tert-butyl vinyl ether, pentyl vinyl ether, hexyl vinyl ether, and octyl vinyl ether; cyclopentyl vinyl ether; Cycloalkyl vinyl ethers such as cyclohexyl vinyl ether; aryl vinyl ethers such as phenyl vinyl ether and trivinyl ether; aralkyl vinyl ethers such as benzyl vinyl ether and phenethyl vinyl ether; allyl ethers such as allyl glycidyl ether and allyl ethyl ether.

Examples of the olefin compound and the diene compound include ethylene, propylene, butylene, vinyl chloride, butadiene, isoprene, chloroprene and the like.

Examples of the unsaturated monomer having a hydrocarbon ring include styrene, α-methylstyrene, phenyl (meth) acrylate, phenylethyl (meth) acrylate, phenylpropyl (meth) acrylate, benzyl (meth) acrylate, Phenoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-
Acryloyloxyethyl hydrogen phthalate, 2
-Acryloyloxypropyl hydrogen phthalate, 2-acryloyloxypropyl hexahydrohydrogen phthalate, 2-acryloyloxypropyl tetrahydrohydrogen phthalate, esterified product of p-tert-butyl-benzoic acid and hydroxyethyl (meth) acrylate, dicyclopentenyl (Meth) acrylate and the like.

Examples of the nitrogen-containing unsaturated monomer include, for example,
N, N-dimethylaminoethyl (meth) acrylate,
N, N-diethylaminoethyl (meth) acrylate,
Nitrogen-containing alkyl (meth) acrylates such as Nt-butylaminoethyl (meth) acrylate; acrylamodo, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) Polymerizable amides such as acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide; 2-vinylpyridine, 1-vinyl-2-pyrrolidone, 4-vinylpyridine and the like Aromatic nitrogen-containing monomers; polymerizable nitriles such as acrylonitrile and methacrylonitrile; allylamine.

As the copolymerization method, a general polymerization method of a vinyl monomer can be used, but a solution-type radical polymerization method in an organic solvent is most suitable in consideration of versatility and cost. That is, aromatic solvents such as xylene and toluene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate, butyl acetate, isobutyl acetate and 3-methoxybutyl acetate; n-butanol and isopropyl alcohol By performing a copolymerization reaction in a solvent such as an alcohol-based solvent in the presence of a polymerization initiator such as azobisisobutyronitrile and benzoyl peroxide, usually at a temperature in the range of about 60 to 170 ° C., the desired polymer can be easily obtained. Coalescence can be obtained.

The copolymerization amount of each of a vinyl monomer having a half ester group or an acid anhydride group, a vinyl monomer having an alkoxysilyl group, and other vinyl monomers is usually set to the following ratio in all monomers. Is appropriate. That is, the amount of the vinyl monomer having a half ester group or an acid anhydride group is about 10 to 40% by weight, preferably 15 to 30% by weight, from the viewpoint of curability and storage stability. The vinyl monomer having an alkoxysilyl group is 1 to 70 from the viewpoint of curability and storage stability.
%, Preferably 2 to 50% by weight. The other vinyl monomer is 5 to 88% by weight.
Suitably, it is about 15 to 80% by weight. The amount of styrene used among the other vinyl monomers is suitably up to about 35% by weight from the viewpoint of the weather resistance of the cured coating film. When a vinyl monomer having an acid anhydride group is used, half-esterification is performed after polymerization as described above.

The polymer (a) obtained by polymerization in the above copolymerization amount usually has an acid value of 50 to 24.
0 mgKOH / g, preferably 80-120 mgKOH
/ G, the content of the alkoxysil group is 0.05 to 2.5 mmol / g, preferably 0.1 to 2.0 mmol / g. Further, the polymer (a) generally has a number average molecular weight of 1,000 to 20,000, preferably 1200 to 150.
Preferably it is in the range of 00.

The polymer (b) used in the present invention is a vinyl polymer containing an epoxy group and a hydroxyl group in one molecule.

The polymer (b) can be easily obtained by copolymerizing a vinyl monomer having an epoxy group, a vinyl monomer having a hydroxyl group and other vinyl monomers in the same manner as in the case of the polymer (a). be able to.

Examples of the vinyl monomer having an epoxy group include glycidyl (meth) acrylate, allyl glycidyl ether, 3,4-epoxycyclohexylmethyl (meth) acrylate, and the like.
The vinyl monomer having a hydroxyl group and other vinyl monomers are the same as those described above. Usually, the copolymerization amount of each of the vinyl monomer having an epoxy group, the vinyl monomer having a hydroxyl group, and other vinyl monomers is suitably set to the following ratio in all the monomers. That is, a vinyl monomer having an epoxy group is 15 to 70 from the viewpoint of curability and storage stability.
% By weight, preferably 30 to 55% by weight. From the viewpoint of curability and storage stability, the vinyl monomer having a hydroxyl group is about 5 to 30% by weight, preferably 5 to 30% by weight.
It is preferably 20% by weight. Further, the content of other vinyl monomers is suitably about 5 to 80% by weight, preferably 10 to 60% by weight. The amount of styrene used among the other vinyl monomers is suitably up to about 35% by weight from the viewpoint of the weather resistance of the cured coating film.

The polymer (b) obtained by polymerization in the above copolymerization amount usually has an epoxy group content of 1.0 to 5.0 mmol / g, preferably 1.5 to 5.0 mmol / g.
4.5 mmol / g, hydroxyl value 5 to 150 mg KOH
/ G, preferably 5-100 mgKOH / g. The polymer (b) usually has a number average molecular weight of 10
It is suitably in the range of from 2000 to 20000, preferably from 1200 to 15000.

In the curable composition of the present invention, if necessary,
A carboxyl group-containing polyester resin having an acid value of 80 to 240 mg KOH / g or a carboxyl group-containing vinyl resin (number average molecular weight: 1500 to 10000) may be blended in an amount of 0 to 70 parts with respect to 100 parts of the polymer (b). In this case, the curability can be further improved based on the reaction with the epoxy group contained in the polymer (b).

The number average molecular weight of the carboxyl group-containing polyester polymer to be used is not particularly limited, but it is usually appropriate to be about 1500 to 2000.

The carboxyl group-containing polyester polymer includes ethylene glycol, butylene glycol, 1,6
-Can be easily obtained by a condensation reaction between a polyhydric alcohol such as hexanediol, trimethylolpropane, and pentaerythritol and a polycarboxylic acid such as adipic acid, terephthalic acid, isophthalic acid, phthalic anhydride, and hexahydrophthalic anhydride. it can. For example, a carboxyl group-containing polyester polymer can be obtained by a one-step reaction under the compounding condition of polycarboxylic acid with excess carboxyl group. After synthesizing the polyester polymer of the above, a carboxyl group-containing polyester polymer can also be obtained by post-adding an acid anhydride group-containing compound such as phthalic anhydride, hexahydrophthalic anhydride and succinic anhydride.

The carboxyl group-containing polyester polymer has a hydroxyl value of 0 to 100 mgKOH / g, preferably 1 to 9 for imparting reactivity with the polymer (a).
It is also effective to introduce a hydroxyl group within a range of 0 mgKOH / g. The introduction of a hydroxyl group can be carried out by stopping the condensation reaction halfway under the compounding condition of excess carboxyl group, and conversely, under the compounding condition of excessive hydroxyl group, after synthesizing a hydroxyl-terminated polyester polymer,
It can be easily performed by blending the acid anhydride group-containing compound to be added later in a smaller amount than the hydroxyl group.

The carboxyl group-containing vinyl resin comprises (a)
Acrylic acid, methacrylic acid, (b) maleic acid, itaconic acid (including anhydride), (c) half esterified product of polymerizable acid anhydride and alcohol, (d) acid anhydride and hydroxyl group-containing polymerization It can be obtained by copolymerizing a carboxyl group-containing vinyl monomer such as a half esterified product with a polymerizable monomer and another polymerizable monomer.

Further, a method is conceivable in which (e) a hydroxyl group-containing vinyl resin is reacted with an acid anhydride to form a half ester to introduce a carboxyl group.

However, the present invention is not limited to these methods. These have a hydroxyl value of 0 to 150 mgK.
The acid value may be in the range of OH / g, and the acid value is 80 to 240 mg.
KOH / g and the number average molecular weight are preferably from 1500 to 10,000.

Other monomers include the above-mentioned (meth) acrylic esters (including hydroxyl monomers); vinyl ethers and aryl ethers; olefinic compounds and diene compounds; And nitrogen-containing unsaturated monomers.

In the curable composition of the present invention, if necessary,
A curing catalyst can be included. As a curing catalyst that can be used, as a catalyst effective for a crosslinking reaction between a carboxyl group and an epoxy group, tetraethylammonium bromide, tetrabutylammonium bromide, tetraethylammonium chloride, tetrabutylammonium fluoride, tetrabutylphosphonium bromide, triphenyl Quaternary salt catalysts such as benzylphosphonium chloride; and amines such as triethylamine and tributylamine. Of these, 4
Grade salt catalysts are preferred. Furthermore, a compound obtained by blending a phosphate compound such as dibutyl phosphoric acid with an equivalent amount of the quaternary salt to the quaternary salt can improve the storage stability of the paint without impairing the curability and reduce the electric resistance value of the paint. (I.e., a decrease in spray coating suitability) is preferred. Also,
Examples of catalysts effective for the alkoxysilyl group crosslinking reaction include tin catalysts such as dibutyltin dilaurate and dibutyltin diacetate; titanium catalysts such as tetrabutyl titanate; and amines such as triethylamine and tributylamine.

The above two curing catalysts can be used alone or in combination. However, it is desirable to use them together from the viewpoint of curability and scratch resistance.

In the curable composition of the present invention, if necessary, a so-called dehydrating agent such as trimethyl orthoacetate can be used in order to suppress the deterioration of the paint due to the solvent contained and the moisture present in the air. It is.

The curable composition of the present invention may contain, if necessary,
Known general pigments such as color pigments, extender pigments, and rust-preventive pigments can be blended.

Examples of the coloring pigment include quinacridone-based pigments such as quinacridone red, azo-based pigments such as pigment red, phthalocyanine blue, phthalocyanine lines, and the like.
Organic pigments such as phthalocyanine based pigments such as perylene red; inorganic pigments such as titanium oxide and carbon black; aluminum flakes, copper flakes, brass flakes, chrome flakes
And metallic pigments such as nickel flake, parmica and colored parmica.

If necessary, various resins such as polyester resins, alkyd resins, silicone resins and fluororesins, and non-aqueous polymer particles can be added to the cured composition of the present invention. Also, for example, melamine resin,
It is also possible to use a small amount of a crosslinking agent such as block isocyanate. Furthermore, if necessary, general paint additives such as an ultraviolet absorber, an antioxidant, a surface conditioner and an antifoaming agent can be blended.

The curable composition of the present invention is generally used as an organic solvent type coating composition. As the solvent, various organic solvents for coatings, for example, aromatic or aliphatic hydrocarbon solvents; alcohol solvents; ester solvents; ketone solvents; ether solvents and the like can be used. As the organic solvent to be used, the one used at the time of adjusting the polymer to be blended may be used as it is, or may be further appropriately added. The solid content of the composition is not particularly limited, but is usually about 20 to 80% by weight, preferably about 30 to 60% by weight.

The curable composition for a coating material of the present invention is applied to various objects to be coated by an ordinary method, usually at about 80 to 180 ° C.
Preferably, the composition is sufficiently cured under a heating condition at a temperature of 100 to 160 ° C. for about 10 to 60 minutes to form a coating film having excellent acid resistance and scratch resistance.

The method for forming a top coat according to the present invention is directed to a method for forming a top coat by sequentially forming a colored base coat and a clear top coat on a material, wherein the colored base coat and / or the clear top coat are used. As the paint to be formed, a paint containing the curable composition of the present invention as a resin component is used.

As the material for forming the overcoat film, specifically, a material obtained by electrodepositing a primer on a chemical conversion-treated steel sheet and, if necessary, applying an intermediate paint, various plastic materials (necessary) Surface treatment and primer according to
Coating, intermediate coating, etc.), and composite members in which these are combined.

In the method for forming a top coat according to the present invention,
As one or both of the paints forming the colored base coat, a paint containing the curable composition of the present invention as a resin component is used.

Since the curable composition of the present invention can form a coating film having particularly excellent acid resistance and abrasion resistance, it is preferable to use this as a resin component of a paint for forming a clear top coat.

The composition of the present invention can be used as it is as a clear topcoat coating composition. Further, a coloring pigment can be added to the clear topcoat coating composition to such an extent that the colored basecoat is not completely concealed.

In the present invention, the curable composition is prepared by appropriately blending the above-mentioned coloring pigment such as an organic pigment, an inorganic pigment, or a metallic pigment with the above-mentioned curable composition. Can be used as

The method for forming a coating film of the present invention is particularly suitable as a method for forming a top coating film for an automobile outer panel or the like. As the forming method, a coating system known in the field of the automobile industry, for example, a colored base coat / clear top coat is formed by a 2-coat 1-bake method or a 2-coat 2-bake method. Method of forming;
Colored basecoat / clear topcoat / clear topcoat in 3 coat 1 bake system or 3 coat 2 bake
For example, a method of forming by a laser method can be applied.

The most preferred method of forming a topcoat film of the present invention is to apply a paint for forming a colored basecoat to a material and then form a clear topcoat on the coated surface without curing. This is a two-coat one-bake system in which a coating material is applied and then both coating films are cured by heating.

Next, a coating method by a two-coat one-bake method using a clear top coat coating composition containing the curable composition of the present invention as a resin component will be described.

In the two-coat one-bake method, a coating composition for a colored base coat is first applied on the material by a conventional method such as spray coating.

As a coating composition for a colored base coat,
A resin composition containing the curable composition of the present invention as a resin component may be used, or a known coating composition for a colored base coat, which has been conventionally used in a method for forming a top coat, may be used. You may.

Examples of known coating compositions for colored basecoats include acrylic resin / amino resin (melamine resin and the like, the same applies hereinafter), alkyd resin / amino resin, and polyester resin / amino resin. And a resin composition containing an acrylic resin / polyisocyanate type, an alkyd resin / polyisocyanate type, a polyester resin / polyisocyanate type, etc. as a curable resin component, and blending the above-mentioned coloring pigment with the curable resin component. The form of these known colored basecoat paint compositions is not particularly limited,
Any form such as an organic solvent type, a non-aqueous dispersion type, an aqueous solution type, an aqueous dispersion type, and a high solid type can be used.

Examples of the coating machine used for spray coating include ordinary air spray guns, airless spray guns, air spray type electrostatic coating machines, airless spray type electrostatic coating machines, rotary An atomizing electrostatic coating machine or the like can be used.

The thickness of the coating composition for a colored basecoat is preferably in the range of about 10 to 30 μm (after curing). Colored base
After the coating composition for coating is applied, the coating composition is allowed to stand at room temperature for several minutes, or forcibly dried at a temperature in the range of about 50 to 80 ° C. for several minutes, and then the curable composition of the present invention is used as a resin component.
A topcoat paint composition is applied.

The coating method and the coating machine for the clear topcoat paint composition can be the same as those used for the colored basecoat paint composition.

The thickness of the coating composition for clear top coat is usually from 20 to 80 μm, preferably from 25 to 50 μm.
(After curing) is preferable.

Next, both the colored basecoat paint film and the clear topcoat paint film are simultaneously cured by heating. The heating condition in this case is usually 80 to 1
At a temperature of 80C, preferably 100-160C,
The baking time is preferably about 60 minutes.

The article coated by the method for forming a coating film of the present invention has a coating film having excellent acid resistance and abrasion resistance, and is particularly suitable for an automobile outer panel and the like.

[0070]

EXAMPLES Hereinafter, Production Examples, Examples and Comparative Examples will be given,
The present invention will be described more specifically. Unless otherwise specified, “parts” or “%” represents a weight basis, and “film thickness” represents a film thickness after drying.

Production Example 1 Production of vinyl polymer (a-1) having a half ester group and an alkoxysilyl group Swazol 1000 (carbonized) was placed in a 5-liter glass flask equipped with a stirrer, thermometer, and condenser. Hydrogen-based solvent: 500 parts of Cosmo Oil Co., Ltd. (trade name), 500 parts of ethyl ethoxypropionate, and 150 parts of an electric heating mantle
C. and at that temperature a mixture of the following monomer composition was evenly dropped over 4 hours. Incidentally, p-tert-butylperoxy-2-ethylhexanoate is a polymerization initiator. 400 parts of maleic anhydride, 370 parts of isobutyl methacrylate, 630 parts of isobutyl acrylate, 400 parts of styrene, 200 parts of γ-methacryloyloxypropyltrimethoxysilane, 200 parts of p-tert-butyl-peroxy-2-ethylhexanoate 270 parts, ethyl ethoxypropionate 800 parts, SWAZOL 1000 (a hydrocarbon solvent, trade name, manufactured by Cosmo Oil Co., Ltd.) 360 parts, and after aging for 30 minutes, 100 parts of ethyl ethoxypropionate, And a mixture of 100 parts of p-tert-butyl-peroxy-2-ethylhexanoate (100 parts of hydrocarbon solvent, Cosmo Oil Co., Ltd.) and 2 parts of p-tert-butyl-peroxy-2-ethylhexanoate were added dropwise over 2 hours. Thus, a solution of a vinyl polymer was obtained. In addition, methanol 480
And 8 parts of triethylamine.
The mixture was heated to reflux for a period of time, and then the pressure was reduced to reduce unreacted methanol.
Then, a solution of the vinyl polymer (a-1) was obtained. The solids content was 55% and the Gardner viscosity was MN. The number average molecular weight of this polymer was about 3000.
The acid value was 104 mgKOH / g and the alkoxysilyl group content was 0.73 mmol / g.

Production Example 2 Vinyl polymer having a half ester group but not having an alkoxysilyl group (a-2) The vinyl polymer was prepared by changing only the monomer composition in Production Example 1 as follows. (A-2) was obtained. 400 parts of maleic anhydride, 570 parts of isobutyl methacrylate, 630 parts of isobutyl acrylate, 400 parts of styrene, the solid content was 55%, and the viscosity was LM. The number average molecular weight was about 3000, and the acid value was 104 mgKOH / g.

Production Example 3 Production of Vinyl Polymer (b-1) Having Epoxy and Hydroxyl Groups Swazol 1000 (hydrocarbon solvent Cosmo) was placed in a 5-liter glass flask equipped with a stirrer, thermometer and cooling tube. 750 parts (trade name, manufactured by Petroleum Co., Ltd.) were charged and heated to 150 ° C. with an electric heating mantle, and at that temperature, a mixture of the following monomer compositions was evenly dropped over 4 hours. 250 parts of styrene, 380 parts of cyclohexyl methacrylate, 550 parts of isobutyl acrylate, 1000 parts of glycidyl methacrylate, 320 parts of 4-hydroxybutyl acrylate, 225 parts of 2,2′-azobis (-2-methylbutyronitrile) After aging for 30 minutes, 10 parts of 2,2'-azobis (-2-methylbutyronitrile) and 1 part of swazol 1
000 (hydrocarbon-based solvent, Cosmo Oil Co., Ltd.) (75 parts) and a monomer mixture of n-butanol (225 parts) were added dropwise over 2 hours to obtain a vinyl polymer (b-1). Was. The solid content was 69%, the Gardner viscosity V, the number average molecular weight was about 4000, the acid value was 47 mg KOH / g, and the epoxy group content was 2.6 mmol / g.

Production Example 4 Production of a vinyl polymer having only an epoxy group but not a hydroxyl group (b-2) Except that the composition of the monomer mixture in Production Example 3 was changed as follows: The same operation as in Example 3 was performed to obtain a vinyl polymer (b-2) having a solid content of 69%, a number average molecular weight of about 4000, and an epoxy group content of 2.6 mmol / g. 250 parts of styrene, 380 parts of cyclohexyl methacrylate, 870 parts of isobutyl acrylate, 1000 parts of glycidyl methacrylate, 225 parts of 2,2′-azobis (2-methylbutyronitrile).

Production Example 5 Production of Organic Solvent-Type Colored Basecoat Paint Composition (Y-1) A mixture of the following components was mixed with 30 parts of toluene, 20 parts of isobutyl alcohol, and 30 parts of cellosolve acetate. And Swazol 1000 (hydrocarbon solvent Cosmo Oil Co., Ltd.)
Co., Ltd.) was adjusted to a viscosity of 13 seconds (Ford cup # 4/20 ° C.) with a mixed solvent of 20 parts to obtain an organic solvent type coating composition (Y-1). 110 parts of 50% acrylic resin (Note 1), 28 parts of 88% Cymel 370 (Note 2), 100 parts of 20% CAB solution (Note 3), 20 parts of aluminum paste (Note 4).

(Note 1) 50% acrylic resin: 30 parts of methyl methacrylate, 59 parts of ethyl acrylate, 10 parts of 2-hydroxyethyl acrylate and 1 part of acrylic acid were mixed with xylene / n-butanol. = 70/30 (weight ratio)
Is an acrylic resin having a number average molecular weight of about 17000 and a resin solid content of 50%, which is polymerized at 100 ° C. in a mixed solvent of

(Note 2) 88% "Cymel 370": trade name, manufactured by Mitsui Cyanimid Co., Ltd., a melamine resin having a resin solid content of 88% in isopropanol. (Note 3) 20% CAB solution: toluene / n-butyl acetate of cellulose acetate butyrate = 50/50
(Weight ratio) 20% solution of mixed solvent. (Note 4) Aluminum paste: trade name “Aluminum paste # 55-519”, manufactured by Toyo Aluminum Co., Ltd.
Metallic pigment.

Production Example 6 Production of Paint Composition (M-1) for Aqueous Colored Basecoat (1) Preparation of Acrylic Resin Aqueous Dispersion (W-1) In a reaction vessel, 140 parts of deionized water, 30 parts % “Newco
l707SF "(manufactured by Nippon Emulsifier Co., Ltd., trade name, surfactant) and 1 part of the following monomer mixture (1) were added, and the mixture was stirred and mixed in a nitrogen stream. A monomer emulsion consisting of 4 parts of ammonium persulfate and 42 parts of deionized water was added to the reaction vessel over 4 hours using a metering pump. After completion of the addition, aging was performed for 1 hour.

Monomer mixture (1) 55 parts of methyl methacrylate, 10 parts of styrene, 9 parts of n-butyl acrylate, 5 parts of 2-hydroxyethyl acrylate, 1 part of methacrylic acid.

Next, at 80 ° C., the following monomer mixture (2)
20.5 parts and 4 parts of 3% ammonium persulfate were simultaneously added to 1.
The solution was dropped in parallel into the reaction vessel over 5 hours. After completion of the addition, the mixture was aged for 1 hour and filtered at 30 ° C. with a 200 mesh nylon cloth. Deionized water was further added to the mixture to adjust the pH to dimethylaminoethanol 7.5, and the average particle diameter was adjusted to 0.1.
1 μm, Tg (glass transition temperature) 46 ° C., nonvolatile content 20
% Acrylic resin aqueous dispersion W-1 was obtained.

Monomer mixture (2) 5 parts of methyl methacrylate, 7 parts of n-butyl acrylate, 5 parts of 2-ethylhexyl acrylate, 3 parts of methacrylic acid, 30% “Newcol 707SF” 0.5 Department.

(2) Preparation of Acrylic Resin Aqueous Solution (W-2) A reaction vessel was charged with 60 parts of butyl cellosolve and 15 parts of isobutyl alcohol, and heated to 115 ° C. in a nitrogen stream. After the temperature reaches 115 ° C, n-butyl acrylate 2
6 parts, methyl methacrylate 47 parts, styrene 10 parts,
A mixture of 10 parts of 2-hydroxyethyl methacrylate, 6 parts of acrylic acid, 1 part of azobisisobutyronitrile and 115 parts of butyl cellosolve was added over 1 hour, and 3 parts were added.
After aging for 0 minutes, the mixture was filtered at 50 ° C. with a 200 mesh nylon cloth. The acid value of the obtained reaction product is 48 mg KO.
H / g, viscosity Z4 (Gardona foam viscometer), nonvolatile content 5
5%, Tg 45 ° C. This is neutralized with dimethylaminoethanol in an equivalent amount, and deionized water is further added to obtain an aqueous acrylic resin solution having a nonvolatile content of 50% (W
-2) was obtained.

(3) Preparation of Paint Composition (M-1) for Aqueous Colored Basecoat Acrylic resin aqueous dispersion (W-1) 275 parts, acrylic resin aqueous solution (W-2) 40 parts, Cymel 350 "(manufactured by Mitsui Toatsu Chemicals, trade name, melamine resin) 25 parts," Aluminum Past AW-500B "(manufactured by Asahi Kasei Metals, trade name, metallic pigment) 20 parts, butyl cellosolve 20 parts and deionized water 253 parts, and “Chixol K-130B” (trade name, thickener manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd.) was added, and the mixture was adjusted to 3000 cps with a B-type viscometer (rotor rotation speed 6 rpm). The viscosity was adjusted so as to obtain a metallic water-based paint (M-1) having a nonvolatile content of about 19%.

Example 1 and Comparative Examples 1 to 3 After adjusting the resin mixed solution with the composition (solid content) shown in Table 1 below, 2 parts of an equivalent composition of tetrabutylammonium bromide and monobutylphosphoric acid, "Tinuvin 900" ( 1 part of trade name, Ciba Geigy Co., Ltd., UV absorber) and "BY
0.1 part of K-300 (trade name, manufactured by Big Chem Co., Ltd., surface conditioner) and diluted with "Swazol 1000" (trade name, manufactured by Cosmo Oil Co., Ltd., hydrocarbon solvent) Adjust the viscosity to 25 seconds (Ford cup # 4/20 ° C)
Compositions of the present invention and comparative curable compositions for coatings were prepared.

[0085]

[Table 1]

Examples 2-3 and Comparative Examples 4-9 Using the above composition as a clear topcoat coating composition, a two-coat, one-coat topcoat was formed as follows. did.

0.8 m thick with zinc phosphate chemical conversion treatment
m on a dull steel plate, electrodeposited an epoxy-based cationic electrodeposition paint so as to have a dry film thickness of about 20 μm.
After baking for a minute, sharpen with # 400 sandpaper,
Degreasing by wiping with petroleum benzine, and then air-coating the intermediate coating surface for automobiles to a dry film thickness of about 25 μm.
After spray painting and baking at 140 ° C for 30 minutes,
The material was ground with a sandpaper of 400, dried with water, dried and then degreased by wiping with petroleum benzene to prepare a test material.

Then, the metallic basecoat paint obtained in the above-mentioned production example was applied on this material so as to have a thickness of 20 μm, and was forcibly dried at room temperature for 5 minutes. -The coating composition for coating is 40 μm
And heated at 140 ° C. for 30 minutes to cure both coating films to form an overcoating film.

The performance test of the obtained top coat was carried out as follows.

Coating appearance: The metallic feeling (glitter, whiteness, etc.) was visually evaluated. The evaluation criteria are as follows.

A indicates that the metallic feeling is excellent, B indicates that the metallic feeling is inferior, and C indicates that the metallic feeling is extremely inferior.

Acid resistance: 1% of test coated plate in 40% sulfuric acid solution
After immersion for 2 hours and left at 50 ° C. for 5 hours, it was washed with water and the coated surface was observed. The evaluation criteria are as follows.

A shows that there is no change, B shows that there is no abnormality in the coated surface, but a slight step is recognized at the boundary between the immersed part and the non-immersed part, and C shows that the coated surface is whitened.

Scratch resistance: After the automobile having the test coated plate adhered to the roof was washed 15 times with a car washer, the coated surface of the coated plate was observed. The car washer was manufactured by Yasui Sangyo
0FWEC "was used. The evaluation criteria are as follows.

A shows almost no scratches by visual observation, B shows
Shows slight scratches, but the degree is very slight, and C indicates that the scratches are conspicuous by visual observation.

Water resistance: After immersion in warm water of 40 ° C. for 240 hours, washing was performed and the coated surface was observed. The evaluation criteria are as follows.

A shows no change, B shows slightly glossy, and C shows whitening of the coated surface.

The test results are shown in Table 2.

[0099]

[Table 2]

[0100]

According to the present invention, there is provided a remarkable effect that a curable composition for coatings having excellent acid resistance and abrasion resistance and a method for forming a top coat using the composition are provided.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Hiromi Kitagawa 4-1-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa F-term (reference) in Kansai Paint Co., Ltd. 4D075 AE12 BB26Z CA02 CA44 DB02 DB31 DC12 EA06 EA07 EA08 EA10 EA43 EB20 EB22 EB32 EB33 EB35 EB36 EB38 EB42 EB45 EB52 EB55 EB56 4J038 CG082 CG132 CG141 CG142 CH122 CH171 CJ131 CL002 DB231 DB261 GA03 GA06 GA07 GA15 MA14 NA04 NA11 PA19 PB07 PC02

Claims (10)

[Claims] 1. A (a) vinyl polymer having a carboxyl group and an alkoxysilyl group as essential components obtained by half-esterifying an acid anhydride group in one molecule, and (b) an epoxy group and a hydroxyl group in one molecule. A curable composition for coatings, comprising a vinyl polymer as an essential component. 2. The polymer (a) has an acid value of 50 to 240 mgK.
OH / g, alkoxysilyl group content 0.05 to 2.5
A composition according to claim 1, wherein the composition is of mmol / g. 3. The polymer (a) has a number average molecular weight of 1,000 to 1,000.
The composition according to claim 1, which is a 20000 acrylic polymer. 4. The polymer (b) has an epoxy group content of 1.0.
-5.0 mmol / g, hydroxyl value 5-150 mgKOH
The composition according to any one of claims 1 to 3, wherein the composition is of the formula: 5. The polymer (b) has a number average molecular weight of 1,000 to 1,000.
The composition according to any one of claims 1 to 4, which is an acrylic polymer of 20,000. 6. The compounding ratio of the polymer (a) to the polymer (b) is such that the equivalent ratio of the former carboxyl group to the latter epoxy group is 2: 1 to 0.5: 1. Item 6. The composition according to any one of Items 1 to 5. 7. A method for forming a top coat by sequentially forming a colored base coat and a clear top coat on a material, wherein the colored base coat and / or the clear top coat is formed. 7. A method for forming an overcoat film, wherein the coating material comprises the curable composition for coating material according to any one of claims 1 to 6 as a resin component. 8. A method of forming a topcoat film, comprising applying a coating material for forming a colored base coat to a material and then applying a coating material for forming a clear top coat on the coated surface without curing. Then, both coats are heat-cured, two coats and one base
8. The method for forming a topcoat film according to claim 7, wherein the method is a lock method. 9. A paint for forming a clear top coat,
8. The method for forming a top coat according to claim 7, wherein the curable composition for a coating according to any one of claims 1 to 6 is used as a resin component. 10. An article coated by the method according to claim 7.