JPH09286949A - Thermosetting coating composition for top-coating clear in motor vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermosetting coating composition for top-coating on motor vehicle excellent in resistance to acid and improved in resistance to damage to the coated layer on the vehicle bodies in washing by crosslinking an oxazolinyl group-containing acrylic resin with a carboxyl group-containing acrylic resin between the oxazolinyl group and the acid group. SOLUTION: This curable coating composition comprises (A) a copolymer prepared by copoymerization of (i) a polyadditionalylly polymerizable oxazoline of the formula (R<1> and R<4> are each H, a halogen, an alkyl, an aralkyl, a cycloalkyl, an aryl; R<5> is am alkenyl, a cycloalkenyl) and (ii) monomers containing an acrylic monomer as an essential component and (B) a copolymer prepared from a monomer component essentially containing at least one selected from ethylenically unsaturated dicarboxylic acid anhydride, a monoester of such acid anhydride and a monoamide of such acid anhydride in the presence of an organic solvent. In addition, (C) an acrylic copolymer containing a fluorocarbon and (D) a melamine resin are preferably formulated to the polymer mixture (A) and (B).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermosetting coating composition. More specifically, a thermosetting coating composition, which is a new crosslink between an oxazolinyl group and a carboxyl group,
In particular, by applying a top coat clear coat by a wet-on-wet method on a base color coat for automobile bodies, baking and drying it gives an excellent acid resistant coating film, chemical resistance, water repellency, A thermosetting type that can form a highly glossy and sharp thermosetting coating film that has car wash resistance, dry wipe resistance, long-term weather resistance, and excellent coating appearance. The present invention relates to a coating composition.

[0002]

2. Description of the Related Art The current (thermosetting acrylic melamine resin composition) car body clear coats are prepared by coexisting each acrylic monomer, unsaturated carboxylic acid, and hydroxyl group-containing acrylic monomer in the presence of an organic solvent. Mainly composed of 80 parts of a copolymer obtained by polymerization and 20 parts of melamine resin, the body clear has almost no acid resistance, chemical resistance, water repellency, car wash scratch resistance and dry wipe scratch resistance. , Does not have long-term weather resistance.

Therefore, as a clear for acid resistant car body,
Acid and epoxy cross-linking of carboxyl group-containing acrylic resin and glycidyl group-containing acrylic resin has become the mainstream, but the problem of yellowing though the appearance is good,
It had a fatal problem of poor storage stability.

[0004]

Due to such drawbacks, the above-mentioned coating film formation is not sufficient in commercial value, and in the thermosetting coating composition which is practically used today, The current situation is that sufficient acid resistance has not been obtained. Therefore, the present invention is to provide a thermosetting coating composition having excellent acid resistance. In addition, the present invention is
A thermosetting coating composition that can be used as an overcoat clear coat for a vehicle body, in particular, a so-called 2 coat 1 bake that is used as an overcoat clear coat on a base coat by a wet-on-wet method to form a coating film by one baking. It has excellent acid resistance, and has improved car wash scratch resistance and dry wipe scratch resistance (property that the paint film does not easily get scratched during car wash or dry wipe) and weather resistance. It is intended to provide a thermosetting coating composition. Further, the present invention provides a thermosetting coating composition having high water repellency in addition to excellent acid resistance, weather resistance, car wash scratch resistance, and dry wipe scratch resistance. Furthermore, the present invention is a so-called 2 coat 1 bake coating method,
An object of the present invention is to provide a coating method capable of forming a coating film having excellent acid resistance, weather resistance, car wash scratch resistance, dry wipe scratch resistance, and water repellency.

[0005]

In view of the above-mentioned circumstances, the inventors of the present invention have earnestly studied in order to solve the above-mentioned drawbacks, and as a result, as a result, an oxazolinyl group of an oxazolinyl group-containing acrylic resin and a carboxyl group-containing acrylic resin has been obtained. The inventors have found that it is appropriate to form a coating film by cross-linking with an acid and have arrived at the present invention. That is, the first invention of the present application is the following general formula (1)

[0006]

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(In the formula, R1, R2, R3 and R4 are the same or different and each represents hydrogen, halogen, an alkyl group, an aralkyl group, a cycloalkyl group, an aryl group or a substituted aryl group, and R5 is an alkenyl group or a cycloalkenyl group. Group), an addition-polymerizable oxazoline (a-
1) and a polymer (A) obtained by copolymerizing a monomer component essentially containing the acrylic monomer (a-2) in the presence of an organic solvent, and an ethylenically unsaturated dicarboxylic acid In the presence of an organic solvent, a monomer component essentially containing at least one monomer selected from an anhydride and a monoesterified product of an ethylenically unsaturated dicarboxylic acid anhydride and a monoamidated product of an ethylenically unsaturated dicarboxylic acid anhydride is used. There is provided a thermosetting coating composition for an automobile topcoat clear, which is characterized by being blended with a polymer (B) obtained by copolymerization.

A second invention of the present application is the same as the first invention, wherein, in addition to the components of the polymer (A) and the polymer (B), an acrylic copolymer (C) containing fluorocarbon and melamine. The present invention provides a thermosetting coating composition for an automobile topcoat clear, which is characterized by being blended with a resin (E), in which fluorocarbon improves water repellency (desirably, an aerial contact angle of water of 75 to 85). Further, the blending of the melamine resin improves the cross-linking density and improves the car-washing scratch resistance and the air-cleaning scratch resistance.

A third invention of the present application is the same as the first invention, except that each component of the polymer (A) and the polymer (B) is added,
A copolymer (D) obtained by copolymerizing acrylic monomers, unsaturated carboxylic acids, and caprolactone-modified (meth) acrylate and / or hydroxyl group-containing acrylic monomers in the presence of an organic solvent, Provided is a thermosetting coating composition for an automobile topcoat clear, which is characterized by being blended with a melamine resin (E). In the third aspect of the present invention, the blending of the melamine resin improves the crosslink density and improves the car wash scratch resistance and the dry wipe scratch resistance. Further, by blending the copolymer (D) containing either one of the hydroxyl group-containing acrylic monomer and the caprolactone, the car wash scratch resistance and the dry wipe scratch resistance are improved, and the hydroxyl group-containing acrylic monomer is further added. The weather resistance is improved by adding both of the above and caprolactone.

A fourth invention of the present application is the same as the first invention, except that each component of the polymer (A) and the polymer (B) is added,
Provided is a thermosetting coating composition for an automobile topcoat clear, which comprises a silyl group-containing acrylic copolymer (F) and a melamine resin (E). In the fourth aspect of the present invention, the blending of the melamine resin improves the crosslink density and improves the car wash scratch resistance and the dry wipe scratch resistance. Further, by blending the silyl group-containing acrylic copolymer (F), car wash resistance and car wipe resistance are improved, and further weather resistance is improved.

A fifth invention of the present application is the same as the first invention, wherein each component of the polymer (A) and the polymer (B) is added,
Provided is a thermosetting coating composition for an automobile topcoat clear, which comprises a melamine resin (E). In the fifth aspect of the present invention, the blending of the melamine resin improves the crosslink density and improves the car wash scratch resistance and the dry wipe scratch resistance.

A sixth invention of the present application is the above-mentioned first to fifth inventions.
In any of the inventions described above, the component of the polymer (A) is
Provided is a thermosetting coating composition for an automobile topcoat clear, which comprises an addition-polymerizable oxazoline (a-1), an acrylic monomer (a-2), and an alkyl (meth) acrylate and / or styrene. .
In the sixth invention of the present application, by adding alkyl (meth) acrylate and / or styrene, the amount of acrylic monomers is relatively reduced, the molecular weight of the copolymer is reduced, and the viscosity of the coating is adjusted to an appropriate value. Can be adjusted.

A seventh invention of the present application is the above-mentioned first to sixth inventions.
In any one of the first to sixth inventions, the acrylic monomer (a-2)
Is a hydroxyl group-containing (meth) acrylate and / or a caprolactone-modified (meth) acrylate, and a thermosetting coating composition for an automobile topcoat clear is provided. A seventh invention of the present application is that, as the acrylic monomer (a-2), by using either one of a hydroxyl group-containing (meth) acrylate and a caprolactone-modified (meth) acrylate, car wash scratch resistance and dry wipe scratch resistance are obtained. The adhesiveness is improved, and the weather resistance is improved by using both the hydroxyl group-containing acrylic monomer and the caprolactone-modified (meth) acrylate.

An eighth invention of the present application is the above-mentioned first to seventh inventions.
In any of the inventions, the component of the copolymer (B) is a monoesterified product of an ethylenically unsaturated dicarboxylic acid anhydride and an ethylenically unsaturated dicarboxylic acid anhydride, and a monoamide of the ethylenically unsaturated dicarboxylic acid anhydride. One or more monomers selected from compounds and alkyl (meth)
Provided is a thermosetting coating composition for an automobile topcoat clear, which comprises an acrylate and / or styrene. In the eighth invention of the present application, by adding alkyl (meth) acrylate and / or styrene, the amount of acrylic monomers is relatively reduced, the molecular weight of the copolymer is reduced, and the viscosity of the coating is adjusted to an appropriate value. Can be adjusted.

A ninth invention of the present application is the above-mentioned first to eighth inventions.
A method of applying the thermosetting coating composition according to any one of the inventions as a clear coat, and more specifically, a base having an L value (brightness) of 30 or less containing any one of an aluminum pigment, a mica pigment, and a coloring pigment. There is provided a coating method in which the thermosetting coating composition according to any one of the first to eighth inventions is applied as a clear coat on a color coat by a wet-on-wet method and then baked. Any of the thermosetting coating compositions according to the above invention can be applied as a so-called 2-coat 1-bake clear coat for vehicle bodies. This clear coat starts with acid resistance,
On a base color coat having an L value (brightness) of 30 or less, including any one of an aluminum pigment, a mica pigment, and a coloring pigment, which are particularly required to have weather resistance, car wash scratch resistance, and dry wipe scratch resistance, It can bring about very effective effects.

As described above, the curable resin composition of the present invention contains the polymer (A) and the polymer (B) as essential components. In the following description, "polymer" includes not only a homopolymer but also a copolymer composed of two or more kinds of plural monomers.

The polymer (A) in the present invention comprises, as essential repeating units, an addition-polymerizable oxazoline (a-1) represented by the general formula (I) and a hydroxyl group-containing monomer (a-2).
Is a polymer containing as an essential repeating unit.

[0018]

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(In the formula, R ¹ , R ² , R ³ and R ⁴ represent hydrogen, halogen, an alkyl group, an aralkyl group, a cycloalkyl group, an aryl group or a substituted aryl group, which may be the same or different, and R 1 ⁵ represents an alkenyl group or a cycloalikenyl group.) That is, the polymer (A) is obtained by radical polymerization of a monomer component containing an addition-polymerizable oxazoline (a-1) and a hydroxyl group-containing monomer (a-2) as essential components. It is what is done.

The addition-polymerizable oxazoline (a-1) represented by the above general formula (I) is a monomer which carries out radical addition polymerization at the R ⁵ part, and is an oxazoline ring in the polymer (A), that is, oxazolinyl. Used to introduce groups.

Specific examples include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline,
2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-
4-methyl-2-oxazoline, 2-isopropenyl-
5-methyl-2-oxazoline, 2-isopropenyl-
5-ethyl-2-oxazoline and the like can be mentioned,
One kind or a mixture of two or more kinds selected from these groups can be used.

As specific examples of the acrylic monomer (a-2) which is another essential constituent of the polymer (A), only typical ones will be exemplified. Methyl (meth) acrylate and ethyl (Meth) acrylate,
n-propyl (meth) acrylate, i-propyl (meth)
Acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth)
Acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, dipromopropyl (meth) acrylate, tripromophenyl (meth) acrylate, acetoacetoxyethyl (meth) Various types such as acrylate can be mentioned.

The acrylic monomer (a-2) is preferably a hydroxyl group-containing monomer (a-2), and specific examples thereof include 2-hydroxyethyl (meth) acrylate and (meth) acrylic acid- 2-hydroxypropyl, 2-hydroxybutyl (meth) acrylate, 1-methyl-2-hydroxyethyl (meth) acrylate,
Examples thereof include (meth) acrylic acid-3-hydroxypropyl, (meth) acrylic acid-3-hydroxybutyl, and (meth) acrylic acid-4-hydroxybutyl. Unsaturated carboxylic acids such as mono (meth) acrylate of polyester diol obtained from phthalic acid and propylene glycol, (meth) acrylic acid, and maleic acid, and a monoepoxide compound (for example, trade name Cardurer E;
Glycidyl esters of branched aliphatic monocarboxylic acids; hydroxyl group-containing (meth) acrylates such as adducts of Yuka Shell Epoxy Co., Ltd. Further, as the acrylic monomer (a-2), a caprolactone-modified (meth) acrylate (for example, trade name Praxel FM: FA
Series; manufactured by Daicel Chemical Industries, Ltd.) can be used, and by using this, high tensile strength of the paint can be obtained.

The composition ratio of the addition-polymerizable oxazoline (a-1) and the acrylic monomer, particularly the hydroxyl group-containing monomer (a-2) is not particularly limited, but it is based on 1.0 equivalent of the oxazolinyl group in the polymer (A). Hydroxyl group is 0.5-2.
It is preferable that the amount is 0 equivalent. When other monomer (a-3) is also used, the content is% by weight,
(A-1): 10 to 60% by weight, (a-2): 10 to 6
0% by weight, (a-3): 80% by weight or less is preferable.

Also during the production of the polymer (A), the addition-polymerizable oxazoline (a-1) and the acrylic monomer (a-
It is preferable to radically polymerize the other monomer (a-3) in 2). Specific examples of the other monomer (a-3) include styrene derivatives such as styrene, vinyltoluene, α-methylstyrene, chloromethylstyrene, styrenesulfonic acid and salts thereof;
(Meth) acrylamide, N-monomethyl (meth) acrylamide, N-monoethyl (meth) acrylamide,
(Meth) such as N, N-dimethyl (meth) acrylamide
Acrylamide derivatives; carboxyl group-containing monomers such as (meth) acrylic acid and itaconic acid; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, etc. ) Alkyl (meth) acrylates synthesized by esterification of acrylic acid and a C ₁ -C ₁₈ alcohol; olefins such as ethylene, propylene and n-butene; ethyl (meth) acrylate 2-sulfonate and salts thereof, Unsaturated sulfonic acids such as vinyl sulfonic acids and salts thereof; vinyl esters such as vinyl acetate, vinyl propionate and vinyl stearate; (meth) acrylonitrile; vinyl ethers of methyl vinyl ether, ethyl vinyl ether, octyl vinyl ether, lauryl vinyl ether Basic monomers such as dimethylaminoethyl acrylate (meth) acrylate, dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, vinylpyridine, vinylimidazole, vinylpyrrolidone; (meth) acrylic acid and ethylene Esters with polyhydric alcohols such as glycol, 1,3-butylene glycol, diethylene glycol, 1,6-hexane glycol, neopentyl glycol, polyethylene glycol, polypropylene glycol, trimethylolpropane, pentaerythritol, dipentaerythritol Such as polyfunctional (meth) acrylates having two or more polymerizable unsaturated groups in the molecule; N-methylol (meth) acrylamide, N-butoxy (meth) acrylamide and other (meth) acrylics Earth;
Glycidyl (meth) acrylate, (meth) acrylic acid 2
-Epoxy group-containing monomers such as methyl glycidyl and acryl glycidyl ether; 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloylamino 1,2,2,6 Polymerizable UV-stable monomers such as 6,6-pentamethylpiperidine; vinyl fluoride, vinylidene fluoride, vinyl chloride, vinylidene chloride, divinylbenzene, diallylflate and the like.

In particular, it is desirable to use styrene when the cured coating film is required to have a high appearance, and 4- (meth) acryloyloxy-1,2,2,6,6 is used when high weather resistance is required. 6 −
It is recommended to use polymerizable UV stable monomers such as pentamethylpiperidine, 4- (meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine. Further, when maleic anhydride is used as the monomer (b), it is preferable to use styrene together with the alkyl (meth) acrylate because maleic anhydride is difficult to copolymerize with the alkyl (meth) acrylate. Also, (meta)
Alkyl (meth) acrylates such as methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, 4- (meth) acryloyloxy-1,2,2,6 , 6-Pentamethylpiperidine, 4- (meth) acryloylamino-
Polymerizable UV-stable monomers such as 1,2,2,6,6-pentamethylpiperidine are preferably used from the viewpoint of coating film performance.

Next, the polymer (B) is one or more monomers (one or more monomers selected from an ethylenically unsaturated dicarboxylic acid anhydride, a monoesterified product of the dicarboxylic acid anhydride and a monoamidated product of the dicarboxylic acid anhydride. A monomer component containing b) as an essential repeating unit and containing at least one monomer (b) as an essential component is polymerized, or a monomer component containing only an ethylenically unsaturated dicarboxylic acid anhydride as an essential component. Of the unsaturated dicarboxylic acid anhydride group by monoesterification or monoamidation during or after the polymerization.

Examples of the monomer (b) used include ethylenic unsaturated dicarboxylic acid anhydrides such as itaconic anhydride, maleic anhydride and citraconic anhydride, and monoesters or monoamidates of these.

In order to monoesterify the acid anhydride group in the polymer (B) during or after the polymerization, a monoesterifying agent may be reacted. As a monoesterification agent,
Low molecular weight alcohols such as methanol, ethanol, i-propanol, t-butanol, i-butanol, methyl cellosolve, dimethylaminoethanol, diethylaminoethanol, acetol and the like can be mentioned.
Similarly, monoamidation can also be performed using a monoamidating agent, and examples of the monoamidating agent include low molecular weight amines such as monoethylamine, monobutylamine, diethylamine and aniline. Of these, particularly preferable compounds are methanol, n-butanol, dimethylaminoethanol, diethylaminoethanol and acetol.

The monoesterification or monoamidation reaction is carried out according to a conventional method at a temperature from room temperature to 120 ° C., and in some cases, using a tertiary amine as a catalyst.
Further, when carried out during the polymerization, if a necessary amount of the above-mentioned monoesterifying agent or monoamidating agent is added to the solvent for polymerization, a part or all of the acid anhydride group is ring-opened to form a monoester. Alternatively, a monoamidation reaction can be performed.

It is important that the polymer (B) contains the monomer (b) as an essential repeating unit. When all the acid anhydride groups in the polymer (B) are, for example, monoesterified, the acid value, which is a numerical value representing the amount of all the carboxyl groups in the polymer (B), is 50 to 200 mgKOH / g. It is preferable to polymerize the above-mentioned monomer (b).
If it is less than 50 mgKOH / g, the crosslink density when formed into a coating film becomes insufficient and the solvent resistance, acid rain resistance and weather resistance are remarkably deteriorated. If it exceeds 200 mgKOH / g, the storage stability will be adversely affected, and it will be difficult to use it in applications requiring water resistance. More preferable acid value is 60 to 150.
It is mgKOH / g.

To produce the polymer (B), in addition to the monomer (b) which is an essential component, a monomer containing other monomer (b-2) in order to improve the physical properties of the coating film after curing. It is preferred to radically polymerize the components. The amount of the other monomer (b-2) used is appropriately determined by adjusting the acid value of the polymer (B) so as to fall within the above preferable range.

As the other monomer (b-2), the other monomer (a) described in the above-mentioned polymer (A) is used.
The same thing as -3) can be used as it is.

In particular, it is desirable to use styrene when the cured coating film is required to have a high appearance, and 4- (meth) acryloyloxy-1,2,2,6,6 is used when high weather resistance is required. 6 −
It is recommended to use polymerizable UV stable monomers such as pentamethylpiperidine, 4- (meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine. Further, when maleic anhydride is used as the monomer (b), it is preferable to use styrene together with the alkyl (meth) acrylate because maleic anhydride is difficult to copolymerize with the alkyl (meth) acrylate. Also, (meta)
Alkyl (meth) acrylates such as methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, 4- (meth) acryloyloxy-1,2,2,6 , 6-Pentamethylpiperidine, 4- (meth) acryloylamino-
Polymerizable UV-stable monomers such as 1,2,2,6,6-pentamethylpiperidine are preferably used from the viewpoint of coating film performance.

When producing the polymer (B) and the polymer (A), known radical polymerization is used. As the radical polymerization, for example, solution polymerization, bulk polymerization, suspension polymerization,
Emulsion polymerization and the like can be mentioned. Solvents that can be used when adopting the solution polymerization include, for example, aromatic hydrocarbons such as toluene, xylene, Solvesso # 100 (manufactured by Esso); acetic acid esters such as ethyl acetate, butyl acetate, isobutyl acetate; methyl ethyl ketone, etc. Ketones; propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate,
Alkylene glycol ethers such as diethylene glycol monomethyl ether acetate; alcohols such as methyl alcohol, butyl alcohol, isopropyl alcohol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, ethylene glycol, etc. can be used alone or as a mixed solvent. To be done.

As the polymerizable initiator, azo compounds such as azobisisobutyronitrile and azobis (2-methyl) butyronitrile; peroxide compounds such as benzoyl peroxide and di (tertiarybutyl) peroxide are used. Typical radical polymerization initiators such as compounds may be mentioned. These initiators are used in the range of 0.1 to 10% by weight based on the total amount of monomers. The reaction temperature is in the range of room temperature to 200 ° C, preferably 40 to 150 ° C. When carrying out the polymerization reaction, a chaining agent or regulator such as lauryl mercaptan, 2-mercaptoethanol or carbon tetrachloride may be used for the purpose of adjusting the number average molecular weight.

Although the mechanism of coating film formation has not been completely elucidated, the amide ester bond by the oxazolinyl group of the component (A) and the carboxyl group of the component (B) is caused by baking (in the presence of thermal energy). It is considered that the coating film is formed by crosslinking between the components. In particular, when the polymer (A) contains a hydroxyl group-containing monomer (a-2), first, an ester group (which is formed by monoesterifying (or monoamidating) the acid anhydride group in the polymer (B)) Alternatively, the amide group and the carboxyl group are closed again at the curing temperature (70 to 140 ° C.) and once returned to the acid anhydride group. Next, the acid anhydride group in the polymer (B) undergoes a monoesterification reaction with the hydroxyl group in the polymer (A),
It again forms an ester group and a carboxyl group. The carboxyl group generated here reacts with the oxazolinyl group in the polymer (A), and the curing proceeds rapidly. That is, this curing reaction proceeds because the dicarboxylic acid anhydride group in the polymer (B) reacts with and bonds to the two functional groups of the oxazolinyl group and the hydroxyl group in the polymer (A), respectively. Things have a strong network structure. Therefore, the obtained cured coating film has excellent weather resistance, acid rain resistance, and chemical resistance. Further, as will be described later, when the polymer (A) contains the hydroxyl group-containing monomer (a-2), it is bonded by a polycondensation reaction between the hydroxyl group and the methylol group or butyrol group of the melamine resin (E) component. ,
Further, the crosslink density is improved.

The compounding ratio of the polymer (B) to the polymer (A) is 1.0 equivalent of all the carboxyl groups when all the acid anhydride groups in the polymer (B) are monoesterified. ,
It is preferable that the oxazolinyl group of the polymer (A) is in the range of 0.3 to 2.0 equivalents and the hydroxyl group is in the range of 0.1 to 3.0 equivalents in order to obtain an excellent cured coating film. Therefore, in the curable resin composition of the present invention, the polymers (B) and (A) may be appropriately blended so as to have the above equivalence ratio, according to each composition. If the oxazolinyl group is less than 0.3 equivalent or the hydroxyl group is less than 0.1 equivalent, the amount of these functional groups does not become a substantially effective amount during the crosslinking and curing reaction. On the contrary, 2.0 equivalents of oxazolinyl group or 3.
Even if the amount exceeds 0 equivalents, the effective amount cannot be achieved. Oxazolinyl group is in the range of 0.7 to 1.3 equivalents, hydroxyl group is 0.5
A range of up to 2.0 equivalents is a more preferable range.

In order to improve the storage stability of the paint, it is preferable to add a basic substance such as a tertiary amine. This basic substance neutralizes and blocks the carboxyl group in the polymer (B) to inhibit the reaction with the oxazonyl group, thereby achieving storage stability.
And in the presence of thermal energy during baking,
The basic substance volatilizes at about 0 to 140 ° C., and the above-mentioned crosslinking reaction is performed to form a coating film. Examples of the basic substance include ammonia, primary amines such as methylamine, secondary amines such as dimethylamine, tertiary amines such as triethylamine, dimethylaminoethanol and diethylhydroxyamine, and aliphatic amines such as n-butylamine and diethylamine. Cycloaliphatic amines such as cyclohexylamine,
Piperidine, morpholine, N-ethylpiperidine, N-
Examples thereof include heterocyclic amines such as ethylmorpholine and pyridine, aromatic amines such as benzylamine, N-methylaniline, and N, N-dimethylamine. These amine compounds may be used alone or in combination of two or more. Can be used.

This basic compound is in the range of 0.3 to 3.0 equivalents based on 1.0 equivalent of all carboxyl groups present when the acid anhydride groups of the polymer (B) are monoesterified. It is desirable to use, more preferably 0.5
Used in the range of up to 2.0 equivalents. If it is less than 0.3 equivalent, it is difficult to obtain sufficient storage stability, and if it exceeds 3.0 equivalent, physical properties such as crosslinkability and weather resistance of the coating film may be adversely affected.

Next, the fluorocarbon-containing acrylic resin as the component (C) is a copolymer obtained by copolymerizing fluorocarbon with an acrylic monomer in the presence of an organic solvent. Has a number average molecular weight of about 2
000 to 10,000, a hydroxyl value of 5 to 150, an acid value of 0.01 to 50, and a Tg point of -15 to + 150 ° C are suitable.

The component (D) is preferably 30 to 95% by weight of acrylic monomers and 0.5% by weight of unsaturated carboxylic acids in total monomers.
When adding a caprolactone-modified (meth) acrylate, it is desirable to use 0.5 to 40% by weight of the total amount of the monomers, and when adding a hydroxyl group-containing acrylic monomer, the total amount of the monomers should be 0. It is desirable to be 5 to 60% by weight. In addition, styrene monomers may be added as the component (D), and in this case, it is desirable that the styrene monomers be 0.5 to 40% by weight of the total amount of the monomers. The number average molecular weight of this copolymer is about 2000-1.
2000, hydroxyl value 80-150, acid value 0.5-2
0, Tg point is -15 to + 150 ° C.

The above-mentioned component (E) is a melamine resin, but a butylated melamine resin, a methylated melamine resin and a methylated / butylated melamine resin are particularly preferable.

The above component (F) is an acrylic silicone resin, which was obtained by copolymerizing an acrylic monomer with a silicone component in the presence of an organic solvent.
The copolymer preferably has a number average molecular weight of 2000 to 6000, a hydroxyl value of 5 to 150, and a Tg point of 10 to 50 ° C.

The coating composition according to each invention of the present application, among aluminum pigments, mica pigments, and colored pigments having stable physical properties,
It can be applied as a clear coat compounded by a wet-on-wet method on a color base coat having an L value (brightness) of 30 or less containing at least one kind, and after coating by this wet-on-wet method,
A coating film is formed by baking. The coating compositions according to the inventions of the present application can of course be used on a color base coat having an L value (brightness) of 30 or more, but in a dark color base coat having an L value (brightness) of 30 or less. Is particularly required to have high car wash scratch resistance and dry wipe scratch resistance, and therefore, the superiority of the coating composition according to the present invention appears even more clearly.

Although the mechanism of coating film formation has not been completely elucidated, as described above, the oxazolinyl group of the component (A) and the carboxyl group of the component (B) are subjected to baking (in the presence of thermal energy). It is considered that an amide-ester bond is formed by the above, and the ingredients are crosslinked to form a coating film. In addition, when the component (C) contains a hydroxyl group, the hydroxyl group and the methylol group or butyrol group of the component (E) are combined by a polycondensation reaction to crosslink between the respective components, thereby forming a coating film. It is thought to be. When a hydroxyl group-containing acrylic monomer is added to the component (A),
An ester bond between the same hydroxyl group and the acid anhydride group obtained by reclosing the monoesterified (or monoamidated) acid anhydride group of the component (B), the same hydroxyl group and the methylol group of the component (E), butyrol The cross-linking density is further improved by the bond with the group by the polycondensation reaction. Also, (F)
The hydroxyl group in the silyl group-containing acrylic copolymer is crosslinked with the melamine resin in the component (E), and a siloxane bond is formed. Here, when mainly considering the oxazolinyl group of the component (A) and the amide ester bond by the carboxyl group of the component (B), the oxazolinyl group equivalent per unit weight in the component (A) and the unit weight in the component (A) It is most preferable that the carboxy group equivalent is equal to, but as described above, it is not limited thereto.

Explaining by the combination of each component,
The component (A) and the component (B) form a coating film in the presence of heat energy by cross-linking the oxazolinyl group in the component (A) and the carboxyl group in the component (B).

The cross-linking of the component (A), the component (B), the component (C) and the component (E) is carried out by cross-linking the oxazolinyl group in the component (A) with the carboxyl group in the component (B), Crosslinking of the hydroxyl group in the fluorocarbon-containing acrylic copolymer in the component with the acid anhydride group in which the monoesterification (or monoamidation) of the component (B) is closed again by heating, and the same hydroxyl group And cross-linking with the melamine resin in the component (E) (however, in this case, the fluorocarbon-containing acrylic copolymer uses a hydroxyl group-containing one),
Crosslinking of the hydroxyl group in the oxazolinyl group-containing acrylic copolymer in the component (A) and the melamine resin in the component (E) (however, in this case, the hydroxyl group-containing acrylic copolymer is used as the component (A)). Is.

The cross-linking of the component (A), the component (B), the component (D) and the component (E) is carried out by cross-linking the oxazolinyl group in the component (A) and the carboxyl group in the component (B), (D). Crosslinking between the hydroxyl group in the acrylic copolymer in the component and the acid anhydride group in which the monoesterified (or monoamidated) component (B) is closed again by heating, and the same hydroxyl group ( Cross-linking with the melamine resin in component E), (A)
Crosslinking between the hydroxyl group in the component and the melamine resin in the component (E) (however, in this case, a hydroxyl group-containing acrylic copolymer is used in the component (A)).

The crosslinking of the component (A), the component (B), the component (E) and the component (F) is carried out by crosslinking the oxazolinyl group in the component (A) with the carboxyl group in the component (B), and (F). The hydroxyl group in the silyl group-containing acrylic copolymer in the component and the acid anhydride group, which has been monoesterified (or monoamidated) in the component (B) by heating, are cross-linked with the acid anhydride group which is closed again. Crosslinking between the hydroxyl group and the melamine resin in the component (E) and siloxane bond. Also, (A)
Crosslinking between the hydroxyl group in the component and the melamine resin in the component (E) (however, in this case, a hydroxyl group-containing acrylic copolymer is used in the component (A)) is carried out.

The cross-linking of the component (A), the component (B) and the component (E) is carried out by cross-linking the oxazolinyl group in the component (A) and the carboxyl group in the component (B), and the cross-linking in the component (A). Crosslinking between the hydroxyl group and the melamine resin in the component (E) (however, in this case, a hydroxyl group-containing acrylic copolymer is used in the component (A)) is carried out.

Here, as the acrylic monomers in the component (D), the acrylic monomers (a-
Those exemplified in 2) can be used. Also,
As the hydroxyl group-containing acrylic monomer in each component of the component (D), those exemplified in the hydroxyl group-containing acrylic monomer (a-2) of the component (A) can be used.

By using the hydroxyl group-containing acrylic monomer, the above-mentioned cross-linking becomes possible, the curability is improved, and the solvent resistance, interlayer adhesion and chemical resistance are improved. In particular, by using caprolactone-modified (meth) acrylate as the hydroxyl group-containing acrylic monomer, it is possible to obtain high tensile strength of the coating material as described in the above-mentioned component (A). When the amount of the hydroxyl group-containing acrylic monomer or the caprolactone-modified (meth) acrylate used is 0.5% by weight or more, the above-mentioned properties are improved, but when the amount is more than 60% by weight, the adhesion is increased. 20% by weight, in other words, a hydroxyl value (solid content) of 20 to 180, preferably 30 to 40% by weight, based on the total weight of monomers of the component (D), since the properties and weather resistance of the coating film are likely to decrease. In other words, the hydroxyl value (solid content) in the range of 80 to 150 is suitable.

Next, only representative examples of the unsaturated carboxylic acid in the component (D) will be given. As the unsaturated dicarboxylic acid, maleic anhydride, fumaric acid,
Itaconic acid, citraconic acid, mesaconic acid, etc. can be mentioned, and as unsaturated monocarboxylic acid, various unsaturated carboxylic acids, such as (meth) acrylic acid, can be mentioned.

The amount of the unsaturated carboxylic acid used in the component (D) is 0.1 to 3% by weight based on the total weight of the monomers of the component (D), in other words, the acid value (solid content) is 0.5 to. A range of 20 to 3 is preferable. When the amount of the compound is less than 0.1% by weight, the crosslinking between the hydroxyl group in the component (D) and the melamine resin is poor and the curability is insufficient, resulting in poor gasoline performance. On the other hand, when the content is more than 3% by weight, the appearance and water resistance of the resulting coating film are deteriorated and the storage stability is further deteriorated.

Regarding the blending ratio of each component, the blending ratio of the (A) component and the (B) component is as described above, and (A) (B) (C).
Among the components (E), the total amount of the components (A) and (B) is 100 parts by weight, and the amount of the components (C) is 35 to 105.
The amount of the component (E) is preferably 15 to 45 parts by weight.
Between the components (A), (B), (D), and (E), the total amount of the components (A) and (B) is 100 parts by weight,
The component (D) is 35 to 70 parts by weight, and the component (E) is 15 to 3 parts.
0 parts by weight is preferred. In addition, (A) (B) (F) (E)
Among the components, the sum of the blending amounts of the component (A) and the component (B) is 100 parts by weight, and the component (F) is 38 to 95 parts by weight,
The component (E) is preferably 2 to 5 parts by weight. Further, (A)
Between the components (B) and (E), the total amount of the components (A) and (B) is 100 parts by weight, and the component (E) is 2 to 2 parts.
0 parts by weight is preferred. In addition to the components (A), (B), (C), and (E), the component (F) can be added.
Similarly, in addition to the components (A), (B), (D) and (E), the component (F) can be blended.

Further, an ultraviolet absorber and a light stabilizer can be added to each of the above-mentioned components, and these are (A), (B), (C), (D) and (E) in total weight solid content. On the other hand, it is desirable to use up to 5% by weight. When the amount used is more than 5% by weight, the effect of these becomes large, but on the other hand, the water resistance is lowered and precipitation occurs, and the cost becomes disadvantageous.

As an example of the ultraviolet absorber and the light stabilizer, for the ultraviolet absorber, 3- [3- (2H-benzotriazol-2-yl) -5-t-butyl-A-
Hydroxyphenyl] bezotriazole, 2- [2-hydroxy-3,5-bis (1,1-dimethylbenzyl) phenyl] -2H-benzotriazole, ethanediamide-N- (2-ethoxyphenyl) -N '. -(4-
Isododecyl phenyl).

For the light stabilizer, bis (2,2,6,
6-Tetramethyl-1-ockernexy-4-piperidyl) decanedioate, 1,3,8-triasa aspyro (4,5) decane-2,4-dione-8-acetyl-3, -dodecyl-7,7 , 9,9-tetramel,
2,2,4,4-Tetramethyl-20- (β-lauryl-oxycarbonyl) -ethyl-7-oxa 3,2
0-deaza dispiro (5,1,11,2) heneicosan-21-one, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (1,2,2,6) 6-pentamethyl-4-piperidyl) -2-butyl-2- (4-hydroxy-3,5
-Ditertiary butylbenzyl) propanedioate, 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,
2,2,6,6-pentamethyl-4-4 piperidyl), bis (1,2,2,6,6-pentamethyl-4)
-4 piperidyl) sebacate and the like.

Next, the present invention will be specifically described with reference to Examples and Comparative Examples, but all parts and percentages are based on weight.

As shown in Table 1 below, as Example 1, the components (A) and (B), and as Example 2, the components (A), (B), (C) and (E), and The component (A), the component (B), the component (D) and the component (E) are used as Example 3, and the component (A), the component (B), the component (E) and component (F) are used as Example 4 and the example 5 is used. As the above, a coating composition was produced in which each of the component (A), the component (B) and the component (E) was blended.
The manufacturing method of each of the components (A), (B), (C), (D), (E), and (F) is as follows.

Component (A) 350 parts of xylene and 150 parts of butyl alcohol were placed in a four-necked flask equipped with a stirrer, a thermometer, a cooler, a dropping funnel and a nitrogen gas introducing tube, and the temperature inside the container was adjusted to 120.
Keep at ° C. Next, a mixture of 100 parts of 2-isopropenyl-2-oxazoline, 100 parts of methyl methacrylate, 150 parts of butyl acrylate, and 150 parts of 2-hydroxyethyl acrylate is added dropwise while blowing nitrogen gas. Simultaneously with the dropping of this mixture, 10 parts of benzoyl peroxide is dropped into the same vessel.
The mixture and the polymerizable initiator were added dropwise over 4 hours, and the reaction was continued at the same temperature for 3 hours after the completion of the addition.

Component (B) 200 parts of xylene and 200 parts of butyl acetate were placed in a four-necked flask equipped with a stirrer, a thermometer, a cooler, a dropping funnel and a nitrogen gas introducing tube, and the temperature inside the container was 120 °. Keep at C. Next, while blowing nitrogen gas, maleic anhydride 80 parts, methyl methacrylate 220 parts, styrene 18
A mixture of 0 part and 120 parts of butyl acrylate is added dropwise. Simultaneously with the dropping of this mixture, 10 parts of benzoyl peroxide is dropped into the same vessel. The mixture and the polymerizable initiator solution were added dropwise over 4 hours, and the reaction was continued by maintaining the same temperature for 3 hours after the completion of the addition. 100 parts of the obtained polymer was mixed with 10 parts of methanol.
And 1 part of triethylamine were added, and the mixture was reacted at 60 ° C for 2 hours. When the infrared absorption spectrum of the reaction product was measured, the absorption of acid anhydride groups (1785 cm ⁻¹ ) disappeared, and it was confirmed that all acid anhydride groups were monoesterified. This monoesterified polymer is used as the component (B).

Component (C) As the fluorocarbon-containing acrylic resin, Lumiflon LF100 manufactured by Asahi Glass Co., Ltd. was used.

Component (D) 500 parts of xylene was placed in a four-necked flask equipped with a stirrer, a thermometer, a cooler, a dropping funnel and a nitrogen gas introducing tube, and the temperature inside the vessel was kept at 140 ° C. Next, while blowing nitrogen gas, a mixture of 50 parts of methyl methacrylate, 227 parts of butyl methacrylate, 100 parts of 2-ethylhexyl acrylate, 120 parts of 2-hydroxyethyl methacrylate and 3 parts of acrylic acid is added dropwise. Simultaneously with the dropping of this dissolved substance, 10 parts of benzoyl peroxide is dropped into the same vessel. The mixture and the polymerizable initiator were added dropwise over 4 hours, and the reaction was continued at the same temperature for 3 hours after the completion of the addition.

Component (E) As the melamine resin, Uban 120 manufactured by Mitsui Toatsu Kagaku Co., Ltd. was used.

Component (F) As the silyl group-containing acrylic copolymer, Zemlac 3098 manufactured by Kanegafuchi Chemical Co., Ltd. was used.

The above components are blended at the blending ratios shown in Table 1 to obtain coating compositions of Examples 1-5. Example 1
In accordance with a conventional method, the components necessary for a UVA or lower cream coat shown in Table 1 were added to 5, and clear coat paint A was added.
-1, A-2, A-3, A-4, A-5 are obtained.

[0069]

[Table 1]

Next, each of the clear coat paints A-1, A-2, A-3, A-4, A-5 based on Examples 1-5.
On the color base under the conditions shown below.
It was top-coated by the on-wet method and baked.

Step 1 0.8 × 70 × 150 mm, first grade dull cold rolled steel sheet, cationic electrodeposition, intermediate coating baking conditions 140 ° C. × 20 minutes

Step 2 Next, a color base is applied by spraying so as to have a thickness of 15 μ, and then left at room temperature for a flash time of 4 minutes. The color base used had an L value (brightness) of 26 including an aluminum pigment and a coloring pigment.

Step 3 Further, each of the clear coat paints A-1 and A- based on Examples 1 to 5 was formed on the wet coating film.
2, A-3, A-4, A-5 by spraying a film thickness of 30
After applying each so as to have a thickness of μ, setting was performed for 10 minutes, and then baking was performed at 140 ° C. for 20 minutes. Table 2 shows the evaluation of the performance of the coating film obtained through the above steps.

[0074]

[Table 2]

Next, as comparative examples, three examples are shown in Table 3. In comparative example 1, the components (D) and (E) used in the above-mentioned examples are blended, and this is added. The clear coat paint B-1 was obtained by adding the components necessary for a UVA or lower cream coat shown in Table 3. Comparative Example 2 is a commercially available acid / epoxy crosslinked product, and Comparative Example 3
Are commercially available acid / epoxy / fluorine-containing cross-linked products, and are clear coat paints B-2 and B-3, respectively.

[0076]

[Table 3]

Next, each of the clear coat paints B-1, B-2 and B-3 based on Comparative Examples 1 to 3 was wet-on-wet on a color base under the same conditions as those of the above-mentioned Examples. It was overcoated by the method and baked. The evaluation of the performance of the obtained coating film is shown in Table 4.

[0078]

[Table 4]

As described above, it is confirmed that the coating compositions according to the examples of the present invention exhibit excellent acid resistance as compared with the comparative examples, and further exhibit satisfactory performance as a clear coat for vehicle bodies. Was done.

[0080]

As described above, the first invention of the present application is able to provide a thermosetting coating composition for automobile topcoat clear, which has improved acid resistance by cross-linking an oxazonyl group and a carboxyl group.

The second invention of the present application is an automotive top coat clear which has improved water repellency and improved crosslink density due to fluorocarbon in addition to acid resistance, and has improved car wash scratch resistance and dry wipe scratch resistance. The present invention can provide a thermosetting coating composition for use.

The third invention of the present application is, in addition to the acid resistance, the crosslink density is improved, the car wash scratch resistance and the dry wipe scratch resistance are improved, and the weather resistance is further improved. A mold coating composition can be provided.

A fourth invention of the present application is, in addition to acid resistance, a heat density for automobile top coat clear which has improved crosslink density, improved car wash scratch resistance and dry wipe scratch resistance, and improved weather resistance. It is possible to provide a curable coating composition.

The fifth invention of the present application provides a thermosetting coating composition for a topcoat clear for automobiles, which has improved crosslink density in addition to acid resistance and improved car wash scratch resistance and dry wipe scratch resistance. That is what I got.

The sixth invention of the present application is to provide a thermosetting coating composition for an automobile topcoat clear which can adjust the viscosity of the coating to an appropriate value in addition to acid resistance.

The seventh invention of the present application is able to provide a thermosetting coating composition for automobile topcoat clear, which has improved car-washing scratch resistance and dry-wiping scratch resistance, and further improved weather resistance. is there.

The eighth invention of the present application is to provide a thermosetting coating composition for an automobile topcoat clear which can adjust the viscosity of the coating to an appropriate value in addition to acid resistance.

The ninth invention of the present application can be carried out as a so-called 2-coat 1-bake clear coat for a vehicle body, and contains any one of an aluminum pigment, a mica pigment and a coloring pigment, and has an L value (brightness) of 30 or less. On the base color coat of
It is possible to provide a method for coating a clear coat that can improve acid resistance, weather resistance, car wash scratch resistance, and dry wipe scratch resistance.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C09D 135/00 PFY C09D 135/00 PFY 161/32 PHK 161/32 PHK

Claims (9)

[Claims] 1. The following general formula (1): (In the formula, R1, R2, R3 and R4 are the same or different and each represents hydrogen, halogen, an alkyl group, an aralkyl group, a cycloalkyl group, an aryl group or a substituted aryl group,
R5 represents an alkenyl group or a cycloalkenyl group. )
And a monomer component essentially containing the addition-polymerizable oxazoline (a-1) and the acrylic monomer (a-2) represented by the formula (1) are copolymerized in the presence of an organic solvent. At least one monomer selected from the combination (A), ethylenically unsaturated dicarboxylic acid anhydride, monoesterified product of ethylenically unsaturated dicarboxylic acid anhydride, and monoamidated product of ethylenically unsaturated dicarboxylic acid anhydride is essential. A thermosetting coating composition for an automobile topcoat clear, comprising a polymer (B) obtained by copolymerizing a monomer component containing the same in the presence of an organic solvent. 2. In addition to each component of the polymer (A) and the polymer (B), an acrylic copolymer (C) containing a fluorocarbon and a melamine resin (E) are blended. The thermosetting coating composition for an automobile topcoat clear according to claim 1. 3. In addition to each component of the polymer (A) and the polymer (B), an acrylic monomer, an unsaturated carboxylic acid, and a caprolactone-modified (meth) acrylate and / or a hydroxyl group-containing acrylic monomer are organically added. 2. A thermosetting coating composition for an automobile topcoat clear according to claim 1, wherein the polymer (D) obtained by copolymerization in the presence of a solvent and a melamine resin (E) are blended. . 4. A silyl group-containing acrylic copolymer (F) and a melamine resin (E) are added to each component of the polymer (A) and the polymer (B). 1
A heat-curable coating composition for an automobile topcoat clear as described above. 5. A thermosetting coating composition for an automobile topcoat clear according to claim 1, further comprising a melamine resin (E) in addition to each component of the polymer (A) and the polymer (B). . 6. The component of the polymer (A) is an addition-polymerizable oxazoline (a-1) or an acrylic monomer (a-).
2) and an alkyl (meth) acrylate and / or styrene.
5. A thermosetting coating composition for automobile top clear according to any one of 5 above. 7. The acrylic monomer (a-2) is
A thermosetting coating composition for automobile topcoat clear according to any one of claims 1 to 6, which is a hydroxyl group-containing (meth) acrylate and / or a caprolactone-modified (meth) acrylate. 8. The component of the polymer (B) is selected from ethylenically unsaturated dicarboxylic acid anhydrides and monoesterified products of ethylenically unsaturated dicarboxylic acid anhydrides and monoamidated products of ethylenically unsaturated dicarboxylic acid anhydrides. The thermosetting coating composition for a topcoat clear for automobiles according to any one of claims 1 to 7, which comprises one or more kinds of the above-mentioned monomers and an alkyl (meth) acrylate and / or styrene. 9. The heat-curable type according to claim 1, on a base color coat having an L value (brightness) of 30 or less, which contains any one of an aluminum pigment, a mica pigment and a coloring pigment. A coating method in which the coating composition is used as a clear coat and top coating is carried out by a wet-on-wet method, followed by baking.