JP2000178501A - Clear coating for automotive top coating, method for forming multilayer coating film, and vehicle body - Google Patents

Abstract

(57) [Summary] [Problem] To have basic performance such as weather resistance and acid resistance, and
Provided is a clear coating for automotive top coating which has no car wash-free stain resistance and does not cause a defect in storage stability, and also provides a method for forming a multilayer coating film on a vehicle body using the same and a vehicle body. . SOLUTION: A clear paint for automotive top coating comprising a resin component comprising a half ester acid group-containing acrylic copolymer (I), an epoxy group-containing acrylic copolymer (II) and an alcohol-modified silicate compound (III).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clear paint for automotive top coating having weather resistance, acid resistance, and excellent car wash-free excellent stain resistance and storage stability, and an automobile body using the same. The present invention relates to a method for forming a multilayer coating film and an automobile body.

[0002]

2. Description of the Related Art A clear coating for top coating of an automobile constitutes the outermost layer of a coating film for coating an automobile body, so that in addition to storage stability, which is the minimum performance as a coating, cosmetic and weather resistance. It is required to have properties and the like as basic performance. In recent years, the cause of the etching phenomenon of the clear coating film is acid rain, and it has been found that the etching by the acid rain is based on the curing agent melamine present in the coating film, and the acid resistance that prevents the etching by the acid rain In order to provide a curing system, a curing system other than the melamine curing system is being developed.

JP-A-2-45577 and JP-A-3-45577
JP-A-287650, JP-B-6-41576 and JP-A-8-259667 disclose a coating composition that does not use a melamine resin curing agent. This coating composition has good acid resistance because an ester bond generated by reacting an acid group and an epoxy group is used as a crosslinking point. In this curing system (hereinafter also referred to as "acid epoxy curing system"), when the crosslinking density is increased to impart sufficient weather resistance to the coating film, a hard and brittle coating film is easily formed, and soot and dust No study has been made on the easiness of removal of stains when contaminants such as adhere to the coating film, that is, the stain resistance.

Japanese Patent Application Laid-Open No. Hei 10-140077 discloses that an acid epoxy-curable coating material contains tetramethyl silicate and / or
Also disclosed is an automotive topcoat containing a low-condensate of silicate having a degree of condensation of 2 to 10 (low-condensate of silicate). The purpose of this paint is to solve the above-mentioned problem concerning stain resistance. The silicate low-condensate used in this technology is devised to use a low-condensate of tetramethyl silicate and / or tetraethyl silicate to suppress the number of carbon atoms of the alkoxyl group and maintain the reactivity with water. I have. And the coating film of this coating composition, the methoxy group or ethoxy group of the silicate low-condensate, which is much present near the coating film surface, reacts with water by exposure or treatment with an acid to become a hydroxyl group. The basic principle is to exhibit high hydrophilicity due to hydroxyl groups and to exhibit contamination resistance.

[0005] However, when a low-condensate of tetramethylsilicate having only a highly reactive methoxy group is used as a low-condensate silicate, a coating film using a paint in the early stage of storage shows high hydrophilicity and has high resistance to water. It will be excellent in contamination, but if the storage period is long, in the paint,
The silicate low-condensate reacts with each other, or the silicate low-condensate reacts with the hydroxyl group in the epoxy resin, causing an increase in viscosity, resulting in a marked deterioration in storage stability, and a coating obtained from the coating after storage. The membrane does not show sufficient hydrophilicity,
As a result, the stain resistance cannot be sufficiently exhibited. When a low-condensate of tetraethylsilicate having only an ethoxy group is used as the low-condensate silicate, the storage stability of the paint is relatively improved because the reactivity of the ethoxy group is lower than that of the methoxy group. The coating film does not show sufficient hydrophilicity, and cannot sufficiently exhibit stain resistance.

Further, even when a low condensate of tetramethyl silicate and tetraethyl silicate is used as the low silicate condensate, the silicon atom of the low silicate condensate has only a methoxy group or an ethoxy group as a functional group. May cause a problem in storage stability as a coating, and there is a possibility that the hydrophilicity of a coating film obtained from a paint used after storage may not be sufficiently exhibited.

[0007] Judging comprehensively from these, if a composition is obtained in which there is little possibility that the low silicate low-condensate reacts in the coating even with the passage of time, a coating of higher quality can be obtained. Was.

[0008] The stain resistance required for a clear coating film for an automobile top coat is not only meaning that dirt is not easily adhered, but also important from the viewpoint of aesthetics giving an excellent appearance. That is, usually, the outermost layer of the automobile coating film is removed by a user by washing with water and, if necessary, further applying wax to remove the stain on the surface. In the case of a luxury car, waxing for luster is very important from the viewpoint of aesthetics.However, in the case of a practical car, for example, a commercial vehicle, it should not cause discomfort even when repeatedly used. Is important from the viewpoint of cosmetics. Therefore, the function of preventing surface dirt from adhering without particularly removing the dirt by washing with water becomes more important. Therefore, if a contaminant adhered to the surface is washed away by rainwater or the like and a clear coating film having a hydrophilic property necessary for making the car free from the need for removal work is provided, the user does not need to take the trouble of car washing. Therefore, there has been a demand for a clear paint having a hydrophilic property and being excellent in cosmetics for automotive top coating.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention has basic performances such as weather resistance and acid resistance, and has poor storage stability while having car wash-free stain resistance. To provide a clear coating for automotive topcoats that does not cause
It is an object of the present invention to provide a method for forming a multilayer coating film on an automobile body using the same and an automobile body.

[0010]

SUMMARY OF THE INVENTION The present invention relates to an automobile having a resin component comprising an acrylic copolymer containing a half ester acid group (I), an acrylic copolymer containing an epoxy group (II) and an alcohol-modified silicate compound (III). An overcoating clear coating composition, wherein the half-ester acid group-containing acrylic copolymer (I) comprises an acid anhydride group-containing radical polymerizable monomer (Ia) and another radical polymerizable monomer (I). -B)
Is obtained by half-esterifying the acid anhydride group with a low molecular weight alcoholic compound after obtaining a copolymer by the above method. The epoxy group-containing acrylic copolymer (II) has an epoxy group Containing radical polymerizable monomer (II-a) 30 to 70 parts by weight, hydroxyl group containing radical polymerizable monomer (II-b) 10 to 50 parts by weight, and other radical polymerizable monomer (II-a). c) a copolymer obtained by copolymerizing 20 to 60 parts by weight, having a number average molecular weight (Mn) of 1000 to 8000 and an epoxy equivalent of 100 to
800 (solid content equivalent), hydroxyl value 5 to 200 mg KOH
/ G (in terms of solid content), and the alcohol-modified silicate compound (III) is represented by the general formula (1):

[0011]

Embedded image

(Wherein, n represents an integer of 1 to 50. R
Some of them represent a substituted or unsubstituted alkyl group having 2 to 20 carbon atoms and / or an aralkyl group having 7 to 20 carbon atoms having a substituted or unsubstituted group. And the remaining R represents a methyl group. ) Is a clear paint for automotive top coat represented by

In the present invention, an undercoat film layer is formed on an outer panel of an automobile, a base paint containing a coloring pigment and / or a brilliant pigment is applied, and a clear coating for overcoat is applied wet-on-wet. Thereafter, the method is a method for forming a multilayer coating film on an automobile body, which is performed by heating and curing, and the above-mentioned clear coating for top coating is also a method for forming a multilayer coating film on an automobile body using the above-mentioned clear coating for automobile top coating.

The present invention also provides an undercoating film layer on an automobile outer panel, which is coated with a solid paint containing a color pigment and cured by heating, or a base paint and a clear paint are wet-on-wet. A method for forming a multilayer coating film of an automobile body, which comprises applying a clear coating for overcoating on a dry-on-wet basis, followed by heating and curing, after coating and heating and curing, wherein the clear coating for overcoating includes It is also a method for forming a multilayer coating film on an automobile body using a clear coating for automobile top coating.

The present invention further provides an automobile body coated with a multilayer coating film, wherein the outermost layer of the multilayer coating film is formed by the above-mentioned clear coating for automotive top coating. Hereinafter, the present invention will be described in detail.

[0016] The clear paint for top coating of automobiles of the present invention comprises:
The resin composition comprises a half ester acid group-containing acrylic copolymer (I), an epoxy group-containing acrylic copolymer (II) and an alcohol-modified silicate compound (III).

The half-ester acid group-containing acrylic copolymer (I) comprises an acid anhydride group-containing radical polymerizable monomer (Ia) and another radical polymerizable monomer (Ib).
And a half-esterification of the acid anhydride group with a low molecular weight alcohol-based compound after obtaining a copolymer.

The acid anhydride group-containing radically polymerizable monomer (Ia) may be an acid anhydride group-containing radical polymerizable monomer for obtaining the half ester acid group-containing acrylic copolymer (I). It is not particularly limited as long as it is a suitable monomer, and examples thereof include itaconic anhydride, maleic anhydride, and citraconic anhydride. These may be used alone,
More than one species may be used in combination.

The other radical polymerizable monomers (I-
There is no particular limitation on b), for example, styrene, α-
Styrenes such as methylstyrene; methyl acrylate, ethyl acrylate, propyl acrylate, acrylic acid
Acrylic esters such as n, i and t-butyl, 2-ethylhexyl acrylate, lauryl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, -n, i and t-butyl methacrylate, methacrylic acid Methacrylic esters such as -2-ethylhexyl and lauryl methacrylate; and amides such as acrylamide and methacrylamide. These may be used alone or in combination of two or more.

The acid anhydride group-containing radical polymerizable monomer (Ia) and the other radical polymerizable monomer (I-
b) in the copolymer composition when obtaining a copolymer by
The above acid anhydride group-containing radical polymerizable monomer (Ia)
Is 10 to 40% by weight, especially 15% by weight, based on the total monomer weight.
~ 30% by weight is preferred.

The copolymerization method is not particularly limited.
For example, it can be performed by solution polymerization such as ordinary radical polymerization. Number average molecular weight (Mn) of the copolymer
Is preferably from 500 to 10,000, particularly preferably from 1,000 to 8,000. If the number average molecular weight (Mn) is less than 500, the curability of the coating is not sufficient, and if it exceeds 10,000, the viscosity of the copolymer becomes high, making it difficult to obtain a high solid content thermosetting coating. In this specification, the number average molecular weight (Mn) is a number average molecular weight in terms of polystyrene measured by GPC (gel permeation chromatography).

The acid anhydride group in the copolymer is
It contains at least two in one molecule. If the number is less than 2, the curability is insufficient. Preferably 2
There are fifteen.

The above half esterification is performed after obtaining the above copolymer. The half-esterifying agent used for half-esterifying the acid anhydride group is not particularly limited as long as it is a low-molecular-weight alcohol compound. For example, methanol, ethanol, n-propanol, i-
Propanol, n-butanol, i-butanol, t-
Butanol, methyl cellosolve, ethyl cellosolve, dimethylaminoethanol, diethylaminoethanol,
Acetol, allyl alcohol, propargyl alcohol and the like can be mentioned. These may be used alone or in combination of two or more. Among these, particularly preferred compounds are acetol, allyl alcohol, propargyl alcohol and methanol.

The half esterification reaction method is not particularly limited. For example, the half esterification can be carried out at a temperature of from room temperature to 120 ° C. in the presence of a catalyst according to a usual method.
The catalyst is not particularly limited, and includes, for example, tertiary amines such as triethylamine and tributylamine; and quaternary ammonium salts such as benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltributylammonium chloride, and benzyltributylammonium bromide. Is mentioned. These may be used alone or in combination of two or more.

Further, in addition to the above half-ester acid group-containing acrylic copolymer (I), ε-
A carboxyl group-containing polyester resin obtained by half-esterifying a polyester polyol obtained by adding a lactone compound such as caprolactone and performing a chain extension reaction with an acid anhydride group-containing compound may be added.

Since the carboxyl group-containing polyester resin has a sharp molecular weight distribution, the use of the carboxyl group-containing polyester resin enables high solid differentiation (high solidification) of the clear coating for automotive top coating, A coating film having excellent weather resistance and water resistance can be obtained. In addition, excellent chipping resistance is obtained, and a good skin appearance is obtained.

The low-molecular-weight polyhydric alcohol is not particularly limited. For example, those having at least three hydroxyl groups in one molecule are preferable, and trimethylolpropane, trimethylolethane, 1,2,4-butanetriol,
Examples include ditrimethylolpropane, pentaerythritol, dipentaerythritol, glycerin and the like. These may be used alone or in combination of two or more.

The lactone compound may be any cyclic compound which has an oxygen atom in the ring, reacts with a nucleophile, opens the ring, and generates a hydroxyl group at the terminal. Since the ring-opening addition reaction easily occurs, the lactone compound has 4 to 7 carbon atoms.
Are preferred.

The lactone compound is not particularly restricted but includes, for example, ε-caprolactone, γ-caprolactone, γ-valerolactone, δ-valerolactone, γ-butyrolactone and the like. These may be used alone or in combination of two or more. Among these, ε
-Caprolactone, γ-valerolactone and γ-butyrolactone are preferred.

The above chain extension reaction can be carried out under the same conditions as ordinary ring opening addition reactions. For example, the polyester polyol in which the low-molecular-weight polyhydric alcohol is chain-extended can be obtained by reacting in a suitable solvent or without a solvent at a temperature of 80 to 200 ° C. within 5 hours. At this time, a tin-based catalyst or the like may be used.

In the above chain extension reaction, the molar amount of the lactone compound is 0.2 to 10 times the molar amount of the hydroxyl group of the low molecular weight polyhydric alcohol. When the molar amount of the lactone compound is less than 0.2 times the molar amount of the hydroxyl group of the low molecular weight polyhydric alcohol, the coating film becomes hard and the impact resistance of the coating film decreases, and exceeds 10 times the molar amount. In this case, the hardness of the coating film decreases. The amount is preferably 0.25 to 5 times, more preferably 0.3 to 3 times.

The carboxyl group-containing polyester resin has an acid value of 50 to 350 mg KOH / g, a number average molecular weight (Mn) of 400 to 3500, and a weight average molecular weight (Mw) / number average molecular weight (Mn) of 1 .8 or less. If the acid value is less than 50, the curability of the paint is insufficient,
When the acid value exceeds 350, the viscosity of the carboxyl group-containing polyester resin becomes too high, and it is difficult to obtain a high solid content thermosetting paint. When the molecular weight is less than 400, the curability of the paint is insufficient or the water resistance of the coating film is reduced, and the molecular weight is 3
If it exceeds 500, the viscosity of the above-mentioned carboxyl group-containing polyester resin becomes too high to make handling difficult, and it is difficult to obtain a high solid content thermosetting paint. Weight average molecular weight (M
When w) / number average molecular weight (Mn) exceeds 1.8, the water resistance or weather resistance of the coating film decreases.

Preferably, the acid value is 100 to 300 mgK
OH / g and a number average molecular weight (Mn) of 500 to 25
00, and the weight average molecular weight (Mw) / number average molecular weight (Mn) is 1.5 or less. More preferably, the acid value is 150 to 250 mgKOH / g, the number average molecular weight (Mn) is 700 to 2000, and the weight average molecular weight (Mw) / number average molecular weight (Mn) is 1.35 or less. The acid value is a value in terms of solid content.

The method of half-esterification of the polyester polyol with the acid anhydride group-containing compound is not particularly limited. For example, the polyester polyol and the acid anhydride group-containing compound are reacted according to a conventional method. It can be carried out at a temperature from room temperature to 150 ° C. under normal pressure.

The acid anhydride group-containing compound is not particularly restricted but includes, for example, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, trimellitic anhydride, succinic anhydride. And the like. These may be used alone or in combination of two or more.

In general, the molar amount of the acid anhydride group of the acid anhydride group-containing compound is 0.2 to 1.0 times, preferably 0.5 to 1.0 times the molar amount of the hydroxyl group of the polyester polyol.
Preferably, the amount is 0.9 times. If the molar amount of the acid anhydride group of the acid anhydride group-containing compound is less than 0.2 times the molar amount of the hydroxyl group of the polyester polyol, the curability of the coating will be insufficient.

However, it is not necessary to modify all the hydroxyl groups of the polyester polyol to carboxyl groups, and the hydroxyl groups may be left. That is, since the carboxyl group-containing polyester resin having a hydroxyl group simultaneously provides a carboxyl group and a hydroxyl group on the surface of the coating film, for example, when recoated, as compared to the carboxyl group-containing polyester resin having no hydroxyl group. , And excellent adhesion can be provided.

When the carboxyl group-containing polyester resin has a hydroxyl group, the carboxyl group-containing polyester resin has a hydroxyl value of 150 mg KOH.
/ G or less. When the hydroxyl value exceeds 150 mgKOH / g, the water resistance of the coating film decreases. Preferably, 5-1
00 mg KOH / g, more preferably 10 to 80 mg
KOH / g. In addition, a hydroxyl value is a value of solid content conversion.

The carboxyl group-containing polyester resin having a hydroxyl group and a carboxyl group reacts with and binds to both the epoxy group-containing acrylic copolymer (II) and the alcohol-modified silicate compound (III), as described later. As a result, a stronger coating film can be obtained.
In this case, those having an average of 0.1 or more hydroxyl groups in one molecule are preferable.

The carboxyl group-containing polyester resin is contained in an amount of 0 to 70% by weight based on the total amount of the resin components. Preferably it is 5-70% by weight. If it is less than 5% by weight, it becomes difficult to obtain a high solid content thermosetting paint, and if it exceeds 70% by weight, the weather resistance of the coating film is reduced. Preferably, 5-
It is 50% by weight, more preferably 10 to 40% by weight.
In addition, the said weight% is a value of solid content conversion.

The epoxy group-containing acrylic copolymer (II) used in the present invention comprises 30 to 70 parts by weight of an epoxy group-containing radical polymerizable monomer (II-a) and a hydroxyl group-containing radical polymerizable monomer (II). -B) a copolymer obtained by copolymerizing 10 to 50 parts by weight and 20 to 60 parts by weight of another radical polymerizable monomer (II-c).

The epoxy group-containing radical polymerizable monomer (II-a) is not particularly restricted but includes, for example, (meth)
Glycidyl acrylate, 3,4-epoxycyclohexanylmethyl methacrylate and the like can be mentioned. These may be used alone or in combination of two or more.

The hydroxyl-containing radical polymerizable monomer (II)
-B) is not particularly limited and includes, for example, 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid-
4-hydroxybutyl, Praxel FM-1 (trade name,
Daicel). These may be used alone or in combination of two or more.

The other radical polymerizable monomers (II-
c) is not particularly limited, and includes, for example, those similar to the above-mentioned other radically polymerizable monomers (Ib).

The epoxy group-containing acrylic copolymer (I)
I) is obtained by copolymerization with the above-mentioned radical polymerizable monomer and radical polymerization initiator. The copolymerization method is not particularly limited, and can be carried out by solution polymerization such as ordinary radical polymerization.
The polymerization can be performed at 140 ° C. for a polymerization time of 3 to 8 hours.

The radical polymerization initiator is not particularly restricted but includes, for example, t-butylperoxy-2-ethylhexanoate, dimethyl-2,2'-azobisisobutyrate and the like. These may be used alone,
Two or more kinds may be used in combination. The radical polymerization initiator is preferably used in an amount of 3 to 15% by weight based on the total amount of the above-mentioned monomers. A chain transfer agent or the like may be added as an additive to the copolymerization.

The epoxy group-containing acrylic copolymer (I)
I) has a number average molecular weight (Mn) of 1,000 to 8,000, has 2 to 10 epoxy groups in the molecule, and 2 to 12 hydroxyl groups, and has an epoxy equivalent of 100 to 8,000.
800 and a hydroxyl value of 5 to 200 mgKOH / g. When the epoxy equivalent is less than 100, the cured coating film becomes too hard and the weather resistance is deteriorated. When it exceeds 800, the curability of the coating becomes insufficient. The hydroxyl value is 5
When the amount is less than mgKOH / g, the adhesion is poor and the
If it exceeds gKOH / g, the cured coating film has insufficient water resistance. Preferably, it has 3 to 8 epoxy groups and 4 to 10 hydroxyl groups in the molecule, and has an epoxy equivalent of 200 to 600 and a hydroxyl value of 10 to 150 m.
gKOH / g. The epoxy equivalent and the hydroxyl value are values in terms of solid content.

In the resin component in the above-mentioned clear paint for automotive top coating, [the total number of epoxy groups of the epoxy group-containing acrylic copolymer (II)] / [half ester of the half ester acid group-containing acrylic copolymer (I)] Acid anhydride groups and carboxyl groups] = 0.5-1.
5, particularly preferably 0.6 to 1.3, and
[Total number of hydroxyl groups of the epoxy group-containing acrylic copolymer (II)] / [Total number of half-esterified acid anhydride groups of the half-ester acid group-containing acrylic copolymer (I)] =
It is preferably from 0.1 to 1.5, particularly preferably from 0.3 to 1.2. Specifically, the blending amount of the epoxy group-containing acrylic copolymer (II) giving such a ratio is, for example, the half ester acid group-containing acrylic copolymer (I) 100
It is preferably 50 to 250 parts by weight, particularly preferably 80 to 150 parts by weight with respect to parts by weight. If the amount of the epoxy group-containing acrylic copolymer (II) is less than 50 parts by weight, the coating film is not sufficiently cured, and the water resistance and weather resistance of the cured coating film are reduced. If the amount exceeds the above range, unreacted carboxyl groups remain and the chemical resistance decreases.

The alcohol-modified silicate compound (III) used in the present invention has the general formula (1):

[0050]

Embedded image

Is represented by:

In the general formula (1), n represents an integer of 1 to 50. Part of R is a substituted or unsubstituted alkyl group having 2 to 20, preferably 3 to 15 carbon atoms and / or a substituted or unsubstituted carbon group. It represents an aralkyl group of the formulas 7 to 20, and the remaining R represents a methyl group.

In the above general formula (1), when n exceeds 50, the resulting alcohol-modified silicate compound (III)
Has a high viscosity and does not easily migrate to the coating film surface. N is preferably 5 to 30 from the viewpoint that the obtained alcohol-modified silicate compound (III) hardly volatilizes from the surface of the coating film when the coating film is cured by heating, and has an appropriate viscosity. More preferably 7 to 20, even more preferably 10
Fifteen.

The above-mentioned substituted or unsubstituted alkyl group having 2 to 20 carbon atoms, preferably 3 to 15 carbon atoms, and aralkyl having 7 to 20 carbon atoms having a substituted or unsubstituted group. More preferably, the groups each have 3 to 10 carbon atoms and 7 to 10 carbon atoms.
If the number of carbon atoms is less than the above, the reactivity is too high, and the storage stability is deteriorated. If the number of carbon atoms exceeds the above, the hydrophilic function is not obtained.

The above alcohol-modified silicate compound (II
The production method of I) is not particularly limited, and includes, for example, a method in which a methyl silicate represented by the following formula and / or a condensate thereof is subjected to an alcohol exchange reaction as a reaction substrate. In this case, the alcohol-modified silicate compound (III) is obtained by modifying a part of the methyl group of methyl silicate and / or its condensate by an alcohol exchange reaction.

[0056]

Embedded image

In the above formula, n is the same as described above. The methyl silicate and / or condensate thereof is not particularly limited, and may be, for example, “MS-51”, “MS-
56 "(all trade names, manufactured by Mitsubishi Chemical Corporation) and the like.

The alcohol exchange reaction is carried out by reacting the methyl silicate as a reaction substrate and / or the condensate thereof with an alcohol compound as a reaction reagent. As the alcohol compound, a substituted or unsubstituted alkyl alcohol compound having 2 to 20 carbon atoms, preferably 3 to 15 carbon atoms, or a substituted or unsubstituted alkyl alcohol compound having 7 to 7 carbon atoms And 20 aralkyl alcohol compounds. These may be used alone or in combination of two or more.

The above-mentioned alkyl alcohol compound having a substituent or not having a substituent and having 2 to 20 carbon atoms, preferably 3 to 15 carbon atoms, is not particularly limited.
Alkyl alcohol compounds such as ethyl alcohol, propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoamyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, and 2-ethylhexyl alcohol An ether alcohol compound such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, butyldiglycol, methoxypropanol, ethoxypropanol, butoxypropanol and propoxypropanol. These may be used alone or in combination of two or more. Among these,
It is preferable to use propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, butyl cellosolve, methoxypropanol, and ethoxypropanol.

The above-mentioned aralkyl alcohol compound having 7 to 20 carbon atoms which has a substituent or no substituent is not particularly limited.
Chlorobenzyl alcohol, 3-chlorobenzyl alcohol, 4-chlorobenzyl alcohol, 2-bromobenzyl alcohol, 3-bromobenzyl alcohol, 4-chlorobenzyl alcohol
Halogenated benzyl alcohols such as bromobenzyl alcohol, 2-iodobenzyl alcohol, 3-iodobenzyl alcohol, 4-iodobenzyl alcohol and dichlorobenzyl alcohol; 2-methylbenzyl alcohol, 3-methylbenzyl alcohol, 4-methylbenzyl alcohol; Dimethylbenzyl alcohol, 3,
Alkyl-substituted benzyl alcohols such as 4,5-trimethylbenzyl alcohol, 4-ethylbenzyl alcohol, 4-isopropylbenzyl alcohol, 4-butylbenzyl alcohol, and 4-tert-butylbenzyl alcohol; dimethoxybenzyl alcohol, 2-ethoxybenzyl alcohol; 3-ethoxybenzyl alcohol, 4-ethoxybenzyl alcohol, 4-butoxybenzyl alcohol, 2-methoxybenzyl alcohol,
Alkoxy-substituted benzyl alcohols such as 3-methoxybenzyl alcohol and 4-methoxybenzyl alcohol;
Examples include benzyl alcohols such as phenethyl alcohol, benzoin, and phenylpropanol, and phenethyl alcohols. These may be used alone or in combination of two or more. Among them, benzyl alcohol, chlorobenzyl alcohol, methylbenzyl alcohol, ethylbenzyl alcohol, and methoxybenzyl alcohol are preferably used.

At the time of the above alcohol exchange reaction, an alcohol exchange catalyst may be used. The alcohol exchange catalyst is not particularly limited, and includes, for example, an acid or a base. The acid is not particularly limited, and includes, for example, Bronsted acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and sulfonic acid; and Lewis acids such as organic tin compounds. The base is not particularly limited and includes, for example, tertiary amines such as triethylamine, diisopropylethylamine, dimethylbenzylamine, diazabicyclo [2,2,2] octane, and 1,8-diazabicyclo [5,4,0] undecene-7. Amines and the like. These may be used alone or in combination of two or more.

The solvent used in the alcohol exchange reaction need not be particularly used. For example, an alcohol compound as a reaction reagent may be used as a solvent in excess of the reaction substrate.

The solvent is not particularly restricted but includes, for example, aromatic hydrocarbons such as toluene, benzene and xylene; halogenated hydrocarbons such as dichloroethane; THF;
Ethers such as dioxane; ketones such as methyl ethyl ketone and methyl isobutyl ketone; esters such as ethyl acetate and butyl acetate; dimethyl carbamate and acetonitrile. These may be used alone,
Two or more kinds may be used in combination.

The amount of the solvent to be used is not particularly limited, and is, for example, not more than 10 times the total weight of methyl silicate and / or a condensate thereof as a reaction substrate and an alcohol compound as a reaction reagent. Is preferred.

The ratio of methyl silicate and / or its condensate as a reaction substrate and the alcohol compound as a reaction reagent in the alcohol exchange reaction is not particularly limited. For example, the ratio of the alcohol compound to the reaction substrate is small. And 1 mol% or more, the amount necessary for denaturation or more may be used.

The alcohol exchange reaction may be carried out by azeotropically distilling off the methanol produced by the denaturation.

The reaction temperature of the alcohol exchange reaction is not particularly limited, and is generally 0 ° C. to 200 ° C. The reaction time is not particularly limited, but is preferably, for example, 24 hours or less. The pressure during the reaction is not particularly limited, and is generally normal pressure. However, if necessary, the reaction may be performed under reduced pressure to distill off generated methanol.

The reaction rate in the alcohol exchange reaction can be determined by measuring the amount of produced methanol, NMR spectrum or GC (gas chromatography) analysis. The product obtained as described above is generally a colorless to pale yellow oil.

The alcohol-modified silicate compound (II)
Since the methoxy group of I) easily becomes a hydroxyl group with the passage of time, the water contact angle on the surface of the coating film decreases, and the coating film becomes hydrophilic. Therefore, it is considered that a contaminant attached to the surface of the coating film is easily washed away, and the coating film exhibits high stain resistance. In addition, due to the presence of the methoxy group, the alcohol-modified silicate compound (III) has appropriate compatibility with other resin components, and exhibits sufficient stain resistance on the surface of the formed coating film. Furthermore,
The alcohol-modified silicate compound (III) obtained by the alcohol exchange reaction includes, for example, when R is a methyl group, an alkyl group having a large number of carbon atoms in order from the most active methyl group among the methyl groups of the tetramethylsilicate condensate. Or because it is substituted with an aralkyl group and the highly active part is blocked, unlike a mere tetramethyl silicate condensate, it hardly causes a condensation reaction or reaction with other resin components during the storage of the coating, and the storage stability of the coating is improved. Excellent, the coating film obtained from the paint after storage also shows sufficient hydrophilicity, and exhibits high stain resistance on the coating film surface stably even after storage.

The alcohol-modified silicate compound (II)
I) is preferably contained in an amount of 0.1 to 50% by weight based on the total amount of the above resin components. When the amount is less than 0.1% by weight, the hydrophilicity of the coating film is not sufficiently exhibited, and the stain resistance is poor. When the amount exceeds 50% by weight, the glossiness of the coating film decreases, the coating film becomes sticky, and the alkali resistance decreases. There is a possibility that problems such as lowering may occur. More preferably, it is 1 to 20% by weight. In addition, the said weight% is a value of solid content conversion.

An alcohol compound which is a reaction reagent used for obtaining the alcohol-modified silicate compound (III) by the alcohol exchange reaction may be added as a solvent to the above-mentioned clear paint for automotive top coating. The amount of the alcohol compound added is 10 to 20 parts by weight based on 100 parts by weight of the alcohol-modified silicate compound (III).
It is preferably 0 parts by weight. By adding the alcohol compound, it is possible to stabilize the alcohol-modified silicate compound (III) during storage of the clear coating material for automobile top coating, and to prevent a coating film abnormality in a heat curing step. it can.

The above clear coating for automotive top coating usually contains a curing catalyst. The curing catalyst is not particularly limited, and may be a catalyst usually used for an esterification reaction (reaction between an acid and an epoxy). For example, a quaternary ammonium salt is preferable. Specifically, in addition to the above-mentioned quaternary ammonium salts, benzyltriethylammonium chloride, benzyltriethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide and the like can be mentioned. These may be used alone or in combination of two or more.

The clear paint for automotive top coating includes melamine / formaldehyde resin for increasing the crosslink density and improving the water resistance, and UV absorbers and light stabilizers for improving the weather resistance of the coating film. A microgel or a surface conditioner for rheology control, a diluent for viscosity control or the like may be added.

The ultraviolet absorber and light stabilizer are not particularly limited, and include, for example, Tinuvin-900 (manufactured by Ciba-Geigy), Sanol LS-292 (manufactured by Sankyo) and the like. The diluent is not particularly restricted but includes, for example, alcohol solvents such as methanol, ethanol, propanol and butanol; and solvents such as hydrocarbons and esters. These may be used alone or in combination of two or more.

The amount of the curing catalyst is preferably 0.01 to 3.0% by weight based on the total resin solids. The amount of the diluent is preferably up to 60% by weight, more preferably 20 to 55% by weight, based on the total weight of the paint to which the diluent has been added.

The above-mentioned clear paint for automotive top coating usually contains no pigment, but may contain a coloring pigment to the extent that the transparency of the coating film is not impaired. The pigment is not particularly limited and includes, for example, iron oxide, lead oxide, carbon black, coal dust, titanium dioxide, talc, barium sulfate, cadmium yellow, cadmium red, chrome yellow, and metal pigments (for example, aluminum flakes and the like). And organic pigments (for example, phthalocyanine blue, Shinkasia Red and the like), pearl mica and the like. These may be used alone or in combination of two or more.

The solid content of the above clear paint for automotive top coating is 25 to 70% by weight, preferably 35 to 70% by weight.
65% by weight. The solid content at the time of coating is 15 to 65% by weight, preferably 30 to 60% by weight.

In the case where it is previously added to and mixed with the coating material, it is preferable to store it under the condition that water is not mixed so that hydrolysis and condensation reaction do not proceed.

The method for preparing the above-mentioned clear paint for automotive top coating is not particularly limited, and it can be carried out by stirring each of the above-mentioned components with a stirrer or the like. It can also be carried out by kneading. Further, the alcohol-modified silicate compound (III) may be added to the paint before application and mixed, or may be added to the paint in advance and mixed at the stage of producing the paint.

The above clear paint for automotive top coating can be applied by spray coating, brush coating, dip coating, electrostatic coating, roll coating, flow coating, or the like.

The above-mentioned clear coating for automotive top coating has a curing temperature of 100 to 180 ° C., preferably 120 to 160 ° C.
To give a cured coating film with a high degree of crosslinking. The curing time varies depending on the curing temperature and the like, but is suitably from 120 to 160 ° C. for 10 to 30 minutes.

When a copolymer containing only an acid anhydride group is used for a clear coating for automotive top coating, since the reaction with an active hydrogen compound proceeds even at about normal temperature, it is difficult to store the copolymer in the same system as a gel. Is not appropriate. In the case of the clear coating composition for automobile top coating of the present invention, since the acid anhydride group is modified (half-esterified), no further reaction takes place even when an active hydrogen compound is mixed, so that one-pack (one-pack) is obtained. Is possible. Further, as described above, since the alcohol-modified silicate compound (III) hardly causes a condensation reaction or a reaction with other resin components during storage of the paint, the storage stability is excellent.

In the curing reaction with the active hydrogen compound at the time of forming the coating film, the curing speed can be changed by variously changing the modifier of the acid anhydride group, and a coating film having an excellent appearance can be obtained. It can be formed.

The curing reaction of the clear coating for automotive top coating according to the present invention is carried out by first converting the half-esterified ring-opening acid anhydride-modified group in the half-ester acid group-containing acrylic copolymer (I) to a curing temperature. To return to the acid anhydride group once. Then, an epoxy group-containing acrylic copolymer (I
The hydroxyl group in I) reacts to form a half ester again. Next, the remaining carboxyl groups in the half-ester acid group-containing acrylic copolymer (I) react with the epoxy groups in the epoxy group-containing acrylic copolymer (II) to form diesters. Further, the alcohol-modified silicate compound (III) is hydrolyzed and condensed by the acid catalysis of the half-ester acid group-containing acrylic copolymer (I) and simultaneously reacts with the hydroxyl group in the epoxy group-containing acrylic copolymer (II). Curing proceeds. That is, in the above curing reaction, two groups of the epoxy group and the hydroxyl group in the epoxy group-containing acrylic copolymer (II) are acid anhydride modifying groups in the half ester acid group-containing acrylic copolymer (I). The hydroxyl group in the carboxyl group and the ester group, and the hydroxyl group in the epoxy group-containing acrylic copolymer (II) are respectively bonded to the alcohol-modified silicate compound (III) and its hydrolyzed condensate, and three kinds of components are formed. It is considered that the curing proceeds by reacting with each other. Therefore, the cured coating film has a firm structure and is excellent in weather resistance, chemical resistance, scratch resistance, and the like. Also, when the paint is applied to the substrate, the alcohol-modified silicate compound (III) spreads on the surface of the coating film, forming a wet coating film in which the alcohol-modified silicate compound (III) is largely present near the coating film surface. Then, by heating and curing, many methoxy groups and the like derived from the alcohol-modified silicate compound (III) are present on the coating film surface, and the stain resistance can be expressed as described above. Furthermore, since there is no need to use a basic resin such as a melamine resin, the cured coating film has excellent acid resistance.

The cured coating film of the present invention can be given a hydrophilic property by reacting with an acid. However, it may be imparted with stain resistance gradually with the lapse of time. By doing so, stain resistance may be imparted from an early stage.

The clear coating for automotive top coating of the present invention comprises:
An undercoating layer (electrodeposition coating layer or, if necessary, an intermediate coating layer) is formed on the outer panel of an automobile, and a base coating containing a coloring pigment and / or a brilliant pigment is applied, and then a top coating is applied. The present invention can be applied to a method for forming a multilayer coating film for an automobile body, which comprises applying a clear coating material wet-on-wet and then heating and curing.

The base material used for the automobile outer panel is not particularly limited, and examples thereof include metals such as iron, copper, aluminum, tin, zinc, and alloys and castings thereof; glass; plastic; No. The above-mentioned clear coating for automobile top coating can be advantageously used particularly for plastics and metals, but can be particularly preferably used for metal products that can be subjected to cationic electrodeposition coating. The above-mentioned automobile outer panel is not particularly limited, and examples thereof include automobile bodies and parts such as passenger cars, trucks, motorcycles, and buses. It is particularly preferable that these metals have been previously subjected to a chemical conversion treatment with a phosphate, a chromate or the like.

The undercoat layer is not particularly limited, and may be, for example, an electrodeposition coating, or may be an electrodeposition coating and an intermediate coating.

The above-mentioned electrodeposited coating film can be formed by electrodepositing a cationic or anionic electrodeposition coating material, and the cationic electrodeposition coating gives a coating film having excellent corrosion resistance. The cationic electrodeposition coating is a thermosetting electrodeposition coating of a cathodic deposition type, which is made of a basic amino group-containing resin as a base resin, and is rendered water-soluble by neutralizing with an acid. Is done.

The basic amino group-containing resin is not particularly limited. For example, a resin obtained by adding a secondary amine to an epoxy group of a bisphenol-type epoxy resin is preferable.
The secondary amine is not particularly limited, and examples thereof include those in which the primary amine is blocked by ketimination of diethylenetriamine or the like.

The crosslinking agent used in the cationic electrodeposition coating composition is not particularly limited, and for example, a block polyisocyanate sealed with a blocking agent such as alcohols, phenols, oximes, and lactams is preferable.

The above-mentioned cationic electrodeposition paint includes a coloring pigment,
Pigments such as extender pigments and rust-preventive pigments, hydrophilic and / or hydrophobic solvents, additives and the like can be added as necessary. The compounding amount of the pigment can be 5 to 150 parts by weight based on 100 parts by weight of the resin solid content.

The above-mentioned electrodeposition coating film is preferably formed such that the film thickness after baking and drying is usually 10 to 40 μm, more preferably 1 to 40 μm, after applying the above electrodeposition paint.
5 to 25 μm. Further, it is more preferable to perform a normal chemical conversion treatment before the electrodeposition coating.

The above-mentioned intermediate coating film is formed by applying an intermediate coating material on the above-mentioned electrodeposition coating film, concealing base defects, and ensuring surface smoothness after top coating and imparting chipping resistance. And various organic and inorganic coloring pigments and extenders.

The color pigment to be incorporated in the intermediate coating composition is not particularly limited, and examples thereof include azo chelate pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments, and perylene pigments. ,
Organic pigments such as dioxane pigments, quinacridone pigments, isoindolinone pigments, and metal complex pigments; inorganic pigments such as yellow salt, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide; calcium carbonate, barium sulfate, and clay And extender pigments such as talc. These may be used alone or in combination of two or more. As a standard, gray-based intermediate coatings with carbon black and titanium dioxide as the main pigments are often used, but depending on the concealment of the top coat, so-called color intermediate coatings in which various color pigments are combined. Can also be used.

The thermosetting resin blended in the intermediate coating composition is not particularly limited, and examples thereof include film-forming resins such as acrylic resins, polyester resins, alkyd resins, epoxy resins, and urethane resins. Is used in combination with a curing agent such as an amino resin and / or a blocked isocyanate resin. Among these, a combination of an alkyd resin and / or a polyester resin and an amino resin is preferable from the viewpoint of pigment dispersibility or workability.

The solid content in the intermediate coating composition is 30
７０70% by weight, preferably 35-55% by weight. At the time of application, it is 10 to 60% by weight, preferably 20 to 50% by weight.

The method of applying the intermediate coating is preferably performed by applying a method such as electrostatic coating, air spray, airless spray, etc. on the heat-cured or uncured electrodeposition coating film. After coating, the intermediate coating film itself can be cured by heating at a temperature of about 100 to 180 ° C. The dry film thickness of the formed intermediate coating film is generally 1
It is preferably about 0 to 60 μm, more preferably 20 to 5 μm.
It is about 0 μm. When the dry film thickness is less than 10 μm,
If the base cannot be concealed, and if the thickness exceeds 60 μm, problems such as a splash and sagging may occur during coating.

The base paint containing the above pigment is coated with the above-mentioned undercoating layer (electrodeposition coating layer or, if necessary, intermediate coating layer).
Is formed, the undercoat layer is applied in a cured or uncured state. Depending on the saturation of the overcoat, it is preferable to first apply a color base paint to form the first layer of the overcoat. In this case, the second layer of the top coat can be formed of a bright pigment-containing base paint to form a multilayer coat excellent in design.

The color pigment to be blended in the base paint is not particularly limited, and examples thereof include those similar to the color pigment to be blended in the intermediate paint. The glitter pigment is not particularly limited, and examples thereof include aluminum powder, copper powder, nickel powder, stainless steel powder, mica powder, interference mica powder, colored mica powder, alumina flake, graphite flake and the like.

The thermosetting resin blended in the base paint is not particularly limited, and includes, for example, the same thermosetting resins blended in the intermediate paint. Among these, pigment dispersibility, workability, from the viewpoint of weather resistance,
A combination of an acrylic resin and / or a polyester resin with an amino resin is preferred.

The solid content in the base paint is 15
-60% by weight, preferably 20-55% by weight. At the time of application, it is 10 to 50% by weight, preferably 20 to 45% by weight.

The form of the intermediate coating and the base coating is preferably a solution type. If it is a solution type, organic solvent type, aqueous (water-soluble, water-dispersible, emulsion)
And non-aqueous dispersion type. Also, if necessary,
A curing catalyst, a surface preparation agent and the like can be blended.

If the form of the base paint is an aqueous type,
As the binder, a thermosetting resin specifically disclosed in US Pat. No. 5,151,125 and US Pat. No. 5,183,504 can be used. In particular, a thermosetting resin in which an acrylic resin having an acrylamide group, a hydroxyl group and an acid group described in US Pat. No. 5,183,504 and a melamine resin are combined is excellent in terms of finish and appearance performance. . in this case,
In order to obtain a cured coating film with good finish, before applying the clear paint, the base coating film is previously heated to 60 to 100 ° C.
For 2 to 10 minutes.

The above base paint is preferably applied on the electrodeposition coating film or the intermediate coating film by a method such as electrostatic coating or air spray. , At about 100-180 ° C. The dry film thickness of the formed base coating film is generally preferably about 10 to 60 μm, more preferably about 20 to 50 μm. If the dry film thickness is less than 10 μm, the base cannot be concealed, and if it exceeds 60 μm,
Problems such as armpits and sagging may occur during painting.

When the base coating film is formed only of a base coating film containing a color pigment and / or a brilliant pigment, the base coating film is applied, and then a clear top coating material is applied wet-on-wet. By heating and curing, a two-coat, one-bake (2C1B) multilayer coating film can be formed.

When the above-mentioned base coating film is formed of a color base coating film and the above-mentioned glittering pigment-containing base coating film, when the above-mentioned color base coating film is independently cured by heating, the above-mentioned glittering pigment-containing base coating film After painting the paint, and further applying a clear paint for overcoating wet-on-wet, and then curing by heating,
A three-coat, two-bake (3C2B) multilayer coating film can be formed. Further, when the color base coating film is not cured by heating alone, the glitter pigment-containing base coating material is applied thereon by wet-on-wet, and further, a clear coating material for top coating is applied thereon by wet-on-wet. It can be cured by heating. That is, the color base coating film, the bright pigment-containing base coating film, and the clear top coating film are combined in a wet-on-wet manner, and a composite coating film is formed and then heat-cured to form a 3-coat 1-bake (3C1B). A composite coating film can be formed, and a composite coating film showing more excellent design properties can be formed.

The coating film formed by the clear top coating is for ensuring surface smoothness and imparting other properties required for the coating film. Use a clear paint for automotive top coating.

The above clear coating composition for top coating is preferably applied on an uncured bright pigment-containing base coating film by a method such as electrostatic coating or air spraying. The coating itself is 100
A cured coating film can be formed by heating and curing at a temperature of about 200 ° C. If the curing temperature is lower than 100 ° C., the curing is insufficient, and if it exceeds 200 ° C., the cured coating film becomes hard and brittle. Preferably, by heating and curing at a temperature of 120 to 180 ° C., a cured coating film having a high degree of crosslinking can be formed.

The curing time of the clear coating film varies depending on the curing temperature, but is suitably from 120 ° C. to 180 ° C. for 10 to 30 minutes. The dry film thickness of the formed coating film varies depending on the desired use, but in many cases is preferably from 10 to 80 µm, and more preferably from about 15 to 60 µm. If the dry film thickness is less than 10 μm, the substrate cannot be concealed,
When the thickness exceeds μm, defects such as sidearms and sagging may occur during coating.

The clear paint for top coating of automobiles of the present invention comprises:
If the base paint is a solid paint, an undercoat film layer is formed on the outer panel of the automobile, a solid paint containing a color pigment is applied, heat-cured, and then a clear top paint is applied dry-on-wet Then, it can be applied to a method for forming a multilayer coating film of an automobile body by heating and curing (2C2B).

When the base coating film is formed only of a color base coating film, the color base coating material is applied and cured by heating, and then the clear coating material for top coating is applied by dry-on-wet and then cured by heating. ,
A two-coat two-bake (2C2B) coating film can be formed.

When the base coating film is formed of a glitter pigment-containing base coating film and an existing clear coating film, the base coating material and the existing clear coating material are applied on a wet-on-wet basis and heat-cured. The above-mentioned clear coating for top coating is applied by dry-on-wet and then cured by heating to form a three-coat two-bake (3C2B) multilayer coating film. The existing clear coating may be any of the conventionally used clear coatings for automotive top coating.

In any case, the outermost coating film forms a coating film of one coat and one bake (1C1B).

The outermost layer of the multi-layer coating film of the automobile body coated with the above-mentioned method for forming a multilayer coating film using the clear coating film for automobile top coating of the present invention is formed by the clear coating material for automobile top coating of the present invention. Since it is formed, it has basic performance such as weather resistance, is particularly excellent in acid resistance, and has high hydrophilicity, so it can maintain the same effect as maintenance-free car washing. It can exhibit its performance stably even after the paint is stored. Such an automobile body is also one of the present invention.

[0116]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Synthesis Example 1Acrylic containing half ester acid group
Copolymer (a)  Thermometer, stirrer, cooling pipe, nitrogen introduction pipe and dropping funnel
330 parts by weight of xylene and propylene
Renglycol monomethyl ether acetate 110 weight
And heated to 127 ° C. Drops into this reactor
Using a lower funnel, 300 parts by weight of styrene, methacrylic acid
360 parts by weight of 2-ethylhexyl, isobu acrylate
112 parts by weight of chill, 26 parts by weight of acrylic acid, maleic anhydride
Acid 202 parts by weight, propylene glycol monomethyl ester
300 parts by weight of teraacetate and t-butyl peroxy
90 parts by weight of c-2-ethylhexanoate and xylene 1
A solution consisting of 00 parts by weight was added dropwise over 3 hours. drop
After holding at 127 ° C. for 30 minutes after the lower end, t-
Butyl peroxy-2-ethylhexanoate 10 weight
Solution of 50 parts by weight of xylene and 50 parts by weight of xylene in 30 minutes
I dropped it. After the completion of the dropping, the reaction is further performed at 127 ° C. for 1 hour.
The reaction was continued until the number average molecular weight (Mn) was 3000.
Crocodile containing 53% of non-volatile content containing polyanhydride (a) -i
I got it. In 1990 parts by weight of the obtained varnish, methanol
100 parts by weight of the reaction mixture and reacted at 70 ° C. for 23 hours.
Este with a value of 127 mg KOH / g (solid content conversion)
Obtaining a varnish containing a lactic acid group-containing acrylic copolymer (a)
Was. In addition, this half ester acid group-containing acrylic copolymer
The infrared absorption spectrum of the compound (a) -1 was measured, and acid
Absorption of anhydride group (1785cm^-1) Disappears
did.

Synthesis Example 2Polyester containing carboxyl group
Resin (b)  Thermometer, stirrer, cooling pipe, nitrogen inlet pipe, water separator and
136 parts by weight of pentol, ε-
456 parts by weight of caprolactone and dibutyltin oxide
0.1 part by weight was charged, the temperature was raised to 170 ° C., and the heating was continued for 3 hours.
At 170 ° C. Then, the heated melted hex
Add 539 parts by weight of sahydrophthalic anhydride and add
After holding for 1 hour, ethyl 3-ethoxypropionate 4
64 parts by weight, number average molecular weight (Mn) 1700, weight
Weight average molecular weight (Mw) / number average molecular weight (Mn) = 1.2
8, acid value 174mgKOH / g (solid content conversion), hydroxyl group
Group having a valency of 25 mgKOH / g (solid content)
Containing non-volatile content of 71% containing polyester resin (b)
I got a varnish.

Synthesis Example 3Acrylic copolymer containing epoxy group
Body (c) -1  Thermometer, stirrer, cooling pipe, nitrogen introduction pipe and dropping funnel
Charge 500 parts by weight of xylene into a 2 L reaction tank equipped
The temperature was raised to 125 ° C. Using a dropping funnel in this reactor,
380 parts by weight of glycidyl methacrylate, 200 styrene
Parts by weight, 292 weight of 2-ethylhexyl methacrylate
Parts, 128 parts by weight of 4-hydroxybutyl acrylate
And t-butylperoxy-2-ethylhexanoate 1
3 parts of a solution consisting of 00 parts by weight and 100 parts by weight of xylene.
It was dropped over time. 12 for 30 minutes after dropping
After maintaining at 5 ° C., t-butylperoxy-2-ethyl
From 10 parts by weight of hexanoate and 10 parts by weight of xylene
Solution was added dropwise over 30 minutes. After this dripping is completed,
The reaction is continued for 1 hour at 125 ° C., and the number average molecular weight is
(Mn) 3700, epoxy equivalent 400 (solid conversion)
Calculation), hydroxyl value of 47 mgKOH / g (solid content conversion)
Non-volatile content 6 containing oxy group-containing acrylic resin (c) -1
2% varnish was obtained.

Synthesis Example 4Acrylic copolymer containing epoxy group
Body (c) -2  Thermometer, stirrer, cooling pipe, nitrogen introduction pipe and dropping funnel
Charge 500 parts by weight of xylene into a 2 L reaction tank equipped
The temperature was raised to 125 ° C. Using a dropping funnel in this reactor,
500 parts by weight of glycidyl methacrylate, 200 styrene
Parts by weight, 2-ethylhexyl methacrylate 150 parts by weight
Parts, 100 parts by weight of 2-ethylhexyl acrylate,
50 parts by weight of 2-hydroxyethyl acrylate and t-
Butyl peroxy-2-ethylhexanoate 100
Solution for 3 hours with 100 parts by weight of xylene
And dropped. At 125 ° C for 30 minutes after the addition
After holding, t-butylperoxy-2-ethylhexa
A solution consisting of 10 parts by weight of noate and 10 parts by weight of xylene
The solution was added dropwise over 30 minutes. After this dripping is completed, it is 1 hour
While the reaction was continued at 125 ° C., and the number average molecular weight (M
n) 3600, epoxy equivalent 300 (solid content conversion), water
Epoxy group having an acid value of 20 mgKOH / g (solid content)
Content 62% containing acrylic copolymer (c) -3 containing
Varnish was obtained.

Synthesis Example 5Alcohol-modified silicate compound
Object (e) -1  MS-56 as methyl silicate (trade name, Mitsubishi Chemical
Alcohol exchange reaction with butyl alcohol
Thus, the alcohol-modified silicate compound (e)-
Thus, a composition having a nonvolatile content of 100% and containing 1 was obtained. alcohol
The exchange reaction conditions were as follows: 84 g of MS-56, butyl
Mix alcohol 12g and triethylamine 0.2g
Then, after reacting at a temperature of 80 ° C. for 12 hours, under reduced pressure
The produced methanol was distilled off.

Synthesis Example 6Alcohol-modified silicate compound
Object (e) -2  MS-56 as methyl silicate (trade name, Mitsubishi Chemical
Exchange reaction with isopropyl alcohol
The alcohol-modified silicate compound
A composition containing (e) -2 and having a nonvolatile content of 100% was obtained. A
The alcohol exchange reaction conditions were as follows: 74 g of MS-56
Isopropyl alcohol 21 g and triethylamido
And react at a temperature of 80 ° C. for 12 hours.
After that, methanol produced under reduced pressure was distilled off.

Examples 1 to 4 0.3 parts by weight of a tetrabutylammonium bromide curing catalyst and 0.3 parts by weight of a dibutyltin bis (butylmalate) curing catalyst were added to the resin components shown in Table 1, and a UV absorber Tinuvin manufactured by Ciba Geigy Co., Ltd. 900 (trade name) 2 parts by weight, Sankyo LS-440 (trade name) light stabilizer manufactured by Sankyo Co., 1 part by weight, and Monsanto surface modifier Modaflow (trade name)
0.1 parts by weight were blended while stirring with a disper to obtain a clear paint for automotive top coating of the present invention.

Next, each of the obtained clear coatings for automobile top coating was diluted to a coating viscosity with a thinner composed of butyl acetate / xylene = 1/1. Nippon Paint Co., Ltd. cationic electrodeposition paint power top U-3 on phosphoric acid treated steel sheet
Nippon Paint Co., Ltd. was applied to a test plate which was coated with 0 and polyester / melamine type gray intermediate coating paint Olga P-2 (both trade names) so as to have a dry film thickness of 25 μm and 40 μm, respectively, and then heat-cured. Super rack M-1
70 (trade name) of a silver metallic base paint, and a wet-on-wet, diluted automotive top coat clear paint is applied to each of the base paints.
It was baked and dried for 0 minutes to prepare a coating test plate of 2 coats and 1 bake (2C1B) as a coating method. In addition, the cured coating film of the base coating material and the clear coating material was applied such that the dry film thickness became 15 μm and 40 μm, respectively.

Further, Nippon Paint Powertop U-30 and Olga P-2 (both trade names) were applied to a phosphoric acid-treated steel sheet so that the dry film thickness became 25 μm and 40 μm, respectively, and heat-cured. A silver metallic base paint of Nippon Paint Co., Ltd. Super Rack M-170 (trade name) is applied to the test plate, and a 3C2B clear paint of Nippon Paint Co., Ltd. Super Rack O-170 (trade name) is applied on a wet-on-wet basis. 140 ℃
After baking and drying for 30 minutes, each of the diluted clear paints for automotive top coating was applied and baked and dried at 140 ° C. for 30 minutes to prepare a coating test plate of 3 coats and 2 bake (3C2B) as a coating method. The cured coating film made of the silver metallic base paint, the clear paint for exclusive use of 3C2B, and the clear paint has a dry film thickness of 1 each.
Coating was performed so as to be 5 μm, 40 μm, and 40 μm.

The coating films obtained by the following evaluation methods were evaluated. The results are shown in Table 1.

[0127]Evaluation method  (1) Storage stability The initial viscosity of the obtained paint was 3 in 4 Ford Cup
Adjust to 0 seconds, 10 days at 40 ° C in incubator
After leaving still, Viscosity increases for seconds with 4 Ford Cup
Was measured. The smaller the value, the better the storage stability
Which indicates that.

(2) Acid Resistance Test The cured coating film obtained was treated with a 0.1N H ₂ SO ₄ aqueous solution 0.2
After contacting the resulting solution with 80 ml at 80 ° C. for 30 minutes, the coating film surface was visually evaluated according to the following criteria. ：: No change is observed. Δ: Traces are slightly observed. ×: Traces are clearly seen.

(3) Scratch resistance test 1 g of a 50% aqueous dispersion of a cleanser (New Homing Cleanser (trade name) manufactured by Kao Corporation; containing 87% of abrasive, 5% of surfactant and other components). 2x2c
m was attached to a Gakushin-type dyed rub fastness tester (Daiei Kagaku Seiki Co., Ltd.). Next, the obtained cured coating film was rubbed 10 times with a load of 500 g, and a gloss retention (%) of 20 ° G before and after friction was measured using a gloss meter (manufactured by Suga Test Instruments Co., Ltd.).
Was measured. The correspondence with the visual evaluation is shown below. > 90: no change. 80 to 90: A slight change can be seen, but it is not noticeable. 70-80: A slight change is visible. 70 <: The change is clearly visible.

(4) Warm Water Resistance Test After the obtained cured coating film was immersed in warm water at 40 ° C. for 10 days, the coating film surface was visually evaluated according to the following criteria. ：: No change is observed. Δ: Traces are slightly observed. ×: Traces are clearly seen.

(5) Initial water contact angle (°) 0.4 ml of ion-exchanged water was dropped on the obtained cured coating film, and after 30 seconds from the addition, the contact angle was adjusted to Fa, manufactured by Kyowa Interface Science Co., Ltd.
The measurement was performed using an ce automatic interfacial tensiometer CA-Z (trade name).

(6) Outdoor exposure test An outdoor exposure test was performed in accordance with JIS K5400 9.9, and after one and six months, the water contact angle and the lightness difference (ΔL) from the initial coating film were measured.

Comparative Example 1 As shown in Table 1, as the resin components, 56 parts by weight of the half ester acid group-containing acrylic copolymer (a) -1, 28 parts by weight of the carboxyl group-containing polyester resin (b), The epoxy group-containing acrylic copolymer (c) -1 was added to 82
Except that 10 parts by weight of MS-56 (trade name, manufactured by Mitsubishi Chemical Co., Ltd.) was used as a methyl silicate, and a clear coating for automotive top coating was prepared in the same manner as in Example, and two coats were applied as a coating method. One-bake (2C1B) and three-coat, two-bake (3C2B) painted test plates were produced, respectively. The coating film performance was evaluated in the same manner as in the examples. The results are shown in Table 1.

Comparative Example 2 As shown in Table 1, as the resin components, 56 parts by weight of the half ester acid group-containing acrylic copolymer (a) -1, 28 parts by weight of the carboxyl group-containing polyester resin (b), The epoxy group-containing acrylic copolymer (c) -1 was added to 82
In the same manner as in Example, except that 10 parts by weight of ethyl silicate 40 (trade name, manufactured by Colcoat Co., Ltd.) was used as the ethyl silicate, a clear paint for automobile top coating was prepared. Bake (2
A coated test plate of C1B) was prepared. The coating film performance was evaluated in the same manner as in the examples. The results are shown in Table 1.

[0135]

[Table 1]

As is clear from Table 1, the clear coating for automotive top coating obtained in the Examples has excellent storage stability, and the cured coating film has basic properties as an automotive coating film such as abrasion resistance and hot water resistance. Satisfies the performance, has excellent acid resistance, and furthermore, has a low water contact angle after 1 month exposure and 6 months exposure,
The surface of the coating film showed sufficient hydrophilicity and was excellent in stain resistance.

On the other hand, the clear paint for automotive top coating obtained in Comparative Example 1 was inferior in storage stability. The clear paint for automotive top coating obtained in Comparative Example 2 had a large water contact angle after 1 month exposure and after 6 months exposure, the coating film surface did not show sufficient hydrophilicity, and the stain resistance was poor.

[0138]

The clear coating for automotive top coating of the present invention has the above-mentioned constitution, and the cured coating film has a high crosslinking density and therefore excellent weather resistance, especially excellent acid resistance, and high hydrophilicity. In addition, it is car wash-free and has excellent paint storage stability while maintaining its aesthetic appeal. The method for forming a multilayer coating film of an automobile body according to the present invention can form a composite coating film having excellent appearance and coating film performance. The vehicle body of the present invention exhibits excellent appearance and coating film performance, and can be maintenance-free without requiring car washing.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 163/00 C09D 163/00 183/02 183/02 F term (Reference) 4D075 AA02 CA32 CA37 DA06 DB02 DC12 EA07 EB22 EB42 EC37 4J038 CG141 CG142 CG171 CG172 CH121 CH122 CH151 CH152 CH171 CH172 CJ131 CJ132 DL021 DL022 GA03 GA06 KA08 MA14 NA03 NA04 NA05 NA26 PA13 PA14 PA19 PB07

Claims (4)

[Claims] 1. A clear paint for automotive top coating comprising a half ester acid group-containing acrylic copolymer (I), an epoxy group-containing acrylic copolymer (II) and an alcohol-modified silicate compound (III) as resin components, The half ester acid group-containing acrylic copolymer (I) is a copolymer of an acid anhydride group-containing radical polymerizable monomer (Ia) and another radical polymerizable monomer (Ib). Is obtained by half-esterifying the acid anhydride group with a low molecular weight alcohol-based compound, and the epoxy group-containing acrylic copolymer (II) is
Epoxy group-containing radical polymerizable monomer (II-a) 30 to
70 parts by weight of a hydroxyl-containing radical polymerizable monomer (II-
b) a copolymer obtained by copolymerizing 10 to 50 parts by weight and 20 to 60 parts by weight of another radical polymerizable monomer (II-c), and having a number average molecular weight (Mn) of 1,000 to 100;
8000, an epoxy equivalent of 100 to 800 (in terms of solids), a hydroxyl value of 5 to 200 mgKOH / g (in terms of solids), and the alcohol-modified silicate compound (III) is represented by the general formula (1): (In the formula, n represents an integer of 1 to 50. A part of R has a substituent or an unsubstituted alkyl group having 2 to 20 carbon atoms and / or a substituent. Or an unsubstituted aralkyl group having 7 to 20 carbon atoms, and the remaining R is a methyl group.) 2. An undercoating film layer is formed on an automobile outer panel,
A method for forming a multilayer coating film of an automobile body, comprising coating a base coating material containing a coloring pigment and / or a brilliant pigment, applying a clear coating material for top coating in a wet-on-wet manner, and then heating and curing. The method for forming a multilayer coating film on an automobile body, wherein the clear coating material for top coating is the clear coating material for automotive top coating according to claim 1. 3. An undercoating film layer is formed on an outer panel of an automobile,
After applying a solid paint containing a color pigment and heat-curing, or after applying a base paint and a clear paint wet-on-wet and heat-curing, then applying a clear top paint dry-on-wet A method for forming a multi-layer coating film on an automobile body, which comprises heating and curing, wherein the clear coating for top coating is the clear coating for automobile top coating according to claim 1. Film formation method. 4. An automobile body coated with a multilayer coating film, wherein the outermost layer of the multilayer coating film is formed by the clear coating material for automotive top coating according to claim 1. Car body.