JPH0241377A - Coating compound composition of thermosetting curing solvent type having excellent storage stability - Google Patents

Abstract

PURPOSE:To obtain title composition having excellent appearance and qualities, improved acid resistance, reduced occurrence of stains of rain by acidic rain and excellent storage stability by using an acid group-containing acrylic copolymer and an epoxy group-containing acrylic copolymer. CONSTITUTION:(A) An acid group-containing acrylic copolymer having 30-150 kgKOH/g acid value is blended with (B) an epoxy group-containing acrylic copolymer having 200-1,000g/eq epoxy equivalent in the equivalent ratio of the acid group of the component A and the epoxy group of the component B of (1:0.5)-(0.5:1) and (C) >=6wt.% (based on total amounts of the components A, B and C) hydroxyl group-containing solvent to give the aimed composition having high durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a clear paint composition for top coating, which is coated on a base coat by a uniform-on-wet method.

More specifically, in painting automobile bodies, a clear paint composition is used in a coating system in which a base coat containing a colored pigment or a metallic pigment is applied, a clear top coat is applied thereon by a wet-on-wet method, and the coating is simultaneously baked. The present invention relates to a thermosetting solvent-based coating composition that is suitable for use in and has excellent acid resistance, storage stability, durability, and coating film appearance.

[Conventional technology]

Strong demands for automotive paints include high appearance quality, high durability, and good storage stability.

In recent years, in order to satisfy these demands, a two-coat method in which a clear coat is applied on a base coat containing a pigment has been frequently used.

[Problem to be solved by the invention]

Conventionally, acrylic-melamine thermosetting solvent-based paints are often used as clear coat paints. However, acrylic melamine paints do not meet the requirements for appearance quality, mainly gloss. Furthermore, it lacks resistance to acid rain, causing rain stains, and lacks durability.

In addition, although the urethane-based clear coats used in some areas have a high appearance quality, they are inconvenient to handle because they are a two-component type that requires the hardening agent to be mixed immediately before use, and they are resistant to acid rain. It also has the disadvantage of lacking in sexuality.

In addition, acrylic powder coatings that employ a curing reaction between acid groups and epoxy groups have been tried, but they have drawbacks such as poor appearance quality and high baking temperatures, which are typically over 160°C. There is.

Furthermore, as described in JP-A No. 56-24074, acrylic powder coatings use dicarboxylic acids as a curing agent component, but these have poor solvent solubility, and as solvent-based coatings, deposits may form in the coating. It cannot be applied due to stability problems such as occurrence of.

Solvent-based paints using a similar curing method have also been attempted. In this case, although the appearance quality is improved, storage stability, which is normally required for use as an automobile paint, is a problem.

[Means to solve the problem]

The present inventors have taken into consideration that the conventional technology has not reached a sufficient level in terms of appearance quality and storage stability regarding clear paint compositions for top coats that are applied on a base coat by a wet-on-wet method. As a result of intensive research, we found that a thermosetting solvent-based coating composition using an acrylic copolymer with acid groups and an acrylic copolymer with epoxy groups has excellent appearance quality, and has excellent acid resistance and is resistant to acid rain. It was discovered that the occurrence of rain stains is reduced, the paint composition has excellent performance in various physical properties, and it exhibits excellent storage stability by including a solvent having a hydroxyl group in the paint composition, leading to the present invention.

That is, the present invention comprises (a) an acrylic copolymer having an acid group with an acid value of 30 to 150 mgKOH/g, and (b) an acrylic copolymer having an epoxy group with an epoxy equivalent of 200 to 1000 g/eq. , (c) consists of a solvent having a hydroxyl group, and the acid group of (a) and the epoxy group of (b) are bo, 5 to 0.5
:1 equivalent ratio, the amount of (C) is (a) (b)
This is a thermosetting solvent-based coating composition with excellent storage stability in which the amount is 6% by weight or more based on the total amount of (c).

Preferred examples of monomers having acid groups used in the acrylic copolymer (a) in the present invention include acrylic acid and methacrylic acid, and further examples include maleic acid, maleic anhydride, itaconic acid, and their like. Examples include mononis and chilled products, and one or more of these can be used.

The amount of the monomer having an acid group is limited so that the acid value of the acrylic copolymer (a) is 30 to 150. When the acid value is less than 30, curing properties are insufficient and solvent resistance is poor.
If the acid value exceeds 150, the solubility in solvents will be poor, and the stability of the paint will be poor, such as the formation of precipitates, making it impractical as a solvent-based paint.The preferred acid value range is 50 to 120, and Preferably it is 70-100. The acid value is expressed as KOH required to neutralize 1 g of resin, and the unit is KOHmg/g.

Copolymerizable monomers include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate.
Acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, tridecyl (
meth)acrylate, cyclohexyl(meth)acrylate, benzyl(meth)acrylate, phenyl(meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, 1,4-butanediol mono (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)
Esters of acrylic acid and methacrylic acid, such as acrylates, can be used. For example, methyl (
Meth)acrylate refers to methyl methacrylate and methyl acrylate; other copolymerizable monomers include styrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylnitrile, vinyl acetate, vinyl propionate, acrylamide, methacryl Amide, methylol acrylamide, methylol methacrylamide, vinyl chloride, propylene, ethylene, 04
~C Yi.

α-olefins and the like can be mentioned.

Furthermore, examples of copolymerizable monomers include monomers having hydroxyl groups. Monomers with hydroxyl groups include hydroxyethyl (meth)acrylate, hydroxypropyl (
C- of meth)acrylate, hydroxybutyl(meth)acrylate, 1,4-butanediol mono(meth)acrylate, hydroxyethyl(meth)acrylate
caprolactone adducts, ethylene and propylene adducts of hydroxyethyl (meth)acrylate,
One or more of these can be used.

When copolymerizing a monomer having a hydroxyl group, the hydroxyl value of the acrylic copolymer (a) is preferably 5 to 100. Within this range, the crosslinking reaction between the acrylic resin and the amino resin is sufficient. This process improves the resistance of the paint film to gasoline.

The number average molecular weight of the acrylic copolymer (a) is preferably 3,500 or more, and the number average molecular weight is measured using GPC using polystyrene as a standard. When the number average molecular weight is 3,500 or more, solvent resistance is improved, and scratches caused by brushes during car washing are less likely to occur (water resistance is improved, and durability for maintaining good coating film quality is improved). In addition, in wet-on-wet coating with a base coat, a good coating film appearance is obtained without mixing of the base coat and clear coat.The more preferable number average molecular weight is in the range of more than 5,500 and up to 20,000.

The glass transition point of the acrylic copolymer (a) is preferably 50°C or lower, more preferably -20°C to 40°C.

The copolymer having acid groups must be an acrylic copolymer, and if another polymer, such as a polyester resin having acid groups, is used in place of the acrylic copolymer (a), , it has poor acid resistance and causes rain stains due to acid rain, making it impractical.

Acrylic copolymer (a) can be synthesized by conventional methods, and can be produced by any known polymerization method such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. . At that time, as a polymerization initiator, azobisisobutyronitrile, 4.4'-azobis(4-cyanopentaic acid), benzoyl peroxide, t-butylperoxy-2-
Ethylhexanoate, cumene hydroperoxide, potassium persulfate, hydrogen peroxide, 2.2"-
Azobis[2-methyl-N-(2-hydroxyethyl)
propioamide], etc., and, if necessary, dodecyl mercaptan, mercaptoethanol, α-methylstyrene dimer, etc. can be used as a chain transfer agent.

Examples of the amount of a monomer having an epoxy group used in the acrylic copolymer (b) in the present invention include glycidyl methacrylate, glycidyl heptaacrylate, methylglycidyl methacrylate, methylglycidyl acrylate, and allyl glycidyl ether. As copolymerizable monomers in which one or more of these can be used, all the monomers exemplified as copolymerizable monomers described in (a) of the acrylic copolymer can be used. Further, the acrylic polymer (b) can be synthesized by a conventional method in the same manner as the acrylic copolymer (a).
) can be produced using the polymerization method described above, a polymerization initiator, and a chain transfer agent if necessary.

The monomer having an epoxy group is an acrylic polymer (b)
The amount used is limited so that the epoxy equivalent of is 200 to 1000. If the epoxy equivalent exceeds 1000, curing properties will be insufficient and solvent resistance will be poor. In addition, the epoxy equivalent is 200
If it is smaller, the surface of the coating film will not be smooth and a desirable coating quality cannot be obtained.The epoxy equivalent weight is expressed in grams of resin per Ig equivalent of the epoxy group. The unit is g/eq.

The number average molecular weight of the acrylic copolymer (b) is preferably 5000 or less. If it is 5000 or less, the reaction will proceed sufficiently during the curing reaction with the acrylic copolymer (a) during baking, resulting in improved solvent resistance. will improve. This is thought to be because the present invention uses a crosslinking reaction between polymers composed of the acrylic copolymer (a) and the acrylic copolymer (b). When the number average molecular weight is 5000 or less, there is no increase in the viscosity of the uncured paint at the initial stage of the crosslinking reaction, and it is presumed that the frequency of collision reactions between acid groups and epoxy groups does not decrease in the subsequent crosslinking reaction. Preferably, acrylic The number average molecular weight of the acrylic copolymer (b) is preferably lower than that of the acrylic copolymer (a).The acrylic copolymer (b) is a curing agent for the acrylic copolymer (a). Acts as.

The glass transition point of the acrylic copolymer (b) is preferably 50°C or lower, more preferably 0°C to 40'C.

It is necessary to adjust the paint so that the acid groups and epoxy groups of the acrylic copolymers (a) and (b) have an equivalent ratio of 1:0.5 to 0.5:1. Outside this range, the solvent resistance and water resistance of the coating film will be poor.

In the present invention, a solvent (c) having a hydroxyl group is essential. Examples of the solvent (c) having a hydroxyl group include alcohols such as methanol, ethanol, isopropyl alcohol, n-butanol, 5ec-butanol, and tar-butanol, and any of primary, secondary, and tertiary alcohols. Alternatively, cellosolves such as ethyl cellosolve and carpitols such as ethyl carpitol may be used. Alcohols are particularly preferred, and two or more of these solvents may be used in combination.

The amount of solvent (c) having a hydroxyl group is (a) (b) (c
) is required to be at least 6% by weight. 6% by weight
If it is less than that, the viscosity of the paint increases during storage, resulting in poor stability and impractical use.

In the present invention, other solvents that can be used in thermosetting solvent-based coatings may be used as necessary. Examples of such solvents include aliphatic hydrocarbons such as hexane and heptane, toluene and xylene. Aromatic hydrocarbons such as petroleum distillates of various boiling point ranges consisting primarily of aliphatic hydrocarbons but containing some aromatic hydrocarbons, esters such as butyl acetate, ethylene glycol diacetate, 2-ethoxyethyl acetate. , acetone, and ketones such as methyl isobutyl ketone.

In the present invention, amino resins can be added to the coating composition. In this case, the acrylic copolymer (a) is preferably one in which a monomer containing a hydroxyl group is copolymerized.
This is because the crosslinking reaction during paint baking is mainly a reaction between the acid groups of the acrylic copolymer (a) and the epoxy groups of the acrylic copolymer (b), but amino resins also participate in the crosslinking reaction. It's for a reason. That is, the amino resin is a curing agent component that reacts with the hydroxyl groups contained in the acrylic copolymer (a) and the hydroxyl groups generated by the reaction between the acid groups and the epoxy groups. Furthermore, the reaction with the hydroxyl groups mainly contained in the acrylic copolymer (a) from the initial stage of the curing reaction forms a coating film with a high crosslinking density and improves resistance to low-molecular substances such as gasohol. It is presumed to work as an auxiliary curing agent.

The above amino resin is a resin synthesized from formaldehyde and at least one of melamine, urea, benzoguanamine, glycoluril, etc., and is a lower alcohol such as methanol, ethanol, propatool, isopropanol, butanol, isobutanol, etc. One in which part or all of the methylol group is alkyl etherified is used.

The amino resin is 1 to 20% of the total of the acrylic copolymer (a), the acrylic copolymer (b), and the amino resin.
It is preferable that the amount is % by weight; within this range, the gasohol resistance will be improved and the acid resistance will not be deteriorated.

In the present invention, quaternary phosphonium salts can be used as curing catalysts. This is particularly effective in accelerating the hardening reaction when the baking temperature is low (baking around 120°C).

Examples of quaternary borophonium salts include methyltrioctylphosphonium dimethylphosphate, methyltributylphosphonium dimethylphosphate, methyltriphenylphosphonium dimethylphosphate, tetrabutylphosphonium acetate, benzyltriphenylphosphonium acetate, tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, Tetrabutylphosphonium iodide, tetraphenylphosphonium bromide, tetraphenylphosphonium chloride, tetraphenylphosphonium iodide, benzyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, benzyltriphenylphosphonium iodide, tetrabutylphosphonium hydroxide, tetraphenylphosphonium Examples include tetraphenylborate. Further, there are monomers and polymers of p-styryldiphenylphosphonium bromide, and copolymers with monomers copolymerizable therewith. Quaternary borophonium salts can also be used as a mixture of one or more kinds. The quaternary borophonium salt acts as a reaction catalyst between the base and the epoxy group.

Furthermore, quaternary ammonium salts, tertiary amines, organic metal compounds, organic acid metal salts, imidazoles, Lewis acids, and boric acid esters can also be used in combination.

The amount of the quaternary phosphonium salt to be added is preferably 0.01 parts by weight or more and 3 parts by weight or less, based on a total of 100 parts by weight of the acrylic copolymer (a) and the acrylic copolymer (b). If the baking temperature is low (approximately 120°
When the baking temperature is around C), the solvent resistance and water resistance will not deteriorate, and the viscosity of the paint will not increase during storage.

In the present invention, in addition to the above, other commonly used components may be used as necessary, such as viscosity modifiers such as organic montmorillonite, microgel, polyamide, and polyethylene wax,
Silicone, acrylic organic polymer surface conditioning agents, ultraviolet absorbers, blocked isocyanate resins, etc. may be blended.Additionally, a small amount of pigment may be blended into the clear coat to provide coloring to the extent that complete hiding properties are not developed. You may.

As the base coat coating composition, any composition that can be used in automobile coating can be used.

Basecoat coating compositions include a resin and a pigment, which is a coloring agent. Useful resin compositions include acrylic-melamine, polyester (alkyd)-melamine, water-soluble acrylic-melamine, and acrylic polyol and polyester polyol-polymer. Examples include valent isocyanate, acrylic emulsion, and acrylic lacquer. Further, the clear coat resin of the present invention may be used as a base coat resin composition.

Metallic and colored pigments used in the basecoat paint composition include, for example, aluminum flakes, copper bronze flakes, and mica; colored pigments include, for example, inorganic pigments, especially titanium dioxide, iron oxide, chromium oxide, chromic acid; Lead and carbon black, and organic pigments include phthalocyanine blue and phthalocyanine green.

Further, the base coat coating composition may further contain conventional additives such as surfactants, flow control agents, thixotropic agents, microgels, ultraviolet absorbers, catalysts, and the like. Furthermore, a cellulose resin can also be blended.

As a method for using the coating composition of the present invention as a clear coat, the following methods can be typically exemplified.

After the base coat is applied to the substrate, a flash period is allowed and the clear coat is applied. The flash time can be left at room temperature for 1 to 10 minutes, or an appropriate heating process of about 80°C may be added.After the base coat and clear coat have been applied to the object to be coated, the setting time is about 5 to 20 minutes. After some time, the object to be painted will be about 100-18
0°C2 preferably 130-160″C and about 10-60
It will be burned for a minute. -The thickness of the rear film for boat fishing is 2
It is 0 to 60μ.

The clear coat composition may be applied by conventional methods, such as spacing, spraying, dipping, or dipping, but spray coating is preferred in order to provide an excellent coating appearance. Preferred spray coating methods include, for example, air atomization, bell atomization, and the like.

〔Example〕

The following reference examples, working examples, and comparative examples are for explaining the present invention, and in the description, "parts" and "%" are by weight unless otherwise specified.

Reference Example 1 (Preparation of acrylic copolymer (a) containing M group) After purging nitrogen into a four-bottle flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, the flask was filled with Tsurpetz 100 (Esso). Company manufactured, aromatic hydrocarbon, boiling point 15
0 to 177°C) and 15 parts of n-butanol were added and heated to 100°C. The raw materials listed in Table 1 were added dropwise over 5 hours, and then heated at 100°C for 6 hours.
By holding for a period of time, acrylic copolymers (a-1) to (a-10) having acid groups with a solid content of about 50% were obtained.

Reference Example 2 (Preparation of acrylic copolymer (b) having epoxy groups) After purging nitrogen into the same reactor as used in Reference Example 1, a flask was charged with Tsurupez 1100 (manufactured by Esso, aromatic hydrocarbon, 150 parts of boiling point: 150-177°C) were charged, and the temperature was raised to 140°C. The raw materials shown in Table 2 were added dropwise to this mixture over a period of 5 hours, and then heated at 100°C for 6 hours.
After holding for an hour, Tsurpets GTO.

50 parts were heated and distilled off under reduced pressure (~30+ssg),
Acrylic copolymers (b-1) to (b-6) having epoxy groups with a solid content of about 50% were obtained.

Reference Example 3 (3-1, Adjustment of base coat paint) (3-1-1, Adjustment of metallic base coat paint) 100 parts of Kijiroll was charged in a 4-tube flask equipped with a stirrer, thermometer, and condenser, and heated to 100°C. did. Raw materials consisting of 10 parts of styrene, 10 parts of methyl methacrylate, 30 parts of butyl acrylate, 35 parts of isobutyl acrylate, 12 parts of 2-hydroxy methacrylate, 3 parts of methacrylic acid, and 2 parts of azobisbutyronitrile were mixed therein, and the mixture was heated for 4 hours. The mixture was added dropwise and then maintained at the same temperature for 6 hours to obtain an acrylic resin with a solid content of approximately 50%. 180 parts of this acrylic resin, 2051 knee pants! −
60 (butylated melamine resin, manufactured by Mitsui Toatsu Chemical Co., Ltd., solid content 60%) 37.5 parts, aluminum paste 716ON (
(manufactured by Toyo Aluminum Co., Ltd.) were stirred and mixed using a stirrer.

(3-1-2, Preparation of metallic base coat paint) Metallic base coats were blended as shown below and mixed by stirring using a stirrer to obtain a base coat paint composition.

107 parts acrylic copolymer produced in Reference Example 1° (
a-3) 30 parts acrylic copolymer produced in Reference Example 2 (
b-1) Aluminum paste 716ON 10.3 parts (manufactured by Toyo Aluminum Co., Ltd.) The base coat paint composition obtained in (3-1-1) and (3-1-2) above was diluted with the following mixed solvent and used as Ford C.
The viscosity was adjusted to 13 seconds/25° C. at upH4 to obtain a metallic base coat paint.

Ethyl acetate 15 parts toluene
40 parts Tsurupets +1100 (
(manufactured by Esso) 35 parts cellulose acetate
10 parts (3-2, Preparation of solid color base coat paint) A solid color base coat paint was blended as follows.

For the base synthesized in (3-1-1) 60.7 parts Acrylic resin (solid content 50%) Titanium oxide CR-90 (manufactured by Ishihara Sangyo Co., Ltd.) 52 parts Pigment was dispersed in the above formulation using a paint shaker for 1 hour. .

Furthermore, knee pants 203E-60'! 21.7 parts were added, diluted with the following mixed solvent, and the viscosity was adjusted to 13 seconds/25° C. using Ford Cup 4 to obtain a solid color base coat paint.

Toluene 60 parts Trupetz 1100 (manufactured by Esso) 30 parts n-butanol 10 parts Reference Example 4 (Adjustment of clear coat paint) Clear coat paints were blended in the proportions shown in Table 3, and further 0.2 Weight % Remix RL-4
(Leveling agent manufactured by Mitsui Toatsu Chemical Co., Ltd.) was added, stirred with a stirrer, and after preliminary dilution with alcohol such as n-butanol, 110,050 parts of Tsurupez and 115,050 parts of Tsurbenz were added.
diluted with a mixed solvent consisting of
The viscosity was adjusted to 30 seconds/25° C. using Cup 14 to obtain a clear coat paint.

Example 1 Acrylic copolymer (a-1) and acrylic copolymer (
b-1) were blended in the proportions shown in Table 3, and a clear coat paint was prepared by the method shown in Reference Example 4.

The metallic base coat paint prepared in (3-1-1) of Reference Example 3 was coated with cationic electrodeposition paint on a steel plate for an automobile body, and after being applied with air spray to the baked object, after setting for 3 minutes, After applying the above clear coat paint wet-on-wet and setting it for 10 minutes,
A test plate was obtained by heating at 140°C for 20 minutes. Clear film thickness, coating performance, and storage stability test results are shown.
4.

Examples 2.5.6, Comparative Examples 1 to 6 Similarly to Example 1, paints were prepared in the proportions shown in Table 3, and test plates were obtained in the same manner.

Example 3 In the same manner as in Example 1, clear coat paints were prepared in the proportions shown in Table 3.

After applying the solid color base coat paint prepared in (3-2) of Reference Example 3 to the same object as in Example 1 with air spray, let it set for 3 minutes, then apply the above clear coat paint wet-on-wet. After setting for 10 minutes, the test plate was heated at 140°C for 20 minutes. The clear film thickness, coating performance, and storage stability test results are shown in Table 4.

Example 4 In the same manner as in Example 1, clear coat paints were prepared in the proportions shown in Table 3.

After applying the metallic base coat paint prepared in (3-1-2) of Reference Example 3 to the same object as in Example 1 in the same manner as in Example 3, a clear paint was applied and baked using the same method, and a test plate was prepared. Obtained. The clear film thickness, coating performance, and storage stability test results are shown in Table 4.

Note that performance evaluation was performed as follows.

l) Visual appearance An excellent coating film appearance was rated 0, and a poor coating film appearance was rated ×.

2) Add acid-resistant 40vo1% nzso onto the coating film and heat at 50"C.
After leaving it for a while, it was wiped off and observed. Those with no traces were evaluated as ◎, and those with traces were evaluated as ×.

3) The coating surface was rubbed back and forth 50 times with gauze impregnated with solvent-resistant Kijiroru, and then observed. Those with no traces were rated O1, those with some traces were rated O, and those with traces were rated ×.

4) Water resistance After immersing the coating film in 50°C warm water for 48 hours, the coating film was observed. Those with no abnormality were evaluated as ◎, those with slight whitening were evaluated as ○, and those with significant whitening and blisters were evaluated as ×.

5) Scratch Resistance The paint film surface was moved back and forth 1000 times with a car wash brush and the paint film was observed after cleaning. Those with no traces were evaluated with ◎, those with some traces were evaluated with Δ, and those with traces were evaluated with ×.

6) Weather Resistance After testing with a sunshine weather meter for 3000 hours, the gloss retention rate was displayed.

7) Gasohol resistance The coating film was immersed in gasoline containing 5 vol% methanol for 2 hours at room temperature and then observed. Those with no abnormality in the coating film were rated O, and those with blistering and cracking in the coating film were rated ×.

8) Storage stability After adjusting the viscosity of the paint composition and storing it at 50°C for 10 days, the paint viscosity was measured. As a result, those with a slight increase in viscosity were evaluated as Δ, those with a significant increase in O1 viscosity were evaluated as Δ, and those that gelled during the test were evaluated as ×. Polymer (b-1) and amino resin (Niepan 2ON-60 manufactured by Mitsui Toatsu Chemical Co., Ltd.) were blended in the proportions shown in Table 5, and a clear coat paint was prepared by the method shown in Reference Example 4. A test plate was obtained in the same manner as in Example 1.

The clear film thickness, coating performance, and storage stability test results are shown in Table 6.

Example 8.9, Comparative Example 7 Similarly to Example 7, paints were prepared in the proportions shown in Table 5, and test plates were obtained in the same manner.

The clear film thickness, coating performance, and storage stability test results are shown in Table 6.

Example 10-12, Comparative Example 7 The same procedure as in Example 1 was carried out except that quaternary phosphonium salt (benzyltriphenylphosphonium chloride) was added in the amount shown in Table 7 and the amount of n-butanol was changed. A test plate was obtained in the same manner except that the paint was adjusted and heated at 120°C for 8 minutes. The coating film performance is shown in Table 8.

Table-5 Table-7 Table-6 It showed excellent performance.

Table 8 Clear coat compositions exemplified in Examples 10 to 12 showed excellent performance as acid-based automotive paints.

The clear coat composition of Comparative Example 7 showed a significant increase in the coating composition one month after the paint preparation, and the stability of the paint was poor.

Claims (1)

[Scope of Claims] (a) an acrylic copolymer having an acid group with an acid value of 30 to 150 mgKOH/g; (b) an acrylic copolymer having an epoxy group with an epoxy equivalent of 200 to 1000 g/eq and (c) a solvent having a hydroxyl group, in which the acid group of (a) and the epoxy group of (b) are in a ratio of 1:0.5 to 0.
With an equivalence ratio of 5:1, the amount of (c) is (a) (b) (
A thermosetting solvent-based coating composition with excellent storage stability, which is 6% by weight or more based on the total of c).