JPH0551554A - Coating composition - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain a coating composition which gives a coating film excellent in scratch resistance and acid resistance. [Structure] A vinyl monomer containing a terminal carboxy group having a number average molecular weight of 500 to 2000 and a glass transition point of 0 ° C. or less, which is obtained by polymerizing a vinyl monomer polymerization initiator in the presence of a compound having a carboxy group and a thiol compound having a hydroxyl group. 10 to 50% by weight of a vinyl-based monomer (A) obtained by reacting a polymer with a vinyl-based monomer having an epoxy group, a high-molecular polymer composed of a vinyl-based monomer having a carboxy group and other vinyl-based monomers. A high molecular weight polymer (B) having 1 to 2 mol of carboxy groups in 1 kg of a molecular polymer, 10 to 50% by weight of a vinyl monomer (A), a vinyl monomer having an epoxy group and other vinyl monomers A high-molecular polymer (C) consisting of a high-molecular polymer (C) having 1 to 2 mol of epoxy groups in 1 kg of a high-molecular polymer and a melamine resin. The high-molecular polymer {(B) + high-molecular polymer (C )} / Melamine resin = 95/5 to 80/20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition which gives a coating film excellent in scratch resistance and acid resistance.

[0002]

2. Description of the Related Art As a conventional coating composition, for example, Japanese Patent Application Laid-Open Nos. 64-40571, 64-40573, 64-43373 and 64-66274 are used for coating outer panels of automobiles. A coating composition is disclosed that provides a suitable coating with excellent scratch resistance.

[0003]

However, in such a conventional coating composition, since only the melamine resin is used as the cross-linking system of the coating film, the melamine resin accounts for 20% of the total solid content of the resin. More is needed. For this reason, there are problems that acid resistance and scratch resistance due to insufficient cross-linking density due to self-condensation of melamine resin are not sufficiently satisfied because the number of resin structures that are weak against hydrolysis increases.

[0004]

The present invention has a glass transition point of 0.
By imparting elasticity to the coating film by incorporating a resin structure of ℃ or less in the coating film, and also increasing the crosslink density and improving the scratch resistance, at the same time, a carboxy group and an epoxy group or a carboxy group and an epoxy group and It was confirmed that the amount of the melamine resin can be reduced because the crosslinking is caused by the reaction of the silyl group, and the present invention has been accomplished.

Therefore, the first invention of the present invention is a vinyl-based monomer polymerization initiator which is polymerized in the presence of a compound having a carboxy group and a thiol compound having a hydroxyl group and has a number average molecular weight of 500 to 2000 and a glass transition point of 0 ° C. A vinyl-based monomer (A) formed by reacting the following vinyl-based polymer having a terminal carboxy group with a vinyl-based monomer having an epoxy group is used.
A polymer (B) and a vinyl monomer having a carboxyl group in the amount of 0 to 50% by weight and a vinyl polymer having a carboxy group and other vinyl monomers and having 1 to 2 mol of carboxy groups in 1 kg of the polymer. (A) 10 to 50% by weight of a vinyl-based monomer having a hydrolyzable silyl group, a vinyl-based monomer having an epoxy group, and other vinyl-based polymers, and 1 kg of the epoxy group in 1 kg of the polymer. Coating composition consisting of ˜2 mol of high molecular polymer (C) and melamine resin, {high molecular polymer (B) + high molecular polymer (C)} / melamine resin = 95/5 to 80/20 It is about things.

The second invention of the present invention is a vinyl-based monomer polymerization initiator which is polymerized in the presence of a compound having a carboxy group and a thiol compound having a hydroxyl group and has a number average molecular weight of 500 to 2000 and a glass transition point of 0 ° C. The following is a vinyl-based monomer (A) obtained by reacting a vinyl polymer having a terminal carboxy group with a vinyl-based monomer having an epoxy group.
A polymer containing 0 to 50% by weight of a vinyl-based monomer having a hydrolyzable silyl group, a vinyl-based monomer having a carboxy group, and other vinyl-based monomers. 1 to 3 mol, a high molecular polymer (B) having a carboxy group of 1 to 2 mol, a vinyl monomer (A) 10 to 50% by weight and a vinyl monomer having a hydrolyzable silyl group, and an epoxy group A high-molecular polymer composed of vinyl-based monomers and other vinyl-based monomers. 1 kg of the high-molecular polymer has 1 to 1 hydrolyzable silyl group.
3 mol, high molecular polymer having 1 to 2 mol of epoxy groups
The present invention relates to a coating composition comprising (C) and a melamine resin, {polymer (B) + polymer (C)} / melamine resin = 95/5 to 80/20.

In the present invention, vinyl monomer (A)
Is a vinyl monomer polymerization initiator having a carboxyl group, for example, 4,4′-azobis-4-cyanovaleric acid and a thiol compound having a hydroxyl group, such as thioglycerol, and a vinyl monomer such as methyl acrylate, methyl methacrylate, acrylic. Butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, methacrylic acid
Acrylic ester and methacrylic acid ester such as 2-ethylhexyl; 2-: hydroxyethyl acrylate, 2-
A polymer obtained by reacting one or more kinds of hydroxy compounds such as hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate by an ordinary solution polymerization method, and further a vinyl monomer having an epoxy group, for example, Add glycidyl acrylate, glycidyl methacrylate, etc., 80 ° -150 ° C
It is obtained by reacting by heating to. An amine compound or the like may be added as a catalyst in the reaction with the vinyl monomer having an epoxy group, and a polymerization inhibitor such as hydroquinone may be added to prevent polymerization of the vinyl cenomer having an epoxy group.

The high molecular weight polymer (B) is a vinyl monomer (A)
And vinyl monomers having carboxyl groups such as acrylic acid, methacrylic acid and hydroxyl group-containing vinyl monomers such as 2-hydroxyacrylate or 2-hydroxymethacrylate and the like, or compounds having acid anhydride such as succinic anhydride added, or further hydrolyzable A monomer having a silyl group, for example, the following general formula

[Chemical 1] (In the formulas [1] to [4], R represents hydrogen or a methyl group, X
Represents an alkyl group or alkyl ether group having 1 to 14 carbon atoms or an aralkyl group or aralkyl ether group having 6 to 24 carbon atoms. ), And other vinyl-based monomers such as methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and the like. Methacrylic acid ester; 2-hydroxyethyl acrylate
And a hydroxy compound such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate, which are obtained by reacting one or more kinds of hydroxy compounds with a radical polymerization initiator by an ordinary solution polymerization method.

The high molecular polymer (C) is the same as the high molecular polymer (B) except that the vinyl monomer having a carboxyl group is replaced with a vinyl monomer having an epoxy group such as glycidyl acrylate or glycicyl methacrylate. Can be obtained

Examples of the melamine resin used in the present invention include melamine to which formaldehyde is added and then etherified with a monohydric alcohol having 1 to 4 carbon atoms. This melamine resin may be used alone or in combination of two or more.

When the number average molecular weight of the terminal carboxy group-containing vinyl polymer used in the first and second inventions of the present invention is less than 500, the flexibility of the coating film and the adhesion after the moisture resistance test are deteriorated and the scratch resistance is reduced. Is inferior. On the other hand, the number average molecular weight is 2000
When it exceeds, the coating film becomes too soft and the acid resistance is lowered.

If the glass transition point of the terminal carboxy group-containing vinyl polymer exceeds 0 ° C., the flexibility of the coating film decreases and the scratch resistance deteriorates. If the amount of the vinyl-based monomer (A) is less than 10% by weight, the flexibility of the coating film decreases and the scratch resistance is poor, and if it exceeds 50% by weight, the coating film becomes too soft and the acid resistance decreases.

When the amount of the carboxy group in 1 kg of the high molecular weight polymer (B) is less than 1 mol, the cross-linking density of the coating film is lowered and the scratch resistance is poor. On the other hand, when the carboxy group exceeds 2 mol, the polarity of the coating film becomes too high and the moisture resistance is lowered. High polymer (C)
If the epoxy group content per 1 kg is less than 1 mol, the cross-linking density of the coating film will decrease and the scratch resistance will be poor. On the other hand, when the epoxy group exceeds 2 mol, the polarity of the coating film becomes too high and the moisture resistance is lowered.

Further, in the second invention, the hydrolyzable silyl groups of the high molecular polymers (B) and (C) have an effect of increasing the crosslink density, and for this purpose, in 1 kg of the high molecular polymers. The range of 1 to 3 mol is effective. When the ratio of {high molecular polymer (B) + high molecular polymer (C)} / melamine resin exceeds 95/5, the cross-linking density of the coating film decreases and the scratch resistance is poor, and when it is less than 80/20, The amount of melamine resin in the coating film becomes too large and the acid resistance decreases.

[0015]

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples. Example 1, Comparative Example 1 1. Vinyl Monomer (A) Polymerization Initiator 4, 4'-azobis-4-cyanovaleric acid 14
A mixture of 50 parts by weight of butanol and 50 parts by weight of butanol, 59 parts by weight of n-butyl acrylate, 15 parts by weight of 2-hydroxyethyl methacrylate and 12 parts by weight of thioglycerol are heated to 50 parts by weight of xylene under reflux for 3 hours. Then, the mixture was further dropped and reacted for 3 hours under reflux to obtain a resin having a number average molecular weight of 930 and a glass transition point of -38 ° C. 28 parts by weight of glycidyl methacrylate, hydroquinone
Add 0.1 parts by weight and 0.2 parts by weight of N, N-dimethyldodecylamine and react at reflux for 4 hours. Vinyl monomer (A)
A solution was obtained (56% solids).

2. Polymer (B) xylene 39.7 parts by weight was heated to a reflux state, while vinyl monomer (A) solution 22.3 parts by weight (solid content 12.5 parts by weight),
20.3 parts by weight of n-butyl methacrylate, acrylic acid 7.2
Parts by weight, 10 parts by weight of methyl methacrylate, t-butyl-
A mixture of 0.5 parts by weight of peroxybenzoate was added dropwise over 3 hours, and the mixture was heated under reflux for 3 hours to obtain a polymer (B) solution (solid content 50%) (in solid content, vinyl content). System monomer 25%).

3. Polymer (C) The vinyl monomer composition of the method for producing the polymer (B) is 22.3 parts by weight of the vinyl monomer (A) solution (solid content 12.5 parts by weight), n-butyl methacrylate. 16.5 parts by weight, glycidyl methacrylate 14.2 parts by weight, methyl methacrylate
In the same manner, except that 6.8 parts by weight was used
A (C) solution was obtained (50% solids).

80 parts by weight of high molecular polymer (B) solution, 80 parts by weight of high molecular polymer (C) solution, melamine resin Uban 20SE (manufactured by Mitsui Toatsu Chemicals, Inc., butylated melamine resin, solid content 60)
%) 33 parts by weight and Modaflow 0.1 parts by weight were mixed to obtain a coating composition (solid content ratio = 40/40/20). After 0.8 mm thick steel plate is treated with zinc phosphate, it is coated with cationic electrodeposition paint (Aqua
NO4200ED, manufactured by NOF CORPORATION, was applied to a dry film thickness of 20 μm and baked at 170 ° C. for 30 minutes. Next, an intermediate coating (High Epico No. 1 Sealer, manufactured by NOF CORPORATION) was air-sprayed onto this film so that the dry film thickness was 40 μm, and baked at 140 ° C. for 30 minutes. After that, an acrylic base coat (Bellcoat No. 6000, manufactured by NOF CORPORATION) was applied to a dry film thickness of 15 μm, and after setting for 3 minutes, the above clear coating composition was applied to a dry film thickness. It was coated so as to have a thickness of 35 μm, set for about 7 minutes, and then baked at 140 ° C. for 30 minutes to obtain a No. 1 coated plate sample of Example 1.

Next, as shown in Table 4, {(B) + (C)} /
A coated plate sample No. 2 was obtained in the same manner as the coated plate sample No. 1 except that the solid content ratio of the melamine resin was 95/5. As shown in Table 4, except that the glass transition point of the precursor of (A) was −20 ° C.
A No. 3 coated plate sample was obtained. As shown in Table 4, (A)
A coated plate sample No. 4 was obtained in the same manner as the coated plate sample No. 1 except that the weight of was changed to 10%.

As shown in Table 4, the number average molecular weight of (A),
A coated plate sample of NO.5 was obtained in the same manner as the coated plate sample of NO.1 except that the weight and the glass transition point were changed to 1200, 50% and 0 ° C, respectively. As shown in Table 4, No. 6 coated plate sample was obtained in the same manner as No. 1 coated plate sample except that the amount of carboxy groups in (B) and the amount of epoxy groups in (C) were each 1. ..

As shown in Table 4, No. 7 and No. 8 coated plate samples were obtained in the same manner as No. 1 coated plate sample except that the number average molecular weight of (A) was changed to 550 and 1800, respectively. It was As shown in Table 4, except that the number average molecular weight of (A) was changed to 1800, and the amount of carboxy groups of (B) or the amount of epoxy groups of (C) was changed to 1, respectively, the same as No. 1 coated plate sample. No. 9, N
A painted plate sample of o.10 was obtained.

For comparison, as shown in Table 5,
{(B) + (C)} / melamine resin 70/30, 98 /
No. 1 coated plate sample of Comparative Example 1 and No. 2 coated plate sample of inferior scratch resistance were obtained in the same manner as the sample of No. 1 coated plate of Example 1 except that it was 2. As shown in Table 5,
No. 3 coating which is inferior to scratch resistance of Comparative Example 1 in the same manner as the No. 1 coated plate sample of Example 1 except that the number average molecular weight of (A) is 1100 and the glass transition point is 5 ° C. Plate samples were obtained. As shown in Table 5, except that the weight of (A) was set to 60 and 5, respectively, the coating plate sample of Example 1 was prepared in the same manner as in Comparative Example 1 with poor acid resistance No. 4 and scratch resistance. An inferior No. 5 coated plate sample was obtained.

As shown in Table 5, except that the number average molecular weights of (A) were 420 and 2210, respectively, the same as the coated plate sample of Example 1, No. 6, which was inferior in scratch resistance of Comparative Example 1, A No. 7 coated plate sample having poor acid resistance was obtained.

As shown in Table 5, the resistance of Comparative Example 1 was the same as that of the coated plate sample of Example 1 except that the amount of carboxy groups in (B) or the amount of epoxy groups in (C) was 0.5 and 3, respectively. Painted plate samples No. 8 with poor scratch resistance, No. 9 with poor moisture resistance, No. 10 with poor scratch resistance, and No. 11 with poor moisture resistance were obtained.

The vinyl monomer A in the coated plate samples No. 1 to 10 of Example 1 and the coated plate samples No. 1 to 11 of Comparative Example 1,
The formulations of the high molecular weight polymers B and C are shown in Tables 1 to 3. The coated plate sample Nos. 1 to 10 of Example 1 and the coated plate sample Nos. 1 to 11 of Comparative Example 1 were evaluated according to the following measuring methods: a) Scratch resistance, b) Acid resistance, c) Moisture resistance The obtained results are shown in Tables 4 and 5.

Measurement method (a) Using a Gakushin-type friction fastness tester, a scratch is generated in the coating film using a cleanser as an abrasive, and the difference in brightness from the initial stage is measured (the larger the difference in brightness, the more noticeable the scratches are. ). B) After immersing the coating film in a 1% H ₂ SO ₄ solution at 50 ° C., the initial gloss retention rate is calculated. The gloss is measured by a color computer manufactured by Suga Test Instruments. C) After leaving for 120 hours at 50 ° C and 95% RH, perform the eye contact test.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

Example 2 and Comparative Example 2 1. Vinyl Monomer (A) Polymerization Initiator 4, 4'-Azobis-4-cyanovaleric Acid 14
A mixture of 50 parts by weight of butanol and 50 parts by weight of n-butyl acrylate, 15 parts by weight of 2-hydroxyethyl methacrylate and 12 parts by weight of thioglycerol are heated to a reflux state of 50 parts by weight of xylene for 3 hours. Then, the mixture was further reacted for 3 hours under reflux after the dropping to obtain a resin having a number average molecular weight of 930 and a glass transition point of -38 ° C. To this, 28 parts by weight of glycidyl methacrylate, hydroquinone 0.
1 part by weight and 0.2 part by weight of N, N-dimethyldodecylamine were added, and the mixture was reacted under reflux for 4 hours to obtain a vinyl monomer (A) solution (solid content 56%).

2. 32.3 parts by weight of high molecular weight polymer (B) xylene was heated to a reflux state while 22.3 parts by weight of a vinyl monomer (A) solution (solid content 12.5 parts by weight),
n-Butyl methacrylate 19.1 parts by weight, γ-methacryloxypropyltrimethoxysilane 6.2 parts by weight, acrylic acid
A mixture of 7.2 parts by weight, 5 parts by weight of methyl methacrylate, and 0.5 parts by weight of t-butyl-peroxybenzoate was required for 3 hours and further heated under reflux to obtain a polymer (B) solution (solid content 50%).

3. Polymer (C) The vinyl monomer composition of the method for producing the polymer (B) is 22.3 parts by weight of the vinyl monomer (A) solution (solid content 12.5 parts by weight), n-butyl methacrylate. 12.1 parts by weight, γ-methacryloxypropylmethoxysilane 6.2 parts by weight, glycidyl methacrylate 14.2 parts by weight, and methyl methacrylate 5 parts by weight in the same manner except that the polymer (C) was used.
A solution was obtained (50% solids).

90 parts by weight of high molecular polymer (B) solution, 90 parts by weight of high molecular polymer (C) solution, melamine resin Uban 20SE (manufactured by Mitsui Toatsu Chemicals, Inc., butylated melamine resin, solid content 60)
%) 16.7 parts by weight and Modaflow 0.1 parts by weight were mixed to obtain a coating composition (solid content ratio = 45/45/10). After 0.8 mm thick steel plate is treated with zinc phosphate, a cationic electrodeposition coating (Aqua NO.4200ED, manufactured by NOF CORPORATION) is dried to a film thickness of 20 μm.
And was baked at 170 ° C. for 30 minutes.
Next, an intermediate coating (high epico NO.1 sealer,
Nippon Oil & Fat Co., Ltd.) to a dry film thickness of 40 μm.
It was air-sprayed and baked at 140 ° C. for 30 minutes. After that, an acrylic base coat (Bellcoat No. 6000, manufactured by NOF CORPORATION) was applied to a dry film thickness of 15 μm, and after setting for 3 minutes, the above clear coating composition was dried to a film thickness of 35 μm. After coating as described above and setting for about 10 minutes, baking was performed at 140 ° C. for 30 minutes to obtain a No. 11 coated plate sample of Example 2.

Next, as shown in Table 9, No. 12 and No. 13 coated plate samples were prepared in the same manner as No. 11 coated plate sample except that the number average molecular weight of (A) was 550 and 1800, respectively. Got As shown in Table 9, the weight of (A) is 10%,
Same as sample No. 11 except for 50%
No.14 and No.15 coated plate samples were obtained. As shown in Table 9, No. 16 coated plate sample was obtained in the same manner as No. 11 coated plate sample except that the glass transition point of (A) was 0 ° C.

As shown in Table 9, the coating plate sample of No. 11 was prepared in the same manner as in (B) except that the amount of carboxy groups was 1.
A No. 17 coated plate sample was obtained. As shown in Table 9,
A coated plate sample No. 18 was obtained in the same manner as the coated plate sample No. 11 except that the epoxy group content of (C) was 1. As shown in Table 9, except that the silyl groups of (B) and (C) were changed to 1, respectively, No. 19, N was prepared in the same manner as No. 11 coated plate sample.
A painted plate sample of o.20 was obtained. As shown in Table 9, (B),
No.21 coated plate sample in the same manner as No.11 coated plate sample except that the amount of silyl group of (C) was changed to 3 and {(B) + (C)} / melamine resin was changed to 95/5. Got As shown in Table 9, a coated plate sample of NO.22 was obtained in the same manner as the coated plate sample of NO.11 except that the {(B) + (C)} / melamine resin was changed to 80/20.

For comparison, as shown in Table 10, (A)
No. 12, which is inferior in scratch resistance of Comparative Example 2, and No. 13 inferior in acid resistance, in the same manner as the sample of coated plate of No. 11 of Example 2 except that the number average molecular weights of No. 13 and No. 13 of Example 2 are respectively changed. A coated plate sample of was obtained. As shown in Table 10, except that the weight of (A) was changed to 5 and 54, respectively, similarly to the coated plate sample of No. 11 of Example 2, No. 14, which was inferior in scratch resistance of Comparative Example 2, ,
A No. 15 coated plate sample having poor acid resistance was obtained.

As shown in Table 10, No. 16 which is inferior in scratch resistance of Comparative Example 2 in the same manner as the coated plate sample of Example No. 11 except that the glass transition point of (A) is 5 ° C. A coated plate sample of was obtained. As shown in Table 10, the scratch resistance of Comparative Example 2 was inferior as in No. 11 coated plate sample of Example 2 except that the amounts of carboxy groups in (B) were 0.5 and 3, respectively.
o.17, No.18 painted plate sample with inferior moisture resistance was obtained. table
As shown in 10, the amount of epoxy groups in (C) was 0.5, 3 and 3, respectively.
Except for the above, the coated plate sample of Comparative Example 2 was obtained in the same manner as the coated plate sample of No. 11 in Example 2, except that the coated plate sample was No. 19 having poor scratch resistance and No. 20 having poor moisture resistance.

As shown in Table 10, the same as the No. 11 coated plate sample of Example 2 except that the silyl group amount of (B) was 0.5 and 3.5, and the silyl group amount of (C) was 3 respectively. As a result, No. 21 and No. 22 coated plate samples of Comparative Example 2 having inferior scratch resistance were obtained. As shown in Table 10, the amount of silyl groups in (B) is 3, respectively, the amount of silyl groups in (C) is 0.5, respectively.
No. 23, which is inferior to the scratch resistance of Comparative Example 2, in the same manner as the No. 11 coated plate sample of Example 2, except that the value was 3.5.
A No. 24 coated plate sample was obtained. As shown in Table 10,
The amount of silyl groups in (B) and (C) is 3, {(B) + (C)}, respectively.
A No. 25 coated plate sample having inferior scratch resistance of Comparative Example 2 was obtained in the same manner as the No. 11 coated plate sample of Example 2 except that the melamine resin was changed to 98/2. As shown in Table 10,
A coated plate sample No. 26 having poor acid resistance was obtained in the same manner as the coated plate sample No. 11 of Example 2 except that the amount of {(B) + (C)} / melamine resin was changed to 75/25.

Tables 6 to 8 show the composition of the vinyl-based monomer A and the high molecular weight polymers B and C in the coated plate samples Nos. 11 to 22 of Example 2 and the coated plate samples Nos. 12 to 26 of Comparative Example 2, respectively. Show. A) Scratch resistance, B) Acid resistance, C) Moisture resistance was evaluated according to the following measuring methods for the coated plate samples No. 11 to 22 of the above-mentioned Example 2 and the coated plate samples No. 12 to 26 of the comparative example 2. The obtained results are also shown in Table 9 and Table 10.

Measurement method a) In the Gakushin-type friction fastness test method, scratches are generated by polishing the surface of the coating film using a cleanser as an abrasive, and the gloss ratio with the initial value is obtained to maintain the initial gloss value. The rate is measured (the lower the gloss retention value, the lower the scratch resistance). B) A 10 wt% H ₂ SO ₄ solution is dropped on the coating film at 30 ° C., and the coating film surface is observed after 1 hour. If stains are found, it is judged that the acid resistance is low. C) After leaving for 120 hours at 50 ° C and 95% RH, perform the eye contact test.

[0043]

[Table 6]

[0044]

[Table 7]

[0045]

[Table 8]

[0046]

[Table 9]

[0047]

[Table 10]

As described above, the coating composition of the present invention contains the vinyl monomer (A) in an amount of 10 to 50% by weight.
And a polymer (B), a polymer (C) and a melamine resin, and a polymer {(B) + (C)}
/ Melamine resin = 95/5 to 80/20 The coating composition gives elasticity and improves scratch resistance.
Further, since crosslinking is carried out by the reaction of a carboxy group and an epoxy group or a carboxy group, an epoxy group and a silyl group, a coating film excellent in acid resistance can be obtained by reducing the amount of melamine resin.

Front page continued (72) Inventor Hiroaki Tamura 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Toshio Hayashi 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Invention Yutaka Enokida 3-5-802 Wakabadai, Asahi-ku, Yokohama-shi, Kanagawa (72) Inventor Yoichi Moriya 473 Shimokurata-cho, Totsuka-ku, Yokohama-shi, Kanagawa (72) Norikazu Takizuka Shimokurata-cho, Totsuka-ku, Yokohama-shi, Kanagawa 473

Claims (2)

[Claims] 1. A terminal carboxy group having a number average molecular weight of 500 to 2000 and a glass transition point of 0 ° C. or less, which is obtained by polymerizing a vinyl monomer polymerization initiator in the presence of a compound having a carboxy group and a thiol compound having a hydroxyl group. A high molecular polymer comprising 10 to 50% by weight of a vinyl monomer (A) obtained by reacting a vinyl polymer with a vinyl monomer having an epoxy group, a vinyl monomer having a carboxy group, and other vinyl monomers. Polymer polymer (B) having 1 to 2 moles of carboxy groups in 1 kg of polymer, vinyl monomer (A) 10 to 50% by weight, vinyl monomer having epoxy group and other vinyl monomers A high molecular weight polymer consisting of 1 kg of high molecular weight polymer having 1 to 1 epoxy groups
A coating composition consisting of 2 mol of high molecular polymer (C) and melamine resin, {high molecular polymer (B) + high molecular polymer (C)} / melamine resin = 95/5 to 80/20 .. 2. A vinyl monomer polymerization initiator, which is polymerized in the presence of a compound having a carboxy group and a thiol compound having a hydroxyl group and has a number average molecular weight of 500 to 2000 and a glass transition point of 0 ° C. or less, containing a terminal carboxy group. 10 to 50% by weight of a vinyl monomer (A) obtained by reacting a vinyl polymer and a vinyl monomer having an epoxy group, a vinyl monomer having a hydrolyzable silyl group, a vinyl monomer having a carboxy group, and A high-molecular polymer (B) having 1 to 2 mol of hydrolyzable silyl groups and 1 to 2 mol of carboxy groups in 1 kg of a high-molecular polymer composed of other vinyl-based monomers, and a vinyl-based monomer (A) 10 to 50
1 to 3 mol of a hydrolyzable silyl group in 1 kg of a high-molecular polymer, which is a high-molecular polymer composed of a vinyl-based monomer having a weight% and a hydrolysable silyl group, a vinyl-based monomer having an epoxy group, and other vinyl-based monomers. , Consisting of a high molecular polymer (C) having an epoxy group of 1 to 2 moles and a melamine resin, {high molecular polymer (B) + high molecular polymer (C)} / melamine resin = 95/5 to 80 / A coating composition which is 20.