Two-component paint composition and multilayer coating formation method using this

Abstract

[Purpose] Among two-component top coat paints for the automobile coatings field, wherein the base resin paint is circulated from a main tank with a pump upstream of the coating gun, and mixing and coating are effected using a curing agent supplied from a nitrogen-sealed tank and a two-component mixing device, to provide a paint composition with which problems such as thickening and gelling of the circulating base resin paint do not occur, coating is possible with a stabilized constant coating viscosity, and with which the paint film after stoving exhibits excellent Scratch resistance, stain resistance, acid resistance and gasoline resistance, and a multilayer coating formation method using this. [Solution] The present invention provides a two-component paint composition which is applied directly after mixing a base resin and a curing agent, wherein the base resin (A) contains a hydroxy group-containing acrylic resin (A-1) and a curing catalyst (A-2) as essential components, the curing agent (B) contains an isocyanate Compound (B-1) and an alkoxysilyl group-containing copolymer (B-2) as essential components, the aforesaid hydroxy group-containing acrylic resin (A-1) has a hydroxyl value of 80 to 180 mg KOH/g, a glass transition temperature of ?40 to 40? C., and a weight average molecular weight of 2,000 to 20,000 g/mol, the aforesaid alkoxysilyl group-containing copolymer (B-2) is a copolymer obtained by copolymerizing 30 to 80 parts by weight of a vinylic monomer containing alkoxysilyl groups and 20 to 70 parts by weight of other copolymerizable monomers, its weight average molecular weight is 2,000 to 20,000 g/mol, and it does not contain hydroxy groups, carboxyl groups or amino groups which react with isocyanate groups.

Claims

1. A two-component paint composition, comprising (A) a base resin and (B) a curing agent, wherein, the base resin (A) comprises a hydroxy group-containing acrylic resin (A-1) and a curing catalyst (A-2); the curing agent (B) comprises an isocyanate compound (B-1) and an alkoxysilyl group-containing copolymer (B-2); the hydroxy group-containing acrylic resin (A-1) has a hydroxyl value of 80 to 180 mg KOH/g, a glass transition temperature of ?40 to 40? C. and a weight average molecular weight of 2,000 to 20,000 g/mol; and the alkoxysilyl group-containing copolymer (B-2) is a copolymer obtained by copolymerizing 30 to 80 parts by weight of a vinylic monomer comprising alkoxy-silyl groups and 20 to 70 parts by weight of other copolymerizable monomers, its weight average molecular weight is 2,000 to 20,000 g/mol, and it does not contain hydroxy groups, carboxyl groups amino groups which react with isocyanate groups.

2. The two-component paint composition as claimed in claim 1, wherein the hydroxy group-containing acrylic resin (A-1) is a hydroxy group-containing acrylic resin derived from 4-hydroxybutyl (meth)acrylate and having a hydroxyl value of 80 to 160 mg KOH/g.

3. The two-component paint composition as claimed in claim 1, which is mixed such that the isocyanate groups of the isocyanate compound (B-1) are in a proportion of 0.5 to 1.5 equivalents per equivalent of hydroxy groups in the hydroxyl group-containing acrylic resin (A-1).

4. The two-component paint composition as claimed in claim 1, wherein in the curing agent (B), non-volatiles content of the alkoxysilyl group-containing copolymer (B-2) is in a proportion of 20 to 80 parts by weight per 100 parts by weight of combined non-volatiles contents of the isocyanate compound (B-1) and the alkoxysilyl group-containing copolymer (B-2).

5. A method for forming multilayer paint films, the method comprising: applying an intermediate coat paint onto an electro-coated steel plate; wet-on-wet applying a base coat paint; wet-on-wet applying the two-component paint composition of claim 1; and performing simultaneous thermal curing to obtain a multilayer paint film.

6. A method for forming multilayer paint films, the method comprising; applying intermediate coat paint onto an electro-coated steel plate; wet-on-wet applying base coat paint; then wet-on-wet applying a clear paint composition; performing thermal curing; then applying the two-component paint composition of claim 1; and performing thermal curing to obtain a multilayer paint film.

Description

PRACTICAL EXAMPLES

(1) Next, the present invention is illustrated more specifically by means of practical examples, but the present invention is in no way restricted by these practical examples. It should be noted that in the practical examples and comparative examples parts means parts by weight, and % means mass %.

(2) The properties of the paint films obtained using the two-component paint compositions of the present invention were determined as follows:

(3) (1) External appearance (transparency of paint film) The paint films were assessed by visual inspection according to the following standard: ? no clouding observed, X: clouding observed.

(4) (2) Carwash Scratch Resistance

(5) After applying muddy water (made by mixing JIS Z 8901 test dust 8/water/neutral detergent in weight ratio=10/99/1) to the test plates with a brush, the test plates were washed with running water in an automobile carwash for 10 seconds with carwash brushes rotating at 150 rpm. After repetition of the above operation 10 times, the degree of scratching of the test piece surface was measured with a colorimeter (brand name CR-331, Minolta Camera (Co.)). The degree of scratching was assessed by measuring the absolute value of the difference in lightness (?L) before and after the test. The lower this value is, the better the scratch resistance. ?: ?L?3.0 ?: 3.0<?L?5.0 ?: 5.0<?L?10.0 X: 10.0<?L?15.0 XX: 15.0<?L

(6) With assessments of ? or better, it was judged that the paint films had good carwash scratch resistance.

(7) (3) Stain Resistance

(8) A mixture of carbon black/JIS Z test dust 8/water in a weight ratio=1/1/98 was sprayed onto test plates, and dried for 10 mins at 60? C. After repeating the above operation 5 times, staining was removed by rubbing the test plate surface 3 times backwards and forwards with a flannel under running water flowing at 2 L/min from a mains water tap. After removal of water drops with an air blower, the degree of staining of the test piece surfaces was measured with a colorimeter (brand name CR-331, Minolta Camera (Co.)). The degree of staining was assessed by measuring the absolute value of the difference in lightness (?L) before and after the test.

(9) The lower this value is, the better the stain resistance. ?: ?L?1.0 ?: 1.0<?L?3.0 ?: 3.0<?L?6.0 X: 6.0<?L?9.0 XX: 9.0<?L

(10) With assessments of ? or better, it was judged that the paint films had good stain resistance.

(11) (4) Acid Resistance

(12) 0.2 ml of 40% aqueous sulfuric acid was placed in spot form on the test pieces, and they were heated for 15 mins at 60? C., after which they were washed with water and visually examined for stain formation. ?: practically no change seen in paint film ?: slight water staining seen on paint film X: pronounced water staining seen on paint film.

(13) (5) Gasoline Resistance

(14) The test plates were immersed for 24 hours at 20? C. in unleaded regular gasoline (described in JIS K2202 ? 2), and their appearance was observed visually, and assessed according to the standard shown below: ?: no abnormality observed ?: abnormalities such as slight yellowing and swelling observed X: abnormalities such as yellowing and swelling observed.

Production Example A1

(15) Production Of Hydroxy Group-containing Acrylic Resin Varnish A-1-1

(16) 27.0 parts of xylene and 9.0 parts of propylene glycol monomethoxy ether acetate were placed in a 4-neck flask fitted with a thermometer, reflux condenser, stirrer and dropping funnel, and this was heated with stirring under a nitrogen flow and maintained at 130? C. Next, at temperature 130? C., 11.0 parts of styrene, 0.8 parts of methacrylic acid, 16.9 parts of 4-hydroxybutyl acrylate, 24.7 parts of i-butyl methacrylate and 1.5 parts of n-butyl methacrylate radical polymerizable monomers, and 1.0 part of t-butyl peroxy-2-ethylhexanoate as the polymerization initiator were homogeneously mixed and added dropwise from the dropping funnel at a constant rate over 3 hours. After completion of the dropwise addition, the temperature was maintained at 130? C. for 1 hour, then the reaction temperature was lowered to 110? C.

(17) Then, as supplementary catalyst, 0.1 parts of t-butyl peroxy-2-ethylhexanoate were added as polymerization initiator, and then after maintaining the temperature at 110? C. for 2 hours, it was thinned and cooled by adding 7.9 parts of xylene, and the hydroxy group-containing acrylic resin varnish A-1?1 was obtained.

Production Examples A2 to A13

(18) Production of Hydroxy Group-containing Acrylic Resin Varnishes A-1?2 to 13

(19) The hydroxy group-containing acrylic resin varnishes A-1-2 to 13 were obtained by the same production method as for A-1-1, except that the quantities introduced of the starting materials shown in table 1 were varied.

(20) TABLE-US-00001 TABLE 1 production example A1 A2 A3 A4 A5 A6 A7 hydroxy group-containing acrylic resin (A-1) varnish A-1-1 A-1-2 A-1-3 A-1-4 A-1-5 A-1-6 A-1-7 starting solvents xylene 27.0 27.0 27.0 27.0 27.0 27.0 27.0 propylene glycol monomethoxy ether acetate 9.0 9.0 9.0 9.0 9.0 9.0 9.0 monomers added 4-hydroxybutyl acrylate 16.9 12.7 12.7 21.2 8.5 16.9 dropwise hydroxyethyl acrylate 6.4 2.6 26.8 styrene 11.0 5.5 11.0 11.0 5.5 5.5 11.0 i-butyl methacrylate 24.7 5.3 16.5 19.4 8.3 n-butyl methacrylate 1.5 24.3 8.5 40.2 butyl acrylate 5.5 21.9 18.0 methacrylic acid 0.8 0.8 0.8 0.8 0.8 0.8 0.8 catalyst t-butyl peroxy-2-ethylhexanoate 1.0 1.0 1.0 1.0 1.0 1.0 1.0 supplementary catalyst t-butyl peroxy-2-ethylhexanoate 0.1 0.1 0.1 0.1 0.1 0.1 0.1 thinning solvent xylene 7.9 7.9 7.9 7.9 7.9 7.9 7.9 total 100 100 100 100 100 100 100 resin hydroxyl number (mgKOH/g) 120 140 90 170 60 210 120 4-hydroxybutyl acrylate-derived resin hydroxyl number (mgKOH/g) 120 90 90 150 60 0 120 resin design glass transition temperature (? C.) 0 0 0 ?9 4.9 4.2 ?30 non-volatiles content (%) 55 55 55 55 55 55 55 weight average molecular weight 10,000 10,000 10,000 10,000 10,000 10,000 10,000 production example A8 A9 A10 A11 A12 A13 hydroxy group-containing acrylic resin (A-1) varnish A-1-8 A-1-9 A-1-10 A-1-11 A-1-12 A-1-13 starting solvents xylene 27.0 27.0 27.0 27.0 27.0 27.0 propylene glycol monomethoxy ether acetate 9.0 9.0 9.0 9.0 9.0 9.0 monomers added 4-hydroxybutyl acrylate 12.7 16.9 16.9 16.9 8.5 dropwise hydroxyethyl acrylate 3.9 15.3 6.8 styrene 27.5 11.0 11.0 11.0 11.0 11.0 i-butyl methacrylate 10.1 24.7 24.7 24.7 10.2 13.0 n-butyl methacrylate 1.5 1.5 1.5 17.7 2.0 butyl acrylate 12.8 methacrylic acid 0.8 0.8 0.8 0.8 0.8 0.8 catalyst t-butyl peroxy-2-ethylhexanoate 1.0 1.6 0.7 0.6 1.0 1.0 supplementary catalyst t-butyl peroxy-2-ethylhexanoate 0.1 0.1 0.1 0.1 0.1 0.1 thinning solvent xylene 7.9 7.3 8.2 8.3 7.9 8.0 total 100 100 100 100 100 100 resin hydroxyl number (mgKOH/g) 120 120 120 120 120 120 4-hydroxybutyl acrylate-derived resin hydroxyl number (mgKOH/g) 90 120 120 120 0 60 resin design glass transition temperature (? C.) 26 0 0 0 50 0 non-volatiles content (%) 55 55 55 55 55 55 weight average molecular weight 10,000 4,000 20,000 26,000 10,000 10,000

Production Examples B1-B7

(21) Production of Alkoxysilyl Group-containing Copolymer Solutions B-2-1-7

(22) The alkoxysilyl group-containing copolymer solutions B-2-1-7 were obtained by the same production method as for comparative example A1, except that the quantities of the starting materials shown in table 2 introduced were varied.

(23) TABLE-US-00002 TABLE 2 production examples B1 B2 B3 B4 B5 B6 B7 alkoxysilyl group-containing copolymer (B-2) solution B-2-1 B-2-2 B-2-3 B-2-4 B-2-5 B-2-6 B-2-7 starting solvent xylene 36.0 36.0 36.0 36.0 36.0 36.0 36.0 monomers added 3-methacryloxypropyltrimethoxysilane 25.0 20.0 35.0 10.0 45.0 25.0 25.0 dropwise styrene 5.0 5.0 5.0 5.0 5.0 5.0 5.0 methyl methacrylate 20.0 25.0 10.0 35.0 20.0 20.0 catalyst t-butyl peroxy-2-ethylhexanoate 0.9 0.9 0.9 0.9 0.9 1.4 0.7 supplementary catalyst t-butyl peroxy-2-ethylhexanoate 0.1 0.1 0.1 0.1 0.1 0.1 0.1 thinning solvent xylene 13.0 13.0 13.0 13.0 13.0 12.5 13.2 total 100 100 100 100 100 100 100 content of alkoxysilyl group-containing vinylic monomer in 50 40 70 20 90 50 50 monomer composition (%) non-volatiles content (%) 50 50 50 50 50 50 50 weight average molecular weight 10,000 10,000 10,000 10,000 10,000 4,000 17,000

Practical Examples 1-23, Comparative Examples 1-7

(24) The starting materials shown in tables 3-5 were mixed consecutively and stirred so that they became homogeneous, thus making the two-component compositions made up of the base resin (A) and the curing agent (B).

(25) TABLE-US-00003 TABLE 3 practical example 1 2 3 4 5 6 7 8 9 10 11 12 clear coat paint name CC- CC- CC- CC- CC- CC- CC- CC- CC- CC- CC- CC- 1 2 3 4 5 6 7 8 9 10 11 12 base hydroxy group-containing A-1-1 49.8 54.8 45.7 57.2 38.3 62.4 17.8 resin acrylic resin (A-1) varnish A-1-2 46.3 51.4 42.2 53.9 34.9 curing catalyst (A-2) NACURE4167 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 UV absorber Tinuvin 384-2 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 photostabilizer Tinuvin 292 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 surface modifier BYK-300 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 solvent Solvesso 100 8.6 7.5 9.6 10.0 6.5 9.4 8.3 10.3 11.0 6.9 11.0 2.7 curing isocyanate compound (B-1) Sumidure 11.3 9.9 12.4 13.0 8.7 12.3 10.9 13.4 14.2 9.2 14.1 4.0 agents N3300 alkoxysilyl group- B-2-1 20.5 18.1 22.6 10.1 36.8 22.3 19.8 24.3 11.1 39.2 2.9 65.8 containing copolymer (B-2) solution solvent xylene 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 total 100 100 100 100 100 100 100 100 100 100 100 100 quantity of curing catalyst (A-2) added (non-volatiles 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 content %) isocyanate compound (B-1) NCO/hydroxy 1 0.8 1.2 1 1 1 0.8 1.2 1 1 1 1 group-containing acrylic resin (A-1) OH mole ratio Proportion (%) of (B-2) non-volatiles content relative 50 50 50 30 70 50 50 50 30 70 10 90 to non-volatiles content of (B-1) + (B-2)

(26) TABLE-US-00004 TABLE 4 practical example 13 14 15 16 17 18 19 20 21 22 23 clear coat paint name CC- CC- CC- CC- CC- CC- CC- CC- CC- CC- CC- 13 14 15 16 17 18 19 20 21 22 23 base hydroxy group- A-1-1 49.8 49.8 49.8 49.8 resin containing acrylic A-1-3 56.2 resin (A-1) varnish A-1-4 41.9 A-1-7 49.8 A-1-8 49.8 A-1-9 49.8 A-1-10 49.8 A-1-13 49.8 curing catalyst NACURE4167 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 (A-2) UV absorber Tinuvin 384-2 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 photostabilizer Tinuvin 292 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 surface modifier BYK-300 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 solvent Solvesso 100 7.2 10.4 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 curing isocyanate compound Sumidure 9.5 13.5 11.3 11.3 11.3 11.3 11.3 11.3 11.3 11.3 11.3 agents (B-1) N3300 alkoxysilyl group- B-2-1 17.4 24.5 20.5 20.5 20.5 20.5 20.5 containing copolymer B-2-2 20.5 (B-2) solution B-2-3 20.5 B-2-6 20.5 B-2-7 20.5 solvent xylene 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 total 100 100 100 100 100 100 100 100 100 100 100 quantity of curing catalyst (A-2) added (non- 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 volatiles content %) isocyanate compound (B-1) NCO/hydroxy group- 1 1 1 1 1 1 1 1 1 1 1 containing acrylic resin (A-1) OH mole ratio Proportion (%) of (B-2) non-volatiles content 50 50 50 50 50 50 50 50 50 50 50 relative to non-volatiles content of (B-1) + (B-2)

(27) TABLE-US-00005 TABLE 5 comparative example 1 2 3 4 5 6 7 clear coat paint name CC- CC- CC- CC- CC- CC- CC- 24 25 26 27 28 29 30 base hydroxy group-containing A-1-1 49.8 49.8 49.8 resin acrylic resin (A-1) varnish A-1-5 64.4 A-1-6 37.2 A-1-11 49.8 A-1-12 49.8 curing catalyst (A-2) NACURE4167 2.0 2.0 2.0 2.0 2.0 2.0 UV absorber Tinuvin 384-2 1.5 1.5 1.5 1.5 1.5 1.5 1.5 photostabilizer Tinuvin 292 1.0 1.0 1.0 1.0 1.0 1.0 1.0 surface modifier BYK-300 0.2 0.2 0.2 0.2 0.2 0.2 0.2 solvent Solvesso 100 10.6 5.4 11.5 8.6 8.6 8.6 8.7 curing isocyanate compound (B-1) Sumidure N3300 11.3 7.3 14.8 11.3 11.3 11.3 11.3 agents alkoxysilyl group-containing B-2-1 20.5 13.3 26.8 20.5 20.5 copolymer (B-2) solution B-2-4 20.5 B-2-5 20.5 solvent xylene 5.0 5.0 5.0 5.0 5.0 5.0 5.0 total 100 100 100 100 100 100 100 quantity of curing catalyst (A-2) added (non-volatiles 0 0.5 0.5 0.5 0.5 0.5 0.5 content %) isocyanate compound (B-1) NCO/hydroxy 1 1 1 1 1 1 1 group-containing acrylic resin (A-1) OH mole ratio Proportion (%) of (B-2) non-volatiles content relative 50 50 50 50 50 50 50 to non-volatiles content of (B-1) + (B-2)

Notes to Tables

(28) 1) NACURE 4167: brand name, King Industries (Co.), amine blocked phosphate compound solution (non-volatiles content 25 mass %). 2) Tinuvin 384-2: brand name, BASF Japan (Co.), benzo-triazole UV absorber (non-volatiles content 95 mass %). 3) Tinuvin 292: brand name, BASF Japan (Co.), photo-stabilizer. 4) BYK-300, brand name, Byk Chemie (Co.), silicone surface modifier (non-volatiles content 52 mass %). 5) Solvesso 100: brand name, Exxon-Mobil (Co.), aromatic hydrocarbon solvent. 6) Sumidure N3300: brand name, Sumitomo Bayer Urethanes (Co.), HDI isocyanurate resin (non-volatiles content 100 mass %, NCO % content 21.8 mass %).
Production of Test Pieces and Study of Paint Film Performance

(29) Zinc-plated steel plates 0.8 mm thick, 150 mm long and 70 mm wide were chemically treated with zinc phosphate and then electrocoating was performed using the cationic electrocoat paint Cathoguard 500 (brand name, BASF Japan (Co.)) so as to give a dry film thickness of 25 ?m and this was stoved for 30 mins at 170? C., then spray-coated with the intermediate coat paint HS-H300 Dark Gray (brand name, BASF Japan (Co.)) so as to give a dry film thickness of 30 ?m, and stoved for 20 mins at 140? C. Next, as the base coat paint, a polyurethane-polyester-melamine resin aqueous base coat paint Aqua BC-3 Black (brand name, BASF Japan (Co.)) was spray-coated so as to give a dry film thickness of 15 pm, and this was dried for 5 mins at 80? C. After cooling the test plates to room temperature, the two-component clear coat paints CC-1 to 19 base resins and curing agent were homogeneously mixed and spray-coated so as to give a dry film thickness of 30 ?m and after maintaining for 10 mins at room temperature they were stoned for 20 mins at 140? C. to give the test pieces. However, for stain resistance test pieces, the tests were performed on white test plates, wherein the white HS-H300 White was used as the intermediate coat paint, and the white Aqua BC-3 White as the aqueous base coat paint.

(30) The paint film performance test results are shown in Tables 6 to 8.

(31) TABLE-US-00006 TABLE 6 practical example 1 2 3 4 5 6 clear coat paint name CC-1 CC-2 CC-3 CC-4 CC-5 CC-6 paint hydroxy group-containing acrylic resin (A-1) A-1-1 A-1-1 A-1-1 A-1-1 A-1-1 A-1-2 composition resin hydroxyl number (mgKOH/g) 120 120 120 120 120 140 characteristic 4-hydroxybutyl acrylate-derived resin 120 120 120 120 120 90 values and hydroxyl number (mgKOH/g) component resin design glass transition temperature (? C.) 0 0 0 0 0 0 percentages weight average molecular weight 10,000 10,000 10,000 10,000 10,000 10,000 quantity of curing catalyst (A-2) added (non-volatiles 0.5 0.5 0.5 0.5 0.5 0.5 content %) isocyanate compound (B-1) NCO/hydroxy 1.0 0.8 1.2 1.0 1.0 1.0 group-containing acrylic resin (A-1) OH mole ratio alkoxysilyl group-containing copolymer (B-2) B-2-1 B-2-1 B-2-1 B-2-1 B-2-1 B-2-1 content of alkoxysilyl group-containing 50 50 50 50 50 50 vinylic monomer in monomer composition (%) weight average molecular weight 10,000 10,000 10,000 10,000 10,000 10,000 proportion (%) of (B-2) non-volatiles content 50 50 50 30 70 50 relative to non-volatiles content of (B-1) + (B-2) assessment external appearance (paint film transparency) ? ? ? ? ? ? results carwash scratch resistance ? ? ? ? ? ? stain resistance ? ? ? ? ? ? acid resistance ? ? ? ? ? ? gasoline resistance ? ? ? ? ? ? practical example 7 8 9 10 11 12 clear coat paint name CC-7 CC-8 CC-9 CC-10 CC-11 CC-12 paint hydroxy group-containing acrylic resin (A-1) A-1-2 A-1-2 A-1-2 A-1-2 A-1-1 A-1-1 composition resin hydroxyl number (mgKOH/g) 140 140 140 140 120 120 characteristic 4-hydroxybutyl acrylate-derived resin 90 90 90 90 120 120 values and hydroxyl number (mgKOH/g) component resin design glass transition temperature 0 0 0 0 0 0 percentages (? C.) weight average molecular weight 10,000 10,000 10,000 10,000 10,000 10,000 quantity of curing catalyst (A-2) added (non-volatiles 0.5 0.5 0.5 0.5 0.5 0.5 content %) isocyanate compound (B-1) NCO/hydroxy 0.8 1.2 1.0 1.0 1.0 1.0 group-containing acrylic resin (A-1) OH mole ratio alkoxysilyl group-containing copolymer (B-2) B-2-1 B-2-1 B-2-1 B-2-1 B-2-1 B-2-1 content of alkoxysilyl group-containing 50 50 50 50 50 50 vinylic monomer in monomer composition (%) weight average molecular weight 10,000 10,000 10,000 10,000 10,000 10,000 proportion (%) of (B-2) non-volatiles content 50 50 30 70 10 90 relative to non-volatiles content of (B-1) + (B-2) assessment external appearance (paint film transparency) ? ? ? ? ? ? results carwash scratch resistance ? ? ? ? ? ? stain resistance ? ? ? ? ? ? acid resistance ? ? ? ? ? ? gasoline resistance ? ? ? ? ? ?

(32) TABLE-US-00007 TABLE 7 practical example 13 14 15 16 17 18 clear coat paint name CC-13 CC-14 CC-15 CC-16 CC-17 CC-18 paint hydroxy group-containing acrylic resin (A-1) A-1-6 A-1-7 A-1-8 A-1-9 A-1-10 A-1-11 composition resin hydroxyl number (mgKOH/g) 90 170 120 120 120 120 characteristic 4-hydroxybutyl acrylate-derived 90 150 120 120 120 120 values and resin hydroxyl number (mgKOH/g) component resin design glass transition temperature 0 0 ?30 26 0 0 percentages (? C.) weight average molecular weight 10,000 10,000 10,000 10,000 4,000 20,000 quantity of curing catalyst (A-2) added (non-volatiles 0.5 0.5 0.5 0.5 0.5 0.5 content %) isocyanate compound (B-1) NCO/hydroxy 1.0 1.0 1.0 1.0 1.0 1.0 group-containing acrylic resin (A-1) OH mole ratio alkoxysilyl group-containing copolymer (B-2) B-2-1 B-2-1 B-2-1 B-2-1 B-2-1 B-2-1 content of alkoxysilyl group-containing 50 50 50 50 50 50 vinylic monomer in monomer composition (%) weight average molecular weight 10,000 10,000 10,000 10,000 10,000 10,000 proportion (%) of (B-2) non-volatiles content 50 50 50 50 50 50 relative to non-volatiles content of (B-1) + (B-2) assessment external appearance (paint film transparency) ? ? ? ? ? ? results carwash scratch resistance ? ? ? ? ? ? stain resistance ? ? ? ? ? ? acid resistance ? ? ? ? ? ? gasoline resistance ? ? ? ? ? ? practical example 19 20 21 22 23 clear coat paint name CC-19 CC-20 CC-21 CC-22 CC-23 paint hydroxy group-containing acrylic resin (A-1) A-1-1 A-1-1 A-1-1 A-1-1 A-1-13 composition resin hydroxyl number (mgKOH/g) 120 120 120 120 120 characteristic 4-hydroxybutyl acrylate-derived 120 120 120 120 60 values and resin hydroxyl number (mgKOH/g) component resin design glass transition temperature 0 0 0 0 0 percentages (? C.) weight average molecular weight 10,000 10,000 10,000 10,000 10,000 quantity of curing catalyst (A-2) added (non-volatiles 0.5 0.5 0.5 0.5 0.5 content %) isocyanate compound (B-1) NCO/hydroxy 1.0 1.0 1.0 1.0 1.0 group-containing acrylic resin (A-1) OH mole ratio alkoxysilyl group-containing copolymer (B-2) B-2-4 B-2-5 B-2-6 B-2-7 B-2-1 content of alkoxysilyl group-containing 40 70 50 50 50 vinylic monomer in monomer composition (%) weight average molecular weight 10,000 10,000 4,000 17,000 10,000 proportion (%) of (B-2) non-volatiles content 50 50 50 50 50 relative to non-volatiles content of (B-1) + (B-2) assessment external appearance (paint film transparency) ? ? ? ? ? results carwash scratch resistance ? ? ? ? ? stain resistance ? ? ? ? ? acid resistance ? ? ? ? ? gasoline resistance ? ? ? ? ?

(33) TABLE-US-00008 TABLE 8 comparative example 1 2 3 4 5 6 7 clear coat paint name CC- CC- CC- CC- CC- CC- CC- 24 25 26 27 28 29 30 paint hydroxy group-containing acrylic resin (A-1) A-1-1 A-1-5 A-1-6 A-1-12 A-1-1 A-1-1 A-1-11 composition resin hydroxyl number (mgKOH/g) 120 60 210 120 120 120 120 characteristic 4-hydroxybutyl acrylate-derived 120 60 0 0 120 120 120 values and resin hydroxyl number (mgKOH/g) component resin design glass transition temperature 0 5 4 50 0 0 0 percentages (? C.) weight average molecular weight 10,000 10,000 10,000 10,000 10,000 10,000 26,000 quantity of curing catalyst (A-2) added (non- 0.0 0.5 0.5 0.5 0.5 0.5 0.5 volatiles content %) isocyanate compound (B-1) NCO/hydroxy 1.0 1.0 1.0 1.0 1.0 1.0 1.0 group-containing acrylic resin (A-1) OH mole ratio alkoxysilyl group-containing copolymer (B-2) B-2-1 B-2-1 B-2-1 B-2-1 B-2-2 B-2-3 B-2-1 content of alkoxysilyl group-containing 50 50 50 50 20 90 50 vinylic monomer in monomer composition (%) weight average molecular weight 10,000 10,000 10,000 10,000 10,000 10,000 10,000 proportion (%) of (B-2) non-volatiles content 50 50 50 50 50 50 50 relative to non-volatiles content of (B-1) + (B-2) assessment external appearance (paint film transparency) ? ? X ? ? X X results carwash scratch resistance X X X ? X X ? ? ? stain resistance X X ? ? X X ? ? acid resistance X ? ? ? ? ? ? gasoline resistance X ? ? ? ? ? ?

(34) Practical examples 1 to 23 of the present invention showed excellent scratch resistance, stain resistance, acid resistance and gasoline resistance, with no paint film transparency problems such as clouding due to poor compatibility. With comparative examples 1 to 7, it was not possible to pass all the tests.