JPH05105840A - Coating composition and method of coating - Google Patents

Abstract

PURPOSE:To prepare a coating compsn. which gives a coating film excellent in scratch resistance, weatherability, etc. CONSTITUTION:A coating compsn. is prepd. by compounding a fluorocopolymer contg. fluoroolefin units and units based on a long-chain-hydroxyalkyl vinyl ether of the formula: CH2=CHO(CH2)nOH (wherein n is 7-18) and having a Tg of -30 to 50 deg.C, a hydroxyl value of 50-160, an acid value of 0-30, and an Mn of 4,000-40,000 with a curative.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for paints, and more particularly to a resin composition for paints which has significantly improved scratch resistance and is also excellent in weather resistance and chemical resistance. ..

[0002]

2. Description of the Related Art As a top coat for automobile bodies, etc., the finish appearance (gloss, smoothness) of the coating film, weather resistance, chemical resistance,
Mechanical properties, adhesion to undercoat, adhesion when recoating and overcoating are generally required properties, but in recent years, with the increasing need for coating color designability, clear coating with dark colors such as dark blue, black, and red is possible. Since the proportion of color has increased, deterioration of the finished appearance due to scratches on the surface of the coating film has become a problem. Scratch on the car body is a cloth, brush, car-washing machine or scuffed by hair fluttering used for car washing, and scratches caused by collision of flying sand while driving, and durability and resistance to these scratches. Scratch resistance is a performance required for a coating film immediately after coating and after natural exposure.

Conventionally, as a thermosetting resin composition for coatings having excellent weather resistance and improved low-temperature flexibility, a lactone-modified fluorine-containing copolymer obtained by graft-adding a lactone compound to a fluorine-containing copolymer and a curing agent. Is proposed (JP-A-59-96177).

The coating film obtained from this resin composition has a high degree of flexibility and excellent weather resistance, but it is 100 to 160.
Since the modification reaction is carried out at a temperature of several hours for several hours, the polymer solution is colored, and the storage stability of the lactone-modified fluorocopolymer is poor.

Further, in order to improve this problem, a fluorine-containing copolymer prepared by copolymerizing a vinyl ether to which a lactone compound has been graft-added has been proposed (Japanese Patent Laid-Open No. HEI-1).
-16815).

This resin composition has excellent storage stability, has flexibility at low temperature when formed into a coating film, absorbs external force of scratches, and has extremely excellent scratch resistance. However, this resin composition has problems in water resistance, chemical resistance, and weather resistance.

Further, as a composition having excellent scratch resistance of plastics, there has been proposed a coating composition containing a silane compound and a fluorine-containing copolymer using ω-hydroxyalkyl vinyl ether as essential components (USP 3 , 4
29,845). This composition has a short alkyl chain length of ω-hydroxyalkyl vinyl ether (n = 2 to
6) A fluorine-containing copolymer alone does not show sufficient scratch resistance, and since it is a binary alternating copolymer of fluoroolefin and ω-hydroxyalkyl vinyl ether, it has a high hydroxyl value and is highly polar solvent such as alcohol. It had a problem that it was only dissolved.

That is, in a two-coat one-bake coating method in which an undercoat base coating material and a topcoat coating material are applied over each other and both coating materials are cured at the same time, undercoating is performed to ensure the separability of both coating films and improve the coating appearance. Since a quick-drying polar solvent is used for the coat base and a non-polar solvent that does not dissolve the undercoat base is generally used for the top coat, there is a serious problem in coatability.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to overcome the above-mentioned problems of the prior art and to provide a top coat for automobile bodies and the like with excellent scratch resistance, weather resistance and chemical resistance. It is intended to provide a resin composition having general coating film properties such as durability, water resistance, and sharpness, and coating properties such as colorability and storage stability.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. A) CH ₂ = CRO (CH ₂ ) _n OH (R is H or C
H ₃ and n are integers of 7 to 18) and units containing 5 to 50 mol% of a unit based on a hydroxyl group-containing long-chain alkyl vinyl ether and 30 to 70 mol% of a unit based on a fluoroolefin. Temperature is -30 to 50
C, hydroxyl value is 50-160 mgKOH / g, acid value is 0
~ 30 mg KOH / g, number average molecular weight 4,000-4
Fluorine-containing copolymer of 10,000, b) a curing agent having a functional group capable of reacting with a hydroxyl group, are added as essential components, and the total amount of the components a) and b) is
The present invention provides a coating composition characterized by containing a) component in an amount of 50 to 95% by weight and b) component in an amount of 5 to 50% by weight.

In the fluorine-containing copolymer a) used in the composition of the present invention, a hydroxyl group-containing long-chain alkyl vinyl ether monomer is used as an essential component in terms of scratch resistance.

By copolymerizing the monomer, a side chain having a relatively long chain and abundant flexibility and having a crosslinking site at the terminal is introduced into the fluorocopolymer. The cured coating film obtained by curing the fluorocopolymer having such a side chain forms an elastic coating film having excellent self-repairing property. As a result, the coating film absorbs the external force of the scratches as an elastic deformation without being destroyed, and when the external force disappears, the deformation is promptly recovered and the scratches do not occur, or the degree of the scratches is slight and inconspicuous.

In the fluorocopolymer of the present invention, tetrafluoroethylene and chlorotrifluoroethylene are preferably selected as the fluoroolefin, but they can be used in combination. The copolymerization ratio is 30
It is necessary to be 70 mol%. If it is 30 mol% or less, sufficient weather resistance cannot be obtained, and if it is 70 mol% or more, the solubility in the coating solvent becomes insufficient.

Next, the methylene chain length of the hydroxyl group-containing long-chain alkyl vinyl ether monomer must be 7 to 18. When the methylene chain length is 6 or less, a sufficient elastic coating film effective for scratch resistance cannot be obtained, and when it is 19 or more, the solubility of the polymer in an aromatic solvent is impaired.

Further, the fluorine-containing copolymer in the present invention is
In addition to the above two components, a copolymerizable vinyl monomer may be copolymerized. The copolymerizable vinyl monomer is not limited as long as it copolymerizes with a fluoroolefin and a hydroxyl group-containing long-chain alkyl vinyl ether monomer, but is not limited to any vinyl ether monomer, particularly ethyl vinyl ether, n. -Butyl vinyl ether, cyclohexyl vinyl ether,
Hydroxybutyl vinyl ether and the like are preferably adopted. Furthermore, as these monomers, those in which a part or all of the molecule is fluorinated can be adopted.
Further, these monomers may have functional groups other than hydroxyl groups such as epoxy groups and carboxy groups.

The fluorine-containing copolymer of the present invention has a hydroxyl value of 50 to 160 mgKOH / g. If the hydroxyl value is too low, a sufficient crosslinked density cannot be obtained as a cured coating film, and the mechanical strength and solvent resistance of the coating film will be insufficient, such being undesirable. Further, if the hydroxyl value is too high, the solubility in a solvent decreases, which is not preferable. If the hydroxyl value is too high, it cannot be used as a top coat paint in the two-coat one-bake coating system as described later, because it is soluble only in some polar solvents such as alcohol.

The hydroxyl value is adjusted by adjusting the copolymerization ratio of the fluoroolefin and the hydroxyl group-containing long-chain alkyl vinyl ether. In addition to the above two components, the hydroxyl value can be lowered by copolymerizing a comonomer such as a vinyl ether compound as described above. Further, the hydroxyl value can be increased by copolymerizing another hydroxyl group-containing monomer such as hydroxybutyl vinyl ether.

Further, the fluorine-containing copolymer of the present invention has an acid value of 0 to 30 mgKOH / g. A fluorine-containing copolymer having an acid value is preferable because it improves the dispersibility of the pigment and has a catalytic action to accelerate the reaction with the curing agent. However, if the acid value is too high, the solubility in a solvent is lowered as in the case of the high hydroxyl value, which is not preferable.

The acid value can be added, for example, by introducing a carboxylic acid group into the method described in JP-B-61-49323.

The fluorine-containing copolymer of the present invention has a glass transition temperature (hereinafter abbreviated as T _g ) of -30.
~ 50 ° C. If the T _g is too low, the hardness of the coating film decreases and the scratch resistance deteriorates. In addition, the stain resistance may decrease or tack may easily occur. On the other hand, if T _g is too high, the flexibility, adhesion and chipping resistance of the coating film deteriorate, which is not preferable.

The number average molecular weight of the fluorine-containing copolymer of the present invention is 4,000-40,000.
If the number average molecular weight is too small, a coating film having sufficient strength cannot be obtained, which is not preferable. On the other hand, if it is too large, not only the viscosity of the solution becomes high, but not only the coatability is lowered, but also the sharpness of the coating film is lowered, which is not preferable.

The above-mentioned copolymer is subjected to a copolymerization reaction by allowing a polymerization initiator or a polymerization initiation source such as ionizing radiation to act on a monomer mixture in a predetermined ratio in the presence or absence of a polymerization medium. It can be manufactured by tightening.

As the polymerization initiator, a water-soluble one or an oil-soluble one can be appropriately used depending on the type of polymerization or the polymerization medium. Specifically, as the water-soluble initiator, a persulfate such as potassium persulfate, hydrogen peroxide or a redox initiator composed of a combination of these with a reducing agent such as sodium bisulfite and sodium thiosulfate, and further these Inorganic initiators such as those in which a small amount of iron, ferrous salt, silver nitrate, etc. coexist, or dibasic acid oxides such as disuccinic acid peroxide, diglutaric acid peroxide, and monosuccinic acid peroxide, azobisisobutylamidine dihydrochloride Examples are organic initiators such as salts.

As the oil-soluble initiator, peroxyester type peroxides such as t-butylperoxyisobutyrate and t-butylperoxyacetate, dialkylperoxydicarbonates such as diisopropylperoxydicarbonate, Benzoyl peroxide,
Azobisisobutyronitrile etc. are illustrated.

The amount of the polymerization initiator used can be appropriately changed depending on the type, the copolymerization reaction conditions and the like, but usually 0.005 to 5% by weight based on the total amount of the monomers to be copolymerized. In particular, about 0.05 to 0.5% by weight is adopted.

In the above copolymerization reaction, the reaction mode is not particularly limited, and bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization and the like can be adopted, but the stability of the polymerization reaction operation, the produced copolymer From the standpoint of ease of separation, etc., emulsion polymerization in an aqueous medium or alcohols such as t-butanol,
Solution polymerization using an ester, a saturated halogenated hydrocarbon containing one or more fluorine atoms, an aromatic hydrocarbon such as xylene, etc. as a solvent is preferably employed. When the copolymerization reaction is carried out in an aqueous medium, it is preferable to add a basic buffering agent so that the pH value of the liquid during polymerization does not fall below 4, preferably 6. The addition of the basic substance is also effective in the case of solution polymerization. Further, it goes without saying that the method of the present invention can be carried out by operations such as a batch system, a semi-continuous system and a continuous system.

In the copolymerization reaction, the copolymerization reaction temperature may be appropriately selected within the range of -30 ° C to + 150 ° C depending on the polymerization initiator, the type of the polymerization medium, etc. When the polymerization reaction is performed, 0 ° C to +10
0 ° C., preferably about 10 ° C. to 90 ° C. can be adopted.
The reaction pressure can be appropriately selected, but is usually 1 to
It is desirable to adopt 100 kg / cm ² , especially about ² to 50 kg / cm ² . It is also possible to carry out the copolymerization reaction in the coexistence of a chain transfer agent as appropriate.

The composition of the present invention contains a curing agent b) having a functional group capable of reacting with a hydroxyl group. As such a curing agent, it is important to use a polyfunctional compound having reactivity with a hydroxyl group contained as a curing site in the copolymer.

As such a curing agent, first, a melamine curing agent, a urea resin curing agent, a polybasic acid curing agent, a block polyvalent isocyanate, or the like heat-curing type, which is used in ordinary thermosetting acrylic paints, is used. The thing can be illustrated. Examples of the melamine curing agent include butylated melamine, methylated melamine, and epoxy-modified melamine, and those with various degrees of modification of 0 to 6 can be used depending on the application, and the degree of self-condensation can also be appropriately selected. . Examples of the urea resin include methylated urea and butylated urea. As the polybasic acid curing agent, long-chain aliphatic dicarboxylic acids, aromatic polyvalent carboxylic acids or their anhydrides are useful.
As the block polyvalent isocyanates, the block compounds of polyvalent isocyanates described below are suitable. When using a melamine or urea-based curing agent, the curing can be promoted by adding an acidic catalyst.

As the curing agent in the present invention, a room temperature curing type such as a polyvalent isocyanate can also be used. As the polyvalent isocyanate, non-yellowing diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, and adducts thereof are particularly useful. When performing room temperature curing using isocyanates, it is possible to accelerate the curing by adding a curing catalyst such as dibutyltin dilaurate.

A compound having an epoxy group can also be used as a curing agent. As such a curing agent, an epoxy compound having an average of two or more epoxy groups in one molecule and an epoxy equivalent of 100 to 2,000 is suitable. Further, the epoxy group is preferably a so-called alicyclic epoxy group such as dicyclopentadiene dioxide because it has excellent reactivity with a hydroxyl group. Such epoxy compounds are exemplified in JP-A-2-73825 and the like.

A silane compound can also be used as a curing agent. As such a silane compound, a silane compound having an average of two or more functional groups selected from an alkoxysilyl group, a silanol group and an acyloxysilyl group in one molecule is preferably adopted. Such silane compounds are commercially available under the names such as silane coupling agents, silane-based curing agents, silicone-based curing agents, alkoxysilanes, and silane alkoxides.

As the curing agent, only one of the above may be used alone, or a plurality of it may be mixed and used.

The composition of the present invention can be dissolved in a paint solvent and used as a solution type paint. As the solvent, those commonly used for paints can be used without particular limitation. Also, 2 coats 1
When used as a top coat paint in the bake coating method, it is preferable to select a solvent having a solubility parameter of 9 or less, or a mixed solvent. In this case, the fluorocopolymer needs to be dissolved in a solvent having a solubility parameter of 9 or less. The undercoat paint at this time is preferably a solution paint using a solvent having a solubility parameter of 9 or more. This combination is preferable because the finished appearance is excellent. When the solvent of the undercoat paint and the solvent of the topcoat paint are reversed or the same, the undercoat paint is redissolved when the topcoat paint is applied, and the finished appearance is significantly deteriorated, which is not preferable.

Solvents having a solubility parameter of 9 or less include toluene, xylene, pentane, hexane, heptane, nonane, cyclohexane, Solvesso # 100 (exxon), Solvesso # 150 (exxon),
Swazol # 1000 (Maruzen Petrochemical Co., Ltd.), Swazol # 1500 (Maruzen Petrochemical Co., Ltd.), Swazol # 18
00 (made by Maruzen Petrochemical Co., Ltd.).

Solvents having a solubility parameter greater than 9 include methanol, ethanol, propanol, butanol, isobutanol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, diacetone alcohol, methyl cellosolve, cellosolve, butyl cellosolve. , Cellosolve acetate, ethyl acetate, butyl acetate,
Examples include isobutyl acetate, benzene, methyl ethyl ketone, methyl isobutyl ketone, isophorone, and cyclohexanone.

It is also preferable to apply the coating composition of the present invention onto a water-dilutable water-based base coat paint by a two-coat one-bake coating method because a good finished appearance can be obtained.

When preparing the coating composition of the present invention,
Various equipment used for usual coating such as a ball mill, a paint shaker, a sand mill, a jet mill, a triple roll, and a kneader can be used. At this time, a pigment, a dispersion stabilizer, a viscosity modifier, a leveling agent, an anti-gelling agent, an ultraviolet absorber, a light stabilizer and the like and other synthetic resins may be added within a range not impairing the purpose.

When the coating composition of the present invention is used as a heat-curable so-called baking coating, melamine, urea resin, polybasic acid or its anhydride, block polyvalent isocyanates, etc. may be prepared in the above preparation. A curing agent is also mixed at the same time and used as a one-pack type paint.

On the other hand, when used as a room temperature curing type coating composition using non-block polyvalent isocyanates etc., the curing agent components are separately prepared to give a two component type coating composition. In this case, the pot life of about 1 to 10 hours can be obtained by adjusting the types and addition amounts of the isocyanate and the catalyst, the copolymer concentration, the content of units based on the hydroxyalkyl vinyl ether in the copolymer, and the like. Have a few hours ~
The coating composition can be cured at room temperature in a few days to give a coating film having good physical properties.

The coating composition used in the present invention contains the above-mentioned components a) and b) as main components, and the composition ratio of these components is 5) based on the total weight of the components a) and b).
0 to 95% by weight, preferably 60 to 85% by weight, and b) is 5 to 50% by weight, preferably 15 to 40% by weight.
When the content of component a) is less than 50% by weight, the coating film does not exhibit sufficient self-healing property against external force of scratches, while
If it exceeds 5% by weight, the solvent resistance and stain resistance of the cured coating film deteriorate, which is not preferable.

If the amount of component b) is less than 5% by weight, the coating film will not be sufficiently cured and the elastically deformed coating film having an effect on scratch resistance will not be sufficiently formed. The film becomes too hard and brittle, and the scratch resistance decreases, which is not preferable.

The coating system of the coating composition of the present invention comprises a base plate on which an undercoat or an intermediate coating film has been formed, if necessary, in the case of 1 coat solid, directly in the case of 2 coat 1 bake clear, and then enamel coated and then wet. Painted on wet.

The coating method may be an air atomization method, a rotary atomization method, an airless method, electrostatic coating, dip coating, or the like.

The curing conditions after coating are, depending on the type of the object to be coated, the type of curing agent used, etc., a curing coating excellent in scratch resistance, which is the object of the present invention, by curing at room temperature to 250 ° C. for 1 to 60 minutes. A film is obtained.

[0046]

The present invention will be described in more detail with reference to the following examples. Parts and% in the examples represent parts by weight and% by weight, unless otherwise specified.

Synthetic Example of Fluorine-Containing Copolymer According to the method described in JP-B-60-21686, copolymerization was carried out with the monomer compositions shown in Table 1, and then JP-B-61-61.
By the method described in No. 49323, modification was performed to obtain a fluorine-containing copolymer shown in Table 1.

[0048]

[Table 1]

Example 1 As the fluorine-containing copolymer, A-1 in Table 1 was used. A-1
To 100 parts, xylene 54 parts, butylated melamine (Uban 20SE60, manufactured by Mitsui Toatsu Co., Ltd.) 50 parts,
n-Butyl alcohol 10 parts, UV absorber (Tinuvin # 900, manufactured by Ciba Geigy) 10% xylene solution 30
Parts, 14 parts of 10% xylene solution of light stabilizer (Tinuvin # 144, manufactured by Ciba Geigy), surface conditioner (BYK30
0, manufactured by BYK Chemie) with stirring and mixing 0.5 parts of composition B
-1 was prepared.

The above composition was diluted with Solvesso # 100 in Ford cup # 4 at 25 seconds / 20 ° C. and then applied.

Examples 2 to 5 Compositions (B-2 to B-5) were prepared in the same manner as in Example 1 except that A-2 to A-5 in Table 1 were used as the fluorine-containing copolymer. did.

Example 6 As a fluorine-containing copolymer, A-6 in Table 1 was used, and A-6 was used.
To 100 parts, 21 parts of an isocyanate-based curing agent (Coronate HX: made by Nippon Polyurethane), 54 of xylene
Parts, curing catalyst (dibutyltin dilaurate) 0.003
Parts, 30 parts of a 10% xylene solution of an ultraviolet absorber, 14 parts of a 10% xylene solution of a light stabilizer (Tinuvin # 144 manufactured by Ciba Geigy), and 0.5 parts of a surface conditioner (made by BYK300, BYK Chemie) are mixed with stirring. , Composition (B-6) was prepared.

The above composition was diluted with Ford's cup # 4 using Solvesso # 100 at 25 seconds / 20 ° C., and applied for coating.

Comparative Examples 1 to 3 Compositions (B-7 to B-9) were prepared in the same manner as in Example 1 except that A-7 to A-9 shown in Table 1 were used as the fluorine-containing copolymer. did.

Production Example of Paint for Base Coat 10 parts of styrene, 25 parts of methyl methacrylate, 35 parts of ethyl acrylate, 15 parts of n-butyl methacrylate and 2 parts of acrylic acid were used in xylene using the polymerization initiator azobisisobutyronitrile. Polymerization was performed to obtain an acrylic resin solution D-1 having a resin content of 48%. Using this acrylic resin solution, a solvent-type base coat C-1 was prepared with the following composition. Acrylic resin solution (D-1) 200 parts Cymel 303 ¹⁾ 20 p-toluenesulfonic acid solution 4.0 Carbon black FW ^# 200 ²⁾ 2.0 Note 1) Melamine resin manufactured by Mitsui Cyanamid Co., Ltd. 2) Degussa Made carbon black

Next, this base coat E-1 was mixed with toluene 4
A mixed solution of 0 parts, 40 parts of ethyl acetate and 20 parts of cellosolve acetate has a viscosity of 13.5 seconds (Ford cup #
It was diluted to 4/20 ° C.) and used for coating.

Preparation and Evaluation of Test Plates A cationic electro-deposition paint for automobiles was applied on a 0.8 mm thick dull steel plate which had been subjected to zinc phosphate chemical conversion treatment, and the test plate was coated at 170 ° C. for 3 days.
It was baked for 0 minutes. Next, apply an intermediate coating for automobiles and
After baking for 30 minutes at 40 ° C, water-sanding with # 600 sandpaper, drying, and degreasing with white gasoline,
It was used as a test material.

After adjusting the viscosity of the base coating material E-1 to 13.5 seconds on this material, the air spray gun W-6 was used.
1 (manufactured by Iwata Cup Co., Ltd.) was applied so that the dry film thickness would be 18μ, and after leaving at room temperature for 3 minutes, clear coat paint C-1 adjusted to have a viscosity of 25 seconds was applied to an air spray gun W-61. It was used for wet-on-wet coating with a dry film thickness of 30 μ, left at room temperature for 10 minutes, and then baked at 140 ° C. for 30 minutes in a hot air drying oven to prepare a test plate.

The clear coats C-1 to C-8 of Examples 1 to 6 and Comparative Examples 1 to 2 were evaluated for scratch resistance and general coating film performance, and the results are shown in Table 2.

Composition B-9 of Comparative Example 3 was Solvesso # 1.
It did not dissolve in 00 and could not be coated.

[0061]

[Table 2]

Evaluation method Scratch resistance The following is the evaluation criteria for observing the state of the coated surface of an automobile having a test plate adhered to the roof after being washed 20 times with a car wash machine. ◎ Pass with almost no scratches by visual observation ○ Slight scratches are found, but the degree is very slight △ Scratch is not noticeable × Marked scratches are noticeably failed

Pencil Hardness Scratch hardness was measured using Mitsubishi Pencil Co., Ltd. Uni.

Moisture resistance A test plate is placed in a constant temperature and humidity tank of 50 ° C. and 98% RH for 120 hours, and the state of the coated surface immediately after removal is evaluated.

Gasoline resistance After dipping in regular gasoline (manufactured by Nisseki Co., Ltd.) at room temperature for 24 hours, the appearance is visually evaluated.

Acid-proof 10% sulfuric acid 0.3 cc was spotted on the coated surface and kept at 20 ° C. for 2 hours.
After leaving it for 4 hours, it was washed with water and the coated surface was observed.

Alkali resistance 0.3 cc of a 10% aqueous sodium hydroxide solution was spotted on the coated surface, allowed to stand at 20 ° C. for 24 hours, washed with water, and the coated surface was observed.

Weather resistance The gloss retention of the coating film after exposure for 3000 hours with a sunshine weather meter was expressed.

[0069]

The coating composition of the present invention forms an excellent weather resistant coating film having excellent scratch resistance and having a well-balanced hardness, water resistance, chemical resistance and chemical resistance. It is extremely useful for painting automobile bodies and home appliances.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display area C09D 175/04 PHR 8620-4J 183/04 PMM 8319-4J

Claims (7)

[Claims] 1. a) CH ₂ ═CRO (CH ₂ ) _n OH (R
Is H or CH ₃ , and n is an integer of 7 to 18), and 5 to 50 mol% is a unit based on a hydroxyl group-containing long-chain alkyl vinyl ether, and 3 is a unit based on fluoroolefin.
The glass transition temperature is −0 to 70 mol%.
30-50 ° C, hydroxyl value 50-160mgKOH /
g, an acid value of 0 to 30 mgKOH / g and a number average molecular weight of 4,000 to 40,000 fluorine-containing copolymer, b) a curing agent having a functional group that reacts with a hydroxyl group, and 50 to 95% by weight of the component a) and 5 to 5 of the component b) based on the total of the components a) and b).
A coating composition comprising 0% by weight. 2. The coating composition according to claim 1, wherein the component b) is a partially or completely alkyletherified melamine resin. 3. The coating composition according to claim 1, wherein the component b) is an isocyanate-containing compound. 4. An epoxy group-containing compound in which the component b) has an average of two or more epoxy groups in one molecule and an epoxy equivalent of 100 to 2,000, and / or an average of one in one molecule. The coating composition according to claim 1, which is a silane compound having a functional group selected from the above alkoxysilyl group, silanol group, and acyloxysilyl group. 5. A two-coat, one-bake coating method in which an undercoat base paint and a top coat clear paint are applied repeatedly, and then both coats are simultaneously cured, and the coating composition according to claim 1 is used as the top coat clear paint. The painting method used. 6. The coating method according to claim 5, wherein a solvent-type base coat soluble in a polar solvent having a solubility parameter of 9 or more is used as the undercoat base coat. 7. The coating method according to claim 5, wherein a water-dilutable water-based base coat paint is used as the undercoat base paint.