JPH05179191A - Water-based coating composition - Google Patents

Abstract

PURPOSE:To obtain the title composition markedly reduced in the escape of solvents during coating and drying and giving a maintenance-free coating film by mixing an aqueous solution or dispersion of a fluorocopolymer with a blocked isocyanate, an antifoamer and water. CONSTITUTION:The title composition comprises an aqueous solution or dispersion (A) of a fluorocopolymer prepared by neutralizing with a basic compound at least part of the carboxyl groups of a fluorocopolymer composed of a fluoroolefin and an ethylenically unsaturated compound, containing 30-70% fluoroolefin-derived units and having a hydroxyl value of 30-200mgKOH/g, an acid value of 2-200mgKOH/g and a number-average molecular weight of 3000-40000, a water-soluble or-dispersible melamine resin or a water-soluble or-dispersible blocked isocyanate (B), an anionic or nonionic antifoamer (C) and water (D). The amount of component A is 50-95wt.% (in terms of the composition of nonvolatiles) and the amount of component B is 5-50wt.%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an aqueous coating composition.

[0002]

2. Description of the Related Art In recent years, in order to protect the natural environment, pollution problems such as global warming due to organic solvent discharge and photochemical smog have been avoided, and strict solvent discharge regulations are being implemented in Europe and the United States.

In response to such legal regulations, development of a coating method for increasing the coating efficiency and making effective use of the coating,
The introduction of high-solid type paints has been implemented to increase the solid content of paints and reduce the amount of solvent discharged. However, regulations on the emission of organic solvents from fixed sources are inevitably strict worldwide, and there is a limit to solvent reduction with high-solid type paints, making it impossible to respond. In order to reduce the amount of solvent used, for example, water-based topcoat base coat enamel, which emits the most solvent in automobile painting, has been developed and put to practical use in Europe and the United States.

At present, the base coat enamel is used to make the top coat of 2 coat 1 bake type water-soluble, but the clear coat is either the conventional acrylic melamine solvent type or the high solidified type mentioned above. Clear solvent reduction measures must meet the requirements of the market as a top clear paint for automobiles, that is, maintenance-free properties such as acid rain resistance, car wash scratch resistance, and water and oil repellency. Is becoming

Further, recently, as an electrodeposition coating composition having excellent weather resistance, those obtained by dispersing or dissolving a fluoropolymer in an aqueous medium are disclosed in JP-A Nos. 62-59676 and 62-62.
No. 127362, etc.

[0006]

DISCLOSURE OF THE INVENTION The present invention significantly reduces the amount of solvent discharged in the coating and drying processes in accordance with the regulation of organic solvent discharge, and when formed into a coating film, has acid rain resistance and weather resistance. An object of the present invention is to provide an aqueous coating composition having a maintenance-free function such as water repellency.

[0007]

The present invention has been made to solve the above-mentioned problems, and is (A) a copolymer of a fluoroolefin and an ethylenically unsaturated compound, which is polymerized based on the fluoroolefin. Contains 30 to 70% of the unit and has a hydroxyl value of 30 to 200 mg
KOH / g, oxidation 2 to 200 mg KOH / g, number average molecular weight 300
Fluorine-containing copolymer aqueous solution or dispersion obtained by neutralizing at least a part of the carboxyl groups of the fluorine-containing copolymer of 0 to 40,000 with a basic compound (B) Water-soluble or water-dispersible melamine resin or Water-soluble or water-dispersed blocked isocyanate (C) Anionic or nonionic defoamer (D) Water The above components (A) to (D) are blended as essential components, and the component (A) is 50 ~ 95% by weight, (B)
The present invention provides an aqueous coating composition having excellent atomization coating properties, which is characterized by containing 5 to 50% by weight of components.

The fluorine-containing polymer having a carboxyl group in the present invention can be obtained by the method described in JP-A-58-136605, that is, a fluorine-containing polymer having a hydroxyl group is treated with a dibasic acid anhydride. Fluorine-containing polymer having a carboxyl group obtained by the method of introducing a carboxyl group, a fluorine-containing polymer hydrolyzing the ester bond in the polymer to generate a carboxyl group, a monomer having a carboxyl group A polymer obtained by copolymerizing a fluorine-containing monomer is used.

Specifically, a fluorine-containing polymer obtained by addition-copolymerizing or grafting a unit based on a hydroxyl group-containing monomer such as hydroxyalkyl vinyl ether, hydroxyalkyl acrylate, hydroxyalkyl methacrylate, allyl alcohol or methallyl alcohol. Conversion of the site of a fluoropolymer containing a unit based on a monomer having a group capable of being converted to a hydroxyl group by hydrolysis, such as coalescence, vinyl carboxylate, and allyl carboxylate by hydrolysis or alcoholysis, into a hydroxyl group Those having a hydroxyl group-containing fluorine-containing polymer such as a condensation polymer type obtained by a reaction of fluorine-containing polyols and epichlorohydrin, etc., succinic anhydride, glutaric anhydride, itaconic anhydride, adipic anhydride, Anhydrous 1,2-cyclohexa Dicarboxylic acid, anhydride cis-4-
Dibasic acid anhydrides such as cyclohexene-1,2-dicarboxylic acid, phthalic anhydride, 1,8-naphthalic anhydride and maleic anhydride are reacted to react at least a part of the hydroxyl groups with the general formula -O-CORCOOH. A fluoropolymer having a carboxyl group can be obtained by converting it into an ester group represented and introducing a carboxyl group.

Further, a fluoropolymer obtained by copolymerizing a monomer such as a vinyl ester compound or an allyl ester compound which produces a carboxyl group by hydrolysis is prepared by hydrolyzing a fluoropolymer having a carboxyl group. Obtainable.

Further, the fluoropolymer having a carboxyl group has 3 units of polymerized units based on fluoroolefin.
Those containing 0 to 70 mol% are preferably adopted. A copolymer of fluoroalkyl ester of acrylic acid or methacrylic acid produces excellent effects such as oil repellency, but in terms of weather resistance, it is a fluoropolymer copolymerized with a fluoroolefin, that is, a carbon atom in the main chain. It is not preferable because it is slightly worse than the polymer having a fluorine atom directly bonded to.

If the ratio of the polymerized units based on the fluoroolefin is less than the above range, the weather resistance of the weather resistant coating is not sufficiently exhibited, which is not preferable. On the other hand, if it is more than the above-mentioned ratio, it becomes difficult to make it water-soluble or water-dispersible, so that it may not be suitable for an aqueous paint, which is not preferable.

The fluoroolefin is an unsaturated bond.
At least one of the groups bonded to the carbon forming the bond
It is a compound that is an elementary group. Specifically, CClF = CF₂, CHCl
= CF₂, CCl₂= CF₂, CClF = CClF, CHF = CCl₂, CH₂= CClF, CCl
₂= Fluoroethylene such as CClF, CF₂ClCF = CF₂, CF₃CCl = CF
₂, CF₃CF = CFCl, CF₂ClCCl = CF₂, CF₂ClCF = CFCl, CFCl₂CF
= CF₂, CF₃CCl = CClF, CF₃CCl = CCl₂, CClF₂CF = CCl₂, CCl₃
CF = CF₂, CF₂ClCCl = CCl ₂, CFCl₂CCl = CCl₂, CF₃CF = CHCl,
CClF₂CF = CHCl, CH₃CCl = CHCl, CHF₂CCl = CCl₂, CF₂ClCH = C
Cl₂, CF₂ClCCl = CHCl, CCl₃CF = CHCl, CH₂BrCF = CCl₂ Etc.
Fluoropropenes, CF₃CCl = CFCF₃, CF₂= CFCF₂CClF₂,
CF₃CF₂CF = CCl₂ Fluoroolefins with 4 or more carbon atoms
Examples thereof include system compounds.

As the monomer into which the carboxyl group is introduced, as described above, a hydroxyl group-containing monomer capable of introducing the carboxyl group by acting a dibasic acid anhydride, that is, a hydroxyalkyl vinyl ether, Examples thereof include hydroxyalkyl allyl ether, hydroxyalkyl vinyl ester, hydroxyalkyl allyl ester, vinyl alcohol, allyl alcohol, hydroxyalkyl acrylate and hydroxyalkyl methacrylate.

Among them, hydroxyalkyl vinyl ether and hydroxyalkyl allyl ether are preferably used from the viewpoint of copolymerizability with the above-mentioned fluoroolefin. From the viewpoint of reactivity with the dibasic acid anhydride, those containing a hydroxyl group in the primary or secondary form are preferably adopted. In particular, ω-hydroxyalkyl vinyl ether or ω-hydroxyalkyl allyl ether represented by CH ₂ = CH (CH ₂ ) _m O (CH ₂ ) _n OH (m is 0 or 1, n is an integer of 2 to 18) is preferably adopted. To be done.

The hydroxyl value of the fluoropolymer is 30 to 200.
It must be mgKOH / g. Hydroxyl value is 30 mg KO
Those less than H / g are difficult to be made water-based and are not preferable as water-based paints. Further, those having a hydroxyl value of more than 200 mgKOH / g are not preferable because the chemical resistance and water resistance of the coating film are deteriorated. A fluorine-containing polymer having a hydroxyl value of about 50 to 200 mgKOH / g, and more preferably 80 to 150 mgKOH / g is preferably used.

The reaction for converting the hydroxyl group of the fluoropolymer to the carboxyl group may be carried out for a part of the hydroxyl group or for all the hydroxyl groups.

As the monomer having a carboxyl group, particularly CH ₂ = CH (CH ₂ ) _k O (CH ₂ ) _m OCO (CH ₂ ) _n COOH (k is 0
Alternatively, a compound represented by 1, m is an integer of 2 to 6 and n is an integer of 2 to 10 is preferably used.

The acid value of the fluoropolymer having a carboxyl group is preferably at least 2 mgKOH / g. The amount of carboxyl groups is too small, that is,
Those having an acid value of less than 2 mgKOH / g are difficult to be made water-based and may not be suitable for water-based paints, which is not preferable. If the acid value is too large, the alkali resistance and boiling water resistance of the coating film may be deteriorated, which is not preferable. A fluorine-containing polymer having an acid value of about 2 to 200 mgKOH / g, particularly about 5 to 100 mgKOH / g is preferably used.

Further, it is preferable that at least a part of the above-mentioned hydroxyl group remains because it can react with the curing agent to obtain a coating film excellent in solvent resistance and the like. In particular, those containing a hydroxyl group at a hydroxyl value of about 80 to 150 mgKOH / g are preferably used.

The fluorine-containing copolymer of the present invention has a molecular weight of 30.
The range of 00 to 40,000 is preferable. Molecular weight 3000
If it is less than 1, it is not preferable because the weather resistance when formed into a coating film decreases. When the molecular weight is more than 40,000, the viscosity in an aqueous solution is too high, the coating property is deteriorated, and the coating film appearance is also deteriorated, which is not preferable.

Further, the fluoropolymer having a carboxyl group may be composed of only the polymerized unit based on the fluoroolefin as described above, the polymerized unit having a carboxyl group and the polymerized unit having a hydroxyl group, Further, another copolymerizable monomer may be copolymerized. Alkyl vinyl ether, alkyl allyl ether, alkyl vinyl ester, alkyl allyl ester, fluoroalkyl vinyl ether, etc. may be appropriately copolymerized depending on desired physical properties of the coating film (hardness, gloss, pigment dispersibility, etc.). Even when these monomers are copolymerized, it is preferable that the content ratio of the polymerized unit based on the fluoroolefin, the acid value, and the hydroxyl value are within the above ranges.

In the present invention, at least a part of the carboxyl groups of the fluoropolymer having a carboxyl group is neutralized with a basic compound having a boiling point of 200 ° C. or less.
Examples of such a basic compound include ammonia, or primary and secondary compounds such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine and dibutylamine. Alkanolamines such as primary to tertiary alkylamines, monoethanolamine, monoisopropanolamine, dimethylaminoethanol and diethylaminoethanol, diamines such as ethylenediamine, propylenediamine, tetramethylenediamine, hexamethylenediamine,
There are alkyleneimines such as ethyleneimine and propyleneimine, piperazine, morpholine, pyrazine and pyridine.

The component (B) is a component which acts as a curing agent. As the component (B), a curing agent having a functional group capable of reacting with a hydroxyl group is preferably used, and examples thereof include a melamine resin, an isocyanate compound, a phenol resin, a xylene resin, and a toluene resin. Isocyanate compounds are preferable because a coating film having excellent weather resistance and mechanical properties can be easily obtained.

Examples of the melamine resin include alkyl etherified melamine resins such as methyl etherified, butyl etherified, and isobutyl etherified,
From the viewpoint of water solubility, a melamine resin at least a part of which is methyl etherified is preferable.

Blocked isocyanates are preferably used as the isocyanate compound, and examples of such blocked isocyanates include hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4'-.
Burette type adducts such as diphenylmethane diisocyanate and 4,4′-methylenebis (cyclohexyl isocyanate), isocyanuric ring type adducts,
Examples include block products such as polyhydric alcohol adducts.
Among these, non-yellowing type ones such as hexamethylene diisocyanate type, isophorone diisocyanate type, tolylene diisocyanate type, xylylene diisocyanate type are preferable from the viewpoint of weather resistance. Particularly, hexamethylene diisocyanate-based or isophorone diisocyanate-based ones are preferable.

As the blocking agent for the blocked isocyanate, those usually used, for example, phenol type, alcohol type, oxime type, lactam type, active methylene type and the like can be mentioned.

Examples of the anionic and nonionic antifoaming agents as the component (C) include fatty acid salts, higher alcohol sulfates,
Liquid fatty oil sulfates, sulfates of fatty amines and amids, fatty alcohol phosphates, sulfonates of dibasic fatty acid esters, fatty acid amide sulfonates, alkylallyl sulfonates, formalin condensation Naphthalene sulfonates, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters,
Examples thereof include polyoxyethylene sorbitan alkyl esters, acrylic polymers, silcon mixed acrylic polymers, vinyl polymers, and polysiloxane compounds.

Among these defoaming agents, the defoaming effect depends on the balance between the hydrophilic group and the hydrophobic group (HLB value), and those having HLB of 6 or less, particularly 4 or less are preferably adopted.

The fluorine-containing polymer (A) and the compound as the component (B) have a nonvolatile content of 50 to 95% by weight of the component (A) and 5 to 50% by weight of the component (B). It is preferably a ratio. The aqueous coating composition of the present invention,
The above-mentioned fluoropolymer (A), curing agent (B), defoaming agent (C) and water (D) are essential components. Here, in order to enhance the stability of the water-based coating composition, it is possible to add a water-soluble organic solvent.

Specifically, methanol, ethanol, n
-Propanol, isopropanol, n-butanol,
Alcohols such as isobutanol, secondary butanol, tertiary butanol, pentanol, etc., methyl cellosolve, ethyl cellosolve, isopropyl cellosolve,
Cellosolves such as butyl cellosolve, secondary butyl cellosolve, propylene glycol methyl ether,
A propylene glycol derivative such as dipropylene glycol methyl ether or propylene glycol methyl ether acetate, or ethylene glycol ethyl ether acetate is used. The amount of organic solvent of the water-based coating composition,
It is used in the range of 2.5 to 150% by weight with respect to the coating film forming component.

The aqueous coating composition of the present invention is usually used by adjusting the resin solid content concentration to a range of about 3 to 50% by weight. At this time, conventional colorants, pigments, ultraviolet absorbers, paint additives and the like can be mixed and used.

Particularly when used as a top coat as a transparent paint, the ultraviolet absorber used in the present invention includes, for example, methyl salicylate, phenyl salicylate, cresyl salicylate,
Salicylates such as benzyl salicylate;

2-hydroxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-5-chlorobenzophenone, 2-aminobenzophenone and T from Adeka Argus Co. Benzophenones such as high molecular weight modified products sold as -57;

2- (2'-hydroxy-5'-t-butylphenyl) benzotriazole, 2- (2'-hydroxy-5'-t-butylphenyl) -5-chlorobenzotriazole, 2- (2 '-Hydroxy-5'-methoxyphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-neopentylphenyl) benzotriazole, and Tinuvin 90 from Ciba-Geigy.
Benzotriazoles such as high molecular weight modified products sold as 0, 1130;

Substituted acrylonitriles such as ethyl 2-cyano-3,3-diphenylacrylate, 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, and methyl α-cyano-β-methyl-4-methoxycinnamate. ;

2,2'-thiobis (4-octylphenolate) nickel complex salt, {2,2'-thiobis (4-t
-Octylphenolate)}-n-butylamine / nickel complex salt such as nickel complex salt;

An ultraviolet absorber group such as dimethyl p-methoxybenzylidene malonate, resorcinol monobenzoate, hexamethylphosphoric triamide, 2,5-diphenyl-p-benzoquinone and bis (2,2,6,6-
Tetramethyl-4-piperidine) sebacate, dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, 2- (3,5-di-succinate) t-Butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,2)
6,6-pentamethyl-4-piperidyl) and the like, and these may be used alone or in combination as a mixture of two or more.

The ultraviolet absorber is preferably used in the range of about 0.1 to 15 parts by weight per 100 parts by weight of the fluoropolymer. If the amount of the ultraviolet absorber is too small, the effect of improving the light resistance cannot be sufficiently obtained, and if it is too large, the effect is saturated, which is not appropriate.

Further, examples of the light stabilizer include hindered amine compounds such as MARK LA 57,62,63,67,68 manufactured by ADEKA ARGUS and TINUVIN 622LD manufactured by Ciba Geigy. These can also be used in combination with an ultraviolet absorber as one kind or a mixture of two or more kinds.

The aqueous coating composition of the present invention has a coating film baked at 100 to 250 ° C., preferably 120 to 230.
It has the advantage that it is achieved under the conditions of 60 to 1 minute at ° C.

When it is necessary to adjust the gloss of the coating film, a conventional inorganic or organic matting agent may be added. When coloring is required, a commercially available organic pigment, inorganic pigment, organic dye, and a pigment or dye in which these are combined may be dispersed or mixed and added.

[0043]

EXAMPLES Examples will be shown below to more specifically describe the present invention. The parts in the examples are parts by weight unless otherwise specified.

Synthesis Example [Synthesis Example of Fluorine-Containing Polymer] According to the method described in JP-B No. 60-21686, copolymerization is carried out with the monomer composition shown in Table 1, and then described in JP-B No. 61-49323. Modification was carried out by the above method to obtain a fluorocopolymer.

[0045]

[Table 1]

The abbreviations in Table 1 are as follows. CTFE: Chlorotrifluoroethylene TFE: Tetrafluoroethylene CHVE: Cyclohexyl vinyl ether HBVE: Hydroxybutyl vinyl ether EVE: Ethyl vinyl ether

Example 1 A-1 in Table 1 was used as the fluorinated copolymer, and 43 parts of butoxyethanol was added to 100 parts of the fluorinated copolymer to prepare a varnish.
And 166.6 parts of deionized water are added to prepare a fluorocopolymer aqueous solution. 312.5 parts of the resin aqueous solution, 50 parts of hexamethoxymethylol melamine nicarac MW30 (manufactured by Sanwa Chemical Co., Ltd.), surface modifier BYK335 (BY
K Chemy) 0.5 part, antifoaming agent BYK080 (BYK Chemy) 1.0 part, UV absorber Tinuvin 1130 (Ciba Geigy) 3.0 parts, light stabilizer Sanol LS765
A composition was prepared by stirring and mixing 0.5 part (manufactured by Sankyo).
This composition was diluted with deionized water to a Ford Cup No. 4 was diluted to 26 seconds / 20 ° C. to obtain a composition B-1.

Examples 2 to 4 In the same manner as in Example 1, the composition B-based on the formulation of Table 2 was used.
2-B-4 were prepared.

Comparative Example 1 154 parts of a xylene solution of the fluorine-containing copolymer A-4, methylcametilol melamine nilacac MW-12LF
(Manufactured by Sanwa Chemical Co., Ltd.) 0.5 part, antifoaming agent BYK065 (B
YK Chemie) 0.5 parts, UV absorber Tinuvin 113
0 (manufactured by Ciba Geigy) 3.0 parts, light stabilizer Sanol LS
765 (manufactured by Sankyo) was stirred and mixed to obtain a composition B-5.
Was prepared.

Comparative Example 2 Composition B-6 was prepared in the same manner as in Example except that 250 parts of water-soluble acrylic resin Watersol S-745 (manufactured by Dainippon Ink) was used instead of the aqueous fluorocopolymer solution. Prepared.

[0051]

[Table 2]

In Table 2, X is a water-soluble acrylic resin Watersol S-745 (manufactured by Dainippon Ink), and A is
Nikarac MW30 (manufactured by Sanwa Chemical), B is Neo
RezR990 (Water-soluble blocked isocyanate manufactured by ICI), C is Cymel 303 (partially methylated melamine resin manufactured by Mitsui Cyanamid), and D is Uban 20S.
E Mitsui Toatsu's melamine resin), a is BYK080
(Manufactured by BYK Chemie), b is DISPARLON EXK-51
(Kunumoto Kasei Co., Ltd. nonionic defoamer), c is Efka
-27 (Nonionic defoamer manufactured by EFCA), d is BY
K065 (manufactured by BYK Chemie).

[Production Example of Base Coat Paint] 10 parts of styrene, 35 parts of methyl methacrylate, 15 parts of ethyl acrylate, 25 parts of n-butyl methacrylate and 2 parts of acrylic acid were prepared using a polymerization initiator azobisisobutyronitrile. Polymerization in xylene gave an acrylic resin solution with a solid content of 48%. A solvent type base coat E-1 was prepared with the following composition using this acrylic resin solution.

Acrylic resin 200 parts Cymel 303 ¹⁾ 20 parts p-toluenesulfonic acid solution 4.0 parts Aluminum paste 7770N ²⁾ 10.0 parts Note 1) Melamine resin manufactured by Mitsui Cyanamid 2) Aluminum paste manufactured by Toyo Aluminum Co., Ltd. Next This base coat E-1 was diluted with a mixed solvent consisting of 50 parts of toluene and 50 parts of ethyl acetate so as to have a viscosity of 13.5 seconds (Ford cup # 4/20 ° C) and prepared for coating.

[Preparation of Test Plate and Its Evaluation] A cationic electrodeposition paint for automobiles was coated on a 0.8 mm thick dull steel plate which had been subjected to a zinc phosphate chemical conversion treatment, and baked at 170 ° C. for 30 minutes. Next, apply an intermediate coating for automobiles, and apply 3 at 140 ° C.
After baking for 0 minutes, it was sanded with # 800 sandpaper, dried, and degreased with white gasoline to prepare a test material.

On this material, base coating E-1
Was adjusted to a viscosity of 13.5 seconds and then coated with an air sprayer so that the dry film thickness was 16 μ, and allowed to stand at room temperature for 3 minutes, after which the aqueous clear coat paints of Examples and Comparative Examples were treated with deionized water for a viscosity of 28 seconds. It was diluted to (Ford cup # 4/20 ° C.) and wet-on-wet coated so that the dry film thickness was 30 μm.

Next, the test plate was 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. Examples 1 to 4 and Comparative Example 1 thus obtained
Tables 3 and 4 show the results of evaluating the coating film performance and the amount of discharged solvent for each of the test plates Nos.

[0058]

[Table 3]

[0059]

[Table 4]

1) The scratch hardness was measured using a Mitsubishi pencil Uni. 2) Put the test plate in a thermo-hygrostat at 50 ° C. × 98% RH for 120 hours, and evaluate the state of the coated surface immediately after removal. 3) Regular gasoline (made by Nippon Oil Co., Ltd.) 24 at 20 ℃
After immersion for a period of time, the appearance is visually evaluated. 4) Spot 10% sulfuric acid 0.3cc on the coated surface, 20 ℃
After leaving it for 24 hours, it was washed with water and the coated surface was observed. 5) 0.3 cc of 10% sodium hydroxide aqueous solution was spotted on the coated surface, left at 20 ° C. for 24 hours, washed with water, and the coated surface was observed. 6) The coating film after accelerated exposure with QUV for 3000 hours was observed to evaluate the gloss retention rate. Comparative Example 2 caused cracks at 2000 hours. 7) 0.15 ml of water droplets were spotted on the coated surface and the contact angle was measured. 8) The amount of the organic solvent discharged when forming a coating film of 1 m ² and the solution type coating material are 100.

[0061]

EFFECT OF THE INVENTION The water-based coating composition of the present invention reduces the amount of organic solvent discharged in accordance with the regulation of solvent discharge, and has weather resistance,
It is extremely useful as a coating composition that gives a maintenance-free coating film having high functionality required for top coatings such as water repellency and chemical resistance, and contributes to global environment protection and resource protection by improving durability.

Claims (4)

[Claims] 1. A copolymer of (A) a fluoroolefin and an ethylenically unsaturated compound, containing 30 to 70% of a polymerized unit based on a fluoroolefin, and having a hydroxyl value of 3
Fluorine-containing copolymer obtained by neutralizing at least a part of the carboxyl groups of the fluorine-containing copolymer having 0 to 200 mgKOH / g, acid value of 2 to 200 mgKOH / g, and number average molecular weight of 3000 to 40,000 with a basic compound. Aqueous solution or dispersion (B) Water-soluble or water-dispersible melamine resin or water-soluble or water-dispersed blocked isocyanate (C) Anionic or nonionic defoamer (D) Water The above (A) to (D) are added. 50% to 95% by weight of the component (A) in the composition of non-volatile components, (B)
An aqueous coating composition containing 5 to 50% by weight of components. 2. The aqueous coating composition according to claim 1, wherein the component (B) is a melamine resin at least partially methylated. 3. The aqueous coating composition according to claim 1, wherein the component (B) is a hexamethylene diisocyanate-based or isophorone diisocyanate-based blocked isocyanate. 4. The aqueous coating composition according to claim 1, wherein the component (C) is an antifoaming agent having an HLB of 6 or less.