JPH08104829A - Ordinary temperature curable one pack type aqueous coating composition - Google Patents

Abstract

PURPOSE: To obtain the subject composition comprising a specific aqueous emulsion, an aqueous dispersion and a catalyst for accelerating a Michael reaction, capable of satisfying both storage stability and crosslinkability at ordinary temperature, giving excellent coating films, and capable of being utilized for the Michael addition reaction. CONSTITUTION: This composition comprises (A) the aqueous emulsion of an acrylic copolymer having plural active methylene groups in the molecule, (B) the aqueous solution or aqueous dispersion of a compound having plural ethylenically unsaturated bonds in the molecule, and (C) a catalyst capable of accelerating the Michael reaction between the components A and B. The component A is obtained by emulsion-copolymerizing (i) an active methylene group-having acrylic monomer, concretely 2-acetylacetoxyethyl (meth)acrylate, with (ii) an ethylenically unsaturated monomer capable of being copolymerized with the component (i), and has an active methylene group concentration of at least 0.1-mmol/g in the solid content. The component B is preferably a (meth) acrylate ester of a polyhydric alcohol.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION The present invention relates to a room temperature curable one-part aqueous coating composition.

From the viewpoint of resource saving and environmental protection, water-based coatings containing no organic solvent are of interest. Widely used emulsion paints have a film-forming mechanism that physically fuses emulsion particles by evaporation of water after coating, and is therefore suitable for bake-curing paints in terms of coating performance such as water resistance, solvent resistance, and chemical resistance. It does not reach. A system utilizing a crosslinking reaction at room temperature by a crosslinking agent, especially a system designed to have a high crosslinking density, generally has to be a two-component type. This is because such a system cannot be stably stored for a long period of time when it is a one-component system.

A system utilizing a Michael addition reaction in which an active methylene group is added to a polarized double bond such as an α, β-unsaturated carbonyl group as a curing mechanism does not generate a reaction by-product and is newly formed. It has excellent characteristics such that the formed bond is a chemically stable carbon-carbon bond. Even in this system, if it is a one-liquid type, it does not have long-term storage stability.

For example, an acrylic polymer having a plurality of acetoacetate pendant groups introduced into a polymer skeleton, which is disclosed in US Pat. No. 4,408,018, is crosslinked using a basic catalyst such as trimethylolpropane triacrylate. A system that is crosslinked with a monomer lacks long-term storage stability when it is made into a one-liquid type instead of allowing the crosslinking reaction to proceed at room temperature.

The system disclosed in JP-A-5-247372, which does not contain a catalyst for crosslinking a resin having an α, β-unsaturated carbonyl group capable of Michael addition with an active methine compound, has no problem in storage stability. However, the crosslinking reaction does not proceed unless it is heated to 100 ° C. or higher.

Japanese Unexamined Patent Publication (Kokai) No. 6-234954 discloses an aqueous coating composition utilizing the Michael reaction as a curing mechanism.
Although the composition is said to be curable at low temperatures, such as 60 ° C, at least one of the Michael reaction component and the catalyst must be stored separately from the other components until just prior to use.

A curing system utilizing the reaction of a carbonyl group and a hydrazide group is also known. For example, Japanese Patent Laid-Open No. 2-15
No. 5956 discloses a room temperature crosslinkable one-part aqueous coating composition obtained by adding a polyhydrazide compound to an emulsion of a carbonyl group-containing copolymer. Even in this system, if it is designed so that a high crosslink density can be obtained, storage stability cannot be obtained. Furthermore, in this system, since the bond newly formed by crosslinking is a Schiff base type bond, it is more easily chemically decomposed than the carbon-carbon bond formed by the Michael addition reaction, and the coating performance, especially the acid resistance Is not enough.

Therefore, the present invention is capable of achieving both storage stability and room temperature crosslinkability, and gives excellent coating performance.
Provided is a room temperature curable one-part water-based coating composition utilizing a Michael addition reaction.

DISCLOSURE OF THE INVENTION The present invention relates to (a) an aqueous emulsion of an acrylic copolymer having a plurality of active methylene groups in the molecule, (b) an aqueous solution of a compound having a plurality of ethylenically unsaturated bonds in the molecule. Alternatively, provided is a room temperature curable one-component water-based coating composition comprising an aqueous dispersion and (c) a catalyst that promotes the Michael reaction between the components (a) and (b).

Preferred Embodiment (a) Component The acrylic copolymer having a plurality of active methylene groups is an acrylic monomer having an active methylene group, such as 2-acetoacetoxyethyl (meth) acrylate or 2-cyanoacetoxyethyl (meth). Acrylate, N- (2-
Cyanoacetoxyethyl) acrylamide, N- (2-
Propionylacetoxybutyl) acrylamide, N-
(4-acetoacetoxymethylbenzyl) acrylamide, N- (2-acetoacetylaminoethyl) acrylamide, 2- (N-acetoacetylaminoethyl) (meth) acrylate, and other acrylic and / or non-acrylic monomers Can be produced by copolymerizing

Acrylic monomers that can be used for the copolymerization include methyl, ethyl, propyl, n-butyl, i-butyl, t-butyl of acrylic acid or methacrylic acid,
2-ethylhexyl, lauryl, phenyl, benzyl,
2-hydroxyethyl, 2-hydroxypropyl ester, Praxel FM-1 (addition product of 2-hydroxyethyl acrylate and polycaprolactone, manufactured by Daicel Chemical Industries, Ltd.), acrylamide, and N-methylolacrylamide. There are derivatives, acrylonitrile, and the like, and non-acrylic monomers include styrene, α-methylstyrene, itaconic acid, maleic acid, vinyl acetate, and the like. A smaller proportion of polyfunctional monomer,
For example, divinylbenzene, polyhydric alcohol poly (meth)
Acrylate may be included. The addition of polyfunctional monomers allows the crosslink density of the coating to be increased or the proportion of active methylene group containing monomers to be correspondingly reduced to obtain the desired level of crosslink density.

For use in aqueous coating compositions, the monomer mixture is copolymerized by emulsion polymerization in an aqueous medium using conventional emulsifiers and polymerization initiators. The emulsifiers can be customary anionic, cationic, nonionic or amphoteric surfactants. As the initiator, potassium persulfate, ammonium persulfate, 4,4′-azobis (4-cyanovaleric acid, 2,2′-azobis (2-methylpropionamidine) dihydrochloride (V-50), 2,2 ′ -Azobis (N, N'-dimethyleneisobutyroamidine) (VA
Water-soluble initiators such as -061) are used. As the emulsifier, a commercially available reactive emulsifier such as Antox
MS-60 (Nippon Emulsifier), Aqualon HS-10
(Daiichi Kogyo Seiyaku Co., Ltd.), ADEKA RIASOAP SE-10N (Asahi Denka Kogyo), or the like may be used.

The active methylene concentration in the component (a) is generally 0.1 to 20 mmol / g in the solid content, but it is preferably at least 1 mmol / g when a high crosslinking density is desired.

A compound having two or more radically polymerizable ethylenically unsaturated groups in the component (b) molecule can be used. As an example thereof, a polymerizable unsaturated monocarboxylic acid ester compound of polyhydric alcohol (for example, ethylene glycol diacrylate,
Ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,4-butanedioldi Acrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, pentaerythritol diacrylate, pentaerythritol dimethacrylate, pentaerythritol triacrylate, Pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol Lumpur tetra methacrylate, glycerol diacrylate, glycerol dimethacrylate, glycerol Acro alkoxy dimethacrylate,
1,1,1-Trishydroxymethylethane diacrylate, 1,1,1-Trishydroxymethylethane dimethacrylate, 1,1,1-Trishydroxymethylethane triacrylate, 1,1,1-Trishydroxymethylethane Trimethacrylate, 1,1,1-trishydroxymethylpropane diacrylate, 1,
1,1-trishydroxymethylpropane dimethacrylate, etc.), polymerizable unsaturated alcohol ester compounds of polybasic acid (eg, diallyl terephthalate, diallyl phthalate, triallyl trimellitate, etc.), substituted with two or more vinyl groups Aromatic compounds (for example, divinylbenzene), adducts of epoxy group-containing ethylenically unsaturated monomer and carboxyl group-containing ethylenically unsaturated group monomer (for example, glycidyl acrylate or glycidyl methacrylate and acrylic Acid, methacrylic acid,
Crotonic acid, a reaction product with maleic acid, etc.).

These ethylenically unsaturated compounds may be used alone or in admixture of two or more.

The (meth) acrylate of a polyhydric alcohol / ethylene oxide adduct, for example, trimethylolpropane-ethylene oxide adduct triacrylate (TMPTA-30E manufactured by Shin-Nakamura Chemical Co., Ltd.) is water-soluble (b).
It is an example of an ingredient.

As a method for preparing the component (b) as an aqueous dispersion for use in an aqueous coating composition, a conventional emulsifier or dispersion stabilizer may be used to mechanically emulsify or disperse in an aqueous medium.

There are many known catalysts that promote the Michael addition reaction of the component (c) . They are alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, alkali metal carbonates such as potassium carbonate and sodium carbonate, quaternary ammonium bases and their carbonates, organic acid salts and halides.

Although quaternary ammonium compounds having various cation moieties can be used, tetraalkylammonium salts and trialkylaralkylammonium salts in which at least a part of alkyl groups may be substituted with hydroxyl groups are easily available. You may use the quaternary ammonium salt of nitrogen-containing heterocyclic compounds, such as pyridine, piperidine, piperazine, and morpholine. Specifically, tetrabutylammonium, tetramethylammonium, tetraethylammonium, trimethylbenzylammonium, tetrapropylammonium, tetrahexylammonium, tetraoctylammonium, tetradecylammonium, tetrahexadecylammonium, triethylhexylammonium, 2-hydroxyethyltrimethylammonium. (Choline), methyltrioctylammonium, cetyltrimethylammonium, 2-chloroethyltrimethylammonium, and methylpyridinium.

The counter anion is hydroxide, halide, carboxylate, sulfonate, sulfate and the like. Specific examples thereof include acetate, laurate, glycolate, benzoate, salicylate, chloride, bromide, iodide, methanesulfonate, p-toluenesulfonate, dodecylbenzenesulfonate, triflate, nitrate, sulfate and methosulfate.

When a quaternary ammonium salt is used, an epoxy compound can be used in combination as disclosed in Japanese Patent Application No. 5-292736 of the present applicant.

Amidines and guanidines can also be used as catalysts. When the component (a) is produced by emulsion polymerization as described above, V-5 is used as an initiator.
By using an initiator having an amidine structure at the terminal, such as 0 or VA-061, the remaining amidine skeleton sufficiently exerts its function as a catalyst.

The coating composition (a) component, (b) component and (c) component can be blended as one liquid and need not be separately stored separately. One of the important advantages of the present invention is that the composition is stable for long-term storage but still retains curability at room temperature. Of course, curing under heating conditions is also possible.

The ratio of component (a) / component (b) is, of course, preferably a stoichiometric ratio, but fluctuations in the molar ratio of functional groups in the range of 3/1 to 1/3 are permissible. It
The addition amount of the component (c) is 0.1 to 10% with respect to the total solid content weight of the component (a) and the component (b).

The coating composition of the present invention comprises a conventional extender pigment,
Color pigments, organic solvents for adjusting film-forming properties, surface conditioners,
Conventional additives such as defoamers, viscosity modifiers and the like can be included.

The production examples, examples and comparative examples are shown below, in which "part" and "%" are based on weight.

Production Example 1 In a flask equipped with a stirrer, a condenser tube and a dropping funnel,
Charge 200 parts of deionized water and 1.2 parts of Antox MS-60 (reactive emulsifier manufactured by Nippon Emulsifier Co., Ltd.)
The temperature was raised to ° C. Then, an initiator comprising 120 parts of deionized water and 1.2 parts of potassium persulfate, 280 parts of deionized water,
A monomer pre-emulsion prepared in advance from 3.2 parts of Antox MS-60, 214 parts of acetoacetoxyethyl methacrylate, 40 parts of styrene, 76.4 parts of methyl methacrylate, 69.6 parts of 2-ethylhexyl acrylate was added dropwise over 2 hours. . Then 80 contents
The temperature was kept at 1 ° C for 1 hour to obtain an emulsion. 2.5 more
% Tetramethylammonium hydroxide aqueous solution (60 parts) was added to adjust the pH to 7.5. 38% solids,
Particle size 130 nm (by laser light scattering method; the same applies hereinafter)

Production Example 2 An emulsion was obtained in exactly the same manner as in Production Example 1, except that the pH adjustment was carried out with an aqueous sodium hydroxide solution. Solid content 38%, particle size 130 nm

Production Example 3 An emulsion was obtained in exactly the same manner as in Production Example 1, except that the pH was adjusted with an aqueous dimethylaminoethanol solution. Solid content 38%, particle size 130 nm

Production Example 4 In Production Example 1, the aqueous initiator solution was replaced with deionized water 120.
Parts, 1.2 parts of azobiscyanovaleric acid, and 0.78 parts of tetramethylammonium hydroxide, except that the solution was changed to obtain an emulsion in exactly the same manner. Solid content 38%, particle size 180 nm

Production Example 5 First, a cationic reactive emulsifier was produced from N, N'-dimethylaminoethyl methacrylate and lauryl bromide (solid content 100%). Next, the flask used in Production Example 1 was charged with 150 parts of deionized water and 3 parts of the above cationic emulsifier, and the temperature was raised to 80 ° C. Next, 90 parts of deionized water, V-50 (2,2'-azobis (2 manufactured by Wako Pure Chemical Industries, Ltd.
-Methylpropionamidine) dihydrochloride) 1.5 parts of an aqueous initiator solution, 210 parts of deionized water, 12 parts of the above cationic emulsifier, 160.5 parts of acetoacetoxyethyl methacrylate, 30 parts of styrene, 57. 3 parts, 2-ethylhexyl methacrylate 5
A monomer pre-emulsion prepared in advance from 2.2 parts was added dropwise over 2 hours and then kept at 80 ° C. for 1 hour to obtain an emulsion. Solid content 37%, particle size 220 nm

Production Examples 6 to 8 In Production Example 1, acetoacetoxyethyl methacrylate (AAEM), styrene (ST), methyl methacrylate (MMA), 2-ethylhexyl acrylate (2
-EHA) and an emulsion was obtained in the same manner as in Production Example 1, except that the following monomer mixture consisting of ethylene glycol dimethacrylate (EGDM) was used.

Monomer (part) Production Example 6 Production Example 7 Production Example 8 AAEM 42 8 8 ST 40 40 40 MMA 148.4 182.4 162.4 2-HEA 169.6 169.6 149.6 EGDM ─── ─── 40

Production Example 9 104 parts of acetoacetoxyethyl methacrylate, 64 parts of styrene, 120 parts of methyl methacrylate and 2-ethylhexyl acrylate 1 as a monomer mixture.
Solid content 3 in the same manner as in Production Example 1 except that 12 parts were used.
An emulsion having 8% and a particle diameter of 140 nm was obtained.

Production Example 10 As a monomer mixture, 104 parts of acetoacetoxyethyl methacrylate, 64 parts of styrene, 120 parts of methyl methacrylate and 1 part of 2-ethylhexyl acrylate.
12 parts were used and 60 parts of 7.1% tetrabutylammonium hydroxide aqueous solution was used for neutralization, the same as in Example 1 except that the solid content was 39% and the particle size was 14
A 0 nm emulsion was obtained.

Production Example 11 (solvent type resin varnish for comparative example) 240 parts of methoxypropanol were charged into the flask used in Production Example 1 and the temperature was raised to 110 ° C. Next, 152.6 parts of acetoacetylethyl methacrylate, 154.6 parts of methyl methacrylate, 92.9 parts of 2-ethylhexyl acrylate, Kayaester O (manufactured by Kayaku Akzo Co., Ltd.
-Butyl peroctoate) was added dropwise over 3 hours, and then the mixture was kept at 110 ° C for 1 hour. Next, a mixture of 2 parts of Kayaester O and 18 parts of methoxypropanol was added dropwise over 30 minutes, and 110 minutes for another 90 minutes.
The temperature was kept at 0 ° C. to obtain a resin varnish. Solid content 62%, number average molecular weight 5000 (according to GPC method)

Production Example 12 (Emulsion for Comparative Example) The flask used in Production Example 1 was charged with 68 parts of deionized water and Kotamin 86P Conc (cationic emulsifier manufactured by Kao).
6 parts were charged and the temperature was raised to 80 ° C. Then deionized water 9
A monomer prepared in advance from an initiator aqueous solution consisting of 0 part and 0.5 part of V-50, 100 parts of deionized water, 3 parts of Kotamine 86P conc, 40 parts of diacetone acrylamide, 16 parts of styrene and 44 parts of 2-ethylhexyl acrylate. Pre-emulsion is added dropwise over 2 hours, then 1
The emulsion was obtained by holding at 80 ° C. for an hour. Solid content 28
%, Particle size 230 nm

Production Example 13 10 parts of 10% polyvinyl alcohol aqueous solution, 60 parts of trimethylolpropane triacrylate (TMPTA),
A TMPTA dispersion was prepared from 30 parts of deionized water. T
MPTA content 60%

Production Example 14 816 parts of ethoxypropanol, acrylic acid 61.2
Part, methacrylic acid 438 parts, 2-ethylhexyl acrylate 460.8 parts, styrene 240 parts, Kayaester O 21.6 parts by an acid value by solution polymerization
A polymer dispersant having a solid content of 60% was prepared. Next, 75 parts of the above dispersant, 11.4 parts of a 25% tetramethylammonium hydroxide aqueous solution, and 105 parts of TMPTA were mixed, and 258 parts of deionized water was further added to the mixture, and
A dispersion was prepared. TMPTA content 23%

Production Example 15 (hydrazide curing agent for comparative examples) 174.2 parts of dimethyl adipate, 100.1 parts of hydrazine hydrate, 224 parts of deionized water at 80 ° C.
Adipic acid dihydrazide was produced over time.

Production Example 16 (Pigment Dispersion) SMA-1440 (Pigment Dispersion Resin with Acid Value 180, AT
10% 25% aqueous solution obtained by neutralizing OCHEM) with an equivalent amount of tetramethylammonium hydroxide 10.
Parts, titanium dioxide 100 parts, and deionized water 33 parts to obtain a pigment dispersion. Titanium dioxide content 70%

Production Example 17 (Pigment Dispersion) A pigment dispersion having a titanium dioxide content of 70% was obtained in the same manner as in Production Example 16 except that tetrabutylammonium hydroxide was used as the neutralizing agent.

Example 1 26.4 parts of the emulsion of Preparation Example 1 and TM of Preparation Example 13
4.2 parts of the PTA dispersion liquid was mixed to obtain a clear paint.
This coating was applied on a glass plate with an 8 mil doctor blade and dried at room temperature for 1 week. Methyl ethyl ketone rubbing test (20 times and 50 times) for this coating film
I went. Storage stability was also tested at 40 ° C. 1
There was no change in the paint condition after a month. Rubbing test (20)
Times). The results are shown in Table 1.

Examples 2 to 10 The component (a) emulsion and the component (b) dispersion were mixed to obtain clear paints shown in Table 1. Using this paint, a rubbing test and a storage stability test were conducted in the same manner as in Example 1. The results are shown in Table 1.

[0045]

[Table 1]

Example 11 A dispersion having an epoxy compound content of 60% was prepared from 60 parts of diglycidyl phthalate, 10 parts of a 10% aqueous polyvinyl alcohol solution and 30 parts of deionized water. Next, 26.4 parts of the emulsion of Production Example 3 and TMPT of Production Example 13
A dispersion 4.2 parts, 5% tetrabutylammonium bromide aqueous solution 1.6 parts, the above epoxy compound dispersion 1.
4 parts were mixed to obtain a clear paint. When a rubbing test and a storage stability test were carried out in the same manner as in Example 1 using this paint, all were good.

Example 12 26.4 parts of the emulsion of Preparation Example 1 and TM of Preparation Example 13
4.2 parts of PTA dispersion and 15 parts of pigment dispersion of Production Example 16 were mixed to obtain an enamel coating. When a rubbing test and a storage stability test were carried out in the same manner as in Example 1 using this paint, all were good.

Example 13 26.4 parts of the emulsion of Production Example 9 and TM of Production Example 13
4.2 parts of PTA dispersion and 15 parts of pigment dispersion of Production Example 16 were mixed to obtain an enamel coating. When a rubbing test and a storage stability test were carried out in the same manner as in Example 1 using this paint, all were good.

Example 14 26.4 parts of the emulsion of Preparation Example 10 and T of Preparation Example 13
4.2 parts of MPTA dispersion, pigment dispersion 15 of manufacture example 17
The parts were mixed to give an enamel paint. When a rubbing test and a storage stability test were carried out in the same manner as in Example 1 using this paint, all were good.

Comparative Example 1 Example 1 using Cybinol NP-617 (non-crosslinked type normally dry acrylic emulsion paint manufactured by Saiden Chemical Co., Ltd.)
A rubbing test and a storage stability test were conducted in the same manner as in. The coating film was dissolved by rubbing with methyl ethyl ketone, and the base material of the glass plate was exposed. No abnormality was found in the storage stability test at 40 ° C. for 1 month.

Comparative Example 2 16.6 parts of varnish of Production Example 11 and 2.5 parts of TMPTA,
1 part of a 3% tetramethylammonium hydroxide aqueous solution was uniformly mixed to obtain a clear coating. This coating was applied on a glass plate with an 8 mil doctor blade and dried for 1 week. No abnormality was found in the methyl ethyl ketone rubbing test. When this paint was left at room temperature, it gelled in 1 hour.

Comparative Example 3 26.4 parts of the emulsion of Production Example 1 to which no tetramethylammonium hydroxide aqueous solution was added,
The same test as in Example 1 was carried out using a clear coating obtained by mixing 4.2 parts of the TMPTA dispersion of Production Example 13.
In the rubbing test, the coating film was dissolved and the glass plate substrate was exposed. No abnormality was found in the storage stability test.

Comparative Example 4 The emulsion of Production Example 12 and the hydrazide curing agent of Production Example 15 were mixed so that the carbonyl group and the hydrazide group would be equivalent to each other to obtain a clear coating. When this paint was used and tested in the same manner as in Example 1, slight rubbing marks were observed in the rubbing test. In the storage stability test, gelation occurred at 40 ° C for 2 days.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kei Aoki 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Toru Yagi 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Within the corporation

Claims (10)

[Claims] 1. An aqueous emulsion of (a) an acrylic copolymer having a plurality of active methylene groups in the molecule, (b) an aqueous solution or dispersion of a compound having a plurality of ethylenically unsaturated bonds in the molecule, and (C) A room temperature curable one-component aqueous coating composition comprising a catalyst that promotes the Michael reaction between the components (a) and (b). 2. The coating composition according to claim 1, wherein the component (a) is produced by emulsion polymerization of an acrylic monomer having an active methylene group and an ethylenically unsaturated monomer copolymerizable with the acrylic monomer. 3. The acryl monomer is 2-acetoacetoxyethyl (meth) acrylate, 2-cyanoacetoxyethyl (meth) acrylate, N- (2-propionylacetoxybutyl) acrylamide, N- (4-acetoacetoxymethylbenzyl). ) Acrylamide, N-
(2-acetoacetylaminoethyl) acrylamide,
Alternatively, the coating composition according to claim 2, which is selected from 2- (N-cyanoacetylamino) ethyl (meth) acrylate. 4. The coating composition according to claim 1, wherein the component (a) has an active methylene group concentration of at least 0.1 mmol / g in its solid content. 5. The coating composition according to claim 1, wherein the compound having a plurality of ethylenically unsaturated bonds in the molecule is an acrylic acid or methacrylic acid ester of a polyhydric alcohol. 6. The ratio of the component (a) to the component (b) is such that the molar ratio of active methylene: ethylenically unsaturated bond is 3: 1 to 1: 3. The coating composition of any one of. 7. The coating composition according to claim 1, wherein the component (c) is a quaternary ammonium base or a salt thereof. 8. The coating composition according to claim 1, wherein the component (c) is a combination of a quaternary ammonium salt and an epoxy compound. 9. The coating composition according to claim 1, wherein the component (c) is an organic or inorganic strong base. 10. The amount of the component (c) is 0.1 to 10 of the total solid weight of the components (a) and (b).
%, The coating composition according to any one of claims 1 to 10.