JPH11100544A - Thermosetting water-based coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition being excellent in storage stability and low- temperature setting properties and giving a cured film excellent in smoothness, salt spray resistance and flex resistance by including a resin having OH groups and COOH groups, an epoxy resin prepared by polymerizing a specified alicyclic epoxy-containing unsaturated compound and a quaternary ammonium compound. SOLUTION: This composition comprises a resin having OH groups and COON groups (e.g. a resin obtained from acrylic acid, hydroxyethyl acrylate, methyl acrylate and styrene), an epoxy resin prepared by polymerizing an alicyclic epoxy-containing unsaturated compound represented by the formula: R<2> -O- CO-NH-CH=CH-R<1> and a quaternary ammonium compound (e.g. tetraethylammonium hydroxide). In the formula, R<1> is H, an aromatic hydrocarbon group or (un)saturated aliphatic hydrocarbon group; R<2> is a group of formula II or III; R<4> and R<5> are each H, CH3 or C2 H5 ; m is 4-8; and n is 1-10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting aqueous coating composition comprising a polymer of a specific epoxy group-containing unsaturated compound and a quaternary ammonium compound in a vinyl resin or the like, and more particularly to a storage stability. And a thermosetting aqueous coating composition having excellent curability of a coating film.

[0002]

2. Description of the Related Art Water-based paints are widely used in various fields because water is a medium and does not use an organic solvent as a medium. For example,
As such an aqueous paint, a paint obtained by neutralizing a resin composition containing a hydroxyl group-containing polycarboxylic acid resin and an aminoaldehyde resin with an amine compound and then dispersing the same is known.

[0003]

However, conventional water-based paints need to be baked at a temperature of 180 ° C. or higher, and the resulting coating films have chemical and physical properties such as curability, weather resistance and acid resistance. There is a disadvantage that the properties are inferior. Further, in a conventional coating composition in which a bisphenol epichlorohydrin type epoxy resin is used in place of the aminoaldehyde resin, the coating system thickens and gels during storage, and does not provide a practical water-based coating.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies for the purpose of improving the storage stability of the water-based coating composition and the curability of the coating film in a well-balanced manner. It has been found that an aqueous coating composition containing a thermosetting resin composition obtained by blending a specific epoxy resin and a quaternary ammonium compound with a resin having a group can achieve the above object, and completed the present invention. I came to.

That is, the present invention provides a resin (A) having a hydroxyl group and a carboxyl group, an epoxy resin (B) obtained by polymerizing an alicyclic epoxy group-containing unsaturated compound represented by the following formula (1), It is intended to provide a thermosetting aqueous coating composition comprising a quaternary ammonium compound (C). Hereinafter, the present invention will be described in detail.

[0006]

Embedded image

[0007]

DETAILED DESCRIPTION OF THE INVENTION Resin (A) Resin (A) used in the thermosetting aqueous coating composition of the present invention.
Is not particularly limited as long as it has a hydroxyl group and a carboxyl group. For example, any resin conventionally known in the field of paints based on a vinyl resin, a polyether resin or the like can be used. Specifically, the following resins can be exemplified. (1) Vinyl Resin As the vinyl resin, a copolymer of a vinyl monomer having a hydroxyl group and a vinyl monomer having a carboxyl group can be exemplified. When the vinyl monomer contains a hydroxyl group and a carboxyl group, a homopolymer thereof can also be used. Examples of hydroxyl group-containing vinyl monomers include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, polycaprolactone diol mono (meth) acrylate, and polyoxyethylene glycol mono (meth) acrylate. A hydroxyl group-containing monomer can be exemplified. One or more of these vinyl monomers can be used in combination. As a vinyl monomer containing a carboxyl group,
Examples thereof include (meth) acrylic acid, carboxyethyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and β-carboxyethyl (meth) acrylate. In addition, modified unsaturated monocarboxylic acids such as adducts of (meth) acrylic acid and ε-caprolactone can also be used. Here, the modified unsaturated monocarboxylic acid is not particularly limited as long as it has an unsaturated group and a carboxyl group, and is a modified unsaturated monocarboxylic acid having a chain extended between the unsaturated group and the carboxyl group. For example, a compound obtained by lactone-modifying (meth) acrylic acid represented by the following formula (A) or a lactone-modified unsaturated monoester having a terminal hydroxyl group represented by the following formula (B) acid-modified with an acid anhydride has an ester bond. Examples thereof include carboxyl group-containing compounds such as carboxylic acids and modified unsaturated monocarboxylic acids having an ether bond represented by the following formula (C). Further, together with a carboxyl group-containing vinyl monomer, methyl (meth) acrylate, ethyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate may be used, if necessary. , Acrylonitrile, acrylamide, styrene, vinyl toluene, vinyl acetate, i-propyl vinyl ether, n-
Examples thereof include those obtained by copolymerizing a radical polymerizable unsaturated group-containing monomer having no functional group that reacts with a hydroxyl group or a carboxyl group such as butyl vinyl ether or methoxyethyl vinyl ether. In addition, each vinyl monomer can be used alone or in combination of two or more.

[0008]

Embedded image

(2) Polyester resin As polyester resin, for example, trimethylolethane, trimethylolpropane, pentaerythritol,
Polyol components such as glycerin, ethylene glycol, propylene glycol, 1,3-butylene glycol, neopentyl glycol, 1,6-hexanediol, and (phthalic anhydride), isophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and adipine Acid, (anhydrous)
Polyester resin obtained by polycondensation with a polycarboxylic acid component such as trimellitic acid; Modified polyester resin with fatty acid or epoxy resin; Modified polyester resin grafted with acryl; Modified bisphenol / epichlorohydrin type epoxy resin with fatty acid Modified polyester resin obtained by adding an acid anhydride such as maleic anhydride to the obtained esterified product; examples include those obtained by polymerizing a bisphenol / epichlorohydrin type epoxy resin in the presence of a catalyst and adding a polycarboxylic acid or the like. it can. Among the above-mentioned resins (A), a coating film having excellent aesthetics, weather resistance, etc. can be obtained, and thus can be obtained by polymerizing with a hydroxyl group-containing vinyl monomer and a carboxyl group-containing vinyl monomer and, if necessary, other monomers. Vinyl resins are particularly preferred.

The resin (A) has a number average molecular weight of 1,000.
~ 100,000, especially 2,000 ~ 8
It is preferable that the softening point is 130 ° C. or lower, particularly 115 ° C. or lower, and the acid value is 1 to 100, particularly preferably 10 to 80. Is preferably 10 to 5,000, particularly preferably 20 to 2,000. When the number average molecular weight is less than 1,000, the coating properties such as hardness, flex resistance and corrosion resistance are liable to decrease, while the number average molecular weight is 10
If it exceeds 000, the appearance of the coating film such as smoothness tends to deteriorate. If the softening point is higher than 130 ° C., the coating film tends to have poor smoothness. On the other hand, when the acid value is less than 1, it is difficult to make the composition aqueous, and when the acid value is more than 100, the storage stability of the coating material is deteriorated, and the hydroxyl value is 10 or less.
If the value is smaller, the curability of the coating film decreases, and the film performance such as hardness and bending resistance tends to decrease. On the other hand, if the hydroxyl value is more than 5,000, the film performance such as water resistance and corrosion resistance is observed. Is undesirably reduced.

In addition to the above-mentioned hydroxyl group and carboxyl group, functional groups such as phenolic hydroxyl group, alkoxysilane group and hydroxysilane group may be introduced into the resin (A) as required. The method for introducing these functional groups is not particularly limited, and a known method can be used.
For example, the phenolic hydroxyl group may be introduced by using bisphenol-modified (meth) acrylate as the vinyl monomer component of the vinyl resin. The alkoxysilane group or the hydroxysilane group may be introduced by using γ-methacryloxypropyltrimethoxysilane and Copolymerization may be performed using a compound such as a hydrolyzate as a vinyl monomer component of the vinyl resin.

Epoxy resin (B) Epoxy resin (B) used in the coating composition of the present invention
Is obtained by polymerizing the alicyclic epoxy group-containing unsaturated compound represented by the formula (1). In addition, besides the alicyclic epoxy group-containing unsaturated compound, the following compounds may be used in combination for copolymerization. Here, in the following compounds, R ⁷ is a linear or branched alkylene group,
That is, methylene, ethylene, propylene, trimethylene,
Examples include tetramethylene, ethylethylene, pentamethylene, and hexamethylene groups. Also, as R ⁸ ,
Examples include methylene, ethylene, propylene, trimethylene, tetramethylene, ethylethylene, pentamethylene, hexamethylene, polymethylene, phenylene, cyclohexylene, and p-xylylene groups.

[0013]

Embedded image

The epoxy resin (B) further includes, in addition to the alicyclic epoxy group-containing unsaturated compound and the above-mentioned other compounds, methyl (meth) acrylate, ethyl (meth) acrylate, i-propyl (meth) acrylate, The reaction between hydroxyl and carboxyl groups such as -butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, acrylonitrile, acrylamide, styrene, vinyltoluene, vinyl acetate, i-propyl vinyl ether, n-butyl vinyl ether, and methoxyethyl vinyl ether. The resulting radically polymerizable unsaturated group-containing monomer having no functional group can also be copolymerized.

The compound represented by the formula (1) is obtained by reacting a compound represented by the formula (5) with a hydroxyl group-containing compound represented by the following formula (4-1) or (4-2). It can be manufactured by the method of causing.

[0016]

Embedded image

The hydroxyl group-containing compound represented by the formula (4-1) is 3,4-epoxycyclohexylmethyl alcohol. Further, the hydroxyl group-containing compound represented by the formula (4-2) is a lactone polymer obtained by polymerizing lactone at a ratio of 1 to 10 mol with respect to 1 mol of 3,4-epoxycyclohexylmethyl alcohol. Equation (4-
The hydroxyl group-containing compound represented by 2) is specifically produced by ring-opening polymerization of a lactone such as ε-caprolactone by an ordinary method using an active hydrogen such as alcohol (compound (4-1)) as an initiator. be able to. As for the lactone, in addition to ε-caprolactone, valerolactone or the like may be homopolymerized, or ε-caprolactone and valerolactone may be copolymerized.

The compound represented by the formula (5) can be prepared, for example, by adding an acid chloride R ² —CH ＝ CH— to an aqueous solution of an alkali or alkaline earth metal salt represented by sodium azide as a metal azide. It can be obtained by reacting COCl. R ² is of the same groups as R ² of the compound represented by the formula (1) as the target compound. As for the reaction ratio between the metal azide and the acid chloride, it is preferable that the acid chloride is reacted in an amount of 0.01 to 1.5 mol per 1 mol of the metal azide. The reaction is carried out by dropping a solution of acid chloride in an aqueous solution of metal azide. The solvent for the acid chloride is not particularly limited, but ketones such as acetone and methyl ethyl ketone are preferred. In addition, the dripping into the metal azide aqueous solution,
The reaction can be performed at a temperature of -78 to 100 ° C, but is preferably performed at room temperature or lower in consideration of the stability of the metal azide.

The compound represented by the formula (1) is usually prepared by adding the hydroxyl group-containing compound represented by the formula (4-1) or (4-2) to 1 mol of the compound represented by the formula (5). 0.5 ~
It is produced by adding 10.0 mol and reacting. The reaction temperature is
From the relationship between the stability of the compound represented by the formula (5) and the reaction temperature, the temperature is preferably from 0 to 150 ° C. Further, a catalyst can be used for the reaction. Preferred catalysts include triethylamine and dimethylbenzylamine.
4 such as secondary amine and tetraethylammonium chloride
Examples include phosphines such as secondary amines and triphenylphosphine.

The epoxy resin (B) has a number average molecular weight of 1
94 to 100,000, especially 194 to 2,
000, particularly preferably 194 to 1,000, an epoxy equivalent of 50 to 2,000, particularly preferably 55 to 1,000, and a softening point of 1
It is preferably 30 ° C. or lower, particularly preferably 115 ° C. or lower. Those having a number average molecular weight of less than 100 are difficult to obtain, while those having a number average molecular weight of more than 100,000 are not preferred because the coated surface smoothness deteriorates. Those having an epoxy equivalent of less than 50 are difficult to obtain, while those having an epoxy equivalent of more than 2,000 tend to decrease the curability of the coating film. If the softening point is higher than 130 ° C., the smoothness of the coating film tends to deteriorate.

At least one selected from an epoxy group on the alicyclic hydrocarbon ring and an epoxy group directly bonded to a carbon atom forming the alicyclic hydrocarbon ring in combination with the epoxy resin (B). Those having at least two or more epoxy groups in one molecule can also be used. The alicyclic hydrocarbon ring may be from 3 to 7 or more ring members, and the ring may be monocyclic or polycyclic, and the ring may be an organic hydrocarbon ring. It may form a hydrogen ring. As specific examples of the epoxy resin (B) that can be used in combination,
The following bifunctional or higher epoxy resins can be exemplified.

[0022]

Embedded image

[0023]

Embedded image

Other epoxy resins having an epoxy group, such as a glycidyl ether type epoxy resin and an aliphatic internal epoxy resin, can be used in combination with the above epoxy resin (B). The other epoxy resin is preferably used in a proportion of 25% by weight or less based on the total amount of both, from the viewpoint of the storage stability of the paint and the curability of the coating film.

[0025] The quaternary ammonium compounds used in the quaternary ammonium compound coating composition of the present invention ^{(C) (R 20 R 21} R 22 R 23 N (+)) X (-) in what is shown Can be used. Where R ²⁰ , R
²¹ , R ²² and R ²³ each represent a hydrocarbon group;
These may be the same or different. Further, the hydrocarbon group may be substituted with a hydroxy group. X represents a halogen ion or an anionic residue of an acid.
1, Br, F, I, SO ₄ , HSO ₄ , NO ₃ , PO ₄ Cl
O ₄ , HCOO, CH ₃ COO, OH and the like can be exemplified.

The following compounds can be exemplified as preferred quaternary ammonium compounds (C) used in the present invention. Tetramethylammonium chloride, tetraethylammonium chloride, tetrabutylammonium chloride, methyltriethylammonium chloride,
Examples thereof include tetraalkylammonium halides such as tetramethylammonium bromide, tetraethylammonium fluoride, and tetraethyliodide. Examples thereof include tetraalkylammonium organic acid salts such as tetramethylammonium acetate and tetraethylammonium formate. Tetramethyl ammonium hydrogen sulfate, tetraethyl ammonium hydrogen sulfate, tetramethyl ammonium nitrate,
Examples thereof include tetraalkylammonium inorganic acid salts such as tetraethylammonium nitrate, tetraethylammonium perchlorate, and tetraethylammonium phosphate. Tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, tetraisoamylammonium hydroxide, tetradodecylammonium hydroxide, methyltriethylammonium hydroxide, ethyltrimethyl Ammonium hydroxide, decyltrimethylammonium hydroxide, monohydroxyethyltrimethylammonium hydroxide, monohydroxyethyltriethylammonium hydroxide, dihydroxyethyldimethylammonium hydroxide, dihydroxyethyldiethylammonium hydroxide, trihydroxyethylmonomethylammoniumhydro Sid, trihydroxyethyl monoethyl ammonium hydroxide, benzyltrimethylammonium hydroxide, benzyltriethylammonium hydroxide, benzyl methyl diethyl ammonium hydroxide, quaternary ammonium hydroxides, such as cyclohexyl trimethylammonium hydroxide can be exemplified. Among them, the quaternary ammonium hydroxide easily disperses the resin (A) and the epoxy resin (B) in water to give a coating composition having excellent storage stability, and has excellent water resistance and corrosion resistance. It is particularly preferable in that a coated film can be formed.

Thermosetting Water-Based Coating Composition The thermosetting water-based coating composition of the present invention has a resin (A) of 40 to 40 in terms of the total weight of the resin (A) and the epoxy resin (B).
97% by weight, preferably 50 to 95% by weight, more preferably 60 to 90% by weight, epoxy resin (B) 3 to 60% by weight, preferably 5 to 50% by weight, and more preferably 10 to 50% by weight.
It is preferable to mix within the range of ４０40% by weight. When the amount of the resin (A) is less than 40% by weight and the amount of the epoxy resin (B) is more than 60% by weight, the water dispersibility of the obtained coating composition is reduced. On the other hand, when the resin (A) is more than 97% by weight and the epoxy resin (B) is less than 3% by weight,
Film performance such as water resistance, corrosion resistance, and bending resistance deteriorates.

The epoxy resin (B) has a hydroxyl group in the resin (A) in an equivalent ratio (hydroxyl group / epoxy group) of 0.3 or more, preferably an epoxy group in the epoxy resin (B). It is preferable to mix with the resin (A) so as to be in the range of 0.5 to 5, more preferably 0.7 to 4.
If the equivalent ratio is less than 0.3, the unreacted resin (A) component increases in the coating film, and the coating film performance such as bending resistance, water resistance, and corrosion resistance may decrease.

The epoxy resin (B) is stably dispersed in water by the carboxyl group in the resin (A). The equivalent ratio of epoxy groups is 0.1 to
1, particularly preferably in the range of 0.1 to 0.6.

The quaternary ammonium compound (C) is used in an amount of 0.01 to 10 based on the total weight of the resin (A), the epoxy resin (B) and the quaternary ammonium compound (C).
%, Preferably 0.1 to 7% by weight, more preferably 0.1 to 5% by weight. This is because a resin having sufficient weather resistance and acid resistance can be obtained in this range.

The following method can be exemplified as a method for producing the thermosetting aqueous coating composition of the present invention. First, an epoxy resin (B) or a solution in which an epoxy resin (B) is dissolved or dispersed in an organic solvent is mixed with a solution in which the resin (A) is dissolved or dispersed in an organic solvent. Next, a quaternary ammonium compound (C) and, if necessary, a neutralizing agent are added to the obtained mixture, and the mixture is dispersed in water to produce the mixture. The organic solvent that can be used for dissolving or dispersing the resin (A) or the epoxy resin (B) is preferably an organic solvent that is substantially inactive with respect to the functional group of the resin. Specific examples include alcohol solvents, ether solvents, ketone solvents, ester solvents, and hydrocarbon solvents. Among these, it is particularly preferable to use a hydrophilic solvent such as an alcohol solvent or an ether solvent as a main solvent. Further, as the neutralizing agent, for example, ammonia, trimethylamine, triethylamine, tributylamine, dimethylethanolamine, diethylethanolamine, dimethylpropanolamine, methyldiethanolamine, ethyldiethanolamine, triethanolamine and the like can be used. When a quaternary ammonium hydroxide is used as the quaternary ammonium compound (C), the resin component can be dispersed in water without using a neutralizing agent. If necessary, the quaternary ammonium compound (C) and the neutralizing agent may be used in combination.

The coating composition of the present invention may contain other compounds. Polycarbonate-free polyols such as polytetramethylene glycol, bisphenol A / ethylene oxide adduct, polycaprolactone polyol, polycarbonate diol, polyurethane polyol, vinyl alcohol (co) polymer, styrene-allyl alcohol copolymer, etc. A resin or the like can be blended. Examples of catalysts intended to cure coating films at lower temperatures include phenol compounds such as catechol, silanol compounds such as diphenylsilanediol, metals such as Al, Ti, V, Fe, Zn, Zr, and Sn and acetoacetic acid. Examples of the metal chelate compound include a chelate compound with a β-diketone such as ethyl, trifluoroacetylacetone, and dibenzoylacetylacetone. The catalyst is preferably blended in the range of 0.01 to 10 parts by weight based on 100 parts by weight of the total of the resin (A) and the epoxy resin (B). Further, if necessary, a coloring pigment such as titanium white, carbon black and red iron, an extender such as clay, talc and silica, a pigment dispersant, a repelling inhibitor, and a paint additive such as a fluidity modifier may be blended. Can be.

The method for forming a coating film using the coating composition of the present invention is not particularly limited. For example, it can be carried out by applying and drying the surface of the base material by means such as electrodeposition coating, spray coating, dip coating, roller coating, brush coating and the like. The coating film thickness is not particularly limited, but it is sufficient in the range of 10 to 100 μm for normal use. Drying of the coating film is preferably in the range of 0 to 200 ° C, more preferably 5 to 200 ° C.
0-180 ° C., at 120 ° C. for 30 minutes, 1
At 80 ° C., it can be performed in about 10 minutes. The substrate to be applied is also not particularly limited, but steel, aluminum, alumite, copper, plated steel in which zinc, tin, chromium, aluminum, etc. are plated on the surface of steel, or the surface of steel is chemically treated with chromic acid or phosphoric acid. It can be preferably used for a wide range of metals such as those treated or electrolytically treated.

[0034]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. "Parts" means "parts by weight" unless otherwise indicated.
“%” Indicates “% by weight” unless otherwise indicated.

(Measurement method) (1) Storage stability: After standing at 30 ° C. for one month, the sedimentation and separation of the dispersion are visually observed, and there is no color change due to the sedimentation of the dispersant in the coating composition. Was regarded as no abnormality. (2) Smoothness of the coating film: The unevenness of the surface of the coating film was visually observed. (3) Salt spray resistance: Tested according to JIS Z-2371, creep width from cut part of coating film 2 mm on one side
Those that were within were considered acceptable. The test time was 1,000 hours. (4) Pencil hardness: Tested according to JISK-5400. (5) Bending resistance: The test plate was bent at a right angle in an atmosphere of a temperature of 20 ° C. in 1 to 2 seconds, and a test piece having no abnormality such as peeling or cracking of a coating film in a bent portion was accepted. (6) Gel fraction: The dried coating film was peeled off, placed in a 300 mesh stainless steel mesh container, and extracted with a Soxhlet extractor using acetone / methanol = 1/1 solvent at reflux temperature for 6 hours. The gel fraction was calculated according to the following equation. The gel fraction (%) was evaluated by (weight of coating film after extraction / weight of coating film before extraction).

Example 1 A four-necked flask was charged with 75 parts of methylpropanol and heated to 110 ° C. 3 parts of acrylic acid, 20 parts of hydroxyethyl acrylate,
A mixture of 57 parts of methyl methacrylate and 20 parts of styrene, and a mixture of 1 part of 2,2'-azobisisobutylnitrile and 5 parts of methyl isobutyl ketone were added dropwise over 1 hour. This was aged for 1.5 hours to obtain a resin solution (A) having an acid value of 23, a hydroxyl value of 97, a number average molecular weight of 20,000 and a solid content of 55%. Next, 25 parts of methylpropanol was charged into a four-necked flask and heated to 110 ° C., and a mixture of 25 parts of the following compound (1), 5 parts of 2,2′-azobisisobutylnitrile, and 5 parts of methylisobutylketone was added for 3 hours. It dripped over. This was further aged for 3 hours to obtain an epoxy equivalent of 200, an average molecular weight of about 3,000, and a solid content of 42%.
To obtain a resin solution (B). To 181 parts by weight of the resin solution (A) and 60 parts by weight of (B), 19.5 parts of a 20% aqueous solution of tetraethylammonium hydroxide was added, and while stirring, 166 parts of deionized water was added thereto to obtain a solid content of 30%, average An aqueous dispersion having a particle size of 0.15 μm was obtained. Regarding the storage stability of the obtained water-dispersed product, there was no abnormality in both the paint state and the coating film performance. The water-dispersed product before the storage test was spray-coated on a zinc phosphate-treated steel sheet so as to have a dry film thickness of 20 μm, dried at 80 ° C. for 10 minutes, and further dried at 120 ° C.
For 20 minutes to obtain a coated product. This painting is
The coating film smoothness was good, the salt spray resistance was passed, the pencil hardness was H, and the bending resistance was also passed. The gel fraction of the coating film was 97%.

[0037]

Embedded image

Example 2 A four-necked flask was charged with 64 parts of methylpropanol and heated to 110 ° C. 4 parts of methacrylic acid and 25 parts of hydroxyethyl methacrylate
Parts, 2-ethylhexyl methacrylate 10 parts, methyl methacrylate 51 parts, styrene 10 parts mixture and 2,
A mixture of 1 part of 2'-azobisisobutylnitrile and 5 parts of methyl isobutyl ketone was added dropwise over 1 hour. This was further aged for 1.5 hours to obtain an acid value of 26 and a hydroxyl value of 10
8. A resin solution (A) having a number average molecular weight of 25,000 and a solid content of 59% was obtained. Next, 25 parts of methylpropanol was charged into a four-neck flask and heated to 110 ° C., and a mixture of 10 parts of the above compound (1) and 5 parts of the following compound (2) was added to the flask.
A mixture of 5 parts of 2,2'-azobisisobutylnitrile and 5 parts of methyl isobutyl ketone was added dropwise over 3 hours. This was further aged for 3 hours, epoxy equivalent 200,
A resin solution (B) having an average molecular weight of about 3,000 and a solid content of 30% was obtained. 170 parts by weight of resin solution (A) and (B)
To 60 parts by weight, 16.2 parts of a 10% aqueous solution of tetramethylammonium hydroxide was added, and 148 parts of deionized water was added with stirring to obtain a solid content of 30% and an average particle size of 0.18.
μ of an aqueous dispersion was obtained. The storage stability of the obtained water-dispersed product was not abnormal in both the paint state and the coating film performance. Further, the water dispersion before the storage test was painted in the same manner as in Example 1,
Upon drying, a coated product was obtained. The coated product had good coating smoothness, passed salt spray resistance, had a pencil hardness of 3H, and passed bending resistance. In addition, the gel fraction of the coating film was 97%.

[0039]

Embedded image

Example 3 150 parts of the 55% resin solution (A) obtained in Example 1, 10 parts of the 42% resin solution (B) obtained in Example 1, 3,4-epoxycyclohexylcarboxymethylcyclohexene oxide While stirring a mixture of 10 parts, 17.9 parts of a 10% aqueous solution of tetrabutylammonium hydroxide and 2 parts of triethylamine, 160 parts of deionized water was added to the mixture to obtain a solid content of 27% and an average particle size of 0.1 part.
An aqueous dispersion of 1 μm was obtained. The storage stability of the obtained water-dispersed product was not abnormal in both the paint state and the coating film performance. The water-dispersed product before the storage test was spray-coated on a zinc phosphate-treated steel sheet so that the dry film thickness became 20 μm.
After drying for 10 minutes at 140 ° C., drying was further performed at 140 ° C. for 20 minutes to obtain a coated product. This painted product has good coating smoothness,
The salt spray resistance was also passed, the pencil hardness was 2H, and the bending resistance was also passed. The gel fraction of the coating film was 93%.

Comparative Example 1 In Example 1, 20 parts of hydroxyethyl acrylate and 57 parts of methyl methacrylate were used in 77 parts of methyl methacrylate, 19.5 parts of a 20% aqueous solution of tetraethylammonium hydroxide were used in 3.4 parts of triethylamine. 166 parts of deionized water
An aqueous dispersion having a solid content of 30% was obtained in the same manner as in Example 1 except that the amount was changed to 80 parts. The storage stability of the obtained aqueous dispersion was not abnormal. Further, the water oxide before storage was coated and dried in the same manner as in Example 1 to obtain a coated product. This painted product had good coating smoothness, but failed salt spray resistance, had a pencil hardness of 4B, and failed flex resistance. In addition, the gel fraction of the coating film was 55%.

[0042]

In the thermosetting aqueous coating composition of the present invention, the reaction between the functional groups of the hydroxyl group in the resin (A) and the epoxy group in the epoxy resin (B) hardly proceeds at about room temperature. When baking is performed at about 100 ° C., a reaction similar to the functional group rapidly proceeds. For this reason, it is particularly excellent in storage stability and low-temperature curability of the coating film. Further, the cured film obtained from the thermosetting aqueous coating composition of the present invention has good coating smoothness,
Excellent salt spray resistance and bending resistance.

Claims (1)

[Claims] 1. A thermosetting aqueous coating composition containing the following components (A), (B) and (C). (A) a resin having a hydroxyl group and a carboxyl group (B) an epoxy resin obtained by polymerizing an unsaturated compound having an alicyclic epoxy group represented by the formula (1) (C) a quaternary ammonium compound