JPH0621271B2 - Aqueous coating composition containing cationic gel particles - Google Patents

Description

Description: BACKGROUND AND PROBLEM OF THE INVENTION The present invention relates to an aqueous coating composition containing cationic gel particles, and more particularly to a matte cationic electrodeposition coating composition.

Conventionally, it is known to add fine resin particles (microgel) made of a polymer of an internally crosslinked ethylenically unsaturated monomer to an electrodeposition paint. See JP-A-58-93762 and JP-A-56-49766. These are intended to obtain unevenness on the surface of the coating film by adding the microgel and to obtain a matte effect by diffuse reflection of light.

However, since these microgels do not have the electric charge necessary for electrodeposition, are insoluble in an aqueous medium, and do not heat-fuse at the baking temperature of the coating film, they cannot be electrodeposited by themselves, and are soluble in water or dispersed in water. Must be used in combination with a water-based resin that has the necessary electric charge for positive electrodeposition. In that case, however, the microgel tends to settle out during storage of the paint due to the above-mentioned properties, and if it is added in an amount sufficient to obtain a sufficient matting effect, the workability of electrodeposition tends to be impaired.

Japanese Patent Application Laid-Open No. 61-31199 discloses a matte electrodeposition coating composition which neutralizes a heating reaction product of an α, β-ethylenically unsaturated polycarboxylic acid resin and an alkoxylated methylolmelamine to prepare an aqueous dispersion. ing. Since this coating does not use crosslinked resin gel particles as a matting agent, it is difficult to obtain a sufficient matting effect, and since the entire resin is heated uniformly before emulsification, it will become a polymer if heated too much. It becomes difficult to make the resin water-soluble.

Therefore, in the present invention, the core is insoluble and infusible at the time of baking of the coating film, but the shell has a positive charge necessary for electrodeposition, and it is an aqueous solution that adheres to the object to be coated by electrodeposition and forms an electrodeposition coating film. Made of resin,
An aqueous coating composition containing cationic gel particles is provided.

Solution The present invention provides (A) 100 parts by weight of amine-modified epoxy resin or aminated polybutadiene resin in terms of solid content, and (B) methylol phenols obtained by reacting with formaldehyde of phenols in terms of solid content. Two
A water-based coating composition characterized by containing cationic gel particles obtained by emulsifying a resin composition containing 50 parts by weight in an aqueous medium and heating the resulting emulsion at a temperature not lower than the reaction temperature of the methylolphenols. Provide things.

The cationic gel microparticles of the present invention have a positive charge that allows the particles themselves to be electrodeposited, and the hydrophilic water-based resin serves as a layer to cover the core. The wearing workability is not impaired, and the storage stability of the paint is not impaired.

Also, it adheres to the coated object by shell electrodeposition, forms an electrodeposition coating film, and the core forms fine irregularities on the coating film without fluidizing when baking the coating material, so it exhibits an excellent matting effect. To do. Aqueous paint containing the cationic gel particles of the present invention,
Not only electrodeposition but also coating by dipping, spraying or the like can be carried out to obtain a glossy coating film.

Preferred Embodiment The cationic film-forming aqueous resin (A) is used as a film-forming resin in the production of a cationic electrodeposition coating composition. They have cationic functional groups such as amino groups that give the resin a positive charge and hydrophilicity. Various types of such resins are known and the aqueous resins that can be used in the present invention are amine modified epoxy resins and aminated polybutadiene resins.

The amine-modified epoxy resin can be produced by reacting a primary or secondary amine of polyglycidyl compound. The polyglycidyl compound is an epoxy compound having two or more glycidyl groups in the molecule and can be obtained by reacting an aromatic or aliphatic polyhydric alcohol with epichlorohydrin. A specific example is Epototo YD-011 (Toto Kasei Co., Ltd.), which is a bisphenol A type.
Manufactured by Denacol EX-212 (Nagase Kasei)
Co., Ltd.) and PG-207 (manufactured by Tohto Kasei Co., Ltd.), a phenol novolac-based Epotote YDPN-638 (Tohto Kasei Co., Ltd.)
Manufactured) etc.

Primary or secondary addition to these polyglycidyl compounds
Examples of the primary amine include primary amines such as monomethylamine, monoethylamine, n-butylamine and monoethanolamine, and secondary amines such as dimethylamine, diethylamine, diisopropylamine, N-methylethanolamine, N-ethylethanolamine and diethanolamine. Examples include amines and diketimines obtained by dehydration reaction of diethylenetriamine and methyl isobutyl ketone. These amines can be reacted in an approximately equivalent ratio to the epoxy equivalent of the polyglycidyl compound.

An aminated polybutadiene resin is (1) a carbon-carbon double bond having a molecular weight of 500 to 5,000 and an iodine value of 50 to 500, and an oxirane oxygen of 3-1.
2% by weight of the polymer compound (2) 30 to 300 mmol per 100 g of the polymer compound, the general formula (In the formula, R ₁ and R ₂ represent a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a hydroxyl group, or R ₁ and R ₂
Represents a ring structure containing nitrogen and optionally other heteroatoms.

The amine compound represented by the formula (3) is further reacted, and (3) the compound of the general formula (Wherein R ₃ and R ₄ represent a hydrogen atom or a methyl group), an α, β unsaturated carboxylic acid or a molecular weight of 100
A reaction product obtained by reacting an unsaturated fatty acid containing 10% by weight or more of a carbon-carbon conjugated double bond or a mixture thereof at ˜350.

For example, liquid butadiene having a molecular weight of 500 to 5000 is partially epoxidized with a peroxide so as to have an oxirane oxygen content of 3 to 12% by weight, and 30 to 300 mmol of the above-mentioned primary or secondary amine per 100 g is added thereto. And optionally further liquid polybutadiene 10
Obtained by reacting up to 200 mmol acrylic or methacrylic acid per 0 g.

These resins are neutralized with an acid and diluted with water to form an aqueous solution or dispersion.

Methylolphenols obtained by reacting phenols and formaldehyde in the presence of an alkali catalyst are
A cross-linking agent that self-crosslinks and / or crosslinks with the aqueous resin. These are well known as a resol type phenol resin initial condensate, and are produced using phenol, p-cresol, pt-butylphenol, p-amylphenol, p-phenylphenol, bisphenol A and the like as raw materials.

Since the cross-linking agent (B) undergoes a cross-linking reaction in water, it must be cross-linkable at a temperature of 100 ° C. or lower when it is reacted at atmospheric pressure. However, if the reaction is carried out under pressure in an autoclave, it is also possible to use crosslinking agents which react at temperatures above 100 ° C.

The water-based resin (A) and the cross-linking agent (B) can contain an organic solvent in order to reduce the viscosity and facilitate emulsion formation. Examples of such solvents include ethyl cellosolve, propyl cellosolve, butyl cellosolve, methanol, ethanol, isopropyl alcohol, n-butanol, isobutanol, ethylene glycol dimethyl ethene,
Water-miscible organic solvents such as diacetone alcohol, 4-methoxy-4-methylpentanone-2, acetone, methyl ethyl ketone, methoxybutanol, dioxane, ethylene glycol monoethyl ether acetate, xylene, toluene, methyl isobutyl ketone, hexane, There are water-immiscible organic solvents such as carbon tetrachloride, 2-ethylhexanol, isophorone, cyclohexane and benzene.

The aqueous resin (A) and the cross-linking agent (B) may contain a catalyst such as dinonylnaphthalene sulfonic acid and dinonyl naphthalene disulfonic acid for accelerating the reaction of the cross-linking agent.

To emulsify a resin composition containing an aqueous resin (A) and a crosslinking agent (B) in an aqueous medium to prepare an emulsion,
At least 20 mol% of amino groups in the aqueous resin (A) may be neutralized with an acid, and the crosslinking agent (B) and the aqueous medium may be added to emulsify. The ratio of the aqueous resin (A) and the crosslinking agent (B) is 10 to 250 of the latter per 100 parts by weight of the former in terms of solid content.
Parts by weight.

The acid that neutralizes the aqueous resin (A) is preferably acetic acid, propionic acid, lactic acid, or the like.

The aqueous medium is water and may include a surfactant to promote emulsification. Examples of nonionic surfactants include polyethylene glycol alkyl phenyl ether, polyethylene glycol alkyl ether, polyoxyalkylene alkyl ether, polyethylene glycol sorbitan monostearate, polypropylene glycol polyethylene glycol ether and the like. Examples of cationic surfactants include lauryl trimethyl ammonium chloride, distearyl dimethyl ammonium chloride, alkyl picolinium chloride and the like.

It is desirable that the solvent in the emulsion be removed by azeotropic distillation after preparing the emulsion and before heating. This accelerates the crosslinking reaction.

The emulsion thus obtained contains the crosslinking agent (B)
Depending on the reaction temperature, heating at normal pressure or under pressure at a temperature of the reaction temperature or higher gives the desired aqueous dispersion of cationic gel particles having a core / shell structure.

The core / shell type emulsion of the present invention has good thermal stability because it is stably dispersed in water due to the repulsive force of electric charges having the same sign, and therefore the thermal crosslinking reaction of the crosslinking agent (B) in the emulsion form. proceed. The crosslinking reaction in the form of such an emulsion can be confirmed by adding a large amount of a resin-melting solvent such as tetrahydrofuran to the emulsion before and after heating. If it is not crosslinked, the emulsion is transparently dissolved in the solvent, and if it is crosslinked, it becomes insoluble and the solvent becomes cloudy. The aqueous dispersion of the cationic gel particles can be air-dried and dried under reduced pressure, and the particles can be observed with an electron microscope.

The cationic gel fine particle dispersion thus obtained is
It can be used as an aqueous paint, especially as a cationic electrodeposition paint. The coating composition can optionally contain a water-soluble or water-dispersible cationic film-forming resin, and if necessary, the cationic film-forming resin can be colored pigments such as titanium dioxide, red iron oxide, carbon black, and silicic acid. Extender pigments such as aluminum and precipitated barium sulfate,
Also, rust preventive pigments such as aluminum phosphomolybdate, strontium chromate, basic lead silicate, and lead chromate can be added.

Water-soluble or water-dispersible cationic film-forming resins include polyether-based, polyester-based, polyurethane-based, polyamide-based, phenolic resin-based, acrylic resin-based, etc. in addition to the amino-modified epoxy resin and aminated polybudadiene resin described above. Various things are known. Depending on their curing mechanism, these are classified into self-crosslinking type by radical polymerization and oxidative polymerization reaction, type that is cured by a crosslinking agent such as melamine resin and block polyisocyanate compound, and type that uses both self-crosslinking reaction and crosslinking agent crosslinking. To be In addition, in order to improve the performance of the electrodeposition coating film, a water-insoluble epoxy acrylate resin, for example, may be added to the water dispersion of these water-soluble or water-dispersible cationic film-forming resins in the form of emulsion. There is. The aqueous coating composition of the present invention may include all of these types of water soluble or water dispersible cationic film forming resins.

The coating composition adjusts the nonvolatile content to about 10 to 20%,
It can be cured by electrodeposition to a dry film thickness of 15 to 30 μm and baking.

The production examples, examples and comparative examples of the present invention are shown below. In these, parts and percentages are by weight.

Production Example 1 Aminated Polybutadiene A Nisseki Polybutadiene B-2000 (Number average molecular weight 2000, 1,2 bond
65%) was epoxidized with peracetic acid to produce epoxidized polybutadiene having an oxirane oxygen content of 6.4%.

After charging 1000 g of this epoxidized polybutadiene and 354 g of ethyl cellosolve in 2 autoclaves, 62.1 g of dimethylamine was added, and the mixture was reacted at 150 ° C. for 5 hours. Unreacted amine was distilled off to prepare an aminated polybutadiene resin solution.

The amine value of this product was 120 mmol / 100 g (solid content). Nonvolatile content 75% Production Example 2 Aminated polybutadiene B Nisseki Polybutadiene B-2000 (number average molecular weight 2000, 1,2 bond 65%) is epoxidized with peracetic acid to give epoxidation with oxirane oxygen content of 6.4%. A polypudadiene was produced.

After 1,000 g of this epoxidized polybutadiene and 354 g of ethyl cellosolve were charged in a 2 autoclave, 62.1 g of dimethylamine was added and reacted at 150 ° C. for 5 hours. After distilling off the unreacted amine, the mixture was cooled to 120 ° C. and acrylic acid 79.3 g and hydroquinone 7.6.
and a mixture of 26.4 g of ethyl cellosolve were added, and the mixture was further reacted at 120 ° C. for 3 hours and 45 minutes.

This had an amine value of 85.2 mmol / 100 g, an acid value of 10.0 mmol / 100 g, and a solid content concentration of 75.4%.

Production Example 3 Epotote YD-012 700 parts and butyl cellosolve 227
Part 2 is charged in an autoclave and dissolved. 73 parts of diethylamine was charged, the temperature was raised to 100 ° C., and the mixture was kept warm for 90 minutes for reaction. Unreacted amine was distilled off to prepare an aminated epoxy resin solution.

The amine value of this product was 128 mmol / 100 g (solid content). Nonvolatile content 70.5% Production Example 4 Epoxidized polybutadiene E 1800-6.5 and butyl cellosolve were charged in an autoclave, dimethylamine was added, and the mixture was reacted at 150 ° C. for 5 hours. After the unreacted amine was distilled off, the mixture was cooled to 60 ° C., 50% lactic acid, deionized water and a mixed solution were added, and the mixture was kept at 80 ° C. for 30 minutes with dry stirring. After this, add phenyl glycidyl ether and add 110
The temperature of the mixture was raised to ℃, and the acid value of the contents was measured by a usual method using phenolphthalene as an indicator and alcoholic KOH as a normal solution, and the reaction was carried out until an oxidation of 0.1 or less was confirmed. After that, the manufacturing ends. Nonvolatile content 55% After adding 315 g of deionized water to the quaternary ammonium resin to dissolve it, a pigment is added and the mixture is stirred and mixed with a disper for about 1 hour. This mixture was added with glass beads, dispersed with a sand mill to a particle size of 20 μm or less, and 1633 g of deionized water was added to separate the glass beads to complete the production.
Nonvolatile content 20% Example 1 To 100 parts of the aminated polybutadiene of Production Example 1, 33.3 parts of Tamanol 722 and 2.8 parts of glacial acetic acid are added and stirred sufficiently. To this, 363.9 parts of deionized water was added and emulsified to obtain a resin emulsion A. Take a part of it,
When 100 times the amount of etrahydrofuran was added, it dissolved transparently.

The solvent was removed under reduced pressure while adding deionized water, and then the resin emargor A was kept at 95 ° C. for 6 hours and cooled to obtain a cationic gel particle dispersion.

This product did not dissolve transparently in tetrahydrofuran and became cloudy.

Next, a tin number was dipped in a gel fine particle dispersion liquid having a nonvolatile content of 10%, air-dried, dried under reduced pressure at room temperature, and then observed with an electric microscope. As a result, fine particles having a particle size of 100 nm or less were observed.

The cationic gel fine particle dispersion obtained above was subjected to cationic electrodeposition coating using the article to be coated as a cathode, and baked at 170 ° C. for 20 minutes to obtain a 20 μ clear coated plate. Table of test results
Shown in 1.

Example 2 To 100 parts of the aminated polybutadiene of Production Example 1, 33.3 parts of Tamanol 722 and 2.8 parts of glacial acetic acid are added and stirred sufficiently. To this, 36.39 parts of deionized water was added and emulsified to obtain a resin emulsion B. Take a part of it,
When it was added to 100 times the amount of tetrahydrofuran, it dissolved transparently.

The solvent was removed under reduced pressure while adding deionized water, and then the resin emulsion B was kept at 95 ° C. for 6 hours and cooled to obtain a cationic gel particle dispersion.

This product did not dissolve transparently in tetrahydrofuran and became cloudy.

Next, a tin plate was dipped in a gel fine particle dispersion liquid having a nonvolatile content of 10%, air-dried, dried under reduced pressure at room temperature, and then observed with an electron microscope. As a result, fine particles having a particle size of 100 nm or less were observed.

The cationic gel fine particle dispersion liquid obtained above was subjected to cationic electrodeposition coating using the article to be coated as a cathode and baked at 170 ° C. for 20 minutes to obtain a 20 μ clear coated plate. Table I of test results
Shown in.

Example 3 To 107 parts of the aminated epoxy resin of Preparation Example 3, 33.3 parts of Tamanol 722 and 2.6 parts of glacial acetic acid are added and stirred sufficiently. This was added with 357.1 parts of deionized water and emulsified to obtain a resin emulsion C. Take a part of it, 10
When it was added to 0 times the amount of tetrahydrofuran, it dissolved transparently. The solvent was removed under reduced pressure while adding deionized water, and then the resin emulsion C was kept at 55 ° C. for 7 days and cooled to obtain a cationic gel particle dispersion.

This product did not dissolve transparently in tetrahydrofuran and became cloudy.

Next, a tin plate was dipped in a gel fine particle dispersion liquid having a nonvolatile content of 10%, air-dried, dried under reduced pressure at room temperature, and then observed with an electron microscope. As a result, fine particles having a particle size of 100 nm or less were observed.

The cationic gel fine particle dispersion liquid obtained above was subjected to cationic electrodeposition coating using the article to be coated as a cathode, and baked at 20 ° at 170 ° C. to obtain a 20 μ clear coating film. Table of test results
Shown in I.

Example 4 400 g of the heated resin emulsion A of Example 1 and 100 g of the pigment paste of Production Example 4 were mixed and kept warm at 55 ° C. for 7 days and cooled.

This product was subjected to cationic electrodeposition coating using the object to be coated as a cathode and baked at 170 ° C. for 20 minutes to obtain a 20 μ-coated plate. The test results are shown in Table-I.

Example 5 Same as Example 1 except that the resin emulsion is heated in an autoclave at 110 ° C. for 5 hours and used.

Comparative Example 1 Same as Example 1 except that the resin emulsion A was used without heating.

Comparative Example 2 Same as Example 2 except that the resin emulsion B was used without heating.

Comparative Example 3 Same as Example 3 except that the resin emulsion C was used without heating.

Comparative Example 4 100 g of the pigment paste of Production Example 4 was added to 400 g of the resin Mulsion A of Example 1 before heating, and cationic electrodeposition coating was performed using the article to be coated as a cathode, followed by baking at 170 ° C. for 20 minutes to obtain a 20 μ coating film. Got The test results are shown in Table-I.

Claims (6)

[Claims] (1) 100 parts by weight of (A) amine-modified epoxy resin or aminated polybutadiene resin in terms of solid content, and (B) methylolphenols obtained by reacting phenols and formaldehyde in 10 to 25 in terms of solid content.
A water-based coating composition characterized by containing cationic gel particles obtained by emulsifying a resin composition containing 0 part by weight in an aqueous medium and heating the resulting emulsion at a temperature not lower than the reaction temperature of the methylolphenols. object. 2. The aqueous coating composition according to claim 1, wherein the heating of the emulsion is performed under pressure. 3. The aqueous coating composition according to claim 1 or 2, wherein the emulsion contains an organic solvent, and the step of removing the organic solvent before the heating is included. 4. The aqueous coating composition according to any one of claims 1 to 3, wherein the amine-modified epoxy resin is an amine-modified epoxy resin obtained by adding a primary or secondary amine to a polyglycidyl compound. object. 5. The aminated polybutadiene resin comprises (1) a carbon-carbon double bond having a molecular weight of 500 to 5,000 and an iodine value of 50 to 500 and an oxirane oxygen of 3 to 3.
12% by weight of the polymer compound (2) 30 to 300 mmol per 100 g of the polymer compound of the general formula (In the formula, R ₁ and R ₂ represent a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a hydroxyl group, or
₁ and R ₂ represent ring structures containing nitrogen and optionally other heteroatoms. ) The amine compound represented by the formula (3) is further reacted, and (3) 0 to 200 mmol of the general formula (100) per 100 g of the polymer compound (1) is used. (In the formula, R ₃ and R ₄ represent a hydrogen atom or a methyl group.) An α, β unsaturated carboxylic acid represented by the formula or a compound having a molecular weight of 100 to 350 and containing 10% by weight or more of a carbon-carbon conjugated double bond. The aqueous coating composition according to any one of items 1 to 3, which is a reaction product obtained by reacting a saturated fatty acid or a mixture thereof. 6. The aqueous coating composition according to any one of claims 1 to 5, wherein the aqueous coating composition is a cationic electrodeposition coating composition.