JPS63137973A - Aqueous coating composition containing cationic gel fine particles - Google Patents

Abstract

PURPOSE:To provide the titled composition outstanding in matte effect without impairing electrodeposition operability and storage stability, containing cationic gel fine particles produced by emulsifying, in an aqueous medium, an aqueous resin carrying positive electric charge in water and water-insoluble thermosetting crosslinking agent followed by heating. CONSTITUTION:The objective composition can be obtained by emulsifying, in an aqueous medium, a resin composition comprising (A) 100pts.wt. of a film- forming aqueous resin carrying positive electric charge in water (e.g., aminated polybutadiene resin) and (B) 10-250pts.wt. of a water-insoluble thermosetting crosslinking agent (e.g., an etherified methylolphenol) followed by heating the resultant emulsion at temperatures higher than the crosslinking temperature for the component B to produce cationic gel fine particles. This composition does not impair the electrodeposition operation because said particles themselves carry electric charge capable of electrodeposition and the aqueous resin covers the cores, giving matte effect with the cores forming asperities in the baking of the coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aqueous coating composition containing cationic gel particles, particularly a matte cationic electrodeposition coating composition.

It is conventionally known to add minute resin particles (microgel) made of internally crosslinked polymers of ethylenically unsaturated monomers to electrodeposition paints. See JP-A-58-93762 and JP-A-56-49766. These methods create irregularities on the surface of the coating film by adding microgel, and aim to achieve a matting effect by diffusely reflecting light.

However, these microgels do not have the charge necessary for electrodeposition, are insoluble in aqueous media, and do not thermally fuse at the baking temperature of the coating film, so they cannot be electrodeposited alone; It must be used in conjunction with a water-based resin that has the necessary charge for electrocoating. However, in this case, due to the above-mentioned properties of the microgel, the microgel tends to settle during storage of the paint, and if added in an amount sufficient to obtain a sufficient matting effect, there is a tendency to impair the workability of electrodeposition.

JP-A-61-31199 discloses a matte electrodeposition paint in which a heated reaction product of α,β-ethylenically unsaturated polycarboxylic acid resin and alkoxylated methylolmelamine is neutralized and made into an aqueous dispersion. ing. This paint does not use cross-linked resin gel particles as a matting agent, so it is difficult to obtain a sufficient matting effect, and the entire resin is uniformly heated before emulsification, so if you heat it too much, it will become a polymer. It becomes difficult to make the resin water-soluble.

Therefore, in the present invention, the core is insoluble and infusible when the coating film is baked, but the shell has a positive charge necessary for electrodeposition, and is an aqueous base that is electrodeposited and adheres to the object to be coated to form an electrodeposited coating film. Made of resin,
An aqueous coating composition containing cationic gel particles is provided.

In the present invention, the solid content is (A) 100 parts by weight of a film-forming aqueous resin having a positive charge in water, and (B) self-crosslinking and/or the above aqueous resin (A) by condensation or addition reaction. A resin composition containing 10 to 250 parts by weight of a water-insoluble thermosetting crosslinking agent crosslinked with the crosslinking agent (B) is emulsified in an aqueous medium, and the resulting emulsion is mixed with the crosslinking agent (B).
Provided is an aqueous coating composition characterized by containing cationic gel particles obtained by heating at a temperature equal to or higher than the crosslinking temperature.

The cationic gel particles of the present invention have a positive charge that can be electrodeposited by themselves, and a hydrophilic water-based resin forms a shell and covers the core. The wearability is not impaired, and the storage stability of the paint is not impaired either.

In addition, the shell is electrodeposited and adheres to the object to be coated, forming an electrodeposited coating, while the core does not fluidize when the coating is baked, forming fine irregularities on the coating, resulting in an excellent matting effect. Demonstrate. The water-based paint containing cationic gel particles of the present invention can be applied not only by electrodeposition but also by dipping, spraying, etc.
It is also possible to form a matte coating.

The film-forming aqueous resin (A) having a positive charge in water is used as a film-forming resin in the production of cationic electrodeposition paints. They have cationic functional groups such as amino groups that give the resin a positive charge and hydrophilicity. Although various types of such resins are known and can be used in the present invention, a typical preferred water-based resin is an aminated polybutadiene resin.

This resin is produced by, for example, converting liquid polybutadiene with a molecular weight of 500 to 5,000 into an oxirane with an oxygen content of 3 to 5000 by using peroxide.
It is obtained by partially epoxidizing it to 12% by weight and reacting it with 30 to 3 mmol of primary or secondary amine per 100 g. This product is neutralized with acid and diluted with water to create an aqueous solution or dispersion.

Typical examples of water-insoluble thermosetting crosslinking agents (B) that self-crosslink and/or crosslink with the aqueous resin through condensation or addition reactions are etherified methylolphenols,
More preferred is a β-hydroxyphenol ether compound. Further, when oxirane oxygen remains in the aminated polybutadiene resin, tetrabromobisphenol A can be used in combination.

Methylolphenols include phenol, p-cresol, p-t-butylphenol, amylphenol, and p-cresol.
- Etherified methylolphenols are obtained by reacting phenols such as phenylphenol and bisphenol A with formaldehyde in the presence of an alkali catalyst. oxidizing agent, such as RX(R
etc., X is halogen) or by partially or completely etherifying with a monoepoxy compound.

When the etherification agent is a monoepoxy compound, the etherified methylolphenol is a β-hydroxyphenol ether compound and is highly reactive, so it is preferable.

Since the crosslinking agent (B) performs the crosslinking reaction in water, it must be capable of crosslinking at a temperature of 100° C. or lower when the reaction is carried out at normal pressure. However, if the reaction is carried out under pressure in an autoclave, crosslinking agents which react at temperatures above 100° C. can also be used.

The aqueous resin (A) and crosslinking agent (B) can contain an organic solvent in order to lower the viscosity and facilitate emulsion formation.

Examples of such solvents include ethyl cellosolve, propyl cellosolve, butyl cellosolve, methanol, ethanol, isopropyl alcohol, n-7'tanol, isobutanol, ethylene glycol dimethyl ether, diacetone alcohol, 4-methoxy-4-methylpentanone -2, water-miscible organic solvents such as acetone, methyl ethyl ketone, methoxybutanol, dioxane, ethylene glycol monoethyl ether acetate, xylene, toluene, methyl isobutyl ketone, hexane, carbon tetrachloride, 2-ethylhexanol, isophorone, cyclohexane, There are water-immiscible organic solvents such as benzene.

The aqueous resin (A) and the crosslinking agent (B) can contain a catalyst to promote the reaction of the crosslinking agent. When the crosslinking agent is a β-hydroxyphenol ether compound, examples of the catalyst include dinonylnaphthalenesulfonic acid and dinonylnaphthalene disulfonic acid.

To prepare an emulsion by emulsifying a resin composition containing an aqueous resin (A) and a crosslinking agent (B) in an aqueous medium, at least 20 mol% of the amino groups in the aqueous resin (A)
What is necessary is to neutralize it with an acid, add the crosslinking agent (B) and an aqueous medium, and emulsify it. The ratio of aqueous resin (A) and crosslinking agent (B) is
The former per 100 parts by weight in terms of solid content, the latter 10-25
It is 0 parts by weight.

The acid that neutralizes the aqueous resin (A) is acetic acid.

Propionic acid, lactic acid, etc. are preferred.

The aqueous medium is water and can contain a surfactant to promote emulsification. Examples of nonionic surfactants include polyethylene glycol alkylphenyl 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 lauryltrimethylammonium chloride, distearyldimethylammonium chloride, alkylpicolinium chloride, and the like.

It is desirable to remove the solvent in the emulsion by azeotropic distillation or the like after the emulsion is produced and before heating. This accelerates the crosslinking reaction.

The emulsion thus obtained contains the crosslinking agent (B)
By heating at a temperature equal to or higher than the crosslinking temperature under normal pressure or increased pressure depending on the crosslinking temperature, an aqueous dispersion of cationic gel particles having the desired core/shell structure can be obtained.

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 charges of the same sign, and therefore the thermal crosslinking reaction of the crosslinking agent (B) in the emulsion form is stable. proceed. The crosslinking reaction in the form of such an emulsion can be confirmed by adding a large amount of a resin-dissolving solvent, such as tetrahydrofuran, to the emulsion before and after heating. If the emulsion is not cross-linked, it will dissolve transparently in the solvent; if it is cross-linked, it will be insoluble and the solvent will become cloudy.

Further, the aqueous dispersion of cationic gel particles is air-dried, and after drying under reduced pressure, the particles can be observed with an electron microscope.

The cationic gel particle dispersion thus obtained can be used as an aqueous paint, especially a cationic electrodeposition paint. The coating composition may optionally contain a water-soluble or water-dispersible cationic film-forming resin, and if necessary, a coloring pigment such as titanium dioxide, red iron oxide, or carbon blank may be added to the cationic film-forming resin.
Extender pigments such as aluminum silicate and precipitated barium sulfate, and antirust pigments such as aluminum phosphomolybdate, strontium chromate, basic lead silicate, and lead chromate may also be added.

The coating composition has a non-volatile content adjusted to about 10 to 20%,
It can be electrodeposited to a dry film thickness of 15 to 30 microns and cured by baking.

Production examples, examples and comparative examples of the present invention are shown below. In these, parts and percentages are based on weight.

Production example 1 Minpo1butadiene Nisseki polybutadiene B-2000 (number average molecular weight 2,0
00°1.2 bonds (65%) was epoxidized using peracetic acid to produce epoxidized polybutadiene with an oxirane oxygen content of 6.4%.

1000g of this epoxidized polybutadiene and 354g of ethyl cellosolve were mixed into 2I! After charging the mixture into an autoclave, 62.1 g of dimethylamine was added, and the mixture was reacted at 150°C for 5 hours. Unreacted amine was distilled off to produce an aminated polybutadiene resin solution. The amine value of this product was 120 mmol/100 g (solid content). Nonvolatile content 75% Production Example 2 Monohydroxyphenol ether Hetamanol 722*1) 60 parts Butyl glycidyl ether *2) 23Mn-Butanol 10 parts Methoxybutanol 10 parts Dimethylbenzylamine
0.4 parts *1) Resol type phenolic resin manufactured by Arayo Kagaku Kogyo *2) Monoepoxy compound manufactured by Tobu Kasei ■ 60 parts of Tamanol 722 was charged in a reaction vessel, and 10 parts of n-butanol and 10 parts of methoxybutanol were added. and then 23 parts of butyl glycidyl ether. When the temperature was raised to 100° C. while stirring uniformly, 0.4 g of dimethylbenzylamine was added. While being careful about fever 1
After keeping the temperature at 00°C for 3 hours with sufficient stirring,
When the glycidyl group content of the reaction product was measured, it was found to be 5% or less based on the amount charged, so it was cooled. As a result of analysis of the obtained compound, the phenolic OH group disappeared, and a β-hydroxyphenol ether compound having a methylol group and a secondary alcohol group was obtained.

Example 1 Emulgin A Aminated polybutadiene resin 66.7 50 Glacial acetic acid 1.8 Deionized water
369 To 66.7 parts of the aminated polybutadiene of Production Example 1, 62.7 parts of the β-hydroxyphenol ether compound of Production Example 2 was added.
Add 5 parts and 1.8 parts of glacial acetic acid and stir thoroughly.

Deionized water was added to this to emulsify it, and the solvent was removed under reduced pressure while adding deionized water to obtain resin emulsion A. A portion of the solution was taken and added to 100 times the amount of tetrahydrofuran, and the solution was dissolved transparently.

Next, resin emulsion A 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, but became cloudy.

Next, a tin plate was dipped in a gel particle dispersion containing 10% non-volatile content, air-dried, and after drying under reduced pressure at room temperature, it was observed under an electron microscope, and fine particles with a particle size of 1100 nm or less were observed.

The cationic gel particle dispersion obtained above was subjected to cationic electrodeposition using the object to be coated as a cathode, and baked at 170° C. for 20 minutes to obtain a 20 μm clear coated plate. Display test results -
Shown in ■.

Example 2 Aminated polybutadiene resin 66.7 50 Tetrabromobisphenol A3050 Xylene
10 Butyl cellosolve 5 Ethyl cellosolve 5 Glacial acetic acid 1.8 Deionized water
361.5 66.7 parts of the aminated polybutadiene resin of Production Example 1, 50 parts of tetrabromobisphenol A, 10 parts of xylene, 5 parts of butyl cellosolve,
Add 5 parts of ethylcetate and 1.8 parts of glacial acetic acid and stir thoroughly. Deionized water is gradually added to this to emulsify it, and the solvent is removed under reduced pressure while adding deionized water.
Resin emulsion B was obtained. This material dissolves transparently in tetrahydrofuran.

Next, resin emulsion B 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 but became cloudy.

The cationic gel particle dispersion obtained above was subjected to cationic electrodeposition using the object to be coated as a cathode, and baked at 170° C. for 20 minutes to obtain a 20 μm clear coating film. Display test results -
Shown in ■.

Manufacturing example 3 4 Ammonium E 1800-6.5 (Japan Petrochemicals side.

(epoxidized polybutadiene) 1000g butyl cellosolve 349g dimethylamine 46g 50% lactic acid
138g deionized water
473g phenyl glycidyl ether 117g epoxidized polybutadiene 818
After charging 00-6.5 and butyl cellosolve into an autoclave, dimethylamine was added and reacted at 150°C for 5 hours. After distilling off unreacted amine, 60”c
After adding a mixture of 50% lactic acid and deionized water, the mixture was stirred and kept at 80° C. for 30 minutes. After that, phenylglycidyl ether was added, the temperature was raised to 110"C, and while stirring and keeping warm, the acid value of the contents was measured by the usual method using phenolphthalene as an indicator and alcoholic KOH as a normal solution. After reacting until confirmation of 0.1 or less, production is terminated. Non-volatile content 55% Aged quaternary ammonium resin face 231g Deionized water 315g Carbon black 16g Titanium dioxide
92g kaolin
220g basic lead silicate
58g deionized water 16
After adding 315 g of deionized water to 33 g of quaternary ammonium resin and melting it, the pigment was added and mixed with stirring using a disper for about 1 hour. After adding glass peas to this mixture, they were dispersed in a sand mill to a particle size of 20μ or less, and deionized water was added at 163 °C.
After adding 3g and zeroing out the glass beads, the production is finished. Non-volatile content 20% Example 3 400 g of the resin emulsion A of Production Example 1 and 100 g of the pigment paste of Production Example 3 were mixed and cooled by keeping at 55° C. for 7 parts.

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

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

Comparative Example 2 The resin emulsion B was used in the same manner as in Example 2 without being heated.

Comparative Example 3 100 g of the pigment paste of Production Example 3 was added to 400 g of the resin emulsion A of Production Example 1, and cationic electrodeposition was performed without heating using the object to be coated as a cathode.
A coating film of 20 μm was obtained by baking. Table of test results -■
Shown below.

Table - ■ Note) Electrodeposition coating is applied to a degreased polished steel plate to a film thickness of 20 μm, and after baking under specified conditions, the gloss is measured under the condition of incident light of 60°.

Claims (9)

[Claims] (1) As a solid content, (A) 100 parts by weight of a film-forming aqueous resin having a positive charge in water, and (B) water that self-crosslinks and/or crosslinks with the aqueous resin (A) through condensation or addition reaction. A resin composition containing 10 to 250 parts by weight of an insoluble thermosetting crosslinking agent is emulsified in an aqueous medium, and the resulting emulsion is mixed with the crosslinking agent (B).
An aqueous coating composition characterized by containing cationic gel particles obtained by heating at a temperature equal to or higher than the crosslinking temperature. (2) The aqueous coating composition according to item 1, wherein the emulsion is heated at normal pressure. (3) The aqueous coating composition according to item 1, wherein the emulsion is heated under pressure. (4) The water-based coating composition according to any one of Items 1 to 3, wherein the Elmudgeon contains an organic solvent and includes a step of removing the organic solvent before heating. (5) The water-based coating composition according to any one of items 1 to 4, wherein the water-based resin (A) is an aminated polybutadiene resin. (6) The aqueous coating composition according to any one of items 1 to 5, wherein the crosslinking agent (B) is an etherified methylolphenol. (7) The aqueous coating composition according to item 5, wherein the crosslinking agent (B) is tetrabromobisphenol A. (8) The aqueous coating composition according to item 6, wherein the etherified methylolphenol is a β-hydroxyphenol ether compound. (9) The first aqueous coating composition is for cationic electrodeposition coating.
The composition according to any one of Items 1 to 8.