JPS63170443A - Production of aqueous dispersion of anionic gel fine particles - Google Patents

Abstract

PURPOSE:To obtain a dispersion containing fine particles of core-shell structure, capable of enhancing matte effect and electrodeposition characteristics without impairing electrodeposition workability and coating film characteristics when incorporated in an electrodeposition coating, by emulsifying an aqueous acrylic resin and a methylolphenol in an aqueous medium followed by heating. CONSTITUTION:A resin composition comprising (A) 100pts.wt. on a solid basis, of an aqueous acrylic resin carrying negative electric charge in water and (B) as the crosslinking agent, 10-250pts.wt. on a solid basis, of a methylolphenol or etherified one (beta-hydroxyphenol either compound) is emulsified in an aqueous medium. The resulting emulsion is heated either under pressure or at atmospheric pressure to temperatures higher than the crosslinking temperature for said crosslinking agent, thus obtaining the objective aqueous dispersion.

Description

[Detailed Description of the Invention] It has been known to obtain a matte coating film by adding microscopic resin particles (microgel) made of internally crosslinked polymers of ethylenically unsaturated monomers to electrodeposition paints. It is. Japanese Patent Publication No. 58-9
3762 and JP-A-56-49766, the addition of microgels to electrodeposition paints is effective not only for the purpose of matting, but also for improving coating film performance and throwing power.

However, these microgels do not have the charge necessary for electrodeposition, are insoluble in aqueous media, and do not thermally fuse at the 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 dispersive electrodeposition. However, in this case, the microgel cannot be added in large amounts because it impairs the storage stability of the coating material and the workability of electrodeposition due to the above-mentioned properties.

Therefore, in the present invention, the core is made of a thermosetting crosslinked resin,
The present invention provides a method for producing an aqueous dispersion of a new type of anionic gel fine particles with a core/shell structure, in which the shell is made of an aqueous resin having a negative charge and a hydrophilic group necessary for electrodeposition.

The present invention includes (A) 100 parts by weight of an aqueous acrylic resin having a negative charge in water as a solid content, and (B) 10 parts by weight of a solid content of methylolphenols or etherified methylolphenols as a crosslinking agent. Production of an aqueous dispersion of anionic gel particles, characterized in that a resin composition containing ~250 parts by weight is emulsified in an aqueous medium, and the resulting emulsion is heated at a temperature equal to or higher than the crosslinking temperature of the crosslinking agent (B). provide a method.

In the aqueous dispersion of anionic gel particles of the present invention, the particles themselves have a negative charge that can be electrodeposited, and a hydrophilic resin forms a shell covering a core of an insoluble thermosetting crosslinked resin. Therefore, when it is added to an anionic electrodeposition paint, it does not impair the workability of electrodeposition or coating film performance, nor does it have an adverse effect on the storage stability of the paint.

Water-based acrylic tree with a negative charge when photographed at the entrance of the hill
(A) is used as a film-forming resin in the production of anionic electrodeposition paints. These are resins obtained by introducing acid groups such as carboxyl groups, sulfonic acid groups, and phosphate groups into the resin. The acid groups of these resins are neutralized with a base and diluted with water to create an aqueous solution or dispersion.

The anionic acrylic resin can be obtained by copolymerizing a (meth)acrylic ester, an ethylenically unsaturated monomer having an acid group, and optionally other ethylenically unsaturated monomers.

Examples of (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, and (meth)acrylate.
2-ethylhexyl acrylate, lauryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (
Examples include glycidyl meth)acrylate.

Examples of ethylenically unsaturated monomers having an acid group include carboxylic acids such as (meth)acrylic acid, crotonic acid, itaconic acid, and maleic anhydride, sulfonic acids such as sulfoacrylate, and mono(2-hydroxyethyl acrylate) acid phosph. Examples include phosphates such as neat.

Ethylenically unsaturated monomers other than those mentioned above that are optional components include styrene, vinyltoluene, acrylonitrile, acrylamide, vinyl acetate, and the like. Commercially available water-soluble acrylic resins, such as Kota Sox H-804 and Kotax E-832 manufactured by Toshishiku Co., Ltd., may be used.

Methylolphenols, which are crosslinking agents, include phenol,
p-cresol, p-t-butylphenol, amylphenol, p-phenylphenol, bisphenol A
It is obtained by reacting Nato phenols with formaldehyde in the presence of an alkali catalyst. The etherified methylolphenols can be prepared by converting the phenolic OH group of the methylolphenols with a suitable etherification agent, such as RX (
R is -CH3, -CH2-CH=sCHz, -CH
zCeHs.

(X is a halogen) or by partially or completely etherifying it with a monoepoxy compound. When the etherification agent is a monoepoxy compound, the etherified methylolphenols are preferred because they are β-hydroxyphenol ether compounds and have high reactivity.

If the crosslinking agent (B) is not water-insoluble, it will be difficult to form an emulsion in an aqueous medium, so it will not form the core of the gel particles.For this reason, methylolphenols that do not etherify phenolic OH groups are nearly water-soluble and are not very effective. Undesirable.

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, when the reaction is carried out under pressure in an autoclave, Crosslinking agents that react at temperatures above 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 the formation of emulsion silane. Examples of such solvents include ethyl cellosolve, propyl cellosolve, butyl cellosolve, methanol, ethanol, isopropyl alcohol, n-butanol, isobutanol, ethylene glycol dimethyl ether, diacetone alcohol, 4-methoxy-4-methylpentanone-2, Water-miscible organic solvents such as acetone, methyl ethinosiketone, 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.

To prepare an emulsilane 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 acid groups in the aqueous resin (A) are emulsified with a base. The ratio of aqueous resin (A) and crosslinking agent (B) is 100 to 250 parts by weight of the latter in terms of solid content.
Parts by weight.

Examples of the base that neutralizes the aqueous resin (A) include ammonia,
jetanolamine, triethanolamine, methylethanolamine, N,N-dimethylethanolamine,
N,N-diethylethanolamine, diethylamine,
These include triethylamine, morpholine, and potassium hydroxide.

The aqueous medium is water and can contain surfactants to promote emulsification. Examples of nonionic surfactants include polyethylene glycol alkylphenyl ether, polyethylene glycol J-kyl ether, polyoxyalkylene alkyl ether, polyethylene glycol sorbitan monostearate, polypropylene glycol polyethylene glycol ether, and the like. Examples of anionic surfactants include polyoxyethylene alkylphenyl ether sulfate ammonium salts.

Examples include polyoxyethylene alkyl ether sulfate ammonium salt.

It is desirable to remove the solvent in the emulsion silane by azeotropy or the like after preparing the emulsion and before heating the emulsion, thereby promoting the crosslinking reaction.

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

The core/shell type emulsilane 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. progresses. Such a crosslinking reaction in the form of an emulsion can be confirmed by adding a large amount of a resin-dissolving solvent such as tetrahydrofuran to the emulsion silane before and after heating. If not crosslinked, emulsilane will dissolve transparently in the solvent; if crosslinked, it will become insoluble and the solvent will become cloudy.

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

The aqueous dispersion of anionic gel particles obtained by the present invention can be added to known anionic electrodeposition paints for the purpose of matting, improving the performance of electrodeposition coatings, and the like. In that case, even if a relatively large amount is added, electrodeposition workability, coating film performance, storage stability, etc. will not deteriorate.

The above dispersion can also be added to general aqueous coating compositions for the same purpose.

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

Production example 1 Tamanol with hydroxyphenol ether 722$1) 60 parts Butyl glycidyl ether $2) 23 parts n-butanol 10 parts Methoxybutanol 10 parts Dimethylbenzylamine 0.4 parts *1) Manufactured by Arayo Kagaku Kogyo@, Resol Type phenylene resin *2) Monoepoxy compound manufactured by Tobu Kasei@ 60 parts of Tamanol 722 is charged into a reaction vessel, 10 parts of n-butanol and 10 parts of methoxybutanol are added, and further 23 parts of butyl glycidyl ether are added. When the temperature was raised to 100℃ while stirring uniformly, 0.4 g of dimethylbenzylamine was added.
After keeping the temperature at 00°C for 3 hours with sufficient stirring,
When the amount of glycidyl base as a 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 Kotax-E-804*3) 91
50 Triethylamine 1.4 Deionized water 334*3) To 91 parts of water-soluble anionic acrylic resin Kotaksu E-804 manufactured by Toshi ■, β-hydroxyphenol ether compound 7
3.5 parts of triethylamine and 1.4 parts of triethylamine were added thereto, thoroughly stirred, and deionized water was gradually added to emulsify. The solvent was removed under reduced pressure while adding ionized water to obtain a resin emulsion.

A portion of the solution was taken and added to 100 times the amount of tetrahydrofuran, and the solution was dissolved transparently.

Next, the resin emulsion was kept at 55° C. for one week and cooled to obtain an anionic gel particle dispersion.

This product did not dissolve transparently in tetrahydrofuran but became cloudy. Further, when observed with an electron microscope, fine particles with a particle size of 100 rv or less were observed.

Claims (5)

[Claims] (1) (A) 100 parts by weight of an aqueous acrylic resin having a negative charge in water as a solid content, and (B) 10 to 250 parts by weight of a methylolphenol or etherified methylolphenol as a crosslinking agent. A method for producing an aqueous dispersion of anionic gel particles, which comprises emulsifying a resin composition containing the above-mentioned resin composition in an aqueous medium and heating the resulting emulsion at a temperature equal to or higher than the crosslinking temperature of the crosslinking agent (B). (2) The method for producing an aqueous dispersion of anionic gel particles according to item 1, wherein the etherified methylolphenol is a β-hydroxyphenol ether compound. (3) The method for producing an aqueous dispersion of anionic gel particles according to item 1 or 2, wherein the emulsion is heated at normal pressure. (4) The first part in which the emulsion is heated under pressure.
A method for producing an aqueous dispersion of anionic gel particles according to item 1 or 2. (5) The method for producing an aqueous dispersion of anionic gel particles according to any one of items 1 to 4, wherein the emulsion contains an organic solvent, and the method includes a step of removing the organic solvent before heating.