JPH0637598B2 - Resin composition for electrodeposition coating - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin composition for electrodeposition coating.

More specifically, the present invention relates to a resin composition for electrodeposition coating, which has excellent properties such as chemical resistance, heat resistance, and electrical insulation, and which forms a coating film having excellent adhesion to an object to be coated.

(Prior Art) Conventionally, electrodeposition coating has been widely used for corrosion protection and surface finishing of automobiles, aluminum building materials, home appliances, office equipment, etc., and has been applied to various base materials. On the other hand, in the electronics field, technological innovation is remarkable, and especially in the IC substrate, high density and high quality are being rapidly made, and more precise and advanced technological development is required. One of the targets is an aluminum base printed circuit board, which is formed by anodizing the surface of an aluminum substrate to form an oxide film, and then forming an insulating layer on it and then plating it with copper. It has been recognized that it is extremely superior to other ceramic-based substrates and polymer-based substrates in characteristics such as dimensional stability and heat dissipation.

(Problems to be Solved by the Invention) However, in the production of aluminum-based substrates, many complicated steps are required to obtain a reliable and high-quality product, and the simplification of the steps is a problem. Has become.
As a means of simplifying this process, electrodeposition coating is attracting attention because of its excellent coverage of edges and through holes. However, none of the current electrodeposition coating liquids sufficiently satisfy various properties such as heat resistance and electric insulation required for aluminum-based printed circuit boards, and it is a fact that improvement thereof is earnestly desired.

An object of the present invention is to greatly improve the performance of conventional electrodeposition coating solutions, and to provide a resin composition for electrodeposition coating which can impart various performances required for an aluminum base printed circuit board. .

(Means for Solving the Problem) When the present invention is outlined, a film-forming component is A. (A) α,
β-ethylenically unsaturated carboxylic acid 2 to 15% by weight,
(B) 5 to 85% by weight of an alkyl ester of α, β-ethylenically unsaturated carboxylic acid, (c) a hydroxyalkyl-containing ester of α, β-ethylenically unsaturated carboxylic acid 3 to 3
It has an acid value of 5 to 100 obtained by reacting 30% by weight, (d) 0 to 60% by weight of another copolymerizable monomer, and (e) 3 to 30% by weight of a monomer represented by the following structural formula. 45 to 98% by weight of polycarboxylic acid resin and B.I. A resin composition for electrodeposition coating, which comprises 2 to 55% by weight of a melamine-formaldehyde resin.

However, the structural formula of (e) is According to the study by the present inventors, maleimides having a specific structural formula are used together during the synthesis of α, β-ethylenically unsaturated polycarboxylic acid resins, whereby chemical resistance, heat resistance, and
The present invention has been completed by finding that a polycarboxylic acid resin excellent in performance such as electric insulation can be obtained.

The present invention will be described in more detail. In the resin composition for electrodeposition coating, the coating film forming component is A. A polycarboxylic acid resin and B. It is composed of a curing agent.

A. The polycarboxylic acid resin of is prepared by reacting the following monomer compositions.

(A) α, β-ethylenically unsaturated carboxylic acid 2 to 15% by weight, (b) α, β-ethylenically unsaturated carboxylic acid alkyl ester 5 to 85% by weight, (c) α, β-ethylenic 3-30% by weight of hydroxyalkyl-containing ester of unsaturated carboxylic acid, (d) other copolymerizable monomers 0-6
0% by weight and (e) monomers 3 to 3 represented by the following structural formula
Obtained by reacting 0% by weight. (However, the total amount of the monomers is 100% by weight.) When the blending amount of the α, β-ethylenically unsaturated carboxylic acid as the component (a) is less than 2% by weight, the polycarboxylic acid cannot have sufficient water dispersibility, while when it is more than 15% by weight, the water resistance is It is not preferable because the properties such as resistance and alkali resistance are deteriorated.

The hydroxyalkyl-containing ester of the α, β-ethylenically unsaturated carboxylic acid as the component (c) is an important component for imparting crosslinking reactivity to the polycarboxylic acid resin, and when the compounding amount is less than 3% by weight. However, if the cross-linking density of the coating film is insufficient, the strength and heat resistance of the coating film are poor. On the other hand, if it exceeds 30% by weight, the coating film becomes brittle and cracks easily occur, which is not preferable.

In order to impart excellent chemical resistance, heat resistance and electric insulation to the electrodeposition coating film, it is necessary to use the component (e) at least 3% by weight of the total monomer composition.

On the other hand, if it exceeds 30% by weight, gelation tends to occur in the reaction, which is not preferable.

The alkyl ester of α, β-ethylenically unsaturated carboxylic acid as the component (b) provides the resin composition according to the present invention as a stable aqueous liquid, and also improves the film-forming property during electrodeposition. , Used to efficiently achieve electrodeposition.

If the blending amount is less than 5% by weight, the stability as an aqueous liquid is inferior, and almost no film-forming property is exhibited under the normally performed electrodeposition conditions. Performance such as heat resistance and electric insulation based on the maleimide-based monomer forming the skeleton cannot be sufficiently obtained, which is not preferable.

This A. The polycarboxylic acid resin is synthesized by heating and mixing a composition composed of the following monomers in the presence of an organic solvent and a polymerization catalyst, and controlling the reaction by adding a polymerization regulator.

Suitable (a) α, β-ethylenically unsaturated carboxylic acids include acrylic acid, α-chloroacrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid,
These are citraconic acid, mesaconic acid and the like, or a functional derivative thereof having at least one carboxyl group, such as unsaturated polymerizable partial ester or amide of di- or poly-carboxylic acid.

(B) Examples of the alkyl ester of α, β-ethylenically unsaturated carboxylic acid include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl. There are acrylates, butyl methacrylates, lauryl acrylates, lauryl methacrylates, stearyl acrylates, stearyl methacrylates, hexyl acrylates, 2-ethylhexyl methacrylates, heptyl acrylates, heptyl methacrylates, etc., and similar esters with up to about 20 carbon atoms in the alkyl group are used. it can.

Examples of the hydroxyalkyl-containing ester of (c) α, β-ethylenically unsaturated carboxylic acid include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate and 3-hydroxypropyl acrylate. , 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate and the like.

(D) Other copolymerizable monomers include acrylamide, methacrylamide, methylolacrylamide, methylolmethacrylamide, alkoxymethylolacrylamide, alkoxymethylolmethacrylamide,
Examples include α, β-ethylenically unsaturated carboxylic acid amides or amide derivatives such as diacetone acrylamide and diacetone methacrylamide, styrene, α-alkylstyrene, α-chlorostyrene, vinyltoluene, acrylonitrile, vinyl acetate and the like.

(E) structural formula, As the monomer represented by, N-phenylmaleimide,
There are N-2-methylphenylmaleimide, N-2-ethylphenylmaleimide, N-2-chlorophenylmaleimide and the like. Polycarboxylic acid resin is water or isopropyl alcohol, ethylene glycol monoethyl ether,
It is prepared by emulsion polymerization, suspension polymerization, or solution polymerization at a polymerization temperature of 40 to 130 ° C. using a hydrophilic solvent such as ethylene glycol monobutyl ether. At this time, if necessary, ammonium persulfate, potassium persulfate, α, α′-
Azobisisobutyronitrile, 4,4'-azobis-4
-Cyanovaleric acid, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, and other polymerization initiators, ferric chloride and other reducing agents, sodium alkylbenzene sulfonate, alkyl ether sulfonates Surfactants such as The compound can be used alone or as a mixture of two or more kinds.

The polycarboxylic acid resin preferably has an acid value of 5 to 100 mgKOH and a hydroxyl value of 10 to 15 mgKOH. When the acid value is less than 5 mgKOH, sufficient water dispersibility as an electrodeposition coating cannot be obtained,
In addition, the electrophoretic property is poor, which is not preferable. On the other hand, 100 mg KOH
If it is larger, the chemical properties such as water resistance and alkali resistance of the coating film are significantly deteriorated, which is not preferable.

When the hydroxyl value is less than 10, a sufficient crosslink density cannot be obtained and the coating film strength becomes insufficient, and when the hydroxyl value exceeds 150, the chemical resistance becomes poor and the coating film becomes brittle, which is not preferable.

In the resin composition of the present invention, the proportion of the polycarboxylic acid resin as the component A and the melamine-formaldehyde resin as the component B is 45 to 98% by weight for the component A and 2 to 55 for the component B.
It is suitable to use in the range of weight%. As the melamine-formaldehyde resin, a melamine resin, particularly,
Preference is given to using methylolmelamine at least partially etherified with one or more lower alcohols such as methanol, ethanol, propanol, butanol and the like.

When the content of the melamine-formaldehyde resin is less than 2% by weight, the coating film is not sufficiently crosslinked and the coating film performance is deteriorated. On the other hand, when it is more than 55% by weight, the coating film becomes brittle, which is not preferable.

The resin composition for electrodeposition coating of the present invention is prepared, for example, by the following method.

A polycarboxylic acid resin, a melamine-formaldehyde resin and an organic solvent are charged into a reaction vessel equipped with a stirrer and a thermometer, and then stirred and sufficiently mixed.

Examples of the organic solvent include methanol, ethanol, n
-Propanol, isopropanol, n-butanol,
Alcohols such as isobutanol, secondary butanol, tertiary butanol, pentanol, etc., methyl cellosolve, ethyl cellosolve, isopropyl cellosolve,
Cellulosolves such as butyl cellosolve, secondary butyl cellosolve and the like are used.

As a method for producing an electrodeposition coating liquid from the resin composition for electrodeposition coating thus prepared, a basic compound is added to the resin composition, and at least the carboxyl group present in the polycarboxylic acid resin molecule is added. A part of the solution is neutralized to make it dispersible in water, and deionized water is added to this to dilute it to an appropriate resin solid content concentration to obtain an electrodeposition coating solution.

The basic compound that can be used may be one that is normally used, for example, ammonia, or monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monoamine. Primary to tertiary alkylamines such as butylamines, dibutylamines and tributylamines, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, dimethylaminoethanol and Alkanolamines such as diethylaminoethanol, ethylenediamine, propylenediamine, diethylenetriamine and triethylene Alkylene polyamines such as tetramine, alkylene imine such as ethylene imine and propylene imine, piperazine, Horumorin, there is pyrazine and pyridine, and the like.

The electrodeposition coating liquid usually has a resin solid content of 3 to 50% by weight.
It is preferably prepared and used in the range of about 7 to 30% by weight.

At this time, if necessary, a reaction catalyst such as paratoluenesulfonic acid or dibutyltin dilaurate, an antioxidant or an ultraviolet absorber such as paramethoxyphenol, dibutylthiodipropionate, or tertiary butyl catechol, an antifoaming agent, and a leveling agent. Agents, paint additives such as anti-settling agents, pigments such as titanium oxide, talc, carbon black and the like can be mixed and used.

A conductive article in the electrodeposition coating solution prepared in this manner as an anode, after applying a direct current voltage between the counter electrode, pulling up the conductive article, and after heating or baking without washing, A uniform electrodeposition coating film is formed on the surface of the conductive article.

In the resin composition for electrodeposition coating of the present invention, for example, the coating film is heated and baked at 130 to 250 ° C, preferably 140 to 230 ° C.
Is achieved under the condition of 15 to 60 minutes.

(Example) In order to more specifically describe the present invention, an example will be shown below.

[Preparation of polycarboxylic acid resin A] Ethylene glycol monobutyl ether 2 was placed in a four-necked flask equipped with a thermometer, a stirrer and a reflux condenser.
50 g and tertiary butyl peroxy-2-ethylhexanoate 7.5 g are charged and the temperature is raised to 80 ° C. To this, 190 g of methyl methacrylate, n-methacrylic acid
Butyl 100 g, 2-hydroxyethyl methacrylate 8
0 g, 2-ethylhexyl acrylate 100 g, methacrylic acid 15 g, N-phenylmaleimide 15 g and 2,4-diphenyl-4-methyl-1-pentene 1.0
The mixture having the monomer composition of g is dropped into the flask over 240 minutes, and then the mixture is stirred for another 240 minutes. Then, a mixture of 30 g of ethylene glycol monobutyl ether and 1.5 g of tertiary butyl peroxy-2-ethylhexanoate is added three times every 60 minutes. Then, stirring was continued at 80 ° C. for 240 minutes to prepare polycarboxylic acid resin A.

[Preparation of Polycarboxylic Acid Resins B to J] In the method for preparing the polycarboxylic acid resin A, the same method was carried out except that the monomer composition was changed to the content shown in Table 1. ~ J were prepared.

Example 1 120 g of a polycarboxylic acid resin A and a melamine resin (trade name Cymel HM-6 manufactured by Mitsui Cyanamid Co., Ltd.) in a container.
30 g was collected and sufficiently stirred to prepare a resin composition for electrodeposition coating.

Examples 2 to 5 and Comparative Examples 1 to 5 In the same method as in Example 1, the same method was used except that the kind of polycarboxylic acid resin was changed to the content shown in Table 2 to obtain a resin composition for electrodeposition coating. Was prepared.

Examples 6 to 7 and Comparative Examples 6 to 7 The same method as in Example 1 was repeated except that the compounding ratio of the polycarboxylic acid resin and the melamine resin was changed as shown in Table 3. A coating resin composition was prepared.

Experimental Example The resin compositions prepared in Examples 1 to 7 and Comparative Examples 1 to 7 were used, triethylamine and 2-ethylhexyl alcohol were added thereto, and the mixture was sufficiently stirred. While further stirring, deionized water was gradually added to prepare an electrodeposition coating solution having a resin solid content of about 15% by weight.

Next, using each of the above electrodeposition coating solutions, an aluminum plate anodized by a conventional method was used as an anode, and a stainless plate was connected to the cathode to perform DC electrodeposition coating. The electrodeposition coating conditions are
It is as follows.

Aluminum material: JIS A-1100 Alumite thickness: 8 to 10 μm Voltage: 160 V Energizing time: 5 minutes Coating baking: 180 ° C. × 30 minutes As a result, an electrodeposition coating having the performance shown in Table 4 was obtained. .

However, the coating film performance test was performed as follows.

1. Alkali resistance: The method of JIS H-8602 was carried out and evaluated by rating NO.

2. Weather resistance: The method of JIS H-8602 was carried out and evaluated by rating NO.

3. Boiling water resistance: The method of JIS H-8602 was carried out and evaluated by rating NO.

4. Heat resistance: The thermal decomposition start temperature was measured in a nitrogen gas atmosphere with a thermal analyzer. The larger the value, the better the heat resistance.

5. Pinhole test: 1Kv with pinhole detector
Voltage was applied to inspect for pinholes.

○: No pinhole × × With pinhole 6. Insulation resistance: evaluated in a normal state according to JIS C6481.

(Effects of the Invention) When the resin composition for electrodeposition coating of the present invention is used for electrodeposition coating, an electrodeposition coating film excellent in various properties such as heat resistance, electrical insulation and chemical resistance can be obtained. .

Claims (1)

[Claims] 1. A coating film forming component is A. (A) α, β-ethylenically unsaturated carboxylic acid 2 to 15% by weight, (b) α, β
-Alkyl esters of ethylenically unsaturated carboxylic acids 5
85% by weight, (c) 3 to 30% by weight of hydroxyalkyl-containing ester of α, β-ethylenically unsaturated carboxylic acid,
(D) 0-60% by weight of other copolymerizable monomer and (e)
45 to 98% by weight of a polycarboxylic acid resin having an acid value of 5 to 100 obtained by reacting 3 to 30% by weight of a monomer represented by the following structural formula, and B.I. A resin composition for electrodeposition coating, which comprises 2 to 55% by weight of a melamine-formaldehyde resin. However, the structural formula of (e) is