JPH0637599B2 - Electrodeposition coating method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrodeposition coating method. More specifically, the present invention relates to an electrodeposition coating method for forming a coating film on a conductive article which is excellent in various properties such as chemical resistance, heat resistance, and electrical insulation, and which is also excellent in 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 simplification of the steps is a problem. As a means of simplifying this process, attention has been paid to electrodeposition coating, which is excellent in the coverage of edges and through holes. However, in the current electrodeposition coating method, it is not possible to obtain the ones that sufficiently satisfy various performances such as heat resistance and electric insulation required for the aluminum base printed circuit board, and it is a reality that improvement thereof is earnestly desired. is there.

An object of the present invention is to greatly improve the performance of conventional electrodeposition coating films, and to provide an electrodeposition coating method capable of forming an electrodeposition coating film having various properties required for an aluminum base printed circuit board. It is a thing.

(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 comprising 2 to 55% by weight of a melamine-formaldehyde resin is neutralized with a basic compound so as to be at least water-dispersible, and then an aqueous liquid dissolved or dispersed in water is used. It is an electrodeposition coating method.

However, the structural formula of (e) is According to the study by the present inventors, maleimides having a specific structural formula are used together in the synthesis of α, β-ethylenically unsaturated polycarboxylic acid resin, and the obtained polycarboxylic acid resin is used together with melamine-formaldehyde resin. The inventors have found that the electrodeposition coating can form an electrodeposition coating film having excellent properties such as chemical resistance, heat resistance, and electrical insulation, and have completed the present invention.

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

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.

Structural formula (e), As the monomer represented by, N-phenylmaleimide,
Examples include N-2-methylmaleimide, N-2-ethylmaleimide, N-2-chloromaleimide and the like.

The polycarboxylic acid resin 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 water or isopropyl alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether. At this time, if necessary, ammonium persulfate, potassium persulfate, α. Polymerization initiators such as α'-azobisisobutyronitrile, 4.4'-azobis-4-cyanovaleric acid, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate , A reducing agent such as ferric chloride, and a surfactant such as sodium alkylbenzene sulfonate and alkyl ether sulfonate. 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 5 mgKOH or less, 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
The above is not preferable because the chemical properties such as water resistance and alkali resistance of the coating film are remarkably reduced.

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 of the component A, preferably 50 to 50% by weight.
90 wt%, B component 2 to 55 wt%, preferably 10
It is suitable to use in the range of 50% by weight. As the melamine-formaldehyde resin, it is preferable to use a melamine resin, in particular, a methylol melamine at least partially etherified with one or more lower alcohols such as methanol, ethanol, propanol and butanol.

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 solution from the resin composition for electrodeposition coating prepared in this manner, a basic compound is added to the resin composition, and a carboxyl group existing in the molecule of the polycarboxylic acid resin is added. At least a part of the solution is neutralized to make it dispersible in water, and deionized water is added to the solution 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 is used as an anode in the thus prepared electrodeposition coating solution, a direct current voltage is applied between the counter electrode and the conductive article, and the conductive article is pulled up from the solution and heated or baked after washing or without washing. Then, an electrodeposition coating film is formed on the surface of the conductive article.

The electrodeposition coating condition of the present invention is 1 at a voltage of 10 to 300 volts.
DC energization is performed for 0 to 900 seconds.

In the present invention, the heating and baking of the electrodeposition coating film is performed at 130 to 250 ° C.
It is preferably achieved at 140 to 230 ° C. for 15 to 60 minutes.

The conductive article targeted by the present invention may be any one having conductivity, and is not limited to the shape, size, material, etc., for example, iron, copper, aluminum, magnesium, titanium, or the like, or Examples thereof include alloys thereof, and plastics having a metal plating layer or other conductive layer formed on the surface thereof. These electrically conductive articles are usually subjected to chemical conversion treatment before electrodeposition coating.
For example, various phosphate treatments, chromate treatments, boehmite treatments, anodic oxidation treatments and the like are suitable.

(Examples) The following examples are given to more specifically describe the present invention.

[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.

[Preparation of electrodeposition coating liquid A] Polycarboxylic acid resin A 120 g and melamine resin (trade name Cymel HM-6 manufactured by Mitsui Cyanamid) in a container.
30 g was taken and then 1.90 g triethylamine,
0.5 g of 2-ethylhexyl alcohol was added and sufficiently stirred. Deionized water was gradually added with further stirring to prepare an electrodeposition coating solution A having a resin solid content of 15% by weight.

[Preparation of electrodeposition coating liquids B to N] In the method for preparing electrodeposition coating liquid A, the type of polycarboxylic acid resin, the blending amount of melamine resin, triethylamine, 2
-Electrodeposition coating solutions B to N were prepared in the same manner except that the addition amount of ethylhexyl alcohol was changed as shown in Table 2.

Example 1 An electrodeposition coating solution A was built in an electrodeposition coating bath, an aluminum plate having an anodic oxide film (10 μm) formed thereon was connected to the anode in this bath, and a stainless plate was connected to the cathode, and the distance between the electrodes was 5 cm. ,
Under the condition that the bath temperature was 20 ° C., direct current was applied at a voltage of 160 V for 5 minutes. Then, the aluminum plate was pulled up from the bath, washed with water, and then baked at 180 ° C. for 30 minutes.

As a result, an anodized aluminum plate having an electrodeposition coating film having the performance shown in Table 3 was obtained.

Examples 2 to 7 and Comparative Examples 1 to 7 In the method of Example 1, except that the electrodeposition coating liquids A to B were used instead of the electrodeposition coating liquid A, the anodized aluminum plates were all electrodeposited in the same manner. I painted it.

As a result, an anodized aluminum plate having an electrodeposition coating film having the performance shown in Table 3 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 Examples 8 to 10 In the method of Example 1, the object to be coated was changed to an anodized aluminum plate, and a chemical conversion treatment (phosphate) was applied to the iron plate, nickel plating (thickness). Electrodeposition coating was performed using an iron plate having a thickness of 10 μm) and a polyester filament shear fabric having a copper plating (thickness of 2 μm).

The electrodeposition coating conditions were as shown below.

As a result, in each case, a uniform electrodeposition coating film was formed, and the coating film performance was the same as in Example 1.

(Effects of the Invention) The electrodeposition coating method of the present invention can form an electrodeposition coating film having excellent properties such as heat resistance, electric insulation resistance, and chemical resistance on the surface of a conductive article. Has the effect.

Claims (1)

[Claims] 1. A conductive article as an anode is immersed in an aqueous liquid containing a polycarboxylic acid resin and a melamine-formaldehyde resin as a main component for forming a coating film, and a direct current is applied between the counter electrode and the conductive article. When forming an electrodeposition coating film on A. (A) α, β-ethylenically unsaturated carboxylic acid 2-1
5% by weight, (b) 5 to 85% by weight of α, β-ethylenically unsaturated carboxylic acid alkyl ester, (c) 3 to 30% by weight of α, β-ethylenically unsaturated carboxylic acid hydroxyalkyl-containing ester, (D) Other copolymerizable monomer 0
To 60% by weight and (e) a monomer 3 represented by the following structural formula
45 to 98% by weight of a polycarboxylic acid resin having an acid value of 5 to 100 obtained by reacting 30 to 30% by weight of B. A resin composition comprising 2 to 55% by weight of a melamine-formaldehyde resin is neutralized with a basic compound so as to be at least water-dispersible, and then an aqueous liquid dissolved or dispersed in water is used. Electrodeposition coating method. However, the structural formula of (e) is