JPH09124979A - Cationic electrodeposition coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cationic electrodeposition coating composition which does not contain a highly toxic heavy metal such as lead, has rustproofness comparable to those of lead-containing coating materials now in use, and has excellent film performances in, e.g. curability, solvent resistance and mechanical properties. SOLUTION: This coating composition contains phosphorus molybdate, a cationic amine-modified epoxy resin (base resin) obtained by reacting diglycidyl ether of a polyol, diglycidyl ether of a dihydric phenol, and a dihydric phenol to give an epoxy resin, reacting the epoxy resin with an amine to give an amine-modified epoxy resin and forming a cationic resin therefrom, and a blocked polyisocyanate (curing agent).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel cationic electrodeposition coating composition which is excellent in rust prevention and has excellent coating properties such as curability, solvent resistance and mechanical properties.

[0002]

2. Description of the Related Art Electrodeposition coating is superior to air spray coating and electrostatic spray coating for members having a bag structure, such as automobiles and electric appliances, and has excellent throwing power and less environmental pollution. Although it has been widely put to practical use as a primer coating, a rust preventive pigment has been added for the purpose of further improving the rust preventive property.

[0003]

Lead-type pigments are typical rust preventive pigments, but paints containing lead-type pigments are not preferable in view of recent trends in environmental regulations and legal regulations. Although some non-toxic or low-toxic rust preventive pigments have been developed, when used in cationic electrodeposition paints, none of them have sufficient rust preventive power compared to lead pigments. There was a problem.

[0004]

From the above, the inventors of the present invention did not contain a heavy metal having a high toxicity such as lead, and were excellent in rust prevention, curability, solvent resistance, mechanical properties and the like. Extensive studies were conducted for the purpose of developing a cationic electrodeposition coating composition having film performance. As a result, when phosphomolybdate is selected as the rust preventive pigment, and the base resin specified in the present invention is used as the base resin to be combined therewith,
For the first time, they have found that the above objectives can be achieved.

That is, according to the present invention, an amine is reacted with an epoxy resin obtained by reacting (A) phosphomolybdate with (B) a polyol diglycidyl ether, a dihydric phenol diglycidyl ether and a dihydric phenol. Cationic amine-modified epoxy resin (base resin) obtained by cationizing the resulting amine-modified epoxy resin
And (C) a blocked polyisocyanate (curing agent), which is a cationic electrodeposition coating composition.

As the (A) phosphomolybdate in the present invention, aluminum phosphomolybdate, zinc phosphomolybdate, potassium phosphomolybdate, sodium phosphomolybdate, calcium phosphomolybdate, etc. are used, with phosphorus being particularly preferred. Although it is an aluminum molybdate, it is possible to further improve the rust preventive performance by using a composite of aluminum phosphomolybdate mixed with zinc oxide by dry mixing or wet mixing. As a commercially available product, PM-30 manufactured by Kikuchi Dye Industry Co., Ltd.
0, PM-308, etc. can be illustrated.

The (B) cationic amine-modified epoxy resin (base resin) in the present invention is an epoxy resin obtained by reacting a diglycidyl ether of a polyol, a diglycidyl ether of a dihydric phenol and a dihydric phenol. Is a cationic amine-modified epoxy resin in which an amine-modified epoxy resin obtained by reacting an amine is cationized. The epoxy equivalent of the epoxy resin is preferably 400 to 5000, particularly preferably 50.
0 to 2000.

Examples of the diglycidyl ether of the above polyol include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, diethylene glycol diglycidyl ether, and triethylene glycol diglycidyl ether. Examples thereof include glycidyl ether, 1,4-cyclohexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, and the like, or a mixture thereof.

As the diglycidyl ether of the above dihydric phenol, resorcin diglycidyl ether, hydroquinone diglycidyl ether, bisphenol A
Diglycidyl ether, 4,4'-dihydroxybenzophenone diglycidyl ether, 1,1-bis- (4-
Hydroxyphenyl) -methanediglycidyl ether,
Examples thereof include 1,1-bis- (4-hydroxyphenyl) -ethanediglycidyl ether, 4,4′-dihydroxybiphenyl diglycidyl ether and the like, or a mixture thereof.

As the above dihydric phenol, resorcin, hydroquinone, bisphenol A, 4,4'-
Examples thereof include dihydroxybenzophenone, 1,1-bis- (4-hydroxyphenyl) -methane, 1,1-bis- (4-hydroxyphenyl) -ethane, 4,4′-dihydroxybiphenyl and the like or a mixture thereof. .

As the amine, methylamine, ethylamine, n-propylamine, isopropylamine,
Monoethanolamine, n-propanolamine, isopropanamine, diethylamine, diethanolamine, N-methylethanolamine, N-ethylethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminopropyl Examples thereof include amines and mixtures thereof, and the primary amino group may be reacted with a ketone in advance to form a block, and then the remaining active hydrogen may be reacted with an epoxy group.

The reaction of the diglycidyl ether of a polyol with the diglycidyl ether of a dihydric phenol and the dihydric phenol can be carried out in the melt without a solvent, but it can also be carried out in a system with a small amount of solvent added. Is. The solvent is not particularly limited as long as it does not react with the epoxy group. The reaction temperature is suitably 70 to 180 ° C. Amination by reacting an epoxy resin with an amine is carried out in a solvent,
Alternatively, it can be carried out in a melt without a solvent, and the reaction temperature is suitably 40 to 150 ° C.

A specific method for cationizing an amine-modified epoxy resin can be carried out by neutralizing an amino group with a protic acid. Particularly preferred acids are formic acid, acetic acid, lactic acid, propionic acid, There are citric acid, malic acid, sulfamic acid, etc. or mixtures thereof.

The (C) blocked polyisocyanate (curing agent) in the present invention is a reaction product of a polyisocyanate and a blocking agent, and the polyisocyanate may be aromatic or aliphatic (including alicyclic). A polyisocyanate, for example, 2,4- or 2,6
-Tolylene diisocyanate and mixtures thereof, p-
Phenylene diisocyanate, diphenylmethane-4,
4'-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, cyclohexylmethane-4,4'-diisocyanate, 1,3 or 1,4-bis- (isocyanatomethyl) -cyclohexane, dicyclohexyl Methane-
4,4'-diisocyanate, bis- (isocyanatomethyl) -norbornane, 3 or 4-isocyanatomethyl-1-methylcyclohexyl isocyanate, m
-Or p-xylylene diisocyanate, m- or p-tetramethylxylylene diisocyanate, further burette modified product or isocyanurate modified product of the above isocyanate, or part of the isocyanate group of the above isocyanate, ethylene glycol, propylene glycol, Low-molecular diols such as 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol and 1,4-cyclohexanediol, oligomer diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and polylactone diol, and trimethylol Polyisocyanates linked with polyols such as ethane, trimethylolpropane and pentaerythritol, or mixtures of these. Mention may be made of things.

Examples of the blocking agent include aliphatic alcohol compounds such as methanol, ethanol, n-butanol and 2-ethylhexanol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether,
Cellosolve compounds such as ethylene glycol monohexyl ether, carbitol compounds such as diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, oxime compounds such as acetone oxime, methyl ethyl ketone oxime, cyclohexanone oxime, lactam compounds such as ε-caprolactam, phenol, cresol. , Phenol compounds such as xylenol, and active methylene group-containing compounds such as acetoacetic acid ethyl ester and malonic acid diethyl ester.

The reaction between the polyisocyanate and the blocking agent can be carried out in a solvent or in a melt without a solvent. As the solvent used in the reaction, a solvent that does not react with the polyisocyanate, for example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, and isophorone, and aromatics such as benzene, toluene, xylene, chlorobenzene, and nitrobenzene Examples thereof include hydrocarbons, cyclic ethers such as tetrahydrofuran and dioxane, and halogenated hydrocarbons such as chloroform and carbon tetrachloride. The reaction temperature is not particularly limited, but is preferably 30 to 1
50 ° C.

The content of the phosphomolybdate (A) in the cationic electrodeposition coating composition of the present invention is not particularly limited, but is preferably 0.1 per 100 parts by weight of the resin solid content.
１５15 parts by weight. The content ratio of (B) cationic amine-modified epoxy resin (base resin) and (C) blocked polyisocyanate (curing agent) is 90 to 90% by weight of solid content.
40 / 10-60, preferably 85-40 / 15
-60, more preferably 80-55 / 20-45. A part of the component (B) may be blended in place of the cationized resin other than the usual amine-modified epoxy resin other than the component (B), but the amount thereof is 3 with respect to the component (B).
It is preferably 0% by weight or less.

The cationic electrodeposition coating composition of the present invention comprises
If necessary, ordinary paint additives, for example, titanium white, carbon black, color pigments such as red iron oxide,
Extenders such as kaolin, talc, aluminum silicate, calcium carbonate, mica, clay, silica, zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, tripolyphosphorus A rust preventive pigment such as aluminum acid salt, zinc molybdate, aluminum molybdate, calcium molybdate, etc., an antifoaming agent, an anti-repellent agent, an aqueous solvent or a curing catalyst may be contained. Further, other resins such as acrylic resin, polyester resin, urethane resin, butadiene resin and the like can be contained.

The cationic electrodeposition coating composition of the present invention can be applied to a desired substrate surface by a known cationic electrodeposition coating, usually in a state of being dispersed in water. Specifically, the solid content concentration of the paint is preferably adjusted to about 5 to 40% by weight, more preferably 15 to 25% by weight, and the pH is adjusted to 5 to 8,
The object to be coated can be applied as a cathode under the conditions of a bath temperature of 15 to 35 ° C. and a load voltage of 100 to 450V. After washing the coated object with water, in a baking oven at 100-200 ° C for 10-
It can be baked for 30 minutes to obtain a cured coating film. The coating film thickness obtained from the cationic electrodeposition coating composition of the present invention is not particularly limited, but in the cured coating film 5 to 60 μm,
It is preferably 10 to 40 μm.

[0020]

EXAMPLES The present invention will be described below with reference to production examples of amine-modified epoxy resin (base resin) and blocked isocyanate (curing agent), and examples and comparative examples.

Production Example 1 (Production of Base Resin B1) Using the raw materials shown in Table 1, the amine-modified epoxy resin of the present invention was produced by the following method.

[0022]

[Table 1]

Raw material (1) Glycier PP-300P manufactured by Sanyo Kasei Co., Ltd. Raw material (2) Epototo YD-128 manufactured by Toto Kasei Co., Ltd. (2) and (3) were charged, stirred and heated to raise the temperature to 150 ° C. After holding at 150 ° C for 6 hours, the raw material (4) was gradually added and cooled to 80 ° C. Then, the raw material (5) was charged and the temperature was raised to 100 ° C.
After keeping at 100 ° C. for 2 hours, it was cooled to 80 ° C. and taken out. The obtained amine-modified epoxy resin B1 had a solid content of 70.1%.

Production Example 2 (Production of Base Resin B2) Using the raw materials shown in Table 2, the amine-modified epoxy resin of the present invention was produced by the method shown below.

[0025]

[Table 2]

Raw material (1) Denacol EX-212 manufactured by Nagase Kasei Co., Ltd. Raw material (2) Epototo YD-128 manufactured by Toto Kasei Co., Ltd. In a 5 liter 4-necked flask equipped with a stirrer, thermometer, and cooling tube, the raw material (1) , (2), (3) were charged and stirred,
Heating was performed to raise the temperature to 150 ° C. After holding at 150 ° C for 6 hours, the raw material (4) was gradually added and cooled to 80 ° C. Then, the raw material (5) was charged and the temperature was raised to 100 ° C. After keeping at 100 ° C. for 2 hours, it was cooled to 80 ° C. and taken out. The obtained amine-modified epoxy resin B2 is
The solid content was 69.9%.

Production Example 3 (Production of Amine-Modified Epoxy Resin B3 for Comparison) Using the raw materials shown in Table 3, a comparative amine-modified epoxy resin was produced by the following method.

[0028]

[Table 3]

Raw Material (1) Topo Kasei's Epotote YD-128 Raw Material (2) Toto Kasei's Epotote YD-011 Into a 5 liter 4-necked flask equipped with a stirrer, thermometer and cooling tube, the raw material (1) , (2), (3) were charged and stirred,
Heating was performed and the temperature was raised to 100 ° C. After holding at 100 ° C. for 1 hour, it was cooled to 80 ° C. Next, the raw material (4),
(5) was charged and the temperature was raised to 100 ° C. After keeping at 100 ° C. for 2 hours, it was cooled to 80 ° C. and taken out. The obtained amine-modified epoxy resin B3 had a solid content of 70.1%.

Production Example 4 (Production of Curing Agent C) Using the raw materials shown in Table 4, a blocked isocyanate was produced by the following method.

[0031]

[Table 4]

Raw Material (1) Millionate MR-400 manufactured by Nippon Polyurethane Co., Ltd. A raw material (2), (3), (4) was charged into a 3 liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube, and stirred. ,
Heating was performed, the temperature was raised to 45 ° C., and the temperature was maintained for 30 minutes. Then, while maintaining the temperature in the flask at 45 ° C, the raw material (1) was charged over 1 hour, and reacted at 40 to 50 ° C for 3 hours. Next, the same temperature was maintained, and the raw material (5) was added dropwise over 1 hour. After the dropping, the temperature was raised to 100 ° C., the temperature was maintained at 100 ° C. for 2 hours, then cooled to 80 ° C., and taken out. The obtained blocked isocyanate C had a solid content of 75.0%.

Examples 1, 2, 3 and Comparative Examples 1, 2, 3 Electrodeposition paints were prepared with the formulations shown in Table 5 and their performances were evaluated.

[0034]

[Table 5]

Method for preparing test plate Using the electrodeposition coating solution obtained above, a carbon electrode was used as an anode, and a zinc phosphate treated plate (Bt manufactured by Nippon Test Panel Co., Ltd.) was used.
(3004, 0.8 × 70 × 150 mm) was used as a cathode, electrodeposition coating was performed under the condition that the film thickness after baking was 20 μm, and baking was performed at 175 ° C. for 25 minutes. The results of coating film performance evaluation are shown in Table 5. Evaluation method (1) Appearance It is visually judged to be o when no cracks or spots are observed. (2) Solvent resistance The coating film is wiped with a solvent using a mixed solution having an ethanol / acetone weight ratio of 1/1. ◯: No change in coating film after 10 consecutive runs ×: Part of coating film dissolves within 10 times (3) Impact resistance Dupont type 1/2 inch 1 kg
Drop distance (cm) (4) Erichsen Distance until peeling occurs when the coating film is deformed (mm) (5) Salt spray resistance It was measured according to JIS-Z-2731. A flaw reaching the substrate is put on the electrodeposition coated surface with a cutter knife, and the rust width after 1000 hours is evaluated.

[0036]

EFFECTS OF THE INVENTION According to the present invention, it does not contain heavy metals having a high toxicity such as lead, has the same rust preventive property as the current lead-containing paint, and is excellent in curability, solvent resistance, mechanical properties, etc. A cationic electrodeposition coating composition having coating film performance can be provided.

Claims (3)

[Claims] 1. An epoxy resin obtained by reacting (A) phosphomolybdate with (B) a polyol diglycidyl ether, a dihydric phenol diglycidyl ether and a dihydric phenol, obtained by reacting an amine with an epoxy resin. A cationic electrodeposition coating composition containing a cationic amine-modified epoxy resin (base resin) obtained by cationizing the amine-modified epoxy resin as described above, and (C) a blocked polyisocyanate (curing agent). 2. The cationic electrodeposition coating composition according to claim 1, wherein the phosphomolybdate is aluminum phosphomolybdate. 3. The cationic electrodeposition coating composition according to claim 1, wherein the phosphomolybdate is a complex of aluminum phosphomolybdate and zinc oxide.