JPH09241546A - Cationic electrodeposition coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cationic electrodeposition coating compsn. which does not coating any highly toxic heavy metal (e.g. lead) and provides a coating film excellent in rust prevention, curability, solvent resistance, mechanical properties, etc. SOLUTION: This compsn. contains a cationic amine-modified epoxy resin (a base resin) obtd. by cationizing an amine-modified epoxy resin obtd. by reacting an amine with an epoxy resin obtd. by reacting a glycidyl ether of a polyol, a glycidyl ether of a dihydric phenol, and a dihydric phenol, a blocked polyisocyanate (curative), and a di- or trivalent metal salt of phosphrous acid (a rust-preventive pigment).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel cationic electrodeposition coating composition having excellent rust-preventing properties and 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, the above object can be achieved only when a divalent or trivalent metal salt of phosphorous acid 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. Found out.

That is, according to the present invention, (A) an epoxy resin obtained by reacting a glycidyl ether of a polyol, a glycidyl ether of a dihydric phenol, and a dihydric phenol with an amine-modified epoxy resin obtained by reacting an amine with a cation. Containing a cationic amine-modified epoxy resin (base resin), (B) blocked polyisocyanate (curing agent), and (C) divalent or trivalent metal salt of phosphorous acid (rust preventive pigment) It is a cationic electrodeposition coating composition.

The (A) cationic amine-modified epoxy resin (base resin) in the present invention is an epoxy resin obtained by reacting a glycidyl ether of a polyol, a glycidyl ether of a dihydric phenol and a dihydric phenol with an amine. It is a cationic amine-modified epoxy resin obtained by cationizing an amine-modified epoxy resin obtained by reacting. Epoxy equivalent of epoxy resin is 30
0 to 5000 is preferable, and particularly preferably 400 to 20
00.

Examples of the glycidyl 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 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 glycidyl ether of dihydric phenol, resorcin diglycidyl ether, hydroquinone diglycidyl ether, bisphenol A diglycidyl ether, 4,4'-dihydroxybenzophenone diglycidyl ether, 1,1-bis- (4- Hydroxyphenyl) -methanediglycidyl ether,
1,1- (2,4'-dihydroxyphenyl) -methane diglycidyl ether, 1,1-bis- (4-hydroxyphenyl) -ethane diglycidyl ether, 4,4 '
Examples thereof include dihydroxybiphenyl diglycidyl ether and the like, or a mixture thereof.

As the above dihydric phenol, resorcin, hydroquinone, bisphenol A, 4,4'-
Dihydroxybenzophenone, 1,1-bis- (4-hydroxyphenyl) -methane, 1,1- (2,4'-dihydroxyphenyl) -methane, 1,1-bis- (4-
Examples thereof include hydroxyphenyl) -ethane, 4,4′-dihydroxybiphenyl and the like, or a mixture thereof.

As the amine, methylamine, ethylamine, n-propylamine, isopropylamine,
Monoethanolamine, n-propanolamine, isopropanolamine, diethylamine, diethanolamine, N-methylethanolamine, N-ethylethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminopropylamine And the like, or a mixture thereof. Further, 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 the polyol with the diglycidyl ether of the 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 there. 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 protonic acid. Particularly preferred acids are formic acid, acetic acid, lactic acid, propionic acid, Examples include citric acid, malic acid, sulfamic acid, etc., or a mixture thereof.

The blocked polyisocyanate (curing agent) (B) 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, 1,3 or 1,4-bis- (isocyanate methyl) -cyclohexane, dicyclohexylmethane-4,4'-diisocyanate, bis- (isocyanatemethyl) -norbornane, 3 or 4-isocyanate Methyl-1-methylcyclohexyl isocyanate, m- or p-xylylene diisocyanate, m
-Or p-tetramethylxylylene diisocyanate, or a burette-modified or isocyanurate-modified isocyanate, or a part of the isocyanate group of the isocyanate is converted to ethylene glycol, propylene glycol, 1,6-hexanediol, neopentyl Glycol, diethylene glycol,
Linked with low molecular weight diols such as triethylene glycol and 1,4-cyclohexanediol, oligomer diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and polylactone diol, and polyols such as trimethylolethane, trimethylolpropane and pentaerythritol And mixtures thereof.

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

The reaction of the polyisocyanate with the blocking agent can be carried out in a solvent or in a solvent-free melt. 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

Examples of the (C) divalent or trivalent metal salt of phosphorous acid in the present invention include calcium phosphite, strontium phosphite, barium phosphite, zinc phosphite, aluminum phosphite, and the like. Particularly preferred is aluminum phosphite. Further, in order to improve the rust preventive property, the metal salt of phosphorous acid can be surface-treated. Commercially available products are YM- from Taihei Chemical Industry Co., Ltd.
60, YM-70, YM-92NS, YM-102N
S, Toho Pigment Industry Co., Ltd. NP-1530, NP-16
00, NP-1100, NP-1110 and the like.

The content of the (C) divalent or trivalent metal salt of phosphorous acid used in the cationic electrodeposition coating composition of the present invention is not particularly limited, but is preferably 100 parts by weight of the resin solid content. 0.1 to 15 parts by weight. The content ratio of (A) cationic amine-modified epoxy resin (base resin) and (B) blocked polyisocyanate (curing agent) is 90 to 40/10 to 60 in terms of solid content weight ratio, and preferably 85 to 85. 40 / 15-60, more preferably 80-55
/ 20 to 45. Further, a part of the component (A) can be blended in place of a cationized resin other than the usual amine-modified epoxy resin other than the component (A), but the amount thereof is 30% by weight or less based on the component (A). Is preferred.

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 cyanide, zinc oxide, aluminum tripolyphosphate, molybdic acid Zinc, aluminum molybdate,
A rust preventive pigment such as calcium molybdate, 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 A1) 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 Chemical Co., Ltd. Raw material (2) Epotote YD-128 manufactured by Toto Kasei Co., Ltd. Charge (2), (3), (4),
The temperature was raised to 150 ° C. by stirring and heating. After holding at 150 ° C for 6 hours, the raw material (5) was gradually added and cooled to 80 ° C. Next, the raw material (6) 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. Obtained amine-modified epoxy resin A1
Had a solid content of 70.1%.

Production Example 2 (Production of Base Resin A2) Using the raw materials shown in Table 2, the amine-modified epoxy resin of the present invention was produced by the following method.

[0025]

[Table 2]

Raw material (1) Denase Coal EX-212 manufactured by Nagase Kasei Co., Ltd. Raw material (2) Epototo YD-128 manufactured by Tohto Kasei Co., Ltd. , (2), (3) and (4) were charged, stirred and heated to 150 ° C. 150
After maintaining at 6 ° C. for 6 hours, the raw material (5) was gradually charged and
Cooled to ° C. Next, the raw material (6) 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 A2 had a solid content of 69.9%.

Production Example 3 (Production of Base Resin A3 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 A3 had a solid content of 70.1%.

Production Example 4 (Production of curing agent B) Using the raw materials shown in Table 4, a blocked polyisocyanate was produced by the following method.

[0031]

[Table 4]

Raw Materials (1) Millionate MR-400 manufactured by Nippon Polyurethane Co., Ltd. Raw materials (2), (3) and (4) were 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 resulting blocked polyisocyanate B had a solid content of 75.0%.

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

Preparation of Resin Aqueous Dispersion A mixture of a base resin and a curing agent was placed in a mixture of propylene glycol monomethyl ether, formic acid and deionized water with good stirring to obtain an aqueous resin dispersion. Preparation of pigment paste Base resin, formic acid, deionized water, diethylene glycol monobutyl ether, carbon black, titanium oxide, kaolin, dibutyltin oxide, and rust preventive pigment are thoroughly stirred with a dissolver, and then a horizontal sand mill is used to make a grain gauge particle size of 1
The pigment paste was obtained by dispersing until it became 0 μm or less. Preparation of Electrodeposition Paint The above aqueous resin dispersion and pigment paste were blended in the amounts shown in Table 5 to obtain an electrodeposition coating liquid.

[0035]

[Table 5]

Method for producing test plate Using the electrodeposition coating solution obtained above, a carbon phosphate 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 (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. (6) Hot Salt Water Immersion Test After immersing the coated test plate in a 5% saline solution at 50 ° C. for 1000 hours, the ratio of the coating film peeling area to the entire test plate is measured and expressed in%.

[0037]

INDUSTRIAL APPLICABILITY According to the present invention, a cationic electrodeposition coating composition containing no heavy metal having a high toxicity such as lead and having excellent coating performance in rust prevention, curability, solvent resistance, mechanical properties, etc. You can provide things.

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Claims (2)

[Claims] 1. An amine-modified epoxy resin obtained by reacting an amine with an epoxy resin obtained by reacting a glycidyl ether of a polyol (A), a glycidyl ether of a dihydric phenol, and a dihydric phenol is cationized, Cationic charge containing cationic amine-modified epoxy resin (base resin), (B) blocked polyisocyanate (hardener), and (C) divalent or trivalent metal salt of phosphorous acid (rust preventive pigment). Coating composition. 2. The cationic electrodeposition coating composition according to claim 1, wherein the divalent or trivalent metal salt of phosphorous acid is aluminum phosphite.