JPH09183923A - Cationic electrodeposition coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cationic electrodeposition coating composition excellent in curability and capable of giving a coating film improved in rust-preventive properties, solvent resistance, mechanical properties, etc., by mixing a resin having cationic groups with a blocked isocyanate and a specified rust-preventive pigment. SOLUTION: An epoxy resin obtained by reacting polyphenol glycidyl ether with diol glycidyl ether and polyphenol is reacted with an amine to obtain an amine-modified epoxy resin, This amine-modified epoxy resin is cationized to obtain a cationic-group-containing resin (A) comprising a cationic amine- modified epoxy resin. One hundred (100) pts.wt. resin solid component comprising 90-40wt.% component A and 10-60wt.% blocked polyisocyanate (B) is mixed with 0.1-15 pts.wt. rust-preventive pigment (C) represented by the formula: Mo.nFe2 O3 (wherein M is a bivalent metal ion; and the ratio m/n is 20/1 to 1/20).

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, as a rust preventive pigment,
When a complex oxide containing an iron ion represented by the following general formula (I) is selected and a cation group-containing resin is used as a base resin and a blocked polyisocyanate is used as a curing agent, the above object is achieved. I found what I could do.

That is, the present invention provides (A) a resin having a cationic group (base resin), (B) a blocked polyisocyanate (curing agent), and (C) an anticorrosive pigment represented by the general formula (I). It is a cationic electrodeposition coating composition containing.

General formula (I) mMO.nFe ₂ O ₃ (where M is a divalent metal ion, the ratio of m / n is 20/1
From 1/20)

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Regarding the resin having a cation group used as the base resin (A) of the present invention, an amino group is introduced into epoxy resin, epoxy group-containing acrylic resin, epoxy group-free acrylic resin, polyurethane resin and the like. It is then obtained by cationizing this amino group with an acid. Particularly preferred acids include formic acid, acetic acid, lactic acid, propionic acid, citric acid, malic acid, sulfamic acid and the like. The amount of amino groups is not particularly limited, but usually 0.5 to 3 equivalents per 1000 g of resin is suitable. Particularly preferred resins having a cationic group are epoxy resins and acrylic resins.

The epoxy resin is preferably an epoxy resin having an average of two epoxy groups per molecule, and its molecular weight is 400 to 7,000, particularly 400 to 7,000.
4000 is preferred. To give a concrete example, one is 1
It is a glycidyl ether of polyphenol having two phenolic hydroxyl groups in the molecule, and preferable polyphenols are resorcin, hydroquinone, and 2,2.
-Bis- (4-hydroxyphenyl) -propane (commonly called bisphenol A), 4,4'-dihydroxybenzophenone, 1,1-bis- (4-hydroxyphenyl)-
Methane, 1,1-bis- (4-hydroxyphenyl)-
Examples thereof include ethane and 4,4′-dihydroxybiphenyl. Others are glycidyl ethers of diols having two alcoholic hydroxyl groups in one molecule, and preferable diols are ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol and neo. Examples thereof include low molecular weight diols such as pentyl glycol, diethylene glycol, triethylene glycol and 1,4-cyclohexanediol, and oligomer diols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol, but are not limited thereto. A mixture of the above epoxy resins is also possible.

In order to obtain a suitable molecular weight, the epoxy resin is made to have a high molecular weight by using a linking agent. Preferred linking agents include the above-mentioned polyphenols or diols, and further dicarboxylic acids having two carboxyl groups in one molecule such as adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, Examples thereof include isophthalic acid, dimer acid, a butadiene polymer containing a carboxyl group, and a butadiene / acrylonitrile copolymer. As the amine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine,
Examples thereof include primary amines such as monoethanolamine, dimethylaminopropylamine and diethylaminopropylamine, and diamines in which each amino group of hexamethylenedimine is secondaryized. It is also possible to extend the chain length with a polyisocyanate. Particularly preferable high molecular weight is a method in which the glycidyl ether of the above-mentioned polyphenol and the glycidyl ether of the above-mentioned diol are linked and reacted with the above-mentioned polyphenol, and the reaction temperature is suitably from 70 to 180 ° C.

Regarding the epoxy group-containing acrylic resin,
It is obtained by copolymerizing an epoxy group-containing unsaturated monomer, an acrylic monomer and, if necessary, an unsaturated monomer other than the acrylic monomer in the presence of a polymerization initiator. Examples of the epoxy group-containing unsaturated monomer include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. As the acrylic monomer,
Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate,
2-hydroxyethyl acrylate, methyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, cyclohexyl methacrylate, acrylamide, methacrylamide, N-methylol acrylamide, N- (n-butoxymethyl)-
Examples of acrylamide and the like and unsaturated monomers other than the acrylic monomer include, but are not limited to, styrene, α-methylstyrene, vinyltoluene, cyclohexyl vinyl ether, acrylonitrile, and the like.

As the aminating agent for aminating the epoxy group of the epoxy resin or the epoxy group-containing acrylic resin, methylamine, ethylamine, n-propylamine, isopropylamine, monoethanolamine, n-propanolamine, isopropanolamine is used. , Diethylamine, diethanolamine, N-methylethanolamine, n-ethylethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminopropylamine and the like or a mixture thereof.
Of these, alkanolamines having a hydroxyl group are particularly preferred. Alternatively, after the primary amino group is previously reacted with a ketone to form a block, the remaining active hydrogen may be reacted with an epoxy group. As a specific method of amination,
It can be carried out in a solvent or in a melt without a solvent, and the reaction temperature is suitably 40 to 150 ° C.

Regarding the epoxy group-free acrylic resin,
Dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylamide, an amino group-containing unsaturated monomer such as diallylamine and the above acrylic monomer and optionally an unsaturated monomer other than an acrylic monomer, It is obtained by copolymerization in the presence of a polymerization initiator.

Regarding the polyurethane resin, a diisocyanate having two isocyanate groups per molecule is reacted with a diol having two hydroxyl groups per molecule, and an amino alcohol having a tertiary amino group in the terminal isocyanate group is reacted. And an epoxy group of a polyurethane resin obtained by reacting a terminal isocyanate group with glycidol or the like by an amination by the method described above.

The (B) blocked polyisocyanate (curing agent) in the present invention is a reaction product of a polyisocyanate and a blocking agent. As the polyisocyanate, aromatic or aliphatic (including alicyclic) is used. 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 monoethyl ether,
Cellosolve compounds such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether, carbitol compounds such as diethylene glycol monoethyl ether and diethylene glycol monobutyl ether, oxime compounds such as acetone oxime, methyl ethyl ketone oxime and cyclohexanone oxime, ε
Examples thereof include lactam compounds such as caprolactam, phenolic compounds such as phenol, cresol and xylenol, and active methylene group-containing compounds such as ethyl acetoacetate and diethyl malonate.

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 rust preventive pigment (C) represented by the general formula (I) in the present invention is a composite oxide, generally called ferrite, which is a composite of a divalent metal oxide and iron oxide. . As the divalent metal ion M, calcium, magnesium, zinc, manganese, cobalt, iron, nickel,
Each ion such as copper or a mixture thereof can be exemplified, but the ion is not limited thereto. A particularly preferred metal is calcium, and a commercially available product is Toda Kogyo Co., Ltd.
RUSTACK # 100 (calcium ferrite) can be exemplified.

Examples of the production method include a method in which powders of metal oxide and iron oxide are fired at a high temperature, and a method in which a metal oxide and iron oxide are melted by adding a flux and then cooled to precipitate crystals. However, it is not limited thereto.

The content of the rust preventive pigment (C) in the cationic electrodeposition coating composition of the present invention is not particularly limited, but is preferably 0.1 to 15 parts by weight with respect to 100 parts by weight of the resin solid content. . The content ratio of (A) a resin having a cationic group (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 40. / 15 to 60, and more preferably 80 to 55/20 to 45.

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, aluminum phosphite, zinc cyanide, Anticorrosion pigments such as zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate, zinc phosphomolybdate, aluminum phosphomolybdate, etc. Can be included. 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 coated on 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.

[0022]

EXAMPLES In the following, the present invention is carried out by cationizing (A) an amine-modified epoxy resin as a base resin, (B)
A production example of blocked polyisocyanate (curing agent),
An example and a comparative example will be described.

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.

[0024]

[Table 1]

Raw material (1) Glycier PP-300P manufactured by Sanyo Chemical Co., Ltd. Raw material (2) Epototo YD-128 manufactured by Tohto Kasei Co., Ltd. The raw material (1) was placed in a 5-liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube. (4) were charged, stirred and heated to 150 ° C. 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. 100
After holding at ℃ for 2 hours, it was cooled to 80 ℃ and taken out. The obtained amine-modified epoxy resin A1 has a solid content of 7
0.1%.

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 method shown below.

[0027]

[Table 2]

Raw material (1) Denacol E manufactured by Nagase Kasei Co., Ltd.
X-212 Raw material (2) Etoto YD-128 manufactured by Tohto Kasei Co., Ltd. Raw materials (1) to (4) were charged in a 5 liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube, followed by stirring and heating. Up to 150 ° C. 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. 100
After holding at ℃ for 2 hours, it was cooled to 80 ℃ and taken out. The resulting amine-modified epoxy resin A2 has a solid content of 6
9.9%.

Production Example 3 (Production of Base Resin A3) Using the raw materials shown in Table 3, the amine-modified epoxy resin of the present invention was produced by the method shown below.

[0030]

[Table 3]

Raw material (1) Epotote Y manufactured by Tohto Kasei Co., Ltd.
D-014 The raw materials (1) and (2) were charged in a 5 liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube, and the mixture was stirred and heated to 90 ° C. Then, while maintaining the same temperature, the raw material (3) was added dropwise over 1 hour, followed by heat retention for 2 hours, and after completion of heat retention, it was cooled to 70 ° C. and taken out. The obtained amine-modified epoxy resin A3 had a solid content of 70.0%.

Production Example 4 (Production of Base Resin A4) Using the raw materials shown in Table 4, the amine-modified epoxy resin of the present invention was produced by the method shown below.

[0033]

[Table 4]

Raw material (1) Epotote Y manufactured by Tohto Kasei Co., Ltd.
D-128 Raw material (2) Epotote YD-011 manufactured by Tohto Kasei Co., Ltd. Raw materials (1) to (3) were charged in a 5 liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube, followed by stirring and heating. Up to 100 ° C. After holding at 100 ° C. for 1 hour, it was cooled to 80 ° C. Then, the raw materials (4) and (5) were 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 A4 had a solid content of 70.1%.

Production Example 5 (Production of Base Resin A5) Using the raw materials shown in Table 5, the amine-modified acrylic resin of the present invention was produced by the following method.

[0036]

[Table 5]

Raw materials (1) to (3) were charged in a 3-liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube, stirred, heated, heated to 105 ° C., and then refluxed. The mixed solution of (4) to (9) was added dropwise over 2 hours and then kept warm for 4 hours, and after completion of the warming, it was cooled to 70 ° C. and taken out.
The resulting amine-modified acrylic resin A5 had a solid content of 70.
4%.

Production Example 6 (Production of curing agent B) Using the raw materials shown in Table 6, a blocked polyisocyanate was produced by the following method.

[0039]

[Table 6]

Raw materials (1) Millionate MR-400 manufactured by Nippon Polyurethane Co., Ltd. Raw materials (2) to (4) were charged in a 3-liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube, followed by stirring and heating. The temperature was raised to 45 ° C. and held 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 addition, the temperature was raised to 100 ° C. and the temperature was maintained at 100 ° C. for 2 hours.
It was cooled to ℃ and taken out. The resulting blocked polyisocyanate B had a solid content of 75.0%.

Examples 1, 2, 3, 4, 5 Comparative Example 1 Electrodeposition paints were prepared with the formulations shown in Table 7 and their performance was evaluated.

[0042]

[Table 7]

Calcium ferrite: manufactured by Toda Kogyo Co., Ltd.
CaO ・ Fe ₂ O ₃ magnesium ferrite: MgO ・ Fe manufactured by Toda Kogyo Co., Ltd.
₂ O ₃ Bals-S: Mizusawa Chemical Co., Ltd. basic lead silicate

Preparation of Resin Aqueous Dispersion A mixture of a base resin and a curing agent was mixed with phenoxypropanol,
The mixture was charged into a mixed solution of 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 resin aqueous dispersion and pigment paste were blended in the amounts shown in Table 7 to obtain an electrodeposition paint liquid.

Method of 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 Japan 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 7. 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 test It was performed 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%.

[0046]

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. A resin having a cationic group (base resin), and a blocked polyisocyanate (B) (curing agent).
And (C) a cationic electrodeposition coating composition containing the anticorrosive pigment represented by the general formula (I). General formula (I) mmO.nFe ₂ O ₃ (where M is a divalent metal ion, and the ratio of m / n is 20/1.
From 1/20) 2. The cationic electrodeposition coating composition according to claim 1, wherein the resin having a cationic group is a cationic amine-modified epoxy resin obtained by cationizing an amine-modified epoxy resin obtained by reacting an epoxy resin with an amine. Stuff. 3. An epoxy resin obtained by reacting a glycidyl ether of a polyphenol, a glycidyl ether of a diol, and a polyphenol, with a resin having a cationic group, is cationized with an amine-modified epoxy resin obtained by reacting an amine, The cationic electrodeposition coating composition according to claim 1, which is a cationic amine-modified epoxy resin.