JPH08209042A - Resin composition for cationic electrodeposition coating - Google Patents

Abstract

PURPOSE: To obtain the subject composition comprising a cationic group- containing resin as a base material resin and a uretidione group-containing compound as a curing agent. CONSTITUTION: This resin composition comprises (A) a base material resin containing cationic groups (especially preferably an epoxy resin and an acrylic resin), and (B) a curing agent having a structure of the formula (R is a 1-20C aliphatic group or aromatic group; A is non-aromatic diol residue; B is non- aromatic monoalcohole residue, non-aromatic diol residue, etc.; (n) is 0-30). The components A and B are compounded in an A/B weight ratio of (90-40)/(10-60), preferably (85-50)/(15-50), more preferably (80-55)/(20-45).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel resin composition for cationic electrodeposition coating. More specifically, the present invention relates to a resin composition for a cationic electrodeposition coating, which has a small amount of heat loss component during baking, and has excellent coating performance in curability, corrosion resistance, solvent resistance, mechanical properties, etc. Is.

[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. Widely used as a primer coating. As the resin used for electrodeposition coating, a cationic resin is currently in the mainstream, and a resin obtained by cationizing the amino group of a modified epoxy resin having an amino group in the molecule is used as a base resin, and tolylene diisocyanate is used. A typical example thereof is a resin composition containing a blocked polyisocyanate as a curing agent, which is obtained by reacting an aromatic isocyanate such as diphenylmethane diisocyanate with a blocking agent. Examples of the blocking agent used include methanol, ethanol, n-butanol, 2-ethylhexanol,
There are methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, acetone oxime, methyl etiketone oxime, cyclohexanone oxime, ε-caprolactam and the like.

[0003]

One of the recent problems in electrodeposition coating is to reduce the components that evaporate during baking as much as possible. When there are many volatile components, one part of this component accumulates as a tar component on the inner wall of the baking oven, which requires a great deal of cost for periodic cleaning of the baking oven. On the other hand, as a method of treating the exhaust gas generated during baking, a method of incineration and releasing it into the atmosphere is generally adopted, and a metal catalyst is used, but it is affected by the catalyst poison by the volatile component. However, there is a problem that the life of the catalyst becomes very short. On the other hand, the fact that the amount of volatile components is large is a big problem from the standpoint of reducing the amount of coating film forming components, wasting resources, and protecting the global environment. The reason for the increase in volatile components is that the blocking agent of the blocked polyisocyanate, which is mainly used as the curing agent, is desorbed during baking, and thus the content of the blocking agent, which is an alternative to the conventional blocked polyisocyanate, is small. A curing agent is needed.

[0004]

From the above, the present inventors have found that the heating loss during baking is small, the curability,
Corrosion resistance, solvent resistance, having excellent coating performance in mechanical properties, etc., as a result of diligent study on the development of a resin composition for a cationic electrodeposition coating, by using a compound having a uretdione group as a curing agent, It was found that the purpose of can be achieved.

That is, the present invention provides a resin composition for a cationic electrodeposition coating composition containing a base resin having a cationic group and a curing agent, wherein the curing agent is represented by the following structural formula. A resin composition for coating material.

[0006]

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Here, R is one or more groups selected from an aliphatic group having 1 to 20 carbon atoms, an alicyclic group or an aromatic group, A is a non-aromatic diol residue B is not One or more selected from aromatic monoalcohols, non-aromatic diols, phenols, lactams, oximes, active methylene group-containing compounds or non-aromatic secondary amines. The residue n of the compound is 0 to 30.

Regarding the resin having a cation group used as the base resin of the present invention, an amino group is introduced into epoxy resin, epoxy group-containing acrylic resin, epoxy group-free acrylic resin, polyurethane resin, etc. It is obtained by protonating at. 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 the molecular weight thereof 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)-
Examples thereof include methane, 1,1-bis- (4-hydroxyphenyl) -ethane, 4,4′-dihydroxybiphenyl and the like. Other examples 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. Pentyl glycol, diethylene glycol, triethylene glycol,
Low molecular weight diols such as 1,4-cyclohexanediol,
Polyethylene glycol, polypropylene glycol,
Examples thereof include oligomer diols such as polytetramethylene glycol, but are not limited thereto, and 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 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 polyisocyanate.

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 and isopropanolamine are used. , Diethylamine, diethanolamine, N-methylethanolamine, n-ethylethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminopropylamine and the like or a mixture thereof.
Among these, alkanolamines having a hydroxyl group are particularly preferable. Alternatively, 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 the epoxy group. As a specific method of amination,
It can be carried out in a solvent or in a melt without solvent, a reaction temperature of 40 to 150 ° C. being suitable. Specific methods include US Pat. No. 3,984,299, US Pat. No. 4,017,438 and JP-A-59-403.
No. 013 specification is referred to.

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.

With respect to 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 at 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.

Regarding the curing agent used in the present invention, R in the chemical formula 1 represents a portion other than the isocyanate group of the aliphatic, alicyclic or aromatic diisocyanate,
The number of carbon atoms is 1 to 20, and even if all are the same in the formula, or if there are two or more types, there is no problem.

An example of diisocyanate is 2,4-
Or 2,6-tolylene diisocyanate or a mixture thereof, p-phenylene diisocyanate, diphenylmethane-4,4'-diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 1,3- or 1,4-bis (isocyanate) Natomethyl) cyclohexane, m- or p-xylylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate,
Examples thereof include, but are not limited to, m- or p-tetramethylxylylene diisocyanate and the like, or a mixture thereof.

A in the above Chemical Formula 1 represents the remaining portion of the non-aromatic diol that has reacted with the isocyanate group, and there is no problem even if one or more diols are used.

Examples of diols are ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol,
Low molecular weight diols such as 1,4-cyclohexanediol,
Polyethylene glycol, polypropylene glycol,
Examples thereof include oligomer diols such as polytetramethylene glycol and polylactone diol, and mixtures thereof, but are not limited thereto.

B at both ends in the chemical formula 1 is a non-aromatic monoalcohol, a non-aromatic diol, a phenol, a lactam, an oxime, an active methylene group-containing compound or a non-aromatic system. The compound selected from the secondary amines (hereinafter referred to as component B) represents the remaining portion reacted with the isocyanate group, and there is no problem even if both are the same or different.

Examples of the component B are methanol, ethanol, n-butanol, isobutanol, tert-butanol, 2-ethylhexanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, ethyl carbitol, butyl carbitol,
The non-aromatic monoalcohols such as triethylene glycol monoethyl ether and triethylene glycol monobutyl ether, and the non-aromatic diols include the above-exemplified compounds, phenols such as phenol, cresol and xylenol, and ε-caprolactam. Such as lactams, oximes such as acetone oxime, methyl ethyl ketoxime, and cyclohexane oxime, active methylene group-containing compounds such as acetoacetic acid ethyl ester and malonic acid diethyl ester, ethyl isopropylamine, di-n-
Propylamine, diisopropylamine, isopropyl-tert-butylamine, di-n-butylamine, diisobutylamine, dicyclohexylamine, di-
(3,5,5-trimethylcyclohexyl) amine, piperidine, 2,6-dimethylpiperidine, pyrrolidine,
Non-aromatic secondary amines such as 2,5-dimethylpyrrolidine, 2,2,6,6-tetramethylpiperidine, morpholine, 2,6-dimethylmorpholine, isopropylcyclohexylamine, and the like, or a mixture thereof. However, the present invention is not limited to these.

The content of the component B in the curing agent is preferably as small as possible, specifically, it is preferably 15% by weight or less. Further, the range of n in the above chemical formula 1 is 0 to 30, but a more preferable range is 3 to 15.

The curing agent used in the present invention can be manufactured, for example, as follows. That is, as the first step, in the presence or absence of a solvent, using a catalyst such as alkylphosphine, alkylarylphosphine, pyridine, methylpyridine, trialkylamine, to react diisocyanate, diisocyanate having a uretdione group It produces a dimer. Subsequently, an excess or deficiency of non-aromatic diols is reacted with the remaining isocyanate groups in an equivalent amount, and in the case of deficiency, further non-aromatic monoalcohols, phenols,
The desired product is obtained by reacting a lactam, an oxime, an active methylene group-containing compound or a non-aromatic secondary amine. The reaction temperature is 0-40 in the first stage
C. is preferable, and 20 to 60.degree. C. is preferable in order to suppress dissociation of the uretdione group even in the second step.

In the present invention, the mixing ratio of the base resin having a cationic group and the curing agent is 90 to 40/10 by weight.
Is 60 to 60, preferably 85 to 50/15 to 50, and more preferably 80 to 55/20 to 45.

The acid-neutralized composition for cationic electrodeposition coating composition of the present invention is usually used for electrodeposition coating in a state of being dispersed in water. It is also possible to use an organic solvent other than water together if necessary. For example, isopropanol,
Examples include n-butanol, isobutanol, 2-ethylhexanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, methoxypropanol, phenoxypropanol, butyl carbitol, isophorone, toluene and xylene.

The resin composition for a cationic electrodeposition coating composition of the present invention may further contain a conventional coating composition, for example, if necessary.
Coloring pigments such as titanium white, carbon black, red iron oxide, and yellow lead, extenders such as kaolin, talc, calcium carbonate, mica, clay, silica, strontium chromate, zinc chromate, lead silicate, basic lead silicate, Lead chromate, basic lead chromate, lead phosphate, red lead, cyanamide lead, lead zincate, lead sulfate, basic lead sulfate,
A rust preventive pigment such as aluminum phosphomolybdate or aluminum tripolyphosphate, an antifoaming agent, an anti-repellent agent, or a curing catalyst may be contained.

The resin composition for a cationic electrodeposition coating composition of the present invention can be coated on a desired substrate surface by a known cationic electrodeposition coating. Specifically, the solid content concentration of the paint is preferably about 5 to 40% by weight, more preferably 15% by weight.
-25%, PH is adjusted to 5-8 depending on the amount of acid used, and the object to be coated can be applied as a cathode under the conditions of a bath temperature of 15-35 ° C and a load voltage of 100-450V, but this condition is not limiting. It is not something that will be done. The coating film thickness obtained from the coating resin composition of the present invention is not particularly limited, but in the cured coating film, 5 to 60 μm, preferably 10 to 40 μm is suitable.

Hereinafter, the present invention will be described in more detail with reference to production examples and examples, but the present invention is not limited thereto.

Production Example 1 Production of Hardener A A 4-necked flask equipped with a reflux condenser, thermometer and stirrer was charged with 1078 g of methyl isobutyl ketone and 483 g of 1,4-butanediol and heated to 45 ° C. After the temperature was raised, the temperature was kept at 45 to 50 ° C. and crushed 2.
1519 g of 4-tolylene diisocyanate dimer (manufactured by Nippon Polyurethane Co., Ltd.) was added over 2 hours, and after addition 3
After being kept warm for a time, a curing agent A having a solid content of 65% was obtained.

Production Example 2 Production of curing agent B Into a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer, 646 g of methoxypropanol was charged, the temperature was kept at 40 ° C., and IPDI-BF154 manufactured by Hüls.
Dissolve 1200 g of 0 (isophorone diisocyanate derivative uretdione group content about 15%), solid content 65%
Hardening agent B was obtained.

Production Example 3 Production of Hardener C In a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer, 227 g of isophorone, 106 g of toluene and 328 g of ε-caprolactam were charged, and the temperature was raised to 45 ° C. and ε-
Dissolve caprolactam. After dissolution, 812 g of polymethylene polyphenyl isocyanate (Millionate MR-400 manufactured by Nippon Polyurethane Co., Ltd.) was charged over 1 hour,
The reaction was carried out at 40 to 50 ° C for 3 hours. After the reaction, 483 g of butyl cellosolve was added dropwise over 1 hour while maintaining the same temperature, and after the addition, the temperature was raised to 90 ° C. and the temperature was kept for 2 hours to give a solid content of 75.
% Curing agent C was obtained.

Production Example 4 Production of Base Resin A A bisphenol A type epoxy resin having an epoxy equivalent of 950 (Sumiepoxy ESA-014 manufactured by Sumitomo Chemical Co., Ltd.) was placed in a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer.
Charge 1805g, 855g methoxy propanol,
Heat up to 90 ° C. Next, while maintaining the same temperature, 190 g of diethanolamine was added dropwise over 1 hour, and after the addition, the temperature was kept for 2 hours to obtain a base resin A having a solid content of 70%.

Production Example 5 Production of Base Resin B In a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer, 145 g of ethyl cellosolve and 1 of butyl cellosolve were added.
Charge 45g and 110g isopropanol, 105 ℃
After heating up to 450 g of butyl acrylate, 100 g of methyl methacrylate, 150 g of styrene, 200 g of 2-hydroxyethyl methacrylate, 100 g of dimethylaminopropyl acrylamide, and 30 g of azobisisobutyronitrile under reflux, the mixture was added dropwise over 2 hours. Then, the temperature was kept for 4 hours to obtain a base resin B having a solid content of 70%.

Production Example 6 Production of Dispersion Resin A bisphenol A type epoxy resin having an epoxy equivalent of 186 (Sumiepoxy ELA-128 manufactured by Sumitomo Chemical Co., Ltd.) was placed in a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer.
372 g, bisphenol A type epoxy resin having an epoxy equivalent of 475 (Sumiepoxy ESA-01 manufactured by Sumitomo Chemical Co., Ltd.
1) 950 g, methoxypropanol 779 g, diethanolamine 105 g, and diethylaminopropylamine 390 g were charged, the temperature was raised to 120 ° C., and the reaction was carried out at the same temperature for 3 hours to obtain a dispersion resin having a solid content of 70%.

Production Example 7 Production of Pigment Paste In a stainless steel cylindrical container, 286 g of the dispersion resin of Production Example 6,
Charge 9.2 g of formic acid, 983 g of deionized water, 2.6 g of carbon black, 300 g of titanium oxide, 300 g of kaolin, 50 g of basic lead silicate, 40 g of butyl carbitol, stir with a dissolver for 30 minutes, then granulate with a horizontal sand mill. Dispersion was performed until the gauge particle size became 10 μm or less, and a pigment paste having a solid content of 45% was obtained.

Examples 1 to 5 and Comparative Examples 1 and 2 Production of Aqueous Dispersion of Resin Composition for Cationic Electrodeposition Coating A clear resin for cationic electrodeposition coating was prepared according to the formulation shown in Table 1. Manufacturing Example 4 for producing clear resin,
The base resin of Example 5, the curing agent of Production Examples 1, 2, and 3 and phenoxypropanol are mixed, and the mixture is poured into a mixed solution of deionized water and formic acid at a constant speed with sufficient stirring to emulsify the electrodeposition coating composition. Clear resin for use.

Test Examples 1 to 7 Production of Cationic Electrodeposition Paint and Evaluation of Paint As shown in Table 2, a container made of polyethylene was used to prepare Examples 1 to 1.
5328 and 3328 g of the cationic electrocoating clear resin obtained in Comparative Examples 1 and 2 were charged, and 563 g of the pigment paste obtained in Production Example 7 and 2.3 g of the curing catalyst dibutyltin oxide were added with sufficient stirring, and the mixture was thoroughly mixed. The mixture was stirred and mixed to obtain an electrodeposition paint.

Coating Method The cationic electrodeposition coating compositions obtained in Test Examples 1 to 7 were coated on an object under the condition that the average film thickness after baking was 20 μm.
An untreated cold-rolled steel sheet (150 × 70 × 0.
8 mm) was used.

Test Method (1) Heat Loss: A coating film dried at 105 ° C. for 3 hours was baked at 170 ° C. for 20 minutes and then evaluated for weight reduction. (2) Curability A coating film baked at each temperature for 10 minutes was treated with ethanol. The solvent is wiped with a mixed solvent having a weight ratio of / acetone of 1/1. ◯: No change in the coating film 10 times continuously ×: Part of the coating film dissolves within 10 times (3) Corrosion resistance A coating film baked at 170 ° C. for 20 minutes was sprayed with salt water according to JIS-Z-2731. The test was conducted according to the test method. A scratch reaching the substrate is put on the electrodeposition coated surface with a cutter knife, and the peeled state and rust width of the coating film after 500 hours are evaluated.

General physical property evaluation (1) Impact test method Dupont type 1/2 inch Drop distance at 1 kg (c
m) (2) Erichsen test Evaluation of the coating film when the test plate was deformed by a certain distance ◯: Good. Δ: Fairly good. X: Inferior

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

According to the present invention, a resin having a cation group is used as a base resin and a compound having a uretdione group is used as a curing agent, so that the heating loss during baking is small, and the curability, corrosion resistance, and corrosion resistance are reduced. It is possible to provide a resin composition for a cationic electrodeposition coating, which has excellent coating performance in solvent properties, mechanical properties, and the like.

Claims (1)

[Claims] 1. A resin composition for a cationic electrodeposition coating composition containing a base resin having a cationic group and a curing agent, wherein the curing agent is represented by the following structural formula. Resin composition. Here, R is one or two or more groups selected from an aliphatic group having 1 to 20 carbon atoms, an alicyclic group or an aromatic group A is a non-aromatic diol residue B is a non-aromatic group One or more compounds selected from monoalcohols, non-aromatic diols, phenols, lactams, oximes, active methylene group-containing compounds or non-aromatic secondary amines of The residue n represents 0 to 30.