JPH0892508A - Resin composition for cationic electrodeposition paint - Google Patents

Abstract

PURPOSE: To provide a cationic electrodeposition paint excellent in resistances to corrosion, shock, chipping and the like which comprises a cationic amine- modified epoxy resin, a blocked polyisocyanate and a specific cationic latex. CONSTITUTION: This resin composition comprises (A) a cationic amine-modified epoxy resin, (B) a blocked polyisocyanate and (C) a cationic latex prepared by cationizing the amino groups in a copolymer from an amino group-containing ethylenically unsaturated monomer such as dimethylaminoethyl acrylate, a styrenic monomer such as styrene and a diene monomer such as butadiene, as essential components. The component A is obtained by modifying an epoxy resin with an amine followed by reaction with a cationizing agent, and the epoxy resin is preferably a glycidyl ether of a polyphenol, the amine is an OH-containing alkanolamine, and the cationizing agent is preferably formic acid or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for a cationic electrodeposition coating which has excellent corrosion resistance and also has excellent impact resistance, Erichsen resistance and chipping resistance.

[0002]

2. Description of the Related Art A conventional cationic electrodeposition coating composition is mainly composed of a cation-modified epoxy resin and a blocked polyisocyanate, with a focus on the rust preventive power of the coating film.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
A conventional electrodeposition coating composition has impact resistance of an electrodeposition coating, general physical properties typified by Erichsen, and resistance of a process coating obtained by applying an intermediate coating film or a top coating film on the electrodeposition coating film. It has a problem in chipping property. Therefore, there is a strong demand for a cationic electrodeposition coating composition that retains the same corrosion resistance as conventional ones, retains excellent flexibility, and has impact resistance and excellent properties in Erichsen.

As one means for solving the above problems, a method of introducing a flexible structure into an epoxy resin or a blocked polyisocyanate used has been attempted. In this case, impact resistance, elixir, Although the chipping resistance is improved to some extent, there is a problem that the corrosion resistance is reduced.

[0005]

Means for Solving the Problems As a result of earnest research to solve the above problems, the present inventors have found that a cationic latex can be used in combination with an existing resin for cationic electrodeposition coating to form an electrodeposition coating film. The inventors have found that the problem can be solved by flexural modification, and have completed the present invention. That is, the present invention provides (A) a cationic amine-modified epoxy resin, (B) blocked polyisocyanate, (C) an amino group-containing ethylenically unsaturated monomer, a styrene-based monomer, and a diene-based monomer which are polymerized as essential components. A resin composition for a cationic electrodeposition coating, comprising a cationic latex in which the amino groups of the coalesced are cationized.

The component (A) cationic amine-modified epoxy resin used in the present invention is obtained by reacting an amine-modified epoxy resin obtained by reacting an epoxy resin with an amine with a cationizing agent. The epoxy resin used for this purpose is preferably an epoxy resin having two epoxy groups per molecule on average, and the molecular weight thereof is 400 to 7,000, especially 4
00-4000 are preferable. Specifically, one is a glycidyl ether of polyphenol having two phenolic hydroxyl groups in one molecule, and preferable polyphenols are resorcin, hydroquinone,
2,2-bis- (4-hydroxyphenyl) -propane (commonly called bisphenol A), 4,4'-dihydroxybenzophenone, 1,1-bis- (4-hydroxyphenyl) -methane, 1,1-bis- ( 4-hydroxyphenyl) -ethane, 4,4'-dihydroxybiphenyl and the like can be mentioned. Other examples are glycidyl ethers of diols having two alcoholic hydroxyl groups in one molecule, and preferable diols are ethylene glycol, propylene glycol, 1,6-hexanediol, neopentyl glycol, diethylene glycol and triethylene. Examples thereof include low molecular weight diols such as glycol and 1,4-cyclohexanediol, and oligomer diols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol, but the present invention is not limited to these and a mixture thereof 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, and a carboxyl group-containing butadiene polymer or butadiene / acrylonitrile copolymer. The amine used for the linking agent may be a primary amine such as ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, monoethanolamine, dimethylaminopropylamine, diethylaminopropylamine, or hexamethylenedimine. Examples thereof include diamines in which each amino group is secondaryized. It is also possible to extend the chain length with polyisocyanate.

The reaction for increasing the molecular weight using a linking agent can be carried out in a melt without a solvent, but it can also be carried out in a system to which a small amount of a solvent is added. The solvent is not particularly limited as long as it does not react with the epoxy group. Reaction temperature is 7
0 to 180 ° C is suitable.

Further, as the amine for modifying the epoxy group of the epoxy resin obtained by reacting each of the above components with an amine,
Methylamine, ethylamine, n-propylamine, isopropylamine, monoethanolamine, n-propanolamine, isopropanamine, diethylamine, diethanolamine, N-methylethanolamine, N-ethylethanolamine, ethylenediamine,
Examples thereof include, but are not limited to, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminopropylamine and the like, and mixtures 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.

The amine modification in which an epoxy resin is reacted with an amine can be carried out in a solvent or in a melt without a solvent, and the reaction temperature is preferably 40 to 150 ° C. Specific methods include U.S. Pat. No. 3,984,299, U.S. Pat.
The specification of 9-403013 etc. is referred.

The cationic amine-modified epoxy resin of the present invention can be obtained by neutralizing the amino group of the amine-modified epoxy resin thus obtained with an acid to cationize it. Particularly preferred acids include formic acid, acetic acid, lactic acid, propionic acid, citric acid, malic acid, sulfamic acid and the like.

Examples of the polyisocyanate used as the blocked polyisocyanate of the component (B) that can be used in the present invention include aromatic or aliphatic (including alicyclic) polyisocyanates. For example, 2, 4
-Or 2,6-toluylene diisocyanate and mixtures thereof, p-phenylene diisocyanate, diphenylmethane-4,4'-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, cyclohexylmethane-4,
4'-diisocyanate, m- or p-xylylene diisocyanate, and further, a burette modified product or an isocyanurate modified product of the above isocyanate,
Alternatively, a part of the isocyanate group of the above isocyanate may be ethylene glycol, propylene glycol, 1,
6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, 1,4-
Examples thereof include, but are not limited to, low molecular weight diols such as cyclohexane diol, polyisocyanates linked with oligomer diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polylactone diol, and mixtures thereof. .

As the blocking agent for reacting with these polyisocyanates, known blocking agents can be used alone or in combination. For example, aliphatic alcohol compounds such as methanol, ethanol, n-butanol, 2-ethylhexanol, etc., Cellulose compounds such as ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, oxime compounds such as acetone oxime, methyl ethyl ketoxime, cyclohexane oxime, ε-
Examples include, but are not limited to, lactam compounds such as caprolactam.

The reaction between the polyisocyanate and the blocking agent can be carried out in a solvent or in a melt. The reaction temperature is preferably 30 to 100 ° C. As the solvent used in the reaction, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone and isophorone, aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene and nitrobenzene, tetrahydrofuran, dioxane and the like. Examples thereof include halogenated hydrocarbons such as cyclic ether, chloroform and carbon tetrachloride.

The cationic latex of the component (C) which can be used in the present invention contains the amino group of a copolymer obtained by polymerizing an amino group-containing ethylenically unsaturated monomer, a styrene monomer and a diene monomer as essential components. It is a cationized cationic latex, which can be obtained usually by combining the above-mentioned monomers and, if necessary, other monomers and carrying out emulsion polymerization. Emulsion polymerization can be carried out in the presence of a polymerization initiator in an aqueous medium in the presence of a surfactant and / or a protective colloid, but if necessary, a pH adjusting agent, a polymerization degree adjusting agent, a defoaming agent, etc. Can be added as appropriate. The reaction temperature is not particularly limited, but is preferably 30 to 100 ° C.

Examples of the monomer used include amino group-containing ethylenically unsaturated monomers such as dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylamide, diallylamine, etc. It is not limited to these.

As an example of the styrenic monomer,
Styrene, α-methylstyrene, vinyltoluene, α,
Examples include, but are not limited to, ar-dimethylstyrene, ar, ar-dimethylstyrene, ar-ethylstyrene, t-butylstyrene, vinylnaphthalene, hydroxystyrene, methoxystyrene, monochlorostyrene and dichlorostyrene.

Further, the diene-based monomer means conjugated dienes, such as butadiene, isoprene,
Examples include, but are not limited to, chloroprene, 2,3-dichlorobutadiene and the like.

In the present invention, in addition to the above-mentioned essential monomers, monomers copolymerizable therewith can also be used. Examples of these are 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, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, acrylamide, methacrylamide, N-methylol acrylamide, N- (n-butoxymethyl) -acrylamide, cyclohexyl vinyl ether, acrylonitrile and the like.

The resin composition for cationic electrodeposition coating composition of the present invention comprises the above-mentioned components, and the compounding ratio of (A) cationic amine-modified epoxy resin and (B) blocked polyisocyanate is preferable. Is 90-by weight
40/10 to 60, and more preferably 85 to 5
0/15 to 50, particularly preferably 80 to 55/20
45.

The amount of the (C) cationic latex used in the present invention is preferably 1 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the total of the components (A) and (B). preferable. The resin composition for cationic electrodeposition coating composition of the present invention containing each of the above components is usually used for electrodeposition coating in a state of being dispersed in water.

In the resin composition for cationic electrodeposition coating composition of the present invention, if necessary, a conventional coating additive, for example, coloring pigment such as titanium white, carbon black, red iron oxide, yellow lead, talc, calcium carbonate, Mica, clay,
Extender pigments such as 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, base It may contain anticorrosive pigments such as water-soluble lead sulfate, aluminum phosphomolybdate, aluminum tripolyphosphate, zinc phosphate and zinc phosphite, antifoaming agents, cissing inhibitors, aqueous solvents or curing catalysts.

The cationic electrodeposition coating resin composition of the present invention can be applied to a desired surface of an object to be coated 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 adjusted to 5.0-8.0, bath temperature 15-
The article to be coated can be applied as a cathode under the conditions of 35 ° C. and a load voltage of 100 to 450V. The electrodeposition coated film is
1 at 100 to 200 ° C, preferably 140 to 180 ° C
A cured coating film is obtained by baking for 0 to 30 minutes. The thickness of the coating film obtained is not particularly limited, but in the cured coating film,
60 μm, preferably 10-40 μm.

[0024]

EXAMPLES The present invention will be described in more detail with reference to the following examples. Parts and% in the examples represent weight.

Production Example 1 Using the compounding ingredients shown in Table 1, an amine-modified epoxy resin was produced by the following method.

[Table 1]

A 5 liter 4-necked flask equipped with a cooling tube, a thermometer, and a stirrer was charged with the above-mentioned compounding component (2), and the mixture was added to 100
The temperature is raised to 0 ° C., and the compounding component (1) is gradually added and dissolved. Thereafter, this resin liquid was cooled to 80 ° C., and the compounding component (3) was added. The mixture was kept at 100 ° C. for 2 hours while paying attention to heat generation, and an amine-modified epoxy resin containing a tertiary amino group of 0.9 mmol / g solid content was obtained. The solid content of this amine-modified epoxy resin A-1 was 70%.

Production Example 2 Using the compounding ingredients shown in Table 2, a blocked polyisocyanate type curing agent was produced by the following method.

[Table 2]

The above-mentioned blending components (2) and (3) are charged into a 3 liter four-necked flask equipped with a cooling tube, a thermometer and a stirrer, dissolved at 60 ° C., and then the blending component (1) is added. Then, the temperature is raised to 100 ° C., and the reaction is continued at 100 ° C. until the residual isocyanate group ratio by the titration method becomes 0, and a blocked polyisocyanate curing agent B having a solid content of 70% is obtained.
-1 was obtained.

Production Example 3 Using the ingredients shown in Table 3, a cationic latex was produced by the method shown below.

[Table 3]

A 2 liter autoclave equipped with a stirrer was charged with the raw materials shown in the blending amount C-1 in Table 3 at a temperature of 6
The temperature was raised to 0 ° C. and the reaction was carried out at the same temperature for 10 hours to obtain a cationic latex C-1.

Production Example 4 A cationic latex C-2 was obtained in the same manner as in Production Example 3 using the raw materials shown in the blending amount C-2 in Table 3.

Production Example 5 In the raw materials shown in the blending amount C-2 in Table 3, diethylaminoethyl methacrylate was replaced with acrylic acid, and H in (6) was used.
Cl was not used, other raw materials were the same, and Production Example 3 was used.
Cationic latex C-3 was obtained by the same method as described in (1) above.

Production Examples 6 and 7 Cationic latices C-4 and C-5 were produced in the same manner as in Production Example 3 using the ingredients shown in Table 4.

[Table 4]

As the pigment dispersion liquid, the amine-modified epoxy resin A-1 was used as a pigment dispersion resin, and carbon black, titanium white, basic lead silicate, kaolin, and a curing catalyst were used as constituent components in a pearl mill. Dispersion was carried out until the particle size measured by a tube gauge was 10 μm or less, and the solid content was adjusted to 50% before use.

Examples 1 to 4 and Comparative Examples 1 to 4 Each resin and solvent having the composition shown in Table 4 was charged into a 3 liter four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a decompressor. A predetermined amount of solvent was removed at 90 ° C. under a pressure of 50 to 60 mmHg. After that, the resin mixture solution which had been subjected to desolvation was gradually put into a cylindrical stainless steel container charged with deionized water and formic acid under sufficient stirring to emulsify to obtain a resin emulsion having a solid content of 33%. Further, a predetermined amount of deionized water and a pigment dispersion liquid were added thereto to obtain an electrodeposition coating solution having a solid content of 20%.

Test Example A conductive object to be coated was immersed in an electrodeposition bath solution containing each electrodeposition paint bath solution composition having a bath temperature of 28 ° C. according to the following coating method, and baked between it and an anode as a counter electrode. A current was applied for 3 minutes at a voltage such that the film thickness afterwards became 20 μm. The properties and performances of the obtained coating film were evaluated by the following test methods, and the obtained results are shown in Table 4.

Coating object SPCC plate specified by JIS G 3141 (150 × 70 × 0.8 mm) Baking conditions 170 ° C. × 20 minutes

Test Method Corrosion Resistance Test Method A warm salt spray test specified in JIS Z 2371 was carried out. The SPCC plate has a cross cut reaching the substrate on the electrodeposition coated surface, and a salt spray test is conducted for 1000 hours.
The degree of rusting was confirmed. The evaluation was performed as follows. ◯: Good. Δ: Fairly good. X: Inferior

Test method for chipping resistance A test was conducted under the following conditions using a gravure flying stone tester. Granite (crushed stone): 500 g Discharge force: 4 kg Distance from discharge port to object: 30 cm Temperature of test plate: -20 ° C Evaluation was performed by measuring the size of peeling of the panel after the test.

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

[0041]

[Table 4]

[0042]

By using a cationic latex in combination with a cationic amine-modified epoxy resin and a blocked polyisocyanate, the coating film can be made tough and flexible. As a result, impact resistance, Erichsen,
It is possible to obtain a resin composition for a cationic electrodeposition coating which can improve chipping resistance and the like and can maintain the corrosion resistance of the coating film at the same level as the current coating film.

Claims (1)

[Claims] 1. A copolymer obtained by polymerizing (A) a cationic amine-modified epoxy resin (B) blocked polyisocyanate (C) an amino group-containing ethylenically unsaturated monomer, a styrene monomer and a diene monomer as essential components. A resin composition for a cationic electrodeposition coating, which comprises a cationic latex in which the amino groups of the coalesced are cationized.