JPH0892509A - Production of resin composition for cationic electrodeposition paint - Google Patents

Abstract

PURPOSE: To enable complete removal of an organic solvent used in the production of resin by azeotropically distilling away the solvent remaining in a resin composition for cationic electrodeposition coating from the system, as it is replaced with water and reuse the recovered solvent. CONSTITUTION: The organic solvent remaining in a resin composition for cationic electrodeposition coating comprising (A) a cationic group-containing resin as a base resin and (B) a blocked polyisocyanate as a curing resin is azeotropically distilled away with water and replaced with water. In an embodiment where the solvent is distilled off from a resin composition as a mixture of components A and B, deionized water is added to the composition in an amount of 5-50 pts.wt. on the solid basis of the composition and they are heated with stirring at 90-150 deg.C under atmospheric pressure. The organic solvent is preferably benzene or toluene. The component A is preferably prepared by introducing amino groups into an epoxy resin or acrylic resin and protonizing the amino groups with formic acid, acetic acid, or the like.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention makes it possible to easily remove the amount of the organic solvent in the resin composition for a cationic electrodeposition coating by completely distilling the organic solvent out of the system and substituting with water. The present invention relates to a method for producing a resin composition for a cationic electrodeposition coating, which is capable of controlling industrial waste and reducing raw material costs by reusing the organic solvent distilled out of the system.

[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 into practical use as a primer coating, most of the composition of the cationic electrodeposition paint is currently composed of two components, (1) resin emulsion and (2) pigment dispersion. . The resin emulsion is a mixture of a resin having a cationic group (base resin) and a blocked polyisocyanate (curing agent resin), which is stabilized and dispersed in water, but since these resins contain an organic solvent. Depending on the amount and type, it is difficult to stabilize and disperse, and even if it is possible to stabilize and disperse, in order to make the electrodeposition paint coatable, open stirring is 1
It is necessary to reduce the amount of organic solvent in the paint by carrying out ~ 2 weeks or by discarding the ultrafiltrate, which requires a lot of time and cost. Have been distilled off. However, the organic solvent used for the synthesis of the resin cannot be completely removed out of the system depending on its type, and therefore remains as a resin emulsion composition regardless of whether it is necessary or not. On the other hand, the organic solvent that has been distilled off is a mixture of various organic solvents and is therefore subject to waste liquid treatment.

[0003]

However, in view of recent environmental regulation trends, it is preferable that the organic solvent in the electrodeposition paint is as small as possible (low VOC), and the organic solvent distilled out of the system. It is preferable to collect and reuse the solvent as much as possible (recycling).

[0004]

From the above, the inventors of the present invention have a method of completely distilling off the solvent in the resin composition for cationic electrodeposition coating and reusing the distilled organic solvent. I studied about it. As a result, they have found that the above object can be achieved by synthesizing a resin composition with a single organic solvent, distilling the organic solvent out of the system while azeotroping the organic solvent and substituting with water.

That is, the present invention is contained in a resin composition for a cationic electrodeposition coating composition containing (A) a resin having a cationic group (base resin) and (B) a blocked polyisocyanate (curing agent resin). A method for producing a resin composition for a cationic electrodeposition coating, which comprises azeotropically distilling an organic solvent with water out of the system and substituting with water.

In the present invention, the organic solvent is distilled off by azeotropic distillation with water, and the mixed resin composition of the base resin precursor and the curing agent resin before the protonation of the amino group with an acid or the protonated group is used. It can be distilled off not only from the mixed resin composition itself of the agent resin and the curing agent resin, but also from the resin emulsion in which the mixed resin composition is dispersed in water. Specifically, when distilling off the solvent from a mixed resin composition of a base resin and a curing agent resin synthesized with a solvent, which will be described in detail below, the solvent content is 5 relative to the solid content weight of the mixed resin composition. Add ˜50 parts by weight of deionized water and heat with stirring. The solvent used,
Reflux starts from the azeotropic point of water and is removed outside the system, whereby the organic solvent in the mixed resin composition can be distilled off almost completely. At this time, azeotropic deionized water is separated from the organic solvent by a separator, and may be distilled off while returning it to the mixed resin composition being heated and stirred, or may be distilled out of the system together with the organic solvent. it can. Since these operations are carried out at the boiling point of the system under normal pressure, they are usually carried out at 90 to 105 ° C. If it is desired to lower the temperature for solvent removal for some reason, the temperature of the system can be controlled by performing it under reduced pressure. Further, when distilling off the mixed resin liquid from the resin emulsion liquid dispersed in water, it is possible to distill off by the same operation as above, but in this case, if the thermal stability of the emulsified particles is taken into consideration, depressurization is carried out. It is preferable to control the temperature below. Further, during the distillation, the rectification can be removed by combining with a rectifier. According to the present invention, the organic solvent used in the production of the base resin or the curing agent resin can be distilled off almost completely.

The solvent used in the production of the base resin or the curing agent resin, which is a constituent of the present invention, does not suppress the formation reaction of the base resin or the curing agent resin and is azeotropic with water. The solvent is chosen. For example, ethyl acetate, propyl acetate, butyl acetate, dioxane, 1,2-
Dichloroethane, trichloroethylene, 1,2-dichloropropane, 1,2-diethoxyethane, 1,4-dimethoxybutane, dibutyl ether, benzene, toluene, xylene, cumene, chlorobenzene, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, Methyl hexyl ketone, methyl amyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone,
Solvents having cyclopentanone, isophorone, etc., and having an azeotropic composition with water rich in organic solvents are more preferable. Further, from the viewpoint of recovering and using the solvent, the compatibility with water is not so great, and in the liquid composition, an organic solvent that separates from water is particularly preferable. Examples are benzene, toluene, xylene, methyl isobutyl ketone, methyl amyl ketone, and diisobutyl ketone.

The (A) cationic group-containing resin (base resin) in the present invention is obtained by introducing an amino group into an epoxy resin, an epoxy group-containing acrylic resin, an epoxy group-free acrylic resin, a polyurethane resin or the like. Can be obtained by protonating 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 normally 0.5 to 3 equivalents per 1000 g of resin is suitable. Organic solvents that can be used for resin synthesis include ethyl acetate, propyl acetate, butyl acetate, dioxane, 1,2-dichloroethane, trichloroethylene, 1,2-dichloropropane, 1,2-diethoxyethane, 1,4- Dimethoxybutane, dibutyl ether,
Benzene, toluene, xylene, cumene, chlorobenzene, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl hexyl ketone, methyl amyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone, cyclopentanone, isophorone, etc. are particularly preferable. Is benzene, toluene, xylene, methyl isobutyl ketone, methyl amyl ketone,
Diisobutyl ketone may be mentioned. Particularly preferred resins having a cationic group are epoxy resins and acrylic resins.

The epoxy resin is preferably an epoxy resin having two epoxy groups per molecule on average, and the molecular weight thereof is 400 to 7,000, particularly 400 to 4
000 is preferable. More specifically, one is a glycidyl ether of polyphenol having two phenolic hydroxyl groups in one molecule, and preferable polyphenols are resorcin, hydroquinone, and 2,2-.
Bis- (4-hydroxyphenyl) -propane (common name bisphenol A), 4,4'-dihydroxybenzophenone, bis- (4-hydroxyphenyl) -methane (common name bisphenol F), 1,1-bis- (4-hydroxy) Examples thereof include phenyl) -ethane and 4,4'-dihydroxybiphenyl. In addition, 1
It is a glycidyl ether of a diol having two alcoholic hydroxyl groups in the molecule, and preferable diols include ethylene glycol, propylene glycol, 1,
Low-molecular diols such as 4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol and 1,4-cyclohexanediol, and oligomer diols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol are mentioned. However, the mixture is not limited to these, and a mixture of the above epoxy resins is also possible. Particularly preferred epoxy is bisphenol A
System, bisphenol F epoxy, or a copolymer system of these epoxies and polypropylene epoxy.

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 styrene, α-methylstyrene, vinyltoluene, cyclohexyl vinyl ether, and acrylonitrile.

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,
U.S. Pat. No. 3,984,299, U.S. Pat. No. 4,017,438, JP-A-59-40301.
Reference is made to No. 3, etc.

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.

The blocked polyisocyanate (B) in the present invention is a reaction product of a polyisocyanate and a blocking agent, and the polyisocyanate is an aromatic or aliphatic (including alicyclic) polyisocyanate, Illustrative are 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-
Alternatively, p-xylylene diisocyanate, further a buret modified product or an isocyanurate modified product of the above isocyanate, or a part of the isocyanate group of the above isocyanate may be replaced with ethylene glycol, propylene glycol, 1,6-hexanediol, neopentyl glycol, diethylene glycol. 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. Mention may be made of linked polyisocyanates or mixtures thereof, for blocking agents methanol, Aliphatic alcohol compounds such as tanol, n-butanol and 2-ethylhexanol, cellosolve compounds such as ethylene glycol monomethyl ether, ethylene glycol monobutyl ether and ethylene glycol monohexyl ether, oxime compounds such as acetone oxime, methyl ethyl ketone oxime and cyclohexanone oxime. And lactam compounds such as ε-caprolactam. The reaction between the polyisocyanate and the blocking agent can be carried out in a solvent or in a solvent-free melt. Organic solvents that can be used for resin synthesis are ethyl acetate, propyl acetate,
Butyl acetate, dioxane, 1,2-dichloroethane, trichloroethylene, 1,2-dichloropropane, 1,2
-Diethoxyethane, 1,4-dimethoxybutane, dibutyl ether, benzene, toluene, xylene, cumene, chlorobenzene, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl hexyl ketone, methyl amyl ketone, diethyl ketone, diisobutyl ketone, Cyclohexanone, cyclopentanone,
Examples thereof include isophorone, and particularly preferable examples include benzene, toluene, xylene, methyl isobutyl ketone, methyl amyl ketone, and diisobutyl ketone.
The reaction temperature is not particularly limited, but is preferably 30.
~ 150 ° C.

In the present invention, the mixing ratio of the resin having a cation group (base resin) and the blocked polyisocyanate (curing agent) is 90 to 40/10 to 60, preferably 85 to 50 /. It is 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.

The cationic electrodeposition coating resin composition of the present invention may further contain a conventional coating additive, 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.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to production examples of amine-modified epoxy resin and curing agent resin, examples and comparative examples, but the present invention is not limited thereto.

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

[0022]

[Table 1]

Raw materials (1), (2) and (3) were charged in a 5 liter 4-necked flask equipped with a stirrer, a thermometer and a cooling tube, stirred and heated to a temperature of 150 ° C. 15
After holding at 0 ° C for 6 hours, the raw material (4) was gradually added and
Cooled to 0 ° C. Next, the raw material (5) is charged and the temperature is 100 ° C.
The temperature was raised to. After holding at 100 ° C. for 2 hours, it was cooled to 80 ° C. and taken out. The obtained amine-modified epoxy resin A-1 had a solid content of about 70%.

Production Example 2 Amine-modified epoxy resin A- having a solid content of about 70% was prepared by changing the raw material (4) in Table 1 to xylene under the same reaction conditions as above.
2 was obtained.

Production Example 3 An acrylic resin (B-1) was produced by the following method using the ingredients shown in Table 2.

[0026]

[Table 2]

A raw material (1) was charged into a 2-liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube, stirred, heated, heated, and heated to reflux under the raw materials (2), (3), ( 4),
A base resin B having a solid content of about 70% is prepared by adding the mixed solution of (5), (6) and (7) dropwise over 2 hours and keeping the temperature for 4 hours after the addition.
-1 was obtained.

Blocked polyisocyanates were produced by the following method using the ingredients shown in Table 3.

[0029]

[Table 3]

Raw materials (1), (2), and (3) were charged in a 2-liter 4-necked flask equipped with a stirrer, a thermometer, and a cooling tube, and the mixture was stirred and heated to a temperature of 40 ° C. 40 After the temperature was maintained at 0 ° C for 2 hours, the raw material (4) was added dropwise over 1 hour while maintaining the temperature inside the flask at 40 ° C. Then, the raw material (5) was charged and the temperature was raised to 100 ° C. After holding at 100 ° C. for 2 hours, it was cooled to 80 ° C. and taken out. The blocked polyisocyanate C-1 obtained had a solid content of about 70%.

Production Example 4 The blocked polyisocyanate C-2 having a solid content of about 70% was obtained by changing the starting material (2) in Table 3 to xylene under the same reaction conditions as above.

Production Example 5 (Production Example of Conventional Solvent-Type Amine-Modified Epoxy Resin for Comparison) The raw material (4) in Table 1 above was changed to propylene glycol monomethyl ether (PGM), and the solid content was changed under the same reaction conditions. About 70% of amine-modified epoxy resin A-3 was obtained.

Production Example 6 (Production Example of Conventional Solvent-type Blocked Polyisocyanate Resin for Comparison) In the above Table 3, the raw material (2) was changed to isophorone, and a block having a solid content of about 70% was obtained under the same reaction conditions. As a result, a modified polyisocyanate C-3 was obtained.

Examples 1 to 3 and Comparative Examples 1 to 3 A 2 liter 4-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a decompressor was blended with each amine-modified epoxy resin and blocked according to the formulation shown in Table 4. When polyisocyanate and deionized water were charged and the solvent was removed as much as possible in the production equipment under the conditions of temperature and reduced pressure shown in Table 4, the amount of solvent that could be distilled off varied depending on the desolvation conditions. A 3 liter stainless steel container was charged with formic acid and deionized water, and the resin mixture solution which had been desolvated with sufficient stirring was gradually added and emulsified to obtain an emulsion liquid having a solid content of 35%.

The solvent amounts in the desolvated and emulsified resin solutions of Examples 1 to 3 and Comparative Examples 1 to 3 were analyzed by gas chromatography to determine the type and amount of the solvent. Table 4 shows a summary of the obtained results.

[0036]

[Table 4]

Electrodeposition Test Examples 1 to 6 Emulsified resins were prepared by uniformly mixing 2.0 parts by weight of hexyl cellosolve as a solvent for securing the electrodeposition film thickness with the desolvated mixed resin solutions of Examples 1 to 3 and Comparative Examples 1 to 3. A liquid was prepared and diluted with deionized water to obtain an electrodeposition clear liquid having a solid content of about 15% by weight.

Table 5 shows the results of electrodeposition coating in which the above clear liquid was applied by the following coating method.

Coating method The cationic electrodeposition coatings obtained in the electrodeposition test examples 1 to 6 were prepared immediately after the electrodeposition clear was prepared, and the clear solution was subjected to 2 hours under open stirring at 30 ° C.
The film that was kept warm for a week was painted at each coating voltage, and the film thickness was confirmed. Untreated cold-rolled steel sheet (150 x
70 × 0.8 mm) was used.

[0040]

[Table 5]

[0041]

According to the present invention, the organic solvent used in the production of the base resin or curing agent resin in the emulsion resin liquid is completely removed, and the paint is designed with the solvent necessary for ensuring the coating quality. It is possible to provide a manufacturing method which can be performed (reduced VOC) and can reuse the removed solvent (recycled).

Claims (1)

[Claims] 1. An organic solvent contained in a resin composition for a cationic electrodeposition coating composition, which comprises (A) a resin having a cationic group (base resin) and (B) a blocked polyisocyanate (curing agent resin). Is distilled out of the system while azeotropically distilling with water to replace with water, and a method for producing a resin composition for a cationic electrodeposition coating composition.