JPS61233068A - Production of resin for cationic electrodeposition coating - Google Patents

Abstract

PURPOSE:To obtain a cationic electrodeposition coating resin for the under coating of automobile, storable without causing viscosity increase and gelation and having high stability and excellent coating film property, by reacting an epoxy resin with a compound containing active hydrogen to eliminate the epoxy group and reacting the product with epsilon-caprolactone. CONSTITUTION:(A) An resin [e.g. 2,2-bis(4-hydroxyphenyl)propane] is compounded with (B) a compound containing active hydrogen atom. The resultant reaction product is made to react with (C) 5-35 wt% epsilon-caprolactone and preferably (D) 1-10,000 ppm of a metal compound (e.g. tin octanoate) to obtain the objective resin for cationic electrodeposition coating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a resin for cationic electrodeposition paint. More specifically, the present invention relates to a method for producing a resin for cationic electrodeposition coatings that does not cause viscosity increase or gelation during production, can obtain a stable aqueous dispersion, and has excellent coating film performance.

[Conventional technology]

Cationic electrodeposition paints are widely used as undercoating paints for automobiles in place of conventional anionic electrodeposition paints due to their excellent corrosion resistance and throwing power. It has disadvantages such as inferior coating appearance and secondary adhesion.

In order to improve the material defects, a modified epoxy resin with a linear structure incorporated into the resin skeleton was manufactured by subjecting e-caprolactone to a ring-opening addition reaction on the secondary hydroxyl group of an epoxy resin. A method has been used in which a resin for cationic electrodeposition coatings is obtained by reacting a compound containing an amino group or an imino group with a compound containing an amino group or an imino group.

[Problem that the invention seeks to solve]

In the above method, the secondary hydroxyl group of the epoxy resin and C
-Since the ring-opening addition reaction with caprolactone requires a relatively high temperature, the epoxy groups of the epoxy resin also react, resulting in large variations in the epoxy equivalent of the resulting modified epoxy resin, which limits the epoxy equivalent of the modified epoxy resin. It is very difficult to control within the specified range. When producing a resin for cationic electrodeposition coatings by reacting a modified epoxy resin with large variations in epoxy equivalent with a compound containing an amino group or an imino group, if the jepoxy equivalent is lower than the set equivalent, excess epoxy groups may be used. If the epoxy equivalent is higher than the set equivalent, the water dispersibility of the reaction product will decrease because low molecular weight compounds containing amino or imino groups will remain. 〇The present invention does not cause viscosity increase or gelation when producing resin for cationic electrodeposition paints incorporating t-caprolactone,
It is also an object of the present invention to obtain a resin with good water dispersibility and excellent coating film performance.

[Means for solving problems]

The present invention avoids the reaction between epoxy resin and e-caprolactone, and instead reacts e-caprolactone with the reaction product of epoxy resin and active hydrogen-containing compound, which has been used as a resin for conventional cationic electrodeposition paints. I discovered that I could achieve my goal by doing so.

That is, the present invention provides a method for producing a resin for cationic electrodeposition paint, which comprises reacting an epoxy resin with an active hydrogen-containing compound to make the epoxy resin substantially free of epoxy groups, and then reacting the resin with C-caprolactone. It comes out.

The epoxy resin used in the present invention may contain Fi or hydroxyl groups, but in order to obtain good water dispersibility and mg performance, at least one or more Fi and hydroxyl groups must be present in one molecule. Epoxy equivalent containing epoxy group 1
Epoxy resins having a molecular weight of 70 to 1000 are preferred. Examples include polygrindyl ethers of polyphenols, polyglycidyl ethers of polyols, polyglycidyl esters of polycarboxylic acids, and copolymers of ethylenically unsaturated monomers containing glycidyl (meth)acrylate. From the viewpoint of corrosion resistance of the resulting coating film, polyphenol, particularly polyglycidyl ether of 2,2-bis(4-hydroxyphenyAl)propane (hereinafter referred to as bisphenol A), is preferred.

Examples of the active hydrogen-containing compound used in the present invention include a compound containing an amino group, a compound containing an imino group, a compound containing an alcoholic hydroxyl group, and a compound containing a carboxyl group.

Examples include compounds containing a phenolic hydroxyl group or mixtures of these compounds.

Examples of compounds containing amino groups include monoamines such as monoalkylamines (ethylamine, propylamine, butylamine), monoalkanolamines (monoethanolamine), dialkylaminoalkylamines (dimethylaminoethylamine, dimethylaminepropylamine), etc. Examples include diamines.

Examples of compounds containing imino groups include dialkylamines (dimethylamine, diethylamine), N-
Alkylalkanolamines (N-methylethanolamine, N-methylethanolamine), dialkanolamines (jetanolamine, dibrobanolamine)
Monoamines such as, reaction products of monoalkylaminoalkylamines and ketones (reaction products of monomethylaminoethylamine and methyl isobutyl ketone), reaction products of dialkylene triamines and ketones (reaction products of diethylenetriamine and methyl ethyl ketone), aminoalkyl alkanolamines and ketones reaction product (reaction product of N-(β-aminoethyl)ethanolamine and methyl isobutyl ketone),
A secondary amine in which all amine groups are blocked with ketimine, such as a reaction product of trialkylenetetramine and a ketone (a reaction product of triethylenetetramine and methyl isobutyl ketone), 1 mole of alkylene diamine and 1 glycidyl group of 2 moles. Examples include diamines containing two imino groups in the molecule, such as a reaction product of the containing compound (a reaction product of 1 mol of ethylene diamine and 2 mol of butyl glycidyl ether).

Examples of compounds containing alcoholic hydroxyl groups include alkylene diols (ethylene glycol, 1,6
hexane diol), polyalkylene glycol (polyethylene glycol, polypropylene glycol), polyester diol (a reaction product of 1 mol of adipic acid and 2 mol of diethylene glycol), and the like.

Examples of compounds containing a carboxyl group include dicarboxylic acids having 2 to 28 carbon atoms and their acid anhydrides (adipic acid, maleic anhydride, talic acid), polyester dicarboxylic acids (2 moles of ethylene glycol and 3 moles of (reactant of phthalic anhydride), etc.

As a compound containing a phenolic hydroxyl group, bisphenol A%111-bis(4-hydroxyphenyl)
Ethane, 2-methyl-1,1-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3
-t-butylphenyl)propane, bis(2-hydroxynaphthyl)methane, 5-dihydroxynaphthalene, and the like.

The reaction between the epoxy resin and the active hydrogen-containing compound may be carried out by any known method, but usually at a temperature of 30 to 130°C.
for at least 1 hour until substantially no epoxy groups are present, as determined by measurement of the epoxy group content.
In other words, 95 of the epoxy groups present before the reaction
Continue the reaction until at least 1 reacts.

Next, the reaction between the active hydrogen in the reaction product of the epoxy resin and the active hydrogen-containing compound and e-caprolactone may be carried out using any known method, such as tin octoate, dibutyltin dilaurate, dibutyltin oxide, , using a metal compound such as tetrabutyl titanate as a catalyst, based on the total amount of the reaction product and direct-caprolactone.

Using 1 to 110,000 pp, 1 to 1 at 100 to 250"C
Allow to react for 20 hours.

Through this reaction, a primary hydroxyl group and a linear structure can be introduced into the molecules of the resin for cationic electrodeposition coatings, which improves the reactivity with isocyanates, the adhesion and flexibility of the resulting coating film to the steel plate material, etc. However, the amount of e-caprolactone introduced into the resin solid content of the paint is
It is preferably 5 to 35% by weight. If the amount of ε-caprolactone introduced is less than 5% by weight, the modification effect will not be sufficiently exhibited, and if it exceeds 35% by weight, the corrosion resistance of the resulting coating film will be reduced.

The resin for cationic electrodeposition coating of the present invention is preferably crosslinked by baking in order to improve the corrosion resistance, moisture resistance, and physical properties of the resulting coating film.

Examples of crosslinking reactions include reaction between active hydrogen and isocyanate groups, crosslinking reaction using melamine resin, transesterification reaction,
Examples include polymerization reactions of double bonds, but reactions between active hydrogen and incyanate groups are particularly preferred.

In the reaction between the active hydrogen and the inocyanate group, the isocyanate mountain in which the inocyanate group of the inocyanate group-containing compound is partially or completely blocked is reacted with the resin-saving cationic electrodeposition paint.

The ring-opening reaction of ε-caprolactone requires a relatively high temperature;
In addition, since a compound which also serves as a dissociation catalyst for the inocyanate group blocking agent may be used as a reaction catalyst, it is preferable to introduce the partially blocked isocyanate after the ring-opening addition reaction of C-caprolactone is completed.

Examples of isocyanate group-containing compounds include 2,4
- or 2,6-dolylene diisocyanate, 4,4'
Examples include diisocyanates such as -diphenylmethane diisocyanate, xylylene diisocyanate, 1,6-hexamethylene diisocyanate, and isophorone diisocyanate, and polyincyanates produced by reacting these diisocyanates with polyols and water.

As a blocking agent for isocyanate groups, for example, n-
Aliphatic alcohols such as butanol and 2-ethylhexanol, aromatic alkyl alcohols such as phenylcarbinol and methylphenylcarbinol, ether alcohols such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether, phenol, cresol, etc. Phenols, oximes such as acetone oxime and methyl ethyl ketoxime, C-
Examples include lactams such as caprolactam and r-caprolactone, and alkanolamines such as 2-dimethylamineethanol and 2-diethylaminoethanol.

The resin for cationic electrodeposition coating of the present invention obtained as described above is neutralized with an inorganic or organic acid, and water is added while thoroughly mixing to obtain an aqueous dispersion capable of electrodeposition.

Here, as the inorganic acid or organic acid, for example, hydrochloric acid,
Examples include phosphoric acid, formic acid, acetic acid, propionic acid, and lactic acid.

A paint using the resin for cationic electrodeposition paint of the present invention includes a modifying resin, a plasticizer, a surfactant, which are the components used in ordinary cationic electrodeposition paints, in the resin for cationic electrodeposition paint.
Pigments, organic solvents, water, etc. are uniformly mixed and dispersed using a dispersing machine such as a sand grind mill, attritor, or roll mill to produce a cationic electrolyte, which is an aqueous dispersion with a resin solid content of approximately 10 to 25% by weight. Obtain a deposited paint.

Electrodeposition is performed in the obtained cationic electrodeposition paint bath in the same manner as normal cationic electrodeposition using the conductive housing as the cathode, and after washing with water, baking at 150 to 200°C for 10 to 40 minutes. A cured coating is obtained.

〔Effect of the invention〕

The resin for cationic electrodeposition coatings obtained by the present invention does not cause an increase in viscosity or gelation during production, and has excellent stability over time.

In addition, the cationic electrodeposition paint obtained from the resin for cationic electrodeposition paint of the present invention has excellent water dispersibility and electrodeposition properties, and the resulting coating film has excellent coating appearance, adhesion, impact resistance, and removability. Excellent secondary adhesion and corrosion resistance.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In the examples, parts are parts by weight and 俤 is % by weight.

Example 1 A flask equipped with a stirrer, a thermometer, a nitrogen inlet tube and a reflux condenser was charged with a number average molecular weight of 140 obtained by the reaction of bispheno-A/A and epichlorohydrin.
Charge 570 parts of epoxy resin with a 0% epoxy equivalent of 950, add and dissolve 336 parts of methyl isobutyl ketone,
The temperature was raised to 80 °C under a nitrogen stream, 161 parts of diketimine obtained by a condensation reaction of 103 parts of diethylene trypmine and 200 parts of methyl ethyl ketone was added, and the temperature was raised to 100 °C over 30 minutes. After the reaction was carried out until the epoxy value became O, 278 parts of 8-caprolactone and 3.4 parts of dibutyltin dilaurate were added, the temperature was raised to 140°C, and the reaction was carried out for 10 hours.

Then, after cooling to 80"C, 1044 parts of 2.4-)lylene dicyane) and 8 parts of 2-ethylhexanol were added.
Partially blocked incyanate 33 obtained from 19 parts
3 parts were added, and the reaction was continued until there was no absorption of incyanate groups in the infrared absorption spectrum. Then, after removing methyl isobutyl ketone under reduced pressure at 100 to 120"C, ethylene glycol motsubutyl ether 448
Resin A for cationic electrodeposition paints with a non-volatile content of 71 parts
I got it.

To 211 parts of the obtained resin A for cationic electrodeposition paint.

39 parts of ethylene glycol monobutyl ether, 6.4 parts of acetic anhydride and 418 parts of deionized water were added and dispersed uniformly, and the resulting dispersion was mixed with 2 parts of dibutyltin oxide.
5 parts of titanium oxide, 5.5 parts of carbon bran, and 65.5 parts of aluminum silicate were placed in a ball mill.
Pigment dispersion A was obtained by dispersing for 24 hours.

Next, 1,350 parts of deionized water was added to 423 parts of resin A for cationic electrodeposition paint and 5.4 parts of acetic anhydride for dispersion, and then 222 parts of pigment dispersion A was added to give a solid content of 20 yen, based on the resin solid content in the paint. The amount of 1-caprolactone introduced is 21.7
% electrodeposition paint A was obtained.

The obtained electrocoating paint A was electrocoated at 280V for 3 minutes on an electrogalvanized steel plate treated with zinc phosphate, then washed with water and baked at 180°C for 25 minutes to form a smooth dry film with a thickness of 25μ. A cured coating film was obtained.

Table 1 shows the test results of the film performance of the obtained cured coating film, the stability over time of Resin A for cationic electrodeposition paint, and the water dispersibility of Electrodeposition paint A.

Example 2 A flask similar to Example 1 was charged with 3325 parts of an epoxy resin having a number average molecular weight of 900 and an epoxy equivalent of 475 obtained by the reaction of bisphenol A and epichlorohydrin, and 928 parts of ethylene glycol monoethyl ether acetate was added. After dissolving, the temperature was raised to 80°C under a nitrogen stream, and dimethylaminopropyshif 4F33
In the F part, a mixture of 200 parts of jetanolamine was added dropwise over 1 hour. Then, the temperature was raised to <xoo'c>, and the reaction was carried out until the epoxy value became O.

Next, 387 parts of C-caprolactone and 3 parts of dibutyltin dilaurate were added, and the temperature was raised to 140°C.
The reaction was carried out for a period of time to obtain a resin B for cationic electrodeposition coatings having a non-volatile content of 81 cm.

To 185 parts of the obtained resin B for cationic electrodeposition paint, 65 parts of ethylene glycol motubutyl ether and 5.0 parts of acetic anhydride were added.
After adding 3 parts of dibutyltin oxide and 446 parts of deionized water for uniform dispersion, the resulting dispersion and 25 parts of dibutyltin oxide,
230 parts of titanium oxide, 5.5 parts of carbon black, and 65.5 parts of aluminum silicate were placed in a ball mill and dispersed for 24 hours to obtain pigment dispersion B.

Next, 268 parts of resin B for cationic electrodeposition paint, 2.4-
After mixing and uniformly dispersing 92 parts of fully blocked isocyanate obtained from 1044 parts of tolylene diisocyanate, 819 parts of 2-ethylhexanol, and 134 parts of trimethylolpropane, 4.3 parts of acetic anhydride, and 1054 parts of deiosized water. , 222 parts of Pigment Dispersion B was added to obtain an electrodeposition paint B having a solid content of 20 inches and an amount of e-caprolactone introduced in the resin solid content of the paint of 6.7 inches.

The obtained electrodeposition paint B was applied to the same steel plate as in Example 1 for 20 minutes.
After applying electrodeposition for 3 minutes at 0V, washing with water and applying 180
It was baked at .degree. C. for 25 minutes to obtain a smooth cured coating with a dry thickness of 18/A.

Table 1 shows the test results for the film performance of the obtained cured coating film, the stability over time of Resin B for cationic electrodeposition paint, and the water dispersibility of Electrodeposition paint B.

Example 3 Bisphenol A was added to an ffl flask as in Example 1.
Epoxy resin 28 with a number average molecular weight of 370 and an epoxy equivalent of 189 obtained by the reaction of and epichlorohydrin
After adding and dissolving 200 parts of methyl isobutyl ketone, 114 parts of bisphenol A and 0.9 parts of dimethylbenzylamine were added. Then, the temperature was raised to 120°C under one nitrogen stream, and the reaction was allowed to proceed until the epoxy equivalent reached 790. Then, it was cooled to 80''C, 81 parts of diketimine and 20 parts of jetanolamine, which were the same as in Example 1, were added, and the temperature was raised to 100'G over 30 minutes.
The reaction was continued until the epoxy value reached O. Next, 285 parts of C-caprolactone and 3 parts of dibutyltin dilaurate were added, and the temperature was raised to 130"C and reacted for 12 hours. Then, 220 parts of methyl isobutyl ketone was added, and the temperature was raised to 80°C.
C. and partially blocked isocyanate 2 of Example 1.
42 parts were added, and the reaction was allowed to proceed until the absorption of incyanate groups disappeared in the infrared absorption spectrum. Then, under reduced pressure 1
After removing methylinobutyl ketone at 00 to 120°C, 250 parts of ethylene glycol mobutyl ether was added to obtain Resin C for cationic electrodeposition paints having a non-volatile content of 79 parts.

After mixing and uniformly dispersing 0,380 parts of the obtained resin for cationic electrodeposition paint, 6 parts of acetic anhydride, and 1,392 parts of deionized water, 222 parts of the pigment dispersion A of Example 1 was added, and the solid content was 20%, and the paint Electrodeposition paint C was obtained in which the amount of C-caprolactone introduced in the resin solid content was 29.24.

The obtained electrodeposition paint C was applied to the same steel plate as in Example 1 at 160°C.
After 3 minutes of electroplating with V, wash with water and 180'
C. for 25 minutes to obtain a smooth cured coating film with a dry thickness of 22 .mu.m.

Table 1 shows the test results of the film performance of the obtained cured coating film, the stability over time of Resin C for cationic electrodeposition paint, and the water dispersibility of Electrodeposition paint C.

Example 4 A flask similar to Example 1 was charged with 760 parts of an epoxy resin with a number average molecular weight of 900 and an epoxy equivalent of 475 obtained by the reaction of bisphenol A and epichlorohydrin, and 351 parts of methyl isobutyl ketone was added and dissolved. , 58 parts of adipic acid and 1.5 parts of 2-dimethylaminoethanol were added. Then, under a nitrogen stream for 10
The temperature was raised to 0°C, and the reaction was continued until the acid value became 1 or less. Then, it was cooled to 80°C and diketimine 1 of Example 1 was added.
51 parts and 23 parts of jetanolamine were added, the temperature was raised to 100°C over 30 minutes, and the reaction was allowed to occur until the epoxy value reached zero. Then, 273 parts of ε-kabu lactone and 5 parts of dibutyltin dilaurate were added, and the mixture was heated to 140"C.
After raising the temperature to I let it react until it ran out.

After removing methyl isobutyl ketone under reduced pressure at 100 to 120 DEG C., 314 parts of ethylene glycol monobutyl ether was added to obtain a resin for cationic electrodeposition paint with a non-volatile content of 77.

390 parts of the resulting cationic electrodeposition coating resin D.

After mixing and uniformly dispersing 4.8 parts of acetic anhydride and 1384 parts of deionized water, pigment dispersion A222 of Example 1 was prepared.
part, solid content 20%, C- in the resin solid content in the paint
An electrodeposition paint with an introduced amount of caprolactone of 17.4 cm was obtained.

The obtained electrodeposition paint was applied to the same steel plate as in Example 1 at 220°C.
After 3 minutes of electrocoating with V, wash with water and apply 180°
C. for 25 minutes to obtain a smooth cured coating film with a dry film thickness of 23 μm.

Table 1 shows the test results for the film performance of the obtained cured coating, the stability over time of the cationic electrodeposition resin, and the water dispersibility of the electrodeposition paint.

Example 5 Into a flask similar to Example 1, 665 parts of an epoxy resin with a number average molecular weight of 900 and an epoxy equivalent of 475 obtained by the reaction of bisphenol A and epichlorohydrin was charged, and 300 parts of methyl imbutyl ketone was added and dissolved. Thereafter, 41 parts of 1,6-hexanediol and 184 parts of diketimine from Example 1 were added. Then, the temperature was raised to 130°C under a nitrogen stream, and the reaction was carried out until the epoxy value reached O. Then, 160 parts of C-caprolactone and 4.2 parts of dibutyltin dilaurate were added, and 114Q″G
After reacting for 9 hours at elevated temperature, 702 parts of methyl in butyl ketone was added, cooled to 80°C, 260 parts of partially blocked incyanate from Example 1 was added, and the absorption of isocyanate groups was determined by infrared absorption spectrum. I let it react until it ran out. Next, methyl isobutyl ketone was distilled off at 100 to 120°C under reduced pressure, and 262 parts of ethylene glycol monobutyl ether was added to obtain Resin E for cationic electrodeposition paints with a nonvolatile content of 76%.

After mixing and uniformly dispersing 395 parts of the obtained resin E for cationic electrodeposition paint, 6 parts of acetic anhydride, and 1377 parts of deionized water, 222 parts of the pigment dispersion A of Example 1 was added, and the solid content was 20 parts, and the paint Electrodeposition paint E was obtained in which the amount of C-caprolactone introduced in the resin solid content was 13.3%.

The obtained electrodeposition paint E was applied to the same steel plate as in Example 1 at 260
After 3 minutes of electrodeposition coating with V, wash with water and apply 180'
C for 25 minutes to obtain a smooth cured coating film with a dry film thickness of 24μ.90 Test results of the coating performance of the obtained cured coating film, stability over time of resin E for cationic electrodeposition coatings, and electrodeposition coating E The water dispersibility test results are shown in Table 1.

Example 6 After dissolving 760 parts of an epoxy resin with a number average molecular weight of 900 and an epoxy equivalent of 475 obtained by the reaction of bisphenol A and epichlorohydrin in 404 parts of ethylene glycol monobutyl ether acetate, the temperature was raised to 80°C under a nitrogen stream. , 54 parts of dimethylamine propylamine, 75 parts of the diketimine of Example 1, while maintaining the temperature.
30 parts of a mixture of 52.5 parts of jetanolamine and 52.5 parts of
It was added dropwise over a period of minutes.

Then, the temperature was raised to 100°C over 60 minutes, and the reaction was allowed to occur until the epoxy value reached O. Then, 228 parts of C-caprolactone and 4.7 parts of dibutyltin dilaurate were added, and the temperature was raised to 140"C and reacted for 10 hours. Then, 592 parts of methyl isobutyl ketone was added, and the mixture was cooled to 80°C. Example 10 371 parts of partially blocked inocyanate was added and the reaction was carried out until the absorption of isocyanate groups disappeared in the infrared absorption spectrum.Then, the solvent was distilled off under reduced pressure at 100 to 120'C, and 308 parts of ethycine glycol monobutyl ether was added. power]
Resin F for cationic electrodeposition paint having a non-volatile content of 72 was obtained.

17 parts of the obtained cationic electrodeposition coating resin F4, 4.5 parts of acetic anhydride and 1357 parts of deionized water were mixed and dispersed uniformly, and then 222 parts of the pigment dispersion A of Example 1 was added to give a solid content of 20 parts. Electrodeposition paint F was obtained.

The obtained electrodeposition paint F was applied to the same steel plate as in Example 1 at 240°C.
After 3 minutes of electrodeposition coating with V, wash with water and apply 1180'
C. for 25 minutes to obtain a smooth cured coating film with a dry film thickness of 19 microns.

Table 1 shows the test results for the film performance of the obtained cured coating film, the stability over time of the resin F for cationic electrodeposition paint, and the water dispersibility of the electrodeposition paint F.

Comparative Example 1 In a flask similar to Example 1, a sample having a number average molecular weight of 900. 3325 parts of an epoxy resin having an epoxy equivalent of 475 was charged, and 928 parts of ethylene glycol monoethyl ether acetate was added and dissolved.

Then, 387 parts of ε-caprolactone and 15 parts of dibutyltin dilaurate were added, and the mixture was heated at 140°C under nitrogen atmosphere.
The temperature was raised to 1, and the mixture was reacted for 3 hours.

Then, after cooling to 80°C, while maintaining the same temperature,
A mixture of 337 parts of dimethylamine propylamine and 7200 parts of jetanolamine was added dropwise over 30 minutes.

Then, the temperature was raised to 100"0 and the reaction was continued, resulting in gelation after 1.5 hours.

Comparative Example 2 In a flask similar to Example 1, ketone 336 obtained by the reaction of bisphenol A and epichlorohydrin was added.
part was added and dissolved.

Next, 278 parts of %C-caprolactone and 3.4 parts of dibutyltin dilaurate were added, and the mixture was heated to 140% under a nitrogen stream.
After raising the temperature to .degree. C. and reacting for 10 hours, the mixture was cooled to 80.degree.

Next, 161 parts of the diketimine of Example 1 was added, the temperature was raised to 100"C over 30 minutes, the mixture was allowed to react until the epoxy value reached 0, and then the mixture was cooled to 80"C, followed by adding the partially blocked isocyanate of Example 10. 333 parts were added and the reaction was carried out until the absorption of incyanate groups disappeared in the infrared absorption spectrum.

Next, methyl imbutyl ketone was distilled off at 100 to 120 DEG C. under reduced pressure, and 448 parts of ethylene glycol mobutyl ether was added to obtain Resin G for cationic electrodeposition paints with a nonvolatile content of 72 parts.

3 parts, 6 parts, 12 parts, and 16 parts of acetic anhydride were added to 17 parts of the obtained resin G4 for cationic electrodeposition paint to neutralize it, and then 1071 parts of deionized water were added to each.
No good dispersion was obtained in either case. In addition, 417 parts of cationic resin A was neutralized by adding 16 parts of acetic anhydride, and then 1,504 parts of a dispersion obtained by adding 1,071 parts of deionized water were added to Example When 222 parts of Pigment Dispersion A of No. 1 was added, agglomeration occurred.

Comparative Example 3 In a flask similar to Example 1, 760 parts of an epoxy resin with a number average molecular weight of 900 and an epoxy equivalent of 475 obtained by the reaction of bisphenol A and epichlorohydrin were charged, and 404 parts of ethylene glycol monobutyl ether acetate) was added. and dissolved.

Then, the temperature was raised to 80°C under a nitrogen stream, and while maintaining that temperature, 54 parts of dimethylaminopropylamine, 75 parts of the diketimine of Example 1, and 52.5 parts of jetanolamine were added.
% of the mixture was added dropwise over 30 minutes.

Then, the temperature was raised to 100°C over 30 minutes, and the reaction was carried out until the epoxy value became O. Methyl isobutyl ketone 4
After adding 71 parts and cooling to 80°C, 371 parts of the partially blocked isocyanate of Example 1 was added and the mixture was reacted until no absorption of incyanate groups was observed in the infrared absorption spectrum.

Then, methyl
After distilling off the butyl ketone, 262 parts of ethylene glycol monobutyl ether was added to obtain Resin H for cationic electrodeposition paints with a nonvolatile content of 75 parts.

After mixing and uniformly dispersing 400 parts of the obtained resin H for cationic electrodeposition coating, 4.5 parts of acetic anhydride, and 1374 parts of deionized water, 222 parts of the pigment dispersion A of Example 1 was added to give a solid content of 20 parts. An electrodeposition paint H was obtained.

The obtained electrodeposition paint H was applied to the same steel plate as in Example 1 at a temperature of 240
After 3 minutes of electrodeposition painting with V, wash with water and apply 180"
C. for 25 minutes to obtain a cured coating film with a dry film thickness of 22 μm.

Table 1 shows the test results for the film performance of the obtained cured coating film, the stability over time of Fat H for cationic electrodeposition paint, and the water dispersibility of Electrodeposition Paint H.

As is clear from Table 1, Comparative Example 1 is a method in which an epoxy resin is reacted with C-caprolactone and then cationized. Good story. Comparative Example 2 is a method in which epoxy resin is reacted with caprolactone and then cationized, and the epoxy equivalent of the epoxy resin is
Although the epoxy group and the equivalent amount of active hydrogen in the reactive active hydrogen-containing compound are equal, the water dispersibility of the electrodeposition paint is poor. In Comparative Example 3, after reacting the epoxy group in the epoxy resin with a reactive active hydrogen-containing compound,
This method produces a cationic resin by reacting a partially blocked incyanate, and is inferior in quality. In contrast, it can be seen that Examples 1 to 6 of the present invention are excellent in the stability of resins for cationic electrodeposition paints, water dispersibility of electrodeposition paints, and coating film performance.

Claims (1)

[Claims] 1. A method for producing a resin for cationic electrodeposition coatings, which comprises reacting an epoxy resin with an active hydrogen-containing compound to make it substantially free of epoxy groups, and then reacting it with ε-caprolactone.