JPH07126557A - Resin for improving surface smoothness of cationic electrodeposition coating material - Google Patents

Abstract

PURPOSE:To obtain a resin which, when added to an epoxy resin cationic electrodeposition coating material, can allow the coating material to form a coating film improved in surface smoothness for example by opening all of the epoxy rings of a specified epoxy resin by reaction with an active hydrogen compound for introducing cationic groups. CONSTITUTION:The objective resin is a modified resin obtained by opening all of the epoxy rings of a t-alkylphenol novolac epoxy resin of an epoxy equivalent of 200-500 by reaction with an active hydrogen compound for introducing cationic groups selected from among a prim. amine, a sec. amine, a tert. amine salt and a sulfide/acid mixture or by reaction with an active hydrogen compound selected from among a monophenol, a monoalcohol, an aliphatic monocarboxylic acid, an aliphatic hydroxycarboxylic acid and a mercaptoalkanol.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION The present invention relates to a novel modified resin which, when added to an epoxy resin-based cationic electrodeposition coating composition, can improve surface smoothness without adversely affecting other performances, and a cationic electrodeposition coating composition containing the resin. It relates to a composition.

Amine-modified epoxy resins which can be used as a film-forming resin for cationic electrodeposition coating compositions are known from, for example, JP-A-54-4978 and JP-A-56-34186. These amine-modified epoxy resins open all epoxy rings by reacting a bisphenol type epoxy resin with amines, or some epoxy rings are monophenols, monocarboxylic acids, hydroxycarboxylic acids, polycaprolactone. It is obtained by ring-opening with a diol, polyether diol, etc., and ring-opening the remaining epoxy ring by reaction with amines. These amine-modified epoxy resins are dispersed in an aqueous medium containing an acid as a neutralizing agent together with an external crosslinking agent such as a melamine resin or a blocked polyisocyanate. The self-crosslinking amine-modified epoxy resin is obtained by adding a half-blocked polyisocyanate compound to the secondary hydroxyl group in the chain of the polyepoxy resin and then opening the terminal epoxy ring with an amine.

Cationic modified epoxy resins derived from these bisphenol type epoxy resins cause many craters in the coating film after curing due to the adhesion of oil droplets scattered from the surroundings to the electrodeposition coating film before curing. There is a drawback that the surface smoothness is easily damaged.

As one of the countermeasures, there is a method of adding a silicone cissing inhibitor, or adding a reaction product of an epoxy resin and polyoxypropylenediamine in order to suppress the flowability of a coating film at the time of curing. Has been adopted.
However, these methods have a tendency to reduce the adhesiveness with an intermediate coating or an overcoat coating that is subsequently applied over the electrodeposition coating, and adversely affect other physical properties such as the adhesiveness with the overcoat coating. It has been desired to develop an epoxy resin-based cationic electrodeposition coating having excellent smoothness.

DISCLOSURE OF THE INVENTION The present invention provides an epoxy resin-based cationic electrodeposition coating composition having excellent surface smoothness without adversely affecting other properties such as adhesion to a top coating film.

The electrodeposition coating composition of the present invention comprises a t-alkylphenol novolac epoxy resin as a surface smoothness improving resin, (i) a primary amine, a secondary amine, a tertiary amine acid salt and a sulfide-acid mixture. All epoxy rings are opened by reaction with an active hydrogen compound for introducing a cationic group selected from the group, or (ii) monophenol, monoalcohol, aliphatic monocarboxylic acid,
Opening all of the epoxy rings by reaction with an active hydrogen compound selected from the group consisting of aliphatic hydroxycarboxylic acids and mercaptoalkanols, or (ii
i) A modified resin obtained by opening a part of the epoxy ring by reaction with the other active hydrogen compound and opening the remaining epoxy ring by reaction with the active hydrogen compound for introducing a cationic group. Including.

The cationic electrodeposition coating composition of the present invention comprises a cationic modified epoxy resin derived from a bisphenol type epoxy resin as a main component, the modified resin for improving surface smoothness, a curing agent and a neutralizing agent. It is dispersed in an aqueous medium containing it.

Detailed Discussion Surface Smoothness Improving Resin Generally, a novolac epoxy resin is produced by reacting a novolac resin obtained by polycondensing phenols and formaldehyde in the presence of an acid catalyst with epichlorohydrin. It can be used in the present invention when the starting phenol usually has a tertiary alkyl group in the para position.
A novolak epoxy resin which is an alkylphenol. Novolak epoxy resins starting from p-t-butylphenol, p-t-amylphenol, p-t-octylphenol and mixtures thereof are commercially available from Toto Kasei Co., Ltd. and the like.

All of the epoxy rings of the t-alkylphenol novolac epoxy resin are opened with an active hydrogen compound capable of introducing a cationic group such as an amine, or all epoxy rings are opened with another active hydrogen compound such as monophenol. Or a part of the epoxy rings may be opened with another active hydrogen compound and the rest of the epoxy rings may be opened with an active hydrogen compound introducing a cationic group. The reaction itself and the active hydrogen compounds which can be used are well known.

As active hydrogen compounds capable of introducing a cationic group, acid salts of primary amine, secondary amine and tertiary amine,
Or there is a sulphide / acid mixture. Examples include butylamine, octylamine, diethylamine,
In addition to dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N-dimethylethanolamine acetate, diethyldisulfide / acetic acid mixture, aminoethylethanolamine ketimine and diethylenetriamine. There are secondary amines obtained by blocking primary amines such as diketimine. A plurality of amines may be used in combination.

Other active hydrogen compounds that can be used to open the epoxy ring include phenol, cresol,
Monophenols such as nonylphenol and nitrophenol; hexyl alcohol, 2-ethylhexanol, stearyl alcohol, monoalcohols such as monobutyl- or monohexyl ether of ethylene glycol or propylene glycol; aliphatic monocarboxylic acids such as stearic acid and acetic acid Glycolic acid,
Aliphatic hydroxycarboxylic acids such as dimethylolpropionic acid, hydroxypivalic acid, lactic acid, citric acid; and mercaptoalkanols such as mercaptoethanol.

It is desirable that these active hydrogen compounds are reacted in such a ratio that the epoxy groups of the t-alkylphenol novolac epoxy resin and the active hydrogen atoms are almost equivalent. Further, the ratio of the active hydrogen compound capable of introducing the cationic group is such that the amine equivalent of the resin after ring opening is 0.3 to 4.0 me.
The ratio is selected so that it becomes q / g.

Mainly Cationic Epoxy Resin The cationically modified epoxy resin, which is the main component of the film-forming resin component of the cationic electrodeposition coating composition of the present invention, is the above-mentioned JP-A-54-4978 and JP-A-56-34186.
Known resins described in, for example, No.

[0014] Typically, all of the epoxy rings of the bisphenol type epoxy resin are opened with an active hydrogen compound capable of introducing the above-mentioned cationic group, or some epoxy rings are opened with other active hydrogen compounds. And the remaining epoxy ring is opened with an active hydrogen compound capable of introducing a cationic group.

A typical example of the bisphenol type epoxy resin is a bisphenol A type or bisphenol F type epoxy resin. As the former commercial product, Epicoat 828
(Yukaka Shell Epoxy Co., Ltd., epoxy equivalent 180-1
90), Epicoat 1001 (the same, epoxy equivalent 450
~ 500), Epicoat 1010 (the same, epoxy equivalent 3
000 to 4000), and the latter commercially available products include Epicoat 807 and (the same, epoxy equivalent 170). These resins have 0.3 to 4.0 meq / after ring opening.
It is desirable to perform ring opening with an active hydrogen compound so that the amine equivalent of g is obtained. As described above, the main resin is known, and the starting epoxy resin, the active hydrogen compound for introducing a cationic group used for ring opening of the epoxy ring and other active hydrogen compounds, reaction conditions, etc. are also well known. Therefore, no more detailed explanation is necessary.

The crosslinking agent- based resin and the surface smoothness improving resin can be crosslinked with a crosslinking agent such as a melamine resin or a blocked polyisocyanate.

The melamine resin is methylolated melamine and its lower alkanol ether compounds such as methanol and butanol.

The blocked polyisocyanate compound is an addition reaction product of a theoretical amount of the polyisocyanate compound and an isocyanate blocking agent, and is a cross-linking agent for the base resin. As this polyisocyanate compound,
For example, tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanatomethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate, aromatic such as dimers or trimers of these diisocyanate compounds, Aliphatic and aliphatic polyisocyanate compounds and terminal isocyanates obtained by reacting excess amounts of these isocyanate compounds with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, and castor oil. Including prepolymers. Further, the isocyanate blocking agent is one which blocks by adding to the isocyanate group of the polyisocyanate compound.
It is important that the blocked polyisocyanate compound formed by addition is stable at room temperature and can dissociate the blocking agent to regenerate a free isocyanate group when heated above the dissociation temperature.

Specifically, phenol-based blocking agents such as phenol, cresol, xylenol, chlorophenol and ethylphenol; ε-caprolactam,
Lactam-based blocking agents such as δ-palerolactam, γ-butyrolactam and β-propiolactam; active methylene-based blocking agents such as ethyl acetoacetate and acetylacetone; methanol, ethanol, propanol,
Butanol, amyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, benzyl alcohol, methyl glycolate, butyl glycolate, diacetone alcohol, methyl lactate and ethyl lactate. Oxime blocking agents such as formamidoxime, acetoaldoxime, acetoxime, methylethylketoxime, diacetylmonoxime, cyclohexaneoxime; butylmercaptan, hexylmercaptan, t-butylmercaptan, thiophenol, methylthiophenol, ethyl Mercaptan block such as thiophenol Acid amide blocking agents such as acetic acid amide and benzamide; imide blocking agents such as succinimide and maleic acid imide; amine blocking agents such as xylidine, aniline, butylamine, dibutylamine; imidazole, 2-ethylimidazole, etc. Examples thereof include imidazole type blocking agents; imine type blocking agents such as ethyleneimine and propyleneimine. Of these, an oxime-based blocking agent such as methyl ethyl ethoxime is particularly suitable in terms of the balance of the stability of the coating material and the curability of the coating film.

A self-crosslinking amine-modified epoxy resin obtained by adding a half-blocked polyisocyanate compound to the secondary hydroxyl group in the chain of the polyepoxy resin described above and then opening the terminal epoxy ring with an amine or the like is used. You may use it as all or one part of a main resin and a crosslinking agent. The self-crosslinking amine-modified epoxy resin is obtained by blocking not all of the isocyanate groups of the polyisocyanate compound with the above-mentioned blocking agent and carrying out the addition reaction between the remaining free isocyanate groups and the secondary hydroxyl groups of the epoxy resin. In the same manner as the main resin, it can be produced by opening the epoxy ring with an active hydrogen compound capable of introducing a cationic group such as amine.

Electrodeposition Coating Composition The electrodeposition coating composition of the present invention is prepared by dispersing the main resin, the surface smoothness control resin, and the crosslinking agent in an aqueous medium containing a neutralizing agent. The surface smoothness control resin is dispersed in an aqueous medium containing a main resin and a cross-linking agent in one place and a neutralizing agent, or is dispersed separately from the main resin by an appropriate cationic resin and then dispersed in a dispersion liquid of the main resin. It can be added and compounded. Neutralizers include hydrochloric acid, nitric acid, phosphoric acid, formic acid,
It is an inorganic or organic acid such as acetic acid or lactic acid.

The amount of crosslinking agent must be sufficient to react with functional groups such as hydroxyl groups in the resin during curing to give a good cured coating, generally 5 to 50% by weight of resin solids.
Is used. The amount of neutralizing agent is sufficient to neutralize at least 20%, preferably 30-60%, of the amino groups of the resin.

The amount of the surface smoothness control resin is 0.05 to 30% by weight, preferably 0.5 to 20% by weight based on the total solid content of the main resin and the crosslinking agent. If this amount is too small, there is no effect of improving the surface smoothness, and if it is too large, the surface smoothness deteriorates.

The electrodeposition coating composition may contain a tin compound such as dibutyltin dilaurate and dibutyltin oxide in a system containing a blocked polyisocyanate, and a usual urethane cleavage catalyst. The amount is usually 0.1 to 5% by weight of the blocked polyisocyanate compound.

The electrodeposition coating composition includes coloring pigments such as titanium dioxide, carbon black and red iron oxide, basic lead silicate, rust preventive pigments such as aluminum phosphomolybdate, extender pigments such as kaolin, clay and talc, and water-miscible pigments. It may contain conventional additives for coatings such as a water-soluble organic solvent, a surfactant, an antioxidant and an ultraviolet absorber. Examples and comparative examples of the present invention will be shown below.

Example 1 A flask equipped with a stirrer, a condenser, a nitrogen injection tube, a thermometer and a dropping funnel was equipped with a P-alkyl-substituted phenol novolac type epoxy resin (manufactured by Tohto Kasei Co., Ltd .: epoxy equivalent: 311; alkyl = t-). 311 parts by weight of butyl group, number average molecular weight: 1160) and 96.2 parts by weight of methyl isobutyl ketone were weighed and heated to 80 ° C. to uniformly dissolve them. After cooling to 40 ° C., 74 parts by weight of N-methylethanolamine was added to the reaction vessel while paying attention to heat generation. Then, the reaction was continued at 80 ° C., and the reaction was carried out until the epoxy group disappeared (epoxy equivalent measurement, reaction trace by infrared spectrophotometer) to obtain a surface smoothness control resin A. Nonvolatile matter: 80%.

Example 2 A P-alkyl-substituted phenol novolac type epoxy resin (manufactured by Toto Kasei Co., Ltd .: epoxy equivalent: 330, alkyl = t-) was placed in a flask equipped with a stirrer, a condenser, a nitrogen injection tube, a thermometer and a dropping funnel. 330 parts by weight of amyl group, number average molecular weight: 1100) and 101 parts by weight of methyl isobutyl ketone were weighed, heated to 80 ° C. and uniformly dissolved. After cooling to 40 ° C., 74 parts by weight of N-methylethanolamine was added to the reaction vessel while paying attention to heat generation. Then, the reaction was continued at 80 ° C., and the reaction was carried out until the epoxy group disappeared (epoxy equivalent measurement, reaction traced by an infrared spectrometer) to obtain a surface smoothness control resin B. Nonvolatile matter: 8
It was 0%.

Example 3 A P-alkyl-substituted phenol novolac type epoxy resin (manufactured by Toto Kasei Co., Ltd .: epoxy equivalent: 367, alkyl = t-) was placed in a flask equipped with a stirrer, a condenser, a nitrogen injection tube, a thermometer and a dropping funnel. 337 parts by weight of octyl group, number average molecular weight: 1200) and 125 parts by weight of methyl isobutyl ketone were weighed and heated to 80 ° C. to uniformly dissolve them. Then, 134 parts by weight of dimethylolpropionic acid was added, and the temperature was raised to 120 ° C. Subsequently, 2.5 parts by weight of dimethylbenzylamine was added and the temperature was raised to 150 ° C.
After holding for 1 hour, the reaction was continued at 140 ° C., and the reaction was continued until the epoxy group disappeared (epoxy equivalent measurement, the reaction was traced by an infrared spectrometer) to obtain a surface smoothness control resin C. Nonvolatile matter: 80%.

Example 4 A P-alkyl-substituted phenol novolac type epoxy resin (manufactured by Tohto Kasei Co., Ltd .: epoxy equivalent: 325, alkyl = t-) was added to a flask equipped with a stirrer, a condenser, a nitrogen injection tube, a thermometer and a dropping funnel. Butyl group / t-octyl group = 1/1, number average molecular weight: 1200) 325 parts by weight, methyl isobutyl ketone 114 parts by weight were weighed, and
The temperature was raised to 0 ° C. to uniformly dissolve it. Then, 134 parts by weight of dimethylolpropionic acid was added, and the temperature was raised to 120 ° C. Subsequently, 2.3 parts by weight of dimethylbenzylamine was added, the temperature was raised to 150 ° C., the temperature was maintained for 1 hour, and then 140 ° C.
The reaction was continued until the epoxy group disappeared (epoxy equivalent measurement, reaction trace by infrared spectrophotometer), and surface smoothness control resin D was obtained. Nonvolatile matter: 80%.

Example 5 A P-alkyl-substituted phenol novolac type epoxy resin (manufactured by Toto Kasei Co., Ltd .: epoxy equivalent: 311, alkyl = t-) was placed in a flask equipped with a stirrer, a condenser, a nitrogen injection tube, a thermometer and a dropping funnel. 311 parts by weight of butyl group, number average molecular weight: 1160) and 96.2 parts by weight of methyl isobutyl ketone were weighed, heated to 80 ° C. and uniformly dissolved. Then, 103 parts by weight of nonylphenol and 2.0 parts by weight of dimethylbenzylamine were added, and the temperature was raised to 130 ° C. to react. Then, after cooling to 60 ° C., 37 parts by weight of N-methylethanolamine was added to the reaction vessel while paying attention to heat generation. Then, the reaction was continued at 100 ° C., and the reaction was continued until the epoxy group disappeared (epoxy equivalent measurement, reaction trace by infrared spectrometer) to obtain a surface smoothness control resin E. Nonvolatile matter: 80%.

Comparative Example 1 An unsubstituted phenol novolac type epoxy resin (manufactured by Toto Kasei Co., Ltd .: epoxy equivalent: 1) was placed in a flask equipped with a stirrer, a cooler, a nitrogen injection tube, a thermometer and a dropping funnel.
69, number average molecular weight: 440) 169 parts by weight, and methyl isobutyl ketone 60.8 parts by weight were weighed out and uniformly dissolved. At 40 ° C., 74 parts by weight of N-methylethanolamine was added to the reaction vessel while paying attention to heat generation. Then 8
The reaction was continued at 0 ° C., and the reaction was continued until the epoxy group disappeared (epoxy equivalent measurement, the reaction was traced by an infrared spectrometer) to obtain a comparative resin a. Nonvolatile matter: 80%.

Comparative Example 2 P-alkyl-substituted phenol novolac type epoxy resin (manufactured by Toto Kasei Co., Ltd .: epoxy equivalent: 389, alkyl = n-) was added to a flask equipped with a stirrer, a condenser, a nitrogen injection tube, a thermometer and a dropping funnel. 389 parts by weight of nonyl group, number average molecular weight: 1250) and 116 parts by weight of methyl isobutyl ketone were weighed out and uniformly dissolved at 80 ° C. Four
After cooling to 0 ° C., 74 parts by weight of N-methylethanolamine was added to the reaction vessel while paying attention to heat generation. Then 8
The reaction was continued at 0 ° C., and the reaction was continued until the epoxy group disappeared (epoxy equivalent was measured and the reaction was traced by an infrared spectrometer) to obtain a comparative resin b. Nonvolatile matter: 80%.

Production Example 1 Synthesis of Main Resin In a flask equipped with a stirrer, a cooler, a nitrogen injection tube, a thermometer and a dropping funnel, 285.0 g of an epoxy resin having an epoxy equivalent of 475 synthesized from bisphenol A and epichlorohydrin and 285.0 g of an epoxy equivalent were prepared. Epoxy resin 3
80 g, P-nonylphenol 77.0 g and methyl isobutyl ketone 82.4 g were respectively weighed, heated to a uniform temperature and then dissolved in benzyldimethylamine 3.0.
g, and reacted at a reaction temperature of 150 ° C. to obtain an epoxy equivalent of 1
The reaction was allowed to reach 140. Then, the mixture was cooled, and 19.2 g of diethanolamine, 27.0 g of N-methylethanolamine and a ketimine compound of aminoethylethanolamine (79% methyl isobutyl ketone solution) 30.
6 g was added and the reaction continued at 110 ° C. for 2 hours. Then, the main resin I was obtained by diluting with methyl isobutyl ketone until the nonvolatile content became 80%.

Preparation Example 2 Synthesis of Main Resin 54.0 g of 2,4- / 2,6-tolylene diisocyanate (80/20 wt ratio) was placed in a flask equipped with a stirrer, a cooler, a nitrogen injection tube, a thermometer and a dropping funnel. And methyl isobutyl ketone 136g and dibutyltin dilaurate 0.5g are weighed and stirred with methanol 1
0.9 g was added dropwise from the dropping funnel over 30 minutes. The temperature started from room temperature and was raised to 60 ° C. Then, after continuing the reaction for 30 minutes, 54 g of ethylene glycol mono-2-ethylhexyl ether was added dropwise from the dropping funnel over 1 hour. The reaction was carried out mainly while maintaining the temperature in the range of 60 ° C to 65 ° C. The reaction continued until the isocyanate groups disappeared by infrared spectroscopy. Then, an epoxy equivalent of 47 was synthesized from bisphenol F and epichlorohydrin.
285.0 g of an epoxy resin of No. 5 and 380 g of an epoxy resin having an epoxy equivalent of 950 are added to a reaction vessel, uniformly mixed, and heated to 120 ° C., and benzyldimethylamine.
62 g was added, and by-product methanol was distilled off using a decanter, and the reaction was carried out until the epoxy equivalent became 1120. Then cool down and then diethanolamine 2
9.1 g, N-methylethanolamine 21.5 g, and aminoethanolamine ketimine compound (79% methyl isobutyl ketone solution) 32.9 g were added. The reaction was performed at 110 ° C. and the reaction was performed for 2 hours. Diluted with methyl isobutyl ketone to a non-volatile content of 80% to obtain the main resin II
Got

Production Example 3 Synthesis Example of Hardener Hexamethylene diisocyanate trimer (Coronate HX: Nippon Polyurethane) in a flask equipped with a stirrer, a cooler, a nitrogen injection tube, a thermometer and a dropping funnel 1
99 g, methyl isobutyl ketone 32 g, and dibutyltin dilaurate 0.1 g were weighed, stirred, and bubbled with nitrogen, and methyl ethyl ketoxime 87.0 g
Was dropped from the dropping funnel over 1 hour. Temperature is 50 ℃
The temperature was raised to 70 ° C. for the first time.

Production Example 4 Preparation of Pigment Dispersion Paste Mixing with the following composition and dispersing with a sand grind mill,
The pigment dispersion paste was prepared by pulverizing to a particle size of 10 μm or less. Blending Pigment dispersion resin (sulfonium salt: manufactured by Nippon Paint Co., Ltd.) 125.0 g (resin solid content 75.0 g) Deionized water 400.0 g Carbon black 8.5 g Kaolin 72.0 g Titanium oxide 345.0 g Aluminum phosphomolybdate 75.0 g

Examples 6 to 12 Main resin / curing agent / surface smoothness control resin were mixed at a solid content ratio in a composition as shown in Table 1, and ethylene glycol monohexyl ether was added at 2 wt% based on the solid content. The mixture was added and neutralized with glacial acetic acid to 42.5%, and then slowly diluted with ion-exchanged water. This is solid content 3
Methyl isobutyl ketone was removed under reduced pressure to 6.0%. 2000 g of the obtained Main Elma John, 460 g of a pigment dispersion paste, and ion-exchanged water were added to each to prepare a cationic electrodeposition coating composition having a solid content of 20.0%.
Dry film thickness of the prepared coating on cold-rolled steel sheet treated with zinc phosphate 2
It was electrodeposited to 0 μm and baked at 160 ° C. for 10 minutes. After that, various coating film evaluations were performed. The obtained results are shown in Table 1.

Comparative Examples 3-8 As shown in Table 1, the composition was evaluated in the same manner as in Examples 6-12. The obtained results are shown in Table 1.

[0039]

[Table 1]

Repelling / denting: Unit area (100c
The number of dents per m ² ) was used for evaluation. ○ (3 or less); △ (4-10); × (11 ≤) Smoothness (Ra): Surface roughness measuring instrument (Tokyo Seimitsu Co., Ltd. E-
30) (Unit: μm) Adhesion of top coat: intermediate coating (alkyd resin (oil length: 20
%) / Butylated melamine resin system) was spray-coated on the electrodeposition coating film, baked at 140 ° C. for 20 minutes, and then subjected to a cross-cut adhesion test (1 × 1 mm 100 pieces). Corrosion resistance: A cross-cut flaw was added to the electrodeposition coating film with a knife so as to reach the substrate, and this was evaluated according to JIS-Z2371. ◯: Good Δ: Detectable blisters and blisters are present x: Full face and blisters are present

Front page continuation (72) Inventor Toshiyuki Ishii 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd.

Claims (6)

[Claims] 1. A t-alkylphenol novolac epoxy resin having an epoxy equivalent of 200 to 500 is introduced with a cationic group selected from the group consisting of (i) primary amine, secondary amine, tertiary amine acid salt and sulfide-acid mixture. Open all epoxy rings by reaction with active hydrogen compounds, or (ii) selected from the group consisting of monophenols, monoalcohols, aliphatic monocarboxylic acids, aliphatic hydroxycarboxylic acids and mercaptoalkanols Of the epoxy ring by the reaction with the active hydrogen compound of (iii), or (iii) a part of the epoxy ring is opened by the reaction with the other active hydrogen compound and the remaining epoxy ring is replaced by the cationic A modified resin obtained by ring-opening by reaction with an active hydrogen compound for introducing a group. 2. A t-alkylphenol novolac epoxy resin is pt-butyl-, pt-amyl-, p-.
The modified resin according to claim 1, which is a t-octylphenol novolac epoxy resin or a mixture thereof. 3. A cationically modified epoxy resin derived from a polyphenol type epoxy resin having an epoxy equivalent of 150 to 4,000, (b) the modified resin according to claim 1 or 2, and (c) a crosslinking agent. A cationic electrodeposition coating composition comprising a dispersion liquid dispersed in an aqueous medium containing a solvating agent. 4. The cationic electrodeposition coating composition according to claim 3, wherein the ratio of the component (b) to the total of the components (a) and (c) is 0.05 to 30.0% by weight. 5. The cationic electrodeposition coating composition according to claim 4, wherein the crosslinking agent is a blocked polyisocyanate. 6. The cationic electrodeposition coating composition according to claim 4, wherein the crosslinking agent is a melamine resin.