Cationically Electrodepositable Resin Composition Based on 4-Vinylcyclohexene-1-Oxide

Hereinbelow, the present invention will be explained more specifically by examples. All parts and percentages in the following examples are by weight.

FIGS. 1 to 4 referred to in examples are described below, respectively.

FIG. 1 is a schematic drawing of apparatus using to test throwing power of electrodepositable paint, FIG. 2 is a schematic drawing of outer plate film measuring plate using for the test, FIG. 3 is a schematic drawing of inner plate throwing power measuring plate using for the test, and FIG. 4 is a drawing for explaining the coated height of the inner plate.

A mixture of 155 parts of EHPE 3150 (epoxy equivalent 175 to 195) [(A) component], 70 parts of diethanolamine (B) component) and (C) component (whole product obtained by heating 475 parts of bisphenol A diglycidyl ether having an epoxy equivalent of 190, 285 parts of bisphenol A, 53 parts of diethanolamine and 80 parts of carbitol to make a solution, cooling the solution and then subjecting the solution to reaction by holding it at 130.degree. C. for 3 hours) was subjected to reaction at 160.degree. C. for 5 hours, and 692 parts of methylpropanol was added thereto to obtain a cationic resin (Y-1) having a solid content of 60%, an amine value of 63 and a primary hydroxyl group value of 127.

To 100 parts of this cationic resin (Y-1), 37.5 parts of EHPE-3150 of a solid content of 80% dissolved in ethylcellosolve (curing agent (Z-1)) and 0.7 part of formic acid were added, and 319 parts of deionized water was thereto with sufficient stirring to obtain an emulsion (1) having a solid content of 20%, a pH of 6.5 and an emulsion particle size of 0.10 micron. When this emulsion (1) was allowed to stand at 30.degree. C. for one month, there were not observed separation of emulsion, sedimentation, increase of particle size, etc.

To 100 parts of the above cationic resin (Y-1) were added 50 parts of titanium white, 50 parts of clay, 30 parts of basic lead silicate, 3.0 parts of formic acid and 75 parts of deionized water were added, and the mixture was kneaded. Then, after addition of 800 parts of glass beads the solids were dispersed in a paint shaker to obtain a pigment dispersion (1) having a solid of 62%.

The above emulsion (1) (1,000 parts) and 90 parts of the above pigment dispersion (1) were mixed and the mixture was diluted with 188 parts of deionized water to obtain a cationically electrodepositable paint bath having a pH of 6.2 and a solid content of 20%.

A zinc phosphate-treated plate was subjected to electrodeposition coating in this electrodeposition bath at a bath temperature of 30.degree. C. and 250 V for 3 minutes. The resulting paint film was baked at 160.degree. C. for 3 minutes to obtain a paint film having a film thickness of 13 microns and a pencil hardness of 3H. This coated plate had a salt spray resistance of 2,000 hours pass, an impact resistance of 1 kg, 50 cm pass and throwing power of 21 cm, and its painted surface state was good (test method are described below).

Bisphenol A diglycidyl ether type polyepoxide having an epoxy equivalent of 190 (380 parts), 340 parts of polypropylene glycol diglycidyl ether having an epoxy equivalent of 340, 342 parts of bisphenol A, 105 parts of diethanolamine and 90 parts of ethylene glycol monobutyl ether were mixed to make a solution. After cooling, the solution was subjected to reaction at 150.degree. C. for 3 hours to obtain a (C) component. EHPE-3150 [(A) component] (370 parts) was added to this (C) component and the mixture was subjected to reaction at 150.degree. C. for 5 hours. Bisphenol A diglycidyl ether (48 parts) having an epoxy equivalent of 190 was added thereto and the mixture was maintained at 160.degree. C. for 3 hours. Then, after addition of 147 parts of diethanolamine [(B) component], the mixture was maintained at 150.degree. C. for 3 hours and then 1065 parts of methylpropanol was added thereto to obtain a cationic resin (Y-2) having a solid content of 60%, an amine value of 78.1 and a primary hydroxyl group value of 155.

To 100 parts of the above cationic resin (Y-2) were added 50 parts of EHPE-3150 dissolved in methyl isopropanol (solid content: 80%) and 0.8 part of formic acid, and under sufficient stirring 359 parts of deionized water was added to obtain an emulsion (2) having a solid content of 20%, a pH of 6.8 and an emulsion particle size of 0.05 micron. When this emulsion was allowed to stand at 30.degree. C. for one month, there were not observed separation, sedimentation, increase of the particle size, etc.

To the above cationic resin (Y-2) (100 parts) were added 30 parts of titanium white, 70 parts of talc, 5 parts of basic lead silicate, 10 parts of litharge, 3.5 parts of formic acid and 80 parts of deionized water, and the mixture was kneaded. Then, the solid contents were dispersed in a ball mill to obtain a pigment dispersion (2) having a particle size of 15 microns and a solid content of 59%.

The above emulsion (2) (1,000 parts) and 60 parts of the pigment dispersion (2) were mixed and then diluted with 583 parts of deionized water to obtain an electrodepositable paint bath having a solid content of 20% and a pH of 6.6.

A zinc phosphate-treated plate was subjected to electrodeposition coating in this electrodepositable paint bath at a bath temperature of 30.degree. C. and 200 V for 3 minutes. The resulting paint film was baked at 160.degree. C. for 30 minutes to obtain a paint film having a film thickness of 17 microns and a pencil hardness of 3H. This paint film had a salt spray resistance of 2,000 hour pass, an impact resistance of 1 kg, 50 cm pass, a throwing power of 20 cm and a good painted surface state.

Bisphenol A diglycidyl ether (760 parts) having an epoxy equivalent of 190, 456 parts of bisphenol A, 105 parts of diethanolamine and 132 parts of ethylene glycol hexylcellosolve were heated to make a solution. The solution was cooled and held at 150.degree. C. for 3 hours to carry out reaction until all the epoxy groups disappeared, whereby a (C) component was obtained. To this (C) component were added 278 parts of EHPE-3150 [(A) component and 136 parts of diethanolamine [(B) component], and the mixture was held at 170.degree. C. for 5 hours. After ascertainment of disappearance of the epoxy groups, 150 parts of bisphenol A diglycidyl ether having an epoxy equivalent of 190 was added and the mixture was subjected to reaction at 160.degree. C. until the epoxy groups disappeared (4 hours). Thereafter, 1125 parts of methylpropanol was added to obtain a cationic resin (Y-3) having a solid content of 60%, an amine value of 68 and a primary hydroxyl group value of 137.

A solution obtained by dissolving 2 parts of azobisdimethylvaleronitrile in 33.4 parts of METHB (3,4-epoxycyclohexylmethyl methacrylate) was added dropwise over a period of 2 hours to a mixed solvent of 10 parts of methyl isobutyl ketone and 10 parts of butylcellosolve heated to 100.degree. C. After one hour aging, the mixture was heated to 125.degree. C. and further aged for one hour to obtain a curing agent (Z-2) having a solid content of 60% and an epoxy equivalent of 196.

To 100 parts of the cationic resin (Y-3) were added 50 parts of the curing agent (Z-2), 1.3 parts of 38% lead octoate and 0.53 part of formic acid, and under sufficient stirring 298 parts of deionized water was added to obtain an emulsion (3) having a solid content of 20%, a pH of 6.6 and an emulsion particle size of 0.04 micron. When this emulsion was allowed to stand at 30.degree. C. for one month, there were not observed separation of emulsion, sodimentation, increase of particle size, etc.

The cationic resin (Y-3) (100 parts), 30 parts of titanium white, 60 parts of clay, 0.5 part of carbon, 5 parts of lead tripolyphosphates, 10 parts of lead oxide, 3 parts of formic acid and 70 parts of deionized water were kneaded, and 1,000 parts of glass beads were added. The solid components were dispersed in a paint shaker to obtain a pigment dispersion having a solid content of 59%.

The above emulsion (3) (1,000 parts) and 70 parts of the pigment dispersion (3) were mixed and diluted with 136 parts of deionized water to obtain an electrodeposition bath having a solid content of 20% and a pH of 6.4.

A zinc phosphate-treated plate was subjected to electrodeposition coating with this electrodeposition bath at a bath temperature of 30.degree. C. and 250V for 3 minutes, and the resulting paint film was baked at 160.degree. C. for 30 minutes to obtain a paint film having a thickness of 14 microns and a pencil hardness of 3H. This paint film had a salt spray resistance of 2,000 hour pass, an impact resistance of 500 g, 50 cm pass, a throwing power of 21 cm and a good painted surface state.

A mixture of 152 parts of an aqueous 50% hydroxyethylhydrazine solution and 200 parts of methyl isobutyl kentone was heated, and 94 parts of water was removed with gradual temperature up from 90 to 130.degree. C. Then, the mixture was held under reduced pressure at 130.degree. C. for 30 minutes to remove excess methyl isobutyl ketone, whereby 165 parts of a condensate of hydroxyethylhydrazine and methyl isobutyl ketone (95% in methyl isobutyl ketone) [(B) component] was obtained.

EHPE 3150 [(A) component] (180 parts) and 80 parts of methylisopropanol were heated to make a solution, 108 parts of the above condensate and 36 parts of diethanolamine were added at 100.degree. C. to cause a reaction. Then, 92 parts of butylcellosolve was added thereto to obtain a cationic resin (X) having a solid of 60%, an amine value of 176 and a primary hydroxyl group value of 220.

The same procedures as in Example 1 was carried out except that cationic resin (X) was substituted for the cationic resin (Y-1) in (2) and (3) in Example 1. As a result, as for emulsion was obtained one having a solid content of 20%, a pH of 6.3 and an emulsion particle size of 0.15 micron. When this emulsion was allowed to stand at 30.degree. C. for one month, there were not observed separation of emulsion, sediment, increase of particle size, etc. Further, as for electrodepositable paint bath, a cationically electrodepositable paint bath having a pH of 6.7 and a solid content of 20%.

A zinc phosphate-treated plate was subjected to electrodeposition coating in this electrodeposition bath at a bath temperature of 30.degree. C. and 250V for 3 minutes, and the resulting paint film was baked at 160.degree. C. for 30 minutes to obtain a paint film having a thickness of 15 microns and a pencil hardness of 3H. This paint film had a salt spray resistance of 1,000 hours pass, an impact resistance of 500 g, 50 cm pass, a throwing power of 20 cm and a good painted surface state.

Preparation of block polyisocyanate compound (curing agent)

To 174 parts of tolylenediisocyanate and 30 parts of methyl isobutyl ketone was added dropwise 180 parts of ethylene glycol monoethyl ether at 50.degree. C. over a period of 2 hours, and the mixture was further maintained at 80.degree. C. for one hour to obtain 384 parts of a block isocyanate compound having a solid content of 92%.

To the thus obtained block polyisocyanate compound were added 1765 parts of the cationic resin (Y-3) of Example 3, 74 parts of 38% lead octoate, 7 parts of dibutyltin acetate and 18 parts of acetic acid. Then, 4812 parts of deionized water was added thereto with sufficient stirring to obtain an emulsion (5) having a solid content of 20%, a pH of 6.4 and an emulsion particle size of 0.09.mu.. When this emulsion was allowed to stand at 30.degree. C. for one month, there were not observed separation of emulsion, sedimentation, increase of particle size, etc.

The same procedures as in Example 3 were carried out using 1,000 parts of the emulsion (5) and 70 parts of the pigment dispersion (3) of the above Example 3.

A zinc phosphate-treated plate was subjected to electrodeposition coating in this electrodeposition bath at a bath temperature of 30.degree. C. and 250V for 3 minutes, and the resulting paint film was baked at 160.degree. C. for 30 minutes to obtain a paint film having a thickness of 15.mu. and a pencil hardness of 3H. This paint film had a salt spray resistance of 2,000 hours pass, an impact resistance of 500 g, 50 cm pass, a throwing power of 22 cm and a good painted surface state.

Dimethylbenzylamine (0.3 part) was added to 1140 parts of bisphenol A glycidyl ether having an epoxy equivalent of 190 and 456 parts of bisphenol A, and the mixture was heated to 140.degree. C. to make a solution, which was maintained at that temperature for 2 hours to obtain a resin having an epoxy equivalent of 795. To this resin were added 1204 parts of methylpropanol and 210 parts of diethanolamine [(B) component]. The mixture was subjected to reaction at 100.degree. C. for 3 hours and disappearance of all the epoxy groups was ascertained to obtain a cationic resin (1) having a solid content of 60%, an amine value of 62 and a primary hydroxyl group value of 124. This resin (1) has no functional group represented by the aforementioned structural formula (I).

When 100 parts of the above cationic resin (1), 32.6 parts of the curing agent used in Example 5 and 0.7 parts of formic acid were mixed, and deionized water was added thereto with sufficient stirring, water separated and such a stable dispersion as in the examples could not be obtained. Thus, a four times layer quantity of formic acid (i.e. 2.8 parts) was added to prepare a water dispersion. Although an emulsion (6) having a solid content of 20% was obtained by adding 314 parts of deionized water to this dispersion, the emulsion had only a low pH of 4.9 and had an average particle size of 0.20 micron. When this emulsion (6) was allowed to stand at 30.degree. C. for 2 weeks, it separated into two layers. Further, 90 parts of a pigment dispersion (6) prepared by substituting the above cationic resin (1) for the cationic resin (Y-3) in the pigment dispersion (3) of Example 3 was mixed with 1,000 parts of the above emulsion (6) of this comparative example, followed by dilution with 188 parts of deionized water to prepare an electrodeposition bath having a pH of 5.1 and a solid content of 20%. A paint film obtained by electrodeposition with this electrodeposition bath at a bath temperature of 30.degree. C. and 250 V for 3 minutes was baked at 160.degree. C. for 30 minutes to prepare a paint film having a thickness of 11 microns and a pencil hardness of 3H. Although this paint film had a salt spray resistance of 1,000 hours pass and an impact resistance of 500 g, 50 cm pass, many gas pinholes were generated and thus the painted surface state was inferior. Further, its throwing power was 15 cm and thus insufficient.

Bisphenol A diglycidyl ether having an epoxy equivalent of 190 (950 parts), 340 parts of polypropylene glycol diglycidyl ether having an epoxy equivalent of 340, 456 parts of bisphenol A and 21 parts of diethanolamine were mixed and reacted at 120.degree. C. until epoxy value thereof became 1.02 m moles/g. The reaction mixture was then diluted with 479 parts of ethylene glycol monobutyl ether and cooled. While the temperature was maintained at 100.degree. C., 158 parts of diethanolamine and 17.8 parts of ethylethanolamine was added to carry out reaction for 3 hours and disappearance of the epoxy groups was ascertained, whereby a cationic resin (2) was obtained having a solid content of 80%, an amine value of 55 and a primary hydroxyl group value of 104. This resin (2) has no functional group represented by the aforementioned structural formula (I).

When deionized water was added to a mixture of 75 parts of this cationic resin (2), 43.5 parts of the curing agnet of Example 5 and 0.8 part of formic acid under sufficient stirring, water separated and such a stable water dispersion as in the examples could not be obtained. Further, a stable water dispersion could be obtained by adding 1.6 parts of formic acid corresponding to two times larger quantity. Further, 383 parts of deionized water was added thereto to obtain an emulsion (7) having a solid content of 20%. This emulsion had a low pH of 5.5 and a good average particle size of 0.1 micron, but when it was allowed to stand at 30.degree. C. for 2 weeks, particle size increased to 0.35 micron, and after 4 weeks the emulsion separated into two layers. Further, 60 parts of a pigment dispersion (7) prepared by replacing the above cationic resin (2) by the cationic resin (Y-3) in the pigment dispersion (3) of Example 3 was mixed with 1,000 parts of the above emulsion (7), and diluted with 583 parts of deionized water. The resulting electrodeposition bath had a low pH of 5.7. A zinc phosphate-treated plate was subjected to electrodeposition coating with this electrodeposition bath at a bath temperature of 30.degree. C. and 200 V for 3 minutes, and the resulting paint film was baked at 160.degree. C. for 30 minutes to obtain a paint film having a thickness of 18 microns and a pencil hardness of 3H. Although this paint film had a salt spray resistance of 1,000 hours pass and an impact resistance of 500 g, 50 cm pass, its throwing power was 14 cm and insufficient.

This test was carried out according to JIS Z 2371. When swelling of the paint film within a creep width of 2.0 mm in one side from the cut (linear incisure) site and swelling of the paint film in other parts than the cut site are less than 8F (ASTM), the paint film is judged to pass the test.

After a test plate is placed under constant temperature and constant humidity conditions of a temperature 20.degree..+-.1.degree. C. and a humidity of 75.+-.2% for 24 hours, prescribed-sized cradle and impact center and set in a du Pont impact testor and the test plate is put between them so that the painted surface of the paint film faces upward. Then, a prescribed weight is dropped on the impact center from the prescribed height. When breaking and exfoliation of the paint film due to the impact are not observed, the paint film is judged to pass the test.

Apparatus for throwing power test: schematically illustrated in the attached FIGS. 1 to 3.

Each symbol in the figures has the following meaning:

V: round vessel made of stainless steel (.phi.=100 mm, t=1 mm) having no magnetism

Z: insulator

D: supporting rod (.phi.=3 mm, h=170 mm)

P: stainless pipe (.phi.=16 mm, h=340 mm, t=1 mm) having no magnetism

A: outer plate film thickness measuring plate (30.times.150.times.0.8 mm) (Please refer to FIG. 2)

B: inner plate throwing power measuring plate (15.times.300.times.0.4 mm) (Please refer to FIG. 3)

T: mercury thermometer (50.degree. C. scale)

K: rotor

C: water tank for cooling (made of a plstic)

M: magnetic stirrer

L: liquid level of the paint

Procedures

1) A paint is placed in such a stainless round vessel V as illustrated in FIG. 1 up to a height L of 27 cm from the bottom, adjusted to the prescribed temperature (usually 30.degree. C.) and uniformly stirred. (bath temperature: .degree. C.).

2) The outer plate A, the pipe D and the inner plate B were inserted into the supporting rod D and then placed in the vessel V.

3) Anode and cathode were set and it is ascertained that there is no short.

4) Voltage is increased in 10 seconds from 0 to the prescribed voltage at which film thickness of the outer plate becomes 25 microns. In this operation, increase speed is adjusted so that the electric current does not exceed 10A.

5) After 3 minutes electrifying, the switch is turned off, and the outer plate, the inner plate and the pipe are washed with water.

6) The outer plate and the inner plate are baked and dried.

7) The pipe is subjected to two stages of washing with detergent, and particularly the inner surface of the pipe is sufficiently washed.

8) Coated height of the inner plate is measured (Please refer to FIG. 4).