Method for preparing cationic electrodeposition coating composition

Patent metadata

Field	Value
Publication number	US-10479899-B2
Application number	US-201615555180-A
Country	US
Kind code	B2
Filing date	Mar 4, 2016
Priority date	Mar 6, 2015
Publication date	Nov 19, 2019
Grant date	Nov 19, 2019

Abstract

The objective of the present invention is to provide a method for preparing a cationic electrodeposition coating composition that contains a bismuth compound and exhibits excellent coating material stability, curability, coating film appearance and the like. The present invention provides a method for preparing a cationic electrodeposition coating composition, which comprises a step for mixing a resin emulsion (i) and a pigment-dispersed paste, and wherein: the resin emulsion (i) contains an aminated resin (A) and a blocked isocyanate curing agent (B); the pigment-dispersed paste contains a bismuth mixture (C) that is obtained by mixing a bismuth compound (c1) and an organic acid (c2) in advance, a pigment-dispersed resin (D), an amine-modified epoxy resin emulsion (ii) that contains an amine-modified epoxy resin (E), and a pigment (F); the pigment-dispersed resin (D) has a hydroxyl number of 20-120 mgKOH/g; and the amine-modified epoxy resin (E) has a hydroxyl number of 150-650 mgKOH/g.

First claim

The invention claimed is:

1. A method for preparing a cationic electrodeposition coating composition, wherein the method comprises the steps of:
preparing a resin emulsion (i) by respectively dissolving an aminated resin (A) and a blocked isocyanate curing agent (B) in organic solvents to prepare respective solutions, mixing the respective solutions to achieve a mixed solution, and then neutralizing the mixed solution with a neutralizing acid to obtain the resin emulsion (i) comprising the aminated resin (A) and the blocked isocyanate agent (B),
preparing a pigment dispersion paste comprising a bismuth mixture (C) obtained by mixing a bismuth compound (c1) and an organic acid (c2) in advance; a pigment dispersion resin (D); an amine-modified epoxy resin emulsion (ii) comprising an amine-modified epoxy resin (E); and a pigment (F), according to any one of the following methods of:
mixing the bismuth mixture (C) and the pigment dispersion resin (D), then the obtained mixture being mixed with the amine-modified epoxy resin emulsion (ii), and next, the pigment (F) being mixed in the obtained mixture;
mixing the bismuth mixture (C), the pigment dispersion resin (D) and the amine-modified epoxy resin emulsion (ii), and then the pigment (F) being mixed in the obtained mixture; or
mixing the bismuth mixture (C) and the amine-modified epoxy resin emulsion (ii), and then, the obtained mixture, the pigment dispersion resin (D) and the pigment (F) being mixed, and

mixing the resin emulsion (i) and the pigment dispersion paste to obtain the cationic electrodeposition coating composition, wherein
the pigment dispersion resin (D) has a hydroxyl value of 20 to 120 mg KOH/g, and
the amine-modified epoxy resin (E) has a primary amino group, a hydroxyl value of 150 to 650 mg KOH/g, and an amine value of 20 to 80 mg KOH/g.

2. The method for preparing a cationic electrodeposition coating composition according to claim 1 , wherein:
the cationic electrodeposition coating composition obtained by the method comprises the bismuth compound (c1) in an amount of 0.05 to 1.0% by mass in terms of metal element based on a resin solid content of the resin emulsion (i).

3. The method for preparing a cationic electrodeposition coating composition according to claim 1 , wherein:
a ratio of pigment (F)/pigment dispersion resin (D) in the pigment dispersion paste is 1/0.1 to 1/1 in terms of solid content mass ratio; and
a ratio of pigment (F)/amine-modified epoxy resin (E) in the pigment dispersion paste is 1/0.02 to 1/0.3 in terms of solid content mass ratio.

4. The method for preparing a cationic electrodeposition coating composition according to claim 1 , wherein:
the amine-modified epoxy resin (E) has a number average molecular weight of 1000 to 5000, and
a milligram equivalent (MEQ (B)) of a base per 100 g of the solid content of the amine-modified epoxy resin (E) is 50 to 350.

5. The method for preparing a cationic electrodeposition coating composition according to claim 1 , wherein:
the amine-modified epoxy resin emulsion (ii) is an emulsion neutralized with one or more acid(s) selected from the group consisting of formic acid, acetic acid and lactic acid.

6. The method for preparing a cationic electrodeposition coating composition according to claim 1 , wherein:
the organic acid (c2) is one or more selected from the group consisting of lactic acid, dimethylolpropionic acid and methanesulfonic acid.

7. The method for preparing a cationic electrodeposition coating composition according to claim 1 , wherein:
the cationic electrodeposition coating composition further comprises a salt (G) of a rare earth metal selected from the group consisting of neodymium, yttrium, lanthanum, cerium, praseodymium, and ytterbium.

8. A cationic electrodeposition coating composition obtained by the method for preparing a cationic electrodeposition coating composition according to claim 1 .

9. A cationic electrodeposition coating composition comprising a resin emulsion (i) and a pigment dispersion paste, wherein:
the resin emulsion (i) comprises an aminated resin (A) and a blocked isocyanate curing agent (B),
the pigment dispersion paste comprises a bismuth mixture (C) obtained by mixing a bismuth compound (c1) and an organic acid (c2) in advance; a pigment dispersion resin (D); an amine-modified epoxy resin emulsion (ii) comprising an amine-modified epoxy resin (E); and a pigment (F),
the pigment dispersion resin (D) has a hydroxyl value of 20 to 120 mg KOH/g,
the amine-modified epoxy resin (E) has a primary amino group, a hydroxyl value of 150 to 650 mg KOH/g, an amine value of 20 to 80 mg KOH/g, and a number average molecular weight of 1000 to 5000,
a milligram equivalent (MEQ (B)) of a base per 100 g of the solid content of the amine-modified epoxy resin (E) is 50 to 350, and
the pigment dispersion paste is prepared according to any one of the following methods of:
mixing the bismuth mixture (C) and the pigment dispersion resin (D), then the obtained mixture being mixed with the amine-modified epoxy resin emulsion (ii), and next, the pigment (F) being mixed in the obtained mixture;
mixing the bismuth mixture (C), the pigment dispersion resin (D) and the amine-modified epoxy resin emulsion (ii), and then the pigment (F) being mixed in the obtained mixture; or
mixing the bismuth mixture (C) and the amine-modified epoxy resin emulsion (ii), and then, the obtained mixture, the pigment dispersion resin (D) and the pigment (F) being mixed.

10. The cationic electrodeposition coating composition according to claim 9 , wherein the coating composition further comprises a salt (G) of a rare earth metal selected from the group consisting of neodymium, yttrium, lanthanum, cerium, praseodymium, and ytterbium.

Assignees

• Nippon Paint Automotive Coatings Co Ltd

Inventors

• Miyamae Nobuhiro
• Kotani Masayuki
• Ohara Tetsuya

Classifications

• C09D163/00

  Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins · CPC title

• C09D175/04

  Polyurethanes · CPC title

• C25D13/04

  with organic material · CPC title

• C09D5/4446 Primary

  Aliphatic groups, e.g. ester · CPC title

• C09D5/4465

  Polyurethanes · CPC title