Aqueous dip-coating composition for electroconductive substrates, comprising dissolved bismuth

Patent metadata

Field	Value
Publication number	US-9920205-B2
Application number	US-201315037278-A
Country	US
Kind code	B2
Filing date	Nov 18, 2013
Priority date	Nov 18, 2013
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

The present invention relates to an aqueous coating composition (A) having a pH in a range from 4.0 to 6.5 and comprising at least one cathodically depositable binder (A1), a total amount of at least 130 ppm of Bi, based on the total weight of (A), including at least 30 ppm of Bi in a form (A3) in solution in (A) and optionally at least 100 ppm of Bi in a form (A4) not in solution in (A), and at least one at least bidentate complexing agent (A5) suitable for complexing Bi, (A5) being a compound of the general formula (1) or an anion of this compound, for at least partly coating an electrically conductive substrate with an electrocoat material, to a method for producing (A), to the use of (A) for at least partly coating an electrically conductive substrate with an electrocoat material, to a corresponding coating method, to an at least partly coated substrate obtainable by this method, and to a method for setting and/or maintaining the concentration of component (A3) and/or optionally (A4) in the coating composition (A) during the coating method.

First claim

What is claimed is:

1. An aqueous coating composition (A) for at least partly coating an electrically conductive substrate with an electrocoat material, comprising:
(A1) at least one cathodically depositable binder;
(A2) optionally at least one crosslinking agent;
bismuth; and
(A5) at least one at least bidentate complexing agent of formula (1) or an anion of said compound which is suitable for complexing bismuth;
the coating composition (A) having a pH in a range from 4.0 to 6.5,
wherein the coating composition (A) comprises a total amount of at least 130 ppm of bismuth, based on the total weight of the coating composition (A), including:
(A3) at least 30 ppm of bismuth, based on the total weight of the coating composition (A), in a form in which it is in solution in the coating composition (A), and
(A4) optionally at least 100 ppm of bismuth, based on the total weight of the coating composition (A), in a form in which it is not in solution in the coating composition (A),

wherein
R 1 is a C 1-6 aliphatic radical substituted by at least one OH group,
m is 0 or 1,
R a and R b in each case independently of one another are selected from the group consisting of H and C 1-6 aliphatic radicals, optionally substituted by at least one OH group, and mixtures thereof,
R 2 , R 3 , R 4 , and R 5 in each case independently of one another are H or are a C 1-6 aliphatic radical optionally substituted by at least one OH group,
n is 1 or 2,
o is 1 or 2,
p is 0, 1, 2, or 3, and
R 6 is C(═O)OH, S(═O) 2 OH, P(═O)(OH) 2 , NR 7 R 8 , or a C 1-6 aliphatic radical which is substituted by at least one OH group,
where R 7 and R 8 in each case independently of one another are selected from the group consisting of H and C 1-6 aliphatic radicals which are optionally substituted by at least one OH group and mixtures thereof;
with the proviso that at least one of the radicals R 7 and R 8 is a C 1-6 aliphatic radical which is substituted by at least one OH group.

2. The coating composition (A) as claimed in claim 1 , wherein at least 100 ppm of bismuth, based on the total weight of the coating composition (A), are present as component (A3) in a form in which it is in solution in the coating composition (A).

3. The coating composition (A) as claimed in claim 1 , wherein the radical R 6 is C(═O)OH or is NR 7 R 8 or is a C 1-6 aliphatic radical which is substituted by at least one OH group.

4. The coating composition (A) as claimed in claim 1 , wherein:
R 1 is a C 1-4 aliphatic radical substituted by at least one OH group,
m is 0 or 1,
R a and R b in each case independently of one another are selected from the group consisting of H and C 1-4 aliphatic radicals, optionally substituted by at least one OH group, and mixtures thereof,
R 2 , R 3 , R 4 , and R 5 in each case independently of one another are H or are a C 1-4 aliphatic radical optionally substituted by at least one OH group,
n is 1 or 2,
o is 1 or 2,
p is 0, 1, or 2, and
R 6 is C(═O)OH, NR 7 R 8 , or a C 1-4 aliphatic radical which is substituted by at least one OH group,
where R 7 and R 8 in each case independently of one another are selected from the group consisting of H and C 1-6 aliphatic radicals which are optionally substituted by at least one OH group, and mixtures thereof;
with the proviso that at least one of the radicals R 7 and R 8 is a C 1-6 aliphatic radical which is substituted by at least one OH group.

5. The coating composition (A) as claimed in claim 1 , wherein component (A5) is selected from the group consisting of N,N,N′,N′-tetrakis-2-hydroxypropylethylenediamine, N,N′-bis(2-hydroxyethyl)glycine, N-(tri(hydroxy-methyl)methyl)glycine, N-hydroxyethylaminoacetic acid, triethanolamine, triisopropanolamine, and N,N,N′N′-tetrakis-2-hydroxyethylethylenediamine, and mixtures thereof.

6. The coating composition (A) as claimed in claim 1 , wherein the at least one complexing agent (A5) is present in the aqueous coating composition (A) in a fraction of at least 5 mol %, based on the total amount of bismuth present in the coating composition (A).

7. The coating composition (A) as claimed in claim 1 , wherein components (A3) and (A5) are present in the form of a complex and/or salt of components (A3) and (A5) in the coating composition (A).

8. The coating composition (A) as claimed in claim 1 , wherein the coating composition (A) comprises:
(A4) at least 100 ppm of bismuth, based on the total weight of the coating composition (A), in a form in which it is not in solution in the coating composition (A).

9. The coating composition (A) as claimed in claim 1 , wherein the coating composition (A) comprises a total amount of at least 300 ppm of bismuth, based on the total weight of the coating composition (A), including
(A3) at least 100 ppm of bismuth, based on the total weight of the coating composition (A), in a form in which it is in solution in the coating composition (A), and
(A4) at least 200 ppm of bismuth, based on the total weight of the coating composition (A), in a form in which it is not in solution in the coating composition (A).

10. The coating composition (A) as claimed in claim 1 , wherein the total amount of bismuth present in the coating composition (A) is in a range from at least 500 ppm to 20 000 ppm.

11. The coating composition (A) as claimed in claim 1 , wherein the coating composition (A) is obtainable by at least partly converting at least one water-insoluble bismuth compound, by partial reaction of this compound with at least one at least bidentate complexing agent (A5) suitable for complexing bismuth, into at least one water-soluble bismuth compound (A3) in water, optionally in the presence of at least one of components (A1) and/or (A2), to give a mixture comprising at least components (A3) and (A5), and optionally (A1) and/or (A2) and/or (A4), of the coating composition (A), and optionally mixing the resulting mixture at least with component (A1) and optionally component (A2), to give the coating composition (A).

12. The coating composition (A) as claimed in claim 1 , wherein the binder (A1) is a polymeric resin which has at least partly protonated tertiary amino groups.

13. The coating composition (A) as claimed in claim 12 , wherein the tertiary amino groups each independently of one another have at least two C 1-3 alkyl groups each at least singly substituted by a hydroxyl group.

14. A method for producing the aqueous coating composition (A) as claimed in claim 1 , wherein the method comprises at least step (0):
(0) at least partly converting at least one water-insoluble bismuth compound, by at least partial reaction of this compound with at least one complexing agent (A5), into at least one water-soluble bismuth compound (A3) in water, to give a mixture comprising at least components (A3) and (A5) and also, optionally, (A4) of the coating composition (A).

15. A method for producing an electrically conductive substrate comprising coating at least part of an electrically conductive substrate with a coating composition according to claim 1 .

16. A method for at least partly coating an electrically conductive substrate with an electrocoat material, comprising at least a step (1):
(1) contacting the electrically conductive substrate, connected as cathode, with the aqueous coating composition (A) as claimed in claim 1 ,
step (1) being carried out in at least two successive stages (1a) and (1b):

Assignees

• Basf Coatings Gmbh
• Henkel Ag & Co Kgaa

Inventors

• Wapner Kristof
• Gaspar Florian
• Hammer Christian

Classifications

• C09D5/08

  Anti-corrosive paints · CPC title

• C09D5/4488 Primary

  Cathodic paints (C09D5/4403 - C09D5/4476 take precedence) · CPC title

• C09D5/4492

  containing special additives, e.g. grinding agents · CPC title

• C09D5/4496 Primary

  characterised by the nature of the curing agents · CPC title

• C25D13/18

  using modulated, pulsed, or reversing current · CPC title