Coating composition for metal surface pre-treatment, its preparation and use thereof

Patent metadata

Field	Value
Publication number	US-2016145444-A1
Application number	US-201615012905-A
Country	US
Kind code	A1
Filing date	Feb 2, 2016
Priority date	Aug 6, 2013
Publication date	May 26, 2016
Grant date	—

Abstract

This invention provided an aqueous coating composition for metal surface pre-treatment comprising:
(i) at least one organosilane with at least one hydrolyzable substituent; (ii) at least one water soluble and/or water dispersible silane-functional oligomer; (iii) at least one water-soluble compound of the elements Zr and/or Ti;

The resultant sol-gel coating composition reveals an extended shelf life and after surface pre-treatment using the invented coating compositions the metal substrates have higher resistance to corrosion, humidity and solvent and at the same time have better surface conductivity and paintability.

First claim

1 . An aqueous coating composition for metal surface pre-treatment having a pH in a range of from 3 to 6, comprising:
(i) at least one organosilane with at least one hydrolyzable substituent; (ii) at least one water soluble and/or water dispersible silane-functional oligomer; (iii) at least one water-soluble compound of elements Zr and/or Ti.

2 . The coating composition according to claim 1 , wherein the organosilane is selected from a compound according to Formula (I):

wherein n is an integer from 1 to 3; residue R is selected from C1 to C6 alkyl groups; residue Y is selected from alkyl groups having not more than 10 carbon atoms carrying at least one epoxy, amino, hydroxyl, vinyl and/or thiol group wherein the residues Y are selected mutually independently from each other.

3 . The coating composition according to claim 1 , wherein the organosilane has a weight-average molecular weight of less than 400 g/mol.

4 . The coating composition according to claim 1 , wherein the organosilane is selected from vinyltriacetoxysilane, vinyltrialkoxysilanes, aminoethyltrialkoxysilanes, aminopropylalkoxysilanes, bis-trialkoxysilypropylamines, aminoethylaminopropyltrialkoxysilanes, aminoethylaminopropyltrialkoxysilanes, mercaptopropyltrialkoxysilanes, bis-trialkoxysilylpropyl-tetrasulfides, 3-glycidoxypropyltrialkoxysilanes, and mixtures thereof, wherein any alkoxy groups present have not more than 3 carbon atoms.

5 . The coating composition according to claim 1 , wherein the coating composition further comprises a silane according to Formula (II):

wherein R′ is selected from C1 to C6 alkyl groups.

6 . The coating composition according claim 1 , wherein the silane-functional oligomer (ii) has a weight-average molecular weight from 400 g/mol to 10,000 g/mol.

7 . The coating composition according to claim 1 , wherein the silane-functional oligomer (ii) includes at least one of a polyurethane, polyacrylate, polyester and/or polyether backbone.

8 . The coating composition according to claim 7 , wherein the silane-functional oligomer (ii) includes a polyurethane backbone and is a reaction product of at least one diisocyanate, at least one hydroxyl-functional tertiary amine, at least one amino-functional organosilane and at least one polyol.

9 . The coating composition according to claim 7 , wherein the silane-functional oligomer (ii) includes a polyacrylate backbone and is a reaction product of at least one (meth)acrylate, at least one vinyl-functional silane, and at least one tertiary amine acrylate.

10 . The coating composition according to claim 7 , wherein the silane-functional oligomer (ii) includes a polyether backbone and is a reaction product of at least one epoxy resin, at least one amino-functional organosilane, and at least one multifunctional organic compound having at least two functional groups selected from hydroxyl and/or amino groups.

11 . The coating composition according to claim 1 , wherein the said water-soluble compound (iii) is one or more selected from hexafluorotitanic acid, hexafluorozirconic acid, zirconium aceto acetate, zirconium acetate and ammonium zirconium carbonate.

12 . The coating composition according to claim 1 , wherein a molar ratio of element Si to a sum of the elements Zr and/or Ti is from 10 to 500.

13 . The coating composition according to claim 1 , wherein the amount of the water-soluble compound (iii) of the elements Zr and/or Ti in the overall composition is from 0.1 wt.-% to 5 wt.-%, with respect to the elements Zr and Ti.

14 . The coating composition according to claim 8 , wherein the silane-functional polyurethane oligomer (ii) is obtained through a process wherein
i) hydroxyl-functional tertiary amines, amino-functional organosilanes and polyols are pre-mixed under water-free conditions thereby forming a pre-mixture, and ii) the diisocyanates are added dropwise to the pre-mixture while the temperature is kept in a range of from 60° C.-90° C.

15 . The coating composition according to claim 14 , wherein the amino-functional organosilanes in step i) are selected from aminopropyltrialkoxysilanes, aminophenyltrialkoxysilanes, aminopropylmethyldialkoxysilanes, wherein the alkoxy groups have not more than 3 carbon atoms.

16 . A process for electroless coating of metal substrates wherein the metal substrate is contacted with the coating composition according to claim 1 .

17 . The process according to claim 16 , wherein the metal substrates are selected from hot dip galvanized steel, electrolytically galvanized steel, steel, iron, zinc, aluminum and aluminum alloys.

18 . A metal substrate coated with a coating composition according to claim 1 .

Assignees

• Henkel Ag & Co Kgaa

Inventors

• Qiu Xueting

Classifications

• C23C18/1295

  with after-treatment of the deposited inorganic material · CPC title

• C08G77/58

  Metal-containing linkages · CPC title

• C08G77/26

  nitrogen-containing groups · CPC title

• C09D133/08

  Homopolymers or copolymers of acrylic acid esters · CPC title

• C09D183/14

  in which at least two but not all the silicon atoms are connected by linkages other than oxygen atoms (C09D183/10 takes precedence) · CPC title