Polyurethane coating composition, multilayer surface coatings having a matt surface produced therefrom and processes for producing the multilayer surface coatings

Patent metadata

Field	Value
Publication number	US-9546285-B2
Application number	US-201113988440-A
Country	US
Kind code	B2
Filing date	Oct 28, 2011
Priority date	Nov 18, 2010
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

The invention relates to coating compositions based on organic solvents and comprising at least one hydroxyl-containing compound (A), at least one crosslinking agent (B) having groups reactive toward hydroxyl groups, and at least one silica gel based matting agent (M), wherein
(i) the matting agent (M) is surface-modified with one or more waxes, and (ii) the coating composition further comprises at least one hydrophobic silica based rheological assistant (R).

The present invention further provides multistage coating methods using these coating compositions, and also the use of the coating compositions as clearcoat or application of the coating method for automotive OEM finishing, for the finishing of parts for installation in or on automobiles, and for automotive refinishing.

First claim

What is claimed is:

1. A clearcoat coating composition based on organic solvents and comprising: 30-70% by weight of at least one hydroxyl-containing compound (A); 20-50% by weight of at least one crosslinking agent (B) having groups reactive toward hydroxyl groups; 2-20% by weight of at least one silica gel based matting agent (M) comprising silica gel that is surface-modified with one or more waxes; and 0.01-3.0% by weight of at least one hydrophobic silica based rheological assistant (R); wherein the weight percents are based on the nonvolatile constituents of the coating composition, and wherein the at least one hydrophobic silica based rheological assistant (R) is prepared by surface modification of fumed silicon dioxide with compounds having hydrophobic groups, wherein, upon curing, the clearcoat coating composition is effective to not increase gloss, at an angle of 60°, by more than 10 gloss units after shearing by pumped circulation in a circuit line.

2. The clearcoat coating composition of claim 1 , wherein the silica gel based matting agent (M) comprises an average particle size of 4 to 14 μm, determined by laser light scattering at room temperature on a dispersion of the particles in butyl acetate using a Malvern Mastersizer 2000 with the MSI mini-dispersing unit at 2000 revolutions per minute and with Fraunhofer evaluation.

3. The clearcoat coating composition of claim 1 , wherein the silica gel based matting agent (M) has a pore volume of 1.2 to 2.5 ml/g.

4. The clearcoat coating composition of claim 1 , wherein the hydrophobic silica based rheological assistant (R) has a primary particle size of 2 to 40 nm.

5. The clearcoat coating composition of claim 1 , wherein the hydrophobic silica based rheological assistant (R) has a BET surface area of 35 to 350 m 2 /g.

6. The clearcoat coating composition of claim 1 , wherein the hydroxyl-containing compound (A) has an OH number of 80 to 250 mgKOH/g.

7. A method for improving circuit line stability of a matted clearcoat coating composition in an automotive OEM finishing or refinishing process, the method comprising:
a) forming a binder mixture by combining
i) 30%-70% by weight, based on the nonvolatile constituents of the coating composition, of at least one hydroxyl containing compound (A);
ii) 2%-20% by weight, based on the nonvolatile constituents of the coating composition, of at least one silica gel based matting agent (M) comprising silica gel that is surface-modified with one or more waxes, and;
iii) 0.01%-3.0% by weight, based on the nonvolatile constituents of the coating composition, of at least one hydrophobic silica based rheological assistant (R), wherein the at least one hydrophobic silica based rheological assistant (R) is prepared by surface modification of fumed silicon dioxide with compounds having hydrophobic groups;

b) adding to the binder mixture 20%-50% by weight, based on the nonvolatile constituents of the coating composition, of at least one crosslinking agent (B) having groups reactive toward hydroxyl groups; and
c) stirring,

thereby producing a matted clearcoat coating composition which, after shearing by pumped circulation in the circuit line, application to the automotive OEM finishing or refinishing substrate, and curing, does not increase in glossiness by more than 10 gloss units at an angle of 60°.

8. The method of claim 7 , further comprising coating an optionally precoated substrate with a pigmented basecoat film and thereafter applying a film of the matted clearcoat coating composition of claim 1 .

9. A The method of claim 8 , wherein the substrate is selected from the group consisting of automotive OEM finishing substrates, substrates for utility vehicle finishing and/or refinishing, substrates for coating interior and/or exterior bodywork components, and mixtures of two or more of the foregoing.

10. The method of claim 7 , further comprising applying the matted clearcoat coating composition in a multistage coating process in the OEM finishing or refinishing process.

11. The method of claim 7 , further comprising applying the matted clearcoat coating composition by spraying, knifecoating, spreading, casting, dipping, impregnating, trickling or rolling in the OEM finishing or refinishing process.

12. The method of claim 7 , wherein the matted clearcoat coating composition produced has improved sedimentation stability and an expanded operational window.

13. The method of claim 7 , wherein the amount of the at least one hydroxyl containing compound (A) is 40%-60% by weight, based on the nonvolatile constituents of the coating composition.

14. The method of claim 7 , wherein the amount of the at least one crosslinking agent (B) is 25%-45% by weight, based on the nonvolatile constituents of the coating composition.

15. The method of claim 7 , wherein the least one crosslinking agent (B) is a polyisocyanates, and (B) is added to the binder mixture such that a ratio of isocyanate groups of (B) to hydroxyl groups of the hydroxyl-containing compounds (A) is between 0.7:1 and 1:1.3, between 0.8:1 and 1.2:1, or between 0.9:1 and 1.1:1.

16. The method of claim 7 , wherein the at least one silica gel based matting agent (M) is dispersed with a portion of the at least one hydroxyl containing compound (A) to form a paste which is added to the remaining binder mixture.

17. The method of claim 7 , wherein the at least one hydrophobic silica based rheological assistant (R) is dispersed with a portion of the at least one hydroxyl containing compound (A) to form a paste which is added to the remaining binder mixture.

18. The method of claim 7 , wherein the at least one crosslinking agent (B) is combined with the at least one hydroxyl containing compound (A), the at least one silica gel based matting agent (M), and the at least one hydrophobic silica based rheological assistant (R) shortly before application of the matted clearcoat coating composition.

19. The method of claim 7 , further comprising combining a carbamate group containing compound (E) with the binder mixture.

20. The method of claim 7 , wherein the at least one silica gel based matting agent (M) is modified with one or more different, linear, unbranched polyolefin waxes.

Assignees

• Gebauer Beate
• Melzer Julia
• Weiher Christian
• Janssen Andreas
• Krumm Holger
• Basf Coatings Gmbh

Inventors

• Gebauer Beate
• Melzer Julia
• Weiher Christian
• Janssen Andreas
• Krumm Holger

Classifications

• C09D7/1225

  Chemistry & Metallurgy · mapped topic

• C09D175/04 Primary

  Polyurethanes · CPC title

• C08K3/36

  Silica · CPC title

• C08G18/6229

  Polymers of hydroxy groups containing esters of acrylic or methacrylic acid with aliphatic polyalcohols · CPC title

• B05D2601/22

  Silica · CPC title