Process for the production of a dark-color multi-layer coating

• US 8,784,941 B2
• Filed: 09/14/2009
• Issued: 07/22/2014
• Est. Priority Date: 09/15/2008
• Status: Active Grant

• Current Assignee: Axalta Coating Systems Ip Co Llc (Axalta Coating Systems Ltd.)
• Original Assignee: Axalta Coating Systems Ip Co Llc (Axalta Coating Systems Ltd.)
• Inventors: Richter, Gunter, Doessel, Karl-Friedrich, Dutt, Wilfried
• Primary Examiner(s): FLETCHER III, WILLIAM P
• Application Number:
  US13/063,207
• Publication Number:
  US 20110171375A1
• Time in Patent Office: 1,772 Days
• Field of Search: 427/407.1, 427/409, 427/410, 427/372.2, 427/384, 427/385.5, 427/388.1
• US Class Current: 427/407.1
• CPC Class Codes: B05D 1/02 performed by spraying
• CPC Class Codes: B05D 2202/10 based on Fe
• CPC Class Codes: B05D 7/14 to metal, e.g. car bodies involving a chemical reaction between the metal and the coating C23
• CPC Class Codes: B05D 7/572 all layers being cured or baked together
• CPC Class Codes: B05D 7/574 at least some layers being let to dry at least partially before applying the next layer B05D7/577 takes precedence
• CPC Class Codes: C08K 3/08 Metals
• CPC Class Codes: C08K 3/22 of metals
• CPC Class Codes: C08K 5/01 Hydrocarbons C08K5/0091 takes precedence
• CPC Class Codes: C09D 7/61 inorganic
• CPC Class Codes: C09D 7/70 characterised by shape, e.g. fibres, flakes or microspheres

Abstract

A process for the production of a dark-color multi-layer coating, comprising the successive steps:

• (1) applying an NIR-opaque coating layer A′ from a waterborne pigmented coating composition A to a substrate,
• (2) applying a coating layer B′ from a waterborne pigmented coating composition B onto the substrate provided with coating layer A′,
• (3) subjecting the coated substrate obtained in step (2) to a drying step,
• (4) applying a clear coat layer, and
• (5) curing the coating layers simultaneously;
• wherein both coating compositions A and B comprise aqueous microgel and sheet silicate,
• wherein the pigment content of coating composition A comprises <90 wt. % of aluminum flake pigments and has such a composition that coating layer A′ exhibits low NIR absorption,
• wherein the pigment content of coating composition B consists 50 to 100 wt. % of black pigment with low NIR absorption and 0 to 50 wt. % of further pigment.

Claims

1. A process for the production of a dark-color multi-layer coating, comprising the successive steps:

(1) applying an NIR-opaque coating layer A′

from a waterborne pigmented coating composition A to a substrate,

(2) applying a coating layer B′

from a waterborne pigmented coating composition B onto the substrate provided with coating layer A′

,

(3) subjecting the coated substrate obtained in step (2) to a drying step,

(4) applying a clear coat layer from a clear coat composition onto the coated substrate obtained in step (3), and

(5) curing the coating layers applied in steps (1), (2), and (4) simultaneously;

wherein both waterborne coating compositions A and B comprise aqueous microgel and sheet silicate,

wherein the pigment content of coating composition A comprises <

90 wt. % of aluminum flake pigments and is composed in such a way that NIR-opaque coating layer A′

exhibits low NIR absorption,

wherein the pigment content of coating composition B consists 50 to 100 wt. % of at least one black pigment with low NIR absorption and 0 to 50 wt. % of at least one further pigment, which is selected in such a way that coating layer B′

exhibits low NIR absorption and that the dark-color multi-layer coating exhibits a brightness L* (according to CIEL*a*b*, DIN

     6174), measured at an illumination angle of 45 degrees to the perpendicular and an observation angle of 45 degrees to the specular, of at most 10 units, and

wherein the sum of the respective wt. % equals 100 wt. %.

2. The process of claim 1, wherein the pigment content of coating composition A comprises less than 25 wt. % of aluminum flake pigments.

3. The process of claim 1, wherein coating composition A is a solid color coating composition free of special effect pigments.

4. The process of claim 1, 2 or 3, wherein the pigment content of coating composition A comprises 80 to 100 wt. % of titanium dioxide.

5. The process of claim 4, wherein coating composition A does not contain any carbon black.

6. The process of claim 4, wherein coating composition A comprises a binder solids comprising 30 to 100 wt. % of aqueous microgel.

7. The process of claim 4, wherein coating composition A comprises 0.1 to 1.6 wt. % sheet silicate.

8. The process of claim 4, wherein the at least one black pigment with low NIR absorption is selected from the group consisting of iron oxide black pigments, mixed metal/iron oxide black pigments and perylene black pigments.

9. The process of claim 4, wherein coating composition B does not contain any carbon black.

10. The process of any claim 4, wherein coating composition B comprises a binder solids comprising 30 to 100 wt. % of aqueous microgel.

11. The process of claim 4, wherein coating composition B comprises 0.1 to 1.6 wt. % sheet silicate.

12. The process of claim 4, wherein coating layer B′

is a transparent or a visually opaque coating layer.

13. The process of claim 4, wherein coating composition B is applied to coating layer A′

when at least 50 wt. % of the volatiles of coating composition A are still present in coating layer A′

.

14. The process of claim 4, wherein coating composition B is applied within 10 to 300 seconds of the application of coating composition A.

15. The process of claim 4 being carried out in the context of an industrial mass production coating process.