Method for preparing color-clear composite coatings having resistance to acid etching

• US 5,989,642 A
• Filed: 10/07/1994
• Issued: 11/23/1999
• Est. Priority Date: 10/30/1992
• Status: Expired due to Term

• Current Assignee: PPG Industries Ohio Incorporated (Nouryon BV)
• Original Assignee: PPG Industries Ohio Incorporated (Nouryon BV)
• Inventors: Swarup, Shanti, Singer, Debra L., Mayo, Michael A.
• Primary Examiner(s): ACHUTAMURTHY, PONNATHAPURA N
• Application Number:
  US08/320,793
• Time in Patent Office: 1,873 Days
• Field of Search: 427/407.1
• US Class Current: 427/407.1
• CPC Class Codes: C08F 8/30 Introducing nitrogen atoms or nitrogen-containing groups
• CPC Class Codes: C08L 2666/14 Macromolecular compounds according to C08L59/00 - C08L87/00; Derivatives thereof
• CPC Class Codes: C08L 2666/16 Addition or condensation polymers of aldehydes or ketones according to C08L59/00 - C08L61/00; Derivatives thereof
• CPC Class Codes: C08L 61/20 Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen with aminophenols C08L61/04
• CPC Class Codes: C09D 133/062 Copolymers with monomers not covered by C09D133/06
• CPC Class Codes: C09D 201/06 containing oxygen atoms C09D201/025 takes precedence
• CPC Class Codes: Y10T 428/31551 Of polyamidoester [polyurethane, polyisocyanate, polycarbamate, etc.]
• CPC Class Codes: Y10T 428/31573 Next to addition polymer of ethylenically unsaturated monomer
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]
• CPC Class Codes: Y10T 428/31794 Of cross-linked polyester
• CPC Class Codes: Y10T 428/31797 Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31855 Of addition polymer from unsaturated monomers

Abstract

A color-plus-clear coating system is disclosed. A pigmented or colored basecoat is first applied to a substrate followed by the application of a transparent topcoat to the basecoat. The transparent topcoat composition is a crosslinkable composition comprising (1) a material containing a plurality of carbamate and/or urea functional groups and (2) an aminoplast crosslinking agent. The topcoat composition provides a composite coating with improved acid etch resistance, making the composite coating particularly useful as an automotive topcoat.

Claims

1. A method of producing a color-plus-clear composite coating on a substrate comprising the steps of applying a colored coating composition to said substrate, and applying a clear coating composition over the colored coating composition, wherein the clear coating composition is a curable coating composition comprising:

(a) a first component comprising a polymer backbone having appended thereto at least one carbamate functional group, said first component represented by randomly repeating units according to the formula;

##STR3## wherein R represents CH₃,

L represents a divalent linking group,

A represents repeating units derived from one or more ethylenically unsaturated monomers,

x represents about 29.2 weight %, and

y represents about 70.8 weight %, and

(b) a second component comprising a compound having a plurality of functional groups that are reactive with said carbonate group.

2. A method according to claim 1, and wherein, prior to cure, the clear coating composition has a calculated hydroxyl value less than 50 based on solid weight of the clear coating composition, excluding any hydroxyl functionality associated with any N-methylol groups present in (a) or (b).

3. A method according to claim 2, wherein --L-- is ##STR4## .

4. A method of producing a color-plus-clear composite coating on a substrate comprising the steps of applying a colored coating composition to said substrate, and applying a clear coating composition over the colored coating composition, wherein the clear coating composition is a curable coating composition comprising:

(a) a first component comprising a polymer backbone having appended thereto at least one carbamate functional group, said first component represented by randomly repeating units according to the formula;

##STR5## wherein R represents H or CH₃,

L represents a divalent linking group,

A represents repeating units derived from one or more ethylenically unsaturated monomers,

and the weight percentages of x and y are selected such that the polymer has a carbamate equivalent weight of less than 5000, and

(b) a second component comprising a compound having a plurality of functional groups that are reactive with said carbamate group.

5. A method according to claim 4 wherein said polymer backbone is derived from one or more ethylenically unsaturated monomers.

6. A method according to claim 5 wherein said ethylenically unsaturated monomers comprise a carbamate group.

7. A method according to claim 5, wherein said ethylenically unsaturated monomers comprise one or more acrylic monomers.

8. A method according to claim 7, wherein said acrylic monomers comprise a carbamate group.

9. A method according to claim 5 wherein the predominant portion of said ethylenically unsaturated monomers are acrylic monomers.

10. A method according to claim 4 wherein the predominant portion of said ethylenically unsaturated monomers are acrylic monomers.

11. A method according to claim 4 wherein component (b) is an aminoplast resin.

12. A method according to claim 11 wherein said aminoplast resin is melamine formaldehyde resin.

13. A method according to claim 12 wherein said melamine formaldehyde resin is fully or partially alkylated.

14. A method according to claim 4 wherein R represents CH₃.

15. A method according to claim 4 wherein --L-- is represented by the formula --COO--L'"'"'-- where L'"'"' is a divalent linking group.

16. A substrate having thereon a color-plus-clear composite coating prepared according to the method of claim 4.

29. A method of producing a color-plus-clear composite coating on a substrate as set forth in claim 4, and wherein, prior to cure, the clear coating composition has a calculated hydroxyl value less than 50 based on solid weight of the clear coating composition, excluding any hydroxyl functionality associated with any N-methylol groups present in (a) or (b).

30. A substrate having thereon a color-plus-clear composite coating prepared according to the method of claim 29.

17. A method of producing a color-plus-clear composite coating on a substrate comprising the steps of applying a colored coating composition to said substrate, and applying a clear coating composition over the colored coating composition, wherein the clear coating composition is a curable coating composition comprising, in an organic solvent medium:

(a) a first component comprising a polymer backbone having appended thereto at least one carbamate functional group, said first component represented by randomly repeating units according to the formula;

##STR6## wherein R represents H or CH₃,

R₂ represents H or alkyl,

L represents a divalent linking group,

A represents repeating units derived from one or more ethylenically unsaturated monomers,

and the weight percentages of x and y are selected such that the polymer has a carbamate equivalent weight of less than 5000, and

(b) a second component comprising a compound having a plurality of functional groups that are reactive with said carbamate group.

18. A method according to claim 17 where in said ethylenically unsaturated monomers comprise a carbamate group.

19. A method according to claim 17 wherein said ethylenically unsaturated monomers comprise one or more acrylic monomers.

20. A method according to claim 19, wherein said acrylic monomers comprise a carbamate group.

21. A method according to claim 17 wherein component (b) is selected from aminoplasts having a plurality of active methylol or methylol ether groups.

22. A method according to claim 17 wherein component (b) is an aminoplast resin.

23. A method according to claim 22 wherein said aminoplast resin is melamine formaldehyde resin.

24. A method according to claim 17 wherein R represents CH₃.

25. A method according to claim 17 wherein --L-- is represented by the formula --COO--L'"'"'-- wherein L'"'"' is a divalent linking group.

26. A method according to claim 17 wherein R₂ represents H.

27. A method according to claim 17 wherein R₂ represents alkyl.

28. A method according to claim 17 wherein said substrate is an automobile body panel.

31. A method of producing a color-plus-clear composite coating on a substrate as set forth in claim 17, and wherein, prior to cure, the clear coating composition has a calculated hydroxyl value less than 50 based on solid weight of the clear coating composition, excluding any hydroxyl functionality associated with any N-methylol groups present in (a) or (b).

32. A curable composition having a calculated hydroxyl value less than 50 based on the solid weight of the composition comprising:

(a) a first component comprising a copolymer having a carbamate equivalent weight of less than 5000 comprising;

(i) a carbamate group-containing monomer comprising carbamyloxy propyl methacrylate, and

(ii) a mixture of monomers comprising at least one acrylate, at least one methacrylate, and optionally styrene,

(b) a second component comprising a melamine compound having a plurality of functional groups that are reactive with said carbamate group.