Process for the application of powder coatings to non-metallic substrates

• US 6,458,250 B1
• Filed: 10/26/2000
• Issued: 10/01/2002
• Est. Priority Date: 10/26/2000
• Status: Expired due to Fees

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Wilson, Craig, Holliday, Martin L., Piearce, Colin G.
• Primary Examiner(s): Mayekar, Kishor
• Application Number:
  US09/697,997
• Time in Patent Office: 705 Days
• Field of Search: 204/164, 427/475
• US Class Current: 204/164
• CPC Class Codes: B05B 5/032 for spraying particulate materials
• CPC Class Codes: B05B 7/22 electrically , magnetically or electromagnetically, e.g. by arc B05B7/20 takes precedence
• CPC Class Codes: B05D 1/045 on non-conductive substrates

Abstract

The present invention describes a process for the application of a powder coating to a non-conductive substrate by first exposing the non conductive substrate to a combination of steam and heat at temperatures between 70° C. and 140° C. for a period between 5 seconds and up to 10 minutes, followed by electrostatic application of a powder coating to the substrate which is grounded; this simple and reliable pre-treatment method allows an efficient application of powder coatings to non-conductive substrates resulting in uniform and even deposition of the powder coating over the whole surface including edges and with no adverse effects on the subsequent curing of the powder film.

Claims

1. A process for the application of a powder coating to a non-conductive substrate, which comprises treating a surface of the non-conductive substrate with steam and heat at temperatures between 70°

C. and 140°

C. for a time period between 5 seconds and up to 10 minutes;

stabilizing the treated surface for a stabilization period; and

subsequently applying a powder coating by electrostatic spraying application of the powder coating to the stabilized surface.

2. The process according to claim 1 wherein the steam and heat temperatures are between 80°

C. and 130°

C. and the time period is between 5 seconds and 5 minutes.

3. The process according to claim 1 wherein the stabilization period is between 5 seconds and up to 5 minutes.

4. The process according to claim 1 wherein the stabilization period is between 30 seconds and up to 1 minute.

5. The process according to claim 1 wherein the substrate to be treated is placed into a saturated atmosphere of steam followed by circulated hot air.

6. The process according to claim 1 wherein the temperature of the substrate surface during the powder application is maintained between room temperature and 90°

C.

7. The process according to claim 1 wherein the temperature of the substrate surface during the application of the powder coating is between 45 and 70°

C. and below the glass transition temperature of the powder coating.