Method for preparing powder coating compositions having improved particle properties

• US 5,472,649 A
• Filed: 04/13/1994
• Issued: 12/05/1995
• Est. Priority Date: 04/13/1994
• Status: Expired due to Fees

• Current Assignee: PPG Industries Incorporated (Nouryon BV)
• Original Assignee: Eastman Chemical Company
• Inventors: Treece, Lanney C., Jernigan, Joseph C., Chang, Yeong-Ho
• Primary Examiner(s): THEISEN, MARY LYNN F
• Application Number:
  US08/227,224
• Time in Patent Office: 601 Days
• Field of Search: 264/15
• US Class Current: 264/15
• CPC Class Codes: C08J 3/16 by coagulating dispersions C08J3/122 takes precedence
• CPC Class Codes: C09D 5/03 Powdery paints

Abstract

A method of preparing a powder coating composition comprises: (a) forming a mixture comprising solid particles which include a curable resin and a cross-linking agent that is reactive with the curable resin suspended in an aqueous liquid phase comprising water, a surfactant, a stabilizer, and a promoter; (b) warming the mixture to a temperature sufficient to effect reshaping and rounding of the particles; (c) separating the particles from the liquid phase; and (d) drying the particles to form a powder.

Claims

1. A method of preparing a powder coating composition that comprises:

(a) forming a mixture comprising solid particles which include a curable resin and a cross-linking agent that is reactive with said curable resin suspended in an aqueous liquid phase comprising water, a surfactant, a stabilizer, and a promoter;

(b) warming said mixture to a temperature sufficient to effect reshaping and rounding of said particles;

(c) separating said particles from said aqueous liquid phase; and

(d) drying said particles to form a powder.

2. A method according to claim 1 wherein said mixture further comprises a pigment or a dye.

3. A method according to claim 1 wherein said mixture further comprises a degassing agent.

4. A method according to claim 1 wherein said mixture further comprises a flow control agent.

5. A method according to claim 1 wherein said curable resin is a hydroxy-, epoxy-, amino-, or carboxy- substituted polyester or polyether, or a hydroxy-, epoxy-, amino-, or carboxy-substituted acrylic or methacrylic polymer.

6. A method according to claim 1 wherein said cross-linking agent is a polyisocyanate, a blocked polyisocyanate, a carboxylic anhydride, or an epoxy-substituted compound.

7. A method according to claim 1 wherein said curable resin is an epoxy-substituted polyester or polyether and said cross-linking agent is a carboxylic anhydride.

8. A method according to claim 1 wherein said curable resin is an epoxy-substituted acrylic or methacrylic polymer and said cross-linking agent is a carboxylic anhydride.

9. A method according to claim 1 wherein said curable resin is a hydroxy-substituted polyester or polyether and said cross-linking agent is a polyisocyanate or a blocked polyisocyanate.

10. A method according to claim 1 wherein said curable resin is a hydroxy-substituted acrylic or methacrylic polymer and said cross-linking agent is a polyisocyanate or a blocked polyisocyanate.

11. A method according to claim 1 wherein said curable resin is a carboxy-substituted polyester or polyether and said cross-linking agent is an epoxy-substituted compound.

12. A method according to claim 1 wherein said curable resin is a carboxy-substituted acrylic or methacrylic polymer and said cross-linking agent is an epoxy-substituted compound.

13. A method according to claim 1 wherein said particles are about 1 to 50 weight percent of said aqueous liquid phase.

14. A method according to claim 13 wherein said particles are about 5 to 25 weight percent of said aqueous liquid phase.

15. A method according to claim 1 wherein said particles after said drying have a mean particle size of about 20 μ

m to 200 μ

m.

16. A method according to claim 15 wherein said particles have a mean particle size of about 40 μ

m to 100 μ

m.

17. A method according to claim 1 wherein said surfactant is a nonionic compound.

18. A method according to claim 1 wherein said stabilizer is silica, alumina, or titanium dioxide.

19. A method according to claim 18 wherein said stabilizer is colloidal silica.

20. A method according to claim 1 wherein said promoter is poly(diethanolamine adipate) or poly-(methylaminoethanol adipate).

21. A method according to claim 1 wherein said warming of said mixture is carried out at a temperature from about 40°

C. above to about 40°

C. below the glass transition temperature of said curable resin.

22. A method according to claim 21 wherein said warming is carried out at a temperature from about 10°

C. above to about 10°

C. below the glass transition temperature of said curable resin.

23. A method according to claim 21 wherein said warming is maintained from about 0.5 hour to 2 hours.