Methods for preparing powder coating compositions

Patent metadata

Field	Value
Publication number	US-9957394-B2
Application number	US-201615258268-A
Country	US
Kind code	B2
Filing date	Sep 7, 2016
Priority date	Sep 7, 2016
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

Disclosed is a method for preparing powder coating compositions. The method includes mixing in an aqueous medium a carboxylic acid functional polymer having a high glass transition temperature, with a polycarbodiimide having a high glass transition temperature, drying the mixture, and grinding the resulting solid particles to obtain a powder.

First claim

We claim:

1. A method for preparing a powder coating composition comprising:
a) mixing in an aqueous medium
(i) a carboxylic acid functional polymer having a glass transition temperature of at least 50° C., with
(ii) a polycarbodiimide, having urethane and/or urea linkages and having a glass transition temperature of at least 50° C., wherein the polycarbodiimide is prepared by reacting a polyisocyanate in the presence of a catalyst to form a polycarbodiimide and extending the polycarbodiimide by the addition of a cyclic diol during or after polycarbodiimide formation;

b) drying the mixture of (i) and (ii) to obtain solid particles; and
c) grinding the solid particles to obtain a powder.

2. The method of claim 1 in which the urea linkages are within terminal positions of the polycarbodiimide.

3. The method of claim 1 in which the cyclic diol is a cycloaliphatic diol.

4. The method of claim 1 in which the polycarbodiimide is prepared from at least one cyclic diisocyanate.

5. The method of claim 1 in which the polycarbodiimide comprises at least 30 percent by weight of cyclic groups based on weight of the polycarbodiimide.

6. The method of claim 1 in which the polycarbodiimide is prepared from methylene-bis-(4-cyclohexylisocyanate), isophorone diisocyanate, tetramethylxylylene diisocyanate, and/or a mixture thereof.

7. The method of claim 1 in which the carboxylic acid functional polymer is in the form of solid particles.

8. The method of claim 1 in which the polycarbodiimide is in the form of solid particles.

9. The method of claim 1 in which the calculated molar ratio of carboxylic acid functional groups from the carboxylic acid functional polymer of (i) to carbodiimide groups from the polycarbodiimide of (ii) is from 0.5 to 1.5:1.

10. The method of claim 1 in which carboxylic acid functional polymer has a weight average molecular weight of at least 1000 g/mol.

11. The method of claim 1 in which the pH of the aqueous medium is 9.0 or higher.

12. The method of claim 1 in which the melt viscosity of the polycarbodiimide is less than 300 poise at 200° C.

13. The method of claim 1 in which the melt viscosity of the carboxylic acid functional polymer is less than 300 poise at 200° C.

14. A coating composition prepared according to the method of claim 1 .

15. A substrate at least partially coated with the coating composition of claim 14 .

16. The substrate of claim 15 , wherein the coating composition is spray applied to at least a portion of the substrate.

17. The substrate of claim 16 , wherein the substrate comprises metal, wood, plastic, and/or a composite.

18. The substrate of claim 15 , wherein the substrate is a package.

Assignees

• Ppg Ind Ohio Inc

Inventors

• Zhou Hongying
• Chasser Anthony
• Swarup Shanti

Classifications

• C09D5/03 Primary

  Powdery paints · CPC title

• C08G18/166

  Catalysts not provided for in the groups C08G18/18 - C08G18/26 · CPC title

• C08G18/758

  containing two or more cycloaliphatic rings · CPC title

• C08G18/808

  Monoamines · CPC title

• C08G18/2865

  Compounds having only one primary or secondary amino group; Ammonia · CPC title