Powder coating composition, process for producing cured film and coated article

1. A powder coating composition comprising: a fluorinated resin (A); a polyester polymer (B); a curing agent (C); and an ultraviolet absorber (D) which is selected from the group consisting of an inorganic ultraviolet absorber and an organic ultraviolet absorber having a molecular weight of from 200 to 1,000, a melting point of from 50 to 150° C., and a volatilization temperature of from 220 to 350° C., wherein the polyester polymer (B) comprises units derived from isophthalic acid and units derived from a C 2-10 polyhydric alcohol compound, and wherein a cured film formed from the powder coating composition comprises a polyester polymer layer made from the polyester polymer (B) and a fluorinated resin layer made from the fluorinated resin (A) with the ultraviolent absorber (D) localized in the fluorinated resin layer.

2. The powder coating composition according to claim 1 , wherein the fluorinated resin (A) is a hydroxyl group-containing fluorinated polymer (A1).

3. The powder coating composition according to claim 1 , wherein the fluorinated resin (A) is a polyvinylidene fluoride.

4. The powder coating composition according to claim 1 , wherein the polyester polymer (B) contains from 30 to 60% of units derived from the isophthalic acid per the total units in the polyester polymer and has a number average molecular weight of from 500 to 5,000.

5. The powder coating composition according to claim 1 , wherein the content ratio of the fluorinated resin (A) to the polyester polymer (B) is from 70/30 to 10/90 by mass ratio.

6. The powder coating composition according to claim 1 , wherein the content of the curing agent (C) is from 10 to 100 parts by mass per 100 parts by mass in total of the fluorinated resin (A) and the polyester polymer (B).

7. The powder coating composition according to claim 1 , further comprising a pigment (E).

8. The powder coating composition according to claim 1 , further comprising a hindered amine light stabilizer (G) having a molecular weight of from 300 to 5,000 and a melting point of from 50 to 250° C.

9. A process for producing a cured film, comprising: coating a substrate with the powder coating composition as defined in claim 1 to form a coating film made of a melt of the powder coating composition on the substrate; reacting reactive components in the powder coating composition; and then cooling the coating film in the molten state to room temperature for solidification.

10. A coated article comprising: an article body; and a cured film produced by the process as defined in claim 9 on a surface of the article body.

11. The powder coating composition according to claim 1 , wherein the ultraviolet absorber (D) is the organic ultraviolet absorber.

12. The powder coating composition according to claim 1 , wherein the melting point of the organic ultraviolet absorber is from 50 to 113.5° C.

13. A coated article comprising: an article body; and a cured film of the powder coating composition as defined in claim 1 provided on a surface of the article body, wherein the cured film comprises a fluorinated resin layer made from the fluorinated resin (A) and a polyester polymer layer made from the polyester polymer (B), and the ultraviolet absorber (D) is localized in the fluorinated resin layer.

14. A powder coating composition comprising: a hydroxyl group-containing fluorinated polymer (A1); a polyester polymer (B); a blocked isocyanate curing agent (C1); and an ultraviolet absorber (D1) which is selected from the group consisting of an inorganic ultraviolet absorber and an organic ultraviolet absorber having a molecular weight of from 200 to 1,000, a melting point of from 50 to 150° C., and a volatilization temperature of from 220 to 350° C., wherein the polyester polymer (B) comprises units derived from isophthalic acid and units derived from a C 2-10 polyhydric alcohol compound, and wherein a cured film formed from the powder coating composition comprises a polyester polymer layer made from the polyester polymer (B) and a fluorinated resin layer made from the hydroxyl group-containing fluorinated resin (A1) with the ultraviolent absorber (D1) localized in the fluorinated resin layer.

15. The powder coating composition according to claim 14 , wherein the ultraviolet absorber (D1) is the organic ultraviolet absorber.

16. The powder coating composition according to claim 14 , wherein the melting point of the organic ultraviolet absorber is from 50 to 113.5° C.

17. A coated article comprising: an article body; and a cured film of the powder coating composition as defined in claim 14 provided on a surface of the article body, wherein the cured film comprises a fluorinated resin layer made from the hydroxyl group-containing fluorinated resin (A1) and a polyester polymer layer made from the polyester polymer (B), and the ultraviolet absorber (D1) is localized in the fluorinated resin layer.