THERMAL CURABLE POWDER COATING COMPOSITION
The present invention provides a powder coating composition comprising at least one hydroxyl functional polyuretdione resin binder, wherein the at least one hydroxyl functional polyuretdione resin binder having a melting temperature of 60 to 180° C., in particular, 80 to 160° C. The powder coating composition according to the invention comprising the specific kind of the polyuretdione resin binder makes it possible to provide desired technological properties, in particular, thin films and high flexibility in combination with an excellent weather resistance of the coating layers.
1 . A powder coating composition comprising at least one hydroxyl functional polyuretdione resin binder, wherein the at least one hydroxyl functional polyuretdione resin binder having a melting temperature of 60 to 180° C.
2 . The powder coating composition of claim 1 wherein the at least one hydroxyl functional polyuretdione resin binder having a melting temperature of 80 to 160° C.
3 . The powder coating composition of claim 1 wherein the at least one hydroxyl functional polyuretdione resin binder has a hydroxyl value in the range of 20 to 300 mg KOH/g and a number-average molar mass in a range of 1000 to 5000, determined according to ISO 13885-1.
4 . The powder coating composition of claim 1 wherein the at least one hydroxyl functional polyuretdione resin binder is produced by reacting NCO functional uretdiones based on aliphatic diisocyanates with linear diols.
5 . The powder coating composition of claim 1 comprising
(A) 25 to 99.9 wt % of at least one hydroxyl functional polyuretdione resin binder,
(B) 0 to 75 wt % and optionally, 1 to 50 wt % of at least one resin binder and optionally at least one curing agent, different from (A), and
(C) 0.1 to 60 wt % of pigments, fillers and/or coating additives,
the wt % amounts based on the total weight of the powder coating composition (A) to (C), wherein the at least one hydroxyl functional polyuretdione resin binder (A) having a melting temperature of 60 to 180° C.
6 . The powder coating composition of claim 1 comprising
(A) 40 to 95 wt % of at least one hydroxyl functional polyuretdione resin binder,
(B) 0 to 50 wt % and optionally, 1 to 50 wt % of at least one resin binder and optionally at least one curing agent, different from (A), and
(C) 5 to 50 wt % of pigments, fillers and/or coating additives,
the wt % amounts based on the total weight of the powder coating composition (A) to (C), wherein the at least one hydroxyl functional polyuretdione resin binder (A) having a melting temperature of 80 to 160° C.
7 . A method for coating a substrate applying the powder coating composition according to claim 1 on the substrate and curing the applied powder coating composition.
8 . A substrate coated with the powder coating composition of claim 1 and cured.