Low temperature heat-curable powder coating composition comprising a crystalline polyester resin, an amorphous resin and a peroxide

摘要

Heat-curable powder coating compositions are provided which include i) at least one crystalline polyester resin present in an amount of at least 7.5 wt %; ii) at least one amorphous polyester resin present in an amount of at most 92.5 wt %; and iii) at least one peroxide present in an amount of at least 0.65 parts of peroxide in hundred parts of i)+ii) (pph), wherein the at least one crystalline polyester resin has 2-butenedioic acid ethylenic unsaturations and/or the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations. The compositions may be cured to an acceptable degree at low temperature, e.g., 130° C. /20 minutes offering powder coatings that may exhibit enhanced flexibility and good adhesion. In addition, the compositions can suitably be used on heat- and/or non heat-sensitive substrates, even if the composition is highly pigmented.

主权项

1. A heat-curable powder coating composition comprising:
i) at least one crystalline polyester resin present in an amount of at least 7.5 wt %; ii) at least one amorphous polyester resin present in an amount of at most 92.5 wt % ; and iii) at least one peroxide present in an amount of at least 0.65 parts of peroxide in hundred parts of i)+ii) (pph), wherein, the composition contains no crosslinking agent; and wherein the at least one crystalline polyester resin and/or the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations, and wherein the at least one crystalline polyester resin has a melting temperature (Tm) of at least 30° C. and at most 160° C., a theoretical weight per ethylenic unsaturation (WPU) of at least 250 and at most 2000 g/mol and a crystallization temperature (Tc) which is at most 55° C. lower than its Tm; and wherein if the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations, then the theoretical weight per ethylenic unsaturation (WPU) of the at least one amorphous polyester resin is at most 850 g/mol; each of Tm and Tc is measured via differential scanning calorimetry (DSC); and the wt % is based on the total amount of i)+ii); and wherein the peroxide is at least one selected from the group consisting of: (a) peresters and monopercarbonates according to formula (I)  wherein
R1 represents an optionally substituted C1-20alkyl, a C6-20aryl or OR5, where R5 represents an optionally substituted C1-20alkyl or an optionally substituted C6-20aryl; andR2 represents an optionally substituted C1-20alkyl or an optionally substituted C6-20aryl; (b) peranhydrides of formula (II)  wherein R3 and R4 each independently stand for an optionally substituted C1-20alkyl, a C6-20aryl or OR6, wherein R6 represents an optionally substituted C1-10alkyl or a C6-20aryl; and (c) any combination of peroxides according to formula (I) and formula (II) thereof.