| 摘要 |
Disclosed are thermosetting, powder coating compositions comprised of blends of certain amorphous polyesters and semi-crystalline polyesters in combination with a blocked polyisocyanate which, when applied to a substrate and heated, provide cross-linked coatings having a combination of desirable properties including good gloss, impact strength and flexibility. The semi-crystalline polyesters have a Tg of less than 50 DEG C, a hydroxyl number of 20 to 100, an inherent viscosity of 0.1 to 0.5, a melting range of 70 to 150 DEG C, a number average molecular weight of 1500 to 10,000 and a heat of fusion (second heating cycle of differential scanning calorimetry) of greater than 5 cal/g- DEG C and are comprised of: (i) diacid residues comprised of (a) 80 to 98 mole percent terephthalic acid and (b) 2 to 20 mole percent of 1,4-cyclohexanedicarboxylic acid residues, 1,3-cyclohexanedicarboxylic acid residues, adipic acid residues or a mixture thereof; and (ii) glycol residues comprised of at least 50 mole percent of residues having the formula -O-(CH2)n-O- wherein n is 4 to 12. h
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