| 摘要 |
A powder coating composition comprises a component (A) containing carboxylic acid or anhydride functionality and a component (B) containing hydroxy functionality. The components (A) and (B) are both solids at temperatures up to 50 DEG C. and at least one of them is a synthetic resin having a glass transition temperature in the range 0 DEG to 120 DEG C. The carboxylic acid or anhydride-functional component (A) is a compound or polymer containing at least two cyclic carboxylic anhydride groups per molecule or is a compound containing a moiety of the formula: <IMAGE> where X is a hydrogen atom or an alkyl group, or a cyclic anhydride thereof. The hydroxy-functional component (B) contains at least two hydroxy groups per molecule and contains at least one amine group in its molecule to catalyze the reaction of the carboxylic acid or anhydride groups of component (A) with the hydroxy groups of component (B). The composition is prepared by mixing the ingredients, extruding them at a temperature above the glass transition temperature of at least one of the components but below the fusion temperature, and comminuting the extrudate. The composition is applied to substrates and heated to cause fusion and reaction of the ingredients to cure the coating layer formed.
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