A crosslinking agent that is an ungelled reaction product of (a) an
aminoplast resin and (b) a carboxylic acid-containing compound wherein
the crosslinking agent is essentially free of reactive carboxylic acid
groups and has a glass transition temperature of at least 10.degree. C.
is disclosed. Methods for preparing crosslinking agents are also
disclosed. Further provided is a curable powder coating composition
including a polymer having a glass transition temperature of at least
30.degree. C. containing reactive functional groups and the present
crosslinking agent; a multilayer composite coating composition and
substrates coated therewith are also disclosed.