Adhesion promoter for a primer and primer composition

摘要

An adhesion promoter for a primer, comprising a silane compound that is a reaction product between a polyisocyanate and a silane coupling agent having a secondary amino group, the nitrogen atom of which is directly connected to a phenyl group or a derivative thereof, the silane compound having in average one or more NCO group and in average one or more hydrolyzable alkoxysilyl group in the molecule. Also, a primer composition comprising the adhesion promoter for a primer and a film forming resin is disclosed. The adhesion promoter has high adhesion to various adherends and retains that effect after prolonged storage and the primer composition is excellent in adhesion to various adherends and retains adhesion after prolonged storage.