Epoxy silanes in reactive polymer emulsions

Epoxy silanes are effective additives for the crosslinking of carboxy and amino latexes and polyurethane dispersions. A series of epoxy silane additives have been evaluated in both one-pack and two-pack systems. It is found that the structure and water solubility of the epoxysilane as well as the pH of the latex determine silane stability. New water insoluble epoxy silanes achieve long-term shelf stability in emulsions yet crosslink upon application of the coating. Formulating principles, performance improvements, and catalytic cure profiles are reported. Carboxyl-modified waterborne polymer dispersions with post-added epoxy silanes provide curable coatings, in which properties such as mar, chemical and solvent resistance, adhesion, and durability are dramatically improved. In many applications, this approach is a potential candidate for crosslinkable waterborne systems free of aziridines and formaldehyde.