Reactive acid curing waterborne microparticles

Abstract

This paper describes and evaluates different techniques for introducing acetal functional groups on waterborne microparticles. Aqueous dispersions of microparticles consisting of 70 wt.% styrene and 30 wt.% ethylacrylate were prepared by emulsion polymerization. Copolymer particles and core-shell particles were produced. The particle diameters were varied in the range from about 50 to 150 nm. The particles surfaces were modified by introducing an acetal functionality. Surface functionalization was performed in two different ways. Surface reactivity was introduced by the use of an acetal functional group containing an acrylic monomer in the polymerization step. The acetal functional groups were also introduced through post-polymerization grafting techniques. The particle surfaces were modified by introducing an acetal functionality, suitable for waterborne acid curing binder systems. The functionality in question is a diacetal, which recently has proved to undergo acid catalyzed crosslinking at ambient temperatures [1]. Acetal functionalized microparticles might replace amino resins. Crosslinking between amino resins produces formaldehyde but crosslinking based on acetals does not produce formaldehyde.