Novel Metal Containing Crosslinkers for High Solids and Hot Melt Acrylic, 2003 PLACE Conference & GLOBAL HOT MELT Symposium

This paper will introduce a new line of crosslinkable raw materials for the manufacture of high solids, solvent-recoverable acrylic pressure sensitive and hot melt adhesives. These materials are classified as soluble divalent metal salts of alpha-beta ethylenically unsaturated carboxylic acids. When used as a co-reactant in the preparation of a PSA or hot melt PSA acrylic copolymer adhesive resin prepared by either bulk, solution or emulsion polymerization, they introduce ionic crosslinks into the backbone. The ionic crosslinks yield thermoset behaviour and enhanced adhesive properties at ambient temperatures . Adhesive polymers containing these materials exhibit higher glass transition temperature (Tg’s) and increased modulus or stiffness compared to conventional acrylic adhesive polymers, while maintaing sufficient tack to perform as a pressure sensitive material. More importantly, adhesive resins prepared with these unique ionic crosslinkers still exhibit thermoplastic behaviour or flow when heated to allow for ease of application by breaking of the crosslinks. This “reversible crosslinking” phenomenon is described and demonstrated by thermal analysis techniques and peel and shear adhesion tests.