HOT MELT ADHESIVES COMPRISING LOW FREE MONOMER, LOW OLIGOMER ISOCYANATE PREPOLYMERS.

摘要

A method for adhesively joining or sealing two substrates which comprises: (1) applying at about 50 degree to 150 degree C onto a substrate a solvent-free, moisture curable urethane hot melt adhesive composition comprising the polyisocyanate prepolymer reaction product of (a) a polyol and (b) a polyisocyanate; (2) contacting the adhesive disposed on the substrate to a second substrate such that a green bond is formed, and (3) exposing the adhesive bond to ambient moisture causing a crosslinking reaction within the adhesive, thereby forming a moisture cured bond. The improvement is characterized in that the polyisocyanate prepolymer is prepared reacting a polyisocyanate with a functionality of at least 2 with a polyol with a functionality of at least 2, the reaction product comprising at least l90 wt percent "perfect" prepolymer and less than 2 wt percent unreacted isocyanate monomer and the prepolymer having a free NCO functionality ranging from 0.2 to 8 wt percent.