A
polyurethane adhesive which is useful in bonding porous and non-porous surfaces is provided. The
adhesive is especially useful in bonding
windshield glass into automotive frames under a variety of environmental conditions, particularly in after market
windshield replacement applications. The
polyurethane includes at least one urethane
prepolymer which is based on at least one
thermoplastic polyol. In one embodiment, the urethane
prepolymer may be formed from one or more polyisocyanates, one or more polyetherpolyols and one or more
thermoplastic polyesterpolyols, wherein the
prepolymer has a free
isocyanate content of from about 0.6 to about 3.5 % by weight, based on the weight of the
polyurethane. In another embodiment, a one-part
adhesive composition is provided which includes an
isocyanate-functional and
thermoplastic polyurethane prepolymer having a free
isocyanate content of from about 0.6 to about 3.5 % by weight, based on the weight of the polyurethane, and a combination of several catalysts which are capable of catalyzing the reaction of isocyanate moieties with isocyanate-reactive moieties while providing less temperature dependent catalyzing of the reaction between isocyanate moieties and water. Also provided is a process for bonding two or more substrates together utilizing the
polyurethane adhesive. In automotive
windshield replacement applications, the
polyurethane adhesive allows for a sufficient working time and development of green strength to provide a safe drive-away time within 1 hour at a temperature from about 0 to about 100° C.