Hot melt adhesive with open time above 10 minutes - contains slow-crystallising polyurethane prepolymer, tackifying resin and opt. plasticiser

摘要

A hot-melt adhesive (I) is claimed, with open time above 10 mins. Pref. (I) has initial strength above 1 MPa immediately after joining, Shore A hardness below 65 immediately after cooling to room temp., and glass temp. (Tg) 0-30 deg.C; (I) consists of (a) NCO-terminated PUR prepolymer which does not crystallise within the open time, (b) a tackifier with softening range 40-150 deg.C and opt. (c) a plasticiser; pref. (b) is a phenol-modified coumarone-indene resin with softening range 55-105 deg.C; (I) contains 1-50 (pref. 5-30) wt.% (b) and 0-25 (pref. 1-10) wt.% (c). USE/ADVANTAGE - (I) is useful as a hot melt adhesive which is applied to both sides of the joint, after which the parts are bonded together as with a contact adhesive (claimed); also claimed is (1) a process for bonding parts, by applying molten (I) to both joint surfaces, cooling to room temp. within 8 mins. and then pressing the parts together after more than 10 mins., without reheating, and (2) a joint component with hot melt adhesive (I). The method provides an adhesive compsn. with the desirable properties of both hot melt and contact adhesives; handling properties are improved without adversely affecting the strength, etc., and without the disadvantages of the latter type (emission of solvents, long drying times for water-based systems, poor thermal stability, e