Bonding water vapour-impermeable substrates - by applying moisture-cured hot melt adhesive to pre-moistened substrate surfaces

摘要

A process is claimed for bonding moisture- and/or water vapour-impermeable substrate surfaces with moisture-curing or -crosslinking hot melt adhesives (I) of viscosity at least 5 Pa.s at 90 deg.C, by applying molten (I) at 80-150 deg.C to at least one of the substrate surfaces and then joining the substrates together; the novelty is that at least one of the substrates is moistened before applying (I) and/or before joining the surfaces together. The substrates are moistened by steam treatment, wiping, brushing, washing or spraying, pref. with water-contg. vapours and/or prepns.; when brought into contact with (I), the applied moisture is at 20-100 (pref. 80-95) deg.C; (I) has viscosity above 10 (pref. above 15) Pa.s at 90 deg.C, and is applied at 100-130 deg.C; pref., (I) has viscosity not above 50 Pa.s (esp. pref. about 15 Pa.s or below) at the temp. of application; (I) are based on a polyester- and/or polyether-polyurethane structure, and are hardened by the action of moisture on alkoxysilane and/or NCO gps., pref. end-gps.; substrates are moisture-impermeable organic polymers, metals or alloys, and/or inorganic glasses; pref., (I) is applied to an unmoistened substrate which is then joined to a moistened substrate. USE/ADVANTAGE - The process enables the bonding of moisture-impermeable substrates without mixing (I) with water immediately before application, and without using odorous amine-based primers (contrast prior-art compsns.); the process ensures that sufficient moisture is available on the surface for rapid and reproducible crosslinking of (I) to give a high bond strength.