Polyurethane sealant compsn for metal joints - contg. stabilising alumino-silicate molecular sieves and catalyst releasable by water contact

摘要

A water-hardenable sealant compsn. comprises an NCO gp.-terminated polyurethane prepolymer, a first aluminosilicate molecular sieve (I) capable of removing residual water from the compsn. and a second alumino-silicate molecular sieve (IIe contg. a catalyst and protecting the prepolymer against reaction with the catalyst but capable of releasing the latter when the compsn. is in contact with or immersed in, water to initiate the hardening reaction. Used particularly for sealing metal joints, e.g. ball-cock components. The compsn. hardens in a relatively short time (12-35 hrs.) when in contact with water reaching shore hardness values 60, pref. 75-85, after complete cure.