GB1306372A - - Google Patents

Abstract

1306372 Heat curable polyurethane forming froth UNION CARBIDE CORP 29 Jan 1970 [31 Jan 1969] 4405/70 Heading C3R [Also in Division B2] A heat curable froth which is substantially structurally and chemically stable but workable under ambient conditions, comprises a substantially non-aqueous mixture reactive at temperatures above 70‹ C. to form a polyurethane, the mixture containing a polyisocyanate, an active hydrogen-containing compound, a surfactant for structurally stabilizing the froth until cured and an inert gas substantially uniformly dispersed throughout the mixture to form the froth. The froth may contain a catalyst as long as it does not initiate polymerization at ambient temperatures. Conventional polyisoeyanates which may be masked are used. The active hydrogen-containing compound is suitably a polyether polyol or a polymer of a cyclic ester. Organosilicon surfaetants are preferred, especially trimethylsiloxy-silicate copolymers consisting of SiO 2 units and (CH 3 ) 3 SiO 0À5 units in a mol. ratio of 0À8 : 1 to 2À2 : 1, and partially cross-linked siloxane-polyoxyalkylene block copolymers wherein the siloxane blocks and polyoxyalkylene blocks are linked by silicon to carbon, or by silicon to oxygen to carbon linkages. Nickel catalysts, e.g. nickel acetylacetonate, may be used and conventional tin catalysts may be used in the presence of the trimethylsiloxy-silicate copolymer surfactants. Auxiliary blowing agents, e.g. high-boiling fluorocarbons, may be used. The inert gas which is preferably air, but may be nitrogen or carbon dioxide, is incorporated in the liquid phase by mechanical beating in amounts which must be adequate to provide a froth having a density of less than 45% of the density of the liquid phase prior to frothing. The froths can be shaped by moulds or doctor blades and cured by heating to temperatures above 70‹ C.