Abstract: The present invention relates to a process for the preparation of flexible, soft polyurethane foams having viscoelastic, structure-borne soundproofing properties in a temperature range of from -20.degree. C. to +80.degree. C. by reactinga) a polyoxyalkylene-polyol mixture containingai) block polyoxypropylene-polyoxyethylene-polyol mixture having a hydroxyl number of from 14 to 65 and containing from 2 to 9% by weight of terminal ethylene oxide units, based on the weight of the polyoxypropylene units, prepared by anionic polymerization, at elevated temperatures, of 1,2-propyleneoxide onto an initiator molecule mixture having a mean functionality of from 2.3 to 2.

Abstract: Flexible polyurethane foams having low compressive strength and relatively good tensile strength are prepared by reactinga) a block polyoxypropylenepolyoxyethylenepolyol mixture which has a hydroxyl number of from 14 to 65, contains from 2 to 9% by weight, based on the weight of the polyoxypropylene units, of ethylene oxide units bonded in the terminal position and is prepared by anionic polymerization of the alkylene oxides with an initiator mixture having an average functionality of from 2.3 to 2.8 and consisting of water and glycerol and/or trimethylolpropane, or a mixture of these block polyoxypropylenepolyoxyethylenepolyol mixtures with bi- and/or trifunctional polyoxypropylenepolyoxyethylenepolyols having a hydroxyl number of from 20 to 70, andb) if required, low molecular weight chain extenders withc) organic and/or modified organic polyisocyanates in the presence ofd) catalysts,e) blowing agents, preferably water, and if required,f) assistants and/or additives.

Abstract: The invention deals with composite elements having improved resistance against stress cracking corrosion especially for low temperature housing compartments, comprising:(a) at least one top layer of polystyrene, preferably toughened polystyrene, having certain mechanical properties; and(B) a layer of polyurethane foam, preferably polyurethane rigid foam;said polyurethane rigid foam prepared while using difluorochloromethane as a blowing agent or a blowing agent mixture which essentially comprises water, difluorochloromethane, and optionally trichlorofluoromethane.