Abstract: A process for the preparation of moldings, in particular resilient elements, which by virtue of a densified surface zone with substantially closed cells, have only a low water absorption, wherein a mixture comprising:(a) 100 parts by weight of an NCO-containing prepolymer, having an NCO content of from 3 to 6% by weight and based on organic diisocyanates and substantially linear polyester-polyols or polytetramethylene ether glycol,(b) from 0.5 to 1.6 parts by weight of water,(c) one or more catalysts, preferably a tertiary amine, in an amount of from 0.01 to 2.0 parts by weight and(d) assistants, with or without additives, is reacted in a closed mold, while undergoing densification, the surface temperature of the inner wall of the mold being from 50.degree. to 70.degree. C.

Abstract: A process for the manufacture of non-cellular and cellular polyurethane elastomers by(a) preparing a hydroxyl group-containing prepolymer by reacting a higher molecular weight polyhydroxyl compound and optionally a chain extender with an organic diisocyanate at a weight ratio of OH groups to NCO groups of 1.2:1 to 2:1,(b) dividing the prepolymer into two components A and B in a weight ratio of about 80:20 to 20:80,(c) reacting component A with 1,5-naphthylene diisocyanate (NDI) in a weight ratio of OH:NCO groups of about 1:2.5 to 1:12 to produce a terminal NCO group-containing NDI-polyurethane adduct,(d) mixing component B with chain extenders and/or cross-linking agents and/or water, and optionally auxiliaries and additives, and(e) reacting the NDI-polyurethane adduct (from step c) with the mixture from step d.

Abstract: The invention concerns a process for the manufacture of flame resistant flexible polyurethane foams by reacting a mixture of diphenylmethane diisocyanates and polyphenylene polymethylene polyisocyanates having a functionality greater than 2 containing 40 to 90 percent by weight diphenylmethane diisocyanate based on the total weight of said mixture; polyols, cyanic acid derivatives such as cyanamide, dicyandiamide, guanidine, biguanidine, melamine, cyanuric alkyl esterhydrazides and -amides as flame inhibitors, and blowing agents; as well as, possibly, chain extenders and other additives. The flexible polyurethane foams are suited for the familiar areas of applications, but especially as sound-insulation material for the construction industry.