Abstract: The invention relates to a process for the preparation of aromatic polyester-carbonates wherein, in a first stage, aromatic oligo-esters or oligo-ester-carbonates having hydroxyl end groups are prepared from diaryl esters of aromatic dicarboxylic acids (or their starting materials) and diphenols and, optionally, a diaryl carbonate, by trans-esterification in the melt, and in a second stage these oligo-esters or oligo-ester-carbonates are condensed with phosgene by the phase boundary process to give the polyester-carbonate.

Abstract: The instant invention is directed to a process for the production of a cellular polyurethane elastomer having a density of 0.45 to 0.8 g/cm.sup.3, comprising:(a) preparing a prepolymer having an isocyanate content of 10 to 25% by weight from aromatic polyisocyanates and a portion of one or more polyhydroxyl compounds having a molecular weight of from 400 to 6,000; and(b) reacting said prepolymer with the remainder of said polyhydroxyl compound and water;wherein the quantity of said water is 0.3 to 1% by weight and the equivalent ratio of isocyanate groups to isocyanate reactive compounds is in the range of 0.95:1 to 1.1:1, characterized in that from 0.1 to 0.8% by weight, based on the whole reaction mixture, of aromatic diprimary diamines having a molecular weight from 108 to 500 are also used in (a) or (b).

Abstract: This invention relates to a new process for the production, in inert organic solvents, of physiologically compatible polyisocyanates containing isocyanurate groups which have a monomeric diisocyanate content, based on solids, of at most 0.7%, by weight. The process uses Mannich bases as the trimerizing catalyst at temperatures below 60.degree. C and the reaction is terminated at the desired degree of trimerization by thermally decomposing the catalyst or by deactivating with a catalyst poison.