Process for the production of moldings

Claim 1

A process for the production of an elastomeric molding having average density of from 0.8 to 1.4 g/cm 3 and of a sealed surface layer reacting a reaction mixture in a closed mold, said reaction mixture comprising: (a) an organic polyisocyanate and (b) a solution of (1) a chain-lengthening agent, selected from the group consisting of (i) alkane diols having a molecular weight of from 62 to 400, which may contain ether groups, (ii) aromatic diamines having molecular weights of from 108 to 400 and (iii) mixtures of (i) and (ii), in (2) a polyhydroxyl compound having an average molecular weight of from 1800 to 12,000 and an average hydroxyl functionality of from 2 to 3, provided that polyhydroxyl compounds having molecular weights of more than 400 and less than 1800 and/or hydroxyl functionalities of more than 3, can be used so long as the average molecular weight of the resultant mixture is from 1800 12,000 and the average hydroxyl functionality of the resultant mixture is from 2 to 3. (c) catalyst for the isocyanate polyaddition reaction, and (d) an internal mold release agent characterized in that component (d) comprises an ester group-containing condensation product with an osmometrically-determinable average molecular weight of from 900 to 4500, an acid number of less than 5 and a hydroxyl number of from 12.5 to 125, which product is produced from 3 to 15 mols of ricinoleic acid and either one mol of a mono- or poly-valent alcohol having a molecular weight of from 32 to 400 or one mol of a mixture of several such alcohols, said release agent being used in a quantity of from 0.3 to 30% by weight based on the total quantity of the reaction mixture.