Abstract: A hollow fiber separatory device is provided wherein a polyurethane prepolymer is cross-linked or cured with an ester of a polyhydric alcohol which contains two or three hydroxyl groups, e.g., propylene glycol monoricinoleate, and an aliphatic acid of at least 12 carbon atoms and one or more epoxy and/or hydroxy groups per molecule.

Abstract: Liquid 4,4'diphenylmethane diisocyanate (MDI) prepolymers have been produced which remain fluid and do not crystallize at temperatures below 40.degree. F. These prepolymers comprise the reaction product of a polyol, 4,4'diphenylmethane diisocyanate (MDI) and an aliphatic and/or cycloaliphatic diisocyanate. The polyol employed is selected from the group consisting of castor oil, polyoxypropylene glycol, polyhydric alcohol mono- and di-esters of hydroxyacids of at least 12 carbon atoms and mixtures thereof.The reaction product contains the polyol in amount from about 10% to about 40%, the 4,4'diphenylmethane diisocyanate in amount from about 50% to about 70% and the aliphatic or cycloaliphatic isocyanate in amount from about 10% to about 20%. The prepolymer should be prepared such that the NCO/OH ratio should fall within the range of about 3 to about 7.