used as the liquid tertiary amine catalyst is an aliphatic tertiary amine particularly tris 3 dimethylamino propylamine preferably used as the tertiary amine are 2 2 u2032 dimorpholinodiethylether and n n u2032 dimethylpiperazine the amount of tertiary amine catalyst used is typically from 0 01 to 1 0 parts by weight preferably from 0 01 to 0 5 parts by weight most preferably from 0 1 to 0 25 parts by weight the organic polyisocyanate used to prepare the organic polyisocyanate pre polymer is an organic polyisocyanate having a functionality of two or more preferably 2 to 5 it may be aliphatic cycloaliphatic aromatic or a hybrid polyisocyanate mixtures of such polyisocyanates may be used representative examples of organic polyisocyanates are aliphatic polyisocyanates such as hexamethylene diisocyanate alicyclic polyisocyanates such as 4 4 u2032 dicyclohexylmethane diisocyanate and aromatic polyisocyanates such as 2 4 u2032 diphenylmethane diisocyanate and 2 6 toluene diisocyanate and dimethyl derivatives thereof other examples of suitable organic polyisocyanates are 1 5 naphthalene diisocyanate triphenylmethane triisocyanate xylylene diisocyanate and the methyl derivatives thereof polymethylenepolyphenyl isocyanates chlorophenylene 2 4 diisocyanate and the like the organic polyisocyanate is used in a liquid form solid or viscous polyisocyanates must be used in the form of organic solvent solutions the solvent generally being present in a range of up to 80 percent by weight of the solution it may be useful in some cases to blend the pre polymer with an organic polyisocyanate if an organic polyisocyanate is blended with the organic polyisocyanate pre polymer the amount of organic polyisocyanate blended is from 1 to about 10 percent by weight based upon the weight of the organic polyisocyanate pre polymer typical compounds having free hydroxyl groups include polyhydric alcohols e g glycols.