Process for producing shaped polyurethane hydrogel articles

Claim 1

A continuous, solventless process for producing water swellable, lightly crosslinked, hydrogel polymer comprising the steps of: (a) preparing a plurality of at least two feed compositions consisting of poly(oxyalkylene)polyol, organic polyisocyanate and catalyst, with the provisos that the catalyst is not in the same composition in which both of the poly(oxyalkylene)polyol and organic polyisocyanate are present and that the feed compositions are devoid of organic solvents, (b) feeding metered amounts of each of the feed compositions continuously through at least one in-line mixer to achieve uniform, homogeneous mixture, (c) continuously feeding the said uniform, homogeneous mixture into the inlet end and through tubular reactor means and producing an isocyanato terminated prepolymer of high specific viscosity, (d) extruding the said isocyanato terminated prepolymer through appropriate dies at the exit of said tubular reactor to form a shaped article, (e) lightly crosslinking said shaped article as it exits said tubular reactor with an equivalent amount of a crosslinking agent of the group water or organic polyamine; and (f) recovering the shaped polyurethane hydrogel polymer article produced; wherein said isocyanato terminated prepolymer comprises the reaction product of: (i) a poly(oxyalkylene) polyol having an average molecular weight up to about 25,000, wherein the alkyleneoxy group contains from 2 to 4 carbon atoms, and (ii) an organic polyisocyanate, and, further, wherein said poly(alkyleneoxy) polyol is a mixture of a major amount of poly(ethyleneoxy)diol having an average molecular weight of from about 4,000 to about 25,000 and a minor amount of poly(alkyleneoxy) triol or poly(alkyleneoxy) tetrol or aliphatic polyhydroxyl compound of the formula C n H 2n+2-m (OH) m wherein n has a value of 3 to 6 and m has a value of 3 to 4, or mixtures thereof, said triol or tetrol having an average molecular weight of from about 92 to 5,000, wherein the mole ratio of diol to higher polyol in said mixture is from about 6:1 to 40:1; and wherein the equivalents ratio of isocyanato groups to hydroxyl groups is from about 1.05:1 to about 2:1; and wherein said polyamine is a primary or secondary diamine or triamine and wherein the equivalents of reactive crosslinking groups in said crosslinking agent used is equivalent to the number of equivalents of isocyanato groups present in said prepolymer.