Method of forming shaped hydrogel articles

Claim 1

In the method of preparing shaped hydrogel articles by forming a polymerization mixture comprising one or more hydrophilic monomers, a cross-linking agent, and from about 20 to 95% by volume of a inert water displaceable diluent, polymerizing said mixture in substantially the desired configuration of the shaped hydrogel article to obtain a shaped gel of a hydrophilic polymer and said diluent, and thereafter replacing said diluent with water to obtain said shaped hydrogel article, the improvement comprising employing as said diluent an organic compound or mixture of compounds having a viscosity and R-value falling within Area A of FIG. I, said viscosity being from about 100 to 500,000 M Pa sec at 30° C., and said R-value being from 0 to about 16 as determined by the Hansen cohesion parameters for the diluent and the polymer according to the following equation R=[(δ.sub.p1 -δ.sub.p2).sup.2 +(δ.sub.h1 -δ.sub.h2).sup.2 ].sup.0.5 wherein δ p1 , δ h1 respectively are Hansen polar and hydrogen bonding cohesion parameters for the polymer, and δ p2 , δ h2 , are the corresponding parameters of the diluent.