| abstract |
Stable three dimensional hydrogels which absorb water, but are insoluble in water, and are particularly useful for the making of soft contact lenses, are prepared by reacting a water insoluble polyvinyl resin which contains reactive hydroxyl groups in its polymer chain, with a di- or poly-basic acid anhydride, to thereby introduce pendant carboxyl groups into the polymer chain, followed by treatment of the thus obtained carboxylated polymer to effect a limited amount of crosslinking thereof whereby a sparingly crosslinked hydrophilic polymer is obtained which when immersed in water absorbs water and swells to form a hydrogel, which does not dissolve in water. |