Polymerized hydrogel adhesives comprising low amounts of residual monomers

The present invention relates to polymerized hydrogel adhesives, in particular those wherein the hydrogel is formed from monomers which include acrylamido-2-methane propanesulfonic acid or salts thereof (AMPS monomers) and those which contain glycerol as a humectant. In such adhesives, the levels of unpolymerized residual monomers, such as unpolymerized AMPS, acrylonitrile, acrylamide and t-butyl acrylamide; and the levels of other impurities such as acrolein, are kept very low. The present invention also relates to a process for making hydogel adhesives with very low levels of such unwanted materials. Such a process involves preparation of reaction mixtures under selected pH and/or temperature conditions and polymerization of AMPS monomers using selected conditions of pH and UV curing.