Pyrrolidone-methacrylate graft copolymers from 3-stage polymerization process

摘要

A contact lens composition, having improved dimensional stability, suitable for use in the preparation of a corrective hydrated lens or an eye bandage, comprises polymerized random graft copolymers containing (in the dry state) from 67.2 to 79.3% HEMA; from 14.25 to 35% PVP; from 0.1 to 4.04% EDMA; from 0.1 to 2.5% MA; from 0.1 to 5.0% water; from 0 to 4 ppm HQ inhibitor; and from 50 to 250 ppm MEHQ inhibitor. The contact lens composition contains from 45 to 65% water after hydration. An improved method for shaping, polymerizing, and cutting and hydrating the contact lens composition is provided. The polymerization is conducted using only a low temperature initiator, by de-gassing prior to polymerization to remove substantially all oxygen, and by conducting the initial polymerization reaction at from 23° to 30° C for 16 to 30 hours, during which the heat of the reaction is continuously absorbed to control the reaction exotherm. A closed, rod-shaped casting mold, lined with a polyester film material, is used and the polymeric rod obtained may be cut, machined and polished to obtain the contact lens composition. Thereafter, hydration is conducted in a buffered, 0.85 to 0.9% saline solution, at a pH of 7.0 to 7.1.