As monomers for preparing ophthalmic lenses, monomers having silicon-containing groups are known. For example, 3-[tris(trimethylsiloxy)silyl]propyl methacrylate is widely used as a monomer for preparing ophthalmic lenses. The polymer obtained by copolymerizing 3-[tris(trimethylsiloxy)silyl]propyl methacrylate and N,N-dimethylacrylamide which is a hydrophilic monomer has advantageous features that it is transparent and has a high oxygen permeability. However, if a carboxylic acid such as methacrylic acid is used as a copolymerization component in order to obtain a higher moisture content, the silicone component is gradually hydrolyzed, so that the physical properties of the contact lens may be degraded when the contact lens is stored for a long period.
On the other hand, to improve the hydrolysis resistance, 3-[tris(triethylsiloxy)silyl]propyl methacrylate described in U.S. Pat. No. 3,377,371 was prepared, and hydrolysis test was conducted after adding a carboxylic acid. As a result, although the polymer exhibited a relatively good stability at 80° C., it was proved that it is hydrolyzed at 90° C.
Thus, conventional silicon-containing materials typically fail to provide satisfactory hydrolysis resistance while retaining advantageous transparency and oxygen permeability. Therefore, there remains a need for methods and compositions that overcome these deficiencies and that effectively provide hydrolysis resistant silicon-containing materials.
USPTO Backgrounds
USPTO Backgrounds