Disposable, hydrogel soft contact lenses

Claim 1

A method of preparing a stable, three dimensional Xerogel, which when immersed in dilute aqueous alkali at a pH of 7-11 absorbs water to form a water insoluble Hydrogel, which comprises: (I) introducing pendant carboxyl groups into (a) a water insoluble, linear vinyl polymer containing free hydroxyl groups and selected from the group consisting of vinyl alcohol-vinyl acetate copolymers composed, by weight, of from about 92.5% to about 53% vinyl acetate groups and from about 7.5% to about 47% vinyl alcohol groups and polyvinyl acetals, by heating a mixture of a major amount of said polymer and (b) a predetermined minor amount of an anhydride of a polybasic carboxylic acid to produce a carboxylated adduct of said polymer by reaction of free hydroxyl groups on said polymer with said anhydride to form monoesters of said polybasic acid with said polymer containing free pendant carboxyl groups; and (II) thereafter sparingly crosslinking to a predetermined amount the thus obtained carboxylated adduct under anhydrous conditions by heating (c) said carboxylated adduct to a temperature and for a time to effect reaction between free hydroxyl groups and pendant carboxyl groups on said adduct to form ester groups, or (d) adding to and intimately admixing with said carboxylated adduct a predetermined minor amount of polyfunctional crosslinking agent, the functional groups of which are reactive with the hydroxyl or carboxyl groups of said adduct, and heating such mixture to a temperature and for a time to effect reaction between the functional groups on said crosslinking agent and said hydroxyl or carboxyl groups on said carboxylated adduct; the amount of said anhydride employed in said carboxylation step, the amount of crosslinking effected and amount of crosslinking agent employed in said crosslinking step being such amounts as are predetermined as needed to produce a Xerogel which when immersed in dilute aqueous alkali at a pH of 7-11 absorbs water and swells to form a water insoluble Hydrogel having a water content of about 48% to about 86%.

Claim 2

A method of preparing a stable, three dimensional Xerogel, which when immersed in dilute aqueous alkali at a pH of 7-11 absorbs water to form a water insoluble Hydrogel, which comprises: (I) introducing pendant carboxyl groups into (a) a water insoluble, linear vinyl polymer containing free hydroxyl groups and selected from the group consisting of vinyl alcohol-vinyl acetate copolymers composed, by weight, of from about 92.5% to about 53% vinyl acetate groups and from about 7.5% to about 47% vinyl alcohol groups and polyvinyl acetals, by heating a mixture of a major amount of said polymer and (b) a predetermined minor amount of an anhydride of a polybasic carboxylic acid to produce a carboxylated adduct of said polymer by reaction of free hydroxyl groups on said polymer with said anhydride to form monoesters of said polybasic acid with said polymer containing free pendant carboxyl groups; and (II) thereafter sparingly crosslinking to a predetermined amount the thus obtained carboxylated adduct under anhydrous conditions by heating (c) said carboxylated adduct to a temperature and for a time to effect reaction between free hydroxyl groups and pendant carboxyl groups on said adduct to form ester groups, or (d) adding to and intimately admixing with said carboxylated adduct a predetermined minor amount of polyfunctional crosslinking agent, the functional groups of which are reactive with the hydroxyl or carboxyl groups of said adduct, and heating such mixture to a temperature and for a time to effect reaction between the functional groups on said crosslinking agent and said hydroxyl or carboxyl groups on said carboxylated adduct; the amount of said anhydride employed in said carboxylation step, the amount of crosslinking effected and amount of crosslinking agent employed in said crosslinking step being such amounts as are predetermined as needed to produce a Xerogel which when immersed in dilute aqueous alkali at a pH of 7-11 absorbs water and swells to form a water insoluble Hydrogel having a water content of about 48% to about 86%.