Method for making contact lenses

1. A method for producing a contact lens, comprising: the steps of: introducing a fluid composition into a mold for making a contact lens, wherein the fluid composition comprises a lens-forming material and a Butylated Polyvinylpyrrolidone, wherein the lens-forming material is a water-soluble crosslinkable poly(vinyl alcohol) prepolymer which is crosslinkable and/or polymerizable by actinic radiation or by heating;

crosslinking/polymerizing the lens-forming material in the mold to form a lens having a polymer matrix; and

separating the mold, wherein the Butylated Polyvinylpyrrolidone present in an amount sufficient to reduce an averaged mold separation force by at least about 20% in comparison with that without the Butylated Polyvinylpyrrolidone;

wherein the Butylated Polyvinylpyrrolidone having a molecular weight of about 12,000 Da to 22,000 Da.

2. The method of claim 1 , wherein the water-soluble crosslinkable poly(vinyl alcohol) prepolymer is a polyhydroxyl compound which has a molecular weight of at least about 2000 and comprises from about 0.5 to about 80%, based on the number of hydroxyl groups in the poly(vinyl alcohol), of units of the formula I, I and II, I and III, or I and II and III

wherein R is alkylene having up to 12 carbon atoms; R 1 is hydrogen or lower alkyl having up to seven carbon atoms; R 2 is an olefinically unsaturated, electron-withdrawing, crosslinkable radical having up to 25 carbon atoms; R 3 is hydrogen, a C 1 -C 6 alkyl group or a cycloalkyl group; R 7 is a primary, secondary or tertiary amino group or a quaternary amino group of the formula N + (R′) 3 X − , in which each R′, independently of the others, is hydrogen or a C 1 -C 4 alkyl radical and X is a counterion selected from the group consisting of HSO 4 − , F − , Cr − , Br − , I − , CH 3 COO − , OH − , BF − , and H 2 PO 4 − ; and R 8 is the radical of a monobasic, dibasic or tribasic, saturated or unsaturated, aliphatic or aromatic organic acid or sulfonic acid.

3. The method of claim 1 , wherein the step of crosslinking and/or polymerizing is performed under a spatial limitation of actinic radiation to form a contact lens having a first surface, an opposite second surface, and an edge, wherein the mold is a reusable mold having two molding surfaces, wherein the first and second surfaces are defined by the two molding surface, and the edge is defined by the spatial limitation of actinic radiation.

4. A method for improving quality and production yield of contact lenses, comprising the steps of: adding a Butylated Polyvinylpyrrolidone into a fluid composition including a water-soluble crosslinkable poly(vinyl alcohol) prepolymer lens-forming material in an amount sufficient to reduce an averaged mold separation force by at least about 20% in comparison with that without the Butylated Polyvinylpyrrolidone, wherein the lens-forming material is crosslinkable and/or polymerizable by actinic radiation or by heating in a mold to form a contact lens having a polymer matrix.

5. A fluid composition for making contact lenses, comprising: a water-soluble crosslinkable poly(vinyl alcohol) prepolymer lens-forming material and a Butylated Polyvinylpyrrolidone, wherein the lens-forming material is crosslinkable and/or polymerizable by actinic radiation in a mold to form a contact lens having a polymer matrix, wherein the Butylated Polyvinylpyrrolidone is present in an amount sufficient to reduce an averaged mold separation force by at least about 20% in comparison with that without the Butylated Polyvinylpyrrolidone.