Method for cast molding contact lenses
View Patent ↗An improved method of cast molding contact lenses, wherein a lens forming mixture is cured in the lens-shaped cavity formed between molding surfaces of a male and female mold sections, wherein the improvement comprises at least one of sections is injection molded from a controlled rheology polypropylene.
1. An improved method of cast molding contact lenses, wherein a lens forming material is cured in a lens-shaped cavity formed between molding surfaces of a male and female mold sections, wherein the improvement comprises injection molding at least one of mold sections from a controlled rheology polypropylene, wherein the controlled rheology polypropylene has a higher melt flow rate of at least about 6 g/10 minutes than that of a corresponding pristine polyprolylene, wherein the corresponding pristine polypropylene is a starting polypropylene prior to going through a controlled rheology process, wherein the controlled rheology polypropylene has a melt flow rate of from 12 g/10 minutes to 80 g/10 minutes, wherein the controlled rheology polypropylene having a tangent delta of at least about 5 at 1 rad/second provides the mold section with a less mold warpage, compared to a mold material having the corresponding pristine polypropylene having the same melt flow rate.
2. The improved method of claim 1 , wherein the controlled rheology polypropylene has an increased melt flow rate of at least about 10 g/10 minutes.
3. The improved method of claim 1 , wherein the controlled rheology polypropylene has an increased melt flow rate of at least about 18 g/10 minutes.
4. The improved method of claim 1 , wherein the controlled rheology polypropylene having a melt flow rate from 20 g/10 minutes to 50 g/10 minutes.
5. The improved method of claim 3 , wherein the controlled rheology polypropylene having a tangent delta that is at least about 10 at 1 rad/second.
6. The improved method of claim 1 , wherein a nucleating agent is contacted with the controlled rheology polypropylene.
7. The improved method of claim 6 , wherein the nucleating agent is a sorbitol derivative.
8. The improved method of claim 1 , wherein the controlled rheology polypropylene is a controlled rheology metallocene catalyzed polypropylene.