Macroporous hyperhydroxy polymer and articles made therefrom

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...

Reexamination Certificate

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C526S317100, C526S318400, C526S320000, C526S321000, C526S323100, C526S323200, C526S328000, C526S328500

Reexamination Certificate

active

06326446

ABSTRACT:

FIELD OF THE INVENTION
The present invention is directed to a macroporous hyperhydroxy polymer formed from a monomer mixture of substantially similar fractions of functional acrylic monomers which are combined to form a compound having a polymer skeleton which provides a high number of hydroxyl sites. The result is a material which, when hydrated, has a pore size relative to oxygen and water which provides a high ratio of free water to bound water. When formed into contact lenses, the material exhibits oxygen permeability approaching that of a static layer of tears of equal thickness and water contents of 95% or greater. The polymer is also suitable for use as burn dressings, bandages, soil hydratants, surface treatments, lubricants and coatings, absorbents, transport membranes and the like.
BACKGROUND OF THE INVENTION
Hydrophilic polymers having suitable properties for soft contact lenses have been produced in the past by crosslinking major amounts of a single hydroxyethyl methacrylate with a diester crosslinking agent. Those polymers typically exhibit water contents of 50 to 80% by weight when fully hydrated.
It is preferred that hydrophilic contact lens materials have as high a water content as possible so that tear exchange is not limited and corneal respiration is maintained as close to uninterrupted as possible. At the same time, the lens material must have sufficient strength to resist tearing during manufacture and insertion as well as not dissolving under use.
Since oxygen permeability is dependent on the water content of the lens, a greater water content results in increased permeability and, thereby, greater respiration. However, increasing water content requires that the porosity and water holding quality of the hydrophilic polymer be increased which normally results in a decrease in the physical strength of the polymer.
The present invention has determined that a macroporous hyperhydroxy polymer exhibiting a significantly increased water holding capability can be produced from a monomer mixture comprising substantially similar fractions of functional acrylic monomers with a minimum amount of a polymerization initiator. The resulting polymer has a crosslinked skeleton with a pore size of at least 90 Å and a high ratio of free water to solid when hydrated. Water contents of 95% to 99.75% are possible while maintaining sufficient integrity of structure to permit practical use as a material for contact lenses and other uses.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a macroporous hyperhydroxy polymer having a pore diameter greater than 90 Angstroms.
It is a further object of the present invention to provide a macroporous hyperhydroxy polymer which, upon hydration, has a uniquely high ratio of free water to bound water.
It is a still further object of the present invention to provide a macroporous hyperhydroxy polymer which has the capability of holding upwards of 99.75% water.
It is a further object of the present invention to provide a macroporous hyperhydroxy polymer from a monomer mixture consisting of substantially similar fractions of functional acrylic monomers.
It is an even further object of the present invention to provide a macroporous hyperhydroxy polymer hydrogel formed as a soft contact lens which exhibits a high water content, upwards of 99.75%, and a low coefficient of friction, thereby maintaining corneal respiration and moisturization at nearly uninterrupted levels.
These objectives and others are obtained by the preparation of a macroporous hyperhydroxy polymer from a monomer mixture consisting of substantially similar fractions of functional acrylic monomers.
The macroporous hyperhydroxy polymer comprises: 40-60 parts by weight of a purified monoester of a hydroxyalkyl acrylate having a single olefinic double bond, 40-60 parts by weight of a methacrylic acid, up to 5 parts by weight of a polymerization initiator, wherein the molar ratio of the purified monoester of hydroxyalkyl acrylate to the methacrylic acid is from 1:1 to 2.3:1, and the polymer is capable of holding 90-99.75% water.
The polymer is useful in a method of preparing articles from the macroporous hyperhydroxy polymer essentially comprising substantially similar fractions of functional acrylic monomers, which method comprises, mixing substantially similar fractions of a purified monoester of a hydroxyalkyl acrylate having a single olefinic double bond and a methacrylic acid with a sufficient amount of a polymerization initiator, holding the mixture under polymerization conditions to form a polymer gel, and casting the polymer gel to shape, whereby the article is capable of holding 90-99.75% water.
The polymer exhibits utility in a variety of fields including as a coating for surface treatments such as anti-icing materials, lubricants and the like, as a soil hydratant, as dermatological devices such as bandages, burn dressings, and the like, as chemical transport membranes, as biological implants, and as spill recovery materials. However, a principal use of the polymer is in the fabrication of soft contact lenses which comprise the macroporous hyperhydroxy polymer prepared by polymerizing a mixture comprising 40-60 parts by weight of a purified monoester of a hydroxyalkyl acrylate having a single olefinic double bond, and 40-60 parts by weight of a methacrylic acid, wherein the lens exhibits a water content of from 90-99.75%.
Further objects and advantages will become apparent from the following description.


REFERENCES:
patent: 3234134 (1966-02-01), Rockett
patent: 3244631 (1966-04-01), Van Der Voort
patent: 3367992 (1968-02-01), Bearden
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patent: 3766132 (1973-10-01), Lee, Jr.
patent: 3963685 (1976-06-01), Abrahams
patent: 4574140 (1986-03-01), Sandstrom
patent: 4656237 (1987-04-01), Weber, Jr.
patent: 5442023 (1995-08-01), Argyropoulos
patent: 5612416 (1997-03-01), McCollum

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