Oxygen Permeable Contact Lens Material Comprising Copolymers of Multifunctional Siloxanyl Alkylesters

The human cornea is an independent organism that obtains its sustaining oxygen from the tears of the eye. The oxygen consumption rate of the human cornea is approximated to be 2.8 ml/cm.sup.2 -hr. This value has been determined by Jauregui and Fatt, "Estimation of the Vivo Oxygen Consumption of the Human Corneal Epthelium" in the Americal Journal of Optometry and Archives of American Academy of Optometry, June, 1972, page 507.

Contact lenses have been made from various materials since the early 1950's. Table I illustrates some of the materials, the common term, its composition and its disadvantages.

Attempts have been made in correcting these disadvantages. Some of these attempts have been somewhat successful, but not entirely. In U.S. Pat. No. 4,152,508, they deal with stability, but the increasing of oxygen permeability was never really attained, due to the use of non-oxygen permeable crosslinking agents. The use of dimethacrylates (the preferred embodiments) did improve the stability over that of U.S. Pat. No. 3,808,178, but did decrease oxygen permeability to some degree. Thus, a material with excellent oxygen and carbon dioxide permeability is preferable for metabolic action of the cornea. The surface of the material must be wettable and compatible with fluids of the eye.

The primary object of this invention is to provide a novel contact lens material which is prepared from a combination of monomers so as to have high oxygen, carbon dioxide permeability, and a hydrophilic surface. It would be preferable to have sufficient mechanical strength to permit precision machining and polishing.

Although, lenses could be fabricated by casting or molding if an elasticmeric material is preferable.

According to the invention a contact lens material is prepared by copolymerizing:

(a) from 5 to 90% by weight of a multifunctional siloxanyl alkyl ester monomer having two or more .alpha.,.omega. terminally bonded through divalent hydrocarbon groups to an activated unsaturated groups with;

(b) an effective amount of a copolymerizable monomer up to 90% by weight selected from the group consisting of an ester of acrylic or methacrylic acid or from;

(c) an ester of itaconic acid or mixtures thereof;

(d) from 0.5 to 40% by weight of a hydrophilic monomer for a surface wetting agent;

(e) an effective amount of a copolymerizable monomer up to 20% by weight of an ester crosslinking agent.

Representatives of (a) a multifunctional siloxanyl alkyl ester monomer having two or more .alpha.,.omega. terminally bonded through divalent hydrocarbon groups to an activated unsaturated groups included but not restricted to the following:

Tetrakis-(trimethylsiloxy) bis(methacryloxypropyl)disiloxane

Tretakis-(trimethylsiloxy)bis(methacryloxypropyl)dimethyltrisiloxane

Pentakis-(trimethylsiloxy)tris(methacryloxypropyl)tetramethylpentasiloxane

Hexakis-(trimethylsiloxy)tetrakis-(methacryloxypropyl)hexamethylheptasiloxa ne

Tris(methacryloxymethldimethylsiloxy)methacryloxypropylsiloxane

Tetrakis-(methacryloxymethyldimethylsiloxy)tetramethyl-cyclotetrasiloxane

Tetrakis-(methacryloxymethyldimethylsiloxy)siloxane

Representatives of (b) an ester of acrylic of methacrylic acid include by not restricted to the following:

Butyl acrylate and methacrylate

Cyclohexyl acrylate and methacrylate

2-ethyl acrylate and methacrylate

Glycidyl acrylate and methacrylate

Hexyl acrylate and methacrylate

Lauryl acrylate and methacrylate

Methyl acrylate and methacrylate

Stearyl acrylate and methacrylate

Representatives of (c) esters of itaconic acid but not restricted to the following:

Butyl itaconate

Dibutyl itaconate

Methyl itaconate

Phenyl itaconate

Diphenyl itaconate

Representatives of (d) a hydrophic monomer for a surface wetting agent include but not restricted to the following:

Acrylamide

2-Acrylamido-2 methyl propane sulfonic acid

t-Butylaminoethyl methacrylate

Dimethylaminoethylacrylate and methacrylate

N-(1,1-Dimethyl-3-Oxobutyl)-acrylamide

Glacial acrylic and methacrylic acid

Glyceryl acrylate and methacrylate

Itaconic acid

Propylene glycol monoacrylate and monomethacrylate

Ethylene glycol monoacrylate and monomethacrylate

Methacrylamide

Morpholinoethyl acrylate and methacrylate

Piperidinoethyl acrylate and methacrylate

Triethylene glycol methacrylate

N-vinyl pyrrolidone

The preferred (e) an ester crosslinking agents include but not restricted to the following:

Bis(methacryloxypropyl)tetramethyldisiloxane

1,3 Bis(glycidoxypropyl)tetramethyldisiloxane

Divinyl Diphenyl Silane

Ethylene-Glycol diacrylate and dimethacrylate

Diethylene glycoldiacrylate and dimethacrylate

Trimethylpropane triacrylate and trimethacrylate

Triethyleneglycol diacrylate and methacrylate

Tetraethyleneglycol diacrylate and dimethacrylate

The copolymers of this invention is prepared by conventional polymerization by either free radical initiators or by photoinitiators. Representatives of free radical initiators include but not restricted to the following:

Acetyl Peroxide

2,2, Azobis (2-Methylpropinionitrile)

Benzoyl Peroxide

t-Butyl Peroctoate

Caprylyl Peroxide

Decanoyl Peroxide

Diisopropyl Peroxydicarbonate

2,5-dimethyl-2, 5-bis (2-ethyl hexanoylperoxy)hexane

Lauroyl Peroxide

Tertiarybutyl Percotoate

Tertiarybutyl Peroxypivalate

Representatives of photo-initiators include but not restricted to the following:

Benzoin

Benzophenone

2,2 Azobis(2-Methylpropionitrile)

The following examples are presented to illustrate the invention but not restricted to the following:

This example demonstrates the synthesis of 1,5-Bis(methacryloxypropyl) 1,1,5,5-tetra kis(trimethylsiloxy) 3,3-dimethyl-trisiloxane (BIS). 13 g sulfuric acid is added in a dropwise manner to 5 g ethanol (medical grade) and 10 g of water in a flask equiped with a magnetic stirrer. If the sulfuric acid is added at a rate of one to two drops per second, a water bath is not necessary (any faster drop rate, and a water bath should be used for cooling).

49.62 g (0.2 mole) of methacryloxypropyl trimethoxy silane, 17.63 g (0.1 mole) of dimethyldiacetoxysilane, and 43.48 g (0.4 mole) of trimethyl acetoxy silane are placed in a flask equipped with an ice bath and a magnetic stirrer. Then 13 g of ethanol/sulfuric acid is added in a dropwise manner to the mixture while stirring. Continue ice bath for five minutes after the entire amount of ethanol/sulfuric acid has been added to the mixture. The mixture should be stirred for up to three days at room temperature to assure complete reaction. The organic (upper) layer is separated from the rest. The organic layer is washed with a 5% aquious solution of Sodium Bicarbonate of equal volume, and allowed to separate. The organic layer is dried over anhydrous sodium sulfate and filtered. The remaining by-product (ethyl acetate) is stripped off by means of a vacuum stripper or a vacuum still at a temperature ranging from 35.degree. to 45.degree. depending upon the degree of vacuum pulled. Refrigerated storage is recommended to prevent premature reactions.

This example demonstrates the polymerization of the novel polymer by copolymerizing multifunctional siloxanyl alkyl ester prepared in Example I and an ester of methacrylic acid.

A rod is formed by copolymerizing 45 parts by weight of BIS, 47 parts by weight of methyl methacrylate, (MMA), 5 parts by weight of ethyleneglycol monomethacrylate, (HEMA), and 2 parts by weight of ethylene glycol dimethacrylate, (EDMA), in the presence of 0.25 parts by weight of benzoyl peroxide, (BPO) and placed in a glass tube and sealed. Polymerization is promogated in a water bath maintained at 70.degree. C. for 12 hours. Post-cured in a convection oven at 85.degree. C. for 24 hours. Contact lens blanks and lenses are prepared by conventional lathe cutting techniques. The lenses are hard, transparent, and highly oxygen permeable.

This example demonstrates the synthesis of 1,5,9,-tris(methacryloxypropyl) 1,1,5,9,9-penta-kis(trimethylsiloxy) tetramethylpentasiloxane (PENTA).

Procedures in Example I are exactly followed except 23.51 g (0.1333 mole) of dimethyldiacetoxy silane and 44.07 g (0.333 mole) trimethylacetoxysilane are used to form a more complex molecule having three methacryl end groups for crosslinking.

This example demonstrates the polymerization of the novel polymer by copolymerizing the multifunctional siloxanyl alkyl ester prepared in Example III and an ester of methacrylic acid.

A rod is formed by copolymerizing 40 parts by weight of PENTA, 53 parts by weight of MMA, 5 parts by weight of HEMA and 2 parts by weight of diethylene glycol dimethacrylate in the presence of 0.25 parts by weight of BPO and placed in a glass tube and sealed. Polymerization is promogated in a water bath maintained at 70.degree. C. for 12 hours. Post-cured in a convection oven at 85.degree. C. for 24 hours. Contact lens blanks and lenses are fabricated by conventional lathe cutting techniques. The lenses are hard, transparent and highly oxygen permeable.

This example demonstrates the syntheses of 1,5,9,13-tetrakis9methacryloxypropyl)1,1,5,9,13,13-hexakis-trimethylsiloxy l)hexamethylhepta siloxane, (HEXA).

Procedures in Example I are followed except 25.45 g (0.15 mole) of dimethyldiacetoxy silane and 39.66 g (0.30 mole) of trimethylacetoxy silane for acomplex molecule having molecular weight of 14241.1 and four methacryl end groups for crosslinking.

This example demonstrates the polymerization of the novel polymer by copolymerizing the multifunctional siloxanyl alkyl ester prepared in Example V, an ester of methacrylic acid, and an ester of itaconic acid.

A rod is formed by copolymerizing 46 parts by weight of HEXA, 23.5 parts bu weight of MMA, 23.5 parts by weight of dimethylitaconate, 5 parts by weight of HEMA, and 2 parts by weight of EDMA in the presence of 0.25 parts by weight of 2,2-Azobis(2-methylpropionitrile) and placed in a glass tube and sealed. Polymerization is promogated in a water bath maintained at 70.degree. C. for 12 hours. Post-cured in a convection oven at 85.degree. C. for 24 hours. Contact lens blanks and lenses are fabricated by conventional lathe cutting techniques. The lenses are hard, transparent, and highly oxygen permeable.

This example demonstrates the syntheses of tris(methacryloxymethyldimethylsiloxy)methacryloxypropylsiloxane, (TRIMA).

24.81 g (0.1 mole) of methacryloxypropyltrimethoxysiloxane, 47.22 g (0.33 mole) of chlormethyldimethylchlorosilane, and 50 g of ethyl ether are palced is a flask equipped with a magnetic stirrer and agitated for 5 minutes. In a separate flask 5 g of sodium bicarbonate is dissolved in 50 g of water. The sodium bicarbonate solution is placed in a flask equipped with an ice bath, a magnetic stirrer, and additional funnel with valve to control flow, and a vent port connected to another flask filled with 20% aqueous solution of sodium bicarbonate. The silane mixture is placed in the additional funnel and dropped at a rate of one drop every two seconds. A temperature of 10.degree. C. is maintained for one hour after all of the silane mixture is added, the mix is stirred for 2 hours at room temperature. The mixture is then placed is a sepatory funnel and allowed to separate. The solvent is removed from the organic layer by distillation. The product is then mixed with 100 g of dimethylformamide, 12.42 g of potassium methacrylate and 75 g of methacrylic solvent removed by distillation. TRIMA is then washed twice with 5% aqueous solution sodium bicarbonate of equal volumes over anhydrous sodium sulfate. The remaining by-products are removed by vacuum distillation. Refrigerated storage is recommended to prevent premature reactions.

This example demonstrates the polymerization of the novel polymer by copolymerizing the multifunctional siloxanyl alkyl ester prepared in Example VII and a ester of methacrylic acid.

A rod is formed by copolymerizing 47 parts by weight of TRIMA, 47.5 parts by weight of MMA, 5 parts by weight of HEMA, and 0.5 parts by weight of EDMA in the presence of 0.25 parts by weight of BPO and placed in a glass tube and sealed. Polymerization is promogated in a water bath maintained at 70.degree. C. for 12 hours. Post-cured in a convection oven at 85.degree. C. for 24 hours. Contact lens blanks and lenses are fabricated by conventional lathe cutting techniques. The lenses are hard, transparent, and highly permeable.

Other multifunctional siloxanyl alkyl esters can be prepared to have numerous reactive sites and configurations by changing the molar relationships of the intermediaries and constituents. It also has been found that by replacing at least one methacryloxy alkyl group with a dihydroxypropyl alkyl group, the siloxanyl alkyl ester can be made to be self wetting.

Various modifications can be made without departing from the spirit of this invention or scope of the appended claims. The constants set forth in the disclosure are given as examples and are in no way final or binding. In view of the above, it will be seen that several objects of the invention are achieved and other advantages are obtained. As many changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.