Improved tinted contact lens and method of manufacture thereof

Abstract: An improvement in a process for preparing a contact lens tinted over at least a portion of its surface, having the steps of forming a tinting solution having a reactive dyestuff and applying the tinting solution to a polymeric hydrogel contact lens material, wherein the improvement comprises adding an effective amount of a phosphonium quaternary salt to the tinting solution before the applying step.

Description: The present invention relates to an improvement in the tinting of contact lenses. Successful methods of tinting contact lenses are set forth in U.S. Patent No. 4,468,229, U.S. Patent No. 4,553,975 and U.S. Patent No. 4,559,059, all to Su. The present invention relates to an improvement in a process for preparing a tinted contact lens. In particular, the invention concerns contact lenses comprising polymeric lens material in which reactive dyestuffs have been covalently bonded to monomer units of the polymer backbone. This invention is of particular interest in the area of so-called hydrophilic or "soft" contact lenses, commonly referred to as hydrogel lenses. There are many known methods for tinting or coloring contact lenses. For example, a coloring agent, such as dyestuff or pigment, may be dispersed in a monomer precursor or polymer matrix. This method is typically unsuitable for use in hydrophilic contact lenses, however, because the coloring agent leaches from the plastic upon presence of water in the lens. Another known method of coloring lenses is printing or otherwise applying the coloring agent to the lens surface. This method is also problematic, because a portion of the agent often becomes dissociated from the lens when the lens is placed in water. The primary cause of this problem is insufficient physical adhesion of the coloring agent to the surface. To counteract this problem, it is necessary to use a large amount of agent in the coloring process. It is an object of the invention to provide an improved tinting process for the fiber reactive dyes in the contact lens tinting field. It is another object of the invention to provide improved tinted lenses made by the aforementioned process. Surprisingly, the bonding of a reactive dyestuff to polymeric lens material may be enhanced by providing an effective amount of a phosphonium quaternary salt during the tinting process. Examples of acceptable phosphonium quaternary salts include the tetra-(C₁-C₄-alkyl)phosphonium halides, especially the bromide and chloride salts. It has been found that the use of such a catalyst results in increased bonding of the dyestuff to the lens material, which in turn decreases the cost of producing a tinted lens and also provides a lens having enhanced coloring. The present improvement has been found to be particularly useful in bonding chlorotriazine dyestuff to lens material. According to the present invention, a process for preparing a contact lens tinted over at least a portion of its surface may be improved by the presence of a quaternary phosphonium salt catalyst in the tinting solution during the tinting procedure. The invention is therefore directed to a process for preparing a contact lens, preferably a soft contact lens, tinted over at least a portion of its surface having the steps of forming a tinting solution comprising a reactive dyestuff and applying said tinting solution to a polymeric hydrogel contact lens material, wherein the improvement comprises adding an effective amount of a quaternary phosphonium salt to said tinting solution before said applying step, to a contact lens produced by said process and to a solution for use in said process comprising effective amounts of a reactive dyestuff and a quaternary phosphonium salt. It is preferred that the tinting solution has a pH of at least 10 and/or a temperature from approximately 30°C to 60°C when applied to the lens. While the raised pH is beneficial, pH alone, without the quaternary phosphonium compound as required by the invention, will not achieve the improved desired results in tinting. In a preferred embodiment said process further comprises the steps of maintaining said tinting solution at a temperature from between approximately 30° and 60°C; adding contact lens material to said solution; removing said contact lens material from said solution after a preselected time; and removing unreacted solution from said lens material. In most tinting procedures, such as those set forth in the aforementioned patents to Su, a solution of an effective amount of a reactive dyestuff is covalently bonded to the monomer units of polymeric lens material. For example, a practitioner may place a preformed contact lens in a tinting solution. In a standard tinting procedure, a contact lens is rinsed with deionized water and placed in a dry vial. Base solution (typically a 10 % Na₃PO₄·12H₂O (aq) solution) is added to the vial, followed by tinting solution. The vial is shaken in a shaker bath, and the lens removed. The lens is rinsed with deionized water and extracted with 10 % glycerine (aq) solution at 80°C for two hours. The lens is once again rinsed with water, then stored in saline. The quaternary phosphonium salt catalyst of the present invention is preferably provided in the tinting solution prior to placement of the lens material therein. A number of phosphonium quaternary salts may be used in practicing the present invention, including those of formula I [A] w [B] z [E] t [G] v P⁺Q⁻ (I) wherein each of w, z, t and v is 0-4 and the sum of w+z+t+v is 4, Q⁻ is a counterion selected from HSO₄⁻, F⁻, Cl⁻, Br⁻, I⁻, CH₃COO⁻, OH⁻, BF₄⁻, CH₃-C₆H₄-SO₃⁻, PF₆⁻, and H₂PO₄⁻, and A, B, E and G are each selected from C₁₋₁₈alkyl, preferably C₁₋₇alkyl, more preferably C₁₋₄alkyl; phenyl or phenyl-C₁₋₄alkyl, in which the phenyl ring is unsubstituted or substituted by C₁-C₈alkyl, C₁-C₈alkoxy, halogen, hydroxy, phenoxy, nitro, carboxy, acetamido, phenyl or benzyl; or cycloalkyl having 5-6 ring members; such that a compound of formula I is for example, tri-C₁₋₄alkylbenzylphosphonium chloride, triethylbenzylphosphonium chloride, tetraC₁₋₄alkylphosphonium hydrogen sulfate, especially tetrabutylphosphonium hydrogen sulfate, phenyltriC₁₋₄alkylphosphonium chloride, especially phenyl trimethylphosphonium chloride, benzyltriC₁₋₄alkylphosphonium chloride, especially benzyltributylphosphonium chloride, tetraC₁₋₄alkylphosphonium chloride or bromide, especially tetrabutylphosphonium chloride or bromide, and tetraethylphosphonium chloride or bromide. The phosphonium quaternary salts utilized most preferably in the inventive process are tetra-(C₁-C₄-alkyl)phosphonium salts. The halides are especially useful, especially the bromide and chloride salts. In general, any polymeric material suitable for use in the preparation of a contact lens can be used in the present invention, so long as at least one of the monomeric components which form the material contains an exoskeletal functional group which can react with a reactive dyestuff molecule. Examples of such functional groups commonly present in contact lens materials are the hydroxyl, amino, amido, thio and carboxy groups, and functional derivatives thereof. Monomers having the above groups which are suitable for use in the invention include without limitation: hydroxyalkyl esters of polymerizable unsaturated acids, such as acrylic, methacrylic, fumaric, maleic, etc.; unsaturated acids per se, such as acrylic, methacrylic, fumaric, maleic, etc.; heterocyclic N-vinyl lactams, such as N-vinyl pyrrolidone, etc.; noncyclic amides such as N-(1,1-dimethyl-3-oxobutyl)-acrylamide; amino alkyl esters of unsaturated acids such as 2-aminoethylacrylate, methacrylate, fumarate, or maleate; mercapto alkyl esters of unsaturated acids such as 2-mercaptoethyl acrylate, methacrylate, fumarate or maleate. Particularly suitable as monomers for this purpose are hydroxylalkyl esters of polymerizable unsaturated acids, such as acrylic, methacrylic, itaconic, fumaric and maleic acids. Among such esters, hydroxyethyl methacrylate (HEMA) has been used quite extensively. Useful reactive dyes, according to the present invention, include those commonly referred to as "reactive dyes forming ether linkages". These dyes contain reactive groups which react with cellulose to form an ether linkage and are generally described in Fiber-Reactive Dyes, Chapter VI, by W.F. Beech, SAF International, Inc., New York (1970). U.S. Patent No. 4,553,975 to Su also sets forth typical examples of commercially available dyes which may be used in accordance with the present invention. Among the preferred reactive dyestuffs capable of being used in accordance with the present invention are those having the general formulae II or III wherein D is the radical of an organic dyestuff; R is a divalent organic electron attracting group capable of causing electron withdrawal of the carbon atoms to which it is attached directly or through a conjugated system, thus activating the same; X is hydrogen or halogen, including F, Cl and Br; and Y is a leaving group; or mixtures thereof. The radical D may advantageously be the radical of an azo, phthalocyanine, azomethine, nitro or anthraquinone dye. The divalent group -R- is advantageously bonded directly to an aromatic nuclear carbon of D, or is bonded thereto via an aliphatic group such as an alkylene group, e.g. a lower alkylene group. Most preferably, -R- is directly bonded to a nuclear carbon atom of D. Suitable divalent R groups include -CO-, -SO₂-,-SO-, -NHCO-, -NHSO₂-, -SO₂NH- and the like. Most preferably, -R- is -SO₂-, -SO₂NH-, -CO- or -NHCO-. When X is halogen, it is most preferably chloro or bromo. Suitable leaving groups Y include -Cl, -Br, -OH, di-lower alkylamino, -SO₂-phenyl, -OSO₃⁻Z⁺ where Z⁺ is a cation, -O-SO₃R₁ or -OSO₂R₁ where R₁ in each case is alkyl, aryl, aralkyl or alkaryl. A cation Z⁺ is preferably the cation of an alkali metal, e.g. Na⁺. Advantageously, where R₁ is alkyl, it is alkyl of 1 to 6 carbon atoms, preferably alkyl of 1 to 4 carbons, including for example, methyl, ethyl, isopropyl, butyl and the like. Where R₁ is alkaryl, it is preferably lower alkyl substituted phenyl, such as tolyl or xylyl, and where R₁ is aralkyl, it is preferably lower alkylenephenyl, such as benzyl or phenethyl. "Lower" whenever used herein defines groups having up to 7 carbon atoms, preferably up to 4 carbon atoms. Also, the use of halotriazine dyes, especially chlorotriazine dyes, such as Cibacron® Blue 3R available from Ciba Geigy Corporation, is contemplated by the present invention. These are typically of the formula where D' is a radical of an organic dyestuff bound directly to the triazine ring or through a suitable linker, T is a solubilizing moiety, halogen or another D', and Z is halogen, preferably fluorine, chlorine, or bromine, more preferably fluorine or chlorine, most preferably chlorine. When two halogen groups are present they may be the same as or different from one another. When two D' groups are present, they may be the same as or different from one another. The following examples will illustrate the present invention. These examples illustrate that the process for preparing a contact lens tinted over at least a portion of its surface may be improved by adding a quaternary phosphonium salt to the tinting solution. Example 1: Two groups of 5 Cibasoft® HEMA contact lenses (available from Ciba Vision Corporation) are tinted. The first group is placed in a tinting solution (pH 12.20) comprising 1 ml of 0.05 % Cibracon® Navy F-G (available from Ciba Geigy Corporation), 1 ml of Na₃PO₄·12H₂O (10 % aq) and 0.1 ml of 5.0% tetrabutylphosphonium bromide (aq.). The second group is placed in an identical tinting solution except that the tetrabutylphosphonium bromide is omitted (pH 12.24). Both groups are placed for 30 minutes at 45°C in their respective solution. Each lens is then extracted with 10 % glycerine at 80°C for 2 hours, extracted again in deionized water at 80°C for 1 hour, and then extracted in buffered saline at 80°C for 1 hour. The tinting results are examined visually and by visible spectrum. Visual inspection reveales that the lenses which are tinted in a solution containing tetrabutylphosphonium bromide as catalyst (Group I) are considerably darker blue than the lenses tinted using no catalyst (Group II). Transmittance of the lenses tinted according to the invention (Group I) is 6 %, while transmittance of the lenses according to the art (Group II) is 50 %. This example illustrates that the process for preparing a contact lens tinted over at least a portion of its surface may be improved by adding a quaternary phosphonium salt to the tinting solution.

Claims: A process for preparing a contact lens tinted over at least a portion of its surface comprising the steps of forming a tinting solution comprising a reactive dyestuff and applying said tinting solution to a polymeric hydrogel contact lens material, wherein the improvement comprises adding an effective amount of a quaternary phosphonium salt to said tinting solution before said applying step. The process of claim 1, wherein said quaternary phosphonium salt is a tetra(C₁-C₄-alkyl)phosphonium salt. The process of claim 2, wherein said quaternary phosphonium salt is a tetra(C₁-C₄-alkyl)phosphonium halide. The process of claim 3, wherein said quaternary phosphonium salt is a tetra(C₁-C₄-alkyl)phosphonium chloride or bromide. The process of claim 4, wherein said quaternary phosphonium salt is a tetra(C₁-C₄-alkyl)phosphonium bromide. The process of claim 1 wherein said process further comprises the steps of maintaining said tinting solution at a temperature from between approximately 30° and 60°C; adding contact lens material to said solution; removing said contact lens material from said solution after a preselected time; and removing unreacted solution from said lens material. The process of claim 1, wherein said tinting solution comprises a reactive dyestuff of the formula II or III wherein D is the radical of an organic dyestuff; R is a divalent organic electron attracting group capable of causing electron withdrawal of the carbon atoms to which it is attached directly or through a conjugated system, thus activating the same; X is hydrogen or halogen; and Y is a leaving group; or mixtures thereof. The process of claim 6 wherein said tinting solution comprises a reactive dyestuff of the formula II or III as defined in claim 7. The process of claim 1 or 6, wherein said tinting solution comprises a halotriazine dyestuff. The process of claim 9, wherein said halotriazine dyestuff is a chlorotriazine dyestuff. The process of claim 1, wherein said tinting solution having said quaternary phosphonium salt therein has a pH of at least 10 during said applying step. The process of claim 1, wherein said contact lens material is or comprises hydroxyethyl methacrylate. A contact lens produced by a process which includes the improvement of claim 1.

Inventors: HUNG WILLIAM M, SU KAI C, HUNG, WILLIAM M., SU, KAI C.
Applicants: CIBA GEIGY AG, CIBA-GEIGY AG
Application year: 1991
Main classification: B29D11
IPC codes: G02C7, G02B1, B29D11, D06P3, D06P1