JP2001519252A - Ophthalmic lens manufacturing method - Google Patents

Abstract

  (57) [Summary] Preparing a polymerizable composition comprising an excess oxygen content; contacting the polymerizable composition with a gas that is inert or substantially inert to the polymerizable composition; Deoxidizing or partially deoxidizing the product, transferring all or a part of the polymerizable compound to an ophthalmic lens mold, polymerizing all or a part of the polymerizable compound, Obtaining an ophthalmic lens, comprising: obtaining a polymer lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to a method of manufacturing an ophthalmic lens and a method of deoxygenating an ophthalmic lens polymerizable compound in the method.

[0002] Ophthalmic lenses are manufactured by several known methods, including spin casting, precision lathing and molding. In the spin casting process, a suitable ophthalmic lens formulation is simultaneously polymerized while rotating in a mold, as generally described by Nandu et al. In US Pat. No. 5,260,001. Precision lathe processing
It is performed by lathing a clear piece of polymer material into a lens shape and polishing the lens so formed. Precision turning is generally described by Le Boeuf et al. In U.S. Pat. No. 4,054,624. The molding process is performed by polymerizing the appropriate material in a preform, as generally described by Larsen in US Pat. No. 4,640,489.

[0003] Various compositions are used to produce ophthalmic lenses. The composition selected for a particular application will depend on the physical and optical properties of the lens to be obtained, as well as on the type of method used to manufacture the lens and the specific processing conditions associated with the method. A particularly common type of ophthalmic lens is a soft contact lens made from a hydrophilic, and thus water-absorbing, composition. Typical hydrophilic lenses are based on polymers and copolymers of 2-hydroxyethyl methacrylate.

A widely accepted soft contact lens is a continuous wear lens that can be kept on the corneal surface overnight and for more than seven days. Since the cornea obtains oxygen from diffusion from the surrounding air and contact lenses are physical barriers to such diffusion, continuous wear lenses must meet special physical criteria. To overcome this physical barrier, manufacturers have developed special oxygen permeable compositions for continuous wear lenses. Such oxygen permeable compositions generally contain oxygen attracting elements or compounds such as silicon and fluorine. A variety of siloxane-containing polymers having high oxygen permeability are disclosed, for example, in U.S. Patent Nos. 3,228,741, 3,341,490,
996,187 and 3,996,189.

[0005] Ophthalmic lenses are often manufactured from formulations containing volatiles, such as solvents or diluents. For example, many ophthalmic lenses are made from polymerizable formulations in which the monomer component is solubilized in a suitable solvent. Many ophthalmic lenses are manufactured using carrier volatiles, which after polymerization are extracted from the lens and replaced with water. Whenever volatiles are included in the ophthalmic lens formulation, great care must be taken to prevent evaporation of the volatiles, which would alter the proportions of the components in the formulation. To minimize the risk of evaporation, minimize exposure to ambient gases and minimize excessive turbulence.

[0006] Ophthalmic lenses must meet very strict standards. As pointed out earlier, continuous wear lenses must be sufficiently hydrophilic and oxygen permeable. In addition, ophthalmic lenses must have sufficient strength to resist tearing and must meet stringent dimensional requirements to achieve the prescribed optical correction and conform to the wearer's corneal dimensions. Moreover, the lens must be very thin to promote oxygen permeability and improve comfort for the wearer. The lens must also be clear and distortion free to provide satisfactory and precise optical correction. The processing conditions that can meet strict lens standards are very strict,
Manufacturers establish stringent quality control programs and constantly evaluate and revise their work procedures to minimize the occurrence of defective lenses.

A major challenge in quality control programs is contamination, including contamination from ambient gases. During the process of preparing the polymerizable formulation, various components can be exposed to ambient gases, which are absorbed by those components and contaminate the polymerizable formulation. The absorbed gas, such as oxygen, interferes with the lens manufacturing process by quenching the free radicals generated during polymerization. The gas may also react with the polymer components to produce undesirable by-products. Also, the absorbed gas can cause bubbles in the ophthalmic lens to be polymerized, and such bubbles severely impair the optical and mechanical integrity of the lens.

[0008] Recent advances in ophthalmic lens formulations and polymerization techniques have resulted in corresponding advances in the removal of dissolved contaminants, such as gases, from ophthalmic lens formulations. Ophthalmic lenses manufactured and developed today are much more susceptible to gas contamination than ophthalmic lenses developed only a few years ago. Accordingly, methods have been developed to remove almost all dissolved gases from polymerizable formulations. These methods minimize the risk of solvent volatilization while maximizing gas removal.

[0009] For example, US Pat. No. 5,453,943 to Adams et al. Discloses a method for producing a formulation having an oxygen concentration of less than 1 ppm. The formulation is passed through a selectively porous tube which, when exposed to reduced pressure, vents gas from the formulation through the tube. The '943 patent teaches the removal of all dissolved gases from the formulation.
Moreover, the '943 patent clearly discusses the preference of silicon tubing because of the strong affinity of silicon for oxygen. The strong affinity of silicon, due to the tube,
It makes it possible to withdraw oxygen from polymerizable formulations which also have a high affinity for oxygen. However, the method of the '943 process suffers from its complexity and time requirements. The polymerizable formulation must be withdrawn through a tube longer than 60 meters and is deoxygenated only at a rate of 8.5 ml / min.

[0010] It is therefore surprising to find that high quality ophthalmic lenses can be produced by a method of deoxygenating the formulation by bubbling an inert gas, such as nitrogen, into the formulation. The bubbling of the inert gas surprisingly deoxygenates the polymerizable formulation under short periods of time and under light flow conditions such that only a minimal amount of solvent evaporates. Light inert gas bubbling can result in less than 1/20 of the time required by the porous tubing method disclosed by US Pat. No. 5,453,943, even for polymerizable formulations that exhibit a strong affinity for oxygen. At (see Table 3), the oxygen content is substantially removed from the ophthalmic lens formulation.

Moreover, the method is effective even if only one dissolved gas, oxygen, is replaced by another dissolved gas, for example nitrogen. Lenses made using an inert gas saturated formulation from the bubbling process are not statistically different from prior art lenses where nitrogen and oxygen have been removed.

[0012] The present invention, in one aspect, comprises a step of preparing a polymerizable formulation that contains an excess of oxygen content, and the step of making the polymerizable formulation inert or substantially inert to the polymerizable formulation. Contacting with a gas to deoxygenate or partially deoxygenate the polymerizable composition; transferring all or a portion of the polymerizable composition to an ophthalmic lens mold; The present invention relates to a method for producing an ophthalmic lens, comprising a step of polymerizing a part and a step of obtaining an ophthalmic polymer lens. The present invention further provides an ophthalmic lens manufactured by such a process.

In another aspect, the invention is directed to an ophthalmic lens polymerizable formulation that is saturated or substantially saturated with an inert gas.

[0014] In another aspect, the invention relates to an ophthalmic lens prepared from an ophthalmic lens polymerizable formulation that is saturated or substantially saturated with an inert gas.

In yet another aspect, the invention relates to an ophthalmic lens that is saturated or substantially saturated with an inert gas.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It will be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention, as claimed.

In this specification and in the following claims, reference is made to a number of terms that are defined to have the following meanings.

An “effective amount” of a compound or property described herein refers to an amount that is capable of performing the function of the compound or property for which the effective amount is expressed. The exact requirements will vary from method to method, depending on the variables recognized, for example, the compounds used and the processing conditions observed. Therefore, it is not possible to specify an exact “effective amount”. However, an appropriate effective amount can be determined by one of ordinary skill in the art using only routine experimentation.

“Excessive oxygen content” in a polymerizable formulation refers to substantially preventing radical polymerization of the formulation or substantially affecting the quality, properties or formulation of the ophthalmic lens obtained by polymerizing the formulation. It refers to the concentration of oxygen that affects.

“Hydrophilic” refers to a polymer that associates more readily with water than with lipids. "Hydrophilicity-enhancing prepolymer" refers to a prepolymer that polymerizes to form a hydrophilic polymer.

“Macromer” refers to a polymer having a molecular weight of at least about 800 g per mole. "Macromer" also includes oligomers.

“Substantially” means greater than the minimum and generally falls within the scope of quality control standards and guidelines recognized by those of ordinary skill in the art when implementing the methods of the present invention. It does not interfere with processing or produce unacceptable results or ophthalmic lenses as judged by quality control standards and guidelines that are also recognized by those skilled in the art, for example, certain properties or properties in polymerizable formulations. Eliminate the amount of physical properties.

“Monomer” refers to a polymerizable substance having a molecular weight of less than about 800 g per mole.

An “ophthalmic lens” is a lens that is placed in close contact with the eye or tears, such as a contact lens for correcting vision (eg, spherical, toric, bifocal), to change the color of the eye Contact lenses, intraocular drug delivery devices, eye tissue protection devices (eg, ophthalmic healing promoting lenses) and the like.

“Optional” and “optionally” mean that the event or circumstance described subsequently may or may not occur, and that the description indicates that the event or circumstance occurs and that Includes both cases that do not occur. For example, "optionally substituted lower alkyl" means that the lower alkyl group may be substituted or unsubstituted, and the description includes unsubstituted lower alkyl and substitution. It is meant to include both lower alkyls.

“Oxygen permeable” refers to a polymer that is permeable to oxygen. "
"Oxygen permeability enhancing prepolymer" refers to a prepolymer that polymerizes to form an oxygen permeable polymer.

“Parts by weight” of a particular element or component in a formulation or product refers to the weight relationship between that element or component and other elements or components in the formulation or product in which parts by weight are expressed. For example, in a compound containing 2 parts by weight of the X component and 5 parts by weight of the Y component, X and Y are present in a weight ratio of 2: 5, and in that ratio whether or not additional components are included in the compound. Exists.

“Polymerizable formulation” refers to a formulation containing one or more prepolymers, such as monomers, oligomers, macromers and other units capable of polymerizing, and mixtures thereof.

A “residue” of a species, as used herein and in the last claim, is the resulting product or subsequent composition or chemical product of a species in a particular reaction scheme. A part, regardless of whether that part is actually obtained from a chemical species. For example, ethylene glycol residue in a polyester refers to one or more -OCH ₂ CH ₂ O- units in the polyester, does not matter whether ethylene glycol was used to prepare the polyester. Similarly, a siloxy residue in a composition refers to a silicon moiety in the composition, whether or not that silicon moiety is derived directly from elemental silicon or a silicon-containing compound.

TRIS refers to 3-methacryloxypropyltris (trimethylsiloxy) silane represented by CAS No. 17096-07-0. TRIS also includes dimers of 3-methacryloxypropyl tris (trimethylsiloxy) silane.

“Volatile” often refers to components of a polymerizable formulation, and in such a context, one skilled in the art when treating a polymerizable formulation in accordance with the methods of the present invention will minimize the It refers to the degree of volatility that will foresee greater volatility. A "minimal" amount of volatilization refers to less than a substantial amount of volatilization. "Minimum" can take into account the particular system used. For example, in a system that returns volatilized solvent to the polymerizable formulation, the "minimal" amount of volatilization will be greater than in a system that does not return the volatilized solvent to the formulation.

As used in this specification and the appended claims, the singular forms “a” and “the”
It should be noted that a term includes multiple referents unless the context clearly dictates otherwise. Thus, for example, "hydrophilic enhancing prepolymer" includes a mixture of hydrophilic enhancing prepolymers, "volatile carrier" includes a mixture of two or more such carriers, and so on. is there.

In addition, ranges are often expressed herein as from about one particular value to about another particular value. When such a range is expressed, it will be understood that the more preferred range is typically from that particular value to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value is usually more preferred.

[0034] The polymerizable formulation of the claimed method can be prepared by any method known to those skilled in the art and can include any combination of materials suitable for preparing an ophthalmic lens. . Generally, the formulations are prepared by combining the components of the formulation in a suitable container and blending the components until a homogeneous mixture is obtained.

The present invention is particularly well applied to methods of making hydrophilic lenses and to formulations that are useful in making such lenses. Thus, in a preferred embodiment, the polymerizable formulation contains one or more hydrophilicity-enhancing prepolymer. A wide range of hydrophilicity-enhancing prepolymers are known in the art and are suitable for practicing the present invention. Preferred hydrophilicity enhancing prepolymers are acrylates and methacrylates, such as 2-hydroxyethyl methacrylate, acrylamide, methacrylamide and dimethylacrylamide, poly (alkylene glycol) s,
For example, poly (ethylene glycol), N-vinylpyrrolidones such as N-
Vinyl-2-pyrrolidone and mixtures thereof.

The present invention is also particularly well applied to methods of making oxygen permeable lenses and formulations that, when polymerized, produce such lenses. A wide range of materials can be polymerized to form polymers with relatively high oxygen diffusion rates.
Preferred oxygen permeability enhancing prepolymers are macromers and monomers containing silicon residues, macromers and monomers containing fluorine residues, alkyne macromers and monomers and mixtures thereof. Particularly preferred oxygen permeability enhancing prepolymers are macromers containing silicon residues. Macromers having dialkylsiloxane groups, especially dimethylsiloxane groups, are particularly preferred. Macromers containing dimethylsiloxane oligomer residues and polymers containing dimethylsiloxane residues are widely referred to as polydimethylsiloxanes, regardless of whether the macromer or polymer also contains other residues.

[0037] The polymerizable formulation can further include a wide variety of other polymerizable materials. Crosslinking agents such as ethylene glycol dimethacrylate can be added to improve the structural integrity and mechanical strength of the lens being polymerized. An antimicrobial prepolymer such as a poly (quaternary ammonium) salt can be added to inhibit microbial growth in the lens material. Also, additional hydrophilic or oxygen permeability enhancing prepolymers may be added to adjust the oxygen permeability and hydrophilicity of the final molded lens. A particularly advantageous polymerizable substance is TRIS, which enhances oxygen permeability,
It can both act to improve the modulus.

[0038] In a specific embodiment, the formulation includes a volatile, eg, a solvent that dissolves and mixes the components of the polymerizable formulation. Solvents are particularly useful when both the oxygen permeability enhancing prepolymer and the hydrophilicity enhancing prepolymer are included in the polymerizable formulation, due to the immiscibility often encountered when mixing these prepolymers. Volatiles may also be diluents extracted from the lens immediately after polymerization. Volatiles are usually substantially inert and do not participate in the polymerization of the formulation. However, volatiles
It may be the active ingredient of a formulation involved in the polymerization.

A variety of solvents are known, usually selected based on their interaction with the components of the polymerizable formulation. Suitable solvents are, in principle, all solvents which dissolve the components of the formulation,
For example, water, alcohols and especially lower alkanols, such as ethanol and methanol. In other embodiments, the solvent is an ether such as tetrahydrofuran, diethyl ether, diethylene glycol dimethyl ether or dioxane, a halogenated hydrocarbon such as chloroform, trichloroethane or methylene chloride, a dipolar aprotic solvent such as methyl ethyl ketone, acetonitrile, acetone or dimethyl. Sulfoxides, carboxylic amides such as dimethylformamide, hydrocarbons such as hexane, petroleum ether, toluene or xylene, as well as pyridine or N-methylphorforine and mixtures of suitable solvents, such as mixtures of alcohols and water.

Preferred polymerizable formulations include an oxygen permeability enhancing prepolymer and a hydrophilicity enhancing prepolymer. Particularly preferred formulations are oxygen permeability enhancing prepolymers of about 40 to
About 80 parts by weight and about 10 to about 40 parts by weight of the hydrophilicity enhancing prepolymer. A more preferred polymerizable formulation comprises about 60 to about 70 parts by weight of an oxygen permeability enhancing prepolymer and about 20 to about 30 parts by weight of a hydrophilicity enhancing prepolymer. In an optional embodiment, the formulation preferably has a TRIS of about 10% to about 20% by weight, more preferably
RIS from about 12% to about 15% by weight. In another optional embodiment, the formulation preferably comprises from about 5 to about 45% by weight volatiles, more preferably from about 15 to about 35% volatiles, even more preferably from about 18 to about 30% volatiles. And more preferably from about 20% to about 23% by weight of volatiles. Preferred formulations are also described in WO 97/22
019 and WO 96/31792, the disclosures of which are incorporated herein by reference.

Surprisingly, it has been found that the present invention can be practiced with polymerizable formulations containing volatiles, as well as polymerizable formulations that are sensitive to loss of volatiles from the formulation. . For example, the present invention surprisingly provides a volatile concentration of less than about 10% (based on the weight percent of the components in the formulation), even less than about 5%, and more surprisingly less than about 3%. Can be carried out using compounds having a range of different weights without substantially affecting the lens obtained by polymerization. In addition, the present invention
Irrespective of the volatility of the components, it can be carried out using a polymerizable formulation. The present invention relates, for example, to compounds having a vapor pressure of more than 20 mm Hg at 20 ° C., formulations having a vapor pressure of more than 40 mm Hg at 20 ° C. And with a formulation having a vapor pressure above 60 mmHg.

When the polymerization of the formulation is initiated by photopolymerization, it may be appropriate to add a photoinitiator capable of initiating radical polymerization and / or crosslinking. Examples are commonly known to those skilled in the art. Particularly suitable photoinitiators are benzoin methyl ether, 1-hydroxycyclohexyl phenyl ketone, Darocur and Irgacur products, preferably Darocur 1173 and Irgacur 2959. Also, a reactive photoinitiator that can be incorporated into the macromer or used as a specific comonomer may be used, for example. Particularly suitable examples of them are described in EP 0 632 329. The disclosure of this patent is incorporated herein by reference.

The present invention is particularly well applied to a method of making a continuous wear ophthalmic lens that is hydrophilic and oxygen permeable. The formulations used to make such lenses often contain insoluble hydrophilicity enhancing prepolymers and oxygen permeability enhancing prepolymers that can only be solubilized with solvents. Also, such formulations are often due to the exact proportions of the components that must be observed to obtain a polymer that is hydrophilic and oxygen permeable, and the possibility of solvent volatilization from such formulations. , Very sensitive to changes in the proportions of the components.

Preferably, the method comprises a Dk / t of at least 70 barrer / mm and at least 0. A contact lens having an Ionoton ion permeability of 2 × 10 ⁻⁶ cm ² / s is manufactured. More preferably, the method produces a contact lens having a Dk / t of at least 75 barrer / mm and an Ionoton ion permeability of at least 0.3 × 10 ⁻⁶ cm ² / s. The method further preferably provides a contact lens having a Dk / t of at least 87 barrer / mm and an Ionoton ion permeability of at least 0.4 × 10 ⁻⁶ cm ² / s.

The present invention is particularly applicable to processes where the surface tension and viscosity of the polymerizable formulation are low.
Thus, in a preferred embodiment, the polymerizable formulation has a surface tension of less than about 250 dyn / cm, more preferably, less than about 150 dyn / cm, even more preferably, less than about 75 dyn / cm, and even more preferably, less than about 35 dyn / cm. However, in a more preferred embodiment, the surface tension is less than about 23 dyn / cm. Surface tension generally exceeds about 10 dyn / cm. In another preferred embodiment, the viscosity of the polymerizable formulation is about 300 at 20 ° C.
It is less than 0 cP. In a more preferred embodiment, the viscosity is less than about 750 cP at 20 ° C, more preferably less than about 150 cP at 20 ° C, even more preferably at 20 ° C.
And in a more preferred embodiment, the viscosity of the formulation at 20 ° C. is less than about 30 cP. Viscosity is typically greater than about 15 cP at 20 ° C.

An example of the manufacturing method is as follows. First, a blend is prepared by combining the ingredients of the blend in a container and optionally mixing the ingredients. The polymerizable formulation can be prepared in a different location from the rest of the process, or in another way separate from the rest of the process, but still fall within the scope of the invention. After the formulation has been prepared, the formulation is pumped from the container through a line to a filtration device where the impurities, such as particulates, in the formulation are removed. The materials used in this line, in addition to the other lines in the method, are made from gas impermeable materials that do not chemically react with the formulation. After filtration, the formulation is fed through a line to a container of an inert gas dispersion device.

In the continuous method, the compound is continuously supplied to the raw material of the polymerizable compound already in a container, whereas in the batch process, the raw material is used up and stored in each batch. However, whether the process is continuous or batchwise, the feedstock is deoxygenated by contacting an inert gas with the formulation. The inert gas dispersion device is
Includes a source of inert gas supplied to the feedstock via lines, valves and porous frit. The source of inert gas is preferably pressurized so that actuation of the valve regulates, releases and stops the flow of inert gas to the feed. However, the inert gas is
It may be supplied by a pump.

When the inert gas is supplied, the inert gas passes through the porous frit and diffuses into the raw material. The inert gas then mixes thoroughly with the raw material, rises in the raw material, and finally exits the vessel through the stream. Inert gases suitable for dispersion in the polymerizable formulation include those gases that are inert or substantially inert to the components of the polymerizable formulation and do not substantially interfere with the polymerization of the formulation. . Preferred gases include argon and helium. A more preferred gas is nitrogen.

Many types of devices suitable for dispersing an inert gas in a polymerizable formulation are disclosed in Fi
Available including several devices commercially available from sher Scientific, Kontes and Corning Glass. For smaller scale applications, Fisher Scienti
Particularly preferred are coarse and extremely coarse frit glass gas dispersion tubes having an inner diameter of 8 mm, which are commercially available from fic, most preferably extremely coarse dispersion tubes. The method of using these tubes can be easily extended to large commercial applications. For some applications, it may be best to use more than one dispersion tube. In addition, other types of dispersing devices are suitable, for example frit glass cylinder sealing tubes, also available from Fisher Scientific. This tubular device has a centrally located, sealed fritted glass filter plate, both of which are commercially available in fine, medium, coarse or very coarse porosity suitable for practicing the present invention. For smaller scale applications, 13 mm OD, 25 mm OD and 35 mm OD tubes are all suitable.
Devices of this type can likewise be easily extended to large commercial applications.
Of course, other suitable gas distribution methods and devices are known in the art.

[0050] The inert gas can be obtained from about 0.5 to about 10 psi, more preferably from 0.75 to about 5 psi, and more preferably from about 0.5 to about 10 psi by using a very coarse frit glass gas distribution tube commercially available from Fisher Scientific. Preferably at about 1 to about 3 psi, 200 ml of the polymerizable formulation in a 4 inch inside diameter vessel is fed. In another embodiment, the inert gas is provided from about 0.5 to about 10 psi, more preferably about 0.5 psi, by using a coarse frit glass gas dispersion tube commercially available from Fisher Scientific. Preferably, the feed is 75 to about 5 psi, more preferably about 1 to about 3 psi, into a 4 inch inside diameter, 200 ml vessel of the polymerizable formulation.

If the polymerizable formulation contains a solvent, contacting the inert gas with the polymerizable formulation by a method such as dispersion or bubbling at a rate and for a time such that only a minimal amount of solvent is volatilized, Effective oxygen removal can be achieved. Preferably, the dispersion is performed with minimal disturbance and agitation of the polymerizable formulation to minimize solvent evaporation. Also, the dispersion is preferably carried out at a gas flow rate that thoroughly disperses the microbubbles into the polymerizable formulation. In a preferred embodiment, the inert gas is dispersed in the feed for about 1 to about 30 minutes, more preferably for about 3 to about 10 minutes, and even more preferably for about 5 to about 8 minutes.

By dispersing the inert gas in the polymerizable composition according to the invention, very effective oxygen removal can be achieved. In a preferred embodiment, the deoxygenation step removes oxygen to less than 500 ppm. In a more preferred embodiment, the deoxidizing step removes oxygen to less than 200 ppm, and in a more preferred embodiment, removes oxygen to less than 100 ppm. In a further preferred embodiment, the oxygen is removed to less than 20, 10 or even 5 ppm. In a preferred application, the degree of oxygen removal refers to the amount of oxygen that must be removed to remove excess oxygen content from the formulation.

After the dispersion is complete, the polymerizable formulation is usually saturated with an inert gas and remains saturated with the inert gas during the polymerization to an ophthalmic lens. However, the formulation may lose some inert gas content through subsequent processing steps, such as pumping and dose injection into the mold. Formulations that have lost some of the inert gas through such processing steps are still considered substantially saturated with the inert gas. Lenses obtained from formulations that have lost some inert gas content for such subsequent processing and may have lost some inert gas content during polymerization are still within the scope of the present invention, It is considered substantially saturated with inert gas.

A preferred deoxygenator includes a substantially enclosed body sealed by a cap. A valve device, including a series of valves, allows the polymerizable compound and the dispersing gas to enter the body,
Easy to get out of the body.

In operation, reduced pressure draws the polymerizable formulation through the line into the device and immediately through the filter assembly. The flow control valve may be adjusted to adjust the flow rate of the polymerizable compound entering the device. After being filtered, the polymerizable composition flows by gravity, passes through a valve device, exits and enters the body.

When the body contains sufficient ingredients of the polymerizable formulation, it is deoxygenated by contacting the polymerizable formulation with a suitable inert gas. The distribution valve is adjusted to regulate the flow rate of the pressurized inert gas entering the valve device via the line. The pressurized inert gas extends to the bottom of the body via a porous frit at one end of the tube, where it is discharged to the raw material of the polymerizable compound by a frit glass gas dispersion tube that discharges the inert gas. . Preferably, the porous frit includes a number of pores that allow fine bubbles to be extruded into the polymerizable formulation and dispersed evenly. The conical bottom of the body is particularly effective for thoroughly and evenly dispersing the air bubbles in the formulation. In a specific embodiment, the deoxygenator comprises a coarse or extremely coarse 8 mm inner diameter frit glass gas distribution tube commercially available from Fisher Scientific. In a more preferred embodiment, the apparatus comprises a very coarse 8 mm inner diameter frit glass gas distribution tube commercially available from Fisher Scientific.

The bubbles move through the formulation and effectively displace dissolved gases, especially oxygen, in the formulation with an inert gas. The gas leaving the polymerizable composition first recombines with the polymerizable composition in the body and then leaves the device through a gas discharge valve.

In some cases, a monitor may be provided integral with the deoxygenator to monitor the concentration of oxygen remaining in the polymerizable formulation during dispersion, or to monitor the oxygen in the gas released through the gas outlet valve. The concentration may be monitored to ensure that the polymerizable formulation is removed from the deoxidizer after it has been sufficiently deoxygenated. The deoxygenated polymerizable compound is removed from the body via a tube. The deoxygenated polymerizable compound is preferably withdrawn from the body by a pump integrally connected to the tube via a valve. The valve device may optionally be equipped with a recirculation valve that allows the excess polymerizable compound to be recycled directly to the body while maintaining an inert gas distribution environment.

After sufficient deoxygenation of the polymerizable formulation, all or a portion thereof is transferred to one or more ophthalmic lens-type devices. In a typical method, the deoxygenated polymerizable formulation is first
A pump pumps the deoxygenator from the deoxygenator to a reservoir that is isolated from the surrounding gas and preferably backfilled with an inert gas. In some applications, the formulation may be agitated while in the reservoir to ensure thorough mixing and prevent phase separation. If desired, a pump integrated with the dispensing device draws the formulation from the reservoir through the line and into the dispensing device. The dispensing device dispenses the carefully metered polymerizable compound through a plurality of lines into a mold assembly that includes a plurality of mold cavities. The dispensing device has a ceramic valveless positive displacement dispensing head in combination with a stepping motor control, for example,
It is preferably one of the precision liquid metering and dispensing systems available from Ivek of North Springfield, Vermont, USA.

After dispensing the formulation into the lens mold cavity, the mold is sealed and polymerization is initiated. A variety of lens mold designs suitable for practicing the present invention are known. However, it is preferred that the lens-shaped composition contacted by the polymerizable substance is made of an inert composition. Polypropylene is a particularly suitable type of composition. A suitable mold assembly is
For example, U.S. Patent Nos. 5,658,602, 4,153,349 and
, 640,489. In some cases, the lens may be manufactured in a spin-cast type, such as that disclosed in US Pat. No. 5,260,001. In addition, the shaped lens may be subsequently lathed to produce the final lens.

[0061] The polymerization of the formulation may be initiated by any means known to those skilled in the art, and in some cases by a photoinitiator to carry out the photopolymerization. The photopolymerization can be initiated by actinic radiation, for example light, in particular UV light of a suitable wavelength. After forming the polymer lens, the ophthalmic lens is removed from the mold, for example, by solvent swelling and other methods known to those skilled in the art.

The polymerization is preferably carried out in an environment having almost no oxygen. Suitable gases from which the polymerization can be performed include, without limitation, nitrogen, helium, argon and carbon dioxide, with nitrogen being particularly preferred. Thus, in a preferred embodiment, the polymerization is carried out in an atmosphere having less than about 500 ppm oxygen. More preferably, the atmosphere surrounding the polymerizable formulation contains less than about 200 ppm oxygen. More preferably, the surrounding environment contains less than about 100 ppm oxygen, and most preferably the oxygen content is less than about 20 ppm.

In general, it is preferable to deoxygenate the lens mold and strictly remove oxygen from the molding environment. However, such removal is not always necessary, especially when using molds with low oxygen permeability, for example polypropylene molds. A preferred technique for degassing the lens mold is to store the lens mold in an oxygen-free or substantially free environment for a period of time sufficient to achieve substantial equilibrium. Preferably, the lens mold is stored in an inert, substantially oxygen-free atmosphere, such as nitrogen or carbon dioxide, until use. The preferred method of degassing the mold is to subject the mold half to an inert atmosphere having an oxygen concentration of less than 100 ppm for at least 4 hours. A more preferred method involves exposing the mold half to an inert atmosphere having an oxygen concentration of less than 50 ppm for at least 6 hours. In a further preferred method, the lens mold halves are exposed to an inert atmosphere having an oxygen concentration of less than 20 ppm for at least 8 hours.

In another embodiment of the present invention, the method of manufacture is practiced by inhibiting the release of volatile solvents from the polymerizable formulation during dispersion. In a specific embodiment, the release of volatile solvents is suppressed by bubbling an inert gas through the polymerizable formulation and then through a selectively permeable membrane. The membrane is permeable or substantially permeable to inert gases and oxygen and impermeable or substantially impermeable to volatile solvents. "Substantially permeable" and "impermeable" means that sufficient nitrogen and oxygen are allowed to escape from the inert gas dispersion to obtain an acceptable ophthalmic lens after polymerization, and Refers to the degree of permeation that prevents volatiles in excess. In another embodiment, the solvent evaporated from the polymerizable formulation is condensed during or after dispersion and returned to the polymerizable formulation before polymerization is initiated. The present invention also provides
It can be carried out by applying a vacuum to the formulation to remove entrained air bubbles prior to polymerization. However, in a preferred embodiment, such a depressurization step is omitted.

Moreover, it will be apparent to one skilled in the art that various modifications may be made in the present invention without departing from the scope or spirit of the invention. For example, the various steps of the present invention can be performed in a continuous or batch manner, or by following a modified approach in which one or more of the steps are performed continuously and one or more of the steps are performed in a batch manner. Can also. In addition, the polymerizable compound need not be prepared all at once, but the components of the polymerizable compound may be separately deoxygenated as long as the compound is sufficiently filtered and deoxygenated prior to initiating the polymerization. Or can be added and mixed with other components of the polymerizable formulation at any stage of the process.

Examples The following examples are intended merely to illustrate the invention and not to limit the scope of the invention. Unless indicated otherwise, parts are parts by weight, temperature is in ° C. or is at room temperature, and pressure is at or near atmospheric.

The polymerizable formulations used in Examples 1 and 2 consisted of 50 parts by weight of oxygen permeability enhancing prepolymer (polydimethylsiloxane), 30 parts by weight of hydrophilicity enhancing prepolymer (dimethylacrylamide), 20 parts by weight of TRIS, It was prepared by adding and mixing 33.3 parts by mass of (ethanol) and 0.5 part by mass of a photoinitiator (Darocur). The formulation was aliquoted between two containers and the contents of each container were subjected to a single molding operation.

Example 1-Degassing Comparative Example The contents of the first vessel were degassed on a high efficiency three channel Gastorre apparatus using an in-line porous tube / vacuum method known in the art. The device was made of Teflon tubing and had a total void volume of 36 ml (12 ml per channel). About 4 to about 6 ml of the formulation were degassed per minute.

Example 2 Deoxygenation According to the Method of the Invention The contents of the second vessel were deoxygenated according to the method of the invention. Fisher Scienti
Glass dispersion tube with a porous frit (extremely coarse) obtained from fic (8 m inside diameter)
m) was inserted into the formulation and nitrogen was bubbled through the formulation at about 2 psi for about 10 minutes. The flow rate was adjusted to obtain substantially uniform cell penetration in the formulation while maintaining a smooth laminar flow of cells. To minimize solvent loss, a / k / a parafilm from American National Can, a breathable film designed to prevent water vapor transmission, was wrapped around the formulation container opening. After deoxygenation, cap the container,
Transferred to oxygen sensor.

The starting and ending oxygen concentrations for both deoxygenation methods were recorded in ppm. Table 1 summarizes the results.

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[Table 1]

Terms in Table 1 ^* Based on experiments using similar monomers. ^** Average ppm values at oxygen sensor inlet and oxygen sensor outlet.

The deoxidized formulations from Examples 1 and 2 were also analyzed for% solids to determine the amount of solvent lost by evaporation. A 2 ml sample of each deoxygenated formulation was injected into the gas chromatograph, whereby the retention times were compared to control samples. Regression analysis was performed and% solids was calculated. Since the amount of macromer could not be measured directly, the known amount was subtracted from 100. Table 2 lists the results for the two samples. Control amounts are shown in parentheses at the beginning of the column.

[0074]

[Table 2]

Example 3 Comparative Degassing Method According to US Pat. No. 5,435,943, 8.5 ml / min of a monomer containing excess oxygen (17 ppm) was added to a 60 meter porous silicon tube (1/3 inner diameter). (4 inches) under a reduced pressure of 4 Torr to obtain a monomer having a concentration of 0.58 ppm. Table 3 shows the oxygen removal efficiency of the method of US Patent No. 5,435,943,
5 shows a comparison with the removal efficiency achieved in Example 2 by the method of the present invention.

[0076]

[Table 3]

As shown in Table 3, the nitrogen bubbling of the present invention was performed as described in US Pat.
The polymerizable formulation was deoxygenated at 22.4 times the deoxygenation rate achieved in No. 3.

Example 4 Molding of Lenses from Deoxygenated Formulations The deoxidized formulations of Examples 1 and 2 were subsequently molded by pouring 0.072 ml of each formulation into 400 lens molds. The formulation was infused by a precision dose infusion pump. The lens mold was made of polypropylene. Polymerization was initiated by application of UV light. All lenses obtained from these examples were within quality control standards. The results from the two formulations are listed in Table 4 below. The standard is shown in parentheses at the beginning of the column.

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[Table 4]

Terminology in Table 4 Dk: oxygen flux measured at barrer / mm (ie [(cc oxygen) / cm ² ] × [s / mmHg] × 10 ⁻¹⁰ ) IP: ion permeability (cm ² / s × 10 ⁴ ) O. D. / B. C. : Outer diameter (mm) / base curve (mm) Modulus: Elastic modulus NVE: Non-volatile extractable substance ( ^* NVE standard is based on historical data)

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IS, JP, KE, KG , KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZW (72) Inventor Domushke, Angelica, Georgia, United States of America 30096 Da Ruth Enfield Way 3379 F-term (reference) 4F204 AH63 AH74 AM30 EA03 EB01 EE02 EE21 EF02 EK07

Claims (14)

[Claims] 1. A method comprising: a. Preparing a polymerizable formulation containing an excess oxygen content; b. Contacting the polymerizable composition with a gas that is inert or substantially inert with respect to the polymerizable composition to deoxygenate or partially deoxygenate the polymerizable composition; c. Transferring all or a portion of the polymerizable formulation to an ophthalmic lens mold; d. Obtaining an ophthalmic polymer lens by polymerizing all or a part of the polymerizable compound, to obtain an ophthalmic polymer lens. 2. The polymerizable formulation comprises about 40 to about 80 parts by weight of one or more oxygen permeability enhancing prepolymers, about 10 to about 40 parts by weight of one or more hydrophilicity enhancing prepolymers and about 10 parts by weight of TRIS. The method of claim 1, comprising from about 20% to about 20% by weight. 3. The method of claim 1, wherein said polymerizable formulation includes volatiles. 4. The method of claim 1, wherein said polymerizable formulation comprises from about 10% to about 40% by weight of volatiles. 5. The polymerizable formulation comprises volatiles, and the weight percent of volatiles in the formulation can vary by up to 5% without substantially affecting the ophthalmic lens. The method of claim 1. 6. The method of claim 3 wherein said inert gas is contacted with said polymerizable formulation during a period when said volatiles are completely or minimally volatilized. 7. The method of claim 1, wherein said contacting is performed for about 3 to about 10 minutes. 8. The method of claim 3, further comprising the step of inhibiting the release of volatiles from the polymerizable formulation during dispersion. 9. After contacting the inert gas with the polymerizable formulation, the inert gas is permeable or substantially permeable to the inert gas and oxygen, and non-permeable to volatile volatiles. 9. The method of claim 8, wherein the release of volatiles is suppressed by passing through a selectively permeable membrane that is permeable or substantially impermeable. 10. The method of claim 3, further comprising the step of condensing volatiles volatilized from said polymerizable composition during or after contacting and returning the condensed volatiles to said polymerizable composition. 11. An ophthalmic lens prepared by the method of claim 1. 12. An ophthalmic lens polymerizable formulation that is saturated or substantially saturated with an inert gas. 13. An ophthalmic lens prepared from an ophthalmic lens polymerizable formulation that is saturated or substantially saturated with an inert gas. 14. An ophthalmic lens saturated or substantially saturated with an inert gas.