RU2380229C2 - Method for making batch of soft contact lenses - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention is related to methods and equipment for serial production of ophthalmologic lenses. Method for production of a batch of soft contact lenses from sheet of hard, mostly dry material, consists in the fact that at first batch of lens shaped blanks is molded from material with application of controlled physical force to this material, and then batch of lens shaped blanks is hydrated, and at least immediately after physical moulding of lens blanks, batch of lens shaped blanks is left at least partially attached to sheet of material.

EFFECT: improved quality of produce, and also reduced number of technological process stages, reduced volume of materials required for processes, and reduced negative impact at environment.

26 cl, 1 dwg

Description

FIELD OF THE INVENTION

The invention relates to methods and equipment for the mass production of ophthalmic lenses, such as soft contact lenses, and ophthalmic lenses produced by their use.

State of the art

Traditional methods for the production of ophthalmic lenses are the manufacture of a lens blank by polymerizing a liquid monomer in the form and subsequent machining of the blank by finishing and polishing to remove defects and optical imperfections of the lens. Such methods are both laborious and expensive.

Currently, two-sided casting technology (DSCM) has been developed for these purposes. Technologies of this kind typically include the manufacture by molding of the original disposable positive and negative forms. Liquid monomers are placed in a negative form, after which the positive and negative forms are combined. Further, to form the required polymer lenses, the monomers are cured by heat treatment (the term “cured” in this case means that the material that has cured ceases to be soluble in those solvents in which it was dissolved before processing, and, accordingly, the term generalizes such more specific concepts like polymerization, crosslinking, vulcanization, etc.). Then the lenses are removed from the molds and washed to remove unreacted monomers and / or solvents. After that, the molds are removed, and the lenses are stacked in ready-made kits.

It should be noted that in double-sided casting technology more control is required in the manufacture of disposable molds than in the manufacture of lenses themselves. The most common way to make single-use molds is to mold them between two plates equipped with removable, precision-machined form inserts. Changing the shape configuration (for the production of lenses with different optical properties) is achieved by changing the inserts on the press plates. The inserts are usually made on precision lathes and then polished until the surface defects disappear. Some optical properties of lenses can be obtained by adjusting the position of the positive and negative forms used in double-sided casting technologies.

Thus, the shape and optical properties of the lenses manufactured by the two-sided casting method are determined by the shape of the disposable forms removed after the manufacture of the lenses.

US Pat. No. 5,508,317 provides a method for upgrading standard DSCM technology in which an aqueous prepolymer solution is placed on the mold and cured by crosslinking. In the claims of this invention, it is claimed that thus, in standard DSCM technology, it is possible to more efficiently carry out the washing / removing steps of unreacted reagents.

Other enhancements to standard DSCM technology include the use of at least one mold suitable for reusable or transparent to ultraviolet radiation to use ultraviolet stimulation of polymer cure.

WO 98/42497 proposes a method for curing lenses using only ultraviolet radiation.

Patents US 4,673,539 and US 4,786,445 describe various technological concepts, including the manufacture of thermoplastic blanks of a special form from hydrogels by thermoforming non-crosslinked polymers (in some cases containing an ethylenically unsaturated monomer with at least one trigaloacetoxy substitution group), followed by solvolysis of the blank in the presence of diluent with obtaining a polymer molded product and the final stage of hydration of the already molded product to obtain ophthalmic h. As stated in these patents, such a process allows to obtain lenses with improved and controlled water-absorbing characteristics.

The problems of DSCM double-sided casting technology include inconsistency in product quality, which is caused by both difficulties in controlling the quality of the molds during the two-stage procedure for their manufacture and the instability of the polymer curing process. In the commercialization of this technology, the curing process always turns out to be dependent on deviations in the composition of the monomer and deviations in the composition of the components of the monomer. In practice, the curing process is also sensitive to the curing rate due to fluctuations in the energy of the curing source (usually thermal).

All currently existing technologies have disadvantages associated with low efficiency of manual labor, as in the best case, they require significant involvement of manual labor in the manufacture of batches of products, and in the worst case, it is necessary to use the labor of qualified specialists at each stage of production in the manufacture of products by special order. As a result, the cost of producing ophthalmic lenses is relatively high.

Disclosure of invention

The present invention is to develop a method for the production of ophthalmic lenses with increased efficiency in the use of manual labor compared with the production methods currently used. In particular, the production method proposed in the present invention improves the conditionality and quality of products, as well as reduces the number of stages of the technological process for the production of lenses in comparison with existing methods for their production.

Another objective of the present invention is to reduce the volume of materials required for the pressing and curing processes of the lenses, which, thus, will reduce the negative impact of this production on the environment.

The next objective of the invention is to reduce, compared with existing methods for the production of negative environmental impacts, the processes of pressing and curing lenses by reducing the volume of liquid chemical treatment of polymers and related chemical waste treatment.

To solve the above problems, the present invention provides a method for producing a batch of soft contact lenses using a solid, mainly dry material, soluble in water at a temperature above the threshold. Lots of lens blanks are made from this material by applying controlled physical effort to the material, after which, to obtain a batch of soft contact lenses, shaped blanks are hydrated to the necessary degree at a temperature below the threshold (above which the material is soluble in water). Moreover, at least immediately after the physical formation of the lens blanks, the batch of shaped lens blanks remains, at least partially, bonded to a sheet of material.

In a preferred embodiment of the production method proposed in the present invention, the "threshold temperature" above which the workpiece material is soluble in water is either about 50 ° C or about 65 ° C.

In a preferred embodiment of the method, said material is selected from the group consisting of polyvinyl alcohol, a copolymer of polyvinyl alcohol and polyvinyl acetate, polyethylene maleic anhydride, polymethyl hydroxy propyl cellulose, a copolymer of methyl acrylates and ethyl acrylate with ethylene or a hydroxyl derivative thereof.

Preferably, said material is a copolymer of polyvinyl alcohol and polyvinyl acetate, in which the degree of hydrolysis of the esters to form carboxylic acids is at least 96% per mole with respect to the starting polyvinyl alcohol.

In a preferred embodiment, said material is used, which is predominantly a non-crosslinked polymer containing groups suitable for crosslinking, and before hydration, said shaped lens blanks are treated with high-energy radiation with crosslinking of said polymer with a predetermined, desired density.

Preferably, a material is selected containing additives to enhance crosslinking efficiency due to their reaction to high-energy radiation.

In a preferred embodiment, a batch of shaped lens blanks is irradiated with high-energy radiation selected from the group comprising electron beam irradiation, gamma-ray beam irradiation, microwave irradiation with microwave waves, ultraviolet radiation, infrared light, heat or ultrasound.

Mentioned material is preferably used in the form of a sheet.

A sheet of material can be used as a carrier medium or vehicle for the said batches of shaped lens blanks.

After forming batches of shaped lens blanks, said batches of shaped lens blanks are completely removed from the sheet of material by using a laser cutting device.

Physical molding can be implemented by one of the processes included in the group comprising thermal molding, vacuum molding, pressing, hot molding, cold molding, direct compression, injection molding.

It can also be carried out with intermediate steps: heating the said material to a temperature close to the softening temperature of the material with the possibility of thermal molding, but lower than the melting temperature of the said material while maintaining its physical solidity, and thermally molding the said batches of shaped lens blanks using physical force to the mentioned material.

When thermally forming batches of shaped lens blanks, material can be pressed between two forms or plates.

In physical molding, molds can be used between which said material is placed, compressed together and the aforementioned batches of shaped lens blanks are molded.

It is preferable to subject said batches of shaped lens blanks and / or said batches of soft contact lenses to high-energy radiation, thereby sterilizing them.

Preferably, the high energy radiation is selected from the group consisting of electron beam irradiation, gamma ray beam irradiation, microwave irradiation in the microwave range and ultraviolet radiation.

The batches of lens blanks are subsequently transferred for installation in the form of batches of finished sets. Preferably, pre-packaged kits are sterilized before being laid.

It is advisable to add aseptic or sterilizing solution to sterile ready-made kits, which is also used to hydrate lenses.

It is desirable to expose the material of the shaped lens blanks in the finished sets to a chemical reaction, such as hydrolysis.

All stages of the technological process following physical molding are carried out without human contact and without manual control. Thus, it is an automated or semi-automated process and provides continuous or semi-continuous operation.

In this case, you can control the quality of only shaped lens blanks. Control can be carried out visually or using an optical system.

A soft contact lens made in accordance with all of the above options for producing a batch of soft contact lenses is also provided.

A device is proposed for the production of a batch of soft contact lenses, including means for molding the material with the application of controlled physical force to the sheet of material with molding a batch of shaped blanks of lenses, means for transporting the sheet material.

Means of transporting sheet material may include a roller table provided and / or not equipped with a drive. They may also include means for capturing the edges of the sheet of material and means for guiding the movement of said gripping means along the desired path.

Means of direction of movement may include a chain mechanism or a belt mechanism, equipped and / or not equipped with a drive.

Means for molding the material preferably include a set of molds or plates set to form a batch of shaped lens blanks.

At least one of the aforementioned molds or plates is provided with heating means to provide heating of said sheet of material to facilitate the lens forming process.

The mentioned sets of plates can be equipped with sets of removable upper and lower decorating inserts having a shape that enables the molding of shaped lens blanks with desired optical properties.

Advantageously, the forming inserts are installed with the possibility of transmitting positive or negative pressure to the material.

The device may also include means for stacking the aforementioned shaped blanks of lenses in finished sets.

The styling means are preferably installed with the possibility of styling in a predominantly sterile environment.

The device may also include means for removing said shaped lens blanks from a sheet of material and means for forming peripheral edges of the shaped lens blanks.

Means for removing shaped lens blanks from a sheet of material may be a laser cutting device, which may include a CO ₂ laser.

In a preferred embodiment, the device includes a means of irradiation with high-energy radiation of the aforementioned shaped blanks of lenses and / or soft contact lenses obtained from the said shaped blanks of lenses. Preferably, they include electron beam irradiation means.

A soft contact lens made using the above device is also provided.

The present invention has many advantages over current ophthalmic lens production methods.

When using the present invention, deviations from the required exact shape of the lenses observed in existing methods of lens production due to shrinkage of molds during cooling and due to shrinkage of the volume of the initial monomer during its polymerization (usually the shrinkage value is roughly estimated at 16%, which is very difficult, are eliminated) control with great accuracy).

When using the invention, there is no need to store and maintain a supply of disposable molds that are not currently in use.

Since in this case there is no need for the manufacture of disposable molds that are not part of the finished product, the present invention allows the most radical way to reduce consumption and material loss.

Due to the fact that the steps of the technological process proposed in the present invention are more easily controlled than in existing industries, it becomes possible to more accurately withstand the requirements for the optical power of the lenses, higher surface quality of the lenses and improved compatibility of the lenses with each other compared to lenses, produced by known methods.

Some special versions of the present invention offer a higher degree of sterility, higher quality packaging and operational phased control of production than existing technical solutions. These improvements can lead to less stringent requirements for production facilities.

An advantage of the present invention compared to existing methods of using glass molds of repeated use is that the proposed method for the production of lenses does not require such frequent washing and control of their cleanliness.

In known methods for manufacturing lenses using processing of the material in the form of exclusively ultraviolet radiation, an ultraviolet absorbing agent cannot be placed in the lenses, as this interferes with the polymerization process. Non-ultraviolet irradiation is possible in the present invention, which makes it possible to manufacture lenses containing ultraviolet absorbing agents, if this is desirable for any reason.

Other aspects and advantages of the present invention will become apparent after studying the following detailed description and drawing, in which a specific embodiment of the contact lens manufacturing process is described. In the future, contact lenses are considered as a specific example of ophthalmic lenses, and irradiation with an electron flux is considered as a specific example of a high-energy lens treatment.

The drawing shows a schematic illustration of equipment for the production of contact lenses in accordance with the considered embodiment of the present invention.

The implementation of the invention

The drawing shows a schematic representation of one of the possible embodiments of the invention. The production plant is seasoned with a roll of sheet polymer 1, which is fed into the heat-forming zone 14 of the blanks. Before feeding the preforms to the heat-forming zone, the sheet polymer is examined using an automatic video system 2 to identify significant material defects, such as holes, which lead to unsatisfactory quality of the final product.

In the production process, the Mowiol ^® polymer (a material manufactured by Clariant GmbH) can be used - a copolymer of polyvinyl alcohol and polyvinyl acetate, in which the degree of hydrolysis of esters with the formation of carboxylic acids is at least 96% per mole relative to the initial polyvinyl alcohol.

The polymer sheet is heated to a temperature at which the polymer is easily deformed during thermal molding and takes the desired shape defined by the forming inserts on the pressing plates 3 and 9, however, the polymer sheet retains significant strength, which allows you to control the sheet during the process.

Then, the polymer sheet passes through the heat-forming zone, where plates 3 and 9 are provided with forming inserts (not shown) with optical properties. Plates give the polymer sheet the desired shape. Depending on the properties of the sheet polymer, the press plates and inserts can be heated or cooled, as required to obtain the necessary plastic deformation and optical purity of the formed part of the sheet. To achieve the desired shapes of the workpieces using plates or inserts, both pressure and vacuum can be used. The optical inserts and their body parts mounted in the plates are designed so that the formed parts of the material are not completely separated from the original polymer sheet, so that after the molding process is completed, the formed parts of the sheet move forward together with the polymer sheet 12.

The formed parts are monitored using an automatic video system 4 in order to search for defects. After control, the polymer sheet with molded parts can be stored for future use or processed immediately during a continuous or semi-continuous process by passing it under a sterilizing electron stream emitted by station 5.

In cases where the polymer is not completely crosslinked, the electron irradiation can be adjusted so that its effect on the polymer sheet and the formed parts of the sheet leads to crosslinking that meets the technical requirements, as well as to a sterilization level that meets the technical requirements. The formed parts of the polymer sheet are separated from the sheet and placed in the form of ready-made kits in a sterile environment, schematically shown in the drawing as station 5. However, it should be noted that packaging can occur at a separate station that is not associated with electron irradiation (not shown) .

Ready-made kits are manufactured and / or processed at station 6 in an environment that keeps them and the molded parts of the sheet polymer sterile. Ready-made kits are transported 13 so that molded parts of the sheet polymer can be placed in them. Ready-made kits, already containing the formed parts of the sheet polymer, are fed inside the sterile medium to the metering station 7, where they are added with an aseptic or sterile packaging / hydrating solution at a controlled temperature, which should be lower than the temperature at which the polymer becomes soluble in water. After that, the finished sets with the solution and molded parts of the sheet polymer are sealed at station 8 in metal foil packages, also in a sterile environment, before leaving the working area for final marking.

The term “ophthalmic lenses” as used herein refers to any medical devices or vision correction devices using lenses, including contact lenses, intraocular lenses, inserts and overlays for the cornea, devices for administering drugs to the eye, devices for treating eye wounds, etc. d.

Part of the manufacturing process in which polymer crosslinking occurs involves the irradiation of dry lenses with high-energy radiation. The term "high-energy radiation", as used here, refers to radiation of various nature and includes such radiation as thermal, infrared, ultraviolet, microwave, gamma radiation, ultrasound, electron flow, but is not limited to them.

The term “polymer crosslinking”, as used herein, is used to describe a process in which a soluble polymer is converted into insoluble forms due to the formation of internal bonds between the polymer chains. It will be apparent to those skilled in the art that in a polymer having an insoluble form, in addition to crosslinked structures, there may also be structures known as grafted polymers or woven polymers.

One of the purposes of polymer crosslinking, implied here, is to make it possible to obtain a strong water-saturated lens from a dry lens that meets specified requirements in order to provide correction of optical power for the user.

Water soluble crosslinked polymers are known as hydrogels.

The term “polymer” as used herein refers to a material that allows the lens blank to be molded and includes materials such as copolymers, polymer blends, interpenetrating polymer networks, partially crosslinked polymer systems, as well as polymers with additives that promote crosslinking or reduce the ability to transmit ultraviolet having therapeutic purposes or changing the color of the polymer for cosmetic reasons, etc.

The sources of energy and radiation used to crosslink the polymer can be different, as well as the exposure time, which depends on the composition of the polymer and the required properties of the lens. In common cases of ophthalmic lenses, namely in hydrated contact lenses, the water content in the finished lenses can be from 20 to 75% of their weight. In the general case, the crosslink density of the polymer also determines the water content in the lens, i.e. the higher the crosslink density, the lower the water content.

The required level of both polymer crosslink density and sterility can be achieved simultaneously using optimally selected radiation.

In the general case, it is desirable that any crosslinking process be as fast as possible, preferably in less than 10 minutes, even more preferably in less than 4 minutes, most preferably in less than one minute. In order to withstand the requirements for quality and performance, some polymer compositions may require more than one irradiation cycle. However, at the same time, it is necessary to guarantee the safety of the process control personnel and the clean environment. For these reasons, the radiation energy used for the polymer crosslinking process can be taken lower than what is practically required for crosslinking in one cycle. In these cases, several stitching cycles have to be used.

In those cases in which crosslinking of the polymer by electron beam or gamma rays is effective, the polymer may contain additives known as “proradicals” in an amount of 0.2 to 5% by weight, which stimulates the crosslinking process. These components may be vinyl or allyl compounds, such as triallyl cyanurate, triallyl isocyanurate or pentaerythritol tetramethacrylate.

Doses of radiation depend on the reaction of the irradiated polymer and on the level of prorad in it if used. Typical doses are in the range of 20 to 800 kGy, however, it is desirable to remain in the range of 20 to 500 kGy, preferably in the range of 20 to 200 kGy and even in the range of 40 to 120 kGy.

Finished packaged lenses can also be sterilized using any other suitable means (e.g. ETO, gamma rays, steam treatment, etc.). Sterilization products should be selected carefully enough so that they do not significantly alter the properties or parameters of the lens or package.

Claims (26)

1. A method of manufacturing a batch of soft contact lenses from a sheet of hard, predominantly dry material, in which a batch of shaped lens blanks from said material is first formed with a controlled physical force applied to this material, and then said batch of shaped lens blanks is hydrated, characterized in that at least immediately after the physical formation of the lens blanks, the batch of shaped lens blanks is left at least partially bonded to a sheet of material. 2. The method according to claim 1, characterized in that said solid, predominantly dry sheet material is soluble in water at a temperature above the threshold, and said batch of shaped lens blanks is hydrated at a temperature below the threshold. 3. The method according to claim 2, characterized in that the hydration is carried out at the said threshold temperature, basically equal to 50 ° C. 4. The method according to claim 2, characterized in that the hydration is carried out at the said threshold temperature, mainly equal to 65 ° C. 5. The method according to any one of claims 1 to 4, characterized in that said material is selected from the group consisting of polyvinyl alcohol, a copolymer of polyvinyl alcohol and polyvinyl acetate, polyethylene maleic anhydride, polymethyl hydroxy propyl cellulose, a copolymer of methyl acrylates and ethyl acrylate with ethylene or a hydroxyl derivative thereof. 6. The method according to claim 1, characterized in that the said material is a copolymer of polyvinyl alcohol and polyvinyl acetate, in which the degree of hydrolysis of esters with the formation of carboxylic acids is at least 96% per mole relative to the original polyvinyl alcohol. 7. The method according to claim 1, characterized in that said material is predominantly an uncrosslinked polymer containing groups suitable for crosslinking, and before hydration, said shaped lens blanks are treated with high-energy radiation with crosslinking of said polymer with a predetermined, desired density. 8. The method according to claim 7, characterized in that they choose a material containing additives that enhance the efficiency of crosslinking due to their reaction to high-energy radiation. 9. The method according to claim 7 or 8, characterized in that the batch of shaped lens blanks is irradiated with high-energy radiation selected from the group comprising electron beam irradiation, gamma-ray beam irradiation, microwave irradiation with microwave waves in the microwave range, ultraviolet radiation, irradiation with infrared light, irradiation with heat or ultrasound. 10. The method according to claim 1, characterized in that the said material is sheet. 11. The method according to claim 10, characterized in that the sheet of material is used as a carrier medium or vehicle for said batches of shaped lens blanks. 12. The method according to claim 1, characterized in that after forming a batch of shaped lens blanks, said lots of shaped lens blanks are completely removed from the sheet of material by using a laser cutting device. 13. The method according to claim 1, characterized in that the physical molding is implemented by one of the processes included in the group comprising thermal formation, vacuum formation, pressing, hot molding, cold molding, direct compression, injection molding. 14. The method according to claim 1, characterized in that the said physical molding is carried out with intermediate steps: heating said material to a temperature that is close to the softening temperature of the material with the possibility of thermal molding, but below the melting temperature of the said material while maintaining its physical solidity, carry out the thermal molding of the mentioned batches of shaped lens blanks with the application of physical force to the said material. 15. The method according to 14, characterized in that during the thermoforming of a batch of shaped lens blanks, the material is pressed between two forms or plates. 16. The method according to claim 1, characterized in that during the physical molding use molds, and the said material is placed between the said molds, compress them together and form the aforementioned lot of shaped lens blanks. 17. The method according to claim 1, characterized in that the high-energy radiation sterilize said lot of shaped blanks of lenses and / or said lot of soft contact lenses. 18. The method according to p. 17, characterized in that the said batch of shaped lens blanks are subjected to high-energy radiation selected from the group including electron beam irradiation, gamma-ray beam irradiation, microwave irradiation in the microwave range and ultraviolet irradiation. 19. The method according to claim 1, characterized in that the consignment of lens blanks is transmitted for laying in the form of batches of finished sets. 20. The method according to claim 19, characterized in that the ready-made kits are sterilized before being laid. 21. The method according to claim 19, characterized in that an aseptic or sterilizing solution is added to the sterile finished sets and the lenses are hydrated. 22. The method according to claim 19, characterized in that the material of the shaped lens blanks in the finished sets is subjected to a chemical reaction, such as hydrolysis. 23. The method according to claim 1, characterized in that all stages of the technological process following physical molding are produced without contact with a person and without manual control. 24. The method according to claim 1, characterized in that it is automated or semi-automated with the provision of continuous or semi-continuous operation. 25. The method according to claim 1, characterized in that they control the quality of only shaped lens blanks. 26. The method according to claim 1, characterized in that they carry out visual quality control or quality control using an optical system.
Priorities: November 15, 2004 - claims 1-7, 10-12, 14-26; 01/13/2005 - pp. 8-9, 13.

Images