DE2748568A1 - Hydrophilic silicone resin contact lens prodn. - by treating lens surface with gas plasma and opt. forming hydrophilic resin film by polymerisation - Google Patents

Abstract

A hydrophilic silicone contact lens is produced by: (a) casting a silicone resin monomer into a mould, (b) heading the monomer to polymerise it, (c) forming the obtd. blank into a lens and (d) subjecting the surface of the lens to a low temp. gas plasma to impart hydrophilic props. to the surface. In an alternative process a further step (e) is included comprising forming a hydrophilic resin film on the gas plasma treated surface. The lens has improved flexibility, hydrophilicity and adaptability to the eye.

Description

Process for the production of herdrophilic silicone contact

lenses The invention relates to a method for producing a Contact lens made from a hydrophobic silicone resin with a hydrophilic surface. In particular The invention relates to a method for producing a hydrophilic silicone contact lens, in which the surface of a silicone contact lens has a low temperature exposed gas plasma or the surface of a silicone contact lens is irradiated with a low temperature gas plasma. Further The invention relates to a method for producing a silicone contact lens with stable hydrophilic properties that remain constant over a longer period of time which additionally has a hydrophilic one on the lens surface exposed to the gas plasma Resin film is formed.

Silicone resins have been around for a long time because of their excellent properties Flexibility, oxygen permeability, Transparency, chemical Stability and thermal stability used as a material for contact lenses. However, if a contact lens made of a silicone resin is worn, they can inherent properties of the resin in the finished contact lens because of water repellency of the resin does not come into its own to a sufficient extent. Consequently, silicone resins became not yet unrestrictedly as a material for the manufacture of contact lenses accepted.

According to the invention, a very practical silicone contact lens has now been made Improved portability created by the contact lens in question from a Made of silicone resin and given its surface hydrophilic properties became.

Contact lenses produced according to the invention can, for example, consist of Hard contact lenses with polymethyl methacrylate as the main component and soft contact lenses en with poly-2-hydroxyethyl methacrylate as the main ingredient. The former are fortunate in an excellent way to correct ametropia and are also still relatively easy to use. Consequently, hard contact lenses are predominantly used at present prescribed and worn. However, since resin contact lenses are hard and hydrophobic, are they have the disadvantage that they adapt poorly to the eye and when Carry a large foreign object in the eye.

On the other hand, white contact lenses are made of a flexible hydrophilic Gel. The advantage of soft contact lenses is that they are excellent adapt to the eye tissue and only slight foreign body irritation when worn cause. However, since Veicbkontaktlinsen made of a hydrogel exist, let their dimensional stability, mechanical strength and ability to correct of ametropia left to wish for. In addition, their handling prepares for the necessary sterilization of the lenses difficulties.

Both the hard and soft contact lenses currently in use both have the disadvantage that they do not last for a long time can be worn. The main reason for this is to be found in the oxygen supply to the corneal tissue of the eye when wearing the contact lens is insufficient. Consequently In order to manufacture contact lenses, data should have sufficient oxygen permeability own.

Ultimately, contact lenses should be worn continuously over a long period of time will. It has now also been found that as starting materials for production Silicone resins used by contact lenses have sufficient oxygen permeability to deliver an adequate amount of oxygen to the corneal epithelium. this also applies to closed eyes. So almost ideal contact lenses should be If you can make the silicone resins a greater flexibility and hydrophilicity and improves their adaptability to the eye.

According to the invention it has now surprisingly been shown that the silicone contact lenses with a hydrophilic surface which can be produced according to the invention are all Above mentioned requirements are able to meet in an excellent manner.

While there are a few publications relating to its manufacture of contact lenses made of silicone resins, however, the contact lenses in question have not yet found in practice because they are hydrophobic, a bad one Have adaptability to the eye and irritate foreign bodies when worn cause.

The invention now relates to a method for producing hydrophilic materials Silicone contact lens, which is characterized in that a) is a silicone resin monomer pour into a mold; b) the monomer is heated for polymerization; c) the received Molding processed into a lens and d) on the surface of the lens a low temperature causing gas plasma to act on the lens surface to impart hydrophilic properties.

The invention also relates to a method for production hydrophilic silicone contact lenses, which is characterized in that a) pouring a silicone resin ionomer into a mold; b) the monomer for the polymerization heated; c) the molding obtained is processed into a lens; d) a low temperature gas plasma on the surface of the lens can act to give the lens surface hydrophilic properties, and e) a hydrophilic resin film on the lens surface exposed to the gas plasma trains.

In the context of the method according to the invention, a silicone resin monomer is first used mixed with a catalyst and then mixed in a conventional manner defoamed. The resin mass obtained in this way is in a clean form made of metal, Cast glass or a plastic and heated in it to harden. The one here The molding obtained is then processed into a lens. However, as the silicone resin lens has a hydrophobic surface, poor adaptability to the eye possesses and causes a strong foreign body irritation, it must superficially a Hydrophobic treatment with a low temperature gas plasma Experienced. Here, the surface of the silicone resin lens is given to a depth from 20 to 30 mp (below the surface) hydrophilic properties.

According to the invention, for example gaseous oxygen are suitable as gases or nitrogen or gaseous ammonia.

When using an oxygen plasma, the density of the carbonyl and hydroxyl groups are increased on the surface of the silicone lens. When using a Ammonia gas plasma presumably forms amino groups on the surface of the silicone lens. Even if a nitrogen plasma is used, the surface of the silicone resin lens hydrophilic properties are imparted.

In the irradiation treatment of the surface of the silicone resin lens with a low temperature gas plasma is too high a plasma concentration and too long a treatment duration is undesirable, since in such a case the implementation progresses excessively. Conversely, the lens surface can be too low Plasma concentration and treatment duration that is too short no (sufficient) hydrophilic ones Give properties. Consequently, in order to make the surface of the silicone lens hydrophilic To be able to impart properties, a suitable plasma concentration and a suitable Duration of treatment are adhered to.

According to the invention, it is sufficient if the pressure of the from a 2 gas cylinder outflowing gas flow is 0.1 to 0.5 kg / cm2, in the system a pressure of 1 to 5 mm Hg column prevails, with a high frequency output of 10 to 50 W (plasma concentration) is worked and the treatment duration is 30 sec to 5 min.

Silicone resins customary according to the invention are suitable as silicone resins, for example those of the formulas: wherein R is -CH3, c2H5 or -C6H5. In this way, the surface of the silicone lens treated with a low temperature gas plasma can be given hydrophilic properties. At the same time, their wettability by water is improved. As a rule, the degree of hydrophilic properties is indicated by the contact angle between a drop of water and a flat solid surface to be tested. The contact angle for hydrophobic silicone resins is 1000 to 110 °, for poly-0 methyl methacrylate about 70 and for hydrated poly-2-hydroxy &: ethyl methacrylate about 400. The contact angle for the silicone lenses improved according to the invention is before the irradiation treatment or exposure to the low temperature Gas plasma about 1050 (hydrophobic), after the irradiation treatment or exposure to the low temperature gas plasma 200 to #Oo. This lowering of the contact angle shows that the wettability of the surface of the silicone lens is considerably improved.

If the lens is at a low temperature after the treatment having gas plasma is in air and allowed to dry, the contact angle decreases at the same time the surface of the lens slowly becomes hydrophobic again. It However, it has been shown that the hydrophilic properties - as they are - get preserved if you look at the lens in question after exposure to a low Temperature having gas plasma in water or in physiological saline solution kept. It follows that those with a gas plasma of low temperature treated silicone contact lenses in a hydrophilic state over a long period of time remain usable when stored in water.

The values for the contact angle of the invention with a gas plasma low temperature treated silicone resins can be found in the following table. The table also contains the contact angle values for the untreated Silicone resins and for polymethyl methacrylate.

Table I test specimen treatment contact angle gas immediately after after after bar after 1 2 months 3 moderation month # nasal treatment th * th * customary Silicone resin ** untreated 1050 - - -Polymethyl methacrylate untreated 700 - - -Commercial Silicone resin O2 200 330 330 330 n N2 200 330 350 350 n NH3 200 340 350 390 * in water stored ** Commercially available silicone resin monomer Only by letting it take effect a low-temperature gas plasma can be used to determine the wettability improve the surface of the silicone contact lenses sufficiently and their Increase adaptability to the eye. Furthermore, when keeping the relevant Lenses in water retain their hydrophilic properties for a long time can be obtained.

As mentioned before, go when you leave the lenses in question gradually lost their hydrophilic properties in air. To now also in this Trap to preserve the hydrophilic properties of the lenses in question Additionally on the surface exposed to the action of a low temperature gas plasma A hydrophilic resin film is applied to the silicone contact lenses.

Suitable as the hydrophilic monomers for forming the hydrophilic resin film for example alkylene glycol monoesters of acrylic and methacrylic acid, acrylamide, Methacrylamide and vinyl pyrrolidones. Of course, are suitable for production the hydrophilic resin coating also includes other hydrophilic monomers. If necessary can use a small amount of a hydrophilic one in forming the hydrophilic resin film Crosslinking agents are also used.

There are two different methods of making a hydrophilic one Resin film on a lens.

One method is to add a hydrophilic monomer to the with silicone contact lens treated with a low-temperature gas plasma of a graft polymerization to subjugate. In this case, the monomers mentioned can be used as hydrophilic monomers get used. The graft polymerization then takes place in the presence of water a redox catalyst, e.g. ceric ammonium nitrate or ammonium persulphate and sodium metabisulphite, at room temperature. The surface of a silicone resin is made by the plasma treatment activated so that a hydrophilic resin film is formed thereon without difficulty can.

In order to form the hydrophilic resin film, the one treated with plasma is used Lens in a solution of one part by weight of a monomer in 100 parts by weight entered the catalyst containing water. The implementation takes place by Stir the reaction mixture for one to two hours at room temperature.

The second method is that you get a hydrophilic monomer solution polymerized in a solvent using a low temperature gas plasma the treated silicone contact lens is immersed in this solution and then the one out of the solution removed lens heated in an electric oven to one hand the solvent to remove and, on the other hand, to complete the polymerization.

A film forms on the lens surface. As a solvent all solvents which contain the prepolymer or polymer formed are suitable able to solve evenly. Examples of such solvents are very diverse Alcohols, dimethylformamide, dioxane, benzene, toluene and the like.

However, if greater surface accuracy is required, it must the rate of evaporation must be carefully chosen and controlled.

In contrast to a silicone contact lens, which is only one treatment has experienced with the low temperature gas plasma, can superficially coated with a hydrophilic resin film, prior to the plasma treatment Subjected silicone contact lenses to their hydrophilic properties even when left lying down to retain air for a long time.

The contact angle values of coated with a hydrophilic resin film and silicone contact lenses previously subjected to gas plasma treatment are found in the following Table II. After the formation of the hydrophilic Resin film, the contact angle is initially comparatively large, but it changes later only slightly.

Table II Specimen Resin Film Film Image Contact Angle Formation Method Immediately after 1 month 3 months after the natural film formation commercially available acrylic Graft poly-silicone resin amide merization 330 380 400 2-hydroxy immersion methyl methode 460 490 500 thacrylate According to the invention, silicone contact lenses are more outstanding Oxygen permeability, surface hydrophilicity, transparency and flexibility produce. Furthermore, according to the invention, the possibility of using the relevant contact lenses to wear continuously over a longer period of time, increase.

The inventive change in the hydrophobic properties of silicone resins Hydrophilic properties can not only be found on contact lenses made from them, but also generally to those widely used in the medical field Apply silicone resins.

The following examples, in which all information is parts for "parts by weight" are intended to illustrate the invention in more detail.

Example 1 10 parts of a commercially available silicone resin monomer become mixed with 1 part of a commercially available curing catalyst, whereupon the obtained Resin mass thoroughly stirred, defoamed in a vacuum and then in a plastic / metal lens mold is poured. The resin mass poured into the mold is then used in an electrical Oven heated to a temperature of 650C for 4 hours. After that the will be lenticular solidified and hardened resin mass removed from the mold and to complete the polymerization for 1 hour at a temperature of 1000 and for 30 minutes at a Post-heated temperature of 1500C.

In a corresponding manner, 1 part of the resin composition described is applied poured a clean glass plate and heated to harden. The thin film serves as a test piece to determine the contact angle of the resin.

Thereafter, the obtained silicone lens is put into a vacuum pump placed on a pressure column of 2 mm Hg plasma tube. Through the pipe is gaseous oxygen passed. Now with a high frequency power of 25 W generates an oxygen plasma and treats the lens in the plasma for 1 min.

The silicone contact lens thus treated is thoroughly washed with water moisturizes.

The contact angle of the similar with an oxygen plasma low temperature treated thin silicone film is immediately after Treatment about 200 This means that by treating the hydrophilic properties of the resin can be considerably improved.

Namely, the contact angle of the same resin before the treatment is 1050

If the lens treated with the oxygen plasma and the one with the Oxygen plasma treated thin film kept in water change their hydrophilic properties are not noticeable.

Example 2 In the manner described in Example 1, a silicone contact lens and made a thin silicone film on a glass plate. The surface of the The lens and the thin film are then removed using nitrogen gas instead of the gaseous oxygen of a treatment with a low temperature having subjected to nitrogen gas plasma. The contact angle of the thin film is about 200. If the lens or thin film is kept in water, their or their hydrophilic properties practically do not change.

Example 3 In the manner described in Example 1, but under A silicone contact lens is used to replace gaseous oxygen with gaseous ammonia and a thin silicone film on a glass plate, each with a hydrophilic surface manufactured. The contact angle of the thin film is about 200. When storing of the lens or the thin film in water change their hydrophilic properties practically not.

Example 4 The one prepared according to Example 1, with an oxygen gas plasma treated silicone contact lens and also according to Example 1 made thin and with a low temperature oxygen gas plasma Bell-coated film on a glass plate is dissolved in a solution of 1 part of acrylamide immersed in 100 parts of water. A portion of an 0.1m solution is then used as a catalyst of ceric ammonium nitrate in In-nitric acid added. The implementable is under one A stream of nitrogen is allowed to drain at room temperature with stirring, with a graft polymerization of the hydrophilic acrylamide on the surface of the lens or

of the thin film takes place.

This silicone contact lens retains its hydrophilic properties for a long time, even when stored in air. The contact angle between a drop of water and the thin film on a glass plate is 330 immediately after thin film formation, 380 after one month, and 400 after three months.

Example 5 10 parts of 2-hydroxyethyl methacrylate are used in 100 parts of dimethylformamide and 0.2 part of diisopropyl peroxydicarbonate dissolved. The resulting solution is for 1 hour allowed to react with stirring at a temperature of 500C, whereby a viscous Obtains prepolymer solution. In this prepolymer solution according to example 2 obtained silicone contact lens treated with the low-temperature nitrogen plasma or that also according to Example 2 obtained with the nitrogen plasma low temperature treated thin silicone film dipped on a glass plate. The silicone contact lens will be removed from the prepolymer solution and the thin silicone film for removing the solvent and at the same time completely Polymerization of the resin film in an electric furnace to a temperature of 80 ° C heated.

On this is quietly on the surface of the lens or the thin Film formed a hydrophilic poly-2-hydroxyethyl methacrylate film so that the silicone contact lens provided therewith or the thin silicone film provided therewith a glass plate in each case obtained permanent hydrophilic properties.

The contact angle between a drop of water and the thin film is 460 immediately after the formation of the hydrophilic film on the silicone film, 490 after one month and 500 after three months.

Claims (9)

patentans # rüche 0 Process for the production of hydrophilic silicone contact lenses, characterized in that a) a silicone resin monomer is poured into a mold; b) the monomer is heated for polymerization; c) the molding obtained into one Lens processed and d) apply a low temperature to the surface of the lens having gas plasma can act to the lens surface hydrophilic properties to rent. 2. The method according to claim 1, characterized in that the Lens surface to the gas plasma for 30 sec to 5 min at a pressure of the off a gas flow of 0.1 to 0.5 kg / cm2 flowing out of the gas cylinder, a system pressure of 1 to 5 mm Hg column and a high frequency power of 10 to 50 W. 3. The method according to claim 1, characterized in that as a low temperature gas plasma, an oxygen gas plasma, a nitrogen gas plasma or choose an ammonia gas plasma. 4. A method for making hydrophilic silicone contact lenses, thereby characterized in that a) a silicone resin monomer is poured into a mold; b) the monomer heated for polymerization; c) the molding obtained is processed into a lens; d) a low temperature gas plasma on the surface of the lens can act to give the lens surface hydrophilic properties, and e) a hydrophilic resin film on the lens surface exposed to the gas plasma trains. 5. The method according to claim 4, characterized in that the Lens surface to the gas plasma for 30 sec to 5 min at a pressure of the off a gas flow of 0.1 to 0.5 kg / cm2 flowing out of a gas cylinder from-2, a system pressure of 1 to 5 mm Hg column and a high frequency power of 10 to 50 W. 6. The method according to claim 4, characterized in that as a low temperature gas plasma, an oxygen gas plasma, a nitrogen gas plasma or choose an ammonia gas plasma. 7. The method according to claim 4, characterized in that one for Formation of the hydrophilic resin film is a resin from an alkylene glycol monoester of the Acrylic or methacrylic acid, acrylamide, methacrylamide and / or a vinyl pyrrolidone used. 8. The method according to claim 4, characterized in that one for Formation of the hydrophilic resin film on the lens surface exposed to the gas plasma on the silicone contact lens treated with the low temperature gas plasma in water and in presence; a redox catalyst graft polymerized at room temperature. 9. The method according to claim 4, characterized in that one for Formation of the hydrophilic resin film on the lens surface exposed to the gas plasma a hydrophilic monomer solution-polymerized in a solvent with the a low temperature gas plasma treated silicone contact lens in the solution dips and then the lens is removed from the solution and removed of the solvent and simultaneous completion of the polymerization in one heated electric furnace.