MXPA96004513A - Method for reducing hole faults in the lens in the production of templates for conta lenses - Google Patents

Abstract

The homogeneity and improved uniformity of the surface energy characteristics in a mold surface for the protection of a hydrophilic contact lens is achieved with the temporary application of an active surface agent such as Tween 80, to facilitate wetting of the optical surface of the mold, especially the convex mold with the reactive monomer mixture

Description

METHOD TO REDUCE HOLES DEFECT IN THE LENS IN THE PRODUCTION OF TEMPLATES FOR CONTACT LENSES DESCRIPTION OF THE INVENTION The present invention relates to methods for reducing defects in, and a significant improvement in performance, in the production of templates for contact lenses. You have particularly, provide measures to control and It will lead to rninirno defects in the templates known as lens holes. The contact lens prepared from hydrophilic polymeric materials are now well known, and are prepared commercially in large volume in manufacturing facilities automated. Since these products are designed to maintain intimate contact with you, great care is taken to ensure that they comply with strict standards of quality role. This can result in a high rejection rate, adversely affecting the economy in its production.

Accordingly, it is an object of this invention to contour and minimize stencil defects, specifically lens holes. Furthermore, it is an object of the present invention to provide a method that functions for high speed automated manufacturing operations 2b for improved performance adversely affected by 'rejections due to lens holes. Traditionally, it is an object of the present invention to provide means for reducing the defects of lens holes that originate in the filling operation and which are attributable to an uneven distribution of the mixture of reactive monomers that form the lens template. Finally, it is an object of the present invention to provide a method for effecting even distribution of the mixture of reactive rnonomers around and on the convex or curved back mold. The procedures for preparing idrogel hydrophilic contact lens insoles are well documented. Briefly, the mixture of reactive monomers (RMM) for the formation of hybrid contact lenses is distributed in a concave or forward curve mold, formed from a hydrophobic polymer such as polystyrene, in a filling station. A convex or curved mold is then coupled back with the curve mold to advance and form the lens template therebetween. Thereafter, a mechanically associated assembly formed from the forward bend / RMM / back curve curve through a UV curing tunnel under conditions to cure the RMp is traversed. The products of the cured lens template associated with the forming molds are then dissociated by removing the bend mold backwards. The curing assembly (lens lens / forward bend mold) is then passed through leach and hydration tanks, and thereafter a contact lens is produced.The continuous process that completes the entire manufacturing process uses a lens mold manufacturing zone, which comprises the first and second injection molding stations for the formation of concave and convex molds, respectively and includes a transport line on which the oncave and convex portions of the lens can be transported from zone to zone, a closed zone ("nitrogen tunnel") maintained under nitrogen to remove the gas to the halves or sections of the mold with the reactive monomepca composition, a reliable filling zone filling concave mold sections with mononepca reactive composition, recording the sections concave and convex of the molds in aligned relation, and coupling the same in a molding mating relationship optionally ba or vacuum conditions and previously curing said reactive monomeric composition with ultraviolet light to a gel-like state, and an area of cure in which the cure is completed and the finished lens template is ready for demoulding. It will be appreciated that the whole process <and integrates via means of transport, generally one or more conveyors on or in relation to which are assembled, arranged or intercalated lens molds in the course of transport to said areas or stations in operational sequence. Lens molds may for convenience be located on or on small pallets (e.g., made of cast aluminum, stainless steel or the like) containing a number of lens molds (e.g., eight) regularly arranged thereon in correlated spatial relationship with the treatment stations and the automated material transfer equipment where they are used. All cmturons or transport tunnels are under nitrogen blankets or inert gases. In greater relative detail, the concave or forward bend mold incorporating an optical molding surface with a peripheral zone or flange for interactive engagement with the convex or curved back mold is passed through a marking station in the which a peripheral flange portion of the mold is treated with a surfactant material without coming into contact with the optical surface of the mold. The mold is then filled, sometimes overflowing with the reaction reactive mixture with which the forward bend mold engages in a paired relationship with the convex or curved mold backward (the optical surface of which is untreated). t ípicarnen + e); the matched assembly, juxtaposed including the RNCI molded between them, passes to a curing station and then to a first demolding station in which the sections of the mold are uncoupled. Facilitated by the presence of the surfactant on the peripheral flange of the forward curve mold, the excess material is separated from the remainder of the cured lens template and retained with the convex or curved mold back; the optical portion of the lens is then retained by the forward curve mold with which the excess waste material can be removed from the curve mold backwards by any appropriate mechanical means, whereby the forward curve mold associated with the Lens template retained free of excess peripheral material is passed through leaching and hydration stations at the end to be de-molded, the contact lens to be collected and prepared for packing. As illustrated in Figures 1 and 2, molds 1 and # 2, which are shown in steps 101 and 10? in the flow diagram of Figure 1, respectively mold parts or sections of curved lens molds forwards and backwards curves respectively; they can be located one after the other as shown in Figure 2 or to shorten the exposure to the atmosphere a bit more, it can be localized in a common plane that intersects a bifurcated transport line, even oriented perpendicularly to it in the same place »Robotic means 103, 104 adjacent to the registration and coupling station are provided to receive the concave and convex lens oldes, respectively and transfer * said mold part to an oxygen low environment at a high cycle speed of production such as is observed in step L05. In the course of or after the degassing of the lens mold sections as indicated in the number 10fi of Figure 1, the blades that blunt, concave and convex mold eccities are arranged in interleaved relation and degas when they are enclosed in a powered conveyor so that the automated equipment can affect their operative coupling in relation to molding. The sequencing conveyor 32 including the interleaving station 40 is enclosed and presumed on its full length with an inert gas, conveniently, nitrogen. The amount of nitrogen is not critical, being adequate to use just enough nitrogen pressure to exclude so effective the atmosphere under the operating conditions that are experienced. In the nitrogen tunnel surrounding the sequence carrier 32 the mold templates prepared for contact lenses are degassed as indicated in step 106 of Figure 1. The lens cap molds were wound with the reactive monomer composition in the Step 107 and the concave and convex lens molds are placed in register and are quickly transported for complementary molding ratio. The filling and assembly zone 50 surrounds a portion of the transport means 32, which supply the concave and convex sections of lens molds to the zone pallets, respectively, and at the end of the zone it transports palettes of paired and filled molds to the area of previous curing. The filling and assembly area illustrated in Figures 2 through 50 is defined as a transparent, geometrically appropriate housing generally of rectangular cross section formed of any suitable thermoplastic or metal and thermoplastic construction. As illustrated at number 107 of Figure 1, the concave sections of the lens mold are filled with degassed monomer composition from step 108, and then transported to an assembly module optionally having a vacuum chamber formed intermittently within the nitrogen tunnel in which the concave lens-filled molds are coupled with convex mold sections in vertical alignment and in paired relationship, such that the reactive monomer composition is trapped between the optical surfaces of the respective mold sections and by at least partially sealed by the engagement of the partition edge formed peripherally in each of the lens mold sections. If it is present, the vacuum will be read. Afterwards, the matched mold is passed to nitrogen triads to the previous curing station, an integral delivery of the nitrogen tunnel. After assembly of the mold part, the incipient lens mono-object is previously cured in step 109 in the pre-cure module 60 of the present invention. The pre-cure procedure involves clamping the mold halves in register and then precurating the monomer or mixture of oneroeros to a gel-like state. After the cure, the polymerization of the monomer or monomer mixture is completed in the healing tunnel 75 as indicated in the. step 110 with radiation. In the curing zone (75), the monomer / diluent mixture is then cured in a UV furnace by means of which the polymerization is completed in the rnonomer (s). This radiation with visible or ultraviolet radiation produces a polymer / solvent mixture in the form of the desired final hydrogel. In addition, the curing zone also has a heat source which is effective to raise the temperature of the polyepable composition to a temperature sufficient to assist the propagation of the polymerization and to act against the tendency of the polymeric composition. to shrink during the period that is exposed to ultraviolet radiation. After the polymerization process is completed, the two halves of the mold are separated during a stripping step leaving the contact lens in the first half or curve mold forward 10, from which it is subsequently removed. It should be mentioned that the forward and backward curve mold halves are used for a single molding operation and then they are dumped or discarded. The heating of the backward curved lens mold creates a differential expansion of the heated mold polymer relative to the lens cooling polymer which changes one surface with respect to the other. The resulting cutting force breaks the adhesion of the polymerized lens / polymer mold and aids in the separation of the portions of the mold. The greater the temperature gradient in the surfaces of the mold portions, the greater the shear strength and the easier the mold portions will be separated. This effect is the highest when there is a maximum thermal gradient. As time goes on, the heat is lost by conduction from the rear mold portion to the lens polymer and the mold portion forward and then collectively to the surrounding environment. The heated back mold portion is, therefore, promptly removed so that very little energy is transferred to the polymer lens, avoiding the possibility of thermal decomposition of the lens. The heating can be achieved by techniques known to those skilled in the art such as by steam, lightning and the like. The process of demolding by being is described in the US patent. No. 5,294,379 issued to Ross, et al. If the heating step is hot air or steam, after the warm-up step, the backward curve is lever-pulled from the forward bend and molded into the mold assembly, as indicated in step III. If, on the other hand, the heating is by means of beams or infrared, the lever is not used and the curve mold to spontaneously separates from the forward curve mold. Each one of the LO release assemblies of mold separation 90 physically leverage the curve mold half backward 30 from the forward bend half 10 of each contact lens mold to physically expose each contact lens located in the lens mold for transportation to a hydration station for the hydration of the lenses. The lever utilization process takes place under carefully controlled conditions so that the backward half 30 separates from the forward curving half 10 without destroying the integrity of the lens formed in the lens mold. After the mold assemblies have been separated in the de-molding apparatus 90, each vane containing the forward curve mold halves with a polish-abraded contact lens exposed thereto, is subsequently transported to a hydration station for hydration and demolding from the forward bend, inspection and packing lens mold as indicated in Step 112. In the course of commercial operations including the high-speed production of len is in volume, a small number of defects may affect - Seriously the performance and economy resulting from the procedure. This is particularly the case where, as a result of the use of automated manufacturing equipment, a defect in a single lens can result in the loss of a greater number of lenses with which, for example, the course of its interference is associated. via pallets or integral frames from one manufacturing station to another. Lens defects occur for many reasons, including the simple misalignment of manufacturing equipment, but as the latter can be easily corrected through adjustment of handling, the focus is mainly on the lens holes and the holes formed in the lens. the course of the filling and curing steps, using the rnonometric mixture (Rdrl). The lens holes include voids, i. and. areas that do not contain mono eros, wells, for example, areas of non-uniform thickness and other similar regularities such as uneven edges, being a function of the spreading efficiency of the reactive monomer mixture on the surface of the convex mold of backward curve when the two mold halves come together. The puddles, another lens defect, are generated during the healing step in random configurations or three branches that are along the edge of the lens, and are associated with the concave or forward curve mold. High-speed photography has shown that the formation of lens holes in the filling operation during the spread of the advancing meniscus of the mixture R? 1H over the convex or curved mold backwards. However, the occurrence of the defect is apparently indiscriminate, especially considering the number of sound lenses produced in the same way on the same equipment. It has already been established that on a macroscopic scale, the Rrl well moistens the surface of the polystyrene mold. However, fundamental studies (based on the work reported by R. H. Dettre and R. E. Johnson 3r.

Chem. 68, 1507 (1096) and in Surface and Col 1 oid Science, E. Ilatijevic, Ed., Liley Interscience, NY, 1959, 161.2 pp 85 and S. P. Wesson TRI Progress Report # 49, Textile Research Institute, Ppnceton, N.3., August 23, 1992) show that the surface of the mold, formed of a hydrophobic polymer such as polystyrene, is a low energy heterogneous surface having a small portion of high energy surface domains. This is consistent with the knowledge that the molding resins were typically manufactured for injection molding purposes to contain certain additives including mold release agents which can provide the high energy domains on the surface of the mold. The need for means for modifying the surface activity at the interface between the convex backward curve mold and the reactive monomer mixture in the context of dynamic lens formation during molding and in particular, during the original contact with the Rffl and the advancing meniscus of it over and through the convex mold. In particular, it was desired to establish during the molding an increase in the high energy surface area exhibited by the convex mold.

In order to improve the high-speed molding and mass production of such hydrophilic contact lenses, two pair molds incorporating mold structures supported by vanes have been developed; for example, such as is described in the US patent. No. 4,640,489 issued to Larsen, and methods for forming configured polyimepic hydrogel articles, such as hydrophilic contact lenses elucidated in the disclosures of US Patents. Nos. 4,680, 336 and 5,039,459 issued to Larsen et al. The release of hydrophilic contact lenses from adherent surfaces of mold subsequent to completion of the contact lens molding process can be facilitated or improved on, as disclosed in the description of the US patent. No. 5,264,161 issued to Druskis et al. In that case, surfactants are introduced into the solution to a hydration cloth used in the molding cavities to make molds of hydrophilic polymer structures or contact lenses. The surfactant which is dispersed in the hydration bath at concentrations not exceeding 10% by weight helps to facilitate the release of the lenses from adjoining contiguous mold surfaces in separation, the function of such a surfactant. reducing the surface tension properties of water or liquids and thereby reducing the level of adhesion between the components consisting on one side of the contact lenses and on the other side, the mold surfaces that became adherent during molding. Numerous types of surfactants are described in the present invention, such as polymeric surfactants including polyoxyethylene sorbitan rnononoleates, which are especially suitable for releasing any hydrophilic polymer article in an undamaged state from the adhesive surfaces of the mold. which are made of plastic materials. The patent of E.U.A. 4,159, 292 discloses the use of silicone wax, stearic acid and mineral oil or additives for plastic mold compositions to improve the release of the contact lens from the plastic molds. The use of surfactants applied on the surface as release agents in connection with the manufacture of hydrogel contact lenses is described and claimed in the US patent. 5,542,978 commonly assigned. In that patent, a thin film of surfactant such as T een 80 is applied by a marking head to the surface regions extending around, for example, peripherally to the forward curve of a mold part for forming contact lenses, to facilitate release of the lens after demolding-all or part of the peripheral rings of the RI1M material extruded externally from the mold by virtue of the overflow during the filling. In this application, no active material is applied to the portion of the mold that defines the optical face of the lens. The present invention is directed to a method for modifying the surface energy of hydrophobic contact lens molds to improve the properties of their reactability and release for reactive resin mixtures for hydrophilic hydrogel contact lenses, comprising predominantly monomers of acplato, said method comprising covering the surface of at least one of the optical mating surfaces of said molds with an effective amount of 0.05 to 0.5 by weight of a surfactant, prior to contacting said mold surface with said mono-epca mixture. reactive The present invention further relates to a method for producing hydrogel contact lens insoles comprising forming a lens template from a curable UV curable composition adapted for hadrogel contact lenses between the concave mold surfaces. and paired convexes including the steps of deposition of the composition rnonomepca in and on the concave surface of the mold and coupling the convex mating mold surface to conform from there, the monomer mixture in the form of a contact lens for UV curing, improves which comprises the contact surface of the convex mole and a surface active agent, to increase the surface area comprising the high domains. surface energy in an amount sufficient to reduce the defects of lens holes made in the contact lens insoles thus produced. The present invention is still directed to a method for modifying the contact surface of a convex mold composed of polystyrene for the production of hydrogel contact lens templates, to increase the surface areas of the high energy domains, hence, increasing the hydroceptibility of said surface by means of a hydrophilic nonorneric composition for the molding of templates of hydrogel contact lenses comprising providing said contact surface in or prior to the molding cycle with a uniform application of a sufficient surfactant to reduce the defect? of lens holes in said contact lens templates. In accordance with the present invention, a method is provided for minimizing slow holes in the manufacture of a hydrogel contact lens comprising modifying the surface energy characteristics of the convex or curved back surface. pair that comes into contact with the reactive monomer mixture for said hydrogel contact lens structures. More specifically, the high-energy surface area on the face of the convex mold or of the back curve which in contact with is modified to improve its hurnactability by the reactive monomeca mixture. In a preferred embodiment, the convex mold is pretreated by applying an active surface agent to at least the face of the mold which comes into contact by spraying, dipping or by any appropriate means. Such pretreatment can be effected, for example, by spraying on the contact face of the convex mold a surfactant such as T een 80, Glucam P40 1 Glucam DOE 120, suitably in a solvent carrier therefor such as water, alcohol or mixtures thereof. to provide a concentration of 0.05 to 5.0% w / w of surfactant. The pretreatment may be applied in conjunction with for example, to precede each molding cycle or may be carried out intermittently, to maintain the energy surface requirements necessary for the reduction of lens hole defects. The amount of surfactant to be used will be determined by a certain balance between measurements taken to ensure the desired release of the lens preferentially from the convex molding surface at this stage.; and the demolding of the lens from the concave mold or curve forward following the cure. Thus, in one embodiment, the concave or forward curve mold can be formed from a composition incorporating a compatible agent such as zinc stearate while the surface of the convex or backward curve mold is periodically treated with an agent surfactant according to the present invention as mentioned above.

In this way, it is shown that lens hole defects can be reduced by several percentages in a high-speed automated pilot production line thus effecting savings in the substantial economy while increasing the efficiency of the manufacturing operation. Figure 1 is a flow diagram of the continuous process for the production of contact lenses, including the molding, treatment and handling of molds and contact lenses in a low oxygen environment. Figure 2 is a flat top elevation view of the production line system. In accordance with the present invention, the inter-facial tension between the reactive monomer mixture, specifically the advancing meniscus thereof, and the optical surface of the convex mold or backward curve is controlled and minimized by normalizing and extending the surfaces. of area representing domains of high surface energy at the contact surface of the convex mold. This is achieved by the temporary or transient application of a surfactant to the optical surface of the convex mold in effective amount and characteristics to increase the population of high surface energy area on the surface of the convex mold to provide improved hurnectability by the RfM. and effecting a differential in surface energy as well as between the respective mold halves to overcome the energy required to separate the two halves of the mold and preferentially carry out the retention of the optical lens portion in the forward bend mold. Thus, it would be appropriate to consider the surface characteristic expressed in and on the forward curve mold when applying the precepts of the present invention, since it is desired to ensure that the lens template is demold preferentially from a mold surface consistently to Through the manufacturing process, usually (and as described in the present invention) from the convex mold, thereby allowing the retention of the lens template in the concave mold of forward curve so that it runs towards and through the molds. Remaining manufacturing stages. Accordingly, it is necessary to take into consideration, in relation to the type and amount of surfactant to be applied to the convex mold surface, whether the forward or concave curve mold has been previously treated, usually by an internal additive such as stearate zinc to modify the release characteristics of the mold supe fi ic. Specifically, the practice of the present invention is implemented in a manner that ensures that, with respect to the surface energy retention characteristics of a mold surface, a certain effective differential is induced in the second surface of the mold surface. mold to effect preferential displacement iobe a consistent basis throughout the manufacturing process. As mentioned above, it is understood that it is preferred that the aforementioned differential favors the release from the convex surface, especially because the benefits of the reduced defects in the lens arising from poor wetting of the convex surface with RrM can also vepfi carse. The nature of the surfactant material employed in the present invention is not critical, insofar as it is capable in the wetting characteristics relative to the RMM and in the differential release characteristics relative to the accompanying mold surface to which it is not you apply this to achieve the benefits of the invention as outlined here. Naturally, to the extent that the surfactant is absorbed into the RMM, or remains to some degree on the surface of the Lens after hydration, it will be selected with respect to its physiological or pharmaceutical acceptability for human use upon entering contact with the eye Circumstances that modify the surface tension of the surfactant in the circumstances that are obtained will be determined with respect to the desired differential release property.; and the characteristics that modify the surface energy are determined in relation to the improved homogeneity for the NMR in relation to the mold surface (in particular, the convex mold surface, as mentioned above) in a well-known manner by those skilled in the art. The surfactant material is also selected for its compatibility with the mold materials and the reactive monomer mixture. While, as a consequence, the quantities to be applied may differ in their response to these characteristics, it has been found that in most cases, an application for the surface of the mold selected in the range of 0.05 - 2.0% by weight of a solution of the surfactant material is sufficient, usually 0.05 to 2.0% by weight. In addition to the advantages that reduced lens hole defects provide in the differential release of the mold halves at or after the curing stage, the application of the surfactant to the forward bend mold remains effective in facilitating the release of the contact lens template to par-tir- The mold surface after hydration. that is, the release from the concave mold or curve forward, without the application of heat or special mechanical manipulation. Among other surfactants, antistatic agents, ionic surfactants, nonionic surfactants or lubricating formulas can be used in the present invention. Suitably, the surfactant constitutes a solution or dispersion of the active surface agents in an essentially inert vehicle to facilitate application to the mold surface by spraying,? '? rubbing, depositing steam, washing with sponge, dipping or similar. Thus, an alkanol or mixtures thereof can be used satisfactorily and economically to form a solution or dispersion of the surface active agent. Among the materials that are found that not only help in the wettability of the mold surface but also retain the characteristics of the effective release for the demolding of the lens from the forward bend mold (where they are applied) after the hydration and equilibration in saline are Tween 80, a monooleate of polyethylene oxide, Glucarnate DOE-120 and ethoxylated dioleate (120) of methyl glucoside, and Glucarn P-10, a propoxylate of methylglucose of 10 moles, available from of A erchol Corporation. Water-soluble or water-dispersible materials are generally preferred for their ease of application. As the mole materials are typically manufactured from hydrophobic materials such as polypropylene or polystyrene, the efficiency of wettability for these materials is signi icant. Preferably, the tensile agent is constituted by Tween 80 (registered trademark); for example a Poisorbate 80. This is basically polyethylenesorbide oxide monooleate or the similar equivalent and consists of a sorbitol oleate ester and its anhydrides copolymed with about 20 moles of ethylene oxide for each mole of sorbits and anhydrides. of sorb itol, generally of formula: [The sum of w, x, y, z, is 20; R is (Ci7H33) C00l Other materials suitable for use include the pharmaceutically acceptable ethoxylated amines and the quaternary ammonium compounds such as Larostat 264 A (dimethyl ethyl ammonium ethosulfate of soy sold by PPG), Arrnostat 410 (a tertiary amine etOxylated sold by Akro), Cystat SN (3-Laurarn? do? ro? l? tp and ilaronium ethyl sulfate sold by-Cytec) and Atrner 163 (N, Nb? s (2-hydrolethi) al (i? arnina)). Other quaternary compounds include the dianidoamines, the i idazoles, the quaternary salts of dialkyl dimethyl, the quaternary salts of dialkoxyl alkyl and the quaternary salts of onoalkyl tpmethyl. Some of these materials offer the additional advantage of being soluble in RMn and therefore, are conveniently reabsorbed in the lens material, not affecting the surface of the mold after release and hence making it easier to recirculate for later use , without cleaning it to bring it to a base or neutral condition. In general, suitable surfactant materials can be selected from those described in Kirk Oth er, Encyclopedia of "Chemical Technology, Vol. 22, pp. 379-384 (1983) .The surface active agent can be applied to the surface of mold by spraying, rubbing or dipping, as mentioned above, in such a way that the surface is completely covered with it.The mold dries with or without the aid of heat and is piled in batches for use in the process of The amount of surfactant applied in this manner is adapted to provide a uniform coating of a solution of 0.05 to 0.5% by weight surfactant on the surface of the mold as mentioned above.The application of the surfactant can be suitably integrated with the surfactant. alternately with the manufacturing process so that the mold can be treated immediately before its interpolation with the transport mechanism, or just before the filling operation, so that the surface of the same is completely wetted, for example, not dried at the point of contact with the reactive reactive mixture. In an alternative mode, the surfactant material such as Tween 80 can be incorporated into the reactive onomeca mixture at selected concentrations to reduce and control the lens holes. without inducing the formation of puddles on the concave mold. The molds can be made of any thermoplastic material which is suitable for mass production and which can be molded into an optical quality surface and with mechanical properties that will allow the mold to maintain its critical dimensions under the conditions employed in the process discussed below and that allows the porization with the initiator and the radiant energy source contemplated. The concave and convex mold members can thus be made from thermoplastic resins. Examples of suitable materials include polyolefins such as polyethylene, low, medium and high density polypropylene, including copolymers of them; poly -4-rnet-lpentene; and polystyrene. Other suitable materials are polyester resin, polyacrylic teres, polyarylene sulphate, nylon 6, nylon 66 and nylon 11. Polyester tepnoplies and various fluorinated materials such as fluorinated copolymers of ethylene propane and ethylene copolymers can also be used. fluoroethylene. It has been found that with the need for high quality, a stable mold and especially the use of a plurality of molds in high volume operations, the choice of material for the molds is significant. In the present invention, the quality of production is not assured by the individual inspection and classification of each lens by its power and curvature. Instead, quality is ensured by keeping the dimensions of each individual mold member within very restricted tolerances and processing the molds in particular sequential steps to give all lenses equal treatment. Since polyethylene and polypropylene partially crystallize during cooling from casting, there is a relatively large shrinkage causing dimensional changes that are difficult to control. Thus, it has also been found that the preferred material for the molds used in the present process is the polystyrene which does not crystallize, has little shrinkage and can be molded by injection at a relatively low temperature / for optical quality surfaces. It is understood that other thermoplastics, including those mentioned above, may be used provided they have the same properties. Certain copolymers or blends of polaolefins exhibiting these desirable characteristics are also suitable for the present purposes as are polyester copolymers and blends having such characteristics, as described more fully in US Pat. No. 4,565,348. The soft contact lens templates are formed from a reactive monomer composition which typically incorporates, in addition to the reactive substance, a water-replendable diluent in the case of the preparation of a hydrophilic lens, a polymerization catalyst to aid in healing of the reactive monomer, a crosslinking crosslinking agent and often a surfactant to aid in mold release. The curable compositions preferably include copolymers based on 2-hydroxyethyl ether ("HEMA") and one or more co -omers such as 2-hydroxyl acrylate, methyl acrylate, metacoplat methyl, viml pyrrolidone, N-vinyl acplamide, hydroxypropane ethacrylate, ha-oxyethyl acrylate, hydroxypropyl acrylate, isobutyl methacrylate, styrene, ethoxyethylamine, methoxy methacrylate, glycidyl methacrylate, diacetone acplamide, vinyl acetate, acrylamide, hydroxytrymethylene acrylate, rnetoxyethyl metacrate, acrylic acid, rnetacrylic acid, glycemic metaplatum and dimethylarnin ethyl acralate. Preferred polypnepzable compositions are described in the F.U.A. patent. No. 4,495,313 issued to Lar-sen, the patent of E.U.A. No. 5,039,459 issued to Lar-sen and the patent of E.U.A. No. 4,580,336 issued to Larsen et al. Such compositions comprise anhydrous mixtures of an inerachable polyester hydroxyester of acrylic acid, removable boric acid ester and a polyhydroxy compound preferably having at least 3 hydroxyl groups. Polymerization of such compositions, followed by removal of the acidic ester rich with water, produces a hydrophilic contact lens. The mold assembly used in the present invention can be used to make hydrophobic or rigid contact lenses, but the manufacture of hydrophilic lenses is preferred. The polyenergizable compositions preferably contain a small amount of an entanglement agent, usually from 0.05 to 2% and more frequently from 0.05 to 1% of a diester or triester. Examples of representative entanglement agents include: ethylene glycol diacral, ethylene glycol distenet, 1,2-butylene dimethacrylate, 1,3-butylidene tacritol, 1,4-butyl dimethacrylate, propylene glycol diacrate, propylene glycol dirnetacline, diethylene glycol dynetacral, glycol dimethacrylate, diethyl glycol dineethacrylate, dipropylene glycol dirnetacline, diacp Diethylene glycol lac, dipr-opylene glycol diacrylate, glycerine trinomethacrylate , tprnethylol propan t pacr-i lato, tprnethylol propan tr irnetacrylate and the like. Typical relaxant agents usually, but not necessarily, have at least two ethylene-unsaturated double bonds. The polishable compositions also generally include a catalyst, usually from 0.05 to 1% of a free radical catalyst. Typical examples of such a catalyst include peroxide, rozalo, benzoyl peroxide, isopropyl percarbonate, azobi sisobutyronotion, and redox system known as the combination of sodium mono-metabisulfite persulfate and the like. Radiation with ultraviolet light, electron beams or a radioactive source can also be used to catalyze the polymerization reaction, optionally with the addition of a polymerization initiator. Representative initiators include camphorquinone, ethyl 4- (N, Nd? Met? I-am? No) benzoate, and 4- (2-hydroxyethoxy?) Phen? L-2-hydroxyl-? 2 ~ prop? L cet ona. The polymerization of the polishable composition in the mold assembly is preferably carried out by exposing the composition to polymerization initiating conditions. The preferred technique is to include in the composition initiators that work after exposure to ultraviolet radiation; and exposing the composition to ultraviolet radiation of an effective intensity and duration to initiate the polymerization and allow it to continue. For this reason, the mold halves are preferably transparent to ultraviolet radiation. After the step prior to curing, the monomer is again exposed to ultraviolet radiation until the curing step in which the polymerization is allowed to continue until it is complete. The required duration of the reaction remnant can be easily determined experimentally for any polishable composition. The mold assembly comprises at least two parts, a concave female part (forward curving) and a male convex part (curved backwards), which form a cavity in the middle thereof and when said parts mate, At least one has a tab there. More particularly, the mold assembly comprises a front mold half and a back mold half which come into contact, thereby defining and enclosing a cavity therebetween, and a polymerizable composition in said cavity in contact with said mold halves, the front mold of which has a central curve section with a concave section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said concave surface in contact with said polirnenzahle composition has the curvature of the curve towards in front of a contact lens to be produced in said mold assembly and is sufficiently smooth so that the surface of a contact lens formed by the polymerization of said polymerizable composition in contact with said surface is optically acceptable, said front mold having also an integral annular flange with and surrounding said circumferential edge ci and extending therefrom in a normal plane towards the axis and extending from said flange, while the rear mold has a central curve section with a concave surface, a convex surface and a circular circumferential edge, wherein the portion of said convex surface in contact with said polishable composition has the curvature of the backward curve of a contact lens to be produced in said mold assembly and is sufficiently smooth so that the contact lens surface formed by polymerization of the polyethylene composition in contact with said surface is optically acceptable, said backward curve also having an annular integral flange with and surrounding said circular circumferential edge and extending thereon towards the axis of said convex structure, and a generally triangular appendage located in a normal plane towards said eey extending from that tab, where the The convex structure of said rear mold half comes into contact with the circumferential edge of the front mold half. The internal concave surface of the front mold half defines the external surface of the contact lens, while the convex external surface of the mold base half defines the inner surface of the contact lens resting on the edge. It is now known that the specifications of the constructions are referred to in the U.S. patent. No. 4,640,489 issued to Lar-sen. According to the present invention, a convex mold surface which has been previously treated with the surfactant as mentioned above, is paired in a paired manner with a forward curve mold and the reactive monomer mixture filling the mold cavity in the same manner. They are a hard process in which the optical surface of the convex mold comes into contact and, because of its modified surface, the RMM. It moistens so efficiently that the advancing meniscus uniformly covers the mold surface without the formation of lens holes. The convex mold, when mechanically separated from the concave mold by reason of its modified surface, (and consistently through the procedure, involving an interaction of similarly treated molds), efficiently releases the lens template (which remains with the concave mold for healing) without breaking or otherwise damaging the lens template. In a preferred embodiment, the forward curve mold is formed from a composition that comprises an aggregate mold release agent such as zinc stearate, which helps to unmold the lens template after hydration. Consequently, their surface energy characteristics are modified and an additional level of surfactant may be required in the application of the convex mold surface to balance the release characteristics in such a way as to ensure release of the lens template for retention of the concave mold surface or forward curve. It will be understood in connection with the foregoing description that the concepts as well as the theoretical considerations that affect the demolding are completely different from the problem of adequately wetting the surface of the forming mold with the composition rnonornepca although each consideration is inter-related to the others in the practice, for example, one can demold-successfully a lens template, however, is defective because it has one or more lens holes. The contact portion of the convex lens mold in particular must be receptive to the composition at the point and time of application under the conditions that are obtained then, in the sense that it requires efficient spreading controlled by critical wetness through of the contact surface of the mold to be established, increasing the surface area comprising high energy surface domains in the contact surface of the convex mold. While the present invention has been described with particular reference to the application of the surfactant to the optical surface of the convex mold in a particular manufacturing operation, including a generally vertical arrangement of the mating elements of the mold with the concave member generally supporting the template If the incipient lens is in a supine or inferior position, it will be understood that in order to effect a preferential displacement of the lens jig such as, for example, in other geometrical arrangements, the surfactant may be applied to the optical surface of any lens mold surface.

EXAMPLE 1 The convex molds are immersed in 2% aqueous solutions of Larostat 264 A (PPG), Armostat 410 (Akzo) and Cystat SN (Cytec), respectively, and then dried under ambient conditions for 48 hours. The cover thus formed makes the surface more huctable through the RMM, a composition based on HEMA. When the treated molds are used in an automated manufacturing pilot plant, the lens mold defects are reduced by approximately 34.6%.

EXAMPLE 2 Inert polyester molds for contact lens are rubbed with Glucam P-10, Tween 80 and an aqueous dispersion of Glucarn DOE 120 respectively, and the molds are used to mold contact lenses using a reactive monomer mixture comprising 96"B% of HEMA 1.97% metacpic acid, 0.78% ethylene glycol dirnetacp and 0.1% tlmethylpropane tnemethacrylate, and 0.34% dispersed Darvocur 1173 (48% RMM) in boric acid glycerin ester as an inert diluent removable with water . The mold halves are easily separated without the formation of defects.

EXAMPLE 3 LIM-dimethyl chloride-ammonium chloride is sprayed in an amount of solvent / blowing agent on the optical surface of a curved back mold. A test of tone supplying powders shows that the surfactants are well dispersed throughout the entire mold surface.

Claims (7)

NOVELTY OF THE INVENTION CLAIMS

1. A method for modifying the surface energy of hydrophobic contact lens molds to improve the hurnectability and release characteristics thereof for reactive monomer mixtures for hydrophilic hydrogel contact lenses comprising predominantly acrylate monomers, said method characterized in that it comprises covering the surface of at least one of the optical mating surfaces of said molds with an effective amount of 0.05 to 0.5 by weight of a surfactant, prior to the contact of said mold surface with said reactive monomer mixture.

2. The method according to claim 1, further characterized in that said contact lens molds are essentially composed of reindeer.

3. In a method for producing hydrogel contact lens insoles characterized in that it comprises forming a lens insole from a UV curable monomer composition adapted for hydrogel contact lenses between concave and convex surfaces of surfaces including the deposition steps of the monomerteous composition in and on the concave mold surface and coupling the monomeca composition with the surface of the convex mold to conforming therewith, the monomeric mixture in the form of a contact lens for UV curing, the characterized improvement because it comprises applying to the contact surface of the convex mold a surface active agent, to increase the surface area comprising high energy surface domains, in an amount sufficient to reduce the lens holes verified in the lens templates thus produced .

4. The method according to claim 3, further characterized by the fact that the composition is not hydrophilic.

5. The method according to claim 3, further characterized in that the convex mold is composed of a hydrophobic polymer co.

6. The method according to claim 5, further characterized in that the hydrophobic polymer co is pol test? - ene.

7. A method for modifying the contact surface of a convex mold composed of polystyrene for the production of hydrogel contact lens templates, to increase the surface areas of high-energy domains, thereby increasing the density of said surface by means of a hydrophilic monomer composition for the molding of hydrogel contact lens insoles, characterized in that it comprises providing said surface of contact in or prior to the molding cycle 1e a uniform application of a surfactant in sufficient quantity to reduce the lens holes in said contact lens templates.