MXPA97006417A - Method for unlocking, removing and cleaning polymeric articles with supercrit fluid - Google Patents

Abstract

The present invention relates to methods for unblocking a polymeric article from a mold and / or removing undesirable materials from a polymer article by applying supercritical fluid to the polymeric article. A preferred process is the treatment of ophthalmic lenses such as contact lenses. Supercritical fluid, composed primarily of carbon dioxide, is applied to a fixed contact lens to a mold subsequent to the polymerization step. The application of super-critical fluid (SCF) causes the lens to separate efficiently and consistently from the mold, remove undesirable materials such as monomers, unreacted oligomers or residual solvents from the lens core and / or clean the lens surface of the lens. Adhered burrs

Description

METHOD FOR UNLOCKING, REMOVING AND CLEANING POLYMERIC ARTICLES WITH SUPERCRITICAL FLUID BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates extensively to extraction and cleaning of polymer articles and mold separation processes. More specifically, this invention relates to processes for removing, cleaning and unlocking molded lenses. 2. DESCRIPTION OF THE RELATED TECHNIQUE The use of super-critical fluids (SCF) to clean and extract in the food industry is well known (See Chem. Enar .. Internat.Ed., Vol.100, no.3, p. 114-9). For example, the US patent. No. 3,806,619, issued on April 23, 1974 to Zosel, describes a procedure for decaffeinating coffee with supercritical fluids. Supercritical fluids have also been used to dry porous materials prepared in sol-gel processes. Extraction with supercritical fluids of hydrophobic polymers, such as polypropylene, has also been explored (See J. Appl. Polv. Sci .. 48, No. 9, 6/5/93, pp. 1607-9). In addition, porous sponges of biodegradable polymers have been formed by applying supercritical fluids in a form that requires a marked pressure drop (See PCT Int. Appl. No. WO 9109079, De Ponti). however, the efficient use of super-critical fluids requires high temperatures and pressures, which can damage certain polymeric materials. Numerous polymeric articles are formed by placing a monomer solution in a mold and then initiating polymerization. The efficient removal of molded articles from the mold represents a critical stage in the design of a manufacturing process. After the polymer article is separated from the mold, the article typically must undergo extraction processes to remove unwanted materials such as unreacted or partially reacted monomers (ie short chain oligomers or polymers) and residual solvent. An ophthalmic lens is an example of a polymeric article that can be molded in that way. Ophthalmic lenses such as contact lenses are typically formed from hydrophilic monomers in order to improve biocompatibility with the eye. Contact lenses formed from hydrophilic polymers are convenient, in part because hydrophilic contact lenses move well in the eye. This movement improves the flow of tears and burr separation under the lens, thus improving patient comfort. A method for forming a contact lens involves the lens from a preformed polymer disk, a so-called "button" lens. Another method for forming contact lenses as mentioned previously involves placing a monomer solution in a lens mold and polymerizing the monomer. Molding on both sides is an example of a second type of molding process that has gained popularity in recent years. For molding lenses, after polymerization, the lenses are typically "unlocked", ie they are separated from the mold, and subjected to extraction processes for a period of hours. The extraction processes remove unreacted monomers and partially reacted oligomer, solvents or other undesirable materials. These commercial extraction processes typically involve contacting the lenses with organic solvents such as isopropyl alcohol, to solvate the undesirable ones. These wet extraction processes are time-consuming and costly, producing a wet lens that is not suitable for immediate surface treatment. In addition, these extraction processes produce an effluent stream of solvent and monomer that is not easily discarded. In addition, the stage of unlocking the lens presents manufacturing problems. First, the unlocking must occur quickly and consistently, in order to maximize production efficiency. Secondly, the unlocking must be complete, that is, even smaller proportions of the polymer lenses must not remain attached to the mold. Incomplete locking typically results in substantial burr production volumes because the lenses are likely to tear when removed from the mold. Even moreeven slight imperfections in the lens surface caused by the lens adhering to the mold during unlocking, become large visual distortions for the lens user. In this way, there is a need for improvements in efficiency, safety, cost and minimization of burr in extraction processes and cleaning of polymer articles (especially ophthalmic devices). In addition, there is a need for an improved method for unlocking a polymeric article (especially an ophthalmic device) from a mold, immediately subsequent to polymerization. SUMMARY OF THE INVENTION It is an object of the invention to provide a method for removing undesirable materials from a polymeric article and / or cleaning from the surface of a polymeric article any undesirable materials that have adhered to the surface without introducing excessive organic solvents. Another object of the invention is to provide a method for rapidly and efficiently unblocking a polymeric article from a mold subsequent to forming the polymeric article by polymerization in the mold. A further object of the invention is to provide a method for simultaneously removing undesirable materials from a polymeric article and unlocking a polymeric article from a mold.

Still another objective of this invention is to reduce the production time required to process polymer articles. A further object of the invention is to reduce burrs of production in the manufacture of polymeric articles. Still another object of this invention is to reduce the amount of organic solvents required to produce polymeric articles. One embodiment of the invention relates to a method for removing undesirable materials from hydrophilic polymeric articles. The method involves contacting the polymeric article with a fluid supercritical to conditions and for a sufficient time to remove undesirable materials from the polymeric article. The removal may involve removal of undesirable materials from the polymer core or cleaning of undesirable materials from the polymer surface. In a preferred embodiment, ophthalmic lenses are contacted with supercritical fluids, especially supercritical fluids containing carbon dioxide to remove monomers, oligomers and / or solvents remaining from the preceding lens polymerization process. Another embodiment refers to a method for unlocking mold polymer articles subsequent to polymerization processes. The method includes the step of contacting the polymeric article with a supercritical fluid under conditions and for a time sufficient to separate the polymeric article from the mold. A preferred embodiment relates to a method for unlocking ophthalmic lens from molds subsequent to the lens polymerization process by contacting the lens with a supercritical fluid, preferably one including carbon dioxide. In yet another embodiment, a method is described for simultaneously removing undesirable materials from a polymeric article and unlocking a polymeric article from a mold. The method includes a step of contacting the polymeric article with supercritical fluid under conditions and for sufficient time to both remove certain undesirable materials from the polymeric article and separate the polymeric article from the mold. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view of a batch process super-critical fluid treatment apparatus with multiple components. Figure 2 is a side sectional view of an in-line super-critical fluid treatment apparatus. DESCRIPTION OF THE PREFERRED MODALITIES The present innovative methods for extracting undesirable materials from a polymeric article, unblocking a polymeric article from a mold and / or cleaning undesirable materials from the surface of a polymeric article, involve the steps of: (1) providing a current of supercritical fluid at predetermined pressure and temperature; (2) contacting a polymeric article with the supercritical (or near supercritical) fluid for a predetermined period of time; (3) stirring the supercritical fluid in such a way that at least one of the following occurs: (a) the polymeric article is separated (unblocked) from the mold, (b) monomer, unreacted oligomer and / or solvent are extracted of the polymeric article with the supercritical fluid, and / or (c) undesirable materials are removed from the surface of the polymeric article; and (4) removing the supercritical fluid, which may include monomer, unreacted oligomer and / or solvent of the polymeric article and the mold. A "supercritical fluid" as the term is used herein, means a substance at a temperature and pressure that places the substance at or near the supercritical regime. A temperature of at least about 20 ° C and a pressure of at least about 42.18 kg / cm 2 absolute (600 psia) is considered sufficient to achieve the advantages of the present invention. "Removing undesirable materials" as used herein, means either removing undesirable materials from the polymeric core or cleaning undesirable materials from the surface of the polymeric article. Undesirable materials that can be extracted include monomers, partially reacted oligomers, solvents, polymerization initiators and the like. Undesirable materials that can be cleaned on the surface of the polymeric article, include the aforementioned undesirable materials, burrs or surface contaminants, such as abrasives used in surface polishing processes, oils, and the like. The advantages that are achieved by the practice of the present invention are numerous. First, polymeric articles that are treated with super-critical fluids (SCF) are essentially "dry", ie solvent-free after SCF treatment, while organic solvent extraction, cleaning or unblocking processes result in "wet" products , ie some solvents remain in or on the article. In order to further process a polymeric article that is "wet", the article must be dried for a period of time and typically at elevated temperature. In contrast to the polymeric articles that have undergone SCF treatment they can almost immediately be indexed or passed to the next processing stage (for example a subsequent surface treatment process). Another advantage of the present invention is that the use of organic, potentially toxic, flammable solvents is minimized or eliminated. In this way, the invention increases safety in the manufacturing environment and / or reduces costs associated with protecting workers against the danger of organic solvents. On a similar note, the expenses and hazards associated with the disposal of depleted organic materials are reduced or eliminated with the present invention. The present invention offers yet another advantage to improve extraction efficiency. Extraction of contact lenses with supercritical fluids according to the present teachings can give monomer / oligomer concentrations of less than about 2 weight percent over a period of time of 1.5 to 3 hours, using a SCF-dioxide mixture. 5 percent carbon / 95 percent by weight isopropyl alcohol at approximately 3,785 liters (1 gallon) per minute as a flow expense. In contrast, removal of contact lenses with solvent typically results in monomer / oligomer concentrations at about 2% in a 24 hour time period. In this way, the current SCF extraction process results in the same product quality in a greatly reduced time frame. While the amount of unreacted monomer / oligomer remaining in the finished polymeric article that can be tolerated depends on the intended application of the polymeric article, the specifications for medical devices, ophthalmic lenses and the like are typically quite stringent. In this way, the present invention is particularly suitable for application in those areas that have restrictive regulatory requirements, especially in the ophthalmic lens industry. Polymeric articles that can be treated with supercritical fluids in accordance with the present invention include a wide variety of polymeric articles that are formed upon initiation of polymerization of a monomer mixture in a mold. Examples of these polymeric articles include without limitation, medical devices and components such as drug delivery devices (transdermal, ophthalmic, parenteral, etc.) and their components and in particular ophthalmic devices that include vision correction devices, such as eyeglass lenses. contact, eye implants, superimposed eye inserts and their components. Suitable polymers for the formation of polymeric articles which can advantageously be subjected to the currently described inventive processes include, without limitation, hydrophobic polymers, such as polyethylene, polypropylene, poly (vinyl pyrrolidone) or polysiloxanes.; hydrophilic polymers such as poly (2-hydroxyethyl methacrylate) and poly (vinyl alcohol); biodegradable polymers such as polylactides, polyglycolides and the like; and antimicrobial polymers such as polyquaternary ammonium compounds. Preferably, the SCF treatment processes of the present invention are applied to hydrophilic polymeric articles capable of forming hydro gels when equilibrated with water (i.e. capable of absorbing about 10 percent by weight of water or more). The SCF treatment processes of the present invention are preferably applied to contact lenses which are the copolymerization product of a copolyzable macromer and two or more copolymerizable monomers. The copolymerizable macromer is advantageously a macromer comprising a polysiloxane segment, even more preferably a polydimethylsiloxane segment. The macromer, also preferred, further comprises urethane linkages and two or up to five terminal vinyl groups which are suitable for a polymerization reaction with the copolymerizable monomers. A more preferred macromer comprises a polydi-ethylsiloxane segment to which vinyl isocyanate is attached, such as isocyanate ethyl methacrylate (IEM). The macromer may comprise other segments not specifically mentioned. Examples of these segments are perfluoropolyether segments, diisocyanates or gluconic acid derivatives. The first type of copolymerizable monomer used in conjunction with the macromer is a monovinyl siloxane having up to 15 silicon atoms. A preferred example is 3-tris (trimethylsiloxy) silyl-propyl methacrylate (TRIS). The second type of copolymerizable monomer used in conjunction with the macromer is a hydrophilic copolymerizable monomer as is usually employed in the manufacture of contact lenses. Typical examples are hydroxy-alkyl with 2 to 4 carbon atoms (meth) acrylates, such as 2-hydroxyethyl methacrylate, (meth) acrylic acid, dimethylacrylamide or N-vinyl pyrrolidone, of which dimethylacrylamide (DMA) is especially preferred. In view of the above it is preferred to apply the process of the present invention to a polymeric article which is a contact lens obtained from a mixture of a copolymerizable macromer and two or more, preferably two copolymerizable monomers as previously defined. The mixture of macromer, monomer of the first type and monomer of the second type, typically comprises in percent by weight, macromer: about 30 to 60%, monomer of the first type: about 12.5 to 35%, monomer of the second type: about 27.5 a 35% More preferably, the mixture comprises in percent by weight: macromer: about 33 to 56%, monomer of the first type: about 14 to 33%, monomer of the second type: about 30 to 33%. Three examples of highly preferred mixtures comprise approximately: 50% macromer, 20% monomer of the first type and 30% of the second type; 56% of macromer, 14% of monomer of the first type and 30% of the second type; 33% of macromer, 33% of monomer of the first type and 33% of the second type; In these mixtures, the monomer of the first type in particular is TRIS and the monomer of the second type more preferably is DMA. Especially preferred are the mixtures described in the examples, or the application of the described processes to contact lenses made from said mixtures, respectively. In addition, by applying the supercritical fluid immediately subsequent to substantial completion of the polymerization reaction, ie while the polymeric article is still in the mold, a remarkable advantage is obtained by unlocking the mold article. In this way, application of the SCF's at once immediately subsequent to the termination of polymerization can simultaneously unblock the article from the mold and extract undesirable unreacted monomers, partially reacted oligomers, solvents or other additives. This remarkable discovery provides the aforementioned advantages with respect to solvent reduction or elimination, while simultaneously eliminating the need for additional equipment or materials to separate the polymer article from the mold.

In the production of contact lenses, the present invention exhibits particularly remarkable advantages. Contact lenses that are molded in a two-sided molding process are typically formed in a hydrophobic polymer mold. A monomeric mixture, which commonly includes 2-hydroxyethyl methacrylate for "soft" hydrophilic contact lenses, is introduced into the mold. The mold containing monomer can be irradiated to initiate the polymerization. Once the lens has been formed, ie the polymerization is substantially complete, the lens must be removed, ie unlocked from the mold. Occasionally, the lenses are scraped due to damage caused during the unlocking stages, since the adhesion of the lens to the mold deteriorates the unlocking process. In addition, unreacted monomers and oligomers are undesirable materials that must be removed from the lens. The removal of undesirable materials can involve numerous subsequent processing steps, including solvent extraction and heat treatment for extended periods of time. In this way, many commercial contact lens production processes include numerous processing steps relating to extraction and unlocking. However, according to one embodiment of the present invention, a simultaneous extraction and unlocking step can be replaced by the sequential extraction and unlocking steps of the prior art. It has been unexpectedly found that the application of supercritical fluid to a contact lens in a mold for extraction purposes causes the lens to detach from the mold. This reduction in attractive forces between the lens and the mold allows rapid separation of the lens from the mold, while minimizing the likelihood of lens damage and concomitant waste formation. The supercritical substance can be selected from a wide variety of substances that are gases or liquids at room temperature and pressure, including without limitation, carbon dioxide; Water; alcohols, especially low molecular weight alcohols such as isopropyl alcohol and ethanol; ammonia; ethylene; carbon disulfide; sulfur hexafluoride; hexane; acetone and other common organic solvents and their mixtures. A preferred group of SCF's include alcohols such as isopropyl alcohol and relatively inert harmless gases or fluids such as carbon dioxide or water. Carbon dioxide and isopropyl alcohol are preferred more. While the conditions of the substance used, as a super-critical fluid may vary somewhat, the substance must be at a temperature and pressure that places the substance at or near the super-critical region. The temperature and pressure of the super-critical fluid depends on the selected fluid composition. For carbon dioxide, the temperature and pressure to produce a supercritical fluid are about 76.28 kg / cm2 absolute (1085 psia) and about 31 ° C. A temperature range of 21 to 45'c and a pressure range of 42.18 - 351.5 kg / cm2 absolute (600 to 5000 psia) are considered useful for a current of carbon dioxide. Preferably, the carbon dioxide stream is maintained at a temperature of about 21 to 35 ° C and a pressure of about 63.27-210.9 kg / cm 2 absolute (900 to 3000 psia). Particularly preferred mixtures of fluids useful for removing and unlocking contact lenses include carbon dioxide and isopropyl alcohol (IPA). A preferred fluid composition includes about 70 to about 99 weight percent carbon dioxide and about 1 to about 30 weight percent isopropyl alcohol. A more preferred fluid composition includes about 75 to about 85 weight percent carbon dioxide and about 15 to about 25 weight percent isopropyl alcohol. In order to adequately remove undesirable materials from a contact lens within a lens mold, the supercritical fluid should be adequately agitated. Sufficient agitation of the supercritical fluid can occur by simply contacting a supercritical fluid stream with the polymeric article to be treated. However, a preferred flow rate is in the turbulent range, ie fluid flows having Reynold numbers over 2100.

Equipment for supercritical fluid extraction can be obtained commercially from a variety of sources, including Pressure Products Industries, Inc. (Warminster, Pennsylvania) and Autoclave Engineering (Erie, Pennsylvania). A preferred SCF extractor for ophthalmic devices such as contact lenses is the EP Model 12-3000, available from Autoclave. In a preferred embodiment, the invention relates to a method of treating an ophthalmic lens subsequent to the polymerization of the lens. This embodiment of the invention is discussed with respect to a particularly preferred embodiment - the treatment of a contact lens. However, this embodiment of the invention is not limited to contact lenses but includes intra-ocular lenses, drug delivery lenses, overlapping inserts, corneas, etc. If the lens is manufactured by a molding process on both sides, one half of the mold is separated from the lens before application of super-critical fluids. Typically, the lens remains removably fixed to the base half of the mold (convex mold half), leaving the surface of the front or convex lens exposed. The lens mold can be treated in order to make a more adherent mold half and / or the other less adherent mold half. In order to ensure consistent location of the lens in the desired mold half. Alternatively, detection equipment can be used to determine the mold half to which the lens is removably fixed, such that the half of the lens containing the mold is treated with the supercritical fluid. Regardless of the selected technique, the mold half retaining the lens is treated with supercritical fluid subsequent to the first half mold separation step. Lens treatment in the mold half with supercritical fluid is preferably achieved in a batch process to ensure complete contact with the fluid and to ensure that the fluid remains or cycles through the super-high temperature and pressure ranges. -critics . In order to increase processing efficiencies, a plurality of lenses can be processed in a batch process. Figure 1 schematically illustrates an apparatus capable of batch processing a plurality of lenses. With reference to Figure 1, the lens treatment apparatus 10 is surrounded with sufficient insulation 12 to keep the fluid applied to the desired super-critical temperature and pressure ranges. The trays 14 support a plurality of lenses 16 fixed to the molds 18. The support trays either have perforations or are sufficiently porous to allow super-critical fluid to circulate through the trays. In operation, the trays are loaded in the lens treatment apparatus 10, either manually or by an automated lens distribution system, through an access opening (not shown) with the access opening sealed subsequent to the step of cargo. The supercritical fluid access through the inlet 20 at a rate of about .3785-18.925 liters (0.1 to 5 gallons) per minute, is evenly distributed to passages placed on the walls of the container by means of agitation 22. In a At a point near the top of the apparatus 10, supercritical fluid passes through a flow distribution member 24, which provides uniform super-critical fluid flow through a cross section of the apparatus perpendicular to flow. The supercritical fluid circulates through the trays 14, contacting lenses 16 and molds 18, preferably in a turbulent form, before exiting through the fluid outlet (not shown). An alternate lens treatment apparatus 40 is illustrated in Figure 2. The apparatus 40 illustrated in closed configuration includes the inlet 42 in the upper portion 44 and the outlet 46 in the lower portion 48. The apparatus 40 further includes agitation means 50 and peripheral seal means 52. The seal of the upper portion 44 to the lower portion 48 by the peripheral seal means 52, define the lens treatment cavity 60. In operation, the upper and lower portions 44 and 48 are separated vertically to allow the lens 54 fixed to the mold 56, to be indexed on the conveyor 58 to a position between the upper and lower portions. . After a lens-containing mold is indexed to the desired intermediate position at the upper and lower portions 44 and 48, the upper and lower portions are coupled, thereby forming a liquid impervious seal defined by the peripheral sealing means 52 A supercritical fluid flows through the inlet 42 and is dispersed by agitation means 50, thereby contacting the lens in a turbulent manner. Excess supercritical fluid exits through the outlet 46 and the upper and lower portions 44 and 48 are separated to allow the mold containing the treated lens to be indexed outward and the process started again. While the step of stirring the super-critical fluid is desirable, it is not a required step. In a preferred embodiment, agitation is provided by mechanical means as illustrated in Figures 1 and 2. However, a preferred state of agitation may arise simply from the application of the supercritical fluid at the appropriate pressure, i.e. a turbulent flow it is developed by the dimensions of passage, way of passage and pressure of fluid. Figures 1 and 2 present two designs for suitable equipment to treat lenses with supercritical fluids. However, a wide variety of alternatives will be readily apparent to persons having ordinary skill in the art, and given the teachings of the present invention. Accordingly, the invention will not be strictly restricted to the designs presented in Figures 1 and 2.

The previous description will allow a person with ordinary skill in the specialty to practice the invention. In order to better allow the reader to understand specific modalities and their advantages, reference to the following examples is suggested. EXAMPLE I; Hydrophilic contact lenses are formed in a double-sided molding process. The concave mold halves are manually removed, leaving the lenses predominantly fixed to the convex mold halves. The lenses and the convex mold halves are placed inside the treatment cavity of a Super-critical C02 Treatment System of Autoclave Engineering model EP-2000. Supercritical carbon dioxide fluid at 210.9 kg / cm2 gauge (3000 psig) and 35 ° C, is applied to the lenses and fixed mold halves for a period of approximately 100 minutes. The lenses fixed to the base curve mold halves are not unlocked from the mold halves. EXAMPLE II: Hydrophilic contact lenses and fixed mold halves are treated as described in Example I, with the SCF pressure at 210.9 kg / cm2 gauge (3000 psig) and temperature at 30 ° C. The treatment period is approximately 100 minutes. The lenses fixed to the curve-base mold halves are not unlocked from the mold halves. EXAMPLE III: Hydrophobic contact lenses and fixed mold halves are treated as described in Example I, with SCF pressure at 210.9 kg / cm2 gauge (3000 psig) and temperature of 25 ° C. The treatment period is approximately 100 minutes. The lenses are partially but incompletely unlocked from the curve-base mold halves. EXAMPLE IV: Hydrophilic contact lenses and fixed mold halves are treated as described in Example I, with the fluid pressure almost super-critical at 70.3 kg / cm2 gauge (1000 psig) and temperature of 25 ° C. The treatment period is approximately 100 minutes. The lenses are partially unblocked, but incompletely, from the curve-base mold halves. EXAMPLE V: Hydrophilic contact lenses and fixed mold halves are treated as described in Example I, but a mixture of 19 weight percent isopropyl alcohol (IPA) / 81 weight percent carbon dioxide is used, instead of 100% carbon dioxide of Example I. The pressure is 210.9 kg / cm2 gauge (3000 psig) while the temperature was 30 ° C. The treatment period is approximately 97 minutes. The lenses are unlocked from the curve-base mold halves. EXAMPLE VI: Hydrophobic contact lenses and fixed mold halves are treated as described in Example I, but a mixture of 14% by weight isopropyl alcohol / 86 weight percent carbon dioxide is used instead of 100% of carbon dioxide in Example I. The pressure is pulsed while the temperature is maintained at about 30 ° C. The pressure cycle includes approximately a 10 minute period at 210.9 kg / cm2 gauge (3000 psig) followed by a pressure drop to approximately 70.3 kg / cm2 gauge (1000 psig), then a return to pressure of 210.9 kg / cm2 gauge (3000 psig). The treatment period is approximately 81 minutes. The lenses are unlocked from the curve-base mold halves. EXAMPLE VII: Hydrophobic contact lenses and fixed mold halves are treated as described in Example I, but a mixture of 10% by weight of isopropyl alcohol / 90% by weight of carbon dioxide, SCF, is used instead of 100% carbon dioxide of Example I. The pressure is 210.9 kg / cm2 gauge (3000 psig) while the temperature is 30 ° C. The treatment period is approximately 100 minutes. The lenses are unlocked from the mold halves. The average weight percent of extractables in the lens is approximately 1.6. EXAMPLE VIII fCOMPARATIVES: Hydrophilic contact lenses are unblocked from molds. The lenses are immersed for approximately 15 hours in isopropyl alcohol. Exhausted alcohol is replaced with fresh alcohol, and the lenses are allowed to impregnate again for approximately 8 hours. Average weight percent of extractables in lenses is approximately 1.1. Results are illustrated in Table I for comparison with Example VII. TABLE 1 Axis Pressure Tempe- Time Composition Resul- kg / cm2 ratura Exposure (percents tados man, (psig) f ° C) (minutes 1 in weight) 210.9 (3000) 35 100 100% CO, if unlocking the curves- base II 210.9 (3000) 30 100 100% C02 without unlocking in the curves - base III 210.9 (3000) 25 100 100% CO, incomplete release of the curves - base IV 70.3 (1000) 25 100 100% CO, incomplete release of the curves- base TABLE 1 (Cont.) Axis Pressure Tempe- Time Composition Resul- kg / cm2 ratura Exposure (percent man, fpsigl (° C) (minutes) in weight) V 210.9 (3000) 30 97 81% C02 unlock 19% Complete IPA of the curves - base VI pressed to 210.9 (3000) 30 81 86% C02 unlocking 70.3 (1000) 14% Complete IPA of the negligible removable base curves Vl 210.9 (3000) 30 100 90% C0a unlocking 10% incomplete IPA of the base curves; 1.6% removable VIII approx. 1.033 approx. 21 1380 100% IPA 1.1% (control1 removable In all the examples, the lenses that are fixed to the front curve mold halves are unlocked Unlock variations occur only in lenses fixed to the base curve mold halves. V and VI illustrate that contact lenses can be unlocked from lens molds subsequent to the polymerization steps by applying supercritical isopropyl alcohol / carbon dioxide fluid Unblocking problems in Examples I to VI are considered as a result of non-optimized conditions and / or fixing problems, ie inadequate location of the lenses and mold halves within the SCF treatment cavity Further, a comparison of Example VII with Comparative Example VIII shows that the extraction of the lenses with supercritical fluids produces comparable extractable levels with extraction by impregnating batch in isopropyl alcohol, but over a significantly reduced period of time. JEMPLO IX: Approximately 51.5 g (50 mmoles) of the perfluoropolyether Fomblin1 ** ZDOL (from Ausi ont SpA, Milan) having an average molecular weight of 1030 g / mol and containing 1.96 meq / g of hydroxyl groups according to titration of Extreme group is introduced into a three neck flask together with 50 mg dibutyl tin dilaurate. The contents of the flask are evacuated at about 20 mbar with stirring and subsequently decompressed with argon. This operation is repeated twice. Approximately 22.2 g (0.1 mol) of freshly distilled diisocyanate isophorone which is kept under argon, are subsequently added in counter-current of argon. The temperature in the flask is kept below about 30 ° C when cooling with a water bath. After stirring overnight at room temperature, the reaction is complete. Isocyanate titration gives an NCO content of approximately 1.40 meq / g (theory: 1.35 meq / g). Approximately 202 g of the a-hydroxypropyl terminated polydimethylsiloxane KF-6001 from Shin-Etsu, having an average molecular weight of 2000 g / mol (1.00 meq / g of hydroxyl groups according to the titration) are introduced into the flask. The contents of the flask are evacuated to approximately 0.1 mbar and decompressed with argon. This operation is repeated twice. The degassed siloxane is dissolved in about 202 ml of freshly distilled toluene which is kept under argon, and about 100 mg of dibutyltin dilaurate (DBTDL) are added. After complete homogenization of the solution, all the perfluoropolyether reacted with isophorone diisocyanate (IPDI) is added under argon. After stirring overnight at room temperature, the reaction is complete. The solvent is released with high vacuum at room temperature. The microtiter shows approximately 0.36 meq / g of hydroxyl groups (theory: 0.37 meq / g).

Approximately 13.78 g (88.9 mmol) of 2-isocyanate ethyl methacrylate (IEM) are added under argon to 247 g of the tri-block copolymer polysiloxane-perfluoropolyether-polysiloxane terminated in α, β-hydroxypropyl (a three-block copolymer in stoichiometric average, but other block stretches are also present). The mixture is stirred at room temperature for three days. The microtiter no longer shows any isocyanate groups (limit of detection 0.01 meq / g). Approximately 0.34 meq / g of ethacrylate groups are found (theory: 0.34 meq / g). The macromer prepared in this way is completely colorless and transparent. It can be stored in air at room temperature for several months in the absence of light without any change in molecular weight. Approximately 10.0 grams of the macromer are dissolved in 3.3 grams of ethanol (Fluka, puriss.p.a.). After complete homogenization of the solution, approximately 4.0 grams of 3-tris (trimethylsiloxy) silylpropyl methacrylate (TRIS), from Shin-Etsu, product No. KF-2801), approximately 5.9 g of freshly distilled dimethylacrylamide (DMA), approximately 0.1 g of Blemer ™ QA (a methacrylate having quaternary ammonium substituents, Linz Chemie) and approximately 100 mg of photoinitiator Darocur ™ 1 1173 (Ciba) is added. The solution is filtered through a TEFLON membrane having a pore width of 0.45 mm under an argon pressure from about 1 to 2 at. The filtered solution is frozen in a flask in liquid nitrogen, the flask is evacuated with high vacuum and the solution is returned to room temperature with the flask sealed. This degassing operation is repeated twice. The flask containing the macromer / comonomer solution is then transferred in a glove box with an inert gas atmosphere, where the solution is pipetted into powder-free polypropylene contact lens molds. The molds are closed and the polymerization reaction is carried out with UV irradiation, with simultaneous entanglement. The molds are then opened and placed in isopropyl alcohol, causing the resulting lenses to come off by swelling the molds. The lenses are removed for approximately 24 hours, with almost continuous replenishment of isopropyl alcohol. Subsequently, the lenses are dried under high vacuum. After preparation, the lenses are dried overnight under vacuum. An extraction container of the C02 Super-critical Treatment System model EP-2000 of Autoclave Engineering is loaded with 7 lenses. The extraction vessel is filled with carbon dioxide and the pressure rises to approximately 200 atm, with a temperature of approximately 30 ° C. The vessel is allowed to equilibrate for approximately 10 minutes.

The lenses are extracted with an 80:20 volume / volume ratio of a carbon dioxide / isopropyl alcohol (C02 / IPA) stream at approximately 200 atm and at a temperature of approximately 30 ° C. The flow rate remains almost constant at approximately 1.0 milliliter / minute. The extract is collected in a solid-phase adsorbent trap at about -10 ° C and then desorbed at about 100 ° C by about 3.0 milliliters of isopropyl alcohol wash per trap. The gravimetric analysis of the collected extract residue is carried out after removing isopropyl alcohol by application of a nitrogen stream with vacuum. The previous extraction cycle is applied a total of 10 times. The process is repeated by another set of seven lenses. The extractable products in percent by weight are determined by adding the weights of the extractable products removed and dividing this by the sum of the weights of the extracted lenses. This average weight percent of extractables removed is approximately 6.0%. EXAMPLE X: Contact lenses are prepared according to Example IX. Extraction is performed substantially as described in Example IX, with (a) a current 70:30 COa / IPA, as opposed to a current 80:20 and (b) a total number of extraction cycles of 5 instead of 10 The average weight percent of extractables determined according to the procedure of Example IX is about 6.8%. EXAMPLE XI: Contact lenses are prepared according to Example IX. Extraction is performed substantially as described in Example IX, with (a) a current 70:30 C02 / IPA as opposed to a current 80:20 and (b) a total number of extraction cycles of 10. The percent in Average weight of extractables determined in accordance with the procedure of Example IX is about 6.8%. EXAMPLE XII: Contact lenses are prepared according to Example IX. The extraction is performed substantially as described in Example IX, with (a) a current of 70:30 C02 / IPA, as opposed to a current of 80:20 and (b) a total number of extraction cycles of 2 instead of 10. The average weight percent of extractables determined in accordance with the procedure of Example IX is about 4.0%. EXAMPLE XIII: In a dry box under a nitrogen atmosphere, approximately 200 grams of dry PDMS dipropoxyethanol (Shin-Etsu) is added to a vessel. Isocyanate ethyl methacrylate (IEM) in an amount equal to about 2 moles per mole PDMS dialcanol are added to the vessel. Approximately 0.1 weight percent dibutyltin dilaurate (DBTL) catalyst, based on a weight of PDMS dialcanol, is added to the vessel along with a stir bar. The vessel is immersed in an oil bath on a stir plate, and held in place with a clamp. The UPC air stream at approximately .1406 kg / cm2 gauge (2 psig) is passed over the mixture. The mixture is stirred at room temperature (approximately 22 ° C) for approximately 24 hours. Following an iteractive procedure in which the mixture is analyzed by isocyanate content IEM is added if the PDMS dialcoxialcanol has not been fully reacted. The mixture is stirred for about 24 hours more. The macromer produced is a siloxane-containing macromer. A prepolymerization mixture is prepared by adding about 56 grams of the siloxane-containing macromer, about 14 grams of TRIS, about 29 grams of N, N-dimethylacrylamide (DMA), about 1 gram of methacrylic acid, about 0.5 gram of Darocur ™ 1173 photoinitiator , and approximately 20 grams of hexanol. The mixture is stirred for approximately 20 minutes at room temperature. The mixture is then degassed by a series of freezing and thawing steps. The vessel is placed in a liquid nitrogen bath until the mixture solidifies. A vacuum is applied to the container at a pressure of approximately 200 ml or less for approximately 5 minutes. Then, the container is placed in a bath with water at room temperature until the mixture is again liquid. This procedure is performed a total of three times. The mixture is then polymerized to form contact lenses. The prepolymerization mixture is emptied into polypropylene contact lens molds under a nitrogen atmosphere. The polymerization is carried out by applying UV radiation (approximately 4-6 mW / cm2) for a period of approximately 15 minutes. The lenses are transferred in a plasma coating apparatus where they are surface treated in a mixture of methane / "air" ("air", as used herein, denotes 79% in nitrogen and 21% oxygen) for a period of approximately 5 minutes. The apparatus and the plasma treatment process have been described by H. Yasuda in "Plasma Polymerization", Academic Press, Orlando, Florida (1985), page 319 onwards. The extraction of the lenses is performed substantially as described in Example IX, with (a) a current of 70:30 C02 / IPA as opposed to a current of 80:20 and (b) a total number of extraction cycles of 5 instead of 10. The average percent weight of extractables, determined according to the procedure of Ejßßplo IX, is approximately 0.2%.

EXAMPLE XIV: Before extraction, the functionalized polydimethyl-siloxane amino (a, β-bis-aminopropyl-dimethylpolysiloxane) used for the synthesis (X-22-161-C, Shin Etsu, JP) was finely dispersed in acetonitrile, extracted and then subjected to molecular distillation. The following reactions are carried out with the exclusion of H20. Approximately 200 g of purified amino-functionalized polydimethylsiloxane (0.375 eq of NH2 / g; Mn (VPO) 3400-3900 (VPO, Vapor Pressure Osmo etry)), dissolved in approximately 200 ml of absolute THF, are slowly added dropwise to a suspension of about 13.35 g (75 mmol) of D (+) gluconic acid d-lactone in about 50 ml of absolute THF and the mixture is stirred at about 40 ° C for about 24 hours until the lactone reacted completely. (The verification of the reaction by thin layer chromatography (TLC): silica gel, i-propanol / H20 / ethyl acetate 6: 3: 1, stained with molybdic phosphorus acid solution / Ce (IV) sulphate (CPS reagent) )). After the reaction, the reaction solution is concentrated to dryness and the residue is dried under 3 Pa (0.03 mbar) for 48 hours. 213.3 g of a,? - bis (3-gluconamidopropyl) -poly-dimethylsiloxane are obtained. Titration of the amino groups with perchloric acid shows a conversion of the amino groups greater than 99.8%. The product (from α, β-bis-3-gluconamidopropyl-dimethyl-polysiloxane) obtained above (about 213.3 g) is dissolved in about 800 ml of absolute THF and the solution is heated to about 40 ° C with the addition of catalytic amounts. of dibutyltin dilaurate (DBTDL). Approximately 29.2 g (187.5 mmol) of IEM in approximately 20 ml of absolute THF are added dropwise to this solution over a period of approximately 4 hours. This corresponds to a concentration of 1.2 equivalents of IEM per gluconamide unit. The reaction is carried out in the course of 48 hours (verification of reaction by detection of IR spectroscopy of the NCO bonds). The reaction solution is concentrated and the product is dried in an amber glass flask under 3 Pa (0.03 mbar) for 24 hours, while cooling with ice. 227.2 g of a clear elastic rubber product with high optical transparency. Prior to polymerization, the acrylates employed, N, N-dimethylacrylamide (DMA) and 3-methacryloyloxypropyltris (trimethylsilyloxy) silane (TRIS) are each freed from inhibitors by distillation. Approximately 1.44 g (approximately 14 mmol) of DMA and approximately 1.44 g (3.4 mmol) of TRIS are weighed into a 50 ml round bottom flask and the flask is flushed with N2 for half an hour while cooling with ice. Approximately 1.44 g of the macromer are transferred to a round-bottomed flask with nitrogen connection, degassed under about 3 Pa (0.03 mbar) for 24 hours and then dissolved in 2.7 gd * ethanol which is flushed with N2 for half an hour of hand. The subsequent preparation of samples and the polymerization are carried out inside a box of gloves excluding oxygen. The above monomer mixture and the macromer solution, with the addition of about 0.012 g (0.21 mmol) of Darocur ™ 1173 and the mixture is subjected to microfiltration (0.45 mm filter). Approximately 180 μl of this mixture is introduced into a polypropylene mold, which is then closed with an appropriate polypropylene cap. The mixture is then irradiated with a UV-A high pressure mercury lamp in a nitrogen atmosphere in a UV oven equipped for this for 5 minutes. The lamps (5 each one of mark TLK40W / 10R, Philips) are above and below the inserted support. The intensity of irradiation is 14.5 mW / cm2. The polypropylene mold is opened and the finished discs or lenses are removed. The extraction is carried out substantially as described in Example IX, with (a) a current of 100% C02 as opposed to a current of 80:20 C02 / IPA and (b) a total number of extraction cycles of 10. The average weight percent of extractable materials determined according to the procedure of Example IX, it is approximately 1.6%. EXAMPLE XV: Contact lenses are prepared according to Example XIV. The extraction is performed substantially as described in Example IX, with (a) a current of 95: 5 C02 / IPA as opposed to a current of 80:20 and (b) a total number of extraction cycles of 10. The The average weight percent of extractable materials determined according to the procedure of Example IX is about 1.9%. EXAMPLE XVI: Contact lenses are prepared according to Example XIV. Extraction is carried out substantially as described in Example IX, with (a) a 90:10 stream C02 / IPA as opposed to a current 80:20 and (b) a total number of extraction cycles of 10. The average weight percent of extrables, determined according to the procedure of Example IX, is approximately 2.9%. EXAMPLE XVII: Contact lenses are prepared according to Example XIV. The extraction is carried out substantially as described in Example IX, with (a) a current of 80:20 C02 / IPA and (b) a total number of extraction cycles of 10. The average weight percent of extractables, determined with the procedure of Example IX, is about 4.7%. EXAMPLE XVIII: Contact lenses are prepared according to Example XIV. The extraction is carried out substantially as described in Example IX, with (a) a current 70:30 C02 / IPA as opposed to a current of 80:20 and (b) a total number of extraction cycles of 10. The The average weight percent of extractable materials, determined according to the procedure of Example IX, is about 5.6%. TABLE 3 Ahem. Percent of Numbers of Materials isopro- Alcohol Extractable Cycles Non-pillaled in fluid Extraction Volatiles withdrawn from extraction (percent by weight) IPA / CO, IX 20 10 6.0 X 30 5 6.1 XI 30 10 6.8 XII 30 2 4.0 XIII 30 5 0.2 XIV 0 10 1.6 XV 5 10 1.9 XVI 10 10 2.9 XVII 20 10 4.7 XVIII 30 10 5.6 The invention has been described in detail with reference to certain preferred embodiments, in order to allow the reader to practice the invention without undue experimentation. However, a person having ordinary skill in the art will readily recognize that many of the previous components and parameters may be varied or modified in a certain proportion without departing from the scope and spirit of the invention. In addition, titles, headings or the like are provided to improve the reader's understanding of this document and should not be construed as limiting the scope of the present invention. Accordingly, the intellectual property rights to this invention are defined only by the following claims and any reasonable extensions thereof.

Claims (57)

1. CLAIMS 1. Method for unblocking polymer articles from molds, characterized in that it comprises the steps of: (1) providing a supercritical fluid stream at a predetermined temperature and a predetermined pressure; (2) contacting a hydrophilic polymeric article with the supercritical fluid for a predetermined period of time in such a way that the polymeric article separates (unblocks) from a mold; and (3) removing the supercritical fluid from the polymeric article.
2. 2. A method according to claim 1, characterized in that it further comprises the step of mechanically stirring the supercritical fluid.
3. 3. A method according to claim 1, characterized in that the supercritical fluid stream is provided in a turbulent flow regime.
4. 4. A method according to claim 1, characterized in that the polymeric article is unblocked simultaneously from the mold while removing undesirable materials with the supercritical fluid.
5. 5. A method according to claim 4, characterized in that the removal involves removing unreacted monomers, oligomer and / or core solvent from the polymeric article.
6. 6. A method according to claim 4, characterized in that the removal involves cleaning undesirable materials from the surface of the polymeric article.
7. 7. A method according to claim 1, characterized in that the polymer article is selected from the group consisting of medical devices.
8. 8. A method according to claim 7, characterized in that the polymer article is an ophthalmic device.
9. 9. A method according to claim 8, characterized in that the polymeric article is a contact lens.
10. 10. A method according to claim 1, characterized in that the flow expense of the super-critical fluid stream is between .3785 and 18.9 liters (0.1 and 5 gallons) per minute.
11. 11. A method according to claim 1, characterized in that the supercritical fluid is selected from the group consisting of carbon dioxide, alcohols, hexanes, acetone, sulfur hexafluoride and mixtures thereof.
12. 12. A method according to claim 11, characterized in that the supercritical fluid is selected from the group consisting of carbon dioxide, isopropyl alcohol and mixtures thereof.
13. 13. A method according to claim 12, characterized in that the supercritical fluid is carbon dioxide.
14. 14. A method according to claim 12, characterized in that the supercritical fluid comprises: (a) 70 a 99 percent in carbon dioxide; and (b) 1 to 30 weight percent isopropyl alcohol.
15. 15. A method according to claim 1, characterized in that the supercritical fluid comprises: (a) 75 to 85 percent carbon dioxide; and (b) 15 to 25 weight percent isopropyl alcohol.
16. 16. A method according to claim 1, characterized in that the pressure is between 42.18 and 351.5 kg / cm2 absolute (600 to 5000 psia) and the temperature is between 21 and 45 ° C.
17. 17. A method according to claim 16, characterized in that the pressure is between 63.27 and 210.9 kg / cm2 absolute (900 and 3000 psia) and the temperature is between 21 and 35 ° C. 18. A method according to claim 1, characterized in that it further comprises the step of mechanically stirring the supercritical fluid to produce a turbulent flow regime, wherein the supercritical fluid comprises 70 to 99 weight percent of dioxide of carbon and 1 to 30 weight percent isopropyl alcohol, wherein the flow expense of the supercritical fluid stream is between .3785 and
18. 18.9 liters (0.1 and 5 gallons) per minute and wherein the polymeric article is an ophthalmic device.
19. 19. A method for removing undesirable materials from hydrophilic polymeric articles, characterized in that it comprises the steps of: (1) providing a supercritical fluid stream at a predetermined temperature and a predetermined pressure, (2) contacting the hydrophilic polymeric article with the supercritical fluid for a predetermined period of time in such a way that the undesirable materials are removed from the hydrophilic polymeric article; and (3) removing the supercritical fluid from the hydrophilic polymeric article.
20. 20. A method according to claim 19, characterized in that it further comprises the step of mechanically stirring the supercritical fluid.
21. 21. A method according to claim 19, characterized in that the supercritical fluid stream is provided in a turbulent flow regime.
22. 22. A method according to claim 19, characterized in that the polymer article is unblocked simultaneously from a mold while undesirable materials are removed with the supercritical fluid.
23. 23. A method according to claim 22, characterized in that the removal involves extracting unreacted monomers, oligomer and / or solvent from the core of the polymeric article.
24. 24. A method according to claim 22, characterized in that the removal involves cleaning undesirable materials from the surface of the polymeric article.
25. 25. A method according to claim 19, characterized in that the polymeric article is a medical device.
26. 26. A method according to claim 25, characterized in that the polymeric article is an ophthalmic device.
27. 27. A method according to claim 26, characterized in that the polymer article is a contact lens.
28. 28. A method according to claim 19, characterized in that the flow rate of the super-critical fluid stream is between .3785-18.9 liters (0.1 and 5 gallons) per minute.
29. 29. A method according to claim 19, characterized in that the supercritical fluid is selected from the group consisting of carbon dioxide, alcohols, hexane, acetone, sulfur hexafluoride and mixtures thereof.
30. 30. A method according to claim 29, characterized in that the supercritical fluid is selected from the group consisting of carbon dioxide, isopropyl alcohol and mixtures thereof.
31. 31. A method according to claim 30, characterized in that the supercritical fluid is carbon dioxide.
32. 32. A method according to claim 30, characterized in that the supercritical fluid comprises: (a) 70 to 99 weight percent carbon dioxide; and (b) 1 to 30 weight percent isopropyl alcohol.
33. 33. A method according to claim 32, characterized in that the supercritical fluid comprises: (a) 75 to 85 weight percent carbon dioxide; and (b) 15 to 25 weight percent isopropyl alcohol.
34. 34. A method according to claim 19, characterized in that the pressure is between 42.18-351.5 kg / cm2 absolute (600 to 5000 psia) and the temperature is between 21 and 45 ° C.
35. 35. A method according to claim 34, characterized in that the pressure is between 63.27 - 210.9 kg / cm2 absolute (900 to 3000 psia) and the temperature is between 21 and 35 ° C.
36. 36. A method according to claim 19, characterized in that it further comprises the step of mechanically stirring the supercritical fluid to produce a turbulent flow regime, wherein the supercritical fluid comprises 70 to 99 weight percent of carbon dioxide and 1 to 30 weight percent isopropyl alcohol, wherein the flow expense of the supercritical fluid stream is between .3785 - 18.9 liters (0.1 and 5 gallons) per minute and wherein the polymeric article is a device ophthalmic.
37. 37. A method according to claim 36, characterized in that the ophthalmic device is a contact lens.
38. 38. A method for removing undesirable materials from a medical device or component thereof, characterized in that it comprises the steps of: (1) providing a supercritical fluid stream at a predetermined temperature and a predetermined pressure; (2) contacting a medical device with the supercritical fluid for a predetermined period of time such that the undesirable materials are removed from the medical device; and (3) removing the supercritical fluid from the medical device.
39. 39. A method according to claim 38, characterized in that it further comprises the step of mechanically stirring the supercritical fluid.
40. 40. A method according to claim 38, characterized in that the supercritical fluid stream is provided in a turbulent flow regime.
41. 41. A method according to claim 38, characterized in that the medical device is unblocked simultaneously from a mold while removing undesirable materials with the supercritical fluid.
42. 42. A method according to claim 41, characterized in that the removal involves removing unreacted monomer, oligomer and / or solvent from the core of the medical device.
43. 43. A method according to claim 41, characterized in that the removal involves cleaning undesirable materials from the surface of the medical device.
44. 44. A method according to claim 38, characterized in that the medical device is an ophthalmic device.
45. 45. A method according to claim 45, characterized in that the medical device is a contact lens.
46. 46. A method according to claim 38, characterized in that the flow expense of the supercritical fluid stream is between .3785 - 18.9 liters (0.1 and 5 gallons) per minute.
47. 47. A method according to claim 46, characterized in that the supercritical fluid is selected from the group consisting of carbon dioxide, alcohols, hexane, acetone, sulfur hexafluoride and mixtures thereof.
48. 48. A method according to claim 47, characterized in that the supercritical fluid is selected from the group consisting of carbon dioxide, isopropyl alcohol and mixtures thereof.
49. 49. A method according to claim 48, characterized in that the supercritical fluid is carbon dioxide.
50. 50. A method according to claim 48, characterized in that the supercritical fluid comprises: (a) 70 to 99 weight percent carbon dioxide; and (b) 1 to 30 weight percent isopropyl alcohol.
51. 51. A method according to claim 50, characterized in that the supercritical fluid comprises: (a) 75 to 85 weight percent carbon dioxide; and (b) 15 to 25 weight percent isopropyl alcohol.
52. 52. A method according to claim 38, characterized in that the pressure is between 42.18-351.5 kg / cm2 absolute (600 to 5000 psia) and the temperature is between 21 and 45 ° C.
53. 53. A method according to claim 52, characterized in that the pressure is between 63.27 and 210.9 kg / cm2 absolute (900 and 3000 psia) and the temperature is between 21 and 35 ° C.
54. 54. A method according to claim 38, characterized in that it further comprises the step of mechanically stirring the supercritical fluid to produce a turbulent flow regime, wherein the supercritical fluid comprises 70 to 99 weight percent of dioxide of carbon and 1 to 30 weight percent isopropyl alcohol, where the flow rate of the supercritical fluid stream is between .3785 -18.9 liters (0.1 and 5 gallons) per minute and where the polymeric article is an ophthalmic device.
55. 55. A method according to claim 1, characterized in that the polymer article is a contact lens prepared from a mixture comprising a copolymerizable macromer and two or more copolymerizable monomers.
56. 56. A method according to claim 19, characterized in that the polymer article is a contact lens prepared from a mixture comprising a copolymerizable macromer and two or more copolymerizable monomers.
57. 57. A method according to claim 38, characterized in that the polymeric article is a contact lens prepared from a mixture comprising a copolymerizable macromer and two or more copolymerizable monomers.