Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/28—Preparation of carboxylic acid esters by modifying the hydroxylic moiety of the ester, such modification not being an introduction of an ester group
  • C07C67/29—Preparation of carboxylic acid esters by modifying the hydroxylic moiety of the ester, such modification not being an introduction of an ester group by introduction of oxygen-containing functional groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
  • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
  • C08F20/10—Esters
  • C08F20/26—Esters containing oxygen in addition to the carboxy oxygen
  • C08F20/28—Esters containing oxygen in addition to the carboxy oxygen containing no aromatic rings in the alcohol moiety
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
  • G02B1/041—Lenses
  • G02B1/043—Contact lenses

Definitions

• the present invention relates to a process for the preparation of a diol.
• the diol may be used subsequently used as a monomer for the preparation of a polymeric device or material such as a hemocompatible coating, medical device, water soluble polymer material, paint, water borne coating or an ocular device (such as a contact lens).
• Polymers made from polymerisable monomers have wide spread applications. For example, polymers are used as additives for coating applications, such as paints and adhesives. Polymers are also used to prepare lenses, such as contact lenses.
• Polymers are prepared by polymerising one or more types of polymerisable monomers, such as by emulsion polymerisation, solution polymerisation, suspension polymerisation or bulk polymerisation.
• the monomer(s) may be polymerised in the presence of optional ingredients such as any one of emulsifiers, stabilisers, surface active agents, initiators (such as photoinitiators), inhibitors, dispersants, oxidising agents, reducing agents, viscosity modifiers, catalysts, binders, activators, accelerators, tackifiers, plasticizers, saponification agents, chain transfer agents, surfactants, fillers, dyes, metal salts, and solvents.
• emulsifiers such as emulsion polymerisation, solution polymerisation, suspension polymerisation or bulk polymerisation.
• the monomer(s) may be polymerised in the presence of optional ingredients such as any one of emulsifiers, stabilisers, surface active agents, initiators (such as photoinitiators), inhibitors
• a polymer can be prepared from monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, styrene, butadiene, ethylene, vinyl acetate, vinyl esters, C 9 , Cio and C ⁇ tertiary monocarboxylic acids, vinyl chloride, vinyl pyridine, vinyl pyrrolidine, vinylidene chloride, acrylonitrile, chloroprene, acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid.
• monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, ethyl methacrylate, butyl meth
• polymers are in the preparation of lenses, especially contact lenses or intraocular lenses.
• Examples of teachings for the preparation of contact lenses may be found in EP-A-0359539, which discloses a method of forming a soft contact lens.
• polymers can be fairly easily prepared from polymerisable monomers there can be a problem in reliably and cheaply obtaining suitable monomers in a satisfactory pure form.
• many desired polymerisable monomers are supplied with impurities. These impurities can be detrimental to the final product and so they have to be eliminated before the polymerisation reaction to form the desired polymer.
• Impurities which is particularly problematic are compounds which act as cross-linkers during the polymerisation of the monomer.
• the presence of cross-linkers prevents and/or inhibits the formation of straight chain polymers.
• the presence of cross-linkers in a monomer may prevent the solubilisation of polymers formed therefrom.
• GMA glyceryl methacrylate
• Examples of documents mentioning the use of such a monomer include US-A-5236969, JP-A-04335007, GB-A-2180243 and EP-A- 0100381.
• GMA is a very expensive monomer.
• IPGMA isopropylideneglyceryl methacrylate
• GMA glycidyl methacrylate
• GYMA glycidyl methacrylate
• M.F. Refojo [1965] Journal of Polymer Science 9 pp 3161- 3170.
• This process is particularly disadvantageous because the addition of mineral acid to GMA may result in the formation of glyceryl dimethacrylate which is a cross-linker, and various other dimethacrylates.
• US-A-5532289 discloses a process for forming a soft contact lens. According to the claims of this patent the lens is formed from a copolymer consisting essentially of 2,3- dihydroxypropyl methacrylate (i.e. glyceryl methacrylate [GMA]) and 2-hydroxyethyI methacrylate. Hydroxyethyl methacrylate is sometimes referred to as HEMA.
• GMA glyceryl methacrylate
• HEMA Hydroxyethyl methacrylate
• the process of US-A-5532289 requires a pre-distillation step wherein GMA is distilled. Hence, the process of US-A-5532289 is laborious and costly.
• WO 98/07055 discloses a process of preparing an ocular device (such as a contact lens) consisting essentially of GMA and HEMA, the process comprising the following steps: a) copolymerising a second monomer and a first monomer having attached to it a modifier group, thereby to form a first polymer having associated with it the modifier group; and b) modifying all or some the modifier group associated with the first polymer to form a second polymer different from the first polymer thereby to form the ocular device consisting essentially of GMA and HEMA.
• the present invention seeks to overcome the problems associated with the known processes for preparing polymers.
• an ocular device (such as a contact lens) prepared by the process according to the present invention.
• the apparatus comprising (i) a means for containing an immobilised acid
• reaction product P-C(O)-Q means for removing the gas, comprising reaction product P-C(O)-Q, from the means for containing the immobilised acid.
• the present invention may provide a number of advantages.
• the present invention has the advantage that the presence of impurities which act as cross- linkers during the polymerisation of the monomer is reduced or avoided.
• the present invention provides a monomer capable of polymerisation to form a straight chain polymer without the need to purify the monomer prior to polymerisation.
• the monomer is capable of polymerisation to form a polymer which may be readily solubilised.
• the present invention has the advantage that because of the absence of cross-linker or the low initial cross-linker concentration in the monomer, controlled additions of further cross-linker to achieve the desired/optimum level are possible.
• monomer e.g. GMA
• the level of cross-linker is often already too high to allow further additions without detriment to the mechanical properties of the final polymer, such as a lens.
• This advantage of the present invention is demonstrated if GMA is polymerised. The resultant polymer may simply dissolve into a suitable solvent such as water.
• X, Y, Z or R 1 is a polymerisable group such that the compound of formula I is a polymerisable monomer.
• R 1 is a polymerisable group.
• the acid is a strong acid.
• strong acid it is meant an acid having a pKa of less than 3.
• the acid is immobilised on an ion exchange resin. More preferably the acid is a strong acid immobilised on an ion exchange resin. Yet more preferably the ion exchange resin is Amberlyst 15, obtainable from R ⁇ hm and Haas.ofUSA.
• R 1 is selected from hydrocarbyl group, and hydrocarbyl esters, preferably unsaturated hydrocarbyl esters.
• hydrocarbyl group means a group comprising at least C and H and may optionally comprise one or more other suitable substituents.
• substituents may include halo-, alkoxy-, nitro-, hydroxy, carboxyl, epoxy, acrylic, hydrocarbon, N-acyl, or cyclic group etc.
• a combination of substituents may form a cyclic group.
• the hydrocarbyl group comprises more than one C then those carbons need not necessarily be linked to each other. For example, at least two of the carbons may be linked via a suitable element or group.
• the hydrocarbyl group may contain hetero atoms. Suitable hetero atoms will be apparent to those skilled in the art and include, for instance, sulphur, nitrogen and oxygen.
• hydrocarbyl ester as used herein means a hydrocarbyl group comprising a - C(O)-O- group.
• unsaturated hydrocarbyl ester as used herein means a hydrocarbyl ester comprising at least one carbon-carbon double bond or at least one carbon-carbon triple bond.
• the hydrocarbyl group is a linear or a branched group.
• the branched group may contain one or more branches.
• the linear or a branched hydrocarbyl group may contain from 1 to 20 carbon atoms, from 1 to 15 carbon atoms, from 1 to 10 carbon atoms, from 1 to 5 carbon atoms, or from 1 to 3 carbon atoms.
• the linear or a branched hydrocarbyl group may be saturated or unsaturated. In one aspect, the linear or a branched hydrocarbyl group may saturated.
• the hydrocarbyl group comprises an alkyl backbone.
• the backbone may be interrupted by one or more non-alkyl groups.
• the non-alkyl groups may be selected from ester, ether and combinations thereof.
• the alkyl backbone may contain from 1 to 20 carbon atoms, from 1 to 15 carbon atoms, from 1 to 10 carbon atoms, from 1 to 5 carbon atoms, or from 1 to 3 carbon atoms.
• the alkyl backbone may contain one or more alkyl groups branched from the alkyl backbone.
• each alkyl branch may contain from 1 to 20 carbon atoms, from 1 to 15 carbon atoms, from 1 to 10 carbon atoms, from 1 to 5 carbon atoms, or from 1 to 3 carbon atoms.
• the hydrocarbyl group may be a cyclic group.
• the hydrocarbyl group can be a single ring group or a polycyclic group.
• the term "polycyclic" includes fused and non-fused ring structures including combinations thereof.
• At least one of the cyclic groups of the polycyclic group may be a heterocyclic group (a heterocycle) or a non-heterocyclic group.
• the cyclic group or at least one of the cyclic groups of the polycyclic group may be a saturated ring structure or an unsaturated ring structure (such as an aryl group).
• the hydrocarbyl group may contain any one or more of C, H, O, Si, N, P, halogen (including Cl, Br and I), S and P.
• the alkyl backbone may be interrupted by one or more of any one or more of C, H, O, Si, N, P, halogen (including Cl, Br and I), S and P.
• the hydrocarbyl group is a hydrocarbon group.
• hydrocarbon group means any one of an alkyl group, an alkenyl group, an alkynyl group, an acyl group, which groups may be linear, branched or cyclic, or an aryl group.
• hydrocarbon also includes those groups but wherein they have been optionally substituted. If the hydrocarbon is a branched structure having substituent(s) thereon, then the substitution may be on either the hydrocarbon backbone or on the branch; alternatively the substitutions may be on the hydrocarbon backbone and on the branch.
• the hydrocarbon group may have from 1 to 20 carbon atoms, from 1 to 15 carbon atoms, from 1 to 10 carbon atoms, from 1 to 5 carbon atoms, or from 1 to 3 carbon atoms.
• R 1 is a group of formula III
• R 2 is selected from methyl, ethyl, propyl and butyl and R 3 is selected from an unsaturated C ⁇ - 5 alkyl.
• X, Y, P and Q of formulae given in the present specification are independently selected from a hydrocarbyl group and hydrogen.
• the hydrocarbyl group is a hydrocarbon group. More preferably the hydrocarbyl group is a hydrocarbon group having from 1 to 20 carbons. Yet more preferably, the hydrocarbyl group is selected from methyl, ethyl, propyl and butyl
• X is H
• Y is H
• Z is H
• P is CH 3
• Q is CH 3
• n 0
• the present invention provides a process for the preparation of a polymerisable monomer of formula I
• A is (CH 2 ) 0
• Q is CH 3 and wherein R 1 is a group of formula m
• the present invention provides a process for the preparation of glyceryl methacrylate (GMA), comprising the step of contacting (2,2 l,3-dioxolan-4-yl) methyl methacrylate (GMAK) with an immobilised acid.
• GMA glyceryl methacrylate
• GMAK (2,2 l,3-dioxolan-4-yl) methyl methacrylate
• the process further comprises providing means for containing the immobilised acid, contacting the immobilised acid with the compound of formula II and passing a gas through the immobilised acid.
• the gas contains oxygen. More preferably, the gas is air.
• the immobilised acid is contacted with the compound of formula II in the absence of an organic solvent.
• the means for containing the immobilised acid comprises a fluidised bed reactor.
• the process comprises extracting the gas from the means for containing the immobilised acid after the gas has passed through the immobilised acid.
• the extracted gas may contain a reaction product of the contact of the compound of formula II with the immobilised acid.
• the reaction product may be of the formula P-C(O)-Q.
• the process of the present invention comprises the step of polymerising the polymerisable monomer of formula I.
• Any typical, suitable polymerisation method may be used.
• the preferred method is free radical polymerisation, thermal or UN initiated.
• the process of the present invention further comprises the step of polymerising the polymerisable monomer of formula I to provide a medical device, in particular an ocular device such as a contact lens.
• the present invention is very advantageous for preparing ocular devices, such as contact lenses (both hard and soft contact lenses), intraocular lenses, interocular lenses and intercorneal implants, as well as prostheses and hydrogel articles.
• the present invention not only enables the ocular devices to be made more easily but also it allows a greater control over any one of the shrinkage, the dimensional consistency, the swell, the water sensitivity, the hydrophobicity or the hydrophilicity, or combinations thereof, of the resultant polymer.
• the medical device and/or polymerisable monomer and/or composition may also comprise conventional additional components such as any one or more of emulsifiers, stabilisers, surface active agents, initiators (such as photoinitiators), inhibitors, dispersants, oxidising agents, reducing agents, viscosity modifiers, catalysts, binders, activators, accelerators, tackifiers, plasticizers, saponification agents, chain transfer agents, cross-linking agents, surfactants, fillers, dyes, metal salts, and solvents.
• emulsifiers such as any one or more of emulsifiers, stabilisers, surface active agents, initiators (such as photoinitiators), inhibitors, dispersants, oxidising agents, reducing agents, viscosity modifiers, catalysts, binders, activators, accelerators, tackifiers, plasticizers, saponification agents, chain transfer agents, cross-linking agents, surfactants, fillers, dyes, metal salts, and solvents.
• the surfactants and dispersants can be salts of fatty rosin and naphthenic acids, condensation products of naphthalene sulphonic acid and formaldehyde of low molecular weight, carboxylic polymers and copolymers of the appropriate hydrophile-lipophile balance, higher alkyl sulfates, such as sodium lauryl sulfate, alkyl aryl sulfonates, such as dodecylbenzene sulfonate, sodium or potassium isopropylbenzene sulfonates or isopropylnaphthalene sulfonates; sulfosuccinates, such as sodium dioctylsulfosuccinate alkali metal higher alkyl sulfosuccinates, e.g.
• Typical polymerisation inhibitors that can be used include hydroquinone, monomethyl ether, benzoquinone, phenothiazine and methylene blue.
• the dye is selected from the group consisting of 2- hydroxybenzophenone, oxidiazoles, salicylic acid, resorcinol monobenzoate, benzotriazole, preferably 2H-benzotriazole, benzothiazoloazine. preferably 2N- benzothi-azoloazine, ⁇ -cyano- ⁇ -phenylcinnamic acid, polyalkypiperidine and derivatives thereof.
• the dye is selected from benzotriazole, in particular 2H-benzotriazole and derivatives thereof.
• composition and/or medical device of the present invention may comprise one or more additional comonomers.
• additional comonomers that can be used in the present invention include one of: (alkyl and cycloalkyl) acrylates; (alkyl and cycloalkyl) methacrylates; free-radical polymerisable olefinic acids, including alkoxy-, alkylphenoxy-, alkylphenoxy-(polyethyleneoxide)-, vinyl ester-, amine substituted (including quaternary ammonium salts thereof), nitrile-, halo-, hydroxy-, and acid substituted (for example phospho- or sulpho-) derivatives thereof; and other suitable ethylenically unsaturated polymerisable moieties; including combinations thereof.
• the alkyl and cycloalkyl groups contain up to 20 carbon atoms, e.g. (C ⁇ -C 2 o alkyl and C ⁇ -C 20 cycloalkyl) acrylates, and (C ⁇ -C 20 alkyl and C ⁇ -C 2 o cycloalkyl) methacrylates.
• typical comonomers include any one of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t- butyl acrylate, isobomyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, iso-octyl acrylate, nonyl acrylate, lauryl acrylate, stearyl acrylate, eicosyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, cycloheptyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxymethylacrylate, hydroxymethylmethacrylate, propyl methacrylate, n- butyl methacrylate, t-butyl methacrylate, iso
• 2-ethylhexyl methacrylate isobornyl methacrylate, heptyl methacrylate, cycloheptyl methacrylate, octyl methacrylate, iso-octyl methacrylate, nonyl methacrylate, decyl methacrylate.
• o acrylate octadecene, hexadecene, tetradecene, dodecene, dodecyl methacrylate, pentadecyl methacrylate, cetyl methacrylate, stearyl methacrylate, eicosyl methacrylate, isodecyl methacrylate, nonylphenoxy-(ethyleneoxide) ⁇ - 2 o methacrylate.
• Preferred comonomers include any one of glyceryl methacrylate (GMA), (2,2 dimethyl- l,3-dioxolan-4-yl) methyl methacrylate (GMAK), hydroxy ethyl methacrylate (HEMA), methacrylic acid, acrylic acid, GYMA, N-vinyl pyrrolidone, alkyl methacrylates (such as C[.
• GMA glyceryl methacrylate
• GMAK (2,2 dimethyl- l,3-dioxolan-4-yl) methyl methacrylate
• HEMA hydroxy ethyl methacrylate
• methacrylic acid acrylic acid
• GYMA N-vinyl pyrrolidone
• alkyl methacrylates such as C[.
• alkyl methacrylates more preferably C 1 - 15 alkyl methacrylates, more preferably C MO alkyl methacrylates, more preferably C 1 - 5 alkyl methacrylates, such as methyl methacrylate), alkyl acrylates (such as C ⁇ - 2 o alkyl acrylates, more preferably CM 5 alkyl acrylates, more preferably C MO alkyl acrylates.
• Cj- alkyl acrylates such as methyl acrylate
• aryl methacrylates such as aryl acrylates, diacetone acrylamide, acrylamide, methacrylamide
• N-alkyl acrylamides such as C ⁇ - 2 o N-alkyl acrylamides, more preferably Ci-i- N-alkyl acrylamides, more preferably C MO N-alkyl acrylamides, more preferably C1.5 N-alkyl acrylamides, such as methyl acrylamide
• N-alkyl methacrylamides such as C ⁇ -2 o N-alkyl methacrylamides, more preferably C MS N-alkyl methacrylamides, more preferably C O N-alkyl methacrylamides, more preferably C1-5 N-alkyl methacrylamides, such as methyl methacrylamide
• vinyl acetate vinyl esters, styrene, other substituted olefins, N- dialkyl
• N-dialkyl acrylamides such as N N dimethyl acrylamide
• N-dialkyl methacrylamides such as C ⁇ - 2 o N-dialkyl methacrylamides, more preferably C MS N-dialkyl methacrylamides, more preferably C MO N-dialkyl methacrylamides, more preferably C1-5 N-dialkyl methacrylamides, such as N N dimethyl methacrylamide
• fluoro substituted alkyl and aryl acrylates and methacrylates preferably wherein the alkyl is C1-20 alkyl, more preferably C M5 alkyl, more preferably C MO alkyl, more preferably C1-5 alkyl
• More preferred comonomers include any one of glyceryl methacrylate (GMA), (2,2 dimethyl- 1, 3 -dioxolan-4-yl) methyl methacrylate (GMAK), 2-hydroxy ethyl methacrylate (2-HEMA), methacrylic acid and acrylic acid, or cpmbinations thereof.
• GMA glyceryl methacrylate
• GMAK (2,2 dimethyl- 1, 3 -dioxolan-4-yl) methyl methacrylate
• 2-HEMA 2-hydroxy ethyl methacrylate
• methacrylic acid and acrylic acid or cpmbinations thereof.
• the lists of comonomers also include substituted derivatives of those monomers, such as halogenated monomers, especially fluorinated monomer derivatives, and acetal and ketal derivatives.
• the polymerisable monomer of the present invention and the one or more additional comonomers may be selected so that the composition and/or ocular device of the present invention consists essentially of GMA and HEMA.
• the present invention also provides an ocular device (such as a contact lens) obtained by the process of the present invention wherein the ocular device comprises HEMA in amounts of from 80-20%; GMA in amounts of from 20-80% by weight; and optionally a cross-linking polymerised monomer in an amount of 5% or less; and wherein the ocular device contains less than 0.01% methacrylic acid.
• HEMA in amounts of from 80-20%
• GMA in amounts of from 20-80% by weight
• optionally a cross-linking polymerised monomer in an amount of 5% or less
• the ocular device contains less than 0.01% methacrylic acid.
• the compound of formula II is a derivative of GMA such as (2,2-dimethyl-l,3-dioxolan-4-yl) methyl methacrylate (GMAK).
• GMA such as (2,2-dimethyl-l,3-dioxolan-4-yl) methyl methacrylate
• GMAK can be prepared following the teachings of Mori et al ([1994] Macromolecules 27 pp 35- 39) and Oguchi et al Polym Eng. Sci. ([1990] 30 449).
• This preferred process of the present invention is also of particular interest as GMAK can be readily synthesised from cheap, commercially available materials and it can be prepared in a pure state, i.e. free from the substances normally present in commercial GMA, especially cross-linking substances.
• the compound of formula II is or is part of a polymer. However, as explained above, the compound of formula II is preferably a monomer.
• a polymer prepared in accordance with the present invention may be fabricated as buttons or cast moulded or spun cast lenses.
• the present invention provides an apparatus for use in a process as described above.
• the present invention provides an apparatus for a process for the preparation of a polymerisable monomer of formula I
• reaction product P-C(O)-Q is a volatile compound.
• volatile compound we mean that the compound which has a boiling point and standard temperature and pressure of less than 150°C or a compound which may form an azeotrope with water.
• the present apparatus is advantageous because by removing the reaction product, the equilibrium II ⁇ I + P-C(O)-Q will be driven towards I. Thus the yield of I will be increased. An essentially quantitative yield may be obtained.
• the apparatus of the present invention is advantageous because high yields of monomer suitable for processing without further purification may be obtained utilising simple apparatus.
• the provision of gas through an immobilised acid ensures good contact between the compounds of the process and the acid.
• the immobilised acid is in the form of an ion exchange resin
• the gas agitates the resin ensuring good contact between the resin and the reactants.
• the presence of the oxygen prevents polymerisation of polymerisable monomer I of the present invention.
• an acid may be formed by the reaction.
• GMAK (2,2 dimethyl- 1, 3 -dioxolan-4-yl) methyl methacrylate
• methacrylic acid is formed in small amounts.
• the acid is not subsequently neutralised.
• the process further comprises the step of polymerising the polymerisable monomer of formula I, with the proviso that the polymerisable monomer composition is not neutralised prior to polymerisation.
• the acid is methacrylic acid or acrylic acid.
• GMAK is contacted with an immobilised acid to form GMA
• methacrylic acid present in the composition comprising GMA is neutralised, glycerol dimethacrylate is formed (DGMA).
• Glycerol dimethacrylate is a cross-linker.
• the present invention provides a process for the preparation of a polymer, comprising the steps of (i) contacting a compound of formula II
• Figure 1 shows a reaction scheme of a preferred process in accordance with the present invention.
• the method involves the acid catalysed hydrolysis of the ketal (GMAK) with a strong acid cation exchange resin.
• GMAK was obtained was prepared by transesterification of methyl methacrylate and Solketal (2,2-dimethyl-4-hydroxymethyl- 1 ,3-dioxolane).
• the GMAK Before use the GMAK is washed with its own volume of deionised water to remove any Solketal. If the GMAK contains a high concentration of Solketal separation will be difficult. In this case, addition of further deionised water will effect easier separation.
• the reagents are placed in a 3 litre amber glass bottle and a slow stream (6 litre/min) of filtered air passed through the mixture for 48 hours.
• the cation exchange resin is then filtered off using a Buchner funnel and flask.
• the GMA typically contains 20 to 22% water and 0.1% methacrylic acid.
• the filtrate is transferred to a 2 litre amber glass bottle and a rapid stream of dry filtered air passed through to reduce the water content to ⁇ 2%. 50ppm of MeHQ is dissolved in the resulting monomer which has a methacrylic acid content of ⁇ 0.1%.
• buttons lOg of GMA (prepared in Example 1) was blended with lOg of HEMA. Isopropyl per dicarbonate (0.1 %) was dissolved in the mixture which was then filtered. The mixture was charged into polypropylene button moulds which were sealed and immersed in a water bath. After 16 hours at 32° C the clear colourless buttons were ejected and heated to 120°C for 1 hour and allowed to cool to 50°C at a rate of 17°C/hr. Lenses were cut from the buttons and equilibrated in saline.

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• 1999
  • 1999-04-16 GB GB9908806A patent/GB2348878B/en not_active Revoked
• 2000
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