PROSTHESES CONTACT LENSES AND POLYMERS THEREFOR

Abstract: A polymer for making a prosthesis or contact lens, which polymer is prepared by polymerizing a vinyl siloxane of general formula (I), wherein m has a value of from 1 to 6, n can be from 0 to an integer preferably less than or equal to 6 and each A, which may be same as or different from each other, represents a C1-C5 alkyl group, a phenyl group, or -CH = CH2, with one or more comonomers, preferably a compound of the general formula (II), wherein each B, which may be the same as or different from each other, represents -OR1, R1 being a C1-C5 alkyl group or phenyl, s has a value of from 1 to 5, t has a value of from 1 to 5 and R2 is C1-C5 alkyl, hydrogen or another organo siloxy group as defined in the general formula (II). The invention also includes prostheses and contact lens made from such polymers.

Description: PB0STHESE5 CO TAC IIEHSES MD POLYHERS TΞEREPOB This invention relates to prostheses, contact lenses, to polymer compositions for such prostheses and lenses and to methods for preparation of these compositions. U.S. Patent No. 3,808,178 discloses copolymer compositions for contact lenses which are prepared " by copolymerizing particular polysiloxanylalkyl esters of acrylic cr ethacrylic acid with alkanol esters of acrylic or methacrylic acid. It is asserted that the polymers so prepared are suitable for contact lenses and that some of the polymers are inherently wettable " by human tears although it may be necessary to improve their wettability by surface treatments of various sorts. There remains however a need for oxygen-permeable polymer compositions with the po¬ tential of low surface wetting angle and which can be formulated to be hard and soft, eye-compatible and workable by conventional techniques. Polysiloxanes containing vinyl groups in chain or terminally, have not been favoured for conventional free radical polymerisation through the double bond, and the prior art specifically remarks upon this when advocating the use of activated unsaturated groups. This is because the polarity of the double bond of the vinyl group is increased when adjoining a substituted silicon atom directly, so favouring an ionic over free radical reaction mechanism „- Indeed, it has been thought that vinyl methyl siloxane cannot be homopolymerised under normal free radical polymerisation conditions. However activating groups (e.g.C-o) separating the vinyl group and 0 silicon atom retain the normal free radical reactivity " • as with the siloxy acrylates, which are known as copolymers in the preparation of contact lenses. Por this reason, the polymerisation of polysiloxanes containing vinyl-Si bonds has hitherto employed different catalyst types (e.g. chloroplatinic acid) which may enable other polymerisation modes to occur - e.g. addition of silicon hydrides to vinyl siloxanes„ ■ Other known methods of vinyl siloxane poly¬ merisation entail high temperature (150°σ) curing (τj.S. Patents Eos. 2793223, 3819772 and 3969290), which would not be suitable for organic co--monomers in the present invention. Vinyl polysiloxanes have been used in the manufacture of silicone fluids as lubricants (U.S. Patent o. 2865885), gums and elastomers (U.S. Patent ϊfos. 3228 Ϊ ' 3341 90, 3996187 and 3996189). Although such elastomers have been fabricated as contact lenses and biomedical devices, their lack of adequate strength and rigidity, combined with high hydrophobicity (poor wetting) are major disadvantages in a contact lens. According to a first aspect of the present invention there is provided a prosthesis or contact lens which is composed of a polymer prepared by the polymerisation of a vinyl or aryl siloxane, with a co-monomer. The present invention also embraces such a polymer for use in the preparation of a contact lens or prosthesis. The vinyl alkyl/aryl siloxanes of the present invention are of the general formula (I): wherein: m has a value of from 1 to 6, n can be from 0 to an integer preferably less than or equal to 6 and each A, which may be same as or different from each other, represents a C- - G < - alkyl group, a phenyl group, or - CH = CΞ . It is to be understood that the repeating siloxane units of this prepolymer can repeat in a regular or irregular manner and that the order of the respective units may likewise be irregular. The preferred vinyl alkyl siloxane is vinyl methyl siloxane prepolymer which may be considered to have the following formula: CH2 II CH 3 CH CH 3 O-h i i r i CH 3 —Si—OC-Si—O]^—[—Si—-0] n —Si—CH 3 - I I I I CH3 CH3 CH CH3 Vinyl methyl siloxane prepolymer although as supplied commercially it probably also contains other prepolymers including cyclics. The Applicants have employed vinyl methyl siloxane as commercially available. Surprisingly, in the present ' invention, vinyl siloxanes can be co-polymerised with common and other organic (or semi-organic) monomers using moderate free radical polymerisation conditions (with preferred reaction time-temperatures stages) to yield copolymers with useful and controllable levels of oxygen permeability, hardness, transparency OMPI refractive index and wettability. This is in direct contrast to the teaching of the prior art. Por example in U.S. Patent ϊTo. 3203919, sur ace coatings or ibrous sheet abrics, suedes and 5 fabrics composed of copolymers of vinyl siloxanes with acrylic and other monomers are applied to the article as a liquid before curing to a water repellent finish. U.S. Patent HO. 3763081 discloses vinyl siloxane 10 copolymers but their polymers also essentially contain imide structures and are applied to the manufacture of composite (filled) materials and mouldings. The polymer composition of the present invention may be a -copolymer. of such a vinyl alkyl siloxane 15 of two or more different siloxanes such as vinyl alkyl siloxanes. Alternatively the composition may be a copolymer of a vinyl alkyl siloxane with one or more monomers derived from substituted or unsubstituted acrylic or methacrylic 20 acid such as esters or amides of these acids. Examples of such monomers are: methyl acrylate and methacrylate ethyl acrylate and methacrylate propyl acrylate. and methacrylate 25 isopropyl acrylate and methacrylate butyl acrylate and methacrylate amyl acrylate and methacrylate hexyl acrylate and methacrvlate heptyl acrylate and methacrylate 30 octyl acrylate and methacrylate 2-ethylhexyl acrylate and methacrylate nonyl acrylate and methacrylate decyl acrylate and methacrylate undecyl acrylate and methacrylate 35 lauryl acrylate and methacrylate cetyl acrylate and methacrylate octadecyl acrylate and methacrylate diacetone acr iamlde hydroxy ethyl or propyl methacrylate and *+υ acrylate diethylene glycol mono ethacrylate ' - phenyl acrylate and methacrylate The vinyl siloxanes employed in the present invention may also be copolymerized, in the presence or absence of acrylic or methacrylic monomers, with other- monomers such as ϊT-vinyl pyrrolidone or styrene and/or monomers having the following general formula (II): (II) B wherein: each B, which may be the same as or different from each other, represents -OE^ , F^ being a ■ C^ - σ t = alkyl group or phenyl, _s_ has a value of from 1 to 5, fc has a value of from 1 to 5 and Rp- ^ s C . - C.- alkyl, hydrogen or another organo siloxy group as defined in the general formula II. The monomer of. the foregoing general formula II is preferably gamma methacryloxypropyl trimethoxy silane of the formula (GB OxSi - (CH p ) 5 -0-C-C = CΞ 2 , or gamma methacryloxypropyl triethoxy silane. Preferred compositions are copolymers of such monomers with methyl methacrylate and vinyl methyl siloxane prepolymer. Preferred monomer mixtures contain up to 30 parts by weight of the vinyl siloxane, up to 60 parts by weight of a monomer of general formula II and the balance being a said monomer derived from acrylic or methacrylic acid although, to increase the rigidity of the polymerized composition, a cross-linking agent may be incorporated in amounts which may be as high as 20 or Dparts by weight of the total compo¬ sition. The cross-linking agent may be selected from one or more of divinyl tetramethyl disiloxane ethylene glycol dimethacrylate allyl methacrylate and pentaerythritol tetraacrylate polyethylene glycol dimethacrylate triethoxy glycol dimethacrylate tetraacrylate glycol dimethacrylate divinyl benzene although any suitable cross-li ki g agent can be employed. The compositions may be chemically polymerized or polymerized by electromagnetic irradiation, e.g. 2—irradiation, electron beam irradiation etc-. In the case of chemical polymerization a free radical initiator or catalyst is generally added and the mixture subjected to controlled heat, pre¬ ferably in a stepwise manner to ensure orderly and efficient incorporation of the monomers into the polymer. The temperatures selected are pre¬ ferably from 40-90° C, the polymerization being effected preferably for not less than 3 days. Conventional free radical polymerization initiators may be employed such as azobis buty- ronitrile. benzoyl peroxide, tertiarybutyl peroxypivalate chlorobenzyl peroxide, etc. The -polymer can be cast into discs, rods or sheets for subsequent machining or directly into a lens shaped configuration. When polishing lenses prepared from such formulations it is generally advisable to use a water based polish. In the case of -irradiation, any suitable source may be employed, such as a Cobalt-60 source. The /--irradiation dosage is suitably from 2 to 5 Mega Rads. Embodiments of the present invention will now be described by way of example only be reference to the following Examples. Wetting angle is measured by the sessile droτ method, advancing. TTC/ϋ rPLE 1 Yinylmethylsiloxane prepolymer (VS): parts by weight Methyl methacrylate (MMA): 60 parts by weight Gamma methacryloxypropyl trimethoxy silane (MΞMOS): 25 parts by weight The above ingredients were weighed, thoroughly mixed in the proportions stated and then filtered and degassed at room temperature. Up to 1 part by weight azobisbutyronitrile (AZBN) was added as a polymerization initiator and polymerization was effected at above ambient temperature with gentle stepwise heating to form a rod of polymer which was hard, transparent, had good wettability and a water uptake of approximately 1 part by weight. The oxygen permeability was ascertained by a polarographic —1*1 n electrode technique to be 7 BE x 10 at 20 U C where D has the following units: (cm /sec) (mlO p ml x πiπirTg). Wetting angle was 62.3°. - EXAMPLE 2 VS 27.0 parts by weight MEMOS 18 parts by weight cross-linking agent (All lmethacrylate) 10 parts by weight MMA 5 parts by weight The ingredients were thoroughly mixed and poly¬ merization was effected, using 0.1% AZBN, in the same manner as in Example 1 to produce a rod of polymer which was transparent and machinable, had a water uptake of less than 1 part by weight and an oxygen permeability measured as in Example 1 of 24- Dk x 10- CrLtI 3 °C. The wetting angle was 66.5°. EΣAMPI-E 5 VS 20. parts by weight MMA 50. parts by weight MEMOS 30 parts by weight The ingredients were thoroughly mixed and polymerization effected by ό -irradiation using a Cobalt 60 source to provide a dose of 2-5 MegaRads. A rod of polymer was formed which was hard, reasonably transparent and had an uptake of water of 1.75 parts by weight. The oxygen permeability, measured as hitherto, was 6.5 -Dk x 10 " at 20 C. Wetting angle was 64.5°. • yANPT.-F. - VS 20 parts by weight MEMOS 25 parts by weight Cross-linki g agent* 6 parts by weight MMA parts by weight *The cross-linking agent was an 88: 2.parts by- eight mixture of allyl methacrylate and ethylene glycol dimethacrylate. Polymerization was ef ected using a small percentage of AZEf, in the manner of Example 1, to produce a rod of polymer which was. airly transparent, machinable, had a low water uptake and an oxygen permeability, measured as hitherto, of 15 K x 0~ at 3 °C. EXAMPLE 5 VS 17.5 parts by weight MEMOS 22.5 parts by weight MMA 40 parts by weight Divinyltetra ethyl siloxane (cro.ss-linking agent) 20 parts by weight The mixture was polymerized in the presence of AZBH, in the manner of Example 1 , to produce a rod of opaque, soft polymer (hardness 60.4:shore D) and high oxygen permeability (DE, 21.6). EXAMPLE 6 A polymer was prepared according to the procedures of Example 1 employing a mixture as follows VS 50 parts by weight MMA 40 parts by weight Cross-linking agent (allyl methacrylate) 10 parts by weight AZBN0.1 part by weight. The resultant polymer was opaque, had a oxygen permeability of DK 31.5 and a water uptake of.1.2%. EXAMPLE 7 A polymer was prepared according to the pro¬ cedures of Example 1 employing a mixture as follows ' VS 27 parts by weight MMA 45 parts by weight Vinyl pyrrolidone 13 parts by weight Allyl methacrylate 10 parts by weight AZEN " 0.1 parts by weight. The resultant polymer was translucent, machinable, had an oxygen permeability of UK 9-4 and a water uptake of 0.9%. ' Wetting angle was 76.5°• EXAMPLE 8 Following the procedure of Example 1 a polymer was prepared from a mixture of 17 * 5 parts by weight of vinyl methyl siloxane, ' 5***- parts by weight methyl methacrylate, 22.5 parts by weight of gamma methacryloxypropyl triethoxy silane, 0.1 parts by weight of AZBΪT and 10 parts by weight of allyl methacrylate as cross-linking agent. The resultant polymer was transparent with a refractive index of 1.45. I thad a hardness of 80.46 (shore D) and a water uptake of 0.672%. Wetting angle was 62° and DK 12.4. EXAMPLE 9 A polymer was prepared exactly as in Example 8 but using ethyl methacrylate instead of methyl methacrylate and MEMOS instead of gamma methacryloxy¬ propyl triethoxy silane. The resultant polymer was transparent, machinable, had a water uptake of 0.92% and an oxygen permeability of 20.1 IK. " F^TAMPLE 10 A polymer was prepared * *..exactly as in Example 8 but using 24 and 30 parts by weight respectively of ethyl and methyl methacrylates stead of methyl methacrylate alone. The resultant polymer was transparent, machinable had a water uptake of 1.1 and a DK of 13.2. " r-XAMPT- ' ', 11 A polymer was prepared as in Example 1 using 7 parts by weight vinyl methyl siloxane , 18 parts of gamma methacryloxypropyl trimethoxy silane, 15 parts by weight hexyl methacrylate, 30 parts by weight methyl methacrylate , 10 parts by weight allyl methacrylate and_0. part by weight AZBF. The resultant polymer was transparent, machinable and had a water uptake of 1.34%. DK was 8.7 and the wetting angle was 70° OMFI It will be appreciated that the present invention provides a polymer whose characteristics such as transparency, hardness (or softness), wettability and oxygen permeability can be tailored to meet a . particular requirement. Specifically the present invention provides polymers for contact lenses which can be eye-compatible, relatively bacteriologi- cally inert, scratch resistant, machinable and polishable, hard or soft, transparent or opaque, wettable or not. Preferred polymers are hard and transparent with low wetting angles and high oxygen permeability. In the preferred polymers of the present invention it is believed that the vinyl alkyl siloxane monomer contributes ' to the oxygen permeability by virtue of the high flexibility of the Si-0 bond and low hindrance siloxy group rotation that • the acrylic or methacrylic monomer, if present, contributes to the optical and cutting qualities and that the monomer of general- formula II, if present, contributes to monomer solution/polymerization compatibility, to oxygen permeability and to lens wettability (and hence to wearer comfort).- It is finally to be noted that colouring matter ' can be introduced into the monomer mixtures in order ' that tinted contact lenses can be produced.

Claims: CLAIMS: 1. A polymer for making a prosthesis or contact lens, which polymer is prepared by polymerizing a vinyl siloxane of the following general formula I: to an integer preferably less than or equal to 6 and each A, which may be same as or different from each other, represents a C,* - Cj- alkyl group, a phenyl group, or -CH = CH , with one or more comonomers. 2. A polymer according to claim 1 , wherein the vinyl siloxane comprises vinyl methyl siloxane. 3• A polymer according to claim 1, which is the result of polymerizing vinyl methyl siloxane with a derivative of an acrylic or methacrylic acid, or with IT-vinyl pyrrolidone or with styrene. 4. A polymer according to claim 3 ? which is the result of polymerizing with the vinyl siloxane a derivative of acrylic or methacrylic comonomer and a silane of the following general formula II: 10 (II) ,,B CH, '■ ■■ -- wherein: each B, which may be the same as or different from each other, represents -OR. * , Ry, being a C* - C-. alkyl group or phenyl, _s has a value of from 1 to 5, _t has a value of from 1 to 5 and R 2 is C j - Cr- alkyl, hydrogen or another organo siloxy group as defined in the general formula II. OVP r "" 5. A polymer according to claim 3 or 4,wherein the acrylic or methacrylic acid derivative is selected from the group consisting of: methyl acrylate End Bethacryϊate ethyl acrylate end methacrylate propyl acrylate- and methacrylate isopropyl acrylate and m thecrylβte bυtyl acrylate and methacrylate aπyl acrylate and methacrylate hexyl acrylate and methacrylate neptyl acrylate and methacrylate octyl acrylate and methacrylate 2-rethylhexyl acrylate and methacrylate nonyl acrylate and methacrylate decyl acrylate and methacrylate undecyl acrylate and methacrylate lauryl acrylate and methacrylate cetyl acrylate and methacrylate octadecyl acrylate and methacrylate diacetone .acrylamide hydroxy ethyl or propyl methacrylate and acrylate diethyle_ _gl col ^ q methacrvlate phenylacrylate and methacryla e. 6. A polymar.. according to claim 5, wherein the silane of general formula II comprises gamma methacryloxypropyl trimethoxy or triethoxy silane. 7. A polymer according to claim or 6, which is produced by polymerizing up to 30 parts by weight of the vinyl siloxane and up to 60 parts by weight of the monomer of general formula II, the balance being essentially a said acrylic or methacrylic acid derivative, a cross-linking agent optionally being present. 8. A polymer according to claim 7, wherein a cross-linking agent is present, selected from one or more of divinyl tetramethyl disiloxane ethylene glycol dimethacrylate allyl methacrylate and pentaerylthritol tetraacrylate polyethylene glycol dimethacrylate triethoxy glycol"dimethacrylate tetraacrylate glycol dimethacrylate divinyl benzene 9. A polymer according to any preceding claim, which has been chemically polymerized by a free ra d ical polymerization initiator. 10. A polymer according to claim 9, wherein free radical polymerization initiators comprises azobis butyronitrile, benzoyl peroxide, tertiarybutyl peroxypivalate or chlorobenzyl peroxide. 11. A polymer according to any of Claims 1 to 8, which has been polymerized by ^-irradiation. 12. A polymer according to Claim 1 and substantially as hereinbefore described with reference to any one of the foregoing individual Examples 1 to 11. 13. A contact lens composed of a polymer as claimed in any one of the preceding Claims. 14. A prosthesis composed of a polymer as claimed in any one of the preceding Claims. 15. A contact lens composed of a polymer made by polymerizing a vinyl siloxane of the following general formula I: « wherein: m has a value of f om 1 to 6, , n can be f om 0 to an integer preferably less than or equal to 6 and each A, which may be same as or different from each other, represents a C^ - C,- alkyl group or a phenyl group, with one or more comonomers. 16. A contact lens according to claim 15, composed of a polymer made by polymerizing up to 30 parts by weight- of the vinyl siloxane and up to 60 parts by weight of the monomer of general formula II, the balance being essentially a said acrylic or metha¬ crylic acid derivative, a cross-linking agent optionally being present. OMPI

Inventors: WHITFORD MAURICE JOHN, WHITFORD, MAURICE, JOHN
Applicants: CONTACT LENS MFG LTD, CONTACT LENSES (MANUFACTURING) LIMITED
Application year: 1983
Main classification: C08F230
IPC codes: A61L27, C08F230, G02B1