WO1984000969A1

WO1984000969A1 - Prostheses contact lenses and polymers therefor

Info

Publication number: WO1984000969A1
Application number: PCT/GB1983/000213
Authority: WO
Inventors: Maurice John Whitford
Original assignee: Contact Lens Mfg Ltd
Priority date: 1982-08-27
Filing date: 1983-08-30
Publication date: 1984-03-15
Also published as: IT8322672A0; DK214184A; AU1944383A; EP0116638A1; IT1194382B; DK214184D0

Abstract

A dimensionally stable organosilicon polymer having pendant functional groups which groups are hydrolysable by means of biologically compatible aqueous liquids. The present invention provides a prosthesis, contact lens or contact lens blank which is composed of an organosilicon polymer and which has a renewable wettable surface. Preferably the polymers are prepared by copolymerization of a compound of the general formula I, 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, 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 I.

Description

PROSTHESES, CONTACT LΕNSES, AND POLYMERS THEREFOR.

This invention relates to polymers and to articles produced from such polymers including prostheses and contact lenses.

A wide variety of siloxy-acrylate type monomers has been used to manufacture polymers for contact lenses. Such polymers however have frequently shown poor wettability and the prior art has employed numerous methods to improve the wettability of contact lenses fabricated from these polymers. Such treatments have included the deposition of hydrophilic polyelectrolyte complex coatings (e.g. U.K. Published Patent Application No.2012070A), the generation of hydrophilic (polar) groups on the lens surface by plasma glow discharge (e.g. U.S. Patent No.4143949), and the grafting of hydrophilic monomers to the lens surface.

Such treatments however are unsatisfactory because, being superficial only, the wettability is frequently lost after a short period of wear by the patient. Moreover, a lens which has been so treated may not subsequently be altered by cutting or polishing (e.g. to remove scratches) since this would destroy the wettable surface.

According to a first aspect of the present invention there is provided a dimensionally stable, organosilicon polymer having pendant functional groups which groups are hydrolysable by means of biologically compatible aqueous liquids.

According to a second aspect of the present invention there is provided a prosthesis or contact lens which is composed of an organosilicon polymer and which has a renewable wettable surface.

By the present invention a polymer is provided which has hydrolysable functional groups, so that when a surface of the polymer is contacted by a biologically compatible aqueous liquid, e.g. water, the functional groups at the surface are hydrolysed thus to render the surface wettable. Others of the functional groups which remain within the body of the polymer will not be hydrolysed so that, upon a fresh exposure of polymer (e.g. by cutting or polishing) to a said biologically compatible liquid further hydrolyzation will occur thus providing a renewable wettable surface.

The functional groups may be provided in a siloxy monomer or prepolymer which is polymerised with any other suitable monomer or prepolymer to produce a polymer having desired characteristics, in such a way that the functional groups are not eliminated during the polymerization.

Examples of suitable functional groups which may be bonded to a Si atom of a siloxy monomer or prepolymer are -OR, wherein R represents C₁-C₅ alkyl or phenyl; halo (preferably -C1); dialkyl amino wherein the alkyl groups are each C₁-C₅ and may be the same or different; and dialkyl oximo wherein the alkyl groups are each C₁-C₅ and may be the same or different: and -C=Η The alkoxy groups are preferred, most particularly methoxy groups.

Alternatively or additionally a siloxy monomer or prepolymer (which may or may not contain hydrolysable functional groups of its own) may be copolymerized with one or more monomers or prepolymers which will provide the resultant polymer with the required hydrolysable functional groups.

Examples of suitable monomers are those including cyclic carboxylic anhydrides, amides esters and acetals as shown below:

The non-hydrolysable organo-silicon monomers which may be used with such hydrolysable monomers may be any of those used in prior art formulations. Examples of such monomers are disclosed, for example, in U.S. Patents Nos. 3808178,4120570 and 4216303, the contents of which are incorporated herein by reference.

Generally any hydrolysable silane containing poly merisable ethylenic bonds such as vinyl or acrylic may be employed to provide the hydrolysable functional groups. Preferred systems employ organo-silicon monomers or prepolymers of the following general formula I:

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, 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 I.

Preferably the compound is gamma methacry loxypropyl trimethoxy or triethoxy silane.

In preferred embodiments a compound of the above formula I is polymerised with a monomer derived from acrylic or methacrylic acid such as methyl acrylate and methacrylate ethyl ecrylate and methacrylate propyl acrylate and methacrylate isopropyl acrylate and methacrylate butyl acrylate and methacrylate arcyl acrylate end methacrylate hexyl acrylate and methacrylate heptyl acrylate and methacrylate octyl acrylate and methacrylate

2-ethylhexyl 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 end methacrylate diacetone acrylamide hydrosy ethyl or propyl methacrylate and acrylate diethylene glycol monomethacrylate phenylacrylate and methacrylate The compounds of general formula I may be also be copolymerized with other siloxane monomers such as are referred to in the said U.S. Patents, in the presence or absence of the aforesaid acrylic or methacrylic monomer, or in the presence or absence of one or more other organic monomers such as N-vinyl pyrrolidone or styrene. Preferred formulations incorporate gamma methacryloxypropyl trimethoxy silane, a said acrylic or methacrylic monomer, and a monomer or prepolymer of the following general formula II:

(ID π H.. 1

A - f^; 04-^1 Si - O - A. m

L i n

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 the same as or different from each other, represents a C₁ - C₅ alkyl group, a phenyl group or -CH = CH₂.

A preferred compound of the general formula II is vinyl methyl siloxane prepolymer which may be considered to have the following formula

although as supplied commercially it probably also contains other prepolymers including cyclics. The Applicants have employed vinyl methyl siloxane as commercially available.

Preferred monomer mixtures contain up to 30% by weight of the vinyl siloxane, up to 60% by weight of a monomer of general formula I 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 30% by weight of the total composition. 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 triethylene glycol dimethacrylate tetraethylene glycol dimethacrylate divinyl benzene although any suitable cross-linking agent can be employed.

The compositions may be chemically polymerized or polymerized by electromagnetic irradiation, e.g. -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, preferably in a stepwise manner to ensure orderly and efficient incorporation of the monomers into the polymer. The temperatures selected are preferably 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 butyronitrile, 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 γ-irradiation, any suitable source may be employed, such as a Cobalt-60 source. The γ-irradiation dosage is suitably from 2 to 5 Mega Pads.

Embodiments of the present invention will now be described by way of example only by reference to the following Examples. Wetting angle is measured by the drop method, advancing. EXAMPLE 1

Gamma methacryloxypropy trimethoxy silane: 50% by weight

Methyl methacrylate: 50% by weight The above constituents were weighed, thoroughly mixed in the proportions stated and then filtered and degassed at room temperature. Up to 1% 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 transparent, machinable, had good wettability and a water uptake after 3 days immersion of approximately 2.4% by weight.It had a renewable hydrolysable surface. The oxygen permeability was ascertained by a polarographic electrode technique to be 5.7DK x 10^-11 at 20° where DK has the following units:

(cm²/sec)(m¹O₂/ml x mmHg) The wetting angle was 51º. EXAMPLE 2

By following the procedure of Example 1 a polymer was prepared from a mixture of 40 parts by weight gamma methacryloxypropyl trimethoxy silane 50 parts by weight methyl methacrylate, 10 parts by weight hydroxy ethyl methacrylate and 0.1 parts by weight AZBN. The resultant polymer was transparent, machinable and had a water uptake of 2.36%. It had a renewable hydrolysable surface.

EXAMPLE 3

By following the procedure of Example 1 a polymer was prepared from a mixture of 50 parts by weight gamma methacryloxypropyl trimethoxy silane, 30 parts by weight methyl methacrylate, 20 parts by weight diacetone acrylamide, 0.1 part by weight AZBN and 20 parts by weight of allyl methacrylate as cross-linker. The resultant polymer was transparent and had a renewable hydrolysable surface.

EXAMPLE 4

Following the procedure of Example 1 a polymer was prepared from a mixture of 17.5 parts by weight of vinyl methyl siloxane 54 parts by weight methyl methacrylate, 22.5 parts by weight of gamma methacryloxypropyl triethoxy silane, 0.1 part by weight AZBN and 10 parts by weight of allyl methacrylate as cross-linking agent. The resultant polymer was transparent with a refractive index of 1.45. It had a hardness of 80.46 (shore D) and a water uptake of 0.672%. It had a renewable hydrolysable surface, DK was 12.4 and the wetting angle was 62°. EXAMPLE 5

A polymer was prepared exactly as in example 4 but using ethyl methacrylate instead of methyl methacrylate and gamma methacryloxypropyl trimethoxy siloxane in place of the triethoxy. The resultant polymer was transparent, machinable, had a water uptake of 0.92% and an oxygen permeability of 20.1 DK. The polymer had a renewable hydrolysable surface.

EXAMPLE 6

A polymer was prepared exactly as in Example 5 but using 24 and 30 parts by weight respectively of ethyl and methyl methacrylate instead of ethyl methacrylate alone. The resultant polymer was transparent,machinable had a water uptake of 1.1% and a DK of 13.2. The polymer had a renewable hydrolysable surface.

EXAMPLE 7

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 0.1 part by weight AZBN. The resultant polymer was transparent, machinable and had a water uptake of 1.34%. The polymer had a renewal hydroly sable surface. DK was 8.7 and the wetting angle was 70°.

EXAMPLE 8

A. polymer was prepared following the procedures of Example 1 from a mixture of 16.5 parts by weight vinyl methyl siloxane, 41 parts by weight methyl methacrylate, 22.5 parts by weight gamma methacryloxypropyl trimethoxy silane, 0.1 part by weight AZBN and 20 parts by weight of ethyleneglycol dimethacrylate as a cross-linking agent. The resultant polymer was translucent and machinable, with a water uptake of 1.3% and a DK of 12.4. The polymer had a renewable hydrolysable surface. EXAMPLE 9

A polymer was prepared following the procedure of Example 1 but employing a mixture of 28 parts by weight of vinyl methyl siloxane, 48 parts by weight of methyl methacrylate, 18.9 parts by weight of gamma methacryloxypropyl trimethoxy silane

0.1 part by weight AZBN and 5.3 parts by weight of triethylene glycol dimethacrylate as a cross-linking agent. The resultant polymer was transparent, machinable had a water uptake of 0.21% and a DK of 16.9. The polymer had a renewable hydrolysable surface (wetting angle 68°).

EXAMPLE 10

A polymer was prepared according to the procedure of Example 1 but employing a mixture of 17.5 parts by weight vinyl methyl siloxane, 55 parts by weight methyl methacrylate, 22.5 parts by weight gamma methacryloxypropyl trimethoxy silane, 0.1 part by weight AZBN and 5-0 parts by weight of divinyl tetramethyl disiloxane as a cross-linking agent. The resultant polymer was transparent and machinable and had a water uptake of 1.49%. The polymer had a renewable hydrolysable surface.

EXAMPLE 11

A polymer was prepared by γ-irradiating a mixture containing 15 parts by weight of vinyl methyl siloxane, 60 parts by weight methyl methacrylate and 25 parts by weight of gamma methacryloxypropyl trimethoxy silane. The resultant polymer was transparent, machinable, had a water uptake of 0.5% and a DK of 5.11. The wetting angle was 62.5°. 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 is capable of providing polymers suitable for contact lenses which can be eye-compatible, relatively bacter ilgically inert, scratch-resistant, machinable and polishable, hard or soft, transparent or opaque, and wettable. 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 monomer of general formula I contributes to monomer solution/polymerization compatibility, to oxygen permeability and, importantly, to lens wettability (and hence to wearer comfort), due to the presence of the hydrolysable groups B, whilst the acrylic or methacrylic acid monomer, if present, contributes to the optical and cutting qualities. The compound of general formula II, if present, contributes to oxygen permeability.

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 dimensionally stable organosilicon polymer having pendant functional groups which groups are hydrolysable by means of biologicially compatible aqueous liquids.

2. A polymer according to claim 1, wherein the functional groups are selected from

-OR, wherein R represents C₁-C₅ alkyl or phenyl; halo: dialkyl amino wherein the alkyl groups are each C₁-C₅ and may be the same or different; and dialkyl oximo wherein the alkyl groups are each C₁ - C₅ and may be the same or different: and

present in a polymerisable silane monomer or prepolymer.

3. A polymer according to claim 2, wherein the functional groups comprise methoxy and/or ethoxy groups.

4. A polymer according to claim 2, which is prepared by polymerizing a silane of the following general formula I:

ε f

- Oj (CH₂) -

B -( . - £ . CH,

S 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, 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 I.

5. A polymer according to claim 4, wherein the silane comprises gamma methacryloxypropyl trimethoxy siloxane.

6. A polymer according to claim 4, wherein the silane comprises gamma methacryloxypropyl triethoxy siloxane.

7. A polymer according to claim 4, 5 or 6, which is the result of polymerizing a said silane with a monomer derived from acrylic or methacrylic acid.

8. A polymer according to claim 7, wherein said monomer derived from acrylic or methacrylic acid is selected from methyl acrylate and methacrylate ethyl acrylate and methacrylate propyl acrylete and methacrylate isopropyl acrylate and methacrylate butyl acrylate and methacrylate arsyl acrylete and methacrylate. hexyl acrylete and methacrylate heptyl acrylate and methacrylete octyl acrylate and methecrylate

2-ethylhexyl acrylate end methacrylete nonyl acrylete and moethacrylete decyl ecrylete and methacrylete undecyl acrylete and methacrylate lauryl acrylete and methacrylete cetyl acrylete and methacrylete octedecyl acrylate and methacrylete diacetone diacrylamide hydroxy ethyl or propyl methacrylete and acrylete diethylene glycol monomethacrylate. phenyl acrylate and methacrylate.

9. A polymer according to claims 4, 5 or 6 which is the result of polymerizing a said silane with N-vinyl pyrrolidone or styrene.

10. A polymer according to any preceding claim, which includes siloxane units which do not contain, when in the resultant polymer, hydrolysable functional groups.

11. A polymer according to claims 4 and 10 when dependent thereupon, wherein the silane of general formula I is copolymerized with a vinyl siloxane of the following general formula II:

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 the same as or different from each other, represents a C₁ - C₅ alkyl group or a phenyl group.

12. A polymer according to claim 11, wherein the vinyl siloxane comprises vinyl methyl siloxane.

13. A polymer according to claim 11, which additionally incorporates one or more monomers as defined in claim 7 or 8.

14. A polymer according to claim 13, which contains up to 30 parts by weight of the vinyl siloxane, up to 60 parts by weight of a compound of general formula I and the balance being substantially a said monomer derived from acrylic or methacrylic acid, or styrene or N-vinyl pyrrolidone.

15. A polymer according to claim 14 which incorporates a cross-linking agent.

16. A polymer according to claim 1, wherein the hydrolysable functional groups are derived from one or more organic monomers or prepolymers containing such hydrolysable functional groups, which monomers or prepolymers have been copolymerized with a siloxane.

17. A polymer according to claim 15, wherein the or each organic monomer or prepolymer is selected from cyclic carboxylic anhydrides, amides, esters and acetals.

18. A polymer according to claim 15, wherein the siloxane also contains said hydrolysable functional groups.

19. A polymer according to claim 1 and substantially as hereinbefore described with reference to any one of the foregoing individual Examples 1 to 11.

20. An article made from a polymer as claimed in any preceding claim.

21. An article according to claim 19 in the form of a prosthesis.

22. An article according to claim 19 in the form of a contact lens or contact lens blank.

23. A prosthesis, contact lens or contact lens blank which is composed of an organosilicon polymer and which has a renewable wettable surface.

24. A polymer as claimed in claim 14 or 15 and in the form of a prosthesis, contact lens or contact lens blank.