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 or 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 fa ricated from these polymers. Such treatments have included the deposition of hydrophilic polyelectrolyte complex coatings (e.g. UJv. -Published Patent Application No.2012070A) , the generationof hydrophilic (polar) groups on the lens surface by plasma glow discharge (e.g. TJ.S. Patent No.4-1 -394-9), 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 toa 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

OMPI

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 hydro- lysed 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 wettab__esurface.

The functional groups may be provided in a siloxy monomer or prepoly er which is poly¬ merised 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 _. CJ-C _J - alkyl or phenyl; halo (preferably -C1); dialkyl amino wherein the alkyl groups are each C^-C _c and may be the same or different; and dialkyl oxi o wherein the alkyl groups are each C^-Cj- and may be the same or different: and The alkoxy groups are preferred, most par- ticularly 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:

Carboxylic acid anhydride (cyclic)

Amide — - C —

I

O- C

! <__-

N

/ \

R R

Ester (vinyl), --~ crylic)

Acet

cleavage_, oint

5 The ^' non-hydrolysable organo-silicon monomers which may be used with such hydrolysable monomers may be any of those used in prior art ormulations. Examples of such monomers are disclosed, for example, in U.S. Patents Nos. 3808178,4-120570 and 4-216303, the contents of which 0 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 5 or prepolymers of the following general formula I:

o - i - σ ^L * OH wherein: each B, which may be the same as or different from each other, represents -OR.,, R., being a C-- C^ alkyl group or phenyl, t has a value of from 1 to 5 and _≥ is C- - C^ 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 βcrylate end methacrylate ethyl ecrylβ e and methacrylate propyl acrylate and methacrylate isopropyl acrylate and methacrylate butyl βcrylβte and methacrylate arcyl βcrylβte end methacrylate hexyl acrylate and methacrylate „ heptyl βcrylβte end methacrylate octyl acrylate and methacrylate

2-ethylhexyl βcrylate and methacrylate nonyl acrylate and methacrylate decyl βcrylate and methacrylate undecyl acrylate and methacrylate lauryl acrylate and methacrylate cetyl βcrylate and methacrylate octadecyl βcrylate end methacrylate diacetone ^" acrylamide hydrosy ethyl or propyl methacrylate and acrylate diethylene glycol monomethacrylate pSιe__ylacrylate and methacrylate

^' 'Dhe 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

wherein: 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 Cy- - Cr- alkyl group, a phenyl group or -CH - CE _p .

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

CH2 II

CH CH3 CH3

I I

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

OMPI _Y ^ WIPO

methyl siloxane as commercially available.

Preferred monomer mixtures contain up to 30% by weight of the vi2_yl 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 ally! methacrylate and pentaerythritol tetraacrylate polyethylene glycol dimethacrylate triethylene glycol dimethacrylate tetraethylene glycol dimethacrylate divinyl benzene although any suitable cross-linking agent can be em¬ ployed.

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 4O-90°C, the polymerization being effected preferably for not less than 3 days. Conventional free radical poly¬ merization initiators may be employed such as azobis butyronitrile, benzoyl peroxide, tertiarybutyl peroxy- pivalate, chlorobenzyl peroxide,etc..The polymer can be cast into discs,rods or sheets or 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 Q-irradiation, any suitable source may be employed, such as a Cobalt-60 source. The 0 -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. Vetting angle is measured by the drop method, advancing. ₍ EXAMPLE 1

Gamma methacryloxypropy trimethoxy silane: 50% by weight

Methyl methacrylate: 5 % 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 i iator 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 . DE x 10~ ¹¹ at 20° where DE has the following units:

(cm /sec)(m O _p /ml x irnnHg) The wetting angle was 1 • EXAMPLE 2

By following ths procedure of Example 1 a polymer was prepared from a mixture of 4-0 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 . AZEN. 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.

FXAMPT..4

Following the procedure of Example 1 a polymer was prepared from a mixture of 17-5 parts by weight of vinyl methyl siloxane ^~τ ^- 54- parts by weight methyl methacrylate, 22.5 parts by weight of gamma methacryloxypropyl triethoxy silane, 0.1 part by weight ^* AZEN ^" and 10 parts by weight of allyl methacrylate as cross-linking agent. The resultant polymer was transparent with a refractive index of 1.4-5. It had a hardness of 80.46 (shore D) and a water uptake of 0.672%. It had a renewable hydrolysable surface, DE 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 meth¬ acrylate 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 DE. The polymer had a renewable hydrolysable surf&ce.

EXAMPLE 6

A polymer was prepared exactly as in Example 5 hut 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 DE 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 meth¬ acrylate and 0.1 part by weight -AZEN. The resultant polymer was transparent, machinable and had a water uptake of 1.34%. The polymer had a renewal hydroly- sable surface. DE 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-l nking agent. The resultant polymer was translucent and machinable, with a water uptake of 1.3% and a DE of 12.4. The polymer had a renewable hydrolysable surface.

O. H

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-li king agent. The resultant polymer was transparent, machinable had a water uptake of 0.21% and a DE 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 p__rts 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 tetra ethyl 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 -irradiating a mixture containing 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.^ and a DE 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.