Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Eye prosthesis – Corneal implant
Reexamination Certificate
1999-06-14
2003-12-16
Prebilic, Paul (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Eye prosthesis
Corneal implant
C623S006560, C623S926000, C351S16000R, C523S107000, C556S467000
Reexamination Certificate
active
06663668
ABSTRACT:
The present invention relates to hydratable porous polyorganosiloxane polymers and to processes for producing such hydratable porous polymers. In particular, the present invention relates to a process for polymerising or copolymerising monomers incorporating polyorganosiloxanes to form hydratable porous polyorganosiloxane polymers, and to articles made of hydratable porous polyorganosiloxane polymers including membranes or ophthalmic devices, e.g. contact lenses.
In many applications it has been found advantageous for polymers to be porous. The degree of porosity required depends on the application. For example, membrane filtration depends on the use of microporous polymers to effect separations of various materials. Macroporous sheets of chemically resistant polymers find extensive use as cell dividers in cells for electrolysis or electricity storage. Macroporous materials (open cell foams) produced through the use of blowing agents are used as cushioning materials. Porous materials have also found use in medicine as the medium for the dispensing of medicinal compounds, in medical implants for cell encapsulation or tissue ingrowth, and to achieve certain mechanical properties such as viscoelasticity.
Pores may be formed in the polymer during the process of manufacturing an article of the desired shape or may be formed in the article after manufacture. For example, U.S. Pat. No. 5,213,721 describes a process where holes are mechanically drilled into a block of matrix polymer and the resulting perforated matrix is subject to repetitive drawing and reconsolidation until the holes are reduced to the desired pore size.
Less commonly, the porosity may be an inherent property of the polymer and the porosity maintained as the polymer is formed into the desired shape for a particular application. It is particularly advantageous for the porosity to be introduced during the polymer forming steps. This is generally economical and, in appropriate cases, good control over the porosity and pore size can be achieved.
Polymers based on polyorganosiloxanes in general have many unique and desirable properties which make these polyorganosiloxane based polymers particularly suitable for a variety of applications. These include outstanding flexibility, transparency, high resistance to temperature extremes, and excellent chemical and oxidation resistance. Polyorganosiloxanes also have a number of desirable membrane and solubility characteristics and are often used in devices that require gas permeability and/or leaching of therapeutic drugs.
Polyorganosiloxane based polymers are highly desirable materials for contact lenses and other ophthalmic devices. The use of these polyorganosiloxane based polymers in such applications is limited by the inability to produce an hydrated porous polymer which would allow transfer of tear fluids or nutrients across a contact lens or other ophthalmic device and retain its transparency. Hydratable porous polyorgano-siloxanes are desirable for other uses which will become apparent based on their properties.
Polyorganosiloxanes are generally noted for their hydrophobicity. Polyorganosiloxanes are commonly used in conferring water repellancy to materials and structures. Bulk polyorganosiloxanes have a very low equilibrium water content and are generally regarded as non-hydratable.
We have now found that it is possible to produce an hydratable porous polyorgano-siloxane based polymer. Accordingly there is now provided an hydratable porous polymer comprising a polymerized polyorganosiloxane macromonomer of formula I below:
Q—[M—L]
c
—M—Q (I)
wherein c is in the range of from 0 to 5, preferably in the range of from 0 to 3;
M may be the same or different and is a difunctional block of molecular weight in the range of from 100 to 8000, more preferably from 200 to 8000 and wherein at least one M comprises a residue from a difunctional polymer or copolymer comprising siloxane repeat units of formula II
where R
1
and R
2
may be the same or different and are selected from the group consisting of hydrogen, optionally substituted alkyl, alkenyl, alkynyl, aryl, haloalkyl, haloalkenyl, haloalkynyl, haloaryl, heterocyclyl, and haloheterocyclyl;
L may be the same or different and is a difunctional linking group;
and Q may be the same or different and is a polymerizable group.
We have found that the polymer of the present invention is capable of being hydrated to contain a significant amount of water. This water is held within the internal voids in the polymer mass. The water content capable of being maintained by the polymer of the present invention substantially exceeds the water content capability of polyorganosiloxanes. Typically, bulk polyorganosiloxanes exhibit a water content of below 0.3 weight percent (wt %). We have found that the polymers of the present invention generally have water contents (see Examples) of greater than 5 wt %, more preferably of greater than 10 wt % or 15 wt %, and may be produced with water contents of 25 wt % or more. The macromonomer of formula I, preferably, is substantially free and more preferably, is free of perfluoropolyether blocks, which are also called “PFPE” blocks. It is also preferred that all the variables M comprise units of formula II, or more specifically, that all the variables M are of formula III as specified hereinafter.
The polymers of the invention preferably consist of a polymer matrix with interconnecting voids within the polymer matrix. Various pore sizes and morphologies are possible depending upon the polymerization conditions used. The size of individual pores may be up to about 5 microns, with about 100 nanometers being usual, while the smallest diameter pores are generally about 10 nanometers. Usefully, and especially since the porosity is usually of a tortuous path, the porosity of the product may be expressed in terms of permeability to molecules of defined molecular weight.
In a second aspect there is provided a process for producing an hydratable porous polyorganosiloxane polymer comprising the steps of:
i) dispersing a porogen in a continuous monomer component phase wherein said continuous monomer component comprises at least one macromonomer of formula I;
ii) thereafter polymerising the continuous monomer phase; and
iii) removing the porogen from the porous polymer.
Hereinafter this will be referred to as the “porogen process”.
In a third aspect there is provided a process for the production of an hydratable porous polyorganosiloxane polymer comprising the steps of:
i) forming a mixture comprising a polymerizable component and a solvent wherein the polymerizable component comprises at least one macromonomer of formula I;
ii) polymerizing said mixture wherein immediately after the polymerization of said mixture at least a substantial proportion of said solvent is in the form of a discrete phase and wherein said discrete solvent phase forms an interpenetrating network throughout the mixture or is dispersed throughout the mixture; and
iii) removing the discrete solvent phase.
Hereinafter this process will be referred to as the “two-phase process”.
Q is a polymerizable group which preferably comprises an ethylenically unsaturated moiety which can enter into a free radical polymerization reaction. Preferably Q is a group of the formula A
P
1
—(Y)
m
—(R′—X
1
)
p
— (A)
wherein P
1
is a free-radically-polymerizable group;
Y is —CONHCOO—, —CONHCONH—, —OCONHCO—, —NHCONHCO—, —NHCO—, —CONH—, —NHCONH—, —COO—, —OCO—, —NHCOO— or —OCONH—;
m and p, independently of one another, are 0 or 1;
R′ is a divalent radical of an organic compound having up to 20 carbon atoms;
X
1
is —NHCO—, —CONH—, —NHCONH—, —COO—, —OCO—, —NHCOO— or —OCONH—.
A free-radically-polymerizable group P
1
is, for example, alkenyl, alkenylaryl or alkenylarylenealkyl having up to 20 carbon atoms. Examples of alkenyl are vinyl, allyl, 1-propen-2-yl, 1-buten-2-, -3- and -4-yl, 2-buten-3-yl, and the isomers of pentenyl, hexenyl, octenyl, decenyl and undecenyl. Examples of alkenylaryl are vinylphenyl, vinylnaphthyl or all
Chaouk Hassan
Meijs Gordon Francis
Gardner & Groff, P.C.
Novartis AG
Prebilic Paul
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