Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1998-12-18
2001-03-06
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S034000, C522S080000, C522S099000, C522S148000, C522S904000, C522S905000, C524S588000, C525S903000, C523S107000
Reexamination Certificate
active
06197842
ABSTRACT:
The present invention relates to a material based on crosslinked silicone polymer comprising a crosslinked silicone polymer matrix and photoinitiator groups which are dispersed and attached within the silicone matrix, and to a process for the preparation thereof.
The invention also relates to hydrophilic polymeric products obtained from the material based on silicone polymer, to a process for the preparation thereof and to the application thereof in the manufacture of hydrophilic contact lenses.
Finally, the invention relates to novel photoinitiators especially suited to being incorporated in the above material based on crosslinked silicone polymer and to the use of the process resulting in the hydrophilic polymeric products.
Materials based on silicone or polysiloxanes are well known for their very high permeability to oxygen, in particular polydimethylsiloxanes (PDMS). However, the use of pure polysiloxanes cannot be envisaged for the preparation of contact lenses because this material has the disadvantage of being hydrophobic and thus exhibits an absence of surface wettability which causes splitting of the lacrymal film. Furthermore, contact lenses made of pure silicone lead to suction effects (adhesion to the cornea of the eye).
Various techniques have already been provided in order to make silicone lenses compatible with the eye.
Some techniques are targeted at treating the surface of the lens in order to render it hydrophilic.
For example, a process for rendering contact lenses made of silicone hydrophilic at the surface is known in French Patent FR 2,073,034, which process consists in swelling the silicone matrix using a monomer of monoester or monoamide of acrylic or methacrylic acid type forming a hydrophilic polymer.
The contact lenses thus obtained exhibit a very low level of acrylic or methacrylic polymer incorporated at the surface of the silicone matrix.
Other techniques are targeted at obtaining hydrophilic materials of the interpenetrating polymer network (IPN) type from hydrophobic organosiloxane prepolymers and hydrophilic monomers of the monoester or monoamide of acrylic or methacrylic acid type. The material of IPN type is a material in which the hydrophobic prepolymers and the hydrophilic monomers are mixed together and react simultaneously in order to form two interwoven networks by an independent polymerization of the hydrophobic prepolymers and of the hydrophilic monomers, respectively.
This technique exhibits disadvantages because there are problems of solubility of the hydrophilic monomer in the hydrophobic prepolymer. It is thus difficult to obtain homogeneous materials and this technique is not suited to the production of materials with a high concentration of hydrophilic polymer and thus with high contents of water in the final material.
French Patent FR 2,709,756, on behalf of the Applicant Company, discloses a process for producing a hydrophilic silicone material of IPN type consisting, in a first stage, in swelling a polymer of PDMS type in a composition comprising acrylic acid, a photoinitiator, a crosslinking agent and a solvent for swelling the PDMS polymer and in then bringing about the polymerization of the acrylic acid by subjecting the swollen PDMS polymer to UV irradiation. It is thus possible to obtain materials which are hydrophilic to the core, with high levels of hydrophilicity. Although this process gives satisfactory results, it can still be improved, however. In particular, there exists a possibility of heterogeneity in the photoinitiator/hydrophilic monomer distribution within the matrix, insofar as these compounds diffuse at different rates, which can result in physical and mechanical heterogeneities.
Moreover, it would be desirable further to increase the level of hydrophilicity of the final material.
Finally, it is also desirable to simplify the implementation of the process disclosed in French Patent FR 2,709,756, for its industrial exploitation and for its application to the manufacture of contact lenses.
In order to solve these technical problems, the preparation has been carried out of a material based on crosslinked silicone polymer comprising a crosslinked silicone polymer matrix, that is to say in which the polymer network is three-dimensional, the distinguishing feature of which is to comprise photoinitiator groups which are dispersed and immobilized within the silicone matrix.
The processes for the subsequent treatment of this material based on crosslinked silicone polymer, which are targeted at rendering it hydrophilic to the core, are greatly simplified thereby and the hydrophilic products obtained exhibit particularly interesting and advantageous characteristics.
The material based on crosslinked silicone polymer comprising immobilized initiator groups and the process for the preparation thereof will now be described in more detail.
According to the invention, the crosslinked silicone matrix comprises photoinitiator groups or fragments distributed homogeneously throughout its volume and to the very heart of the matrix.
The photoinitiator groups can be attached by the following techniques:
According to a first technique, the photonitiator groups are attached to the silicone matrix ia a covalent chemical bond.
To this end, a photoinitiator functionalized by an SiH silyl group or by an unsaturated C═C double bond is prepared.
This double bond can be of vinyl, (meth)acrylic or allyl type.
The photoinitiator compound is introduced into a crosslinkable liquid composition comprising:
an oil A of a polysiloxane monomer or oligomer carrying Si-vinyl groups;
an oil B of a polysiloxane monomer or oligomer carrying Si—H groups;
a metal catalyst for the hydrosilylation reaction.
During the crosslinking by a hydrosilylation reaction carried out by the thermal route, the photoinitiator compound is grafted to the polysiloxane network via an Si—C covalent bond.
According to a second immobilization technique, use is made of a long-chain photoinitiator compound. This chain is preferably a polysiloxane chain on which the photoinitiator group(s) is (are) grafted. This photoinitiator compound is, in the same way as in the preceding technique, introduced into the liquid mixture of the polysiloxane precursors.
During the crosslinking of the mixture, the polysiloxane chain of the photoinitiator compound is physically immobilized within the crosslinked silicone polymer matrix obtained.
In this case, in contrast to the preceding technique, there is no chemical bond between the photoinitiator compound and the silicone matrix but a simple retention of physical nature, due in particular to the three-dimensional character of the network of the crosslinked silicone polymer of the matrix.
However, whatever the immobilization technique used, the photoinitiator groups remain attached in the polysiloxane matrix, even when the latter is subjected to extraction treatments with solvents. In other words, it is impossible to separate the photoinitiator groups from the matrix by extraction with solvents, whether these groups are grafted to the polymer forming the matrix or simply grafted to a long-chain compound physically immobilized within the matrix.
Thus, at the end of the hydrosilylation reaction, there is obtained a material based on crosslinked silicone polymer comprising a crosslinked silicone polymer matrix, in which matrix are distributed photoinitiator groups capable of generating free radicals by light irradiation.
The liquid silicone compositions used to produce the silicone polymer matrix are preferably polydimethylsiloxane oils with two constituents, the essential constituent units of which are represented below:
These silicone oils are crosslinked by virtue of a hydrosilylation catalyst. Such catalysts are well known to the person skilled in the art.
They are, for example, platinum, hexachloroplatinic acid, platinum-hydrocarbon complexes and rhodium complexes.
Platinum-based catalysts are generally used at concentrations of 10 ppm to 500 ppm, preferably of 50 to 300 ppm.
The reaction temperatures vary from room temperature to 250° C.
Baude Dominique
Chaumont Philippe
Dourges Marine-Anne
Marchin Brigitte
Steiner Joël
Berman Susan W.
Essilor International (Compagnie Generale d'Optique)
O'Keefe, Egan & Peterman
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