Coating processes – With post-treatment of coating or coating material – Liquid extraction of coating constituent or cleaning coating
Reexamination Certificate
1999-09-07
2001-05-01
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Liquid extraction of coating constituent or cleaning coating
C427S354000, C008S507000, C351S159000, C351S16000R, C351S162000, C351S16000R
Reexamination Certificate
active
06224945
ABSTRACT:
The invention generally relates to a process for the manufacture of crosslinked, transparent, hydrophilic and photochromic polymeric materials and to the use of the latter in the manufacture of optical and ophthalmic articles having photochromic properties and in particular contact lenses.
It is known to manufacture photochromic contact lenses by incorporation of a photochromic compound, such as a spirooxazine compound, in the mixture of polymerizable monomers resulting, after polymerization in a mould, in the final contact lens.
Thus, Patent Application WO 96/04590 discloses the manufacture of photochromic contact lenses made of methyl methacrylate (MMA) and N-vinylpyrrolidone (NVP) copolymer, which consists in introducing a spirooxazine compound into a mixture of MMA and NVP monomers, in the presence of alkyl methacrylate as crosslinking agent and of azobisisobutyronitrile (AIBN) as thermal initiator, and in subsequently thermally polymerizing the mixture.
This technique, commonly known as “cast in place”, is also used in Patent EP-A-277,639, which discloses the incorporation, in a base monomeric mixture (in particular, based on hydroxyethyl methacrylate (HEMA)), of a spirooxazine compound comprising an organic functional group which can be polymerized by addition or by ring opening. The mixture is subsequently polymerized. The photochromic compound, thus fixed within the material constituting the lens, is assumed not to be eluted in the lacrymal medium.
This “cast in place” process for the photochromic compounds exhibits numerous disadvantages.
Photochromic compounds are compounds which are sensitive to the action of the free radicals formed during the polymerization of mixtures of monomers by activation of the initiator. Under the effect of these free radicals, photochromic compounds, in particular spirooxazine compounds, are liable to decompose, generating coloured by-products. The result of this is, on the one hand, an overall decrease in the effectiveness of the photochromic compound, a portion of which has been destroyed, and, on the other hand, a permanent colouring brought about in the lens by these coloured by-products, which is not desired.
In addition, a significant disadvantage is that these by-products can exhibit a toxic nature, while, because of their low molar masses, they can diffuse through the lens towards the eye of the wearer.
Thus, while this “cast in place” technique could be used with some success in the manufacture of opthalmic glasses intended for spectacles, this does not apply in the production of contact lenses and, to the knowledge of the inventors, no photochromic hydrophilic contact lens has been marketed to date.
The possibly toxic nature of the by-products formed during the polymerization renders this “cast in place” technique virtually unusable in the case of contact lenses.
The fact that, in the “cast in place” process for photochromic compound of Patent EP-A-277,639, the latter is fixed to the polymeric network constituting the contact lens is invalid with regard to the decomposition by-products.
Furthermore, the technique of Patent EP-A-277,639 limits the possible choice of the photochromic compounds which can be used.
The “cast in place” technique lacks flexibility at the industrial level insofar as it is impossible to render photochromic already existing lenses, which necessitates disposing of large stocks of photochromic contact lenses.
Finally, the “cast in place” technique does not make it possible to incorporate the photochromic compound in predetermined chosen regions of the lens.
In particular, hydrophilic contact lenses exhibit a diameter greater than that of the iris and it may be aesthetically advantageous to render photochromic just the central part of the contact lens covering the pupilary region of the eye of the wearer.
The object of the invention is therefore to provide a process for the production of crosslinked, transparent, hydrophilic and photochromic polymeric materials which solves the above problems, materials which make it possible to prepare photochromic contact lenses which are preferably resistant to the sterilization treatments, in particular thermal sterilization treatments, conventionally used.
According to the invention, the process for producing a crosslinked, transparent, hydrophilic and photochromic polymer material comprises:
(a) dissolving a photochromic agent in a solvent or mixture of solvents capable of at least partially dissolving the photochromic agent, in order to obtain a photochromic impregnating solution;
(b) impregnating a crosslinked, transparent and hydrophilic polymeric material with the photochromic impregnating solution, in order to obtain a material impregnated with photochromic solution;
(c) rinsing the impregnated material with an aqueous solution, in order to replace, with the aqueous solution, the solvent impregnated in the material; and
(d) recovering the crosslinked, transparent, hydrophilic and photochromic polymeric material.
The process of the invention applies to any type of crosslinked, transparent and hydrophilic polymeric material suitable for the manufacture of contact lenses.
In the context of the present invention, the term “hydrophilic material” is understood to mean any material having a degree of hydrophilicity of greater than or equal to 10% and preferably of greater than or equal to 35%.
Particularly preferred materials are those having a degree of hydrophilicity of 50% or more.
As is conventional, the term “degree of hydrophilicity” is understood to mean the maximum percentage, by weight, of water which a polymeric material can fix.
The hydrophilic polymeric materials are generally obtained by polymerization, preferably in the presence of a crosslinking agent, of at least one of the following monomers:
hydroxyalkyl (meth)acrylates, alkoxy derivatives of hydroxyalkyl (meth)acrylates, aminoalkyl (meth)acrylates, monovinyl ethers, monovinyl polyethers, hydroxylated vinyl ethers, N-vinyllactams, amido derivatives of (meth)acrylic compounds, ionic monomers, zwitterionic monomers, oligomers of the abovementioned monomers and their mixtures.
The recommended hydroxyalkyl (meth)acrylates are those in which the alkyl group generally comprises from 1 to 4 carbon atoms.
Specific examples of hydroxyalkyl (meth)acrylate are 2-hydroxyethyl methacrylate (HEMA), hydroxypropyl acrylate, hydroxypropyl (meth)acrylate and 2,3-dihydroxypropyl methacrylate (glyceryl methacrylate).
The recommended alkoxy derivatives of hydroxyalkyl (meth)acrylates are the mono-, di- or triethoxylated compounds having an alkyl group generally comprising from 1 to 4 carbon atoms.
Mention may be made, among the monomers of the N-vinyllactam type, of N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone and N-vinylcaprolactam.
Mention may be made, among the amido derivatives of (meth)acrylic compounds which are of use, of (meth)acrylamide, N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-diacetone(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-dimethylaminomethyl-(meth)acrylamide, N,N-dimethylaminoethyl-(meth)-acrylamide and N-methylaminoisopropyl(meth)-acrylamide. Mention may be made, among the aminoalkyl (meth)acrylates, of aminoethyl (meth)acrylate, dimethylaminoethyl methacrylate, methylaminoethyl methacrylate and diethylaminoethyl methacrylate.
Mention may be made, among the hydrophilic ionic monomers, of (meth)acrylic acid, as well as of cationic monomers, such as quaternary ammonium derivaties of (meth)acrylic acid.
Mention may be made, among the zwitterionic monomers, of those disclosed in Patent Application WO 92/07885. The latter monomers generally make it possible to reduce the affinity of the hydrogel with respect to the proteins in the lacrymal medium.
Examples of conventional crosslinking agents are ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, such as diethylene glycol di(meth)acrylate or triethylene glycol di(meth)acrylate, long-chain di(meth)acrylates, such as hexamethylene di(meth)acrylate, vinyl (meth)acrylate, allyl (meth)acrylate, divinylbenzene, dially
Cameron Erma
Essilor International (Compagnie Generale d'Optique)
Fulbright & Jaworski L.L.P.
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