Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-10-13
2001-01-23
Niland, Patrick (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C351S106000, C351S106000, C523S106000, C524S507000, C524S589000, C525S123000, C525S455000, C525S920000
Reexamination Certificate
active
06177507
ABSTRACT:
The present invention relates in a general manner to polymerizable compositions comprising a hydrophilic monomer or a mixture of hydrophilic monomers and a crosslinking agent which, after polymerization, results in crosslinked polymers which may be hydrated in order to form hydrogels having improved mechanical properties, in particular the elongation at break, while at the same time having a high degree of hydrophilicity which is often greater than that of the known hydrogel polymers.
The invention also relates to polymers obtained by polymerization of these polymerizable compositions as well as to the corresponding hydrated polymers (hydrogels).
The invention further relates to finished or semifinished articles formed from these polymers and hydrated polymers.
By way of articles which may advantageously be formed from the polymers and hydrated polymers according to the invention, mention may be made of ophthalmic articles, such as contact lenses, and separation membranes, for example membranes for reverse osmosis. The polymers according to the invention are particularly useful, when they have the appropriate transparency, for manufacturing ophthalmic articles such as contact lenses.
The materials for hydrophilic contact lenses must have simultaneously a certain number of advantageous characteristics, namely:
a high degree of hydrophilicity; and
good mechanical properties which make the contact lens suitable to be handled by its user.
This is because if the mechanical properties are insufficient the lens may unfortunately be torn or deformed by the user, and if the degree of hydrophilicity is too low the oxygen permeability of the lens may become insufficient, with the result that there is a risk of opacification of the cornea of the user's eye.
It is difficult to reconcile the two characteristics mentioned above in the same hydrogel material. This is because when the degree of hydrophilicity increases it is generally found that the mechanical properties of the hydrogel material fall.
In the field of contact lenses, it is known to use crosslinked polymers for their manufacture.
A well-known class of crosslinking agents in this field is the class of ethylene glycol dimethacrylate derivatives. However, the hydrogel polymers obtained by means of these crosslinking agents do not have the best combinations of mechanical properties and of degree of hydrophilicity.
In order to improve the mechanical properties of hydrogel polymers, it has been proposed in document U.S. Pat. No. 5,135,965 to crosslink these polymers by means of special crosslinking agents, which are unsaturated polymers, optionally combined with monomer crosslinking agents containing at least two olefin linkages per molecule.
Russian Inventor's Certification USSR 82 5548 proposes crosslinked hydrophilic polymer compositions whose transparency and mechanical properties are improved. The specific crosslinking agents envisaged in the above document are polyethylene glycol dimethacrylate having a molar mass of 1500 and a dimethacrylate oligourethane of 456 molar mass, the crosslinking agent being used in an amount ranging from 5 to 20% by weight.
It is therefore desirable to develop polymerizable compositions which, after polymerization, result in crosslinked hydrogel polymers having improved mechanical properties and high degrees of hydrophilicity.
The subject of the invention is therefore a polymerizable composition comprising a hydrophilic monomer or monomer mixture and a crosslinking agent which, after polymerization, provides a crosslinked hydrogel polymer having a high degree of hydrophilicity and mechanical properties, in particular an elongation at break, which are markedly improved.
The subject of the invention is also the polymers and hydrated polymers obtained by polymerizing the polymerizable compositions according to the invention.
The subject of the invention is also finished and semifinished articles formed from the above polymers, and particularly ophthalmic articles such as contact lenses.
According to the invention, the polymerizable composition comprises a hydrophilic monomer or hydrophilic monomer mixture and an effective amount of crosslinking agents, wherein the crosslinking agent comprises a urethane oligomer having a molar mass of between 500 and 5000, the limits being inclusive, and the chain of which carries two to six (meth)acrylate functional groups or a mixture of these polyurethane oligomers.
The polyurethane oligomers useful as crosslinking agents in the polymerizable compositions of the invention are therefore polyurethane oligomers functionalized by two to six acrylate and/or methacrylate functional groups, preferably two or three functional groups, more preferably with two chain end (meth)acrylate functional groups.
The functionalized polyurethane oligomers particularly recommended are difunctional oligomers, and most particularly those with two chain-end (meth)acrylate functional groups.
The polyurethane oligomers useful in the polymerizable compositions according to the invention have a molar mass of between 500 and 5000, the limits being inclusive, better still ranging from 500 to 3000 and even better still from 1000 to 3000.
According to the invention, the urethane oligomers useful as crosslinking agents may be aliphatic or aromatic oligomers, aliphatic oligomers being preferred.
Finally, among the urethane oligomers useful in the present invention, diacrylate polyurethane oligomers are particularly recommended.
The amount of urethane oligomer used in the compositions according to the invention must be an effective amount, that is to say sufficient to ensure appropriate crosslinking of the composition.
In general, the urethane oligomers useful as crosslinking agents in the polymerizable compositions according to the invention are used in an amount ranging from 0.05 to 4 parts by weight, preferably 0.1 to 1 part by weight and even better 0.1 to 0.5 parts by weight per 100 parts by weight of the mixture of monomers present in the initial polymerizable composition.
According to the invention, the urethane oligomers having a di(meth)acrylic or tri(meth)acrylic functional group may be obtained by reacting a polyol (diol or triol) with a polyfunctional polyisocyanate in the presence of a hydroxylated (meth)acrylate monomer.
In order to obtain di(meth)acrylate oligomers, the diol may be chosen from:
linear aliphatic diols, such as alkanediols, polycaprolactonediols, polyetherdiols, polyesterdiols and polycarbonatediols, and aromatic diols.
Examples of aliphatic diols and processes for obtaining them are described in detail in patent U.S. Pat. No. 5,246,630.
The preferred diol is propylene glycol of formula:
The polyisocyanate used may be of the aliphatic or aromatic type. Examples of aliphatic isocyanates which can be used are also described in U.S. Pat. No. 5,246,630.
The aliphatic urethane oligomers are obtained by reacting an aliphatic polyol with an aliphatic polyisocyanate.
In order to obtain an aromatic urethane oligomer, it is sufficient for at least one of the precursors, either the polyol or the polyisocyanate, to include an aromatic group.
The urethane oligomers according to the invention may also be obtained commercially.
By way of examples of urethane oligomers which can be used in the context of the present invention, and which are commercially available, mention may be made of the following products provided by Cray Valley:
CN 934—aliphatic diacrylate polyurethane, of 1200 molar mass;
CN 965—aliphatic diacrylate polyurethane, of 3000 molar mass;
CN 976—aromatic diacrylate polyurethane, of 1500 molar mass; and
CN 929—aliphatic triacrylate polyurethane, of approximately 1500 molar mass.
As mentioned above, the polymerizable compositions according to the invention contain a hydrophilic monomer or a hydrophilic monomer mixture.
Among the hydrophilic monomers which can be used, mention may be made of hydroxyalkyl (meth)acrylate, alkoxy derivatives of hydroxyalkyl (meth)acrylate, aminoalkyl (meth)acrylates, monovinyl ethers, monovinyl polyethers, hydroxylated vinyl ethers
Essilor International (Compagnie Generale d'Optique)
Niland Patrick
O'Keefe, Egan & Peterman
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