Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-07-15
2001-02-06
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C528S376000
Reexamination Certificate
active
06184323
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates, in general, to polymerizable compositions based on thio(meth)acrylate monomers, producing transparent polymer compositions exhibiting the properties which are required for their application in the field of ophthalmics.
BACKGROUND OF THE INVENTION
It has long been known to employ organic polymer materials for obtaining ophthalmic lenses.
One of the materials most commonly employed is obtained by polymerization of the monomer CR 39
200
(diethylene glycol diallyl carbonate).
However, for a number of years, there has been an increasing demand for lenses which, while guaranteeing substantially the same optical qualities and the same mechanical characteristics as the lenses made of known organic polymer material, are thinner and are therefore lighter in weight.
Various materials have been developed to meet this demand. These new organic materials generally have high refractive indices which can reach, or even exceed, refractive indices n=1.6.
Thus, as a result of this high refractive index, it is possible to manufacture lenses of lower thickness for an equivalent corrective power (optical power).
A class of monomers that have recently been tested for obtaining materials in ophthalmics is the class of thio(meth)acrylates.
Patent EP-A-273 661 describes monomers of thio(meth)acrylate type which can be used in the field of ophthalmic optics, and patent EP-A-273 710 describes polymerizable compositions producing transparent organic polymers which are suitable for the production of ophthalmic lenses. These compositions contain a monomer which has at least one thio(meth)acryloyl group and at least two (meth)acryloyl groups and, optionally, at least one other monomer which is copolymerizable by a radical route.
Patent EP-A-273 710 describes in particular compositions based on bis(2-methacryloylthioethyl) sulfide.
This patent also mentions that the polymerizable compositions can be polymerized by a thermal route, by UV irradiation or by the action of an electron beam.
All the compositions given by way of example in this patent are polymerized either by a purely thermal route (for several hours), or by prepolymerization using UV irradiation followed by a thermal polymerization to obtain a hardened moulded article.
Patent application WO-90/04587 describes 4,4′-bis [(meth)acryloylthiophenyl] sulfide monomers and their use in poymerizable compositions in combination with a copolymerizable vinyl monomer and/or polythiols.
SUMMARY OF THE INVENTION
It would therefore be desirable to produce polymerizable compositions making it possible to obtain transparent hardened polymer compositions exhibiting all the properties that are required for an application in ophthalmic optics.
It would be desirable, in particular, to produce polymerizable compositions resulting in hardened polymer compositions exhibiting high transparency and refractive index, for example a refractive index higher than 1.55 and preferably of the order of 1.6, a high abbe number, a low density, good colourability and good impact strength.
It would also be desirable that the hardened polymer compositions should stand up well to ageing and in particular should have a good resistance to degradation by ultraviolet radiation.
It would also be desirable to obtain polymerizable compositions producing transparent polymer compositions which are useful in ophthalmic optics, which can be photopolymerized in very short periods of time, for example with irradiation times of the order of 3 to 5 minutes.
Such a very short period of time for forming and hardening the polymer composition starting from polymerizable compositions is an advantage that is of particular interest in an industrial content, since it enables the manufacturing time to be appreciably reduced and the production efficiency to be increased.
As mentioned previously, optical and ophthalmic articles made from the compositions according to the invention shall exhibit a high transparency. Transparency may be evaluated by determining visually the absence of diffusion areas within the article and its yellow index. The lower is the yellow index (YI), the higher is the transparency of the article.
The objective of the present invention is therefore to produce polymerizable compositions which have the above mentioned advantages and in particular which can be photopolymerized in a very short time.
A further objective of the present invention is to formulate polymerisable compositions which result in optical and ophthalmic moulded articles having high transparency as quantified by the absence of diffusion areas and lower yellow indices (YI).
Another objective of the present invention is the polymer compositions obtained by polymerization of the polymerizable compositions. Another objective of the present invention is the optical articles manufactured from polymer compositions.
The above objectives are attained, according to the invention, by producing a polymerizable composition comprising, based on the total weight of polymerizable monomers present in the composition:
a) 10 to 70% by weight of a difunctional thio(meth)acrylate monomer, of formula (I):
in which R
1
and R
2
denote a hydrogen atom or a radical —CH
3
,
or of a mixture of at least one monomer of formula (I) with at least one monomer of formula (II):
in which R′
1
and R′
2
denote a hydrogen atom or a radical —CH
3
;
b) 10 to 60% by weight of at least one monomer of formula (III):
in which R
3
and R
4
denote a hydrogen atom or a radical —CH
3
and O≦m+n≦10; and
c) 5 to 30% by weight of at least one aromatic or polycyclane mono(meth)acrylate monomer.
The composition of the invention may further comprise, based on the total weight of polymerizable monomers present in composition:
d) up to 15% by weight of a polyalkylene glycol di(meth)acrylate; and/or
e) up to 15% and preferably up to 10% by weight of a polythiol R(SH)
n
, in which n is an integer varying from 2 to 6 and preferably from 2 to 3, R is an organic group of valency equal to n, or a mixture of these polythiols.
In a preferred embodiment of the invention, the composition comprises, based on the total weight of polymerizable monomers present in the composition:
a) 10 to 70% by weight of a difunctional thio(meth)acrylate monomer, of formula (I):
in which R
1
and R
2
denote a hydrogen atom or a radical —CH
3
,
or of a mixture of at least one monomer of formula (I) with at least one monomer of formula (II):
in which R′
1
and R′
2
denote a hydrogen atom or a radical —CH
3
;
b) 10 to 60% by weight of at least one monomer of formula (III):
in which R
3
and R
4
denote a hydrogen atom or a radical —CH
3
and O≦m+n≦10; and
c) 5 to 30% by weight of at least one aromatic or polycyclane mono(meth)acrylate monomer, and
e) 1 to 10% by weight, preferably 5 to 10% by weight of a polythiol R(SH)
n
in which n is an integer varying from 2 to 6 and preferably from 2 to 3, R is an organic group of valency equal to n, or a mixture of these polythiols.
In the constituents a), the monomer of formula (I) is preferably bis(2-methacryloylthioethyl) sulfide and the monomer of formula (II) is bis(4-methacryloylthiophenyl) sulfide.
The constituent a) of the polymerizable composition according to the invention also preferably represents 20 to 60% by weight relative to the total weight of the components a) to e).
In the constituent a), the monomer of formula (I) is also preferably the major monomer and preferably represents between 50 and 100% by weight of the constituent a).
The monomers of formula (III) of the constituent b) which are recommended are 2,2-bis[4-(meth)acryloyloxyphenyl]propane, 2,2-bis-4-(&ohgr;-(meth) acryloyloxypolyethoxy)phenyl]propane and in particular the monomers of formula (II) in which R
3
═R
4
═CH
3
and m+n=2.6 (EBADMA), m+n=4 (DBADMA) and m+n=10 (OBADMA).
Furthermore, in order to obtain all of the advantageous characteristics of the invention it is preferable that the constituen
Essilor International-Compagnie Generale d'Optique
Henderson Christopher
O'Keefe, Egan & Peterman
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