Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1989-02-24
2001-08-07
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S314000
Reexamination Certificate
active
06271328
ABSTRACT:
The present invention relates to a liquid polymerisable composition, which by polymerisation yields optical articles endowed with a high refractive index. The invention relates also to the optical articles obtained from such a composition.
In the field of organic glasses, the products are interesting, which derive from the polymerization of bis(allyl carbonates) of diols, in particular diethylene glycol bis(allyl carbonate), and this on considering their optical and mechanical characteristics, which render then useful for the preparation of optical articles (F. Strain; “Encylcopaedia of Chemical Processing and Design”, volume I, Interscience Publishers, New York, 1964, pages 799-foll.)
However, in the preparation of the optical articles from such polymerisates, thicknesses are required, which are relatively higher than of articles made from inorganic glass, owing to the relatively low values of refractive index which are typical for the same polymerisates. This is disadvantageous both from the viewpoint of the weight of the articles, and as regards their aesthetical features, besides the difficulties to be coped with, when high-thickness articles endowed with a high optical quality have to be manufactured.
Therefore, in order to overcome this problem, compositions were developed in the art, which are suitable for forming polymerisates endowed with a relatively high value of refractive index. Within the range of the allyl-carbonate derivatives, these compositions according to the prior art generally comprise polymerisable monomers which contain an aromatic moiety, such as bisphenol-A bis(allyl carbonate) and the relevant ethoxylated derivatives thereof, such as disclosed, e.g., in U.S. Pat. No. 4,622,376; in German patent application No. 3,439,395, and in the U.S. patent application Ser. No. 168,162 filed on Mar. 15, 1988 now abandoned.
The present Applicant has found now a liquid, polymerisable composition, containing a particular allyl-carbonate derivative, which makes it possible for optical articles to be obtained, which are endowed with good general characteristics, and display a refractive index which is further improved as compared to those obtainable with the compositions according to the prior art.
In accordance therewith the present invention relates to a liquid composition, polymerisable by means of a free-radical route to yield optical articles endowed with a high refractive index, which contains
A) from 20 to 80% by weight of an allyl-carbonate derivative, which can be represented by means of the formula:
wherein:
R
1
represents the hydrogen atom, or a linear or branched (C
1
-C
6
)-alkyl radical, a phenyl radical or a benzyl radical;
X
1
, X
2
, X
3
, X
4
, X
5
, X
6
represent, independently from one another, the hydrogen atom, or a halogen atom selected from among chlorine and bromine; and
a and b represent, independently from each other, an integer comprised within the range of from 0 to 3;
B) from 80 to 20% by weight of a copolymerisable monomer containing at least one ethylenic unsaturation in its molecule.
The (A) component of the composition according to the present invention can be obtained by means of the reaction of the di-hydroxy precursor and allyl chloroformate in the presence of an acid acceptor.
According to an alternative route, said di-hydroxy precursor can be reacted with phosgene in order to form the corresponding bis(chloroformate), with this latter being then reacted with allyl alcohol in order to obtain the (A) component.
These reactions are per se known in the art.
The preparation of the (A) component, in which a and b are different from zero, can be carried out by means of a trans-esterification between the di-hydroxy precursor and diallyl-carbonate, in the presence of a basic catalyst. Also this trans-esterification reaction is per se known in the art; reference is made, e.g., to the disclosure of European patent No. 35,304. When the reaction is carried out under trans-esterification conditions, the (A) component is obtained in the form of a mixture of monomer and oligomers, the ratio of which may vary as a function of the ratio of the di-allyl-carbonate reactant to the di-hydroxy precursor. From these mixtures, the monomeric (A) component can be separated, or the same mixture can be used as the (A) component. In this latter case, the content of oligomers in the mixture should not preferably exceed the value of 30% by weight.
A preferred (A) component for the composition according to the present invention is 1-phenyl-ethylidene-bis(4,4′-hydroxy-ethoxy-benzene) bis(allyl carbonate), i.e., the compound corresponding to the formula (I) in which:
R
1
=methyl;
X
1
=X
2
=X
3
=X
4
=X
5
=X
6
=H; and
a=b=1:
This preferred (A) component can be obtained by means of the trans-esterification of diallyl carbonate and 1-phenyl-ethylidene-bis(4,4′-hydroxy-ethoxy-benzene):
by operating in the presence of a basic catalyst, and with a molar ratio between the two reactants higher than about 6/1.
Under these conditions, a mixture of compound (II) with its oligomers, definable by means of the formula:
wherein:
Z is the radical of the dihydroxy precursor (III); and
n is comprised within the range of from 1 to about 5,
is obtained.
In the preferred form of practical embodiment of the present invention, the reaction is carried out with a molar ratio of the diallyl-carbonate to the compound (III) which is of the order of 10/1-12/1, and as the reaction product, a mixture of monomer (n=1 in the above formula (IV)) and oligomers (n=1 in said formula (IV)) and oligomers (n>1 in said formula (IV)), is obtained, which contains 80-90% by weight of monomer. Such a mixture can be directly used as the (A) component of the composition according to the present invention.
The (B) component of the composition according to the present invention is preferably selected from the group consisting of diallyl ortho-phthalate, diallyl isophthalate, diallyl terephthalate, triallyl cyanurate, triallyl isocyanurate, phenyl acrylate, phenyl methacrylate, benzyl acrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, vinyl benzoate, m-chlorovinyl benzoate, and mixtures thereof.
The (A) component of the composition is essential in order to obtain the desired values of refractive index in the optical articles, whilst the (B) component is essential in order to obtain a liquid composition showing viscosity values which are suitable for the processing and the transformation into organic glasses.
In the preferred form of practical embodiment, the composition according too the present invention contains from 35 to 65% by weight, of (A) component, and from 65 to 35% by weight of (B) component.
The composition according to the present invention additionally contains a polymerization initiator in an amount comprised within the range of from 2 to 8 parts by weight per each 100 parts by weight of the total of the (A) and (B) components. Such polymerization initiators are soluble in the same composition, and are capable of generating free radicals at a temperature comprised within the range of from about 30° C. to about 100° C. Non-limitative examples of such initiators are di-isopropyl-peroxy-dicarbonate, di-cyclohexyl-peroxy-dicarbonate, di-sec-butyl-peroxy-dicarbonate, di-benzoyl peroxide and tert-butyl-perbenzoate.
In the preferred form of practical embodiment, the polymerization initiator is contained in the composition in an amount comprised within the range of from 3 to 7 parts by weight per each 100 parts by weight of the total of the (A) and (B) components.
The liquid, polymerisable composition according to the present invention may preferably contain one or more conventional additives, such as stabilizers, mould-release agents, dyes, pigments, U.V.- or I.R.-light absorbers and the like, however in a total amount which does not exceed 1 part by weight per each 100 parts by weight of the total of (A) and (B) components.
The liquid, polymerisable composition according to the p
Renzi Fiorenzo
Rivetti Franco
Romano Ugo
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