Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-06-23
2001-11-13
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S204000, C526S217000, C526S220000, C526S230500
Reexamination Certificate
active
06316570
ABSTRACT:
DESCRIPTION OF THE INVENTION
The present invention relates to polymerizable compositions and polymerizates prepared therefrom. Particularly, the present invention relates to polymerizable compositions that contain a major amount of a first component comprising an aliphatic polyol(allyl carbonate) monomer and a minor amount of a second component comprising an aromatic polyol(allyl carbonate) monomer. More particularly, the aromatic polyol(allyl carbonate) monomer is present in the compositions of the invention in at least amounts such that a polymerizate prepared from the composition has reduced cracking defects compared to polymerizates prepared only from the aliphatic polyol(allyl carbonate), and a refractive index of less than 1.530.
Polymerizable compositions based on polyol(allyl carbonate) monomers, particularly aliphatic polyol(allyl carbonate) monomers such as diethylene glycol bis(allyl carbonate), and polymerizates obtained therefrom are well known in the art. Polymerizates of polymerizable compositions based on diethylene glycol bis(allyl carbonate) possess excellent clarity, good flexibility, abrasion resistance and refractive index values of typically less than 1.530, e.g., 1.498.
Monomers such as diethylene glycol bis(allyl carbonate) are used extensively in the preparation of molded articles, such as ophthalmic lenses, noncorrective lenses, face shields, and automotive and aircraft transparencies. Molded ophthalmic lens articles are typically prepared by introducing a polymerizable composition into a mold, e.g., a glass mold, polymerizing the composition within the mold, and then removing the molded article from the mold. Polymerizable compositions based on aliphatic polyol(allyl carbonate), e.g., diethylene glycol bis(allyl carbonate), undergo shrinkage, i.e., a decrease in volume, upon polymerization. This decrease in volume can cause the polymerizing composition to pull away from the interior surfaces of the mold, thereby resulting in the formation of defects in the molded article. Defects due to volume shrinkage include, for example, cracking, warping and surface anomalies, and typically require scrapping of the defective article, resulting in increased production costs. Cracking is typically the most predominant defect attributed to volume shrinkage during in-mold polymerization or casting.
Polymerizates prepared from aliphatic polyol(allyl carbonate) monomers, such as diethylene glycol bis(allyl carbonate), are often tinted with static dyes and/or photochromic substances to form tinted polymerizates, e.g., sun lenses and tinted ophthalmic lenses. Typically, the process of tinting a polymerizate involves a multiple of steps. The polymerizate is first prepared in an undercured state, then tinted by a process of imbibition in which the colorant, e.g., one or more static dyes, is brought into contact with at least a portion of the surface of the undercured polymerizate. Finally, the tinted undercured polymerizate is fully cured. Such a multi-step tinting process takes additional time, increases the risk of damaging the polymerizate and ultimately can result in increased production costs. While adding the colorant to the polymerizable composition prior to polymerization (in what is commonly referred to as a tint-in-place process), could eliminate some of the aforedescribed process steps, the colorant is often destroyed or otherwise inactivated during the polymerization process.
It would be desirable to develop new aliphatic polyol (allyl carbonate) based polymerizable compositions that have reduced cracking defects, while retaining a refractive index less than 1.530. It would also be desirable that tinted polymerizates be preparable from such newly developed compositions.
U.S. Pat. No. 4,613,656 describes polymerizing a mixture of polyol(allyl carbonate) monomer and an adhesion reducing amount of monomer-compatible mold release agent in the presence of a monoperoxycarbonate initiator. The polyol(allyl carbonate) monomer of the '656 patent is described as being an allyl carbonate of linear or branched aliphatic or aromatic liquid polyols, e.g., aliphatic glycol bis(allyl carbonate) compounds or alkylidene bisphenol bis(allyl carbonate) compounds.
U.S. Pat. No. 4,666,976 describes a pourable, polymerizable composition of polyol(allyl carbonate) monomer, bromoxylenol blue and optionally a thermally decomposable polymerization initiator, e.g., a monoperoxycarbonate initiator. The polyol(allyl carbonate) monomer of the '976 patent is described as being an allyl carbonate of linear or branched aliphatic or aromatic liquid polyols, e.g., aliphatic glycol bis(allyl carbonate) compounds or alkylidene bisphenol bis(allyl carbonate) compounds.
In accordance with the present invention, there is provided a polymerizable composition comprising:
(a) a major amount of a first allyl functional monomer represented by the following general formula I,
in which R
1
is a polyvalent residue of an aliphatic polyol, R
2
is an allyl group or a substituted allyl group, and i is a whole number from 2 to 6; and
(b) a minor amount of a second allyl functional monomer represented by the following general formula II,
in which R
3
is a polyvalent residue of an aromatic polyol, R
4
is an allyl group or a substituted allyl group and k is a whole number from 2 to 6,
wherein said second allyl functional monomer is present in said polymerizable composition in at least an amount to provide a polymerizate of said polymerizable composition having (i) reduced cracking defects relative to a polymerizate of said composition free of (b), and (ii) a refractive index of less than 1.530, as determined in accordance with American Standard Test Method (ASTM) number D 542-95.
Other than in the operating examples, or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, etc. used in the specification and claims are to be understood as modified in all instances by the term “about.”
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Bonde Craig J.
Clontz Charles C.
Tracy Diane M.
Franks James R.
Marmo Carol A.
Pezzuto Helen L.
PPG Industries Ohio Inc.
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