Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-12-29
2001-10-30
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...
C526S323200
Reexamination Certificate
active
06310161
ABSTRACT:
This invention is in the area of polymeric compositions for the preparation of optical grade materials, and the optical materials, such as lenses, prepared thereby. The compositions include reactive or nonreactive additives in combination with polymeric materials and optional diluents. The reactive additives can be incorporated into polymer chains during polymerization to modify the properties of the polymer.
Polymers are often used in demanding applications such as matrix materials for advanced composites and as optical components, such as lenses. These materials require high strength and acceptable levels of flexibility and toughness. Three important properties of optical grade polymeric materials include the refractive index, the relative dispersion and color.
The refractive index of a material is the ratio of the velocity of light through a vacuum to the velocity of light through the material. The refractive index is not a constant over the spectrum of light, but changes as a function of wavelength. This change in the refractive index is called dispersion. The refractive index of optical grade polymeric materials is generally tailored to meet very specific requirements. For example, when a polymer is mated with another material, such as during windshield repair or in the preparation of polymer/polymer or polymer glass composites, the refractive indices of the two materials must match almost exactly if the border between the two materials is to remain essentially invisible. High refractive index materials are useful in the production of thin high powered lenses.
Relative dispersion (or its reciprocal that is typically known as the Abbe number) is a measure of the refractive index's dependence on the wavelength of light. Optical grade polymeric materials should exhibit a minimal dependence of refractive index on wavelength (i.e. high Abbe number), and thus, have a low relative dispersion.
Optical grade polymeric materials should also exhibit minimal color.
Some sulfur containing materials reported to act as stabilizers in polymer systems include those disclosed in the following patent documents.
British Patent No. 1 270 114 discloses plasticized thermoplastic polymer compositions that contain a thermoplastic polymer, a polymerizable plasticizer, and a polythiol. The patent states that the mechanism by which the compositions are cured is not certain, but may involve the reaction of the polythiol with the polymerizable plasticizer to produce thioether links. The plasticizer is defined as a compound capable of free-radical initiated homopolymerization, which has two to five units of unconjugated unsaturation. The polythiol has two or more reactive —SH groups, and is preferably an ester of thioglycolic acid, &agr;-mercaptopropionic acid, or &bgr;-mercaptopropionic acid with a polyhydroxy compound having two to six hydroxyl groups.
U.S. Pat. No. 4,226,991 discloses antioxidant stabilizers for polyolefin resins, produced by reacting an olefin of formula R′RC′CH
2
, where R is alkyl and R′ is H or alkyl (and wherein the sum of the number of carbon atoms in R and R′ is from 4 to 38), with a mercaptopropionic acid and a polyol.
U.S. Pat. No. 4,349,468 discloses stabilizers for polyolefin resins, which are the reaction products of an alkylthiopropionic acid with a polyol. The alkylthiopropionic acid is the reaction product of an olefin of formula R′RC═CH
2
, where R is alkyl and R′ is an alkyl group (and wherein the sum of the number of carbon atoms in R and R′ is from 4 to 26) or hydrogen, with a betamercaptopropionic acid compound of formula HSCH
2
CH
2
COR″, where R″ is hydrogen or a lower alkyl group.
U.S. Pat. No. 3,181,971 discloses stabilizers for polypropylene which can prevent copper catalyzed degradation of the polypropylene. The stabilizer composition is a mixture of a phenolic antioxidant, a non-volatile primary or secondary amino compound, and an organic divalent sulfur compound. The exemplified sulfur containing compounds are alkyl esters of dithio propionates and dithio butyrates.
U.S. Pat. No. 3,629,194 discloses mercaptoester antioxidant stabilizers for polyolefins.
U.S. Pat. No. 3,758,549 discloses alkyl esters of alkylthioalkanoic acids used as antioxidants for a variety of materials, including organic polymeric substances.
European Application 0 453 149 A2 discloses a crosslinkable polymeric casting composition that includes a) a polyoxy alkylene glycol diacrylate or dimethacrylate; b) a monomer having a recurring unit derived from at least one radical-polymerizable bisphenol monomer capable of forming a homopolymer having a refractive index of more than 1.55; and c) a urethane monomer having 2 to 6 terminal groups selected from the group comprising acrylic and methacrylic groups.
EPA 0 598 551 A2 discloses a crosslinkable polymeric casting composition for optical lenses comprising 35 to 85% by weight, of an aromatic olefin monomer, 15 to 60% by weight of a polythio compound such as a polyol polyalkylthioester and optionally from 1 to 40% by weight of a polymerizable comonomer such as styrene or a polyoxyalkylene glycol poly(meth)acrylate. This composition however does not meet the required combination of high refractive index, low refractive dispersion and minimal color, presumably because it results from non-reactive mixing of the ingredients at room temperature.
Thus the technical problem to be solved by the present invention is to provide a composition suitable for lenses, possessing a combination of high refractive index, low refractive dispersion and minimal color, and at the same time which is able to be manufactured at an accelerated speed versus prior art compositions, thereby improving the productivity of making lenses and hence improving their manufacturing cost and their time of delivery to customers.
It is therefore an object of the invention to provide an additive for use in polymeric compositions with acceptable optical properties, in particular which enhance the refractive index of the material without adversely affecting its color and refractive dispersion.
It is another object of the invention to provide a polymeric material with excellent optical properties and acceptable flexibility and toughness.
It is still another object of the invention to provide an additive that has a high refractive index, an Abbe number between 25 and 60 and minimal color.
It is yet another object of the present invention to provide a highly reactive polymeric composition which allows the manufacture of optical materials within a reduced period of time while maintaining the overall level of performance of the materials.
Polymeric compositions for the preparation of optical grade materials, and the optical materials prepared thereby, are provided. The compositions contain a class of reactive and non-reactive additives, in combination with a polymer and optionally a diluent. The additives are preferably the reaction product of a thiol containing compound and an unsaturated compound.
The additives optimally have a refractive index between about 1.40 and 1.70, and preferably between 1.50 and 1.70; a relatively high Abbe number (between about 25 and 60) and minimal color. Preferably, the additives have an Abbe number in the range from about 34 to 48. For some applications, additives exhibiting an Abbe number of between 34 and 40 are sufficient. By appropriate selection of the polythiol and unsaturated compound, additives can be prepared that have a refractive index that is higher than the reactants used to prepare it. The additive should also exhibit minimal color (i.e., a color in the CIE system wherein a is greater than −0.5 and b is less than +2.0, and preferably, less than +1.5). Further, the additives are noncrosslinked and are liquids at at least 60° C., and preferably at least 40° C.
These addditives can be incorporated into polymeric material without adversely affecting the optical properties of the polymer. By appropriate selection of the polymer and the additive, the polymeric compositi
Lipman Bernard
UCB S.A.
Wenderoth , Lind & Ponack, L.L.P.
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