Sulfur-containing compounds for optical grade polymeric casting

Details Sulfur-containing compounds for optical grade polymeric casting Sulfur-containing compounds for optical grade polymeric casting

1997-07-25

2000-04-18

Lipman, Bernard

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

560153, C07C32100

Patent

active

060517336

DESCRIPTION:

BRIEF SUMMARY
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, .alpha.-mercaptopropionic acid, or .beta.-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.dbd.CH.sub.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.dbd.CH.sub.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.sub.2 CH.sub.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 but

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