Polymer compositions based on polythiourethanes for the manufacture of organic glasses
AssigneeEssilor International (Compagnie Generale d'Optique)
InventorsLeanirith Yean, Christophe Bochu
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Abstract
The present patent application relates to a polyurethane composition for organic glasses characterized in that it comprises: a first constituent formed by a polyisocyanate at least di-functional, and a second constituent formed by an acyclic saturated monomer bearing at least three reactive functions with respect to isocyanates to form carbamate links, among which reactive functions at least 40% in number are --SH mercapto groups, the proportion of the reactive functions being at least 45% by weight with respect to the molecular weight of the monomer.
Claims23
A polyurethane composition suitable for the production of optical lenses having a refractive index higher than 1.6 and a glass transition temperature higher than 100.degree. C., said polyurethane obtained by reacting a first component made of an at least difunctional polyisocyanate free of intramolecular sulfur atoms and a second component made of an acyclic saturated monomer having at least three reactive groups with respect to isocyanates per molecule, in respective amounts, to polymerize through formation of thiocarbamate and, optionally, carbamate links, wherein said reactive groups are --SH mercapto groups for at least 40% in number and are present in a proportion at least amounting to 45% by weight with respect to the molecular weight of said monomer.
A process for the production of a polymeric lens, said process comprising:
- mixing 2,3-dimercaptopropanol and xylylene diisocyanate in a ratio such that the sum of mercapto and hydroxy groups is substantially equal to the sum of isocyanate groups;
- adding a catalytic amount of a polymerization catalyst;
- degassing the resultant mixture and placing the degassed mixture in an optical lens mold;
- conducting polymerization in said mold according to a temperature cycle comprising about three hours to pass from ambient temperature to about 80.degree. C., then about three hours of polymerization maintained at about 80.degree. C., followed by an increase in temperature from about 80.degree. to about 130.degree. C. for a period of about two hours, and maintaining the polymerization temperature for three hours at about 130.degree. C.;
- and
- removing resultant lens from the mold in order to obtain a perfectly transparent lens having a refractive index of about 1.622, a constringence of about 37, a density of about 1.28 and a glass transition temperature of about 130.degree. C.
Dependencies are inferred from the claim text.