Patent ID: 8022163

Claim:
A composition for polythiourethane optical materials comprising an isocyanate compound, an active hydrogen compound having a mercapto group, and an internal mold release agent, wherein the isocyanate compound is at least one selected from the group consisting of m-xylylene diisocyanate, 2,5-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane, 2,6-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane and hexamethylene diisocyanate; the active hydrogen compound is at least one selected from the group consisting of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane,pentaerythritol tetrakis(3-mercaptopropionate), 1,1,3,3-tetrakis(mercaptomethylthio)propane, 1,1,2,2-tetrakis(mercaptomethylthio)ethane, 4,6-bis(mercaptomethylthio)-1,3-dithiane and 2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane; and the internal mold release agent is obtained by the reaction of an acidic phosphate ester compound represented by the formula (1) with Zn: wherein, in the formula, m represents 1 or 2; n represents an integer of 0 to 20; R 1 represents an alkyl group having 1 to 20 carbon atoms, an alkylphenyl group having 7 to 20 carbon atoms or a phenylalkyl group having 7 to 20 carbon atoms; and R 2 and R 3 each independently represent a hydrogen atom, a methyl group or an ethyl group; and wherein the Zn is in an amount of 0.01 to 20 weight % based on the total amount of the internal mold release agent, and wherein the composition does not contain an organic tin compound.