| abstract |
PURPOSE:To ease the release from lens matrices and at the same time make it possible to obtain a high transparency and a favorable surface accuracy by a method wherein surface active agent is added in advance to a mixture of polyisocyanate and polythiol. CONSTITUTION:About 1-5,000ppm of internal mold release agent is added to a mixture having the predetermined mixing ratio of polyisocyanate to polythiol. Further, when necessary, the predetermined amount of polymerization catalyst such as dibutyltin dilaurate, dimethyltin chloride or the like is prepared to be added to the mixture. The resultant mixture is cast in a mold, which is formed by combining glass or metal matrices and a gasket made of polyethylene or the like so as to be cured by heating and then cooled and finally released from the mold in order to obtain a molded sulfur-containing urethane resin lens. As the internal mold release agent, one selected out of a fluorine- based nonionic surface active agent, silicon-based nonionic surface active agent, alkyl quaternary ammonium salt, acid phosphate or the like is added. |