Patent ID: 8193303

Claim:
A process for producing a plastic lens which comprises preparing a prepolymer comprising sulfur by bringing at least one compound having an epithio group, sulfur and a portion of a polythiol compound into reaction with each other and, thereafter, adding the rest of the polythiol compound to the prepared prepolymer comprising sulfur and allowing polymerization to proceed; wherein the at least one compound having an epithio group is bis(β-epithiopropyl) sulfide, bis(β-epithiopropyl)disulfide, bis(β-epithiopropyl)ether, bis(β-epithiopropyl)methane, 1,2-bis(β-epithio-propyl)ethane, 1,3-bis(β-epithiopropyl)propane, 2,5-bis(β-epithiopropyl)-1,4-dithiane, 1,3- and 1,4-bis(β-epithiopropyl)cyclohexanes, 1,3- and 1,4-bis(β-epithiopropyl)benzenes, bis[4-(β-epithiopropylthio)phenyl]sulfide, or bis[4-(β-epithiopropylthio)cyclohexyl]sulfide; wherein the polythiol compound is at least one of bis(mercaptomethyl)-1,4-dithiane, bis(mercaptoethyl) sulfide, bis(mercaptoethyl)disulfide, 1,2-bis(mercaptoethyl)thio-3-mercaptopropane, pentaerythritol tetrakismercaptoacetate, pentaerythritol tetrakismercaptopropionate, trimethylolpropane trismercaptoacetate, trimethylolpropane trismercaptopropionate, or trimercaptopropane; wherein the at least one compound having an epithio group in the preparing of the prepolymer comprising sulphur is present in an amount from 70 to 95% by weight based on the amount of the amount of the entire raw materials in the preparing of the prepolymer comprising sulfur; and wherein the portion of the polythiol compound in the preparing of the prepolymer comprising sulfur is present in an amount of 10 to 90% by weight based on the amount of the entire polythiol compound used for preparing the plastic lens.