| 摘要 |
A process for producing a polythiourethane resin which comprises (A) a step of synthesizing a polythiol oligomer having disulfide bond by reaction of a polythiol compound having a functionality of two or greater and sulfur and (B) a step of bringing the polythiol oligomer obtained in step (A) and a compound having poly(thio)isocyanate groups into reaction with each other, wherein step (A) is conducted in the absence of solvents using no catalysts or a catalyst substantially inert to the compound having poly(thio)isocyanate groups. A polythiol oligomer exhibiting a greater refractive index than that of the polythiol compound having a functionality of two or greater used as the starting material is produced at a low cost, and a process for producing a practically useful polythiourethane resin exhibiting a stable great refractive index and a great Abbe number is provided.
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