Patent ID: 11856952
Assignee: NIPPON SUISAN KAISHA, LTD.
Field: Pharmaceuticals (Chemistry)
Classification: CPC A  C  Y | IPC A  C

Claim 13:
14. The production method according to claim 13, wherein the rectification step comprises a low-temperature rectification at a column bottom temperature of 160° C. to 220° C. and a minimum pressure in the distillation column of 0.1 Pa to 30 Pa; and a high-temperature rectification at a column bottom temperature of 170° C. to 230° C. and a minimum pressure in the distillation column of 0.1 Pa to 30 Pa, and wherein the column bottom temperature in the high-temperature rectification is 3° C. to 20° C. higher than the column bottom temperature of the low-temperature rectification.