| 摘要 |
A continuous process for converting by transesterification the diester of polytetramethylene ether (PTMEA) to the corresponding polytetramethylene ether glycol (PTMEG). The process is characterized by the fact that the feed, consisting of PTMEA along with an alkanol (preferably methanol) and with an alkali metal oxide, hydroxide or alkoxide catalyst (preferably sodium methaoxide) is made to react in two multistaged reactions in series. In the first reactant, including stages of retention in association with distillation trays of high efficiency, the bulk of conversion is achieved by stripping the alkanol ester formed in the transesterification with vapors of hot alkanol having a reduced content of alkanol ester. The transesterification is completed in the second reaction by stripping the effluent from the first reactor with vapors of hot alkanol almost free of alkanol ester. The PTMEG product is finally purified by neutralizing the alkaline catalyst with a mixture of phosphoric acid and sodium phosphate monobasic. |
