REDUCTION IN MOLECULAR WEIGHT POLYDISPERSITY OF POLYETHER GLYCOL BY MEMBRANE FRACTIONATION

摘要

PURPOSE: To recover a high molecular weight species of a low polydispersity useful as polyurethane starting materials and a low molecular weight species from a polyether glycol of a high polydispersity with the use of a cross flow membrane separator and subjecting the polyether glycol to fractionation free of a solvent under moderate pressure. ;CONSTITUTION: With the use of a cross flow membrane separator comprising a (semi)permeable membrane surface (Af) having a feed/retained substance side (A₁ side) and a permeated substance/ultrafiltration side (A₂ side), so as for the low molecular weight species of poly(tetramethylene ether) glycol (P) to selectively permeate Af, a feed stream (Ps) of molten P free of a solvent is fed to the entire A₁ side at a temperature of higher than the melting point of this low molecular weight species and, at the same time, a lower than the decomposition or melting temperature of Af and P, and from A are recovered a A₂ side fraction rich in low molecular weight P species of polydisperity lower than that of Ps ad an A₁ side fraction rich in high molecular weight P species of polydispersity lower than that of Ps to effect the fractionation of P.;COPYRIGHT: (C)1996,JPO