Patent ID: 6414198
Filing Date: 2002-07-02
Classification: C07C

Abstract:
A process of preparing bisphenol A having low residual contents of oxygen and phenol comprising:(a) melting mixed crystals of bisphenol A and phenol under a nitrogen atmosphere at a temperature of 100Â° C. to 120Â° C.; (b) feeding continuously the melt formed in step (a) into the top of a distillation unit under conditions of 120Â° C. to less than 160Â° C. and a pressure of greater than 80 mbar to 200 mbar; (c) feeding contemporaneously with step (b) 0.5 to 50 vol. % of nitrogen, based on the volume of introduced melt, into the bottom of the distillation unit; (d) allowing the melted feed material and the nitrogen feed to contact each other within the distillation unit, thereby forming a concentrated melt material having, (i) a phenol content reduced to 10 to 25 wt. %, and (ii) a reduced oxygen content; and (e) removing the concentrated melt material of step (d) from the bottom of the distillation unit and passing a stream of nitrogen through the removed concentrated melt material under conditions of at least atmospheric pressure, 180Â° C. to 220Â° C. and a nitrogen partial pressure of 1 to 1.5 bar, thereby further reducing the residual phenol content of the concentrated melt material.