SEPARATION AND PURIFICATION OF PIGMENT SUSPENSIONS AND SUSPENSIONS OF PIGMENT INTERMEDIATES BY A MEMBRANE SEPARATION PROCESS

摘要

Separation and purification of pigment suspensions and suspensions of pigment intermediates by a membrane separation process the Disclosure Process for separating and purifying pigment suspensions and suspensions of pigment intermediates in a liquid by means of a membrane separation process, whereby the suspension to be treated is uniformly fed to and circulated through a microfiltration unit containing at least one semi-permeable membrane and the separated liquid flows off through the membrane as permeate, which process comprises replacing the permeate gradually by a washing liquid that differs from the first liquid such that the total amount of washing liquid fed into the system is 1 to 15 times the total volume of the initial suspension, and separating the resultant suspension from the liquid by means of conventional filtration or drying apparatus. The process is particularly suitable for processing fine pigment suspensions often obtained in pigment synthesis.