POLYMERIC MICROPOROUS ELECTROLYTIC CELL SEPARATOR SELECTION OF PHYSICAL PARAMETERS TO PREDICT PERFORMANCE

摘要

A polymeric microporous electrolytic cell separator particularly suitable for use in producing alkali metal hydroxide at high current efficiencies, having: a. porosity of at least 60%; b. thickness of between 8 and 130 mils; c. hysteresis (as defined) of from 0.3 to 0.99, and d. distribution of pore sizes in a range between 0.004 and 34 microns wherein at least 85% of said pores have a diameter of between 0.12 and 33 microns and at least 60% of said pores have a diameter between 0.59 and 33 microns; the porosity, thickness, hysteresis, and pore size distribution being adapted to provide the separator with the property of exhibiting a high current efficiency including the property of a current efficiency of 85% to 98% when measured at a sodium hydroxide concentration of 150 gpl. The separator possesses hydraulic properties which render it suitable for use in a commercial scale cell. The separator is prepared by a) forming a sheet comprising the polymeric material e.g. polytetrafluoroethylene, a pore-forming additive e.g., calcium carbonate, and a lubricant, e.g., fluorinated surface active agent; b) sintering the sheet; and c) removing the pore forming additive e.g. by leaching with HCl solution.