Process for making a three-zone microporous membrane

A method for manufacturing a three-zone microporous membrane, the method comprising the steps of:

• providing at least one vessel for containing a ternary phase inversion polymer mother dope;
• formulating a ternary phase inversion polymer mother dope in the at least one vessel to effect dissolution and equilibrium mixing of the polymer, solvent and nonsolvent;
• maintaining the mother dope in the vessel at a temperature sufficient to stabilize and maintain the dope formulated after cooling from the formulation temperature;
• providing a dope processing site having at least one dope application means;
• operatively connecting the at least one vessel to the dope processing site such that the mother dope is transported from the at least one vessel to the dope processing site;
• operatively positioning at least one thermal manipulation means between the at least one vessel and the dope processing site;
• thermally manipulating the mother dope transported from the at least one vessel in the at least one thermal manipulation means into any one of a plurality of different possible pore size producing dopes;
• and
• applying a predetermined one of the plurality of different possible pore size producing dopes received from the at least one thermal manipulation means to a scrim at the dope processing site to produce reinforced, three-zone microporous membrane.