Patent ID: 7241367

Claim:
A permeable membrane diaphragm of different layers for electrolytic cell, comprising: a flow-controlling permeable layer, which comprises a thin liquid permeable micro-porous membrane or several thinner similar membranes made of fluoro-containing polymers; wherein the flow-controlling permeable layer is mounted toward the anode; a diffusion-restricting permeable layer, which comprises a thick permeable perforate film, sheet or cloth, or several thinner similar films, sheets or cloths made of anti-corrosive materials which are different from those of the flow-controlling permeable layer; wherein the mean pore diameter of the diffusion-restricting permeable layer is at least 5 times larger than that of the flow-controlling permeable layer, and the thickness of the diffusion-restricting permeable layer is at least 1 times larger than that of the flow-controlling permeable layer; wherein the diffusion-restricting permeable layer is mounted toward the cathode; optionally a protective layer, which comprises one or more liquid permeable film, sheet or cloth made of anti-corrosive materials; wherein the protective layer covers the micro-porous membrane of the flow-controlling permeable layer to protect it; and optionally a fluid impermeable frame made of anti-corrosive material; wherein the fluid impermeable frame is around the above-said layers.