Studies on Preparation of Ethanol Permselective Membranes with High Performance and Development of Apparatus for Membrane Permeation

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Graft copolymers (PMMA-g-PDMS) from dimethylsiloxane macromonomer (DMS) and methylmethacrylate (MMA) and block copolymer (PMMA-b-PDMS) from PDMS macroinitiator and MMA were synthesized as polymer membrane materials for ethanol permselective membrane of aqueous ethanol solutions. Permeation and separation characteristics for an aqueous solution of 10wt% ethanol of PMMA-g-PDMS and PDMA-b-PDMS membranes from these copolymers were significantly dependent on the DMS content in copolymer. The membranes from small amount of DMS were water permselective, but those from large amount of DMS showed ethanol permselective. The difference in these permselectivities could be attributed to morphology of microphase separated structure of the membrane. Continuous PDMS phase in PMMA-b-PDMS membranes was lamellar, and their ethanol permselectivity was higher than that of PMMA-g-PDMS membranes.On the other hand, to prepare ethanol permselective membrane with high permeation rate, porous polymer membranes were prepared from PDMS emulsion using the freeze-dry method. When PDMS porous membranes were applied to the permeation and separation for aqueous ethanol solutions in temperature difference controlling evapomeation, these membranes were ethanol permselective and had high permeation rate. The temperature difference between the feed solution and membrane surrounding, and the pressure difference between the upstream side and the down stream side of the membrane significantly influenced both the ethanol permselectivity and permeation rate.