ULTRAFILTRATION MEMBRANE CONSISTING OF POLYVINYL FORMAL HAVING SMALL MOLECULAR WEIGHT RESTRICTED DISTRIBUTION AND PRODUCTION OF THE MEMBRANE

摘要

PURPOSE:To obtain an ultrafiltration membrane having antibacterial property causing extremely small amt. of adsorption of hydrophobic objects for treatment by using a polyvinyl formal resin and restricting its molecular weight distribution to below a specified value without adding any pore forming agent, etc. CONSTITUTION:A dope having about 10-20wt.% concn. of polyvinyl formal resin having a recurrent unit expressed by formula I is prepd. by dissolving the resin in a mixed solvent consisting of a polar solvent having low diffusion velocity into water and a polar solvent having high diffusion velocity into water, such as a mixed solvent consisting of 1,4-dioxane and N,N-dimethyl formamide. The dope is applied uniformly on the surface of polyester nonwoven fabric, and the fabric is dipped in a coagulation bath contg. water at about 0-45 deg.C to transfer to solvent in the dope to a liquid phase in the coagulation bath. The dope is thus gelled, and the gell is formed to film by a wet film forming method. By this method, an ultrafiltration membrane consisting of polyvinyl formal having extremely high hydrophilic property and =100,000 molecular weight restricted distribution is obtd.