| 摘要 |
PROBLEM TO BE SOLVED: To attempt the improvement in a high salt rejection ratio, high water permeability, and pressure resistance, and the like, by a process in which, in a composite reverse osmosis membrane comprising a porous supporting membrane and a synthetic polymer skin layer, the rejection performance of the porous supporting membrane by the aqueous solution of polyethylene glycol whose weight average molecular weight and concentration are specified. SOLUTION: As a porous supporting membrane applicable to a composite reverse osmosis membrane, when evaluated by using a 5000 ppm polyethylene glycol (weight average molecular weight: 20,000) aqueous solution, an ultrafiltration membrane whose rejection ratio is at least 50% is used. In the evaluation of the supporting membrane, for example, the size of the membrane is 75ϕmm, the weight average molecular weight of the polyethylene glycol is 20,000, the concentration of the aqueous solution is 5,000 ppm, and the temperature of the solution is 25 deg.C. Under these conditions, the PEG rejection performance is set up to be at least 95%. In the measurement of the surface pore diameter of the supporting membrane, for example, SEM(scanning electron microscope) analysis is adopted, and the average pore diameter obtained by image treatment is set up to be 15 nm or below.
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