| 摘要 |
Process for making thin film semipermeable membranes. A porous substrate having pores not greater than about 500 A. at a surface thereof is provided, as by casting from a solution of an organic polymer. A nonporous buffer layer is coated upon that surface to fill the pores, as by applying a water-soluble material, such as polyacrylic acid. The thin film semipermeable membrane is formed in situ upon the buffer layer, as by dipping the coated substrate in a dilute solution of cellulose acetate. A less than 1 weight percent solution of cellulose acetate, having an acetyl content not less than about 39.8 weight percent in chloroform may be used. After drying, the buffer layer is at least partially leached from the composite membrane. The cellulose acetate semipermeable membrane may be less than 1,000 A. in thickness.
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