| 摘要 |
A process is disclosed for the production of a membrane suitable for ultrafiltration and cast from a solution in formic acid of a polyamide or a mixture of polyamides, characterized by bringing the solution produced with the addition of about 1 to 7% polyethylene glycol to a temperature below about 18 DEG C., applying the solution as thin layer onto a carrier film resistant to the constituents of the solution, conducting this solution through a precipitating and washing bath moving in the reverse direction, with said layer, subsequent to emerging from the bath, being stripped from the carrier film as a coagulated and washed membrane and dried thereafter. Preferred embodiments include stretching the membrane, prior to drying, to a ratio from 1.5:1 to 2.5:1; subjecting it to heat setting in conjunction with the drying; using a minimum formic acid concentration of 80% for the solution or mixture; using 12 to 22% polyamide in the solution or mixture; and employing an air stretch of 2 seconds, before the precipitating and washing bath.
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