Abstract A membrane is disclosed of polyamide, a copolyamide or a mixture of polyamides, suitable for ultrafiltration and composed of an ultrafiltration skin and a backing layer. The pore size in the backing layer increases with distance from the ultrafiltration skin. The membrane is prepared by dissolving a polyamide in at least 75% formic acid, applying a casting solution, containing about 12-22% by weight polyamide and about 1-7% by weight polyethylene glycol in formic acid which has been brought to a temperature of below about 18 DEG C., as a thin layer onto a carrier foil resistant to the components of the solution, introducing the casting solution on the carrier foil into a precipitation and washing bath, withdrawing the casting solution as a coagulated and washed membrane from the carrier foil, stretching in at least one direction and subsequently drying this coagulated and washed membrane.
Inventors
👤 Erich Schindler
👤 Franz Maier
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-25 11:37
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/56
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
148 words
Flat membranes of a polyamide, a copolyamide or a mixture of polyamides, suitable for ultrafiltration and comprising an ultrafiltration skin and a porous backing layer, the pore size in said backing layer increasing with distance from said ultrafiltration skin, produced by dissolving the polyamide in at least 75% concentration formic acid, applying said casting solution, containing about 12-22% by weight polyamide and 1-7% by weight polyethylene glycol in formic acid and brought to a temperature of below about 18° C., as a thin layer onto a carrier foil resistant to the solution components, introducing said casting solution on said casting foil into a precipitation and washing bath, withdrawing said casting solution as a coagulated and washed membrane from said carrier foil, stretching said coagulated and washed membrane in at least one direction to a ratio from 1.5:1 up to 2.5:1 and subsequently drying said coagulated and washed membrane.
Claim 2
Dependent Claim
148 words
Flat membranes of a polyamide, a copolyamide or a mixture of polyamides, suitable for ultrafiltration and comprising an ultrafiltration skin and a porous backing layer, the pore size in said backing layer increasing with distance from said ultrafiltration skin, produced by dissolving the polyamide in at least 75% concentration formic acid, applying said casting solution, containing about 12-22% by weight polyamide and 1-7% by weight polyethylene glycol in formic acid and brought to a temperature of below about 18° C., as a thin layer onto a carrier foil resistant to the solution components, introducing said casting solution on said casting foil into a precipitation and washing bath, withdrawing said casting solution as a coagulated and washed membrane from said carrier foil, stretching said coagulated and washed membrane in at least one direction to a ratio from 1.5:1 up to 2.5:1 and subsequently drying said coagulated and washed membrane.
Claim 3
Dependent Claim
30 words
The membrane according to claim 1, produced with said drying effected by initially heating the membrane to about 130° C. and then finish-drying at temperatures between 60° and 80° C.
Claim 4
Dependent Claim
19 words
The membrane according to claim 1, having an ultrafiltration efficiency from about 50 up to 20,000 l/m 2 hbar.