Method of manufacturing a cellulose acetate membrane and the membrane so produced

Claim 1

A cellulose acetate membrane having a pore radius in the range 1.5 Å to 5.0 Å and a standard deviation in the range 0.5 Å to 5.5 Å according to the definition of Gaussian normal distribution.

Claim 4

A method of manufacturing a cellulose acetate membrane, capable of separating gaseous hydrogen from a gaseous mixture of hydrogen and hydrocarbon, comprising: (a) casting, in a casting atmosphere having a temperature in the range 20° to 40° C. and a humidity in the range 30 to 70%, a cellulose acetate film having a thickness in the range 0.02 to 0.05 cm, the film being cast from a casting solution at a temperature in the range 0° to 20° C., the casting solution comprising 10 to 20 wt % cellulose acetate, 60 to 80 wt % acetone, 0.5 to 2.0 wt % magnesium perchlorate, balance water, then (b) evaporating solvent from the cast solution for at least ten seconds so that a membrane is formed having an assymmetric structure, then (c) gelling the cast membrane in ice cold water for at least one hour, then (d) shrinking the gelled membrane in water at a temperature in the range 60° to 90° C. to produce a water wet, shrunk membrane having an average pore radius of less than 7 Å, then (e) replacing, at a temperature in the range about 20° to 25° C., the water in the membrane with aqueous organic alcohol which is substantially a non-solvent for the membrane, then (f) replacing, at a temperature in the range about 20° to 25° C., the aqueous organic alcohol in the membrane with substantially nonaqueous organic alcohol which is readily miscible with a volatile organic solvent, then (g) replacing, at a temperature in the range about 20° to 25° C., the substantially nonaqueous organic alcohol with the said volatile organic solvent, and then (h) evaporating the said volatile organic solvent to dry the membrane to a pore radius in the range 1.5 Å to 5.0 Å and a standard deviation in the range 0.5 Å to 5.5 Å according to the definition of Gaussian normal distribution.

Claim 5

A method of manufacturing a cellulose acetate membrane, capable of separating gaseous hydrogen from a gaseous mixture of hydrogen and hydrocarbon, comprising: (a) casting, in a casting atmosphere having a temperature in the range 20° to 40° C. and a humidity in the range 30 to 70%, a cellulose acetate film having a thickness in the range 0.02 to 0.05 cm, the film being cast from a casting solution at a temperature in the range 0° to 20° C., the casting solution comprising 10 to 20 wt % cellulose acetate, 60 to 80 wt % acetone, 0.5 to 2.0 wt % magnesium perchlorate, balance water, then (b) evaporating solvent from the cast solution for at least ten seconds so that a membrane is formed having an assymmetric structure, then (c) gelling the cast membrane in ice cold water for at least one hour, then (d) shrinking the gelled membrane in water at a temperature in the range 60° to 90° C. to produce a water wet, shrunk membrane having an average pore radius of less than 7 Å, then (e) replacing, at a temperature in the range about 20° to 25° C., the water in the membrane with aqueous organic alcohol which is substantially a non-solvent for the membrane, then (f) replacing, at a temperature in the range about 20° to 25° C., the aqueous organic alcohol in the membrane with substantially nonaqueous organic alcohol which is readily miscible with a volatile organic solvent, then (g) replacing, at a temperature in the range about 20° to 25° C., the substantially nonaqueous organic alcohol with the said volatile organic solvent, and then (h) evaporating the said volatile organic solvent to dry the membrane to a pore radius in the range 1.5 Å to 5.0 Å and a standard deviation in the range 0.5 Å to 5.5 Å according to the definition of Gaussian normal distribution.