초록 ▼

A gas separation membrane has a dense separating layer about 10,000 Angstroms or less thick and a porous support layer 10 to 400 microns thick that is an integral unit with gradually and continuously decreasing pore size from the base of the support layer to the surface of the thin separating layer

A gas separation membrane has a dense separating layer about 10,000 Angstroms or less thick and a porous support layer 10 to 400 microns thick that is an integral unit with gradually and continuously decreasing pore size from the base of the support layer to the surface of the thin separating layer and is made from a casting solution comprising ethyl cellulose and ethyl cellulose-based blends, typically greater than 47.5 ethoxyl content ethyl cellulose blended with compatible second polymers, such as nitrocellulose. The polymer content of the casting solution is from about 10% to about 35% by weight of the total solution with up to about 50% of this polymer weight a compatible second polymer to the ethyl cellulose in a volatile solvent such as isopropanol, methylacetate, methanol, ethanol, and acetone. Typical nonsolvents for the casting solutions include water and formamide. The casting solution is cast in air from about zero to 10 seconds to allow the volatile solvent to evaporate and then quenched in a coagulation bath, typically water, at a temperature of 7°-25°C. and then air dried at ambient temperature, typically 10°-30°C.

대표청구항 ▼

A method of making anisotropic membranes for gas separation which method includes the steps of, forming a casting solution having a base polymer of ethyl cellulose with at least substantially 2.2 ethoxyl groups per anhydroglucose unit and a nonsolvent compatible with said base polymer in a solvent s

A method of making anisotropic membranes for gas separation which method includes the steps of, forming a casting solution having a base polymer of ethyl cellulose with at least substantially 2.2 ethoxyl groups per anhydroglucose unit and a nonsolvent compatible with said base polymer in a solvent system including at least one solvent having relatively high volatility with a low boiling point below 100°C., casting a membrane precursor with said casting solution, exposing said cast membrane precursor to air for a short time interval significantly less than a minute to cause sufficient solvent loss to form an integral skin layer, and then immersing the cast membrane precursor into a leaching agent that dissolves said nonsolvent but not said base polymer sufficiently long to dissolve said nonsolvent and form an anisotropic membrane with pores and an integral, essentially imperfection-free separating skin layer comprising said ethyl cellulose, and then drying said membrane.