PREPARATION OF ASYMMETRIC POLYMER MEMBRANES

• US 3,762,136 A
• Filed: 07/01/1971
• Issued: 10/02/1973
• Est. Priority Date: 05/13/1970
• Status: Expired due to Term

• Current Assignee: Shiro G. Kimura
• Original Assignee: Shiro G. Kimura
• Inventors: Kimura, Shiro G.
• Primary Examiner(s): Hart, Charles N.
• Application Number:
  US05/158,979
• Time in Patent Office: 824 Days
• Field of Search: 55/16,158 264/41
• US Class Current: 96/13
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 67/0011 Casting solutions therefor
• CPC Class Codes: B01D 67/00111 Polymer pretreatment in the casting solutions
• CPC Class Codes: B01D 67/0013 Casting processes
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 71/52 Polyethers
• CPC Class Codes: C08J 2201/0543 the non-solvent being organic
• CPC Class Codes: C08J 2201/0546 the non-solvent being organic
• CPC Class Codes: C08J 9/28 by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
• CPC Class Codes: Y10S 264/14 forming integral skin on a foamed product
• CPC Class Codes: Y10T 428/249961 With gradual property change within a component
• CPC Class Codes: Y10T 428/249979 Specified thickness of void-containing component [absolute or relative] or numerical cell dimension
• CPC Class Codes: Y10T 428/249989 Integrally formed skin
• CPC Class Codes: Y10T 428/268 Monolayer with structurally defined element

Abstract

A method is disclosed for the preparation (by the utilization of a proper solvent system) of dry asymmetric membranes comprising a porous layer of interconnected crystals of polymer material. Membranes of many polymer materials may be optionally prepared either with or without a dense surface layer as one face thereof. In either case the porous layer is structured with graded porosity. A three-component casting solution is prepared containing the polymer, a first good volatile solvent for the polymer and (relative to the first solvent) a poor less-volatile solvent for the polymer, which is miscible with the good solvent. A membrane is cast, allowed to desolvate for a short time and is then immersed in a leaching agent, that is miscible with both the aforementioned solvents but is a non-solvent for the polymer. The membrane is then permitted to dry.

Claims

2. The improvement as recited in claim 1 wherein the polyarylene oxide is polyxylylene oxide and the non-porous skin is less than about 3 microns thick.