Highly assymetric, hydrophilic, microfiltration membranes having large pore diameters

• US 6,045,899 A
• Filed: 12/12/1996
• Issued: 04/04/2000
• Est. Priority Date: 12/12/1996
• Status: Expired due to Term

• Current Assignee: Pall Corporation (Danaher Corporation)
• Original Assignee: USF Filtration & Separations Group, Inc. (Siemens AG)
• Inventors: Morris, Richard A., Wang, I-Fan, Zepf, Robert F.
• Primary Examiner(s): COPENHEAVER, BLAINE R
• Application Number:
  US08/764,321
• Time in Patent Office: 1,209 Days
• Field of Search: 428/36.5, 428/218, 428/310.5, 428/315.9, 428/318.6, 428/318.8, 428/315.7, 428/398, 210/500.41, 210/500.42, 521/51
• US Class Current: 428/315.7
• CPC Class Codes: B01D 2323/02 Hydrophilization
• CPC Class Codes: B01D 2323/08 Specific temperatures applied
• CPC Class Codes: B01D 2323/081 Heating
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2325/02 Details relating to pores or porosity of the membranes
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 2325/0283 Pore size
• CPC Class Codes: B01D 2325/02834 more than 0.1 and up to 1 µm
• CPC Class Codes: B01D 2325/04 Characteristic thickness
• CPC Class Codes: B01D 2325/36 Hydrophilic membranes
• CPC Class Codes: B01D 39/16 of organic material, e.g. synthetic fibres
• CPC Class Codes: B01D 67/0011 Casting solutions therefor
• CPC Class Codes: B01D 67/0013 Casting processes
• CPC Class Codes: B01D 67/00135 Air gap characteristics
• CPC Class Codes: B01D 67/0016 Coagulation
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 69/12 Composite membranes; Ultra-thin membranes
• CPC Class Codes: B01D 69/1216 Three or more layers
• CPC Class Codes: B01D 71/68 Polysulfones; Polyethersulfones
• CPC Class Codes: Y10T 428/24992 Density or compression of components
• 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 428/24998 : Composite has more than two layers
• CPC Class Codes: Y10T 428/249989 : Integrally formed skin
• CPC Class Codes: Y10T 428/2975 : Tubular or cellular
• CPC Class Codes: Y10T 436/25375 : Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]
• CPC Class Codes: Y10T 436/255 : including use of a solid sorbent, semipermeable membrane, or liquid extraction

Abstract

The present invention relates to the field of synthetic polymeric microfiltration membrane materials that are fabricated to separate liquids from solids contained therein. One aspect of the invention relates to a highly asymmetric, hydrophilic microfiltration membrane with high surface porosity. The membrane is rendered hydrophilic through co-casting the sulfone polymer with a hydrophilic polymer, such as polyvinylpyrrolidone. The membranes of the invention are highly useful in testing devices for the quick detection of properties or components contained in liquid samples, such as diagnostic applications, as well as for other filtration applications that demand relatively large pore sizes, thick membranes, high asymmetry, and/or high lateral wicking speeds.

Claims

1. An asymmetric integral sulfone polymer membrane, rendered hydrophilic through co-casting a sulfone polymer with a hydrophilic polymer, the membrane comprising a first microporous skin surface, a porous support, and a second surface having maximum diameter pores, the microporous skin surface possessing skin pores, the skin pores having an average diameter of from about 0.1 micron to about 10 microns, the porous support having a thickness of between 100 microns and 340 microns, said porous support comprising an asymmetric region of gradually increasing pore sizes, wherein the pores on the second surface have an average diameter of about 5 times to about 1000 times the diameter of the skin pores.

2. The membrane of claim 1, wherein the membrane comprises a mean flow pore size of from about 0.1 μ

m to about 10 μ

m.

3. The membrane of claim 1, wherein the membrane possesses a density of skin pores of at least about 15 pores per 1000 μ

m².

4. The membrane of claim 1, wherein the membrane is at least about 150 μ

m in thickness.

5. The membrane of claim 1, wherein the sulfone polymer is selected from the group consisting of polysulfone, polyethersulfone, and polyarylsulfone.

6. The membrane of claim 5, wherein the hydrophilic polymer comprises polyvinylpyrrolidone.

7. The membrane of claim 1, wherein the hydrophilic polymer comprises polyvinylpyrrolidone.

8. The membrane of claim 1, wherein the membrane possesses a lateral wicking speed of water of at least about 5 mm/second.