US4623463A
Expired / Lapsed
US
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Formation of porous membranes
Assignee: Memtec Ltd
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Filing: 1984-05-09
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Granted: 1986-11-18
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Expires: 2004-05-09
Abstract
Abstract This invention relates to a method of forming porous membranes from thermoplastic or polymeric materials and to membranes so formed.
Inventors
- 👤 Douglas L. Ford
- 👤 Clinton V. Kopp
- 👤 Eric W. Anderson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 12:28
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/28; B; B01; B01D; B01D67/00; B01D67/0002; B01D67/0009; B01D67/0011; B01D67/00113; B01D2323/00; B01D2323/12; B01D2323/30; C08J2201/00; C08J2201/04; C08J2201/054; C08J2201/0542; C08J2201/0544
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
136 words
A method of preparing a porous membrane which includes the steps of dissolving a single, chemically homologous, hydrolysable thermoplastic material which has both relatively non-crystalline and relatively crystalline portions into a hydrolytic solvent under conditions of temperature and time which cause the relatively non-crystalline portions of the thermoplastic to dissolve while at least a portion of the relatively crystalline portions of said thermoplastic material do not dissolve, but form a collidal dispersion in said solvent; forming said colloidal dispersion and solvent into a film, and thereafter causing immersion precipitation of the dissolved thermoplastic portions in the said film, to form a porous membrane in which the colloidal, relatively crystalline portions are joined together in the membrane by the precipitated relatively non-crystalline portions, with pores in the membrane being defined by spaces between said relatively crystalline portions.
Claim 2
Independent Claim
136 words
A method of preparing a porous membrane which includes the steps of dissolving a single, chemically homologous, hydrolysable thermoplastic material which has both relatively non-crystalline and relatively crystalline portions into a hydrolytic solvent under conditions of temperature and time which cause the relatively non-crystalline portions of the thermoplastic to dissolve while at least a portion of the relatively crystalline portions of said thermoplastic material do not dissolve, but form a collidal dispersion in said solvent; forming said colloidal dispersion and solvent into a film, and thereafter causing immersion precipitation of the dissolved thermoplastic portions in the said film, to form a porous membrane in which the colloidal, relatively crystalline portions are joined together in the membrane by the precipitated relatively non-crystalline portions, with pores in the membrane being defined by spaces between said relatively crystalline portions.
Claim 3
Dependent Claim
17 words
The method of claim 1 wherein the thermoplastic material is a polyamide, a polyimide or a polyester.
Claim 4
Dependent Claim
13 words
The method of claim 1 wherein the thermoplastic material is an aromatic polyamide.
Claim 5
Dependent Claim
21 words
The method of claim 3 wherein the aromatic polyamide is one in which both acid and base components are wholly aromatic.
Claim 6
Dependent Claim
16 words
The method of claim 1 in which said thermoplastic material is polyamide 6 or polyamide 6,6.
Claim 7
Dependent Claim
16 words
The method of claim 1 in which said solvent is a solution of strong mineral acid.
Claim 8
Dependent Claim
19 words
The method of claim 1 in which said solvent is hydrochloric acid and said thermoplastic material is a polyamide.
Claim 9
Dependent Claim
22 words
The method of claim 6 in which said solvent includes from 5 to 20 percent by volume of ethanol as a co-solvent.
Claim 10
Dependent Claim
11 words
The method of claim 1 wherein the solvent includes a co-solvent.
Claim 11
Dependent Claim
17 words
The method of claim 9 wherein the co-solvent is selected from ethanol, methanol, ethyleneglycol and acetic acid.
Claim 12
Dependent Claim
21 words
The method of claim 1 wherein at least 30% of the relatively crystalline portion of the thermoplastic material is not dissolved.
Claim 13
Dependent Claim
19 words
The method of claim 1 in which said colloidal dispersion is coated as a film onto an inert surface.
Claim 14
Dependent Claim
29 words
The method of claim 12 in which said solvent is a strong mineral acid, and said precipitation step is performed by immersing said coated film into a water bath.
Claim 15
Dependent Claim
13 words
The method of claim 12 wherein the film is about 100 microns thick.
Claim 16
Dependent Claim
16 words
The method of claim 1 wherein the colloidal dispersion and solvent are extruded in fibre form.
Claim 17
Dependent Claim
34 words
The method of claim 1 in which the thermoplastic material is a polyester, the solvent is a mixture of sulphuric and acetic acids and precipitation is effected in an aqueous neutral or basic bath.
Claim 18
Dependent Claim
18 words
A porous membrane when manufactured in accordance with the method defined in any one of the preceding claims.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-11-17 | 1990-05-19 | 1990-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-11-17 | 1994-05-19 | 1994-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-11-17 | 1998-05-19 | 1998-11-18 | $7700.00 | Window Closed / Lapsed |