Patent US4431545A successfully refreshed from Google Patents.
US4431545A
Expired / Lapsed
US
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Microporous filter system and process
Assignee: Pall Corp
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Filing: 1982-05-07
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Granted: 1984-02-14
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Expires: 2002-05-07
Abstract
Abstract A microporous filter system comprises two types of hydrophilic, microporous filter media operating in series. The two filter media have opposite zeta potentials with the upstream or first filter medium preferably having the positive zeta potential and the downstream or second filter having the negative zeta potential. The first filter medium typically has an absolute pore rating of from about 0.1 to about 1.0 micrometer and the second or downstream filter medium typically has an absolute pore rating of from about 0.02 to about 0.1 micrometer. The downstream or second filter has a finer absolute pore rating than the upstream or first filter. Fluids contaminated with ultrafine particles can be purified with an essentially absolute efficiency to remove 99.99 percent or more of the particulate matter in the contaminated fluid. The filter system finds particular use in the preparation of ultrapure effluent water of near theoretical resistivity and in the removal of bacteria and endotoxins to form sterile fluids.
Inventors
- 👤 David B. Pall
- 👤 Abraham Krasnoff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 21:38
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/56; A; A61; A61K; A61K35/00; A61K35/12; A61K35/14; A61K35/16; A61L; A61L2/00; A61L2/02; A61L2/022; B01D39/00; B01D39/14; B01D39/16; B01D39/1607; B01D39/1623; B01D69/00; B01D69/12; C; C02; C02F; C02F1/00; C02F1/28; A61L2103/00; A61L2103/05
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
176 words
A process for the filtration of a contaminated fluid comprising ultrafine particulate material with particle sizes in the range of from about 0.001 to about 10 micrometers said process comprising: (a) passing said fluid through a first filter medium comprised of a surface modified, hydrophilic, microporous member, said first filter medium further characterized by (i) an absolute pore rating in the range of from about 0.05 to about 1.0 micrometer and (ii) a positive zeta potential, to remove electronegatively charged particulate matter from said fluid; and (b) then passing said fluid through a second filter medium comprised of a hydrophilic, microporous member, said second filter medium further characterized by (1) an absolute pore rating finer than that of said first filter membrane and in the range of from about 0.01 to about 0.1 micrometer and (ii) a negative zeta potential, to form a filtrate substantially free of (1) both electronegatively and electropositively charged particulate matter, (2) bacteria and endotoxins, and (3) particulate matter greater in size than the absolute pore rating of said second filter medium.
Claim 2
Dependent Claim
176 words
A process for the filtration of a contaminated fluid comprising ultrafine particulate material with particle sizes in the range of from about 0.001 to about 10 micrometers said process comprising: (a) passing said fluid through a first filter medium comprised of a surface modified, hydrophilic, microporous member, said first filter medium further characterized by (i) an absolute pore rating in the range of from about 0.05 to about 1.0 micrometer and (ii) a positive zeta potential, to remove electronegatively charged particulate matter from said fluid; and (b) then passing said fluid through a second filter medium comprised of a hydrophilic, microporous member, said second filter medium further characterized by (1) an absolute pore rating finer than that of said first filter membrane and in the range of from about 0.01 to about 0.1 micrometer and (ii) a negative zeta potential, to form a filtrate substantially free of (1) both electronegatively and electropositively charged particulate matter, (2) bacteria and endotoxins, and (3) particulate matter greater in size than the absolute pore rating of said second filter medium.
Claim 3
Dependent Claim
21 words
The process of claim 1 wherein both said first filter medium and said second filter medium are comprised of nylon 66.
Claim 4
Dependent Claim
23 words
The process of claim 2 wherein said second filter medium has an absolute pore rating of from about 0.02 to about 0.06 micrometer.
Claim 5
Dependent Claim
11 words
The process of claim 2 wherein said contaminated fluid is water.
Claim 6
Dependent Claim
21 words
The process of claim 2 wherein said filtrate is comprised of ultrapure water having an effluent resistivity greater than 14 megaohms/cm.
Claim 7
Dependent Claim
176 words
A process for the filtration of a contaminated fluid comprising ultrafine particulate matter with particle sizes in the range of from about 0.001 to about 10 micrometers, said process comprising: (a) passing said fluid through a first filter medium comprised of a hydrophilic, microporous member said first filter medium further characterized by (i) an absolute pore rating in the range of from about 0.05 to about 1.0 micrometer and (ii) a negative zeta potential, to remove electropositively charged particulate matter from said fluid; and (b) then passing said fluid through a second filter medium comprised of a surface modified, hydrophilic, microporous member said second filter medium further characterized by (i) an absolute pore rating finer than that of said first filter membrane and in the range of from about 0.01 to about 0.1 micrometer and (ii) a positive zeta potential, to form a filtrate substantially free of (1) both electronegatively and electropositively charged particulate matter, (2) bacteria and endotoxins, and (3) particulate matter greater in size than the absolute pore rating of said second filter medium.
Claim 8
Dependent Claim
176 words
A process for the filtration of a contaminated fluid comprising ultrafine particulate matter with particle sizes in the range of from about 0.001 to about 10 micrometers, said process comprising: (a) passing said fluid through a first filter medium comprised of a hydrophilic, microporous member said first filter medium further characterized by (i) an absolute pore rating in the range of from about 0.05 to about 1.0 micrometer and (ii) a negative zeta potential, to remove electropositively charged particulate matter from said fluid; and (b) then passing said fluid through a second filter medium comprised of a surface modified, hydrophilic, microporous member said second filter medium further characterized by (i) an absolute pore rating finer than that of said first filter membrane and in the range of from about 0.01 to about 0.1 micrometer and (ii) a positive zeta potential, to form a filtrate substantially free of (1) both electronegatively and electropositively charged particulate matter, (2) bacteria and endotoxins, and (3) particulate matter greater in size than the absolute pore rating of said second filter medium.
Claim 9
Dependent Claim
21 words
The process of claim 6 wherein both said first filter medium and said second filter medium are comprised of nylon 66.
Claim 10
Dependent Claim
23 words
The process of claim 7 wherein said second filter medium has an absolute pore rating of from about 0.02 to about 0.06 micrometer.
Claim 11
Dependent Claim
11 words
The process of claim 7 wherein said contaminated fluid is water.
Claim 12
Dependent Claim
22 words
The process of claim 7 wherein said second filtrate is comprised of ultrapure water having an effluent resistivity greater than 14 megaohms/cm.
Claim 13
Dependent Claim
80 words
A filter system comprising, in combination, a first filter medium comprised of a surface modified, hydrophilic, microporous member having a positive zeta potential and an absolute pore rating in the range of from about 0.05 to about 1.0 micrometer and a second filter medium comprised of a hydrophilic, microporous member having a negative zeta potential and an absolute pore rating in the range of from about 0.01 to about 0.1 micrometer and finer than that of said first filter medium.
Claim 14
Dependent Claim
80 words
A filter system comprising, in combination, a first filter medium comprised of a surface modified, hydrophilic, microporous member having a positive zeta potential and an absolute pore rating in the range of from about 0.05 to about 1.0 micrometer and a second filter medium comprised of a hydrophilic, microporous member having a negative zeta potential and an absolute pore rating in the range of from about 0.01 to about 0.1 micrometer and finer than that of said first filter medium.
Claim 15
Dependent Claim
22 words
The filter system of claim 11 wherein both said first filter medium and said second filter medium are comprised of nylon 66.
Claim 16
Dependent Claim
16 words
The filter system of claim 12 wherein said filter system is formed into a filter element.
Claim 17
Dependent Claim
18 words
The filter system of claim 12 wherein said filter system comprises a pleated filter element in cartridge form.
Claim 18
Dependent Claim
35 words
The filter system of claim 12 wherein said system is capable of providing a filtrate of ultrapure water having a resistivity greater than 14 megaohms/cm. after a rinse up time of less than 10 minutes.
Claim 19
Dependent Claim
82 words
A filter system comprising, in combination, a first filter medium comprised of a hydrophilic, microporous polyamide membrane having a negative zeta potential and an absolute pore rating in the range of from about 0.05 to about 1.0 micrometer and a second filter medium comprised of a surface modified, hydrophilic, microporous polyamide membrane having a positive zeta potential and an absolute pore rating in the range of from about 0.01 to about 0.1 micrometer and finer than that of said first filter medium.
Claim 20
Dependent Claim
82 words
A filter system comprising, in combination, a first filter medium comprised of a hydrophilic, microporous polyamide membrane having a negative zeta potential and an absolute pore rating in the range of from about 0.05 to about 1.0 micrometer and a second filter medium comprised of a surface modified, hydrophilic, microporous polyamide membrane having a positive zeta potential and an absolute pore rating in the range of from about 0.01 to about 0.1 micrometer and finer than that of said first filter medium.
Claim 21
Dependent Claim
21 words
The filter system of claim 16 wherein said first filter medium and said second filter medium are comprised of nylon 66.
Claim 22
Dependent Claim
88 words
A filter system comprising, in combination, a first filter medium comprised of a surface modified, hydrophilic, microporous polyamide membrane containing quaternary ammonium groups in the hydroxide form and having a positive zeta potential and an absolute pore rating of from about 0.05 to about 1.0 micrometer and a second filter medium comprised of a hydrophilic, microporous polyamide membrane having a negative zeta potential and an absolute pore rating in the range of from about 0.01 to about 0.1 micrometer and finer than that of said first filter medium.
Claim 23
Dependent Claim
88 words
A filter system comprising, in combination, a first filter medium comprised of a surface modified, hydrophilic, microporous polyamide membrane containing quaternary ammonium groups in the hydroxide form and having a positive zeta potential and an absolute pore rating of from about 0.05 to about 1.0 micrometer and a second filter medium comprised of a hydrophilic, microporous polyamide membrane having a negative zeta potential and an absolute pore rating in the range of from about 0.01 to about 0.1 micrometer and finer than that of said first filter medium.
Claim 24
Dependent Claim
31 words
The filter system of claim 18 wherein said first filter medium has been contacted with an aqueous solution of ammonium hydroxide to convert said quaternary ammonium group to the hydroxide form.
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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) | 1987-02-13 | 1987-08-15 | 1988-02-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-02-13 | 1991-08-15 | 1992-02-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-02-13 | 1995-08-15 | 1996-02-14 | $7700.00 | Window Closed / Lapsed |