US4523995A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Charge-modified microfiber filter sheets
Assignee: Pall Corp
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Filing: 1981-10-19
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Granted: 1985-06-18
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Expires: 2001-10-19
Abstract
Abstract Filter media comprised of charge modified, resin coated inorganic microfibers are prepared by mixing inorganic microfibers with an aqueous solution of a water soluble, noncolloidal cationic thermosetting binder resin to form a dispersion, following which a precipitating agent is added to precipitate the binder resin and coat the microfibers. The coated microfibers may be used in the dispersed or suspended form as a filter aid. Preferably they are formed into a filter sheet which is then dried and cured to form a filter sheet of narrowly distributed pore size, pore sizes as small as one-half micron, and having a positive zeta potential in alkaline media. Glass is the preferred microfiber and polyamine-epichlorohydrins the preferred resins. By providing the normally negative zeta potential microfibers with a positive zeta potential the binder resins used to coat the microfibers substantially enhance particulate removal capabilities of the microfiber filter sheet.
Inventors
- 👤 David B. Pall
- 👤 Peter J. Degen
- 👤 Irving B. Joffee
- 👤 Warren M. Foss
- 👤 Thomas C. Gsell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 02:15
CPC Classifications
B; B01; B01D; B01D39/00; B01D39/14; B01D39/20; B01D39/2003; B01D39/2017; B01D39/2024; B01D2239/00; B01D2239/04; B01D2239/0471
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
106 words
A process for forming a filter sheet exhibiting a positive zeta potential in alkaline media comprising: (1) mixing inorganic microfibers normally having a negative zeta potential with an aqueous solution of a water soluble, non-colloidal cationic thermo-setting binder resin or polymer to form a microfiber dispersion; (2) adding a precipitating agent comprising a synthetic, water soluble or dispersible polymer containing anionic groups to said dispersion to precipitate said binder resin or polymer and coat said microfibers with said binder resin or polymer; and (3) forming the coated microfibers of step (2) into a filter sheet, said filter sheet exhibiting a positive zeta potential in alkaline media.
Claim 2
Dependent Claim
106 words
A process for forming a filter sheet exhibiting a positive zeta potential in alkaline media comprising: (1) mixing inorganic microfibers normally having a negative zeta potential with an aqueous solution of a water soluble, non-colloidal cationic thermo-setting binder resin or polymer to form a microfiber dispersion; (2) adding a precipitating agent comprising a synthetic, water soluble or dispersible polymer containing anionic groups to said dispersion to precipitate said binder resin or polymer and coat said microfibers with said binder resin or polymer; and (3) forming the coated microfibers of step (2) into a filter sheet, said filter sheet exhibiting a positive zeta potential in alkaline media.
Claim 3
Dependent Claim
10 words
The process of claim 1 wherein the microfibers are glass.
Claim 4
Dependent Claim
10 words
The process of claim 1 wherein said microfibers are titanate.
Claim 5
Dependent Claim
15 words
The process of claim 1 wherein said microfibers are a mixture of glass and titanate.
Claim 6
Dependent Claim
17 words
The process of claim 1 wherein said binder resin or polymer is an epoxide-based water soluble resin.
Claim 7
Dependent Claim
15 words
The process of claim 1 wherein said binder resin or polymer is a polyamido/polyamino-epichlorohydrin resin.
Claim 8
Dependent Claim
15 words
The process of claim 1 wherein said binder resin or polymer is a polyamine-epichlorohydrin resin.
Claim 9
Dependent Claim
19 words
The process of claim 1 wherein said binder resin or polymer has a substantial number of quaternary ammonium groups.
Claim 10
Dependent Claim
21 words
The process of claim 1 wherein the pH of said dispersion prior to the addition of said precipitating agent is alkaline.
Claim 11
Dependent Claim
19 words
The process of claim 9 wherein said pH is in the range of from about 8 to about 10.
Claim 12
Dependent Claim
135 words
A process for forming a filter sheet exhibiting a positive zeta potential over a pH range of from about 3 to about 10 comprising: (1) mixing inorganic microfibers normally having a negative zeta potential with water to form a first dispersion; (2) mixing said first dispersion with an aqueous solution of a water soluble, non-colloidal cationic thermosetting binder resin or polymer to form a second dispersion; (3) adding a precipitating agent comprising a synthetic, water soluble or dispersible polymer containing anionic groups to said second dispersion to precipitate said binder resin or polymer and coat said microfibers with said binder resin or polymer; and (4) forming the coated microfibers of step (3) into a filter sheet, said filter sheet exhibiting a positive zeta potential over a pH range of from about 3 to about 10.
Claim 13
Dependent Claim
135 words
A process for forming a filter sheet exhibiting a positive zeta potential over a pH range of from about 3 to about 10 comprising: (1) mixing inorganic microfibers normally having a negative zeta potential with water to form a first dispersion; (2) mixing said first dispersion with an aqueous solution of a water soluble, non-colloidal cationic thermosetting binder resin or polymer to form a second dispersion; (3) adding a precipitating agent comprising a synthetic, water soluble or dispersible polymer containing anionic groups to said second dispersion to precipitate said binder resin or polymer and coat said microfibers with said binder resin or polymer; and (4) forming the coated microfibers of step (3) into a filter sheet, said filter sheet exhibiting a positive zeta potential over a pH range of from about 3 to about 10.
Claim 14
Dependent Claim
10 words
The process of claim 11 wherein said microfibers are glass.
Claim 15
Dependent Claim
10 words
The process of claim 11 wherein said microfibers are titanate.
Claim 16
Dependent Claim
15 words
The process of claim 11 wherein said microfibers are a mixture of glass and titanate.
Claim 17
Dependent Claim
17 words
The process of claim 11 wherein said binder resin or polymer is an epoxide-based water soluble resin.
Claim 18
Dependent Claim
15 words
The process of claim 11 wherein said binder resin or polymer is a polyamide/polyamino-epichlorohydrin resin.
Claim 19
Dependent Claim
15 words
The process of claim 11 wherein said binder resin or polymer is a polyamine-epichlorohydrin resin.
Claim 20
Dependent Claim
19 words
The process of claim 11 wherein said binder resin or polymer has a substantial number of quaternary ammonium groups.
Claim 21
Dependent Claim
22 words
The process of claim 11 wherein the pH of said second dispersion prior to the addition of said precipitating agent is alkaline.
Claim 22
Dependent Claim
18 words
The process of claim 19 wherein said pH is in the range of from about 8 to 10.
Claim 23
Dependent Claim
33 words
The process of claim 11 wherein the weight ratio of said binder resin or polymer to said microfibers present in said second dispersion is in the range from about 1:100 to about 40:100.
Claim 24
Dependent Claim
30 words
The process of claim 21 wherein the weight ratio of said binder resin or polymer to said precipitating agent is in the range of from about 100:1 to about 1:1.
Claim 25
Dependent Claim
25 words
The process of claim 22 wherein the weight ratio of said binder resin or polymer to said microfibers is from about 5:100 to about 30:100.
Claim 26
Dependent Claim
50 words
The process of claim 11 wherein said aqueous solution of a water soluble, non-colloidal cationic thermosetting binder resin or polymer of step (2) of claim 11, prior to mixing with said microfibers, has a concentration of from about 1 to about 10 weight percent of said binder resin or polymer.
Claim 27
Dependent Claim
21 words
The process of claim 24 wherein the precipitating agent is added to said second dispersion as an aqueous solution or dispersion.
Claim 28
Dependent Claim
30 words
The process of claim 25 wherein said aqueous solution or dispersion of said precipitating agent has a concentration in the range of from about 0.01 to about 4.00 weight percent.
Claim 29
Dependent Claim
29 words
The process of claim 26 wherein said aqueous solution or dispersion of said precipitating agent has a concentration in the range of from about 0.01 to about 1 percent.
Claim 30
Dependent Claim
23 words
The process of claim 27 wherein said aqueous solution or dispersion of said precipitating agent has a concentration of about 0.16 weight percent.
Claim 31
Dependent Claim
39 words
The process of claim 11 wherein the pH of said second dispersion is adjusted prior to the addition of said precipitating agent in step (3) to provide a pH in the range of from about 8 to about 10.
Claim 32
Dependent Claim
68 words
The process of claim 11 wherein the said forming of said coated microfibers into a filter sheet comprises the steps of forming a layer or mat of the coated microfibers on a foraminous surface, drawing a vacuum through said foraminous surface to remove water from said layer or mat, drying said layer or mat and curing said binder resin or polymer to form a strong, self-supporting filter sheet.
Claim 33
Dependent Claim
25 words
The process of claim 11 wherein said second dispersion is maintained in a homogeneous form by agitation prior to the addition of said precipitating agent.
Claim 34
Dependent Claim
19 words
The process of claim 31 wherein agitation of said second dispersion is maintained while said precipitating agent is added.
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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) | 1988-06-17 | 1988-12-17 | 1989-06-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-06-17 | 1992-12-17 | 1993-06-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-06-17 | 1996-12-17 | 1997-06-18 | $7700.00 | Window Closed / Lapsed |