US4490431A
Expired / Lapsed
US
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0.1 Micron rated polypropylene membrane and method for its preparation
Assignee: Akzona Inc
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Filing: 1982-11-03
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Granted: 1984-12-25
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Expires: 2002-11-03
Abstract
Abstract There is disclosed a substantially skinless microporous polypropylene membrane characterized by having (a) a bubble point of about 25 to about 50 psi; (b) a thickness of about 3 to about 7 mils; (c) a nitrogen flow rate of at least 0.5 liters per square centimeter-minute; (d) a burst strength of at least 10 psi; and (e) an S value of about 15, or less. There is also disclosed a method of preparing a microporous polypropylene membrane comprising heating a mixture of about 30 percent polypropylene and about 70 percent, N,N-bis(2-hydroxyethyl)tallowamine, by weight, to a temperature and for a time sufficient to form a homogeneous solution, casting or extruding said solution at a thickness of about 3 to about 7 mils, onto a chill roll maintained at a temperature of from about 50 DEG to about 80 DEG C., allowing said solution to solidify on said chill roll to form a solid sheet, removing said solid sheet from said chill roll and removing at least a substantial portion of the liquid from said sheet to form the microporous polypropylene membrane.
Inventors
- 👤 Gunter H. Vitzthum
- 👤 Michael A. Davis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 19:29
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/28; B; B01; B01D; B01D67/00; B01D67/0002; B01D67/0023; B01D67/003; B01D69/00; B01D69/02; B01D71/00; B01D71/06; B01D71/26; B01D71/262; C08J2201/00; C08J2201/02; C08J2201/03; C08J2201/04; C08J2201/052; C08J2201/054; C08J2201/0542; C08J2323/00; C08J2323/02; C08J2323/10; C08J2323/12; Y; Y10; Y10T; Y10T428/00; Y10T428/249921; Y10T428/249953; Y10T428/249978; Y10T428/249979
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
62 words
A substantially skinless microporous polypropylene membrane characterized by having (a) a bubble point of about 25 to about 50 psi; (b) a thickness of about 3 to about 7 mils; (c) a nitrogen flow rate of at least 0.5 liters per square centimeter-minute; (d) a burst strength of at least 10 psi; and (e) an S value of about 15, or less.
Claim 2
Dependent Claim
62 words
A substantially skinless microporous polypropylene membrane characterized by having (a) a bubble point of about 25 to about 50 psi; (b) a thickness of about 3 to about 7 mils; (c) a nitrogen flow rate of at least 0.5 liters per square centimeter-minute; (d) a burst strength of at least 10 psi; and (e) an S value of about 15, or less.
Claim 3
Dependent Claim
17 words
The membrane of claim 1 having a skin throughout no more than 10 percent of its cross-section.
Claim 4
Dependent Claim
15 words
The membrane of claim 1 having a thickness of about 3.5 to about 4.0 mils.
Claim 5
Dependent Claim
17 words
The membrane of claim 1 having a flow rate of at least 0.7 liters per square centimeter-minute.
Claim 6
Dependent Claim
38 words
The membrane of claim 4 having a skin throughout less than 5 percent of its cross-section, having a thickness of about 3.5 to about 4.0 mils, and having a sharpness value of from about 8 to about 14.
Claim 7
Dependent Claim
16 words
The membrane of claim 1 having a sharpness value of from about 8 to about 14.
Claim 8
Independent Claim
111 words
A method of preparing a substantially skinless microporous polypropylene membrane comprising heating a mixture of about 30 percent polypropylene and about 70 percent, N,N-bis(2-hydroxyethyl)tallowamine, by weight, to a temperature and for a time sufficient to form a homogeneous solution, casting or extruding said solution at a thickness of about 3 to about 7 mils, onto a chill roll maintained at a temperature of from about 50 to about 80° C., allowing said solution to solidify on said chill roll to form a solid sheet, removing said solid sheet from said chill roll and removing at least a substantial portion of the amine from said sheet to form the microporous polypropylene membrane.
Claim 9
Independent Claim
111 words
A method of preparing a substantially skinless microporous polypropylene membrane comprising heating a mixture of about 30 percent polypropylene and about 70 percent, N,N-bis(2-hydroxyethyl)tallowamine, by weight, to a temperature and for a time sufficient to form a homogeneous solution, casting or extruding said solution at a thickness of about 3 to about 7 mils, onto a chill roll maintained at a temperature of from about 50 to about 80° C., allowing said solution to solidify on said chill roll to form a solid sheet, removing said solid sheet from said chill roll and removing at least a substantial portion of the amine from said sheet to form the microporous polypropylene membrane.
Claim 10
Dependent Claim
20 words
The method of claim 7 wherein the solution is cast at a thickness of about 3.5 to about 4 mils.
Claim 11
Dependent Claim
14 words
The method of claim 7 wherein the chill roll temperature is about 60° C.
Claim 12
Dependent Claim
12 words
The method of claim 7 wherein the amine is removed with isopropanol.
Claim 13
Dependent Claim
20 words
The method of claim 10 wherein a wiper bar is used on the chill roll, prior to a casting box.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-12-25 | 1988-06-25 | 1988-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-12-25 | 1992-06-25 | 1992-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-12-25 | 1996-06-25 | 1996-12-25 | $7700.00 | Window Closed / Lapsed |