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US4737291A
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Charge modified microporous membrane
Assignee: 3M Purification Inc
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Filing: 1984-08-17
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Granted: 1988-04-12
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Expires: 2004-08-17
Abstract
Abstract A cationic charge modified microporous membrane is provided. The membrane comprises a hydrophilic organic polymeric microporous membrane having bonded thereto, through a cross-linking agent, a charge modifying amount of a cationic charge modifying agent. The charge modifying agent is an aliphatic amine or polyamine, preferably tetraethylene pentamine, and the cross-linking agent is an aliphatic polyepoxide having a molecular weight of less than about 500, preferably 1, 4 butanediol diglycidyl ether. The microporous membrane is preferably nylon. The process for applying the charge modifying agent to the membrane, preferably comprises contacting the membrane with an aqueous solution of the charge modifying agent and then contacting the membrane with a substantially aqueous solution of the cross-linking agent. The preferred process uses high purity water, i.e. water having no significant ionic content, to produce a membrane suitable for use in filtering ultra pure (18 megohm-cm resistivity) water for use in producing electronic devices. Such a membrane exhibits an advantageously low "flush-out" time compared to known cationic charge modified microporous membranes and unmodified microporous membranes.
Inventors
- 👤 Robert G. Barnes, Jr.
- 👤 Chaokang Chu
- 👤 George T. Emond
- 👤 Asit K. Roy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 07:09
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0081; B01D67/0093; B01D67/00931; B01D71/00; B01D71/06; B01D71/56; B01D2323/00; B01D2323/30
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
112 words
A skinless cationic charge modified hydrophilic microporous membrane comprising a skinless hydrophilic organic polymeric microporous filter membrane having an internal microstructure throughout said membrane and a charge modifying amount of a cationic charge modifying agent bonded to substantially all of the membrane microstructure without substantial pore size reduction or pore blockage through an aliphatic polyepoxide cross-linking agent having a molecular weight of less than about 500, wherein the charge modifying agent is selected from the group consisting of: (i) aliphatic amines which are polyamines having at least one primary amine or at least two secondary amines; and (ii) aliphatic amines having at least one secondary amine and a carboxyl or hydroxyl substituent.
Claim 2
Dependent Claim
112 words
A skinless cationic charge modified hydrophilic microporous membrane comprising a skinless hydrophilic organic polymeric microporous filter membrane having an internal microstructure throughout said membrane and a charge modifying amount of a cationic charge modifying agent bonded to substantially all of the membrane microstructure without substantial pore size reduction or pore blockage through an aliphatic polyepoxide cross-linking agent having a molecular weight of less than about 500, wherein the charge modifying agent is selected from the group consisting of: (i) aliphatic amines which are polyamines having at least one primary amine or at least two secondary amines; and (ii) aliphatic amines having at least one secondary amine and a carboxyl or hydroxyl substituent.
Claim 3
Dependent Claim
15 words
The microporous membrane of claim 1, wherein the hydrophilic organic polymeric microporous membrane is nylon.
Claim 4
Dependent Claim
16 words
The microporous membrane of claim 1, wherein the hydrophilic organic polymeric microporous membrane is polyhexamethylene adipamide.
Claim 5
Dependent Claim
43 words
The microporous membrane of claim 1 or 2, wherein the charge modifying agent is an amine of the formula: ##STR8## wherein R 1 and R 2 are alkyl of 1 to 4 carbon atoms and x is an integer from 0 to 4.
Claim 6
Dependent Claim
14 words
The microporous membrane of claim 4, wherein R 1 and R 2 are ethyl.
Claim 7
Dependent Claim
16 words
The microporous membrane of claim 4, wherein the amine is tetraethylene pentamine of the formula: ##STR9##
Claim 8
Dependent Claim
16 words
The microporous membrane of claim 1 or 2, wherein the polyepoxide is a di- or tri-epoxide.
Claim 9
Dependent Claim
20 words
The microporous membrane of claim 7, wherein the polyepoxide has a molecular weight of from about 146 to about 300.
Claim 10
Dependent Claim
33 words
The microporous membrane of claim 8, wherein the polyepoxide has the formula: ##STR10## wherein R is an alkyl of 1 to 6 carbon atoms and n is an integer from 2 to 3.
Claim 11
Dependent Claim
17 words
The microporous membrane of claim 6, wherein the polyepoxide is 1,4-butanediol diglycidyl ether of the formula: ##STR11##
Claim 12
Dependent Claim
91 words
A process for cationically charge modifying a hydrophilic organic polymeric microporous membrane comprising applying to the membrane a charge modifying amount of a cationic charge modifying agent which is bonded to the membrane structure through an aliphatic polyepoxide cross-linking agent having a molecular weight of less than 500, wherein the charge modifying agent is selected from the group consisting of: (i) aliphatic amines having at least one primary amine or at least two secondary amines; and (ii) aliphatic amines having at least one secondary amine and a carboxyl or hydroxyl substituent.
Claim 13
Dependent Claim
91 words
A process for cationically charge modifying a hydrophilic organic polymeric microporous membrane comprising applying to the membrane a charge modifying amount of a cationic charge modifying agent which is bonded to the membrane structure through an aliphatic polyepoxide cross-linking agent having a molecular weight of less than 500, wherein the charge modifying agent is selected from the group consisting of: (i) aliphatic amines having at least one primary amine or at least two secondary amines; and (ii) aliphatic amines having at least one secondary amine and a carboxyl or hydroxyl substituent.
Claim 14
Dependent Claim
93 words
A process for cationically charge modifying a hydrophilic organic polymeric microporous membrane comprising: (a) contacting the membrane with an aqueous solution of a cationic charge modifying agent, wherein the charge modifying agent is selected from the group consisting of: (i) aliphatic amines having at least one primary amine or at least two secondary amines; and (ii) aliphatic amines having at least one secondary amine and a carboxyl or hydroxyl substituent, (b) contacting the membrane with an aqueous solution of an aliphatic polyepoxide cross-linking agent having a molecular weight of less than about 500.
Claim 15
Dependent Claim
93 words
A process for cationically charge modifying a hydrophilic organic polymeric microporous membrane comprising: (a) contacting the membrane with an aqueous solution of a cationic charge modifying agent, wherein the charge modifying agent is selected from the group consisting of: (i) aliphatic amines having at least one primary amine or at least two secondary amines; and (ii) aliphatic amines having at least one secondary amine and a carboxyl or hydroxyl substituent, (b) contacting the membrane with an aqueous solution of an aliphatic polyepoxide cross-linking agent having a molecular weight of less than about 500.
Claim 16
Dependent Claim
15 words
The process of claim 12, wherein the contacting step (a) precedes the contacting step (b).
Claim 17
Dependent Claim
15 words
The process of claim 12, wherein the contacting step (b) precedes the contacting step (a).
Claim 18
Dependent Claim
34 words
The process of claim 12, wherein the contacting steps (a) and (b) are combined and the membrane is contacted with an aqueous solution of a mixture of the charge modifying agent and the polyepoxide.
Claim 19
Dependent Claim
24 words
The process of claim 12, wherein the aqueous solutions of charge modifying agent and polyepoxide are produced with water substantially free of ionic content.
Claim 20
Dependent Claim
17 words
The process of claim 16, wherein the water has a resistivity of at least about 250,000 ohm-cm.
Claim 21
Dependent Claim
24 words
The process of claim 12, wherein the aqueous solution of charge modifying agent contains at least about 0.25% amine by weight of the solution.
Claim 22
Dependent Claim
21 words
The process of claim 12, wherein the aqueous solution of polyepoxide contains at least 1% polyepoxide by weight of the solution.
Claim 23
Dependent Claim
24 words
The process of claim 18, wherein the aqueous solution of the charge modifying agent contains up to 1% amine by weight of the solution.
Claim 24
Dependent Claim
22 words
The process of claim 19, wherein the aqueous solution of polyepoxide contains up to about 4% polyepoxide by weight of the solution.
Claim 25
Dependent Claim
22 words
The process of claim 12, wherein the weight ratio of polyepoxide to charge modifying agent is from about 2:1 to about 10:1.
Claim 26
Dependent Claim
16 words
The process of claim 22, wherein the weight ratio is from about 3:1 to about 5:1.
Claim 27
Dependent Claim
13 words
The process of claim 11 or 12, wherein the microporous membrane is nylon.
Claim 28
Dependent Claim
14 words
The process of claim 11 or 12, wherein the microporous membrane is polyhexamethylene adipamide.
Claim 29
Dependent Claim
42 words
The process of claim 11 or 12, wherein the charge modifying agent is an amine of the formula: ##STR12## wherein R 1 and R 2 are alkyl of 1 to 4 carbon atoms and x is an integer from 0 to 4.
Claim 30
Dependent Claim
13 words
The process of claim 26, wherein R 1 and R 2 are ethyl.
Claim 31
Dependent Claim
17 words
The process of claim 11 or 12, wherein the amine is tetraethylene pentamine of the formula: ##STR13##
Claim 32
Dependent Claim
15 words
The process of claim 11 or 12, wherein the polyepoxide is a di- or tri-epoxide.
Claim 33
Dependent Claim
19 words
The process of claim 29, wherein the polyepoxide has a molecular weight of from about 146 to about 300.
Claim 34
Dependent Claim
34 words
The process of claim 11 or 12, wherein the polyepoxide has the formula: ##STR14## wherein R is an alkyl of 1 to 6 carbon atoms and n is an integer from 2 to 5.
Claim 35
Dependent Claim
16 words
The process of claim 28, wherein the polyepoxide is 1,4-butanediol diglycidyl ether of the formula: ##STR15##
Claim 36
Dependent Claim
21 words
A process for filtration of fluids comprising passing the fluid through a filter media comprising the microporous membrane of claim 1.
Claim 37
Dependent Claim
17 words
The process of claim 33, wherein the fluid is water having at least about 18 megohm-cm resistivity.
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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) | 1991-04-12 | 1991-10-12 | 1992-04-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-04-12 | 1995-10-12 | 1996-04-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-04-12 | 1999-10-12 | 2000-04-12 | $7700.00 | Window Closed / Lapsed |