US4333972A
Expired / Lapsed
US
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Highly anisotropic membranes
Assignee: GELSUB Inc
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Filing: 1980-06-25
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Granted: 1982-06-08
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Expires: 2000-06-25
Abstract
Abstract The discovery that highly anisotropic membranes, e.g. with a degree of anisotropy of five can for the very first time be produced by the dry phase inversion process by a very specific combination of polymers, solvent and non-solvent, optionally along with plasticizers and modifiers, all of which separately are known in membrane technology, the polymers consisting essentially of cellulose nitrate and cellulose nitrate-cellulose acetate mixed ester polymers, the solvent being methyl formate, propylene oxide, or mixtures thereof, and the non-solvents being isopropyl alcohol, t-butyl alcohol or mixtures thereof, is disclosed.
Inventors
- 👤 Robert E. Kesting
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 18:36
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/08; B01D71/12; B01D71/20; A; A61; A61L; A61L2/00; A61L2/02; A61L2/022; B01D67/00; B01D67/0002; B01D67/0009; B01D67/0011; B01D67/00111; B01D71/14; B01D71/16; B01D2325/00; B01D2325/40; B01D61/00; B01D61/14; B01D61/147
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
127 words
A method of manufacturing microporous polymeric membranes comprising the steps of: forming a casting solution consisting essentially of a solvent, a non-solvent and polymer, the solvent being selected from the group consisting of methyl formate, propylene oxide or mixtures thereof, the non-solvent consisting essentially of isopropyl alcohol, t-butyl alcohol or a mixture of said alcohols, and the polymer being selected from the group consisting of cellulose nitrate and mixtures of cellulose nitrate and cellulose acetate, cellulose nitrate content exceeding cellulose acetate content therein; casting said solution onto a substrate; and allowing the solvent and the non-solvent, respectively, to evaporate to thereby form an anisotropic cellulosic membrane having a first pore size adjacent one surface and a second smaller pore size adjacent the other surface of the membrane.
Claim 2
Independent Claim
127 words
A method of manufacturing microporous polymeric membranes comprising the steps of: forming a casting solution consisting essentially of a solvent, a non-solvent and polymer, the solvent being selected from the group consisting of methyl formate, propylene oxide or mixtures thereof, the non-solvent consisting essentially of isopropyl alcohol, t-butyl alcohol or a mixture of said alcohols, and the polymer being selected from the group consisting of cellulose nitrate and mixtures of cellulose nitrate and cellulose acetate, cellulose nitrate content exceeding cellulose acetate content therein; casting said solution onto a substrate; and allowing the solvent and the non-solvent, respectively, to evaporate to thereby form an anisotropic cellulosic membrane having a first pore size adjacent one surface and a second smaller pore size adjacent the other surface of the membrane.
Claim 3
Dependent Claim
130 words
A process for forming an anisotropic polymeric microfiltration membrane consisting essentially of the steps: (a) preparing a solution consisting essentially of a polymer selected from the group consisting of cellulose nitrate and mixtures of cellulose acetate and cellulose nitrate, cellulose nitrate content exceeding cellulose acetate content therein, in an amount of from about 0.1 percent to about 10 percent by weight of the solution, a solvent for the polymer selected from the group consisting of methyl formate and propylene oxide and mixtures thereof, and isopropyl alcohol, t-butyl alcohol or a mixture of said alcohols as a non-solvent; (b) casting the solution to form a thin layer of said solution; and (c) allowing the solvent and the non-solvent to evaporate completely, thereby forming said membrane by a dry phase inversion process.
Claim 4
Dependent Claim
130 words
A process for forming an anisotropic polymeric microfiltration membrane consisting essentially of the steps: (a) preparing a solution consisting essentially of a polymer selected from the group consisting of cellulose nitrate and mixtures of cellulose acetate and cellulose nitrate, cellulose nitrate content exceeding cellulose acetate content therein, in an amount of from about 0.1 percent to about 10 percent by weight of the solution, a solvent for the polymer selected from the group consisting of methyl formate and propylene oxide and mixtures thereof, and isopropyl alcohol, t-butyl alcohol or a mixture of said alcohols as a non-solvent; (b) casting the solution to form a thin layer of said solution; and (c) allowing the solvent and the non-solvent to evaporate completely, thereby forming said membrane by a dry phase inversion process.
Claim 5
Dependent Claim
44 words
The process of claim 2 further including the step of providing a layer of fibers and then casting said solution over said layer of fibers to form a thin layer which includes therein said fibers, the fibers then forming reinforcing for the resultant membrane.
Claim 6
Dependent Claim
37 words
The process of claim 2 including the step of including in the casting solution an amount of glycerol, effective to impart flexibility to the resulting membrane, said glycerol remaining as a leachable component of the resulting membrane.
Claim 7
Dependent Claim
24 words
The process of claim 4 including the additional step of leaching the glycerol from the membrane to provide a membrane free of leachable constituents.
Claim 8
Dependent Claim
44 words
The process of claim 4 further including the step of providing a layer of fibers and then casting said solution over said layer of fibers to form a thin layer which includes therein said fibers, the fibers then forming reinforcing for the resultant membrane.
Claim 9
Dependent Claim
96 words
In the manufacture of microporous polymeric membranes by the dry phase inversion process in which a casting solution of predetermined composition is prepared, cast and dried to form a membrane, the improvement wherein the step of preparing the casting solution comprises preparing a casting solution in which the solvent consists essentially of methyl formate or propylene oxide, a non-solvent selected from the group consisting of isopropyl alcohol, t-butyl alcohol and mixtures of said alcohols, and cellulose nitrate or cellulose nitrate - cellulose acetate mixed ester, cellulose nitrate content exceeding cellulose acetate content therein, as the polymer.
Claim 10
Dependent Claim
96 words
In the manufacture of microporous polymeric membranes by the dry phase inversion process in which a casting solution of predetermined composition is prepared, cast and dried to form a membrane, the improvement wherein the step of preparing the casting solution comprises preparing a casting solution in which the solvent consists essentially of methyl formate or propylene oxide, a non-solvent selected from the group consisting of isopropyl alcohol, t-butyl alcohol and mixtures of said alcohols, and cellulose nitrate or cellulose nitrate - cellulose acetate mixed ester, cellulose nitrate content exceeding cellulose acetate content therein, as the polymer.
Claim 11
Dependent Claim
93 words
In the manufacture of microporous polymeric membranes by the dry phase inversion process in which a casting solution of predetermined composition is prepared, cast and dried to form a membrane, the improvement wherein the step of preparing the casting solution comprises preparing a casting solution in which the solvent consists essentially of propylene oxide, a non-solvent selected from the group consisting of isopropyl alcohol, t-butyl alcohol and mixtures of said alcohols, and cellulose nitrate or cellulose nitrate - cellulose acetate mixed ester, cellulose nitrate content exceeding cellulose acetate content therein, as the polymer.
Claim 12
Dependent Claim
93 words
In the manufacture of microporous polymeric membranes by the dry phase inversion process in which a casting solution of predetermined composition is prepared, cast and dried to form a membrane, the improvement wherein the step of preparing the casting solution comprises preparing a casting solution in which the solvent consists essentially of propylene oxide, a non-solvent selected from the group consisting of isopropyl alcohol, t-butyl alcohol and mixtures of said alcohols, and cellulose nitrate or cellulose nitrate - cellulose acetate mixed ester, cellulose nitrate content exceeding cellulose acetate content therein, as the polymer.
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) | 1985-06-07 | 1985-12-07 | 1986-06-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-06-07 | 1989-12-07 | 1990-06-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-06-07 | 1993-12-07 | 1994-06-08 | $7700.00 | Window Closed / Lapsed |