US4025439A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dried semipermeable membrane and manufacture thereof
Assignee: Mitsubishi Chemical Corp
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Filing: 1975-10-09
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Granted: 1977-05-24
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Expires: 1995-10-09
Abstract
Abstract Dry semipermeable membranes of polyacrylonitrile or copolymers containing more than 65 wt. % of acrylonitrile are prepared by dissolving the polymer in a solvent in a solids concentration of 15-30% by weight; uniformly coating the solution onto a surface in a desired shape under an atmosphere whose relative humidity is 60-85% and dipping said coated surface into a non-solvent medium so as to remove the solvent which forms the membrane; heat-treating the membrane under moist conditions at 60 DEG -90 DEG C; and drying the membrane at a temperature less than the temperature of the heat treatment under conditions such that the coefficient of contraction is less than 1%, whereby a dried semi-permeable membrane having an open-celled structure with a pore size of a diameter less than 0.5 mu and a porosity of 0.40-0.7 is obtained.
Inventors
- 👤 Kensuke Kamada
- 👤 Shunsuke Minami
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:40
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/40; B01D71/42; B01D71/421; B01D67/00; B01D67/0002; B01D67/0009; B01D67/0011
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
158 words
In a process for preparing a dry semi-permeable membrane fabricated of polyacrylonitrile or a copolymer containing more than 65 weight % of acrylonitrile, the improvement which comprises: contacting the polymer with a polar organic solvent selected from the group consisting of dimethylformamide, dimethylacetoamide, dimethylsulfoxide and mixtures thereof in a solids concentration of 15-30% by weight; uniformly coating the solution onto a surface in a desired shape under an atmosphere having a relative humidity of 60-85% and dipping said coated surface into a non-solvent medium so as to remove the solvent which forms the membrane; heat-treating the membrane in water at 50°-90° C.; and drying the membrane at a temperature less than the temperature of the heat treatment under conditions such that the coefficient of contraction of said membrane is less than 1%, whereby a dried semi-permeable membrane having an open celled structure with a pore size of diameter less than 0.5μ and a porosity of 0.40-0.7 is obtained.
Claim 2
Dependent Claim
158 words
In a process for preparing a dry semi-permeable membrane fabricated of polyacrylonitrile or a copolymer containing more than 65 weight % of acrylonitrile, the improvement which comprises: contacting the polymer with a polar organic solvent selected from the group consisting of dimethylformamide, dimethylacetoamide, dimethylsulfoxide and mixtures thereof in a solids concentration of 15-30% by weight; uniformly coating the solution onto a surface in a desired shape under an atmosphere having a relative humidity of 60-85% and dipping said coated surface into a non-solvent medium so as to remove the solvent which forms the membrane; heat-treating the membrane in water at 50°-90° C.; and drying the membrane at a temperature less than the temperature of the heat treatment under conditions such that the coefficient of contraction of said membrane is less than 1%, whereby a dried semi-permeable membrane having an open celled structure with a pore size of diameter less than 0.5μ and a porosity of 0.40-0.7 is obtained.
Claim 3
Dependent Claim
27 words
The process of claim 1, wherein the heat treatment of the membrane is performed in hot water at 65° - 90° C. while maintained at constant length.
Claim 4
Dependent Claim
20 words
The process of claim 2, wherein the membrane is dried from room temperature to the temperature of the heat treatment.
Claim 5
Dependent Claim
23 words
The process of claim 1, wherein said copolymer contains 85-99 wt. % of acrylonitrile and 15-1 wt. % of at least one comonomer.
Claim 6
Dependent Claim
21 words
The process of claim 1, wherein the polymer is dissolved in a solvent in a solids concentration of 18-25% by weight.
Claim 7
Dependent Claim
18 words
The process of claim 5, wherein the solvent is dimethyl acetamide, dimethyl formamide, dimethyl sulfoxide or mixtures thereof.
Claim 8
Dependent Claim
11 words
The process of claim 1, wherein the non-solvent medium is water.
Claim 9
Dependent Claim
24 words
The process of claim 1, wherein the non-solvent medium is a mixture of water and dimethyl acetamide, dimethyl formamide, dimethyl sulfoxide or mixtures thereof.
Claim 10
Dependent Claim
16 words
The process of claim 8, wherein said non-solvent is a mixture containing 40-99 wt. % water.
Claim 11
Dependent Claim
30 words
The process of claim 1, wherein a portion of the solvent in the solution coated on the surface is evaporated and then the product is dipped into the non-solvent medium.
Claim 12
Dependent Claim
26 words
The process of claim 10, wherein the heat treatment is conducted in hot water at 70°-90° C. while the membrane is maintained at a constant length.
Claim 13
Dependent Claim
154 words
A dry semi-permeable membrane prepared by a process, which comprises the steps of: contacting polyacrylonitrile or a copolymer containing more than 65 weight % acrylonitrile with a polar organic solvent selected from the group consisting of dimethylformamide, dimethylacetoamide, dimethylsulfoxide and mixtures thereof in a solids concentration of 15-30% by weight; uniformly coating the solution onto a surface in a desired shape under an atmosphere having a relative humidity of 60-85% and dipping said coated surface into a non-solvent medium so as to remove the solvent which forms the membrane; heat-treating the membrane in water at 50°- 90° C.; and drying the membrane at a temperature less than the temperature of the heat treatment under conditions such that the coefficient of contraction of said membrane is less than 1%, whereby a dried semi-permeable membrane having an open-celled structure with a pore size of a diameter less than 0.5μ and a porosity of 0.40-0.7 is obtained.
Claim 14
Dependent Claim
154 words
A dry semi-permeable membrane prepared by a process, which comprises the steps of: contacting polyacrylonitrile or a copolymer containing more than 65 weight % acrylonitrile with a polar organic solvent selected from the group consisting of dimethylformamide, dimethylacetoamide, dimethylsulfoxide and mixtures thereof in a solids concentration of 15-30% by weight; uniformly coating the solution onto a surface in a desired shape under an atmosphere having a relative humidity of 60-85% and dipping said coated surface into a non-solvent medium so as to remove the solvent which forms the membrane; heat-treating the membrane in water at 50°- 90° C.; and drying the membrane at a temperature less than the temperature of the heat treatment under conditions such that the coefficient of contraction of said membrane is less than 1%, whereby a dried semi-permeable membrane having an open-celled structure with a pore size of a diameter less than 0.5μ and a porosity of 0.40-0.7 is obtained.
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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) | 1980-05-23 | 1980-11-22 | 1981-05-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-05-23 | 1984-11-22 | 1985-05-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-05-23 | 1988-11-22 | 1989-05-24 | $7700.00 | Window Closed / Lapsed |