Patent US4018681A successfully refreshed from Google Patents.
US4018681A
Expired / Lapsed
US
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Filtration of cellulosic solutions
Assignee: Rayonier Inc
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Filing: 1975-11-12
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Granted: 1977-04-19
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Expires: 1995-11-12
Abstract
Abstract Cellulosic solutions are filtered by a process enabling virtual complete recovery and recycling of the undissolved cellulosic components of the solutions. The process comprises filtering the solution through a bed of particulate material until the build-up of undissolved material impedes the further flow of solution through the bed, mixing the undissolved material and particulate bed with a solvent to partially dissolve the undissolved material, which is highly concentrated relative to its original concentration before filtration, adding a solubilizing reactant to said concentrated partial solution of undissolved material to complete the solution of the cellulosic residues, and separating and recycling the resulting solution.
Inventors
- 👤 Edmund M. LaPolla
- 👤 Charles F. Murphy
- 👤 Arthur Sarkisian
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 08:33
CPC Classifications
C; C08; C08B; C08B11/00; C08B11/20; C08B11/22; B; B01; B01D; B01D11/00; B01D11/02; B01D11/0288; C08B3/00; C08B3/22; C08B3/26; C08B9/00; B01D2201/00; B01D2201/08; B01D2201/085; B01D24/00; B01D24/02; B01D24/10; B01D24/105
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
167 words
A process for the filtration of viscose cellulosic solutions containing less than 1% of undissolved cellulosic materials comprising filtering the cellulosic solution through a bed of particulate material inert to the cellulosic solution until the build-up of undissolved material in the bed impedes the further flow of solution through the bed, mixing the particulate bed and build-up of undissolved material with a sodium hydroxide solvent therefor substantially free of cellulosic material to partially dissolve undissolved cellulosic material, the partial solution of said undissolved cellulosic material being highly concentrated relative to its concentration in the original cellulosic solution, the concentration being at least 25 times the concentration of the original solution, adding carbon bisulfide substantially free of cellulosic material to said concentrated solution in an amount by weight in excess of the amount by weight of the undissolved material to complete the solution of the undissolved cellulosic material, separating the solution from the particulate bed, and recycling to unfiltered cellulosic solutions the reactant containing solution of cellulosic material.
Claim 2
Dependent Claim
167 words
A process for the filtration of viscose cellulosic solutions containing less than 1% of undissolved cellulosic materials comprising filtering the cellulosic solution through a bed of particulate material inert to the cellulosic solution until the build-up of undissolved material in the bed impedes the further flow of solution through the bed, mixing the particulate bed and build-up of undissolved material with a sodium hydroxide solvent therefor substantially free of cellulosic material to partially dissolve undissolved cellulosic material, the partial solution of said undissolved cellulosic material being highly concentrated relative to its concentration in the original cellulosic solution, the concentration being at least 25 times the concentration of the original solution, adding carbon bisulfide substantially free of cellulosic material to said concentrated solution in an amount by weight in excess of the amount by weight of the undissolved material to complete the solution of the undissolved cellulosic material, separating the solution from the particulate bed, and recycling to unfiltered cellulosic solutions the reactant containing solution of cellulosic material.
Claim 3
Dependent Claim
20 words
The process of claim 1 in which the sodium hydrotide solvent and carbon bisulfide are added at the same time.
Claim 4
Dependent Claim
13 words
The process of claim 1 in which the particulate bed comprises two layers.
Claim 5
Dependent Claim
21 words
The process of claim 1 in which the mesh size of the particles in the bed range from -20 to +325.
Claim 6
Dependent Claim
20 words
The process of claim 1 in which the filtration is carried out under pressure of from 25 to 400 psig.
Claim 7
Dependent Claim
16 words
The process of claim 1 in which the particulate material of the bed is a metal.
Claim 8
Dependent Claim
22 words
The process of claim 6 in which any metal particles from the bed which remain in the cellulosic solution are removed magnetically.
Claim 9
Dependent Claim
16 words
The process of claim 6 in which the particulate material of the bed is stainless steel.
Claim 10
Dependent Claim
38 words
The process of claim 1 in which the particulate bed and build-up of undissolved material is mixed with from 0.5 to 4.0% by weight of dilute sodium hydroxide solution, based on the weight of the original cellulosic solution.
Claim 11
Dependent Claim
22 words
The process of claim 9 in which the dilute sodium hydroxide solution has a concentration of from 7 to 11% by weight.
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) | 1980-04-18 | 1980-10-18 | 1981-04-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-04-18 | 1984-10-18 | 1985-04-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-04-18 | 1988-10-18 | 1989-04-19 | $7700.00 | Window Closed / Lapsed |