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US3874899A Expired / Lapsed US ⏱️ 0.0 years remaining

Process for the preparation of porous membranes or composite barriers for gaseous diffusion installations

Assignee: Montedison SpA
•
Filing: 1972-08-18
•
Granted: 1975-04-01
•
Expires: 1992-08-18
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Abstract

Abstract A process is disclosed for the preparation of porous barriers or membranes of the composite type, consisting throughout of sintered porous alumina, for applications in the field of gaseous diffusion, the process consisting: IN PREPARING A SUPPORT OF SINTERED POROUS ALUMINA, PREFERABLY BUT NOT NECESSARILY OF TUBULAR SHAPE; IN THEN DEPOSITING ON SAID SUPPORT A MICROPOROUS LAYER BY FILTERING THROUGH THE POROUS WALLS OF SAID SUPPORT AN AQUEOUS SUSPENSION CONTAINING SUBMICRONIC PARTICLES OF ALUMINA AND/OR ALUMINUM HYDRATES, PREFERABLY IN CONCENTRATIONS OF FROM 0.1 TO 10 PERCENT, AND AT LEAST ONE HYDROPHILLIC ETHER OF CELLULOSE, PREFERABLY IN CONCENTRATIONS OF FROM 0.1 TO 2 PERCENT; IN CARRYING OUT THE FILTERING FROM THE INSIDE TOWARDS THE OUTSIDE (IN THE CASE OF A TUBULAR SUPPORT) AND UNDER A SUITABLE PRESSURE DIFFERENCE; IN ELIMINATING THE EXCESS SUSPENSION FROM THE INSIDE OF THE SUPPORT AND BY DRYING THE LAYER; IN CALCINING IN AIR THE MANUFACTURED BODY THEREBY ELIMINATING THE COMBUSTIBLE SUBSTANCES; AND, IN SINTERING IN AIR SAID PRODUCT, AT TEMPERATURES EXCEEDING 900*C, but preferably between 950* and 1,250*C, and possibly subjecting the microporous layer, after the calcination and before the final sintering, to cold compacting. The internal (inside) surface of said support, before the filtering operation, is preferably treated by dry rubbing with alumina powder and/or powders of other materials easily removable, such as for instance carbon black. The filtering operation and the subsequent calcination may be repeated in order to obtain microporous layers of greater thickness. The cold compacting operation is carried out by subjecting the manufactured body to an isostatic compression inside a suitable apparatus, said manufactured body being placed between two deformable tight-fitting membranes, of which the one pressing against the microporous layer is preferably made of pure natural unvulcanized rubber obtained from pure latex.

Inventors

  • 👤 Giorgio Szabo Miszenti
  • 👤 Carlo Alberto Nannetti

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-26 02:00
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/02; B01D71/024; B01D71/025; B01D59/00; B01D59/10; B01D59/12; B01D59/14; B01D67/00; B01D67/0039; B01D67/0041; B01D67/00416; B01D69/00; B01D69/04; B01D2311/00; B01D2311/26; B01D2311/2642

Claims Analysis

Total Claims: 13
Claim 1
Independent Claim 141 words
A PROCESS FOR THE PREPARATION OF POROUS BARRIERS OR MEMBRANES OF THE COMPOSITE TYPE, CONSISTING ESSENTIALLY THROUGHOUT OF SINTERED POROUS ALUMINA, SAID PROCESS COMPRISING: A. PREPARING A SUPPORT OF SINTERED POROUS ALUMINA, B. DEPOSITING ON SAID SUPPORT A MICROPOROUS LAYER BY FILTERING THROUGH THE POROUS WALLS OF SAID SUPPORT UNDER A SUITABLE PRESSURE DIFFERENCE AN AQUEOUS SUSPENSION CONTAINING SUBMICRONIC PARTICLES OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF ALUMINA AND ALUMINUM HYDRATES AND AT LEAST ONE HYDROPHILLIC ETHER OR CELLULOSE, C. ELIMINATING THE EXCESS SUSPENSION FROM THE UPSTREAM SIDE OF THE SUPPORT AND LETTING THE RESULTING LAYER DRY, D. CALCINING THE RESULTING MANUFACTURED ARTICLE IN AIR UNTIL THE COMBUSTIBLE SUBSTANCES ARE ELIMINATED, E. SINTERING THE ARTICLE IN AIR AT TEMPERATURES EXCEEDING 900*C, AND SUBJECTING THE MICROPOROUS LAYER, AFTER THE CALCINATION AND BEFORE THE FINAL SINTERING, TO A COLD COMPACTING STEP.
Claim 2
Dependent Claim 141 words
A PROCESS FOR THE PREPARATION OF POROUS BARRIERS OR MEMBRANES OF THE COMPOSITE TYPE, CONSISTING ESSENTIALLY THROUGHOUT OF SINTERED POROUS ALUMINA, SAID PROCESS COMPRISING: A. PREPARING A SUPPORT OF SINTERED POROUS ALUMINA, B. DEPOSITING ON SAID SUPPORT A MICROPOROUS LAYER BY FILTERING THROUGH THE POROUS WALLS OF SAID SUPPORT UNDER A SUITABLE PRESSURE DIFFERENCE AN AQUEOUS SUSPENSION CONTAINING SUBMICRONIC PARTICLES OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF ALUMINA AND ALUMINUM HYDRATES AND AT LEAST ONE HYDROPHILLIC ETHER OR CELLULOSE, C. ELIMINATING THE EXCESS SUSPENSION FROM THE UPSTREAM SIDE OF THE SUPPORT AND LETTING THE RESULTING LAYER DRY, D. CALCINING THE RESULTING MANUFACTURED ARTICLE IN AIR UNTIL THE COMBUSTIBLE SUBSTANCES ARE ELIMINATED, E. SINTERING THE ARTICLE IN AIR AT TEMPERATURES EXCEEDING 900*C, AND SUBJECTING THE MICROPOROUS LAYER, AFTER THE CALCINATION AND BEFORE THE FINAL SINTERING, TO A COLD COMPACTING STEP.
Claim 3
Dependent Claim 39 words
A process according to claim 1, wherein the porous alumina support of (a) is tubular in shape and the filtering step of (b) is carried out in a direction from the inside toward the outside of the tubular shape.
Claim 4
Dependent Claim 25 words
A process according to claim 1, wherein the concentration of the submicronic particles in the aqueous suspension of (b) is from 0.1 to 10 percent.
Claim 5
Dependent Claim 25 words
A process according to claim 1, wherein the concentration of the cellulose ether in the aqueous suspension of (b) is from 0.1 to 2 percent.
Claim 6
Dependent Claim 17 words
A process according to claim 1, wherein the sintering temperature of (e) is between 950* and 1,250*C.
Claim 7
Dependent Claim 19 words
A process according to claim 1, wherein the aqueous suspension of (b) contains methylcellulose of varying degrees of methylation.
Claim 8
Dependent Claim 41 words
A process according to claim 1, wherein the upstream surface of said support, before said filtering step, is subjected to a dry rubbing with a material selected from the group consisting of alumina powder and easily removable powders of other materials.
Claim 9
Dependent Claim 18 words
A process according to claim 7, wherein the powder employed in the dry rubbing step comprises carbon black.
Claim 10
Dependent Claim 25 words
A process according to claim 1, wherein the filtering step and the subsequent calcination are repeated in order to obtain microporous layers of greater thickness.
Claim 11
Dependent Claim 56 words
A process according to claim 1, wherein the cold compacting step is carried out by subjecting the manufactured article to an isostatic compression inside a suitable apparatus, said manufactured article being placed between two deformable tight-fitting membranes, of which the one facing the microporous layer is made of pure natural unvulcanized rubber obtained from pure latex.
Claim 12
Dependent Claim 22 words
A process accoRding to claim 1, wherein the cold compacting step is carried out at a pressure greater than 400 kg/sq. cm.
Claim 13
Dependent Claim 20 words
A process according to claim 1, wherein the calcination step of (d) is carried out at between 500* and 800*C.

References Cited (Backward Citations)

US3238056A Cited
US3451841A Cited
US3717525A Cited
US3556305A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1978-03-31 1978-09-30 1979-04-01 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1982-03-31 1982-09-30 1983-04-01 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1986-03-31 1986-09-30 1987-04-01 $7700.00 Window Closed / Lapsed

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