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US4118449A
Expired / Lapsed
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Method of making a cellulose acetate low density microcellular foam
Assignee: United States Department of Energy
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Filing: 1976-12-09
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Granted: 1978-10-03
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Expires: 1996-12-09
Abstract
Abstract Low-density microcellular foam having a cell size of not greater than 2 mu m and method of making by dissolving cellulose acetate in an acetone-based solvent, gelling the solution in a water bath maintained at 0-10 DEG C for a selected period of time to allow impurities to diffuse out, freezing the gel, and then freeze-drying wherein water and solvents sublime and the gel structure solidifies into low-density microcellular foam. The foam has a density of 0.065 to 0.6x103 kg/m3 and cell size of about 0.3 to 2 mu m. The small cell size foam is particularly adaptable for encapsulation of laser targets.
Inventors
- 👤 James A. Rinde
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:31
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/28; C08J2201/00; C08J2201/04; C08J2201/048; C08J2201/054; C08J2301/00; C08J2301/08; C08J2301/10; C08J2301/12; Y; Y10; Y10S; Y10S376/00; Y10S376/916
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
185 words
A method for making a cellulose acetate foam having a density in the range of 0.065 to 0.6 × 10 3 kg/m 3 and a cell size in the range of 0.3 to 2μm comprising the steps of: forming a polymer solution by dissolving a cellulose acetate polymer in a solution consisting of anhydrous magnesium perchlorate anhydrous constituting a swelling agent, water constituting a nonsolvent, and ethyl lactate and acetone constituting solvents such that the cellulose acetate is in the range of from 3% to not greater than 22%; shaping the solution; gelling the thus shaped polymer solution by directing same into a water bath maintained at a temperature of 0°-10° C.; soaking the shaped gel in a water bath having a temperature of about 0°-30° C. for sufficient time to substantially diffuse out solvents and swelling agents; freezing the thus soaked gel; and freeze-drying the shaped gel wherein water and solvents sublime and the gel structure solidifies into foam having a cell size ranging from 0.3 to 2μm and a density in the range of 0.065 to 0.6 × 10 3 kg/m 3 .
Claim 2
Independent Claim
185 words
A method for making a cellulose acetate foam having a density in the range of 0.065 to 0.6 × 10 3 kg/m 3 and a cell size in the range of 0.3 to 2μm comprising the steps of: forming a polymer solution by dissolving a cellulose acetate polymer in a solution consisting of anhydrous magnesium perchlorate anhydrous constituting a swelling agent, water constituting a nonsolvent, and ethyl lactate and acetone constituting solvents such that the cellulose acetate is in the range of from 3% to not greater than 22%; shaping the solution; gelling the thus shaped polymer solution by directing same into a water bath maintained at a temperature of 0°-10° C.; soaking the shaped gel in a water bath having a temperature of about 0°-30° C. for sufficient time to substantially diffuse out solvents and swelling agents; freezing the thus soaked gel; and freeze-drying the shaped gel wherein water and solvents sublime and the gel structure solidifies into foam having a cell size ranging from 0.3 to 2μm and a density in the range of 0.065 to 0.6 × 10 3 kg/m 3 .
Claim 3
Dependent Claim
43 words
The method defined in claim 1, wherein the step of forming the polymer solution is carried out by using 6 grams of cellulose acetate, 10 grams of magnesium perchlorate, 30 grams of water, 15 grams of ethyl lactate, and 39 grams of acetone.
Claim 4
Dependent Claim
39 words
The method defined in claim 1, wherein the steps of shaping and gelling the polymer solution in a water bath are carried out by extruding the polymer solution into water maintained at a temperature of 0° to 10° C.
Claim 5
Dependent Claim
31 words
The method defined in claim 1, wherein the step of soaking the shaped gel in the water bath is carried out for a time period ranging from 16 to 24 hours.
Claim 6
Dependent Claim
24 words
The method defined in claim 1, wherein the step of freezing the shaped gel is carried out in -70° to -80° C. liquid pentane.
Claim 7
Dependent Claim
25 words
The method defined in claim 1, wherein the step of freeze-drying the shaped gel is carried out for a period of 4 to 8 hours.
Claim 8
Dependent Claim
39 words
The method defined in claim 1, wherein the shaped gel is soaked in the water bath for about 24 hours, the gel is frozen in -70° to -80° C. liquid pentane, and the gel is freeze-dried for 4-8 hours.
Claim 9
Dependent Claim
22 words
The method defined in claim 1, additionally including the step of cutting the thus shaped foam by a vibrational driven sharp member.
Claim 10
Dependent Claim
25 words
The method defined in claim 1, wherein the step of forming the polymer solution is carried out at a temperature of 25° to 50° C.
References Cited (Backward Citations)
US3428584A
Cited
US4021280A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-10-02 | 1982-04-03 | 1982-10-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-10-02 | 1986-04-03 | 1986-10-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-10-02 | 1990-04-03 | 1990-10-03 | $7700.00 | Window Closed / Lapsed |