Claims
- 1. A process for making a free-standing, porous foam product which consist essentially of PVP molecules hydrogen bonded to H.sub.2 O.sub.2 molecules, optionally including a water-soluble gelling agent, the PVP content being about 20-90% by weight, the H.sub.2 O.sub.2 content being about 5-24% by weight, about 20-60% by weight of a gelling agent, and about 0-8% water by weight, the bulk density being about 0.3-0.5 g/cc or less, and the porosity being about 60-70%, or less, if the gelling agent is present, which comprises
- (a) providing an aqueous solution containing PVP, H.sub.2 O.sub.2, optionally a gelling agent, and water, in amounts of PVP, H.sub.2 O.sub.2 and gelling agent to provide said product after processing,
- (b) freezing the aqueous solution at below about -20.degree. C. to form a soft ice, and
- (c) vacuum drying the soft ice at a reduced pressure of less than about 0.1 mm to remove water therefrom.
- 2. A process according to claim 1 wherein water is removed by sublimation from the soft ice and condensed at about -90.degree. C.
- 3. A process according to claim 1 wherein the aqueous solution includes hydroxyethyl cellulose as a water-soluble gelling agent.
CROSS-REFERENCE TO RELATED PATENT APPLICATION
This application is a continuation-in-part of copending U.S. patent application Ser. No. 721,786, filed Jun. 26, 1991, now abandoned, and assigned to the same assignee as herein.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
3480557 |
Shiraeff |
Nov 1969 |
|
4769013 |
Lorenz et al. |
Sep 1988 |
|
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
721786 |
Jun 1991 |
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