# US 11,028,247 B2 · Process for producing porous alginate-based aerogels

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- Number: US 11,028,247 B2
- Document ID: US11028247B2
- Status: Granted
- Kind: B2
- Application number: 15/978,647
- Filed: 2018-05-14
- Published: 2018-09-13
- Granted: 2021-06-08
- Earliest claimed: 2014-05-19
- Assignees: BASF SE
- Applicants: BASF SE
- Inventors: Marc Fricke; Dirk Weinrich; Wibke Loelsberg; Raman Subrahmanyam; Irina Smirnova; Pavel Gurikov
- Web page: https://patentgrep.com/patent/US11028247B2

## CPC

- C08J 9/28: by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
- C08J 9/0066: {Use of inorganic compounding ingredients}
- C08J 9/122: {Hydrogen, oxygen, CO2, nitrogen or noble gases}
- C08J 9/35: Composite foams, i.e. continuous macromolecular foams containing discontinuous cellular particles or fragments
- C09K 5/14: Solid materials, e.g. powdery or granular
- C08J 2201/026: Crosslinking before of after foaming
- C08J 2201/05: Elimination by evaporation or heat degradation of a liquid phase
- C08J 2201/0502: the liquid phase being organic
- C08J 2203/06: CO2, N2 or noble gases
- C08J 2205/022: Hydrogel, i.e. a gel containing an aqueous composition
- C08J 2205/024: Organogel, i.e. a gel containing an organic composition
- C08J 2205/026: Aerogel, i.e. a supercritically dried gel
- C08J 2205/028: Xerogel, i.e. an air dried gel
- C08J 2205/042: Nanopores, i.e. the average diameter being smaller than 0,1 micrometer
- C08J 2305/04: Alginic acid; Derivatives thereof
- C08J 2483/00: Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE

## Abstract

The present invention relates to a process for preparing a porous material, at least comprising the steps of providing a mixture (I) comprising a water soluble polysaccharide, at least one compound suitable to react as cross-linker for the polysaccharide or to release a cross-linker for the polysaccharide, and water, and preparing a gel (A) comprising exposing mixture (I) to carbon dioxide at a pressure in the range of from 20 to 100 bar for a time sufficient to form a gel (A), and depressurizing the gel (A). Gel (A) subsequently is exposed to a water miscible solvent (L) to obtain a gel (B), which is dried. The invention further relates to the porous materials which can be obtained in this way and the use of the porous materials as thermal insulation material, for cosmetic applications, for biomedical applications or for pharmaceutical applications.

## Claims

### Claim 1

A porous material obtained by a process comprising:
a) providing a mixture (I) comprising
(i) a water soluble polysaccharide,
(ii) a compound which reacts as a cross-linker for the water soluble polysaccharide or which releases a cross-linker for the water soluble polysaccharide, and
(iii) water;
b) preparing a gel (A) by a process comprising
b1) exposing the mixture (I) to carbon dioxide at a pressure of from 20 to 100 bar for a time sufficient to form a gel (A), and
b2) depressurizing the gel (A);
c) exposing the gel (A) to a water miscible solvent (L) to obtain a gel (B); and
d) drying the gel (B),
wherein the water miscible solvent (L) is at least one selected from the group consisting of a C1 to C6 alcohol a C1 to C6 ketone, and a mixture thereof,
wherein the water soluble polysaccharide is an alginate, and wherein the compound which reacts as a cross-linker for the water soluble polysaccharide or which releases a cross-linker for the water soluble polysaccharide in the mixture (I) comprises calcium carbonate,
wherein the porous material has a pore volume in the range of from 2.1 to 9.5 cm3/g for pore sizes <150 nm.

### Claim 2 (depends on 1)

The porous material of claim 1, wherein the preparing in b) is carried out at a temperature of from 10 to 40° C.

### Claim 3 (depends on 1)

The porous material of claim 1, wherein carbon dioxide in the exposing in b1) is gaseous.

### Claim 4 (depends on 1)

The porous material of claim 1, wherein a water insoluble solid (S) is further added to the mixture (I).

### Claim 5 (depends on 1)

The porous material of claim 1, wherein a compound (C) is further added to the mixture (I) in the providing in a), wherein the compound (C) is at least one selected from the group consisting of a natural hydrocolloid forming polymer, a synthetic hydrocolloid-forming polymer, and a mixture thereof.

### Claim 6 (depends on 1)

The porous material of claim 1, wherein the exposing in c) is carried out at a pressure of from 10 to 100 bar.

### Claim 7 (depends on 1)

The porous material according to claim 1, wherein the drying in d) is carried out by converting a liquid in the gel (B) into a gaseous state at a temperature and a pressure below a critical temperature and a critical pressure of the liquid in the gel (B).

### Claim 8 (depends on 1)

The porous material according to claim 1, wherein the drying in d) is carried out under supercritical conditions.

### Claim 9 (depends on 1)

A cosmetic, biomedical, or pharmaceutical product, comprising:
a thermal insulation material comprising the porous material of claim 1.