Method for producing xerogel composites
The invention relates to a process for producing xerogel composites, which comprises: (a) provision of a composition comprising an organic gel precursor (A) comprising a monomer component (A1) composed of at least one polyfunctional isocyanate and a monomer component (A2) composed of at least one compound selected from among polyfunctional amines and polyfunctional hydroxy compounds; (b) reaction of the gel precursor (A) in the presence of an open-celled macroporous foam (B) and a solvent (C) to form a xerogel composite; (c) drying of the xerogel composite by conversion of the solvent (C) into the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the solvent (C). The invention further relates to the xerogel composites which can be obtained in this way and their use as insulating material, for thermal insulation, vacuum insulation panels, in refrigeration units or in buildings.
1. A process for producing a xerogel composite, comprising:
(a) preparing an organic gel precursor (A) comprising a polyfunctional isocyanate monomer component (A1) and a polyfunctional aliphatic amine monomer component (A2);
(b) reacting the polyfunctional isocyanate monomer component (A1) and the polyfunctional aliphatic amine monomer component (A2) in the presence of an open-celled macroporous foam (B) and a solvent (C) to obtain a xerogel composite; and
(c) drying the xerogel composite by conversion of the solvent (C) into the gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the solvent (C),
wherein a porosity of the xerogel is at least 70% by volume,
the xerogel composite is not brought into contact with an organic fluid after (b), and
the polyfunctional aliphatic amine is at least one selected from the group consisting of bis(2-aminoethyl)amine, tris(2-aminoethyl)amine, triethylenetetramine, tetramethylenediamine, ethylenediamine, a diamine of butane, a diamine of pentane, 2-methyl-1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,12-diaminododecane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 4,4′-methylenebis(cyclohexylamine), 4,4′-diaminodicyclohexyl-1,2-propanediamine, 4,4′-diaminodicyclohexyl-1,3-propanediamine, 2,4′-diaminodicyclohexyl-1,2-propanediamine, 2,4′-diaminodicyclohexyl-1,3-propanediamine, 2,2′-diaminodicyclohexyl-1,2-propanediamine, 2,2′-diaminodicyclohexyl-1,3-propanediamine, 2-methyl-1,2-diaminopropane, 2,2-dimethyl-1,3-diaminopropane, bis(4-amino-3-methylcyclohexyl)methane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, bis(1,3-methylamino)cyclohexane, a bishydrazide, a bissemicarbazide, N,N,N-tris(2-aminoethyl)amine, guanidine, N-(2-aminoethyl)-1,3-diaminopropane, tetraethylenepentamine, pentaethylenehexamine, diaminopropyleneethylenediamine, propylenediamine, hexamethylenediamine, diaminocyclohexane, triglycol diamine, 1,3-diaminopropan-2-ol, ω,ω′-diaminodi-n-hexylamine, dimethyl 1,4-diaminoadipate and a polyalkylenepolyamine.
2. The process according to claim 1 , wherein the monomer component (A1) is at least one selected from the group consisting of diphenylmethane 2,2′-diisocyanate, diphenylmethane 2,4′-diisocyanate, diphenylmethane 4,4′-diisocyanate and oligomeric diphenylmethane diisocyanate.
3. The process according to claim 1 , wherein the monomer component (A1) is an oligomeric diphenylmethane diisocyanate having a functionality of at least 2.5.
4. The process according to claim 1 , wherein the components (A1) and (A2) each have a functionality of at least two and the sum of the functionality of component (A1) and the functionality of component (A2) is at least 4.5.
5. The process according to claim 1 , wherein the open-celled macroporous foam (B) has a volume average pore size of from 20 to 1000 microns.
6. The process according to claim 1 , wherein the open-celled macroporous foam (B) is based on reactive polycondensation resins.
7. The process according to claim 1 , wherein the open-celled macroporous foam (B) is a melamine-formaldehyde foam.
8. A xerogel composite obtained by the process according to claim 1 .
9. The process according to claim 1 , wherein the porosity of the xerogel is from 70% to 99% by volume.
10. An insulating material, comprising the xerogel composite according to claim 8 .
11. A thermal insulation, comprising the xerogel composite according to claim 8 .
12. A vacuum insulation panel, comprising the xerogel composite according to claim 8 .
13. A refrigeration unit or a building, comprising the xerogel composite according to claim 8 .