Process for producing porous materials
The present invention relates to a process for preparing a porous material, at least comprising the steps of providing a mixture (I) comprising a composition (A) comprising components suitable to form an organic gel and a solvent (B), reacting the components in the composition (A) in the presence of the solvent (B) to form a gel, and drying of the gel obtained in step b), wherein the composition (A) comprises a catalyst system (CS) at least comprising a catalyst component (C1) selected from the group consisting of ammonium salts and a carboxylic acid as catalyst component (C2). 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 and in vacuum insulation panels and vacuum insulation systems, in particular in interior or exterior thermal insulation systems as well as for the insulation of refrigerators and freezers and in water tank or ice maker insulation systems.
1. A process for preparing a porous material, the process comprising:
a) providing a mixture (I) comprising
(i) a composition (A) comprising components suitable to form an organic gel and
(ii) a solvent (B),
b) reacting the components in the composition (A) in the presence of the solvent (B) to form a gel, and
c) drying the gel obtained in b),
wherein the composition (A)
comprises
a catalyst system (CS) comprising a tetraalkylammonium hydroxide as a catalyst component
(C1) and a carboxylic acid as a catalyst component (C2), and
at least one polyfunctional isocyanate as component (a1),
at least one aromatic amine as component (a2),
optionally water as component (a3), and
optionally at least one further catalyst as component (a4),
wherein 35 to 93.8% by weight of component (a1), from 0.2 to 25% by weight of component (a2), and, when present, from 0.01 to 30% by weight of component (a4), in each case based on the total weight of the components (a1) to (a4), where the % by weight of the components (a1) to (a4) add up to 100% by weight, are used,
wherein the catalyst system (CS) comprises a tetraalkylammonium hydroxide as the catalyst component (C1),
wherein (C2) comprises citric acid, acetic acid, 2-ethylhexanoic acid, or (2E,4E)-hexa-2,4,-dienoic acid, and
wherein the catalyst system (CS) is added in the form of an aqueous solution.
2. The process according to claim 1 , wherein the tetraalkylammonium hydroxide is selected from the group consisting of tetramethyl ammonium hydroxide, tetra(n-butyl)ammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, hexa-decyltrimethylammonium hydroxide, tetrahexylammonium hydroxide, triethylmethylammonium hydroxide, tetraoctylammonium hydroxide, tri-n-butylmethylammonium hydroxide, diethyldimethylammonium hydroxide, octyltrimethylammonium hydroxide, trimethylethylammonium hydroxide, tetrapentylammonium hydroxide, tripropylmethylammonium hydroxide, tetrakisdecylammonium hydroxide, and tributyl ethyl ammonium hydroxide.
3. The process according to claim 1 , wherein the carboxylic acid is acetic acid.
4. The process according to claim 1 , wherein the composition (A) comprises at least one monool.
5. The process according to claim 1 , wherein the drying c) is carried out by converting liquid comprised in the gel into a gaseous state at a temperature and a pressure below the critical temperature and the critical pressure of the liquid comprised in the gel.
6. The process according to claim 1 , wherein the drying c) is carried out under supercritical conditions.
7. The process according to claim 1 , wherein the composition (A) further comprises the water as component (a3).
8. The process according to claim 1 , wherein the composition (A) further comprises the further catalyst as component (a4).
9. A process for preparing a porous material, the process comprising:
providing a mixture (I) comprising a composition (A) comprising components suitable to form an organic gel and a solvent (B), reacting the components in the composition (A) in the presence of the solvent to form a gel, and drying the gel obtained in b), wherein the composition (A) comprises a catalyst system (CS) comprising a tetraalkylammonium hydroxide as a catalyst component (C1) and a carboxylic acid as a catalyst component (C2), and at least one polyfunctional isocyanate as component (a1),
wherein the catalyst system (CS) comprises a tetraalkylammonium hydroxide as the catalyst component (C1), and
wherein (C2) comprises citric acid.
10. The process according to claim 1 , wherein the catalyst system (CS) is present in the composition (A) in an amount of 0.1 to 30% by weight of the total weight of the composition (A).
11. The process according to claim 10 , wherein the catalyst system (CS) comprises catalyst components (C1) and (C2) in a weight ratio of from 1:10 to 10:1.
12. The process according to claim 1 , wherein (C2) comprises 2-ethylhexanoic acid.
13. The process according to claim 11 , wherein (C2) comprises (2E,4E)-hexa-2,4,-dienoic acid.