Process for producing porous materials

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 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.

Claims

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.

Description

EXAMPLES

1. Methods

1.1 Determination of Thermal Conductivity

(1) The thermal conductivity was measured according to DIN EN 12667 with a heat flow meter from Hesto (Lambda Control A50).

1.2 Solvent Extraction with Supercritical Carbon Dioxide

(2) One or several gel monoliths were placed onto sample trays in an autoclave of 25 l volume. Subsequent to filling with supercritical carbon dioxide (scCO.sub.2), the gelation solvent was removed (drying) by flowing scCO.sub.2 through the autoclave for 24 h (20 kg/h). Process pressure was kept between 120 and 130 bar and process temperature at 60? C. in order to maintain carbon dioxide in a supercritical state. At the end of the process, the pressure was reduced to normal atmospheric pressure in a controlled manner. The autoclave was opened, and the obtained porous monoliths were removed.

1.3 Determination of Compressive Strength and E Modulus

(3) The compressive strength and the elastic modulus was measured according to DIN EN ISO 844 with 10% strain.

2. Materials

(4) Component a1: Oligomeric MDI (Lupranat M200) having an NCO content of 30.9 g per 100 g in accordance with ASTM D-5155-96 A, a functionality in the region of three and a viscosity of 2100 mPa.Math.s at 25? C. in accordance with DIN 53018 (hereinafter M200) Component a2: 3,3,5,5-Tetraethyl-4,4diaminodiphenylmethane (hereinafter MDEA) Component a3: Ethane-1,2-diol (hereinafter: MEG) Component a4: Exolit? OP560 (hereinafter: OP560) Component a5: n-Butanol Catalysts: Tetrabutylammonium hydroxide (55 wt % in water, hereinafter TBA-OH) Carboxylic acids: Acetic acid Citric acid 2-Ethylhexanoic acid (2E,4E)-Hexa-2,4-dienoic acid

3. Examples

(5) Thermal conductivity values for all examples are shown in Table 1. Furthermore, data regarding the compressive strength and density are included for several examples.

3.1 Example 1 (Comparative)

(6) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 0.93 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.30 g TBA-OH and 0.13 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was broken upon handling and subsequently not supercritically dried.

3.2 Example 2 (Comparative)

(7) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 0.93 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.10 g 2-ethylhexanoic acid and 0.26 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was broken upon handling and subsequently not supercritically dried.

3.3 Example 3 (Comparative)

(8) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 0.93 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.07 g (2E,4E)-hexa-2,4-dienoic acid and 0.26 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was broken upon handling and subsequently not supercritically dried.

3.4 Example 4 (Comparative)

(9) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 1.00 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.05 g acetic acid and 0.24 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was broken upon handling and subsequently not supercritically dried.

3.5 Example 5

(10) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 0.93 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.32 g TBA-OH, 0.10 g 2-ethylhexanoic acid and 0.12 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was dried through solvent extraction with scCO.sub.2 in a 25 l autoclave leading to a porous material.

(11) The compressive strength was determined according to DIN EN ISO 844 with 6% strain. The compressive strength was 0.461 N/mm.sup.2.

3.6 Example 6

(12) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 0.93 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.30 g TBA-OH, 0.07 g (2E,4E)-hexa-2,4-dienoic acid and 0.13 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was dried through solvent extraction with scCO.sub.2 in a 25 l autoclave leading to a porous material.

(13) The compressive strength was determined according to DIN EN ISO 844 with 6% strain. The compressive strength was 0.469 N/mm.sup.2.

3.7 Example 7

(14) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 1.00 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.39 g TBA-OH, 0.05 g acetic acid and 0.06 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was dried through solvent extraction with scCO.sub.2 in a 25 l autoclave leading to a porous material.

(15) The compressive strength was determined according to DIN EN ISO 844 with 6% strain. The compressive strength was 0.429 N/mm.sup.2.

3.8 Example 8 (Comparative)

(16) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 1.00 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.13 g citric acid and 0.29 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was broken upon handling and subsequently not supercritically dried.

3.9 Example 9

(17) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 1.00 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.32 g TBA-OH, 0.07 g citric acid and 0.07 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was dried through solvent extraction with scCO.sub.2 in a 25 l autoclave leading to a porous material.

(18) The compressive strength was determined according to DIN EN ISO 866 with 6% strain. The compressive strength was 0.366 N/mm.sup.2.

3.10 Example 10

(19) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 1.00 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.64 g TBA-OH, 0.13 g citric acid and 0.13 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was dried through solvent extraction with scCO.sub.2 in a 25 l autoclave leading to a porous material.

(20) The compressive strength was determined according to DIN EN ISO 866 with 6% strain. The compressive strength was 0.309 N/mm.sup.2.

3.11 Example 11

(21) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 1.00 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.32 g TBA-OH, 0.04 g citric acid and 0.04 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was dried through solvent extraction with scCO.sub.2 in a 25 l autoclave leading to a porous material.

(22) The compressive strength was determined according to DIN EN ISO 866 with 6% strain. The compressive strength was 0.366 N/mm.sup.2.

3.12 Example 12

(23) In a polypropylene container, 32.00 g M200 were stirred in 293.33 g MEK at 20? C. leading to a clear solution. Similarly, 5.33 g MDEA, 1.33 g MEG, 1.00 g OP560, 1.00 g water and 2.67 g butanol were dissolved in 293.33 g MEK before a previously prepared solution containing 0.96 g TBA-OH, 0.13 g citric acid and 0.13 g water was added. The solutions were combined in a rectangular container (16 cm?16 cm?3 cm height) by pouring one solution into the other, which led to a homogeneous mixture of low viscosity. The container was closed with a lid and the mixture was gelled at room temperature for 24 h. The resulting monolithic gel slab was dried through solvent extraction with scCO.sub.2 in a 25 l autoclave leading to a porous material.

(24) The compressive strength was determined according to DIN EN ISO 866 with 6% strain. The compressive strength was 0.151 N/mm.sup.2.

4. Results

(25) TABLE-US-00001 TABLE 1 Results. Thermal conductivity Compressive Density [mW/m*K] (p = 1 bar, strength [kg/m.sup.3] T = 10? C.) [kPa] Example 1 (comparative) Not determined, gel instable 5.33 g MDEA, 0.30 g TBA-OH Example 2 (comparative) Not determined, gel instable 5.33 g MDEA, 0.10 g 2-ethylhexanoic acid Example 3 (comparative) Not determined, gel instable 5.33 g MDEA, 0.07 g (2E,4E)-hexa-2,4-dienoic acid Example 4 (comparative) Not determined, gel instable 5.33 g MDEA, 0.05 g acetic acid Example 5 121 17.1 461 5.33 g MDEA, 0.32 g TBA-OH + 0.10 g 2-ethylhexanoic acid Example 6 118 17.4 469 5.33 g MDEA, 0.30 g TBA-OH + 0.07 g (2E,4E)-hexa-2,4-dienoic acid Example 7 126 16.9 429 5.33 g MDEA, 0.39 g TBA-OH + 0.05 g acetic acid Example 8 (comparative) Not determined, gel instable 5.33 g MDEA, 0.13 g citric acid Example 9 114 16.5 366 5.33 g MDEA, 0.32 g TBA-OH + 0.07 g citric acid Example 10 130 16.3 309 5.33 g MDEA, 0.64 g TBA-OH + 0.13 g citric acid Example 11 111 16.7 366 5.33 g MDEA, 0.32 g TBA-OH + 0.04 g citric acid Example 12 177 16.6 151 5.33 g MDEA, 0.96 g TBA-OH + 0.13 g citric acid

5. Abbreviations

(26) OP560 Exolit? OP560 H.sub.2O Water M200 Lupranate M200 (polyisocyanate) MEG Ethane-1,2-diol MEK Methyl ethyl ketone MDEA 4,4-Methylene-bis(2,6-diethylaniline) TBA-OH Tetrabutylammonium hydroxide (55 wt % in water)

Literature Cited

(27) WO 95/02009 A1 WO 2008/138978 A1 WO 2011/069959 A1 WO 2012/000917 A1 WO 2012/059388 A1 WO 2016/150684 A1 PCT/EP2017/05094 PCT/EP2017/050948 WO 2009/027310 A1 Polyurethane, 3.sup.rd edition, G. Oertel, Hanser Verlag, Munich, 1993 Plastics Additive Handbook, 5th edition, H. Zweifel, ed. Hanser Publishers, Munich, 2001