Process for hydrophobizing shaped insulation-material bodies based on silica at ambient pressure

Abstract

The present invention relates to a process for producing a hydrophobized shaped thermal-insulation body, comprising pressing or compacting a thermal-insulation mixture containing a silica, an IR opacifier, an organosilicon compound A and an organosilicon compound B, wherein organosilicon compound A is hexamethyldisilazane (HMDS) and organosilicon compound B corresponds to a substance of the formula R.sub.nSiX.sub.4-n, where R=hydrocarbyl radical having 1 to 18 carbon atoms, n=0, 1 or 2, X=Cl, Br or alkoxy group OR.sup.1 where R.sup.1=hydrocarbyl radical having 1 to 8 carbon atoms, or organosilicon compound B corresponds to a silanol of the formula HO[Si(CH.sub.3).sub.2O].sub.mH, where m=2-100.

Claims

1. A process for producing a hydrophobized shaped thermal-insulation body, comprising pressing or compacting a thermal-insulation mixture: wherein the thermal-insulation mixture comprises: a) 30% to 95% by weight of silica; b) 5% to 50% of an IR opacifier; c) 1% to 20% by weight of organosilicon compound A, wherein organosilicon compound A is hexamethyldisilazane (HMDS); (d) 1% to 20% by weight of organosilicon compound B, wherein organosilicon compound B is a substance of formula R.sub.nSiX.sub.4-n, wherein: R=hydrocarbyl radical having 1 to 18 carbon atoms; n=0, 1 or 2; X=Cl, Br or alkoxy group OR.sup.1 wherein R.sup.1=hydrocarbyl radical having 1 to 8 carbon atoms; or organosilicon compound B corresponds to a silanol of the formula HO[Si(CH.sub.3).sub.2O].sub.mH, where m=2-100; and e) 0.1% to 10% by weight of water; and wherein the hydrophobized shaped thermal-insulation body formed has a density of 50 to 300 g/l and a compressive strength of 65 to 150 kPa.

2. The process of claim 1, wherein the silica is selected from the group consisting of: aerogels: xerogels; perlites; precipitated silicas; fumed silicas; and mixtures thereof.

3. The process of claim 1, wherein the IR opacifier is selected from the group consisting of: silicon carbide; titanium dioxide; zirconium dioxide; ilmenites; iron titanates; iron oxides; zirconium silicates; manganese oxides; graphites; carbon blacks; and mixtures thereof.

4. The process of claim 1, wherein the molar ratio of organosilicon compound A to organosilicon compound B to water when preparing the thermal-insulation mixture is 1:(0.1-20.0):(0.2-10).

5. The process of claim 1, wherein the thermal-insulation mixture contains 1% to 10% by weight of a fibre.

6. The process of claim 1, wherein the preparation of the thermal-insulation mixture is done al a temperature of 10? C. to 40? C.

7. The process of claim 1, wherein the time between the addition of organosilicon compound A and organosilicon compound B to the thermal-insulation mixture and pressing or compacting of the thermal-insulation mixture is 30 minutes at most.

8. The process of claim 1, wherein, after the thermal-insulation mixture has been pressed or compacted, the shaped thermal-insulation body formed is maturated at a temperature of 20? C. to 80? C. within 1 to 24 hours.

9. The process of claim 8, wherein, after the shaped thermal-insulation body has been maturated, it is heat-treated at a temperature of 90? C. to 200? C. within 1 to 24 hours.

10. The process of claim 2, wherein the IR opacifier is selected from the group consisting of: silicon carbide; titanium dioxide; zirconium dioxide; ilmenites; iron titanates; iron oxides; zirconium silicates; manganese oxides; graphites; carbon blacks; and mixtures thereof.

Description

EXAMPLES

(1) Determination of Methanol Wettability

(2) The sheet sample is ground by hand. The powder mixture is sieved across an 800 ?m sieve, and the sieve residue is discarded. From the sieved sample, 200?5 mg are accurately weighed out into centrifuge tubes on an analytical balance. Using an Eppendorf pipette (10 ml), 8.0 ml of methanol/water mixture (from 0% by volume to 90% by volume of MeOH, the methanol content increasing in steps of 5% by volume) are added to each weighed amount. The tubes are closed securely and mixed homogeneously for 30 seconds in a Turbula mixer. This is followed by centrifuging the samples at 2500 rpm for 5 minutes.

(3) The specified value for methanol wettability in % by volume relates to the maximum methanol content in a methanol/water test mixture at which the silica is partially wetted, i.e. after contact with the test mixture, approx. 50% of the silica used separates therefrom and remains unwetted on the surface of the solvent.

(4) Determination of the Thermal Conductivity of the Sheets

(5) The thermal conductivity of the shaped thermal-insulation body was determined in accordance with EN 12667:2001 at a mean measurement temperature of 10? C., a contact pressure of 250 Pa under an air atmosphere and at standard pressure.

(6) Determination of the Mean Compressive Strength of the Sheets

(7) The mean compressive strength of the sheets was determined by measuring the compressive stress arising under pressure in accordance with DIN EN 826:2013 Thermal insulating products for building applicationsDetermination of compression behaviour. The mean value, ascertained from three measurements, is further referred to as mean compressive strength.

(8) Sheet Production (Process Description)

(9) Comparative examples 1?4 and examples 1-5

(10) Mixture A consisted of 82% by weight of an Aerosil? 300 hydrophilic silica (BET=300 m.sup.2/g, manufacturer: EVONIK Resource Efficiency GmbH), of 15% by weight of silicon carbide 1000F (Carsimet, manufacturer: Keyvest) and 3% by weight of short-cut silica fibres (ASIL? diameter 6 ?m; L 6 mm, manufacturer: ASGLSOW? technofibre GmbH) and was prepared by mixing the individual components. Mixture A (3000 g) was mixed at 25? C. with the amounts of HMDS, water and TEOS specified in Table 1 in order to obtain a thermal-insulation mixture. The mixture maturation time (=the time after mixing until pressing) was, in this connection, less than 30 minutes; Table 2 provides more precise details in relation to the mixing time and mixture maturation time for the individual examples and comparative examples.

(11) The pressing of the previously prepared thermal-insulation mixture to form a sheet having dimensions of approx. 30?30?2 cm was done at 25? C. within 20 seconds in a spindle press; the hold time after pressing was 100 seconds. The pressing was followed by sheet maturation at 25-80? C. within 1-24 h in a closed system. More precise sheet maturation time and temperature are specified in Table 2. After maturation, the sheets were heat-treated at 165? C. within 24 h in an open system and left to cool down to 25? C. (room temperature).

(12) The density, compressive strength, methanol wettability and thermal conductivity of the sheets thus produced are summarized in Table 3.

(13) TABLE-US-00001 TABLE 1 Starting materials for the preparation of the thermal-insulation mixtures Mixture A HMDS Water TEOS [g] [g] [g] [g] Comparative 3000 246 0 0 Example 1 Comparative 3000 246 49 0 Example 2 Comparative 3000 0 49 246 Example 3 Example 1 3000 197 49 197 Example 2 3000 197 98 197 Example 3 3000 197 98 197 Example 4 3000 197 98 197 Example 5 3000 197 98 197 Comparative 3000 197 98 0 Example 4

(14) TABLE-US-00002 TABLE 2 Process parameters Mixing Mixture Sheet Sheet time maturation time maturation maturation [min] [min] [h] temp. [? C.] Comparative 7 15-30 1 25-80 Example 1 Comparative 7 15-30 1 25-80 Example 2 Comparative 7 15-30 4 25-80 Example 3 Example 1 4 <15 4 50 Example 2 4 <15 1 25 Example 3 4 15-30 1 25 Example 4 4 <15 4 50 Example 5 4 15-30 4 50 Comparative 4 15-30 4 50 Example 4

(15) TABLE-US-00003 TABLE 3 Material properties of the sheets Mean MeOH compressive wettability Thermal Density strength [% by volume conductivity [g/l] [kPa] MeOH] [mW/m*K] Comparative 142 17 20 Example 1 Comparative 179 51 35-40 Example 2 Comparative 159 93 0 Example 3 Example 1 168 74 45 19.1 Example 2 180 113 40 18.7 Example 3 175 89 40 Example 4 172 98 52 18.3 Example 5 171 85 47 Comparative 171 69 53 Example 4

(16) All sheets except for the one from Comparative Example 3 were hydrophobic and had a methanol wettability of 20% by volume of MeOH. This can be attributed to the action of organosilicon compound A (HMDS). The use of HM DS (organosilicon compound A) without TEOS (organosilicon compound B) led to the resultant sheets having insufficient mechanical strength (mean compressive strength) (Comparative Examples 1, 2, 4). The mean compressive strength of the sheets from Comparative Examples 1, 2 and 4 was lower than for the sheets from Examples 1-5, where HMDS (organosilicon compound A), TEOS (organosilicon compound B) and water were used. Comparative Example 4 was carried out without TEOS, but otherwise under the same conditions as Example 5. This led to a substantially lower compressive strength of the sheet in Comparative Example 4.