Process for hydrophobizing shaped insulation-material bodies based on silica at ambient pressure
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 n SiX 4-n , where R=hydrocarbyl radical having 1 to 18 carbon atoms, n=0, 1 or 2, X=Cl, Br or alkoxy group —OR 1 where R 1 =hydrocarbyl radical having 1 to 8 carbon atoms, or organosilicon compound B corresponds to a silanol of the formula HO[—Si(CH 3 ) 2 O—] m H, where m=2-100.
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 n SiX 4-n , wherein:
R=hydrocarbyl radical having 1 to 18 carbon atoms;
n=0, 1 or 2;
X=Cl, Br or alkoxy group —OR 1 wherein R 1 =hydrocarbyl radical having 1 to 8 carbon atoms;
or organosilicon compound B corresponds to a silanol of the formula HO[—Si(CH 3 ) 2 O—] m H, 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.