High-whiteness hydrophobic precipitated silica with ultralow moisture absorption
AssigneeDegussa AG
InventorsUwe Schachtely, Christian Panz, Ralf Schmoll
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Abstract
The invention relates to hydrophobicized precipitated silicas that possess an extremely high whiteness and extremely low moisture absorption. The hydrophobic precipitated silicas are prepared, inter alia, by coating with silicone oil and oxidative heat treatment.
Claims68
A hydrophobic precipitated silica having the following properties:
- carbon content
- >3.1%;
- methanol wettability
- >60%;
- reflectance
- >94%;
- BET/CTAB ratio
- >1 and <3;
- DBP absorption
- <230 g/100 g;
- BET surface area
- 50–110 m2/g;
- CTAB surface area
- >30 m2/g;
- water vapor absorption at 30° C. and 30% relative
- 1.1 ± 0.2%;
- and
- humidity
- water vapor absorption at 30° C. and 70% relative
- 1.4 ± 0.3%.
- humidity
A process for preparing hydrophobic precipitated silica, the process comprising:
- a) preparing a mixture of an organopolysiloxane derivative and a precipitated silica;
- b) conditioning the mixture at from 10 to 150° C. for a period of from 0.5 to 72 hours;
- and
- c) conducting oxidative heat treatment at more than 300° C. with an oxidizing gas,
- wherein in step a) the preparing comprises simultaneously supplying the precipitated silica and the organopolysiloxane derivative to a spin-flash drier.
A process for preparing hydrophobic precipitated silica, the process comprising:
- a) preparing a mixture of an organopolysiloxane derivative and a precipitated silica;
- b) conditioning the mixture at from 10 to 150° C. for a period of from 0.5 to 72 hours;
- and
- c) conducting oxidative heat treatment at more than 300° C. with an oxidizing gas, wherein
- in step b) the conditioning produces a conditioned silica;
- and
- in step a) the preparing comprises mixing the precipitated silica with the conditioned silica.
A process for preparing hydrophobic precipitated silica, the process comprising:
- a) preparing a mixture of an organopolysiloxane derivative and a precipitated silica;
- b) conditioning the mixture at from 10 to 150° C. for a period of from 0.5 to 72 hours;
- and
- c) conducting oxidative heat treatment at more than 300° C. with an oxidizing gas,
- wherein in step b) the conditioning is at room temperature for at least 48 hours.
A process for preparing hydrophobic precipitated silica, the process comprising:
- a) preparing a mixture of an organopolysiloxane derivative and a precipitated silica;
- b) conditioning the mixture at from 10 to 150° C. for a period of from 0.5 to 72 hours;
- and
- c) conducting oxidative heat treatment at more than 300° C. with an oxidizing gas,
- wherein steps a), b), and c) are carried out a number of times in succession.
Dependencies are inferred from the claim text.