Dry liquids, and processes for their preparation
View Patent ↗Dry liquids having a particle size distribution (cumulative undersize) D10% 80 to 140 μm D50% 140 to 200 μm D90% 190 to 340 μm are prepared by passing the liquids and a hydrophobic, pyrogenically prepared silica through a clearly defined, spatially limited shear zone in which the liquids are broken up into small droplets and are surrounded by the hydrophobic, pyrogenically prepared silica.
1. A process for producing a dry liquid containing a droplet surrounded by a hydrophobic, pyrogenically prepared silica, which comprises
stirring, in a container, the hydrophobic, pyrogenically prepared silica to be passed through a clearly defined, spatially limited shear zone of a rotor stator to avoid or suppress formation of dead zones, wherein the rotor stator has a circumferential velocity of 25 m/s or more,
passing a liquid and the hydrophobic, pyrogenically prepared silica from the container through the clearly defined, spatially limited shear zone axially, wherein passage through the clearly defined, spatially limited shear zone results in the liquid being broken up into small droplets surrounded by the hydrophobic, pyrogenically prepared silica, and
removing the small droplets from the clearly defined, spatially limited shear zone radially to give the dry liquid having a particle size distribution (cumulative undersize) as follows:
D10%
80 to 140 μm
D50%
140 to 200 μm
D90%
190 to 340 μm
Bulk density DIN 53912 kg/m 3
400 to 500
Tamped density DIN ISO 787 kg/m 3
500 to 600
Solids content DIN 53 198%
4 to 10.
2. The process according to claim 1 , wherein the rotor-stator mixer is located at the bottom of the container.
3. The process according to claim 1 , wherein the rotor-stator mixer has a circumferential velocity ranging from 25 m/s to 31 m/s.
4. The process according to claim 1 , wherein the stirring is performed with an anchor stirrer.
5. The process according to claim 1 , wherein the hydrophobic, pyrogenically prepared silica is a fumed silica treated with hexamethyldisilazane.
6. The process according to claim 1 , which further comprises recirculating the dry liquid into the clearly defined, spatially limited shear zone axially.
7. The process according to claim 1 , wherein the hydrophobic, pyrogenically prepared silica and the liquid are stirred together in the container.
8. A method for producing multiple batches of a dry liquid containing a droplet surrounded by a hydrophobic, pyrogenically prepared silica, said method comprises producing each batch by a process which comprises
stirring, in a container, the hydrophobic, pyrogenically prepared silica to be passed through a clearly defined, spatially limited shear zone of a rotor stator to avoid or suppress formation of dead zones,
passing a liquid and the hydrophobic, pyrogenically prepared silica from the container through the clearly defined, spatially limited shear zone axially, wherein passage through the clearly defined, spatially limited shear zone results in the liquid being broken up into small droplets surrounded by the hydrophobic, pyrogenically prepared silica, and
removing the small droplets from the clearly defined, spatially limited shear zone radially,
wherein, independent of batch size, container volume, and container geometry, the dry liquid of the multiple batches have a particle size distribution (cumulative undersize) as follows:
D10%
80 to 140 μm
D50%
140 to 200 μm
D90%
190 to 340 μm
Bulk density DIN 53912 kg/m 3
400 to 500
Tamped density DIN ISO 787 kg/m 3
500 to 600
Solids content DIN 53 198%
4 to 10,
wherein the rotor stator has a circumferential velocity of 25 m/s or more.