Fumed silanized and ground silica
View Patent ↗The invention relates to a hydrophobic fumed silica which is obtained by grinding a fumed silica which, as a result of silanization, has octylsilyl groups fixed on the surface, to a process for preparing it, and to coating formulations comprising this silica.
1. A hydrophobic fumed silica, obtained by a process comprising grinding an unground fumed silica,
wherein the unground fumed silica, as a result of silanization, comprises octylsilyl groups fixed on a surface,
wherein the hydrophobic fumed silica has
a lower grindometer value than the unground fumed silica,
a specific BET surface area of 100 to 250 m 2 /g,
a tamped density of 10 to 100 g/L,
a mean particle size according to Cilas of 5.0 to 20.0 μm, and
in a coating formulation, a haze value of less than 16.
2. The silica of claim 1 , wherein the grinding is effected with a pin mill or air-jet mill.
3. The silica of claim 1 , wherein the silica has a pH in the range of 5.0 to 6.0.
4. A process for producing the fumed silica of claim 1 , the process comprising:
grinding an unground fumed silanized silica which, as a result of silanization, comprises octylsilyl groups fixed on a surface.
5. A coating formulation, comprising:
the hydrophobic fumed silica of claim 1 .
6. The formulation of claim 5 , having a haze value of less than 16.
7. The formulation of claim 5 , wherein the hydrophobic fumed silica has a lower grindometer value than the unground fumed silica.
8. The formulation of claim 5 , wherein the hydrophobic fumed silica has a tamped density of 15 to 65 g/l.
9. The formulation of claim 5 , having a blackness value M y of at least 280.
10. The formulation of claim 5 , comprising 0.5 to 15% by weight of the hydrophobic fumed silica.
11. The formulation of claim 5 , further comprising: 5.0 to 99.5% by weight of solids of a polymer component or of a mixture of two or more physically or chemically crosslinking polymer components;
and/or
up to 99.5% by weight of a low molecular weight component which functions as a solvent or of a mixture of such low molecular weight components.
12. The formulation of claim 5 , further comprising
a binder comprising at least one selected from the group consisting of
a polymer of (meth)acrylic acid,
a polymer of an ester(meth)acrylic acid,
a copolymer of (meth)acrylic acid with at least one further olefinically unsaturated compound, and
a copolymer of at least one ester(meth)acrylic acid with at least one further olefinically unsaturated compound.
13. The formulation of claim 5 , wherein the binder comprises at least one selected from the group consisting of a polyetherpolyol, a polyesterpolyol, a polycarbonate-polyol, a polyurethanepolyol, a epoxy resin, and a fatty acid-modified alkyd resin.
14. The formulation of claim 12 , wherein the copolymer is present and the at least one further olefinically unsaturated compound is styrene.
15. The silica of claim 1 , wherein the tamped density is 15 to 100 g/L.
16. The silica of claim 1 , wherein the tamped density is 15 to 65 g/L.
17. The silica of claim 1 , wherein the tamped density is 60 to 100 g/L.
18. The silica of claim 1 , wherein the tamped density is 10 to 50 g/L.
19. The silica of claim 1 , wherein the tamped density is 50 to 65 g/L.
20. The formulation of claim 6 , wherein the haze value is 15 or less.
21. The silica of claim 1 , wherein the specific BET surface area is 120 to 200 m 2 /g.