Structurally coated silica
View Patent ↗A structurally coated silica can be prepared by spraying and mixing a pyrogenic silica with water and a coating agent in a suitable mixing vessel, then milling and then conditioning the product. The structurally coated silica can be used as a matting agent in lacquers.
1. A structurally coated pyrogenic silica particles consisting essentially of coated silica particles, wherein the coating is organically modified polysiloxanes alone or in combination with wax and wherein the silica particles have a BET surface area of from 80 to 450 m 2 /g, and a DBP index (%) of from 240 to 380.
2. The structurally coated silica as claimed in claim 1 , wherein it has a carbon content of 1 to 30 wt. %.
3. The structurally coated silica as claimed in claim 1 wherein it has a bulk density of from 10 to 60 g/l.
4. A process for preparing a structurally coated silica comprising loading a pyrogenic silica with water and a coating agent in a suitable mixing vessel to form a reaction mixture, milling and subsequently drying the milled silica, wherein the reaction mixture has a pH value from about 7-14.
5. In a lacquer containing matting agents wherein the improvement comprises matting agents composed of the structurally coated silica as claimed in claim 1 .
6. The lacquer of claim 5 wherein the lacquer is a polyurethane.
7. A structurally coated pyrogenic silica having a DBP index (%) of from 240 to 380 obtained by the process according to claim 4 , wherein the coating agent contains organically modified polysiloxanes alone or in combination with wax.
8. A structurally coated silica particles consisting essentially of coated silica particles, wherein the coating is organically modified polysiloxanes and wherein the coating is prepared from an oil-in-water emulsion of about 20% organically modified polysiloxanes where the organic modification is selected from C2-C8 alcohols and EO/PO polyethers and the polysiloxanes have an approximate average molecular weight 1000-5000 g/mol.