Photocatalytically active polysiloxane coating compositions
View Patent ↗The invention is a coating composition comprising photocatalytic titanium dioxide particles, an opacifying agent, a silicone compound, de-HNO 3 particles, styrene resin hollow microspheres, and a solvent. The combination of a silicone compound and styrene resin hollow microspheres in a depolluting coating composition results in improved opacity and durability compared to conventional coatings.
1. A coating composition comprising:
(a) from 1% to 12% by weight, based on the total weight of the coating composition, of photocatalytic titanium dioxide particles having a mean particle size between 5 nm and 40 nm;
(b) from 0.05% to 40% by weight of calcium carbonate particles, wherein the ratio of calcium carbonate particles to photocatalytic titanium dioxide particles is from 0.01 to 50; and
(c) a polysiloxane polymer latex able to provide a silicone-based film wherein said polysiloxane comprises 0.05% to 20% by weight of the coating composition;
(d) a solvent selected from water, an organic solvent or a mixed solvent consisting of water and an organic solvent; and
(e) from 0.1% to 20% based on the total weight of the coating composition, of hollow styrene acrylic copolymer resin microspheres having an outside diameter of from 0.1 μm to 10 μm, wherein
(i) the opacity of a dry film coating formed from said coating composition is greater than the opacity of a dry film coating formed from the same coating composition which is absent said hollow styrene resin microspheres, and
(ii) percent weight loss of said dry film coating over a defined time period is less than percent weight loss of the dry film coating absent the styrene microspheres over the same defined time period.
2. The coating composition of claim 1 wherein the photocatalytic titanium dioxide particles have a surface area of >30 m 2 /g as measured by the BET method.
3. The coating composition of claim 1 wherein the photocatalytic titanium dioxide particles have a surface area of >50 m 2 /g as measured by the BET method.
4. The coating composition of claim 1 wherein the photocatalytic titanium dioxide particles have a surface area of >100 m 2 /g as measured by the BET method.
5. The coating composition of claim 1 wherein the polysiloxane comprises 0.1% to 16% by weight of the coating composition.
6. The coating composition of claim 1 wherein the calcium carbonate particles comprise 0.1% to 16% by weight of the coating composition.
7. The coating composition of claim 1 wherein the ratio of calcium carbonate particles to photocatalytic titanium dioxide particles is from 0.1 to 20.
8. The coating composition of claim 1 wherein the ratio of calcium carbonate particles to photocatalytic titanium dioxide particles is from 0.2 to 5.
9. The coating composition of claim 1 wherein the microspheres have an outside diameter of 0.1 μm to 2 μm.
10. The coating composition of claim 1 wherein the microspheres have an outside diameter of 0.2 μm to 1 μm.
11. The coating composition of claim 1 wherein the microspheres comprise 2% to 15% by weight of the coating composition.