Coated sheet-like plastic material with reduced tendency to colonization by algae, process for the in-line production thereof and use
View Patent ↗A coated sheet-like plastics material comprising a) as base, a thermoplastic substrate; and b) on the base, a photocatalytically active coating comprising a water-spreading layer which involves either a sol-adhesion-promoter layer, layer b1+2), comprising an adhesion promoter and a colloid sol, or a colloid-sol layer b2) arranged on an adhesion-promoter layer b1) applied on the substrate a), and a photocatalytically active layer b3) arranged on the water-spreading layer b1+2) or b2), where b3) is obtainable through application and drying of a mixture comprising, based on the solids content of the mixture in percent by weight b31) from 1 to 25% of titanium dioxide and b32) from 75 to 99% of silicon dioxide and/or of a metal oxide which is not soluble in water or of an anionically modified silicon dioxide or metal oxide; where the titanium dioxide is particulate with an average primary-particle size smaller than 10 nm. In-line process for producing said material, and also use as roofing material or as glazing material, preferably in areas with moist conditions. The coated sheet-like plastics material of the invention combines water-spreading properties with photocatalytic activity, without any damage to the thermoplastic substrates. The coated sheet-like plastics substrate of the invention is produced in a relatively uncomplicated, inexpensive and fast in-line process and, in use, provides impressive substrate stability and impressive effectiveness of the coating in resisting initial algal growth.
1. A coated sheet-like plastics material, comprising
a) as a base, a thermoplastic substrate; and
b) on the base, a photocatalytically active coating comprising
a water-spreading layer b(2) comprising
a colloid-sol layer b(22) arranged on an adhesion-promoter layer b(1) applied on the substrate a),
and
a photocatalytically active layer b(3) arranged on the water-spreading layer,
where the photocatalytically active layer b(3) is obtained by a process comprising drying a mixture comprising, based on solids content of the mixture, in percent by weight,
b(31) from 1 to 25% of titanium dioxide and
b(32) from 75 to 99% of at least one of silicon dioxide and a metal oxide, which is not soluble in water or of an anionically modified silicon dioxide or metal oxide;
where the titanium dioxide is particulate and has an average primary-particle size smaller than 10 nm.
2. The plastics material according to claim 1 ,
wherein:
the adhesion-promoter layer b(1) is obtained by a process comprising drying an organic polymer material which is not soluble in water, is in essence not swellable in water, is soluble in organic solvents and comprises polar groups; and
the water-spreading layer b(2) is obtained by a process comprising drying an inorganic colloid sol.
3. The plastics material according to claim 1 ,
wherein
a rutile form has at most 50% by weight of the titanium dioxide.
4. The plastics material according to claim 1 , wherein
the layers b(2) and b(3) comprise silicon dioxide with the same properties.
5. The plastics material according to claim 1 , wherein:
a thickness of the adhesion-promoter layer b(1) is in the range from 0.01 to 2 μm;
a thickness of the water-spreading layer b(2) is in the range from 0.01 to 2 μm; a thickness of the photocatalytically active layer b(3) is in the range from 0.01 to 1 μm; and
a total thickness of the layers b(2) and b(3) is not greater than 2 μm.
6. The plastics material according to claim 1 , wherein
a ratio of b(3) over b(2) in thickness is in a range from 0.05 to 0.5.
7. The plastics material according to claim 1 , wherein
water-soluble coating b(4) and a protective film b(5) peelably adhere to the photocatalytically active layer b(3).
8. A material for roof or glazing, comprising the plastics material according to claim 1 .
9. The plastics material according to claim 1 , wherein the material has reduced initial tendency toward algal colonization, reduced initial bacterial growth or both.