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De-polluting and self-cleaning epoxy siloxane coating

a technology of epoxy siloxane and coating, applied in the direction of coatings, etc., can solve the problems of reducing durability, difficult to provide coatings with high levels of photocatalyst, and reducing the cost of siloxane type polymers, so as to effectively remove nox compounds from the environment and effectively degrade nox compounds

Inactive Publication Date: 2009-11-12
MILLENNIUM INORGANIC CHEM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013]Provided are self-cleaning photocatalytic coatings and coating compositions that comprise photocatalytic titanium dioxide and a binder that comprises an epoxy-functional silicon compound and an amino-functional compound. The compositions provide durable photocatalytic coatings upon application to a substrate that effectively degrade NOx compounds in the environment when exposed to light. The coating compositions may also comprise one or more pigments, such as pigmentary titanium dioxide and the like, and one or more alkaline extenders. It has been surprisingly been found that coating compositions comprising photocatalytic TiO2 and an epoxy siloxane binder with a total pigment volume concentration of less than about 50% provide durable coatings that effectively remove NOx compounds from the environment. In one embodiment, the total pigment volume concentration of the coating compositions is between about 5% to about 70% by volume of the dry coating (PVC).

Problems solved by technology

Although coating compositions comprising siloxane type polymers show excellent durability, the cost of siloxane type polymers is significantly higher than the cost of other organic polymers such as acrylic or styrene polymers.
Using mixtures of siloxane polymers with organic polymers in coating compositions improves the durability of the corresponding coatings over organic polymer based compositions alone, but still results in progressively diminished durability as the siloxane polymer concentration is reduced.
Accordingly, it has also been difficult to provide coatings having high levels of photocatalyst because the catalyst tends to oxidize and break down the polymeric binder of the coating.
This problem is exacerbated when the coating is exposed to intense UV radiation from direct sunlight, as is the case with an exterior paint.
Furthermore, epoxy siloxane coatings do not contain isocyanate residues, which present a safety hazard to personnel applying the coating.

Method used

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  • De-polluting and self-cleaning epoxy siloxane coating

Examples

Experimental program
Comparison scheme
Effect test

example 1

NO Activity Correlated with Total PVC

[0107]The complete methodology for determining NOx removal is described in U.S. Patent Pub. 2007 / 0167551, the disclosure of which is hereby incorporated by reference. Briefly, the samples were placed in an air-tight sample chamber and sealed. The sample chamber is in communication with a three channel gas mixer (Brooks Instruments, Holland) through which NO (nitric oxide), NO2 (nitrogen dioxide), and compressed air containing water vapor are introduced into the chamber at predetermined levels. Coatings comprising epoxy siloxane binder sold under the trade names SILIKOPON® EF and DYNASYLAN® AMEO were prepared from compositions comprising 7.5% PC105 photocatalytic TiO2 and 15% Tiona 595 pigmentary TiO2 (PVC) with total % PVC levels of 30%, 40%, 50%, 60%, and 70%. The difference in total PVC in the coatings was made up by the extender, calcium carbonate. The samples are irradiated with 8 W / m2 UV radiation in the range of 300 to 400 nm from a UV Lamp...

example 2

Optimization of NO Activity

[0111]The photocatalytic activity and durability of coatings with lower levels of total PVC and catalytic TiO2 were evaluated. Coatings comprising epoxy siloxane binder with 15% PVC Tiona 595 pigmentary TiO2, photocatalytic PC105 TiO2 concentrations of 1%, 2.5% and 5% (PVC) and total PVC levels of 20%, 25%, 30% and 35% were evaluated for NO reduction activity initially and after 7 and 28 days exposure in the Atlas Weatherometer. The pigmentary TiO2 in the samples was kept constant at 15% PVC and the difference in PVC was made up by calcium carbonate. The percentage NO removed as measured with the Nitrogen Oxides Analyser Model ML9841B is shown for 0, 7 and 28 days weathering in Table 1 below. The percentage of NO reduction after 7 days weathering is depicted graphically in FIG. 2.

TABLE 1% Total PVC% PC105InitialAfter 7 daysAfter 28 days350.00.00.00.0200.00.90.40.0201.0000202.50.07.412.8205.00.019.221.5251.0−1.818.57.3252.53.431.326.7255.02.234.326.4301.0−0...

example 3

Coating Durability Correlated to Photocatalyst Level Durability

[0113]The durability of various photocatalytic coatings derived from compositions comprising photocatalytic TiO2 and an epoxy siloxane binder was evaluated. Coatings were applied to stainless steel panels and the durability evaluated as weight loss per 100 cm2 of coating and exposed to accelerated weathering conditions for various timeframes. The complete methodology for determining durability of the paints is described in U.S. Patent Pub. 2007 / 0167551, the disclosure of which is hereby incorporated by reference. The methodology involves accelerated weathering of 20 to 50 micron thick paint films on a stainless steel substrate in a Ci65A Weatherometer (Atlas Electric Devices, Chicago) under a 6.5 kW Xenon source. The level of UV radiation at the panel surface being 0.50 W / m2 UV at 340 nm. The radiant heat from the Xenon light source raising the temperature of the white panels to 35° C. and water spray was applied for 18 ...

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Abstract

De-polluting, self-cleaning coating compositions are disclosed which comprise photocatalytic titanium dioxide and a binder comprising an epoxy siloxane polymer. The compositions produce durable, self-cleaning coatings with photocatalytic activity against pollutants in the air, such as NOx compounds.

Description

FIELD OF INVENTION[0001]The present invention relates to photocatalytic coatings on a substrate and to compositions for imparting the coating on a surface of the substrate. More specifically, the invention relates to de-polluting, self-cleaning coatings and coating compositions comprising titanium dioxide particles and epoxy siloxane.BACKGROUND OF THE INVENTION[0002]The photocatalytic properties of titanium dioxide result from the promotion of electrons from the valence band to the conduction band under the influence of ultraviolet (UV) and near-UV radiation. The reactive electron-hole pairs that are created migrate to the surface of the titanium dioxide particles where the holes oxidize adsorbed water to produce reactive hydroxyl radicals and the electrons reduce adsorbed oxygen to produce superoxide radicals, both of which can degrade NOx and volatile organic compounds (VOCs) in the air. In view of these properties, photocatalytic titanium dioxide has been employed in coatings and...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C08J3/28C09D7/61
CPCC08G77/14C08G77/26C08K3/22C08K3/26C08K5/5435C08K5/544C09D5/1618C09D183/08C09D183/06C09D7/1216C08L83/00C09D7/61C08K2003/2241
Inventor STRATTON, JOHNGOODWIN, GRAHAM
Owner MILLENNIUM INORGANIC CHEM
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