Paints with photocatalysis effect
An innovative approach to preventing growth on facades while reducing air pollutants such as nitrogen oxides is the use of photocatalysis. It ensures cleaner air and longer-lasting clean facades completely without biocides – a real plus for people and the environment. Inorganic, silicate binders are particularly well suited for effective and long-lasting photocatalytic coatings. Inorganic, silicate binding agents are ideal for effective and long-lasting photocatalytic coatings.
Specially insulated facades are often affected by microbial growth such as algae and fungi, as they provide ideal conditions for growth. Such surfaces are often treated with biocide-containing coatings. However, this solution has disadvantages: over time, the biocides used are washed away by rain and thus enter the environment, where they can cause ecological damage. But there is another way, without biocides and using the power of the sun.
Using the power of the sun
In a similar way to how photosynthesis works in plants, photocatalysis is an active process which is also initiated by light. Whilst photosynthesis uses sunlight to produce a substance (glucose), photocatalysis breaks down or converts substances. The term photocatalysis describes a principle of action in which a substance (= "catalyst") is stimulated by light (= "photo") to trigger or accelerate a chemical reaction without consuming itself in the process.
In principle, photocatalysis can also be used in building materials. The active photocatalytic pigment (= catalyst) can even break down things like harmful gases. This process converts the gases into small, harmless components.
Self-cleaning facades thanks to innovative photocatalysis
The photocatalyst activates hydrophilic surface effects when exposed to light. This means that the surface tension of the water on the facade decreases and water droplets run off to form an even film of water – ideal for the natural self-cleaning effect. As soon as rain or dew hits the façade, dirt is loosened and simply washed away by the photocatalytically active surface.
The flat water film creates a larger evaporation surface, which means that the facade dries much faster than with hydrophobic coatings. The extremely large specific surface area of our microporous silicate coatings – far greater than that of organic paints – further enhances rapid drying. This ensures a drier overall facade climate and provides poor growing conditions for algae and fungi. Facades remain clean and visually appealing for longer.
In addition, silicate facade coatings are antistatic and non-thermoplastic. This means that dirt particles can hardly adhere to the surface – an important advantage for permanently clean, easy-care exterior walls.
Clean air thanks to the Minox effect
Natural light activates an innovative photocatalyst in the façade paint. It converts harmful nitrogen oxides in the air into harmless nitrate – and even produces oxygen in the process. Best of all, the effect is permanent – a lifelong effect with no loss of effectiveness.
A photocatalytically active surface makes a valuable contribution to air pollution control – our contribution to a clean environment and healthy living spaces.
Photocatalysing in paints
KEIMFARBEN has been researching photocatalytic pigments that remain stable and effective in paints for many years. In KEIM Soldalit-ME, selected photocatalysts are optimally integrated into a stable, inorganic binder matrix. The result: photocatalytically effective high-performance coatings with extremely high colour stability and a pollutant-reducing effect – the so-called MiNOx effect ("Minimises NOx"). Soldalit-ME thus combines sustainable facade protection with active environmental benefits.
Inorganic, silicate binders are particularly suitable for photocatalytically effective and durable coatings. Photocatalytically active paints can break down pollutants – a real plus for the environment and air quality. The catch: organic binders (e.g. emulsion or silicone resin paints) are themselves susceptible to the process and degrade over time. The result: chalking, premature weathering and reduced service life. Inorganic, silicate binders from KEIM are more robust – they remain unaffected by the photocatalyst and ensure stable, durable coatings:
Clean facades
A photocatalytically active, silicate facade paint becomes hydrophilic under the influence of light.
The high soiling resistance of photocatalytic mineral paints is attributed to three main features.
Effect 1: Self-cleaning effect
A hydrophilic surface supports self-cleaning of facade surfaces when they are wetted by rain or moisture. A photocatalytic silicate facade paint becomes hydrophilic under the influence of light. The coating reduces the surface tension of the water, which makes it easier to wash away dirt.
Effect 2: Fast drying speed
Water spreads out like a thin film over the surface. The spreading enlarges the evaporation surface and thus makes the drying speed higher than a hydrophobic coating. The drying process is clearly faster on the extremely large and specific surface of a microporous silicate coating (compared to a conventional dispersion coating). And drier surfaces do not provide good conditions for algae and fungi growth.
Effect 3: Anti-static and non-thermoplastic
Silicate coatings are anti-static and non-thermoplastic. So dirt particles do not adhere very well to the surface.
Clean air
Photocatalytically active mineral coatings help to break down air pollutants. Photocatalytic mineral paints in exterior spaces contribute to the decomposition of atmospheric air pollutants such as nitrogen oxides, greenhouse gases and superficial contaminations. By doing this, the durability of the inorganically bound coating is not reduced.
Photoactive coatings decompose many other pollutants in addition to nitrogen oxides, for example sulphur dioxide (SO2), ammonia (NH3), carbon monoxide (CO), solvents, formaldehyde or even fats and acids.
