Photocatalysis with titanium dioxide, new trends – new chances?

Dr. Peter Gross, Kronos International, Inc., Germany

Since the beginning of the industrial production of TiO2 Pigments in 1916 most of the research efforts concentrated in the optimization of the processibility and weathering durability of the pigments, i.e., to repel its photocatalytic activity. In the 1980’s intensive work started, mainly in Japan, investigating into the utilization of photocatalytic properties of titanium dioxide. Most photocatalytic applications are linked with the development of special coatings which are inert toward the attack of the radicals generated by the titanium dioxide photocatalyst.
At the same time much work was spent into the extension of the utilization capabilities of TiO2. Since 2003 photocatalysis has arrived in the European coatings industry where up to date most companies have ongoing research projects in order to investigate into the utilisation of this physical property. This was about the same time when developed a new generation of photocatalysts, the KRONOS vlp 7000 series, which even work in the absence of UV-light by extending the catalytic activity into the visible light region. These new photocatalysts even work indoors and in places where just stray light is available.

From dealing with photocatalysis many new questions arise like:

- What exactly is photocatalysis and what does this mean for coatings with respect to durability and formulation strategies?

- What are the suitable methods to determine this effect? Are there standards available?

- Is the TiO2-photocatalyst a Biocide?

- Patents

In the following a summarising update on the new questions shall be given.