Titanium dioxide photocatalyst has
attracted a lot of interest for environmental cleanup catalysis. For the use of
titanium dioxide coating agents, it has to be coated on substrates properly. We
focused attention on the development of an undercoat agent fixing to the
substrate and the top layer of titanium dioxide photocatalyst for a long time.
The undercoat film is also used to prevent the decomposition of an organic
substrate due to the photocatalytic oxidation.
In this fiscal year, we carried out to find
out the optimum condition of producing the undercoat agent, designed and
fabricated a bench-scale production plant for the undercoat agent, operated the
plant to obtain data for scale-up, as well as investigated the optimum
condition for coating the undercoat agent on substrates.
Firstly, we investigated the optimum condition for producing the undercoat
agent which is stable for a long period. We tested various undercoat agents
prepared with using some kinds of additives. We evaluated a shelf life
of the undercoat agent by measuring viscosity and absorbance ratio
with time. In a performance of the coating film, we evaluated by measuring
the decomposition ability of methylene blue. We selected 0.5 wt% of acetyl
acetone as a final candidate material.
Secondly, the life of the coating film was
evaluated by an accelerated weathering test. Test samples were prepared by
coating with the undercoat agent and the photocatalytic coating agent on
organic substrates (clear acrylic sheets ). Test results show that the coating
film with the undercoat agent selected was highly adhesiveness to the substrate
and had an enough performance as a barrier layer, which prevented the
decomposition of the substrate due to photocatalytic oxidation.
Thirdly, refer to the results of optimization tests for producing undercoat
agents, we designed and fabricated the bench-scale production plant. Through
running of the bench-scale plant with changing mixing rates of raw materials,
conditions of stirring reactants, and so on, we obtained data required
for designing of the main reactor, feed pumps, and etc. for scale-up.
Finally, in case of applying photocatalyst
to organic substrates, we defined the quantity of the undercoat agent required
for protecting the substrate from the attack of photocatalytic oxidation. In
addition, we obtained data for designing of an automatic spray coating machine
which is capable of coating undercoat agents efficiently.