TiO2–SiO2 composite filler for thin paper

Spherical TiO2–SiO2 composite, in which the TiO2 coating layer with a width of 10–20 nm was present on the SiO2 sphere, was synthesized by reacting SiO2 seed with a TiCl4 solution in water. As a result of XRD analysis, the initial state of TiO2 that existed on the surface of synthesized composite particles was amorphous, but it changed directly to the rutile crystal phase of TiO2 after heating at 300 °C and the rutile phase did not change even the above 900 °C. Paper with a weight ratio per unit area of 60 g/m2 was prepared by using the composite particle as filler. The opacity measurement using a Hunterʹs whiteness testing method of the prepared paper, showed the value of 94.7% which was superior to that found in currently available light paper of high quality (90.0%). As well, the composite showed greatly superior oil absorbance ability (150–180 ml/100 g) compared to the case of TiO2 (100 ml/100 g) filler, and also it was found that the TiO2–SiO2 composite could control oil absorption efficiently.