PAPER WHITENERS .1. TITANIA COATED SILICA

A well defined white pigment (whitener) was prepared by coating monodispersed silica particles with titania. The hiding power of this powder was evaluated as a function of the particle diameter, the thickness of the titania shell, and the calcination temperature. The calculations of Mie scattering coefficients were used to optimize the optical properties of such whiteners, which showed a close agreement with the measured quantities. In addition, colloidal dispersions of uniform particles of titanium hydrous oxide sols were prepared by precipitation from a homogeneous solution of titanyl sulfate at 90°C. © 1993 Academic Press, Inc.