Abstract: A process for producing a polyester resin composition containing at least 10 wt % of a white inorganic pigment dispersed in a polyester resin, which comprises kneading the polyester resin with the white inorganic pigment and thereafter subjecting the blend to a polycondensation reaction at a temperature ranging from the melting point of the polyester up to 300.degree. C. and at a reduced pressure of not higher than 5 Torr, is disclosed.

Abstract: A process for producing a titanium dioxide containing polyester resin composition from which a white film useful as a reflective photographic support can be prepared is disclosed.Said process is performed by first supplying a polyester resin and titanium dioxide into a continuous kneading extruder, kneading them in molten state, and supplying an additional charge of the polyester resin to give a desired concentration of the titanium dioxide, wherein the first supplied polyester resin has an intrinsic viscosity of at least 0.40, said titanium dioxide having an average particle size of 0.1-0.5 .mu.m and a water content of no more than 0.5% and having been surface-treated with an aluminum compound and/or a silicon compound, and the concentration of titanium dioxide being in the range of 20-70 wt % when kneaded with the polyester resin in molten state.