The invention provides a method for preparing special
titanium dioxide
pigment for plastic sectional materials by a chlorination method, which comprises the following steps that: the chlorination method is adopted for preparing
titanium dioxide primary products into
slurry, and the pH value of the
slurry is regulated to 4.0 to 5.0;
phosphate dispersing agents are added;
grinding treatment is carried out, then,
grinding media is removed, and the temperature is raised; water-soluble
silicate solution is added, the pH value of the
slurry is maintained between 3.5 and 4.5,
amorphous silicon oxide is formed, curing is carried out, and a first covering layer is formed; the pH value of the slurry is regulated to 6.0 to 7.0, curing is carried out, and a second covering layer is formed; aluminum
salt solution is added, the pH value is controlled between 7.0 and 9.0, curing is carried out, a third covering layer is formed, the pH value of the slurry is regulated to 6.0 to 7.0, and curing is carried out; the slurry is washed by de-ionized water until the
conductivity of
filter cake is higher than 15000
ohm*cm, and then,
drying and air
powder treatment are carried out; modified polysiloxane is added in the air
powder process, and a fourth organic covering layer is formed; and materials are recovered through a
bag filter. The
titanium dioxide
pigment prepared by the method provided by the invention has the advantages of high weatherability, high shielding capability, high non-transparency and excellent
processing performance in the field of plastic sectional materials.