Silica Wetcake Treatment Method
New methods of treating silica wetcake during precipitated silica materials manufacturing are provided. Such methods permit a significant increase in high solids content processing while simultaneously reducing high viscosity of the resultant particles for transport facilitation. The resultant precipitated silica wetcake is treated with a borate-containing dispersant to impart the necessary low viscosity characteristics thereto. Such a dispersant accords not only such a viscosity result, but will not char or otherwise discolor the silica particles during evaporation of the liquids within the wetcake itself. Furthermore, such a dispersant, if left on the surfaces of such particles, will not deleteriously affect the abrasivity, fluoride compatibility, or other dentifrice properties of the precipitated silica materials themselves. Also encompassed within this invention are the resultant precipitated silica particles exhibiting borate residues and dentifrices including such materials.
1 . A method for preparing precipitated silica particulate materials, said method comprising the steps of:
a) producing a wetcake of precipitated silica;
b) treating said wetcake of step “a” with from 0.001 to 3% by weight thereof said wetcake of a dispersant compound selected from the group consisting of at least one borate compound, at least one polyphosphate compound, and any mixtures thereof; and
c) mixing said treated wetcake of step “b” into a homogeneous slurry of treated particles of borate-treated and/or polyphosphate-treated precipitated silica.
2 . The method of claim 1 further including the steps of:
d) drying said treated particles of step “c” to a solids content of at most 99%;
e) comminuting said dried individual particles; and
f) incorporating either said treated particles of step “c” or said comminuted individual particles of step “e” into a dentifrice composition.
3 . A dentifrice formulation comprising at least one particle produced by the method of claim 1 .
4 . A dentifrice formulation comprising at least one particle produced by the method of claim 2 .
5 . A precipitated silica particle exhibiting at least 50 ppm of borate residues present on the surface thereof.
6 . A dentifrice formulation comprising at least one particle of claim 5 .
7 . A precipitated silica particle exhibiting at least 0.05% by weight of polyphosphate residues present on the surface thereof.
8 . A dentifrice formulation comprising at least one particle of claim 7 .