| 摘要 |
A new method for producing precipitated silicas having a unique combination of physical and chemical properties is disclosed. The silicas are produced by acidulating a solution of an alkali metal silicate having a specific SiO2/Na2O mol ratio with an acid until precipitation just begins. At this point, the reaction mass is aged for a period of time and thereafter the acid addition is continued until the precipitated product is obtained. Products produced in accordance with the invention exhibit lower wet cake moisture and are characterized by their low structure, low oil absorption, high abrasiveness and high pack density, and as such are distinctly different from silicas used as reinforcing fillers in rubber. In a particularly advantageous embodiment, an adduct material, such as aluminum, is added to control the refractive index of the precipitated pigment silica. Products produced in this manner have particular utility for use as abrasion and gelling agents in clear toothpaste compositions.
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