Showing papers on "Precipitated silica published in 1974"

Amorphous precipitated silica products and method for their production

Abstract: 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 SiO 2 /Na 2 O 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.

Heat vulcanizable silicone rubber compositions resistant to oil degradation

Abstract: A heat vulcanizable silicone rubber composition which is resistant to degradation by hydrocarbon oils and having a specific gravity in the cured state of 1.20 to 1.70 comprising an organopolysiloxane polymer and blends of organopolysiloxane polymers having a viscosity of anywhere from 1,000,000 to 200,000,000 centipoise at 25*C, a curing catalyst, a silica filler selected from the class consisting of fumed silica, precipitated silica and mixtures thereof, an inorganic filler which may be any of the well known inert organic fillers such as, ground silica, diatomaceous earth and etc., and a small concentration of magnesium oxide and mixtures of various magnesium oxide.

Absorption of polymers at the solution–solid interface. XII. Stabilization of dispersed silica by absorbed styrene–methyl methacrylate copolymers

Abstract: The ability of styrene–methyl methacrylate copolymers to stabilize silica dispersions has been investigated. Random, block, and graft copolymers covering the entire composition range have been employed in carbon tetrachloride, trichloroethylene, and benzene solutions. Equilibrium sediment volumes and dispersion turbidities provide adequate and concordant estimates of stabilization efficiency. Polystyrene is not adsorbed by precipitated silica from trichloroethylene or benzene and does not stabilize dispersions in these liquids; although adsorbed from carbon tetrachloride, there is no stabilization. Poly(methyl methacrylate) is an efficient dispersion stabilizer, and its performance is independent of molecular weight over a wide range. Random copolymers having styrene contents in excess of ca. 60% do not stabilize in trichloroethylene but do so in carbon tetrachloride, although well adsorbed in both cases. With this major exception, and that of a low-styrene graft copolymer in carbon tetrachloride, copolymers of all structures and compositions stabilize well, better than poly(methyl methacrylate) in the solvents examined. A substantial degree of surface coverage is necessary for optimum stabilization. Subsidiary solution adsorption and layer thickness measurements are also reported.

Antifoam compositions and process for the preparation and use thereof

Abstract: There are provided antifoam compositions comprising a dimethylpolysiloxane and a precipitated silica reacted with hexamethyldisilazane and a process for the preparation and use thereof.