Precipitated silica

About: Precipitated silica is a research topic. Over the lifetime, 1401 publications have been published within this topic receiving 20992 citations.

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.

In situ catalyst forming compositions and process

Abstract: An organosilicon composition comprises a siloxane resin having a ratio C6H5 : Si of 0.3 to 0.9 : 1, a ratio R : Si of 0.4 to 1.2 : 1 and a ratio (C6H5+R) : Si of 1 to 1.7 : 1 and containing at least 0.25% by weight of Si-bonded OH groups, a filler and a catalyst combination comprising lead monoxide or lead carbonate and a carboxylic acid or ammonium salt thereof, where R is a monovalent hydrocarbon or halohydrocarbon radical other than phenyl. Suitable values of R are, e.g. -CH3, -C2H5, -C3H7, -CH=CH2, -CH2CH2CH2Cl, -CH2CH2CF3, -C6H11, -C6H3Cl2, -C6H4CF3, -CH2C6H5. Phenylmethylsiloxane resins are preferred. Suitable acids are resin acids, linoleic, stearic, oleic, acetic, butyric, naphthenic, octoic, benzoic, lauric, palmitic and 2-ethylhexanoic acids. Acetic, stearic and benzoic acids are preferred. Preferably there should not be less than 0.5 mol. of acid or salt per mol. of lead compound. Suitable fillers are glass, diatomaceous earth, crushed quartz, fume silica, precipitated silica, clays, the silicates of zirconium, magnesium, lithium and aluminium, iron oxide, magnesium oxide, titanium dioxide and calcium carbonate. The catalyst mixture may be added in either order, or in combination with a part of the filler.

Reinforcement of Natural Rubber with Silanized Precipitated Silica Nanofiller

Abstract: The effect of a large amount of precipitated amorphous white silica nanofiller, pre-treated with bis[3-triethoxysilylpropyl-)tetrasulfide (TESPT), on the mechanical properties of a sulfur-cured natural rubber (NR) was studied. TESPT chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulfur-cure. The silica particles were fully dispersed in the rubber, which was cured primarily by using sulfur in TESPT, or, by adding a small amount of elemental sulfur to the cure system. The cure was also optimized by incorporating sulphenamide accelerator and zinc oxide into the rubber. The hardness, tear strength, tensile strength, and stored energy density at break of the vulcanizate were substantially improved when the filler was added. Interestingly, these properties were also enhanced when the rubber was cured primarily by using sulfur in TESPT.

Treatment of geothermal brine sulfate-rich fluids to facilitate the precipitation of silica

Abstract: A method for the treatment of geothermal brines to control the precipitation of silica is disclosed. A sulfate-rich liquid is introduced into geothermal brine within a production well prior to flashing or is introduced into the residual geothermal brine remaining after the brine has been flashed to produce steam. The sulfate in the liquid reacts with the barium, calcium, and/or lead salts within the brine to produce a colloidal suspension which serves to accelerate precipitation of silica from the brine and to adsorb the precipitated silica particles. The colloidal suspension with its adsorbed silica particles is then removed from the brine by conventional gravimetric or filtration methods. The method of the invention substantially reduces the deposition of silica in wellbores and in energy extraction equipment and facilitates removal of the silica from the brine. The method further reduces the deposition of silica in injection wells wherein the silica cleansed brine is discharged.

Stable, pumpable aqueous suspensions of precipitated silica particulates

Abstract: Stable, non-gelling and pumpable aqueous suspensions of precipitated silica particulates, well adapted for the coating of paper and cardboard substrates, include an effective stabilizing amount of at least one biogum heteropolysaccharide and at least one quaternary ammonium, sulfonium or phosphonium compound (cationic surfactant).