Showing papers on "Precipitated silica published in 1991"

Reinforced precipitated silica

Abstract: Reinforced precipitated silica having, on a coating-free and impregnant-free basis, a surface area of from about 220 to about 340 square meters per gram, a pore diameter at the maximum of the volume pore size distribution function of from about 9 to about 20 nanometers, and a total intruded volume of from about 2.6 to about 4.4 cubic centimeters per gram, is produced by a process wherein precipitated silica is heavily reinforced using a multiplicity of precipitation and aging steps.

NMR characterization of elastomers reinforced with in situ precipitated silica

Abstract: Poly(dimethylsiloxane) model networks were reinforced by in situ precipitated silica following the usual sol-gel methods and were characterized by 1 H and 29 Si magic-angle spinning NMR spectroscopy and 1 H NMR two-dimensional Fourier transform spin-echo imaging techniques. The results demonstrate the nonuniform hydrolysis of the tetraethylorthosilicate in the rubber. Under these precipitation conditions, silica precipitates mainly in the simple periphery. These studies indicate the importance of mass transport phenomena and the use of nondestructive test methods such as NMR imaging in the production of bulk specimens of in situ precipitated materials

Infrared evidence for two isolated silanol species on activated silicas

Abstract: Infrared spectroscopy has been used to study the OH stretching vibration of isolated silanol groups on an aerosil and a precipitated silica which have been activated under vacuum at 450, 600 or 800°C. When the 450°C activated samples are cooled to −191°C, the normally asymmetric OH peak splits into two components having a peak maximum near 3750 or 3746 cm −1 for the aerosil and precipitated silica, respectively, and a shoulder near 3738 cm −1

Shear and Biaxial Extension Measurements of Reinforcement from in-situ Precipitated Silica

Abstract: Elastomeric networks were prepared by tetrafunctionally end-linking hydroxyl-terminated polydimethylsiloxane (PDMS) chains and were then filled by the in-situ precipitation of silica. The resulting networks were investigated in shear and biaxial extension. The method employed to produce large shears was to stretch a short, wide strip between two clamps. The deformation produced in this way is pure shear; simple shear was calculated directly from the pure-shear data. Biaxial extension measurements were carried out by inflation of circular sheets of the networks. Compared to the unfilled networks, the silica-filled samples showed large reinforcing effects. Specifically, their values of the modulus, ultimate strength, and rupture energy increase significantly. The results thus indicate that the PDMS networks filled by the in-situ precipitation of silica have good mechanical properties, not only in uniaxial elongation, but in shear and biaxial extension as well.

Synthesis of zeolite Beta

Abstract: A large crystal zeolite Beta having a broad range of silica-to-alumina ratios, i.e. 20-→1000, is synthesized with triethanolamine in the synthesis mixture along with organic directing agents such as tertraethylammonium hydroxide, tetraethylammonium bromide and tetraethylammonium fluoride. The highly silicious zeolite Beta is produced from a silica source comprising precipitated silica and high purity, high silica starter seeds.

Glucoamylase removal using nitrogen-functionalized amorphous precipitated silica

Abstract: An aqueous medium in which glucoamylase is dissolved, is contacted with nitrogen-functionalized amorphous precipitated silica having a pore diameter at the maximum of the volume pore size distribution function of from about 7 to about 100 nanometers, whereby at least a portion of the glucoamylase is adsorbed by the nitrogen-functionalized amorphous precipitated silica. The process is particularly suitable for removing glucoamylase from draught beer.

Precipitated silica paste

Abstract: A precipitated silica paste is produced by dispersing precipitated silica in silicon oil. During the hydrophobing of precipitated silicas, the precipitated silica paste is added as a hydrophobing agent in the suspension phase. The product is spray-dried, tempered and ground.

Low water uptake precipitated silica particulates

Abstract: Novel precipitated silica particulates having low water uptake and high BET and CTAB surfaces, well adapted as reinforcing fillers for, e.g., the silicones, are conveniently prepared by heat treating certain starting material precipitated silica particulates at a temperature of at least 700° C., for at least one minute.

Silicone rubber reinforced with reinforced precipitated silica

Abstract: Elastomeric compositions contain crosslinked poly(diorganosiloxane) and reinforced precipitated silica having, on a coating-free and impregnant-free basis, a surface area of from about 220 to about 340 square meters per gram, a pore diameter at the maximum of the volume pore size distribution function of from about 9 to about 20 nanometers, and a total intruded volume of from about 2.6 to about 4.4 cubic centimeters per gram.

Method of producing granulated material composed of zinc oxide and silica, resulting product and its use

Abstract: A granular material containing zinc oxide and precipitated silica which is readily dispersible in rubber mixtures.

Method of granulating resorcinol/silica mixtures, the granulates obtained in this manner and their use

Abstract: A method of granulating resorcinol/silica mixtures which comprises transporting a mixture of resorcinol and precipitated silica by conveyor worms to two pressing rollers whose shafts are attached vertically above one another and whose contact pressure can be varied, compacting said mixture between said rollers, breaking up the compacted mixture with a cake breaker to obtain a granulate with minimum grain size and separating the remaining dusty portion of said mixture The mixtures can be added to vulcanizable rubber to provide improved adhesion to rubber reinforcements

Immobilization of whole Escherichia coli containing penicillin amidase using cross-linking agents and fillers

Abstract: To obtain a catalyst with good mechanical stress stability and other operational characteristics, cross-linked aggregates of whole Escherichia coli containing penicillin amidase were reinforced with surface modified precipitated silica and chitosan. The immobilized cells plus mixed fillers possess better performance characteristics i.e. higher stability at 4°C and 30°C, least protein leaching capacity and good settling characteristics. Most suitable conditions to prepare catalyst with mixed fillers were: chitosan, 0.3: silica, 0.2 g/g d.wt cell; and minimum moisture content in catalyst, 30% (w/w).

Method for making and transporting an aqueous silicic acid suspension

Abstract: A layer of air-placed concrete or a ready-mixed concrete is produced by using, as mixing water, an aqueous suspension of a synthetically produced silica, for example a precipitated silica.

Process for the desilication of waste liquid

Abstract: of EP0431337In a desilication process, the pH of the waste liquor is lowered in two stages (3 and 3') by mixing in CO2, care being taken that no crystalline silica is yet formed or precipitated silica is redissolved, and that no local overacidification takes place. The silica is then precipitated by further lowering of the pH in a third, substantially identical reactor 3'' at pH = 10.2. The precipitated silica is discharged and, to allow the crystals to grow further, partially recycled. The discharged silica is washed and dehydrated in a filter press 12, the liquid separated off is partially evaporated and incinerated as waste liquor or fuel and partially recycled into the reactors to maintain the viscosity, whereby the foaming problem is also reduced.

Protein removal using precipitated silica

Abstract: A liquid medium in which protein is dissolved, suspended, or dispersed is contacted with amorphous precipitated silica having, on a coating-free and impregnant-free basis, a surface area of from about 190 to about 600 square meters per gram, a pore diameter at the maximum of the volume pore size distribution function of from about 7 to about 30 nanometers and/or an average pore diameter by nitrogen adsorption of from about 3 to about 19 nanometers, and a total intruded volume of from about 2.3 to about 5 cubic centimeters per gram, whereby at least a portion of the protein is adsorbed by the amorphous precipitated silica. The process is particularly suitable for chillproofing beer.

Low temperature-very high structure silica and methods

Abstract: Precipitated silica gels having high surface areas and low oil absorption values are produced by a low temperature synthesis precipitation process. The precipitated silicas have unique flatting characteristics and are additionally useful as conditioning agents for food and salt and in dentifrice formulations.