Showing papers on "Precipitated silica published in 1985"

Precipitated silica having improved morphological characteristics and process for the production thereof

Abstract: A precipitated silica having improved morphological characteristics and a process for making precipitated silica In the precipitated silica of the present invention, the ratio of DBP oil index/CTAB specific surface area is between: 7 and 4 for a range of CTAB of between 50-100 m 2 /g, 4 and 25 for a range of CTAB of between 100-200 m 2 /g, 25 and 2 for a range of CTAB of between 200-250 m 2 /g, 2 and 15 for a range of CTAB of between 250-300 m 2 /g, and 15 and 12 for a range of CTAB of between 300-350 m 2 /g

Bimodal networks and networks reinforced by the in situ precipitation of silica

Abstract: The goal of primary interest in these investigations was the development of novel methods for preparing elastomeric networks having unusually good ultimate properties. The first technique employed involves endlinking mixtures of very short and relatively long functionally-terminated chains to give bimodal networks. Such (unfilled) elastomers show very large increases in reduced stress or modulus at high elongations because of the very limited extensibility of the short chains present in the networks. The second technique employs the in situ precipitation of reinforcing silica either after, during, or before network formation. The reaction involves hydrolysis of tetraethylorthosilicate, using a variety of catalysts and precipitation conditions, and the effectiveness of the technique is gauged by stress-strain measurements carried out to yield values of the maximum extensibility, ultimate strength, and energy of rupture of the filled networks. Information on the filler particles thus introduced is obtained from density determinations, light scattering measurements, and electron microscopy.

Precipitated silica insulation

Abstract: Precipitated silica, formed by the interaction of sodium water glass and sulfuric acid, followed by mechanical processing, is employed as an insulating material having a low thermal conductivity. The precipitated silica is dried, compressed, placed in an evacuable pouch, and evacuated. The resulting board-like insulation configuration is used directly as insulation in, for example, household refrigerators.

Polishing composition and dentifrice

Abstract: A composition of matter useful as a polishing agent combination in a dentifrice, such as a toothpaste. A silica polishing agent is combined with a weakly calcined alumina polishing agent. Preferably, the weakly calcined alumina contains about 50%-90% by weight of alpha aluminum oxide and about 10%-50% by weight of gamma aluminum oxide. Preferably, the silica polishing agent is selected from the group consisting of precipitated silica and silica gel.

Recovery of sodium aluminate from Bayer process red mud

Abstract: A process for recovery of valuable products from Bayer process red mud comprises the steps: (a) digesting red mud with sulphur dioxide in the presence of water to dissolve soda, alumina and silica therein; (b) heating the product of step (a), with or without prior removal of insolubles, to selectively precipitate silica, and removing solids including the precipitated silica, to produce a liquor containing soda and alumina; (c) causticizing the liquor to precipitate calcium sulphite; and (d) separating the precipitated calcium sulphite from the liquor to produce calcium sulphite and sodium aluminate solution as products. In a preferred embodiment calcium sulphite produced in step (c) is calcined to regenerate lime and sulphur dioxide for recycle to the liquor causticization and red mud digestion stages respectively, and sodium aluminate produced in step (d) is returned to the Bayer process.

Process for xylene isomerization using ZSM-23 zeolite

Abstract: An improved process is disclosed for the isomerization of xylenes over a zeolite which may contain a platinum group metal. The improvement resides in the use of ZSM-23 zeolite which exhibits enhanced selectivity which inhibits the production of undesired C 9 + aromatic transalkylation by-products. ZSM-23 having pores substantially unobstructed by silica, such as that made from a forming mixture containing amorphous precipitated silica as a silica source, has been found to be particularly useful in the process of the present invention.

Animal feed supplement

Abstract: Free flowing, substantially dust-free, dense granular amorphous precipitated silica having a principal particle size of between about 0.14 millimeters and about 0.84 millimeters are described. This material is particularly suitable as an inert carrier for water-soluble and fat soluble nutritional supplements, e.g., vitamins, which are added to feeds for livestock.

Process and catalyst for the production of formaldehyde from methane

Abstract: Formaldehyde is made from methane and a molecular oxygen containing gas by using a silica supported catalyst having less than 350 parts per million by weight of sodium and having a catalytically effective amount of MoO3. The low sodium form of the silica support can be made by washing silica gel or precipitated silica, by using a fumed silica or by making an ultrapure form of silica having a silica purity of at least 99.99% silica. The ultrapure form can be made by the hydrolysis of silicon tetraalkoxides. In general, the lower the sodium level, the better is the catalyst.

Soft sealing material, especially for manufacturing high-duty packings for cylinder heads in internal-combustion engines

Abstract: An asbestos-free soft fibre web material in particular for impregnated cylinder head gaskets and exhaust flange seals in internal combustion engines which is based on mixtures of fibres of organic and inorganic, synthetic and/or natural origin, binders and mineral fillers preferably contains as a filler from 30 to 40% by weight of a mixture of pyrogenic silica with feldspar, precipitated silica and/or dolomite in a preferred mixing ratio of from 10:3 to 1:3. Compared with conventional materials, the soft material gives appreciably improved and more uniform impregnant uptake, and the seals produced combine optimum functioning characteristics with a high yield limit and durability.

Production of diorganosiloxane polymer-finely powdery silica mixture

Abstract: PURPOSE: To obtain the titled mixture suitable as chief agent for silicone rubber composition with sufficiently high polymerization degree attainable, by polymerization of a diorganosiloxane oligomer in the presence of each specific precipitated silica and polymerization catalyst. CONSTITUTION: The objective mixture can be obtained by polymerization, while mixing, between the following three components: (A) 100pts.wt. of either diorganosiloxane oligomer of formula HO(R 2 SiO) x H or diorganocyclosiloxane oligomer of formula which may contain another diorganosiloxane oligomer of formula R 3 SiO(R 2 SiO) y SiR 3 or R 3 SiO(R 2 SiO) z H (R is monovalent hydrocarbon; x is 3W200; y is 3W10; z is 0W50), (B) 2W150pts.wt. of precipitated silica with the content of alkali metal <0.35wt% on its oxide basis, and (C) a polymerization catalyst selected from (i) sulfuric acid or sulfonic acids of formula XSO 3 H (X is halogen, etc.), (ii) perfluoroalkanesulfonic acids, and (iii) mixtures of quaternary ammonium carboxylate and carboxylic acid. COPYRIGHT: (C)1987,JPO&Japio

High-purity silica and its manufacture

Abstract: PURPOSE:To manufacture industrially high purity silica in the form of fine powder by converting an aqueous alkali silicate soln. into gel, purifying the resulting silica gel with a volatile acid, dehydrating it under heating, and spouting the dehydrated silica powder into a flame to carry out melting treatment. CONSTITUTION:An aqueous alkali silicate soln. of high purity such as an aqueous sodium silicate soln. prepd. by dissolving crystalline sodium silicate is brought into contact with an ion exchange resin to form acidic silica sol, and this sol is converted into gel by adding an aqueous ammonia soln. Said alkali silicate soln. may be directly converted into gel by neutralization with an acid such as sulfuric acid. Impurities such as radioactive substances are removed from the precipitated silica gel with an acid which is volatilized by the following heat treatment such as nitric acid or hydrochloric acid to purify the silica gel. The resulting silica hydrate is dehydrated under heating by spraying or other method, and the dehydrated silica powder is spouted into a flame at >=about 3,000 deg.C such as an oxyhydrogen flame. The powder is made spherical by melting to obtain high purity silica contg. =80% degree of melting. The electric conductivity of boiling water passed through the silica to carry out leaching or extraction is <=100muS/ cm.

Elame-retardant silicone rubber composition

Abstract: PURPOSE:The titled composition, obtained by incorporting an organopolysiloxane with a fine powdery silicon based filler, platinum (compound) and further an organosilicon compound having nitrogencontaining organic group and unsaturated group and having improved flame retardancy. CONSTITUTION:A flame-retardant silicone rubber composition obtained by incorporating (A) 100pts.wt. organopolysiloxane expressed by the average unit formula I (B is unsubstituted or substituted monofunctional hydrocarbon group; a is 1.9-2.05), preferably raw rubber, consisting of unit formula II and unit formula III, and having >=5,000 average polymerization degree with (B) 20-200 pts.wt. fine powdery silica based filler having >=50mum particle diameter, e.g. fumed silica or precipitated silica, (C) 1-200ppm, expressed in terms of the amount of platinum, platinum or a platinum based compound, e.g. chloroplatinic acid and (D) an organosilicon compound containing nitrogen-containing organic group and unsaturated group, e.g. an organosilane expressed by formula IV or V, in an amount to give 1-500 equivalents based on the amount of the platinum in the component (C), N atoms.

Silica with a high oil-uptake and controlled primary structure, and process for the preparation thereof

Abstract: The present invention relates to precipitated silica aggregates which are as shown in Figure 1 and having an average projected area of greater than 15 000 nm It also conerne a process for obtaining with the addition at constant volume of reagents, reaction with an electrolyte and consolidation of the product obtained by adding a silicate solution and an acidifying agent.

Method of making an anti-foam for water systems

Abstract: 1. Process for the production of anti-foaming agents for aqueous systems by mixing organosiloxane polymers with a finely-divided silica, characterised in that from 90 to 99.5% by weight of an organosiloxane polymer having from 2 to 1 400 siloxane units corresponding to a molecular weight of from 162 to 103 000 are mixed with from 0.5 to 10% by weight of a precipitated silica which has more than once been jet-ground, has a pH of from 5 to 7 after precipitation, is adjusted to a pH of from 8 to 11 during the first or second jet-grinding operation by addition of alkaline solutions and the physical-chemical characteristics of which lie in the following ranges : BET surface m**2 /g from 155 to 300 Pore diameter (maximum) nm from 8 to 16 Pore diameter (average) nm from 11 to 13 Pore volume ml/g from 0.3 to 1.2 Grain size (secondary particles) mu m =< 3 this mixture is then homogenised under a pressure of from 250 to 350 bars and at from 25 to 100 degrees C, is heated with stirring to from 100 to 300 degrees C for a period of from 0.1 to 24 hours and is again homogenised after cooling.