Showing papers on "Precipitated silica published in 2001"

Precipitated silicas, silica gels with and free of deposited carbon from caustic biomass ash solutions and processes

Abstract: Disclosed are amorphous precipitated silicas, silica gels, and amorphous carbons derived from biomass and methods of producing them with and without adhered or deposited amorphous carbons produced by acidifying a caustic silicate solution produced by caustic digestion of biomass ash containing silica with and without activated carbon, the ash being obtained from thermal pyrolysis of the biomass, the acidifying effective to produce a slurry of the precipitated silica and silica gels with and without adhered or deposited amorphous carbon, and separated from the slurry the precipitated silicas and silica gels with and without the adhered or deposited amorphous carbons. The properties of the precipitated silica with adhered or deposited carbon being within the range as utilized in rubber compositions thereby avoiding the blending of silica and carbon components for such use. The precipitated silicas and silica gels without adhered or deposited carbon having metal contaminants present in low concentrations which when used in formulation of chemical-mechanical-planerization slurries used in polishing silicon wafers in the manufacture of computer chips and other electronic devices do not contaminate the wafer and final chip product and the other electronic devices.

New Approaches to Surface-Alkoxylated Silica with Increased Hydrolytic Stability

Abstract: Surface-alkoxylated silica can be prepared by reacting precipitated silica with high-boiling and polymeric alcohols. The structure of the products was investigated through 13C and 29Si MAS NMR expe...

Preparation of Attrition-Resistant Spray-Dried Fe Fischer−Tropsch Catalysts Using Precipitated SiO2

Abstract: Spray-dried Fe Fischer−Tropsch (FT) catalysts can be prepared that have sufficient attrition resistance for use in slurry bubble column reactors without sacrifice of their activities and selectivities. Earlier studies from our group have shown that the type (binder or binder-and-precipitated) and concentration of silica incorporated into Fe spray-dried Fischer−Tropsch (FT) catalysts have significant impacts on catalyst attrition and that attrition resistance is strongly dependent on particle density. Although the use of a refractory oxide such as SiO2 is necessary to produce and maintain the high active surface area of a catalyst, the use of high concentrations of binder or binder-and-precipitated SiO2 results in poorer attrition resistance. This paper reports on the effect of precipitated silica by itself on the attrition resistance of Fe FT catalysts produced by spray drying. Earlier work by others suggested that the use of precipitated SiO2 alone produced less than adequate attrition-resistant Fe catal...

Interface effects in elastomers reinforced by modified precipitated silica

Abstract: The contributions of the so-called “interface effects” on the overall viscoelastic behavior of SBR reinforced by precipitated silica modified by model sizing agents are evaluated by using micromechanical models in a reverse mode. According to the nature of the coupling agent, two kinds of “interface effects” can be distinguished: (i) an overall change in the viscoelastic behavior of the polymer matrix, when the sizing agent is a chemical promotor acting as additional ties of the SBR network, and (ii) the formation of an actual mesophase, when direct interactions between SBR chains and silica could occur, as for example, when the coating agent of silica is an organosilane based on short aliphatic chains. With increasing the length of the aliphatic chains of the coating agent (LOS agent), some a plasticisizing effect of the polymer is detected by DSC. It can affect either the entire polymer matrix or a confined region at the close vicinity of silica aggregates. According to this assumption, the bimodal viscoelastic behavior of the LOS-mesophase revealed by the modeling indicates that in addition to a local plasticisizing effect induced by this agent, some direct interactions could occur between silica surface and SBR constraining the mobility of rubber molecules.

Doped precipitated silica

Abstract: Al-doped precipitated silica particles have a BET surface area above 300 m /g and uniformly distributed Al. An Independent claim is also included for production of the doped silica in which an Al salt solution is added in step (a) and (c) of the following process: (a) heating a water/Na silicate mixture to 70-86 degrees C and neutralizing the Na silicate with H2SO4; (b) ageing the solution for 30-120 minutes; (c) adjusting to pH 3-7 by addition of H2SO4; and (d) filtering and spray drying and milling the washed filter cake.

Preparation of surface modified silica

Abstract: A process for the modification of the surface of a silica with a silane compound comprising mixing an aqueous suspension of precipitated silica particulates with a silane compound which is dissolved in an organic solvent, in the presence of a phase transfer catalyst.

High-structure precipitated silicas

Abstract: A precipitated silica having the following physico-chemical characteristics: pH (5% in water) (ISO 787-9) 3–8 BET surface area (DIN 66131) (m 2 /g) 400–600 DBP absorption value (DIN 53601, (g/100 g) 380–420 in relation to dried substance) Tapped density (ISO 787-11) (g/l) 100–200 ALPINE sieve residue > 63μ (ISO 8130-1) (%) 0.1–40.

Study of silica particle aggregation in a batch agitated vessel

Abstract: The aggregation kinetics of precipitated silica particles is studied in a laboratory batch reactor. A method using destabilisation of a silica sol is developed to observe the aggregation process in absence of any other precipitation phenomena. The evolution of the moments of the particle size distribution (PSD) against time shows that the silica aggregation proceeds in two stages — a perikinetic aggregation stage, for particles smaller than 250 nm, whose kinetic rate depends on physico-chemical parameters, and a rapid orthokinetic aggregation stage, for larger particles. Once they have reached their maximal size, particles undergo breakage, whose rate depends on hydrodynamic conditions. Expressions for the evolution of the first moments (up to sixth order) against operating conditions are derived.

Method for preparing precipitated silica containing aluminium

Abstract: The invention concerns a method for preparing precipitated silica comprising reaction of a silicate with an acidifying agent whereby is obtained a precipitated silica suspension, then separating and drying said suspension. The invention is characterised in that said method comprises the following process: adding to the reaction medium at least a compound A of aluminium; then adding to the reaction medium an acidifying agent, said separation comprising filtration and disintegration of the cake derived from said filtration, said disintegration being preferably carried out in the presence of at least a compound B of aluminium. The thus prepared silica precipitates are particularly well adapted for use as reinforcing elastomer filler.

Effect of Aluminum Powder on Filled Natural Rubber Composites

Abstract: The effect of aluminum powder on the properties of natural rubber composites containing high abrasion furnace black (HAF), general purpose furnace black (GPF), acetylene black, china clay and precipitated silica was studied. In all cases the total filler content including aluminum powder is fixed at 40 parts per hundred rubber (phr). Gradual replacement of these fillers by aluminum powder showed a marked increase in thermal conductivity. This increased thermal conductivity of aluminum powder filled composites decreased the vulcanization time and led to uniform curing throughout the material, especially for thick articles. Mechanical properties like tensile strength, tear strength, rebound resilience, heat build-up, hardness, compression set, etc., are comparatively better for these composites. Aluminum powder incorporated vulcanizates also showed good resistance against thermal aging and oxidative degradation. Thus, use of aluminum powder in rubber compounds can lead to energy saving in the vulca...

Synthesis of basic cancrinite in a butanediol-water system

Abstract: Cancrinite has been synthesized in a 1,3- or 1,4-butanediol/water mixture at temperatures of 353-493 K and reaction times of 24-168 h. Two main series have been performed. In the first series the silica sources (tetraethoxysilane, Aerosil, and precipitated silica) were combined directly with the alumina sources (aluminum sec-butoxide and aluminum isopropoxide) in the synthesis. In the second series organic gels formed from tetraethoxysilane and aluminum sec-butoxide/aluminum isopropoxide as well as inorganic gels formed from hydrolyzation of tetraethoxysilane with aqueous sodium and aluminum nitrate solution or from combination of sodium metasilicate with sodium aluminate were dried and used for synthesis. The products were characterized by X-ray powder diffraction as well as 29 Si and 27 Al MAS NMR spectroscopy. The results show that the sensitivity to the synthesis temperature, duration, and alkalinity depends mainly on the reactivity potential and solubility of the silica/alumina source used in the synthesis. While the directly applied reactants show the highest sensitivity to synthesis temperature and so forth, the gels show even the best synthesis results and cancrinite is formed in a wide range of synthesis parameters (temperature, duration, and sodium hydroxide concentration). A strong relationship between seeding kinetics, crystallization kinetics, and thermodynamic properties of cancrinite seems to be responsible for that behavior under the mild reaction conditions used here. Cancrinite formation as a kinetically controlled process is preferred if both the alumina and silica source dissolve slowly and steadily in the same proportions.

Mixtures comprising a filler and an organosilicon compound

Abstract: Mixture of at least one filler and organosilicon compounds of the general formula Y—S x -Z, wherein the filler is surface-treated, hydrophobic, precipitated silica, are prepared by homogeneously applying an organosilicon compound from a nozzle to the surface-treated, hydrophobic, precipitated silica in a mixing unit at a temperature of less than 50° C. The mixture can be used in rubber mixtures.

Precipitated silica particles for cat litter

Abstract: The invention pertains to precipitated silica particles having edged surfaces and a length : width : depth ratio of 1 : 1 : 1 to 3 : 3-1 : 1 with the length being 0.25 to 15 mm, an absorbing capacity PV water (wt.% >;125, a pore volume PV Hg (ml/g) 0.8-4, a pore volume PV N2 (ml/g) 0.2-1.5, a bulk density BD (g/l) 200-500, and preferably a pH<8, for use as a cat litter.

Use of a high structure and dispersible precipitated silica as thickening or texturing agent in toothpaste compositions

Abstract: The invention concerns the use, as thickening or texturing agent in toothpaste compositions, of a highly dispersible precipitated silica having a pH of 3.5 to 9, a DOP oil absorption higher than 200 ml/g, a CTAB specific surface area from 70 to 250 m2, a median diameter of at least 20 μm determined by ultrasound-free laser diffraction, a residual anion rate, expressed in sodium sulphate, less than 5 wt. %.

Tire having colored tread

Abstract: The present invention relates to a tire having a rubber tread of a lug and groove configuration and which may be of a co-extruded cap/base construction; wherein at least a part of the visible portion of the tread is exclusive of carbon black and thereby of a color other than black. Such non-black colored rubber includes the outer surface of at least one of said tread lugs intended to be ground-contacting. In one aspect of the invention, said non-black colored rubber composition contains (A) a precipitated silica reinforcement which has been pre-treated with a hydrophobation agent and optionally also pre-treated with a coupling agent or (B) a precipitated silica which has been pre-treated with a hydrophobating agent and a coupling agent which does not from an alcohol byproduct upon reacting with hydroxyl groups (e.g. silanol groups) contained on the surface of said precipitated silica. In another aspect of the invention, said non-black colored rubber composition is comprised of at least one diene based elastomer and a brominated poly(isobutylene-co-para-methylstyrene) where a coupling agent for said silica is an organo phosphite.

Methods for synthesizing precipitated silica and use thereof

Abstract: The synthesis of precipitated silica having improved chemical and physical properties of use as a reinforcing filler in polymeric matrices is described. Improvements in the properties result from the synthesis of the silica al a reduced ionic strength. In particular, the use of silicia acid during synthesis, provides a solution of reduced ionic strength, which favors the formation of improved colloidal structure via increased aggregation and reduced agglomeration. In addition, the surface of the silica precipitate formed may be modified by the addition of surface modifying agents, during synthesis to further enhance the desired reinforcing properties of the precipitated silica. The invention also embodies polymeric compositions of improved tensile and elongation strengths, with the compositions including precipitated silica, synthesized at reduced ionic strengths and having modified surfaces, in combination with a polymeric compound.

Measurement of attractive forces between single aerogel powder particles and the correlation with powder flow

Abstract: An atomic force microscope (AFM), which allows the measurement of forces as low as one tenth of a nano-Newton, was used to determine the attractive forces between single silica aerogel powder particles ( 100 μ m diameter) under two different atmospheric conditions. Forces on the order of 10 nN were found to depend mainly on the contact geometry and thus on the surface structure of the powder particles. In a second series of experiments, the surface structure of the silica aerogel powder particles was characterized using the AFM. Smooth surface areas, several micrometers in size, are separated by cliffs and cracks. For comparison, the same measurements were made with precipitated silica powder. Here larger forces and a different surface structure were found. The structure of precipitated silica particles is spheroidal with bumps on it, which are some hundred nanometers in size. In addition to the AFM measurements, powder flow rate from a hopper was measured. The flow of powders depends on the surface structure but also on the atmospheric conditions (e.g. moist atmosphere or vacuum). In contrast to precipitated silica powder, silica aerogel powder showed a significantly higher flow rate under vacuum than in moist air.

Silica reinforced rubber composition which contains stabilized unsymmetrical coupling agents and article of manufacture, including a tire, having at least one component comprised of such rubber composition

Abstract: This invention relates to use of stabilized unsymmetrical coupling agents for use in conjugated diene-based rubber compositions reinforced with silica-based reinforcement, namely use of stabilized 2-benzothiazyl-3-(triethoxysilylpropyl) disulfide and 3-(triethoxysilyl)propyl-N-maleamic acid. Said stabilized unsymmetrical coupling agent materials may be provided for mixing with said diene-based rubber(s), for example, as individual materials, as at least one of said materials being pre-reacted with aggregates of precipitated silica, said precipitated silica having hydroxyl groups (e.g. silanol groups) on its surface. The invention includes an article of manufacture, including a tire, having at least one component comprised of such rubber composition.

Precipitated silicas, silica gels with and free of deposited carbon from caustic biomass ash solutions and processes

Abstract: The present invention, as obtained from amorphous precipitated silica, silica gels, and amorphous carbon, and a thermal decomposition of the biomass is derived from bio-mass caustic produced by caustic degradation of biomass ash containing silica in the presence or absence of activated carbon to acidify the silicate solution, attached to or to produce a slurry of precipitated silica and silica gel, which does not contain or contains a fused amorphous carbon and attached from the resulting slurry, or do not contain, or contains a fused amorphous carbon precipitated silica and silica relates to a method of manufacturing an attached or not containing the deposited amorphous carbon or containing amorphous precipitated silica and silica gel which is produced by the step of separating the gel. Attached to or properties of the precipitated silica containing the carbon deposition is avoided by a combination of in within the same range as that used for the rubber composition, the silica and the carbon component for this purpose. Further, the present invention is a chemical that is used to polish silicon wafers in the production of computer chips and other electronic devices - metal at a low concentration if used in making the planarization slurry, does not contaminate the wafer, and the final chip product with other electronic devices and mechanical precipitated silica and silica gel relates to attachment of contaminants are present or not containing the deposited carbon.

Silicas modified with amino- and mercaptosilanes - fillers of urethane elastomers

Abstract: Determination of the optimum composition of a urethane-silica mixture, which would form crosslinked products, presented a significant problem in these studies. The unmodified silica was dosed at various ratios as compared to urethane elastomer: 2.5, 5.0, 7.5 and 10.0 phr. The optimum amount of the filler (precipitated silica) was found to be 5 phr and this amount of silica was subjected to modification with 3 and 5 weight parts of aminosilane U-15 or mercaptosilane A-189, per 100 weight parts of SiO2.

Thickening precipitated silica granules obtained by granulation and use thereof as thickening agent in dental composition

Abstract: The invention concerns thickening precipitated silica having a median diameter of at least 100 νm and cohesion factor FC of at least 0.3, obtained by wet process granulation of thickening precipitated silica, drying and optionally sieving, the granulation step being carried out in a low-shear granulation apparatus, using at least a precipitated silica powder (a), having a DOP of at least 230 ml/100g, a median diameter D50a of at least 14 νm; particles of at least a precipitated silica (b) having a DOP of at least 230 ml/100g, a median diameter D50b of at least 0.3 νm; and water (W) as binder, the dry extract of the mixture formed by the silicas (a) and (b) and water being between 25 and 40 wt. %, the weight ratio (a)/(b), expressed in dry weight, of silica (a) over silica (b) ranging between 1.5 and 6. The inventive granules are used as thickening agents with sensory effect in the mouth in dental compositions.

Silica reinforced rubber composition which contains oleylammonium bromide and/or mercaptoimidazolium bromide coupling agents to enhance electrical conductivity and article of manufacture, including a tire, having at least one component comprised of such rubber composition

Abstract: This invention relates to a conjugated diene-based rubber composition reinforced with silica-based reinforcement together with a non-silane coupling agent as N-3-(1,2-dihydroxypropyl)-N-oleylammonium bromide and/or N-3-(1,2-dihydroxypropyl)-N-methyl-2-mercaptoimidazolium bromide for endeavoring to both couple synthetic aggregates of precipitated silica to elastomers and enhancing electrical conductivity of such rubber compositions which contain less than 25 parts by weight carbon black per 100 parts by weight elastomer. Said coupling agent materials may be provided for mixing with said diene-based rubber(s), for example, as individual materials, as at least one of said materials being supported on a carbon black carrier or as being pre-reacted, or otherwise pre-treated, with synthetic silica aggregates. The invention includes an article of manufacture, including a tire, having at least one component comprised of such rubber composition.

Aqueous silica suspensions and their applications in compositions based on inorganic binder

Abstract: This invention relates to an aqueous suspension including a mixture of at least one aqueous suspension of precipitated silica and of at least one latex, in which the aqueous suspension of precipitated silica has a solids content of between 10 and 40% by weight, has a viscosity lower than 4×10 −2 Pa s at a shear of 50 s −2 and, after centrifuging at 7500 revolutions per minute for 30 minutes, produces a supernatant containing more than 50% of the weight of the silica initially in suspension. This suspension can be employed in compositions based on an inorganic binder and in concrete compositions.

Tire with silica reinforced carcass ply and/or circumferential carcass belt of a natural rubber-rich, silica reinforcement-rich, rubber composition

Abstract: The present invention relates to a tire with a carcass ply and/or circumferential carcass belt component comprised of a natural rubber-rich diene-based rubber composition which contains a dispersion of precipitated silica reinforcement, with coupling agent, to a substantial exclusion of carbon black.

Precipitated silica for use, e.g., in tires, battery separators or anti-blocking agents is produced in Taylor reactor fed with aqueous silicate solution and acidifying agent

Abstract: The inlet(s) of a Taylor reactor comprising an outer reactor with an inner rotor, and used for the production of precipitated silica, is(are) fed with an aqueous silicate solution and an acidifying agent. An Independent claim is included for the precipitated silica.

Chapter 3 – Synthesis of high-silica zeolites and phosphate-based materials in the presence of fluoride

Abstract: Publisher Summary This chapter covers the synthesis of zeolites, which is prepared by adding a silica source, such as fume silica, colloidal, precipitated silica. The crystals are usually of good quality and the size generally exceeds the values obtained in alkaline type synthesis. When the crystallization is carried out in the presence of an organic cation, as in the case of silica-rich zeolites, fluoride is generally occluded in the pores of the solid as a compensating negative charge, in addition to the negative framework charge, of the organic cations. Fluoride is essentially completely removed on calcination. The most common and preferred fluoride sources are NH4F, NH4HF2 or HF. Fluoride may also be combined with the source of framework elements such as in (NH4)2SiF6 or AlF3.H2O, and be released on hydrolysis. In contrast to the conventional synthesis of silica-based zeolites, the synthesis of phosphate-based materials such as aluminophosphates and gallophosphates has various beneficial effects in the presence of fluoride. The crystallization times are generally shorter and the crystals usually larger and well formed. Another beneficial effect of the presence of fluoride is the production of a number of phases which do not form in a fluoride-free medium, thus showing a structure-directing role of the fluoride ion.

Effect of amorphous precipitated silica on the properties and structure of poly(p-phenylene sulfide)

Abstract: Using a precipitation technique, silicas were obtained from sodium metasilicate solution employing an acidic agent. Alcohol solutions were used in the process of production of highly dispersed silicas, which resulted in partial blocking of the silica surface silanol groups. Moreover, studies on morphology and microstructure using transmission electron microscopy and scanning electron microscopy were performed. The size distributions of primary particles and aggregate and agglomerate structures were determined using a ZetaPlus instrument using the dynamic light scattering method. The structure and molecular dynamics of the nanocomposite, consisting of poly (p-phenylene sulfide) (PPS) and of the precipitated silica, were studied using atomic force microscopy and nuclear magnetic resonance. It was proved that during annealing the fragmentation of PPS agglomerates takes place. This phenomena probably resulted from repulsion forces existing between agglomerates and aggregates. Fragmentation in the polymer network probably resulted from repulsion forces between agglomerates and smaller aggregates.