Showing papers on "Precipitated silica published in 2006"

Comparison of liquid-phase olefin epoxidation over MoOx inserted within mesoporous silica (MCM-41, SBA-15) and grafted onto silica

Abstract: Molybdenum(VI)-containing siliceous-MCM-41 and -SBA-15 mesoporous molecular sieves and silica-supported molybdenum(VI) complexes have been prepared according to an original pathway by the reaction between low-cost Mo(VI) peroxo species and silica precursors (tetraethylorthosilicate), silica beads (pure SiO2) or precipitated silica in an acidic and peroxidic medium (peroxo route). Hydrogen peroxide is added to avoid the formation of iso-(or hetero-)polyoxometalates in the direct one-pot synthesis of mesoporous solids, or in the case of pure SiO2. The resulting calcined materials have been characterized by chemical analysis, X-ray powder diffraction, nitrogen sorption isotherms, TEM and EDX analysis, UV–vis diffuse reflectance spectroscopy, Raman spectrometry and catalysis tests. The peroxo routes lead to inserted and/or supported molybdenum oxide zones which are restricted in size due to the porous structure of the silica-based materials and to the involment of low-condensed and even mononuclear oxoperoxo species. This allows to support MoOx species in a dispersion which cannot be achieved with the systems using heptamolybdate [Mo7O24]6− salts or heteropolyoxometalates, which favor the anchoring of MoO3 clusters. Catalysis tests show that the very dispersive structure of the MoOx-siliceous-MCM-41, -SBA-15 and MoOx/SiO2 promotes the generation of fairly active oxidation catalysts for liquid-phase olefin epoxidation (cyclooctene, R-(+)-limonene from ambient to 40 °C) using anhydrous tert-butylhydroperoxide (TBHP) as oxidant. Under specific conditions, leaching of redox-active species has been minimized (less than 2 ppm) especially with MoOx/SiO2 which is proposed as the simplest catalyst for these oxidations. MCM-41 and SBA-15 do not show clear advantages over silica in epoxidation reactions with TBHP.

Investigation of Precipitation of Calcium Carbonate at High Supersaturations

Abstract: The formation mechanism of precipitated calcium carbonate from aqueous solution under industrial conditions (high supersaturation) was investigated in a semi-batch and in a continuous mixing nozzle process. The influence of potassium hydroxide and magnesium chloride on crystal modification and particle size were investigated in both processes. Rheological properties of the magnesium stabilized amorphous gel structure have been measured. A similarity between the formation process of calcium carbonate and precipitated silica has been proven.

Rheological behavior of CPE/NR blends filled with precipitated silica

Abstract: Blends of elastomeric chlorinated polyethylene (CPE) and natural rubber (NR) at the blend composition ratio of 80/20 CPE/NR with various precipitated silica loadings from 0 to 30 phr were prepared. Their rheological behaviors were determined using two rheometers with different shear modes, i.e., the oscillatory rheometer (Rubber Process Analyzer, RPA2000) and the rate-controlled capillary rheometer (Goettfert Rheotester 2000). Results obtained reveal that the viscoelastic behavior of blends is influenced remarkably by loadings of silica. Within the oscillatory shear strains of 0.3–30%, the unfilled blend appears to be almost insensitive to shear strain that means the unfilled blend possesses a broad linear viscoelastic (LVE) region. As silica is incorporated, the elastic modulus (G′) of blends increases, particularly at silica loadings of 20 and 30 phr. The increase in G′ as a function of silica loading could be explained by a reinforcing effect via a hydrodynamic effect as well as a strong interaction between chlorine atoms on CPE molecules and silanol functional groups on silica surfaces associated with a formation of silica tridimensional transient network, usually known as a secondary filler network. Also, all blends with various loadings of precipitated silica reveal an increase in elasticity with increasing frequency, and those with high silica loadings (i.e., 20 and 30 phr) give a more time-independent elastic response, which supports the presence of filler transient network in these blends. By applying the Cox and Merz concept to the rheological results, the superimposition of flow curves determined from of the oscillatory shear flow and steady shear flow in the highly silica filled blends is possible if the silica transient network effect is eliminated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2565–2571, 2006

The reinforcement and crosslinking of styrene butadiene rubber with silanized precipitated silica nanofiller

Abstract: Synthetic precipitated amorphous white silica nanofiller was used to reinforce and crosslink styrene-butadiene rubber (SBR). The silica surfaces were pre-treated with bis[3-triethoxysilylpropyl-)tetrasulfide (TESPT) bifunctional organosilane. 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 elemental sulfur to the cure system. The cure was also optimized by incorporating different accelerators and activators in the rubber. This study showed that the silica particles could be used both as crosslinking and reinforcing filler in the rubber.

Characterisation of the grafting of (3-aminoethyl)aminopropyltrimethoxy silane on precipitated silica

Abstract: In this study, we have investigated the reaction between (3-aminoethyl)amino-propyltrimethoxysilane (AEPTS) and a precipitated silica in organic solvents. Solid-state 29Si NMR and Karl Fischer titration have been used to produce useful information on the grafted silica samples. AEPTS was chosen in order to characterise the distribution of alkoxysilanes at the silica surface. Indeed, this alkoxysilane has an ethylene diamine function that can form coloured and paramagnetic complexes with copper in 1 ∶ 1 and 2 ∶ 1 molar ratios ([Cu(AEP-Si)]2+ and [Cu(AEP-Si)2]2+). These species have been further identified and quantified by UV-visible and ESR spectroscopies, and the proximity of the alkoxysilanes at the surface was thus traced back through the detection of the 2 ∶ 1 complex [Cu(AEP-Si)2]2+.

Precipitated silica having a specific pore size distribution

Abstract: Preparation of precipitated silicic acid comprises (a) subjecting an aqueous solution of an alkali- and/or earth alkaline silicate and/or an organic or inorganic base; (b) simultaneously adding an alkali- and/or alkaline-earth silicate and an acidifying agent to increase the viscosity; (c) terminating the reaction after 35-85 minutes; (d) simultaneously adding an alkali- and/or alkaline-earth silicate and an acidifying agent to attain a solid content; (e) stirring the obtained suspension; (f) adjusting the pH by adding the acidifying agent; and (g) filtering and (h) drying. Preparation of precipitated silicic acid comprises: (a) subjecting an aqueous solution of an alkali- and/or earth alkaline silicate and/or an organic or inorganic base, where the subjected mixture exhibits the alkali number of 20-40; (b) simultaneously adding an alkali- and/or earth alkaline silicate under stirring at 55-85[deg]C and an acidification agent to increase the viscosity of the mixture; ( (c) terminating the reaction after the addition of mixture that takes place for 35-85 minutes, preferably after reacting the temperature of step (b); (d) simultaneously adding an alkali- and/or alkaline-earth silicate and an acidifying agent under agitation at 55-85[deg]C, to attain a solid content of 90-140 g/l; (e) stirring the obtained suspension for 1-120 minutes at 80-98[deg]C; (f) adjusting the pH of the solution to 2.5-5 by adding the acidifying agent; (g) filtering; and (h) drying. Independent claims are included for: (1) a precipitated silicic acid exhibiting physical-chemical parameters such as relative width (gamma ) of the pore size distribution of 4-10 (g nm)/ml, Brunauer, Emmett and Teller (BET)-surface 90-320 m 2>/g, cetylammonium bromide (CTAB) surface area of 100-200 m 2>/g, sears number (V2) of 25-40 ml/(5 g) and sears number (V2/CTAB) ratio of 0.18-0.28 ml/(5 m 2>); (2) a precipitated silicic acid, obtained by the above process; (3) a vulcanizable rubber mixtures and vulcanizate comprising the precipitated silicic acid as filler material; and (4) a tire, comprising at least a precipitated silicic acid.

Dentifrices comprising biogenic silica materials

Abstract: Unique dentifrices comprising unique abrasive biogenic silica materials are provided. Such compositions exhibit excellent abrasive characteristics, either alone, or in combination with other types of abrasives. In such combinations (with precipitated silica materials, as one example), simultaneously high pellicle film cleaning properties and moderate dentin abrasion levels are possible in order to accord the user a dentifrice that effectively cleans tooth surfaces without detrimentally abrading such surfaces, even at low levels of such biogenic silica additives. Such biogenic silica particles thus surprisingly accord beneficial properties within dentifrice compositions. Encompassed within this invention is the method of utilizing such biogenic silica products within dentifrices, either as the majority abrasive component, or in combination with any other type of commonly used abrasive material.

Preparation of precipitated silicas useful as fillers in silicon matrices

Abstract: Carboxylic acids are employed during the preparation of precipitated silica or a suspension of precipitated silica to provide precipitated silicas with low water uptake, which are useful, for example, as reinforcing fillers for silicon matrices.

Effects of filler–polymer interactions on cold‐crystallization kinetics in crosslinked, silica‐filled polydimethylsiloxane/polydiphenylsiloxane copolymer melts

Abstract: Crystallization in a series of variable crosslink density poly(dimethyldiphenyl)siloxanes random block copolymers reinforced through a mixture of precipitated and fumed silica fillers has been studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). The silicone composite studied was composed of 94.6 mol % dimethoylsiloxane, 5.1 mol % diphenylsiloxane, and 0.3 mol % methyl-vinyl siloxane (which formed crosslinking after peroxide cure). The polymer was filled with a mixture of 21.6 wt % fumed silica and 4.0 wt % precipitated silica previously treated with 6.8 wt % ethoxy-end-blocked siloxane processing aid. Molecular weight between crosslinks and filler-polymer interaction strength were modified by exposure to γ-irradiation in either air or in vacuo. Isothermal DMA experiments illustrated that crystallization at -85 °C occurred over a 1.8 hour period in silica-filled systems and 2.2-2.6 hours in unfilled systems. The crystallization kinetics for irradiated samples were found to be dependent on crosslink density. Irradiation in vacuo resulted in faster overall crystallization rates compared to air irradiation for the same crosslink density, likely due to a reduction in the interaction between the polymer chains and the silica filler surface for samples irradiated in air.

Evaluation of the influence of the polymer-filler interaction on compounds based on epoxidized elastomeric matrix and precipitated silica

Abstract: The introduction of epoxy groups into the main chain of elastomers has emerged as a promising alternative, considering the monitoring of polymer-filler interaction leading to changes in the properties of vulcanizates. The epoxidation reaction (in situ) was chosen to modify elastomers, such as polybutadiene (BR) and copolymer of styrene- butadiene-rubber (SBR), because it is a simple, easily controlled reaction, even considering the small epoxidation degree. The modification degree of the polymeric chain was studied with FT-IR and 1 H-NMR. The shift of the Tg to high temperatures with the increase of the epoxy group in the polymer chain was monitored through differential scanning calorimetry (DSC). An analysis of the dynamic modulus of the material in relation to its dependence on the amplitude and temperature was carried out. The interaction between epoxidized elastomeric matrix and silica as filler was extremely improved, even in the presence of very low content of epoxy groups into the polymer chain.

Cationic resin-modified silica dispersion

Abstract: PROBLEM TO BE SOLVED: To provide a cationic resin-modified silica dispersion which is a highly concentrated silica dispersion with silica modified by mixing with a cationic resin and having a high specific surface area, while having excellent shelf life and transparency. SOLUTION: The cationic resin-modified dispersion is characterized in that: precipitated silica having a high specific surface area of a BET specific surface area not less than 250 m 2 /g is dispersed together with a fumed silica by adding a cationic resin; the total silica concentration is not less than 15 wt.%; the average particle size of the silica particles is less than 300 nm; and the fumed silica is blended by a blending ratio of 8-22 pts.wt. to 100 pts.wt. of the precipitated silica. COPYRIGHT: (C)2007,JPO&INPIT

A process for producing silica and sodium sulfite with sodium sulfate

Abstract: A method is provided to produce silica and sodium sulfite with sodium sulfate, wherein a mixture of quartz sand, sodium sulfate and carbon is reacted to produce solid sodium silicate and sulfur dioxide; said solid sodium silicate is dissolved in water and then filtered to obtain a sodium silicate solution; said sodium silicate solution is brought into contact with the sulfur dioxide to produce precipitated silica and sodium sulfite solution; the resultant mixture is filtered; the filter cake is acidified and then goes through filtration, washing and drying to obtain silica; and the filtrate is concentrated and dried to get sodium sulfite. The process of the present invention has great value due to its simple steps, low production cost and reduction of environmental problems.

Control of Glass Transition, Solubility, and Thermo-Optic Coef-cients of a Siloxane-Containing Polyimide by Silica Hybridization

Abstract: In order to utilize significant enhancement of thermo-optic coefficients (i.e. temperature dependence of refractive index, dn-dT) of polymers above glass transition temperatures (Tg values) for dynamic control of refractive index, the Tg of siloxane-containing polyimide (PI), derived from bis(3,4- dicarboxyphenyl)ether dianhydride and bis(3-aminopropyldimethylsilyl)ether, was controlled by hybridization with silica (amorphous SiO2) particles generated by the in situ sol-gel reaction. The Tg values for the hybrid films were increased from 55 to 105°C with increasing the silica content. In addition, resistance to the organic solvents was significantly improved by the hybridization. These results indicate that the PI chains were physically or chemically bonded to the silica particles in the hybrids. The characteristic high transparency of the matrix PI in the visible light region was retained in the hybrid films without causing light scattering, which demonstrates that the precipitated silica particles were ...

Air filtration media comprising metal-doped precipitated silica materials

Abstract: The present invention relates generally to an environmental control unit for use in air handling systems that provides highly effective filtration of noxious gases (such as ammonia). Such a filtration system utilizes novel metal-doped precipitated silica materials to trap and remove such undesirable gases from an enclosed environment. Such silicas exhibit specific porosity requirements and density measurements. Furthermore, in order for proper metal doping to take effect, such precipitated silicas must be treated while in a wet state. The combination of these particular properties and metal dopant permits highly effective noxious gas filtration such that uptake and breakthrough results are attained, particularly in comparison with prior precipitated silica filtration products. Methods of using and specific filter apparatuses are also encompassed within this invention.

Precipitated silica reinforced epdm rubber formulation manufacturing process, process for the obtainment of a reinforced rubber profile, colored extruded rubber profile and use

Abstract: The present invention refers to a high dissipating precipitated silica reinforced EPDM rubber (monomer of ethylene-propylene-diene) and to a colored extruded polymeric profile comprising said formulation, particularly intended for using in the building and automobile industry The present invention also refers to a process for the manufacturing of said formulation

A process for producing silica, sodium sulfite and sodium hydrogen sulfite with sodium sulfate

Abstract: The present invention provides a process for producing silica, sodium sulfite and sodium hydrogen sulfite with sodium sulfate, wherein quartz sand, sodium sulfate and carbon are mixed and charged into a furnace for reaction and the obtained solid sodium silicate and sulfur dioxide are used to prepare silica, sodium sulfite and sodium hydrogen sulfite according to the following steps: 1) To produce silica: said solid sodium silicate is dissolved in water and filtered to produce a water glass solution; then sulfuric acid is reacted with said water glass solution to produce precipitated silica and sodium sulfate; and the precipitated silica is washed, filtered, liquefied and dried to produce silica; 2) To produce sodium sulfite: soda is added into a sodium hydrogen sulfite solution to produce sodium sulfite solution; one part of said sodium sulfite solution is concentrated and evaporated to obtain dry sodium sulfite; and the other part of the sodium sulfite solution is reacted with the sulfur dioxide produced during the production of the sodium silicate to produce sodium hydrogen sulfite solution, which can be recycled and reused in step (2); 3) To produce sodium hydrogen sulfite: soda is added into a sodium hydrogen sulfite solution followed by reacting with the sulfur dioxide produced during the production of the sodium silicate to produce a supersaturated sodium hydrogen sulfite solution, which is crystallized and dried to obtain a dry solid sodium hydrogen sulfite. The process of the present invention produces various products at low production cost and without causing environmental problems, and thus it has great practical value.

Antyusan-containing tablet

Abstract: PROBLEM TO BE SOLVED: To obtain Antyusan(a kind of Chinese herbal medicine)-containing tablets excellent in compression moldability and characterized in suppressing delay of the disintegration time. SOLUTION: The Antyusan-containing tablets are obtained by the following procedure: Mixed powder comprising about 3-5 mass% of precipitated silica, a low-substitution-degree hydroxypropyl cellulose, Antyusan powder, an excipient and a lubricant is subjected to dry granulation to prepare Antyusan-containing granules, which are then mixed with a lubricant and such an amount of precipitated silica as to be 6-12 mass%, based on the whole tablets, in the sum with the precipitated silica in the granules followed by making a compression molding. COPYRIGHT: (C)2007,JPO&INPIT

Process for preparing a metal hydroxide

Abstract: The invention provides a process for preparing a metal hydroxide comprising the steps of: (a) providing particles of a metal silicate; (b) mixing the particles with a mineral acid solution to obtain a slurry which comprises precipitated silica; (c) separating the precipitated silica from the slurry to obtain a remaining solution; (d) increasing the pH of the remaining solution to such an extent that a metal hydroxide is formed; (e) separating the metal hydroxide so obtained from the remaining solution; and (f) adding to the remaining solution obtained in step (e) an acid solution, thereby forming a salt containing solution, or (g) removing at least part of the base added in step (d) from the remaining solution obtained in step (e), thereby forming a salt containing solution.

Rubber composition containing diene-based elastomer, precipitated silica, coupling agent and alcohol-adsorbing activated carbon and pneumatic tire with component

Abstract: The present invention relates to a rubber composition comprised of diene based elastomer, precipitated silica, particulate low molecular weight alcohol-adsorbing (e.g. alkanol-adsorbing) activated carbon and coupling agent comprised of at least one of organopolyalkoxysilane polysulfide (e.g organopolyalkoxysilyl polysulfide such as a bis(3-trialkoxysilylalkyl polysulfide) and organoalkoxymercaptosilane. The invention further relates to a tire having a component of such rubber composition.

Dentifrices comprising biogenic silica materials and calcium carbonate

Abstract: Unique dentifrices comprising unique abrasive biogenic silica materials are provided. Such compositions exhibit excellent abrasive characteristics, either alone, or in combination with other types of abrasives. In such combinations (with precipitated silica materials, as one example), simultaneously high pellicle film cleaning properties and moderate dentin abrasion levels are possible in order to accord the user a dentifrice that effectively cleans tooth surfaces without detrimentally abrading such surfaces, even at low levels of such biogenic silica additives. Such biogenic silica particles thus surprisingly accord beneficial properties within dentifrice compositions. Encompassed within this invention is the method of utilizing such biogenic silica products within dentifrices, either as the majority abrasive component, or in combination with any other type of commonly used abrasive material.

Modification of Dynamic Properties of SBR Rubber Composites with Silica Fillers

Abstract: Silica fillers are used in rubber composites to modify their dynamic-mechanical properties. Three fillers are used: a commercial filler of precipitated silica type Vulkasil- S and two fillers obtained by its treatment in different ways: thermally and hydrothermally. The purpose is not only to obtain higher hysteresis of the composite at low temperatures and lower hysteresis at elevated temperature (which is optimal for good tire performance), but to understand the reasons of such changes in elastomer materials behavior and also possibilities to increase the corresponding trends. Both modified fillers exhibited required trends in comparison with the original commercial one. More detailed analyses of their dynamical behavior indicate interdependence between of filler particle size, morphology of particle aggregates and ratio of elastic to loss moduli, influencing all together the dynamic properties of products.

Silica nanostructure formation from synthetic R5 peptide

Abstract: Diatoms have the ability to generate highly ornamented nanostructured silicified cell walls under ambient conditions and without harsh chemicals, yet the molecular mechanisms underlying biosilification are still not well understood. The idea of this study is to mimic silica biomineralization of diatom cell walls that may provide the key to the development of new routes towards novel tailor-made silicas. Here the ability of R5 peptide, a peptide from the silaffin-1 protein derived from diatom species of Cylindrotheca fusiformis, to generate silica nanostructure in vitro was investigated. The R5 peptide was synthesized using Fmoc Solid-Phase Peptide Synthesis and purified using reverse phase high performance liquid chromatography. MALDI analysis showed that the peptide was successfully synthesis. With the application of silicic acid as a silica precursor and the peptide as catalyse, the formation of silica nanostructure was achieved. AFM analysis of the precipitated silica from the mixture of silicic acid and the peptide revealed the nanostructure of silica spheres ranging between 50 – 300 nm in diameter. Silica precipitate was not obtained in the absence of R5 (negative control) and when the silicic acid was mixed with poly-L-lysine (positive control), a network of large aggregates of uniform size of silica spheres of about 100 nm in diameter was observed.

Treatment of cooking oils and fats with precipitated silica materials

Abstract: The treatment of cooking oils and fats with specific types of precipitated silica materials to prolong the useful life of such oils and fats within restaurant settings. More particularly, such an invention encompasses the utilization of specific types of precipitated silica materials to filter such oils and/or fats. Such precipitated silica materials and treatments therewith aid to remove large amounts of free fatty acids after such oils and/or fats have been utilized to fry foodstuffs, as well as reduce the amount of additional oil and/or fat potentially necessary to bring the used oils and/or fats up to a level of permitted further utilization within a restaurant environment.

Precipitated silicic acid, method for manufacturing the same, and rubber blend and vulcanized rubber containing the same

Abstract: PROBLEM TO BE SOLVED: To provide precipitated silica and a method for manufacturing the same, with respect to development of precipitated silica for use in a base structure of a tire so as to lower rolling resistance. SOLUTION: The precipitated silica has an Al 2 O 3 content of 0.2-5.0 wt.% and a wk coefficient of COPYRIGHT: (C)2007,JPO&INPIT