Showing papers on "Precipitated silica published in 2004"

Fly ash particles and precipitated silica as fillers in rubbers. I. Untreated fillers in natural rubber and styrene–butadiene rubber compounds

Abstract: In this study, we investigated the effects of untreated precipitated silica (PSi) and fly ash silica (FASi) as fillers on the properties of natural rubber (NR) and styrene- butadiene rubber (SBR) compounds. The cure characteristics and the final properties of the NR and SBR compounds were considered separately and comparatively with regard to the effect of the loading of the fillers, which ranged from 0 to 80 phr. In the NR system, the cure time and minimum and maximum torques of the NR compounds progressively in- creased at PSi loadings of 30 -75 phr. A relatively low cure time and low viscosity of the NR compounds were achieved throughout the FASi loadings used. The vulcanizate prop- erties of the FASi-filled vulcanizates appeared to be very similar to those of the PSi-filled vulcanizates at silica con- tents of 0 -30 phr. Above these concentrations, the properties of the PSi-filled vulcanizates improved, whereas those of the FASi-filled compounds remained the same. In the SBR sys- tem, the changing trends of all of the properties of the filled SBR vulcanizates were very similar to those of the filled NR vulcanizates, except for the tensile and tear strengths. For a given rubber matrix and silica content, the discrepancies in the results between PSi and FASi were associated with filler- filler interactions, filler particle size, and the amount of nonrubber in the vulcanizates. With the effect of the FASi particles on the mechanical properties of the NR and SBR vulcanizates considered, we recommend fly ash particles as a filler in NR at silica concentrations of 0 -30 phr but not in SBR systems, except when improvement in the tensile and tear properties is required. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2119 -2130, 2004

Synthesis and characterization of acrylic rubber/silica hybrid composites prepared by sol‐gel technique

Abstract: The organic-inorganic hybrid composites comprising acrylic rubber and silica were synthesized through sol-gel technique at ambient temperature. The composites were generated through the acid-catalyzed hydrolysis and subsequent condensations of inorganic tetraethoxysilane (TEOS) in the organic acrylic rubber (ACM), solvated in tetrahydrofuran. The morphology of the hybrid materials was investigated by using the transmission electron microscope (TEM) and scanning electron microscope (SEM). Transmission electron micrographs revealed that the silica particles, uniformly distributed over the rubber matrix, are of nanometer scale (20-90 nm). The scanning electron micrographs demonstrated the existence of silica frameworks dispersed in the rubber matrix of the hybrid composites. The X-ray silicon mapping also supported that observation. There was no evidence of chemical interaction between the rubber phase and the dispersed inorganic phase, as confirmed from the infrared spectroscopic analysis and solubility measurements. Dynamic mechanical analysis indicated mechanical reinforcements within the hybrid composites. The composites containing in situ silica, formed by sol-gel technique, demonstrated superior tensile strengths and tensile modulus values at 300% elongations with increasing proportions of tetraethoxysilane. However, the improvements in physical properties with similar proportions of precipitated silica were not significant. Maximum tensile strength and tensile modulus were obtained when the rubber phase in the hybrid composites was cured with ammonium benzoate and hexamethylenediamine carbamate system, as compared with benzoyl peroxide cured system. Thermal stability of the hybrid composites was not improved appreciably with respect to the virgin rubber specimen. Residue analysis from thermogravimetric study together with infrared spectroscopic analysis indicated the presence of unhydrolyzed tetraethoxysilane in the hybrid composites.

Characterization of rice hull ash

Abstract: Rice hulls, a byproduct of the rice industry, contain 60-90% silica and are unique within nature. The annual worldwide output of rice-hull-derived silica is more than 3.2 million tons, which poses environmental concerns because of disposal issues. Burning rice hulls, as a preparative step for energy production, is a useful solution to the growing environmental concern, a desirable outcome would be the economic use of the resulting silica-rich hull ash. The economical usefulness of this silica ash in the filler market has been undermined by its limited dispersion abilities and poor interaction capability with polymers. In this study, some of the reasons for the poor performance of silica ash as a reinforcing filler in various polymeric composites were linked to its inherent characteristics: factors such as its impurity, irregular topography, porosity, and chemical and thermodynamic nature arising from its surface polarity that negatively influence the filler-matrix interactions. The silica ash obtained from a novel combustion process had about 6% (w/w) impurity, of which around 3% was volatile. We also propose that the silanation efficiency of silica ash is lower compared to other commercial silicas because of its porosity, which could hide a fraction of the silane used. Also, processing changed the particle size distribution, and this could have affected the agglomerating tendencies and seriously marked the reinforcing capabilities of the silica ash. The estimation of the surface silanol groups of the rice hull ash by thermogravimetric studies indicated that the surface silanol density was about 16/nm2. On a comparative scale, this value is comparable to the silanol density on precipitated silica, but a thermodynamic study of silica ash surface revealed a high surface free energy that contributed to its high aggregation tendencies and poor distribution and dispersion abilities.

Rheology and structure of precipitated silica and poly(dimethyl siloxane) system

Abstract: The reinforcing capability of precipitated silica in poly(dimethyl siloxane: PDMS) was characterized by means of bound rubber formation, solvent swelling, yield stress, rheological and dynamic properties. Volume concentration of precipitated silica in PDMS was varied from 0 to 0.16. The homogeneity of the compounds after mixing was confirmed by studying a uniformity of dispersion of silica particles in PDMS via SEM morphology of vulcanizates. Bound rubber measurements of the compounds and solvent swelling studies of vulcanizates showed that the precipitated silica exhibited much stronger interaction with PDMS than that of typical carbon black with rubbers but less than that of fumed silica with PDMS. At high volume concentrations of silica (0.128 and 0.160), a yield behavior was evident from the storage modulus measurements. The network formation due to an interaction between the precipitated silica and PDMS was visualized via dynamic property measurements.

Method of inhibiting or controlling formation of inorganic scales

Abstract: A well treating composition of a composite containing a scale inhibitor adsorbed onto a water-insoluble adsorbent is useful in the control, formation and treatment of inorganic scales in a subterranean formation or wellbore. In addition, the well treating composition is useful in controlling the rate of release of scale inhibitor in the wellbore. The water-insoluble adsorbent may be activated carbon, silica particulate, precipitated silica, zeolite, diatomaceous earth, ground walnut shells, fuller's earth and organic synthetic high molecular weight water-insoluble adsorbents. The composite may be introduced into an oil or gas well with a carrier fluid.

Precipitated silica product with low surface area, dentifrices containing same, and processes

Abstract: Precipitated silica product having low surface area and enhanced flavor compatibility. The precipitated silica product is especially well-adapted for use in dentifrices containing cetylpyridinium chloride, which do not attach to the low surface area silica product in a meaningful level and thus remain available for antimicrobial action. Processes for making the low surface area silica product are also provided.

Polishing composition and polishing method

Abstract: A polishing composition contains silicon dioxide, an alkaline compound, and water. Silicon dioxide is, for example, colloidal silica, fumed silica, or precipitated silica. The alkaline compound is, for example, ammonium carbonate, potassium carbonate, sodium carbonate, ammonium hydrogen carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, ammonium phosphate, potassium phosphate, sodium phosphate, ammonium hydrogen phosphate, potassium hydrogen phosphate, or sodium hydrogen phosphate. The polishing composition can be suitably used in applications for polishing a glass substrate.

Precipitated silica product, dentrifices containing same, and processes

Abstract: Precipitated silica comprising porous silica particles having a cumulative surface area for all pores having diameters greater than 500 A of less than 8 m2/g, as measured by mercury intrusion, and a percentage cetylpyridinium chloride (% CPC) Compatibility of greater than about 55%. The precipitated silica product is especially well-adapted for use in dentifrices containing cetylpyridinium chloride, which do not attach to the low surface area silica product in a meaningful level and thus remain available for antimicrobial action. Processes for making the silica product are also provided.

Tire with low hydrocarbon emission rubber combination of tread and sidewall components with compositional limitations

Abstract: The invention relates to a tire of a structural combination of tire tread and sidewall components with compositional limitations containing minimal, if any, of in situ formed alcohol and methyl isobutyl ketone byproducts. The tread component rubber composition contains pre-hydrophobated silica reinforcement. The sidewall component contains low unsaturation EPDM or brominated copolymer of isobutylene and p-methylstyrene and may contain pre-hydrophobated silica reinforcement. The silica reinforcement for said tread and sidewall components is a pre-hydrophobated precipitated silica. The pre-hydrophobated silica is prepared, prior to mixing with the elastomer(s), by reacting hydroxyl groups (e.g. silanol groups) contained on the surface of a precipitated silica with an alkoxyorganomercaptosilane or a combination of an alkoxyorganomercaptosilane and a substituted alkylsilane or with a bis-3(trialkoxysilylalkyl) polysulfide which contains an average of from 2 to 4 connecting sulfur atoms in its polysulfidic bridge to form a composite thereof. The alcohol byproduct therefrom is removed from the composite prior to its introduction into the rubber composition(s). In another aspect of the invention, the connecting sidewall rubber composition, and optionally the tread composition is free of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine antidegradant (referred herein to as 6PPD) in order to prevent in situ formation of methyl isobutyl ketone byproduct from the reaction of 6PPD with atmospheric oxygen and/or ozone.

Slow release scale inhibitor composites and methods of using the same

Abstract: A well treating composition of a composite containing a scale inhibitor adsorbed onto a water-insoluble adsorbent is useful in the control, formation and treatment of inorganic scales in a subterranean formation or wellbore. In addition, the well treating composition is useful in controlling the rate of release of scale inhibitor in the wellbore. The water-insoluble adsorbent may be activated carbon, silica particulate, precipitated silica, zeolite, diatomaceous earth, ground walnut shells, fuller's earth and organic synthetic high molecular weight water-insoluble adsorbents. The composite may be introduced into an oil or gas well with a carrier fluid.

A novel process and appratus for the manufacture of precipitated silica from rice husk ash

Abstract: A novel process for the manufacture of precipitated silica from rice husk ash, having a surface area ranging from 50-400m2/g and tap density of 80-600kg/m3 having multiple applications in the field of rubbers and plastics, paints, toothpastes, catalyst, carrier agent, insulation, stabilizing and desiccants. The process method for silica precipitation is novel, wherein the chemicals used are regenerated making it a closed loop operation. The extraction process is carried out by digesting silica present in rice husk by the addition of sodium hydroxide to manufacture sodium silicate and precipitating silica from sodium silicate by reaction with carbon dioxide. The regeneration of the sodium hydroxide is carried out by reacting the sodium carbonate from the previous step with calcium oxide or calcium hydroxide.

High-cleaning/low abrasive silica and materials and dentifrice containing such materials

Abstract: Unique abrasive and/or thickening materials that are in situ generated compositions of precipitated silicas and silica gels are provided. Such compositions exhibit different beneficial characteristics depending on the structure of the composite in situ generated material. With low structured composites (as measured via linseed oil absorption levels from 40 to 100 ml oil absorbed/100 g composite), 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. Increased amounts of high structure composite materials tend to accord greater viscosity build and thickening benefits together with such desirable abrasion and cleaning properties, albeit to a lesser extent than for the low structure types. Thus, mid-range cleaning materials will exhibit oil absorption levels from an excess of 100 to 150, and high thickening/low abrasion composite exhibit oil absorption properties in excess of 150. Such an in situ, simultaneously produced precipitated silica/silica gel combination provides such unexpectedly effective low abrasion and high cleaning capability and different thickening characteristics as compared to physical mixtures of such components. Encompassed within this invention is a unique method for making such gel/precipitated silica composite materials for such a purpose, as well as the different materials within the structure ranges described above and dentifrices comprising such.

Highly-Structured Silica Having a Low Water Uptake, Preparation Method Thereof and Uses of Same

Abstract: The invention relates to a highly-structured precipitated silica having a low water uptake and high dispersibility in different pasty or solid matrices or media, elastomers or silicon, and to the preparation method thereof. The invention also relates to the use of said silica, for example, as a reinforcing filler in matrices based on elastomers (clear or semi-clear for shoe soles), in silicon matrices (in particular, for the coating of electric cables), as a filler and/or support and/or vehicle in different compositions (food compositions, cosmetic compositions, pharmaceutical compositions, compositions for the production of paints or paper, compositions for the production of porous membrane separators for batteries) or as a thickening agent in toothpastes.

Effects of mixing conditions on the reaction of 3‐octanoylthio‐1‐propyltriethoxysilane during mixing with silica filler and natural rubber

Abstract: The effects of mixing temperature and mixing time on the reaction of 3-octanoylthio-1-propyltriethoxysilane (NXT silane) during mixing with precipitated silica and natural rubber (NR) were investigated. Results showed that the reaction between NXT silane and precipitated silica can proceed at temperatures above 130°C. Because of the blocking group of NXT silane, the silane–NR coupling reactivity is low, so that the reaction of NXT silane with NR occurs only during the curing period. There is no reaction between NXT silane and NR during mixing, which showed that the mixing time of silica-filled NR compound containing NXT silane must be longer than 10 min at 150°C to obtain the desired silane coupling efficiency. With increasing mill temperature, the coupling efficiency increases. A high mixing temperature promotes improvement of silane–silica coupling efficiency, although the tensile strength, 100% modulus, 300% modulus, and hardness of NR vulcanizates decrease. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2295–2301, 2004

High-cleaning silica materials and dentifrice containing such

Abstract: Unique abrasive and/or thickening materials that are in situ generated compositions of precipitated silicas and silica gels are provided. Such compositions exhibit different beneficial characteristics depending on the structure of the composite in situ generated material. With low structured composites (as measured via linseed oil absorption levels from 40 to 100 ml oil absorbed/100 g composite), 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. Increased amounts of high structure composite materials tend to accord greater viscosity build and thickening benefits together with such desirable abrasion and cleaning properties, albeit to a lesser extent than for the low structure types. Thus, mid-range cleaning materials will exhibit oil absorption levels from an excess of 100 to 150, and high thickening/low abrasion composite exhibit oil absorption properties in excess of 150. Such an in situ, simultaneously produced precipitated silica/silica gel combination provides such unexpectedly effective low abrasion and high cleaning capability and different thickening characteristics as compared to physical mixtures of such components. Encompassed within this invention is a unique method for making such gel/precipitated silica composite materials for such a purpose, as well as the different materials within the structure ranges described above and dentifrices comprising such.

Viscosity-modifying silica materials that exhibit low cleaning and abrasive levels and dentifrices thereof

Abstract: Unique abrasive and/or thickening materials that are in situ generated compositions of precipitated silicas and silica gels are provided. Such compositions exhibit different beneficial characteristics depending on the structure of the composite in situ generated material. With low structured composites (as measured via linseed oil absorption levels from 40 to 100 ml oil absorbed/100 g composite), 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. Increased amounts of high structure composite materials tend to accord greater viscosity build and thickening benefits together with such desirable abrasion and cleaning properties, albeit to a lesser extent than for the low structure types. Thus, mid-range cleaning materials will exhibit oil absorption levels from an excess of 100 to 150, and high thickening/low abrasion composite exhibit oil absorption properties in excess of 150. Such an in situ, simultaneously produced precipitated silica/silica gel combination provides such unexpectedly effective low abrasion and high cleaning capability and different thickening characteristics as compared to physical mixtures of such components. Encompassed within this invention is a unique method for making such gel/precipitated silica composite materials for such a purpose, as well as the different materials within the structure ranges described above and dentifrices comprising such.

High-cleaning/moderate abrasive silica materials and dentifrice containing such materials

Abstract: Unique abrasive and/or thickening materials that are in situ generated compositions of precipitated silicas and silica gels are provided. Such compositions exhibit different beneficial characteristics depending on the structure of the composite in situ generated material. With low structured composites (as measured via linseed oil absorption levels from 40 to 100 ml oil absorbed/100 g composite), 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. Increased amounts of high structure composite materials tend to accord greater viscosity build and thickening benefits together with such desirable abrasion and cleaning properties, albeit to a lesser extent than for the low structure types. Thus, mid-range cleaning materials will exhibit oil absorption levels from an excess of 100 to 150, and high thickening/low abrasion composite exhibit oil absorption properties in excess of 150. Such an in situ, simultaneously produced precipitated silica/silica gel combination provides such unexpectedly effective low abrasion and high cleaning capability and different thickening characteristics as compared to physical mixtures of such components. Encompassed within this invention is a unique method for making such gel/precipitated silica composite materials for such a purpose, as well as the different materials within the structure ranges described above and dentifrices comprising such.

Preparation and characterization of functionalized precipitated silica SYLOID® 244 using ionic liquids as modifiers

Abstract: Studies were performed on the chemical modification of SYLOID® 244 (Grace) precipitated silica using ionic liquids. The unmodified and ionic-liquid-functionalized silica were subjected to a comprehensive physicochemical and dispersive evaluation. Particle size, polydispersity and specific surface area (BET) and porous structure were examined. Moreover, stability of the colloids obtained was evaluated by estimation of isoelectric points. The extent of modification and its type were defined using fourier transform infrared spectroscopy and 29Si-cross-polarization/magic angle spinning/nuclear magnetic resonance techniques. The modification was not observed to deteriorate the dispersive properties of the silica. The silicas obtained exhibited a restricted tendency to form larger accumulations of particles, i.e. aggregates and agglomerates. Moreover, application of ionic liquids with a heptyloxymethyl or octyloxymethyl substituent resulted in complete hydrophobization of the silica surface. Tested powders manifested the highest stability within a pH range of 10–12. Copyright © 2004 John Wiley & Sons, Ltd.

Influence of epoxidation on physical properties of SBR and its interaction with precipitated silica

Abstract: The introduction of epoxy groups on the main chain of polydiene has emerged as a fruitful route to monitor polymer-filler interactions leading to useful changes of physical properties of the vulcanisates. The in situ epoxidation reaction was chosen to modify polybutadiene and poly(butadiene-co-styrene), due to the easy control of the reaction even for small degrees of epoxidation. The extent of modification of the polymer chain was quantitatively accompanied by means of FT-IR and 1H-NMR spectroscopy. The shifts of the Tg's to higher temperatures with the increase of the epoxy content on the polymer chain was monitored using the DSC analysis. From the temperature and amplitude dependency of the dynamic moduli it can be concluded, that the interaction of the epoxidised rubber matrix with silica is greatly improved even for small contents of epoxy groups in the rubber chains.

Method for preparing silica suspension in optionally crosslinkable silicone matrix

Abstract: The invention relates to the preparation of a suspension of precipitated silica in a silicone oil, this suspension being usable for the production of silicones crosslinkable by polyaddition or polycondensation (RTV elastomers). The object of the invention is to seek a compromise between on the one hand the cost and on the other hand the rheology and mechanical properties of the final RTVs. The invention achieves this object by providing a process for the preparation of a suspension of precipitated silica, treated with hexamethyldisilazane (HMDZ), in a crosslinkable silicone oil. This HMDZ is introduced in at least two fractions. The 1st fraction on the one hand corresponds to a proportion less than or equal to 15% by dry weight, based on the total amount of HMDZ, and on the other hand is first brought into contact with the precipitated silica and the water. The invention further relates to the production of a silicone elastomer composition from this suspension and to the composition thus obtained.

Method for making precipitated silica or silicate compositions and products thereof

Abstract: New methods of producing narrower particle size distribution precipitated silica and/or silicate materials are provided. Such a method permits a significant reduction in manufacturing costs through the utilization of more efficient drying/evaporation components, in essence, in one potentially preferred embodiment, production of such silica and/or silicate materials followed directly by a hydraulic chamber press filtering step combined with vacuum dewatering subsequently leading to the needed resultant particle comminution. The resultant precipitated silicas and/or silicates produced thereby exhibit greater density prior to comminution and thus greater propensity for more uniform milling than previously utilized and prevalent spray/flash drying apparatuses. Also encompassed within this invention are the resultant precipitated silica and/or silicate particles produced, including those that surprisingly exhibit extremely high transmittance properties, thereby potentially providing excellent narrow particle distribution silica materials for clear (transparent) end-uses.

Hydrophobic precipitated silica for defoaming compositions

Abstract: Hydrophobically precipitated silica with a BET surface area of less than 110 m 2>/g, a cetyl trimethyl ammonium chloride (CTAB) surface area of less than 150 m 2>/g, a BET/CTAB ratio of less than 3, a carbon content of more than 3.1% and a pH of more than 9, is new. Independent claims are also included for: (1) producing hydrophobic precipitated silica by precipitating silica, filtering the precipitate, diluting the filter cake with water, adding a base, drying the suspension, heat-treating the product at a temperature above 150[deg]C and grinding the product, where a hydrophobizing agent is added to the silica or to a dispersion or filter cake comprising the silica; (2) hydrophobic precipitated silica produced as above.

Use of a pretreated precipitated silica as a reinforcing filler for silicone elastomer and curable compositions thus obtained

Abstract: The invention relates to the use of a precipitated silica, pretreated by at least one organosilane hydrophobing compound or one hydrophobing silicone oil, as a reinforcing filler for silicone elastomer, the said pretreated silica being incorporated in the silicone elastomer by cold mixing and having the following features : a BET specific surface ranging from 50 to 450 m2/g, a water wettability lower than 80, a sulfur content lower than 0.1 % by weight. The invention is directed to the curable silicone elastomer composition thus obtained.

Polymer mixture, useful for tire production, comprises precipitated silica and amino compound which reduces viscosity and improves processing properties

Abstract: Polymer mixture (A) comprises a crosslinkable and/or thermoplastic polymer (I); precipitated silicic acid (II) as filler; standard auxiliaries and additives for rubbers and plastics, and at least one amino compound (III) to reduce the viscosity of the mixture. (III) is an amino acid ester or amide; an N-acylamino acid (or ester or amide), or their reaction products with amines and diamines. An independent claim is also included for a method for reducing the viscosity of silicic acid-filled polymer mixtures by homogeneous incorporation of (III).

Precipitated silica for defoaming compositions

Abstract: Hydrophobic precipitated silica with a BET surface area of 100-190 m 2>/g, a modified Sears number (SN) of 8-20 ml/5 g, a BET/SN ratio of less than 0.12 ml/5 m 2> and a pH of more than 8 is new. Independent claims are also included for: (1) producing precipitated silica by precipitating silica, filtering the precipitate, diluting the filter cake with water, adding a base, drying the suspension and grinding the product; (2) precipitated silica produced as above.

Silane coupling agents for silica-filled tire-tread compounds: the link between chemistry and performance

Abstract: Therefore, it is necessary to reduce the filler-filler interaction and to enhance the compatibility of precipitated silica with hydrocarbon rubbers by modifying the surface of the silica. Bifunctional organo-silanes, such as bis(triethoxysilylpropyl)tetrasulfide (TESPT), are commonly used as coupling agents [7, 8]. The same type of compounds also enhance the rubber-metal bonding of sulphur-cured rubber polymers [9, 10].