EP2079662A2 - Dispersions aqueuses stables de dioxyde de silicium - Google Patents

Dispersions aqueuses stables de dioxyde de silicium

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Publication number
EP2079662A2
EP2079662A2 EP07821445A EP07821445A EP2079662A2 EP 2079662 A2 EP2079662 A2 EP 2079662A2 EP 07821445 A EP07821445 A EP 07821445A EP 07821445 A EP07821445 A EP 07821445A EP 2079662 A2 EP2079662 A2 EP 2079662A2
Authority
EP
European Patent Office
Prior art keywords
dispersion
silica
dispersions
silicon dioxide
dispersing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07821445A
Other languages
German (de)
English (en)
Inventor
Ulrich Fischer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Evonik Operations GmbH
Original Assignee
Evonik Degussa GmbH
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Filing date
Publication date
Application filed by Evonik Degussa GmbH filed Critical Evonik Degussa GmbH
Publication of EP2079662A2 publication Critical patent/EP2079662A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/141—Preparation of hydrosols or aqueous dispersions
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/141—Preparation of hydrosols or aqueous dispersions
    • C01B33/1415—Preparation of hydrosols or aqueous dispersions by suspending finely divided silica in water
    • C01B33/1417—Preparation of hydrosols or aqueous dispersions by suspending finely divided silica in water an aqueous dispersion being obtained
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/02—Granular materials, e.g. microballoons
    • C04B14/04—Silica-rich materials; Silicates
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material

Definitions

  • the invention relates to storage-stable dispersions of precipitated silica and / or silicates, a process for their preparation and their use.
  • Dispersions based on precipitated silica have already been described in the prior art.
  • the core theme of the publications of the prior art is the storage stability of the dispersions.
  • JP-OS-09142827 describes stable silica dispersions.
  • the storage stability of the dispersions disclosed in JP-OS-09142827 is achieved in that the mean particle size of the silica particles is less than 100 nm.
  • These dispersions have the disadvantage that it is very complicated and energy-intensive to grind silica particles to such small particle sizes.
  • the method described in JP-OS-09142827 should therefore not gain any technological relevance from an economic point of view.
  • EP 0368722, EP 0329509, EP 0886628 and EP 0435936 describe stabilizers stabilized dispersions of silicas.
  • the stabilizers are added inter alia to avoid deposits.
  • the stabilizers are, for example, biogum or a system of aluminum compounds and anionic dispersants or latex or finely divided solids that are chemically and physically compatible with the silica.
  • the use of such stabilizers is disadvantageous for reasons of cost as well as with regard to the subsequent use of the dispersions. It would therefore be desirable to be able to prepare dispersions which are storage-stable without stabilizers.
  • EP0768986 dispersions are described without stabilizer. However, the examples show that the dispersions described in EP 0768986 are not sufficiently stable on storage, but an increase in viscosity by a factor of 10 can already be observed after 10 days.
  • Dispersions are disclosed in US 2004/0079504.
  • doped silicas d. H. Silicas on whose surfaces an at least divalent metal ion is bound suspended. This is disadvantageous insofar as initially specially doped silicas must be prepared. This requires on the one hand additional work steps (doping), on the other hand, the costs of production are increased.
  • Silica dopants are also derived from ecological, d. H. z. B. wastewater aspects disadvantageous.
  • the object of the present invention was therefore to provide silica dispersions and a process for their preparation, which have at least some disadvantages of the prior art dispersions, or only to a reduced extent.
  • silica particles in the dispersion have a very small, but again not too small average particle size, the pH of the dispersion in the slightly alkaline to alkaline range is set and the zeta potential of the dispersions is sufficiently low.
  • the present application thus provides silica dispersions and a process for their preparation as defined and described in the claims, the description and the examples of the present application.
  • the present invention relates, in particular, to dispersions containing at least one silicon iodide, characterized in that
  • the silica preferably a precipitated silica and / or a silicate, has a BET surface area greater than 50 m 2 / g,
  • the silica agglomerates in the dispersion have an average particle size d 50 of from 130 to 800 nm,
  • the pH of the dispersion is> 8
  • the zeta potential of the dispersion at pH 9 is less than - 20 mV.
  • the subject of the present invention is also a
  • Process for the preparation of dispersions containing at least one silicon dioxide characterized in that silicon dioxide particles, preferably precipitated silica and / or a silicate, are ground and dispersed in such a way by means of a suitable dispersing aggregate and the pH of the dispersion is adjusted in the course of the process such that the mean particle size d 5 o of the silica particles in the dispersion is between 130 and 800 nm, the pH of the dispersion is> 8 and the zeta potential of the dispersion at pH 9 is less than -20 mV.
  • the invention also relates to the use of the silicas according to the invention
  • the dispersions of the invention are characterized in that they are stable on storage without the addition of stabilizers. This means that on dispersions of the
  • the dispersions according to the invention show no tendency or very little tendency to sedimentation. Ie. It is usually not necessary to stir up deposits before use again or subject the dispersion to a constant stirring process.
  • the dispersions of the invention also have the advantage that they can be prepared without any, possibly interfering with the application additives. As a result, new areas of application can be developed, which previously were not accessible due to the disturbing effects of the stabilizers.
  • Another advantage of the dispersions of the invention is the fact that the average particle size during storage remains largely unchanged, ie no product change, eg. B. by reagglomeration, can be determined.
  • the performance characteristics of the dispersions of the invention meet the necessary requirements such as good storage stability and ease of use.
  • silica or silica particles are preferably precipitated silicas and / or silicates. Particular preference is given to precipitated silicas.
  • Precipitated silica may have BET surface areas up to 800 m 2 / g and is obtained by reaction of at least one silicate, preferably an alkali and / or
  • Erdalkalisilicats with at least one acidifier, preferably at least one mineral acid.
  • at least one acidifier preferably at least one mineral acid.
  • precipitated silicas do not consist of a uniform three-dimensional SiO 2 network but of individual aggregates and agglomerates.
  • a special feature of precipitated silica is the high proportion of such called inner surface, which is reflected in a very porous structure with micro and mesopores.
  • Precipitated silicas differ from pyrogenic silicas, which are also referred to as aerosils (see Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. A23, pp. 635-642). Pyrogenic silicic acids are obtained by flame hydrolysis of silicon tetrachloride. Due to the completely different production process, fumed silicas have, inter alia, a different surface finish. This expresses z. In the lower number of silanol groups on the surface. The behavior of fumed silicas and precipitated silicas in aqueous dispersions, which is mainly determined by the surface properties, therefore can not be compared. Precipitated silicic acid white compared to Among other things, the advantage of pyrogenic silicic acids is that they are considerably less expensive.
  • the dispersions according to the invention are preferably aqueous dispersions, ie at least one constituent, particularly preferably the main constituent, the liquid phase is water, preferably deionized water.
  • the dispersions according to the invention preferably contain no further liquid additives, especially not those which prevent the sedimentation of the silica particles.
  • the dispersions according to the invention contain no further additives in addition to water and silicon dioxide. It is possible that the dispersions of the invention contain the silica as a single solid. This may be useful, in particular, if the dispersions are to serve as masterbatch for various applications.
  • Dispersions of silicon dioxide present are preferably in the range from 50 to 800 m 2 / g, more preferably in the range from 50 to 500 m 2 / g, preferably in the range from 50 to 250 m 2 / g. This is necessary to ensure a high interaction with the surrounding medium.
  • the BET surface area is not measured on individual particles but corresponds to the total surface area of all particles contained in the measured sample, normalized to 1 gram. If several different silicas are present in the dispersions according to the invention, the BET surface does not correspond to the BET surface area of the individual silicas used to prepare the dispersions, but to the total surface area of all particles measured on a representative sample of the dispersion normalized to 1 gram. In this case, the previously mentioned preferred ranges for the BET surface also apply.
  • the average particle size d 5 o of the silica agglomerates of the dispersion according to the invention in the range of 130 to 800 nm, preferably from 150 to 600 nm, particularly preferably from 150 to 450 nm, in particular preferably from 150 to 400 nm, very particularly preferably from 170 to 300 nm and particularly preferably from 180 to 300 nm. Values below 130 nm are technically very expensive to produce.
  • the pH of the dispersions of the invention has an effect especially stabilizing on the
  • Sedimentationseigenschaften of the dispersion is in the range of greater than 8, preferably 8.0 to 14, more preferably 8.5 to 12, most preferably 8.7 to 10 and particularly preferably 9 to 9.5.
  • the zeta potential of the dispersions of the invention is an important criterion for their storage stability.
  • the zeta potential is a measure of the surface charge of the particles and describes the charge interaction between a liquid and the particle surface.
  • the zeta potential is strongly dependent on the pH of the dispersion and can therefore be compared only at the same pH values. The inventors have found that the
  • the dispersions of the invention have a proportion of silicon dioxide of 5 to 50 wt .-%, based on the
  • the silicon dioxide content is particularly preferably from 10 to 50% by weight, very particularly preferably from 20 to 40% by weight and particularly preferably from 20 to 35% by weight.
  • Lower silica dispersions typically show better stability than higher filled dispersions. Dispersions containing less than 5% by weight of silica are not economical due to the high water content.
  • the viscosity of the dispersions according to the invention is therefore preferably less than 500 mPas, particularly preferably from 0.1 to 250 mPas, very particularly preferably from 1 to 100 mPas and particularly preferably from 1 to 50 mPas.
  • the dispersions are first dried in a drying oven and the dried silicon dioxide particles are subsequently examined by means of mercury porosimetry. More detailed information on how to carry out the measurements can be found in the description of the measuring methods further down.
  • the silica particles have a pore volume of the pores with a particle size of 10-1000 nm in the range from 0.05 to 1.0 ml / g, preferably 0, 1 to 0.75 ml / g preferably 0.15 to 0.6 ml / g and most preferably 0.2 to 0.55 ml / g.
  • the pore maximum of the silica particles in the range of 5 - 50 nm, preferably 5 to 40 nm, wherein in a first alternative embodiment, the pore maximum in the range of 5 to 20 nm, preferably 7 to 15 nm and in a second alternative embodiment, the pore maximum is in the range of 20 to 40 nm, preferably 25-35 nm.
  • the dispersions according to the invention can be prepared by a process in which silicon dioxide particles up to an average particle size d.sub.50 are between 130-800 nm, preferably 150-600 nm, more preferably 150-450 nm, particularly preferably 150-400 nm and most preferably 180-50 300 nm are ground so that it is a dispersion having a zeta potential at pH 9 of less than -20 mV, preferably -20 to -45 mV, more preferably -25 to -40 mV, most preferably -30 to -40 mV and a pH> 8, preferably 8.0 to 14, particularly preferably 8.5 to 12, very particularly preferably 8.7 to 10 and particularly preferably 9 to 9.5 are obtained.
  • This method preferably comprises at least some of the following steps:
  • a predispersion is prepared.
  • silica particles are dispersed in a liquid component, preferably water, more preferably deionized water.
  • a filter cake ie not to dry the silica particles first.
  • This second embodiment of the method according to the invention is of course compared with economic advantages. connected to the first embodiment. Any mixed forms These two embodiments are also possible, ie it is possible to redisperse a filter cake and then add dried silica and vice versa. It is also possible to prepare base dispersions of mixtures of at least two different silicas.
  • the preparation of the predispersions is carried out in a manner known per se by means of suitable dispersing aggregates.
  • the dispersion of the silica powder can be carried out in apparatuses which introduce a comparatively low shear energy into the system (e.g., dissolvers, rotor-stator systems).
  • a comparatively low shear energy e.g., dissolvers, rotor-stator systems.
  • a basic component or an acidifier preferably an alkali metal or alkaline earth metal hydroxide or organic bases or ammonia.
  • any acidic agent can be used as acidulant, for. As mineral acids, organic acids.
  • silica whose pH is already adjusted so that the silica itself adjusts the pH of the dispersion to the desired value, i. H.
  • Step b) can be omitted.
  • the pH of the silica in one of the production steps of the silica for example during the precipitation or during drying, can be adjusted by adding suitable basic or acidic agents.
  • suitable basic or acidic agents for example during the precipitation or during drying.
  • the predispersion whose pH has been adjusted accordingly, is comminuted in step c) by means of a suitable aggregate.
  • any suitable dispersing aggregate can be used, provided that it is suitable for influencing the structure and surface of the silicon dioxide in such a way that the zeta potential and, in the particular embodiment, the pore volume are in the appropriate range.
  • the energy input is sufficient to disperse the precipitated silica powder or the filter cake so that the agglomerates have an average particle size of 130 to 800 nm after the dispersion.
  • specific energy inputs of between 0.01 and 10 kWh / kg are required.
  • methods with high power density and low residence time processes with low power density and high residence time and intermediate forms can be used in principle.
  • High-pressure systems such as Nanomizer, Microfluidizer and other nozzle systems, in which the dispersion flows through a nozzle under high pressure of up to 50 to 5000 bar and is dispersed by the energy dissipation in and after the nozzle, achieve very high energy inputs of already 5,000 kJ in a single passage / m 3 to 500,000 kJ / m 3 .
  • Agitator mills lead to significantly lower specific energy inputs per passage of 5 to 500 kJ / m 3 . In order to achieve sufficient particle fineness, the dispersion must be much more frequently the mill happen, resulting in much higher
  • the inventors have found that it is advantageous not to carry out the milling in a high pressure system, i. H. To perform a system with high power density and low residence time, but in a system with low power density and high residence time.
  • This finding explains the fact why in JP-OS-09-142827, there was the milling with a high pressure system, dispersions with particle sizes of the silica particles from 120 to 390 nm did not have sufficient storage stability.
  • the dispersions prepared by the process according to the invention showed good storage stability with the same particle size of the silicas.
  • the type of grinding apparently influences the structure of the resulting silica particles in such a way that the stability of the dispersions is significantly influenced.
  • shearing energies of> 1000 kJ / m 3 should advantageously be applied. Particularly good results are achieved with agitator ball mills, high pressure homogenizers or
  • ball mills in particular stirred ball mills.
  • the flow of product through the mill can be in pendulum or in
  • the circulation rate can vary from 10 to 300 kg / h and is advantageously in the range from 25 to 200 kg / h, more preferably in the range from 50 to 150 kg / h and particularly preferably in the range of 80-120 kg / h.
  • the agitator may be in the form of disks, pins, pin-to-pin arrangements, an annular gap, or the like.
  • a disk arrangement is preferred.
  • the grinding time depends on the dispersibility of the product and the amount used for 10 minutes to 80 hours, preferably 0.5 to 50 hours, more preferably 1 to 25 hours and particularly preferably 5 to 15 hours. As a result, specific energy inputs (based on kg dispersion) of 0.01 to 10 kWh / kg can be achieved.
  • the grinding media may consist of glass, aluminum oxide, zirconium oxide or other inorganic oxides as well as various mixtures of inorganic oxides. Due to the high density, it is advantageous to use zirconium oxide grinding bodies which are stabilized against abrasion by means of yttrium oxide.
  • the size of the grinding media can vary from 20 ⁇ m to a few mm, advantageously grinding bodies of the size from 0.02 to 10 mm, particularly preferably from 0.05 to 5 mm, very particularly preferably from 0.1 to 1 mm and particularly preferably from 0.2 to 0, 4 mm used.
  • the MahlSystem refllgrad, based on the free volume of the grinding chamber can vary from 60 to 99%, preferably 70 to 95%, more preferably 80 to 95% and most preferably 90 to 95%.
  • the peripheral speed of the grinding tool can vary from 1 m / s to 15 m / s, preferably 5 m / s to 15 m / s, more preferably 8 m / s to 12 m / s.
  • the dispersion is concentrated to the desired silica content.
  • This concentration can be carried out by any technique known to the person skilled in the art, for example by Reduction of the liquid medium such. Example by vacuum evaporation, cross-flow filtration, continuous or discontinuous centrifugation, filtration, or by increasing the solids content.
  • any precipitated silica or silicate can be used.
  • the choice of silica or silicate is essentially dependent on the intended application of the dispersion. So it may be z. B. be necessary for dispersions of paper lines to use very absorbent réelleskieselklaren. Examples are silicic acids with a DBP> 150 g / 100g. If the dispersion z. B. in the field of construction chemistry, z. B. are used as concrete admixtures, so are particularly suitable starting silicas or silicates with a BET surface area> 150 m 2 / g. Examples include Sipernat 160 ® and Sipernat 312 ® AM.
  • the dispersions of the invention can be used
  • dispersions of the invention preferably without any additives such.
  • additives such as stabilizers, dispersants, preservatives are used, it is of course not excluded, such additives of Add dispersion and thus adapt the dispersions to specific application requirements.
  • dispersions according to the invention are stable even without stabilizers.
  • the determination of the particle distribution of the dispersions of the invention is carried out according to the principle of laser diffraction on a laser diffractometer (Horiba, LA-920).
  • a sample of the silica dispersion is removed with stirring, transferred to a beaker and diluted by the addition of water without the addition of dispersing additives so that a dispersion having a weight fraction of about 1 wt .-% SiÜ2 is formed.
  • a dispersion having a weight fraction of about 1% by weight of SiO 2 is prepared by stirring the powder in water.
  • the particle size distribution is determined from a partial sample of the dispersion with the laser diffractometer (Horiba LA-920). For the measurement a relative refractive index of 1.09 has to be chosen. All measurements are carried out at room temperature. The particle size distribution and the relevant variables such. B. the average particle size d 5 o are automatically calculated by the device and displayed graphically. The instructions in the operating instructions must be observed. Determination of the BET surface area
  • silica is not present as a solid but in aqueous dispersion, the following sample preparation must be carried out before the BET surface area is determined:
  • the silica dispersion 100 ml of the silica dispersion are removed with stirring, transferred to a porcelain dish and dried for 72 h at 105 0 C. To remove organic components, the dried silica is heated to 500 ° C. for 24 h. After the silica sample has cooled, it is comminuted with a spatula and the BET surface area determined.
  • the BET surface area of silica as a solid is determined according to ISO 5794-1 / Annex D with the TRISTAR 3000 device (Micromeritics) after the multipoint determination in accordance with DIN ISO 9277.
  • the pH of the aqueous dispersions is based on DIN EN ISO 787-9 at 20 0 C. To determine the pH, the dispersions are diluted with water to a weight fraction of 5 wt .-% SiO 2 and measured at room temperature.
  • a 5% aqueous dispersion is prepared (5.00 g of silica to 100 ml of deionized water).
  • the moisture content of silica is determined according to ISO 787-2 after 2 hours of drying in a convection oven at 105 ° C. This drying loss consists predominantly of water moisture. Determination of the loss on ignition
  • DBP number which is a measure of the absorbency of the precipitated silica
  • dibutyl phthalate is added dropwise at room temperature through the "Dosimaten Brabender T 90/50" dibutyl phthalate into the mixture at a rate of 4 ml / min Towards the end of the determination, the mixture becomes pasty as indicated by a steep increase in power demand, and when 600 digits (torque of 0.6Nm) are displayed, an electrical contact will cause both kneader and DBP dosing
  • the synchronous motor for the DBP supply is coupled to a digital counter, so that the consumption of DBP in ml can be read.
  • the DBP recording is given in q / (100 g) and calculated using the following formula:
  • V consumption of DBP in ml
  • the DBP uptake is defined for anhydrous, dried silica. If moist precipitated silicas are used, the correction value K must be taken into account for calculating the DBP absorption. This value can be determined from the following correction table, eg. For example, a water content of the silica of 5.8% would mean a 33 g / (100 g) addition for DBP uptake.
  • the moisture content of the silicic acid is determined according to the method "Determination of moisture or loss of drying".
  • the determination of the tamped density is based on DIN EN ISO 787-11.
  • a defined amount of a previously unsorted sample is filled into a graduated glass cylinder and subjected to a fixed number of stacks by means of a tamping volumeter. During the stamping, the sample condenses. As a result of the examination, the tamped density is obtained. The measurements are carried out on a tamping volumeter with counter from Engelsmann, Ludwigshafen, type STAV 2003.
  • a 250 ml glass cylinder is tared on a precision balance.
  • 200 ml of silica are filled with the aid of a Pulvertrichters so in the tared measuring cylinder that form no voids. This is achieved by tilting and rotating the cylinder about its longitudinal axis during filling.
  • the sample quantity is then weighed to the nearest 0.01 g. Thereafter, lightly tapping the cylinder so that the surface of the silica in the cylinder is horizontal.
  • the measuring cylinder is inserted into the measuring cylinder holder of the tamping volumeter and tamped 1250 times.
  • the volume of the mashed sample is read to 1 ml after a single ramming pass.
  • the tamped density D (t) is calculated as follows:
  • V volume of silica after pounding [ml]
  • the determination of the SiC ⁇ content is carried out according to ISO 3262-19 Determination of Al and Na content
  • Al2O3 The determination of the Al content is carried out as Al2O3, the Na content as Na2Ü. Both determinations are carried out according to ISO 3262-18 by means of flame atomic adsorption spectroscopy.
  • the measuring device Rheo Stress 600 from Haake is used.
  • the sensor is a DC 60/2 ° Ti (double cone) with a gap of 0.092 mm.
  • the temperature control during the measurement takes place via the internal temperature control unit and is controlled by the program.
  • the shear rate is continuously increased from 0.001 l / s to 100 l / s within 10 minutes and then likewise continuously ramped down from 100 l / s to 0.001 l / s within 10 minutes.
  • the measurement is carried out according to the operating instructions. When the measurement is complete, the measurement data is displayed via the integrated software.
  • a DT 1200 electroacoustic spectrometer from Quantachrom GmbH is used.
  • a pH electrode BK511071 from Beckmann Instruments, Inc. is used.
  • About 120 ml of the dispersion to be measured are placed in a 200 ml jacketed vessel and heated to 20 ° C. The measurement is done with constant stirring with a magnetic fish.
  • the electroacoustic spectrometer In the lid of the jacketed vessel are the electroacoustic spectrometer, the pH electrode, a thermocouple and a cannula for dosing a 1 mol / 1 nitric acid or for dosing a 1 mol / 1 potassium hydroxide solution. All components immerse about 1 cm in the dispersion.
  • the zeta potential is automatically determined with the addition of nitric acid in a pH range of 10 to 3.
  • the mercury porosimetric data are determined by means of Hg intrusion in accordance with DIN 66133 (with a surface tension of 480 mN / m and a contact angle of 140 °).
  • silica dispersion 100 ml of the silica dispersion are removed with stirring, transferred to a porcelain dish and dried for 72 h at 105 0 C. To remove organic components, the dried silica is heated to 500 ° C. for 24 h. After the silica sample has cooled, it is comminuted with a spatula and Hg porosimetry is carried out.
  • the silica is subjected to a pressure treatment before the measurement.
  • a Manual Hydraulic Press Order No. 15011 from Specac Ltd., River House, 97
  • silica are weighed into a "pellet die" with an inner diameter of 13 mm from Specac Ltd. and, as indicated charged with 1 t. This load is held for 5 s and readjusted if necessary. The sample is then relaxed and dried for 4 h at 105 ⁇ 2 0 C in a convection oven.
  • the silica is weighed into the penetrometer of type 10 to a precision of 0.001 g and, for a good reproducibility of the measurement, is chosen so that the stem volume used, ie the percentage Hg volume used to fill the penetrometer, is 20% to 40%.
  • the penetrometer is then slowly evacuated to 50 ⁇ m Hg and left at this pressure for 5 min.
  • the operation of the Autopore device is carried out according to the operating instructions with the software version IV 1.05. Each measurement is corrected by one empty measurement of the penetrometer.
  • the measuring range is 0.0025 - 420 MPa, whereby at least 136 equilibrium measurement points (device specific criterion of 10 s) are used (in the range 0.0025 - 0.25 MPa: 30 points, in the range 0.25 - 15 MPa: 53 points, 15 - 150 MPa: 40 points, in the range 150 - 420 MPa: 13 points). Possibly. If the incremental intrusion volume is> 0.04 ml / g, the software inserts additional measurement points. The smoothing of the intrusion curve takes place by means of the "smooth differentials" function of the device software.
  • the dispersions are prepared in a stirred ball mill (LME 4, Netzsch).
  • the grinding chamber and the disk agitator are made of abrasion-resistant ceramic (Al 2 O 3 or ZrCb).
  • the grinding balls of yttrium-stabilized ZrC> 2 have a diameter of 0.2 to 0.4 mm and fill the grinding chamber to 90% (8.84 kg ).
  • step a) a predispersion, wherein 22.5 kg of deionized water in a 501 container with
  • step b) the pH of the dispersion - if necessary (Examples 1 and 2) - is adjusted to 9 with KOH.
  • Example 3 and 4 the pH of the dispersion automatically adjusted to 9 due to the pH of the silica. The pH is checked regularly and readjusted if necessary.
  • the dispersion in a step c) is circulated through the ball mill.
  • the peripheral speed remains constant at 10 m / s and the throughput at approximately 100 kg / h.
  • the concentration of the dispersion of SiO 2 is further increased by adding further silicic acid in the feed container in portions, the mill also being operated in the circulation. Examples 1 - 4
  • Example 4 In Examples 1 to 3 precipitated silicas, in Example 4, a silicate are used.
  • silica according to Example 1 Sipernat 160 ® (Messrs. Degussa AG).
  • silica according to Example 2 is the commercial product Sipernat 312 AM ® Degussa AG.
  • the silica from Example 3 is Sipernat 360 ® also from Degussa AG.
  • the aluminum silicate Sipernat 820 A ® Degussa AG was used.
  • the physico-chemical parameters of the silicas or silicates used for the preparation of the dispersions are given in Table 1.
  • the average particle sizes of the dispersions of Examples 1 to 3 shown in Table 3 show that they did not change after 3 or 7.
  • the observed differences in the absolute measured values are within the scope of the natural error fluctuations. Ie. with regard to the average particle size, the dispersions are storage-stable.
  • Example 2 is a
  • Example 4 again showed a very slight increase in viscosity. With a value of 22 mPas, however, the viscosity is still in an outstanding range even after 7 days at 50 ° C., so that no impairment of the applicability of the dispersions could be ascertained. Redispersion or liquefaction is itself Not necessary after 7 days storage at 50 ° C., all dispersions can be used immediately.
  • the zeta potential on day 1 ie, the date of manufacture of the dispersions before hot storage, and on day 3 and day 7 of storage at 50 0 C determined.
  • the zeta potential was determined in each case as a function of a pH curve, and the zeta potential at pH 9 was derived from the function of a regression polynomial set by the measured values.
  • this procedure was also applied to the measurement on the third day.
  • individual measurements at pH values close to 9 were performed on the third day instead of a measurement with pH curve. On day 7, in all examples 6 to 9, only individual measurements were carried out at pH values close to 9.
  • a graphic plot of the individual measured values of the respective measurements can be taken from FIGS. 1 to 4.
  • Table 5 as extracts from FIGS. 1 to 4, the zeta potentials determined by means of regression polynomials, which were determined by the individual measured values, are shown at pH 9 or, if no measurement with a pH curve was made, the zeta potentials of the individual measurements.
  • Figures 1 to 4 and Table 5 show that the zeta potentials of Examples 6 to 9 have not or only slightly changed during the hot storage.
  • the zeta potential is a measure of the surface charge of the silicas.
  • FIGS. 1 to 4 show that the dispersions according to the invention have a sufficiently negative zeta potential in order to repel each other so strongly that no coagulation of the Particles takes place and thus sedimentation is avoided. Since this Zetapotential does not or only insignificantly changes even after 7 days of warm storage, the storage stability of the dispersions of the invention is confirmed even at high solids contents.
  • Table 5 Zeta potentials of the dispersions according to Examples 6 to 9 at the respectively indicated pH values (RP means that this value was determined from a regression polynomial which was defined by the measured values marked in FIGS. 1 to 4)

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Civil Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Silicon Compounds (AREA)
  • Silicates, Zeolites, And Molecular Sieves (AREA)
  • Pigments, Carbon Blacks, Or Wood Stains (AREA)

Abstract

L'invention concerne des dispersions de dioxyde de silicium stables au stockage. L'invention concerne également un procédé pour la production de ces dispersions, ainsi que l'utilisation de ces dispersions en tant qu'adjuvant de béton dans l'industrie du bâtiment et pour la production ou le couchage du papier dans l'industrie papetière.
EP07821445A 2006-10-20 2007-10-17 Dispersions aqueuses stables de dioxyde de silicium Withdrawn EP2079662A2 (fr)

Applications Claiming Priority (2)

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DE102006049526A DE102006049526A1 (de) 2006-10-20 2006-10-20 Stabile wässrige Dispersionen von Siliciumdioxid
PCT/EP2007/061080 WO2008046854A2 (fr) 2006-10-20 2007-10-17 Dispersions aqueuses stables de dioxyde de silicium

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EP2079662A2 true EP2079662A2 (fr) 2009-07-22

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EP (1) EP2079662A2 (fr)
JP (1) JP5550344B2 (fr)
KR (1) KR101402511B1 (fr)
CN (2) CN104692396A (fr)
DE (1) DE102006049526A1 (fr)
WO (1) WO2008046854A2 (fr)

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CN103922352A (zh) * 2014-03-30 2014-07-16 苏州奈微纳米科技有限公司 纳米二氧化硅分散体及其制备方法
US11236002B2 (en) 2015-12-18 2022-02-01 Heraeus Quarzglas Gmbh & Co. Kg Preparation of an opaque quartz glass body
TWI813534B (zh) 2015-12-18 2023-09-01 德商何瑞斯廓格拉斯公司 利用露點監測在熔融烘箱中製備石英玻璃體
US11492285B2 (en) 2015-12-18 2022-11-08 Heraeus Quarzglas Gmbh & Co. Kg Preparation of quartz glass bodies from silicon dioxide granulate
TWI720090B (zh) 2015-12-18 2021-03-01 德商何瑞斯廓格拉斯公司 於石英玻璃之製備中作為中間物之經碳摻雜二氧化矽顆粒的製備
CN108698885A (zh) 2015-12-18 2018-10-23 贺利氏石英玻璃有限两合公司 石英玻璃制备中硅含量的提升
US10618833B2 (en) 2015-12-18 2020-04-14 Heraeus Quarzglas Gmbh & Co. Kg Preparation of a synthetic quartz glass grain
KR20180095622A (ko) 2015-12-18 2018-08-27 헤래우스 크바르츠글라스 게엠베하 ＆ 컴파니 케이지 내화성 금속으로 제조된 용융 도가니에서 실리카 유리 제품의 제조
EP3390304B1 (fr) 2015-12-18 2023-09-13 Heraeus Quarzglas GmbH & Co. KG Granulation par pulverisation de dioxyde de silicium lors de la fabrication de verre de quartz
JP7048053B2 (ja) 2015-12-18 2022-04-05 ヘレウス クワルツグラス ゲーエムベーハー ウント コンパニー カーゲー マルチチャンバ炉内での石英ガラス体の調製
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Publication number Publication date
CN104692396A (zh) 2015-06-10
WO2008046854A3 (fr) 2008-06-12
DE102006049526A1 (de) 2008-04-24
JP2010506814A (ja) 2010-03-04
US20100319582A1 (en) 2010-12-23
KR20090079961A (ko) 2009-07-22
WO2008046854A2 (fr) 2008-04-24
JP5550344B2 (ja) 2014-07-16
US8545618B2 (en) 2013-10-01
KR101402511B1 (ko) 2014-06-03
CN101568491A (zh) 2009-10-28

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