Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
  • C09C3/08—Treatment with low-molecular-weight non-polymer organic compounds
• • 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
  • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
• • 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
  • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
  • C01B33/181—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process
  • C01B33/183—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process by oxidation or hydrolysis in the vapour phase of silicon compounds such as halides, trichlorosilane, monosilane
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F17/00—Compounds of rare earth metals
  • C01F17/20—Compounds containing only rare earth metals as the metal element
  • C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
  • C01F17/218—Yttrium oxides or hydroxides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F17/00—Compounds of rare earth metals
  • C01F17/20—Compounds containing only rare earth metals as the metal element
  • C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
  • C01F17/224—Oxides or hydroxides of lanthanides
  • C01F17/235—Cerium oxides or hydroxides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
  • C01G23/04—Oxides; Hydroxides
  • C01G23/047—Titanium dioxide
  • C01G23/07—Producing by vapour phase processes, e.g. halide oxidation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G9/00—Compounds of zinc
  • C01G9/02—Oxides; Hydroxides
  • C01G9/03—Processes of production using dry methods, e.g. vapour phase processes
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/0096—Compounds of antimony
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/04—Compounds of zinc
  • C09C1/043—Zinc oxide
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/28—Compounds of silicon
  • C09C1/30—Silicic acid
  • C09C1/3081—Treatment with organo-silicon compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/36—Compounds of titanium
  • C09C1/3607—Titanium dioxide
  • C09C1/3684—Treatment with organo-silicon compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
  • C09C3/12—Treatment with organosilicon compounds

Definitions

• the invention relates to a process for surface modification of metal oxide particles, and to the metal oxide particles obtainable by the process
• a surface modification can be performed by dispersing the unmodified powder in the presence of at least one organic compound which possesses at least one functional group which can react and/or interact with groups present on the surface of the powder particles in water and/or an organic solvent, and then optionally fully or partly removing the liquid phase.
• processes with which especially pyrogenic metal oxide particles can be surface-modified proceed from metal chlorides which are evaporated and combusted with hydrogen and air to form metal oxide particles.
• the metal oxide particles are sprayed with a surface-modifying reagent while mixing vigorously, and then heat-treated at a temperature of 100 to 400°C over a period of 1 to 6 hours.
• One variant of this process envisages mixing the metal oxide particles very substantially homogeneously with an organohalosilane while excluding oxygen, and heating the mixture together with small amounts of steam to temperatures of 200 to 800°C in an upright tubular oven in a continuous cocurrent process.
• a surface modifier is introduced into a gas stream comprising metal oxide particles, and the resulting reaction mixture is exposed to a temperature of 130 to 250°C, preferably of 150 to 230°C, more preferably of 170 to 210°C, for a minimum residence time in the range from 1 to 60 s, preferably 2 to 30 s, more preferably 5 to 10 s, and
• the solid reaction products are removed from the flowing reaction mixture by means of a filter apparatus and the reaction mixture present at the filter is treated at a temperature of 1 10 to 230°C, preferably 130 to 180°C, more preferably 140 to 150°C, for a minimum residence time in the range from 1 min to 1 hour, preferably 10 to 40 min, more preferably 20 to 30 min.
• minimum residence time shall be understood to mean that each particle is exposed to the conditions at least over this period.
• the mean residence time shall be determined by the quotient of the volume of the surface modification zone and the volume flow rate.
• the metal oxide particles used may be subjected beforehand to a steam treatment at temperatures of 200 to 700°C. This may be advisable when impurities removable with steam, such as halides, are to be removed.
• the metal oxide particles according to the invention are those which bear, on their surface, reactive groups which are suitable for entering into a covalent, ionic or coordinate bond with a surface modifier.
• these groups are hydroxyl groups.
• the attachment of the surface modifier may comprise all or only some of the reactive groups available.
• the process according to the invention allows the surface modification of metal oxide particles irrespective of their structure.
• the particles may be present as isolated individual particles and/or as aggregates of joined individual particles.
• the metal oxide particles may be those comprising one, two or more than two metal
• the particles comprising two or more metal components are mixed metal oxide particles wherein the particular proportions of the metal oxide components are not limited.
• coated or partly coated metal oxide particles are also understood to be mixed oxide particles.
• Mixed oxide particles are understood to mean those in which there is intimate mixing of the metal components at the atomic level.
• the origin of the metal oxide particles is unimportant for the performance of the process according to the invention, provided that the metal oxide particles bear reactive groups at the surface thereof.
• metal oxide particles obtainable by precipitation, sol-gel processes, hydrothermal synthesis or pyrogenic processes can be used. As explained later, it may be advantageous to use pyrogenic metal oxide particles.
• "Pyrogenic” is understood to mean hydrolysis, oxidation or a reaction sequence in which both types occur alongside one another, in which metal compounds are hydrolysed and/or oxidized in the gas phase, generally in a flame.
• the flame may be obtained, for example, by the reaction of hydrogen and oxygen. This firstly forms finely divided, nonporous primary particles, which become joined together later in the reaction to form aggregates.
• the BET surface area of these primary particles is between 5 and 600 m 2 /g.
• Pyrogenic metal oxide particles are very substantially free of inner pores and have hydroxyl groups on their surfaces.
• the metal oxide particles are preferably selected from the group consisting of aluminium oxide, antimony oxide, cerium oxide, iron oxide, indium oxide, silicon dioxide, titanium dioxide, vanadium oxide, tungsten oxide, yttrium oxide, zinc oxide, tin oxide and zirconium dioxide. Silicon dioxide shall be considered to be a metal oxide in the context of the invention.
• a process for producing surface-modified metal oxide particles in which in a reactor which comprises, in each case successively, a mixing zone, a combustion zone, a cooling zone, a surface modification zone and a removal zone,
• a stream comprising one or more hydrolysable and/or oxidizable metal compounds in the form of vapour or of an aerosol, one or more hydrogen-containing combustion gases and
• an oxygen-containing gas is obtained, b) this gas is transferred into the combustion zone, ignited there and reacted at a mean residence time of 10 ms to 10 s, preferably 100 ms to 5 s, more preferably 1 s to 5 s,
• a surface modifier is introduced into the stream of the reaction mixture, and the resulting reaction mixture is exposed to a temperature of 130 to 250°C, preferably of 150 to 230°C, more preferably of 170 to 210°C, for a minimum residence time in the range from 1 to 60 s, preferably 2 to 30 s, more preferably 5 to 10 s, and f) in an immediately downstream, second reaction step, the solid reaction products are removed from the flowing reaction mixture by means of a filter apparatus, and the reaction mixture present at the filter is treated at a temperature of 1 10 to 230°C, preferably 130 to 180°C, more preferably
• 140 to 150°C for a minimum residence time in the range from 1 min to 1 hour, preferably 10 to 40 min, more preferably 20 to 30 min.
• the pyrogenic particles are directly surface-modified without further isolation.
• the gas stream comprising the metal oxide particles is obtained by thermal decomposition of at least one metal compound in the presence of one or more hydrolysing and/or oxidizing gases or vapours.
• the oxidizing and/or hydrolysing gases or vapours are preferably used in a stoichiometric excess based on the metal compound.
• the metal compound may preferably be present in vaporous form, liquid form or in the form of an aerosol.
• the temperature needed for thermal decomposition can preferably be provided by a flame, preferably obtained by the ignition of a combustion gas with an oxygen-containing gas.
• Suitable oxygen-containing gases are in particular air and oxygen-enriched air.
• Suitable combustion gases are in particular hydrogen, methane, ethane, propane, butane, natural gas. Particular preference may be given to using a combination of air and hydrogen.
• flame types suitable for performance of the process according to the invention for example laminar or turbulent flames, premixed flames or diffusion flames, low-pressure or high- pressure flames, flames which spread below, at or above the speed of sound, pulsating or continuous flames, reducing or oxidizing flames, secondary flames, closed or open flames, flames from one or more burners, or a mixed form of the aforementioned flame types.
• the metal component of the metal compound may preferably be selected from the group consisting of aluminium, antimony, cerium, iron, indium, silicon, titanium, vanadium, tungsten, yttrium, zinc, tin and zirconium.
• the metal compounds used must be
• the amounts of hydrogenous combustion gas and oxygen-containing gas are generally selected such that the metal compound can be very substantially quantitatively hydrolysed and/or oxidized to the metal oxide.
• A represents one or more metal compounds
• B represents a hydrogenous combustion gas
• C represents an oxygen-containing gas
• D represents the point of introduction of the surface modifier
• E represents the surface modification zone
• G represents the surface-modified metal oxide particles.
• the filter apparatus used comprises filter types known to those skilled in the art. It may be advantageous to operate two or more filter apparatuses, optionally offset in time.
• the pyrogenic particles are directly surface-modified without further isolation.
• the gas stream comprising the metal oxide particles is obtained by thermal decomposition of at least one metal compound in the presence of one or more hydrolysing and/or oxidizing gases or vapours.
• the oxidizing and/or hydrolysing gases or vapours are preferably used in a stoichiometric excess based on the metal compound.
• the metal compound is generally present in vaporous form or in the form of an aerosol.
• the temperature needed for thermal decomposition can preferably be provided by a flame, preferably obtained by the ignition of a combustion gas with an oxygen-containing gas.
• Suitable oxygen-containing gases are in particular air and oxygen-enriched air.
• Suitable combustion gases are in particular hydrogen, methane, ethane, propane, butane, natural gas. Particular preference may be given to using a combination of air and hydrogen.
• flame types suitable for performance of the process according to the invention for example laminar or turbulent flames, premixed flames or diffusion flames, low-pressure or high- pressure flames, flames which spread below, at or above the speed of sound, pulsating or continuous flames, reducing or oxidizing flames, secondary flames, closed or open flames, flames from one or more burners, or a mixed form of the aforementioned flame types.
• the metal component of the metal compound may preferably be selected from the group consisting of aluminium, antimony, cerium, iron, indium, silicon, titanium, vanadium, tungsten, yttrium, zinc, tin and zirconium.
• the metal compounds used must be
• the surface modifier/metal oxide particle ratio in the process according to the invention is preferably selected such that the carbon content of the surface- modified metal oxide particles is 0.1 to 10% by weight. Particular preference may be given to a range of 0.5 to 5% by weight.
• the surface modifier may preferably be introduced in liquid or dissolved form. It is more preferably introduced in the form of fine droplets which are obtained by atomizing the surface modifier by means of a carrier gas.
• the mean diameter of the fine droplets is preferably less than 100 ⁇ , more preferably 30-100 ⁇ .
• the surface modifier used in the process according to the invention has at least one functional group which can chemically react or interact with reactive groups present on the surface of the metal oxide particles to form bonds.
• the bonding may be in the form of chemical bonding, such as covalent, including
• the surface modifier is preferably a substance whose boiling temperature is above the temperature in the first and/or second reaction step.
• Examples of preferred monocarboxylic acids are formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, lauric acid, stearic acid, palmitic acid or oleic acid, glycolic acid, lactic acid, malic acid, tartaric acid, citric acid, isocitric acid, mandelic acid, benzoic acid and pyromellitic acid.
• suitable amines are methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, aniline, N-methylaniline,
• diphenylamine triphenylamine, toluidine, ethylenediamine, diethylenetriamine.
• Preferred hydrolysable silanes have the general formula R x SiY 4-x (I)
• x has the value of 1 , 2 or 3
• the R radicals are the same or different and are nonhydrolysable groups
• the Y radicals are the same or different and are hydrolysable groups or hydroxyl groups.
• hydrolysable Y groups which may be the same or different from one another are, for example,
• halogen for example F, CI, Br or I
• Ci-C6-alkoxy such as methoxy, ethoxy
• aryloxy preferably C6-Cio-aryloxy, such as phenoxy
• Ci-C6-acyloxy such as acetoxy or propionyloxy
• alkylcarbonyl preferably C2-C 7 -alkylcarbonyl, such as acetyl.
• hydrolysable radicals are halogen, alkoxy groups and acyloxy groups. Particularly preferred hydrolysable radicals are Ci-C 4 -alkoxy groups, especially methoxy and ethoxy.
• the nonhydrolysable R radicals which may be the same or different, are R radicals with or without a functional group.
• the nonhydrolysable R radical without a functional group is, for example,
• Ci-Cs-alkyl such as methyl, ethyl
• n-propyl isopropyl, n-butyl, sec-butyl and tert-butyl, pentyl, hexyl, octyl or cyclohexyl;
• alkenyl preferably C2-C6-alkenyl, such as vinyl, 1 -propenyl,
• alkynyl preferably C2-C6-alkynyl, such as propargyl, - aryl, preferably C-6-Cio-aryl, such as phenyl and naphthyl, and
• alkaryls such as tolyl, benzyl and phenethyl.
• Preferred surface modifiers may especially be CH 3 SiCl3, CH 3 Si(OC2H 5 )3, CH 3 Si(OCH 3 ) 3 , C 2 H 5 SiCI 3 , C 2 H 5 Si(OC2H5) 3 , C 2 H 5 Si(OCH 3 ) 3 , C 3 H 7 Si(OC 2 H5) 3 , (C 2 H 5 O) 3 SiC 3 H 6 CI, (CH 3 ) 2 SiCI 2 , (CH 3 ) 2 Si(OC 2 H 5 ) 2 , (CH 3 ) 2 Si(OH) 2 ,
• CH 2 CH-CH 2 -Si(OC 2 H 5 ) 3
• CH 2 CH-CH 2 -Si(OC 2 H 5 ) 3
• CH 2 CH-CH 2 - Si(OOCCH 3 ) 3
• a nonhydrolysable R radical with a functional group may comprise, for example, as a functional group, an epoxy (such as glycidyl or glycidyloxy), hydroxyl, ether, amino, monoalkylamino, dialkylamino, optionally substituted anilino, amide, carboxyl, acryloyi, acryloyloxy, methacryloyl, methacryloyloxy, mercapto, cyano, alkoxy, isocyanato, aldehyde, alkylcarbonyl, acid anhydride and phosphoric acid group.
• an epoxy such as glycidyl or glycidyloxy
• hydroxyl ether
• amino, monoalkylamino, dialkylamino optionally substituted anilino, amide, carboxyl, acryloyi, acryloyloxy, methacryloyl, methacryloyloxy, mercapto, cyano, alkoxy
• nonhydrolysable R radicals with functional groups are a
• - glycidyl- or glycidyloxy-(Ci-C 2 o)-alkylene radical such as beta- glycidyloxyethyl, gamma-glycidyloxypropyl, delta-glycidyloxybutyl, epsilon- glycidyloxypentyl, omega-glycidyloxyhexyl and
• gamma-glycidyloxypropyltrimethoxysilane glycidyloxypropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-isocyanatopropyldimethylchlorosilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, aminomethyltriethoxysilane, aminomethyltrinnethoxysilane,
• aminopropyltnchlorosilane (N-cyclohexylanninonnethyl)triethoxysilane, 2-anninoethyl-3-anninopropyltrinnethoxysilane,
• 3-aminopropyltris(methoxyethoxyethoxy)silane 3-aminopropyltris(trimethylsiloxy)silane, 4-aminobutyltriethoxysilane, aminophenyltrimethoxysilane, bis(2-hydroxyethyl)-3- aminopropyltriethoxysilane, diethylaminomethyltnethoxysilane, N,N- dimethylanninonnethylethoxysilane,
• N-phenylaminomethyltriethoxysilane N-phenylaminomethyltriethoxysilane, phenylbis(dimethylannino)chlorosilane, tert-butylaminopropyltrimethoxysilane, aminopropylsilanetriol,
• N-phenylaminomethyltrinnethoxysilane 3- (nneth)acryloyloxypropyltriethoxysilane and 3- (meth)acryloyloxypropyltrinnethoxysilane.
• silylamines are understood to mean compounds which have at least one Si-N bond and can react with the Si-OH groups present on the surface of the silicon dioxide particles. Examples thereof are vinyldimethylsilylamine, octyldimethylsilylamine, phenyldimethylsilylamine, bis(dimethylanninodinnethylsilyl)ethane,
• n 0,1 ,2,3,... ⁇ , preferably 0,1 ,2,3,... 100 000
• Polysiloxanes or silicone oils are usually thermally activated for surface modification. Particular preference may be given to using citric acid, lauric acid, stearic acid and pyromellitic acid.
• the process according to the invention allows an inexpensive production for surface modification of metal oxide particles. For instance, the apparatus expenditure is low, the reaction time is short and the conversion is high. It is particularly advantageous to link the production of the metal oxide particles by a pyrogenic process to immediately subsequent surface modification. This can be done, for example, by utilizing the heat which arises in the process of preparation of the metal oxide particles, and apparatus as would be required in any case in the production of the metal oxide particles, for example a filter apparatus, for surface modification. The reason why the reaction times are only very short in the process according to the invention even though the reaction takes place in the immobile filtercake, compared to known surface modification processes, is not known to date.
• the solid particles are removed at a filter, the temperature at the filter being 170°C.
• the minimum residence time of the particles from the time of addition of the surface modifier up to the filter is 1 .2 s. In addition, the minimum residence time of the particles on the filter until the filter is cleaned is 8 min.
• the silicon dioxide particles which form are aftertreated with steam at temperatures of 500 to 600°C, and the process gas stream is cooled to 160°C. Subsequently, at this temperature, 2 kg/h of vaporous octyltrimethoxysilane are metered into the process gas stream. Subsequently, the solid particles are removed at a filter, the temperature at the filter being 170°C.
• the minimum residence time of the particles from the time of addition of the surface modifier up to the filter is 1 .8 s.
• the minimum residence time of the particles on the filter until the filter is cleaned is 15 min.
• the solid particles are removed at a filter, the temperature at the filter being 165°C.
• the minimum residence time of the particles from the time of addition of the surface modifier up to the filter is 1 .2 s.
• the minimum residence time of the particles on the filter until the filter is cleaned is 9 min.
• 2.77% by weight of antimony(lll) acetate, 16.03% by weight of acetic anhydride and 5.00% by weight of acetic acid are atomized with 4.0 m 3 (STP)/h of atomizer air by means of a two-substance nozzle.
• the resulting droplets have a droplet size spectrum d3o from 5 to 15 ⁇ .
• the droplets are combusted into a reaction chamber in a flame formed from hydrogen (2.5 m 3 (STP)/h) and air (24.0 m 3 (STP)/h), corresponding to a lambda of 4.1 .
• the antimony-tin mixed oxide particles which form are aftertreated with steam at temperatures of 500 to 600°C, and the process gas stream is cooled to 190°C. Subsequently, at this temperature, 200 g/h of an alcoholic lauric acid solution (10% by weight in ethanol) are metered into the process gas stream. Subsequently, the solid particles are removed at a filter, the temperature at the filter being 200°C.
• the minimum residence time of the particles from the time of addition of the surface modifier up to the filter is 1 .5 s.
• the minimum residence time of the particles on the filter until the filter is cleaned is 8 min.
• the silicon-titanium mixed oxide particles which form are aftertreated with steam at temperatures of 500 to 600°C, and the process gas stream is cooled to 200°C. Subsequently, at this temperature, 200 g/h of alcoholic pyromellitic acid (10% by weight in ethanol) are metered into the process gas stream.
• the solid particles are removed at a filter, the temperature at the filter being 200°C.
• the minimum residence time of the particles from the time of addition of the surface modifier up to the filter is 10.3 s. In addition, the minimum residence time of the particles on the filter until the filter is cleaned is 17 min.
• the minimum residence time of the particles from the time of addition of the surface modifier up to the filter is 1 .1 s. In addition, the minimum residence time of the particles on the filter until the filter is cleaned is 5 min.

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• 2009
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• 2010
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