[go: up one dir, main page]

WO1996036441A1 - COATING OF TiO2 PIGMENT BY GAS-PHASE AND SURFACE REACTIONS - Google Patents

COATING OF TiO2 PIGMENT BY GAS-PHASE AND SURFACE REACTIONS Download PDF

Info

Publication number
WO1996036441A1
WO1996036441A1 PCT/US1996/007886 US9607886W WO9636441A1 WO 1996036441 A1 WO1996036441 A1 WO 1996036441A1 US 9607886 W US9607886 W US 9607886W WO 9636441 A1 WO9636441 A1 WO 9636441A1
Authority
WO
WIPO (PCT)
Prior art keywords
metal
reactor
coating
precursor
group
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.)
Ceased
Application number
PCT/US1996/007886
Other languages
French (fr)
Inventor
Toivo Kodas
Quint Powell
Bruce Anderson
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.)
Kemira Pigments Inc
Original Assignee
Kemira Pigments Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Kemira Pigments Inc filed Critical Kemira Pigments Inc
Priority to AU62501/96A priority Critical patent/AU6250196A/en
Publication of WO1996036441A1 publication Critical patent/WO1996036441A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40—Oxides
    • C23C16/401—Oxides containing silicon
    • C23C16/402—Silicon dioxide
    • 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
    • C09C1/3653—Treatment with inorganic compounds
    • C09C1/3661—Coating
    • 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
    • C09C1/3669—Treatment with low-molecular organic compounds
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40—Oxides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40—Oxides
    • C23C16/403—Oxides of aluminium, magnesium or beryllium
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40—Oxides
    • C23C16/405—Oxides of refractory metals or yttrium
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C01P2002/54—Solid solutions containing elements as dopants one element only
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/19—Oil-absorption capacity, e.g. DBP values

Definitions

  • This invention pertains to a process of coating titanium dioxide particles with metal oxides by gas-phase reaction.
  • the gas-phase reaction of TiCl 4 and 0 2 is used to make particulate Ti0 2 often of a size useful as a white pigment.
  • the pigment particles are usually not used in typical applications such as paint without first coating them with materials including, but not limited to, Si0 2 , A1 2 0 3 and mixtures thereof. To coat the particles, they are typically collected from the gas and dispersed in a liquid where the coating is applied by precipitation. This liquid-phase coating process often results in coatings with high surfaces areas, high oil absorption, and non-uniform thickness.
  • U.S. Patent 4,803,056 describes a method for increasing the capacity of a titanium dioxide producing process. Titanium tetrachloride is added at a second point in the system downstream of the main inlet for titanium tetrachloride to increase the yield of Ti0 2 . The process is exclusively used for the production of uncoated titanium dioxide. The addition of other reagents at the second point of introduction in order to produce a coating on the Ti0 2 particles is not suggested or disclosed.
  • Huncr and Katz disclose a process for forming coated particles in a flame.
  • non-pigmentary Ti0 2 can be coated with Si0 2 in a flame reactor whereby TiCl 4 and SiCl 4 are added simultaneously into the same flame.
  • the reaction conditions must be carefully adjusted such that Ti0 2 condenses before Si0 2 in order to achieve a coating of Si0 2 on the already formed Ti0 2 particles. It is difficult to reliably produce Si0 2 -coated Ti0 2 particles of a uniform quality in terms of size and coating hardness with this process.
  • the process for making pigment-grade Ti0 2 coated with a metal oxide according to the present invention is primarily characterized by the following steps: introducing a thermally decomposable volatile titanium-containing precursor into a reactor; thermally decomposing the titanium- containing precursor within the reactor to form Ti0 2 pigment particles; subsequently injecting at least one thermally decomposable volatile metal-containing coating precursor into the reactor; and reacting the at least one metal- containing coating precursor within the reactor to form a coating of at least one metal oxide on the Ti0 2 pigment particles.
  • the coating is selected from the group consisting of Si0 2 , Al 2 0 3 , Zr0 2 , and mixed metal oxide.
  • the titanium-containing precursor is selected from the group consisting of TiCl 4 , TiBr 4 , and Ti(OR) 4 , wherein R is an alkyl group.
  • the method advantageously further comprises the step of adding a thermally decomposable volatile aluminum-containing precursor to the titanium-containing precursor to form Al-doped Ti0 2 .
  • a thermally decomposable volatile aluminum-containing precursor to the titanium-containing precursor to form Al-doped Ti0 2 .
  • water may also be added to control the particle size of the formed Ti0 2 pigment particles.
  • the metal-containing coating precursor is selected from the group consisting of SiX 4 , A1X 3 , and ZrX 4 , wherein X is Cl, Br or OR, R being an alkyl group.
  • X is Cl, Br or OR, R being an alkyl group.
  • other metal-containing coating precursors can be used equally successfully.
  • metal alkyls metal alkenyls, metal alkynes, metal allyls, metallocenes, metal cyclopentadienes, metal arenes, metal alkoxides, and metal ⁇ -diketonates, all well known to a person skilled in the art. It is also possible to use metal carbonyls, metal oxyhalides, and metal hydrides.
  • the method further comprises the step of adding a co-reactant, preferably water, to the metal-containing coating precursor.
  • a co-reactant preferably water
  • water may be used to modify or control the reaction of the coating precursor.
  • the reactor is advantageously a tubular flow reactor.
  • the method further comprises the step of selecting a location for an injection element for injecting the at least one metal-containing coating precursor downstream of a Ti0 2 -formation zone of the tubular flow reactor.
  • the injection element is selected from the group consisting of a slot, a porous wall element, an annular segment of a coaxial tube of the tubular flow reactor, and a radially extending injection port.
  • At least two of the metal-containing coating precursors are injected at a single point through an injection element selected from the group consisting of a slot and a porous wall segment.
  • the inventive method according to another embodiment further comprises the step of selecting a plurality of locations for injection elements for injecting at least two of the metal- containing coating precursors downstream of a Ti0 2 -formation zone of the tubular flow reactor.
  • the coating precursors may be injected as mixtures, or separately but simultaneously at the same point in the reactor, or may be injected separately at different points in the reactor to produce mixed oxide coatings or to produce a coating comprising separate layers of metal oxides.
  • the injection elements are selected from the group consisting of a slot, a porous wall element, an annular segment of coaxial tube of the tubular flow reactor, and a radially extending injection port.
  • each separate coating layer has a thickness of 1-100 nm.
  • the coating has a total thickness of 1-100 nm.
  • the step of thermally decomposing includes the step of heating by fuel combustion, by conduction or by a plasma arc for initiating the formation of Ti0 2 .
  • the step of introducing the titanium- coating precursor includes the step of selecting a first and a second location of introduction, wherein the second location is arranged downstream of the first location.
  • the step of introducing the titanium- containing precursor and/or the step of injecting the metal-containing coating precursor may include the step of employing a carrier gas, for example, oxygen.
  • the method further comprises the step of collecting the Ti0 2 pigment particles downstream of the flow reactor.
  • the reactor is maintained at atmospheric pressure during the inventive process. It is also possible to maintain less than atmospheric pressure (vacuum) within the reactor or perform the inventive process at a pressure of 1 to 10 atm (atmospheres) within the reactor.
  • the present invention describes a gas- phase method for making coated pigment grade Ti0 2 . It allows multi-component coatings and multilayer coatings.
  • the coatings produced by the inventive process are dense and have low oil absorption. The inventive process eliminates the need to collect the particles before the coating can be applied thereby simplifying the manufacturing process.
  • Ti0 2 pigment particles are produced by a gas-phase reaction of titanium-containing precursors, for example, TiX 4 , suspended in a gas stream and are then coated with a coating of metal oxide(s) produced by gas-phase and surface reactions of thermally decomposable volatile metal atom- or ion-containing coating reactants introduced at a single point or multiple points into a tubular flow system at a location downstream of the formation zone in which the Ti0 2 pigment particles are fully formed.
  • titanium-containing precursors for example, TiX 4
  • the inventive system or apparatus consists of three sections including sequentially: a tubular flow formation zone in which the Ti0 2 particles are formed, a zone in which the thermally decomposable volatile metal atom- or ion-containing coating reactants (precursors) are introduced into the gas stream carrying the Ti0 2 particles to be coated, and a coating zone in which the Ti0 2 particles are coated by the metal oxide(s) being formed from the metal-containing coating precursor(s) .
  • the titanium dioxide particles are formed by gas-phase reaction.
  • the volatile metal-containing coating precursors are injected which react in the gas phase as well as on the surface of the titanium dioxide particles to form a coating.
  • the coated particles are then collected at the exit of the flow reactor.
  • the inventive system consists of the following components: a pigment particle generator (particle formation zone) , an introduction zone for the thermally decomposable volatile metal- containing coating precursor (reactant) , and a coating zone.
  • a pigment particle generator particle formation zone
  • an introduction zone for the thermally decomposable volatile metal- containing coating precursor reactant
  • a coating zone In the particle formation zone, TiCl 4 reacts with 0 2 to form respective Ti0 2 particles (illustrated as small circles) .
  • the drawing shows the introduction of three thermally decomposable volatile metal-containing coating reactants downstream of the particle formation zone: ML n , M'L n , and M''L n where M, M' , M' ' represent a metal atom and L represents a ligand attached to the metal atom. However, the reaction of only one coating reactant ML n is shown.
  • reaction to form the metal oxide can take place in the gas phase (formation of small particles, illustrated by small cross-hatched circles) which are then captured by the preformed Ti0 2 particles to form the coating or can take place at the surface of the Ti0 2 particles resulting in a direct coating of the Ti0 2 particle (the produced coating is schematically represented by cross-hatching) .
  • Preferred compounds are, for example,
  • organic ligands such as metal alkyls, metal alkenyls, metal alkynes, metal allyls, metallocenes, metal cyclopentadienes, metal arenes, metal alkoxides, and metal ⁇ - diketonates
  • inorganic ligands such as metal carbonyls, metal oxyhalides, and metal hydrides.
  • the given compounds are examples only and not meant to limit the scope of the inventive process
  • the drawing shows the sequential nature of the process in which the particles are formed first, followed by introduction of the thermally decomposable volatile metal-containing coating reactants, and then coating. It is also obvious that only one or a plurality of thermally decomposable volatile metal-containing coating reactants can be used, as desired and needed for the Ti0 2 pigment product properties. Thus, the invention is not limited with respect to the number of thermally decomposable volatile metal- containing coating reactants that can be used, the order in which they are introduced into the reactor, or the type of thermally decomposable volatile metal-containing coating reactant.
  • TiCl 4 as a titanium precursor can be mixed with A1C1 3 , introduced into the reactor with oxygen (carrier gas) at a temperature of about 900 °C or higher, and reacted in a tubular flow system to give Ti0 2 particles containing Al.
  • oxygen carrier gas
  • water can be added, as is well known in the art, in order to help adjust or control the Ti0 2 particle size.
  • the gist of the present invention is the addition (injection) of a thermally decomposable volatile metal-containing coating reactant into a reactor tube at a location downstream of the zone in which the Ti0 2 particles are formed, but where the temperature is still high enough to cause reaction of the thermally decomposable volatile metal-containing coating reactants both in the gas phase and on the surfaces of the Ti0 2 pigment particles.
  • thermally decomposable volatile metal-containing coating reactants it is also possible to add two thermally decomposable volatile metal-containing coating reactants at the same time to give a single coating which is a mixed oxide of the two metals.
  • SiX 4 and A1X 3 can be added together resulting in a mixed oxide [Si0 2 ] x [Al 2 0 3 ] y wherein essentially any ratio between the two oxides is possible.
  • two or more thermally decomposable volatile metal-containing coating reactants are added sequentially to give a coating comprised of two or more layers of individual metal oxides.
  • the invention can be carried out in a variety of apparatus configurations.
  • the preferred embodiment is a tubular flow system in which the thermally decomposable volatile metal- containing coating reactants are introduced from the exterior of the reactor tube into the reactor tube at points downstream of the zone in which the Ti0 2 particles are formed but where the temperature is still high enough to cause reaction of the thermally decomposable volatile metal- containing coating reactants both in the gas phase and on the surfaces of the particles.
  • Various approaches can be used to introduce the thermally decomposable volatile metal-containing coating reactants into the reactor.
  • the thermally decomposable volatile metal-containing coating reactants can be 10 added through a porous wall or through radially extending injection points. It is also possible to use coaxial injection.
  • the temperature at which the thermally decomposable volatile metal-containing coating reactants are to be decomposed must be sufficiently high in order for the coating reactants to react at the surface of the Ti0 2 20 particles or for the particles of the coating material, formed in the gas phase, to be able to collide with the Ti0 2 pigment particles and fuse into their surfaces. Temperatures that are too low result in formation of separate particles 25 comprised of the coating material that are not incorporated into the coating. Temperatures that are too high result in reaction of the coating
  • the temperature For the coating of Ti0 2 with Si0 2 using SiCl 4 , the temperature must be greater than 1300°C. When Ti0 2 is to be coated with Al 2 0 3 , the temperature must be greater than 1100°C. For coating Ti0 2 with a mixed Si/Al oxide, the temperature must be greater than 1200°C. However, in any case, the temperature must not be too high in order to prevent interdiffusion and/or reaction between Ti0 2 and the coating material.
  • the flow reactor can be heated to the required reaction temperature by conventional methods such as fuel combustion, conduction, a plasma arc or other means well known to a person skilled in the art.
  • the energy derived from the exothermic reaction of the Ti-containing precursor with oxygen for heating the flow reactor to the desired reaction temperature when the gaseous reactants (Ti- containing precursor and oxygen) are preheated to a suitable preheating temperature.
  • the exothermicity of the reaction aids in reaching the required temperature in all possible process variations.
  • the inventive process can be carried out under various pressures.
  • the reactor can simply be maintained at atmospheric pressure during the inventive process. It is also possible to maintain less than atmospheric pressure (vacuum) within the reactor or perform the inventive process at a pressure of 1 to 10 atm (atmospheres) within the reactor.
  • Example 1 Formation of Ti0 2 particles coated with SiO,
  • a tubular flow reactor was used at a temperature of 1500 °C.
  • Oxygen gas carrier gas
  • the resulting gas mixture was then introduced into a reactor tube with a residence time of less than 10 seconds.
  • the gas mixture reacted to form Ti0 2 particles in the reactor.
  • Liquid SiCl 4 was vaporized by heating at
  • the surface reaction resulted in the direct deposition of a uniform continuous coating with a thickness of 10 nm as shown by Transmission Electron Microscopy.
  • the composition of the coating was confirmed by energy dispersive spectroscopy which showed only Si and O. X-ray diffraction showed only Ti0 2 and confirmed that the coating process did not degrade the properties of the pigment by forming additional undesired phases.
  • Example 2 Formation of Ti0 2 particles coated with A1 2 0 3 .
  • a tubular flow reactor was used at a temperature of 1500 °C.
  • Oxygen (carrier gas) was guided through TiCl 4 to vaporize and introduce TiCl 4 into the carrier gas.
  • the resulting gas mixture was then introduced into a reactor tube with a residence time of less than 10 sec. The gas mixture reacted to form Ti0 2 particles in the reactor.
  • A1C1 3 was vaporized by heating at less than 250 °C and passing a carrier gas over the powder. The vapor was introduced into the hot region of the reactor using tubes inserted from the exit of the reactor. This allowed A1C1 3 to be introduced into the reactor in a region where the temperature was near 1500°C. A1C1 3 reacted both in the gas phase and on the surfaces of the formed Ti0 2 particles. The gas phase reaction of the metal-containing coating precursor A1C1 3 resulted in the formation of small particles of Al 2 0 3 which were captured by the Ti0 2 particles and incorporated into the surface as a coating by sintering. Because of the small size of the Al 2 0 3 particles, sintering was rapid.
  • the particles were collected on a filter after exiting the reactor.
  • the surface reaction resulted in the direct deposition of a uniform continuous coating with a thickness of 10 nm as shown by Transmission Electron Microscopy.
  • the composition of the coating was confirmed by energy dispersive spectroscopy which showed only Al and 0. X-ray diffraction showed only Ti0 2 and confirmed that the coating process did not degrade the properties of the Ti0 2 pigment particles by forming additional undesired phases.
  • a tubular flow reactor was used at a temperature of 1500 °C.
  • Oxygen carrier gas
  • TiCl 4 was guided through TiCl 4 to vaporize and introduce TiCl 4 into the carrier gas.
  • the resulting gas mixture was then introduced into a reactor tube with a residence time of less than 10 sec. The gas mixture reacted to form Ti0 2 particles in the reactor.
  • SiCl 4 was vaporized by heating at 25°C without a carrier gas, and A1C1 3 was vaporized by heating at less than 250°C with carrier gas flowing over the AlCl 3 powder.
  • the streams were combined and introduced as a vapor into the hot region of the reactor using tubes inserted from the exit of the reactor. This allowed the SiCl 4 and A1C1 3 to be introduced into the reactor in a region where the temperature was near 1500°C.
  • SiCl 4 and A1C1 3 reacted both in the gas phase and on the surfaces of the particles.
  • the gas phase reaction resulted in the formation of small metal oxide particles which were captured by the formed Ti0 2 particles and incorporated into the surface as a coating by sintering.
  • the coated Ti0 2 pigment particles were collected onto a filter after exiting the reactor.
  • the surface reaction resulted in the direct deposition of a uniform continuous coating with a thickness of 10 nm as shown by Transmission Electron Microscopy.
  • the composition of the coating was confirmed by energy dispersive spectroscopy which showed only Si, Al and 0. X- ray diffraction showed only Ti0 2 and confirmed that the coating process did not degrade the properties of the pigment by forming additional undesired phases.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Inorganic Chemistry (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

In a process for making pigment-grade TiO2 coated with a metal oxide, a thermally decomposable volatile titanium-containing precursor is introduced into a reactor. The titanium-containing precursor is thermally decomposed within the reactor to form TiO2 pigment particles. Subsequently, one or more thermally decomposable volatile metal-containing coating precursors are injected into the reactor. The one or more metal-containing coating precursors are reacted within the reactor to form a coating of the one or more metal oxides on the TiO2 pigment particles.

Description

COATING OF TiOo PIGMENT BY GAS-PHASE AND SURFACE
REACTIONS Technical Field
This invention pertains to a process of coating titanium dioxide particles with metal oxides by gas-phase reaction. Background Art
The gas-phase reaction of TiCl4 and 02 is used to make particulate Ti02 often of a size useful as a white pigment. The pigment particles are usually not used in typical applications such as paint without first coating them with materials including, but not limited to, Si02, A1203 and mixtures thereof. To coat the particles, they are typically collected from the gas and dispersed in a liquid where the coating is applied by precipitation. This liquid-phase coating process often results in coatings with high surfaces areas, high oil absorption, and non-uniform thickness.
U.S. Patent 4,803,056 describes a method for increasing the capacity of a titanium dioxide producing process. Titanium tetrachloride is added at a second point in the system downstream of the main inlet for titanium tetrachloride to increase the yield of Ti02. The process is exclusively used for the production of uncoated titanium dioxide. The addition of other reagents at the second point of introduction in order to produce a coating on the Ti02 particles is not suggested or disclosed.
Huncr and Katz (J. Mater. Res., 7, 1861 (1992)) disclose a process for forming coated particles in a flame. For example, non-pigmentary Ti02 can be coated with Si02 in a flame reactor whereby TiCl4 and SiCl4 are added simultaneously into the same flame. The reaction conditions must be carefully adjusted such that Ti02 condenses before Si02 in order to achieve a coating of Si02 on the already formed Ti02 particles. It is difficult to reliably produce Si02-coated Ti02 particles of a uniform quality in terms of size and coating hardness with this process.
It is therefore an object of the present invention to provide a simple and reliable process for coating Ti02 pigment particles in the gas phase to give coatings with low surfaces areas, low oil absorption, and uniform thickness. Disclosure of the Invention
The process for making pigment-grade Ti02 coated with a metal oxide according to the present invention is primarily characterized by the following steps: introducing a thermally decomposable volatile titanium-containing precursor into a reactor; thermally decomposing the titanium- containing precursor within the reactor to form Ti02 pigment particles; subsequently injecting at least one thermally decomposable volatile metal-containing coating precursor into the reactor; and reacting the at least one metal- containing coating precursor within the reactor to form a coating of at least one metal oxide on the Ti02 pigment particles. Preferably, the coating is selected from the group consisting of Si02, Al203, Zr02, and mixed metal oxide. The mixed metal oxide is expediently [Si02]x[Al203]y with x = 0-1 and y = 0-1. The titanium-containing precursor is selected from the group consisting of TiCl4, TiBr4, and Ti(OR)4, wherein R is an alkyl group.
The method advantageously further comprises the step of adding a thermally decomposable volatile aluminum-containing precursor to the titanium-containing precursor to form Al-doped Ti02. As is well known in the art, water may also be added to control the particle size of the formed Ti02 pigment particles. The metal-containing coating precursor is selected from the group consisting of SiX4, A1X3, and ZrX4, wherein X is Cl, Br or OR, R being an alkyl group. However, other metal-containing coating precursors can be used equally successfully. For example, they may be selected from the group consisting of metal alkyls, metal alkenyls, metal alkynes, metal allyls, metallocenes, metal cyclopentadienes, metal arenes, metal alkoxides, and metal β-diketonates, all well known to a person skilled in the art. It is also possible to use metal carbonyls, metal oxyhalides, and metal hydrides.
The method further comprises the step of adding a co-reactant, preferably water, to the metal-containing coating precursor. It is known to a person skilled in the art that water may be used to modify or control the reaction of the coating precursor. The reactor is advantageously a tubular flow reactor.
The method further comprises the step of selecting a location for an injection element for injecting the at least one metal-containing coating precursor downstream of a Ti02-formation zone of the tubular flow reactor.
The injection element is selected from the group consisting of a slot, a porous wall element, an annular segment of a coaxial tube of the tubular flow reactor, and a radially extending injection port.
In a preferred embodiment of the present invention, at least two of the metal-containing coating precursors are injected at a single point through an injection element selected from the group consisting of a slot and a porous wall segment.
The inventive method according to another embodiment further comprises the step of selecting a plurality of locations for injection elements for injecting at least two of the metal- containing coating precursors downstream of a Ti02-formation zone of the tubular flow reactor. The coating precursors may be injected as mixtures, or separately but simultaneously at the same point in the reactor, or may be injected separately at different points in the reactor to produce mixed oxide coatings or to produce a coating comprising separate layers of metal oxides. The injection elements are selected from the group consisting of a slot, a porous wall element, an annular segment of coaxial tube of the tubular flow reactor, and a radially extending injection port.
Preferably, each separate coating layer has a thickness of 1-100 nm. Advantageously, the coating has a total thickness of 1-100 nm.
The step of thermally decomposing includes the step of heating by fuel combustion, by conduction or by a plasma arc for initiating the formation of Ti02. The step of introducing the titanium- coating precursor includes the step of selecting a first and a second location of introduction, wherein the second location is arranged downstream of the first location. The step of introducing the titanium- containing precursor and/or the step of injecting the metal-containing coating precursor may include the step of employing a carrier gas, for example, oxygen. Preferably, the method further comprises the step of collecting the Ti02 pigment particles downstream of the flow reactor.
Advantageously, the reactor is maintained at atmospheric pressure during the inventive process. It is also possible to maintain less than atmospheric pressure (vacuum) within the reactor or perform the inventive process at a pressure of 1 to 10 atm (atmospheres) within the reactor. The present invention describes a gas- phase method for making coated pigment grade Ti02. It allows multi-component coatings and multilayer coatings. The coatings produced by the inventive process are dense and have low oil absorption. The inventive process eliminates the need to collect the particles before the coating can be applied thereby simplifying the manufacturing process.
According to the present invention Ti02 pigment particles are produced by a gas-phase reaction of titanium-containing precursors, for example, TiX4, suspended in a gas stream and are then coated with a coating of metal oxide(s) produced by gas-phase and surface reactions of thermally decomposable volatile metal atom- or ion-containing coating reactants introduced at a single point or multiple points into a tubular flow system at a location downstream of the formation zone in which the Ti02 pigment particles are fully formed.
The inventive system or apparatus consists of three sections including sequentially: a tubular flow formation zone in which the Ti02 particles are formed, a zone in which the thermally decomposable volatile metal atom- or ion-containing coating reactants (precursors) are introduced into the gas stream carrying the Ti02 particles to be coated, and a coating zone in which the Ti02 particles are coated by the metal oxide(s) being formed from the metal-containing coating precursor(s) .
In a first step, the titanium dioxide particles are formed by gas-phase reaction. Subsequently, the volatile metal-containing coating precursors are injected which react in the gas phase as well as on the surface of the titanium dioxide particles to form a coating. The coated particles are then collected at the exit of the flow reactor. Thus, the invention described here relies on sequential particle formation and particle coating.
Brief Description of the Drawing
The object and advantages of the present invention will appear more clearly from the following specification in conjunction with the accompanying drawing, in which the only Figure schematically shows the system for coating particles according to the present invention for a specific embodiment. Best Modes for Carrying our the Invention The present invention will now be described in detail with the aid of several specific embodiments utilizing the only Figure in which a specific embodiment is illustrated.
The inventive system consists of the following components: a pigment particle generator (particle formation zone) , an introduction zone for the thermally decomposable volatile metal- containing coating precursor (reactant) , and a coating zone. In the particle formation zone, TiCl4 reacts with 02 to form respective Ti02 particles (illustrated as small circles) . The drawing shows the introduction of three thermally decomposable volatile metal-containing coating reactants downstream of the particle formation zone: MLn, M'Ln, and M''Ln where M, M' , M' ' represent a metal atom and L represents a ligand attached to the metal atom. However, the reaction of only one coating reactant MLn is shown. It is schematically shown that the reaction to form the metal oxide can take place in the gas phase (formation of small particles, illustrated by small cross-hatched circles) which are then captured by the preformed Ti02 particles to form the coating or can take place at the surface of the Ti02 particles resulting in a direct coating of the Ti02 particle (the produced coating is schematically represented by cross-hatching) . Preferred compounds are, for example,
SiCl4, SiBr4, Si(OR)4, AlCl3, AlBr3, A1(0R)3, ZrCl4, ZrBr4, and Zr(OR)4. It is obvious to those skilled in the art that other types of precursors of various structures can be used, for example, coating precursors with organic ligands such as metal alkyls, metal alkenyls, metal alkynes, metal allyls, metallocenes, metal cyclopentadienes, metal arenes, metal alkoxides, and metal β- diketonates or coating precursors with inorganic ligands such as metal carbonyls, metal oxyhalides, and metal hydrides. The given compounds are examples only and not meant to limit the scope of the inventive process
The drawing shows the sequential nature of the process in which the particles are formed first, followed by introduction of the thermally decomposable volatile metal-containing coating reactants, and then coating. It is also obvious that only one or a plurality of thermally decomposable volatile metal-containing coating reactants can be used, as desired and needed for the Ti02 pigment product properties. Thus, the invention is not limited with respect to the number of thermally decomposable volatile metal- containing coating reactants that can be used, the order in which they are introduced into the reactor, or the type of thermally decomposable volatile metal-containing coating reactant.
It is also possible to use an additional metal compound as a dopant together with the titanium-containing precursor. For example, TiCl4 as a titanium precursor can be mixed with A1C13, introduced into the reactor with oxygen (carrier gas) at a temperature of about 900 °C or higher, and reacted in a tubular flow system to give Ti02 particles containing Al. It is obvious to those skilled in the art that other types of dopants can be added to the titanium-containing precursor without departing from the scope of the present invention. In this context it should also be mentioned that water can be added, as is well known in the art, in order to help adjust or control the Ti02 particle size.
It is well known to persons skilled in the art that the particle formation and particle coating within the reactor occur over a short period of time. The gas stream exiting from the reactor is cooled to allow collection of the coated particles.
The gist of the present invention is the addition (injection) of a thermally decomposable volatile metal-containing coating reactant into a reactor tube at a location downstream of the zone in which the Ti02 particles are formed, but where the temperature is still high enough to cause reaction of the thermally decomposable volatile metal-containing coating reactants both in the gas phase and on the surfaces of the Ti02 pigment particles.
It is possible to add only a single thermally decomposable volatile metal-containing coating reactant, such as SiCl4, in order to give a coating of one material (Si02 in the given example) .
However, it is also possible to add two thermally decomposable volatile metal-containing coating reactants at the same time to give a single coating which is a mixed oxide of the two metals. For example, SiX4 and A1X3 can be added together resulting in a mixed oxide [Si02]x[Al203]y wherein essentially any ratio between the two oxides is possible. In this case it is desirable to match the reaction temperatures of the thermally decomposable volatile metal-containing coating reactants to allow reaction at the same location in the reactor.
In another embodiment of the present invention, two or more thermally decomposable volatile metal-containing coating reactants are added sequentially to give a coating comprised of two or more layers of individual metal oxides.
The invention can be carried out in a variety of apparatus configurations. The preferred embodiment is a tubular flow system in which the thermally decomposable volatile metal- containing coating reactants are introduced from the exterior of the reactor tube into the reactor tube at points downstream of the zone in which the Ti02 particles are formed but where the temperature is still high enough to cause reaction of the thermally decomposable volatile metal- containing coating reactants both in the gas phase and on the surfaces of the particles. 5 Various approaches can be used to introduce the thermally decomposable volatile metal-containing coating reactants into the reactor. For example, the thermally decomposable volatile metal-containing coating reactants can be 10 added through a porous wall or through radially extending injection points. It is also possible to use coaxial injection. Those skilled in the art realize other methods that are also equally viable. 15 The temperature at which the thermally decomposable volatile metal-containing coating reactants are to be decomposed must be sufficiently high in order for the coating reactants to react at the surface of the Ti02 20 particles or for the particles of the coating material, formed in the gas phase, to be able to collide with the Ti02 pigment particles and fuse into their surfaces. Temperatures that are too low result in formation of separate particles 25 comprised of the coating material that are not incorporated into the coating. Temperatures that are too high result in reaction of the coating
• material with the particle to be coated, i.e., the metal (s) of the coating material and the Ti02
«• 30 particle react to form mixed metal oxide phases thus degrading the Ti02 pigment particle properties.
For the coating of Ti02 with Si02 using SiCl4, the temperature must be greater than 1300°C. When Ti02 is to be coated with Al203, the temperature must be greater than 1100°C. For coating Ti02 with a mixed Si/Al oxide, the temperature must be greater than 1200°C. However, in any case, the temperature must not be too high in order to prevent interdiffusion and/or reaction between Ti02 and the coating material.
The flow reactor can be heated to the required reaction temperature by conventional methods such as fuel combustion, conduction, a plasma arc or other means well known to a person skilled in the art.
Especially for large scale production processes, it is known in the art to use the energy derived from the exothermic reaction of the Ti-containing precursor with oxygen for heating the flow reactor to the desired reaction temperature when the gaseous reactants (Ti- containing precursor and oxygen) are preheated to a suitable preheating temperature. Of course, the exothermicity of the reaction aids in reaching the required temperature in all possible process variations. The inventive process can be carried out under various pressures. The reactor can simply be maintained at atmospheric pressure during the inventive process. It is also possible to maintain less than atmospheric pressure (vacuum) within the reactor or perform the inventive process at a pressure of 1 to 10 atm (atmospheres) within the reactor. Example 1. Formation of Ti02 particles coated with SiO,
A tubular flow reactor was used at a temperature of 1500 °C. Oxygen gas (carrier gas) was guided through TiCl4 to vaporize and introduce TiCl4 into the carrier gas. The resulting gas mixture was then introduced into a reactor tube with a residence time of less than 10 seconds. The gas mixture reacted to form Ti02 particles in the reactor. Liquid SiCl4 was vaporized by heating at
25°C and introduced as a vapor into the hot region of the reactor using tubes inserted from the exit of the reactor. This allowed the SiCl4 to be introduced into the reactor in a region where the temperature was near 1500 °C. The SiCl4 reacted both in the gas phase and on the surfaces of the formed Ti02 particles. The gas phase reaction of the metal-containing coating precursor resulted in the formation of small metal oxide particles which were captured by the Ti02 particles and incorporated into the surface as a coating by sintering. Because of the small size of the metal oxide particles, sintering was rapid. The coated Ti02 pigment particles were collected on a filter after exiting the reactor.
The surface reaction resulted in the direct deposition of a uniform continuous coating with a thickness of 10 nm as shown by Transmission Electron Microscopy. The composition of the coating was confirmed by energy dispersive spectroscopy which showed only Si and O. X-ray diffraction showed only Ti02 and confirmed that the coating process did not degrade the properties of the pigment by forming additional undesired phases.
Example 2. Formation of Ti02 particles coated with A1203. A tubular flow reactor was used at a temperature of 1500 °C. Oxygen (carrier gas) was guided through TiCl4 to vaporize and introduce TiCl4 into the carrier gas. The resulting gas mixture was then introduced into a reactor tube with a residence time of less than 10 sec. The gas mixture reacted to form Ti02 particles in the reactor.
A1C13 was vaporized by heating at less than 250 °C and passing a carrier gas over the powder. The vapor was introduced into the hot region of the reactor using tubes inserted from the exit of the reactor. This allowed A1C13 to be introduced into the reactor in a region where the temperature was near 1500°C. A1C13 reacted both in the gas phase and on the surfaces of the formed Ti02 particles. The gas phase reaction of the metal-containing coating precursor A1C13 resulted in the formation of small particles of Al203 which were captured by the Ti02 particles and incorporated into the surface as a coating by sintering. Because of the small size of the Al203 particles, sintering was rapid. The particles were collected on a filter after exiting the reactor. The surface reaction resulted in the direct deposition of a uniform continuous coating with a thickness of 10 nm as shown by Transmission Electron Microscopy. The composition of the coating was confirmed by energy dispersive spectroscopy which showed only Al and 0. X-ray diffraction showed only Ti02 and confirmed that the coating process did not degrade the properties of the Ti02 pigment particles by forming additional undesired phases.
Example 3. Formation of Ti02 particles coated with [Si02]x[Al203]y.
A tubular flow reactor was used at a temperature of 1500 °C. Oxygen (carrier gas) was guided through TiCl4 to vaporize and introduce TiCl4 into the carrier gas. The resulting gas mixture was then introduced into a reactor tube with a residence time of less than 10 sec. The gas mixture reacted to form Ti02 particles in the reactor.
SiCl4 was vaporized by heating at 25°C without a carrier gas, and A1C13 was vaporized by heating at less than 250°C with carrier gas flowing over the AlCl3 powder. The streams were combined and introduced as a vapor into the hot region of the reactor using tubes inserted from the exit of the reactor. This allowed the SiCl4 and A1C13 to be introduced into the reactor in a region where the temperature was near 1500°C. SiCl4 and A1C13 reacted both in the gas phase and on the surfaces of the particles. The gas phase reaction resulted in the formation of small metal oxide particles which were captured by the formed Ti02 particles and incorporated into the surface as a coating by sintering. Sintering was rapid because of the small size of the metal oxide particles. The coated Ti02 pigment particles were collected onto a filter after exiting the reactor. The surface reaction resulted in the direct deposition of a uniform continuous coating with a thickness of 10 nm as shown by Transmission Electron Microscopy. The composition of the coating was confirmed by energy dispersive spectroscopy which showed only Si, Al and 0. X- ray diffraction showed only Ti02 and confirmed that the coating process did not degrade the properties of the pigment by forming additional undesired phases.
The present invention is, of course, in no way restricted to the specific disclosure of the specification, examples and drawings, but also encompasses any modifications within the scope of the appended claims.

Claims

CLAIMS:
1. A process for making pigment-grade Ti02 coated with a metal oxide, said method comprising the steps of: introducing a thermally decomposable volatile titanium-containing precursor into a reactor; thermally decomposing the titanium- containing precursor within the reactor to form Ti02 pigment particles; subsequently injecting at least one thermally decomposable volatile metal-containing coating precursor into the reactor; and reacting the at least one metal- containing coating precursor within the reactor to form a coating of at least one metal oxide on the Ti02 pigment particles.
2. A method according to claim 1, wherein said coating is selected from the group consisting of Si02, Al203, Zr02, and mixed metal oxide.
3. A method according to claim 2, wherein the mixed metal oxide is [Si02]x[Al203]y.
4. A method according to claim 1, wherein the titanium-containing precursor is selected from the group consisting of TiCl4, TiBr4, and Ti(0R)4 wherein R is an alkyl group.
5. A method according to claim 1, further comprising the step of adding a thermally decomposable volatile aluminum-containing compound to the titanium-containing precursor to form Al- doped Ti02.
6. A method according to claim 1, wherein the metal-containing coating precursor is selected from the group consisting of SiX4, A1X3, and ZrX4, wherein X is Cl, Br or OR.
7. A method according to claim 6, further comprising the step of adding a co- reactant to the metal-containing coating precursor.
8. A method according to claim 7, wherein the co-reactant is water.
9. A method according to claim 1, wherein the reactor is a tubular flow reactor.
10. A method according to claim 9, further comprising the step of selecting a location for an injection element for injecting the at least one metal-containing coating precursor downstream of a Ti02-formation zone of the tubular flow reactor.
11. A method according to claim 10, wherein the injection element is selected from the group consisting of a slot, a porous wall element, an annular segment of coaxial tube of the tubular flow reactor, and a radially extending injection port.
12. A method according to claim 10, wherein at least two of the metal-containing coating precursors are injected at a single point through an injection element selected from the group consisting of a slot and a porous wall segment.
13. A method according to claim 1, further comprising the step of selecting a plurality of locations for injection elements for injecting at least two of the metal-containing coating precursors downstream of a Ti02-formation zone of the tubular flow reactor to produce a coating comprising separate layers of metal oxides.
14. A method according to claim 13, wherein the injection elements are selected from the group consisting of a slot, a porous wall element, an annular segment of coaxial tube of the tubular flow reactor, and a radially extending injection port.
15. A method according to claim 13, wherein each separate layer of the coating has a thickness of 1-100 nm.
16. A method according to claim 1, wherein the coating has a total thickness of 1-100 nm.
17. A method according to claim 1, wherein the step of thermally decomposing includes the step of heating by fuel combustion for initiating the formation of Ti02.
18. A method according to claim 1, wherein the step of thermally decomposing includes the step of heating by conduction for initiating the formation of Ti02.
19. A method according to claim 1, wherein the step of thermally decomposing includes the step of heating with a plasma arc for initiating the formation of Ti02.
20. A method according to claim 1, wherein in the step of introducing the titanium- containing precursor includes the step of selecting a first and a second location of introduction, • wherein the second location is arranged downstream of the first location.
21. A method according to claim 1, wherein the step of introducing includes the step of employing a carrier gas.
22. A method according to claim 1, wherein the step of injecting includes the step of employing a carrier gas.
23. A method according to claim 1, further comprising the step of collecting the Ti02 pigment particles downstream of the flow reactor.
24. A method according to claim 1, further comprising the step of maintaining atmospheric pressure within the reactor.
25. A method according to claim 1, further comprising the step of maintaining less than atmospheric pressure within the reactor.
26. A method according to claim 1, further comprising the step of maintaining a pressure of 1 to 10 atm within the reactor.
27. A method according to claim 1, wherein the metal-containing coating precursor is selected from the group consisting of metal alkyls, metal alkenyls, metal alkynes, metal allyls, metallocenes, metal cyclopentadienes, metal arenes, metal alkoxides, and metal β- diketonates.
28. A method according to claim 1, wherein the metal-containing coating precursor is selected from the group consisting of metal carbonyls, metal oxyhalides, and metal hydrides.
PCT/US1996/007886 1995-05-17 1996-05-17 COATING OF TiO2 PIGMENT BY GAS-PHASE AND SURFACE REACTIONS Ceased WO1996036441A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU62501/96A AU6250196A (en) 1995-05-17 1996-05-17 Coating of tio2 pigment by gas-phase and surface reactions

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US44305595A 1995-05-17 1995-05-17
US08/443,055 1995-05-17

Publications (1)

Publication Number Publication Date
WO1996036441A1 true WO1996036441A1 (en) 1996-11-21

Family

ID=23759248

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1996/007886 Ceased WO1996036441A1 (en) 1995-05-17 1996-05-17 COATING OF TiO2 PIGMENT BY GAS-PHASE AND SURFACE REACTIONS

Country Status (2)

Country Link
AU (1) AU6250196A (en)
WO (1) WO1996036441A1 (en)

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5728205A (en) * 1996-12-11 1998-03-17 E. I. Du Pont De Nemours And Company Process for the addition of boron in a TiO2 manufacturing process
WO1999032562A1 (en) * 1997-12-23 1999-07-01 E.I. Du Pont De Nemours And Company PROCESS FOR PRODUCING COATED TiO2 PIGMENT USING COOXIDATION TO PROVIDE HYDROUS OXIDE COATINGS
DE19824440C1 (en) * 1998-05-30 1999-09-02 Karlsruhe Forschzent Process for producing a gold-containing pigment
EP0908494A3 (en) * 1997-10-08 1999-11-10 E.I. Dupont De Nemours And Company Uniformly coated particulate metal oxide
WO2000020516A1 (en) * 1998-10-02 2000-04-13 Sri International Dry process for coating titania particles
WO2001081480A3 (en) * 2000-04-27 2002-02-28 Du Pont Process for making durable titanium dioxide pigment by vapor phase deposition
US6416721B1 (en) * 1998-10-02 2002-07-09 Sri International Fluidized bed reactor having a centrally positioned internal heat source
WO2004056927A2 (en) 2002-12-23 2004-07-08 Degussa Ag Titanium dioxide coated with silicon dioxide
WO2005113442A1 (en) * 2004-05-21 2005-12-01 Degussa Ag Ternary metal mixed oxide powder
EP1785395A1 (en) 2005-11-12 2007-05-16 Degussa GmbH Process for the preparation of doped metal oxide particles
DE102005002846A1 (en) * 2005-01-20 2007-05-16 Seoul Nat Univ Ind Foundation Preparation of composite microparticles involves introducing gaseous coating precursor upwardly toward host particles in around a flame, where coating precursor is protected by inert gas introduced around the flame
WO2007085493A3 (en) * 2006-01-30 2007-09-13 Kronos Int Inc Titanium dioxide pigment particles with doped dense sio2 skin and method for the production thereof
WO2008019905A1 (en) * 2006-08-17 2008-02-21 Evonik Degussa Gmbh Silica coated zinc oxide particles obtainable by a flame pyrolysis process
WO2009027433A3 (en) * 2007-08-28 2009-05-14 Basf Se PRODUCTION OF SiO2-COATED TITANIUM DIOXIDE PARTICLES WITH AN ADJUSTABLE COATING
US7763110B2 (en) 2006-01-30 2010-07-27 Kronos International Inc Titanium dioxide pigment particles with doped, dense SiO2 skin and methods for their manufacture
EP2222794A4 (en) * 2007-12-05 2010-12-01 Akhtar M Kamal PROCESS FOR PRODUCING PIGMENTS BASED ON COATED TITANIUM DIOXIDE
US7905953B2 (en) 2006-01-30 2011-03-15 Kronos International Inc Titanium dioxide pigment particles with doped, dense SiO2 skin and methods for their manufacture
CN103298744A (en) * 2011-01-10 2013-09-11 纳幕尔杜邦公司 Process for controlling particle size and additive coverage in the preparation of titanium dioxide
EP2209618A4 (en) * 2007-11-16 2014-01-22 Cristal Usa Inc Gas phase production of coated titania

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3512219A (en) * 1965-10-19 1970-05-19 American Potash & Chem Corp Injection reactor for titanium dioxide production
US4050951A (en) * 1974-12-20 1977-09-27 Societa' Italiana Resine S.I.R. S.P.A. Process for the post-treatment of titanium dioxide pigments

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3512219A (en) * 1965-10-19 1970-05-19 American Potash & Chem Corp Injection reactor for titanium dioxide production
US4050951A (en) * 1974-12-20 1977-09-27 Societa' Italiana Resine S.I.R. S.P.A. Process for the post-treatment of titanium dioxide pigments

Cited By (35)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5728205A (en) * 1996-12-11 1998-03-17 E. I. Du Pont De Nemours And Company Process for the addition of boron in a TiO2 manufacturing process
EP0908494A3 (en) * 1997-10-08 1999-11-10 E.I. Dupont De Nemours And Company Uniformly coated particulate metal oxide
US6086668A (en) * 1997-10-08 2000-07-11 E. I. Du Pont De Nemours And Company Uniformly coated particulate metal oxide
WO1999032562A1 (en) * 1997-12-23 1999-07-01 E.I. Du Pont De Nemours And Company PROCESS FOR PRODUCING COATED TiO2 PIGMENT USING COOXIDATION TO PROVIDE HYDROUS OXIDE COATINGS
US5922120A (en) * 1997-12-23 1999-07-13 E. I. Du Pont De Nemours And Company Process for producing coated TiO2 pigment using cooxidation to provide hydrous oxide coatings
AU750442B2 (en) * 1997-12-23 2002-07-18 E.I. Du Pont De Nemours And Company Process for producing coated TiO2 pigment using cooxidation to provide hydrous oxide coatings
DE19824440C1 (en) * 1998-05-30 1999-09-02 Karlsruhe Forschzent Process for producing a gold-containing pigment
US6416721B1 (en) * 1998-10-02 2002-07-09 Sri International Fluidized bed reactor having a centrally positioned internal heat source
WO2000020516A1 (en) * 1998-10-02 2000-04-13 Sri International Dry process for coating titania particles
WO2001081480A3 (en) * 2000-04-27 2002-02-28 Du Pont Process for making durable titanium dioxide pigment by vapor phase deposition
US6852306B2 (en) * 2000-04-27 2005-02-08 E. I. Du Pont De Nemours And Company Process for making durable rutile titanium dioxide pigment by vapor phase deposition of surface treatments
US7029648B2 (en) 2000-04-27 2006-04-18 E. I. Du Pont De Nemours And Company Process for making durable rutile titanium dioxide pigment by vapor phase deposition of surface treatment
WO2004056927A2 (en) 2002-12-23 2004-07-08 Degussa Ag Titanium dioxide coated with silicon dioxide
DE10260718A1 (en) * 2002-12-23 2004-07-08 Degussa Ag Titanium dioxide coated with silicon dioxide
US7244302B2 (en) 2002-12-23 2007-07-17 Degussa Ag Titanium dioxide coated with silicon dioxide
WO2005113442A1 (en) * 2004-05-21 2005-12-01 Degussa Ag Ternary metal mixed oxide powder
DE102005002846A1 (en) * 2005-01-20 2007-05-16 Seoul Nat Univ Ind Foundation Preparation of composite microparticles involves introducing gaseous coating precursor upwardly toward host particles in around a flame, where coating precursor is protected by inert gas introduced around the flame
DE102005002846B4 (en) * 2005-01-20 2015-07-23 Seoul National University Industry Foundation Apparatus and method for producing coated nanoparticle composite
US8535633B2 (en) 2005-11-12 2013-09-17 Evonik Degussa Gmbh Process for the production of doped metal oxide particles
EP1785395A1 (en) 2005-11-12 2007-05-16 Degussa GmbH Process for the preparation of doped metal oxide particles
WO2007054412A1 (en) * 2005-11-12 2007-05-18 Evonik Degussa Gmbh Process for the production of doped metal oxide particles
RU2404119C2 (en) * 2005-11-12 2010-11-20 Эвоник Дегусса Гмбх Method of obtaining particles of doped metal oxides
WO2007085493A3 (en) * 2006-01-30 2007-09-13 Kronos Int Inc Titanium dioxide pigment particles with doped dense sio2 skin and method for the production thereof
JP2009525368A (en) * 2006-01-30 2009-07-09 クローノス インターナショナル インコーポレイテッド Titanium dioxide pigment particles with dense doped SiO2 coating and method for producing the same
US7905953B2 (en) 2006-01-30 2011-03-15 Kronos International Inc Titanium dioxide pigment particles with doped, dense SiO2 skin and methods for their manufacture
US7763110B2 (en) 2006-01-30 2010-07-27 Kronos International Inc Titanium dioxide pigment particles with doped, dense SiO2 skin and methods for their manufacture
JP2009545509A (en) * 2006-08-17 2009-12-24 エボニック デグサ ゲーエムベーハー Silica coated zinc oxide particles obtained by flame pyrolysis method
WO2008019905A1 (en) * 2006-08-17 2008-02-21 Evonik Degussa Gmbh Silica coated zinc oxide particles obtainable by a flame pyrolysis process
WO2009027433A3 (en) * 2007-08-28 2009-05-14 Basf Se PRODUCTION OF SiO2-COATED TITANIUM DIOXIDE PARTICLES WITH AN ADJUSTABLE COATING
EP2209618A4 (en) * 2007-11-16 2014-01-22 Cristal Usa Inc Gas phase production of coated titania
US8663380B2 (en) 2007-11-16 2014-03-04 Cristal Usa Inc. Gas phase production of coated titania
EP2222794A4 (en) * 2007-12-05 2010-12-01 Akhtar M Kamal PROCESS FOR PRODUCING PIGMENTS BASED ON COATED TITANIUM DIOXIDE
CN103298744A (en) * 2011-01-10 2013-09-11 纳幕尔杜邦公司 Process for controlling particle size and additive coverage in the preparation of titanium dioxide
CN103298744B (en) * 2011-01-10 2015-07-29 纳幕尔杜邦公司 The method of Control granularity and additive fraction of coverage in titanium dioxide preparation
US9416277B2 (en) 2011-01-10 2016-08-16 The Chemours Company Tt, Llc Process for controlling particle size and additive coverage in the preparation of titanium dioxide

Also Published As

Publication number Publication date
AU6250196A (en) 1996-11-29

Similar Documents

Publication Publication Date Title
WO1996036441A1 (en) COATING OF TiO2 PIGMENT BY GAS-PHASE AND SURFACE REACTIONS
JP3356325B2 (en) Fine metal powder
JP3274740B2 (en) Apparatus and method for producing fine metal and ceramic powders
JP3356323B2 (en) Fine metal powder
US5472477A (en) Process for the preparation of finely divided metal and ceramic powders
US5149514A (en) Low temperature method of forming materials using one or more metal reactants and a halogen-containing reactant to form one or more reactive intermediates
Gurav et al. Aerosol processing of materials
EP1242649B1 (en) Method for producing composite layers using a plasma jet source
Wooldridge Gas-phase combustion synthesis of particles
CA2077684A1 (en) Method of coating a substrate in a fluidized bed
EP0677326A1 (en) Method of manufacturing fine ceramic particles and apparatus therefor
Powell et al. Gas-phase coating of TiO2 with SiO2 in a continuous flow hot-wall aerosol reactor
US5384306A (en) Fine-particle oxide ceramic powders
US5389585A (en) Fine non-oxide ceramic powders
Fotou et al. Coating titania aerosol particles with ZrO2, Al2O3/ZrO2 and SiO2/ZrO2 in a gas-phase process
Gitzhofer Induction plasma synthesis of ultrafine SiC
WO1990011858A1 (en) Low temperature method of forming materials using one or more metal reactants and a halogen-containing reactant to form one or more reactive intermediates
Axelbaum et al. A flame process for synthesis of unagglomerated, low-oxygen nanoparticles: Application to Ti and TiB2
Fotou et al. Sequential gas‐phase formation of Al2O3 and SiO2 layers on aerosol‐made TiO2 Particles
Bouyer et al. Characterization of SiC and Si3N4 coatings synthesized by means of inductive thermal plasma from disilane precursors
JPH06247712A (en) Method and apparatus for producing fine ceramic particles
Bouyer et al. Thermal plasma processing of nanostructured Si-based ceramic materials
Okuyama et al. Preparation of micro controlled particles using aerosol process technology
US7214363B2 (en) Method for preparing composite microparticles
Lewis Technique for Producing Mullite and Other Mixed‐Oxide Systems

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AL AM AT AU AZ BB BG BR BY CA CH CN CZ DE DK EE ES FI GB GE HU IS JP KE KG KP KR KZ LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK TJ TM TR TT UA UG UZ VN AM AZ BY KG KZ MD RU TJ TM

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): KE LS MW SD SZ UG AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN ML

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
122 Ep: pct application non-entry in european phase
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

NENP Non-entry into the national phase

Ref country code: CA