Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G23/00—Compounds of titanium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • 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
  • C01G23/053—Producing by wet processes, e.g. hydrolysing titanium salts
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G30/00—Compounds of antimony
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/30—Three-dimensional structures
• • 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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/50—Agglomerated particles
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
• • 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
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K2201/00—Specific properties of additives
  • C08K2201/011—Nanostructured additives
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
  • Y10T428/2991—Coated

Definitions

• NANOPARTICLES HAVING A RUTILE-LIKE CRYSTALLINE PHASE AND METHOD OF PREPARING THE SAME
• This invention relates to nanometer-sized particles comprising oxides of titanium and antimony, and in particular, to methods of making such particles, and compositions and articles containing same.
• Nanocomposite materials that is, materials having homogenously dispersed inorganic nanoparticles in an organic binder, have been used as protective transparent coatings for various applications. Such materials may have improved abrasion resistance and/or optical properties (for example, refractive index) as compared to coatings of the corresponding organic binder not having inorganic nanoparticles dispersed therein.
• Nanocomposite materials containing various inorganic nanoparticles such as titania (that is, titanium dioxide) nanoparticles, have been described. Titania occurs in at least three crystal forms: anatase, brookite, and rutile. Of these, the rutile form has the greatest density, hardness, and refractive index.
• Major problems with preparing titanium oxide sols, and particularly titanium oxide sols having the rutile crystalline phase may include: long process times, the need to use additional stabilizing counterions (for example, chloride, nitrate, etc.) that must be laboriously removed prior to use in applications such as organic protective films, extreme pH values, and/or limited stability.
• additional stabilizing counterions for example, chloride, nitrate, etc.
• the invention provides a composition comprising a plurality of Ti/Sb mixed oxide nanoparticles in the form of an aqueous colloidal dispersion, wherein the Ti/Sb mixed oxide nanoparticles comprise a rutile-like crystalline phase.
• the nanoparticles have at least one organic moiety bound to the nanoparticle surface.
• the invention provides a method for preparing an aqueous colloidal dispersion of Ti/Sb mixed oxide nanoparticles comprising the steps of: a) providing an aqueous titania precursor; b) providing an aqueous antimony oxide precursor; c) combining with mixing both aqueous precursors; and d) hydrothermally processing the mixture; wherein the weight ratio of titanium to antimony is in the range of from 0.14 to
• the method further comprises the step of modifying the surface of the nanoparticles.
• Colloidal dispersions prepared according to the invention typically are highly stable.
• the invention provides a composition comprising agglomerated nanoparticles, wherein the agglomerated nanoparticles comprise Ti/Sb mixed oxide nanoparticles comprising a rutile-like crystalline phase.
• the agglomerated nanoparticles are redispersible into a liquid vehicle.
• the invention provides a nanocomposite precursor comprising a plurality of nanoparticles homogeneously dispersed in an organic binder precursor, wherein the nanoparticles comprise Ti/Sb mixed oxide nanoparticles containing a rutile- like crystalline phase.
• the invention provides a nanocomposite comprising a plurality of nanoparticles dispersed in an organic binder, wherein the nanoparticles comprise Ti/Sb mixed oxide nanoparticles containing a rutile-like crystalline phase.
• the nanoparticles have at least one organic moiety bound to the nanoparticle surface.
• nanocomposites according to the invention may be supported on a substrate.
• Nanocomposites according to the invention are well suited for use as protective coatings, and may have a high refractive index.
• aqueous titania precursor refers to an aqueous titanium containing composition that may be converted to titania by one or more of heating, evaporation, precipitation, pH adjustment, and combinations thereof
• aqueous antimony oxide precursor refers to an aqueous antimony containing composition that may be converted to antimony oxide by one or more of heating, evaporation, precipitation, pH adjustment, and combinations thereof
• hydrophilimal processing means heating in aqueous media, in a closed vessel, to a temperature above the normal boiling point of water;
• nanoparticle means a particle having a maximum particle diameter of less than 500 nanometers
• rutile-like means having a tetragonal crystal structure and a space group of P4 2 /mnm (#136);
• organic moiety means an organic group, ion, or molecule;
• mixture means an intimate mixture of titanium and antimony oxides.
• FIG. 1 is a cross-sectional view of a composite article according to the invention.
• FIG. 2 is a schematic representation of a reaction system useful for preparing Ti/Sb mixed oxide nanoparticles according to the present invention.
• FIG. 3 is a cross-sectional view of one embodiment of a pulse dampener useful in practice of the invention.
• the invention concerns nanoparticles comprising a mixed oxide of titanium and antimony (hereinafter abbreviated Ti/Sb mixed oxide), wherein at least a portion of the Ti/Sb mixed oxide has a rutile-like crystalline phase.
• Ti/Sb mixed oxide a mixed oxide of titanium and antimony
• Nanoparticles of the invention comprise Ti/Sb mixed oxide.
• the weight ratio of titanium to antimony in the nanoparticles is in the range of 0.14 to 1 1.30, desirably in the range of from 0.22 to 5.02, and more desirably in the range of from 0.42 to 2.93.
• Ti/Sb mixed oxide nanoparticles according to the invention desirably comprise a rutile-like crystalline phase.
• the rutile-like crystalline phase may co-exist with other crystalline phases within individual Ti/Sb mixed oxide nanoparticles.
• Individual nanoparticles may comprise up to 100 weight percent of the rutile-like crystalline phase.
• Ensembles of Ti/Sb mixed oxide nanoparticles will typically comprise nanoparticles having a variety of sizes, elemental compositions, and crystalline phases.
• the term "ensemble average" of a parameter refers to the average value of that parameter across the entire ensemble being referred to. Thus, the term refers to a property of the bulk, not necessarily reflective of that property in each individual member of the ensemble.
• the ensemble average rutile-like crystalline phase content of Ti/Sb mixed oxide nanoparticles is at least 20 weight percent, more desirably at least 40 weight percent, more desirably at least 60 weight percent, and even more desirably at least 80 weight percent based on the total weight of Ti/Sb.
• the Ti/Sb mixed oxide nanoparticles may contain a rutile-like crystalline phase.
• the ensemble average relative intensity of rutile-like crystalline phase as compared to anatase, for Ti/Sb mixed oxide nanoparticles of the invention is greater than 1: 10.
• the relative intensity of any anatase or antimony oxide maxima observed by XRD have a relative intensity of less that 1 percent, more desirably less than 0.1 percent, where the relative intensity of the greatest diffraction maximum of the rutile-like phase is defined to be 100 percent.
• the Ti/Sb mixed oxide nanoparticles are free of additional metallic elements, although for some particular applications it may be desirable to add additional elements (including silicon). If additional metallic elements are present, they are desirably in an amount of less than 0.1 moles per mole of titanium present in the ensemble average of Ti/Sb mixed oxide nanoparticles.
• additional metallic elements include the rare earth elements.
• Ti/Sb mixed oxide nanoparticles of the invention typically have an ensemble average particle size of less than 500 nanometers, more desirably less than 100 nanometers, and still more desirably less than 40 nanometers, especially when the nanoparticles are to be incorporated into a transparent coating.
• Ti/Sb mixed oxide nanoparticles may be combined with additional nanoparticles having a different elemental composition (for example, silica, zirconia, alumina, titania, antimony pentoxide). Desirably, such additional nanoparticles, if present, have an average particle size comparable to that of the Ti/Sb mixed oxide nanoparticles. Such nanoparticles may be commercially obtained, for example, from
• nanoparticles are selected such that colloids and nanocomposites are free from a degree of particle agglomeration or coagulation that would interfere with the desired properties of the composition.
• individual, unassociated (that is, non-agglomerated and non-coagulated) particles are dispersed throughout the composition.
• the particles desirably do not irreversibly associate (for example, by covalently bonding and/or hydrogen bonding) with each other.
• the nanoparticles may irreversibly agglomerate, especially when employed without a dispersing medium (for example, liquid vehicle or binder).
• a dispersing medium for example, liquid vehicle or binder
• Nanoparticles may be present in colloidal dispersions of the invention in an amount of up to 30 percent, or more. The amount may vary with density and surface characteristics of the nanoparticle. Desirably, nanoparticles are present in an amount of from 1 to 25 weight percent, more desirably from 10 to 20 weight percent, of the colloidal dispersion.
• the pH of colloidal dispersions of the invention may be any value, but typically range from 4 to 9, desirably from 5 to 8.
• Colloidal dispersions of the invention are typically prepared as a dispersion of nanoparticles in an aqueous vehicle.
• the aqueous vehicle comprises water, typically as the predominant ingredient, and may contain organic solvents (especially solvents that may be present in the titania or antimony oxide precursors).
• Solvent may be added prior to, or more desirably following, hydrothermal processing.
• Exemplary organic solvents include alcohols, ethers, and/or ketones having from 4 to 12 carbon atoms.
• One such desirable solvent is l-methoxy-2-propanol.
• Solvents used in the present invention, if present, are chosen based on volatility and compatibility with the aqueous titania and antimony oxide precursors, binder precursor, and/or binder, depending on the point at which they may be added.
• Nanoparticles according to the invention may be incorporated in a binder to form a nanocomposite.
• the nanoparticles may be either directly incorporated into the binder, or incorporated into a binder precursor that is subsequently cured to form a binder.
• nanoparticles are present in the nanocomposite in an amount of at least 30 weight percent based on the total weight of the nanocomposite.
• Compatibility of inorganic nanoparticles with organic binders is typically achieved by appropriate treatment of the inorganic particles with a coupling agent.
• nanoparticles employed in practice of the present invention are typically surface-modified, which may be achieved by attaching surface-modifying agent(s) to the particle surface.
• Surface-modifying agent(s) attached to the surface of the particle can modify the surface characteristics of the particles to achieve a variety of properties including, for example, to increase the compatibility of the particles with the components of the composition, to facilitate dispersion of the particles in the composition (either from isolated or colloidal form), and to enhance optical clarity of the composition and combinations thereof.
• the particles can also be surface-modified to include surface groups capable of associating with other components of the composition. When the composition is polymerized, for example, the surface groups can associate with at least one component of the composition to become part of the polymer network. Preferably, the surface groups are capable of associating with the first monomer, the second monomer, or a combination thereof.
• the particles are surface-modified to include a combination of surface groups capable of providing compositions having desired dispersion, clarity, adhesive, and rheological properties.
• surface-modifying agents can be represented by the formula A-B where the A group is capable of attaching to the surface of the particle, and where the B group is a compatibilizing group that may be reactive or non-reactive with the components of the composition.
• Compatibilizing groups B that impart polar character to the particles include, for example, polyethers.
• Compatibilizing groups B that impart non-polar character to the particles include, for example, hydrocarbons.
• Exemplary suitable surface-modifying agents include, for example, carboxylic acids, sulfonic acids, phosphonic acids, silanes, phosphates, and combinations thereof.
• Useful carboxylic acids include, for example, long chain aliphatic acids including octanoic acid, oleic acid, and combinations thereof.
• Representative examples of polar modifying agents having carboxylic acid functionality include CH3O(CH2CH2O)2CH2CO2H, 2-(2- methoxyethoxy)acetic acid, and mono(polyethylene glycol) succinate.
• Representative examples of nonpolar surface-modifying agents having carboxylic acid functionality include octanoic acid, dodecanoic acid, and oleic acid.
• Exemplary useful silanes include organosilanes, for example, octyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3- mercaptopropyltrimethoxysilane, n-octyltriethoxysilane, phenyltriethoxysilane, p- tolyltriethoxysilane, vinyltrimethoxysilane, and combinations thereof.
• Exemplary useful non-silane surface-modifying agents capable of associating with organic components of the composition include acrylic acid, methacrylic acid, beta- carboxyethyl acrylate, mono-2-(methacryloxyethyl) succinate, and combinations thereof.
• Nanoparticles can be surface modified using a variety of methods including, for example, adding a surface-modifying agent to nanoparticles (for example, in the form of a powder or an aqueous sol) and allowing the surface-modifying agent to react with the nanoparticles.
• a co-solvent can be added to the composition to increase the compatibility (for example, solubility or miscibility) of the surface-modifying agent and/or surface modified particles with the aqueous mixture.
• the surface-modified nanoparticles may be intimately mixed with a curable binder precursor that may be subsequently processed prior to curing.
• binder precursor is not critical so long as it is not reactive under ambient conditions with the surface-modified nanoparticles.
• Exemplary binder precursors include, but are not limited to, polymerizable materials such as free-radically polymerizable monomers and oligomers such as acrylates, methacrylates, allylic compounds, vinyl ethers, vinyl esters, and the like; epoxy resins; alkyd resins; phenolic resins; cyanate esters; melamine and melamine- formaldehyde resins; polyurethane resins, and mixtures thereof.
• binder precursors comprise acrylates and/or methacrylates.
• the binder precursor may include a catalyst or other curative in order to facilitate cure.
• catalysts and other curatives will depend on the nature of the binder precursor and may include those well known in the curing art, for example, thermal free radical initiators, such as peroxides and azo compounds, photoinitiators, photocatalysts, amine hardeners, mercaptans, etc.
• the binder precursor may be cured to form a binder by application of energy such as heat or actinic radiation (for example, ultraviolet light and electron beam radiation), or through addition of a catalyst or curative.
• a photoinitiator is present in the binder precursor and the mixture is irradiated with ultraviolet actinic radiation from a lamp, desirably in an inert atmosphere such as nitrogen.
• actinic radiation to cure the binder precursor allows a high degree of flexibility in the choice of protecting groups.
• the amount of actinic radiation energy used for curing depends upon a number of factors, such as the amount and the type of reactants involved, the energy source, web speed, the distance from the energy source, and the thickness of the material to be cured.
• actinic radiation typically involves a total energy exposure from 0.1 to 10 Joules per square centimeter
• electron beam radiation typically involves a total energy exposure in the range from less than 1 megarad to 100 megarads or more, desirably 1 to 10 megarads. Exposure times may be from less than 1 second up to 10 minutes or more.
• free-radical generating photoinitiators suitable for the invention include, but are not limited to, benzophenone, benzoin ether, and acylphosphine photoinitiators such as those sold under the trade designations IRGACURE and
• the amount of photoinitiator(s) used typically varies between 0.1 and 15 weight percent, desirably between 0.5 and 7 weight percent, based on the total weight of the binder precursor.
• Co-initiators and amine synergists can be included in order to improve curing rate.
• examples of such include isopropylthioxanthone, ethyl 4-(dimethylamino)benzoate, 2- ethylhexyl dimethylaminobenzoate, and dimethylaminoethyl methacrylate.
• the volume ratio of surface-modified nanoparticles to binder precursor may range from 1:99 up to 70:30, desirably from 5:95 up to 55:45, and more desirably from 10:90 up to 40:60.
• nanoparticles present in the binder precursor and or binder desirably have a small particle size (for example, ⁇ 40 nm) to minimize the effects of light scattering.
• a composite article 100 may comprise a nanocomposite layer 10 containing Ti/Sb mixed oxide nanoparticles 30 dispersed in a binder 40, and supported on a substrate 20, wherein at least a portion of the Ti/Sb mixed oxide nanoparticles contain a rutile-like crystalline phase.
• the substrate may be virtually any solid material.
• Non-limiting examples of such substrates include glass (including electronic displays), quartz, transparent or translucent ceramics, wood, metal, painted surfaces including painted metals, and thermoset and thermoplastic materials such as acrylic polymers (for example, polymethyl methacrylate), polycarbonates, polyurethanes, polystyrene, styrene copolymers, such as acrylonitrile- butadiene-styrene copolymer and acrylonitrile-styrene copolymer, cellulose esters (for example, cellulose acetate, cellulose diacetate, cellulose triacetate, and cellulose acetate- butyrate copolymer), polyvinyl chloride, polyolefins (for example, polyethylene and polypropylene), polyamides, polyimides, phenolic resins, epoxy resins, polyphenylene oxide, and polyesters (for example, polyethylene terephthalate).
• Thermoplastic materials may contain fillers and other adjuvants.
• the substrate is glass or a thermoplastic polymer film.
• Substrates may be either opaque or transparent depending on the application.
• Nanocomposite layer 10 may be prepared by coating a composition comprising nanoparticles 30 and a binder precursor onto substrate 20, and curing the binder precursor. Coating may be accomplished by virtually any known coating means that does not chemically or physically alter properties of the binder precursor. Exemplary coating methods include, for example, spin coating, knife coating, wire coating, flood coating, padding, spraying, exhaustion, dipping, roll coating, foam techniques, and the like.
• the thickness of the mixture of binder precursor and nanoparticle layer that is applied will depend on the particular primary substrate and application.
• the thickness of the resultant cured nanocomposite layer is desirably in the range of from 1 nanometers up to 50 micrometers or even thicker, more desirably from 0.5 micrometers to 10 micrometers, and more desirably from 3 micrometers to 6 micrometers. Thicker nanocomposite layers may lead to crazing and other defects over time; however, thinner layers often do not provide enough surface material to be scratch resistant.
• the ingredients in the nanocomposite layer are desirably chosen so that it has a refractive index close to that of the substrate. This can help reduce the likelihood of Moire patterns or other visible interference fringes.
• Ti/Sb mixed oxide nanoparticles are prepared by combining an aqueous titania precursor with an aqueous antimony oxide precursor.
• aqueous antimony oxide precursors are desirably molecular species (that is, species having a single antimony atom) or loosely associated species that dissociate under reaction conditions. Any titania or antimony oxide precursors meeting this requirement may be used.
• Exemplary aqueous titania precursors include the reaction products of hydrogen peroxide with titanium alkoxides.
• alkoxides include as 1-butoxide, 2- ethylhexoxide, 2-methoxy-l-ethoxide, linear and branched alkoxides (such as ethoxide, 1- propoxide, 2-propoxide, 2-butoxide, iso-butoxide, tert-butoxide, hexoxide, and the like).
• the aqueous titania precursor is a reaction product of a titanium alkoxide with hydrogen peroxide.
• Exemplary aqueous antimony oxide precursors include the reaction products of antimony alkoxides with hydrogen peroxide and HSb(OH)6- Exemplary alkoxides include
• Two or more of the same or different organic ligands may be attached to the antimony.
• aqueous titania and antimony oxide precursors are combined with mixing and simultaneously, or sequentially, are subjected to conditions whereby they form a mixed oxide.
• the amount of each precursor employed is determined based on the stoichiometric quantity required to prepare Ti/Sb mixed oxide nanoparticles of the invention as described above.
• aqueous metallic oxide precursors may be mixed with the aqueous titania and antimony oxide precursors, if desired.
• the mixture is typically subjected to heat and pressure.
• this may be accomplished by means of a pressure vessel such as a stirred or non-stirred pressure reactor, commercially available from Parr Instruments Co. (Moline, IL).
• the vessel should be capable of withstanding pressure and capable of sealing.
• the vessel containing the mixture is sealed, and the solution is heated to a temperature satisfactory to drive the hydrolysis and condensation of the reactants.
• the vessel is heated at a rate of
• Suitable pressures are governed by the temperature and the vessel used to heat the reaction mixture.
• the desired temperature is greater than 120 C and less than 300 C. Desirably, the temperature is between 150 C and 200 C. Heating the solution within the closed vessel creates pressure. The pressure within the vessel is typically between 18 atmospheres to 40 atmospheres. Typically, the solution is heated for up to 5 hours to ensure complete hydrolysis although shorter reaction times can be effective. The length of the heating time is determined by the time necessary to achieve the desired temperature of the bulk. Once this temperature is achieved, the reaction is typically over virtually instantaneously. Additional time at this temperature typically leads to increasing crystallite sizes, which usually trends with decreased colloidal stability of the nanoparticles. Desirably, the ensemble average rutile-like crystallite size of Ti/Sb mixed oxide nanoparticles is less than
• the mixed metal oxide particles are typically observed as a slurry of a solid precipitate (that is, agglomerated Ti/Sb mixed oxide nanoparticles) in the aqueous vehicle.
• the particles may be separated from the liquid by transferring the slurry into centrifuge bottles, centrifuging the slurry, and decanting the supernate.
• Other methods of separating the mixed metal oxide particles from the reaction mixture are possible such as filtration, sedimentation, or flushing.
• any unwanted components of the reaction mixture may be removed by evaporation or by selective distillation.
• the metal oxide particles may, optionally, be dried.
• Ti/Sb mixed oxide nanoparticles can also be prepared using a stirred tube reactor (that is, STR).
• Stirred tube reactors typically have a motor driven shaft that is coaxially positioned along the length of a heated tube. The shaft has multiple paddles mounted to it that provide mixing and heat transfer of the reaction mixture.
• Stirred tube reactors are well known in the art. One particular STR design is described in Example 15.
• a reservoir 210 contains an aqueous mixture of a titania precursor and an antimony oxide precursor having a solids content of 1 - 2 weight percent.
• Pump 220 feeds the aqueous mixture into STR
• pump 220 is capable of maintaining a substantially even flow rate (for example, a diaphragm pump).
• a pulse dampener 240 is desirably disposed between pump 220 and STR 230.
• Hydraulic pulse dampeners are well known in the art. Exemplary pulse dampeners include closed-end pipes and are described in U. S. Pat. Nos. 5,816,291 and 2,504,424. Desirably the pulse dampener comprises a closed-end stand pipe.
• FIG. 3 One particularly useful embodiment of a pulse dampener is depicted in FIG. 3.
• Pulse dampener 300 contains a pressurized fluid 315, and consists of a length of pipe 310 having a cap 320 and an air cavity 325 at the uppermost end of the pipe, and a pressurized fluid inlet 330 at the lowermost end of the pipe.
• Transfer pipe 340 is perpendicularly joined to pipe 310.
• Transfer pipe 340 is joined to back pressure valve 370, which has an outlet pipe 380.
• Pipes 310, 340 and 380 are connected such that fluid travels from the inlet pipe to the outlet pipe without loss of material.
• pressurized fluid emerges from outlet pipe 380 and enters the STR.
• a diaphragm pump may on its forward stroke push a liquid into pressurized fluid inlet 330 causing air cavity 325 to shrink in volume as the air compresses.
• the compressed air acts as a mini-compression feed chamber and returns liquid to the fluid stream. The cycle repeats over and over as the pump operates, thereby smoothing pressure pulses of the fluid being pumped.
• Typical residence times of the aqueous mixture in STR 230 are 10 - 20 minutes.
• the heated mixture passes through a heat exchanger 250 to cool the mixture down before collection.
• a second pump 260 may add a surface functionalizing agent in reservoir 290 to the heated mixture just prior to entering the heat exchanger in order to treat the surface of the particles to prevent agglomeration.
• a backpressure regulator valve 270 is positioned after the heat exchanger and controls the pressure of STR 230 to make sure that the water stays in a liquid state.
• Typical pressures in the STR are around 250 to 350 pounds per square inch (1.7 to 2.4 megaPascals).
• the STR provides internal mixing, which facilitates efficient heat transfer. In addition, the mixing action of the STR provides plug flow conditions inside the reactor.
• the colloidal dispersion of Ti/Sb mixed oxide nanoparticles may contain outlier (that is, excessively large) particles.
• outlier particles may be removed by centrifugation thereby improving the clarity of the colloidal dispersion and narrowing the particle size distribution.
• the colloidal dispersion may be used in that form or solvent (for example, water) may be replaced with an organic solvent or a solution containing an organic solvent and a dispersing aid to form slurry using methods well known in the art.
• Solvents used in the present invention may be chosen based on volatility and compatibility with any binder precursor that may be used in combination with the nanoparticles.
• Typical organic solvents include C5-C12 aliphatic compounds, aromatic compounds, alcohols, ethers, esters, and/or ketones.
• Exemplary aliphatic solvents include cyclohexane, heptane, toluene, xylene, 2-butanone, or 4-methyl-2-pentanone, l-methoxy-2-propanol, and the like. l-Methoxy-2-propanol is especially desirable.
• Ti/Sb mixed oxide nanoparticles of the present invention may be advantageously combined with at least one dispersing aid that attaches an organic moiety, desirably through at least one covalent bond, to the surface of the metal oxide particles.
• Typical dispersing aids include alkoxysilanes such as alkyltrialkoxysilanes, organic acids such as carboxylic acids, alcohols, polyethylene glycols, mono- or di-esters of fatty acids, polyethylene oxide and polypropylene oxide, alkoxylated phosphonic acids and their esters, and combinations thereof.
• dispersing aids include alkoxysilanes, desirably octyltriethoxysilane, octadecyltrimethoxysilane, hexadecyltrimethoxysilane, carboxylic acids, and combinations thereof.
• Dispersing agents include stearic acid, oleic acid, and KEN-REACT Coupling Agent KR TTS, commercially available from Kenrich Petrochemicals (Bayonne, NJ).
• Dispersing aids that are coupling agents may be used.
• a coupling agent is a dispersing aid with two functional groups.
• Suitable coupling agents include methacrylic acid, glycine, glycolic acid, mercaptoacetic acid, methacryloyloxyethyl acetoacetate, allyl acetoacetate, 3-acryloxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 7-octen-l- yltrimefhoxysilane, and allyl triethoxysilane.
• the colloidal dispersion typically has a solids content in the range of from 1 to 2 weight percent, although higher and lower solids contents may also be employed.
• the colloidal dispersion is then stirred, preferably with heating at temperatures greater than 60 C and less than 95 C, until the surface of the colloidally-dispersed particles is substantially coated and/or reacted with the dispersing aid.
• the colloidal dispersion may be concentrated to give a colloidal dispersion having a solids content in the range of from 2 to 20 weight percent, desirably from 5 to 10 weight percent.
• the colloidal dispersion typically has a ratio of dispersing agent to metal oxide of 0.1 to 6.0 millimole/gram, desirably 0.2 to 2.0 millimole/gram.
• An amount of water may then be added in sufficient amount to remove any remaining hydrolyzable groups and further condense dispersing agents to the particle surface.
• base hydrolysis was found to be particularly advantageous for hydrolysis of the alkoxyorganosilane and condensation onto the particle surface.
• An optional step involves the removal of high boiling point by-products from the stable colloidal dispersion, whereby the stable colloidal dispersion is concentrated to a syrup by heat or vacuum drying. If the stable colloidal dispersion comprises a polar liquid, the crystalline nanoparticles are weakly flocculated by the addition of a non-polar liquid. If the stable colloidal dispersion comprises a non-polar liquid, the crystalline nanoparticles are weakly flocculated by the addition of a polar liquid. The flocculated nanoparticles are typically isolated by centrifugation and then washed by re-suspension in one of the flocculating liquids and separated by centrifugation.
• the precipitate may be dried to form a powder, or the precipitate may be dispersed in an organic liquid or solvent to form a colloid.
• Colloids of the present invention are stable dispersions as measured by centrifuging the colloid samples at 2500 rpm for 10 minutes. Colloids (or sols), if substantially free of sediment after centrifugation, are said to be stable dispersions.
• Particle Size was determined by Photon Correlation Spectroscopic analysis using a Coulter N4 Submicron Particle Analyzer, commercially available from Coulter Corp. (Miami, FL). Crystalline Phase X-ray diffraction analysis (that is, XRD) was used to determine the crystalline phase. Data were collected using a Philips vertical diffractometer, commercially available from Philips Electronic Instruments Co. (Mahwah, NJ). The diffractometer was fitted with variable entrance slits, fixed 0.2 degree receiving slit, graphite diffracted beam monochromator, and proportional detector for registry of the scattered radiation. A sealed copper target X-ray source was used at generator settings of 45 kV and 35 mA.
• a 2-liter flask was charged with 848 g deionized water, 85 g of 30 weight percent hydrogen peroxide, commercially available from Fisher Scientific (Pittsburgh, PA) and 32 g of 0.33 M aqueous ammonium hydroxide.
• the stirred contents of the flask were cooled to 10 C in a cold-water bath, and 35.6 g titanium tetraisopropoxide, commercially available from Gelest, Inc. (Tullytown, PA) was added slowly over 3 minutes resulting in an orange-yellow precipitate and the gentle evolution of gas.
• the slurry was allowed to slowly warm to room temperature over 6 hours over which time the precipitate was fully digested to give a yellow, pourable liquid composed of peroxy titanic acid in water (theoretical yield was 1 weight percent Ti ⁇ 2).
• a 1 -liter flask was charged with 469 g deionized water and 21 g of 30 weight percent hydrogen peroxide. The stirred contents were cooled to 5 C in an ice bath, and
• a 0.5-liter flask was charged with 297 g deionized water, 20 g AMBERLITE IR- 120 (plus) ion-exchange resin, and 4.9 g potassium hexahydroxyantimonate.
• the resultant slurry was allowed to mix 14 hours and subsequently heated to 65 C for 1 hour to form a stable white sol.
• the sol was cooled to room temperature and filtered on a C-grade glass frit to give an aqueous white colloid of HSb(OH)6 with a measured pH of 3 (theoretical yield was 1 weight percent Sb2 ⁇ 5).
• a 2-liter pressure reactor commercially available from Pressure Products Industries, Inc. (Warminster, PA) was charged with about 1200 g of a mixture of peroxy titanic acid and colloidal HSb(OH)g in a weight ratio as indicated in Table 1.
• the reactor was heated to 180 C for 3 hours.
• the reactor was allowed to cool slowly to room temperature over 12 hours.
• the resultant transparent colloid was filtered through a GF/B filter (glass fiber filter, 1.0 micrometer pore size), commercially available from Whatman, Inc. (Clifton, NJ).
• EXAMPLE 14 This example describes the preparation of an aqueous colloid of Ti/Sb mixed oxide nanoparticles having a rutile-like crystalline phase.
• a 2-liter pressure reactor was charged with 1369 g of peroxy titanic acid and 342 g colloidal HSb(OH)g (weight ratio was 80 parts titanium dioxide to 20 parts antimony oxide). The reactor was heated to 180 C for 2 hours. The pressure in the reactor reached
• the reactor was cooled quickly to 75 C by packing the outside of the reactor with dry ice.
• the reaction produced a transparent colloid with a slight blue hue and a measured particle size of 31.9 nanometers with a standard deviation of 6.4 nanometers.
• a portion (that is, 5 mL) of the colloid was dried in a 100 C oven and the resultant powder was analyzed by XRD which showed a rutile-like peak with 100 percent relative intensity having a 20.5 nanometers crystallite size and a 49 percent relative intensity anatase peak having a 15.0 nanometers crystallite size.
• There was no evidence of a separate antimony oxide phase instead the observed diffraction maxima for the rutile-like phase were slightly shifted from rutile itself, indicating the antimony atoms were distributed throughout the lattice structure.
• EXAMPLE 15 This example shows the use of a stirred tubular reactor to prepare Ti/Sb according to one embodiment of the invention.
• Colloidal HSb(OH)g was added to peroxy titanic acid such that a calculated weight ratio of Ti ⁇ 2 to Sb2 ⁇ 5 was 80/20 obtained.
• Sufficient concentrated ammonium hydroxide was added to the mixture in order to raise the pH to about 7, which made the precursor stable and prevented gelation.
• the mixture formed an intermediate peroxy complex that was allowed to digest over 3 hours to form a clear orange solution of mixed metal peroxy complex (1 percent Ti ⁇ 2/Sb2 ⁇ 5 by weight).
• the mixture was injected in to a 316 stainless steel 2-liter stirred tube reactor operated at a heater temperature of 204 °C and a residence time of 11.1 minutes.
• the length of the STR was 60 inches and the inside diameter was 2 inches to give an L/D ratio of 30.
• the throughput was 180 grams per minute, and the stirring motor speed was 120 revolutions per minute.
• the system pressure was 300 pounds per square inch (2.1 megaPascals).
• the temperature at the output of the reactor was 190 C.
• the mixture was pumped through the reactor using a diaphragm pump (Model No. EK-1) commercially available from American Lewa, Inc. (Holliston, MA) having a pulse dampener consisting of an air cavity made from an end-capped length of 10 inch 1/2" OD stainless steel pipe, and a back pressure valve arranged as depicted in FIG. 3 contiguously situated between the pump and the inlet to the STR.
• the output mixture from the STR was immediately passed through a heat exchanger to rapidly cool the mixture to about 75-
• the particle size of the resultant colloidal dispersion was determined using a CHDF 2000 particle analyzer obtained from Matec Applied Sciences, Inc. (Northborough,
• the weight average particle size was 123 nanometers.
• This dispersion was centrifuged using a CARR POWERFUGE PILOT gravity centrifuge available from Kendro Laboratory Products (Franklin, MA) using a speed setting of 10 (corresponding to a G-Force of 20,308) resulting in a transparent colloidal dispersion of Ti/Sb mixed oxide nanoparticles, exhibiting a rutile-like crystalline phase, having a weight average particle size of 64 nanometers and a narrow size distribution.
• EXAMPLE 16 This example shows the preparation of a composite article employing colloidal surface modified Ti/Sb mixed oxide nanoparticles having a rutile-like crystalline phase.
• An 8-ounce (237 milliliters) glass jar was charged with 100 grams of antimony doped titanium oxide colloid (as prepared in Example 3) and 600 milligrams SDLQUEST A1230 (a silane coupling agent commercially available from Witco Corp. of Endicott,
• the transparent colloid was placed in an 80 C oven for 16 hours, then cooled to room temperature. The colloid was transferred to a flask and reduced down to 3 grams utilizing a rotary evaporator.
• l-Methoxy-2-propanol (18 grams, commercially available from Aldrich of Milwaukee, WI) was added to the colloid and the mixture was reduced to 7 grams utilizing a rotary evaporator.
• l-Methoxy-2-propanol (12 grams) was added to the colloid and the mixture was reduced utilizing a rotary evaporator to give final colloid with 8.1 weight percent metal oxide. This colloid was mixed with 1.85 grams of a mixture of 30 weight percent SR 295
• 2,4,6-Trimethylbenzoyl-diphenyl-phosphine oxide liquid photoinitiator commercially available from BASF Corp. (Mount Olive, NJ) under the trade designation LUCIRIN LR 8893, was added at 1 percent to the resin that was then bar coated at 0.5 mils thickness onto a 0.125inch polymethyl methacrylate sheeting. The coated sample was cured by passing the coated sample through a Fusion UV
• VPS-6 power supply EPIQ 6000 irradiator obtained from Fusion UV Systems, Corp. (Rockville, MD) that was equipped with a "D"-bulb on full power (600W/in) and operating at a line speed of 40 feet per minute (12.2 meters per minute).
• the resultant cured coated film had a measured refractive index of 1.569.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Nanotechnology (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Physics & Mathematics (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Composite Materials (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Paints Or Removers (AREA)
• Colloid Chemistry (AREA)
• Pigments, Carbon Blacks, Or Wood Stains (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=25536321

Family Applications (1)

Country Status (8)

Cited By (7)

Families Citing this family (51)

Citations (3)

Family Cites Families (33)

• 2001
  • 2001-11-21 US US09/990,604 patent/US6962946B2/en not_active Expired - Fee Related
• 2002
  • 2002-09-16 DE DE60220941T patent/DE60220941T2/de not_active Expired - Lifetime
  • 2002-09-16 JP JP2003547308A patent/JP4276077B2/ja not_active Expired - Fee Related
  • 2002-09-16 EP EP02761684A patent/EP1451108B1/en not_active Expired - Lifetime
  • 2002-09-16 AT AT02761684T patent/ATE365701T1/de not_active IP Right Cessation
  • 2002-09-16 WO PCT/US2002/029392 patent/WO2003045846A1/en not_active Ceased
  • 2002-09-16 CN CNB028228545A patent/CN1268549C/zh not_active Expired - Fee Related
  • 2002-09-16 AU AU2002326930A patent/AU2002326930A1/en not_active Abandoned
• 2004
  • 2004-08-10 US US10/915,308 patent/US7250118B2/en not_active Expired - Fee Related
  • 2004-08-10 US US10/915,295 patent/US7304106B2/en not_active Expired - Fee Related

Patent Citations (3)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events