Abstract: The present invention relates to stabilising compositions, particularly stabilising compositions which can be used to stabilise insulation or semi-conductive compositions, such as are used for electrically insulating wires and cables. The stabilising composition comprises: a first stabilising component comprising at least one fully hindered phenolic antioxidant; a second stabilising component comprising at least one partially hindered phenolic antioxidant; and a third stabilising component comprising at least one sulphur-containing antioxidant.

Abstract: Provided is a method and an apparatus for producing a novel polymer that is easy and convenient to control the reactivity and excellent in film thickness control and a method and an apparatus for producing an organic film. A production apparatus includes: a first means for turning a raw-material solution containing an organic compound into a mist or droplets by an atomization or a droplet-formation; a second means for carrying the mist or droplets onto a substrate using a carrier gas; and a third means for subjecting the mist or droplets to a thermal reaction by heating on the substrate.

Abstract: An assembly that includes a barrier film interposed between a first polymeric film substrate and a first major surface of a pressure sensitive adhesive layer is provided. The first polymeric film substrate has a first coefficient of thermal expansion that is, in some embodiments, up to 50 parts per million per Kelvin. The pressure sensitive adhesive layer has a second major surface opposite the first major surface that is disposed on a second polymeric film substrate. The second polymeric film substrate is typically resistant to degradation by ultraviolet light. In some embodiments, the second polymeric film substrate has a second coefficient of thermal expansion that is at least 40 parts per million per Kelvin higher than the first coefficient of thermal expansion. The assembly is transmissive to visible and infrared light.

Abstract: A method of producing a glass preform including: forming a porous glass soot configured by an inner deposition soot deposited on a start material and an outer deposition soot deposited outside the inner deposition soot; and sintering, after the forming, the porous glass soot while doping with fluorine to form a glass body including an inner glass portion and an outer glass layer. An amount of the fluorine, with which the inner deposition soot is doped at the sintering, is equal to or more than 0 g/cm3 and less than an amount of the fluorine with which the outer deposition soot is doped.

Abstract: The present invention relates to an organic light emitting device and a method of preparing the same. More particularly, the organic light emitting device according to the present invention includes: a substrate; an organic light emitting unit in which a first electrode, an organic material layer, and a second electrode are sequentially stacked on the substrate; and an encapsulating unit configured to seal an external side of the organic light emitting unit, in which a protecting unit is provided on at least a partial region of the substrate, on which the organic light emitting unit and the encapsulating unit are not provided, and at least a partial region in a lateral surface region of the substrate.

Abstract: The present invention includes compositions and methods for synthesis of composite materials involving gas phase plasma polymerization to covalently plasma graft an organic molecule onto inorganic particles; covalently binding an organic monomer to the functionalized inorganic particles; and, polymerizing the organic monomers into inorganic/organic hybrid polymer composite materials.

Abstract: Disclosed herein is a method of coating and curing, including conveying a substantially flat substrate to be coated with a conveyor system through a combination roll coating and curing facility, wherein the combination roll coating and curing facility comprises at least one roll coating facility and at least one curing facility, roll coating the substantially flat substrate with a continuous sol gel coating material with the at least one roll coating facility, and curing the sol gel coating material on the substantially flat substrate with an air knife of the at least one curing facility, wherein the air knife is adapted to direct a heated stream of air to cure the continuous sol gel coating material while an interior of the substantially flat substrate remains at a temperature substantially lower than a temperature of air from the air knife.

Abstract: An apparatus and method for depositing an ultra-thin inorganic coating on to a packaging film substrate is disclosed. Flame pretreatment enhances the quality of the inorganic coating. Multiple coating layers may be deposited onto the substrate by passing the substrate over various one or more flame head configurations in either a stand-alone or in-line manufacturing environment.

Abstract: Process for the production of a flame-retardant plastics piping system which comprises piping components, in particular piping and connecting elements, such as fittings, valves, screw-threaded elements, containers, pumps, and to which, on the exterior surface of the plastics piping system, an intumescent water- or solvent-based coating comprising a crosslinking binder, in particular at least one of the following binders: vinyl acetate, epoxy resin, acrylate, acrylate mixed resin, polyurethane, polyurethane-acrylate, and various fillers, is applied, where a protective layer is applied over the intumescent coating.

Abstract: A solar cell protective sheet comprising a polyethylene terephthalate-containing substrate that has been surface-treated through flame treatment with a silane compound-introduced flame or through atmospheric-pressure plasma treatment, and having, on the treated surface of the substrate, a coating layer that contains a fluoropolymer, has good interlayer adhesiveness after wet heat aging.

Abstract: A water-based primer coating for use on paper and polymeric substrates is provided for enhancing the adhesion of liquid toner to the substrates, which are designed to be printed using an electrophotographic printing device. The primer coating includes an aliphatic polyurethane dispersion and an anionic wax emulsion, and is substantially free of copolymers of ethylene and acrylic acid.

Abstract: An enamel bead-making system involves a novel bead-pulling station and a mandrel (slender rod). The mandrel is for manually dipping a preheated metal bead core into a container of glass powder so that the powder melts and later solidifies on the core, thereby creating an enamel or glass coated bead. To safely remove the hot enamel bead from the mandrel, the mandrel is manually pulled through a V-notch in an upper edge of the bead-pulling station, which forces the bead off the end of the mandrel and into a collection area for cooling. A second V-notch allows a subsequent bead to be removed and cooled at a location spaced apart from the first one. If a bead sticks on the mandrel, the mandrel can be pushed through a small hole in the bead-pulling station, which helps break a glass bond that might develop between the mandrel and the enamel bead.

Abstract: A formulation is provided which comprises at least one phenolic compound in an amount of about 0.5 to about 1.2% of the mass of the formulation; at least one fragrance in an amount of about 0.3 to about 1.0% of the mass of the formulation; and at least one alcohol in an amount of about 90 to about 99% of the mass of the formulation. Said formulation is surfactant free and being capable of rendering anti-microbial finish to fabrics. And also, a process for preparing a fabric with anti-microbial finish is provided.

Abstract: A method for manufacturing a dye sensitized nanocrystal film having the steps of exposing a tin oxide layer on a surface of a substrate to a flame for a time sufficient to form a layer of mesoporous, crystalline titanium oxide on the fluorinated tin oxide layer followed by sintering the substrate at a temperature of from about 300 to about 500° C. The flame contains a fuel gas, such as ethylene and oxygen and titanium organometallic. The concentration of titanium organometallic is from about 10 to about 2000 ppm. During the flame exposure step, the substrate is rotated about a central axis at a speed of from about 100 to about 600 RPM, and the flame is kept at a constant distance from the surface of the substrate. The temperature of the substrate is maintained at a temperature of less than 200° C. via the rotation and jets of gas.

Abstract: The invention is directed to a process for reducing the gas permeability of a plastic material by applying a barrier coating on the plastic material comprising the steps a) pre-treatment of at least a part of the plastic material; b) applying at least one coating layer of polyvinyl alcohol on the pre-treated surface and c) applying at least on top coating layer of polyvinyl acetal on the polyvinyl alcohol layer.

Abstract: A primer coating is provided for use on a variety of substrates which provides enhanced liquid toner or ink adhesion when applied to substrates which are printed using high speed electrophotographic printing devices. The primer coating includes a natural rosin dispersion including a hydrogenated hydrocarbon rosin or rosin ester and a colloid forming material which is blended with a dispersion of a copolymer of ethylene and acrylic or methacrylic acid.

Abstract: A primer coating is provided for use on polymeric substrates to enhance adhesion of liquid toner to the substrates for printing in an electrophotographic printing device. The primer coating includes a dispersion of a copolymer of ethylene and acrylic or methacrylic acid and a compatible adhesion enhancer comprising a hydrogenated rosin or rosin ester dispersion. The coating may also include additives such as wetting agents, antiblocking agents, matting agents, and waxes. The primer coating may be applied to a variety of polymeric substrates including polypropylene, biaxially oriented polypropylene, polyethylene terephthalate, and polyvinyl chloride.

Abstract: A method of adhering a particulate material, such as a hydrocarbon adsorbent material and/or a catalytic material, to a plastic surface, and products comprising the adhered material are disclosed.

Abstract: A method of making a coated article including a transparent conductive oxide (TCO) film supported by a glass substrate is provided. In certain example embodiments, the coated article including the TCO film on the glass substrate is thermally tempered in a tempering furnace. In certain example embodiments, during tempering flame(s) are provided proximate the exposed surface of the TCO in order to burn off excess oxygen near the TCO surface thereby preventing or reducing oxidation of the TCO during the tempering process. A coated article, that is thermally tempered, made by such a product is also provided.

Abstract: Method for producing a multifunctional material includes thermally treating a substrate having a surface layer formed of titanium, titanium oxide, a titanium alloy, or a titanium alloy oxide so that the temperature of the surface layer is raised to 600° C. or higher, to thereby provide, in the interior of the surface layer, a second layer formed of forest microcolumns of titanium oxide or a titanium alloy oxide; and subsequently cutting the second layer in parallel with the surface layer, to yield a material including the substrate and a layer formed of titanium-oxide- or titanium-alloy-oxide-formed forest microcolumns exposed on at least a portion of the substrate, as well as a material including a thin film, numerous continuous small-width with protrusions thereon, and forest microcolumns formed on the protrusions.

Abstract: Certain example embodiments relate to surface-assisted combustion deposition deposited coatings (e.g., metal oxide coatings) formed on glass substrates, and/or methods of making the same. In certain example embodiments, a wet-applied (e.g., sol-gel applied) pre-treatment coating increases a number of nucleation sites on or proximate to the at least one surface of the substrate to be coated, and/or increases a number of binding sites or forms a binding medium on the at least one surface of the substrate to be coated. A combustion deposition deposited growth is formed thereon. The pre-treatment coating may facilitate the combustion deposition depositing of coatings.

Abstract: Certain example embodiments of this invention relate to the combustion deposition depositing of alkaline earth fluoride inclusive coatings on substrates from a metal inclusive organic precursor and a fluorinating reagent, or from a single-source precursor. In certain example embodiments, the fluorinating reagent may be an organic source or an inorganic source. In certain example embodiments, the alkaline earth fluoride inclusive coating may be a magnesium fluoride (e.g., MgF2 or other suitable stoichiometry) inclusive coating, although other Group 2 metals may be used in place of magnesium. In certain example embodiments, the alkaline earth fluoride inclusive coating may be an anti-reflective (AR) coating.

Abstract: The invention relates to a method for producing friction surfaces or friction layers in a carbon-ceramic brake disk for motor vehicles in which the friction surfaces or friction layers in the finished state are treated by a thermal coating method. The invention likewise relates to the corresponding friction surfaces or friction layers of a carbon-ceramic brake disk for motor vehicles which are produced according to such as process.

Abstract: A web of a polymer film (1) is coated with an oxide layer, in particular with an SiOx barrier layer, by transporting the web with the aid of a rotatable drum (12) through a plurality of flame bands, which are directed in a radial direction from above against the circumferential surface of the drum, which extend at a distance from each other across the width of the web being supported and transported on this circumferential surface, and which are fed with a gas mixture including a combustible gas, an oxidant, and a silicon containing compound. Therein the circumferential surface of the rotatable drum is cooled to a predetermined temperature and the web is transported through the area of the tip of the inner flame region. Polymer films with barrier layers produced in the named way have at small layer thicknesses of less than 10 nm very good barrier properties.

Abstract: A method for producing a substrate having a carbon-doped titanium oxide layer, which is excellent in durability (high hardness, scratch resistance, wear resistance, chemical resistance, heat resistance) and functions as a visible light responding photocatalyst, is provided. The surface of a substrate, which has at least a surface layer comprising titanium, a titanium alloy, a titanium alloy oxide, or titanium oxide, is heat-treated in a combustion gas atmosphere of a gas consisting essentially of a hydrocarbon, or in a gas atmosphere consisting essentially of a hydrocarbon, such that the surface temperature of the substrate is 900 to 1,500° C.; or a combustion flame of a gas consisting essentially of a hydrocarbon, is directly struck against the surface of the substrate for heat treatment such that the surface temperature of the substrate is 900 to 1,500° C., thereby forming a carbon-doped titanium oxide layer, whereby the substrate having the carbon-doped titanium oxide layer is obtained.

Abstract: The process for modifying a silicone rubber surface by coating with a functional layer is characterised in that a silicate-containing functional layer is deposited from a flame on the silicone rubber surface, as a result of which the surface is modified in such a way that it has a very low adhesion or tackiness.

Abstract: A unique primer emulsion chemistry yields excellent adhesion of polyethylene terephthalate (PET)resin to clay coated paperboard (with high starch content) at reduced coatweights of the primer emulsion and the resin as compared to other primer and tie-resin chemistries currently employed for moisture barrier applications. A primer used for adhesion enhancement is an ammonium catalyzed, self-crosslinking copolymer of ethylene-vinyl acetate with N-methylol acryl amide functional groups attached to a polymer backbone. Use of the primer in amounts up to about 0.5 pounds per ream permits PET coatweights of as low as 10-12 lbs per ream and lower for some applications.

Abstract: A process for the production of strongly adherent coatings on an inorganic or organic substrate is provided, wherein in a first step a) a low temperature plasma, a corona discharge or a flame is caused to act on the inorganic or organic substrate, in a second step b) one or more photoinitiators or mixtures of photoinitiators with monomers, containing at least one ethylenically unsaturated group, or solutions, suspensions or emulsions of the afore-mentioned substances, are applied at normal pressure to the inorganic or organic substrate, in a third step c) using suitable methods those afore-mentioned substances are dried and irradiated with electromagnetic waves and, optionally, in a fourth step d1) the substrate so pretreated is provided with a coating and the coating is cured or dried.

Abstract: Process for producing a multilayer coating, in which a first coating (A) has applied to it a subsequent coating material (B) which is then cured involves selecting and/or modifying the first coating (A) and/or selecting the coating material (B) in such a way that the quotient (Q) formed from the surface energy of the second coating (B) and the surface energy of the first coating (A) is less than or equal to 1, and its use.

Abstract: A unique primer emulsion chemistry yields excellent adhesion of polyethylene terephthalate (PET) resin to clay coated paperboard (with high starch content) at reduced coatweights of the primer emulsion and the resin as compared to other primer and tie-resin chemistries currently employed for moisture barrier applications. A primer used for adhesion enhancement is an ammonium catalyzed, self-crosslinking copolymer of ethylene-vinyl acetate with N-methylol acryl amide functional groups attached to a polymer backbone. Use of the primer in amounts up to about 0.5 pounds per ream permits PET coatweights of as low as 10-12 lbs per ream and lower for some applications.

Abstract: Method for producing a multifunctional material includes thermally treating a substrate having a surface layer formed of titanium, titanium oxide, a titanium alloy, or a titanium alloy oxide so that the temperature of the surface layer is raised to 600° C. or higher, to thereby provide, in the interior of the surface layer, a second layer formed of forest microcolumns of titanium oxide or a titanium alloy oxide; and subsequently cutting the second layer in parallel with the surface layer, to yield a material including the substrate and a layer formed of titanium-oxide- or titanium-alloy-oxide-formed forest microcolumns exposed on at least a portion of the substrate, as well as a material including a thin film, numerous continuous small-width with protrusions thereon, and forest microcolumns formed on the protrusions.

Abstract: Flame produced vapors for combustion chemical vapor deposition are redirected from the direction of the flame by differential atmospheric pressure, such as positive pressure provided by a blower or negative pressure provided by a vacuum. This allows, for example, lower surface temperatures of substrates being coated with flame-produced vapors and coating of interior surfaces.

Abstract: A coherent material is formed on a substrate (10) by providing a precursor suspension (14) in which particulates are suspended in a carrier fluid, and directing the precursor suspension (14) at the substrate (10) from a first source (12). Generally contemporaneously with application of the deposited precursor suspension (14) to the surface, hot gases, e.g. hot gases produced by a flame (16), are directed at the substrate (10) from a remote second source (18) to fuse the particulates into the coherent material.

Abstract: A unique primer emulsion chemistry yields excellent adhesion of polyethylene terephthalate (PET)resin to clay coated paperboard (with high starch content)at reduced coatweights of the primer emulsion and the resin as compared to other primer and tie-resin chemistries currently employed for moisture barrier applications. A primer used for adhesion enhancement is an ammonium catalyzed, self-crosslinking copolymer of ethylene-vinyl acetate with N-methylol acryl amide functional groups attached to a polymer backbone. Use of the primer in amounts up to about 0.5 pounds per ream permits PET coatweights of as low as 10–12 lbs per ream and lower for some applications.

Abstract: Thin films are disclosed that are suitable as dielectrics in IC's and for other similar applications. In particular, the invention concerns thin films comprising compositions obtainable by hydrolysis of two or more silicon compounds, which yield an at least partially cross-linked siloxane structure. The invention also concerns a method for producing such films by preparing siloxane compositions by hydrolysis of suitable reactants, by applying the hydrolyzed compositions on a substrate in the form of a thin layer and by curing the layer to form a film. In one example, a thin film comprising a composition is obtained by hydrolyzing a monomeric silicon compound having at least one hydrocarbyl radical, containing an unsaturated carbon-to-carbon bond, and at least one hydrolyzable group attached to the silicon atom of the compound with another monomeric silicon compound having at least one aryl group and at least one hydrolyzable group attached to the silicon atom of the compound to form a siloxane material.

Abstract: A method and device of treating an irregularly shaped article to prepare the article for painting is provided. The device includes a burner which can produce an adjustable flame tongue which can fit into crevices, openings and other irregular topographical features of an item to be painted or otherwise coated. The burner device further provides means to apply a grafting chemical on a freshly oxidized surface. Further, the invention provides means to colorize treated objects so that they may be recognized as having been treated. In another embodiment, the grafting chemicals may be enhanced with electrolytic solutions such that electrostatic methods of painting may be subsequently employed on the item. In an alternate embodiment, the burner is adapted to spray a powder inside of a generally enclosed flame, and is used in conjunction with chop guns to manufacture glass or carbon fiber preforms.

Abstract: Coatings, particularly thin films, of polymeric material are produced in accordance with the invention by applying a finely divided aerosol of polymer solution to a substrate and substantially simultaneously applying an energy source to the applied solution to apply the solution. In cases where the polymer is cross-linking, the energy source assists in cross-linking of the polymer. The preferred energy source is a flame that may optionally or desirably deposit material along with the polymer spray. One particular aspect of the invention is directed to production of polyimide films. In accordance with another aspect of the invention, the co-deposition process is used to provide thin polysiloxane coatings on glass and other substrates.

Abstract: The present invention provides a method of modifying the surface of a polymeric substrate, e.g., to improve the wettability of the polymer film surface and/or alter the metal adhesion properties of the surface of the substrate by exposing the substrate to a flame. The flame is supported by an oxidizer and fuel mixture that includes an effective amount, for modifying the polymeric substrate, of at least one sulfur-containing compound that functions as a fuel substitute. In addition, substrates are provided that have increased wettability or increased metal adhesion performance.

Abstract: Disclosed is a process for preparing a multilayered coated article that includes in sequence, a substrate (S), a surface treated silane based scratch-resistant layer (R), and a silane based topcoat layer (T). The scratch-resistant layer (R) is formed by applying a scratch-resistant coating composition onto the substrate, and at least partially curing the applied scratch-resistant coating composition. The scratch-resistant coating composition comprises a polycondensate prepared by a sol-gel process from at least one silane. The surface of the scratch-resistant layer is treated by flame, corona and/or plasma treatment. The topcoat layer is formed by applying a topcoat coating composition to the surface-treated scratch-resistant layer, and curing the applied topcoat coating composition.

Abstract: A method for at least locally providing an article coated with an organic coating with a layer of readily deformable sealing material (so-called compound), which involves a layer of an intermediate of the compound being applied to the coating layer, after which the article is temporarily kept at an elevated temperature in order to form the compound from its intermediate, wherein the coating layer of the article comprises a polyethylene terephthalate and the compound is chosen from the group consisting of urethanes, amides, mixtures thereof and heteropolymers thereof, and in that the free surface of the coating layer prior to the application of the intermediate of the compound, at least at the location where this intermediate is applied, is briefly subjected to a processing operation from the group of equivalent processing operations comprising a flame treatment in the course of which the coating layer does not melt.

Abstract: A process for modifying the surface of a substrate containing a polymeric material by contacting the surface with the modifying agent to bond the modifying agent to the surface the process comprising providing a solution of the modifying agent in a solvent and subjecting the solution of the modifying agent to a zone of elevated temperature to vaporize the solvent and provide diffuse contact between the modifying agent and the surface of the substrate.

Abstract: A method and system for coating a glass contacting surface with a thermal barrier and lubricious coating. The system uses a novel exterior surface mixing tip device wherein oxygen is supplied through a predetermined portion of one supply line, and a predetermined gas is supplied through a predetermined portion of another supply line enveloping the first predetermined portion.

Abstract: A method and an assembly is disclosed for coating a web (1) of paper or board by a dry treatment agent, the method comprising the step of applying the treatment agent to at least one side of the moving web (1). In the method is used a treatment agent contains a binder capable of undergoing a change of state at least under the effect of elevated temperature. The web (1) after being treated with the treatment agent is subjected to at least an elevated temperature at which the binder becomes deformable, and the web is subjected to a lower temperature serving to set the binder so that the same bonds the treatment agent to the web surface. The solids content of the treatment agent is not less than 75%, preferably not less than 90%, whereby a drying step after the treatment is not required.

Abstract: The invention relates to the use of a polyolefinic film, with at least one layer, which is made from polyolefinic polymers, whereby said polyolefinic film comprises a bonding layer as outer layer. Said bonding layer contains at least 50 wt. % based on the weight of the layer of a maleic anhydride modified polyolefin. The film is used for printing, metallising or coating.

Abstract: A method and device of treating an irregularly shaped article to prepare the article for painting is provided. The device includes a burner which can produce an adjustable flame tongue which can fit into crevices, openings and other irregular topographical features of an item to be painted or otherwise coated. The burner device further provides means to apply a grafting chemical on a freshly oxidized surface. Further, the invention provides means to colorize treated objects so that they may be recognized as having been treated. In another embodiment, the grafting chemicals may be enhanced with electrolytic solutions such that electrostatic methods of painting may be subsequently employed on the item. In an alternate embodiment, the burner is adapted to spray a powder inside of a generally enclosed flame, and is used in conjunction with chop guns to manufacture glass or carbon fiber preforms.

Abstract: A process for the metalization of substrates is disclosed. The metal either forms a coating over the entire substrate, or it is patternwise deposited on the substrate surface. Metal is patternwise formed on the substrate either by forming a pattern of resist material on the substrate and depositing the material in the interstices defined by the pattern or by forming a patterned resist layer over a metal layer and transferring the pattern into the substrate using conventional techniques. The patterned resist layer is formed on the substrate using conventional techniques. The substrate is treated with reagents that promote the electroless plating of metal on the substrate surface. If the resist material has been previously formed on the substrate surface, the substrate surface is then dried. The remaining resist is then removed from the substrate surface.

Abstract: Method for preventing the formation of coating defects in polymeric coated surfaces in a coating process comprising a plurality of steps that occur prior to the polymeric coating of said surfaces and that contact organic and metal surfaces with a plurality of aqueous compositions in which accumulate in suspension resin particles released from said metal surfaces. Suspended resin particles are prevented from re-depositing on the organic surfaces by converting said surfaces to hydrophilic character by means of oxidizing said surfaces prior to contacting the oxidized surfaces with said suspensions.

Abstract: The present invention relates to the improvement of metal bonding strength in polypropylene films through the addition of ethylene in a mini-random ethylene-propylene copolymer in an amount of no more than about 1 weight percent, more preferably no more than about 0.7 weight percent, and most preferably between about 0.3 weight percent and about 0.5 weight percent, or even amounts between about 0.05 weight percent and about 0.2 weight percent. The invention allows the improvement of metal bond strength in metallizable films. The invention encompasses both the resulting films with enhanced metal bond strength and the process for producing such films.

Abstract: The invention provides a manufacturing method of an optical waveguide able to precisely manufacture the optical waveguide having a waveguide construction as designed, and improve yield as one example. In this manufacturing method, a hydrolysis reaction of raw material gas of glass is caused within an oxygen-hydrogen flame by flowing the raw material gas, oxygen gas and hydrogen gas from a burner, and an optical waveguide forming area is formed by depositing glass particulates on a substrate. The oxygen-hydrogen flame is injected toward the optical waveguide forming area in a slanting direction on the substrate. An exhaust pipe is arranged on the discharging side of an injecting flow. Surplus glass particulates unattached to the optical waveguide forming area are sucked and exhausted by the exhaust pipe.

Abstract: Size-enlarged sludge particles 12 having nuclei of objective particles and having a particle size in a range of from 1 &mgr;m inclusive to 2000 &mgr;m exclusive are mixed with slurry containing fine alumina powder so that a mixture is prepared. Then, the mixture is dried by removal of the water content in the mixture. Then, the mixture is baked at a temperature in a range of from 1200° C. to 1500° C. so that alumina on surfaces of the size-enlarged sludge particles 12 are sintered. By the aforementioned method, light-weight alumina particles can be produced with the particle size controlled well to a uniform value.