27 results about "Methylethyl ketone" patented technology

The invention discloses thermoplastic epoxy glue capable of resisting strong acid and strong alkali as well as a preparation method and application of the thermoplastic epoxy glue. Wherein the thermoplastic epoxy glue consists of the following components in parts by weight: 38.2-44 parts of bisphenol A epoxy resin; 19.2 to 22 parts of novolac epoxy resin; 7.7 to 8.5 parts of carboxyl-terminated nitrile rubber; 2.85 to 3.5 parts of nano silicon dioxide powder; 1.4 to 1.8 parts of a silane coupling agent; 4 to 4.5 parts of dicyandiamide; 1.4 to 1.9 parts of a urea accelerator; 53.5 to 60 parts of methyl ethyl ketone; and 22 to 28 parts of toluene. The thermoplastic epoxy glue can tolerate strong acid and strong alkali, the surface is smooth and free of initial adhesion after curing, construction is convenient, firm adhesion can be achieved through hot pressing under the appropriate temperature condition, the bonding strength is high, and good thermoplasticity is achieved. The thermoplastic epoxy glue disclosed by the invention can be suitable for severe environments with harsh requirements.

The invention discloses a high-strength and high-impact-resistance automobile structure adhesive and a preparation method thereof, and relates to the technical field of sealing adhesives and epoxy resin materials. The high-strength and high-impact-resistance automobile structure adhesive is prepared from core-shell particle toughening modified epoxy resin, a closed block polyurethane toughening agent, chelating modified epoxy resin, filler, dicyandiamide, a curing accelerator, an epoxy resin reactive diluent and fumed silica, wherein the core-shell particle toughening modified epoxy resin is a self-made closed block polyurethane toughening agent resin; the preparation method comprises the following steps: firstly synthesizing an isocyanate group-terminated macromolecular prepolymer, and then carrying out end capping by using methyl ethyl ketoxime. The high-strength and high-impact-resistance automobile structure adhesive disclosed by the invention has the characteristics of high peel strength and good impact resistance, the rigidity, the impact peel strength and the fatigue resistance of an automobile body can be remarkably improved after the adhesive is cured, the safe reliability and the lightweight level of the automobile body are improved, and the requirements of high-end automobile structure adhesives are met.

A method for producing a highly polymerizable N-vinyl carboxylic acid amide monomer includes (A) melting a crude N-vinyl carboxylic acid amide monomer including 50 to 88 mass % of an N-vinyl carboxylic acid amide monomer by heating, followed by cooling for precipitation, and subjecting precipitated N-vinyl carboxylic acid amide monomer crystals to solid-liquid separation, and (B) further dissolving the N-vinyl carboxylic acid amide monomer crystals separated in step (A) in a mixed solvent of methyl ethyl ketone and an aliphatic hydrocarbon having 6 to 7 carbon atoms, then performing crystallization, performing solid-liquid separation, and recovering an N-vinyl carboxylic acid amide monomer purified product, wherein a mass ratio of methyl ethyl ketone / N-vinyl carboxylic acid amide monomer crystal in step (B) is 0.01 to 0.5, and a mass ratio of aliphatic hydrocarbon having 6 to 7 carbon atoms / N-vinyl carboxylic acid amide monomer crystal in step (B) is 0.5 to 3.0.

The present application provides a kind of anticorrosive coating composition and corrosion protection coating and corrosion protection method for crude oil storage tank.The coating includes modified polyurethane coating consisting of first component and second component, and high solid content elastic protective weatherable topcoat consisting of third component and fourth component; the raw materials of first component are polyester dihydric alcohol, isocyanate, etc.; the raw materials of second component are chain extender, polyester dihydric alcohol, whisker and catalyst, etc.; the raw materials of third component are polyaspartic ester, methyl ethyl ketone, whisker and coupling agent, etc.; the raw materials of fourth component are curing agent and methyl ethyl ketone.The corrosion protection coating includes modified polyurethane coating and high solid content elastic protective weatherable topcoat coating.The construction period of the corrosion protection coating of the present application is short, environment-friendly, has excellent impact resistance, salt spray resistance, and long protection period, and is suitable for crude oil storage tank, especially tank top and safety accessories in coastal areas.

The application discloses a radiation refrigeration coating with a recyclable function and a preparation method thereof, and belongs to the technical field of refrigeration coatings.The coating is composed of base oil 500SN, hollow silica microspheres (SiO2@APTES) modified by a silane coupling agent, a liquid metal-based crosslinking agent (GLM) composed of a self-prepared urea-based monomer (UM), cetyl methacrylate (CMA) modified liquid gallium (Ga), talcum powder, calcium carbonate, ethylene glycol butyl ether, polyacrylate, methyl ethyl ketone oxime and methyl methacrylate.The GLM crosslinking agent in the coating has a reversible thermal stimulation response, can reversibly perform phase conversion under thermal stimulation, and simultaneously endows the coating with recyclable performance.Meanwhile, the introduction of the SiO2@APTES realizes high reflection of sunlight and high emission of a medium and far infrared band, and guarantees excellent radiation refrigeration performance of the coating.

The present invention discloses a core-shell thermal conductive powder and a preparation method for reducing the viscosity of polyurethane potting glue, and relates to the technical field of core-shell thermal conductive powder. The present application constructs an anchoring-bridging dual action mechanism through molecular-level interface engineering design. First, N-(N-butyl)-3-aminopropyltrimethoxysilane is used to graft thermal conductive powder. Its silane group condenses with the hydroxyl group on the filler surface to form Si-O covalent bonds, and the aminopropyl group provides an active site; then hexamethylene diisocyanate trimer is introduced to graft isocyanate groups. After being blocked with methyl ethyl ketone oxime, it cross-links with the polyurethane matrix during high-temperature curing to form a cross-scale covalent network. The outer layer is coated with a long-chain aliphatic compound, and the nano-scale monodispersion of the thermal conductive powder is achieved through the steric effect, thereby reducing the viscosity of the system.

The invention relates to the technical field of methyl ethyl ketone peroxide production, in particular to a preparation method and application of methyl ethyl ketone peroxide. Comprising the following steps: adding [BMIM] PF6 ionic liquid into a reaction kettle, and then adding a composite catalyst, triethyl borate and methyl ethyl ketone; after cooling, dropwise adding H2O2, raising the temperature to 20-30 DEG C, and adding MnHCF dispersion liquid; cooling and crystallizing the reaction liquid, and filtering to obtain a methyl ethyl ketone peroxide primary crystal; performing reduced pressure distillation on filtrate to recover ionic liquid; dehydrating through a vacuum film; after polyurethane acrylate and DPGDA are added, the mixture is coated with a gelatin-Arabic gum wall material, and methyl ethyl ketone peroxide is obtained through spray drying. Through three innovations of MnHCF bimetallic catalysis, boric acid ester stabilization and microcapsule safety design, the core pain point in MEKP production and application is effectively solved, and remarkable advantages are shown in catalytic efficiency, storage stability, safety performance and practical application.

The high flash point alkyd paint and the preparation method thereof belong to the field of paint, wherein the high flash point alkyd paint comprises: high flash point alkyd resin, various color environmental protection pigments, precipitated barium sulfate, organic bentonite, dispersing agent, defoaming agent, 8% cobalt octoate drier, 12% zirconium octoate drier, 4% calcium octoate drier, 4% zinc octoate drier, low naphthalene S150 solvent oil, D60 solvent oil, DPM solvent, N, N-dimethyl ethanolamine and methyl ethyl ketone oxime anti-skinning agent. The high flash point alkyd paint has a flash point of more than 60 DEG C (closed), belongs to non-dangerous chemical category, can be stored and transported according to general chemicals, meets the requirements of the recommended national standard GB / T 25251-2010 alkyd resin paint, is convenient to operate, has excellent performance, strictly executes the harmful substance limitation in GB 30981-2020 industrial protective paint, and is safe and environmentally friendly.

The invention discloses dual photo-thermal curing 3D printing polyurethane acrylate photosensitive resin and a preparation method thereof, and belongs to the technical field of 3D printing manufacturing. The preparation method comprises the following steps: carrying out a reaction on dicyclomethane diisocyanate, 1, 5-pentanediol and a catalyst to prepare a polyurethane oligomer; then reacting with methyl ethyl ketoxime to prepare a polyurethane prepolymer sealed by isoacid radicals; finally, mixing and stirring with a cross-linking agent and zinc dimethacrylate to obtain a component A; methyl methacrylate, 1, 6-hexanediol dienoic acid ester and trimethylolpropane triacrylate are mixed and stirred, and a component B is prepared; the component A and the component B, the photoinitiator, the flatting agent and the polymerization inhibitor are mixed and stirred, and the coating is prepared. Through dual photo-thermal curing effects, an interpenetrating cross-linked network structure is formed, the toughness and impact resistance of a product are effectively improved while rapid curing is performed, the toughness and modulus are reduced, and the problem that low-modulus and high-elasticity products are difficult to prepare from existing DLP resin is solved.

The invention discloses a special protective coating for a polyethylene film, belongs to the technical field of polyethylene film coatings, and solves the problems of poor binding force and insufficient heat resistance of the existing coating and a PE film. The low-density polyethylene plastic is prepared from the following raw materials in parts by weight: 45-55 parts of low-density polyethylene plastic particles, 90-110 parts of xylene, 2.5-3.5 parts of benzoyl peroxide and 45-55 parts of functional monomer mixed liquor, wherein the functional monomer mixed liquor is prepared from 12-18 parts of butyl acrylate, 18-22 parts of styrene, 8-12 parts of hydroxyethyl acrylate and 4-6 parts of acrylic acid; the coating is diluted by methyl ethyl ketone or cyclohexanone until the solid content is 28-32%, and then the coating is used for coating a PE film. The compatibility is improved by taking PE as a matrix, the binding force and rigidity are synergistically enhanced by functional monomers, and the reaction stability is guaranteed by adding the initiator in batches. The coating is excellent in adhesive force after being coated, can obviously improve the thermal deformation temperature of the PE film, and is stable in performance under high temperature and high humidity.

The invention belongs to the technical field of tent fabrics, and relates to a preparation method of a moisture-permeable, heat-insulating and anti-ultraviolet tent fabric, which comprises the following steps: firstly, carrying out bottom layer gluing and drying on polyester filament tent base cloth, and then carrying out surface layer gluing and drying on the glued surface of the bottom layer to obtain the moisture-permeable, heat-insulating and anti-ultraviolet tent fabric. A coating agent I adopted for bottom layer gluing is obtained by uniformly mixing a polyurethane emulsion I, triethylene diamine, alumina powder and tributyl phosphate and then ultrasonically defoaming; a coating agent II adopted in surface layer gluing is obtained by uniformly mixing a polyurethane emulsion II, methyl ethyl ketone, N, N-dimethylformamide and rutile type nano titanium dioxide and then ultrasonically defoaming; a synthesis method of the polyurethane emulsion II comprises the following steps: firstly, adding vanillin into the polyurethane prepolymer, stirring for reaction, then adding sinapyl alcohol at the temperature of 60-75 DEG C, cooling after stirring for reaction, and adding deionized water to obtain the polyurethane emulsion II. The tent fabric prepared by the method disclosed by the invention is good in shading, moisture-permeable and heat-insulating properties.

The invention relates to the technical field of methyl ethyl ketone peroxide preparation, in particular to a micro-reaction synthesis process and system for methyl ethyl ketone peroxide. According to the specific technical scheme, the micro-reaction synthesis process of methyl ethyl ketone peroxide comprises the following steps: respectively preheating methyl ethyl ketone and nitric acid-hydrogen peroxide, mixing, adding octyl acetate, diluting, cooling, adding a magnesium sulfate or sodium chloride solution, mixing, and splitting phases. The invention solves the problems that in order to control the reaction heat and prevent decomposition explosion, the traditional kettle type reaction can only be slowly dropwise added, the heat and mass transfer is poor, the local temperature is difficult to control, the reaction time is long and the product composition is uncontrollable; the reactor is too large in liquid holdup, high in safety risk and incapable of continuously dividing phases.

The invention discloses an isocyanate low-temperature curing cross-linking agent as well as a preparation method and application thereof, and the low-temperature curing cross-linking agent is prepared from the following raw materials in parts by mass: 80-90 parts of diisocyanate, 55-65 parts of a dispersing agent, 8-20 parts of a drier, 30-50 parts of a sealing agent A, 30-60 parts of a sealing agent B and 40-60 parts of a sealing agent C, the sealing agent A is selected from at least one of methyl ethyl ketoxime and acetoxime; the sealing agent B is selected from polyether polyol; and the sealing agent C is selected from at least one of 4-hydroxyacetophenone and isopropyl salicylate. The low-temperature curing cross-linking agent is low in raw material cost, does not need to use high-cost raw materials such as a tin drier, is high in stability, can be cured at 130 DEG C, and has excellent corrosion resistance; and the prepared cathode electrophoretic paint has no special requirements on the used color paste, can use the general color paste, and can still keep excellent stability.

The present application belongs to the technical field of tent fabric, and relates to a preparation method of a moisture-permeable, heat-insulating and ultraviolet-resistant tent fabric. The moisture-permeable, heat-insulating and ultraviolet-resistant tent fabric is prepared by first performing bottom layer gluing on a polyester filament tent base cloth and drying, and then performing surface layer gluing on the surface of the bottom layer gluing and drying. The coating agent I used for the bottom layer gluing is obtained by uniformly mixing polyurethane emulsion I, triethylenediamine, aluminum oxide powder and tributyl phosphate, and then ultrasonic defoaming. The coating agent II used for the surface layer gluing is obtained by uniformly mixing polyurethane emulsion II, methyl ethyl ketone, N,N-dimethylformamide and rutile type nano titanium dioxide, and then ultrasonic defoaming. The synthesis method of the polyurethane emulsion II is as follows: first, vanillin is added to the polyurethane prepolymer, and then stirred and reacted; after that, mustard alcohol is added at a temperature of 60-75 DEG C, and then stirred and reacted; after that, the temperature is lowered, and deionized water is added, so as to obtain the polyurethane emulsion II. The tent fabric prepared by the method has good light-shielding, moisture-permeable and heat-insulating properties.

The application relates to the technical field of mixing, in particular to a multi-raw-material precise proportioning and mixing device suitable for DTBP micro-reaction, which comprises a plate-type reactor, a raw material supply unit, a proportioning and mixing unit and a linkage adjusting mechanism. The raw material supply unit comprises methyl ethyl ketone feeding pipes and hydrogen peroxide feeding pipes for respectively feeding methyl ethyl ketone and hydrogen peroxide, a DMP feeding pipe for feeding DMP and a sodium sulfate feeding pipe for feeding sodium sulfate. The proportioning and mixing unit comprises a first mixer, a second mixer, a third mixer and a mixing flow guide shell arranged in the three mixers. Two mixing pipes are arranged at the upstream of the mixing flow guide shell. The linkage adjusting mechanism comprises an adjusting assembly arranged at the upstream of the mixing flow guide shell, an electromagnet push rod for controlling the adjusting assembly and a flow channel switching assembly linked with the adjusting assembly. The flow channel switching assembly comprises a movable connecting seat which can be driven to move by the electromagnet push rod, and the movement of the movable connecting seat can synchronously change the guiding state of the fluid after passing through the adjusting assembly.

By controlling the proportion of particles having specific particle diameters, fluidity became high, and filling ability was improved. A silica particle material of the present disclosure has a D50 of 0.8 μm to 2.5 μm and a D90 / D10 of 2.0 or higher. In 0.35 μL of a liquid dispersion in which 1 mass % of the silica particle material is dispersed in methyl ethyl ketone (MEK), the number of particles of 3 μm or larger is 50 or less, the number of particles of 2 μm or larger and smaller than 3 μm is 1000 or more, and the number of particles of 1 μm or larger and smaller than 2 μm is 10000 or more. A slurry composition in which 75 mass % of the silica particle material is dispersed in an epoxy resin has a viscosity of 10000 Pa·s or lower at a shear rate of 1.0 / s.

The invention discloses a nano-ceramic coating for renovating a galvanized guardrail steel plate coating and a preparation method of the nano-ceramic coating, and belongs to the technical field of coatings. The nano ceramic coating for renovating the galvanized guardrail steel plate coating comprises the following raw material components in parts by mass: 20-30 parts of an epoxy resin base material, 4-6 parts of an epoxy diluent, 30-45 parts of a titanium-containing filler, 0.5-1 part of a dispersing agent, 0.5-1 part of a defoaming agent, 0.5-1 part of an accelerant, 5-10 parts of a solvent, 8-10 parts of an amine curing agent and 1-3 parts of carbon disulfide. The titanium-containing filler is obtained by carrying out in-situ hydrolysis on titanium tetrachloride on the surface of hexagonal boron nitride; the amine curing agent comprises 4, 5-dimethyl-1, 2-phenylenediamine, a phosphamide curing agent, modified polyamide and modified fatty amine; the accelerant comprises any one or more of bis (triphenylphosphine) ammonium chloride, phenol, salicylic acid and tri-(dimethylaminomethyl) phenol; the solvent is any one or more of methyl ethyl ketone, xylene, butanol, methyl isobutyl ketone and methylbenzene.

The embodiment of the invention discloses polyurethane reactive dye deepening printing paste as well as a preparation method and application thereof, and belongs to the technical field of textile pigment printing and reactive dye dyeing. The polyurethane reactive dye darkening printing paste is prepared from the following raw materials in parts by weight: 30 to 50 parts of polyoxypropylene ether trihydric alcohol, 40 to 60 parts of polycarbonate diol, 50 to 70 parts of polyester polyol, 40 to 70 parts of isophorone diisocyanate, 10 to 15 parts of N-methyldiethanolamine, 4 to 7 parts of methyl ethyl ketoxime, 0.05 to 0.1 part of dibutyltin dilaurate, 4.5 to 6.5 parts of glacial acetic acid and 500 to 800 parts of water. The polyurethane reactive dye deepening printing paste can improve the dyeing fastness of fabrics, has the characteristics of softness and smoothness, does not influence the original hand feeling of the fabrics, is suitable for printing and dyeing one-step reactive printing of fabrics such as pure cotton, rayon, tencel and the like, and has the advantages of simple process and low cost.

The invention relates to the technical field of mixing, in particular to a multi-raw-material accurate proportioning and mixing device suitable for DTBP micro-reaction, which comprises a plate-type reactor and further comprises a raw material supplying and conveying unit, and the raw material supplying and conveying unit comprises a methyl ethyl ketone inlet pipe and a hydrogen peroxide inlet pipe which are respectively used for conveying methyl ethyl ketone and hydrogen peroxide; the DMP inlet pipe is used for conveying DMP; the sodium sulfate inlet pipe is used for conveying sodium sulfate; the proportioning and mixing unit comprises a first mixer, a second mixer, a third mixer and a mixing flow guide shell arranged in the first mixer, the second mixer and the third mixer, and two mixing pipes are arranged at the upstream of the mixing flow guide shell; the linkage adjusting mechanism comprises an adjusting assembly arranged on the upstream of the mixed flow guide shell, an electromagnet push rod used for controlling the adjusting assembly, and a flow channel switching assembly linked with the adjusting assembly; the flow channel switching assembly comprises a movable connecting base which can be driven by the electromagnet push rod to move, and the guide state of fluid passing through the adjusting assembly can be synchronously changed through movement of the movable connecting base.

An inkjet ink that includes (A) a terpene resin made from α-pinene and (B) methyl ethyl ketone, which is characterized by extended decap times as well as quick drying properties when applied onto a substrate. A printed article including the inkjet ink in dried form, and a method of forming a printed image with a thermal inkjet printhead are also provided.

The invention relates to a radiation refrigeration coating with a recoverable function and a preparation method thereof, and belongs to the technical field of refrigeration coatings. The coating is prepared by mixing base oil 500SN, hollow silicon dioxide microspheres (SiO2 (at) APTES) modified by a silane coupling agent, a self-made ureido monomer (UM), a liquid metal-based cross-linking agent (GLM) composed of cetyl methacrylate (CMA) modified liquid gallium (Ga), talcum powder, calcium carbonate, ethylene glycol butyl ether, polyacrylate, methyl ethyl ketoxime, methyl methacrylate and the like. The GLM cross-linking agent in the coating has reversible thermal stimulation response, reversibly performs phase conversion under thermal stimulation, and simultaneously endows the coating with recoverability. Meanwhile, due to the introduction of SiO2 (at) APTES, high reflection of sunlight and high emission of middle and far infrared bands are realized, and excellent radiation refrigeration performance of the coating is guaranteed.

This utility model discloses a heat transfer oil heating system for a methyl ethyl ketone (MEK) dehydrogenation reactor, relating to the field of heat transfer oil heating technology. The technical solution includes a fuel gas buffer tank connected to a natural gas inlet pipeline, a butane inlet pipeline, a MEK unit tail gas pipeline, and an outlet pipeline. The outlet pipeline is connected to a heat transfer medium furnace, which is connected to a heat transfer oil feed pipeline, a heat transfer oil discharge pipeline, and a first flue gas outlet pipeline. The first flue gas outlet pipeline is connected to an air preheater, which is connected to an air inlet pipeline, a second flue gas outlet pipeline, and an air outlet pipeline. An induced draft fan is installed on the air inlet pipeline. This utility model uses butane gas and MEK unit tail gas as fuel gas to partially replace natural gas, which not only increases the safety and stability of the unit but also achieves the requirements of low carbon emissions and economy.

This invention relates to the field of methyl ethyl ketone peroxide (MEKP) production technology, specifically to a method for preparing MEKP and its applications. The method includes the following steps: adding [BMIM]PF6 ionic liquid to a reaction vessel, followed by a composite catalyst, triethyl borate, and MEKP; cooling and then adding H2O2 dropwise, heating to 20-30°C, and adding a MnHCF dispersion; cooling the reaction solution to crystallize, and filtering to obtain preliminary MEKP crystals; recovering the ionic liquid by vacuum distillation of the filtrate; dehydrating the solution using a vacuum membrane; adding polyurethane acrylate and DPGDA, then coating the solution with a gelatin-gum arabic wall material, and spray drying to obtain MEKP. This invention effectively solves the core pain points in MEKP production and applications through triple innovation: MnHCF bimetallic catalysis, borate ester stabilization, and microcapsule safety design. It demonstrates significant advantages in catalytic efficiency, storage stability, safety performance, and practical applications.

Provides is a resin film containing a poly(3-hydroxyalkanoate) resin component. A tensile modulus of the resin film is from 500 to 2000 MPa. A swelling degree of the resin film, as measured by immersion of the resin film in methyl ethyl ketone for two hours, is from 1 to 5. Preferably, the poly(3-hydroxyalkanoate) resin component is a mixture of at least two poly(3-hydroxyalkanoate) resins differing in types and / or contents of constituent monomers.

This adhesive sheet (100) for workpiece processing is provided with a base material (10) and an adhesive layer (20) provided on at least one surface of the base material (10). The pressure-sensitive adhesive layer (20) contains an ionic material that does not contain any one of a halogen element and a metal element, the ionic material is insoluble in water and is dissolved as an organic solvent at least in methyl ethyl ketone, and the surface resistivity of the pressure-sensitive adhesive layer (20) is 1.0 * 1012 [Omega] / sq.or less.

The application discloses a kind of nano porcelain coating for galvanized guardrail steel plate coating renovation and a preparation method thereof, and belongs to the technical field of coating.The nano porcelain coating for galvanized guardrail steel plate coating renovation of the application comprises, by mass fraction, 20-30 mass parts of epoxy resin base material, 4-6 mass parts of epoxy diluent, 30-45 mass parts of titanium-containing filler, 0.5-1 mass part of dispersant, 0.5-1 mass part of defoaming agent, 0.5-1 mass part of accelerator, 5-10 mass parts of solvent, 8-10 mass parts of amine curing agent and 1-3 mass parts of carbon disulfide.The titanium-containing filler is obtained by in-situ hydrolysis of titanium tetrachloride on the surface of hexagonal boron nitride.The amine curing agent comprises 4,5-dimethyl-1,2-phenylenediamine, phosphoramide curing agent, modified polyamide and modified aliphatic amine.The accelerator comprises any one or several of bis(triphenylphosphine)ammonium chloride, phenol, salicylic acid and tris(dimethylaminomethyl)phenol.The solvent is any one or several of methyl ethyl ketone, dimethylbenzene, butanol, methyl isobutyl ketone and toluene.

The present invention addresses the problem of providing a modified metal oxide particle material having high dispersibility even if the amount of the modified material is small. The dispersibility can be improved by interposing the modified material between the metal oxide particle materials. In particular, by suppressing the reaction between the modified materials, sufficient effects can be achieved even if the number of the modified materials is reduced. Specifically disclosed is a modified metal oxide particle material which comprises a metal oxide particle material having a functional group other than a phenyl group on the surface and a modified material that is composed of a silicon-containing compound having a phenyl group and adheres to the surface of the metal oxide particle material. Furthermore, after cleaning with methyl ethyl ketone, the value of C / H, calculated from the surface area H (m2) and the carbon content C (mass%) per 1 g, decreases by 0.03 or more and less than 0.1, is 20 [mu] m or less as measured by a particle size meter, and the value of C / H after cleaning is 0.07 or less.