JP2015131762A - Composition for refractory brick, refractory brick, and method for producing refractory brick - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for refractory brick which makes it possible to obtain refractory brick with excellent properties such as thermal shock resistance and strength.SOLUTION: This invention relates to a composition for refractory brick that combines a liquid binding agent for binder and a coated refractory aggregate prepared by coating the surface of a refractory aggregate with a solid coating layer comprising a binding agent for coating. The coating layer comprising the binding agent for coating is formed of thermosetting resin having a thermosetting property in uncured state.

Description

  The present invention relates to lining of molten metal containers such as blast furnaces, kneading wheels, converters, ladles, smelting reduction furnaces, blast furnace outlet filling materials, nozzles provided in continuous casting equipment, immersion nozzles, long nozzles, sliding The present invention relates to a composition for refractory bricks suitably used for a melting furnace crucible for other non-ferrous metals, such as nozzles and stoppers.

  The composition used to make the refractory bricks used in the above applications is blended with a refractory aggregate as a binder and a kneading agent such as Simpson Mill, Melanja, Eirich, Speed Maller, and Warle Mix. Generally, it is prepared by kneading with an apparatus. The composition is then press-molded with an oil press, friction press, vacuum press, isostatic press, or the like, and then heated, dried, cured, or fired to obtain a refractory brick (see, for example, Patent Document 1). ).

  Here, in the composition for refractory bricks, the amount of the binder blended with the refractory aggregate is generally as small as about 1 to 22% by mass, and the binder is uniformly dispersed in the refractory aggregate. Difficult to mix. For this reason, when forming such a composition for firebricks and producing a firebrick, it is difficult to combine a fireproof aggregate with strength with a binder. Therefore, there is a problem with respect to thermal shock such as explosion and cracking when the refractory brick is heated to a high temperature, and there is also a problem that the strength of the refractory brick such as compressive strength becomes insufficient.

JP 2003-89571 A

  The present invention has been made in view of the above points, and an object of the present invention is to provide a composition for refractory bricks capable of obtaining a refractory brick excellent in characteristics such as thermal shock resistance and strength. It is another object of the present invention to provide a firebrick having such excellent characteristics and a method for producing the firebrick.

  The firebrick composition according to the present invention comprises a coated refractory aggregate prepared by coating a surface of a refractory aggregate with a solid coating layer composed of a binder for coating, and a binder for liquid binder. It is a composition for a firebrick that is blended and the coating layer made of a binder for coating is formed of a thermosetting resin that is uncured and has thermosetting properties. .

  Since the coating layer made of the binder for coating is coated on the surface of the fireproof aggregate, the binder for binder can bind the fireproof aggregate through the coating layer made of this binder for coating. The refractory aggregate can be firmly bonded by bonding between the binders, and a refractory brick excellent in characteristics such as thermal shock resistance and strength can be obtained. Moreover, when the coating binder coated on the surface of the refractory aggregate is baked, a carbonized layer adhered to the surface of the refractory aggregate can be formed, and characteristics such as thermal shock resistance and strength can be formed. It is possible to obtain refractory bricks with improved quality.

  In addition, if the binder coated on the surface of the refractory aggregate has thermosetting properties, the binder for coating and the binder for binder can be reacted and bonded together. The bond strength of the refractory aggregate by the binder can be increased.

  In the firebrick composition of the present invention, as the binder for the binder, one selected from a thermosetting resin, a saccharide, and a thermoplastic resin can be used.

  Since the thermosetting resin has a high bond strength, the strength of the refractory brick can be improved. In addition, saccharides can only produce carbon dioxide and water when thermally decomposed, and do not release toxic gases, so that refractory bricks can be produced without polluting the environment. . In addition, the thermoplastic resin has a lower bond strength than the thermosetting resin, but can further improve the thermal shock resistance of the refractory brick.

  In the refractory brick composition of the present invention, a phenol resin can be used as the thermosetting resin for the binder for coating and the binder for binder.

  The phenolic resin has high bond strength, and the phenolic resin has a large amount of residual carbon, so that a refractory brick with low wettability of the molten metal can be obtained and the resistance to erosion to the molten metal can be improved. .

  In the refractory brick composition of the present invention, the saccharide can be mixed with a carboxylic acid as a curing agent.

  By curing the saccharide with carboxylic acid, the bond strength due to the saccharide can be increased, and the thermal shock resistance of the refractory brick can be further improved.

  In the firebrick composition of the present invention, a water-soluble thermoplastic resin can be used as the thermoplastic resin.

  The water-soluble thermoplastic resin can be used in a state dissolved in water, and can be used to prepare a firebrick composition without environmental pollution problems as in the case of using an organic solvent.

  In the firebrick composition of the present invention, at least one of magnesia and alumina can be used as the fireproof aggregate.

  Magnesia has a high melting point and excellent corrosion resistance against slag and the like, and alumina has a low coefficient of thermal expansion and excellent thermal shock resistance.

  In the composition for a refractory brick according to the present invention, a coated refractory aggregate coated with a coating layer and a refractory aggregate not coated with a coating layer can be mixed and blended.

  Since the particle size of the refractory aggregate is changed by coating the coating layer, it is possible to mix the refractory aggregate with a predetermined particle size distribution by mixing and using the refractory aggregate not coated with the coating layer. The refractory aggregate can be uniformly dispersed and contained at a high packing density.

  The refractory brick according to the present invention is formed by molding the above-mentioned refractory brick composition, and the coated refractory aggregate is bonded by a binder for a binder that is solidified, cured, or carbonized. Yes, as described above, it is excellent in characteristics such as thermal shock resistance and strength.

A method for producing a refractory brick according to the present invention is characterized in that the above-mentioned composition for a refractory brick is molded, and this molded product is heated to solidify, cure, or carbonize the binder for the binder. At least a part of the heating step can be performed using water vapor.

  Since steam has a high latent heat of condensation, this latent heat is transmitted when the steam comes into contact with the molded product formed from the refractory brick composition, and the molded product can be instantaneously heated to raise the temperature. This processing can be performed in a short time. In addition, even if harmful gas is generated due to decomposition of the binder during the heat treatment, this gas can be absorbed by the condensed water of the water vapor, and the pollution of the environment can be reduced. It can be done.

  In the method for producing a refractory brick according to the present invention, superheated steam can be used as the steam.

  Superheated steam is high-temperature dry steam, and it is less likely that condensed water is generated excessively from the steam, and the temperature rise rate of the molded product can be increased, and the temperature of superheated steam rises to about 900 ° C. In addition to drying and solidifying and curing the binder, carbonization is facilitated.

  According to the present invention, since the surface of the refractory aggregate is coated with the coating layer made of the binder for coating, the binder for binder is refractory aggregate through the coating layer made of the binder for coating. It is possible to bond refractory aggregates firmly by binding the binders together, and it is possible to produce a refractory brick excellent in thermal shock resistance and properties such as strength. . Moreover, when the coating binder coated on the surface of the refractory aggregate is baked, a carbonized layer adhered to the surface of the refractory aggregate can be formed, and characteristics such as thermal shock resistance and strength can be formed. It is possible to produce a refractory brick that is more improved.

  In addition, since the coating layer made of the binder for coating is formed of an uncured thermosetting resin having thermosetting properties, the binder for coating and the binder for binder are reacted and bonded. It is possible to increase the bond strength of the refractory aggregate by the binder for binder.

  Embodiments of the present invention will be described below.

  In the present invention, as the refractory aggregate, various materials generally used as a raw material for refractory bricks can be used, and any refractory raw material from coarse particles to fine powders can be mixed and used. . For example, fused materials such as fused alumina, fused magnesia, sintered products such as sintered magnesia, natural raw materials such as natural magnesia, bauxite, andalusite, zircon, sillimanite, calcined alumina, silica flour, etc. The raw material of ultra fine powder can be used. The particle size of the refractory aggregate is not particularly limited, but is preferably in the range of 0.001 to 10 mm.

  As the refractory aggregate, one of the above-mentioned materials may be used alone, or two or more materials may be used in combination. Among these, magnesia and alumina are particularly preferable. Magnesia has a high melting point of 2850 ° C. (alumina has a melting point of 2040 ° C.), has excellent corrosion resistance to slag, and is less expensive than alumina. Alumina has a lower thermal expansion coefficient than magnesia and can further improve thermal shock resistance.

Moreover, in order to improve corrosion resistance, the powder of a carbonaceous material with poor wettability with molten slag can be mix | blended as a part of fireproof aggregate. The carbonaceous material may be any carbonaceous material such as natural graphite, artificial graphite, pitch, coke, carbon black, quiche graphite, mesophase carbon, and charcoal, but it should be as pure as possible. preferable. As the refractory aggregate, Al, Mg, Ca, Si, or one or more of these alloys can be blended and used. Moreover, various carbides, borides, nitrides such as SiC, B ₄ C, BN, Si ₃ N _{4 and the} like can be blended as an antioxidant for the carbonaceous material.

  In the present invention, the surface of the above refractory aggregate is coated with a coating layer made of a binder for coating, and used as a coated refractory aggregate. An example of the binder for coating is a thermosetting resin.

  Moreover, as a binder for binders, any binder that can be used in refractory bricks can be used without particular limitation. For example, a thermosetting resin such as a phenol resin, tar, pitch, etc. Saccharides and water-soluble thermoplastic resins can also be used.

  As the thermosetting resin, those conventionally used as binders for refractory bricks such as phenol resin, furan resin, epoxy resin, melamine resin, isocyanate resin can be used. Among these, a phenol resin that has a high bond strength with the refractory aggregate and that can obtain a refractory brick that has a large amount of residual carbon and high wettability with the molten metal is more preferable.

  Here, as the phenol resin, a novolac type phenol resin or a resol type phenol resin prepared by reacting phenols and aldehydes in the presence of a reaction catalyst can be used.

  Phenols mean phenol and derivatives of phenol. For example, in addition to phenol, trifunctional compounds such as m-cresol, resorcinol and 3,5-xylenol, and tetrafunctional compounds such as bisphenol A and dihydroxydiphenylmethane. Bifunctional o- or p such as o-cresol, p-cresol, p-ter-butylphenol, p-phenylphenol, p-cumylphenol, p-nonylphenol, 2,4 or 2,6-xylenol -Substituted phenols can be mentioned, and also halogenated phenols substituted with chlorine or bromine can be used. Of course, in addition to selecting and using one of these, a plurality of types can be mixed and used.

  As the aldehyde, formalin in the form of an aqueous solution is optimal, but forms such as paraformaldehyde, acetaldehyde, benzaldehyde, trioxane, and tetraoxane can also be used. It can be used by replacing with aldehyde or furfuryl alcohol.

  The blending ratio of the above phenols and aldehydes is preferably set so that the molar ratio is in the range of 1: 0.5 to 1: 3.5. As a reaction catalyst, when preparing a novolac-type phenol resin, inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid, organic acids such as oxalic acid, paratoluenesulfonic acid, benzenesulfonic acid and xylenesulfonic acid, and acetic acid Zinc or the like can be used. When preparing a resol-type phenolic resin, an alkaline earth metal oxide or hydroxide can be used, and an aliphatic group such as dimethylamine, triethylamine, butylamine, dibutylamine, tributylamine, diethylenetriamine, or dicyandiamide. Primary, secondary, tertiary amine, aliphatic amines having aromatic rings such as N, N-dimethylbenzylamine, aromatic amines such as aniline and 1,5-naphthalenediamine, ammonia, hexamethylenetetramine, etc. Other divalent metal naphthenic acids and divalent metal hydroxides can also be used.

  The novolac-type phenol resin and the resol-type phenol resin may be used singly or may be used by mixing both in an arbitrary ratio. Various modified phenolic resins such as silicon modified, rubber modified, boron modified, etc. can be used. However, it does not matter whether the storage stability is stable or the refractory aggregate is acidic (for example, silica) or basic (for example, MgO). Considering the points that can be used, novolak type phenol resin is most preferable.

  In order to improve the adhesion between the refractory aggregate and the phenol resin, a coupling agent such as γ-aminopropyltriethoxysilane, γ- (aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. Can also be used.

  On the other hand, as saccharides, monosaccharides, oligosaccharides, and polysaccharides can be used. From various monosaccharides, oligosaccharides, and polysaccharides, one type can be selected and used alone, or multiple types can be selected and used in combination. You can also

  Although it does not specifically limit as monosaccharide, Glucose (glucose), fructose (fructose), galactose, etc. can be mentioned.

  Examples of oligosaccharides include disaccharides such as maltose (malt sugar), sucrose (sucrose), lactose (lactose), and cellobiose.

  Furthermore, as polysaccharides, there are starch sugar, dextrin, xanthan gum, curdlan, pullulan, cycloamylose, chitin, cellulose, starch, etc., and one of these can be selected or used in combination of two or more. it can. Examples of starch include raw starch and processed starch. Specifically, raw starch such as potato starch, corn starch, high amylose, sweet potato starch, tapioca starch, sago starch, rice starch, amaranth starch, and these modified starches (roasted dextrin, enzyme-modified dextrin, acid-treated starch, Oxidized starch), dialdehyde starch, etherified starch (carboxymethyl starch, hydroxyalkyl starch, cationic starch, methylolated starch, etc.), esterified starch (acetic acid starch, phosphate starch, succinate starch, octenyl succinate starch, Acid starch, higher fatty acid esterified starch, etc.), cross-linked starch, kraft starch, and wet heat-treated starch. Of these, low-viscosity starches such as roasted dextrin, enzyme-modified dextrin, acid-treated starch, oxidized starch, and crosslinked starch are preferred. Furthermore, saccharide-containing plants such as wheat, rice, potato, corn, tapioca, sweet potato, sago, amaranth and the like can be used. In addition, sugars that are commercially available for food use, such as white crude, medium crude, granulated sugar, invert sugar, super white sugar, medium white sugar, tri-warm sugar, and the like can also be used. Furthermore, phenol-modified saccharides obtained by reacting saccharides with phenols can also be used.

  Carbohydrates may be added to the saccharides, particularly as a polysaccharide curing agent. The carboxylic acid is not particularly limited, and examples thereof include oxalic acid, maleic acid, succinic acid, citric acid, butanetetradicarboxylic acid, methyl vinyl ether-maleic anhydride copolymer, and benzoic acid. The blending amount of the carboxylic acid with respect to the saccharide is preferably within a range of 0.1 to 10 parts by mass of the carboxylic acid with respect to 100 parts by mass of the saccharide. Carboxylic acid is preferably mixed with saccharide in a state of being dissolved in water in advance because the effect as a curing agent is exhibited highly.

  Furthermore, as a thermoplastic resin, arbitrary things, such as polyethylene, a polypropylene, an acrylic resin, can be used, Furthermore, shellac, rosin, gum arabic, a xylene resin, etc. can also be used. In the present invention, it is preferable to use a water-soluble thermoplastic resin among the thermoplastic resins. Since the water-soluble thermoplastic resin can be used in a state of being dissolved in water, a firebrick composition can be prepared without the problem of environmental pollution as in the case of using an organic solvent.

  The water-soluble thermoplastic resin is not particularly limited, but polyacrylamide, polyacrylic acid, polymethacrylic acid, polyitaconic acid, polyvinyl alcohol, polyethylene oxide, polyvinyl pyrrolidone, polyvinyl methyl ether, methyl cellulose, methoxylated nylon, etc. Can be mentioned. Any one of these water-soluble thermoplastic resins can be selected and used alone, or a plurality of water-soluble thermoplastic resins can be used in combination.

  In the present invention, a thermosetting resin, a saccharide, and a thermoplastic resin may be used alone, but two or more kinds may be used in any combination. When using 2 or more types together, a compounding ratio can be set arbitrarily.

  When two or more binders are used in combination, for example, when a phenol resin and a saccharide are used in combination, the bond strength is lower than when the phenol resin is used alone, so the mechanical strength of the molded product is slightly reduced. However, when the saccharide is used in combination, the amount of residual carbon when the refractory brick is fired is smaller than that of the phenol resin alone, and the effect of improving the thermal shock resistance can be increased. When the phenol resin and saccharide are used in combination, the blending ratio is not particularly limited, but the mass ratio is preferably in the range of 95: 5 to 5:95, more preferably in the range of 85:15 to 15:85, 75 : The range of 25-25: 75 is further more preferable (all are 100 in total). If the saccharide is less than this range, the effect of improving impact resistance by using the saccharide cannot be sufficiently obtained. Conversely, if the phenol resin is less than this range, the mechanical strength of the refractory brick is lowered. There is a risk.

  Then, by coating the refractory aggregate particles with a binder for coating, and mixing the coating layer containing the binder for coating on the surface of the refractory aggregate, a coated refractory aggregate is obtained. It is something that can be done. Here, in order to improve the fluidity of the coated refractory aggregate, a lubricant may be included in the coating layer. Examples of lubricants include aliphatic hydrocarbon lubricants such as paraffin wax and carnauba wax, higher aliphatic alcohols, aliphatic amide lubricants such as ethylenebisstearic acid amide and stearic acid amide, metal soap lubricants, and fatty acid ester lubricants. A composite lubricant or the like can be used, and among them, a metal soap-based lubricant is preferable. As the metal soap-based lubricant, calcium stearate, barium stearate, zinc stearate, aluminum stearate, magnesium stearate, or a combination of these can be used.

  The amount of the coating layer coated on the refractory aggregate differs depending on the components and applications, and cannot be specified unconditionally. However, the solid content of the binder for coating is 0.1 to 5% with respect to 100 parts by mass of the refractory aggregate. A range of 0 parts by mass is preferred. Moreover, when it contains a lubricant, it is generally preferable to set the blending amount of the lubricant in a range of 0.02 to 1.0 parts by mass in solid content with respect to 100 parts by mass of the refractory bone agent. Examples of methods for coating the surface of the refractory aggregate with a coating layer include a hot coat method, a cold coat method, a semi-hot coat method, and a powder solvent method.

  In the hot coating method, a solid coating binder is added to and mixed with a refractory aggregate heated to 110 to 180 ° C., and the solid coating binder is melted by heating with the refractory aggregate. In this method, the surface of the refractory aggregate is wetted and coated with the above-mentioned coating binder, and then cooled while maintaining the mixing, thereby obtaining a granular and free-flowing coated refractory aggregate. Alternatively, by coating a refractory aggregate heated to 110-180 ° C. with a coating binder dispersed or dissolved in a solvent such as water and coating it, the solvent is stripped off to obtain a coated refractory. is there.

  In the cold coating method, a coating binder is dispersed or dissolved in a solvent such as water or methanol to form a liquid, and this is added to and mixed with the particles of the refractory aggregate to volatilize the solvent. This is a method for obtaining aggregates.

  In the semi-hot coating method, a coating binder dispersed or dissolved in a solvent is added to and mixed with refractory aggregate particles heated to 50 to 90 ° C., and the solvent is volatilized to obtain a coated refractory aggregate. Is the method.

  In the powder solvent method, a solid coating binder is pulverized, the pulverized coating binder is added to the refractory aggregate particles, and a solvent such as water or methanol is added, and then mixed. This is a method for obtaining a coated refractory aggregate by volatilizing a solvent.

  In any of the above methods, the surface of the refractory aggregate can be coated with a solid coating layer at room temperature (30 ° C.) to obtain a coated free-flowing coated refractory aggregate. Hot coating is preferred. In addition, when mixing the binder for coating with the refractory aggregate as described above, various curing agents and silane coupling agents for making the refractory aggregate and the binder for coating compatible with each other as necessary. Coupling agents and carbonaceous materials such as graphite can also be blended.

  When two or more types of thermosetting resin, saccharide, and thermoplastic resin are used in combination as a binder for coating, two or more types selected from thermosetting resin, saccharide, and thermoplastic resin are simultaneously coated on the refractory aggregate. Thus, a coating layer in which two or more selected from thermosetting resins, sugars, and thermoplastic resins are mixed can be formed. In addition, the surface of the refractory aggregate was individually coated with two or more types selected from thermosetting resin, saccharide, and thermoplastic resin, thereby laminating the thermosetting resin, saccharide, and thermoplastic resin in separate layers. A coating layer having a two-layer or three-layer structure can be formed.

  Here, as the refractory aggregate, in order to uniformly disperse the refractory aggregate and to increase the packing density, it is often used by mixing those having different particle sizes so as to have a particle size distribution. For example, refractory aggregates mixed so as to have a particle size distribution contained at a predetermined ratio from a relatively large particle size of about 3 mm to a small particle size of 0.21 mm or less are often used. . However, when coating the coating layer by mixing the coating binder with the refractory aggregate as described above, it is difficult to make the thickness of the coating layer formed on the surface of the refractory aggregate uniform. If the thickness of the coated refractory aggregate is not uniform, the particle size distribution of the coated refractory aggregate is not uniform. In particular, a fine refractory aggregate having a small particle size, for example, a refractory aggregate having a particle size of 0.21 mm or less is aggregated with a binder for coating to increase the particle size, and a small particle size has a small particle size distribution. easy. Therefore, in the present invention, in order to obtain a predetermined particle size distribution in the refractory aggregate, not only the coated refractory aggregate coated with the coating layer but also the refractory aggregate not coated with the coating layer is used in combination. It is preferable to mix and use, and it is particularly preferable to mix and use a fine refractory aggregate having a particle size of 0.21 mm which is not coated with a coating layer. The mixing ratio of the coated refractory aggregate covered with the coating layer and the refractory aggregate not covered with the coating layer is not particularly limited, but a mass ratio range of 98: 2 to 15:85 is preferable. .

  According to the present invention, the coated refractory aggregate prepared as described above is mixed with a refractory aggregate that does not cover the coating layer as necessary, and a binder binder is mixed and mixed and kneaded. A composition for a refractory brick can be obtained. And the refractory brick which concerns on this invention can be obtained by shape | molding this heat-resistant brick composition, and heat-processing, after shape | molding.

  The combination of the binder for coating coated on the refractory aggregate and the binder for binder can be arbitrarily set, and the binder for binder and binder for binder are the same kind of binder. Or a combination of different types of binders.

  The blending amount of the binder binder for the coated refractory aggregate is not particularly limited, but the binder binder is 0.1 to 10 in terms of solid content with respect to 100 parts by mass of the coated refractory aggregate. A range of parts by mass is preferred.

  A liquid binder is used for the binder, but in the case of a solid binder, it is preferably used in a state of being dispersed or dissolved in a solvent to form a liquid. Any solvent can be used as long as it can disperse or dissolve the binder. Examples thereof include water, methanol, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene recall. , Tetraethylene glycol, furfural, glycerin, polyglycerin, diglycerin, n-decanol, secondary undecyl alcohol, secondary tetradecyl alcohol, secondary heptadecyl alcohol, butylene glycol, 2-methyl-2,4-pentadiol Hexanediol-2,5, heptanediol-2,4, dipropylene glycol, dibutyl phthalate, di-2-ethylhexyl phthalate, diethyl phthalate, diheptyl phthalate, propylene Carbonate, furfural, and the like can be given furfuryl alcohol. These solvents can be used alone, but can also be used as a mixed solvent in which a plurality of solvents are mixed. When using a mixed solvent, it is preferable to use a combination of a plurality of solvents having different boiling points.

  And after molding the composition for refractory bricks prepared by blending the coated refractory aggregate and the binder for binder as described above, this molded product is heat-treated, dried, solidified, or cured. Alternatively, refractory bricks can be obtained by further firing and carbonizing. Here, the molded product can be heated using a drying furnace or the like generally used for the production of refractory bricks, or can be performed using water vapor.

  Refractory bricks are formed by bonding refractory aggregates with binder binder, but the surface of the refractory aggregate is coated with a coating layer consisting of a binder for coating, The binder is capable of binding the refractory aggregate through the coating layer made of the binder for coating, and can firmly bond the refractory aggregate due to the adhesion between the binders. Is. Furthermore, when the refractory brick is fired, the binder for the binder is carbonized, and at the same time, the binder for the coating on the surface of the refractory aggregate is also carbonized. It can be formed. And by improving the bond strength and forming the carbonized layer, the thermal shock resistance and strength of the firebrick can be improved.

  Here, when using a phenolic resin as a binder for coating or a binder for binder, the phenolic resin has a high bond strength with the refractory aggregate, so that a refractory brick with excellent mechanical strength can be obtained. is there. Further, since the phenol resin has a large amount of residual carbon when baked and carbonized, it is possible to obtain a refractory brick with low wettability of the molten metal and to improve the erosion resistance against the molten metal. In addition, saccharides only release carbon dioxide and water when thermally decomposed, and do not release toxic gases. For this reason, refractory bricks can be manufactured without polluting the environment.

  Moreover, when using saccharide | sugar as a binder for binders, saccharide | sugar has little residual carbon amount when baked and carbonized. For this reason, the mechanical strength of refractory bricks is inferior to that of the above-mentioned phenol resin, but the carbonized layer formed on the refractory bricks has microscopic voids, and thermal shock due to rapid heating is absorbed by these voids. The thermal shock resistance can be further improved.

  The coating layer formed on the coated refractory aggregate is in a state where the binder for coating is uncured and has thermosetting properties, and is in an insoluble and infusible state that is completely cured and no longer exhibits thermosetting properties. Absent. This insoluble and infusible state means "Kyoto Daiten Dictionary" issued by Kyoritsu Publishing Co., Ltd., "Plastic Daijiten" issued by Industrial Research Co., Ltd., "Science Dictionary" published by Iwanami Shoten Co., Ltd. It is described in the items of “thermosetting” and “thermosetting resin” in “Plastics Glossary”, “Science and Technology Dictionary” published by Nikkan Kogyo Shimbun Co., Ltd. and “Chemical Glossary” published by Gihodo Publishing Co., Ltd. In this way, the thermosetting resin is cured by a cross-linking reaction. For example, in the case of a phenol resin, when the amount of phenol resin dissolved in methanol is 5% by mass or less, the phenol resin can be in an insoluble and infusible state.

  When a coating layer composed of a binder for coating has a thermosetting coated fireproof aggregate, it is heat treated after molding a firebrick composition containing a coated fireproof aggregate and a binder binder. When the binder binder is subjected to a curing reaction, the coating binder of the coating layer also melts and undergoes a curing reaction, and the binder is bonded to the binder by binding the binder for coating and the binder binder through a polymerization reaction. The binder for curing can be cured. For this reason, when the refractory aggregate is bonded with the binder for the binder through the coating layer made of the binder for the coating, the bonding force becomes higher, and the refractory brick to which the refractory aggregate is bonded more firmly is formed. It can be obtained. In particular, when the binder for coating and the binder for binder are the same type of thermosetting resin, bonding by reaction occurs easily, and even different types of thermosetting resins react with each other. Any combination can be used.

  On the other hand, when a coated refractory aggregate in which a coating layer made of a coating binder is cured in an insoluble and infusible state, the coating binder and the binder binder cannot be bonded by a polymerization reaction.

  In addition, a carbonized layer adhered to the surface of the refractory aggregate can be formed by pre-carbonizing the binder of the coating layer coated on the surface of the refractory aggregate by heat treatment of the coated refractory aggregate. Since the carbonized layer exhibits an effect as a cushion layer against rapid heating, the thermal shock resistance of the refractory brick can be further increased.

  Next, a description will be given of the heat treatment performed using water vapor when the molded product of the refractory brick composition is heated to produce the refractory brick.

  First, the molded product is set in a heat treatment device. Then, by blowing water vapor into the heat treatment device, the molded product can be heated by the heat of the water vapor. Here, the water vapor may be obtained by heating and boiling water, and the vapor pressure is not particularly limited. In addition, the heat treatment device includes a blow-in port for introducing water vapor into the heat treatment device, and an exhaust port through which air and excess water vapor in the heat treatment device, and volatile components and pyrolysis gas generated in the heating process are discharged. Provided, and those other than the blowing port and the exhaust port are sealed.

  When steam is blown into the heat treatment device in this way, the steam contacts the surface of the molded product, so that the water vapor is deprived of latent heat by the molded product, but the steam has high latent heat. The temperature of the surface of the molded product rises rapidly. The condensed condensed water is evaporated by the sensible heat of the water vapor, and the temperature of the molded product is further increased by this sensible heat of the water vapor. Here, when the molded product is heated with a gas such as heated air, since the heat capacity of the gas is small, it takes time to raise the surface temperature of the molded product, but when heated with water vapor, the water vapor has Since the molded product can be heated with a large latent heat, the surface temperature of the molded product can be increased in a short time. When the surface temperature of the molded product rises rapidly in this way, heat transfer to the inside of the molded product is also performed quickly, and the entire molded product can be heated at a uniform temperature in a short time.

  Therefore, with a short heat treatment, the binder in the molded product can be dried and solidified, or the binder can be cured, and a refractory brick can be produced with high productivity. . At this time, by using water vapor having a temperature equal to or higher than the carbonization temperature of the binder, the binder can be carbonized in a short time.

  Moreover, since the entire molded product can be heated to a uniform temperature in a short time, the solidification and curing of the binder near the surface of the molded product proceeds faster than the binder inside the molded product. It is possible to suppress this and prevent cracks and explosions. That is, if it takes a long time to heat the interior of the molded product, the binder is solidified and cured in the vicinity of the surface of the molded product, and a film is formed on the surface of the molded product in which gas is difficult to pass. As a result, the volatile components inside the molded product are contained inside and the gas pressure becomes high, and there is a risk that it will eventually explode and destroy the molded product or cause cracks on the surface. Such a crack or explosion can be prevented from occurring in the molded product by heating the entire molded product to a uniform temperature in a short time using.

  Here, when heat treatment is performed using high-temperature steam, the temperature rise of the molded product may be abrupt, and blistering may occur in the obtained refractory. At this time, after the heat treatment of the molded product using low-temperature steam, the heat treatment is then performed on the molded product using high-temperature steam, such a blister or the like is generated by performing the heat treatment in two stages. Can be prevented. Of course, the molded product may be heat-treated not only in two stages but also in a plurality of stages in which the temperature of the water vapor is increased in order for each stage, such as three stages or four stages. Further, as the first stage, after the heat treatment at about 150 ° C. or less, which is hardly affected by oxidation, is performed by a conventional arbitrary method, the second and subsequent stages may be performed by the heat treatment with steam according to the present invention.

  In addition, when steam is blown into the heat treatment apparatus in which the molded product is set as described above and heated, the air containing oxygen in the heat treatment apparatus is pushed out of the exhaust port and eliminated. Since only a few ppm of oxygen is present in the water vapor generated from water, the atmosphere in the heat treatment device becomes almost oxygen-free when the water is blown into the water vapor to eliminate the air. Therefore, it is possible to prevent the binder from thermally decomposing under the influence of oxygen when the binder in the molded product is heat-treated to dry, solidify, cure, and carbonize, such as the strength of refractory bricks. The physical properties of the refractory bricks can be prevented from being deteriorated, and the corners of the refractory bricks can be prevented from being generated, and the surface of the refractory bricks can be prevented from being deteriorated. At this time, it is desirable that the oxygen concentration in the atmosphere in the heat treatment device is 3% or less in terms of volume percentage. When the oxygen concentration is 3% or less by volume percentage, the binder can be heat-treated while substantially preventing the binder from thermally decomposing. It is easy to keep the oxygen concentration at 3% or less by volume percentage by blowing water vapor and discharging the air in the heat treatment device.

  In addition, when the molded product is heat-treated as described above, even if volatile gas or decomposition gas is generated from the binder or the like, this gas component is absorbed by the condensed water of the steam whose temperature has decreased, and the odor of the gas is generated. It can be prevented from being released into the working atmosphere as it is. Therefore, it is possible to prevent the working environment from being deteriorated by these gases, to prevent adverse effects on the environment such as air pollution, and further, there is no risk of flammable explosion due to gas. Is. In addition, these volatile gases and cracked gases can be drained in a state where the toxicity of the gas is confined in condensed water, and in particular, water vapor condenses, so the volume from gas to liquid is remarkably reduced. Compared with the case where the volatile gas or decomposition gas generated by the heat treatment is discharged as it is, it can be absorbed in condensed water and discharged in a very small volume, and the processing becomes easy.

  Here, although the temperature of water vapor | steam is not specifically limited, It is desirable that it is 110 degreeC or more, and it can set arbitrarily in the temperature range below the temperature which decomposes | disassembles a binder. As the water vapor, saturated water vapor can be used, but superheated water vapor can also be used. Superheated steam is water vapor in a complete gas state that is further heated to saturated boiling water to a temperature equal to or higher than the boiling point, and is dry steam at 100 ° C. or higher. The superheated steam can raise the temperature up to about 900 ° C., so that the binder can be heat-treated at a high temperature and the binder can be easily carbonized. Of course, when it is desired to treat the refractory brick obtained by heat treatment with water vapor at a higher temperature, the refractory brick may be subjected to heat treatment in a conventional heating furnace or the like.

  The time required to heat-treat the molded product with water vapor varies depending on the type of binder, the temperature of the water vapor, the size of the molded product, etc., for example, when heat-treating using steam and heated air at the same temperature When using water vapor, it is possible to shorten the time to about 1/2 to 1/10 of that of heated air. The effect of shortening the time becomes higher as the volume of the molded product increases.

  When the molded product is heat-treated with water vapor as described above, the molded product may be heated only with water vapor until drying, solidification, curing, and further carbonization, but heating with water vapor and heating with other means are also possible. May be used in combination to dry, solidify, cure, and further carbonize the molded product.

  For example, after heating a molded object with water vapor | steam, the molded object can be heat-processed by further heating a molded object with the heated gas. That is, steam is first blown into the heat treatment apparatus in which the molded product is set as described above, and the molded product is heated by the latent heat of condensation of water vapor. Since steam has a high latent heat as described above, the entire molded product can be heated at a uniform temperature in a short time as described above. In this way, when steam is blown into the heat treatment device to heat-treat the molded product with water vapor, it is not necessary to perform heating with water vapor until the binder of the molded product is dried, solidified, cured, and carbonized. What is necessary is just to heat up the whole molded object uniformly until it becomes the temperature which becomes easy to harden | cure and carbonize. Next, simultaneously with stopping the blowing of water vapor into the heat treatment device, the heated gas is blown into the heat treatment device. This heated gas is a gas heated to a temperature higher than the temperature of water vapor, and is a dry gas containing less water than water vapor. The temperature of the heated gas is preferably 20 ° C. or higher than the temperature of water vapor.

  After steam is blown into the heat treatment device as described above to raise the temperature of the molded product in a short time, a heating gas higher than the water vapor is blown into the heat treatment device in this way, and the molded product is heated with the heating gas. Thus, the binder of the molded product can be dried, solidified, cured, or further carbonized, and a refractory brick can be produced.

  Here, when the refractory aggregate easily reacts with water, for example, when the refractory aggregate contains a component that easily reacts with water such as CaO as an impurity, it reacts with water contained in water vapor, and a molded product. Expands. Moreover, when this molded product is heated to a high temperature, it is dehydrated and returns to the original CaO, and the volume also returns to the original state. Therefore, when the molded product is heated using water vapor, the refractory aggregate reacts with water and the molded product expands and contracts, so that the binding strength of the refractory aggregate due to the binder decreases, and the refractory brick cracks. May occur, or the strength of the refractory bricks may decrease.

  On the other hand, as described above, the temperature of the molded product is increased by heating with water vapor, and then the molded product is heated with a heated gas so that the binder is dried, solidified, cured, and carbonized. Even if the aggregate contains a component that easily reacts with water, it is possible to reduce the action of moisture of water vapor on the refractory aggregate. Therefore, the strength of the refractory is reduced by preventing the refractory aggregate from reacting with the moisture of the water vapor and preventing the bonding strength of the refractory aggregate due to the binder from decreasing due to the expansion / contraction of the molding. It is possible to prevent the occurrence of cracks and cracks.

  Although it does not specifically limit as a gas of heating gas, Air in air | atmosphere can be used as it is, and inert gas like nitrogen and argon can also be used. Of course, a mixed gas in which two or more of these air, nitrogen, and argon are mixed at an arbitrary ratio can also be used. Furthermore, a mixed gas of a gas such as air, nitrogen, or argon and water vapor can also be used.

  Also, steam and heated gas are blown into a heat treatment apparatus in which the molded product is set, and the molded product is heated with a mixed gas of water vapor and heated gas to dry and solidify the binder of the molded product, or It can be hardened or further carbonized to produce refractory bricks. Since the water vapor contained in the mixed gas has a high latent heat as described above, the entire molded product can be heated at a uniform temperature in a short time as described above. In addition, the molded product can be heated by the heated gas contained in the mixed gas, so that the amount of water vapor can be reduced, and the water content of the water vapor acts on the refractory aggregate as compared with the case of heating with water vapor alone. This can be reduced. For this reason, it is possible to prevent the refractory aggregate from reacting with the moisture of the water vapor, and to prevent the bond strength of the refractory aggregate due to the binder from decreasing due to expansion / contraction of the molded product. It is possible to prevent the strength of the object from being lowered or cracking from occurring.

  The mixing ratio of the water vapor and the heated gas is not particularly limited, but is set to a volume ratio of 8: 2 to 2: 8 in order to effectively exhibit each action of the water vapor and the heated gas. preferable. The steam and the heated gas may be blown into the heat treatment device in a mixed state, or the water vapor and the heated gas may be separately blown into the heat treatment device so that the water vapor and the heated gas are mixed in the heat treatment device. Good. In short, what is necessary is just to act on the molded article in the heat treatment device in a gas state in which water vapor and heated gas are mixed.

  Next, still another example of the method of using heating with water vapor and other heating means will be described. In this method, a heat treatment apparatus as described above for blowing water vapor and a heating furnace equipped with a heating means such as a gas burner or an electric heater that generates heat by combustion or electric resistance are used. First, steam is blown into the heat treatment apparatus in which the molded product is set as described above, and the molded product is heated by the latent heat of condensation of water vapor. Since steam has a high latent heat as described above, the entire molded product can be heated at a uniform temperature in a short time as described above. In this way, when steam is blown into the heat treatment device to heat-treat the molded product with water vapor, it is not necessary to perform heating with water vapor until the binder of the molded product is dried, solidified, cured, and carbonized. What is necessary is just to heat up the whole molded object uniformly until it becomes the temperature which becomes easy to harden | cure and carbonize.

  Thereafter, the blowing of water vapor into the heat treatment device is stopped, and the molded product is quickly transferred from the heat treatment device to the heating furnace. The heating furnace has a high temperature atmosphere due to the heat generated by the heating means, and the molded product transferred to the heating furnace is heated in the heating furnace. The heating temperature in the heating furnace may be a temperature higher than the temperature of the water vapor, and is preferably a temperature that is 20 ° C. or more higher than the temperature of the water vapor.

  After blowing water vapor into the heat treatment device as described above to raise the temperature of the molded product in a short time, by heating the molded product in the heating furnace in this way, the binder of the molded product is dried and solidified, or It can be hardened or further carbonized to obtain a refractory brick. Here, since the molded product is heated by the heat generated in the heating furnace in this way to solidify, harden, and carbonize the binder, the refractory aggregate of the molded product contains a component that easily reacts with water. This prevents moisture from acting on the refractory aggregate and prevents the bonding strength of the refractory aggregate from being reduced by the binder due to expansion and contraction of the molded product, reducing the strength of the refractory and cracking. Can be prevented from occurring.

  Next, still another example of the method of using heating with water vapor and other heating means will be described. As described above, the heat treatment apparatus is configured to be able to blow water vapor, and further, a heat treatment apparatus provided with a heating means such as a gas burner or an electric heater that self-heats by combustion or electric resistance is used. First, steam is blown into the heat treatment apparatus in which the molded product is set as described above, and the molded product is heated by the latent heat of condensation of water vapor. Since steam has a high latent heat as described above, the entire molded product can be heated at a uniform temperature in a short time as described above. In this way, when steam is blown into the heat treatment device to heat-treat the molded product with water vapor, it is not necessary to perform heating with water vapor until the binder of the molded product is dried, solidified, cured, and carbonized. What is necessary is just to heat up the whole molded object uniformly until it becomes the temperature which becomes easy to harden | cure and carbonize.

  Thereafter, the blowing of water vapor into the heat treatment device is stopped, the inside of the heat treatment device is brought into a high-temperature atmosphere by the heat generated by a heating means such as a gas burner, and the molded product is further heated. This heating temperature should just be a temperature higher than the temperature of water vapor | steam, and it is preferable that it is a temperature 20 degreeC or more higher than the temperature of water vapor | steam. In this way, by heating the molded product with heat generated by a heating means such as a gas burner, the binder of the molded product can be dried, solidified, cured, or further carbonized to obtain a refractory brick. is there. Here, since the molded product is heated by the heat generated by the heating means such as a gas burner to solidify, cure, and carbonize the binder, the refractory aggregate of the molded product contains a component that easily reacts with water. However, the moisture of the water vapor does not act on the refractory aggregate, and the strength of the refractory is reduced by preventing the bonding strength of the refractory aggregate due to the binder due to the expansion / contraction of the molding. It is possible to prevent the occurrence of cracks and cracks.

  Using this heat treatment device, the molded product can be heat-treated by other methods. That is, first, a molded product is set in a heat treatment device, and steam is blown into the heat treatment device, and at the same time, a heating means such as a gas burner is operated, and the molded product in the heat treatment device is heated with a heating means such as water vapor and a gas burner. With this simultaneous heating, the binder of the molded product can be dried, solidified, cured, or further carbonized to produce a refractory brick.

  In this way, when the molded product in the heat treatment apparatus is heated by heat generation means such as water vapor and a gas burner, since the steam has a high latent heat as described above, the entire molded product can be made uniform in a short time as described above. It can be heated at a temperature. In addition, the molded product can be heated by a heat generating means such as a gas burner. The amount of water vapor can be reduced, and the water content of water vapor acts on the refractory aggregate more than when heating with water vapor alone. Can be reduced. For this reason, it is possible to prevent the refractory aggregate from reacting with the moisture of the water vapor, and to prevent the bond strength of the refractory aggregate due to the binder from decreasing due to expansion / contraction of the molded product. It is possible to prevent the strength of the object from being lowered or cracking from occurring.

  Using this heat treatment device, the molded product can be heat-treated by another method. First, steam is blown into the heat treatment device to heat the molded product set in the heat treatment device. Since steam has a high latent heat as described above, the entire molded product can be heated at a uniform temperature in a short time as described above. In this way, when steam is blown into the heat treatment device to heat-treat the molded product with water vapor, it is not necessary to perform heating with water vapor until the binder of the molded product is dried, solidified, cured, and carbonized. What is necessary is just to heat up the whole molded object uniformly until it becomes the temperature which becomes easy to harden | cure and carbonize.

  Then, while continuing to blow water vapor into the heat treatment device, the heating means such as a gas burner is operated, and the molded product in the heat treatment device is also heated by the heat generated by the heat generation device. Refractory bricks can be obtained by drying, solidifying, curing, or further carbonizing. Here, since the heating of the molded product is performed by using both steam and a heating means such as a gas burner in this way, the amount of water vapor blown into the heat treatment apparatus can be reduced by heating the molded product with the heating means. It can reduce that the water | moisture content of water vapor | steam acts on a fireproof aggregate rather than the case where it heats only with water vapor | steam. For this reason, the strength of the refractory is reduced by preventing the refractory aggregate from reacting with the moisture of the water vapor and preventing the bonding strength of the refractory aggregate due to the binder from decreasing due to the expansion / contraction of the molding. It is possible to prevent the occurrence of cracks and cracks.

  Next, the present invention will be specifically described with reference to examples.

(Preparation of coating binder A)
A reaction vessel was charged with 940 parts by weight of phenol, 568 parts by weight of 37% by weight formalin, and 3.76 parts by weight of oxalic acid, and refluxed for about 1 hour with stirring, and reacted at the reflux temperature for 3 hours. Next, heating was performed while dehydrating until the internal temperature reached 170 ° C. Furthermore, after depressurizing while reducing pressure until the internal temperature reached 200 ° C. at 40 hPa, the contents of the reaction vessel were discharged onto a stainless steel vat. The softening point of the novolac type phenol resin thus obtained is 78 ° C. This novolac type phenol resin is used as a binder A for coating.

(Preparation of binder A for binder)
30 parts by mass of ethylene glycol was added to 70 parts by mass of the novolac type phenol resin prepared as described above and mixed well to obtain a novolac type phenol resin resin liquid having a viscosity of 8.5 Pa · s (at 25 ° C.). The novolac-type phenol resin resin liquid thus obtained is used as a binder A for binder.

(Preparation of binder B for coating)
400 parts by mass of phenol and 453 parts by mass of 37% by weight formalin were added to a reaction vessel, and 40 parts by mass of hexamethylenetetramine was added thereto as a catalyst, and the temperature was raised to 90 ° C. in about 60 minutes with stirring. For 30 minutes. Next, the solution was immediately drained to 65 ° C. under a reduced pressure of 133 hPa, and then the reaction product was quickly discharged from the reaction vessel to a stainless steel vat to obtain a hydrous resol type phenol resin containing 7.9% by mass of water. And after putting this in a -10 degreeC freezer and freezing, it grind | pulverized and dried with the fluid bed type | mold dryer, and the solid resol type phenol resin with a softening point of 65 degreeC was obtained. The resol type phenol resin thus obtained is used as a binder B for coating.

(Preparation of binder B for binder)
To 70 parts by mass of the resol type phenol resin prepared as described above, 30 parts by mass of ethylene glycol was added and mixed well to obtain a resol type phenol resin resin liquid having a viscosity of 6.8 Pa · s (at 25 ° C.). The resol type phenolic resin liquid thus obtained is used as binder B for binder.

(Preparation of binder C for binder)
70 parts by mass of dextrin (“No4-C” manufactured by Nissho Kagaku Co., Ltd.) was added to 30 parts by mass of ethylene glycol and mixed well to be dispersed. The ethylene glycol solution of dextrin thus obtained is used as binder C for binder.

(Preparation of coated refractory aggregate A)
30 kg of electrofused magnesia (MgO content: 98.3% by mass) having a particle diameter of 3 to 1 mm heated to 150 ° C. was placed in a whirl mixer, and 450 g of a binder A for coating made of a novolac type phenol resin was added thereto. Kneaded for 2 seconds. While further kneading, 450 g of an aqueous solution in which 45 g of hexamethylenetetramine is dissolved is added, 30 g of calcium stearate is added after 60 seconds, and after 45 seconds, the solid coating is formed from the binder A for coating novolac phenol resin. Coated refractory aggregate A coated with the layer was obtained. In this coated refractory aggregate A, the mass ratio of the coating layer to the refractory aggregate was 1.5% by mass.

  In addition, the description of “particle size 3 to 1 mm” means particles having a size that passes through a 3 mm mesh sieve and turns on on the 1 mm mesh sieve. The following particle sizes are the same, and “particle size 0.21 mm to 0.0 mm” means particles that pass through a 0.2 mm mesh sieve.

(Preparation of coated refractory aggregate B)
Coated refractory bone coated with a coating layer comprising a novolac type phenolic resin coating binder A in the same manner as above except that electrofused magnesia having a particle size of 1 to 0.5 mm is used as the refractory aggregate. Material B was obtained.

(Preparation of coated refractory aggregate C)
Coated coated with a coating layer comprising a novolac phenolic resin coating binder A in the same manner as above except that electrofused magnesia having a particle size of 0.5 to 0.21 mm was used as the refractory aggregate. A refractory aggregate C was obtained.

(Preparation of coated refractory aggregate D)
30 kg of electrofused magnesia (MgO content: 98.3% by mass) having a particle diameter of 3 to 1 mm heated to 150 ° C. was placed in a whirl mixer, and 450 g of a binder B for coating made of a resol type phenol resin was added thereto. Kneaded for 2 seconds. Coated refractory aggregate coated with a solid coating layer composed of a binder B for coating with a resole phenolic resin by adding 30 g of calcium stearate after 60 seconds while adding 400 g of water and kneading after 45 seconds. D was obtained. In this coated refractory aggregate D, the mass ratio of the coating layer to the refractory aggregate was 1.5% by mass.

(Preparation of coated refractory aggregate E)
Coated refractory bone coated with a coating layer comprising a binder B for coating with a resole phenolic resin in the same manner as described above except that electrofused magnesia having a particle size of 1 to 0.5 mm is used as the refractory aggregate. Material E was obtained.

(Preparation of coated refractory aggregate F)
Coated coated with a coating layer composed of a binder B for coating with a resole-type phenol resin in the same manner as above except that electrofused magnesia having a particle size of 0.5 to 0.21 mm is used as the refractory aggregate. A refractory aggregate F was obtained.

(Preparation of coated refractory aggregate G)
30 kg of electrofused magnesia (MgO content: 98.3% by mass) having a particle diameter of 3 to 1 mm heated to 130 ° C. was placed in a whirl mixer, and dextrin (“No4-C” manufactured by Nissho Kagaku Co., Ltd.). 850 g of mixed water in which 450 g of the binder for coating C was dispersed and kneaded for about 90 seconds After the kneaded material was disintegrated, 30 g of calcium stearate was added, kneaded for 15 seconds, and further aerated, A coated refractory aggregate G coated with a solid coating layer comprising a saccharide coating binder C was obtained, and in this coated refractory aggregate G, the mass ratio of the coating layer to the refractory aggregate was 1.5% by mass. there were.

(Preparation of coated refractory aggregate H)
A coated refractory aggregate H coated with a coating layer made of a binding agent C for saccharide coating was used in the same manner as above except that electrofused magnesia having a particle size of 1 to 0.5 mm was used as the refractory aggregate. Obtained.

(Preparation of coated refractory aggregate I)
A coated refractory aggregate coated with a coating layer comprising a binder C for saccharide coating in the same manner as above except that electrofused magnesia having a particle size of 0.5 to 0.21 mm is used as the refractory aggregate. I was obtained.

  In the above coated fireproof aggregates A to F, the coating binders A to B for the coating layer were uncured and had thermosetting properties.

(Preparation of coated refractory aggregates J to L)
The coated refractory aggregate A obtained as described above is spread on a stainless steel bat, placed in a hot air circulating dryer set at 120 ° C. in advance, and subjected to heat curing for 6 hours. From the novolac type phenolic resin of the coating layer The resulting binder A for coating was cured in an insoluble and infusible state. In addition, when the test which melt | dissolves the phenol resin which is the binding agent A for coating of a coating layer in methanol was conducted, the amount of dissolution of a phenol resin was 5 mass% or less.

  Table 1 shows the compositions of the refractory aggregate and the coating layer for the coated refractory aggregates A to L.

(Examples 1-12, Reference Examples 13-17)
Coated refractory aggregates A to L, electrofused magnesia (no coating layer), and graphite were put in a Henschel mixer in the blending amounts shown in Table 2 and stirred for 5 minutes. Next, binder binders A to C are blended in the blending amounts shown in Table 2, and hexamethylenetetramine is added as necessary. The mixture is stirred and kneaded at a rotational speed of 285 rpm for 15 minutes, and then discharged and fireproof. A brick composition was obtained.

(Comparative Examples 1-3)
Electrofused magnesia (no coating layer) and graphite were placed in a Henschel mixer at the blending amounts shown in Table 2 and stirred for 5 minutes. Next, binder binders A to C are blended in the blending amounts shown in Table 2, and hexamethylenetetramine is added as necessary. The mixture is stirred and kneaded at a rotational speed of 285 rpm for 15 minutes, and then discharged and fireproof. A brick composition was obtained.

  After putting the composition for firebricks prepared in Examples 1-12, Reference Examples 13-17 and Comparative Examples 1-3 in a plastic bag for 24 hours, gold having a cylindrical cavity with a diameter of 45 mm 285 g was put into a mold and pressed to a height of 60 mm to obtain a cylindrical molded product. The molded product is placed in a hot air circulation dryer set at 200 ° C. in advance, dried and cured by heating for 4 hours, and then taken out and cooled to obtain a binder for coating and a binder for binder. A molded refractory brick for testing in which the agent solidified or hardened was obtained.

  For the molded fire bricks of Examples 1 to 12, Reference Examples 13 to 17 and Comparative Examples 1 to 3 thus obtained, bulk specific gravity, volatile content, dimensional change rate, compressive strength, appearance, spalling resistance, The oxidation resistance was measured.

  Further, this molded refractory brick was put in a heat-resistant box and then covered with coke, and set in an electric furnace (“Silicnit Electric Furnace Model BSH-1530” manufactured by Siliconit Co., Ltd.). And it heated up to 600 degreeC at the temperature increase rate of 10 degree-C / min, and also by baking on the conditions which hold | maintain at this temperature for 3 hours, and then temperature-fall, the fire refractory brick for a test was obtained.

  With respect to the fired bricks of Examples 1 to 12, Reference Examples 13 to 17 and Comparative Examples 1 to 3 thus obtained, bulk specific gravity, volatile content, dimensional change rate, compressive strength, and appearance were measured.

(Bulk specific gravity)
It measured based on JIS R2001.

(Volatile)
For molded refractory bricks, measure the mass (g) before heating treatment and heating (g) after heating treatment of heating at 200 ° C for 4 hours, and firing refractory bricks at 600 ° C for 3 hours. And
[100- (mass after heat treatment / mass before heat treatment) × 100] (mass%)
The volatile content was obtained from the formula of

(Dimensional change rate)
For molded refractory bricks, measure dimensions (mm) before heat treatment and dimensions (mm) after heat treatment for heating at 200 ° C. for 4 hours and for fired refractory bricks at 600 ° C. for 3 hours. And
[(Size after heat treatment / size before heat treatment) × 100] -100 (%)
The dimensional change rate was obtained from the equation

(Compressive strength)
The measurement was performed according to JIS R2206.

(appearance)
Appearance is measured by visual observation. ◎ indicates that there are no blisters or cracks, and there are several bulges, but ◯ indicates that there are no cracks. Was determined.

(Spalling resistance)
The spalling resistance test was conducted by immersing the refractory brick in molten iron at 1600 ° C. and water-cooling five times, and examining the occurrence of cracks. The results were evaluated as “◎” for no crack, “◯” for crack occurrence, and “x” for crack and flaking.

(Oxidation resistance)
The oxidation resistance test was performed by leaving the refractory brick in air at 800 ° C. for 4 hours. As a result, the decarbonized thickness was evaluated as “×” when the thickness was 5 mm or more, and “◯” when the thickness was less than 5 mm.

  As can be seen from Table 3, it is confirmed that the examples have excellent characteristics such as thermal shock resistance and strength.

(Preparation of coated refractory aggregate M)
30 kg of fused alumina having a particle diameter of 3 to 0.21 mm heated to 150 ° C. was placed in a whirl mixer, and 450 g of the binder A for coating made of a novolac type phenol resin was added thereto and kneaded for 40 seconds. While further kneading, 450 g of an aqueous solution in which 45 g of hexamethylenetetramine is dissolved is added, 30 g of calcium stearate is added after 60 seconds, and the mixture is discharged after 45 seconds, thereby forming a coating layer made of a binder A for coating novolac-type phenolic resin. A coated coated refractory aggregate M was obtained. In this coated refractory aggregate M, the mass ratio of the coating layer to the refractory aggregate was 1.5% by mass.

(Examples 18 and 19)
Coated refractory aggregate M, electrofused alumina (without coating layer), and graphite were added to a Henschel mixer in the amounts shown in Table 4 and stirred for 5 minutes. Next, the binder A for binder and hexamethylenetetramine are blended in the blending amounts shown in Table 4, and ethylene glycol is further added as necessary. The mixture is stirred and kneaded at a rotational speed of 285 rpm for 15 minutes, and then discharged. A composition for refractory bricks was obtained.

(Comparative Example 4)
Fused alumina (no coating layer) and graphite were added to a Henschel mixer at the blending amounts shown in Table 4 and stirred for 5 minutes. Next, the binder A for binder and hexamethylenetetramine were blended in the blending amounts shown in Table 4, and the mixture was stirred and kneaded for 15 minutes at a rotational speed of 285 rpm, and then discharged to obtain a composition for refractory bricks.

  Using the firebrick composition prepared in Examples 18 and 19 and Comparative Example 4, a molded firebrick for test and a fired brick for test were obtained in the same manner as described above. The bulk specific gravity, volatile content, dimensional change rate, compressive strength, appearance, spalling resistance, and oxidation resistance of the molded refractory bricks of Examples 18 and 19 and Comparative Example 4 The volatile content, the dimensional change rate, the compressive strength, and the appearance were measured.

  In Example 19, 2635 parts by mass of the coated refractory aggregate M contains 40 parts by mass (= 2635 × 0.015) of phenolic resin, and 283 parts by mass of binder binder A has 198 parts. Since the mass part (= 283 * 0.7) phenol resin is contained, the composition for firebricks of Example 19 contains a total of 238 mass parts phenol resin. On the other hand, in Comparative Example 4, 340 parts by mass of binder Binder A contains 238 parts by mass (= 340 × 0.7) of phenolic resin. Contains a total of 238 parts by weight of phenolic resin. Thus, although the same amount of phenolic resin is contained in the composition for refractory bricks of Example 19 and Comparative Example 4, as seen in Table 4, Example 19 has better thermal shock resistance, strength, etc. It was excellent in the characteristics.

(Preparation of coated refractory aggregate N)
30 kg of electrofused magnesia (MgO content: 98.3% by mass) having a particle diameter of 3 to 1 mm heated to 130 ° C. was placed in a whirl mixer, and dextrin (“No4-C” manufactured by Nissho Kagaku Co., Ltd.). 450 g of the binder C for coating and 850 g of mixed water in which 9 g of citric acid was dispersed as a curing agent were added and kneaded for about 90 seconds, after the kneaded material was disintegrated, 30 g of calcium stearate was added and kneaded for 15 seconds. By further aeration, a coated refractory aggregate N coated with a solid coating layer made of a saccharide coating binder C containing a curing agent was obtained. The mass ratio of the coating layer was 1.5% by mass.

(Preparation of coated refractory aggregate O)
Coated refractory coated with a coating layer composed of a binder C for coating saccharides containing a curing agent in the same manner as above except that electrofused magnesia having a particle size of 1 to 0.5 mm is used as the refractory aggregate. Aggregate O was obtained.

(Preparation of coated refractory aggregate P)
Covered with a coating layer composed of a binder P for coating saccharides containing a hardener in the same manner as above except that electrofused magnesia having a particle size of 0.5 to 0.21 mm was used as the refractory aggregate. Coated refractory aggregate P was obtained.

  Table 5 shows the composition of the refractory aggregate and the coating layer for the coated refractory aggregates N to P.

(Reference Examples 20-22)
Coated refractory aggregates N to P, electrofused magnesia (no coating layer) and graphite were added to a Henschel mixer in the blending amounts shown in Table 6 and stirred for 5 minutes. Next, the binders A to C for the binder were blended in the blending amounts shown in Table 6, and if necessary, hexamethylenetetramine and citric acid were added and kneaded after stirring for 15 minutes at a rotational speed of 285 rpm. The composition for fireproof bricks was obtained by paying out.

  Using the firebrick composition prepared in Reference Examples 20 to 22, a test firebrick and a test firebrick were obtained in the same manner as described above. And about this molded fire brick of Reference Examples 20-22, bulk specific gravity, volatile content, dimensional change rate, compressive strength, appearance, spalling resistance, oxidation resistance, fired fire brick, bulk specific gravity, volatile content, The dimensional change rate, compressive strength, and appearance were each measured.

  The refractory bricks of Reference Examples 20 to 22 are those using a saccharide mixed with a curing agent as a binder, and as shown in Table 7, any of the refractory bricks of Reference Examples 20 to 22 is also resistant to thermal shock. It has excellent characteristics in terms of strength and strength.

(Preparation of coated refractory Q)
30 kg of electrofused magnesia (MgO content: 98.3% by mass) having a particle diameter of 3 to 1 mm heated to 130 ° C. was placed in a whirl mixer, and dextrin (“No4-C” manufactured by Nissho Kagaku Co., Ltd.). 850 g of mixed water in which 225 g of the binder for coating C was dispersed and 225 g of binder for coating B made of a resol type phenol resin were added and kneaded for about 90 seconds. In addition, the coated refractory aggregate Q coated with a solid coating layer composed of a binder B for coating with a resole phenolic resin and a binder C for coating with a saccharide by kneading for 15 seconds and further aeration. In this coated refractory aggregate Q, the mass ratio of the coating layer to the refractory aggregate is 1.5 mass. %Met.

(Preparation of coated refractory aggregate R)
From the binder B for coating of resole phenolic resin and the binder C for coating of saccharide in the same manner as above except that electrofused magnesia having a particle size of 1 to 0.5 mm is used as the refractory aggregate. A coated refractory aggregate R coated with the coating layer was obtained.

(Preparation of coated refractory aggregate S)
Resole-type phenol resin coating binder B and sugar coating binder in the same manner as above except that electrofused magnesia having a particle size of 0.5 to 0.21 mm is used as the refractory aggregate. Coated refractory aggregate S coated with a coating layer made of C was obtained.

  Table 8 shows the composition of the refractory aggregate and the coating layer for the coated refractory aggregates Q to S.

(Examples 23 to 25)
Coated refractory aggregates Q to S, electrofused magnesia (no coating layer), and graphite were added to a Henschel mixer at the blending amounts shown in Table 9 and stirred for 5 minutes. Next, the binders A to C for the binder were blended in the blending amounts shown in Table 9, and hexamethylenetetramine was further added as necessary. The mixture was stirred and kneaded at a rotational speed of 285 rpm for 15 minutes, then discharged and fire-resistant. A brick composition was obtained.

  Using the firebrick composition prepared in Examples 23 to 25, a molded firebrick for test and a fired brick for test were obtained in the same manner as described above. And about the molded refractory bricks of Examples 23 to 25, the bulk specific gravity, the volatile content, the dimensional change rate, the compressive strength, the appearance, the spalling resistance, the oxidation resistance, the fired refractory brick, the bulk specific gravity, the volatile content, The dimensional change rate, compressive strength, and appearance were each measured.

  Although the firebrick of Examples 23-25 is what uses saccharides and a phenol resin together as a binder for coating, as shown in Table 10, as for any firebrick of Examples 23-25, thermal shock resistance It has excellent characteristics in terms of strength and strength.

(Preparation of coated refractory aggregate T)
10 kg of magnesia with a particle size of 0.21 to 0.0 mm is heated to 80 ° C. and charged into a mixer, and 0.1 kg of coating binder A made of novolac-type phenolic resin and 0.01 kg of hexamethylenetetramine are each added. A liquid dispersed in 0.1 kg of methanol was put into a mixer. Then, the air was fed by a fan and kneaded by a mixer while volatilizing methanol. After the kneaded material was disintegrated after it became viscous, the kneading was continued for 60 seconds, then discharged and cooled. This was sieved through a 0.105 mm mesh sieve to obtain a fine coated refractory aggregate T having a particle size of 0.105 to 0.0 mm.

(Preparation of coated refractory aggregate U)
Coated refractory bone with a fine particle size in the same manner as above except that the binder B for coating made of a resol type phenol resin is used in place of the binder A for coating, and hexamethylenetetramine is not used. Material U was obtained.
(Preparation of coated refractory aggregate V)

  Heat 10kg of magnesia with a particle size of 0.21-0.0mm to 80 ° C and put it into the mixer. Also put 0.3kg of coating binder C made of dextrin into 0.3kg of water and put it into the mixer. did. Then, the air was fed by a fan and kneaded by a mixer while volatilizing methanol. After the kneaded material was disintegrated after it became viscous, the kneading was continued for 60 seconds, then discharged and cooled. This was sieved through a 0.105 mm mesh sieve to obtain a fine coated refractory aggregate V having a particle size of 0.105 to 0.0 mm.

  Table 11 shows the composition of the refractory aggregate and the coating layer for the coated refractory aggregates T to V.

(Examples 26 and 27, Reference Example 28)
Coated refractory aggregates A to I, coated refractory aggregates T to V, and graphite were added to a Henschel mixer in the amounts shown in Table 12, and stirred for 5 minutes. Next, the binders A to C for the binder were blended in the blending amounts shown in Table 12, and hexamethylenetetramine was added as necessary. The mixture was stirred and kneaded at a rotational speed of 285 rpm for 15 minutes, and then discharged and fire-resistant. A brick composition was obtained.

  Using the firebrick composition prepared in Examples 26 and 27 and Reference Example 28, a molded firebrick for test and a fired firebrick for test were obtained in the same manner as described above. The bulk specific gravity, volatile content, rate of dimensional change, compressive strength, appearance, spalling resistance, and oxidation resistance of the molded fire bricks of Examples 26 and 27 and Reference Example 28 are determined. The volatile content, the dimensional change rate, the compressive strength, and the appearance were measured.

  Examples 26 and 27 and Reference Example 28 are refractory bricks prepared with a composition in which a refractory aggregate having no coating layer is not blended by using coated refractory aggregates T to V having a fine particle size. However, all the refractory bricks had excellent thermal shock resistance and strength as shown in Table 13.

(Preparation of coated refractory aggregates A-1 to I-1)
The above coated refractories A to F are spread on a stainless steel vat, placed in a hot air circulating dryer set at 120 ° C. in advance, and subjected to heat curing for 6 hours, and a coating caking comprising a novolac type phenolic resin in the coating layer. The binder A for coating consisting of the agent A and the resol type phenol resin was cured in an insoluble and infusible state. In addition, when the test which melt | dissolves the phenol resin which is the binder B for coating of the coating layer and the binder B for coating in methanol was carried out, the amount of dissolution of a phenol resin was 5 mass% or less in all.

  Next, the coated refractories A to F in which the coating layer is cured in an insoluble and infusible state and the coated refractories G to I coated with a binder for coating C composed of sugars are placed in a heat-resistant box, respectively. It was put in a larger heat-resistant box, and coke was filled into this large heat-resistant box. And after putting this in an electric furnace, it heated up to 1000 degreeC with the temperature increase rate of 4 degree-C / min, and also hold | maintained at this temperature for 3 hours. It was allowed to cool naturally. In this way, coated fireproof aggregates A-1 to I-1 obtained by carbonizing the binder of the coating layer were obtained.

(Preparation of coated refractory aggregate W)
30 kg of natural scale graphite with an average particle diameter of 6 μm heated to 130 ° C. is placed in a whirl mixer, and dextrin (the binding agent C for saccharide coating consisting of “No4-C” manufactured by Nissho Kagaku Co., Ltd.) is cured with 450 g. Add 850 g of mixed water in which 9 g of citric acid is dispersed as an agent and knead for about 90 seconds.After the kneaded material is disintegrated, add 30 g of calcium stearate, knead for 15 seconds, and further aeration to enter a curing agent. The coated refractory aggregate W was coated with a solid coating layer comprising a saccharide coating binder C. In this coated refractory aggregate W, the mass ratio of the coating layer to the refractory aggregate was 1.5% by mass. Met.

(Reference Examples 29-32)
Coated refractory aggregates A-1 to I-1, coated refractory aggregate W, electrofused magnesia (without coating layer), and graphite (without coating layer) were placed in a Henschel mixer in the amounts shown in Table 14 and stirred for 5 minutes. Next, the binders A to C for the binder were blended in the blending amounts shown in Table 14, and hexamethylenetetramine was added as necessary. The mixture was stirred and kneaded at a rotational speed of 285 rpm for 15 minutes, and then discharged and fire-resistant. A brick composition was obtained.

  Using the firebrick composition prepared in Reference Examples 29 to 32, a molded firebrick for test and a fired brick for test were obtained in the same manner as described above. And about these molded fire bricks of Reference Examples 29 to 32, bulk specific gravity, volatile content, dimensional change rate, compressive strength, appearance, spalling resistance, oxidation resistance, fired fire brick, bulk specific gravity, volatile content, The dimensional change rate, compressive strength, and appearance were each measured.

  Reference Examples 29 to 32 were used as coated refractories in a state where the binder of the coating layer was previously carbonized, but any of the refractory bricks of Reference Examples 29 to 32 is shown in Table 15. As can be seen, it has excellent thermal shock resistance and strength.

(Examples 33, 34, 36, Reference Example 35, Comparative Example 5)
After putting the firebrick composition prepared in the above Examples 7, 10, 15 and Reference Example 13 and Comparative Example 1 into a plastic bag and curing for 24 hours, it was formed into a mold having a cylindrical cavity having a diameter of 45 mm. 285 g was placed and pressed to a height of 60 mm to obtain a cylindrical shaped product.

  Further, as the heat treatment device, a superheated steam small batch tester (“Model GE-10B” manufactured by Nomura Engineering Co., Ltd.) having an effective dimension in the warehouse of 390 mm wide, 370 mm deep, and 390 mm high was used. This heat treatment device is provided with a blow-in port for introducing water vapor at the bottom and an exhaust port at the ceiling, and can be sealed by closing the door at the front opening.

  Then, the above molded product was set on a metal net in a heat treatment device. At this time, as the molded product, a hole from the center of the side surface to the inner center of the molded product was inserted and a temperature sensor was inserted, and a molded product without such a hole was used. (The same applies to the following examples and comparative examples).

  After setting the molded product in the heat treatment device in this way, 450 ° C superheated steam was supplied at 60 kg / h and started to blow from the blow port, and thereafter the superheat was performed so that the temperature in the container was maintained at 300 ° C. While controlling the supply flow rate of water vapor to about 20 kg / h, the blowing of superheated water vapor was continued.

  Thus, when the temperature rise of the central part of the molded product was measured with a temperature sensor while blowing superheated steam, it reached 200 ° C in 9 minutes from the start of blowing superheated steam, 250 ° C in 16 minutes, and 300 ° C in 32 minutes. . Moreover, when the oxygen concentration in the container was measured with a gas concentration detector ("testo 325-2" manufactured by Test Co., Ltd.), the measurement limit was 0.2 vol% or less (volume percentage ratio) immediately after the start of superheated steam blowing. there were.

  Then, after the temperature of the molded product reached 300 ° C., the heating treatment was continued by blowing superheated steam for 3 hours to cure the phenol resin binder of the molded product, and Examples 33, 34 and 36, Reference The refractory bricks of Example 35 and Comparative Example 5 were obtained. About this example 33, 34, 36, the reference example 35, and the firebrick of the comparative example 5 (those which are not perforated), bulk specific gravity, volatile matter, dimensional change rate, compressive strength, appearance, spalling resistance, Each oxidation resistance was measured and shown in Table 16.

  As shown in Table 16, all the refractory bricks of Examples 33, 34, and 36 had excellent thermal shock resistance and strength.

(Examples 37, 38, 40, Reference Example 39, Comparative Example 6)
After putting the firebrick composition prepared in the above Examples 7, 10, 15 and Reference Example 13 and Comparative Example 1 into a plastic bag and curing for 24 hours, it was formed into a mold having a cylindrical cavity having a diameter of 45 mm. 285 g was placed and pressed to a height of 60 mm to obtain a cylindrical shaped product. This molded product was set on a metal net in the same heat treatment apparatus as described above.

  First, as a first step, superheated steam at 300 ° C. is supplied and blown into the heat treatment device, and the superheated steam supply flow rate is controlled to about 20 kg / h so that the temperature in the heat treatment device is maintained at 200 ° C. While continuing to blow superheated steam. Thus, when the temperature rise of the center part of the molding was measured while blowing superheated steam, it reached 150 ° C. in 13 minutes and 200 ° C. in 28 minutes from the start of blowing superheated steam. After the temperature of the molded product reached 200 ° C., this superheated steam was continuously blown for 60 minutes for heat treatment.

  Subsequently, as the second stage, superheated steam at 450 ° C. is supplied and blown into the heat treatment device, and the superheated steam supply flow rate is controlled to about 30 kg / h so that the temperature in the heat treatment device is maintained at 300 ° C. While continuing to blow superheated steam. Thus, when the temperature rise of the center part of the molded product was measured while blowing superheated steam, the temperature reached 250 ° C. in 5 minutes and 300 ° C. in 15 minutes from the start of blowing of 450 ° C. superheated steam. After the temperature of the molded product reached 300 ° C., this superheated steam was continuously blown for 1 hour to perform heat treatment.

  Further, as a third stage, superheated steam at 800 ° C. is supplied and blown into the heat treatment device, and the supply flow rate of superheated steam is controlled to about 45 kg / h so that the temperature in the heat treatment device is maintained at 600 ° C. Then, the heating treatment was performed by continuing to blow superheated steam for 3 hours.

  Thus, the baking of Example 37, 38, 40, the reference example 39, and the comparative example 6 by which the phenol resin binder and dextrin binder in the refractory were carbonized by heat-processing in high temperature in the 3rd step. Got refractory bricks. For the fired bricks of Examples 37, 38, 40, Reference Example 39, and Comparative Example 6, the bulk specific gravity, volatile content, dimensional change rate, compressive strength, appearance, spalling resistance, and oxidation resistance were measured. It shows in Table 17.

  As seen in Table 17, all the fired refractory bricks of Examples 37, 38 and 40 had excellent thermal shock resistance and strength.

Claims (12)

  A refractory brick composition comprising a coated refractory aggregate prepared by coating a solid coating layer composed of a binder for coating on the surface of a refractory aggregate, and a liquid binder binder. The said coating layer which consists of a binder for coating is formed with the thermosetting resin which is uncured and has thermosetting property, The composition for refractory bricks characterized by the above-mentioned.   The refractory brick composition according to claim 1, wherein the binder for a binder is selected from a thermosetting resin, a saccharide, and a thermoplastic resin.   The composition for refractory bricks according to claim 1 or 2, wherein a phenol resin is used as the thermosetting resin.   4. The refractory brick composition according to claim 2, wherein a carboxylic acid is blended in the saccharide as a curing agent.   5. The firebrick composition according to claim 2, wherein a water-soluble thermoplastic resin is used as the thermoplastic resin.   6. The solid coating layer according to claim 1, wherein the solid coating layer is formed by adding and mixing a binder for coating to a refractory aggregate heated to 110 to 180 ° C. The composition for refractory bricks described in 1.   The fireproof brick composition according to any one of claims 1 to 6, wherein the fireproof aggregate contains at least one of magnesia and alumina.   The composition for a refractory brick according to any one of claims 1 to 7, wherein a coated refractory aggregate coated with a coating layer and a refractory aggregate not coated with a coating layer are mixed and blended. .   A fire-resistant brick formed by molding the fire-resistant brick composition according to any one of claims 1 to 8, wherein the coated fire-resistant aggregate is bound by a binder for a binder that is solidified, hardened, or carbonized. Bricks.   A method for producing a refractory brick, comprising molding the refractory brick composition according to any one of claims 1 to 8, and heating the molded product to solidify, cure, or carbonize the binder for the binder. .   The method for producing a refractory brick according to claim 10, wherein the binder binder is solidified, cured, or carbonized through a step of heating with steam.   The method for producing a refractory brick according to claim 11, wherein superheated steam is used as the steam.