Solid binder for refractories and refractory comprising the solid binder

Abstract

This invention relates to solid binders for refractory materials, comprising basic refractory raw materials and primary reactants of organic acids containing three or more functional groups, as well as refractory materials and refractory bricks including solid binders.

Description

Technical Field

[0001] This invention relates to solid binders for refractory materials that can produce refractory materials with less harmful gas generation and excellent quality, as well as refractory materials containing solid binders. Background Technology

[0002] Refractory materials with high heat resistance and high corrosion resistance are used in industrial applications involving high-temperature melts, such as ironmaking and steelmaking. These refractories are used in electric furnaces, ladles, converters, or torpedo-type ladle cars, and in refining processes such as steelmaking and ironmaking. Conventional carbon-containing refractories consist of carbon-containing refractory aggregates and binders. In this case, phenolic resins are typically used as the binder.

[0003] However, in refractories containing adhesives containing organic materials such as phenolic resins, the organic materials are thermally decomposed during high-temperature exposure or sintering, resulting in reduced bond strength and the release of volatile organic compounds (VOCs) such as phenol into the surrounding environment during the thermal decomposition process. VOCs are substances that cause air pollution due to their high vapor pressure and easy volatilization into the air at room temperature. They are known to have inherent biological toxicity (vapors or fumes can irritate the nose, throat, and lungs, and may corrode the eyes and skin, leading to blindness) and chemical reactivity, and produce odors and some carcinogens. Therefore, there is a health risk for steel smelter workers and residents living near smelters.

[0004] As an alternative, Korean Patent No. 967408 (Patent Document 1) discloses a carbon-containing refractory composition comprising carbon-containing refractory aggregate and a binder, wherein the binder comprises magnesium sulfate, lignin sulfonate, and water. However, as in Patent Document 1, the refractory containing magnesium sulfate and lignin sulfonate may have poor thermal properties and corrosion resistance because the refractory is thermally decomposed during high-temperature exposure.

[0005] Therefore, there is a need to research and develop adhesives for refractory materials and refractory materials containing such adhesives, which can prepare refractory materials that produce less harmful gas during high-temperature exposure and have excellent physical properties such as thermal properties, strength and corrosion resistance. Summary of the Invention

[0006] Technical issues

[0007] The present invention provides a solid binder for refractory materials and a refractory material comprising the solid binder, the solid binder being capable of preparing a refractory material that produces fewer harmful gases during high-temperature exposure and has excellent physical properties such as thermal properties, strength and erosion resistance.

[0008] Technical solution

[0009] According to an aspect of the invention, a solid binder for refractory materials is provided, comprising an alkaline refractory raw material and a primary reactant of an organic acid containing three or more functional groups.

[0010] According to another aspect of the invention, a refractory is provided, comprising a solid binder for refractory and a refractory material.

[0011] According to another aspect of the invention, a refractory brick is provided, comprising a solid binder for refractory materials and refractory materials.

[0012] Beneficial effects

[0013] Since the solid binder for refractory materials according to the present invention does not contain organic resins such as phenolic resins, it generates fewer harmful gases during high-temperature exposure and is therefore environmentally friendly. Furthermore, because the solid binder for refractory materials has better kneading properties than phenolic resins, which are conventionally used binders, the kneading time is shortened, resulting in excellent economic efficiency. Moreover, while phenolic resins require an aging time of 3 to 24 hours after kneading due to their thermosetting properties, and require long-term drying at high temperatures after molding, the solid binder for refractory materials according to the present invention can be molded immediately after kneading, thus improving productivity, and also offers energy savings due to the reduced drying time caused by the properties of water-based binders.

[0014] Furthermore, because refractory materials and / or refractory bricks containing solid binders for refractory materials possess excellent physical properties such as thermal properties, strength, and erosion resistance, they can be used in industrial applications involving high-temperature melts, such as ironmaking and steelmaking. In particular, due to their excellent refractory properties, refractory materials and / or refractory bricks can be used in various processes and fields, such as electric furnaces, ladles, converters, torpedo-type ladle cars, and refining processes such as steelmaking and ironmaking. Attached Figure Description

[0015] Figure 1 The images are scanning electron microscope (SEM) images of solid adhesives for refractory materials based on the adhesive of Comparative Example 1.

[0016] Figure 2 This is a SEM image of a solid adhesive for refractory materials based on the adhesive of Example 1;

[0017] Figure 3 and Figure 4 The photograph illustrates a measurement of the reaction temperature after water was added to the adhesive of Comparative Example 1 or Example 1.

[0018] Figure 5 and Figure 6 The results of harmful gas analysis are respectively from Comparative Example 2 and Example 18;

[0019] Figure 7 The photograph illustrates the expansion test of the permanent gasket at the joint of Comparative Example 2; and

[0020] Figure 8 This is a photograph illustrating the permanent linear expansion of the joint in Embodiment 24. Detailed Implementation

[0021] The invention will be described in detail below.

[0022] Solid adhesives for refractory materials

[0023] The solid binder for refractory materials according to the present invention comprises an alkaline refractory raw material and a primary reactant of an organic acid containing three or more functional groups.

[0024] Solid binders for refractory materials can be in the form of a simple mixture of refractory raw materials and organic acids, but this can present problems, such as reactions due to moisture during storage and deterioration of thermal properties due to unreacted binders after molding. Therefore, solid binders for refractory materials contain primary reactants obtained by reacting the refractory raw materials with organic acids. In this case, the primary reactants are in the form of hydrates, which ensures storage stability and improves the kneading properties of the refractory, preventing problems such as deterioration of thermal properties due to unreacted binders during product manufacturing.

[0025] alkaline refractory materials

[0026] Alkaline refractory materials impart viscosity to binders by reacting with organic acids.

[0027] Alkaline refractory materials may include at least one selected from magnesium oxide, quicklime (CaO), hydrated lime (Ca(OH)2), and calcined dolomite (MgO·CaO). Specifically, alkaline refractory materials may be products obtained by reacting water with at least one reactant selected from magnesium oxide, quicklime (CaO), hydrated lime (Ca(OH)2), and calcined dolomite (MgO·CaO).

[0028] In this case, magnesium oxide may be selected from at least one of caustic calcined magnesium oxide, fused magnesium oxide, sintered magnesium oxide, and recalcined magnesium oxide.

[0029] More specifically, the basic refractory raw material may include magnesium oxide and at least one reaction rate modifier selected from quicklime (CaO), hydrated lime (Ca(OH)2), and calcined dolomite (MgO·CaO). In this case, magnesium oxide and the reaction rate modifier may be contained in a weight ratio of 1:0.005 to 1:0.1 or 1:0.01 to 1:0.05. When the weight ratio of magnesium oxide to the reaction rate modifier is within the above range, the reaction rate between the refractory raw material and the organic acid can be appropriately controlled. When the weight ratio of magnesium oxide to the reaction rate modifier is greater than the above range, that is, when the weight of the reaction rate modifier is excessive relative to the weight of magnesium oxide, the physical properties of the prepared refractories may be poor due to volume expansion or separation during the hydration process, or precipitation may occur in the binder, thus deteriorating the properties of the binder.

[0030] The amount of reaction rate regulator can be adjusted based on the amount of calcium oxide (CaO) contained in magnesium oxide, and for example, based on 100 parts by weight of calcium oxide (CaO) in magnesium oxide, the amount of reaction rate regulator can be 0.5 parts by weight to 10 parts by weight or 1 part by weight to 5 parts by weight.

[0031] Furthermore, the reaction rate regulator can have an average diameter of less than 0.3 mm, 0.045 mm to 0.3 mm, or 0.045 mm to 0.1 mm. When the average diameter of the reaction rate regulator is within these ranges, it acts as a catalyst for reactions with high specific surface areas, thus reducing reaction time. Conversely, when the average diameter of the reaction rate regulator is greater than these ranges, the rate regulator may not function properly due to decreased reactivity, and unreacted rate regulators may adversely affect product properties, such as thermal strength.

[0032] organic acids

[0033] Organic acids impart viscosity to binders by reacting with basic refractory materials.

[0034] Organic acids contain three or more functional groups. In this case, the functional group can be a carboxyl group (COOH). As described above, if an organic acid containing three or more functional groups is used, the organic acid can react with substances such as MgOH produced during the hydration of the refractory raw material. + and CaOH + The basic functional groups react to exhibit high viscosity.

[0035] Specifically, the organic acid may include at least one selected from citric acid and ethylenediaminetetraacetic acid.

[0036] Solid binders for refractory materials may contain refractory raw materials and organic acids in weight ratios of 1:0.25 to 1:4.0, 1:0.5 to 1:2.0, or 1:0.8 to 1:1.2. When the weight ratio of refractory raw materials to organic acids is less than these ranges, i.e., when a small amount of organic acid is present based on the weight of the refractory raw materials, it is difficult to achieve sufficient viscosity to aid in post-reaction molding. Furthermore, when the weight ratio of refractory raw materials to organic acids is greater than these ranges, i.e., when an excessive amount of organic acid is present based on the weight of the refractory raw materials, the physical properties may deteriorate due to unreacted organic acid.

[0037] Specifically, the solid binder for refractory materials may comprise a primary reactant in the form of a hydrate, wherein an alkaline refractory material, an organic acid containing three or more functional groups, and water react. In this case, the primary reactant may be a primary reactant in which the refractory material, the organic acid, and water react in a weight ratio of 1:0.25 to 4.0:0.2:1.5, 1:0.5 to 2.0:0.3:0.9, or 1:0.8 to 1.2:0.3:0.7. When the weight ratio of refractory material to water is less than the above ranges, i.e., when a small amount of water is contained based on the weight of the refractory material, there is a problem that the formation of the binder hydrate is reduced due to water evaporation caused by heat generation. Furthermore, when the weight ratio of refractory material to water is greater than the above ranges, i.e., when an excessive amount of water is contained based on the weight of the refractory material, an unnecessary drying process may occur due to the residual water after the reaction.

[0038] Solid binders for refractory materials may further include at least one selected from stabilizers and pot life modifiers.

[0039] stabilizer

[0040] Stabilizers improve the stability of adhesives by preventing cracking caused by the evaporation of organic acids and / or moisture.

[0041] In addition, the stabilizer may include at least one selected from inorganic salts and inorganic acids. Specifically, the stabilizer may include at least one selected from magnesium sulfate, aluminum sulfate, magnesium phosphate, aluminum phosphate, phosphoric acid, and boric acid.

[0042] More specifically, the stabilizer may include at least one selected from MgSO4, MgSO4·7H2O, Mg3(PO4)2, H3PO4, Al2(SO4)3, H3BO3 and AlPO4.

[0043] Based on the total weight of the solid binder for refractory materials, it may contain a stabilizer in amounts of 5 wt% to 30 wt% or 7.0 wt% to 20 wt%. If the amount of stabilizer is less than the above ranges, cracks may occur on the surface of the binder during the drying process, and if the amount of stabilizer is greater than the above ranges, a reduction in thermal strength and molding strength may occur.

[0044] Product life regulator

[0045] Pot life conditioners control the pot life of adhesives by preventing stability loss due to moisture evaporation from solid binders used in refractory materials and by controlling the moisture content of the binder.

[0046] In addition, the pot life regulator may include at least one selected from glycerin, ethylene glycol, propylene glycol, stearic acid, carbomer, xanthan gum, cellulose and methylcellulose.

[0047] Based on the total weight of the solid binder for refractory materials, a pot life modifier may be included in an amount of 0.2 wt% to 5 wt% or 0.5 wt% to 3.0 wt%. If the amount of pot life modifier is less than the above ranges, it may not function properly as a pot life modifier, and if the amount of pot life modifier is greater than the above ranges, it may reduce the molding density and dry strength of the prepared product.

[0048] Furthermore, the solid binder for refractory materials according to the invention, as described above, may further contain coke powder. In the case where coke powder is further contained as described above, the solid binder can be used as a surface treatment for refractory materials, particularly as an adhesive for coating. In this case, the amount of coke powder used is not particularly limited, provided that it has suitable viscosity and processability for surface treatment, particularly for coating.

[0049] Because the solid binder for refractory materials according to the present invention, as described above, has better kneading properties than phenolic resins used as conventional binders, the kneading time is shortened, resulting in superior economic efficiency. Furthermore, phenolic resins, due to their thermosetting nature, require an aging time of 3 to 24 hours after kneading and prolonged drying at high drying temperatures after molding. However, with the solid binder for refractory materials according to the present invention, molding can be performed immediately after kneading, thus improving productivity. Additionally, energy savings are achieved because the drying time is reduced due to the properties of water-based binders.

[0050] Refractory

[0051] The refractory according to the present invention comprises a solid binder for refractory and a refractory material.

[0052] Refractory materials can be used without particular restriction, as long as they are commonly used as raw materials for refractory materials, and may include, for example, at least one selected from magnesia-based refractories, alumina-based refractories, chromium-based refractories, silica-based refractories, and graphite-based refractories. In this case, graphite-based refractories may include natural graphite, crystalline graphite, or expandable graphite.

[0053] Specifically, the refractory material may include at least one selected from magnesia-carbon-based refractory materials, magnesia-alumina-carbon-based refractory materials, alumina-magnesia-carbon-based refractory materials, magnesia-based refractory materials, magnesia-chromium-based refractory materials, magnesia-spinel-based refractory materials, and alumina-silicon carbide-carbon-based refractory materials.

[0054] The refractory may comprise 100 parts by weight of refractory material and 1 to 5 parts by weight of solid binder for refractory. When the weight of the solid binder for refractory is less than the above range, i.e., when the refractory material contains a small amount of solid binder for refractory, the erosion resistance of the refractory decreases due to reduced molding strength, increased porosity, and increased absorption rate. Conversely, when the weight of the solid binder for refractory is greater than the above range, i.e., when the refractory material contains an excessive amount of solid binder for refractory, the life (erosion resistance) of the refractory may decrease due to reduced strength and increased porosity caused by the volatilization of the binder at high temperatures.

[0055] Furthermore, the refractories may further comprise at least one selected from stabilizers and service life modifiers. In this case, the stabilizers and service life modifiers are the same as those described in the solid binders for refractories.

[0056] The refractories may contain 100 parts by weight of refractory material, 0.1 to 5 parts by weight or 0.1 to 2 parts by weight of stabilizer, and 0.2 to 5 parts by weight or 0.5 to 3.0 parts by weight of service life modifier. If the amount of stabilizer is less than the above ranges, cracks may occur on the surface of the refractories during the drying process; if the amount of stabilizer is greater than the above ranges, the thermal strength and forming strength of the refractories may be reduced. Furthermore, if the amount of service life modifier is less than the above ranges, the moisture content in the refractories may be excessive; if the amount of service life modifier is greater than the above ranges, the forming density and dry strength of the refractories may be reduced.

[0057] Refractory materials may further contain thermal property modifiers.

[0058] Thermal property improver

[0059] Thermal property modifiers improve the thermal strength, corrosion resistance, or oxidation resistance of refractory materials.

[0060] In this case, thermal property improvers can be used without particular restriction, as long as they can be typically added to refractories to improve thermal properties, and may include, for example, at least one selected from bitumen, silicon nitride (Si3N4), boron carbide (B4C) and carbon black.

[0061] Based on 100 parts by weight of refractory material, it may contain 0.1 to 3 parts by weight or 0.1 to 1.0 parts by weight of a heat property modifier. If the amount of heat property modifier is less than the above ranges, the heat property improvement effect may not be adequately exhibited; and if the amount of heat property modifier is greater than the above ranges, the forming strength and dry properties of the refractory may decrease or may affect the steel grade.

[0062] Refractory bricks

[0063] The refractory bricks according to the present invention comprise a solid binder for refractory materials and refractory materials.

[0064] In this case, the refractory material is the same as that described in the section on refractory materials.

[0065] Refractory bricks can be magnesia-carbon refractory bricks, magnesia-alumina-carbon refractory bricks, alumina-silica refractory bricks, magnesia-chrome refractory bricks, alumina-carbon refractory bricks, or magnesia-based refractory bricks.

[0066] In addition, refractory bricks can be reduction-fired bricks, fired bricks, or unfired bricks.

[0067] Since the refractories and / or refractory bricks according to the invention, as described above, do not contain organic resins such as phenolic resins, no volatile organic compounds (VOCs) are generated during the preparation process, making them eco-friendly. Furthermore, the refractories and / or refractory bricks exhibit excellent properties essential to refractories, such as compressive strength, porosity, erosion resistance, or thermal shock resistance.

[0068] The invention will now be described in more detail with reference to the following embodiments. However, these embodiments are intended only to illustrate specific implementations of the invention and are not intended to limit or confine the scope of the invention to the content described in these embodiments.

[0069] [Example]

[0070] Example 1 and Comparative Example 1. Preparation of solid binders for refractory materials

[0071] A solid binder for refractory materials was prepared by using the amounts of each component listed in Table 1, and... Figure 1and Figure 2 The image shows a scanning electron microscope (SEM) image of the solid binder used to prepare the refractory. Figure 1 The image shows an SEM image of the adhesive used in Comparative Example 1. Figure 2 This is an SEM image of the adhesive from Example 1.

[0072] Specifically, in Comparative Example 1, a solid binder for refractory materials was prepared by simply mixing refractory raw materials and organic acids. Furthermore, in Example 1, after mixing refractory raw materials and organic acids, then adding water and reacting to obtain a primary reactant, the primary reactant was dried at 80±20°C for 12 hours and then ground using an impact mill as the grinding equipment to prepare a solid binder for refractory materials with an average particle size of 0.074 mm.

[0073] Then, after adding 200 parts by weight of water to 200 parts by weight of the solid binder for refractory, the maximum value of the temperature (reaction temperature) was measured using a digital thermometer, and in this case, at Figure 3 and Figure 4 The test results are shown in the example.

[0074] [Table 1]

[0075]

[0076] As shown in Table 1, for the adhesive of Comparative Example 1 prepared by simple mixing, the reaction with the mixture and water added for kneading increased the temperature by 37°C relative to the initial temperature of 25°C.

[0077] Conversely, for the binder of Example 1 prepared by grinding the reactants of the primary reaction, the temperature did not change significantly because the temperature increased by 2°C relative to the initial temperature of 25°C. The temperature increase during kneading in refractory preparation is a factor that greatly affects the surface dryness and formability of the refractory material. Since the temperature change in Example 1 was very small compared to Comparative Example 1, it was able to maintain stable kneading and a sufficient service life for the refractory material.

[0078] Examples 2 to 11. Preparation of solid binders for refractory materials

[0079] Solid binders for refractory materials were prepared by using the amounts of each component listed in Table 2.

[0080] Specifically, after mixing refractory raw materials and organic acids, water is added and the mixture is reacted to obtain a primary reactant. The primary reactant is then dried at 80±20°C for 12 hours and then ground using an impact mill as the grinding equipment to prepare a solid binder for refractory materials with an average particle size of 0.074 mm.

[0081] In this case, EDTA in Table 2 is ethylenediaminetetraacetic acid. The reaction temperature is measured by using a digital thermometer to measure the maximum temperature, and the reaction time is measured by visually determining the time when the reaction begins.

[0082] [Table 2]

[0083]

[0084] As shown in Table 2, the reaction rates of refractory materials and organic acids follow the order of quicklime, hydrated lime, calcined dolomite, caustic calcined magnesia, recalcined magnesia (DBM), sintered magnesia, and fused magnesia. It can be understood that the reaction rate is determined by the hydration rate of the refractory raw materials. Therefore, it can also be understood that the reaction rate can be controlled by adding quicklime, hydrated lime, or calcined dolomite to magnesia such as fused magnesia, sintered magnesia, DBM, and caustic calcined magnesia.

[0085] Furthermore, it is understood that the reaction temperature and reaction time can be controlled by adjusting the mixing ratio of sintered magnesia and caustic calcined magnesia, which are used as refractory raw materials.

[0086] Examples 12 to 16. Preparation of Refractory Materials

[0087] Refractory materials were prepared by using the amounts of each component listed in Table 3.

[0088] Specifically, after mixing refractory raw materials and organic acids in a 1:1 weight ratio, water is added and the mixture is reacted to obtain a primary reactant. Then, after drying the primary reactant at 80±20°C for 12 hours, a stabilizer is added and the mixture is ground using an impact mill as the grinding equipment to prepare a solid binder for refractory materials with an average particle size of 0.074 mm.

[0089] Then, after mixing magnesium oxide, aluminum oxide and crystalline graphite as refractory materials, a solid binder for refractory is added, kneaded at 25°C to 30°C for 15 minutes, and the mixture is shaped into a size of 60mm×60mm×60mm and dried at 200°C for 12 hours to prepare the refractory.

[0090] Then, the prepared refractory was subjected to a rapid heating test at 900°C. Specifically, after the refractory was placed in an electric furnace at 900°C and rapidly heated for 4 minutes, the presence of cracks on the exterior of the refractory was visually observed.

[0091] [Table 3]

[0092]

[0093] As shown in Table 3, when MgSO4, Al2(SO4)3 or H3BO3 as stabilizers are added to the binder for refractory materials, the generation of surface microcracks tends to be reduced during rapid heating and the overall dry properties are improved compared to Example 12 in which no such additives were added.

[0094] Preparation of refractory materials: Examples 17 to 23, and Comparative Examples 2 and 3.

[0095] Refractory materials were prepared by using the amounts of each component listed in Table 4.

[0096] Specifically, after mixing refractory raw materials and organic acids, water is added and the mixture is reacted to obtain a primary reactant. Then, after drying the primary reactant at 80±20°C for 12 hours, boric acid (H3BO3) is added as a stabilizer and the mixture is ground using an impact mill to prepare a solid binder for refractory materials with a particle size of 0.074 mm.

[0097] Then, after mixing magnesium oxide, aluminum oxide and crystalline graphite as refractory materials, a solid binder for refractory is added, kneaded at 25°C to 35°C for 15 minutes, and the mixture is shaped into a size of 60mm×60mm×60mm, dried at 200°C for 12 hours and sintered at 1,000°C for 12 hours to prepare the refractory.

[0098] In this case, it will have 0.98 g / cm³. 3 Specific gravity of 1m 2 Products with a specific surface area of ​​ / g and an average particle size of 350μm were used as crystalline graphite, and products with an average particle size of 4mm were used as magnesium oxide. In addition, 8027 manufactured by KANGNAMCHEMICAL was used as a phenolic resin, and molasses manufactured by DAESANG (total solids content: 80wt% or more) was used as molasses.

[0099] The physical properties of the prepared refractories were measured by the following method, and the specific gravity after molding, physical properties after drying, physical properties after sintering, and erosion resistance were compared with the increase of the amount of citric acid added during the preparation of the binder.

[0100] 1) Bulk Specific Gravity

[0101] According to KSL 3114 (2010), the refractory is placed in white kerosene (impregnation liquid), and the bulk density after drying or sintering is calculated using the following Equation 1.

[0102] [Equation 1]

[0103] ρ b(Specific gravity) = m1 / (m3-m2) × ρ liq

[0104] m1: Dry mass of the refractory material (g)

[0105] m2: Apparent mass (g) of the impregnated refractory.

[0106] m3: Mass (g) of the sample after impregnation.

[0107] ρ liq Density of the impregnation solution

[0108] 2) Compressive strength

[0109] The compressive strength of a dry refractory with dimensions of 60 mm × 60 mm × 60 mm was measured using a hydraulic compressive strength tester, according to the method described in KSL 3115.

[0110] 3) Porosity

[0111] According to KSL 3114 (2010), the refractory is immersed in white kerosene (impregnation liquid), and the apparent porosity after drying or sintering is calculated using the following Equation 2.

[0112] [Equation 2]

[0113] π a (Porosity) = (m3-m1) / (m3-m2)×100

[0114] m1: Dry mass of the refractory material (g)

[0115] m2: Apparent mass (g) of the impregnated refractory.

[0116] m3: Mass (g) of the sample after impregnation.

[0117] 4) Corrosion resistance

[0118] The refractory was heated to 1,650°C to 1,700°C using a burner, and steel and steel slag were mixed as erosives in a 1:1 weight ratio to measure the erosion resistance of the mixture using a rotary erosion tester.

[0119] Specifically, corrosion resistance is expressed as a relative corrosion index, where the corrosion amount in Example 20 is 100. In this case, the lower the corrosion index, the better the corrosion resistance.

[0120] 5) Analysis of harmful gases

[0121] The composition of the gases emitted during the thermal decomposition analysis of the adhesive as weight decreases (decomposition gases) was analyzed using thermal analysis and solid-state mass spectrometry (STA-MS). Figure 5 and Figure 6 The analysis results are displayed in the image. Figure 5 The results are the gas component analysis results of Comparative Example 2, and Figure 6 This is the gas component analysis result of Example 18.

[0122] [Table 4]

[0123]

[0124] As shown in Table 4, the molding specific gravity, physical properties after drying, and physical properties after sintering of Examples 18 to 22 are equal to those of Comparative Examples 2 and 3. In particular, Example 20, in which the weight ratio of refractory material to citric acid is 1:1, has better erosion resistance than Comparative Example 2, which uses phenolic resin.

[0125] Because the amount of organic acid in Example 17 was low relative to the total amount of refractory raw materials, the properties of the binder were poor. Furthermore, in Example 23, because the amount of organic acid was excessive relative to the amount of refractory raw materials, the organic acid reacted with the mixture, causing surface drying, and consequently, reducing the forming strength of the refractory material.

[0126] like Figure 5 As shown, for Comparative Example 2, benzene (C6H6), toluene (C7H8), and phenol (C6H5OH) were released. Conversely, as... Figure 6 As shown, the adhesive of Example 18 has excellent environmental friendliness because it does not release harmful substances such as benzene (C6H6), toluene (C7H8) and phenol (C6H5OH) at all.

[0127] Examples 24 to 28. Preparation of Refractory Materials

[0128] Refractory materials were prepared by using the amounts of each component listed in Table 5.

[0129] Specifically, after mixing 34 parts by weight of sintered magnesia, 16 parts by weight of caustic calcined magnesia, and 50 parts by weight of citric acid, water was added and the mixture was reacted to obtain a primary reactant. Then, after drying the primary reactant at 80±20°C for 12 hours, 10 parts by weight of boric acid and 5 parts by weight of magnesium sulfate were added as stabilizers, and the mixture was ground using an impact mill to prepare a solid binder-1 for refractory materials with an average particle size of 0.074 mm.

[0130] Then, after mixing magnesium oxide, aluminum oxide and crystalline graphite as refractory materials, a solid binder for refractory-1 is added, kneaded at 25°C to 30°C for 15 minutes, and the mixture is shaped into a size of 60mm×60mm×60mm, dried at 200°C for 12 hours and sintered at 1,000°C for 12 hours to prepare the refractory.

[0131] In this case, CARBORES-P pitch manufactured by RUTGERS was used as a thermal property improver, and carbon black with an average diameter of 0.01 mm was used. Additionally, 8027 manufactured by KANGNAM CHEMICAL was used as a phenolic resin.

[0132] The physical properties after drying, the physical properties after sintering, and the erosion resistance of the prepared refractories were measured in the same manner as in Example 17, and the thermal shock resistance and permanent linear expansion were measured by the following methods.

[0133] 1) Thermal shock resistance

[0134] After melting green billet metal at 1,650°C in a high-frequency induction furnace to prepare molten steel, a refractory with dimensions of 230 mm × 40 mm × 40 mm is immersed in the molten steel for 60 seconds and then cooled in air for 5 minutes, which is defined as one cycle. The number of cycles until spalling (cracking) occurs in the refractory is recorded. The higher the measured number of cycles, the better the thermal shock resistance.

[0135] 2) Permanent linear expansion

[0136] The linear change of the refractory after sintering was measured. After a refractory with dimensions of 50 mm × 40 mm × 60 mm was placed in a crucible filled with coke to induce a reducing atmosphere, it was sintered at 1,500 °C for 5 hours and cooled to room temperature. The length change of the refractory relative to its initial length was then measured to determine the linear change. In this case, Figure 7 and Figure 8 The image shows photographs of the refractory before and after sintering. Figure 7 It is a photograph of the refractory material of Comparative Example 2, and Figure 8 This is a photograph of the refractory material of Example 24.

[0137] [Table 5]

[0138]

[0139] As shown in Table 5, compared to those in Example 25 which did not contain thermal property modifiers, the refractory materials of Examples 26 to 30, which contained thermal property modifiers such as pitch and carbon black, showed improved molding specific gravity, physical properties after drying, and physical properties after sintering. In particular, Examples 25 to 28 exhibited better erosion resistance and thermal shock resistance than Comparative Example 2. Furthermore, for Example 28 containing silicon nitride (Si3N4), erosion resistance was improved by 10% or more compared to Comparative Example 2, and permanent linear expansion was significantly improved compared to Comparative Example 2 which used conventional phenolic resin.

[0140] like Figure 7 and Figure 8 As shown in Table 5, since the refractory of Example 24 has better permanent linear expansion than the refractory of Comparative Example 2 which uses phenolic resin as a conventional adhesive, corrosion at the joint is prevented by preventing molten steel from penetrating into the joint (brick joint).

Claims

1. A solid binder for refractory materials, said solid binder comprising: The reaction product is prepared from a mixture of i) water, ii) at least one alkaline refractory material selected from magnesium oxide, quicklime (CaO), hydrated lime (Ca(OH)2) and calcined dolomite (MgO·CaO), and iii) an organic acid containing three or more carboxyl groups. The weight ratio of the alkaline refractory material to the organic acid is 1:0.5 to 1:4.

0.

2. The solid binder for refractory materials as described in claim 1, wherein the refractory material is magnesium oxide.

3. The solid binder for refractory materials as claimed in claim 2, wherein the magnesium oxide is at least one selected from caustic calcined magnesium oxide, fused magnesium oxide, sintered magnesium oxide, and reheated magnesium oxide.

4. The solid binder for refractory materials as claimed in claim 1, wherein the organic acid comprises at least one selected from citric acid and ethylenediaminetetraacetic acid.

5. The solid binder for refractory materials as claimed in claim 1, wherein the solid binder for refractory materials comprises the refractory raw material and the organic acid in a weight ratio of 1:0.5 to 1:2.

0.

6. The solid binder for refractory materials as claimed in claim 1, further comprising at least one selected from stabilizers and pot life modifiers.

7. The solid binder for refractory materials as claimed in claim 6, wherein the stabilizer comprises at least one selected from inorganic salts and inorganic acids.

8. The solid binder for refractory materials as claimed in claim 6, wherein the amount of the stabilizer contained is from 5 wt% to 20 wt% based on the total weight of the solid binder for refractory materials.

9. The solid binder for refractory materials as claimed in claim 6, wherein the pot life regulator comprises at least one selected from glycerol, ethylene glycol, propylene glycol, stearic acid, carbomer, xanthan gum, cellulose, and methylcellulose.

10. Refractory materials, including: Solid adhesive for refractory materials according to any one of claims 1 to 9; and Refractory materials.

11. The refractory as claimed in claim 10, wherein the refractory material comprises at least one selected from magnesium oxide-based refractory materials, alumina-based refractory materials, chromium-based refractory materials, silica-based refractory materials, and graphite-based refractory materials.

12. The refractory as claimed in claim 10, further comprising at least one selected from stabilizers and pot life regulators.

13. The refractory of claim 12, wherein the stabilizer comprises at least one selected from inorganic salts and inorganic acids.

14. The refractory of claim 12, wherein the pot life regulator comprises at least one selected from glycerol, ethylene glycol, propylene glycol, stearic acid, carbomer, xanthan gum, cellulose, and methylcellulose.

15. The refractory of claim 12, wherein the refractory comprises 100 parts by weight of the refractory material, 5 to 20 parts by weight of the stabilizer, and 0.2 to 5 parts by weight of the pot life modifier.

16. The refractory of claim 10, wherein the refractory comprises 100 parts by weight of the refractory material and 1 to 5 parts by weight of the solid binder for the refractory.

17. Refractory bricks, including: Solid adhesive for refractory materials according to any one of claims 1 to 9; and Refractory materials.

18. The refractory brick of claim 17, wherein the refractory material comprises at least one selected from magnesium oxide-based refractory materials, alumina-based refractory materials, chromium-based refractory materials, silica-based refractory materials, and graphite-based refractory materials.

19. The refractory brick as claimed in claim 17, wherein the refractory brick is a magnesia-carbon refractory brick, a magnesia-alumina-carbon refractory brick, an alumina-silica refractory brick, a magnesia-chrome refractory brick, an alumina-carbon refractory brick, or a magnesia-based refractory brick.

20. The refractory brick of claim 17, wherein the refractory brick is a reduction-fired brick, a fired brick, or an unfired brick.

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