An ultralight corundum thermal insulation material and its preparation method

Abstract

This invention discloses a method for preparing an ultralight corundum thermal insulation material: A foaming agent and a modifier are mixed and then water is added and stirred to obtain a modified foaming agent dispersion; hollow alumina spheres, corundum powder, micro powder, binder, dispersant, and fibers are mixed evenly to obtain a mixed raw material; the modified foaming dispersion is added to the mixed raw material, stirred, and fully foamed to obtain a mixed slurry; the mixed slurry is poured into a mold, and after the slurry automatically fills the mold, the surface is smoothed; after curing, the material is demolded and dried to obtain a green body; the green body is sintered, and the resulting ultralight corundum thermal insulation material has a porosity of 55-80% and a bulk density of 0.90-1.20 g / cm³. 3 The compressive strength after firing at 1200℃ is greater than or equal to 15MPa. This invention can solve the problems of poor pore uniformity, low material strength, and high thermal conductivity in lightweight alumina hollow sphere insulation materials.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials technology. Specifically, it relates to an ultralight corundum thermal insulation material and its preparation method. Background Technology

[0002] Hollow alumina spheres are a new type of thermal insulation material with a thin-shell structure. The main component is α-alumina, which has the characteristics of high temperature resistance, good thermal insulation performance, stable chemical properties, and is not affected by changes in atmosphere.

[0003] Traditional lightweight alumina hollow sphere insulation materials are mostly manufactured using vibration molding or machine pressing processes. Vibration molding easily causes the hollow spheres to float, resulting in material segregation and affecting insulation performance. Machine pressing, on the other hand, is difficult to control in terms of pressure, easily causing the hollow spheres to crush, increasing material density and reducing insulation performance. This is because the matrix is ​​relatively dense or the pores are mainly in the form of millimeter-scale holes. Traditional alumina hollow sphere insulation materials cannot simultaneously meet the requirements of lightweight and high strength simply by adjusting the proportion of alumina hollow spheres.

[0004] Chinese patents "A Lightweight High-Strength Magnesium Aluminum Spinel Hollow Sphere Porous Ceramics and Its Preparation Method" (CN112209739A) and "An Ultra-Lightweight Corundum Castable and Its Preparation Method" (CN108675809A) introduce methods for achieving lightweighting of hollow sphere castable matrices. However, using single or simple composite chemical foaming agents makes it difficult to prepare foams with large bubble volume and good stability, and it is impossible to obtain ultra-lightweight thermal insulation materials with uniform pores, high porosity, and pores mainly existing at the micron level. During mechanical stirring and foaming, the upper and lower layers of slurry produce bubbles with poor pore size uniformity due to differences in stirring agitation. The upper layer of slurry has more contact with air, resulting in faster bubble growth and larger pores after drying, while the lower layer of slurry has less contact with air, resulting in slower bubble growth and smaller pores after drying. This poorly uniform slurry cannot produce materials with good pore uniformity after drying, thus the material has lower strength and higher thermal conductivity. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide an ultralight corundum thermal insulation material and its preparation method, so as to solve the technical problems mentioned in the background art, such as poor pore uniformity, low material strength and high thermal conductivity of alumina hollow sphere lightweight thermal insulation material.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A method for preparing an ultralight corundum thermal insulation material includes the following steps:

[0008] Step (1): Mix the foaming agent and the modifier, add water and stir to obtain a modified foaming agent dispersion;

[0009] Step (2): Mix alumina hollow spheres, corundum powder, micro powder, binder, dispersant and fiber evenly to obtain mixed raw materials;

[0010] Step (3): Add the modified foaming dispersion to the mixed raw materials, stir and foam thoroughly to obtain a mixed slurry;

[0011] Step (4): Pour the mixed slurry into the mold. After the mixed slurry automatically fills the mold, smooth the surface. After curing, demold and dry to obtain the green body.

[0012] Step (5): Sinter the blank. After sintering, the ultralight corundum heat insulation material is obtained.

[0013] Micronized powder is a key component of the mixed raw materials, enabling the mixed slurry to have good fluidity and facilitating the obtaining of a uniformly foamed slurry. The modified foaming agent dispersion mainly enables the alumina hollow spheres, corundum powder, and micronized powder (collectively referred to as the raw material matrix) in the mixed raw materials to participate in foaming. Furthermore, the raw material matrix in the uniformly porous green body formed after foaming reacts with the binder during high-temperature sintering, forming a strong ceramic bond that enhances the strength of the material. In addition, the binder also promotes the solidification of the mixed slurry in the mold to form a green body with initial strength. The ultralight corundum thermal insulation material prepared by the method of this invention has the characteristics of low bulk density, high porosity (mainly existing in micron-sized pores), low thermal conductivity, high strength, and high operating temperature, reducing energy consumption and carbon emissions in high-temperature industries.

[0014] This invention involves adding a modified foaming agent (modified foaming agent dispersion) after the raw materials are evenly mixed. After stirring and fully foaming, a mixed slurry is obtained. The mixed slurry is directly poured into a mold, which is automatically filled without vibration, making the operation simple and the construction efficiency high. This invention uses hollow alumina balls as aggregate and a modified protein-based foaming agent as foaming agent. After stirring and foaming, a slurry with large foaming volume and stable bubbles is obtained. After drying and sintering, an ultra-lightweight, high-strength corundum thermal insulation material with micron-level pores, a thermal conductivity of <0.55W / (m·K) at 1200℃, and a compressive strength of ≥15MPa is obtained. It plays a good role in heat preservation and insulation in high-temperature kilns, achieving good energy-saving and emission-reduction effects.

[0015] In the preparation method of the above-mentioned ultralight corundum thermal insulation material, in step (1), the mass ratio of foaming agent to modifier is (0.1~1):(0.05~2); the mass ratio of foaming agent to water in the modified foaming agent dispersion is 1:(30~60). This invention controls the amount of modifier in the modified foaming agent dispersion and controls the concentration of the modified foaming agent dispersion so that after mixing and foaming with a specific proportion of mixed raw materials, it can form a mixed slurry with suitable fluidity. Furthermore, at the specified amount of modified foaming agent, the matrix portion of the mixed raw materials can be fully foamed to form a mixed slurry with uniform and stable pore size.

[0016] In the preparation method of the above-mentioned ultralight corundum thermal insulation material, in step (1), the foaming agent is a protein foaming agent. The protein foaming agent utilizes its hydrolytic properties; the hydrolyzed active substances encapsulate air to form foam. The principle is that the active substances after hydrolysis encapsulate air to form foam. This type of foam has a stable double-electron-layer structure and high stability. The protein content in the protein foaming agent is greater than or equal to 95 wt%. The modifier is one or a mixture of two or more of the following: sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, sodium α-olefin sulfonate, sodium carboxymethyl cellulose, or sodium polyacrylate.

[0017] In the preparation method of the above-mentioned ultralight corundum thermal insulation material, in step (2), the mixed raw materials are: 20-70 parts by weight of alumina hollow spheres, 15-40 parts by weight of corundum powder, 5-30 parts by weight of micro powder, 4-20 parts by weight of binder, 0.1-1 parts by weight of dispersant, and 0.1-1 parts by weight of fiber. If the amount of corundum powder exceeds this range, it will not only affect the foaming effect and the fluidity of the mixed slurry, thus affecting the pore structure, but also affect the sintering effect and ultimately affect the strength of the sintered ceramic. If the amount of binder exceeds this range, the mixed slurry will solidify too slowly or too quickly after being filled into the mold, resulting in the green body obtained by demolding having too high or too low strength (too high strength may cause cracking during drying, while too low strength will affect its formability). At the same time, the reaction effect between binder and alumina hollow spheres, corundum powder or micro powder during sintering will also be affected, thus affecting the ceramic strength. In addition, the amount of fiber has a significant impact on the foaming effect of the mixed raw materials. If too much fiber is used, it will affect the fluidity of the mixed slurry and make it impossible to fill it evenly in the mold. If too little fiber is used, it will not have an ideal disturbance effect on the bottom slurry during the mixing and foaming process, making it difficult to obtain a foaming effect with uniform foaming of the upper and lower slurries.

[0018] In the preparation method of the above-mentioned ultralight corundum thermal insulation material, in step (2), the particle size distribution of the alumina hollow spheres is as follows: the mass ratio of alumina hollow spheres with a particle size of 0.2-1 mm, 1-2 mm, 2-3 mm, and 3-5 mm is (5-20):(5-20):(5-25):(5-25). Using alumina hollow spheres with this particle size distribution is beneficial for obtaining a mixed slurry with good stability and good uniformity of alumina hollow sphere distribution; it enables the final ultralight corundum thermal insulation material to have high strength even with high porosity; if the proportion of alumina hollow spheres of a certain particle size is adjusted beyond the above range, the uniformity of alumina hollow sphere distribution in the mixed slurry will be reduced, and the strength and thermal conductivity of the prepared ultralight corundum thermal insulation material will ultimately be affected.

[0019] In the preparation method of the above-mentioned ultralight corundum thermal insulation material, in step (2), the content of alumina in the alumina hollow spheres is greater than or equal to 99 wt%.

[0020] The corundum powder is one or a mixture of two or more of the following: high-grade bauxite powder, brown corundum powder, white corundum powder, tabular corundum powder, or chromium corundum powder; the particle size of the corundum powder is 0.045 to 0.088 mm; corundum powder with this particle size can be stably and uniformly dispersed in the mixed slurry without settling.

[0021] The micro powder is one or a mixture of two or more of the following: alumina micro powder, ρ alumina micro powder, magnesium aluminum spinel micro powder, or calcium carbonate micro powder; the median particle size D50 of the micro powder is 1-6 μm; micro powders with this particle size have good activity, good reaction effect during sintering, and can effectively improve the stability of the mixed slurry.

[0022] The binder is aluminate cement, and the calcium oxide content in the aluminate cement is less than or equal to 30 wt%, and the alumina content is greater than or equal to 70 wt%; the median particle size D50 of the binder is 0.01 to 0.06 mm.

[0023] The dispersant is one or a mixture of two or more of sodium tripolyphosphate, sodium hexametaphosphate, calcium lignosulfonate, FS10 or FS20; among them, FS10 and FS20 dispersants have good dispersibility and can play a steric hindrance role, so that the powder is dispersed evenly.

[0024] The fibers are one or a mixture of two or more of glass fibers, paper fibers, or organic fibers; the glass fibers are 3–10 cm long and 10–100 μm in diameter; the paper fibers are 1–5 mm long and 5–30 μm in diameter; the organic fibers are 0.2–0.6 cm long and 10–100 μm in diameter. Excessive glass fiber length will affect the fluidity of the mixed slurry, while insufficient length will prevent it from agitating the bottom layer of slurry. The main function of the added glass fibers is to agitate the bottom layer of slurry, ensuring uniform distribution between the upper and lower layers. Therefore, the glass fibers must possess suitable toughness and have an appropriate diameter.

[0025] In the preparation method of the above-mentioned ultralight corundum thermal insulation material, in step (3), the amount of modified foaming agent dispersion added is such that the mass ratio of the modifier to the hollow alumina spheres in the mixed slurry is (0.05~2):(20~70); after stirring, it is fully foamed for 3~5 minutes.

[0026] In the preparation method of the above-mentioned ultralight corundum thermal insulation material, in step (4), the curing time is 24h; the drying conditions are: drying at 110℃ for 24h. The drying temperature of 110℃ is conducive to the discharge of free water and can also enable the blank to obtain a certain strength; if the temperature is too high, it may cause the material to crack.

[0027] In the preparation method of the above-mentioned ultralight corundum thermal insulation material, the sintering conditions in step (5) are: 1000~1500℃, holding for 60~300min. The thermal insulation material obtained by sintering under these conditions has good strength and will not have serious linear shrinkage problems after sintering, and the pore structure of the blank can be completely preserved.

[0028] An ultralight corundum thermal insulation material is prepared using the aforementioned method for preparing ultralight corundum thermal insulation materials; it has a porosity of 55-80% and a bulk density of 0.90-1.20 g / cm³. 3 The compressive strength after firing at 1200℃ is greater than or equal to 15MPa, the linear shrinkage rate after firing at 1500℃ is 0 to 0.5%, and the thermal conductivity at 1200℃ is less than or equal to 0.55W / (m·K).

[0029] The technical solution of the present invention achieves the following beneficial technical effects:

[0030] 1. The preparation method of the ultralight high-strength corundum thermal insulation material of the present invention involves first preparing a foaming agent and a modifier into a dispersion, and then stirring and foaming it with specific mixed raw materials. The resulting mixed slurry is directly poured into a mold, and the mixed slurry can automatically fill the mold without the need for vibration molding. Compared with existing pressing or vibration molding, the present invention is more convenient to construct, significantly improves efficiency, and effectively reduces the bulk density of the corundum thermal insulation material after foaming.

[0031] 2. This invention uses hollow alumina spheres as aggregate and achieves microporous matrix through matrix foaming. The invention introduces fibers with a length of 3-10 cm into the raw material composition. These fibers increase the agitation of the bottom slurry during stirring, improve the foaming of the bottom slurry, and enhance the overall uniformity of the slurry. This results in the formation of uniformly structured micropores in the dried green body, meeting the requirement of higher strength while further reducing bulk density, and significantly increasing porosity to 79%, thereby substantially reducing the high-temperature thermal conductivity of the material (thermal conductivity at 1200℃ < 0.55 W / (m·K)).

[0032] 3. Unlike previous methods that used single or several ionic foaming agents, this invention uses a protein-based foaming agent. Foam is formed by hydrolyzing high-molecular-weight proteins to encapsulate air. The resulting foam has a double-electron-layer outer wall, small bubble size, high foam stability, and is not easily broken. Furthermore, introducing a modifier into the foaming agent further enhances foaming capacity, increases foam volume, prevents pore rupture, reduces bleeding, and improves the stability of the mixed slurry. Attached Figure Description

[0033] Figure 1 Optical photograph of the cross section of the ultralight corundum thermal insulation material prepared in Example 1 of this invention;

[0034] Figure 2 Scanning electron microscope image of the ultralight corundum thermal insulation material prepared in Example 1 of this invention. Detailed Implementation

[0035] Example 1

[0036] The ultralight corundum thermal insulation material of this embodiment is prepared from the components shown in Table 1, and its preparation method includes the following steps:

[0037] Step (1): Mix the foaming agent and modifier, add water and stir to obtain a modified foaming agent dispersion; the mass ratio of foaming agent to modifier is 0.3:0.1; the mass ratio of foaming agent to water in the modified foaming agent dispersion is 1:40;

[0038] Step (2): Mix the alumina hollow spheres, corundum powder, micro powder, binder, dispersant and fiber in Table 1 evenly to obtain the mixed raw materials;

[0039] Step (3): Add modified foaming dispersion to the mixed raw materials, stir and foam fully for 3 minutes to obtain a mixed slurry; the amount of modified foaming agent dispersion added is such that the mass ratio of the modifier to the alumina hollow spheres in the mixed slurry is 0.1:60.

[0040] Step (4): Pour the mixed slurry into the mold. After the mixed slurry automatically fills the mold, smooth the surface. After curing for 24 hours, demold and dry at 110℃ for 24 hours to obtain the green body.

[0041] Step (5): Place the blank in a high-temperature kiln and sinter at 1200℃ for 180 minutes. After sintering, cool to room temperature to obtain ultralight corundum thermal insulation material.

[0042] Table 1

[0043]

[0044] Table 1 shows that the 71 pure aluminate cement was produced by KENOS Company, with a calcium oxide content of 29%, an alumina content of 70%, and a D50 of 0.025 mm; the liquid protein foaming agent mother liquor contained a protein content greater than 95 wt%; the mass ratio of glass fiber to organic fiber was 2:1; the glass fiber length was 3–10 cm and the diameter was 10–100 μm; the organic fiber length was 0.4 cm and the diameter was 30 μm.

[0045] Example 2

[0046] The ultralight corundum thermal insulation material of this embodiment is prepared from the components shown in Table 2, and its preparation method includes the following steps:

[0047] Step (1): Mix the foaming agent and modifier, add water and stir to obtain a modified foaming agent dispersion; the mass ratio of foaming agent to modifier is 0.4:0.12; the mass ratio of foaming agent to water in the modified foaming agent dispersion is 1:40;

[0048] Step (2): Mix the alumina hollow spheres, corundum powder, micro powder, binder, dispersant and fiber in Table 2 evenly to obtain the mixed raw materials;

[0049] Step (3): Add modified foaming dispersion to the mixed raw materials, stir and foam fully for 3 minutes to obtain a mixed slurry; the amount of modified foaming agent dispersion added is such that the mass ratio of modifier to alumina hollow spheres in the mixed slurry is 0.12:60.

[0050] Step (4): Pour the mixed slurry into the mold. After the mixed slurry automatically fills the mold, smooth the surface. After curing for 24 hours, demold and dry at 110℃ for 24 hours to obtain the green body.

[0051] Step (5): Place the blank in a high-temperature kiln and sinter at 1200℃ for 180 minutes. After sintering, cool to room temperature to obtain ultralight corundum thermal insulation material.

[0052] Table 2

[0053]

[0054] Table 2 shows that the 71 pure aluminate cement was produced by KENOS Company, with a calcium oxide content of 29%, an alumina content of 70%, and a D50 of 0.025 mm; the liquid protein foaming agent mother liquor contained a protein content greater than 95 wt%; the mass ratio of glass fiber to organic fiber was 2:1; the glass fiber length was 3–10 cm and the diameter was 10–100 μm; the organic fiber length was 0.4 cm and the diameter was 30 μm.

[0055] Example 3

[0056] The ultralight corundum thermal insulation material of this embodiment is prepared from the components shown in Table 3, and its preparation method includes the following steps:

[0057] Step (1): Mix the foaming agent and modifier, add water and stir to obtain a modified foaming agent dispersion; the mass ratio of foaming agent to modifier is 0.5:0.17; the mass ratio of foaming agent to water in the modified foaming agent dispersion is 1:50.

[0058] Step (2): Mix the alumina hollow spheres, corundum powder, micro powder, binder, dispersant and fiber in Table 3 evenly to obtain the mixed raw materials;

[0059] Step (3): Add modified foaming dispersion to the mixed raw materials, stir and foam fully for 3 minutes to obtain a mixed slurry; the amount of modified foaming agent dispersion added is such that the mass ratio of modifier to alumina hollow spheres in the mixed slurry is 0.17:60.

[0060] Step (4): Pour the mixed slurry into the mold. After the mixed slurry automatically fills the mold, smooth the surface. After curing for 24 hours, demold and dry at 110℃ for 24 hours to obtain the green body.

[0061] Step (5): Place the blank in a high-temperature kiln and sinter at 1200℃ for 180 minutes. After sintering, cool to room temperature to obtain ultralight corundum thermal insulation material.

[0062] Table 3

[0063]

[0064] Table 3 shows that the 71 pure aluminate cement was produced by KENOS Company, with a calcium oxide content of 29%, an alumina content of 70%, and a D50 of 0.025 mm; the liquid protein foaming agent mother liquor contained a protein content greater than 95 wt%; the mass ratio of sodium tripolyphosphate to sodium hexametaphosphate in the dispersant was 1:1; the mass ratio of glass fiber to organic fiber was 2:1; the glass fiber length was 3–10 cm and the diameter was 10–100 μm; the organic fiber length was 0.4 cm and the diameter was 30 μm.

[0065] Example 4

[0066] The ultralight corundum thermal insulation material of this embodiment is prepared from the components shown in Table 4, and its preparation method includes the following steps:

[0067] Step (1): Mix the foaming agent and the modifier, add water and stir to obtain a modified foaming agent dispersion; the mass ratio of the foaming agent to the modifier is 0.3:0.1; the mass ratio of the foaming agent to water in the modified foaming agent dispersion is 1:45;

[0068] Step (2): Mix the alumina hollow spheres, corundum powder, micro powder, binder, dispersant and fiber in Table 4 evenly to obtain the mixed raw materials;

[0069] Step (3): Add modified foaming dispersion to the mixed raw materials, stir and foam fully for 3 minutes to obtain a mixed slurry; the amount of modified foaming agent dispersion added is such that the mass ratio of modifier to alumina hollow spheres in the mixed slurry is 0.1:65.

[0070] Step (4): Pour the mixed slurry into the mold. After the mixed slurry automatically fills the mold, smooth the surface. After curing for 24 hours, demold and dry at 110℃ for 24 hours to obtain the green body.

[0071] Step (5): Place the blank in a high-temperature kiln and sinter at 1500℃ for 60 minutes. After sintering, cool to room temperature to obtain ultralight corundum thermal insulation material.

[0072] Table 4

[0073]

[0074] Table 4 shows that the 71 pure aluminate cement was produced by KENOS Company, with a calcium oxide content of 29%, an alumina content of 70%, and a D50 of 0.025 mm; the liquid protein foaming agent mother liquor contained a protein content greater than 95 wt%; the mass ratio of sodium tripolyphosphate to sodium hexametaphosphate in the dispersant was 1:1; the mass ratio of glass fiber to paper fiber was 2:1; the length of the glass fiber was 3–10 cm and the diameter was 10–100 μm; the length of the paper fiber was 1–5 mm and the diameter was 5–30 μm.

[0075] Example 5

[0076] The ultralight corundum thermal insulation material of this embodiment is prepared from the components shown in Table 5, and its preparation method includes the following steps:

[0077] Step (1): Mix the foaming agent and modifier, add water and stir to obtain a modified foaming agent dispersion; the mass ratio of foaming agent to modifier is 0.5:0.6; the mass ratio of foaming agent to water in the modified foaming agent dispersion is 1:40.

[0078] Step (2): Mix the alumina hollow spheres, corundum powder, micro powder, binder, dispersant and fiber in Table 4 evenly to obtain the mixed raw materials;

[0079] Step (3): Add modified foaming dispersion to the mixed raw materials, stir and foam fully for 3 minutes to obtain a mixed slurry; the amount of modified foaming agent dispersion added is such that the mass ratio of modifier to alumina hollow spheres in the mixed slurry is 0.6:65.

[0080] Step (4): Pour the mixed slurry into the mold. After the mixed slurry automatically fills the mold, smooth the surface. After curing for 24 hours, demold and dry at 110℃ for 24 hours to obtain the green body.

[0081] Step (5): Place the blank in a high-temperature kiln and sinter at 1500℃ for 60 minutes. After sintering, cool to room temperature to obtain ultralight corundum thermal insulation material.

[0082] Table 5

[0083]

[0084] Table 5 shows that the 71 pure aluminate cement was produced by KENOS Company, with a calcium oxide content of 29%, an alumina content of 70%, and a D50 of 0.025 mm; the liquid protein foaming agent mother liquor contained a protein content greater than 95 wt%; the mass ratio of glass fiber to paper fiber was 2:1; the length of the glass fiber was 3–10 cm and the diameter was 10–100 μm; the length of the paper fiber was 1–5 mm and the diameter was 5–30 μm.

[0085] The proportions of each component in the ultralight high-strength corundum thermal insulation materials of Examples 1 to 5 are shown in Table 6.

[0086] Table 6

[0087]

[0088] The properties of the ultralight and high-strength corundum thermal insulation materials prepared in Examples 1 to 5 are shown in Table 7.

[0089] Table 7

[0090]

[0091] The compressive strength in Table 7 was measured after the insulation material was calcined in a kiln at 1200℃ for 3 hours; the thermal conductivity was measured at 1200℃; and the linear change rate was measured after firing at 1500℃.

[0092] Figure 1 and Figure 2 The images show cross-sectional optical and scanning electron microscope (SEM) photographs of the ultralight corundum thermal insulation material prepared in Example 1. As can be seen from the figures, the thermal insulation material exhibits good pore uniformity, with pore sizes primarily in the micrometer range. The ultralight corundum thermal insulation materials prepared in Examples 1 to 5 all possess similar structures, and will not be described again here. Furthermore, samples were taken from different parts of the prepared ultralight corundum thermal insulation material to observe its pore structure, particularly the portion formed at the bottom of the mold. The pore distribution in this portion is essentially consistent with that in other parts of the material, indicating that the preparation method of this invention, compared to methods in the prior art, can avoid the problem of differences in bubble formation between the upper and lower layers of the slurry.

[0093] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing an ultralight corundum thermal insulation material, characterized in that, Includes the following steps: Step (1): Mix the foaming agent and modifier, add water and stir to obtain a modified foaming agent dispersion; the foaming agent is a protein foaming agent; the protein content in the protein foaming agent is greater than or equal to 95 wt%; the modifier is one or a mixture of two or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, sodium α-olefin sulfonate, sodium carboxymethyl cellulose or sodium polyacrylate; the mass ratio of foaming agent to modifier is (0.1~1): (0.05~2); the mass ratio of foaming agent to water in the modified foaming agent dispersion is 1: (30~60); Step (2): Mix alumina hollow spheres, corundum powder, micro powder, binder, dispersant and fiber evenly to obtain mixed raw materials; the mixed raw materials are: 20-70 parts by weight of alumina hollow spheres, 15-40 parts by weight of corundum powder, 5-30 parts by weight of micro powder, 4-20 parts by weight of binder, 0.1-1 parts by weight of dispersant and 0.1-1 parts by weight of fiber; The particle size distribution of alumina hollow spheres is as follows: the mass ratio of alumina hollow spheres with a particle size of 0.2-1 mm, alumina hollow spheres with a particle size of 1-2 mm, alumina hollow spheres with a particle size of 2-3 mm, and alumina hollow spheres with a particle size of 3-5 mm is (5-20):(5-20):(5-25):(5-25); The fiber is one or a mixture of two or more of glass fiber, paper fiber or organic fiber; the glass fiber has a length of 3 to 10 cm and a diameter of 10 to 100 μm; the paper fiber has a length of 1 to 5 mm and a diameter of 5 to 30 μm; the organic fiber has a length of 0.2 to 0.6 cm and a diameter of 10 to 100 μm. Step (3): Add modified foaming dispersion to the mixed raw materials, stir and foam fully to obtain a mixed slurry; the amount of modified foaming agent dispersion added is such that the mass ratio of the modifier to the alumina hollow spheres in the mixed slurry is (0.05~2):(20~70); after stirring, foam fully for 3~5 minutes; Step (4): Pour the mixed slurry into the mold. After the mixed slurry automatically fills the mold, smooth the surface. After curing, demold and dry to obtain the green body. Step (5): Sinter the blank. After sintering, the ultralight corundum heat insulation material is obtained.

2. The method for preparing the ultralight corundum thermal insulation material according to claim 1, characterized in that, In step (2), the alumina content in the hollow alumina spheres is greater than or equal to 99 wt%; The corundum powder is one or a mixture of two or more of the following: high-grade bauxite powder, brown corundum powder, white corundum powder, tabular corundum powder, or chromium corundum powder; the particle size of the corundum powder is 0.045–0.088 mm. The micro powder is one or a mixture of two or more of alumina micro powder, magnesium aluminum spinel micro powder or calcium carbonate micro powder; the median particle size D50 of the micro powder is 1 to 6 μm. The binder is aluminate cement, and the calcium oxide content in the aluminate cement is less than or equal to 30 wt%, and the alumina content is greater than or equal to 70 wt%; the median particle size D50 of the binder is 0.01 to 0.06 mm. The dispersant is one or a mixture of two or more of sodium tripolyphosphate, sodium hexametaphosphate, calcium lignosulfonate, FS10 or FS20.

3. The method for preparing the ultralight corundum thermal insulation material according to claim 1, characterized in that, In step (4), the curing time is 24 hours; the drying conditions are: drying at 110℃ for 24 hours.

4. The method for preparing the ultralight corundum thermal insulation material according to claim 1, characterized in that, In step (5), the sintering conditions are: 1000~1500℃, holding for 60~300min.

5. A lightweight corundum thermal insulation material, characterized in that, It is prepared using the preparation method of ultralight corundum thermal insulation material as described in any one of claims 1-4; the porosity is 55-80%, and the bulk density is 0.90-1.20 g / cm³. 3 The compressive strength after firing at 1200℃ is greater than or equal to 15MPa, the linear shrinkage rate after firing at 1500℃ is 0 to 0.5%, and the thermal conductivity at 1200℃ is less than or equal to 0.55 W / (m·K).

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