A preparation method of sintered hollow bricks

Abstract

The present invention discloses a preparation method of sintered hollow bricks. Mix 40 - 45 parts by weight of silica fume, 35 - 38 parts by weight of slag, 15 - 20 parts by weight of perlite, and 6 - 8 parts by weight of pretreated straw powder, then add 5 - 6 parts by weight of 5 - hydroxymethylfurfural, 2 - 3 parts by weight of calcium fluoride, 18 - 22 parts by weight of modified carboxymethyl cellulose emulsion, and 35 - 45 parts by weight of water, stir and mix, age, extrude into shape, dry, and fire to obtain sintered hollow bricks. In the raw materials of the hollow bricks of the present invention, pretreated straw powder which is soaked in ammonia water and then treated with polyethylene glycol diacrylate and N - hydroxysuccinimide is added, and a modified carboxymethyl cellulose emulsion which is a mixture of 2,5 - furandimethanol, polypropylene fiber, alkyl polyglycoside, tripolyphosphate, and carboxymethyl cellulose is added, so that the obtained sintered hollow bricks have the advantages of high flexural strength and compressive strength, good heat preservation effect and sound insulation effect, and strong durability.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a preparation method of sintered hollow bricks. Background Art

[0002] Sintered hollow bricks are mainly made of clay, shale, coal gangue or fly ash as the main raw materials through processes such as crushing, mixing, forming, drying, and sintering. Sintered hollow bricks are commonly used building materials in the construction industry. They are widely used in filling walls, partition walls, and parapet walls on the roof. Sintered hollow bricks help improve the overall performance of buildings and reduce construction costs.

[0003] Traditional hollow bricks are made by firing clay into bricks. Currently, the market mainly uses environmentally friendly raw materials such as coal gangue and tailings for mixing, forming, and firing, which is economical and environmentally friendly. However, there are problems such as poor sound insulation, low strength, and poor durability, resulting in a poor experience after the house is decorated and occupied. Therefore, researching a process for sintered hollow bricks to improve the strength, sound insulation effect, durability and other properties of hollow bricks is the direction that technicians in this industry have been working hard on.

[0004] Publication No. CN107445590B discloses a preparation method of sintered hollow bricks, which is to mix rice husk, activated sludge and compound coal gangue and ferment for 20 - 30 days, then obtain the fermented mixture through sterilization treatment. Subsequently, the fermented mixture is mixed with organic binders and inorganic binders, supplemented with emulsifiers, and uniformly mixed by high-speed stirring and then injection-molded. Then, it is vacuum freeze-dried for 2 - 4h to obtain brick blanks, and the brick blanks are soaked and modified with sodium silicate solution, carbonized at 500 - 600°C for 2 - 4h, and high-temperature sintered at 800 - 1000°C for 3 - 5h. Then, it is subjected to constant temperature and humidity carbonization treatment at a carbon dioxide concentration of 18 - 20%, a temperature of 20 - 22°C, and a humidity of 60 - 65% for 12 - 24h to obtain sintered hollow bricks. This method has a long fermentation time and also requires freeze-drying, secondary carbonization and high-temperature sintering, which takes a long time, consumes a lot of energy, has a high cost, and is complex in operation, and is not suitable for large-scale production in factories.

[0005] Publication number CN104177068A discloses a hollow brick, which comprises the following raw materials: shale, coal gangue, fly ash, modified loess, quicklime powder, ore tailings and paper scraps. The mass ratio of the shale, coal gangue, fly ash, modified loess, quicklime powder, ore tailings and paper scraps is: 35-45:20-30:5-10:16-20:13-18:9-14:5-10. The raw materials are mixed with water and then extruded into shape, and then fired at 1200-1250 °C for 11 hours. By adopting shale, coal gangue, fly ash, modified loess, quicklime powder and ore tailings and a reasonable component ratio, it is easy to sinter, and after sintering, the bonding strength is high, thus making the strength of the double-link rotation high. While the paper scraps are burned during the firing process, which reduces the weight of the brick body. This method has a long firing time and high energy consumption under high-temperature conditions. The paper scraps are light in weight and are not evenly mixed with other raw materials, which easily leads to unstable quality of the hollow brick, thus resulting in poor quality of the hollow brick.

[0006] Therefore, there is an urgent need to provide a preparation method for sintered hollow bricks to solve problems such as low strength, poor sound insulation and poor durability of sintered hollow bricks. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method for sintered hollow bricks to solve the problems of low strength, poor sound insulation and poor durability of sintered hollow bricks as mentioned in the above background technology.

[0008] To achieve the above purpose, the present invention provides the following technical solution: A preparation method for sintered hollow bricks, which comprises the following steps:

[0009] S1. Preparation of pretreated straw powder: Cut the straw into 6-10 mm in length and soak it in an ammonia water solution with a mass concentration of 5-7% for 12-14 h, then wash it with clear water, filter and dry it; Crush the dried straw into 60-100 meshes, weigh 45-50 parts by weight of the crushed straw in 50-60 parts by weight of water, add 4-6 parts by weight of polyethylene glycol diacrylate and 2-3 parts by weight of N-hydroxysuccinimide, and stir at 45-50 °C for 30-35 min, then filter and dry to obtain pretreated straw powder.

[0010] S2. Preparation of modified carboxymethyl cellulose emulsion: Weigh 45-50 parts by weight of carboxymethyl cellulose and 5-8 parts by weight of 2,5-furandimethanol, mix them evenly and then place them in a plasma device for treatment for 15-20 min, then place them in a reaction kettle at 120-125 °C, add 10-12 parts by weight of polypropylene fiber, 5-6 parts by weight of alkyl polyglycoside, 3-5 parts by weight of tripolyphosphate and 55-60 parts by weight of water, and treat for 35-40 min to obtain a modified carboxymethyl cellulose emulsion.

[0011] S3. Weigh 40 - 45 parts by weight of silica fume, 35 - 38 parts by weight of slag, 15 - 20 parts by weight of perlite, and 6 - 8 parts by weight of pretreated straw powder. After mixing them evenly, add 5 - 6 parts by weight of 5 - hydroxymethylfurfural, 2 - 3 parts by weight of calcium fluoride, 18 - 22 parts by weight of modified carboxymethyl cellulose emulsion, and 35 - 45 parts by weight of water, and stir and mix to obtain a mixture.

[0012] S4. Place the mixture into a stirring device and stir and age it at a rotation speed of 20 - 25 rpm for 4 - 5 h.

[0013] S5. Place the aged mixture into a vacuum extruder to extrude and form a hollow brick blank, with a forming pressure of 0.9 - 1.1 MPa.

[0014] S6. Place the brick blank into a drying chamber at a temperature of 40 - 50 °C and dry it for 6 - 7 h to make the moisture content of the brick blank reach 4 - 6%.

[0015] S7. Place the dried brick blank into a roasting kiln, heat it at a heating rate of 5 °C / min to 650 - 700 °C and hold for 80 - 90 min, then heat it at a heating rate of 5 °C / min to 950 - 980 °C and hold for 50 - 60 min, and cool it to room temperature to obtain a sintered hollow brick with a porosity of 45 - 47%.

[0016] As a preferred technical solution of the present invention, the charge density of the plasma device is 1300 - 1350 C / cm 3 , the gas flow rate is 1.7 - 1.8 L / min, the pressure in the treatment chamber is 98 - 105 kPa, and the temperature in the treatment chamber is 45 - 50 °C.

[0017] As a preferred technical solution of the present invention, before weighing the perlite, it further includes: crushing the perlite so that the particle size of the perlite is less than or equal to 0.3 mm, and then soaking the crushed perlite in an acidic solution for 70 - 80 min, filtering, and drying.

[0018] As a preferred technical solution of the present invention, the acidic solution is composed of sodium silicate and sulfuric acid in a mass ratio of 1:15 - 20.

[0019] As a preferred technical solution of the present invention, the mass concentration of the sulfuric acid is 8 - 10%.

[0020] As a preferred technical solution of the present invention, before weighing the slag, it further includes: crushing the slag so that the particle size of the slag is less than or equal to 0.3 mm.

[0021] As a preferred technical solution of the present invention, the tripolyphosphate is composed of sodium tripolyphosphate and magnesium tripolyphosphate in a mass ratio of 0.8 - 1:1.

[0022] As a preferred technical solution of the present invention, water needs to be sprayed twice during the mixing and aging process of the mixture, and the amount of water sprayed each time is 0.8-1.0% of the weight of the mixture, and the interval time between the two sprays is 1.5-2 h.

[0023] As a preferred technical solution of the present invention, the straw is any one or a mixture of two of corn straw, wheat straw, and rice straw.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. In the process of manufacturing the sintered hollow brick of the present invention, pretreated straw powder is added. After being treated, the straw can be better dispersed in the hollow brick, reducing stress concentration, improving the compressive and flexural strength and anti-aging performance of the hollow brick, and extending the service life. The cross-linking effect of polyethylene glycol diacrylate can improve the toughness of the hollow brick and reduce the brittle fracture of the hollow brick. The treatment with polyethylene glycol diacrylate and N-hydroxysuccinimide helps to form uniform pores in the hollow brick, enhancing the heat insulation and heat preservation performance of the brick body. After cutting the straw and soaking it in an ammonia water solution, the waxy layer on the surface of the straw and the ester bond between lignin and polysaccharide in the straw are destroyed, improving the fiber structure of the straw, increasing its bonding area and bonding force with other materials, helping the straw to be fully mixed with other materials during the production process of the hollow brick, and improving the forming performance and overall performance of the brick. Polyethylene glycol diacrylate can cross-link with cellulose and hemicellulose in the straw to form a stable network structure, improving the compressive strength, impact resistance, water resistance, heat insulation and heat preservation performance of the brick body. N-hydroxysuccinimide can activate the carboxylic acid groups on the surface of the straw, making it easier to react with the minerals in the brick matrix, improving the interfacial compatibility, enhancing the interaction force between the straw and the brick body material, making the overall structure of the hollow brick more stable, and improving the durability of the sintered hollow brick. In addition, the addition of N-hydroxysuccinimide may also help to reduce the pyrolysis and volatilization of the straw during the sintering process, improving the thermal conductivity, water resistance and anti-aging properties of the hollow brick.

[0026] 2. In the production process of the sintered hollow brick of the present invention, modified carboxymethyl cellulose is added, which improves the compressive strength and sound insulation effect of the hollow brick. The hydroxyl group of 2,5-furan dimethanol forms an ester bond crosslink with the carboxyl group of carboxymethyl cellulose, enhancing the stability of the network structure and improving the compressive strength of the hollow brick. Mixing and modifying polypropylene fiber and carboxymethyl cellulose can make carboxymethyl cellulose disperse evenly in the material, forming tiny pores and channels. These pores can scatter and absorb sound waves, reducing the direct propagation of sound waves and improving the sound insulation effect. Alkyl polyglycoside can reduce the surface tension of water, enhance the wettability and dispersibility of raw material particles, improve the forming performance and strength of the brick blank. At the same time, alkyl polyglycoside can form an adsorption layer on the particle surface, enhancing the binding force between particles, reducing the cracking and deformation of the hollow brick. Moreover, alkyl polyglycoside can promote the uniform evaporation of moisture during the drying and sintering processes, reducing internal stress, preventing cracking, and improving the drying and sintering efficiency. Tripolyphosphate can improve the fluidity of the mixed raw materials, reduce the phenomena of air bubbles and particle agglomeration in the raw materials, improve the uniformity and stability of the raw materials, and thus enhance the strength and durability of the hollow brick.

[0027] 3. In the present invention, perlite is crushed and then soaked and treated with a mixed solution of sodium silicate and sulfuric acid. During the soaking process, hydrogen ions in sulfuric acid can replace calcium, magnesium, potassium, sodium and other ions in the interlayer of perlite, making perlite have active hydrogen atoms, improving the surface characteristics of perlite, increasing its microporosity and specific surface area. And soaking and treating perlite can remove impurities such as carbonates distributed in the pores of perlite, improving the performance of perlite. The silicate ions and sodium ions in sodium silicate molecules can undergo chemical reactions with the polar groups on the surface of perlite to form chemical bonds, enhancing the bonding strength between components. The addition of perlite can reduce the sintering temperature of the sintered hollow brick, reduce energy consumption, reduce the shrinkage and deformation of the brick body during sintering, improve the yield. Moreover, perlite treated with acid has a porous structure, which can effectively absorb sound waves and improve the sound insulation performance of the hollow brick.

[0028] 4. In the production process of the sintered hollow brick of the present invention, 5-hydroxymethylfurfural is added. The active functional groups such as hydroxyl group and aldehyde group in 5-hydroxymethylfurfural can react with other components in the brick body to form a crosslinked structure, improving the strength and durability of the brick body. And 5-hydroxymethylfurfural can decompose to produce gas at high temperature, forming a microporous structure in the brick body, thereby reducing the density of the hollow brick and improving the heat insulation and sound insulation performance of the hollow brick. Moreover, 5-hydroxymethylfurfural can improve the fluidity and plasticity of the brick body raw materials, reduce cracks and defects, and improve the compressive strength of the hollow brick.

[0029] 5. During the aging process of the mixture in the present invention, a stirring device is used to stir and age at a speed of 20 - 25 rpm. By stirring the mixture at a low speed, mutual friction and collision occur between the raw material particles, enhancing the interaction between moisture and raw material particles, improving the plasticity of the raw materials, making their particle size distribution more reasonable, increasing the content of fine powder materials. These fine powder materials fill the voids between larger particles, making it easier to form a uniform and dense green body during the extrusion molding of the raw materials, improving the compressive strength and flexural strength of the green body, and thus enabling the sintered hollow brick to have better mechanical properties. Through stirring, the reaction between various components in the material can be accelerated, making the contact between raw material particles more sufficient and the moisture distribution more uniform, shortening the aging time and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flowchart for manufacturing the hollow brick of the present invention;

[0031] Figure 2 is a broken line graph of the durability compressive strength of the hollow brick of the present invention. SPECIFIC EMBODIMENTS

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] As Figure 1 shown, a preparation method of a sintered hollow brick of the present invention includes the following preparation steps: S1. Preparation of pretreated straw powder: The straw is immersed in an ammonia water solution, then washed, filtered, dried, and pulverized with clear water. The pulverized straw is stirred, filtered, and dried together with polyethylene glycol diacrylate and N-hydroxysuccinimide to obtain pretreated straw powder. S2. Preparation of modified carboxymethyl cellulose emulsion: Carboxymethyl cellulose and 2,5-furandimethanol are mixed evenly and then treated in a plasma device, and then placed in a reaction kettle at 120 - 125 °C, and polypropylene fiber, alkyl polyglycoside, tripolyphosphate, and water are added for treatment together to obtain a modified carboxymethyl cellulose emulsion. S3. Pulverize perlite, and then soak the pulverized perlite in an acidic solution, filter, and dry it; mix silicon ash, slag, perlite treated with an acidic solution, and pretreated straw powder evenly, and then add 5-hydroxymethylfurfural, calcium fluoride, modified carboxymethyl cellulose emulsion, and water and stir and mix to obtain a mixture. S4. Place the mixture in a stirring device for stirring and aging. S5. Place the aged mixture in a vacuum extruder to extrude and form a hollow brick green body. S6. Place the green body in a drying chamber for drying. S7. Place the dried green body in a roasting kiln for roasting and cooling to room temperature to obtain a sintered hollow brick.

[0034] The present invention prepares an ammonia water solution with a mass concentration of 5-7%, cuts the straw and soaks it in the ammonia water solution. The ammonia water can not only destroy the wax layer on the surface of the straw, but also break the ester bond between lignin and polysaccharide in the straw, soften the straw fiber, improve the fiber structure of the straw, increase the bonding area and bonding force between the straw and other materials, help the straw to be fully mixed with other materials during the production process of the hollow brick, form a uniform and stable slurry, and improve the forming performance and overall performance of the hollow brick.

[0035] As a kind of environmentally friendly polymer material with good biocompatibility and degradability, polyethylene glycol diacrylate can crosslink with cellulose and hemicellulose in the straw to form a stable network structure, enhance the mechanical properties of the straw, improve the compressive strength, impact resistance, water resistance, heat insulation and heat preservation performance of the brick body, thus reducing problems such as brick body expansion and cracking caused by water absorption of the hollow brick, and can maintain the indoor temperature and reduce energy consumption.

[0036] N-hydroxysuccinimide can activate the carboxylic acid groups on the surface of the straw, help to improve the chemical properties of the straw surface, make it more likely to react with the minerals in the hollow brick, and improve the interfacial compatibility. Straw is an organic material with relatively low durability. Treating the straw with N-hydroxysuccinimide can increase the number of active functional groups on the straw surface, improve the interaction force between the straw and the raw materials of the hollow brick, make the overall structure of the hollow brick more stable, and improve the durability of the sintered hollow brick. In addition, the addition of N-hydroxysuccinimide also helps to reduce the pyrolysis and volatilization of the straw during the sintering process, further improving the quality of the hollow brick, and improving the thermal conductivity, water resistance, anti-aging performance and other properties of the sintered hollow brick, making it more suitable for different building environments.

[0037] The hydroxyl group of 2,5-furandimethanol forms an ester bond crosslink with the carboxyl group of carboxymethyl cellulose to enhance the stability of the network structure and improve the compressive strength of the hollow brick. Mixing and modifying polypropylene fiber and carboxymethyl cellulose can make carboxymethyl cellulose more evenly dispersed in the raw materials of the hollow brick, forming tiny pores and channels. These pores can effectively scatter and absorb sound waves, reduce the direct propagation of sound waves, and improve the sound insulation effect. Polypropylene fiber has a relatively high tensile strength, which can make up for the lack of mechanical properties of carboxymethyl cellulose as a polymer material and improve the overall strength of the hollow brick.

[0038] Alkyl polyglycoside is a surfactant that can reduce the surface tension of water, enhance the wettability and dispersibility of raw material particles, and improve the forming performance and strength of brick billets. At the same time, alkyl polyglycoside can also form an adsorption layer on the surface of material particles, enhance the bonding force between particles, reduce the cracking and deformation of hollow bricks. Moreover, alkyl polyglycoside can promote the uniform evaporation of moisture during the drying and sintering processes, reduce internal stress, prevent cracking, and improve the drying and sintering efficiency.

[0039] Tripolyphosphate can improve the fluidity of the mixed raw materials, reduce the phenomena of bubbles and particle agglomeration in the raw materials, and improve the uniformity and stability of the raw materials, thus contributing to the formation of a more compact and uniform structure during the production of hollow bricks and enhancing the strength and durability of hollow bricks. As an ionic crosslinking agent, magnesium tripolyphosphate can undergo a crosslinking reaction with the functional groups on the molecular chain of carboxymethyl cellulose, improve the stability in sintered hollow bricks, and enhance the overall performance of the brick body.

[0040] Perlite is soaked in an acidic solution. Hydrogen ions in sulfuric acid can replace calcium, magnesium, potassium, sodium and other ions between the layers of perlite, enabling perlite to have active hydrogen atoms, thereby improving its surface characteristics, increasing its microporosity and specific surface area. Moreover, soaking-treated perlite can remove impurities such as carbonates distributed in the pores of perlite, improving the performance of perlite. The silicate ions and sodium ions in sodium silicate can undergo a chemical reaction with the polar groups on the surface of perlite to form chemical bonds, enhancing the bonding strength between components. The addition of perlite can reduce the sintering temperature of sintered hollow bricks, reduce energy consumption, reduce the shrinkage and deformation of the brick body during sintering, improve the yield. In addition, acid-treated perlite has a porous structure, can effectively absorb sound waves, improve the sound insulation performance of hollow bricks, and reduce the transmission of noise.

[0041] 5-Hydroxymethylfurfural contains active functional groups such as hydroxyl and aldehyde groups. These active functional groups can react with other components in the brick body to form a crosslinked structure, improving the strength and durability of the brick body. 5-Hydroxymethylfurfural has a certain hydrophobicity. Adding it to the brick body can improve the waterproof performance of the brick body, reduce water penetration, making the hollow brick suitable for humid environments such as bathrooms. In addition, 5-hydroxymethylfurfural can decompose to produce gas at high temperatures, forming a microporous structure in the brick body, thereby reducing the density of the brick body and improving the thermal insulation performance. Moreover, 5-hydroxymethylfurfural can improve the fluidity and plasticity of the brick body raw materials, making the forming process easier, while reducing cracks and defects, and providing the compressive strength of the hollow brick. In addition, 5-hydroxymethylfurfural can reduce the melting point of the raw materials, promote sintering, reduce energy consumption, and improve the density and strength of the brick body.

[0042] During the sintering process of hollow bricks, the raw materials need to undergo a series of physical and chemical reactions at high temperatures to form a dense structure. Calcium fluoride can react with components such as silica in the raw materials to form compounds with low melting points, reducing the overall sintering temperature and shortening the sintering time, thereby saving energy and reducing the wear and tear of equipment such as kilns. At the same time, under high-temperature conditions, calcium fluoride can react with the surface of raw material particles to form a stable compound layer, tightly connecting adjacent raw material particles and promoting the bonding between particles. As a result, the structure of the sintered hollow bricks is more dense, the internal porosity is reduced, and the hollow bricks have higher compressive strength and flexural strength, enabling them to withstand greater loads without being easily damaged.

[0043] The raw materials used in the present invention are all commercially available raw materials.

[0044] Example 1:

[0045] A preparation method of sintered hollow bricks includes the following preparation steps:

[0046] S1. Preparation of pretreated straw powder: Cut corn straw into pieces with a length of 6 - 10 mm, soak it in an ammonia water solution with a mass concentration of 5% for 14 h, then wash, filter, and dry it with clean water; crush the dried straw into 60 - 100 meshes, weigh 45 parts by weight of the crushed corn straw in 50 parts by weight of water, add 4 parts by weight of polyethylene glycol diacrylate and 2 parts by weight of N-hydroxysuccinimide, stir at 45°C for 35 min, filter, and dry to obtain pretreated corn straw powder.

[0047] S2. Preparation of modified carboxymethyl cellulose emulsion: Weigh 45 parts by weight of carboxymethyl cellulose and 5 parts by weight of 2,5-furandimethanol, mix them evenly, place them in a plasma equipment for treatment for 20 min, then place them in a reaction kettle at 120°C, add 10 parts by weight of polypropylene fiber, 5 parts by weight of alkyl polyglycoside, 3 parts by weight of tripolyphosphate (composed of sodium tripolyphosphate and magnesium tripolyphosphate in a mass ratio of 0.8:1), and 55 parts by weight of water for treatment for 40 min to obtain a modified carboxymethyl cellulose emulsion. When treated with the plasma equipment, the charge density is 1300 C / cm 3 , the gas flow rate is 1.7 L / min, the pressure in the treatment chamber is 98 kPa, and the temperature in the treatment chamber is 45°C.

[0048] S3. Crush the perlite so that the particle size of the perlite is less than or equal to 0.3 mm, and then soak the crushed perlite in an acidic solution (the acidic solution is composed of sodium silicate and sulfuric acid in a mass ratio of 1:15, and the mass concentration of sulfuric acid is 8%). After soaking for 80 min, filter and dry; weigh 40 parts by weight of silica fume, 35 parts by weight of slag (the particle size of the slag is less than or equal to 0.3 mm), 15 parts by weight of perlite treated with the acidic solution, and 6 parts by weight of pretreated corn straw powder. Mix them evenly and then add 5 parts by weight of 5-hydroxymethylfurfural, 2 parts by weight of calcium fluoride, 18 parts by weight of modified carboxymethyl cellulose emulsion, and 35 parts by weight of water and stir to mix to obtain a mixture.

[0049] S4. Place the mixture in a stirring device and stir and age it at a speed of 20 rpm for 5 h. During the aging process, water needs to be sprayed twice, and the amount of water sprayed each time is 0.8% of the weight of the mixture, and the interval time between the two sprays is 1.5 h.

[0050] S5. Place the aged mixture in a vacuum extruder to extrude and form a hollow brick blank, and the forming pressure is 0.9 MPa.

[0051] S6. Place the brick blank in a drying chamber at a temperature of 50 °C and dry it for 7 h to make the moisture content of the brick blank reach 4%.

[0052] S7. Place the dried brick blank in a roasting kiln, heat it up to 650 °C at a heating rate of 5 °C / min and keep it warm for 90 min, then heat it up to 950 °C at a heating rate of 5 °C / min and keep it warm for 60 min, and cool it to room temperature to obtain a sintered hollow brick with a porosity of 45%.

[0053] Example 2:

[0054] A preparation method of a sintered hollow brick, comprising the following preparation steps:

[0055] S1. Preparation of pretreated straw powder: Cut wheat straw into 6 - 10 mm in length and soak it in an ammonia water solution with a mass concentration of 7% for 12 h, then wash, filter, and dry it with clean water; crush the dried straw into 60 - 100 mesh, weigh 50 parts by weight of the crushed wheat straw in 60 parts by weight of water, add 6 parts by weight of polyethylene glycol diacrylate and 3 parts by weight of N-hydroxysuccinimide, stir at 50 °C for 30 min, filter, and dry to obtain pretreated wheat straw powder.

[0056] S2. Preparation of modified carboxymethyl cellulose emulsion: Weigh 50 parts by weight of carboxymethyl cellulose and 8 parts by weight of 2,5-furandimethanol, mix them evenly, then place them in a plasma device for 15 minutes of treatment. After that, put them into a reaction kettle at 125 °C, add 12 parts by weight of polypropylene fiber, 6 parts by weight of alkyl polyglycoside, 5 parts by weight of tripolyphosphate (composed of sodium tripolyphosphate and magnesium tripolyphosphate in a mass ratio of 1:1), and 60 parts by weight of water for 35 minutes of treatment to obtain the modified carboxymethyl cellulose emulsion. When treated by the plasma device, the charge density is 1350 C / cm 3 , the gas flow rate is 1.8 L / min, the pressure in the treatment chamber is 105 kPa, and the temperature in the treatment chamber is 50 °C.

[0057] S3. Crush the perlite so that the particle size of the perlite is less than or equal to 0.3 mm. Then soak the crushed perlite in an acidic solution (the acidic solution is composed of sodium silicate and sulfuric acid in a mass ratio of 1:20, and the mass concentration of sulfuric acid is 10%) for 70 minutes, then filter and dry it. Weigh 45 parts by weight of silica fume, 38 parts by weight of slag (the particle size of the slag is less than or equal to 0.3 mm), 20 parts by weight of perlite treated with the acidic solution, and 8 parts by weight of pretreated wheat straw powder, mix them evenly, then add 6 parts by weight of 5-hydroxymethylfurfural, 3 parts by weight of calcium fluoride, 22 parts by weight of the modified carboxymethyl cellulose emulsion, and 45 parts by weight of water, and stir and mix to obtain a mixture.

[0058] S4. Place the mixture in a stirring device and stir and age it at a speed of 25 rpm for 4 hours. During the aging process, water needs to be sprayed twice, with the amount of water sprayed each time being 1.0% of the weight of the mixture, and the interval between the two sprays is 2 hours.

[0059] S5. Place the aged mixture in a vacuum extruder to extrude the formed hollow brick blank, with a forming pressure of 1.1 MPa.

[0060] S6. Place the brick blank in a drying chamber at 40 °C and dry it for 6 hours to make the moisture content of the brick blank reach 6%.

[0061] S7. Place the dried brick blank in a roasting kiln, heat it at a heating rate of 5 °C / min to 700 °C and hold for 80 minutes, then heat it at a heating rate of 5 °C / min to 980 °C and hold for 50 minutes, and cool it to room temperature to obtain a sintered hollow brick with a porosity of 47%.

[0062] Example Three:

[0063] A method for preparing a sintered hollow brick, comprising the following preparation steps:

[0064] S1. Preparation of pretreated straw powder: Cut rice straw into pieces with a length of 6 - 10 mm, soak it in an ammonia water solution with a mass concentration of 6% for 13 h, then wash, filter, and dry it with clear water; crush the dried straw into 60 - 100 meshes, weigh 48 parts by weight of the crushed straw, add it to 55 parts by weight of water, add 5 parts by weight of polyethylene glycol diacrylate and 2.5 parts by weight of N - hydroxysuccinimide, stir at 48 °C for 32 min, filter, and dry to obtain pretreated rice straw powder.

[0065] S2. Preparation of modified carboxymethyl cellulose emulsion: Weigh 48 parts by weight of carboxymethyl cellulose and 7 parts by weight of 2,5 - furandimethanol, mix them evenly, place them in a plasma device for 18 min, then place them in a reaction kettle at 122 °C, add 11 parts by weight of polypropylene fiber, 5.5 parts by weight of alkyl glucoside, 4 parts by weight of tripolyphosphate (composed of sodium tripolyphosphate and magnesium tripolyphosphate in a mass ratio of 0.9:1), and 58 parts by weight of water, and treat for 38 min to obtain a modified carboxymethyl cellulose emulsion. When treated with the plasma device, the charge density is 1320 C / cm 3 The gas flow rate is 1.7 L / min, the pressure in the treatment chamber is 102 kPa, and the temperature in the treatment chamber is 48 °C.

[0066] S3. Crush perlite so that the particle size of the perlite is less than or equal to 0.3 mm, then soak the crushed perlite in an acidic solution (the acidic solution is composed of sodium silicate and sulfuric acid in a mass ratio of 1:18, and the mass concentration of sulfuric acid is 9%.) for 75 min, then filter and dry; weigh 42 parts by weight of silica fume, 36 parts by weight of slag (the particle size of the slag is less than or equal to 0.3 mm), 17 parts by weight of perlite treated with the acidic solution, 7 parts by weight of pretreated rice straw powder, mix them evenly, then add 5.5 parts by weight of 5 - hydroxymethylfurfural, 2.5 parts by weight of calcium fluoride, 20 parts by weight of modified carboxymethyl cellulose emulsion, and 40 parts by weight of water, and stir and mix to obtain a mixture.

[0067] S4. Place the mixture in a stirring device and stir and age at a speed of 22 rpm for 4.5 h. During the aging process, water needs to be sprayed twice, each time the spraying amount of water is 0.9% of the weight of the mixture, and the interval time between the two sprays is 1.5 h.

[0068] S5. Place the aged mixture in a vacuum extruder to extrude a formed hollow brick blank, and the forming pressure is 1.0 MPa.

[0069] S6. Place the brick blank in a drying chamber at a temperature of 45 °C and dry for 6.5 h to make the moisture content of the brick blank reach 5%.

[0070] S7. Place the dried brick blanks into a roasting kiln, heat them up to 680 °C at a heating rate of 5 °C / min and hold for 85 min, then heat them up to 960 °C at a heating rate of 5 °C / min and hold for 55 min, and cool to room temperature to obtain sintered hollow bricks with a porosity of 46%.

[0071] Comparative Example 1:

[0072] The difference from Example 1 is that the straw in Example 1 is not soaked in the ammonia water solution.

[0073] Comparative Example 2:

[0074] The difference from Example 1 is that polyethylene glycol diacrylate is not added during the pretreatment of the straw in Example 1.

[0075] Comparative Example 3:

[0076] The difference from Example 1 is that N-hydroxysuccinimide is not added during the pretreatment of the straw in Example 1.

[0077] Comparative Example 4:

[0078] The difference from Example 1 is that the modified carboxymethyl cellulose emulsion in Example 1 is removed.

[0079] Comparative Example 5:

[0080] The difference from Example 1 is that the carboxymethyl cellulose in Example 1 is not modified, and "18 parts by weight of modified carboxymethyl cellulose emulsion" in S3 is changed to "5 parts by weight of carboxymethyl cellulose".

[0081] Comparative Example 6:

[0082] The difference from Example 1 is that 5-hydroxymethylfurfural in Example 1 is removed.

[0083] Comparative Example 7:

[0084] The difference from Example 1 is that calcium fluoride in Example 1 is removed.

[0085] Comparative Example 8:

[0086] The difference from Example 1 is that the perlite is not treated with the acidic solution.

[0087] Comparative Example 9:

[0088] The difference from Example 1 is that the mixture is not stirred during the aging process.

[0089] Perform performance tests on the sintered products prepared in Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4, 5, 6, 7, 8, 9.

[0090] The flexural strength and compressive strength of the hollow bricks were detected using GB / T 2542-2012 "Test Methods for Burnt Clay Bricks", the thermal conductivity of the hollow bricks was detected using GB / T 32064-2015 "Transient Plane Source Method for Measuring Thermal Conductivity and Thermal Diffusivity of Building Materials", and the sound insulation quantity was detected using GB / T 19889.3-2005 "Acoustics - Measurement of Sound Insulation in Buildings and Building Elements".

[0091] As shown in Table 1, the sintered hollow bricks prepared in Examples 1, 2, and 3 had relatively high flexural strength, compressive strength, and sound insulation quantity, and relatively low thermal conductivity. The flexural strength and compressive strength of the sintered hollow bricks prepared in Comparative Examples 1, 2, 4, 5, 6, 7, and 9 were relatively low. The flexural strength of the sintered hollow bricks prepared in Comparative Examples 1, 2, 4, 5, 6, 7, and 9 was 17.4%, 21.7%, 28.3%, 21.7%, 26.1%, 28.3%, and 23.9% lower than that of Example 1 respectively, and the compressive strength was 12.9%, 16.9%, 25.3%, 20.9%, 27.6%, 30.2%, and 23.1% lower than that of Example 1 respectively. The thermal conductivities of the sintered hollow bricks prepared in Comparative Examples 2, 3, and 6 were 0.31 W / m·K, 0.37 W / m·K, and 0.76 W / m·K respectively, which were 138.5%, 184.6%, and 484.6% higher than that of the hollow bricks prepared in Example 1 respectively. The sound insulation quantity (R) is an index for evaluating the sound insulation effect of buildings. The larger the sound insulation quantity, the smaller the transmitted sound energy, that is, the better the sound insulation effect of the material. The sound insulation quantities of the sintered hollow bricks prepared in Comparative Examples 4, 5, and 8 were 40.2 dB, 42.3 dB, and 41.3 dB respectively, which were 21.6%, 17.5%, and 19.5% lower than that of the hollow bricks prepared in Example 1 respectively.

[0092] Soaking straw with ammonia water destroys the waxy layer on the surface of straw and the ester bond between lignin and polysaccharide in straw, improves the fiber structure of straw, increases the bonding area and bonding force between straw and other materials, thereby enhancing the flexural strength and compressive strength of hollow bricks. Polyethylene glycol diacrylate can crosslink with cellulose and hemicellulose in straw to form a stable network structure, improving the flexural strength, compressive strength and thermal insulation performance of hollow bricks. N-hydroxysuccinimide can reduce the pyrolysis and volatilization of straw during sintering, improve the quality of hollow bricks, reduce the thermal conductivity of hollow bricks, and thus enhance the heat insulation performance of hollow bricks. Carboxymethyl cellulose can enhance the flexural strength and compressive strength of hollow bricks and improve the sound insulation effect through mixing and modification with polypropylene fiber, alkyl glycoside and tripolyphosphate. 5-Hydroxymethylfurfural can lower the melting point of raw materials, promote sintering, reduce energy consumption and increase the strength of brick bodies. At the same time, 5-hydroxymethylfurfural can decompose to produce gas at high temperature, forming a microporous structure in the brick bodies, thereby reducing the density of brick bodies and improving the thermal insulation performance. Calcium fluoride can react with the surface of raw material particles to form a stable compound layer, making the structure of sintered hollow bricks more dense and reducing the internal porosity, so that the hollow bricks have higher compressive strength and flexural strength and can bear greater loads without being easily damaged. Perlite treated by soaking in acidic solution is added to hollow bricks, making the hollow bricks have a porous structure, which can effectively absorb sound waves, improve the sound insulation performance of hollow bricks and reduce the transmission of noise. Stirring and aging with a stirring device can cause mutual friction and collision between raw material particles, enhance the interaction between moisture and raw material particles, improve the plasticity of raw materials, and thus increase the compressive strength and flexural strength of hollow bricks.

[0093] Table 1: Performance Test Table of Sintered Hollow Bricks

[0094]

[0095] After stacking the hollow bricks prepared in Example 1, Comparative Example 3 and Comparative Example 4 outdoors for 6 months, 9 months, 12 months and 15 months, their compressive strengths were detected.

[0096] As Figure 2 shown, the initial compressive strengths of the hollow bricks prepared in Example 1, Comparative Example 3 and Comparative Example 4 were 22.5 MPa, 21.5 MPa and 16.8 MPa respectively. As the stacking time of the hollow bricks outdoors increased, their compressive strengths showed a downward trend. Since the 9th month, the compressive strengths of the hollow bricks in Comparative Example 3 and Comparative Example 4 decreased significantly. By the 12th month, the compressive strengths of the hollow bricks in Example 1, Comparative Example 3 and Comparative Example 4 decreased by 14.7%, 37.2% and 42.9% respectively compared with the initial values.

[0097] The treatment of straw with N-hydroxysuccinimide can increase the number of active functional groups on the surface of the straw, enhance the interaction force between the straw and the raw materials of the hollow brick, make the overall structure of the hollow brick more stable, and improve the durability of the sintered hollow brick. After modification, carboxymethyl cellulose can improve the uniformity and stability of the raw materials, thus contributing to the formation of a more compact and uniform structure during the production of the hollow brick and improving the durability of the hollow brick. Through the present invention, the durability of the hollow brick can be improved, enabling it to maintain a high compressive strength even under harsh conditions.

[0098] In summary, the sintered hollow brick prepared by the present invention has high flexural strength and compressive strength, good heat insulation and sound insulation effects, and strong durability.

[0099] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions or modifications made based on the present invention to solve substantially the same technical problems and achieve substantially the same technical effects are all covered by the protection scope of the present invention.

Claims

1. A method for preparing sintered hollow bricks, characterized in that: The following steps are involved: S1. Preparation of pretreated straw powder: Cut the straw into 6-10 mm long and soak it in a 5-7% ammonia solution for 12-14 h, then wash it with water, filter it and dry it; crush the dried straw into 60-100 mesh, weigh 45-50 parts by weight of the crushed straw into 50-60 parts by weight of water, add 4-6 parts by weight of polyethylene glycol diacrylate and 2-3 parts by weight of N-hydroxysuccinimide, stir it at 45-50°C for 30-35 min, filter it and dry it to obtain pretreated straw powder; S2. Preparation of modified carboxymethyl cellulose emulsion: 45 to 50 parts by weight of carboxymethyl cellulose and 5 to 8 parts by weight of 2,5-furan dimethanol were weighed and mixed evenly, and then placed in a plasma device for treatment for 15 to 20 minutes, and then placed in a reactor at 120 to 125°C, 10 to 12 parts by weight of polypropylene fiber, 5 to 6 parts by weight of alkyl glycoside, 3 to 5 parts by weight of tripolyphosphate, and 55 to 60 parts by weight of water were added for treatment for 35 to 40 minutes to obtain a modified carboxymethyl cellulose emulsion; S3. Weigh 40 to 45 parts by weight of silica fume, 35 to 38 parts by weight of slag, 15 to 20 parts by weight of perlite, and 6 to 8 parts by weight of pretreated straw powder, mix well, then add 5 to 6 parts by weight of 5-hydroxymethylfurfural, 2 to 3 parts by weight of calcium fluoride, 18 to 22 parts by weight of modified carboxymethyl cellulose emulsion, and 35 to 45 parts by weight of water, stir and mix to obtain a mixture; S4. Place the mixture in a stirring device and stir at 20 to 25 rpm for 4 to 5 hours; S5. The aged mixture is placed in a vacuum extruder to extrude hollow bricks at a molding pressure of 0.9 to 1.1 MPa; S6. Place the bricks in a drying room at 40-50°C and dry for 6-7 hours until the moisture content of the bricks reaches 4-6%; S7. The dried bricks are placed in a baking kiln, heated to 650-700°C at a heating rate of 5°C / min and kept warm for 80-90min, then heated to 950-980°C at a heating rate of 5°C / min and kept warm for 50-60min, and cooled to room temperature to obtain sintered hollow bricks having a porosity of 45-47%; Before the perlite is weighed, the method further comprises: crushing the perlite to make the particle size of the perlite less than or equal to 0.3 mm, and then soaking the crushed perlite in an acid solution for 70 to 80 minutes, filtering and drying the resulting perlite.

2. The method for preparing a sintered hollow brick according to claim 1, characterized in that: The charge density of plasma equipment is 1300~1350C / cm 3 , gas flow rate is 1.7~1.8L / min, processing chamber pressure is 98~105kPa, and processing chamber temperature is 45~50℃.

3. The method for preparing a sintered hollow brick according to claim 1, characterized in that: The acidic solution is composed of sodium silicate and sulfuric acid in a mass ratio of 1:15 to 20.

4. The method for preparing a sintered hollow brick according to claim 3, characterized in that: The mass concentration of sulfuric acid is 8-10%.

5. The method for preparing a sintered hollow brick according to claim 1, characterized in that: Before weighing the slag, the method further includes: crushing the slag to make the particle size of the slag less than or equal to 0.3 mm.

6. The method for preparing a sintered hollow brick according to claim 1, characterized in that: Tripolyphosphate is composed of sodium tripolyphosphate and magnesium tripolyphosphate in a mass ratio of 0.8 to 1:

1.

7. The method for preparing a sintered hollow brick according to claim 1, characterized in that: The mixture needs to be sprayed with water twice during the mixing and aging process. The amount of water sprayed each time is 0.8-1.0% of the weight of the mixture, and the interval between the two sprayings is 1.5-2h.

8. The method for preparing a sintered hollow brick according to claim 1, characterized in that: The straw is any one of corn straw, wheat straw and rice straw or a mixture of two of them.

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