Magnesium oxysulfate cement fireproof plate as well as preparation method and application thereof

Abstract

The invention relates to the technical field of building materials, in particular to a magnesium oxysulfate cement fireproof plate and a preparation method and application thereof. According to the magnesium oxysulfate cement fireproof plate provided by the invention, brucite and ammonium sulfate are adopted to replace the existing material magnesium sulfate heptahydrate, and hollow titanium dioxide microspheres are doped into the magnesium oxysulfate cement fireproof plate. The preparation method is low-carbon and environment-friendly, and the obtained magnesium oxysulfate cement fireproof plate not only has good fireproof performance and mechanical performance, but also can efficiently adsorb nitrogen oxides in the atmosphere, enriches the functions of the cement fireproof plate, and has great scientific and engineering significance in the field of building materials.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a magnesium oxysulfate cement fireproof board, a preparation method thereof, and an application thereof. Background Art

[0002] Due to its excellent fireproof performance and environmental protection characteristics, the magnesium oxysulfate cement fireproof board is widely used in the fields of architecture and decoration. The magnesium oxysulfate cement fireproof board also has the advantages of light weight, high strength, outstanding heat insulation and heat preservation performance, waterproof and moisture-proof, and remarkable sound insulation effect, and can be compounded with a variety of heat insulation materials to form a composite heat insulation board.

[0003] As one of the raw materials of the magnesium oxysulfate cement fireproof board, magnesium sulfate heptahydrate currently has a variety of preparation methods, such as the sulfuric acid method, the seawater solar salt bittern method, etc. However, these methods all require heat treatment in the preparation process, which will release a large amount of carbon dioxide.

[0004] Therefore, exploring a more low-carbon and environmentally friendly preparation method of magnesium sulfate, and developing a magnesium oxysulfate cement fireproof board that can adsorb nitrogen oxides in the environment has great scientific significance and engineering significance for the field of building materials. Summary of the Invention

[0005] In view of this, the present invention provides a magnesium oxysulfate cement fireproof board, a preparation method thereof, and an application thereof. The raw materials used in the magnesium oxysulfate cement fireproof board are low-carbon and environmentally friendly, and while having excellent fireproof performance, can also efficiently adsorb nitrogen oxides in the atmosphere.

[0006] To solve the above technical problems, a first aspect of the present invention provides a magnesium oxysulfate cement fireproof board, the main components of which include magnesium sulfate and light-burned magnesia. Among them, the magnesium sulfate is prepared by reacting brucite with ammonium sulfate, and the mass of the light-burned magnesia is 5 to 9 times that of the brucite; hollow titanium dioxide microspheres are evenly distributed in the magnesium oxysulfate cement fireproof board, and the hollow titanium dioxide microspheres account for 3% to 6% of the weight of the light-burned magnesia.

[0007] The present invention first uses brucite, a natural magnesian material, and ammonium sulfate to prepare magnesium sulfate. The obtained magnesium sulfate can be used to replace the magnesium sulfate heptahydrate used in the existing method for preparing magnesium oxysulfate cement fireproof boards, thereby realizing the low-carbon preparation of magnesium oxysulfate cement fireproof boards. The magnesium oxysulfate cement fireproof board provided by the present invention not only has excellent fireproof performance, but also the hollow titanium dioxide microspheres contained therein enable the magnesium oxysulfate cement fireproof board to efficiently adsorb nitrogen oxides in the atmosphere, especially nitric oxide, under photocatalysis, which is of great significance for reducing the content of nitrogen oxides in the atmosphere. Among them, the incorporated hollow titanium dioxide microspheres have a significant cavity structure inside compared with commercially available nano-titanium dioxide. When used as a filler in the magnesium oxysulfate cement fireproof board, its own hollow structure and the pores between it and the fireproof board matrix can not only enhance the adsorption performance of the fireproof board for nitrogen oxides, but also the pores between it and the fireproof board matrix can store air to achieve heat insulation of the fireproof board. Moreover, the hollow titanium dioxide microspheres themselves have good heat reflectivity, thus obtaining a highly efficient fireproof material with both nitric oxide gas adsorption performance and heat reflectivity.

[0008] Combined with the first aspect, polyvinyl alcohol fibers are also dispersed in the magnesium oxysulfate cement fireproof board; wherein, the polyvinyl alcohol fibers account for 7.5% - 10% of the weight of the light-burned magnesia in the magnesium oxysulfate cement fireproof board.

[0009] Preferably, the polyvinyl alcohol fibers account for 7.9% - 9.6% of the weight of the light-burned magnesia in the magnesium oxysulfate cement fireproof board.

[0010] Combined with the first aspect, the length of the polyvinyl alcohol fibers is 4.5 - 5 mm, the diameter is 18 - 20 μm, the density is 1.0 - 1.2 g / cm 3 , and the melting point is 155 - 165 °C.

[0011] Further preferably, the breaking elongation rate of the polyvinyl alcohol fibers is 28% - 32%, the elastic modulus is 35 - 40 GPa, and the tensile strength is 1490 - 1510 MPa.

[0012] Combined with the first aspect, the hollow titanium dioxide microspheres are prepared according to the following method: Add cationic polyacrylamide emulsion and ammonia water to ethanol, mix evenly, and then dropwise add a mixed solution of tetrabutyl titanate, triethanolamine and ethanol. After the dropping is completed, heat up to 300 - 320 °C and react for 7 - 9 h. After the reaction is completed, centrifuge, wash and dry, and calcine the dried product at 300 - 320 °C to obtain the hollow titanium dioxide microspheres.

[0013] Preferably, the hollow titanium dioxide microspheres are prepared as follows: 13-16 parts by weight of cationic polyacrylamide emulsion and 70-80 parts by weight of ammonia water are added to 100 parts by weight of absolute ethanol and mixed evenly, then transferred to a three-necked flask equipped with a stirrer and a condenser, and constantly stirred at a speed of 280-300 r / min at room temperature for 15-20 min; a mixture of 15-20 parts by weight of tetrabutyl titanate, 1-2 parts by weight of triethanolamine and 20-22 parts by weight of absolute ethanol is slowly added dropwise to the three-necked flask at a uniform speed. After the addition is completed, the temperature of the system is raised to 300-320 °C for reaction. After reacting for 7-9 h, centrifugation and washing are carried out in sequence, and the product is dried at a temperature of 60±5 °C, and then calcined at 300-320 °C for 10-12 h and cooled to obtain the hollow titanium dioxide microspheres.

[0014] Preferably, the percentage content of cationic polyacrylamide in the cationic polyacrylamide emulsion is not less than 95 wt%, and the concentration of ammonia water is 13-15 mol / L.

[0015] The second aspect of the present invention provides a preparation method of the above-mentioned magnesium oxysulfate cement fireproof board, and the steps include:

[0016] Add brucite to ammonium sulfate solution, stir to generate magnesium sulfate slurry, then add light-burned magnesia and citric acid, and stir to obtain magnesium oxysulfate cement paste;

[0017] Mix the magnesium oxysulfate cement paste with the aqueous dispersion containing the hollow titanium dioxide microspheres and stir evenly to obtain a mixed slurry;

[0018] Add polyvinyl alcohol fiber to the mixed slurry, stir evenly, then pour it into a mold, remove the mold and cure to obtain the magnesium oxysulfate cement fireproof board.

[0019] The preparation method of the magnesium oxysulfate cement fireproof board provided by the present invention uses brucite as a raw material, and magnesium hydroxide in brucite reacts with ammonium sulfate to generate magnesium sulfate at room temperature. The reaction conditions are mild, environmentally friendly and low-carbon. At the same time, by adding self-made hollow titanium dioxide microspheres to the magnesium oxysulfate cement paste, it will not only not affect the fireproof performance of the cement fireproof board, but also endow the fireproof board with the function of efficiently adsorbing nitrogen oxides.

[0020] Preferably, the brucite includes the following raw material components in mass percentage: 75.14%-85.4% Mg(OH)2, 11.82%-17.1% SiO2, 2.28%-4.28% CaO, 0.5%-3.48% other components.

[0021] The light-burned magnesia includes raw material components with the following mass percentages: 88% - 92% MgO, 0.9% - 1.1% Al2O3, 1.22% - 3.1% CaO, 0.66% - 0.9% Fe2O3, 1.6% - 2.8% SiO2, 3.62% - 4.4% other components.

[0022] Light-burned magnesia, also known as light-burned magnesium, is obtained by calcining magnesite, brucite, and magnesium hydroxide extracted from seawater or brine at about 800 - 1000 °C to decompose and expel CO2 or H2O. Light-burned magnesia is widely used in multiple fields such as building materials, chemical industry, metallurgy, and medicine, and is an ideal material for producing fireproof boards, lightweight partition boards, magnesium sulfate, and papermaking, etc.

[0023] Combined with the second aspect, the mass ratio of ammonium sulfate to brucite is 1.5 - 2.5:1, and the mass proportion of ammonium sulfate in the ammonium sulfate solution is 20% - 30%.

[0024] Combined with the second aspect, the addition amount of the light-burned magnesia is 6 - 8 times the mass of the brucite.

[0025] Combined with the second aspect, the mass ratio of water to light-burned magnesia in the mixed slurry is 65 - 88:100.

[0026] Among them, the water in the mixed slurry mainly includes the solvent water in the ammonium sulfate solution used for preparing the magnesium oxysulfate cement paste and the water used for dispersing the hollow titanium dioxide microspheres.

[0027] Combined with the second aspect, the particle size of the brucite is 200 - 325 mesh, and the content of magnesium hydroxide contained is 75wt% - 90wt%.

[0028] Preferably, the steps for preparing the magnesium oxysulfate cement fireproof board include:

[0029] Weigh each component according to the designed ratio. Dissolve 4 - 7 parts by weight of ammonium sulfate in water to obtain an ammonium sulfate solution. Mix 3 - 5 parts by weight of brucite with the obtained ammonium sulfate solution, and place it in a cement mortar mixer to stir at a speed of 60 - 65 r / min for 2 - 3 min. Then add 20 parts by weight of light-burned magnesia and 0.1 - 0.2 parts by weight of citric acid, and continue to stir at a speed of 60 - 65 r / min for 5 - 6 min to obtain a magnesium oxysulfate cement paste. Mix 0.6 - 1.2 parts by weight of hollow titanium dioxide microspheres with water and disperse them evenly by ultrasonic treatment. Set the power of the ultrasonic crusher to 650 W and disperse ultrasonically for 20 - 30 min. Put the evenly dispersed hollow titanium dioxide microsphere dispersion and the magnesium oxysulfate cement paste together into a cement mortar mixer and stir at a speed of 60 - 65 r / min for 55 - 60 s to obtain a mixed paste. Then add 1.5 - 2 parts by weight of polyvinyl alcohol fibers to the obtained mixed paste and continue to stir at a speed of 60 - 65 r / min for 2 - 3 min to obtain a magnesium oxysulfate cement fireproof board paste. Pour the obtained magnesium oxysulfate cement fireproof board paste into a mold with dimensions of 1000 mm × 190 mm × 80 mm, and vibrate it on a horizontal vibrating table for 2 - 3 min. After demolding, cure the magnesium oxysulfate cement fireproof board in a constant temperature and humidity incubator at 23 ± 2 °C and a relative humidity of 50 ± 5 RH%, and then the magnesium oxysulfate cement fireproof board can be obtained. Among them, the sum of the parts by weight of water used to dissolve ammonium sulfate and the parts by weight of water used to disperse hollow titanium dioxide microspheres is 13 - 18 parts.

[0030] The third aspect of the present invention provides an application of the above-mentioned magnesium oxysulfate cement fireproof board or the magnesium oxysulfate cement fireproof board prepared according to the above preparation method in adsorbing nitrogen oxides in the atmosphere.

[0031] Preferably, the nitrogen oxides can be nitric oxide, nitrogen dioxide, dinitrogen monoxide, etc., and more preferably nitric oxide.

[0032] The beneficial effects obtained by the present invention: The present invention first uses magnesium sulfate prepared from natural magnesium material brucite and ammonium sulfate to replace the currently used material magnesium sulfate heptahydrate in the magnesium oxysulfate cement fireproof board, realizing the low-carbon preparation of the magnesium oxysulfate cement fireproof board. Secondly, by incorporating self-made hollow titanium dioxide microspheres into the magnesium oxysulfate cement fireproof board, the obtained magnesium oxysulfate cement fireproof board can not only maintain the original mechanical properties and flame retardant properties, but also efficiently adsorb nitric oxide in the atmosphere under photocatalysis, which has great scientific and engineering significance for the field of building materials. Description of the Drawings

[0033] Figure 1 It is the SEM image of the self-made hollow titanium dioxide microspheres of the present invention. Detailed Embodiments

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] The hollow titanium dioxide microspheres used in the following examples or comparative examples can be prepared by the following method:

[0036] 13-16 parts by weight of cationic polyacrylamide emulsion and 70-80 parts by weight of ammonia water are added to 100 parts by weight of absolute ethanol and mixed evenly, then transferred to a three-necked flask equipped with a stirrer and a condenser, and stirred at a constant speed of 280-300 r / min at room temperature for 15-20 min; 15-20 parts by weight of tetrabutyl titanate, 1-2 parts by weight of triethanolamine and 20-22 parts by weight of absolute ethanol mixed solution are slowly added dropwise to the three-necked flask at a constant speed. After the addition is completed, the temperature of the system is raised to 300-320 °C for reaction. After reacting for 7-9 h, centrifugation and washing are carried out in sequence, and the product is dried at a temperature of 60±5 °C, and then calcined at 300-320 °C for 10-12 h, and cooled to obtain hollow titanium dioxide microspheres.

[0037] Exemplarily, 15 parts by weight of cationic polyacrylamide emulsion and 75 parts by weight of ammonia water are added to 100 parts by weight of absolute ethanol and mixed evenly, then transferred to a three-necked flask equipped with a stirrer and a condenser, and stirred at a constant speed of 300 r / min at room temperature for 18 min; 18 parts by weight of tetrabutyl titanate, 2 parts by weight of triethanolamine and 21 parts by weight of absolute ethanol mixed solution are slowly added dropwise to the three-necked flask at a constant speed. After the addition is completed, the temperature of the system is raised to 310 °C for reaction. After reacting for 8 h, centrifugation and washing are carried out in sequence, and the product is dried at a temperature of 60±5 °C, and then calcined at 310 °C for 11 h, and cooled to obtain hollow titanium dioxide microspheres.

[0038] The preparation method of the original hollow titanium dioxide microspheres used in the following comparative examples is basically similar to the preparation method of the hollow titanium dioxide microspheres, except that the cationic polyacrylamide emulsion is replaced with an equal amount of cationic polystyrene emulsion.

[0039] The average content of magnesium hydroxide in the brucite used is 80%-90%.

[0040] Example 1

[0041] This example provides a magnesium oxysulfate cement fireproof board, and the preparation steps include:

[0042] S1. Dissolve 66 g of ammonium sulfate in 140.5 g of water to obtain an ammonium sulfate solution. Mix 44.5 g of brucite with the obtained ammonium sulfate solution, place it in a cement mortar mixer, and stir at a speed of 60 r / min for 2 min. Then add 200 g of light-burned magnesia and 1 g of citric acid monohydrate, and continue to stir at a speed of 60 r / min for 5 min to obtain a magnesium oxysulfate cement paste.

[0043] S2. Mix 6 g of the prepared hollow titanium dioxide microspheres with 35 g of water and disperse them evenly by ultrasonic treatment. Set the power of the ultrasonic crusher to 650 W and disperse ultrasonically for 20 min. Put the evenly dispersed hollow titanium dioxide microsphere dispersion and the magnesium oxysulfate cement paste together into a cement mortar mixer and stir at a speed of 60 r / min for 55 s to obtain a mixed paste.

[0044] S3. Add 19.15 g of polyvinyl alcohol fiber to the obtained mixed paste, and continue to stir at a speed of 60 r / min for 2 min to obtain a magnesium oxysulfate cement fireproof board paste. Pour the obtained magnesium oxysulfate cement fireproof board paste into a mold with dimensions of 1000 mm × 190 mm × 80 mm, vibrate on a horizontal vibrating table for 2 min, demold after 1 d, and cure the magnesium oxysulfate cement fireproof board in a constant temperature and humidity incubator at 23 ± 2 °C and a relative humidity of 50 ± 5 RH% for 28 d to obtain a magnesium oxysulfate cement fireproof board.

[0045] Example 2

[0046] This example provides a magnesium oxysulfate cement fireproof board, and the preparation steps include:

[0047] S1. Dissolve 55 g of ammonium sulfate in 87 g of water to obtain an ammonium sulfate solution. Mix 34.75 g of brucite with the obtained ammonium sulfate solution, place it in a cement mortar mixer, and stir at a speed of 65 r / min for 3 min. Then add 200 g of light-burned magnesia and 1 g of citric acid monohydrate, and continue to stir at a speed of 65 r / min for 6 min to obtain a magnesium oxysulfate cement paste.

[0048] S2. Mix 10 g of the prepared hollow titanium dioxide microspheres with 59 g of water and disperse them evenly by ultrasonic treatment. Set the power of the ultrasonic crusher to 650 W and disperse ultrasonically for 30 min. Put the evenly dispersed hollow titanium dioxide microsphere dispersion and the magnesium oxysulfate cement paste together into a cement mortar mixer and stir at a speed of 65 r / min for 60 s to obtain a mixed paste.

[0049] S3. Add 17.07 g of polyvinyl alcohol fiber to the obtained mixed slurry, and continue to stir at a speed of 65 r / min for 3 min to obtain a magnesium oxysulfate cement fireproof board slurry. Pour the obtained magnesium oxysulfate cement fireproof board slurry into a mold with dimensions of 1000 mm × 190 mm × 80 mm, vibrate on a horizontal vibrating table for 3 min, demold after 1 d, and cure the magnesium oxysulfate cement fireproof board in a constant temperature and humidity incubator at 23 ± 2 °C and a relative humidity of 50 ± 5 RH% for 28 d to obtain a magnesium oxysulfate cement fireproof board.

[0050] Example 3

[0051] This example provides a magnesium oxysulfate cement fireproof board, and the preparation steps include:

[0052] S1. Dissolve 47.04 g of ammonium sulfate in 60 g of water to obtain an ammonium sulfate solution. Mix 31.68 g of brucite with the obtained ammonium sulfate solution, place it in a cement mortar mixer, and stir at a speed of 63 r / min for 2.5 min. Then add 200 g of light-burned magnesia and 1 g of citric acid monohydrate, and continue to stir at a speed of 63 r / min for 5.5 min to obtain a magnesium oxysulfate cement neat paste.

[0053] S2. Mix 12 g of the prepared hollow titanium dioxide microspheres and 70 g of water, and disperse them evenly by ultrasonic wave. Set the power of the ultrasonic crusher to 650 W and disperse ultrasonically for 25 min. Put the evenly dispersed hollow titanium dioxide microsphere dispersion liquid and the magnesium oxysulfate cement neat paste into a cement mortar mixer and stir at a speed of 63 / min for 58 s to obtain a mixed slurry.

[0054] S3. Add 15.83 g of polyvinyl alcohol fiber to the obtained mixed slurry, and continue to stir at a speed of 63 r / min for 2.5 min to obtain a magnesium oxysulfate cement fireproof board slurry. Pour the obtained magnesium oxysulfate cement fireproof board slurry into a mold with dimensions of 1000 mm × 190 mm × 80 mm, vibrate on a horizontal vibrating table for 2.5 min, demold after 1 d, and cure the magnesium oxysulfate cement fireproof board in a constant temperature and humidity incubator at 23 ± 2 °C and a relative humidity of 50 ± 5 RH% for 28 d to obtain a magnesium oxysulfate cement fireproof board.

[0055] Comparative Example 1

[0056] This comparative example provides a magnesium oxysulfate cement fireproof board. The raw material ratio and preparation steps are similar to those of Example 3, and the only difference is that brucite and ammonium sulfate are not used in the raw materials, but magnesium sulfate heptahydrate (i.e., the method for preparing magnesium oxysulfate cement fireproof board in the prior art) is used. The preparation steps include:

[0057] S1. Dissolve 87.56 g of magnesium sulfate heptahydrate in 68.39 g of water to obtain a magnesium sulfate solution, and place it in a cement mortar mixer. Then add 200 g of light-burned magnesia and 1 g of citric acid monohydrate, and stir at a speed of 63 r / min for 5.5 min to obtain a magnesium oxysulfate cement paste.

[0058] S2. Mix 12 g of the prepared hollow titanium dioxide microspheres with 20 g of water, and disperse them evenly by ultrasonic wave. Set the power of the ultrasonic crusher to 650 W and disperse ultrasonically for 25 min. Put the evenly dispersed hollow titanium dioxide microsphere dispersion liquid and the magnesium oxysulfate cement paste into the cement mortar mixer together, and stir at a speed of 63 / min for 58 s to obtain a mixed paste.

[0059] S3. Add 15.83 g of polyvinyl alcohol fiber to the obtained mixed paste, and continue to stir at a speed of 63 r / min for 2.5 min to obtain a magnesium oxysulfate cement fireproof board paste. Pour the obtained magnesium oxysulfate cement fireproof board paste into a mold with dimensions of 1000 mm×190 mm×80 mm, vibrate on a horizontal vibrating table for 2.5 min, remove the mold after 1 day, and cure the magnesium oxysulfate cement fireproof board in a constant temperature and humidity incubator at 23±2°C and relative humidity 50±5RH% for 28 days to obtain a magnesium oxysulfate cement fireproof board.

[0060] Comparative Example 2

[0061] This comparative example provides a magnesium oxysulfate cement fireproof board. The raw material ratio and preparation steps are similar to those of Example 3, with the only difference being that only a certain amount of brucite and ammonium sulfate are used in the raw materials to prepare magnesium sulfate, and the balance is replaced by magnesium sulfate heptahydrate (that is, half of the magnesium sulfate heptahydrate used in the method for preparing magnesium oxysulfate cement fireproof board in the prior art is replaced by an appropriate amount of brucite and ammonium sulfate). The preparation steps include:

[0062] S1. Dissolve 23.57 g of ammonium sulfate in 95.7 g of water to obtain an ammonium sulfate solution. Mix 12.93 g of brucite with the obtained ammonium sulfate solution, place it in a cement mortar mixer, and stir at a speed of 63 r / min for 2.5 min. Then add 43.93 g of magnesium sulfate heptahydrate, 200 g of light-burned magnesia and 1 g of citric acid monohydrate, and continue to stir at a speed of 63 r / min for 5.5 min to obtain a magnesium oxysulfate cement paste.

[0063] S2. S3 are the same as steps S2 and S3 in Comparative Example 1, and will not be elaborated here.

[0064] Comparative Example 3

[0065] This comparative example provides a magnesium oxysulfate cement fireproof board. The raw material ratio and preparation steps are similar to those of Example 3, with the only difference being that the self-made hollow titanium dioxide microspheres are not added, and the other raw material formulas and steps are the same as those of Example 3.

[0066] Comparative Example 4

[0067] This comparative example provides a magnesium oxysulfate cement fireproof board. The raw material ratio and preparation steps are similar to those of Example 3, except that the hollow titanium dioxide microspheres in Example 3 are replaced with an equal amount of nano-titanium dioxide, and the remaining raw material formulations and steps are the same as those of Example 3.

[0068] Comparative Example 5

[0069] This comparative example provides a magnesium oxysulfate cement fireproof board. The raw material ratio and preparation steps are similar to those of Example 3, except that the hollow titanium dioxide microspheres in Example 3 are replaced with an equal amount of the original hollow titanium dioxide microspheres prepared by the above method, and the remaining raw material formulations and steps are the same as those of Example 3.

[0070] Comparative Example 6

[0071] This comparative example provides a magnesium oxysulfate cement fireproof board. The raw material ratio and preparation steps are similar to those of Example 1, except that the hollow titanium dioxide microspheres in Example 1 are replaced with an equal amount of nano-titanium dioxide, and the remaining raw material formulations and steps are the same as those of Example 1.

[0072] Comparative Example 7

[0073] This comparative example provides a magnesium oxysulfate cement fireproof board. The raw material ratio and preparation steps are similar to those of Example 1, except that the hollow titanium dioxide microspheres in Example 1 are replaced with an equal amount of the original hollow titanium dioxide microspheres, and the remaining raw material formulations and steps are the same as those of Example 1.

[0074] Perform performance tests on the magnesium oxysulfate cement fireproof boards obtained in Examples 1 to 3 and Comparative Examples 1 to 7 respectively. The experiments are as follows:

[0075] Inspection Example 1

[0076] According to the national standard GB / T 17671-2020 "Test Method for Strength of Cement Mortar (ISO Method)", test the flexural strength and impact strength of the magnesium oxysulfate cement fireproof boards obtained in Examples 1 to 3 and Comparative Examples 1 to 7 respectively; among them, the flexural strength is tested using a cement compressive and flexural testing machine, and the loading speed is 50 N / s; the impact strength is tested using an impact testing machine.

[0077] According to the national standard GB / T 2419-2005 "Determination Method for Fluidity of Cement Mortar", test the fluidity of the pastes of the magnesium oxysulfate cement fireproof boards obtained in Examples 1 to 3 and Comparative Examples 1 to 7 respectively, and use a cement mortar fluidity tester for testing.

[0078] The test results of the fluidity of the magnesium oxysulfate cement fireproof board paste, the flexural strength and the impact strength of the magnesium oxysulfate cement fireproof board obtained in Examples 1 to 3 and Comparative Examples 1 to 7 are shown in Table 1.

[0079] Table 1

[0080]

[0081]

[0082] As can be seen from Table 1, the fluidity of the magnesium oxysulfate cement fireproof board paste obtained in Examples 1 to 3 is greater than 160 mm, meeting the casting conditions; the flexural strength is greater than 16.0 MPa, meeting the condition that the flexural strength of the magnesium oxysulfate fireproof board, a magnesium-based cementitious material product for building use of Class A, is ≥ 11.0 MPa.

[0083] Comparing Comparative Examples 1 and 2, it can be seen that when about 50% of magnesium sulfate heptahydrate is replaced by brucite and ammonium sulfate, under the condition of the same other raw material ratios, the fluidity of the magnesium oxysulfate cement fireproof board paste decreases by 2.59%; comparing Example 3 with Comparative Example 1, it can be seen that when magnesium sulfate heptahydrate is completely replaced by brucite and ammonium sulfate, under the condition of the same other raw material ratios, the fluidity of the paste in Example 3 decreases by 3.75%, indicating that after using brucite and ammonium sulfate to completely replace magnesium sulfate heptahydrate directly, although the fluidity of the obtained paste decreases to some extent, it still meets the casting conditions. Comparing Example 3 with Comparative Example 3, it can be seen that when magnesium sulfate heptahydrate is completely replaced by brucite and ammonium sulfate, under the condition of the same other raw material ratios, the fluidity decreases by 4.02% after adding the self-made hollow titanium dioxide microspheres but is still greater than 160 mm, indicating that after adding the self-made hollow titanium dioxide microspheres, although the fluidity of the obtained paste decreases to some extent, it still meets the casting conditions.

[0084] Comparing Comparative Examples 1 and 2, it can be seen that when about 50% of magnesium sulfate heptahydrate is replaced by brucite and ammonium sulfate, under the condition of the same other raw material ratios, the flexural strength increases by 8.16%; comparing Example 3 with Comparative Example 1, when magnesium sulfate heptahydrate is completely replaced by brucite and ammonium sulfate, under the condition of the same other raw material ratios, the flexural strength increases by 16.35%. The above shows that after using brucite and ammonium sulfate to replace magnesium sulfate heptahydrate directly, the flexural performance of the obtained fireproof board is significantly improved. Comparing Example 3 with Comparative Example 3, it can be seen that when magnesium sulfate heptahydrate is completely replaced by brucite and ammonium sulfate, under the condition of the same other raw material ratios, after adding hollow titanium dioxide microspheres, the flexural strength increases by 4.52%, indicating that after adding hollow titanium dioxide microspheres, the flexural strength of the obtained fireproof board increases to some extent.

[0085] It can also be seen from Table 1 that the impact strength of the magnesium oxysulfate cement fireproof boards obtained in Examples 1 to 3 is greater than 7.5 kJ / m 2, much higher than the standard requirement that the impact resistance of magnesia cementitious material products for Class A buildings, magnesium oxysulfate fireproof board, is not less than 3.0 kJ / m 2 .

[0086] Comparing Comparative Examples 1 and 2, when about 50% of magnesium sulfate heptahydrate was replaced by brucite and ammonium sulfate, under the condition of the same raw material ratio of other components, the impact resistance increased by 15.09%; comparing Example 3 with Comparative Example 1, when magnesium sulfate heptahydrate was completely replaced by brucite and ammonium sulfate, under the condition of the same raw material ratio of other components, the impact resistance increased by 71.05%. The above shows that after using brucite and ammonium sulfate to replace the direct use of magnesium sulfate heptahydrate, the impact resistance of the obtained fireproof board has been significantly improved. Comparing Example 3 with Comparative Example 3, it can be seen that when magnesium sulfate heptahydrate was completely replaced by brucite and ammonium sulfate, under the condition of the same raw material ratio of other components, after adding the self-made hollow titanium dioxide microspheres, the impact resistance corresponding to Example 3 increased by 9.80%, indicating that adding the self-made hollow titanium dioxide microspheres can improve the impact resistance of the fireproof board.

[0087] Comparing Example 3 with Comparative Examples 4-5, it can be seen that when the self-made hollow titanium dioxide microspheres added in Example 3 were replaced by nano-titanium dioxide or the original hollow titanium dioxide microspheres respectively, the fluidity of the obtained fireproof board slurry was comparable, but the flexural strength and impact resistance decreased to varying degrees, indicating that the incorporation of the self-made hollow titanium dioxide microspheres provided by the present invention is beneficial to improving the mechanical properties of the fireproof board.

[0088] Similarly, comparing Example 1 with Comparative Examples 6-7, it can be seen that the fluidity of the fireproof board slurry, the flexural strength and impact resistance of the fireproof board obtained in Comparative Examples 6-7 decreased compared with Example 1, indicating that the incorporation of the self-made hollow titanium dioxide microspheres has a certain promoting effect on the fluidity, flexural performance and impact resistance of the obtained magnesium oxysulfate cement fireproof board.

[0089] Inspection Example 2

[0090] According to the national standards GB / T 8624-2012 "Classification of burning behavior of building materials and products" and GB / T5464-2010 "Test method for non-combustibility of building materials", the furnace temperature rise ΔT, mass loss rate Δm and continuous burning time tf of the magnesium oxysulfate cement fireproof boards obtained in Examples 1-3 and Comparative Examples 1-7 were tested using a heating furnace. The specific test process was as follows: Specimens were prepared from each of the prepared magnesium oxysulfate cement fireproof boards. The specimens were cylindrical with a volume of (76±8) cm 3, with a diameter of (45 ± 2) cm and a height of (50 ± 3) cm; place the specimen in a ventilated drying oven at 60 ± 5 °C and dry it for 20 - 24 h, then place it in a desiccator to cool to room temperature, weigh each group of specimens, accurate to 0.01 g; preheat the heating furnace at 750 ± 5 °C for at least 10 min. When its temperature drift (linear regression) does not exceed 2 °C within 10 min and the maximum deviation from the average temperature (linear regression) does not exceed 10 °C within 10 min, place the specimen in the heating furnace for 30 min, then take it out, weigh the mass after cooling (accurate to 0.01 g), and record the specimen temperature. The specific test results are shown in Table 2.

[0091] Table 2

[0092] Group Temperature rise in furnace ΔT / °C Mass loss rate Δm / % Sustained combustion time tf / s Combustion performance grade Example 1 24 36.66 0 A1 Example 2 23 36.76 0 A1 Example 3 25 37.23 0 A1 Comparative example 1 23 36.56 0 A1 Comparative example 2 24 36.98 0 A1 Comparative example 3 25 36.67 0 A1 Comparative example 4 23 36.83 0 A1 Comparative example 5 24 37.01 0 A1 Comparative example 6 25 36.69 0 A1 Comparative example 7 24 36.74 0 A1

[0093] The national standard GB / T 8624 - 2012 "Classification of the Burning Behavior of Building Materials and Products" stipulates that if the three conditions of the temperature rise in the furnace ΔT ≤ 30 °C, the mass loss rate of the specimen Δm ≤ 50%, and the continuous burning time of the specimen tf = 0 are simultaneously met, the building material will be judged as a non - combustible product of Class A1. It can be seen from the results in Table 2 that the magnesium oxysulfate cement fire - proof boards obtained in Examples 1 - 3 and Comparative Examples 1 - 7 all meet the above conditions and can be recognized as non - combustible products of Class A1, indicating that the replacement of magnesium sulfate heptahydrate and the incorporation of hollow titanium dioxide microspheres have no impact on the fire - proof performance of the magnesium oxysulfate cement fire - proof board.

[0094] Inspection Example 3

[0095] Use a nitrogen oxide analyzer to test the photocatalytic degradation efficiency of the magnesium oxysulfate cement fire - proof boards obtained in Examples 1 - 3 and Comparative Examples 1 - 7 for nitrogen monoxide gas respectively. The analyzer is equipped with an 8W ultraviolet lamp, a photocatalytic polymerization glass reactor with dimensions of 30 cm × 15 cm × 10 cm, and a humidification chamber. The test range of nitrogen oxide concentration is 0 - 1000 ppb. The specific test process is as follows: Take specimens from the prepared magnesium oxysulfate cement fire - proof boards, place the specimens with dimensions of 100 * 100 * 25 mm in the reaction chamber of the nitrogen oxide analyzer, place the 8W ultraviolet lamp directly above the reactor, then slowly introduce the gas. The gas flow is completely premixed by a gas mixer, and the flow rates of the gas flow and nitrogen monoxide are controlled at 2.4 L / min and 24 mL / min respectively by mass flow controllers. The nitrogen monoxide gas is diluted to about 800 ppb by the gas flow. The relative humidity of the required nitrogen monoxide gas is controlled at 50% by passing the gas flow through the humidification chamber first. After reaching the adsorption - desorption equilibrium, turn on the ultraviolet lamp for catalysis for 30 min. Continuously measure the concentration of nitrogen monoxide in the reaction chamber by the nitrogen oxide analyzer to obtain the ability of the specimen to photocatalytically degrade nitrogen monoxide gas under ultraviolet light. The specific test results are shown in Table 3.

[0096] Table 3

[0097] Group <![CDATA[Rate of nitric oxide degradation (ppb / h / m 2 )]]> Example 1 15.6 Example 2 18.9 Example 3 22.23 Comparative example 1 20.69 Comparative example 2 21.28 Comparative example 3 5.36 Comparative example 4 12.3 Comparative example 5 16.7 Comparative example 6 9.9 Comparative example 7 11.8

[0098] As can be seen from Table 3, when the self-made hollow titanium dioxide microspheres are not added (Comparative Example 3), the degradation rate of nitrogen monoxide is 5.36 ppb / h / m 2 , and when the self-made hollow titanium dioxide microspheres are incorporated at different dosages (Examples 1 to 3), the degradation rate of nitrogen monoxide of the obtained fireproof boards is significantly improved, which are 15.6 ppb / h / m 2 , 18.9 ppb / h / m 2 and 22.23 ppb / h / m 2 . As can be seen from Examples 1 to 3, after incorporating the self-made hollow titanium dioxide microspheres, the adsorption performance of the magnesium oxysulfate cement fireproof board for nitrogen monoxide gas is increased by photocatalysis, and the higher the dosage of the hollow titanium dioxide microspheres, the faster the degradation rate of the fireproof board for nitrogen monoxide gas. By comparing Example 3 with Comparative Examples 4 to 5 or comparing Example 1 with Comparative Examples 6 to 7, it can be seen that compared with the fireproof boards obtained by incorporating an equal amount of nano-titanium dioxide or the original hollow titanium dioxide microspheres, the incorporation of the self-made hollow titanium dioxide microspheres of the present invention makes the fireproof board have a faster degradation rate of nitrogen monoxide and a stronger performance in degrading nitrogen monoxide gas.

[0099] In summary, the present invention first uses the natural magnesia material brucite and ammonium sulfate to prepare magnesium sulfate, and replaces the original material magnesium sulfate heptahydrate in the magnesium oxysulfate cement fireproof board with it, realizing the low-carbon preparation of the magnesium oxysulfate cement fireproof board. Secondly, by internally incorporating the self-made hollow titanium dioxide microspheres, the function of the magnesium oxysulfate cement fireproof board with high adsorption of nitrogen monoxide gas under the action of photocatalysis is realized. The magnesium oxysulfate cement fireproof board prepared in the examples of the present invention uses natural mineral materials and is used in combination with the self-made hollow titanium dioxide microspheres, so that the obtained magnesium oxysulfate cement fireproof board has the performance of high adsorption of nitrogen monoxide, which not only produces high environmental benefits, but also increases the functions of the magnesium oxysulfate cement fireproof board, and has great scientific and engineering significance in the field of building materials.

[0100] The above is only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A magnesium oxysulfate cement fireproof board, the main components of which include magnesium sulfate and light-burned magnesium oxide, characterized in that: in, The magnesium sulfate is prepared by reacting brucite and ammonium sulfate, and the mass of light-burned magnesium oxide is 5 to 9 times that of brucite; hollow titanium dioxide microspheres are evenly distributed in the magnesium oxysulfide cement fireproof board, and the hollow titanium dioxide microspheres account for 3% to 6% of the weight of the light-burned magnesium oxide.

2. The magnesium oxysulfate cement fireproof board according to claim 1, characterized in that: Polyvinyl alcohol fibers are also dispersed in the magnesium oxysulfide cement fireproof board; wherein the polyvinyl alcohol fibers account for 7.5% to 10% of the weight of the light-burned magnesium oxide in the magnesium oxysulfide cement fireproof board.

3. The magnesium oxysulfate cement fireproof board according to claim 2, characterized in that: The polyvinyl alcohol fiber has a length of 4.5 to 5 mm, a diameter of 18 to 20 μm, and a density of 1.0 to 1.2 g / cm 3 , melting point is 155~165℃.

4. The magnesium oxysulfate cement fireproof board according to claim 1, characterized in that: The hollow titanium dioxide microspheres are prepared according to the following method: cationic polyacrylamide emulsion and ammonia water are added to ethanol and mixed evenly, and then a mixture of tetrabutyl titanate, triethanolamine and ethanol is added dropwise thereto, and after the addition is completed, the temperature is raised to 300-320° C. and reacted for 7-9 hours. After the reaction is completed, the mixture is centrifuged, washed and dried, and the dried product is calcined at 300-320° C. to obtain the hollow titanium dioxide microspheres.

5. A method for preparing the magnesium oxysulfate cement fireproof board according to any one of claims 1 to 4, characterized in that the steps include: Add brucite to ammonium sulfate solution, stir to generate magnesium sulfate slurry, then add light-burned magnesium oxide and citric acid, stir to obtain magnesium oxysulfate cement slurry; The magnesium oxysulfate cement slurry is mixed with the aqueous dispersion containing the hollow titanium dioxide microspheres and stirred evenly to obtain a mixed slurry; Polyvinyl alcohol fiber is added to the mixed slurry, and after being evenly stirred, the mixture is poured into a mold, demolded and cured to obtain the magnesium oxysulfate cement fireproof board.

6. The method for preparing the magnesium oxysulfate cement fireproof board according to claim 5, characterized in that: The mass ratio of ammonium sulfate to brucite is 1.5-2.5:1, and the mass proportion of ammonium sulfate in the ammonium sulfate solution is 20%-30%.

7. The method for preparing the magnesium oxysulfate cement fireproof board according to claim 5, characterized in that: The amount of light-burned magnesia added is 6 to 8 times the mass of brucite.

8. The method for preparing the magnesium oxysulfate cement fireproof board according to claim 5, characterized in that: The mass ratio of water to light-burned magnesium oxide in the mixed slurry is 65-88:

100.

9. The method for preparing the magnesium oxysulfate cement fireproof board according to claim 7, characterized in that: The particle size of the brucite is 200-325 meshes, and the content of magnesium hydroxide contained in it is 75wt%-90wt%.

10. Use of the magnesium oxysulfate cement fireproof board according to any one of claims 1 to 4 or the magnesium oxysulfate cement fireproof board prepared by the preparation method according to any one of claims 5 to 9 in adsorbing nitrogen oxides in the atmosphere.

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