Modified desulfurized gypsum powder and method for preparing the same

Abstract

The application belongs to the technical field of wall material preparation, and particularly relates to modified desulfurization gypsum powder and a preparation method thereof, which comprises the following steps: modifying VAE latex powder by using a silane hydrolysis solution to obtain modified VAE latex powder; drying desulfurization gypsum powder, placing the desulfurization gypsum powder in an inert atmosphere, adding the silane hydrolysis solution, the modified VAE latex powder, a catalytic solution and an isopropyl alcohol aqueous solution for mixing reaction, and obtaining modified desulfurization gypsum powder after drying; the silane hydrolysis solution is prepared by mixing 1,6-bis(triethoxysilyl)hexane and KH-570 in an acidic ethanol solution for mixing reaction; and the catalytic solution is prepared by mixing PHMS, a platinum-based catalyst and isopropyl alcohol. The application can reduce the water absorption performance of the gypsum board while improving the toughness of the gypsum board, so that the gypsum board has good use stability under vibration working conditions.

Description

Technical Field

[0001] This invention belongs to the field of wall material preparation technology, and particularly relates to a modified desulfurized gypsum powder and its preparation method. Background Technology

[0002] Desulfurized gypsum is an industrial byproduct produced during the limestone-gypsum wet flue gas desulfurization process in coal-fired power plants and other facilities. Its main component is CaSO4·2H2O. It has poor water resistance and insufficient strength stability. When used directly as a wall material, it is prone to problems such as uncontrolled condensation and a sharp drop in strength when exposed to moisture, which does not meet the requirements for wall panels.

[0003] CN104944882A discloses a high-strength water-resistant gypsum composite board and its manufacturing process. The method for preparing modified desulfurized gypsum includes the following steps: phenolic resin, silane coupling agent KH-550, and acrylate carbonate are completely dissolved in ethanol, mixed with desulfurized gypsum powder and an expanding agent, stirred evenly, and dried to constant weight. Through the bridging effect of KH-550, the phenolic resin is effectively coated onto the surface of the desulfurized gypsum. The acrylate carbonate and phenolic resin entangle to form a coating layer on the outside of the desulfurized gypsum, resulting in modified desulfurized gypsum dry powder. This powder is then mixed with the expanding agent and hot-pressed. The melting and fusion of the coating layer connects and fixes adjacent desulfurized gypsum dry powders, resulting in a gypsum board. This gypsum board has a dense structure and low water absorption, effectively improving its stability in humid environments. However, both the phenolic resin and desulfurized gypsum in this gypsum board are brittle phases. Although KH-550 forms a chemical bridge between the two, the interface layer itself has no ductility, resulting in poor toughness of the gypsum board. When used in long-term medium- and high-frequency vibration conditions such as equipment rooms, it cannot dissipate energy through plastic deformation, which makes the gypsum board prone to fatigue and cracking, resulting in poor stability in use. Summary of the Invention

[0004] This invention provides a modified desulfurized gypsum powder and its preparation method. By covalently bridging VAE latex powder and desulfurized gypsum powder through silane hydrolysis liquid and catalyst liquid, the water absorption performance of gypsum board is reduced while the toughness of gypsum board is improved, so that gypsum board has better stability under vibration conditions.

[0005] To solve the above problems, the present invention adopts the following technical solution: A method for preparing modified desulfurized gypsum powder includes the following steps: S1. VAE latex powder is modified by using silane hydrolysate to obtain modified VAE latex powder. S2. After drying the desulfurized gypsum powder, place it in an inert atmosphere, add silane hydrolysis solution, modified VAE latex powder, catalyst solution and isopropanol aqueous solution, mix and react, and then dry to obtain modified desulfurized gypsum powder. The silane hydrolysate is prepared by adding 1,6-bis(triethoxysilyl)hexane and KH-570 to an acidic ethanol solution and reacting them together; the catalyst is prepared by mixing PHMS, a platinum-based catalyst and isopropanol.

[0006] This invention uses a silane hydrolysate to treat VAE latex powder and desulfurized gypsum powder after removing surface free water. The silane hydrolysate contains 1,6-bis(triethoxysilyl)hexane and the hydrolysis products of KH-570 (hereinafter referred to as hydrolysate). The hydrolysate adheres to the surface of VAE latex powder under the action of hydrogen bonding, and to the surface of desulfurized gypsum powder under the action of ionic dipoles and hydrogen bonding. Through the condensation reaction of the hydrolysate, an organic-inorganic network containing carbon-carbon double bonds and hexane chains is formed on VAE latex powder and desulfurized gypsum powder respectively. Under the catalysis of a platinum-based catalyst, the silanol groups of PHMS (polymethylhydrosiloxane) react with the carbon-carbon double bonds of the organic-inorganic network to generate silicon-carbon bonds, covalently bridging adjacent VAE latex powder and desulfurized gypsum powder. Unreacted PHMS is hydrolyzed in the action of isopropanol aqueous solution and reacts with the residual silanol groups in the organic-inorganic network to obtain modified desulfurized gypsum powder.

[0007] During the process of mixing modified desulfurized gypsum powder with aluminum sulfate, water, etc., and then curing it to form gypsum board, the desulfurized gypsum powder hydrates to form dihydrate gypsum crystals, which then connect at the grain boundaries to form a dihydrate gypsum skeleton. The modified VAE latex powder then forms a film and connects to form a flexible network that penetrates the grain boundaries. When the gypsum board is subjected to high-frequency vibration, the hexane chains in the flexible network and the organic-inorganic network dissipate energy through elastic deformation. At the same time, because the desulfurized gypsum powder is covalently bridged with the VAE latex powder through the organic-inorganic cross-linking network and silicon-carbon bonds, the interfacial bonding strength between the dihydrate gypsum skeleton and the flexible network is enhanced, inhibiting the initiation of microcracks caused by interfacial debonding, and improving the toughness and stability of the gypsum board under high vibration conditions. Through the hydrosilylation of PHMS and the condensation reaction of PHMS with silanol groups, a suitable amount of hydrophobic methyl side chains are introduced into the organic-inorganic network, which improves the hydrophobicity of the gypsum board, effectively inhibits water penetration into the gypsum board, reduces the water absorption rate of gypsum, and improves the stability of the gypsum board in humid environments.

[0008] Furthermore, the silane hydrolysate is prepared by adding formic acid solution dropwise to a 90-93 wt% ethanol solution, adjusting the pH to 4.5-5, adding 1,6-bis(triethoxysilyl)hexane and KH-570, and reacting for 1-1.5 h to obtain the silane hydrolysate.

[0009] The pH value of the silane hydrolysate was adjusted by using formic acid solution. Subsequently, the silane hydrolysate was mixed with VAE latex powder and desulfurized gypsum powder respectively. Under the condition of 70-75℃, formic acid is more volatile than water, which makes the pH value of the system rise. This prevents the high concentration of hydrogen ions from having an adverse effect on the dehydration condensation between silanol groups and is conducive to the formation of organic-inorganic network.

[0010] Furthermore, in step S1, the VAE latex powder is modified in the following manner: under nitrogen protection, the VAE latex powder is mixed with silane hydrolysate, heated to 70-75℃, reacted for 1.5-2 hours, and dried under reduced pressure to obtain modified VAE latex powder.

[0011] Further, in step S2, the desulfurized gypsum powder is dried in an environment of 100-105℃ for 1-2 hours, cooled under nitrogen protection, mixed with silane hydrolysis solution, heated to 70-75℃ and reacted for 1-1.5 hours, cooled to 40-45℃, the pressure is adjusted to 7-10 kPa, dried for 2-3 hours and then restored to normal pressure, mixed with modified VAE latex powder, cooled to 25-30℃, mixed with catalytic solution, heated to 65-70℃ and reacted for 1.5-2 hours, mixed with 80-85wt% isopropanol aqueous solution and reacted for 1-1.5 hours, and dried under reduced pressure to obtain modified desulfurized gypsum powder.

[0012] Before adding the catalyst, the system is dried at 40-45℃ and 7-10kPa to remove residual water and free formic acid, thus preventing the platinum-based catalyst from deactivating due to water reaction and avoiding premature hydrolysis of PHMS. This ensures the effectiveness of the reaction between the silane groups and carbon-carbon double bonds of PHMS, achieving bridging between the modified VAE latex powder and desulfurized gypsum powder, and improving the toughness and vibration resistance of the gypsum board.

[0013] Furthermore, the silane hydrolysate, catalyst, and isopropanol aqueous solution are mixed with the desulfurized gypsum powder by atomization spraying; the silane hydrolysate is combined with VAE latex powder by atomization spraying.

[0014] Atomized spraying of silane hydrolysate can promote the uniform adhesion of silane hydrolysate to desulfurized gypsum powder and VAE latex powder, improve the coating uniformity of the organic-inorganic network, and control the density of the organic-inorganic network by controlling the amount of silane hydrolysate added and the reaction time. This allows the dihydrate gypsum crystals formed by dehydrated calcium sulfate and the re-film formed by VAE latex powder to seep out from the pores of the organic-inorganic network and form an interfacial bond during the hydration stage, ensuring the mechanical strength of the gypsum board.

[0015] Furthermore, in step S2, after adding silane hydrolysate and mixing, fumed silica is added and mixed, and then the temperature is raised to 70-75℃ and reacted for 1-1.5 hours.

[0016] Fumed silica is added to desulfurized gypsum powder while the ethanol has not completely evaporated and the surface is still wetted. Through the condensation of silanol groups between fumed silica and hydrolysis products, fumed silica is covalently introduced into the organic-inorganic network on the desulfurized gypsum powder. Fumed silica can maintain stable positioning during the hydration process of desulfurized gypsum powder and does not drift with the slurry. This allows fumed silica to be positioned at the grain boundaries of dihydrate gypsum, and through nano-pinning effect, it deflects and extends the crack propagation path, further improving the vibration resistance of the gypsum board.

[0017] Furthermore, the platinum-based catalyst is Pt(0)-DVTMDS.

[0018] Furthermore, the organic sulfur content of the desulfurized gypsum powder is ≤50mg / kg.

[0019] A modified desulfurized gypsum powder, prepared by the above-mentioned method for preparing modified desulfurized gypsum powder, comprises the following raw materials in parts by weight: 1000-1015 parts of desulfurized gypsum powder, 60-65 parts of modified VAE latex powder, 320-328 parts of silane hydrolysis solution, 7-8 parts of PHMS, 0.03-0.04 parts of platinum-based catalyst, and 25-30 parts of 80-85wt% isopropanol aqueous solution; the silane hydrolysis solution comprises the following raw materials in parts by weight: 1.7-2.1 parts of 1,6-bis(triethoxysilyl)hexane, 9-10 parts of KH-570, and 400-410 parts of 90-93wt% ethanol solution; the modified VAE latex powder comprises the following raw materials in parts by weight: 100-104 parts of VAE latex powder and 60-65 parts of silane hydrolysis solution.

[0020] Furthermore, it also includes 18-22 parts of fumed silica.

[0021] The present invention has the following beneficial effects: The silane hydrolysate prepared in this invention contains hydrolysis products, which can form an organic-inorganic network containing carbon-carbon double bonds and hexane chains on VAE latex powder to obtain modified VAE latex powder. It can also form an organic-inorganic network containing carbon-carbon double bonds and hexane chains on desulfurized gypsum powder. Through the catalysis of a platinum-based catalyst, the carbon-carbon double bonds on the organic-inorganic network react with the silanol groups of PHMS, covalently bridging adjacent modified latex powder and desulfurized gypsum powder. The unreacted PHMS is hydrolyzed in the action of isopropanol aqueous solution and reacts with the silanol groups of the organic-inorganic network to obtain modified desulfurized gypsum powder. The gypsum board prepared from the desulfurized gypsum powder of this invention can dissipate energy under high vibration conditions through the flexible network formed by VAE latex powder and the elastic deformation of hexane chains in the organic-inorganic network. At the same time, due to the covalent bridging of organic-inorganic crosslinking network and silicon-carbon bonds between VAE latex powder and desulfurized gypsum powder, the interfacial bonding strength between the flexible network formed by VAE latex powder and the dihydrate gypsum skeleton formed by desulfurized gypsum powder is enhanced, thereby improving the vibration resistance of the gypsum board. The introduction of hydrophobic methyl groups into the modified desulfurized gypsum powder through the hydrosilylation of PHMS and the condensation reaction of PHMS with silanol groups improves the stability of the gypsum board in humid environments. Detailed Implementation

[0022] Example 1 Add 1 wt% formic acid solution dropwise to 400 g of 90 wt% ethanol solution to adjust the pH to 4.5. Add 1.8 g of 1,6-bis(triethoxysilyl)hexane and 10 g of KH-570 (γ-methacryloyloxypropyltrimethoxysilane) and stir at 300 rpm for 1 h to obtain a silane hydrolysate. Under nitrogen protection, mix 7 g of PHMS (polymethylhydrosiloxane, Mn=600 g / mol), 0.03 g of Pt(0)-DVTMDS (platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex) and 180 g of isopropanol and stir at 300 rpm for 5 min to obtain a catalyst solution. Add 20 g of fumed silica with a particle size of 100 nm to 20 g of anhydrous ethanol and sonicate at 50 W for 20 min to obtain a silica suspension.

[0023] 100g of VAE (vinyl acetate-acetic acid copolymer, ethylene content 18%) latex powder with a particle size of 2μm was placed in a mixer. Under nitrogen protection, 60g of silane hydrolysate was atomized and sprayed in at 600rpm with stirring. After spraying, the mixture was mixed at 600rpm for 10min, heated to 70℃, stirred at 100rpm for 2h, and then placed in an environment of 45℃ and 10kPa with stirring at 300rpm for 1h to obtain modified VAE latex powder.

[0024] 1000g of desulfurized gypsum powder with a particle size of 80 mesh was dried at 105℃ for 1 hour, then transferred to a mixer and cooled to room temperature under nitrogen protection. 320g of silane hydrolysate was atomized and sprayed in under stirring at 200 rpm. After spraying, the mixture was stirred at 200 rpm for 30 minutes. Silica suspension was slowly added under stirring at 600 rpm. After addition, the mixture was stirred at 600 rpm for 25 minutes, heated to 70℃, stirred at 400 rpm for 1 hour, cooled to 40℃, and the pressure was adjusted to 7 kPa. The mixture was stirred at 300 rpm for 2 hours, then returned to normal pressure. 60g of modified VAE latex powder was slowly added under stirring at 400 rpm. After addition, the mixture was stirred at 400 rpm for 10 minutes, cooled to 30℃, and catalytic solution was atomized and sprayed in under stirring at 300 rpm. After spraying, the mixture was stirred at 300 rpm for 20 minutes, heated and maintained at 70℃, mixed at 300 rpm for 1.5 hours, and then atomized and sprayed in 25g of... After spraying in an 80wt% isopropanol aqueous solution, stir at 300rpm for 1h, place in an environment of 30℃ and 10kPa, and stir at 200rpm for 3h to obtain modified desulfurized gypsum powder.

[0025] The desulfurized gypsum powder used in this embodiment has an organic sulfur content of 50 mg / kg.

[0026] Example 2 Add 1 wt% formic acid solution dropwise to 410 g of 90 wt% ethanol solution to adjust the pH to 4.5. Add 1.7 g of 1,6-bis(triethoxysilyl)hexane and 9 g of KH-570 and stir at 300 rpm for 1 h to obtain silane hydrolysis solution. Under nitrogen protection, mix 7.5 g of PHMS (Mn=600 g / mol), 0.035 g of Pt(0)-DVTMDS and 180 g of isopropanol and stir at 300 rpm for 5 min to obtain catalytic solution. Add 18 g of fumed silica with a particle size of 100 nm to 20 g of anhydrous ethanol and sonicate at 50 W for 20 min to obtain silica suspension.

[0027] 102g of VAE (18% ethylene content) latex powder with a particle size of 2μm was placed in a mixer. Under nitrogen protection, 62g of silane hydrolysate was atomized and sprayed in at 600rpm with stirring. After spraying, the mixture was mixed at 600rpm for 10min, heated to 70℃, stirred at 100rpm for 2h, and then placed in an environment of 45℃ and 10kPa with stirring at 300rpm for 1h to obtain modified VAE latex powder.

[0028] 1010g of desulfurized gypsum powder with a particle size of 80 mesh was dried at 105℃ for 1 hour, then transferred to a mixer and cooled to room temperature under nitrogen protection. 326g of silane hydrolysate was atomized and sprayed in under stirring at 200 rpm. After spraying, the mixture was stirred at 200 rpm for 30 minutes. Silica suspension was slowly added under stirring at 600 rpm. After addition, the mixture was stirred at 600 rpm for 25 minutes, heated to 70℃, stirred at 400 rpm for 1 hour, cooled to 40℃, and the pressure was adjusted to 7 kPa. The mixture was stirred at 300 rpm for 2 hours, then returned to normal pressure. 60g of modified VAE latex powder was slowly added under stirring at 400 rpm. After addition, the mixture was stirred at 400 rpm for 10 minutes, cooled to 30℃, and catalytic liquid was atomized and sprayed in under stirring at 300 rpm. After spraying, the mixture was stirred at 300 rpm for 20 minutes, heated and maintained at 70℃, mixed at 300 rpm for 1.5 hours, and then atomized and sprayed in 27g of... After spraying in an 80wt% isopropanol aqueous solution, stir at 300rpm for 1h, place in an environment of 30℃ and 10kPa, and stir at 200rpm for 3h to obtain modified desulfurized gypsum powder.

[0029] The desulfurized gypsum powder used in this embodiment has an organic sulfur content of 50 mg / kg.

[0030] Example 3 Add 1 wt% formic acid solution dropwise to 400 g of 93 wt% ethanol solution to adjust the pH to 4.8. Add 2 g of 1,6-bis(triethoxysilyl)hexane and 9.5 g of KH-570 and stir at 300 rpm for 1.2 h to obtain silane hydrolysis solution. Under nitrogen protection, mix 8 g of PHMS (Mn=600 g / mol), 0.04 g of Pt(0)-DVTMDS and 180 g of isopropanol and stir at 300 rpm for 5 min to obtain catalytic solution. Add 22 g of fumed silica with a particle size of 100 nm to 20 g of anhydrous ethanol and sonicate at 50 W for 20 min to obtain silica suspension.

[0031] 104g of VAE (18% ethylene content) latex powder with a particle size of 2μm was placed in a mixer. Under nitrogen protection, 63g of silane hydrolysate was atomized and sprayed in at 600rpm with stirring. After spraying, the mixture was mixed at 600rpm for 10min, heated to 75℃, stirred at 100rpm for 1.5h, and then placed in an environment of 45℃ and 10kPa with stirring at 300rpm for 1h to obtain modified VAE latex powder.

[0032] 1015g of desulfurized gypsum powder with a particle size of 80 mesh was dried at 100℃ for 1.5h, transferred to a mixer, and cooled to room temperature under nitrogen protection. 322g of silane hydrolysate was atomized and sprayed in under stirring at 200rpm. After spraying, the mixture was stirred at 200rpm for 30min. Silica suspension was slowly added under stirring at 600rpm. After addition, the mixture was stirred at 600rpm for 25min, heated to 75℃, stirred at 400rpm for 1.5h, cooled to 45℃, and the pressure was adjusted to 10kPa. The mixture was stirred at 300rpm for 3h, and then returned to normal pressure. 62g of modified VAE latex powder was slowly added under stirring at 400rpm. After addition, the mixture was stirred at 400rpm for 10min, cooled to 25℃, and catalytic liquid was atomized and sprayed in under stirring at 300rpm. After spraying, the mixture was stirred at 300rpm for 20min, heated and maintained at 68℃, mixed at 300rpm for 1.8h, and then atomized and sprayed in 30g of... After spraying in an 82wt% isopropanol aqueous solution, stir at 300rpm for 1.3h, place in an environment of 30℃ and 10kPa, and stir at 200rpm for 3h to obtain modified desulfurized gypsum powder.

[0033] The desulfurized gypsum powder used in this embodiment has an organic sulfur content of 40 mg / kg.

[0034] Example 4 Add 1 wt% formic acid solution dropwise to 408 g of 93 wt% ethanol solution to adjust the pH to 4.8. Add 2.1 g of 1,6-bis(triethoxysilyl)hexane and 9.7 g of KH-570 and stir at 300 rpm for 1.2 h to obtain silane hydrolysis solution. Under nitrogen protection, mix 7.5 g of PHMS (Mn=600 g / mol), 0.035 g of Pt(0)-DVTMDS and 180 g of isopropanol and stir at 300 rpm for 5 min to obtain catalytic solution. Add 19 g of fumed silica with a particle size of 100 nm to 20 g of anhydrous ethanol and sonicate at 50 W for 20 min to obtain silica suspension.

[0035] 103g of VAE (18% ethylene content) latex powder with a particle size of 2μm was placed in a mixer. Under nitrogen protection, 65g of silane hydrolysate was atomized and sprayed in at 600rpm with stirring. After spraying, the mixture was mixed at 600rpm for 10min, heated to 75℃, stirred at 100rpm for 1.5h, and then placed in an environment of 45℃ and 10kPa with stirring at 300rpm for 1h to obtain modified VAE latex powder.

[0036] 1000g of desulfurized gypsum powder with a particle size of 80 mesh was dried at 100℃ for 1.5h, transferred to a mixer, and cooled to room temperature under nitrogen protection. 325g of silane hydrolysate was atomized and sprayed in under stirring at 200rpm. After spraying, the mixture was stirred at 200rpm for 30min. Silica suspension was slowly added under stirring at 600rpm. After addition, the mixture was stirred at 600rpm for 25min, heated to 75℃, stirred at 400rpm for 1.5h, cooled to 45℃, and the pressure was adjusted to 10kPa. The mixture was stirred at 300rpm for 3h, and then returned to normal pressure. 62g of modified VAE latex powder was slowly added under stirring at 400rpm. After addition, the mixture was stirred at 400rpm for 10min, cooled to 25℃, and catalytic liquid was atomized and sprayed in under stirring at 300rpm. After spraying, the mixture was stirred at 300rpm for 20min, heated and maintained at 68℃, mixed at 300rpm for 1.8h, and then atomized and sprayed in 28g of... After spraying in an 82wt% isopropanol aqueous solution, stir at 300rpm for 1.3h, place in an environment of 30℃ and 10kPa, and stir at 200rpm for 3h to obtain modified desulfurized gypsum powder.

[0037] The desulfurized gypsum powder used in this embodiment has an organic sulfur content of 40 mg / kg.

[0038] Example 5 Add 1 wt% formic acid solution dropwise to 405 g of 91 wt% ethanol solution to adjust the pH to 5, add 2 g of 1,6-bis(triethoxysilyl)hexane and 10 g of KH-570, stir at 300 rpm for 1.5 h to obtain silane hydrolysis solution; under nitrogen protection, mix 8 g of PHMS (Mn=600 g / mol), 0.04 g of Pt(0)-DVTMDS and 180 g of isopropanol, stir at 300 rpm for 5 min to obtain catalytic solution; add 21 g of fumed silica with a particle size of 100 nm to 20 g of anhydrous ethanol, and sonicate at 50 W for 20 min to obtain silica suspension.

[0039] 104g of VAE (18% ethylene content) latex powder with a particle size of 2μm was placed in a mixer. Under nitrogen protection, 60g of silane hydrolysate was atomized and sprayed in at 600rpm with stirring. After spraying, the mixture was mixed at 600rpm for 10min, heated to 72℃, stirred at 100rpm for 1.7h, and then placed in an environment of 45℃ and 10kPa with stirring at 300rpm for 1h to obtain modified VAE latex powder.

[0040] 1010g of desulfurized gypsum powder with a particle size of 80 mesh was dried at 102℃ for 2 hours, then transferred to a mixer and cooled to room temperature under nitrogen protection. 328g of silane hydrolysate was atomized and sprayed in under stirring at 200rpm. After spraying, the mixture was stirred at 200rpm for 30 minutes. Silica suspension was slowly added under stirring at 600rpm. After addition, the mixture was stirred at 600rpm for 25 minutes, heated to 72℃, stirred at 400rpm for 1.2 hours, cooled to 42℃, and the pressure was adjusted to 8kPa. The mixture was stirred at 300rpm for 2.5 hours, and then returned to normal pressure. 65g of modified VAE latex powder was slowly added under stirring at 400rpm. After addition, the mixture was stirred at 400rpm for 10 minutes, cooled to 28℃, and catalytic liquid was atomized and sprayed in under stirring at 300rpm. After spraying, the mixture was stirred at 300rpm for 20 minutes, heated and maintained at 65℃, mixed at 300rpm for 2 hours, and then atomized and sprayed in 30g of... After spraying in an 85wt% isopropanol aqueous solution, stir at 300rpm for 1.5h, place in an environment of 30℃ and 10kPa, and stir at 200rpm for 3h to obtain modified desulfurized gypsum powder.

[0041] The desulfurized gypsum powder used in this embodiment has an organic sulfur content of 45 mg / kg.

[0042] Example 6 Add 1 wt% formic acid solution dropwise to 405 g of 91 wt% ethanol solution to adjust the pH to 5, then add 2 g of 1,6-bis(triethoxysilyl)hexane and 10 g of KH-570, and stir at 300 rpm for 1.5 h to obtain silane hydrolysis solution; under nitrogen protection, mix 8 g of PHMS (Mn=600 g / mol), 0.04 g of Pt(0)-DVTMDS and 180 g of isopropanol, and stir at 300 rpm for 5 min to obtain catalytic solution.

[0043] 104g of VAE (18% ethylene content) latex powder with a particle size of 2μm was placed in a mixer. Under nitrogen protection, 60g of silane hydrolysate was atomized and sprayed in at 600rpm with stirring. After spraying, the mixture was mixed at 600rpm for 10min, heated to 72℃, stirred at 100rpm for 1.7h, and then placed in an environment of 45℃ and 10kPa with stirring at 300rpm for 1h to obtain modified VAE latex powder.

[0044] 1010g of desulfurized gypsum powder with a particle size of 80 mesh was dried at 102℃ for 2 hours, then transferred to a mixer and cooled to room temperature under nitrogen protection. 328g of silane hydrolysate was atomized and sprayed in under stirring at 200rpm. After spraying, the mixture was stirred at 200rpm for 30 minutes, heated to 72℃, stirred at 400rpm for 1.2 hours, cooled to 42℃, and the pressure was adjusted to 8kPa. The mixture was stirred at 300rpm for 2.5 hours, and then returned to normal pressure. 65g of modified VAE latex powder was slowly added under stirring at 400rpm. After addition, the mixture was stirred at 400rpm for 10 minutes, cooled to 28℃, and catalytic liquid was atomized and sprayed in under stirring at 300rpm. After spraying, the mixture was stirred at 300rpm for 20 minutes, heated and maintained at 65℃, mixed at 300rpm for 2 hours, and then atomized and sprayed in 30g of... After spraying in an 85wt% isopropanol aqueous solution, stir at 300rpm for 1.5h, place in an environment of 30℃ and 10kPa, and stir at 200rpm for 3h to obtain modified desulfurized gypsum powder.

[0045] The desulfurized gypsum powder used in this embodiment has an organic sulfur content of 45 mg / kg.

[0046] The present invention also includes comparative examples and related experiments.

[0047] Comparative Example 1 The difference between this comparative example and Example 5 is that 1,6-bis(triethoxysilyl)hexane was not added to the silane hydrolysate. The remaining operation steps and reaction conditions were the same as in Example 5, and modified desulfurized gypsum powder was obtained.

[0048] Comparative Example 2 The difference between this comparative example and Example 5 is that KH-570 was not added to the silane hydrolysate. The remaining operation steps and reaction conditions are the same as in Example 5, and modified desulfurized gypsum powder is obtained.

[0049] Comparative Example 3 The difference between this comparative example and Example 5 is that the catalyst solution is replaced with a mixture of PHMS and isopropanol, while the remaining operation steps and reaction conditions are the same as in Example 5, resulting in modified desulfurized gypsum powder.

[0050] Comparative Example 4 The difference between this comparative example and Example 5 is that the catalyst solution is replaced with a mixture of platinum-based catalyst and isopropanol. The remaining operation steps and reaction conditions are the same as in Example 5, and modified desulfurized gypsum powder is obtained.

[0051] The modified desulfurized gypsum powder prepared in each example and comparative example was mixed with water and aluminum sulfate in a mass ratio of 100:65:2 to prepare gypsum boards with a thickness of 12 mm. The following tests were conducted on each gypsum board: Vibration performance test Referring to GB / T 17669.3-2023 standard, a universal testing machine was used to test each gypsum board, and the flexural strength R0 (MPa) of each gypsum board was recorded. Each gypsum board was fixed on a vibration testing machine, and vibration with a continuously increasing frequency was applied to each gypsum board. The bending resonance frequency f0 of each gypsum board was measured. The vibration was maintained at a constant frequency, with a pause every 0.5 hours. The time t (h) at which the first crack with a width ≥ 0.1 mm appeared was recorded. After 8 hours of vibration, vibration with a continuously increasing frequency was applied to each gypsum board, and the bending resonance frequency f1 of the gypsum board at this time was measured according to the following formula:

[0052] Calculate the vibration frequency attenuation rate (%); The flexural strength R of each gypsum board after 8 hours of vibration was tested using a universal testing machine. n (MPa), as shown in Table 1.

[0053] Table 1

[0054] Water absorption test The water contact angle θ (°) of each gypsum board was tested according to GB / T 9775 standard. Each gypsum board was dried at 40℃ to constant weight, and its mass m0 was measured. After immersion in distilled water for 24 hours, the surface moisture was wiped off, and its mass m1 was measured. The mass m1 was measured according to the following formula:

[0055] The water absorption rate W (%) of each gypsum board was calculated, as shown in Table 2.

[0056] Table 2

[0057] According to Tables 1 and 2, after 8 hours of vibration, the gypsum board made from the desulfurized gypsum powder in Example 5... Smaller than Example 6, R nThe vibration resistance of the gypsum board is greater than that of Example 6, and no cracks appeared, indicating that the addition of fumed silica can deflect and prolong the crack propagation path through its nano-pinning effect, thereby improving the vibration resistance of the gypsum board. The vibration resistance of the gypsum board made from desulfurized gypsum powder in Example 5 is better than that of Comparative Example 1, indicating that 1,6-bis(triethoxysilyl)hexane can form an organic-inorganic network containing flexible hexane chains on desulfurized gypsum powder and VAE latex powder, introducing flexible spacers between desulfurized gypsum and VAE latex powder, improving the toughness of the gypsum board and its stability under high vibration conditions. The vibration resistance of the gypsum board made from desulfurized gypsum powder in Example 5 is better than that of the Comparative Example. Examples 2 and 3 demonstrate that the addition of KH-570 and platinum-based catalyst enables covalent bridging of the organic-inorganic network on the surface of the modified VAE latex powder and desulfurized gypsum powder, inhibiting the debonding of the flexible network and dihydrate gypsum crystal skeleton, thereby inhibiting the initiation of stress defect sources and improving the toughness of gypsum board and its stability under high vibration conditions. In Example 5, the water contact angle of the gypsum board made from desulfurized gypsum powder is greater than that of Comparative Example 4, and the water absorption rate is less than that of Comparative Example 4, indicating that PHMS can effectively increase the water contact angle of the gypsum board through its hydrophobic methyl groups, inhibiting water penetration into the gypsum board and improving the stability of the gypsum board in humid environments.

Claims

1. A method for preparing a modified desulfurized gypsum powder, characterized by, Includes the following steps: S1. VAE latex powder is modified by using silane hydrolysate to obtain modified VAE latex powder. S2. After drying the desulfurized gypsum powder, place it in an inert atmosphere, add silane hydrolysis solution, modified VAE latex powder, catalyst solution and isopropanol aqueous solution, mix and react, and then dry to obtain modified desulfurized gypsum powder. The silane hydrolysate is prepared by adding 1,6-bis(triethoxysilyl)hexane and KH-570 to an acidic ethanol solution and reacting them together; the catalyst is prepared by mixing PHMS, a platinum-based catalyst and isopropanol.

2. The method of claim 1, wherein the modified desulfurized gypsum powder is prepared by adding a dispersant to the desulfurized gypsum powder, and then adding a modifier to the desulfurized gypsum powder. The silane hydrolysate is prepared by adding formic acid solution dropwise to a 90-93 wt% ethanol solution, adjusting the pH to 4.5-5, adding 1,6-bis(triethoxysilyl)hexane and KH-570, and reacting for 1-1.5 h to obtain the silane hydrolysate.

3. The method of claim 2, wherein the modified desulfurized gypsum powder is prepared by adding a dispersant to the desulfurized gypsum powder, and then adding a modifier to the desulfurized gypsum powder. In step S1, the VAE latex powder is modified in the following way: under nitrogen protection, the VAE latex powder is mixed with silane hydrolysate, heated to 70-75℃, reacted for 1.5-2 hours, and dried under reduced pressure to obtain modified VAE latex powder.

4. The method of claim 2, wherein the modified desulfurized gypsum powder is prepared by adding a dispersant to the desulfurized gypsum powder, and then adding a modifier to the desulfurized gypsum powder. In step S2, the desulfurized gypsum powder is dried in an environment of 100-105℃ for 1-2 hours, cooled under nitrogen protection, mixed with silane hydrolysis solution, heated to 70-75℃ and reacted for 1-1.5 hours, cooled to 40-45℃, the pressure is adjusted to 7-10 kPa, dried for 2-3 hours and then restored to normal pressure, mixed with modified VAE latex powder, cooled to 25-30℃, mixed with catalytic solution, heated to 65-70℃ and reacted for 1.5-2 hours, mixed with 80-85wt% isopropanol aqueous solution and reacted for 1-1.5 hours, and dried under reduced pressure to obtain modified desulfurized gypsum powder.

5. The method of claim 4, wherein the modified desulfurized gypsum powder is prepared by adding a dispersant to the desulfurized gypsum powder, and then adding a modifier to the desulfurized gypsum powder. The silane hydrolysate, catalyst, and isopropanol aqueous solution are mixed with the desulfurized gypsum powder by atomization spraying; the silane hydrolysate is combined with VAE latex powder by atomization spraying.

6. The method of claim 4, wherein the modified desulfurized gypsum powder is prepared by adding a dispersant to the desulfurized gypsum powder, and then adding a modifier to the desulfurized gypsum powder. In step S2, after adding silane hydrolysate and mixing, fumed silica is added and mixed, and then the temperature is raised to 70-75℃ and reacted for 1-1.5 hours.

7. The method for preparing modified desulfurized gypsum powder according to claim 1, characterized in that, The platinum-based catalyst is Pt(0)-DVTMDS.

8. The method for preparing modified desulfurized gypsum powder according to claim 1, characterized in that, The organic sulfur content of the desulfurized gypsum powder is ≤50mg / kg.

9. A modified desulfurized gypsum powder, characterized in that, The modified desulfurized gypsum powder is prepared by the method according to any one of claims 1-8, comprising the following raw materials in parts by weight: 1000-1015 parts of desulfurized gypsum powder, 60-65 parts of modified VAE latex powder, 320-328 parts of silane hydrolysis solution, 7-8 parts of PHMS, 0.03-0.04 parts of platinum-based catalyst, and 25-30 parts of 80-85 wt% isopropanol aqueous solution; wherein the silane hydrolysis solution comprises the following raw materials in parts by weight: 1.7-2.1 parts of 1,6-bis(triethoxysilyl)hexane, 9-10 parts of KH-570, and 400-410 parts of 90-93 wt% ethanol solution; wherein the modified VAE latex powder comprises the following raw materials in parts by weight: 100-104 parts of VAE latex powder and 60-65 parts of silane hydrolysis solution.

10. The modified desulfurized gypsum powder according to claim 9, characterized in that, It also includes 18-22 parts of fumed silica.

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