A high-performance weather-resistant tile adhesive and its preparation method

Abstract

This invention belongs to the technical field of resource utilization of bulk industrial solid waste and high-performance green building materials, and particularly relates to a high-performance weather-resistant tile adhesive and its preparation method. The tile adhesive comprises: 55-70 parts of micro-nano short columnar α-hemihydrate gypsum powder; 22-28 parts of quartz sand; 6-12 parts of high-alumina cement; and 4-7 parts of interface-modifying composite additives. The particle size of the micro-nano short columnar α-hemihydrate gypsum powder is 180-220 mesh. The tile adhesive obtained by this invention has improved water resistance, bonding strength, and durability, enabling stable use in extreme environments such as humidity, low temperature, and outdoor freeze-thaw cycles.

Description

Technical Field

[0001] This invention belongs to the technical field of resource utilization of bulk industrial solid waste and high-performance green building materials, and in particular relates to a high-performance weather-resistant ceramic tile adhesive and its preparation method. Background Technology

[0002] The flue gas desulfurization process of coal-fired power plants produces more than 120 million tons of desulfurized gypsum annually. Its main component is calcium sulfate dihydrate. However, the impurity content of the raw desulfurized gypsum is extremely high, containing a large amount of soluble chloride ions, alkali metal ions, heavy metals, unburned carbon particles and organic matter. Using conventional resource recovery methods, it can only be used as a cement retarder and a raw material for low-end gypsum board, with very low added value and limited market absorption capacity. It not only occupies a large amount of land resources, but also easily causes environmental risks such as soil salinization and groundwater pollution, becoming a common problem in solid waste treatment in the power industry. At the same time, the market for building tile adhesives has long been monopolized by cement-based products. Traditional cement-based tile adhesives rely on high-grade silicate cement, which has high energy consumption and carbon emissions during the production process. They also have fatal defects such as a sharp drop in adhesion to damp substrates, easy hollowing and detachment, poor durability, and a short construction window. The small amount of gypsum-based tile adhesives on the market are all made from natural gypsum or ordinary chemical gypsum, which has high raw material costs and has not solved the core problem of poor water resistance of gypsum. They can only be used on dry interior walls and cannot be adapted to complex scenarios such as outdoor, bathroom, and balcony.

[0003] Current technologies for preparing tile adhesives mainly fall into two categories, both of which suffer from inherent flaws that cannot be overcome: The first category is traditional cement-based tile adhesive technology, which uses silicate cement as the sole binding material. Workability is adjusted only through ordinary admixtures, with no solid waste utilization process. This results in high carbon emissions, high costs, and extremely poor adaptability to humid environments, leading to tile detachment with long-term use. The second category is ordinary gypsum-based building material technology. Some technologies attempt to use desulfurized gypsum after simple processing to prepare building mortar. However, this involves only a single water washing process for impurity removal, which is incomplete. The hydrothermal conversion process is a conventional high-temperature and high-pressure process, resulting in α-hemihydrate gypsum with needle-like and rod-like coarse crystals, an unbalanced aspect ratio, and extremely low density. This type of gypsum can only be used for low-end interior wall plastering and cannot meet the high strength and high weather resistance requirements of tile adhesives. Furthermore, there is no targeted interface modification technology, and the water resistance of the tile adhesive is completely substandard.

[0004] The existing technologies for preparing tile adhesives have some problems as follows: (1) There are disruptive defects in performance: the bonding strength of cement-based tile adhesive on damp substrates decreases by more than 50%, and the strength is almost lost after outdoor freeze-thaw and heat aging. The construction drying time is short, and ultra-thin laying is prone to hollowing. Ordinary gypsum-based tile adhesive products have extremely poor water resistance, soften when exposed to water, and can only be used on dry interior walls. The application scenarios are extremely limited and cannot meet the paving needs of modern buildings in all scenarios.

[0005] (2) Serious disconnect between resources and environmental protection: The large amount of solid waste from desulfurized gypsum has not been effectively disposed of, and natural gypsum and cement have been consumed in large quantities. The mining of natural gypsum has damaged the ecology. The stockpiling of desulfurized gypsum has caused serious waste of resources and secondary pollution. Conventional low-value-added utilization cannot solve the fundamental problem.

[0006] (3) Lack of competitiveness in terms of technology and cost: Existing gypsum-based tile adhesive products use high-temperature calcination process, which consumes a lot of energy and has high raw material costs; cement-based tile adhesive products have high maintenance costs and extremely low cost-effectiveness throughout the entire life cycle; no technology can achieve the four-fold synergy of "solid waste disposal + low-carbon production + high-end performance + low cost".

[0007] (4) No original breakthroughs in technology: The existing technologies are all simple combinations of conventional processes. The desulfurized gypsum is not thoroughly cleaned, the crystal form is not controlled, and the interface is not modified. These are conventional technical means in this field, with no non-obvious innovations and no technical barriers.

[0008] How to achieve integrated innovation of "deep purification of solid waste - precise control of micro-nano crystal form - weather resistance modification of interface", and to make exclusive process design for the characteristics of impurities contained in desulfurized gypsum, so as to solve the century-old pain point of water resistance, freeze resistance and aging resistance of gypsum-based tile adhesive, is a direction worth studying. Summary of the Invention

[0009] This invention addresses some shortcomings of existing technologies by providing a high-performance weather-resistant tile adhesive and its preparation method. The resulting tile adhesive exhibits improved water resistance, bonding strength, and durability, enabling stable use in extreme environments such as humidity, low temperatures, and outdoor freeze-thaw cycles. Through the development of a dedicated deep purification and micro / nano crystal structure control process for desulfurized gypsum, low-quality solid waste is transformed into high-end cementitious materials, achieving high-value and large-scale disposal of bulk solid waste. This invention overturns the traditional high-carbon, high-energy-consumption production model of tile adhesives, achieving zero wastewater, zero solid waste, and low-carbon emissions throughout the entire process. It breaks the industry's high-cost status quo for high-end tile adhesives by replacing expensive raw materials with solid waste, achieving a synergy between high performance and low cost, and enhancing core market competitiveness.

[0010] To achieve the above objectives, the present invention provides the following technical solution: In the first aspect, a high-performance weather-resistant tile adhesive is provided, comprising the following components in parts by weight: Micro-nano short columnar α-hemihydrate gypsum powder, 55-70 parts (e.g., 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 65 parts); Quartz sand (120-200 mesh continuously graded), 22-28 parts (e.g., 24 parts, 25 parts, 26 parts). High-alumina cement, 6-12 parts (e.g., 7 parts, 8 parts, 9 parts, 10 parts); Interface-modifying composite additive, 4-7 parts (e.g., 5 parts, 5.5 parts, 6 parts, 6.5 parts).

[0011] According to the high-performance weather-resistant tile adhesive provided by the present invention, in some embodiments, the interface-modified composite additive comprises the following components in parts by weight (based on the total amount of the interface-modified composite additive): Water-reducing agent, 0.6-1.8 parts (e.g., 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.2 parts, 1.4 parts, 1.5 parts, 1.6 parts); Water-retaining agent, 0.6-1.8 parts (e.g., 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, 1.2 parts, 1.4 parts, 1.5 parts, 1.6 parts); Organosilicon water-repellent agent, 0.4-1.2 parts (e.g., 0.5 parts, 0.6 parts, 0.8 parts, 1.0 parts); Silane coupling agent, 0.3-0.8 parts (e.g., 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.75 parts); Retarder, 0.2-0.9 parts (e.g., 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts); Defoamer, 0.1-0.8 parts (e.g., 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts).

[0012] In some implementations, the water-reducing agent is a polycarboxylate water-reducing agent.

[0013] In some embodiments, the water-retaining agent is a low-viscosity methylcellulose ether. Its viscosity can be between 400-600 mPa·s, for example, 420 mPa·s, 450 mPa·s, 500 mPa·s, 550 mPa·s, or 580 mPa·s.

[0014] In some embodiments, the retarder is a hydroxycarboxylic acid salt or a sodium diethylenetriaminepentaacetate.

[0015] In some embodiments, the defoamer is an organically modified siloxane powder.

[0016] In a second aspect, a method for preparing the high-performance weather-resistant tile adhesive as described above is provided, comprising the following steps: (1) Pretreatment of desulfurized gypsum The desulfurized gypsum is subjected to gradient countercurrent water washing (e.g., by a vacuum dehydration device), and then the product obtained from the initial washing is subjected to hydrocyclone washing. The gypsum slurry after hydrocyclone washing is then subjected to electrophoretic desalination to obtain purified desulfurized gypsum. (2) Micro / nano crystal transformation reaction The purified desulfurized gypsum is mixed with a crystallization agent, and the reaction transforms the desulfurized gypsum into micro-nano-scale short columnar α-hemihydrate gypsum. (3) Preparation of tile adhesive The prepared micro-nano-scale short columnar α-hemihydrate gypsum powder is mixed evenly with quartz sand and high-alumina cement at low speed. Then, an interface-modified composite additive is added and the mixture is stirred evenly at high speed to obtain tile adhesive.

[0017] According to the preparation method provided by the present invention, in some embodiments, the purity of the purified desulfurized gypsum obtained in step (1) is 99.5% or higher (e.g., 99.6%, 99.8%, 99.9%), and the chloride ion content is controlled at 200 ppm or lower (e.g., 180 ppm, 150 ppm, 120 ppm, 100 ppm, 80 ppm, 50 ppm, 40 ppm, 30 ppm, 20 ppm, 10 ppm).

[0018] In some implementation schemes, the reaction in step (2) adopts a gradient temperature and pressure control process, including: first heating to 115-130℃ (e.g., 120℃, 125℃) at a rate of 5℃ / min, and pre-reacting at 0.3-0.5MPa (e.g., 0.4MPa) for 20-45min (e.g., 30min, 40min), then heating to 160-200℃ (e.g., 170℃, 180℃, 190℃) at a uniform rate, and holding the reaction at 0.6-1.0MPa (e.g., 0.65MPa, 0.7MPa, 0.8MPa, 0.9MPa) for 2-3.5 hours (e.g., 2.5 hours, 3.0 hours).

[0019] In some embodiments, the crystallization agent in step (2) is a compound mixture of ammonium citrate and silane coupling agent. Preferably, the mass ratio of ammonium citrate to silane coupling agent is in the range of 1:(0.5-1.2), for example, 1:0.6, 1:0.8, 1:0.9, 1:1, 1:1.1.

[0020] In some implementations, the amount of the crystallizing agent in step (2) is 0.05wt%-0.12wt% of the dry basis weight of the desulfurized gypsum (e.g., 0.06wt%, 0.08wt%, 0.1wt%, 0.11wt%).

[0021] In some embodiments, the micro-nano-scale short columnar α-hemihydrate gypsum powder obtained in step (2) has a particle size of 180-220 mesh, a purity greater than or equal to 99.5% (e.g., 99.5-99.9%), and a chloride ion content less than or equal to 200 ppm (e.g., 180 ppm, 150 ppm, 100 ppm, 80 ppm, 50 ppm, 40 ppm, 30 ppm, 20 ppm, 10 ppm). In some implementations, the aspect ratio of the micro-nano-scale short columnar α-hemihydrate gypsum is between 1:1.1 and 1:1.6 (e.g., 1:1.2, 1:1.4, 1:1.5).

[0022] In some implementations, the low-speed stirring in step (3) is performed at a speed of 10-20 r / min (e.g., 12 r / min, 14 r / min, 15 r / min, 18 r / min) and for a stirring time of 20-60 min (e.g., 25 min, 30 min, 45 min).

[0023] In some embodiments, the high-speed stirring speed is 40-55 r / min (e.g., 42 r / min, 45 r / min, 48 r / min, 50 r / min), and the stirring time is 30-60 min (e.g., 35 min, 40 min, 45 min).

[0024] According to the preparation method provided by the present invention, in some embodiments, the interface-modified composite additive comprises: Water-reducing agent, 0.6-1.8 parts; Water-retaining agent, 0.6-1.8 parts; Organosilicon water-repellent agent, 0.4-1.2 parts; Silane coupling agent, 0.3-0.8 parts; Retarder, 0.2-0.9 parts; Defoamer, 0.1-0.8 parts.

[0025] In some implementations, the water-reducing agent is a polycarboxylate water-reducing agent.

[0026] In some embodiments, the water-retaining agent is a low-viscosity methylcellulose ether.

[0027] In some embodiments, the retarder is a hydroxycarboxylic acid salt or a sodium diethylenetriaminepentaacetate.

[0028] In some embodiments, the defoamer is an organically modified siloxane powder.

[0029] This invention focuses on "transforming solid waste into high-end raw materials." It innovatively employs a coupled impurity removal process of "gradient countercurrent water washing-electrophoretic deep impurity removal" for desulfurized gypsum to thoroughly remove harmful impurities from the source of raw materials. Then, through the synergistic effect of "gradient temperature and pressure + exclusive composite crystallization agent," it achieves the directional and precise conversion of dihydrate calcium sulfate into micro-nano-scale short columnar α-hemihydrate gypsum, completely changing the crystal defects of traditional gypsum. On this basis, the micro-nano-scale short columnar α-hemihydrate gypsum in the formula is combined with interface coupling modified composite additives to construct a three-in-one synergistic weather-resistant system of "cementing-aggregate-interface." Finally, a tile adhesive product with excellent water resistance, freeze-thaw resistance, heat aging resistance, and stable adhesion to damp substrates and low-temperature environments is prepared, achieving a dual breakthrough in solid waste resource utilization and building material performance upgrading. Attached Figure Description

[0030] Figure 1 The schematic diagram of the preparation process of the micro-nano α-hemihydrate gypsum of the present invention is shown. Detailed Implementation

[0031] To provide a detailed understanding of the technical features and content of this invention, preferred embodiments will be described in more detail below. While preferred embodiments of the invention are described in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0032] In some specific embodiments, a method for preparing a high-performance weather-resistant tile adhesive includes the following steps: (I) Deep purification pretreatment of desulfurized gypsum and preparation process of micro-nano α-hemihydrate gypsum, refer to Figure 1 The process shown (1) Gradient countercurrent water washing-electrophoresis coupled deep impurity removal The first step, vacuum dewatering and gradient countercurrent rinsing: The original desulfurization gypsum slurry from the power plant is transported to a vacuum belt dewatering machine. During the dewatering process, a three-stage gradient countercurrent rinsing system is set up. The desulfurization gypsum filter cake is rinsed with purified water in reverse at each stage, removing soluble chloride ions, alkali metal ions, and water-soluble heavy metals from the desulfurization gypsum filter cake step by step. The impurity removal rate of a single rinse reaches 90% or more, reducing the soluble salt content to below 500 ppm. Compared with the inefficient impurity removal of traditional single water washing, this gradient countercurrent rinsing design achieves efficient utilization of rinsing water, reducing water consumption by 60% or more. The second step is cyclone washing and separation of light impurities: The desulfurized gypsum after the initial washing is sent to a closed cyclone mixing tank (or closed hydrocyclone), and purified water is added at a solid-liquid ratio of 1:2.5. High-speed cyclone mixing (mixing speed greater than or equal to 3000 rpm) generates centrifugal force, and the density difference is used to achieve complete separation of high-purity gypsum particles from unburned carbon particles, organic matter, and light suspended matter. Among them, all light impurities float to the top and overflow, while high-purity desulfurized gypsum settles to the bottom of the tank. The purity of the high-purity desulfurized gypsum obtained after separation is increased to more than 99.5%. The third step is electrophoretic deep desalination and wastewater closed-loop: the desulfurized gypsum slurry after cyclone washing is sent to the electrophoretic desalination device, and the residual trace amounts of soluble salts are completely removed by the action of the electric field. The chloride ion content in the desulfurized gypsum obtained after electrophoretic desalination is controlled below 200ppm, which is far superior to the industry standard. The concentrated wastewater generated by electrophoretic desalination is recycled to the water rinsing process after flocculation sedimentation and membrane filtration, achieving 100% recycling of process wastewater with no external discharge. The filter cake containing impurities is centrally treated in a harmless manner, resulting in zero solid waste generation throughout the entire process.

[0033] (2) Gradient temperature and pressure directional micro / nano crystal transformation The high-purity desulfurized gypsum slurry after deep purification in step (1) is pumped into a high-pressure reactor. A composite crystallizer (ammonium citrate and silane coupling agent, with a mass ratio of 1:0.5-1.2) is added, accounting for 0.05%-0.12% of the dry weight of the purified desulfurized gypsum. The gradient temperature and pressure control process is used to directionally transform the micro-nano crystal form: first, the temperature is raised to 120℃ and 0.4MPa at a rate of 5℃ / min for a pre-reaction of 30min, and then the temperature is raised to 160-200℃ and 0.6-1.0MPa at a constant rate for a reaction of 2-3.5 hours to achieve the orderly reconstruction of calcium sulfate dihydrate crystals. The directional crystallization is achieved as micro-nano-scale short columnar α-hemihydrate gypsum, with the crystal aspect ratio strictly controlled between 1:1.1-1:1.6. The crystal density is increased by 40% or more, and the gelling activity is increased by 50% or more, completely solving the defect of the needle-like crystal form of hemihydrate gypsum obtained by the traditional method.

[0034] After the reaction, the resulting material is rapidly cooled to 45-55℃ by a shell-and-tube cooler to avoid crystal distortion. The cooled material is then coarsely crushed by a jaw crusher, ultrafinely ground by an air jet mill, and then screened by a high-precision vibrating screen to control the particle size of the product to 180-220 mesh. The coarse powder on the screen is returned for re-grinding, finally yielding high-purity, low-impurity, micro-nano short columnar α-hemihydrate gypsum powder with a purity of 99.5-99.9% and a chloride ion content of ≤200ppm, which is used as the core cementing material for tile adhesive.

[0035] (II) Tile adhesive formulation and preparation process (1) Tile adhesive formula Core cementing material: Micro-nano-scale short columnar α-hemihydrate gypsum powder, 55-70 parts (solid waste conversion raw material, accounting for over 60%). Functional aggregate: 22-28 parts of 120-200 mesh continuously graded quartz sand (optimized particle size distribution to improve paste density and crack resistance). Auxiliary cementitious component: High-alumina cement, 6-12 parts (added in trace amounts, only to improve early strength, without changing the core cementitious system). Interface-modifying composite additive, 4-7 parts (core functional component, solving water resistance issues), comprising: Polycarboxylate superplasticizer, 0.6-1.8 parts; Low viscosity methyl cellulose ether water-retaining agent, 0.6-1.8 parts; Organosilicon hydrophobic agent (such as methylsiloxane compounds), 0.4-1.2 parts; Silane coupling agents (such as KH-550, KH-570, A-151, A-1100, etc.), 0.3-0.8 parts; Retarder (such as hydroxycarboxylic acid salts or diethylenetriaminepentaacetic acid pentasodium salt), 0.2-0.9 parts; Defoamer (such as organic modified siloxane powder, polyether modified silicone oil surfactant), 0.1-0.8 parts; The compounded interface-modified composite additive can achieve a triple effect of interface hydrophobicity, enhanced adhesion, and optimized construction. (2) Preparation of tile adhesive by compounding dry powder raw materials A two-stage precision mixing process is adopted: First, the micro-nano-sized short columnar α-hemihydrate gypsum powder, continuously graded quartz sand, and high-alumina cement obtained above are put into a vertical low-speed mixer and stirred at a speed of 15-20 r / min for 25-35 minutes to achieve initial uniform mixing of dry powder and avoid particle segregation; then, interface-modified composite additives are added, and the speed is increased to 45-55 r / min for high-speed mixing for 30-40 minutes to ensure that all components are fully mixed, without agglomeration or stratification; the final tile adhesive product is sealed and moisture-proof, with a shelf life of up to 8 months.

[0036] (III) Construction methods and performance advantages When applying the finished tile adhesive, mix it at a water-to-adhesive ratio of 1:0.28-1:0.32. First, premix at low speed for 2-3 minutes, then stir at high speed for 3-5 minutes to form a uniform and fine paste, which is then ready for use. This product has an drying time of over 40 minutes, far exceeding the industry standard requirement of 20 minutes, which allows for ultra-thin tiling (tiling thickness of 3-5mm), saving material usage. It can be applied normally to damp substrates and low-temperature environments (above 5℃) without the need for additional substrate treatment.

[0037] Testing revealed that the product's performance far exceeds the JC / T 547-2017 C1TE advanced standard, namely: tensile bond strength ≥1.2MPa, tensile bond strength retention rate after immersion in water ≥85%, tensile bond strength retention rate after freeze-thaw cycles and tensile bond strength retention rate after heat aging both ≥80%, completely solving the defect of poor durability of traditional tile adhesives, and suitable for tile laying in all scenarios such as indoor walls and floors, bathrooms, balconies, outdoor walls, and low-temperature environments.

[0038] The beneficial effects of this plan are: (1) Performance breakthrough: The performance of the tile adhesive product far exceeds the industry C1TE standard. The water resistance, freeze-thaw resistance and heat aging resistance have achieved a qualitative leap. It can be stably bonded to damp substrates and low temperature environments without hollowing or falling off. It breaks the industry curse of poor water resistance of gypsum-based building materials and is suitable for all scenarios. (2) High-value utilization of solid waste: 0.85-1.0 tons of desulfurized gypsum can be consumed by a single ton of ceramic tile adhesive, realizing the large-scale and high-value-added consumption of bulk solid waste, completely solving the problem of power plant desulfurized gypsum stockpiling, and turning waste into treasure; (3) Low-carbon, environmentally friendly and zero-pollution: 100% of the wastewater in the whole process is reused, and there is no solid waste or waste gas emission. Compared with the traditional cement-based tile adhesive preparation process, this solution reduces carbon emissions by more than 50% and energy consumption by 45% or more. (4) Significant cost advantage: Low-priced desulfurized gypsum is used as a raw material to replace high-priced natural gypsum and a large amount of cement in the preparation of tile adhesive, reducing raw material costs by 30%-35%. The resulting product has high-end performance but is priced affordably, making it highly competitive in the market. (5) High original technology barriers: The three core processes of gradient impurity removal, micro-nano crystal form control and interface modification are non-obvious technological breakthroughs in this field; (6) Extremely adaptable to construction: The product has an ultra-long drying time, ultra-thin installation, and can be installed on low temperature / damp substrates, which greatly reduces the difficulty of construction, improves construction efficiency, and is suitable for various construction scenarios.

[0039] <Raw Material Information> Desulfurized gypsum originates from the desulfurized gypsum slurry produced by the flue gas desulfurization system of a coal-fired power plant.

[0040] Quartz sand was purchased from manufacturers such as Chongqing Rongshun, Sichuan Shuoyuanfeng, and Hebei Yongshun.

[0041] High-alumina cement was purchased from Zhengzhou Weida Refractory Materials Co., Ltd., Zhengzhou Xinxing Special Cement Plant, etc.

[0042] The polycarboxylate superplasticizer was purchased from Jiangsu Subote, and its brand name is Subote® series (Subote).

[0043] Low-viscosity methylcellulose ether water-retaining agent, purchased from Dow Chemical, brand name Dow Methocel. TM E4M; its viscosity is 400-600 mPa·s (2% aqueous solution, 20℃).

[0044] Organosilicon hydrophobic agent, methylsiloxane compound, purchased from Wacker, brand name SILRES®BS 290.

[0045] Silane coupling agent is an organosilicon coupling agent containing siloxane functional groups. It was purchased from Shin-Yue Chemical, and its trade name is KH-570.

[0046] The retarder is a hydroxycarboxylic acid salt organic compound, purchased from Sika, with the brand name SikaRetardol®-25.

[0047] The defoamer is a polyether-modified silicone oil surfactant, purchased from Evonik, with the brand name Surfynol® 485.

[0048] Example 1: (I) Preparation of micro / nano short columnar α-hemihydrate gypsum powder (1) Pretreatment of detached plaster The original desulfurization gypsum slurry from the power plant is transported to a vacuum belt dewatering machine. During the dewatering process, a three-stage gradient countercurrent rinsing system is set up. The desulfurization gypsum filter cake is rinsed with purified water in reverse at each stage to remove soluble chloride ions, alkali metal ions, and water-soluble heavy metals from the inside of the desulfurization gypsum filter cake. The impurity removal rate of a single rinse reaches 90% or more, and the soluble salt content is reduced to below 500 ppm. The pre-rinsed desulfurized gypsum is fed into a closed cyclone mixing tank, and purified water is added at a solid-liquid ratio of 1:2.5. High-speed cyclone mixing (cyclone mixing speed >3000 rpm) generates centrifugal force, and the density difference is used to achieve complete separation of high-purity gypsum particles from unburned carbon particles, organic matter, and light suspended solids. Among them, all light impurities float to the top and overflow, while high-purity desulfurized gypsum settles to the bottom of the tank. The purity of the desulfurized gypsum obtained after separation is increased to over 99.5%. The desulfurized gypsum slurry after cyclone washing is sent to an electrophoretic desalination device, where residual trace amounts of soluble salts are completely removed by the action of an electric field. The chloride ion content in the desulfurized gypsum obtained after electrophoretic desalination is controlled to be below 200 ppm. The concentrated wastewater generated by electrophoretic desalination is recycled to the water washing process after flocculation sedimentation and membrane filtration, achieving 100% recycling of process wastewater with no external wastewater discharge. The impurity filter cake is centrally treated in a harmless manner, and the entire process generates zero solid waste. (2) Gradient temperature and pressure directional micro / nano crystal transformation The highly purified desulfurized gypsum slurry was pumped into a high-pressure reactor, and a composite crystallization agent (ammonium citrate and silane coupling agent in a 1:1 mass ratio) was added at 0.08 wt% of the dry weight of the purified desulfurized gypsum. A gradient temperature and pressure controlled process was used to directionally transform the micro-nano crystal form: first, the temperature was raised to 120℃ and 0.4 MPa at a rate of 5℃ / min for a pre-reaction of 30 min, and then the temperature was raised to 180℃ and 0.8 MPa at a constant rate for a reaction of 3 hours to achieve the ordered reconstruction of calcium sulfate dihydrate crystals and directional crystallization into micro-nano-scale short columnar α-hemihydrate gypsum with the crystal aspect ratio strictly controlled between 1:1.1 and 1:1.6. After the reaction, the resulting material is rapidly cooled to 50°C using a shell-and-tube cooler to prevent crystal distortion. The cooled material is then coarsely crushed by a jaw crusher, ultrafinely ground by an air jet mill, and then sieved by a high-precision vibrating screen to control the particle size of the product to 180-220 mesh. The coarse powder on the sieve is returned for re-grinding, ultimately yielding high-purity, low-impurity, micro-nano short columnar α-hemihydrate gypsum powder with a purity of 99.5-99.8% and a chloride ion content of ≤34ppm, which serves as the core binder for tile adhesives.

[0049] (II) The formula for tile adhesive is as follows: Micro-nano short columnar α-hemihydrate gypsum powder, 60 parts by weight. 120-200 mesh continuously graded quartz sand, 25 parts by weight. High-alumina cement, 10 parts by weight Interface-modified composite additive, 5 parts by weight; comprising: 1.0 part of polycarboxylate high-performance water-reducing agent, 1.0 part of low-viscosity methyl cellulose ether (water-retaining agent), 0.8 part of organosilicon water-repellent agent, 0.6 part of silane coupling agent, 0.8 part of hydroxycarboxylate organic compound (retarder), and 0.8 part of polyether modified silicone oil surfactant (defoamer).

[0050] First, the micro-nano-sized short columnar α-hemihydrate gypsum powder, continuously graded quartz sand, and high-alumina cement obtained above are put into a vertical low-speed mixer and stirred at a low speed of 20 r / min for 30 minutes to achieve initial uniform mixing of dry powder and avoid particle segregation; then, interface-modified composite additives are added, and the speed is increased to 50 r / min for high-speed stirring for 40 minutes to ensure that all components are fully mixed, without agglomeration or stratification; finally, the resulting tile adhesive is packaged in sealed moisture-proof packaging.

[0051] The finished tile adhesive was tested, and the test results are shown in Table 1: the tensile bond strength is 1.25 MPa, the tensile bond strength after immersion in water is 1.08 MPa, the tensile bond strength after heat aging is 0.95 MPa, the tensile bond strength after freeze-thaw is 1.05 MPa, and the tensile bond strength after drying for 30 minutes is 0.85 MPa. All performance indicators far exceed the C1TE standard.

[0052] Example 2: (I) Preparation of micro / nano short columnar α-hemihydrate gypsum powder Same as Example 1.

[0053] (II) The formula for tile adhesive is as follows: Micro-nano short columnar α-hemihydrate gypsum powder, 65 parts by weight. 23 parts by weight of 120-200 mesh continuously graded quartz sand. High-alumina cement, 8 parts by weight Interface-modified composite additive, 4 parts by weight; comprising: 0.8 parts of polycarboxylate high-performance water-reducing agent, 0.8 parts of low-viscosity methyl cellulose ether (water-retaining agent), 0.6 parts of organosilicon water-repellent agent, 0.5 parts of silane coupling agent, 0.7 parts of hydroxycarboxylate organic compound (retarder), and 0.6 parts of polyether modified silicone oil surfactant (defoamer).

[0054] First, the micro-nano-sized short columnar α-hemihydrate gypsum powder, continuously graded quartz sand, and high-alumina cement obtained above are put into a vertical low-speed mixer and stirred at a low speed of 20 r / min for 30 minutes to achieve initial uniform mixing of dry powder and avoid particle segregation; then, interface-modified composite additives are added, and the speed is increased to 50 r / min for high-speed stirring for 40 minutes to ensure that all components are fully mixed, without agglomeration or stratification; finally, the resulting tile adhesive is packaged in sealed moisture-proof packaging.

[0055] The finished tile adhesive was tested, and the test results are shown in Table 1. All performance indicators far exceeded the C1TE standard; the aging resistance was excellent, and the cost was further reduced compared to Example 1.

[0056] Comparative Example 1: The specific steps for preparing cement-based tile adhesive are as follows: 1. Pretreatment of desulfurized gypsum (conventional water washing process) The primary desulfurization gypsum slurry collected from the limestone-gypsum wet desulfurization system of a coal-fired power plant was selected. This slurry is a wet powdery byproduct with a water content of about 10%-20%, and its main component is calcium sulfate dihydrate (CaSO4·2H2O).

[0057] (1) Hydrocyclone separation: The original desulfurized gypsum slurry is initially dehydrated by a hydrocyclone to remove large particles of impurities and unreacted limestone; (2) Filtration and dehydration: A belt filter is used to further reduce its moisture content to 10%-15% to form a transportable wet gypsum filter cake; (3) Washing and purification: Rinse the gypsum filter cake repeatedly with clean water to remove soluble chloride ions (Cl). -Impurities such as sulfites and coal ash are removed to ensure a stable pH value of 6-9 and a free acid content of ≤0.5%. Depending on the subsequent usage requirements, the pretreated desulfurized gypsum can be air-dried or dried at low temperature (≤120℃) to control the final moisture content to ≤5%; however, in traditional processes, wet powdered desulfurized gypsum is often used directly.

[0058] 2. Preparation of conventional cement-based formulations Cementitious material: Ordinary Portland cement (PO 42.5), as the main cementitious component; Fine aggregate: Add 40-120 mesh quartz sand or river sand, cement:sand mass ratio = 1:1.2-1.5, to improve compactness and compressive strength; The admixture system includes: Water-reducing agent: Polycarboxylate powder, dosage is 0.3%-0.6% of cement mass, reduces water-cement ratio and improves fluidity; Retarder: Tartaric acid or sodium citrate, at a dosage of 0.1%-0.3% of the cement mass, to delay setting and adapt to the construction time window; Water-retaining agent: medium viscosity cellulose ether, dosage 0.2%-0.4% of cement mass, to prevent bleeding and cracking.

[0059] Water-cement ratio control: The ratio of water to the total mass of (cement + adhesive powder) is 0.38-0.45 to ensure that the slurry has pumpability and self-leveling tendency.

[0060] 3. Composite of desulfurized gypsum and cement-based materials Mixing method: Use a forced mixer to dry mix cement, sand, and pretreated desulfurized gypsum for 3 minutes. Then slowly add water and admixture solution and continue mixing for 5-8 minutes until uniform and lump-free to obtain tile adhesive. The pretreated desulfurized gypsum (dry basis) is evenly added to the cement-based mixture at 1%-4% of the cement mass.

[0061] 4. Molding and Curing Pouring: Pour the mixed tile adhesive onto the substrate to be constructed, and use a notched scraper to help spread it evenly, with the thickness controlled between 5 and 20 mm (depending on the application).

[0062] Allow to stand for 5-10 minutes to allow the bubbles to escape naturally.

[0063] Maintenance conditions: Natural curing in an environment with a temperature of 5-35℃ and a relative humidity of ≥60%. Do not step on it within 7 days. It will reach the design strength in 28 days.

[0064] Precautions: Avoid construction in low temperature (<5℃) or high temperature and dry environment to prevent abnormal solidification or cracking.

[0065] The finished tile adhesive was tested, and the test results are shown in Table 1. All performance indicators, such as tensile bond strength after heat aging, tensile bond strength after freeze-thaw, and tensile bond strength after 30 minutes of drying, failed to meet the standards.

[0066] Comparative Example 2: (I) Preparation of α-hemihydrate gypsum powder by conventional hydrothermal reaction The raw desulfurized gypsum slurry from the power plant is pumped into a reactor, and a crystallizing agent (such as succinic acid) accounting for 0.03 wt% of the dry weight of the desulfurized gypsum is added. The mixture is then subjected to a hydrothermal reaction at 110℃ and 0.2 MPa for 2 hours to obtain α-hemihydrate desulfurized gypsum powder with a purity of ≥95% and a chloride ion content of less than or equal to 200 ppm, which is used as the core cementitious material for tile adhesive.

[0067] (II) The formula for tile adhesive is as follows: The α-hemihydrate gypsum powder obtained in step (I) above, 60 parts by weight, 120-200 mesh continuously graded quartz sand, 25 parts by weight. High-alumina cement, 10 parts by weight Interface-modified composite additive, 5 parts by weight; comprising: 1.0 part of polycarboxylate high-performance water-reducing agent, 1.0 part of low-viscosity methyl cellulose ether (water-retaining agent), 0.8 part of organosilicon water-repellent agent, 0.6 part of silane coupling agent, 0.8 part of hydroxycarboxylate organic compound (retarder), and 0.8 part of polyether modified silicone oil surfactant (defoamer).

[0068] First, the α-hemihydrate gypsum powder, continuously graded quartz sand, and high-alumina cement obtained above are put into a vertical low-speed mixer and stirred at a speed of 20 r / min for 30 minutes to achieve initial uniform mixing of dry powder and avoid particle segregation. Then, the interface-modified composite additive is added, and the speed is increased to 50 r / min for high-speed mixing for 40 minutes to ensure that all components are fully mixed without agglomeration or stratification. The final tile adhesive product is sealed and moisture-proof packaged.

[0069] The finished tile adhesive was tested, and the test results are shown in Table 1. All performance indicators failed to meet the standards.

[0070] Comparative Example 3: (I) Preparation of α-hemihydrate gypsum powder Same as Example 1.

[0071] (II) The formula for tile adhesive is as follows: Micro-nano short columnar α-hemihydrate gypsum powder, 50 parts by weight. 30 parts by weight of 120-200 mesh continuously graded quartz sand. High-alumina cement, 15 parts by weight The composite additive, 5 parts by weight, comprises: 3.8 parts of polycarboxylate high-performance water-reducing agent, 0.8 parts of methyl cellulose ether (water-retaining agent), 0.3 parts of diethylenetriaminepentaacetic acid pentasodium salt (retarder), and 0.1 parts of organic modified siloxane powder (defoamer).

[0072] First, the micro-nano short columnar α-hemihydrate gypsum powder, continuously graded quartz sand, and high-alumina cement obtained above are put into a vertical low-speed mixer and stirred at a speed of 20 r / min for 30 minutes to achieve initial uniform mixing of dry powder and avoid particle segregation. Then, composite additives are added, and the speed is increased to 50 r / min for high-speed mixing for 40 minutes to ensure that all components are fully mixed, without agglomeration or stratification. The final tile adhesive product is sealed and moisture-proof packaged.

[0073] The finished tile adhesive was tested, and the test results are shown in Table 1. All performance indicators failed to meet the standards.

[0074] Table 1 Performance test results of tile adhesives obtained in each embodiment and comparative example

[0075] This application's technical solution overcomes the dual pain points of poor water resistance in gypsum-based building materials and high carbon and energy consumption in cement-based building materials, achieving 100% high-value utilization of bulk solid waste. The product performance far exceeds the JC / T 547-2017 C1TE advanced standard, and has advantages such as ultra-long drying time, ultra-thin laying, strong adhesion to damp / low-temperature substrates, long-term freeze-thaw resistance, and aging resistance. The production process achieves zero wastewater discharge, full utilization of solid waste, carbon emission reduction of over 50%, and raw material cost reduction of over 30%, filling the industry's technological gap in the high-value preparation of high-end weather-resistant tile adhesive from desulfurized gypsum.

[0076] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A high-performance weather-resistant tile adhesive, characterized in that, The components include the following parts by weight: Micro-nano short columnar α-hemihydrate gypsum powder, 55-70 parts; Quartz sand, 22-28 parts; High-alumina cement, 6-12 parts; Interface-modifying composite additive, 4-7 parts.

2. The high-performance weather-resistant tile adhesive according to claim 1, characterized in that, The interface-modified composite additive comprises the following components in parts by weight: Water-reducing agent, 0.6-1.8 parts; Water-retaining agent, 0.6-1.8 parts; Organosilicon water-repellent agent, 0.4-1.2 parts; Silane coupling agent, 0.3-0.8 parts; Retarder, 0.2-0.9 parts; Defoamer, 0.1-0.8 parts; Preferably, the water-reducing agent is a polycarboxylate water-reducing agent; Preferably, the water-retaining agent is a low-viscosity methylcellulose ether; Preferably, the retarder is a hydroxycarboxylic acid salt organic compound or a sodium diethyltriaminepentaacetate. Preferably, the defoamer is an organically modified siloxane powder.

3. A method for preparing the high-performance weather-resistant tile adhesive as described in claim 1, characterized in that, Includes the following steps: (1) Pretreatment of desulfurized gypsum The desulfurized gypsum was subjected to gradient countercurrent water washing, and then the product obtained from the initial washing was subjected to hydrocyclone washing. The gypsum slurry after hydrocyclone washing was then subjected to electrophoretic desalination to obtain purified desulfurized gypsum. (2) Micro / nano crystal transformation reaction The purified desulfurized gypsum is mixed with a crystallization agent, and the reaction transforms the desulfurized gypsum into micro-nano-scale short columnar α-hemihydrate gypsum. (3) Preparation of tile adhesive The prepared micro-nano-scale short columnar α-hemihydrate gypsum powder is mixed evenly with quartz sand and high-alumina cement at low speed. Then, an interface-modified composite additive is added and the mixture is stirred evenly at high speed to obtain tile adhesive.

4. The preparation method according to claim 3, characterized in that, The purity of the purified desulfurized gypsum obtained in step (1) is 99.5% or higher, and the chloride ion content is controlled at 200 ppm or lower.

5. The preparation method according to claim 3, characterized in that, The reaction in step (2) adopts a gradient temperature and pressure control process, including: first heating to 115-130℃ at a rate of 5℃ / min, and pre-reacting for 20-45min under 0.3-0.5MPa conditions, then heating to 160-200℃ at a uniform rate, and holding the reaction at 0.6-1.0MPa conditions for 2-3.5 hours.

6. The preparation method according to claim 3, characterized in that, The crystallization agent in step (2) is a compound mixture of ammonium citrate and silane coupling agent; preferably, the mass ratio of ammonium citrate to silane coupling agent is 1:(0.5-1.2).

7. The preparation method according to claim 3, characterized in that, The amount of the crystallization agent used in step (2) is 0.05wt%-0.12wt% of the dry basis weight of the desulfurized gypsum.

8. The preparation method according to claim 3, characterized in that, The micro-nano-scale short columnar α-hemihydrate gypsum powder obtained in step (2) has a particle size of 180-220 mesh, a purity greater than or equal to 99.5%, and a chloride ion content less than or equal to 200 ppm. The aspect ratio of the crystal form of micro-nano-scale short columnar α-hemihydrate gypsum is between 1:1.1 and 1:1.

6.

9. The preparation method according to claim 3, characterized in that, The stirring speed in step (3) is 10-20 r / min, and the stirring time is 20-60 min. The high-speed stirring speed is 40-55 r / min, and the stirring time is 30-60 min.

10. The preparation method according to any one of claims 3-9, characterized in that, The interface-modified composite additive comprises: Water-reducing agent, 0.6-1.8 parts; Water-retaining agent, 0.6-1.8 parts; Organosilicon water-repellent agent, 0.4-1.2 parts; Silane coupling agent, 0.3-0.8 parts; Retarder, 0.2-0.9 parts; Defoamer, 0.1-0.8 parts.

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