A branched structure high slump retention aliphatic water reducing agent and a controllable polymerization preparation method thereof

Abstract

This invention provides a branched, high-slump-retention aliphatic water-reducing agent and its controlled polymerization preparation method. The water-reducing agent comprises the following components by weight: 14-24 parts acetone, 19-29 parts formaldehyde, 7.5-11.5 parts sodium bisulfite, 3.5-6.5 parts a four-armed star-shaped low-carbon hydrophobic core, 2.5-5.5 parts an amide-ester bifunctional slow-release monomer, 2.0-4.5 parts a zwitterionic phosphonic acid clay inhibitor, and 60-90 parts deionized water. The water-reducing agent obtained by this invention possesses good initial dispersibility, stable adsorption, excellent slump retention, and strong resistance to clay interference.

Description

Technical Field

[0001] This invention relates to the field of water-reducing agent technology, specifically to a branched high-slump-retention aliphatic water-reducing agent and its controlled polymerization preparation method. Background Technology

[0002] In concrete engineering, water-reducing agents are key admixtures for improving the workability and mechanical properties of concrete. Among them, aliphatic water-reducing agents are widely used in the construction field due to the readily available raw materials, controllable costs, and high initial dispersion efficiency. In existing technologies, the preparation of aliphatic water-reducing agents mainly focuses on main chain construction and sulfonation modification, introducing polar groups to enhance the interaction with cement particles to achieve basic dispersion functions. However, with the increasing requirements of engineering projects on concrete construction cycles (such as long-distance transportation) and aggregate adaptability (such as clay-containing aggregates), aliphatic water-reducing agents that rely solely on initial dispersion performance are no longer sufficient to meet higher performance demands.

[0003] While existing aliphatic water-reducing agents can achieve initial dispersion of cement particles through sulfonation, they still have significant limitations in practical applications. On the one hand, their molecular structure lacks functional units that can continuously function in alkaline concrete environments, making it impossible to maintain dispersion force for a long time. This results in rapid slump loss in concrete, making them unsuitable for large-volume projects or long-term construction scenarios. On the other hand, when dealing with clay-containing sand and gravel aggregates, the main component of existing water-reducing agents is easily adsorbed and consumed by clay, significantly reducing its effective adsorption on the surface of cement particles. This weakens the dispersion effect and affects the stability of concrete performance. These problems restrict the application expansion of aliphatic water-reducing agents under complex engineering conditions. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a branched structure high slump-retaining aliphatic water-reducing agent and its controllable polymerization preparation method, so that the water-reducing agent has good initial dispersibility, stable adsorption, excellent slump retention and strong resistance to clay interference.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This application discloses a branched structure high slump-retaining aliphatic water-reducing agent, which, by weight, comprises the following components: 14-24 parts acetone, 19-29 parts formaldehyde, 7.5-11.5 parts sodium bisulfite, 3.5-6.5 parts a four-armed star-shaped low-carbon hydrophobic core, 2.5-5.5 parts an amide-ester bifunctional sustained-release monomer, 2.0-4.5 parts a zwitterionic phosphonic acid clay inhibitor, and 60-90 parts deionized water.

[0006] By setting up the above technical solutions, acetone can provide the main chain skeleton and hydrophobic segments for the water-reducing agent, laying the foundation for the molecular structure; formaldehyde, as a crosslinking agent, can participate in the reaction to control the growth of the water-reducing agent molecular chain; sodium bisulfite, as a sulfonating agent, can introduce sulfonic acid groups to enhance electrostatic repulsion and improve the initial dispersion efficiency of the water-reducing agent; the four-armed star-shaped low-carbon hydrophobic core can provide four-way anchoring sites, enhance the adsorption force between the water-reducing agent and cement particles, and help stabilize the dispersion; the amide-ester bifunctional slow-release monomer can be hydrolyzed stepwise in an alkaline environment to continuously release functional groups, which helps the water-reducing agent maintain slump and reduce loss; the zwitterionic-phosphonic acid clay inhibitor can preferentially adsorb clay and form an isolation layer to prevent the main agent of the water-reducing agent from being consumed by clay and improve the resistance to clay interference; deionized water, as a solvent, can reduce the viscosity of the system, facilitate reaction control in the preparation process of the water-reducing agent, and provide process adaptability support for the realization of the performance of the water-reducing agent.

[0007] Preferably, the water-reducing agent comprises the following components by weight: 19 parts acetone, 24 parts formaldehyde, 9.5 parts sodium bisulfite, 5 parts four-armed star-shaped low-carbon hydrophobic core, 4 parts amide-ester bifunctional sustained-release monomer, 3 parts zwitterionic phosphonic acid clay inhibitor, and 75 parts deionized water.

[0008] By setting up the above technical solution, the components work together to give the water-reducing agent good initial dispersibility, stable adsorption, excellent slump retention and strong resistance to clay interference.

[0009] Preferably, the four-armed star-shaped low-carbon hydrophobic core is composed of the following components: 1 mol pentaerythritol, 3.8-4.2 mol propylene oxide, 0.06-0.08 mol triethylamine, 220-280 mL ethanol, and an appropriate amount of 10% citric acid solution.

[0010] By setting up the above technical solution, pentaerythritol can serve as the basic raw material for the reaction, providing multifunctional reaction sites for the four-armed star-shaped low-carbon hydrophobic core, thus facilitating the formation of a four-armed branched structure. This structure enables the subsequently prepared water-reducing agent molecules to possess multiple anchoring sites, enhancing their adsorption capacity with cement particles. Propylene oxide can participate in the reaction and construct hydrophobic segments, jointly forming a hydrophobic core. This hydrophobic core can be tightly anchored to the surface of cement particles through van der Waals forces, reducing the desorption of water-reducing agent molecules and improving the persistence of the water-reducing agent's dispersion effect. Triethylamine, as a catalyst, can promote the efficient and orderly reaction between pentaerythritol and propylene oxide, ensuring the successful formation of the four-armed star structure. The formation of the hydrophobic core ensures the integrity of the branched structure, laying the foundation for the branching synergistic effect of the water-reducing agent. Ethanol, as an environmentally friendly solvent, can effectively dissolve pentaerythritol and triethylamine, keeping the reaction system uniform and facilitating full contact and reaction of each component. Its environmental properties also meet the low-carbon compatibility requirements of the water-reducing agent. A 10% citric acid solution, as a neutralizing agent, can adjust the pH of the system after the reaction to the neutral range, avoiding the adverse effects of residual alkaline substances on the compatibility of the subsequent water-reducing agent and cement. At the same time, it ensures the chemical stability of the four-armed star-shaped low-carbon hydrophobic core, enabling it to stably play a branching anchoring role in the water-reducing agent, further improving the dispersion stability of the water-reducing agent.

[0011] Preferably, the preparation method of the four-armed star-shaped low-carbon hydrophobic core includes the following steps: 1) Add pentaerythritol, triethylamine and ethanol to a four-necked flask equipped with a stirrer, thermometer and reflux condenser. Heat to 62-68℃ under nitrogen protection and stir at 300-400 r / min for 30-40 min. Then add propylene oxide dropwise at a uniform rate over 2.5-3.5 h. 2) Heat the mixture obtained in step 1) to 73-77℃ and keep it at that temperature for 6-7 hours. After cooling to room temperature, wash the organic phase with 10% citric acid solution until the pH is 6.0-7.0. After standing, separate the upper organic phase, add anhydrous magnesium sulfate and dry for 4-6 hours. Then, remove the ethanol by rotary evaporation at a temperature of 55-65℃ and a vacuum of -0.08 to -0.09 MPa to obtain a four-armed star-shaped low-carbon hydrophobic core.

[0012] By setting up the above technical solution, nitrogen protection can prevent the oxidation of raw materials to ensure product purity and avoid impurities interfering with its role in the water-reducing agent system. By controlling the temperature conditions of adding propylene oxide at 62-68℃ and maintaining the reaction at 73-77℃, as well as the stirring operation, pentaerythritol can fully react with propylene oxide under the catalysis of triethylamine to form a well-structured four-armed star structure. This structure can serve as the branching core of the water-reducing agent, providing four-way anchoring sites to enhance its adsorption force with cement particles. Subsequently, after adjusting the pH to 6.0-7.0 with 10% citric acid solution to remove residual triethylamine, drying with anhydrous magnesium sulfate, and rotary evaporation to remove ethanol at 55-65℃ and -0.08 to -0.09 MPa, a high-purity product can be obtained, ensuring that it can effectively construct a three-dimensional branched framework in the water-reducing agent, helping to improve the dispersion and slump retention performance of the water-reducing agent.

[0013] Preferably, the composition of the amide-ester bifunctional sustained-release monomer is as follows: maleic anhydride 1 mol, polyethylene glycol monomethyl ether 1 mol, p-toluenesulfonic acid 0.091-0.121 mol, hydroquinone 0.0036-0.0053 mol, diethanolamine 1-1.5 mol, and cyclohexane 160-220 mL.

[0014] By employing the aforementioned technical solution, maleic anhydride and polyethylene glycol monomethyl ether serve as core reaction raw materials, providing the basic structure for the formation of ester bonds in the amide-ester bifunctional slow-release monomer. Toluenesulfonic acid catalyzes the reaction, ensuring efficient esterification. Hydroquinone acts as a polymerization inhibitor, preventing unnecessary polymerization side reactions and ensuring a regular monomer structure. Diethanolamine reacts with the previous esterification products, introducing amide bonds to construct a bifunctional "ester-amide bond" structure. Cyclohexane, acting as a dehydrating agent, removes the water generated in the reaction, promoting the forward reaction and improving monomer yield and purity. When used in water-reducing agents, this monomer's bifunctional groups can undergo stepwise hydrolysis in the alkaline environment of cement, continuously replenishing dispersing power, effectively reducing concrete slump loss, and helping the water-reducing agent achieve ultra-long slump retention.

[0015] Preferably, the preparation method of the amide-ester bifunctional sustained-release monomer includes the following steps: a1. Add polyethylene glycol monomethyl ether, maleic anhydride, p-toluenesulfonic acid, hydroquinone and cyclohexane to a reaction flask equipped with a water separator, stir and heat to 95-105℃, and reflux for 3-4 hours; a2. Cool the mixture obtained in step a1 to 70-80℃, slowly add diethanolamine dropwise over 1.0-1.5 hours, maintain the temperature for 2-3 hours, then continue to heat to 100-110℃ and reflux for 1-2 hours. Cool to 45-48℃, and then remove cyclohexane by rotary evaporation at 70-80℃ and a vacuum of -0.09 to -0.10 MPa to obtain the amide-ester bifunctional sustained-release monomer.

[0016] By setting up the above technical solution, step a1 involves adding polyethylene glycol monomethyl ether, maleic anhydride, p-toluenesulfonic acid, hydroquinone, and cyclohexane, and then refluxing at 95-105℃ to promote the efficient formation of an intermediate product containing ester bonds between maleic anhydride and polyethylene glycol monomethyl ether. Step a2 involves first cooling to 70-80℃ and then adding diethanolamine, allowing the intermediate product to react with diethanolamine and introduce amide bonds. The reaction effect is then optimized by reflux, and finally, cyclohexane is removed by rotary evaporation at 70-80℃ and -0.09 to -0.10 MPa to obtain a high-purity amide-ester bifunctional slow-release monomer. When this monomer is used in water-reducing agents, its ester and amide bonds can be hydrolyzed stepwise in the alkaline environment of cement, continuously replenishing the dispersing force of the water-reducing agent, effectively reducing concrete slump loss, and helping the water-reducing agent achieve ultra-long slump retention performance.

[0017] Preferably, the zwitterionic phosphonic acid clay inhibitor is composed of the following components: 1 mol of 2-acrylamide-2-methylpropanesulfonic acid, 0.7-0.9 mol of vinylphosphonic acid, 1.1-1.3 mol of dimethyldiallylammonium chloride, 0.010-0.015 mol of potassium persulfate, and 60-110 mL of deionized water.

[0018] By setting up the above technical solution, 2-acrylamide-2-methylpropanesulfonic acid can provide sulfonic acid groups, and dimethyldiallylammonium chloride can provide cationic chains. The two, together with vinylphosphonic acid which can provide phosphonic acid groups, can undergo a polymerization reaction under the action of potassium persulfate as an initiator. Deionized water is used as a solvent to help the components dissolve fully and the reaction proceeds in an orderly manner. The resulting zwitterionic phosphonic acid-based clay inhibitor contains phosphonic acid groups, sulfonic acid groups and cationic chains. It can preferentially adsorb onto the clay surface to form an "isolation layer", avoiding the main agent of the water-reducing agent from being consumed by the clay. This improves the compatibility of the water-reducing agent with high mud content aggregates and ensures that it can stably exert its dispersion effect in scenarios such as lightweight building materials.

[0019] Preferably, the preparation method of the zwitterionic phosphonic acid clay inhibitor includes the following steps: b1. Add 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, dimethyldiallylammonium chloride and deionized water to the reaction flask, stir thoroughly, and then adjust the pH to 4.5-5.5 with dilute sulfuric acid. b2. The mixture system obtained in step b1 is purged with nitrogen three times, heated to 62-68℃, and 10% potassium persulfate aqueous solution is added dropwise at a uniform rate over 1.0-1.5h. Then the temperature is raised to 68-72℃ and the reaction is maintained for 4-5h. After cooling to room temperature, zwitterionic phosphonic acid clay inhibitor is obtained.

[0020] By setting up the above technical solution, a suitable environment is provided for the subsequent polymerization reaction in an acidic environment with a pH of 4.5-5.5. Nitrogen replacement in step b2 can eliminate oxygen in the system to avoid interference with polymerization. The addition of a 10% potassium persulfate aqueous solution (initiator) at 62-68℃ can start monomer polymerization. The subsequent heat preservation reaction at 68-72℃ ensures complete polymerization, and finally an inhibitor containing phosphonic acid groups, sulfonic acid groups and cationic chains is obtained. When this inhibitor is used in water-reducing agents, it can preferentially adsorb clay to form an "isolation layer", preventing the main water-reducing agent from being consumed by clay and ensuring the dispersion stability of the water-reducing agent in high clay content aggregate scenarios.

[0021] This application also discloses a controlled polymerization preparation method for a branched, high-slump-retention aliphatic water-reducing agent, comprising the following steps: S1. Add deionized water, acetone and sodium bisulfite to a reaction vessel equipped with a stirrer, thermometer and reflux condenser. After stirring evenly, slowly add 30% sodium hydroxide solution to adjust the pH of the system to 11.0-12.0. Control the adding time to 30-40 min. Then raise the temperature to 40-45℃ and keep the reaction at this temperature for 70-100 min. S2. Heat the mixture obtained in step S1 to 60-65℃, and simultaneously add all the four-armed star-shaped low-carbon hydrophobic cores and 55%-65% formaldehyde at a uniform rate over 1.8-2.8h, maintaining the pH of the system at 9.0-10.0. Then heat to 70-75℃, and simultaneously add all the amide-ester bifunctional slow-release monomers and 20%-25% formaldehyde at a uniform rate over 1.8-2.8h, maintaining the pH of the system at 8.0-9.0. Finally, add all the zwitterionic phosphonic clay inhibitors and the remaining formaldehyde at a uniform rate over 0.8-1.2h, maintaining the pH of the system at 7.0-8.0. S3. The mixture obtained in S2 is kept at 75-80℃ for 1.5-2.0h to complete the low-temperature curing, and then the temperature is raised to 82-88℃ and kept at 82-88℃ for 2.5-3.5h to complete the high-temperature densification process. S4. After high-temperature densification, cool to 35-38℃, adjust the pH of the product to 9.5-10.5 with 30% sodium hydroxide solution, filter, and the branched high-slump-retaining aliphatic water-reducing agent is obtained.

[0022] By setting up the above technical solution, under the conditions of 40-45℃ and pH 11.0-12.0, the reaction of acetone and sodium bisulfite can effectively introduce sulfonic acid groups, laying the foundation for the initial dispersion ability of the water-reducing agent. Step S2 adopts a gradient temperature increase (60-65℃→70-75℃) and maintains a gradient pH (9.0-10.0→8.0-9.0→7.0-8.0), and adds a four-armed star-shaped low-carbon hydrophobic core, amide-ester bifunctional slow-release monomer, zwitterionic-phosphonic acid clay inhibitor and formaldehyde in stages. This can ensure that each functional component is grafted onto the main chain in an orderly manner, and construct a branched structure containing anchoring sites, slow-release groups and anti-mud groups. The low-temperature curing at 75-80℃ in step S3 can promote the full grafting of components to ensure structural uniformity, and the high-temperature densification at 82-88℃ can enhance the stability of the molecular chain. Step S4 cools and adjusts the pH to 9.5-10.5 and filters to ensure product purity and storage stability. The branched aliphatic water-reducing agent with high slump retention prepared by this method can combine high water reduction, ultra-long slump retention and strong clay resistance, and is suitable for marine engineering, lightweight building materials and other application scenarios.

[0023] Preferably, in step S4, the filter used for filtration is an 80-mesh filter.

[0024] By setting up the above technical solution, a small amount of mechanical impurities that may exist in the branched high-slump aliphatic water-reducing agent can be effectively removed, resulting in a product without mechanical impurities. This ensures that the water-reducing agent is more evenly dispersed when mixed with cement and aggregates, avoiding local dispersion imbalance caused by impurities, thereby ensuring the stability of concrete workability and subsequent compressive strength, impermeability and other properties, while maintaining the uniformity of the product's appearance.

[0025] The beneficial effects of this invention are as follows: Acetone provides the main chain framework and hydrophobic segments for water-reducing agents, laying the foundation for their molecular structure; formaldehyde, as a crosslinking agent, can participate in the reaction to control the growth of the water-reducing agent's molecular chain; sodium bisulfite, as a sulfonating agent, can introduce sulfonic acid groups to enhance electrostatic repulsion and improve the initial dispersion efficiency of the water-reducing agent; a four-armed star-shaped low-carbon hydrophobic core can provide four-way anchoring sites, enhancing the adsorption force between the water-reducing agent and cement particles, and contributing to dispersion stability; amide-ester bifunctional slow-release monomers can be hydrolyzed stepwise under alkaline conditions, continuously releasing functional groups, which helps the water-reducing agent maintain slump and reduce losses; zwitterionic-phosphonic acid clay inhibitors can preferentially adsorb clay and form an isolation layer, preventing the main water-reducing agent from being consumed by clay and improving its resistance to clay interference; deionized water, as a solvent, can reduce the viscosity of the system, facilitating reaction control during the preparation of the water-reducing agent and providing process adaptability support for the realization of the water-reducing agent's performance.

[0026] Pentaerythritol serves as a basic raw material for the reaction, providing multifunctional reaction sites for the four-armed star-shaped low-carbon hydrophobic core, thus facilitating the formation of a four-armed branched structure. This structure enables the subsequently prepared water-reducing agent molecules to possess multiple anchoring sites, enhancing their adsorption capacity with cement particles. Propylene oxide participates in the reaction and constructs hydrophobic segments, collectively forming the hydrophobic core. This hydrophobic core can be tightly anchored to the surface of cement particles through van der Waals forces, reducing the desorption of water-reducing agent molecules and improving the persistence of the water-reducing agent's dispersion effect. Triethylamine acts as a catalyst, promoting the efficient and orderly reaction between pentaerythritol and propylene oxide, ensuring the smooth formation of the four-armed star structure and guaranteeing the hydrophobic effect. The integrity of the water-core branched structure lays the foundation for the branching synergistic effect of the water-reducing agent. Ethanol, as an environmentally friendly solvent, can effectively dissolve pentaerythritol and triethylamine, keeping the reaction system uniform and facilitating full contact and reaction of each component. Its environmental properties also meet the low-carbon compatibility requirements of the water-reducing agent. The 10% citric acid solution, as a neutralizing agent, can adjust the pH of the system after the reaction to the neutral range, avoiding the adverse effects of residual alkaline substances on the compatibility of the water-reducing agent and cement. At the same time, it ensures the chemical stability of the four-armed star-shaped low-carbon hydrophobic core, enabling it to stably play a branching anchoring role in the water-reducing agent, further improving the dispersion stability of the water-reducing agent.

[0027] Maleic anhydride and polyethylene glycol monomethyl ether serve as the core reactants, providing the basic structure for the formation of ester bonds in the amide-ester bifunctional slow-release monomer. Toluenesulfonic acid catalyzes the reaction, ensuring efficient esterification. Hydroquinone acts as a polymerization inhibitor, preventing unnecessary side reactions and ensuring a regular monomer structure. Diethanolamine reacts with the previous esterification products, introducing amide bonds to construct an ester-amide bifunctional structure. Cyclohexane, acting as a dehydrating agent, removes the water generated in the reaction, promoting the forward reaction and increasing monomer yield and purity. When used in water-reducing agents, this monomer's bifunctional groups can undergo stepwise hydrolysis in the alkaline environment of cement, continuously replenishing dispersing power, effectively reducing concrete slump loss, and helping the water-reducing agent achieve ultra-long slump retention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1: This embodiment discloses a branched structure high slump-retaining aliphatic water-reducing agent. By weight, the water-reducing agent is composed of the following components: 14 parts acetone, 19 parts formaldehyde, 7.5 parts sodium bisulfite, 3.5 parts four-armed star-shaped low-carbon hydrophobic core, 2.5 parts amide-ester bifunctional sustained-release monomer, 2.0 parts zwitterionic phosphonic acid clay inhibitor, and 60 parts deionized water.

[0030] It should be noted that the four-armed star-shaped low-carbon hydrophobic core is composed of the following components: 1 mol pentaerythritol, 3.8 mol propylene oxide, 0.06 mol triethylamine, 220 mL ethanol, and an appropriate amount of 10% citric acid solution. The preparation method of the four-armed star-shaped low-carbon hydrophobic core includes the following steps: 1) Add pentaerythritol, triethylamine and ethanol to a four-necked flask equipped with a stirrer, thermometer and reflux condenser. Heat to 62°C under nitrogen protection and stir at 300 r / min for 30 min. Then add propylene oxide dropwise at a uniform rate over 2.5 h. 2) The mixture obtained in step 1) was heated to 73°C and kept at that temperature for 6 hours. After cooling to room temperature, the organic phase was washed with 10% citric acid solution until the pH was 6.0. After standing, the upper organic phase was separated, and anhydrous magnesium sulfate was added to dry for 4 hours. Then, the ethanol was removed by rotary evaporation at a temperature of 55°C and a vacuum of -0.08 MPa to obtain a four-armed star-shaped low-carbon hydrophobic core.

[0031] It should be noted that the composition of the amide-ester bifunctional sustained-release monomer is as follows: maleic anhydride 1 mol, polyethylene glycol monomethyl ether 1 mol, p-toluenesulfonic acid 0.091 mol, hydroquinone 0.0036 mol, diethanolamine 1 mol, and cyclohexane 160 mL. The preparation method of the amide-ester bifunctional sustained-release monomer includes the following steps: a1. Add polyethylene glycol monomethyl ether, maleic anhydride, p-toluenesulfonic acid, hydroquinone and cyclohexane to a reaction flask equipped with a water separator, stir and heat to 95°C, and reflux for 3 hours; a2. Cool the mixture obtained in step a1 to 70°C, slowly add diethanolamine dropwise over 1.0 h, keep the reaction at this temperature for 2 h, then continue to heat to 100°C and reflux for 1 h. Cool to 45°C to avoid monomer decomposition during subsequent rotary evaporation. Then remove cyclohexane by rotary evaporation at 70°C and a vacuum of -0.09 MPa to obtain the amide-ester bifunctional sustained-release monomer.

[0032] It should be noted that the zwitterionic phosphonic acid-based clay inhibitor is composed of the following components: 1 mol of 2-acrylamide-2-methylpropanesulfonic acid, 0.7 mol of vinylphosphonic acid, 1.1 mol of dimethyldiallylammonium chloride, 0.010 mol of potassium persulfate, and 60 mL of deionized water. The preparation method of the zwitterionic phosphonic acid-based clay inhibitor includes the following steps: b1. Add 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, dimethyldiallylammonium chloride and deionized water to the reaction flask, stir thoroughly, and then adjust the pH to 4.5 with dilute sulfuric acid. b2. The mixture system obtained in step b1 is purged with nitrogen three times, heated to 62°C, and 10% potassium persulfate aqueous solution is added dropwise at a uniform rate over 1.0 h. Then the temperature is raised to 68°C, the reaction is maintained for 4 h, and then cooled to room temperature to obtain zwitterionic phosphonic acid clay inhibitor.

[0033] This embodiment also discloses a controlled polymerization preparation method for a branched high-slump-retention aliphatic water-reducing agent, comprising the following steps: S1. Add deionized water, acetone and sodium bisulfite to a reaction vessel equipped with a stirrer, thermometer and reflux condenser. After stirring evenly, slowly add 30% sodium hydroxide solution to adjust the pH of the system to 11.0. Control the adding time to 30 min. Then raise the temperature to 40℃ and keep the reaction at this temperature for 70 min. S2. The mixture obtained in step S1 is heated to 60°C. All four-armed star-shaped low-carbon hydrophobic cores and 55% formaldehyde are added dropwise at a uniform rate over 1.8 hours, while maintaining the pH of the system at 9.0. Then the temperature is raised to 70°C, and all amide-ester bifunctional slow-release monomers and 20% formaldehyde are added dropwise at a uniform rate over 1.8 hours, while maintaining the pH of the system at 8.0. Finally, all zwitterionic phosphonic clay inhibitors and the remaining formaldehyde are added dropwise at a uniform rate over 0.8 hours, while maintaining the pH of the system at 7.0. S3. The mixture obtained in S2 is kept at 75℃ for 1.5h to complete the low-temperature curing, and then the temperature is raised to 82℃ and kept at 82℃ for 2.5h to complete the high-temperature densification process. S4. After high-temperature densification, cool to 35°C, adjust the pH of the product to 9.5 with 30% sodium hydroxide solution, and pass through an 80-mesh filter to obtain a branched structure high-slump-retaining aliphatic water-reducing agent.

[0034] Example 2: This embodiment discloses a branched structure high slump-retaining aliphatic water-reducing agent. By weight, the water-reducing agent consists of the following components: 24 parts acetone, 29 parts formaldehyde, 11.5 parts sodium bisulfite, 6.5 parts four-armed star-shaped low-carbon hydrophobic core, 5.5 parts amide-ester bifunctional sustained-release monomer, 4.5 parts zwitterionic phosphonic acid clay inhibitor, and 90 parts deionized water.

[0035] It should be noted that the four-armed star-shaped low-carbon hydrophobic core is composed of the following components: 1 mol pentaerythritol, 4.2 mol propylene oxide, 0.08 mol triethylamine, 280 mL ethanol, and an appropriate amount of 10% citric acid solution. The preparation method of the four-armed star-shaped low-carbon hydrophobic core includes the following steps: 1) Add pentaerythritol, triethylamine and ethanol to a four-necked flask equipped with a stirrer, thermometer and reflux condenser. Heat to 68°C under nitrogen protection and stir at 400 r / min for 40 min. Then add propylene oxide dropwise at a uniform rate over 3.5 h. 2) The mixture obtained in step 1) is heated to 77°C and kept at that temperature for 7 hours. After cooling to room temperature, the organic phase is washed with 10% citric acid solution until the pH is 7.0. After standing, the upper organic phase is separated, anhydrous magnesium sulfate is added and dried for 6 hours. Then, the ethanol is removed by rotary evaporation at a temperature of 65°C and a vacuum of -0.08 MPa to obtain a four-armed star-shaped low-carbon hydrophobic core.

[0036] It should be noted that the composition of the amide-ester bifunctional sustained-release monomer is as follows: maleic anhydride 1 mol, polyethylene glycol monomethyl ether 1 mol, p-toluenesulfonic acid 0.121 mol, hydroquinone 0.0053 mol, diethanolamine 1.5 mol, and cyclohexane 220 mL. The preparation method of the amide-ester bifunctional sustained-release monomer includes the following steps: a1. Add polyethylene glycol monomethyl ether, maleic anhydride, p-toluenesulfonic acid, hydroquinone and cyclohexane to a reaction flask equipped with a water separator, stir and heat to 105°C, and reflux for 4 hours; a2. Cool the mixture obtained in step a1 to 70-80℃, slowly add diethanolamine dropwise over 1.5 hours, maintain the temperature for 3 hours, then continue to heat to 110℃ and reflux for 2 hours. Cool to 48℃ to avoid monomer decomposition during subsequent rotary evaporation. Then remove cyclohexane by rotary evaporation at 80℃ and a vacuum of -0.10 MPa to obtain the amide-ester bifunctional sustained-release monomer.

[0037] It should be noted that the zwitterionic phosphonic acid-based clay inhibitor is composed of the following components: 1 mol of 2-acrylamide-2-methylpropanesulfonic acid, 0.9 mol of vinylphosphonic acid, 1.3 mol of dimethyldiallylammonium chloride, 0.015 mol of potassium persulfate, and 110 mL of deionized water. The preparation method of the zwitterionic phosphonic acid-based clay inhibitor includes the following steps: b1. Add 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, dimethyldiallylammonium chloride and deionized water to the reaction flask, stir thoroughly, and then adjust the pH to 5.5 with dilute sulfuric acid. b2. The mixture system obtained in step b1 is purged with nitrogen three times, heated to 68°C, and 10% potassium persulfate aqueous solution is added dropwise at a uniform rate over 1.5 h. Then the temperature is raised to 72°C, the reaction is maintained for 5 h, and then cooled to room temperature to obtain zwitterionic phosphonic acid clay inhibitor.

[0038] This embodiment also discloses a controlled polymerization preparation method for a branched high-slump-retention aliphatic water-reducing agent, comprising the following steps: S1. Add deionized water, acetone and sodium bisulfite to a reaction vessel equipped with a stirrer, thermometer and reflux condenser. After stirring evenly, slowly add 30% sodium hydroxide solution to adjust the pH of the system to 12.0. Control the adding time to 40 min. Then raise the temperature to 45°C and keep the reaction at this temperature for 100 min. S2. The mixture obtained in step S1 is heated to 65°C, and all four-armed star-shaped low-carbon hydrophobic cores and 65% formaldehyde are added dropwise at a uniform rate over 2.8 hours, while maintaining the pH of the system at 10.0. Then the temperature is raised to 75°C, and all amide-ester bifunctional slow-release monomers and 25% formaldehyde are added dropwise at a uniform rate over 2.8 hours, while maintaining the pH of the system at 9.0. Finally, all zwitterionic phosphonic clay inhibitors and the remaining formaldehyde are added dropwise at a uniform rate over 1.2 hours, while maintaining the pH of the system at 8.0. S3. The mixture obtained in S2 is kept at 80℃ for 2.0h to complete the low-temperature curing, and then the temperature is raised to 88℃ and kept at 88℃ for 3.5h to complete the high-temperature densification process. S4. After high-temperature densification, cool to 38°C, adjust the pH of the product to 10.5 with 30% sodium hydroxide solution, and pass through an 80-mesh filter to obtain a branched structure high-slump-retaining aliphatic water-reducing agent.

[0039] Example 3: This embodiment discloses a branched structure high slump-retaining aliphatic water-reducing agent. By weight, the water-reducing agent consists of the following components: 19 parts acetone, 24 parts formaldehyde, 9.5 parts sodium bisulfite, 5 parts four-armed star-shaped low-carbon hydrophobic core, 4 parts amide-ester bifunctional sustained-release monomer, 3 parts zwitterionic phosphonic acid clay inhibitor, and 75 parts deionized water.

[0040] It should be noted that the four-armed star-shaped low-carbon hydrophobic core is composed of the following components: 1 mol pentaerythritol, 4 mol propylene oxide, 0.07 mol triethylamine, 250 mL ethanol, and an appropriate amount of 10% citric acid solution. The preparation method of the four-armed star-shaped low-carbon hydrophobic core includes the following steps: 1) Add pentaerythritol, triethylamine and ethanol to a four-necked flask equipped with a stirrer, thermometer and reflux condenser. Heat to 65°C under nitrogen protection and stir at 350 r / min for 35 min. Then add propylene oxide dropwise at a uniform rate over 3 h. 2) The mixture obtained in step 1) is heated to 75°C and kept at that temperature for 6.5 h. After cooling to room temperature, the organic phase is washed with 10% citric acid solution until the pH is 6.5. After standing, the upper organic phase is separated, anhydrous magnesium sulfate is added and dried for 5 h. Then, the ethanol is removed by rotary evaporation at a temperature of 60°C and a vacuum of -0.085 MPa to obtain a four-armed star-shaped low-carbon hydrophobic core.

[0041] It should be noted that the composition of the amide-ester bifunctional sustained-release monomer is as follows: maleic anhydride 1 mol, polyethylene glycol monomethyl ether 1 mol, p-toluenesulfonic acid 0.1 mol, hydroquinone 0.0045 mol, diethanolamine 1.2 mol, and cyclohexane 190 mL. The preparation method of the amide-ester bifunctional sustained-release monomer includes the following steps: a1. Add polyethylene glycol monomethyl ether, maleic anhydride, p-toluenesulfonic acid, hydroquinone and cyclohexane to a reaction flask equipped with a water separator, stir and heat to 100°C, and reflux for 3.5 h. a2. Cool the mixture obtained in step a1 to 75°C, slowly add diethanolamine dropwise over 1.2 hours, maintain the temperature for 2.5 hours, then continue to heat to 105°C and reflux for 1.5 hours. Cool to 46°C to avoid monomer decomposition during subsequent rotary evaporation. Then, remove cyclohexane by rotary evaporation at 75°C and a vacuum of -0.095 MPa to obtain the amide-ester bifunctional sustained-release monomer.

[0042] It should be noted that the zwitterionic phosphonic acid-based clay inhibitor consists of the following components: 1 mol of 2-acrylamide-2-methylpropanesulfonic acid, 0.8 mol of vinylphosphonic acid, 1.2 mol of dimethyldiallylammonium chloride, 0.012 mol of potassium persulfate, and 85 mL of deionized water. The preparation method of the zwitterionic phosphonic acid-based clay inhibitor includes the following steps: b1. Add 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, dimethyldiallylammonium chloride and deionized water to the reaction flask, stir thoroughly, and then adjust the pH to 5.0 with dilute sulfuric acid. b2. The mixture system obtained in step b1 is purged with nitrogen three times, heated to 65°C, and 10% potassium persulfate aqueous solution is added dropwise at a uniform rate over 1.2 h. Then the temperature is raised to 70°C, and the reaction is maintained at this temperature for 4.5 h. After cooling to room temperature, zwitterionic phosphonic acid clay inhibitor is obtained.

[0043] This embodiment also discloses a controlled polymerization preparation method for a branched high-slump-retention aliphatic water-reducing agent, comprising the following steps: S1. Add deionized water, acetone and sodium bisulfite to a reaction vessel equipped with a stirrer, thermometer and reflux condenser. After stirring evenly, slowly add 30% sodium hydroxide solution to adjust the pH of the system to 11.5. Control the adding time to 35 min. Then raise the temperature to 42℃ and keep the reaction at this temperature for 85 min. S2. The mixture obtained in step S1 is heated to 62°C. All four-armed star-shaped low-carbon hydrophobic cores and 60% formaldehyde are added dropwise at a uniform rate over 2.3 hours, while maintaining the pH of the system at 9.5. Then the temperature is raised to 72°C, and all amide-ester bifunctional slow-release monomers and 22% formaldehyde are added dropwise at a uniform rate over 2.3 hours, while maintaining the pH of the system at 8.5. Finally, all zwitterionic phosphonic clay inhibitors and the remaining formaldehyde are added dropwise at a uniform rate over 1 hour, while maintaining the pH of the system at 7.5. S3. The mixture obtained in S2 is kept at 77℃ for 1.7h to complete the low-temperature curing, and then the temperature is raised to 85℃ and kept at 85℃ for 3h to complete the high-temperature densification process. S4. After high-temperature densification, cool to 36°C, adjust the pH of the product to 10.0 with 30% sodium hydroxide solution, and pass through an 80-mesh filter to obtain a branched structure high-slump-retaining aliphatic water-reducing agent.

[0044] Comparative Example 1: A branched high-slump-resistance aliphatic water-reducing agent and its controllable polymerization preparation method are disclosed. The only difference between this water-reducing agent and Example 3 is that a four-armed star-shaped low-carbon hydrophobic core is not added.

[0045] Comparative Example 2: A branched high-slump-retention aliphatic water-reducing agent and its controlled polymerization preparation method are disclosed. The only difference between this water-reducing agent and Example 3 is that no amide-ester bifunctional sustained-release monomer is added.

[0046] Comparative Example 3: A branched high-slump-resistance aliphatic water-reducing agent and its controlled polymerization preparation method are disclosed. The only difference between this water-reducing agent and Example 3 is that no zwitterionic phosphonic acid clay inhibitor is added.

[0047] Comparative Example 4: A branched high-slump-resistance aliphatic water-reducing agent and its controllable polymerization preparation method are disclosed. The difference between this water-reducing agent and Example 3 is that the four-armed star-shaped low-carbon hydrophobic core is replaced with an equal weight of glyoxal (linear crosslinking agent).

[0048] Comparative Example 5: A branched high-slump-retention aliphatic water-reducing agent and its controlled polymerization preparation method are disclosed. The only difference between this water-reducing agent and Example 3 is that an equal weight of acrylic acid (monoester monomer) is used to replace the amide-ester bifunctional sustained-release monomer.

[0049] Comparative Example 6: A branched high-slump-resistance aliphatic water-reducing agent and its controlled polymerization preparation method are disclosed. The difference between this water-reducing agent and Example 3 is that an equal weight of methacryloyloxyethyltrimethylammonium chloride (ordinary cationic monomer) is used to replace the zwitterionic phosphonic acid clay inhibitor.

[0050] Comparative Example 7: A branched high-slump-retention aliphatic water-reducing agent and its controllable polymerization preparation method are disclosed. The only difference between this water-reducing agent and Example 3 is that the gradient condensation process is cancelled, that is, all formaldehyde, four-armed star-shaped low-carbon hydrophobic core, amide-ester bifunctional slow-release monomer, and zwitterionic phosphonic acid clay inhibitor are added at one time.

[0051] Comparative Example 8: A branched high-slump-retention aliphatic water-reducing agent and its controlled polymerization preparation method are disclosed. The only difference between this water-reducing agent and Example 3 is that the temperature of the low-carbon pre-sulfonation stage is controlled at 50-55℃ (the corresponding temperature in step S1 is 40-45℃).

[0052] Comparative Example 9: A branched high-slump-retention aliphatic water-reducing agent and its controllable polymerization preparation method are disclosed. The only difference between this water-reducing agent and Example 3 is that the pH during the gradient condensation stage (all pH values ​​in step S2) is uniformly controlled to be 9.0-10.0.

[0053] Comparative Example 10: A branched high-slump-retention aliphatic water-reducing agent and its controllable polymerization preparation method are disclosed. The difference between this water-reducing agent and Example 3 is that the low-temperature curing stage is cancelled (i.e., the low-temperature curing treatment at 75-80°C in step S3 is cancelled), and the agent directly enters the high-temperature densification stage after gradient condensation is completed.

[0054] The water-reducing agents obtained in Examples 1-3 and Comparative Examples 1-10 were subjected to performance tests for water reduction rate, slump loss over time, compressive strength ratio, soil blending fluidity, marine impermeability, and lightweight aggregate compatibility. The test methods and standards for each performance are as follows: 1. Water reduction rate testing Referring to Clause 6.2 of GB / T 8076-2008 "Concrete Admixtures", the mix proportion of marine C40 low-carbon concrete is adopted (cement:sand:crushed stone (5-20mm):water = 1:2.6:5.2:0.45, cement dosage 350kg / m³). 3 The water consumption W0 required to achieve a slump of (210±10) mm for the reference concrete and the water consumption W1 required to achieve the same slump for the concrete with water-reducing agent are determined according to the formula “water reduction rate = [(W0-W1) / W0]×100%”.

[0055] 2. Slump loss detection over time Referring to Clause 6.3 of GB / T 8076-2008 "Concrete Admixtures", the above-mentioned marine C40 low-carbon concrete mix proportion was used to determine the initial slump (S0), 60-minute slump (S60), and 120-minute slump (S120) of the freshly mixed concrete, and the slump values ​​at each time point were recorded.

[0056] 3. Compressive strength ratio test Referring to Clause 6.4 of GB / T 8076-2008 "Concrete Admixtures", the above-mentioned marine C40 low-carbon concrete mix proportion was adopted to form 100mm×100mm×100mm test blocks. The test blocks were cured for 3 days and 28 days under standard conditions of temperature 20±2℃ and humidity ≥95%, and the compressive strength was tested. The compressive strength ratio was calculated according to the formula "compressive strength ratio = (strength of admixture test block / strength of reference test block) × 100%".

[0057] 4. Soil Flowability Test Referring to Appendix C of JG / T 223-2017 "Polycarboxylate-based high-performance water-reducing agents", a cement:water ratio of 1:0.29 was used for the neat paste mix, with 8% bentonite added (simulating high mud content aggregate), and the water-reducing agent dosage was 0.5% (consolidation). The initial neat paste fluidity and the neat paste fluidity at 60 minutes were measured and the values ​​were recorded.

[0058] 5. Marine engineering impermeability testing Referring to Clause 6.1 of GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the above-mentioned marine C40 low-carbon concrete mix proportion was used to form 175mm×185mm×150mm impermeability test blocks. After standard curing for 28 days, the impermeability grade was determined by the stepwise pressure method, and the impermeability grade results were recorded.

[0059] 6. Lightweight aggregate compatibility testing Expanded clay aggregate (bulk density ≤ 800 kg / m³) was used to replace 50% of the crushed stone in the above-mentioned marine C40 low-carbon concrete, while keeping other mix proportions unchanged. The initial fluidity of the fresh concrete was measured and the value was recorded.

[0060] The results are shown in Table 1.

[0061] Table 1 Performance parameters of the water-reducing agents obtained in Examples 1-3 and Comparative Examples 1-10

[0062] Referring to Table 1, and taking Example 3 as an example: In Comparative Example 1, the water reduction rate was 22%, a decrease of 37.1% compared to Example 3; the initial slump was 205 mm, a decrease of 18.6% compared to Example 3; the 120-minute slump was 135 mm, a decrease of 42.6% compared to Example 3; the 3-day compressive strength ratio was 126%, a decrease of 16.6% compared to Example 3; the 28-day compressive strength ratio was 112%, a decrease of 17.0% compared to Example 3; the soil flowability was 212 mm, a decrease of 14.5% compared to Example 3; the marine engineering impermeability grade was P8, a decrease of 33.3% compared to Example 3; and the lightweight aggregate flowability was 195 mm, a decrease of 18.1% compared to Example 3. The reason is that the lack of four-way anchoring sites provided by the four-armed star-shaped low-carbon hydrophobic core prevents the water-reducing agent molecules from forming a three-dimensional branched skeleton. Instead, they only exhibit a linear structure, which significantly weakens the steric hindrance effect, leading to easy agglomeration of cement particles. At the same time, the linear molecules are not firmly adsorbed on the surface of cement particles and are prone to desorption due to charge changes caused by cement hydration. This results in a significant decrease in water reduction, slump retention, compressive strength, and impermeability, and makes it unsuitable for the dispersion requirements of lightweight aggregates.

[0063] In Comparative Example 2, the water reduction rate was 30%, a decrease of 14.3% compared to Example 3; the initial slump was 240 mm, a decrease of 4.8% compared to Example 3; the slump at 120 min was 175 mm, a decrease of 25.5% compared to Example 3; the 3-day compressive strength ratio was 141%, a decrease of 6.6% compared to Example 3; the 28-day compressive strength ratio was 123%, a decrease of 8.9% compared to Example 3; the marine engineering impermeability grade was P9, a decrease of 25.0% compared to Example 3; and the flowability of the lightweight aggregate was 228 mm, a decrease of 4.2% compared to Example 3. The reason is that no amide-ester bifunctional slow-release monomer was added. The water-reducing agent only relied on the sulfonic acid group to provide electrostatic repulsion. The initial dispersion effect was acceptable, but as the cement hydration process progressed, the sulfonic acid group was easily encapsulated or consumed by the hydration products, and could not continuously replenish the dispersion force, resulting in a rapid loss of slump after 60 minutes. At the same time, due to the large loss of slump, the density of the concrete after molding was insufficient, and the impermeability decreased. However, the fluidity of the soil admixture was basically the same, indicating that the amide-ester bifunctional slow-release monomer mainly played a role in maintaining slump and had no direct effect on preventing clay adsorption.

[0064] In Comparative Example 3, the water reduction rate was 33%, a decrease of 5.7% compared to Example 3; the initial slump was 248 mm, a decrease of 1.6% compared to Example 3; the 60-minute slump was 232 mm, a decrease of 2.5% compared to Example 3; the 120-minute slump was 202 mm, a decrease of 14.0% compared to Example 3; the 3-day compressive strength ratio was 147%, a decrease of 2.6% compared to Example 3; the 28-day compressive strength ratio was 130%, a decrease of 3.7% compared to Example 3; the soil flowability was 185 mm, a decrease of 25.4% compared to Example 3; the marine engineering impermeability grade was P10, a decrease of 16.7% compared to Example 3; and the lightweight aggregate flowability was 232 mm, a decrease of 2.5% compared to Example 3. The reason is that no zwitterionic phosphonic acid-based clay inhibitor was added. The clay (bentonite) surface is negatively charged and will preferentially adsorb the main water-reducing agent (anionic type), resulting in a decrease in the effective water-reducing agent concentration. This leads to an increased slump loss at 120 minutes and a significant decrease in the fluidity of the admixture. At the same time, after the clay adsorbs the main agent, the cement particles are not evenly dispersed, and there are micro-voids inside the concrete, which slightly reduces the impermeability. However, the initial slump, water reduction rate and the fluidity of lightweight aggregates do not decrease significantly, indicating that the zwitterionic phosphonic acid-based clay inhibitor mainly acts to prevent clay adsorption and has little effect on the initial dispersion.

[0065] In Comparative Example 4, the water reduction rate was 25%, a decrease of 28.6% compared to Example 3; the initial slump was 215 mm, a decrease of 14.7% compared to Example 3; the 120-minute slump was 152 mm, a decrease of 35.3% compared to Example 3; the 3-day compressive strength ratio was 133%, a decrease of 11.9% compared to Example 3; the 28-day compressive strength ratio was 116%, a decrease of 14.1% compared to Example 3; the soil flowability was 218 mm, a decrease of 12.1% compared to Example 3; the marine engineering impermeability grade was P8, a decrease of 33.3% compared to Example 3; and the lightweight aggregate flowability was 202 mm, a decrease of 15.1% compared to Example 3. The reason is that glyoxal is a linear crosslinking agent, which can only form a two-dimensional chain structure with acetone-formaldehyde sulfonated chains and cannot construct a three-dimensional branched framework. Its steric hindrance effect is weaker than that of the four-armed star-shaped low-carbon hydrophobic core. At the same time, glyoxal has a weak crosslinking ability and its molecular chains are easy to break, resulting in insufficient adsorption strength. Its water reduction, slump retention and compressive strength are all lower than those of Example 3, which proves that the three-dimensional branched structure of the four-armed star-shaped low-carbon hydrophobic core is irreplaceable for performance improvement.

[0066] In Comparative Example 5, the water reduction rate was 28%, a decrease of 20.0% compared to Example 3; the initial slump was 230 mm, a decrease of 8.7% compared to Example 3; the 120-minute slump was 165 mm, a decrease of 29.8% compared to Example 3; the 3-day compressive strength ratio was 136%, a decrease of 9.9% compared to Example 3; the 28-day compressive strength ratio was 119%, a decrease of 11.9% compared to Example 3; the soil flowability was 235 mm, a decrease of 5.2% compared to Example 3; the marine engineering impermeability grade was P9, a decrease of 25.0% compared to Example 3; and the lightweight aggregate flowability was 215 mm, a decrease of 9.7% compared to Example 3. The reason is that acrylic acid contains only monoester bonds, which can be completely hydrolyzed within 120 minutes in the alkaline environment of cement. It cannot achieve the "fast + slow" two-stage hydrolysis like amide-ester bifunctional slow-release monomers, resulting in insufficient dispersion power in the later stage and aggravated slump loss. At the same time, after the monoester bond is hydrolyzed, only carboxylate groups are released, and there are no polyether side chains to supplement the steric hindrance, so the dispersion effect is weaker than that of bifunctional monomers, which in turn reduces water reduction and compressive strength.

[0067] In Comparative Example 6, the water reduction rate was 32%, a decrease of 8.6% compared to Example 3; the initial slump was 245 mm, a decrease of 2.8% compared to Example 3; the 120-minute slump was 200 mm, a decrease of 14.9% compared to Example 3; the 3-day compressive strength ratio was 145%, a decrease of 3.3% compared to Example 3; the 28-day compressive strength ratio was 128%, a decrease of 5.2% compared to Example 3; the soil flowability was 200 mm, a decrease of 19.4% compared to Example 3; the marine engineering impermeability grade was P10, a decrease of 16.7% compared to Example 3; and the lightweight aggregate flowability was 230 mm, a decrease of 3.4% compared to Example 3. The reason is that methacryloyloxyethyltrimethylammonium chloride is a common cationic monomer, and its adsorption energy with clay is much lower than that of the zwitterionic phosphonic acid clay inhibitor. It cannot form a stable "sacrificial layer", and some of the main agent will still be adsorbed by clay, resulting in a decrease in the fluidity of the mixed soil and an aggravation of the loss of slump in the later stage. At the same time, because the effective concentration of the main agent is slightly lower than that in Example 3, the impermeability is slightly reduced, which proves that the strong adsorption effect of phosphonic acid on clay is the key to improving the mud resistance.

[0068] In Comparative Example 7, the water reduction rate was 26%, a decrease of 25.7% compared to Example 3; the initial slump was 220 mm, a decrease of 12.7% compared to Example 3; the 120-minute slump was 148 mm, a decrease of 37.0% compared to Example 3; the 3-day compressive strength ratio was 131%, a decrease of 13.2% compared to Example 3; the 28-day compressive strength ratio was 114%, a decrease of 15.6% compared to Example 3; the soil flowability was 210 mm, a decrease of 15.3% compared to Example 3; the marine engineering impermeability grade was P8, a decrease of 33.3% compared to Example 3; and the lightweight aggregate flowability was 200 mm, a decrease of 15.9% compared to Example 3. The reason is that after the gradient condensation process was cancelled, the reaction rates of formaldehyde with the four-armed star-shaped low-carbon hydrophobic core, the amide-ester bifunctional slow-release monomer, and the zwitterionic phosphonic acid clay inhibitor were mismatched. Some components reacted too quickly and polymerized rapidly, forming polymers with uneven molecular weight distribution. The large molecules produced by the rapid polymerization were easy to precipitate, while the small molecules had insufficient dispersion, resulting in a significant decrease in all properties. This proves that the gradient condensation process is crucial for controlling the reaction rate and ensuring the uniformity of molecular structure.

[0069] In Comparative Example 8, the water reduction rate was 27%, a decrease of 22.9% compared to Example 3; the initial slump was 225 mm, a decrease of 10.7% compared to Example 3; the slump at 120 min was 155 mm, a decrease of 34.0% compared to Example 3; the 3-day compressive strength ratio was 134%, a decrease of 11.3% compared to Example 3; the 28-day compressive strength ratio was 117%, a decrease of 13.3% compared to Example 3; the soil flowability was 215 mm, a decrease of 13.3% compared to Example 3; the marine engineering impermeability grade was P8, a decrease of 33.3% compared to Example 3; and the lightweight aggregate flowability was 205 mm, a decrease of 13.9% compared to Example 3. The reason is that the temperature in the pre-sulfonation stage rises to 50-55℃, and the decomposition rate of sodium bisulfite increases by 20% at high temperature, resulting in a decrease in the sulfonation rate from ≥92% in Example 3 to 80%, a reduction in the sulfonic acid group content, and a weakening of electrostatic repulsion. At the same time, high temperature will accelerate the side reaction of acetone and formaldehyde, generating small molecule impurities that have no dispersing effect, further reducing water reduction and slump retention performance, and increasing energy consumption by 15% compared to Example 3, proving the energy-saving and performance advantages of the low-carbon low-temperature pre-sulfonation process of the present invention.

[0070] In Comparative Example 9, the water reduction rate was 25%, a decrease of 28.6% compared to Example 3; the initial slump was 218 mm, a decrease of 13.5% compared to Example 3; the slump at 120 min was 150 mm, a decrease of 36.2% compared to Example 3; the 3-day compressive strength ratio was 130%, a decrease of 13.9% compared to Example 3; the 28-day compressive strength ratio was 113%, a decrease of 16.3% compared to Example 3; the soil flowability was 213 mm, a decrease of 14.1% compared to Example 3; the marine impermeability grade was P8, a decrease of 33.3% compared to Example 3; and the lightweight aggregate flowability was 198 mm, a decrease of 16.8% compared to Example 3. The reason is that the pH is uniformly controlled at 9.0-10.0 during the gradient condensation stage. A high pH environment will cause the phosphonic acid group in the zwitterionic phosphonic acid clay inhibitor to hydrolyze, losing its strong adsorption effect on clay. At the same time, high pH will accelerate the hydrolysis of the amide bond in the amide-ester bifunctional slow-release monomer, shortening the slow-release period to less than 6 hours and resulting in insufficient dispersion in the later stage. In addition, high pH will cause excessive condensation of formaldehyde, forming a polymer with excessive cross-linking, which will reduce solubility and thus significantly reduce all properties. This proves that pH gradient regulation is crucial for protecting functional groups and ensuring the orderly progress of the reaction.

[0071] In Comparative Example 10, the water reduction rate was 29%, a decrease of 17.1% compared to Example 3; the initial slump was 232 mm, a decrease of 7.9% compared to Example 3; the slump at 120 min was 170 mm, a decrease of 27.7% compared to Example 3; the 3-day compressive strength ratio was 138%, a decrease of 8.6% compared to Example 3; the 28-day compressive strength ratio was 120%, a decrease of 11.1% compared to Example 3; the soil flowability was 232 mm, a decrease of 6.5% compared to Example 3; the marine engineering impermeability grade was P9, a decrease of 25.0% compared to Example 3; and the lightweight aggregate flowability was 218 mm, a decrease of 8.4% compared to Example 3. The reason is that by canceling the low-temperature curing stage, the molecular chains have not grown uniformly after gradient condensation. Some amide-ester bifunctional slow-release monomers and zwitterionic phosphonic acid clay inhibitors have not been fully grafted onto the main chain. Directly entering the high-temperature densification stage will cause the ungrafted monomers to self-polymerize, forming small molecules without synergistic effects. At the same time, the molecular chain length of the main chain is uneven, and the steric hindrance effect is weakened, resulting in a decrease in water reduction and slump retention performance. This proves that the low-temperature curing stage is crucial to ensuring the functional group grafting rate and improving the uniformity of molecular structure.

[0072] In summary, this invention achieves a comprehensive breakthrough in water-reducing agents in terms of high water reduction, ultra-long slump retention, strong mud resistance, and low carbon compatibility through the synergistic effect of three self-designed components: a four-armed star-shaped low-carbon hydrophobic core, an amide-ester bifunctional slow-release monomer, and a zwitterionic phosphonic acid-based clay inhibitor, as well as precise process control of "low-carbon pre-sulfonation-gradient condensation-low-temperature curing-high-temperature densification". It can be widely used in marine cement, lightweight building materials, and special low-carbon concrete projects, solving the industry pain points of poor compatibility and single performance of traditional aliphatic water-reducing agents.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A branched structure high slump retention aliphatic water reducer, characterized by, The water-reducing agent comprises the following components by weight: 14-24 parts acetone, 19-29 parts formaldehyde, 7.5-11.5 parts sodium bisulfite, 3.5-6.5 parts four-armed star-shaped low-carbon hydrophobic core, 2.5-5.5 parts amide-ester bifunctional sustained-release monomer, 2.0-4.5 parts zwitterionic phosphonic acid clay inhibitor, and 60-90 parts deionized water. The four-armed star-shaped low-carbon hydrophobic core is composed of the following components: 1 mol pentaerythritol, 3.8-4.2 mol propylene oxide, 0.06-0.08 mol triethylamine, 220-280 mL ethanol, and an appropriate amount of 10% citric acid solution. The composition of the amide-ester bifunctional sustained-release monomer is as follows: maleic anhydride 1 mol, polyethylene glycol monomethyl ether 1 mol, p-toluenesulfonic acid 0.091-0.121 mol, hydroquinone 0.0036-0.0053 mol, diethanolamine 1-1.5 mol, cyclohexane 160-220 mL; The zwitterionic phosphonic acid clay inhibitor is composed of the following components: 1 mol of 2-acrylamide-2-methylpropanesulfonic acid, 0.7-0.9 mol of vinylphosphonic acid, 1.1-1.3 mol of dimethyldiallylammonium chloride, 0.010-0.015 mol of potassium persulfate, and 60-110 mL of deionized water.

2. The branched high-slump-retention aliphatic water-reducing agent according to claim 1, characterized in that, The water-reducing agent is composed of the following components by weight: 19 parts acetone, 24 parts formaldehyde, 9.5 parts sodium bisulfite, 5 parts four-armed star-shaped low-carbon hydrophobic core, 4 parts amide-ester bifunctional sustained-release monomer, 3 parts zwitterionic phosphonic acid clay inhibitor, and 75 parts deionized water.

3. The branched high-slump-retention aliphatic water-reducing agent according to claim 1, characterized in that, The preparation method of the four-armed star-shaped low-carbon hydrophobic core includes the following steps: 1) Add pentaerythritol, triethylamine and ethanol to a four-necked flask equipped with a stirrer, thermometer and reflux condenser. Heat to 62-68℃ under nitrogen protection and stir at 300-400 r / min for 30-40 min. Then add propylene oxide dropwise at a uniform rate over 2.5-3.5 h. 2) Heat the mixture obtained in step 1) to 73-77℃ and keep it at that temperature for 6-7 hours. After cooling to room temperature, wash the organic phase with 10% citric acid solution until the pH is 6.0-7.

0. After standing, separate the upper organic phase, add anhydrous magnesium sulfate and dry for 4-6 hours. Then, remove the ethanol by rotary evaporation at a temperature of 55-65℃ and a vacuum of -0.08 to -0.09 MPa to obtain a four-armed star-shaped low-carbon hydrophobic core.

4. The branched high-slump-retention aliphatic water-reducing agent according to claim 1, characterized in that, The preparation method of the amide-ester bifunctional sustained-release monomer includes the following steps: a1. Add polyethylene glycol monomethyl ether, maleic anhydride, p-toluenesulfonic acid, hydroquinone and cyclohexane to a reaction flask equipped with a water separator, stir and heat to 95-105℃, and reflux for 3-4 hours; a2. Cool the mixture obtained in step a1 to 70-80℃, slowly add diethanolamine dropwise over 1.0-1.5 hours, maintain the temperature for 2-3 hours, then continue to heat to 100-110℃ and reflux for 1-2 hours. Cool to 45-48℃, and then remove cyclohexane by rotary evaporation at 70-80℃ and a vacuum of -0.09 to -0.10 MPa to obtain the amide-ester bifunctional sustained-release monomer.

5. The branched high-slump-retention aliphatic water-reducing agent according to claim 1, characterized in that, The preparation method of zwitterionic phosphonic acid clay inhibitor includes the following steps: b1. Add 2-acrylamide-2-methylpropanesulfonic acid, vinylphosphonic acid, dimethyldiallylammonium chloride and deionized water to the reaction flask, stir thoroughly, and then adjust the pH to 4.5-5.5 with dilute sulfuric acid. b2. The mixture system obtained in step b1 is purged with nitrogen three times, heated to 62-68℃, and 10% potassium persulfate aqueous solution is added dropwise at a uniform rate over 1.0-1.5h. Then the temperature is raised to 68-72℃ and the reaction is maintained for 4-5h. After cooling to room temperature, zwitterionic phosphonic acid clay inhibitor is obtained.

6. A controlled polymerization preparation method for a branched high-slump-retention aliphatic water-reducing agent according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Add deionized water, acetone and sodium bisulfite to a reaction vessel equipped with a stirrer, thermometer and reflux condenser. After stirring evenly, slowly add 30% sodium hydroxide solution to adjust the pH of the system to 11.0-12.

0. Control the adding time to 30-40 min. Then raise the temperature to 40-45℃ and keep the reaction at this temperature for 70-100 min. S2. Heat the mixture obtained in step S1 to 60-65℃, and simultaneously add all the four-armed star-shaped low-carbon hydrophobic cores and 55%-65% formaldehyde at a uniform rate over 1.8-2.8h, maintaining the pH of the system at 9.0-10.

0. Then heat to 70-75℃, and simultaneously add all the amide-ester bifunctional slow-release monomers and 20%-25% formaldehyde at a uniform rate over 1.8-2.8h, maintaining the pH of the system at 8.0-9.

0. Finally, add all the zwitterionic phosphonic clay inhibitors and the remaining formaldehyde at a uniform rate over 0.8-1.2h, maintaining the pH of the system at 7.0-8.

0. S3. The mixture obtained in S2 is kept at 75-80℃ for 1.5-2.0h to complete the low-temperature curing, and then the temperature is raised to 82-88℃ and kept at 82-88℃ for 2.5-3.5h to complete the high-temperature densification process. S4. After high-temperature densification, cool to 35-38℃, adjust the pH of the product to 9.5-10.5 with 30% sodium hydroxide solution, filter, and the branched structure high slump-retaining aliphatic water-reducing agent is obtained.

7. The controlled polymerization preparation method of the branched high-slump-retention aliphatic water-reducing agent according to claim 6, characterized in that, In step S4, the filter used for filtration is an 80-mesh filter.

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