Borate crosslinking type high-temperature stable polycarboxylic acid pumping agent and preparation process thereof

Abstract

The invention provides a boric acid ester cross-linking type high-temperature stable polycarboxylic acid pumping agent and a preparation process of the boric acid ester cross-linking type high-temperature stable polycarboxylic acid pumping agent. The pumping agent is prepared from the following components in parts by weight: 45 to 60 parts of isopentenyl polyoxyethylene ether, 15 to 20 parts of allyl polyoxyethylene ether, 18 to 22 parts of acrylic acid, 4 to 6 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3 to 5 parts of N-vinyl pyrrolidone, 2 to 3 parts of maleic anhydride, 5 to 7 parts of 3-acrylamido phenylboronic acid, 5 to 7 parts of boric acid ester dynamic cross-linking agent, 1.5 to 2.5 parts of KH550 modified nano ZnO and 0.9 to 1.2 parts of initiator. 0.4-0.6 part of a chain transfer agent, 10-15 parts of a phosphate buffer solution and 210-250 parts of deionized water. The prepared pumping agent has the comprehensive advantages of high-temperature stability, excellent water-retaining property and dispersibility, segregation resistance, high strength and the like.

Description

Technical Field

[0001] This invention relates to the field of pumping agent technology, specifically to a borate ester crosslinked high-temperature stable polycarboxylate pumping agent and its preparation process. Background Technology

[0002] Polycarboxylate pumping agents are key materials for achieving efficient construction in concrete engineering. Their core function is to maintain the workability of concrete during mixing, transportation and pumping through the synergistic effect of adsorption groups (such as carboxyl groups and sulfonic acid groups) and steric hindrance groups (such as polyether side chains) in the molecular structure.

[0003] With the increasing demands for adaptability to construction environments in modern engineering projects, the need for concrete pumping in high-temperature environments (80-100℃) is becoming increasingly prominent, such as in summer open-air operations, construction in areas with abundant geothermal energy, and special high-temperature curing projects. In such scenarios, traditional polycarboxylate pumping agents often suffer from insufficient molecular chain thermal stability and easy failure of adsorption sites, resulting in excessively rapid slump loss and poor anti-segregation properties of concrete, which seriously affects construction efficiency and project quality.

[0004] In existing technologies, dynamic cross-linking structures have been introduced to improve the high-temperature stability of concrete. Cross-linking networks are constructed through reversible covalent bonds such as borate ester bonds, attempting to achieve slow decross-linking at high temperatures by adjusting bond energy. However, the simple dynamic bond design is prone to insufficient initial fluidity due to excessively high cross-linking density, and lacks precise control of temperature response. In environments above 80°C, bond breakage and loss of control are likely to occur, which will exacerbate slump loss. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a borate ester crosslinked high-temperature stable polycarboxylate pumping agent and its preparation process.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This application discloses a borate ester crosslinking type high-temperature stable polycarboxylic acid pumping agent. The pumping agent is composed of the following components by weight: 45-60 parts of isopentenyl polyoxyethylene ether, 15-20 parts of allyl polyoxyethylene ether, 18-22 parts of acrylic acid, 4-6 parts of 2-acrylamido-2-methylpropanesulfonic acid, 3-5 parts of N-vinylpyrrolidone, 2-3 parts of maleic anhydride, 5-7 parts of 3-acrylamidophenylboronic acid, 5-7 parts of borate ester dynamic crosslinking agent, 1.5-2.5 parts of KH550 modified nano ZnO, 0.9-1.2 parts of initiator, 0.4-0.6 parts of chain transfer agent, 10-15 parts of phosphate buffer, and 210-250 parts of deionized water.

[0007] Preferably, the pumping agent comprises the following components by weight: 51 parts isopentenyl polyoxyethylene ether, 17 parts allyl polyoxyethylene ether, 20 parts acrylic acid, 5 parts 2-acrylamide-2-methylpropanesulfonic acid, 4 parts N-vinylpyrrolidone, 2.5 parts maleic anhydride, 6 parts 3-acrylamide-phenylboronic acid, 6 parts borate ester dynamic crosslinking agent, 2 parts KH550 modified nano-ZnO, 1.05 parts initiator, 0.5 parts chain transfer agent, 12.5 parts phosphate buffer, and 230 parts deionized water.

[0008] By implementing the above technical solutions, isopentenyl polyoxyethylene ether (IPEG2400) provides a branched structure, enhancing water retention and reducing high-temperature bleeding; the allyl structure in allyl polyoxyethylene ether (APEG2200) imparts higher thermal stability to the molecular chain, improving dispersion persistence under high-temperature conditions; acrylic acid provides carboxyl groups, achieving initial dispersion of cement particles through electrostatic repulsion; 2-acrylamido-2-methylpropanesulfonic acid introduces sulfonic acid groups, enhancing the hydrophilicity and anti-salting ability of the molecular chain, and improving stability under highly alkaline conditions; N-vinylpyrrolidone (NVP) is a thermosensitive monomer (LCST≈35℃), undergoing hydrophobic shrinkage at high temperatures, reducing slump loss caused by water evaporation. The loss of adsorption sites is compensated by the ring-opening reaction of maleic anhydride (MAH) at high temperatures, which generates additional carboxyl groups. 3-Acrylamidophenylboronic acid provides borate ester groups, forming dynamic covalent bonds with hydroxyl groups in the system, achieving reversible crosslinking of molecular chains. The borate ester bond (-BOC-) in the borate ester dynamic crosslinking agent (BDE) molecule can form reversible covalent bonds with hydroxyl groups in polycarboxylic acid molecular chains (such as the polyether hydroxyl groups in the side chains of IPEG2400 and APEG2200). In the pre-crosslinking stage (25-35℃), a preliminary crosslinking network is formed first. This network, as the molecular skeleton, provides an ordered structural basis for subsequent polymerization reactions, avoiding disordered entanglement of molecular chains and ensuring the stability of initial dispersion performance. The borate ester bond (-BOC-) in the borate ester dynamic crosslinking agent (BDE) molecule is temperature sensitive and undergoes reversible hydrolysis (borate ester bond + H2O) at high temperatures (80-100℃). Boric acid groups and hydroxyl groups cause partial dissociation of the cross-linking network, releasing more free dispersed groups (such as carboxyl groups and sulfonic acid groups). This "high-temperature decrosslinking" characteristic can specifically compensate for the loss of adsorption sites in cement particles at high temperatures, maintaining the fluidity of the slurry. KH550 modified nano-ZnO uses Zn... 2+ It inhibits the early hydration heat release of cement, and the surface amino and carboxyl groups react to achieve anchoring, thereby improving the dispersion uniformity of the pumping agent.

[0009] Preferably, the mass ratio of isopentenyl polyoxyethylene ether to allyl polyoxyethylene ether is 3:1, the initiator is composed of potassium persulfate and tert-butyl hydroperoxide in a mass ratio of 2:1, and the chain transfer agent is mercaptoacetic acid.

[0010] By setting up the above technical solution, the 3:1 compounding ratio of IPEG2400 and APEG2200 not only ensures sufficient steric hindrance (IPEG2400 provides long side chains), but also improves the thermal stability of the molecular chain through the allyl structure of APEG2200.

[0011] Preferably, the composition of KH550 modified nano-ZnO by weight is as follows: 8-12 parts nano-ZnO, 3-5 parts silane coupling agent KH550, 50-70 parts anhydrous ethanol and 10-15 parts deionized water.

[0012] The preferred method for preparing KH550 modified nano-ZnO is as follows: 1) Add nano-ZnO to an ethanol-water mixture with a volume ratio of 5:1 and ultrasonically disperse it for 30-40 min at 300-400 W. 2) Heat to 60-70℃, add KH550 dropwise under stirring at 300-400r / min, and keep the temperature for 2-3h. 3) Centrifuge the product obtained in step 2) at a speed of 3000-4000 r / min for 15-20 min, wash the precipitate with ethanol 3-4 times, and then vacuum dry at 60-70℃ for 4-6 h to obtain KH550 modified nano ZnO.

[0013] Preferably, the composition of the borate ester dynamic crosslinking agent, by weight, is as follows: 10-12 parts of 3-hydroxyphenylboronic acid, 6-8 parts of ethylene glycol, 0.5-0.8 parts of p-toluenesulfonic acid, and 80-100 parts of toluene.

[0014] Preferably, the preparation method of the borate ester dynamic crosslinking agent is as follows: 3-hydroxyphenylboronic acid, ethylene glycol, p-toluenesulfonic acid and toluene are added to a three-necked flask equipped with a water separator, thermometer and stirring device. Nitrogen gas is introduced for protection, the temperature is raised to 110-120℃, and the reaction is stirred at 250-350 r / min for 4-6 h. After cooling to room temperature, the solution is neutralized to pH 7-8 with sodium carbonate solution. The organic phase is separated and then rotary evaporated to remove toluene to obtain the borate ester dynamic crosslinking agent.

[0015] This application also discloses a preparation process for a borate ester crosslinked high-temperature stable polycarboxylate pumping agent, comprising the following steps: S1. Pre-crosslinking reaction stage: In a 1000mL four-necked flask equipped with a thermometer, stirrer, and condenser, add 45-60 parts of isopentenyl polyoxyethylene ether, 15-20 parts of allyl polyoxyethylene ether, and 80-100 parts of deionized water. Heat to 25-35℃ and stir at 180-220r / min until completely dissolved. Then add borate ester dynamic crosslinking agent and phosphate buffer with pH 7.5. Stir at 250-300r / min for 50-70min to form a preliminary crosslinking network through borate ester bonds. Finally, add 3-5 parts of N-vinylpyrrolidone and 5-7 parts of acrylic acid, and dropwise add 0.3-0.4 parts of tert-butyl hydroperoxide dissolved in 5-8 parts of deionized water. After stirring evenly, maintain the reaction at 25-35℃ for 40-50min to form a prepolymer with N-vinylpyrrolidone as the temperature-sensitive core. S2, Gradient-triggered aggregation phase: a. Dissolve 0.6-0.8 parts of potassium persulfate in 8-10 parts of deionized water and stir until completely dissolved to obtain a potassium persulfate solution; b. Dissolve 2-acrylamido-2-methylpropanesulfonic acid, maleic anhydride, 3-acrylamidophenylboronic acid and the remaining acrylic acid in 20-25 parts of deionized water and stir until completely dissolved to obtain a monomer mixture. c. Maintain a stirring speed of 240-250 r / min, heat the reaction system to 40℃, add the initiator solution dropwise over 28-30 min, and add potassium persulfate solution dropwise simultaneously, controlling the dropping rate to ensure that the monomer mixture is added evenly over 55-60 min; During the entire dropping process, the temperature was increased to 50℃ at a rate of 1℃ / 15min. The temperature sensitivity of N-vinylpyrrolidone was used to gradually trigger the ring-opening of maleic anhydride. Ten minutes after the start of the monomer mixture dropping, 0.4-0.6 parts of mercaptoacetic acid dissolved in 8-10 parts of deionized water were added simultaneously to control the chain length distribution index to be 1.8-2.2. S3, Nano-anchoring and Post-processing Stage: The final product system obtained in S2 is heated to 55-60℃, and KH550 modified nano-ZnO is added at once. The mixture is stirred at 300-350 r / min for 90-100 min to form Si-OC covalent bonds between the silane coupling agent and the polymer carboxyl groups. After the reaction is completed, the temperature is lowered to 35-38℃, and the pH is adjusted to 6.0-7.0 with 30% sodium hydroxide solution. Deionized water is added until the solid content is 40±2%. Finally, a pressure spray drying process is used to obtain a white powder of borate ester crosslinked high-temperature stable polycarboxylic acid pumping agent.

[0016] By setting up the above technical solution and using phosphate buffer to maintain pH=7.5, the stability of borate ester bonds during polymerization can be ensured (they are easily hydrolyzed at pH>8, and insufficient cross-linking is likely to occur at pH<7). Maintaining a heating rate of 1℃ / 15min during the dropwise addition process allows NVP to undergo a gradual conformational change within the 35-45℃ range, creating a synergistic effect with the MAH ring-opening reaction.

[0017] Preferably, the KH550 modified nano-ZnO in step S3 needs to be ultrasonically dispersed in 9-10 parts of deionized water before use.

[0018] Preferably, in the pressure spray drying process, the inlet air temperature is 180℃, the outlet air temperature is 85℃, and the atomization pressure is 2.5MPa.

[0019] By setting up the above technical solution, the inlet air temperature for spray drying needs to be controlled at around 180℃ to prevent the boronic acid ester bonds from overheating and decomposing.

[0020] The beneficial effects of this invention are as follows: The borate bond (-BOC-) in the borate ester dynamic crosslinking agent (BDE) molecule is temperature sensitive and undergoes reversible hydrolysis at high temperatures (80-100℃) (borate bond + H2O). The boric acid group + hydroxyl group causes partial dissociation of the cross-linking network, releasing more free dispersed groups (such as carboxyl groups and sulfonic acid groups). This "high-temperature decrosslinking" characteristic can specifically compensate for the loss of adsorption sites of cement particles at high temperatures and maintain the fluidity of the slurry.

[0021] When the temperature is below 35℃, N-vinylpyrrolidone hydrophilically extends, and BDE forms a stable cross-linked network, slowly releasing the dispersed components; when the temperature is above 35℃, NVP hydrophobically shrinks and compresses the network, causing the dynamic bonds of BDE to break, releasing more dispersed groups, while MAH opens the ring to generate carboxyl groups, forming a "dual compensation" mechanism.

[0022] The long branches of isopentenyl polyoxyethylene ether (IPEG2400) provide dispersion space for nano-ZnO, while the rigid structure of allyl polyoxyethylene ether (APEG2200) enhances the binding force between nanoparticles and molecular chains. Nano-ZnO is connected to the polycarboxylic acid backbone through the -Si-O- bonds of KH550, forming a three-dimensional network of "point-line" bonding, which improves structural stability at high temperatures.

[0023] Gradient heating and stepwise processing enable NVP polymerization to complete within the 35-45℃ range, avoiding competitive reactions with the borate bonds in the borate ester dynamic crosslinking agent molecules at high temperatures. The redox reaction initiated by the tert-butyl hydroperoxide (TBHP) / potassium persulfate (KPS) composite lowers the activation energy, ensuring polymerization can be started at a low temperature (35℃), thus reducing energy consumption. Detailed Implementation

[0024] 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.

[0025] Example 1: This embodiment discloses a borate ester crosslinking type high-temperature stable polycarboxylic acid pumping agent. The pumping agent is composed of the following components by weight: 45 parts of isopentenyl polyoxyethylene ether, 15 parts of allyl polyoxyethylene ether, 18 parts of acrylic acid, 4 parts of 2-acrylamido-2-methylpropanesulfonic acid, 3 parts of N-vinylpyrrolidone, 2 parts of maleic anhydride, 5 parts of 3-acrylamidophenylboronic acid, 5 parts of borate ester dynamic crosslinking agent, 1.5 parts of KH550 modified nano ZnO, 0.9 parts of initiator, 0.4 parts of chain transfer agent, 10 parts of phosphate buffer, and 210 parts of deionized water.

[0026] The mass ratio of isopentenyl polyoxyethylene ether to allyl polyoxyethylene ether is 3:1, the initiator is composed of potassium persulfate and tert-butyl hydroperoxide in a mass ratio of 2:1, and the chain transfer agent is mercaptoacetic acid.

[0027] The composition of KH550-modified nano-ZnO by weight is as follows: 8 parts nano-ZnO, 3 parts silane coupling agent KH550, 50 parts anhydrous ethanol, and 10 parts deionized water. The preparation method of KH550-modified nano-ZnO is as follows: 1) Add nano ZnO to an ethanol-water mixture with a volume ratio of 5:1 and ultrasonically disperse it for 30 min at 300 W. 2) Heat to 60℃, add KH550 dropwise under stirring at 300r / min, and keep the temperature for 2h. 3) The product obtained in step 2) was centrifuged at 3000 r / min for 15 min, the precipitate was washed with ethanol 3 times, and then vacuum dried at 60℃ for 4 h to obtain KH550 modified nano ZnO.

[0028] The composition of the borate ester dynamic crosslinking agent by weight is as follows: 10 parts of 3-hydroxyphenylboronic acid, 6 parts of ethylene glycol, 0.5 parts of p-toluenesulfonic acid, and 80 parts of toluene. The preparation method of the borate ester dynamic crosslinking agent is as follows: 3-hydroxyphenylboronic acid, ethylene glycol, p-toluenesulfonic acid, and toluene are added to a three-necked flask equipped with a water separator, thermometer, and stirring device. Nitrogen gas is introduced for protection, the temperature is raised to 110℃, and the reaction is stirred at 250 r / min for 4 h. After cooling to room temperature, the solution is neutralized to pH 7 with sodium carbonate solution. The organic phase is separated and then the organic phase is rotary evaporated to remove toluene, thus obtaining the borate ester dynamic crosslinking agent.

[0029] This embodiment also discloses a preparation process for a borate ester crosslinked high-temperature stable polycarboxylate pumping agent, which includes the following steps: S1. Pre-crosslinking reaction stage: In a 1000mL four-necked flask equipped with a thermometer, stirrer, and condenser, add 45 parts of isopentenyl polyoxyethylene ether, 15 parts of allyl polyoxyethylene ether, and 80 parts of deionized water. Heat to 25℃ and stir at 180r / min until completely dissolved. Then add borate ester dynamic crosslinking agent and phosphate buffer with pH 7.5. Stir at 250r / min for 50min to form a preliminary crosslinking network through borate ester bonds. Finally, add 3 parts of N-vinylpyrrolidone and 5 parts of acrylic acid, and dropwise add 0.3 parts of tert-butyl hydroperoxide dissolved in 5 parts of deionized water. After stirring evenly, maintain the reaction at 25℃ for 40min to form a prepolymer with N-vinylpyrrolidone as the temperature-sensitive core. S2, Gradient-triggered aggregation phase: a. Dissolve 0.6 parts of potassium persulfate in 8 parts of deionized water and stir until completely dissolved to obtain a potassium persulfate solution; b. Dissolve 2-acrylamido-2-methylpropanesulfonic acid, maleic anhydride, 3-acrylamidophenylboronic acid and the remaining acrylic acid in 20 parts of deionized water and stir until completely dissolved to obtain a monomer mixture. c. Maintain a stirring speed of 240 r / min, heat the reaction system to 40℃, add the initiator solution dropwise over 28 min, and add potassium persulfate solution dropwise simultaneously, controlling the dropping rate to ensure that the monomer mixture is added evenly over 55 min; During the entire dropping process, the temperature was increased to 50°C at a rate of 1°C / 15 min. The temperature sensitivity of N-vinylpyrrolidone was used to gradually trigger the ring-opening of maleic anhydride. Ten minutes after the monomer mixture was dropped, 0.4 parts of mercaptoacetic acid dissolved in 8 parts of deionized water were added simultaneously to control the chain length distribution index to 1.8. S3, Nano-anchoring and Post-processing Stage: The final product system obtained in S2 was heated to 55℃, and KH550 modified nano-ZnO (pre-dispersed ultrasonically in 9 parts of deionized water) was added in one go. The mixture was stirred at 300 r / min for 90 min to form Si-OC covalent bonds between the silane coupling agent and the polymer carboxyl groups. After the reaction was completed, the temperature was lowered to 35℃, and the pH was adjusted to 6.0 with 30% sodium hydroxide solution. Deionized water was added until the solid content was 40±2%. Finally, a pressure spray drying process was used (inlet air temperature 180℃, outlet air temperature 85℃, atomization pressure 2.5MPa) to obtain a white powdery borate ester crosslinked high-temperature stable polycarboxylic acid pumping agent.

[0030] Example 2: This embodiment discloses a borate ester crosslinking type high-temperature stable polycarboxylic acid pumping agent. The pumping agent is composed of the following components by weight: 60 parts of isopentenyl polyoxyethylene ether, 20 parts of allyl polyoxyethylene ether, 22 parts of acrylic acid, 6 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts of N-vinylpyrrolidone, 3 parts of maleic anhydride, 7 parts of 3-acrylamidophenylboronic acid, 7 parts of borate ester dynamic crosslinking agent, 2.5 parts of KH550 modified nano-ZnO, 1.2 parts of initiator, 0.6 parts of chain transfer agent, 15 parts of phosphate buffer, and 250 parts of deionized water.

[0031] The mass ratio of isopentenyl polyoxyethylene ether to allyl polyoxyethylene ether is 3:1, the initiator is composed of potassium persulfate and tert-butyl hydroperoxide in a mass ratio of 2:1, and the chain transfer agent is mercaptoacetic acid.

[0032] The composition of KH550-modified nano-ZnO by weight is as follows: 12 parts nano-ZnO, 5 parts silane coupling agent KH550, 70 parts anhydrous ethanol, and 15 parts deionized water. The preparation method of KH550-modified nano-ZnO is as follows: 1) Add nano ZnO to an ethanol-water mixture with a volume ratio of 5:1 and ultrasonically disperse it for 40 min at 400 W. 2) Heat to 70℃, add KH550 dropwise while stirring at 400r / min, and keep the temperature for 3h. 3) The product obtained in step 2) was centrifuged at 4000 r / min for 20 min, the precipitate was washed with ethanol 4 times, and then vacuum dried at 70℃ for 6 h to obtain KH550 modified nano ZnO.

[0033] The composition of the borate ester dynamic crosslinking agent by weight is as follows: 12 parts of 3-hydroxyphenylboronic acid, 8 parts of ethylene glycol, 0.8 parts of p-toluenesulfonic acid, and 100 parts of toluene. The preparation method of the borate ester dynamic crosslinking agent is as follows: 3-hydroxyphenylboronic acid, ethylene glycol, p-toluenesulfonic acid, and toluene are added to a three-necked flask equipped with a water separator, thermometer, and stirring device. Nitrogen gas is introduced for protection, the temperature is raised to 120℃, and the reaction is stirred at 350 r / min for 6 h. After cooling to room temperature, the solution is neutralized to pH 8 with sodium carbonate solution. The organic phase is separated and then the organic phase is rotary evaporated to remove toluene, thus obtaining the borate ester dynamic crosslinking agent.

[0034] This embodiment also discloses a preparation process for a borate ester crosslinked high-temperature stable polycarboxylate pumping agent, which includes the following steps: S1. Pre-crosslinking reaction stage: In a 1000mL four-necked flask equipped with a thermometer, stirrer, and condenser, add 60 parts of isopentenyl polyoxyethylene ether, 20 parts of allyl polyoxyethylene ether, and 100 parts of deionized water. Heat to 35℃ and stir at 220r / min until completely dissolved. Then add borate ester dynamic crosslinking agent and phosphate buffer with pH 7.5. Stir at 300r / min for 70min to form a preliminary crosslinking network through borate ester bonds. Finally, add 5 parts of N-vinylpyrrolidone and 7 parts of acrylic acid, and dropwise add 0.4 parts of tert-butyl hydroperoxide dissolved in 8 parts of deionized water. After stirring evenly, maintain the reaction at 35℃ for 50min to form a prepolymer with N-vinylpyrrolidone as the temperature-sensitive core. S2, Gradient-triggered aggregation phase: a. Dissolve 0.8 parts of potassium persulfate in 10 parts of deionized water and stir until completely dissolved to obtain a potassium persulfate solution; b. Dissolve 2-acrylamido-2-methylpropanesulfonic acid, maleic anhydride, 3-acrylamidophenylboronic acid and the remaining acrylic acid in 25 parts of deionized water and stir until completely dissolved to obtain a monomer mixture. c. Maintain a stirring speed of 250 r / min, heat the reaction system to 40℃, add the initiator solution dropwise over 30 min, and add potassium persulfate solution dropwise simultaneously, controlling the dropping rate to ensure that the monomer mixture is added evenly over 60 min; During the entire dropping process, the temperature was increased to 50°C at a rate of 1°C / 15 min. The temperature sensitivity of N-vinylpyrrolidone was used to gradually trigger the ring-opening of maleic anhydride. Ten minutes after the monomer mixture was dropped, 0.6 parts of mercaptoacetic acid dissolved in 10 parts of deionized water were added simultaneously to control the chain length distribution index to be 2.2. S3, Nano-anchoring and Post-processing Stage: The final product system obtained in S2 was heated to 60℃, and KH550 modified nano-ZnO (pre-dispersed ultrasonically in 10 parts of deionized water) was added in one go. The mixture was stirred at 350 r / min for 100 min to form Si-OC covalent bonds between the silane coupling agent and the polymer carboxyl groups. After the reaction was completed, the temperature was lowered to 38℃, and the pH was adjusted to 7.0 with 30% sodium hydroxide solution. Deionized water was added until the solid content was 40±2%. Finally, a pressure spray drying process was used (inlet air temperature 180℃, outlet air temperature 85℃, atomization pressure 2.5MPa) to obtain a white powdery borate ester crosslinked high-temperature stable polycarboxylic acid pumping agent.

[0035] Example 3: This embodiment discloses a borate ester crosslinking type high-temperature stable polycarboxylic acid pumping agent. The pumping agent is composed of the following components by weight: 51 parts of isopentenyl polyoxyethylene ether, 17 parts of allyl polyoxyethylene ether, 20 parts of acrylic acid, 5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 4 parts of N-vinylpyrrolidone, 2.5 parts of maleic anhydride, 6 parts of 3-acrylamidophenylboronic acid, 6 parts of borate ester dynamic crosslinking agent, 2 parts of KH550 modified nano-ZnO, 1.05 parts of initiator, 0.5 parts of chain transfer agent, 12.5 parts of phosphate buffer, and 230 parts of deionized water.

[0036] The mass ratio of isopentenyl polyoxyethylene ether to allyl polyoxyethylene ether is 3:1, the initiator is composed of potassium persulfate and tert-butyl hydroperoxide in a mass ratio of 2:1, and the chain transfer agent is mercaptoacetic acid.

[0037] The composition of KH550-modified nano-ZnO by weight is as follows: 10 parts nano-ZnO, 4 parts silane coupling agent KH550, 60 parts anhydrous ethanol, and 12 parts deionized water. The preparation method of KH550-modified nano-ZnO is as follows: 1) Add nano-ZnO to an ethanol-water mixture with a volume ratio of 5:1 and ultrasonically disperse it for 35 min at 350 W. 2) Heat to 65℃, add KH550 dropwise while stirring at 350r / min, and maintain the temperature for 2.5h. 3) The product obtained in step 2) was centrifuged at 3500 r / min for 17 min, the precipitate was washed three times with ethanol, and then dried under vacuum at 65℃ for 5 h to obtain KH550 modified nano ZnO.

[0038] The composition of the borate ester dynamic crosslinking agent by weight is as follows: 11 parts of 3-hydroxyphenylboronic acid, 7 parts of ethylene glycol, 0.65 parts of p-toluenesulfonic acid, and 90 parts of toluene. The preparation method of the borate ester dynamic crosslinking agent is as follows: 3-hydroxyphenylboronic acid, ethylene glycol, p-toluenesulfonic acid, and toluene are added to a three-necked flask equipped with a water separator, thermometer, and stirring device. Nitrogen gas is introduced for protection, the temperature is raised to 115℃, and the reaction is stirred at 300 r / min for 5 h. After cooling to room temperature, the solution is neutralized to pH 7.5 with sodium carbonate solution. The organic phase is separated and then subjected to rotary evaporation to remove toluene, thus obtaining the borate ester dynamic crosslinking agent.

[0039] This embodiment also discloses a preparation process for a borate ester crosslinked high-temperature stable polycarboxylate pumping agent, which includes the following steps: S1. Pre-crosslinking reaction stage: In a 1000mL four-necked flask equipped with a thermometer, stirrer, and condenser, add 51 parts of isopentenyl polyoxyethylene ether, 17 parts of allyl polyoxyethylene ether, and 90 parts of deionized water. Heat to 30℃ and stir at 200r / min until completely dissolved. Then add borate ester dynamic crosslinking agent and phosphate buffer with pH 7.5. Stir at 275r / min for 60min to form a preliminary crosslinking network through borate ester bonds. Finally, add 4 parts of N-vinylpyrrolidone and 6 parts of acrylic acid, and dropwise add 0.35 parts of tert-butyl hydroperoxide dissolved in 6 parts of deionized water. After stirring evenly, maintain the reaction at 30℃ for 45min to form a prepolymer with N-vinylpyrrolidone as the temperature-sensitive core. S2, Gradient-triggered aggregation phase: a. Dissolve 0.7 parts of potassium persulfate in 9 parts of deionized water and stir until completely dissolved to obtain a potassium persulfate solution; b. Dissolve 2-acrylamido-2-methylpropanesulfonic acid, maleic anhydride, 3-acrylamidophenylboronic acid and the remaining acrylic acid in 22 parts of deionized water and stir until completely dissolved to obtain a monomer mixture. c. Maintain a stirring speed of 245 r / min, heat the reaction system to 40℃, add the initiator solution dropwise over 29 min, and add potassium persulfate solution dropwise simultaneously, controlling the dropping rate to ensure that the monomer mixture is added evenly over 57 min; During the entire dropping process, the temperature was increased to 50℃ at a rate of 1℃ / 15min. The temperature sensitivity of N-vinylpyrrolidone was used to gradually trigger the ring-opening of maleic anhydride. Ten minutes after the monomer mixture was dropped, 0.5 parts of mercaptoacetic acid dissolved in 9 parts of deionized water were added simultaneously to control the chain length distribution index to 2.0. S3, Nano-anchoring and Post-processing Stage: The final product system obtained in S2 was heated to 57℃, and KH550 modified nano-ZnO (pre-dispersed ultrasonically in 9.5 parts of deionized water) was added in one go. The mixture was stirred at 325 r / min for 95 min to form Si-OC covalent bonds between the silane coupling agent and the polymer carboxyl groups. After the reaction was completed, the temperature was lowered to 36℃, and the pH was adjusted to 6.5 with 30% sodium hydroxide solution. Deionized water was added until the solid content was 40±2%. Finally, a pressure spray drying process was used (inlet air temperature 180℃, outlet air temperature 85℃, atomization pressure 2.5MPa) to obtain a white powdery borate ester crosslinked high-temperature stable polycarboxylic acid pumping agent.

[0040] Comparative Example 1: A borate ester crosslinked high-temperature stable polycarboxylate pumping agent, which differs from Example 3 only in that BDE is not added.

[0041] Comparative Example 2: A borate ester crosslinked high-temperature stable polycarboxylate pumping agent, which differs from Example 3 only in that it does not contain NVP.

[0042] Comparative Example 3: A borate ester crosslinking type high-temperature stable polycarboxylic acid pumping agent, the only difference between this pumping agent and Example 3 is that: no KH550 modified nano-ZnO is added.

[0043] Comparative Example 4: A borate ester crosslinked high-temperature stable polycarboxylic acid pumping agent, the only difference between this pumping agent and Example 3 is that unmodified nano-ZnO is used instead of KH550 modified nano-ZnO.

[0044] Comparative Example 5: A borate ester crosslinking type high-temperature stable polycarboxylic acid pumping agent, the only difference between this pumping agent and Example 3 is that: no gradient heating is used, and the reaction is carried out directly at 50°C.

[0045] Comparative Example 6: A borate ester crosslinking type high-temperature stable polycarboxylic acid pumping agent, the only difference between this pumping agent and Example 3 is that the pre-crosslinking step is omitted and the polymerization reaction is carried out directly.

[0046] Comparative Example 7: A borate ester crosslinked high-temperature stable polycarboxylic acid pumping agent, which differs from Example 3 only in that ordinary boric acid is used instead of BDE.

[0047] Comparative Example 8: A borate ester crosslinked high-temperature stable polycarboxylate pumping agent, which differs from Example 3 only in that it does not contain MAH.

[0048] Comparative Example 9: A borate ester crosslinking type high-temperature stable polycarboxylate pumping agent, the only difference between this pumping agent and Example 3 is that the addition ratio of IPEG2400 and APEG2200 is 1:1.

[0049] Comparative Example 10: A borate ester crosslinking type high-temperature stable polycarboxylic acid pumping agent, which differs from Example 3 only in that the initiator used is KPS.

[0050] The pumping agents obtained in Examples 1-3 and Comparative Examples 1-10 were subjected to additional tests on cement paste fluidity, concrete workability, compressive strength, and high-temperature stability, respectively. (a) Cement paste fluidity test (refer to GB / T8077-2012) Sample preparation: Accurately weigh 3g of the powdered pumping agent from Examples 1-3 and Comparative Examples 1-10 according to the "converted to solids" principle (i.e., the mass converted to pure active ingredient; since the solid content of the sample is 40±2%, the actual powder mass weighed is approximately 7.5-7.8g). The baseline group does not add pumping agent and is tested only with cement and water.

[0051] Mixing method: Add 87g of water (water-cement ratio 0.29) and the weighed pumping agent sample to 300g of cement in sequence, and mix according to the process of "low speed mixing for 30s → stop mixing for 15s → high speed mixing for 30s" to ensure that the pumping agent is evenly dispersed in the cement paste.

[0052] High temperature test treatment: For the 90℃ 1h flowability test, the mixed cement paste was placed in a 90℃ water bath environment for constant temperature curing for 1 hour, during which moisture evaporation was avoided (cling film can be used for covering). After removal, it was stirred in the same manner and the flow diameter was measured to evaluate the dispersion stability of the pumping agent under high temperature environment.

[0053] (ii) Concrete workability test (refer to GB / T50080-2016) Mix proportioning: Following the concrete mix proportion of "400 kg / m³ cement, 650 kg / m³ sand, 1150 kg / m³ aggregate, and 160 kg / m³ water," add 4 kg of pumping agent per cubic meter of concrete (the powdered pumping agent used in Examples 1-3 and Comparative Examples 1-10 is added directly in powder form without additional dissolution, as the moisture during mixing will allow it to disperse sufficiently). The baseline group does not add pumping agent and prepares concrete solely according to the above mix proportions.

[0054] Initial performance test: The concrete material mixed with pumping agent was placed into the test mold in three layers, and each layer was tamped 25 times. After the tamping was completed, the surface was leveled, and the slump (height of the cylinder minus the height of the highest point of the specimen) and spread (calculated as the average diameter of two mutually perpendicular directions) were measured immediately. The initial workability data were recorded.

[0055] High-temperature performance test: The molded concrete specimens were placed in an 80℃ environmental chamber for 1 hour, and the humidity inside the environmental chamber was maintained during the period (to avoid excessive evaporation of water from affecting the test results). After being taken out, the specimens were manually stirred 20 times (simulating secondary stirring in actual construction). The slump loss and spread were measured again to evaluate the workability retention of the pumping agent after high-temperature storage.

[0056] (III) Compressive strength test (refer to GB / T50081-2019) Specimen preparation: Add the corresponding pumping agent (Examples 1-3 or Comparative Examples 1-10) according to the concrete mix proportion, stir evenly, and then pour into 150mm×150mm×150mm specimens. After compaction, scrape the surface smooth. The reference group specimens are also prepared according to the mix proportion but without adding pumping agent.

[0057] Curing and Testing: The test blocks were placed in a standard curing environment (20±2℃, RH≥95%) for 1 day, 3 days, 7 days, and 28 days respectively. After the curing period, they were removed and their compressive strength was tested using a pressure testing machine. The 28-day compressive strength ratio of the test blocks of each embodiment and comparative example to the baseline group test blocks was calculated to evaluate the enhancing effect of the pumping agent on the concrete strength.

[0058] (iv) Additional high-temperature stability test Segregation resistance test: The concrete mixture with pumping agent (same mix proportion and dosage as in the workability test) was placed into a 10L graduated cylinder. After standing for 30 minutes, 5L of mortar was taken from the bottom and top of the graduated cylinder respectively, and the mass difference was measured and the percentage (segregation resistance difference) was calculated. The example and comparative samples demonstrated their ability to inhibit concrete segregation through this test, while the baseline group served as a blank control.

[0059] Apparent viscosity test: A concrete mixture containing the pumping agent was incubated in a 60°C constant temperature water bath for 30 minutes. The apparent viscosity was then measured using a rotational viscometer (selecting an appropriate rotor and rotation speed). Comparison with examples (e.g., Example 3, viscosity 324) was used. ) and comparative examples (e.g., Comparative Example 7, viscosity 660) The values ​​of ) are used to evaluate the pumping agent's ability to maintain the fluidity of concrete at high temperatures.

[0060] The results of each test are shown in Table 1.

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

[0062] As shown in Table 1: Comparative Example 1 (without BDE): The absence of dynamic borate ester bonds prevents the formation of a reversible cross-linked network at high temperatures. The flowability was 145 mm after 1 hour at 90°C (265 mm in Example 3), and the slump loss reached 90 mm, proving that BDE is the core for maintaining high-temperature dispersion stability.

[0063] Comparative Example 2 (without NVP): The temperature-sensitive regulation function was lost, the molecular chains could not shrink and retain water at high temperatures, and the expansion at 80°C for 1 hour was significantly lower than that of Example 3, verifying that NVP plays a key role in inhibiting water evaporation.

[0064] Comparative Example 3 (Nano ZnO without KH550 modification): Lacking nano-anchoring effect, the segregation resistance difference increased to 8.0% (2.8% in Example 3), and the 28-day compressive strength ratio decreased significantly, indicating that the nanoparticles improved the slurry density through uniform dispersion.

[0065] Comparative Example 4 (Unmodified Nano ZnO): Nanoparticle aggregation led to a decrease in anchoring effect, with an apparent viscosity of 530 at 60℃. (Example 3 is 324) This indicates that KH550 modification is key to achieving uniform dispersion of nanoparticles.

[0066] Comparative Example 5 (without gradient heating): The uncontrolled polymerization sequence of monomers led to a conflict between the temperature-sensitive groups and the dynamic bond reaction, and the fluidity retention rate at 90°C dropped to 76.5% (91.4% in Example 3), proving that gradient heating is a necessary condition for achieving a concerted reaction.

[0067] Comparative Example 6 (without pre-crosslinking): The lack of initial crosslinking network caused disorder in molecular structure and comprehensive deterioration of various properties. The initial slump was reduced by 31.5% compared with Example 3, which confirms the rationality of the three-step process.

[0068] Comparative Example 7 (using ordinary boric acid instead of BDE): Boric acid is easily hydrolyzed, leading to unstable cross-linking and the worst high-temperature performance (the expansion at 80℃ for 1 hour was only 275 mm, compared to 517 mm in Example 3), highlighting the structural advantages of BDE.

[0069] Example 3 achieves superior overall performance compared to a single mechanism through a triple synergy of "dynamic bond-temperature-sensitive group-nanoparticle": Synergistic effect of dynamic bond (BDE) and temperature-sensitive group (NVP): The slump loss (25mm) at 80℃ for 1h is much lower than the total loss when either is missing alone (90+80=170mm), which reflects a nonlinear synergistic effect.

[0070] Nano-anchoring and synergistic effect of two macromonomers: The long side chains of IPEG provide dispersion space for nano-ZnO, and the rigid structure of APEG enhances anchoring stability, reducing the segregation resistance difference to 2.8%, which is 65% lower than Comparative Example 3 (without nano-ZnO).

[0071] 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 borate ester crosslinked high-temperature stable polycarboxylate pumping agent, characterized in that, The pumping agent comprises the following components by weight: 45-60 parts isopentenyl polyoxyethylene ether, 15-20 parts allyl polyoxyethylene ether, 18-22 parts acrylic acid, 4-6 parts 2-acrylamido-2-methylpropanesulfonic acid, 3-5 parts N-vinylpyrrolidone, 2-3 parts maleic anhydride, 5-7 parts 3-acrylamidophenylboronic acid, 5-7 parts borate ester dynamic crosslinking agent, 1.5-2.5 parts KH550 modified nano-ZnO, 0.9-1.2 parts initiator, 0.4-0.6 parts chain transfer agent, 10-15 parts phosphate buffer, and 210-250 parts deionized water.

2. The borate ester crosslinked high-temperature stable polycarboxylate pumping agent according to claim 1, characterized in that, The pumping agent comprises the following components by weight: 51 parts isopentenyl polyoxyethylene ether, 17 parts allyl polyoxyethylene ether, 20 parts acrylic acid, 5 parts 2-acrylamido-2-methylpropanesulfonic acid, 4 parts N-vinylpyrrolidone, 2.5 parts maleic anhydride, 6 parts 3-acrylamidophenylboronic acid, 6 parts borate ester dynamic crosslinking agent, 2 parts KH550 modified nano-ZnO, 1.05 parts initiator, 0.5 parts chain transfer agent, 12.5 parts phosphate buffer, and 230 parts deionized water.

3. The borate ester crosslinked high-temperature stable polycarboxylate pumping agent according to claim 1 or 2, characterized in that, The mass ratio of isopentenyl polyoxyethylene ether to allyl polyoxyethylene ether is 3:1, the initiator is composed of potassium persulfate and tert-butyl hydroperoxide in a mass ratio of 2:1, and the chain transfer agent is mercaptoacetic acid.

4. The borate ester crosslinked high-temperature stable polycarboxylate pumping agent according to claim 3, characterized in that, The composition of KH550 modified nano-ZnO by weight is as follows: 8-12 parts nano-ZnO, 3-5 parts silane coupling agent KH550, 50-70 parts anhydrous ethanol and 10-15 parts deionized water.

5. The borate ester crosslinked high-temperature stable polycarboxylate pumping agent according to claim 4, characterized in that, The preparation method of KH550 modified nano-ZnO is as follows: 1) Add nano-ZnO to an ethanol-water mixture with a volume ratio of 5:1 and ultrasonically disperse it for 30-40 min at 300-400 W. 2) Heat to 60-70℃, add KH550 dropwise under stirring at 300-400r / min, and keep the temperature for 2-3h. 3) Centrifuge the product obtained in step 2) at a speed of 3000-4000 r / min for 15-20 min, wash the precipitate with ethanol 3-4 times, and then vacuum dry at 60-70℃ for 4-6 h to obtain KH550 modified nano ZnO.

6. The borate ester crosslinked high-temperature stable polycarboxylate pumping agent according to claim 4, characterized in that, The composition of the borate ester dynamic crosslinking agent by weight is as follows: 10-12 parts of 3-hydroxyphenylboronic acid, 6-8 parts of ethylene glycol, 0.5-0.8 parts of p-toluenesulfonic acid and 80-100 parts of toluene.

7. The borate ester crosslinked high-temperature stable polycarboxylate pumping agent according to claim 6, characterized in that, The preparation method of the borate ester dynamic crosslinking agent is as follows: 3-hydroxyphenylboronic acid, ethylene glycol, p-toluenesulfonic acid and toluene are added to a three-necked flask equipped with a water separator, thermometer and stirring device. Nitrogen gas is introduced for protection, the temperature is raised to 110-120℃, and the reaction is stirred at 250-350 r / min for 4-6 h. After cooling to room temperature, the pH is neutralized to 7-8 with sodium carbonate solution. The organic phase is separated and then the organic phase is rotary evaporated to remove toluene to obtain the borate ester dynamic crosslinking agent.

8. A preparation process for a borate ester crosslinked high-temperature stable polycarboxylate pumping agent according to any one of claims 3-7, characterized in that, It includes the following steps: S1. Pre-crosslinking reaction stage: In a 1000mL four-necked flask equipped with a thermometer, stirrer, and condenser, add 45-60 parts of isopentenyl polyoxyethylene ether, 15-20 parts of allyl polyoxyethylene ether, and 80-100 parts of deionized water. Heat to 25-35℃ and stir at 180-220r / min until completely dissolved. Then add borate ester dynamic crosslinking agent and phosphate buffer with pH 7.

5. Stir at 250-300r / min for 50-70min to form a preliminary crosslinking network through borate ester bonds. Finally, add 3-5 parts of N-vinylpyrrolidone and 5-7 parts of acrylic acid, and dropwise add 0.3-0.4 parts of tert-butyl hydroperoxide dissolved in 5-8 parts of deionized water. After stirring evenly, maintain the reaction at 25-35℃ for 40-50min to form a prepolymer with N-vinylpyrrolidone as the temperature-sensitive core. S2, Gradient-triggered aggregation phase: a. Dissolve 0.6-0.8 parts of potassium persulfate in 8-10 parts of deionized water and stir until completely dissolved to obtain a potassium persulfate solution; b. Dissolve 2-acrylamido-2-methylpropanesulfonic acid, maleic anhydride, 3-acrylamidophenylboronic acid and the remaining acrylic acid in 20-25 parts of deionized water and stir until completely dissolved to obtain a monomer mixture. c. Maintain a stirring speed of 240-250 r / min, heat the reaction system to 40℃, add the initiator solution dropwise over 28-30 min, and add potassium persulfate solution dropwise simultaneously, controlling the dropping rate to ensure that the monomer mixture is added evenly over 55-60 min; During the entire dropping process, the temperature was increased to 50℃ at a rate of 1℃ / 15min. The temperature sensitivity of N-vinylpyrrolidone was used to gradually trigger the ring-opening of maleic anhydride. Ten minutes after the start of the monomer mixture dropping, 0.4-0.6 parts of mercaptoacetic acid dissolved in 8-10 parts of deionized water were added simultaneously to control the chain length distribution index to be 1.8-2.

2. S3, Nano-anchoring and Post-processing Stage: The final product system obtained in S2 is heated to 55-60℃, and KH550 modified nano-ZnO is added at once. The mixture is stirred at 300-350 r / min for 90-100 min to form Si-OC covalent bonds between the silane coupling agent and the polymer carboxyl groups. After the reaction is completed, the temperature is lowered to 35-38℃, and the pH is adjusted to 6.0-7.0 with 30% sodium hydroxide solution. Deionized water is added until the solid content is 40±2%. Finally, a pressure spray drying process is used to obtain a white powder of borate ester crosslinked high-temperature stable polycarboxylic acid pumping agent.

9. The preparation process of the borate ester crosslinked high-temperature stable polycarboxylate pumping agent according to claim 8, characterized in that, Before use, the KH550 modified nano-ZnO in step S3 needs to be ultrasonically dispersed in 9-10 parts of deionized water.

10. The preparation process of the borate ester crosslinked high-temperature stable polycarboxylate pumping agent according to claim 8, characterized in that, In the pressure spray drying process, the inlet air temperature is 180℃, the outlet air temperature is 85℃, and the atomization pressure is 2.5MPa.

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