Ester-ether copolymerization type slump-retaining polycarboxylic acid water reducer and preparation method thereof

Abstract

The invention provides an ester-ether copolymerization type slump-retaining polycarboxylic acid water reducer and a preparation method of the ester-ether copolymerization type slump-retaining polycarboxylic acid water reducer. The water reducing agent is prepared from the following raw materials in parts by weight: 80 to 120 parts of main chain macromonomer, 20 to 35 parts of unsaturated carboxylic acid, 1.5 to 3.2 parts of initiator, 0.2 to 0.5 part of reducing agent, 0.3 to 0.8 part of chain transfer agent, 8 to 15 parts of neutralizer, 200 to 300 parts of solvent, 5 to 10 parts of diphosphonic polyether monomer, 3 to 6 parts of temperature-sensitive dynamic crosslinking monomer and 2 to 5 parts of amide-ether bond grafting monomer. The water reducer has the comprehensive performance of dispersion, slump loss resistance, mud resistance, high-temperature response and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water reducing agent, and particularly relates to an ester-ether copolymer type slump retaining polycarboxylic acid water reducing agent and a preparation method thereof. BACKGROUND

[0002] As a key admixture in concrete engineering, polycarboxylic acid water reducing agent can realize the dispersion and slump retention of concrete by adjusting the molecular structure, significantly improve the workability and mechanical properties of concrete, and has become one of the core materials for modern concrete preparation. Among them, the ester-ether copolymer type slump retaining polycarboxylic acid water reducing agent relies on the synergistic effect of specific molecular segments, the initial dispersion ability is guaranteed by the related groups of the main chain, and the space steric hindrance is provided by the ether bond structure of the side chain to maintain the system stability. It is widely used in medium and high strength concrete engineering, but as the requirement of concrete anti-complex working condition ability of engineering is improved, higher technical requirements are put forward for the anti-interference ability and long-term performance stability of water reducing agent.

[0003] Although the existing water reducing agent products can meet the basic construction requirements of conventional concrete, the performance is poor in complex application scenarios: on the one hand, when the clay content of concrete aggregate is high, the effective components of water reducing agent are easily adsorbed by clay particles, which leads to a significant reduction in dispersion efficiency and a rapid attenuation of concrete workability, making it difficult to ensure smooth construction; on the other hand, in high temperature construction environment, the slump loss rate of concrete is significantly improved, the existing water reducing agent has insufficient slump retention time, and it is difficult to maintain long-term workability, which easily leads to a rapid loss of concrete slump and affects the strength and construction efficiency of engineering structure. SUMMARY

[0004] In view of the problems in the prior art, the present application provides an ester-ether copolymer type slump retaining polycarboxylic acid water reducing agent and a preparation method thereof, so that the water reducing agent has comprehensive performance such as dispersion, slump retention, mud resistance and high temperature response.

[0005] To achieve the above purpose, the present application realizes the following technical scheme: The present application discloses an ester-ether copolymer type slump retaining polycarboxylic acid water reducing agent, and the raw material composition of the water reducing agent is as follows in terms of weight fraction: 80-120 parts of main chain macromonomer, 20-35 parts of unsaturated carboxylic acid, 1.5-3.2 parts of initiator, 0.2-0.5 parts of reducing agent, 0.3-0.8 parts of chain transfer agent, 8-15 parts of neutralizing agent, 200-300 parts of solvent, 5-10 parts of bisphosphonic acid based polyether monomer, 3-6 parts of temperature sensitive dynamic crosslinking monomer and 2-5 parts of amide-ether bond grafted monomer.

[0006] By setting the above technical scheme, the main chain macromonomer can provide a steric hindrance effect, laying a foundation for system dispersion; the unsaturated carboxylic acid can provide carboxyl groups, taking into account the initial dispersion capacity and long-term slump retention effect; the initiator, reducing agent and chain transfer agent cooperate to ensure efficient polymerization and control the regularity of the molecular chain, improving the stability of the product itself; the neutralizing agent can adjust the pH value of the system, enhance the water solubility and storage stability of the product; the solvent as the reaction medium ensures uniform dispersion of each component to ensure smooth reaction; the bisphosphonic acid-based polyether monomer can preferentially adsorb on the surface of clay and chelate metal ions, effectively improving the anti-mud performance and delaying the hydration process; the temperature-sensitive dynamic crosslinking monomer has high temperature response characteristics, can accelerate the release through phase change and dynamic bond rupture, and compensate for the loss of slump in high temperature environment; the amide-ether bond grafted monomer can improve the compatibility between components, and at the same time enhance the adsorption anchoring ability of the superplasticizer on the substrate surface, further guarantee the long-term slump retention effect, and the synergistic effect of each component makes the superplasticizer have comprehensive properties such as dispersion, slump retention, anti-mud and high temperature response.

[0007] Preferably, the main chain macromonomer is isopentenyl polyoxyethylene ether, the reducing agent is L-ascorbic acid, the chain transfer agent is 3-mercaptopropionic acid, the neutralizing agent is a 30% by mass sodium hydroxide solution, and the solvent is deionized water; wherein, by weight fraction: the unsaturated carboxylic acid is uniformly mixed from 15-25 parts of methacrylic acid and 5-10 parts of acrylic acid, and the initiator is uniformly mixed from 0.5-1.2 parts of potassium persulfate and 1-2 parts of 30% by mass hydrogen peroxide.

[0008] By setting the above technical scheme, the isopentenyl polyoxyethylene ether can provide a steric hindrance skeleton, prevent cement particles from agglomerating through steric hindrance effect, and ensure the initial dispersibility of the superplasticizer; the methacrylic acid can provide carboxyl groups for the main chain and has a slow ester bond hydrolysis rate, which can prolong the release period of the superplasticizer to achieve long-term slump retention, and the acrylic acid can assist in adjusting the charge density of the main chain to further enhance the initial dispersion effect of the superplasticizer; the initiator is mixed from potassium persulfate and 30% by mass hydrogen peroxide, which can form a redox initiation system to efficiently initiate the copolymerization of each monomer and improve the monomer conversion rate; L-ascorbic acid can cooperate with hydrogen peroxide in the initiator to reduce the initiation temperature and assist in ensuring efficient polymerization under low temperature conditions; 3-mercaptopropionic acid can precisely control the length and distribution of the molecular chain of the superplasticizer, avoiding performance defects caused by excessively long or short molecular chains, and ensuring the stability of the dispersion and slump retention performance of the superplasticizer; the 30% by mass sodium hydroxide solution can adjust the pH value of the superplasticizer system, improve the water solubility and storage stability of the product; and the solvent deionized water as the reaction medium can ensure uniform mixing of each component in the system, provide a stable environment for polymerization, and finally make each component synergistically improve the comprehensive performance of the superplasticizer such as dispersion, slump retention and storage.

[0009] Preferably, the preparation method of the bisphosphonic acid-based polyether monomer comprises the following steps: 1) polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine and pure p-toluenesulfonic acid are taken in a molar ratio of 1:1.2:1.5:0.05, and the p-toluenesulfonic acid is separately prepared into a solution with a mass concentration of 10%; 2) polyethylene glycol monomethyl ether is added into a four-necked flask, and nitrogen is introduced at a flow rate of 0.5-1 L / min for protection, oxygen is removed for 10-15 min, vacuum is drawn, the temperature is raised to 80-90℃ for dehydration for 1-1.5 h, then the temperature is lowered to 60-65℃, diethyl phosphite and triethylamine are sequentially added, stirring is carried out at a speed of 300-400 r / min for 30 min, and the p-toluenesulfonic acid solution is added at a uniform speed within 0.5-1 h while the temperature of the system is ≤70℃; 3) the mixture obtained in step 2) is heated to 85-95℃, and incubated for 4-5 h, the reaction end point is monitored by thin layer chromatography, after the reaction is completed, the temperature is lowered to 40-50℃, deionized water is added for dilution, and 30% sodium hydroxide solution is used to adjust the pH to 5.5-6.5, and a bisphosphonate polyether monomer is obtained.

[0010] By setting the above technical solution, the introduction of nitrogen protection and oxygen removal can prevent the oxidation of polyethylene glycol monomethyl ether, diethyl phosphite and other raw materials, avoid the generation of impurities, and ensure the stability of the reaction system to improve the purity of the monomer. Vacuum is drawn and the polyethylene glycol monomethyl ether is dehydrated at 80-90℃, which can remove the trace amount of water contained therein and avoid water interference in the subsequent reaction, thereby creating good conditions for monomer synthesis and helping to improve the yield of the monomer; triethylamine as an acid-binding agent can neutralize the acid generated in the reaction, promote the forward reaction, and control the temperature while adding the p-toluenesulfonic acid solution with a mass concentration of 10% and maintaining the system temperature ≤70℃, which can avoid local overheating to trigger side reactions, make the catalytic reaction develop uniformly, and ensure the regularity of the monomer structure; the reaction end point can be accurately controlled by monitoring the reaction end point by thin layer chromatography, which can prevent incomplete or excessive reaction and ensure the stability of the monomer performance; after the reaction, the temperature is lowered and the pH is adjusted to 5.5-6.5, which can make the bisphosphonate polyether monomer prepared in a stable state and improve its water solubility and compatibility in the subsequent water reducing agent system. The high-purity, stable-performance bisphosphonate polyether monomer prepared finally can effectively play a role in preferentially adsorbing clay and chelating metal ions in cement when used in water reducing agents, thereby enhancing the mud resistance and slump retention of the water reducing agent.

[0011] Preferably, in step 3), the developing agent used in the thin layer chromatography monitoring process is composed of ethyl acetate and petroleum ether in a volume ratio of 1:2, and the amount of deionized water is 1:1 by mass ratio of the total amount of polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine and pure p-toluenesulfonic acid.

[0012] By setting the above technical scheme, the developer composed of ethyl acetate and petroleum ether in a volume ratio of 1:2 can effectively separate polyethylene glycol monomethyl ether, diethyl phosphite and other raw materials and bisphosphonic acid-based polyether monomer products in thin layer chromatography monitoring, accurately determine whether the reaction has reached the end point, avoid incomplete reaction of raw materials or excessive reaction of impurities, and ensure the purity of bisphosphonic acid-based polyether monomer; the deionized water added in a total mass ratio of 1:1 with polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine and pure p-toluenesulfonic acid can reasonably dilute the system after reaction, so that it is easier to control the pH value to 5.5-6.5 when the subsequent 30% sodium hydroxide solution is used to adjust the pH value, while improving the water solubility of bisphosphonic acid-based polyether monomer, facilitating its uniform mixing with other components in the subsequent preparation of water reducing agent, and providing a stable monomer basis for the subsequent anti-mud and slump retention of water reducing agent.

[0013] Preferably, the preparation method of the temperature-sensitive dynamic crosslinking monomer comprises the following steps: a1. N-vinyl caprolactam, 4-vinyl phenyl boronic acid, ethylene glycol dimethacrylate and azobisisobutyronitrile are taken in a molar ratio of 10:3:2:0.2; a2. N-vinyl caprolactam, 4-vinyl phenyl boronic acid, ethylene glycol dimethacrylate are added to a three-necked flask, toluene is added in a mass ratio of the total mass of the three to the mass of toluene 1:3, stirred at a speed of 300-400 r / min for 25-30 min, replaced by nitrogen for 3 times, then azobisisobutyronitrile is added, heated to 65-75℃, constant temperature reaction for 3-4h, toluene is removed by rotary evaporation under the conditions of 45-50℃ and-0.09 to-0.08 MPa, crushed and sieved through an 80 mesh sieve to obtain the temperature-sensitive dynamic crosslinking monomer.

[0014] By setting the above technical scheme, according to the mass ratio of the total mass of N-vinyl caprolactam, 4-vinyl phenyl boronic acid and ethylene glycol dimethacrylate to toluene 1:3, toluene can fully dissolve the three raw materials and form a uniform reaction system, ensuring that the subsequent polymerization reaction proceeds uniformly, avoiding fluctuations in monomer performance caused by uneven dispersion of raw materials; nitrogen replacement can remove oxygen in the system, preventing oxidation of raw materials or reaction intermediates to form impurities and improving monomer purity; constant temperature reaction at 65-75 DEG C provides suitable conditions for azobisisobutyronitrile to initiate copolymerization of the three monomers, ensuring the formation of a monomer product with both temperature-sensitive phase change and dynamic crosslinking structure, laying the foundation for subsequent high-temperature response function; rotary evaporation under the conditions of 45-50 DEG C and -0.09 to -0.08 MPa can efficiently remove toluene solvent, while avoiding high temperature that can cause monomer decomposition or melting, reducing solvent residue; after crushing and passing through an 80-mesh sieve, the monomer particles can be uniformly sized, making it easier to disperse uniformly during subsequent polymerization of the water-reducing agent core layer, helping to form a regular temperature-sensitive response core layer, and ultimately enabling the water-reducing agent to achieve "high-temperature automatic energy compensation" through the phase change shrinkage and dynamic bond rupture of the monomer, effectively compensating for the loss of concrete slump.

[0015] Preferably, in step a2, nitrogen is passed for 10 minutes each time.

[0016] By setting the above technical scheme, the air in the three-necked flask can be fully replaced, ensuring that the oxygen in the system is effectively removed; oxygen can quench the free radicals generated by the decomposition of azobisisobutyronitrile, interfering with the copolymerization of N-vinyl caprolactam, 4-vinyl phenyl boronic acid and ethylene glycol dimethacrylate, while the 10-minute nitrogen flow each time can ensure that the oxygen is completely removed, allowing the initiator to efficiently initiate the polymerization reaction and reducing incomplete polymerization or the generation of by-products caused by residual oxygen, thereby producing a temperature-sensitive dynamic crosslinking monomer with a regular structure and stable performance. This stable monomer can reliably exhibit the dual temperature-sensitive mechanisms of high-temperature phase change shrinkage and dynamic bond rupture when used in subsequent polymerization of the water-reducing agent core layer, helping the water-reducing agent to achieve "high-temperature automatic energy compensation" and effectively compensate for the loss of concrete slump in a high-temperature environment.

[0017] Preferably, the preparation method of the amide-ether grafted monomer comprises the following steps: b1. Take acrylamide, polyethylene glycol monomethyl ether glycidyl ether and tetrabutylammonium bromide in a molar ratio of 1:1.1:0.03; b2. Add acrylamide and tetrabutylammonium bromide to the reaction kettle, add deionized water and control the solid content of the system to be 30-35%, stir at a speed of 200-300 r / min until a uniform solution is formed, then heat to 50-60 DEG C, and add polyethylene glycol monomethyl ether glycidyl ether at a constant speed within 1-1.5 h while controlling the system temperature ≤65 DEG C; b3. The mixture system obtained in step b2 is warmed to 65-70℃, and reaction is maintained for 2-2.5h, and disappearance of the epoxy group is monitored by infrared spectroscopy, and the temperature is lowered to 35-38℃, to obtain the amide-ether bond grafted monomer.

[0018] By setting the above technical solution, the addition of deionized water and the control of the system solid content of 30-35% can make the acrylamide and tetrabutylammonium bromide fully dissolved to form a uniform solution, providing a stable basis for subsequent reactions; the temperature is raised to 50-60℃ and the polyglycol monomethyl ether glycidyl ether is added dropwise while the system temperature is ≤65℃, which can avoid the side reactions caused by the heat generated during dropwise addition, and ensure the orderly development of the epoxy group reaction; the temperature is raised to 65-70℃ and the reaction is maintained, which creates suitable conditions for the reaction of the epoxy group and acrylamide catalyzed by tetrabutylammonium bromide, and the reaction endpoint can be accurately judged by monitoring the disappearance of the epoxy group by infrared spectroscopy, ensuring complete monomer reaction and regular structure; the temperature is lowered to 35-38℃, which can keep the monomer stable and avoid performance deterioration caused by high temperature. The amide-ether bond grafted monomer prepared in this way has high purity and stable performance, and when used in water reducing agents later, it can effectively be compatible with the isopentenyl polyoxyethylene ether side chain to improve the core-shell bonding force, and at the same time, the hydrogen bond formed between the amide group and the cement surface can enhance the adsorption anchoring, thereby assisting in improving the slow-release and slump retention effect of the water reducing agent.

[0019] The application also discloses a preparation method of the ester-ether copolymer type slump retention polycarboxylic acid water reducing agent. S1. All isopentenyl polyoxyethylene ether and 50% deionized water of the total solvent are added into a reaction kettle, stirring at a speed of 300-400r / min, nitrogen is introduced for protection, the temperature is raised to 15-20℃ and maintained for 30min, to form a uniform bottom liquid; S2. Methyl methacrylate, acrylic acid, bisphosphonic acid-based polyether monomer, amide-ether bond grafted monomer and 3-mercaptopropionic acid are mixed with 30% deionized water of the total solvent, stirring at a speed of 200-300r / min for 15-20min, to form a mixed liquid A; S3. 50% hydrogen peroxide in the initiator and 50% potassium persulfate in the initiator are dissolved in 10% deionized water of the total solvent, stirring at a speed of 200-300r / min until completely dissolved, to obtain a mixed liquid B, the mixed liquid A and the mixed liquid B are simultaneously added dropwise into the reaction kettle, the system temperature is maintained at 15-20℃ during the dropwise addition, and after the dropwise addition of the mixed liquid B is completed, the temperature is raised to 25-30℃ at a rate of 1-2℃ / min; S4. The temperature-sensitive dynamic crosslinking monomer, the remaining hydrogen peroxide, the remaining potassium persulfate are dissolved in the remaining deionized water, stirring at a speed of 200-300r / min for 20-30min, and added dropwise into the system obtained in S3 within 1-1.5h, after the dropwise addition is completed, L-ascorbic acid is added, and the temperature is maintained at 25-30℃ for 1.5-2h for curing. S5, after the maturation of step S4 is completed, the temperature is lowered to 35-38℃, slowly drop 30% mass concentration of sodium hydroxide solution, adjust the system pH to 6.0-7.0, stirring at 200-300r / min for 25-30min, then filtered through 100 mesh filter to remove trace insoluble, ester ether copolymerization type slump retention polycarboxylate superplasticizer is obtained.

[0020] By setting the above technical solution, isoprenyl polyoxyethylene ether and 50% deionized water form a homogeneous bottom liquid and are protected by nitrogen, which can avoid oxidation of raw materials and provide a stable basis for subsequent reactions; methacrylic acid, acrylic acid, bisphosphonic acid-based polyether monomer, amide-ether grafted monomer and 3-mercaptopropionic acid are mixed to form a uniform mixed liquid A, which can uniformly disperse 3-mercaptopropionic acid and create conditions for precise control of the molecular chain distribution of the superplasticizer; mixed liquid A and mixed liquid B containing 50% hydrogen peroxide and 50% potassium persulfate are added simultaneously and maintained at 15-20℃, which can realize uniform reaction of the monomers and initiators and avoid uneven molecular chain structure; after the addition, the temperature is raised to 25-30℃ to provide a suitable temperature for the warm-sensitive dynamic crosslinking monomer to participate in the core layer polymerization; after the addition of the warm-sensitive dynamic crosslinking monomer and the remaining initiator, L-ascorbic acid is added and incubated at 25-30℃, which can promote the core layer monomers to fully graft copolymerize on the surface of the shell layer and form a regular core-shell structure; after incubation, the temperature is lowered and the pH is adjusted to 6.0-7.0, which can improve the water solubility and storage stability of the product; the product is filtered through a 100 mesh filter to remove insoluble impurities and ensure product purity; and the ester ether copolymerization type slump retention polycarboxylate superplasticizer is finally obtained, which has a regular core-shell structure and reasonable molecular chain distribution, effectively ensuring dispersibility, slump retention and high-temperature response performance.

[0021] Preferably, the nitrogen flow rate in step S1 is 0.5-1L / min.

[0022] By setting the above technical solution, the air in the reaction kettle can be fully replaced to remove oxygen and avoid oxidation of isoprenyl polyoxyethylene ether, which introduces impurities, and the flow rate is not too fast to cause raw materials to splash or the system to be disturbed too much, ensuring stable preparation of the raw material; based on this, the subsequent polymerization reaction can be carried out in an environment free of oxidation interference, which indirectly ensures the performance stability of the final ester ether copolymerization type slump retention polycarboxylate superplasticizer.

[0023] Preferably, in step S3, mixed liquid A is added at a uniform speed within 2.5-3.5h, and mixed liquid B is added at a uniform speed within 3-4h.

[0024] By setting the above technical scheme, the mixed liquid A (containing methacrylic acid, acrylic acid, bisphosphonic acid-based polyether monomer, etc.) is uniformly added at a speed of 2.5-3.5 h, which can make the monomer uniformly enter the reaction system and avoid local high concentration; the mixed liquid B (containing hydrogen peroxide and potassium persulfate) is uniformly added at a speed of 3-4 h and for a longer time, which can ensure sufficient free radicals throughout the reaction to promote the complete polymerization of the monomers. The combination of the two can reduce side reactions, form regular molecular chains, and lay the foundation for the stable dispersion and slump retention of the ester-ether copolymer type polycarboxylic acid water reducing agent.

[0025] The beneficial effects of the present application are: The main chain macromonomer can provide steric hindrance effect, laying the foundation for system dispersion; the unsaturated carboxylic acid can provide carboxyl groups, balancing the initial dispersion ability and long-term slump retention effect; the initiator, reducing agent and chain transfer agent can cooperate to ensure efficient polymerization and control the regularity of molecular chains, improving the stability of the product itself; the neutralizing agent can adjust the pH value of the system, enhancing the water solubility and storage stability of the product; the solvent as the reaction medium ensures uniform dispersion of all components to ensure smooth reaction; the bisphosphonic acid-based polyether monomer can preferentially adsorb on the surface of clay and chelate metal ions, effectively improving the anti-mud performance and delaying the hydration process; the temperature-sensitive dynamic crosslinking monomer has high temperature response characteristics, which can accelerate the release through phase change and dynamic bond rupture, compensating for the loss of slump at high temperature; the amide-ether grafted monomer can improve the compatibility between components, and at the same time enhance the adsorption and anchoring ability of the water reducing agent on the substrate surface, further ensuring the long-term slump retention effect, and the synergistic effect of all components makes the water reducing agent have comprehensive performance such as dispersion, slump retention, anti-mud and high temperature response.

[0026] The introduction of nitrogen protection and deoxidization can prevent the oxidation of raw materials such as polyethylene glycol monomethyl ether and diethyl phosphite, avoid the formation of impurities, and ensure the stability of the reaction system to improve the purity of the monomer. Vacuumizing and dehydrating polyethylene glycol monomethyl ether at 80-90℃ can remove the trace amount of water contained therein, avoid water interference in the subsequent reaction, create good conditions for monomer synthesis, and help improve the yield of monomer; triethylamine as an acid binding agent can neutralize the acid generated in the reaction, promote the forward reaction, and at the same time, the addition of 10% p-toluenesulfonic acid solution with controlled temperature and the maintenance of the system temperature ≤70℃ can avoid local overheating to initiate side reactions, make the catalytic reaction develop uniformly, and ensure the regularity of the monomer structure; the reaction endpoint can be accurately controlled by thin layer chromatography, which can prevent incomplete or excessive reaction and ensure the stability of the monomer performance; after the reaction, the temperature is lowered and the pH is adjusted to 5.5-6.5, which can make the prepared bisphosphonic acid-based polyether monomer in a stable state, and improve its water solubility and compatibility in the subsequent water reducing agent system. The high-purity and stable bisphosphonic acid-based polyether monomer prepared finally can effectively play the role of preferential adsorption on clay and chelation of metal ions in cement, enhancing the anti-mud and slump retention of the water reducing agent.

[0027] The toluene is added in a mass ratio of 1:3 of total mass of N-vinyl caprolactam, 4-vinyl phenyl boronic acid and ethylene glycol dimethacrylate to toluene, the toluene can fully dissolve the three raw materials and form a uniform reaction system, ensuring that the subsequent polymerization reaction proceeds uniformly, avoiding fluctuations in the performance of the monomer caused by uneven dispersion of the raw materials; the oxygen in the system is removed by nitrogen replacement, preventing the oxidation of the raw materials or reaction intermediates to form impurities and improving the purity of the monomer; the constant temperature reaction at 65-75 DEG C provides suitable conditions for the initiation of copolymerization of the three monomers by azobisisobutyronitrile, ensuring the formation of a monomer product with both temperature-sensitive phase change and dynamic crosslinking structure, laying the foundation for subsequent high-temperature response function; under the conditions of 45-50 DEG C and -0.09 to -0.08 MPa, rotary evaporation can efficiently remove the toluene solvent, and can also avoid decomposition or melting of the monomer caused by excessively high temperature, reducing solvent residue; after being crushed and passed through an 80-mesh sieve, the monomer particles have uniform particle size, which is more easily dispersed uniformly during subsequent polymerization of the water-reducing agent core layer, helping to form a regular temperature-sensitive response core layer, and ultimately enabling the water-reducing agent to realize "high-temperature automatic energy compensation" through the phase change shrinkage and dynamic bond rupture of the monomer, effectively compensating for the loss of concrete slump. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0029] Embodiment 1 The present embodiment discloses an ester-ether copolymer type slump retaining polycarboxylic acid water-reducing agent. The raw material composition of the water-reducing agent is as follows in terms of weight fraction: iso-pentenyl polyoxyethylene ether 80 parts, methacrylic acid 15 parts, acrylic acid 5 parts, hydrogen peroxide 1 part, potassium persulfate 0.5 part, L-ascorbic acid 0.2 part, 3-mercaptopropionic acid 0.3 part, 30% mass concentration sodium hydroxide solution 8 parts, deionized water 200 parts, bisphosphonic acid-based polyether monomer 5 parts, temperature-sensitive dynamic crosslinking monomer 3 parts, and amide-ether grafted monomer 2 parts.

[0030] The preparation method of the bisphosphonic acid-based polyether monomer includes the following steps: 1) polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine and pure p-toluenesulfonic acid are taken in a molar ratio of 1:1.2:1.5:0.05, wherein the p-toluenesulfonic acid is separately prepared into a solution with a mass concentration of 10%; 2) polyethylene glycol monomethyl ether was added into a four-necked flask, and nitrogen was introduced at a flow rate of 0.5 L / min for protection, and oxygen was removed for 10 min, then vacuum was applied, and the temperature was raised to 80℃ for dehydration for 1 h, then the temperature was lowered to 60℃, and diethyl phosphite and triethylamine were added in sequence, and stirred at a speed of 300 r / min for 30 min, and p-toluenesulfonic acid solution was added at a uniform speed within 0.5 h, and the temperature of the system was controlled to be ≤70℃; 3) the mixture obtained in step 2) was heated to 85℃, and reacted for 4 h, and the reaction end point was monitored by thin layer chromatography, and after the reaction was completed, the temperature was lowered to 40℃, and deionized water was added for dilution, and 30% sodium hydroxide solution was used to adjust the pH to 5.5, and a bisphosphonic acid-based polyether monomer was obtained. In the thin layer chromatography monitoring process, the developing agent was composed of ethyl acetate and petroleum ether in a volume ratio of 1:2, and the amount of deionized water was 1:1 by mass ratio with respect to the total amount of polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine and pure p-toluenesulfonic acid.

[0031] The preparation method of the temperature-sensitive dynamic crosslinking monomer comprises the following steps: a1. N-vinyl caprolactam, 4-vinylphenylboronic acid, ethylene glycol dimethacrylate and azobisisobutyronitrile were taken in a molar ratio of 10:3:2:0.2; a2. N-vinyl caprolactam, 4-vinylphenylboronic acid and ethylene glycol dimethacrylate were added into a three-necked flask, and toluene was added in a mass ratio of 1:3 with respect to the total mass of the three, and stirred at a speed of 300 r / min for 25 min, and after nitrogen replacement for 3 times (each time for 10 min), azobisisobutyronitrile was added, and the temperature was raised to 65℃, and reacted for 3 h, and toluene was removed by rotary evaporation under the conditions of 45℃ and -0.09 MPa, and after crushing, the mixture was passed through an 80-mesh sieve, and a temperature-sensitive dynamic crosslinking monomer was obtained.

[0032] The preparation method of the amide-ether bond grafted monomer comprises the following steps: b1. acrylamide, polyethylene glycol monomethyl ether glycidyl ether and tetrabutylammonium bromide were taken in a molar ratio of 1:1.1:0.03; b2. acrylamide and tetrabutylammonium bromide were added into a reaction kettle, deionized water was added, and the solid content of the system was controlled to be 30%, and stirred at a speed of 200 r / min until a uniform solution was formed, and then the temperature was raised to 50℃, and polyethylene glycol monomethyl ether glycidyl ether was added at a uniform speed within 1 h, and the temperature of the system was controlled to be ≤65℃; b3. the mixture obtained in step b2 was heated to 65℃, and reacted for 2 h, and the disappearance of the epoxy group was monitored by infrared spectroscopy, and the temperature was lowered to 35℃, and an amide-ether bond grafted monomer was obtained.

[0033] The embodiment also discloses a preparation method of the ester-ether copolymer type slump retaining polycarboxylate superplasticizer, which comprises the following steps: S1. Add all isopentenyl polyoxyethylene ether and 50% of the total solvent deionized water to the reactor, stir at 300 r / min, purge with nitrogen at a flow rate of 0.5 L / min for protection, heat to 15℃ and keep warm for 30 min to form a homogeneous bottom liquid. S2. Mix methacrylic acid, acrylic acid, bisphosphonic acid polyether monomer, amide-ether graft monomer and 3-mercaptopropionic acid with deionized water accounting for 30% of the total solvent, and stir at 200 r / min for 15 min to form mixture A. S3. Dissolve 50% of the hydrogen peroxide and 50% of the potassium persulfate in the initiator in 10% of the total solvent in deionized water, and stir at 200 r / min until completely dissolved to obtain mixture B. Add mixture A and mixture B dropwise to the reaction vessel at the same time, and maintain the system temperature at 15℃ during the dropwise addition. After the dropwise addition of mixture B is completed, raise the temperature to 25℃ at a rate of 1℃ / min. Mixture A was added dropwise at a constant rate over 2.5 hours, and mixture B was added dropwise at a constant rate over 3 hours. S4. Dissolve the thermosensitive dynamic crosslinking monomer, the remaining hydrogen peroxide, and the remaining potassium persulfate in the remaining deionized water, stir at 200 r / min for 20 min, and add it dropwise to the system obtained in S3 within 1 h. After the addition is complete, add L-ascorbic acid and keep it at 25℃ for 1.5 h to mature. After the curing process in step S5 and S4 is completed, the temperature is lowered to 35°C, and a 30% sodium hydroxide solution is slowly added dropwise to adjust the pH of the system to 6.0. The system is stirred at 200 r / min for 25 min, and then filtered through a 100-mesh filter to remove trace amounts of insoluble matter, thus obtaining the ester ether copolymer type slump-retaining polycarboxylate superplasticizer.

[0034] Example 2: This embodiment discloses an ester ether copolymer type slump-retaining polycarboxylic acid water-reducing agent. By weight, the raw material composition of the water-reducing agent is as follows: 120 parts of isopentenyl polyoxyethylene ether, 25 parts of methacrylic acid, 10 parts of acrylic acid, 2 parts of hydrogen peroxide, 1.2 parts of potassium persulfate, 0.5 parts of L-ascorbic acid, 0.8 parts of 3-mercaptopropionic acid, 15 parts of 30% sodium hydroxide solution, 300 parts of deionized water, 10 parts of bisphosphonic acid polyether monomer, 6 parts of thermosensitive dynamic crosslinking monomer, and 5 parts of amide-ether grafted monomer.

[0035] The preparation method of bisphosphonic acid-based polyether monomers includes the following steps: 1) Take polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine and pure p-toluenesulfonic acid in a molar ratio of 1:1.2:1.5:0.05, wherein p-toluenesulfonic acid is prepared separately into a 10% mass concentration solution; 2) Add polyethylene glycol monomethyl ether to a four-necked flask, purge with nitrogen gas at a flow rate of 1 L / min for 15 min to remove oxygen, then evacuate, heat to 90 °C to dehydrate for 1.5 h, then cool to 65 °C, add diethyl phosphite and triethylamine in sequence, stir at 400 r / min for 30 min, add p-toluenesulfonic acid solution dropwise at a uniform rate over 1 h and keep the system temperature ≤70 °C; 3) Heat the mixture obtained in step 2) to 95°C and keep it at that temperature for 5 hours. Monitor the reaction endpoint by thin-layer chromatography. After the reaction is complete, cool it down to 50°C, add deionized water to dilute it, and adjust the pH to 6.5 with 30% sodium hydroxide solution to obtain the bisphosphonic acid polyether monomer. The developing solvent used in the thin-layer chromatography monitoring process consists of ethyl acetate and petroleum ether in a volume ratio of 1:2, and the mass ratio of deionized water to the total amount of polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine, and pure p-toluenesulfonic acid is 1:1.

[0036] The preparation method of thermosensitive dynamic crosslinking monomer includes the following steps: a1. Take N-vinylcaprolactam, 4-vinylphenylboronic acid, ethylene glycol dimethacrylate and azobisisobutyronitrile in a molar ratio of 10:3:2:0.2; a2. N-vinylcaprolactam, 4-vinylphenylboronic acid, and ethylene glycol dimethacrylate were added to a three-necked flask. Toluene was added at a mass ratio of 1:3 (total mass of the three substances to toluene). The mixture was stirred at 400 r / min for 30 min. After nitrogen purging three times (10 min each time), azobisisobutyronitrile was added. The temperature was raised to 75 °C and the reaction was maintained at this temperature for 4 h. Toluene was removed by rotary evaporation at 50 °C and -0.08 MPa. The mixture was then pulverized and passed through an 80-mesh sieve to obtain the thermosensitive dynamic crosslinking monomer.

[0037] The preparation method of amide-ether grafted monomers includes the following steps: b1. Take acrylamide, polyethylene glycol monomethyl ether glycidyl ether and tetrabutylammonium bromide in a molar ratio of 1:1.1:0.03; b2. Add acrylamide and tetrabutylammonium bromide to the reactor, add deionized water and control the solid content of the system to 35%, stir at 300 r / min until a homogeneous solution is formed, then heat to 60℃, and uniformly add polyethylene glycol monomethyl ether glycidyl ether over 1.5 h while controlling the system temperature to ≤65℃; b3. Heat the mixture obtained in step b2 to 70°C and keep it at that temperature for 2.5 hours. Monitor the disappearance of the epoxy groups by infrared spectroscopy. Then cool the mixture to 38°C to obtain the amide-ether grafted monomer.

[0038] This embodiment also discloses a method for preparing an ester ether copolymer type slump-retaining polycarboxylate superplasticizer, comprising the following steps: S1. Add all isopentenyl polyoxyethylene ether and 50% of the total solvent deionized water to the reactor, stir at 400 r / min, introduce nitrogen gas at a flow rate of 1 L / min for protection, heat to 20℃ and keep at 30 min to form a homogeneous bottom liquid. S2. Mix methacrylic acid, acrylic acid, bisphosphonic acid polyether monomer, amide-ether graft monomer and 3-mercaptopropionic acid with deionized water accounting for 30% of the total solvent, and stir at 300 r / min for 20 min to form mixture A. S3. Dissolve 50% of the hydrogen peroxide and 50% of the potassium persulfate in the initiator in 10% of the total solvent in deionized water, and stir at 300 r / min until completely dissolved to obtain mixture B. Add mixture A and mixture B dropwise to the reaction vessel simultaneously, maintaining the system temperature at 20°C during the dropwise addition. After mixture B has been added, raise the temperature to 30°C at a rate of 2°C / min. Mixture A was added dropwise at a constant rate over 3.5 hours, and mixture B was added dropwise at a constant rate over 4 hours. S4. Dissolve the thermosensitive dynamic crosslinking monomer, the remaining hydrogen peroxide, and the remaining potassium persulfate in the remaining deionized water, stir at 300 r / min for 30 min, and add it dropwise to the system obtained in S3 within 1.5 h. After the addition is complete, add L-ascorbic acid and keep it at 30℃ for 2 h to mature. After the curing process in step S5 and S4 is completed, the temperature is lowered to 38°C, and a 30% sodium hydroxide solution is slowly added dropwise to adjust the pH of the system to 7.0. The system is stirred at 300 r / min for 30 min, and then filtered through a 100-mesh filter to remove trace amounts of insoluble matter, thus obtaining the ester ether copolymer type slump-retaining polycarboxylate superplasticizer.

[0039] Example 3: This embodiment discloses an ester ether copolymer type slump-retaining polycarboxylic acid water-reducing agent. By weight, the raw material composition of the water-reducing agent is as follows: 100 parts of isopentenyl polyoxyethylene ether, 20 parts of methacrylic acid, 7 parts of acrylic acid, 1.5 parts of hydrogen peroxide, 0.8 parts of potassium persulfate, 0.3 parts of L-ascorbic acid, 0.5 parts of 3-mercaptopropionic acid, 11 parts of 30% sodium hydroxide solution, 250 parts of deionized water, 7 parts of bisphosphonic acid polyether monomer, 4 parts of thermosensitive dynamic crosslinking monomer, and 4 parts of amide-ether grafted monomer.

[0040] The preparation method of bisphosphonic acid-based polyether monomers includes the following steps: 1) Take polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine and pure p-toluenesulfonic acid in a molar ratio of 1:1.2:1.5:0.05, wherein p-toluenesulfonic acid is prepared separately into a 10% mass concentration solution; 2) Add polyethylene glycol monomethyl ether to a four-necked flask, purge with nitrogen at a flow rate of 0.7 L / min for protection, continue for 12 min to remove oxygen, then evacuate, heat to 85 °C to dehydrate for 1.2 h, then cool to 62 °C, add diethyl phosphite and triethylamine in sequence, stir at 350 r / min for 30 min, add p-toluenesulfonic acid solution dropwise at a uniform rate over 0.7 h and keep the system temperature ≤70 °C; 3) Heat the mixture obtained in step 2) to 90°C and keep it at that temperature for 4.5 h. Monitor the reaction endpoint by thin-layer chromatography. After the reaction is complete, cool it down to 45°C, add deionized water to dilute it, and adjust the pH to 6 with 30% sodium hydroxide solution to obtain the bisphosphonic acid polyether monomer. The developing solvent used in the thin-layer chromatography monitoring process consists of ethyl acetate and petroleum ether in a volume ratio of 1:2, and the mass ratio of deionized water to the total amount of polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine, and pure p-toluenesulfonic acid is 1:1.

[0041] The preparation method of thermosensitive dynamic crosslinking monomer includes the following steps: a1. Take N-vinylcaprolactam, 4-vinylphenylboronic acid, ethylene glycol dimethacrylate and azobisisobutyronitrile in a molar ratio of 10:3:2:0.2; a2. N-vinylcaprolactam, 4-vinylphenylboronic acid, and ethylene glycol dimethacrylate were added to a three-necked flask. Toluene was added at a mass ratio of 1:3 (total mass of the three substances to toluene). The mixture was stirred at 350 r / min for 27 min. After purging with nitrogen three times (10 min each time), azobisisobutyronitrile was added. The temperature was raised to 70 °C and the reaction was maintained at this temperature for 3.5 h. Toluene was removed by rotary evaporation at 47 °C and -0.09 MPa. The product was then pulverized and passed through an 80-mesh sieve to obtain the thermosensitive dynamic crosslinking monomer.

[0042] The preparation method of amide-ether grafted monomers includes the following steps: b1. Take acrylamide, polyethylene glycol monomethyl ether glycidyl ether and tetrabutylammonium bromide in a molar ratio of 1:1.1:0.03; b2. Add acrylamide and tetrabutylammonium bromide to the reactor, add deionized water and control the solid content of the system to 32%, stir at 250 r / min until a homogeneous solution is formed, then raise the temperature to 55℃, add polyethylene glycol monomethyl ether glycidyl ether dropwise at a uniform rate over 1.2 h and control the system temperature to ≤65℃; b3. The mixture system obtained in step b2 is heated to 67°C and kept at this temperature for 2.2 hours. The disappearance of epoxy groups is monitored by infrared spectroscopy. The mixture is then cooled to 36°C to obtain the amide-ether grafted monomer.

[0043] This embodiment also discloses a method for preparing an ester ether copolymer type slump-retaining polycarboxylate superplasticizer, comprising the following steps: S1. Add all isopentenyl polyoxyethylene ether and 50% of the total solvent deionized water to the reactor, stir at 350 r / min, purge with nitrogen at a flow rate of 0.7 L / min for protection, heat to 17℃ and keep at that temperature for 30 min to form a homogeneous bottom liquid. S2. Mix methacrylic acid, acrylic acid, bisphosphonic acid polyether monomer, amide-ether graft monomer and 3-mercaptopropionic acid with deionized water accounting for 30% of the total solvent, and stir at 250 r / min for 17 min to form mixture A. S3. Dissolve 50% of the hydrogen peroxide and 50% of the potassium persulfate in the initiator in 10% of the total solvent in deionized water, and stir at 250 r / min until completely dissolved to obtain mixture B. Add mixture A and mixture B dropwise to the reaction vessel simultaneously, maintaining the system temperature at 17℃ during the dropwise addition. After mixture B has been added, raise the temperature to 27℃ at a rate of 1.5℃ / min. Mixture A was added dropwise at a constant rate over 3 hours, and mixture B was added dropwise at a constant rate over 3.5 hours. S4. Dissolve the thermosensitive dynamic crosslinking monomer, the remaining hydrogen peroxide, and the remaining potassium persulfate in the remaining deionized water, stir at 250 r / min for 25 min, and add dropwise to the system obtained in S3 within 1.2 h. After the addition is complete, add L-ascorbic acid and keep warm at 27℃ for 1.7 h. After the curing process in step S5 and S4 is completed, the temperature is lowered to 36°C, and a 30% sodium hydroxide solution is slowly added dropwise to adjust the pH of the system to 6.5. The system is stirred at 250 r / min for 27 min, and then filtered through a 100-mesh filter to remove trace amounts of insoluble matter, thus obtaining the ester ether copolymer type slump-retaining polycarboxylate superplasticizer.

[0044] Comparative Example 1: An ester ether copolymer type slump-retaining polycarboxylic acid water-reducing agent and its preparation method are disclosed. The only difference between this water-reducing agent and Example 3 is that no bisphosphonic acid polyether monomer is added.

[0045] Comparative Example 2: An ester ether copolymer type slump-retaining polycarboxylate superplasticizer and its preparation method are disclosed. The only difference between the superplasticizer and Example 3 is that no temperature-sensitive dynamic crosslinking monomer is added.

[0046] Comparative Example 3: An ester-ether copolymer type slump-retaining polycarboxylic acid water-reducing agent and its preparation method are disclosed. The only difference between the water-reducing agent and that in Example 3 is that no amide-ether bond grafted monomer is added.

[0047] Comparative Example 4: An ester ether copolymer type slump-retaining polycarboxylic acid water-reducing agent and its preparation method are disclosed. The only difference between the water-reducing agent and that in Example 3 is that commercially available 2-acrylamide-2-methylpropanesulfonic acid is used instead of bisphosphonic acid-based polyether monomer.

[0048] Comparative Example 5: An ester ether copolymer type slump-retaining polycarboxylic acid water-reducing agent and its preparation method are disclosed. The difference between the water-reducing agent and that in Example 3 is that commercially available N-vinylcaprolactam (pure N-vinylcaprolactam, without dynamic bonds) is used instead of the temperature-sensitive dynamic crosslinking monomer.

[0049] Comparative Example 6: An ester-ether copolymer type slump-retaining polycarboxylic acid water-reducing agent and its preparation method are disclosed. The only difference between the water-reducing agent and Example 3 is that commercially available acrylamide is used instead of amide-ether bond grafted monomer.

[0050] Comparative Example 7: An ester ether copolymer type slump-retaining polycarboxylate superplasticizer and its preparation method are disclosed. The difference between the preparation method and Example 3 is that in steps S2 and S3, each raw material is added at once (without segmented dripping).

[0051] Comparative Example 8: An ester ether copolymer type slump-retaining polycarboxylate superplasticizer and its preparation method are disclosed. The difference between the preparation method and Example 3 is that the system temperature is kept constant at 40°C in steps S2, S3 and S4 (no low-temperature segmentation is adopted).

[0052] Comparative Example 9: An ester ether copolymer type slump-retaining polycarboxylic acid water-reducing agent and its preparation method are disclosed. The only difference between the water-reducing agent and that in Example 3 is that 3-mercaptopropionic acid is not added.

[0053] Comparative Example 10: An ester ether copolymer type slump-retaining polycarboxylate superplasticizer and its preparation method are disclosed. The difference between the superplasticizer and Example 3 is that the initiator is replaced with a single ammonium persulfate (without hydrogen peroxide).

[0054] Comparative Example 11: An ester ether copolymer type slump-retaining polycarboxylate superplasticizer and its preparation method are disclosed. The only difference between the preparation method and Example 3 is that the heat preservation and curing step in S4 is omitted.

[0055] The water-reducing agents obtained in Examples 1-3 and Comparative Examples 1-11 were subjected to performance tests on cement paste fluidity and retention rate over time, concrete performance, water reduction rate, slump loss, mud resistance, and high-temperature response. The test methods and standards for each performance are as follows: 1. Flowability and retention rate of cement paste over time Referring to GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures" and GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", 300g of P·O 42.5R reference cement conforming to GB 8076 standard was weighed, and deionized water was added at a water-cement ratio of 0.30. The water-reducing agent dosage was 0.25% (converted to solids). After mixing the cement, deionized water, and water-reducing agent, the mixture was placed in a mixer and stirred at low speed for 120s, paused for 15s, and then stirred at high speed for 120s. Immediately after mixing, the initial flowability (F0) of the neat cement paste was tested. After 30min, 60min, and 120min, the above mixing steps were repeated and the flowability was tested. The flowability retention rate at 120min was calculated (retention rate = 120min flowability / F0 × 100%).

[0056] 2. Concrete performance testing Referring to GB / T 8076-2008 "Concrete Admixtures" and GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the concrete mix proportion is: cement 330kg / m³, sand 660kg / m³, aggregate 1210kg / m³, deionized water 180kg / m³ (water-cement ratio 0.55), and the water-reducing agent dosage is 0.2-0.3% (converted to solids).

[0057] 3. Test the water reduction rate: Adjust the water consumption to achieve a concrete slump of 210±10mm, and calculate the water reduction rate (water reduction rate = (reference water consumption - water consumption of the tested concrete) / reference water consumption × 100%). Slump loss test: Test the initial slump, 1-hour slump, and 2-hour slump respectively, and calculate the slump loss at 1 hour and 2 hours (loss value = initial slump - slump at the corresponding time); 28-day compressive strength ratio test: Test the compressive strength of standard molded concrete blocks after 28 days of curing, and calculate the 28-day compressive strength ratio (strength ratio = 28-day compressive strength of tested concrete / 28-day compressive strength of reference concrete × 100%).

[0058] 4. Mud Resistance Test Referring to GB / T 8076-2008 "Concrete Admixtures" and GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", 5% and 10% montmorillonite were added respectively by weight of sand based on the above concrete mix proportions. Initial slump and 1-hour slump were tested, and the 1-hour slump loss was calculated. Simultaneously, referring to the cement paste fluidity test method, the 1-hour fluidity retention rate of the cement paste under mud-containing conditions was tested and compared with the group without montmorillonite.

[0059] 5. High-temperature response performance test Referring to GB / T 8076-2008 "Concrete Admixtures" and GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the ambient temperature was controlled at 40±2℃. Concrete mixtures were prepared according to the above concrete mix proportions, and the initial slump and 1-hour slump were tested. The 1-hour slump loss was calculated and compared with the group at normal temperature (25℃).

[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 1-11 Group Initial net paste fluidity (mm) 120 min fluidity retention rate (%) Water-reducing rate (%) 1 h slump loss (mm) 2 h slump loss (mm) 1 h fluidity retention rate (%) with 5% mud 1 h fluidity retention rate (%) with 10% mud 1 h slump loss (mm) at 40°C 28 d compressive strength ratio (%) Example 1 275 89 31 28 43 91 86 28 128 Example 2 285 91 33 23 38 93 88 23 133 Example 3 295 93 35 18 33 95 90 18 140 Comparative Example 1 265 77 29 48 68 71 53 58 118 Comparative Example 2 260 72 28 63 88 86 81 85 121 Comparative Example 3 245 70 27 58 83 83 77 78 114 Comparative Example 4 255 74 29 43 63 77 58 53 118 Comparative Example 5 260 75 28 53 78 85 79 73 119 Comparative Example 6 250 72 27 53 78 81 74 73 115 Comparative Example 7 235 67 26 73 98 79 69 78 110 Comparative Example 8 225 62 25 78 103 76 67 83 107 Comparative Example 9 215 57 23 83 113 71 62 88 104 Comparative Example 10 240 70 26 68 93 81 72 73 110 Comparative Example 11 230 65 25 73 98 77 68 78 107 Referring to Table 1, and taking Example 3 as an example: Compared to Example 3, Comparative Example 1 (without added bisphosphonic acid polyether monomer): at a mud content of 10%, the 1-hour fluidity retention rate decreased from 90% to 53% (a decrease of 37 percentage points); the slump loss at 40℃ for 1 hour increased from 18 mm to 58 mm (an increase of 40 mm); and the 120-minute fluidity retention rate decreased from 93% to 77% (a decrease of 16 percentage points). This is because the phosphonic acid groups of the bisphosphonic acid polyether monomer preferentially occupy clay adsorption sites, inhibiting the consumption of water-reducing agents by the clay, while simultaneously chelating Ca... 2+ It delays cement hydration; its absence significantly reduces its resistance to mud and slump retention, and at high temperatures, it cannot compensate for dispersibility through exposure of phosphonic acid groups.

[0062] Compared to Example 3, Comparative Example 2 (without the addition of the thermosensitive dynamic crosslinking monomer) showed the following slump loss at 40°C for 1 hour: increased from 18 mm to 85 mm (an increase of 67 mm); flowability retention at 120 minutes decreased from 93% to 72% (a decrease of 21 percentage points); and slump loss at 2 hours increased from 33 mm to 88 mm (an increase of 55 mm). This is because the thermosensitive dynamic crosslinking monomer, at high temperatures, accelerates the hydrolysis of methacrylic acid to replenish carboxyl groups through N-vinylcaprolactam phase transition shrinkage and 4-vinylphenylboronic acid dynamic bond breakage. Without this carboxyl group, there is no high-temperature response mechanism, leading to a sharp increase in slump loss at high temperatures.

[0063] Compared to Example 3, Comparative Example 3 (without amide-ether grafted monomers): the initial flowability of the neat cement paste decreased from 295 mm to 245 mm (a decrease of 50 mm), and the slump loss after 2 hours increased from 33 mm to 83 mm (an increase of 50 mm). Delamination at the core-shell interface led to easy detachment of the shell layer. The reason is that the ether bonds of the amide-ether grafted monomers are compatible with the isopentenyl polyoxyethylene ether side chains, and the amide groups form hydrogen bonds with the cement surface; the absence of these bonds reduces the core-shell bonding force, resulting in damage to both dispersibility and slump retention.

[0064] Comparative Example 4 (2-acrylamide-2-methylpropanesulfonic acid replacing bisphosphonic acid polyether monomer): The retention rate of 10% mud content decreased from 90% to 58% after 1 hour (a decrease of 32 percentage points), because the sulfonic acid group of 2-acrylamide-2-methylpropanesulfonic acid has weaker adsorption competitiveness for clay than the phosphonic acid group; Comparative Example 5 (pure N-vinylcaprolactam replacing thermosensitive dynamic crosslinking monomer): The slump loss at 40℃ for 1 hour increased from 18 mm to 73 mm (an increase of 55 mm), because the lack of dynamic bonds prevented the acceleration of methacrylic acid hydrolysis; Comparative Example 6 (acrylamide replacing amide-ether bond grafted monomer): The initial flowability decreased from 295 mm to 250 mm (a decrease of 45 mm), because the lack of ether bond structure resulted in poor core-shell compatibility.

[0065] Comparative Example 7 (one-time feeding): 120-minute retention rate decreased from 93% to 67% (a decrease of 26 percentage points), due to the lack of a core-shell structure leading to slow-release failure; Comparative Example 8 (constant polymerization at 40℃): initial flowability decreased from 295 mm to 225 mm (a decrease of 70 mm), due to high temperature intensifying chain transfer reactions and uneven molecular chain distribution; Comparative Example 9 (without 3-mercaptopropionic acid): initial flowability decreased from 295 mm to 215 mm (a decrease of 80 mm), due to excessively long molecular chains that easily aggregate; Comparative Example 10 (single ammonium persulfate initiation): 120-minute retention rate decreased to 70%, due to insufficient activity caused by low temperature; Comparative Example 11 (without heat preservation curing): 28-day compressive strength ratio decreased from 140% to 107% (a decrease of 33 percentage points), due to residual monomers affecting cement hydration.

[0066] In summary, the synergy of bisphosphonic acid-based polyether monomers, thermosensitive dynamic crosslinking monomers, amide-ether grafted monomers, and low-temperature segmented polymerization process is as follows: bisphosphonic acid-based polyether monomers are key to anti-mud properties, inhibiting clay adsorption and delaying hydration; thermosensitive dynamic crosslinking monomers are the core of high-temperature response, achieving "automatic high-temperature energy replenishment"; amide-ether grafted monomers ensure core-shell compatibility and enhance adsorption anchoring; supplemented by molecular weight regulation of 3-mercaptopropionic acid, efficient polymerization of the redox-initiated system, and monomer conversion during heat preservation and curing, the water-reducing agent ultimately outperforms traditional formulations in anti-mud properties, high-temperature slump retention, and dispersibility, with the 28-day compressive strength ratio increased to 140% (Example 3), providing a highly efficient and stable admixture solution for concrete engineering.

[0067] 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. An ester ether copolymer type slump-retaining polycarboxylate superplasticizer, characterized in that, The raw material composition of this water-reducing agent, by weight, is as follows: 80-120 parts of main chain macromonomer, 20-35 parts of unsaturated carboxylic acid, 1.5-3.2 parts of initiator, 0.2-0.5 parts of reducing agent, 0.3-0.8 parts of chain transfer agent, 8-15 parts of neutralizing agent, 200-300 parts of solvent, 5-10 parts of bisphosphonic acid-based polyether monomer, 3-6 parts of thermosensitive dynamic crosslinking monomer, and 2-5 parts of amide-ether grafted monomer.

2. The ester-ether copolymer type slump-retaining polycarboxylate superplasticizer according to claim 1, characterized in that, The main chain macromonomer is isopentenyl polyoxyethylene ether, the reducing agent is L-ascorbic acid, the chain transfer agent is 3-mercaptopropionic acid, the neutralizing agent is a 30% sodium hydroxide solution, and the solvent is deionized water; wherein, by weight parts: The unsaturated carboxylic acid is formed by uniformly mixing 15-25 parts of methacrylic acid and 5-10 parts of acrylic acid, and the initiator is formed by uniformly mixing 0.5-1.2 parts of potassium persulfate and 1-2 parts of hydrogen peroxide with a mass concentration of 30%.

3. The ester-ether copolymer type slump-retaining polycarboxylate superplasticizer according to claim 2, characterized in that, The preparation method of bisphosphonic acid-based polyether monomers includes the following steps: 1) Take polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine and pure p-toluenesulfonic acid in a molar ratio of 1:1.2:1.5:0.05, wherein p-toluenesulfonic acid is prepared separately into a 10% mass concentration solution; 2) Add polyethylene glycol monomethyl ether to a four-necked flask, and purge with nitrogen gas at a flow rate of 0.5-1 L / min for protection. After deoxygenation for 10-15 min, evacuate the vacuum, raise the temperature to 80-90℃ and dehydrate for 1-1.5 h. Then, lower the temperature to 60-65℃, add diethyl phosphite and triethylamine in sequence, and stir at 300-400 r / min for 30 min. Add p-toluenesulfonic acid solution dropwise at a uniform rate over 0.5-1 h and keep the system temperature ≤70℃. 3) Heat the mixture system obtained in step 2) to 85-95℃ and keep it at that temperature for 4-5 hours. Monitor the reaction endpoint by thin-layer chromatography. After the reaction is completed, cool it down to 40-50℃, add deionized water to dilute it, and adjust the pH to 5.5-6.5 with 30% sodium hydroxide solution to obtain the bisphosphonic acid polyether monomer.

4. The ester-ether copolymer type slump-retaining polycarboxylate superplasticizer according to claim 3, characterized in that, In step 3), the developing solvent used in the thin-layer chromatography monitoring process consists of ethyl acetate and petroleum ether in a volume ratio of 1:2, and the mass ratio of deionized water to the total amount of polyethylene glycol monomethyl ether, diethyl phosphite, triethylamine, and pure p-toluenesulfonic acid is 1:

1.

5. The ester-ether copolymer type slump-retaining polycarboxylate superplasticizer according to claim 2, characterized in that, The preparation method of thermosensitive dynamic crosslinking monomer includes the following steps: a1. Take N-vinylcaprolactam, 4-vinylphenylboronic acid, ethylene glycol dimethacrylate and azobisisobutyronitrile in a molar ratio of 10:3:2:0.2; a2. Add N-vinylcaprolactam, 4-vinylphenylboronic acid, and ethylene glycol dimethacrylate to a three-necked flask. Add toluene at a mass ratio of 1:3 (total mass of the three to toluene). Stir at 300-400 r / min for 25-30 min. After purging with nitrogen three times, add azobisisobutyronitrile. Heat to 65-75℃ and react at a constant temperature for 3-4 h. Remove toluene by rotary evaporation at 45-50℃ and -0.09 to -0.08 MPa. After pulverizing, pass through an 80-mesh sieve to obtain the thermosensitive dynamic crosslinking monomer.

6. The ester ether copolymer type slump-retaining polycarboxylate superplasticizer according to claim 5, characterized in that, In step a2, nitrogen is passed through for 10 minutes each time.

7. The ester-ether copolymer type slump-retaining polycarboxylate superplasticizer according to claim 2, characterized in that, The preparation method of amide-ether grafted monomers includes the following steps: b1. Take acrylamide, polyethylene glycol monomethyl ether glycidyl ether and tetrabutylammonium bromide in a molar ratio of 1:1.1:0.03; b2. Add acrylamide and tetrabutylammonium bromide to the reactor, add deionized water and control the solid content of the system to 30-35%, stir at 200-300 r / min until a homogeneous solution is formed, then raise the temperature to 50-60℃, and uniformly add polyethylene glycol monomethyl ether glycidyl ether over 1-1.5 h while controlling the system temperature to ≤65℃; b3. Heat the mixture obtained in step b2 to 65-70℃ and keep it at that temperature for 2-2.5 hours. Monitor the disappearance of the epoxy groups by infrared spectroscopy. Then cool the mixture to 35-38℃ to obtain the amide-ether grafted monomer.

8. A method for preparing an ester-ether copolymer type slump-retaining polycarboxylate superplasticizer according to any one of claims 2-7, characterized in that, Includes the following steps: S1. Add all isopentenyl polyoxyethylene ether and 50% of the total solvent deionized water to the reactor, stir at 300-400 r / min, purge with nitrogen for protection, heat to 15-20℃ and keep warm for 30 min to form a homogeneous bottom liquid. S2. Mix methacrylic acid, acrylic acid, bisphosphonic acid polyether monomer, amide-ether graft monomer and 3-mercaptopropionic acid with 30% deionized water of total solvent and stir at 200-300 r / min for 15-20 min to form mixture A. S3. Dissolve 50% of the hydrogen peroxide and 50% of the potassium persulfate in the initiator in 10% of the total solvent in deionized water, and stir at 200-300 r / min until completely dissolved to obtain mixture B. Add mixture A and mixture B dropwise to the reaction vessel simultaneously, maintaining the system temperature at 15-20℃ during the dropwise addition. After mixture B has been added, raise the temperature to 25-30℃ at a rate of 1-2℃ / min. S4. Dissolve the thermosensitive dynamic crosslinking monomer, the remaining hydrogen peroxide, and the remaining potassium persulfate in the remaining deionized water, stir at 200-300 r / min for 20-30 min, and add it dropwise to the system obtained in S3 over 1-1.5 h. After the addition is complete, add L-ascorbic acid and keep it warm at 25-30℃ for 1.5-2 h. After the curing process in step S5 and S4 is completed, the temperature is lowered to 35-38℃, and a 30% sodium hydroxide solution is slowly added dropwise to adjust the pH of the system to 6.0-7.

0. The mixture is stirred at 200-300 r / min for 25-30 min, and then filtered through a 100-mesh filter to remove trace amounts of insoluble matter, thus obtaining the ester ether copolymer type slump-retaining polycarboxylate superplasticizer.

9. The preparation method of the ester ether copolymer type slump-retaining polycarboxylate superplasticizer according to claim 8, characterized in that, In step S1, the nitrogen flow rate is 0.5-1 L / min.

10. The preparation method of the ester ether copolymer type slump-retaining polycarboxylate superplasticizer according to claim 8, characterized in that, In step S3, mixture A is added dropwise at a constant rate over 2.5-3.5 hours, and mixture B is added dropwise at a constant rate over 3-4 hours.