Sulfate-resistant polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention relates to the technical field of concrete admixtures, in particular to a sulfate-resistant polycarboxylate superplasticizer and a preparation method thereof. The sulfate-resistant polycarboxylate superplasticizer is prepared by copolymerization reaction of ethylene glycol monovinyl polyglycol ether, first unsaturated carboxylic acid, unsaturated phosphate and a functional monomer XS under the action of an initiator and a chain transfer agent. The sulfate-resistant polycarboxylate superplasticizer provided by the invention has excellent sulfate resistance and good working performance. A normal-temperature free radical solution copolymerization synthesis technology is adopted for synthesis, heating is not needed in the preparation process, preparation steps are simple and convenient, raw materials are easy to obtain, equipment is conventional, and actual industrial application requirements can be met.

Description

Technical Field

[0001] The present application relates to the technical field of concrete admixtures, and in particular to a sulfate-resistant polycarboxylate water-reducing agent and a preparation method thereof. Background Art

[0002] With the development of the times, the infrastructure construction at home and abroad has gradually increased, the amount of engineering projects has continued to expand, and the demand for various raw materials and admixtures of cement concrete used in engineering projects has also continued to increase. As a high-performance concrete admixture, polycarboxylate water reducer has been widely used in the construction industry for its excellent water-reducing effect and good adaptability.

[0003] However, when polycarboxylate water-reducing agent is used in cement concrete, its adsorption performance is restricted by many factors, especially the competitive adsorption of sulfate ions in concrete, which will significantly weaken the dispersion effect of polycarboxylate water-reducing agent on cement. In cement paste or fresh concrete, sulfate ions quickly occupy the positive charge sites on the surface of cement minerals due to their strong negative charge, resulting in the desorption of adsorbed polycarboxylate water-reducing agent. The sensitivity of polycarboxylate water-reducing agent to sulfate is closely related to its molecular structure.

[0004] In order to solve the compatibility problem between polycarboxylate superplasticizer and sulfate, a common method is to introduce more carboxyl groups on the main chain of polycarboxylate superplasticizer to enhance its adsorption capacity, thereby improving sulfate resistance. However, although this method can improve sulfate resistance, it will accelerate the loss of paste fluidity and significantly reduce the working performance of concrete.

[0005] Therefore, developing a sulfate-resistant polycarboxylate water-reducing agent with excellent sulfate resistance and good working performance is of great significance to the development of the construction industry. Summary of the invention

[0006] In order to solve the problems of the prior art mentioned in the above background technology, the present application provides a sulfate-resistant polycarboxylate water-reducing agent, and its technical solution is as follows: The sulfate-resistant polycarboxylic acid water-reducing agent is prepared by copolymerization of ethylene glycol monovinyl polyglycol ether, a first unsaturated carboxylic acid, an unsaturated phosphate ester and a functional monomer XS under the action of an initiator and a chain transfer agent; The structural formula of the functional monomer XS is as follows: ; Wherein, R1 is H or CH3.

[0007] In some embodiments, the preparation process of the functional monomer XS is: adding 3-(3-aminophenoxy)propyltrimethoxysilane and a second unsaturated carboxylic acid into a reactor to form a mixture; wherein the molar ratio of 3-(3-aminophenoxy)propyltrimethoxysilane to the second unsaturated carboxylic acid is (1.0-1.2):1; adding an organic solvent to the mixture under a protective atmosphere, and adding a catalyst; under the action of the catalyst, heating to 40-60°C to react for 3-6 hours, and finally filtering the reaction solution in turn, removing the organic solvent, to obtain the functional monomer XS.

[0008] It should be noted that the amount of organic solvent used is based on the ability of 3-(3-aminophenoxy)propyltrimethoxysilane and the second unsaturated carboxylic acid to disperse in the solvent and react. Since the solvent will be removed by rotary evaporation later, there is no excessive restriction on the amount of organic solvent used.

[0009] In some embodiments, the second unsaturated carboxylic acid is at least one of acrylic acid and methacrylic acid.

[0010] In some embodiments, the organic solvent is at least one of dichloromethane, chloroform, methyl acetate, and tetrahydrofuran.

[0011] In some embodiments, the catalyst is at least one of 4-dimethylaminopyridine, dicyclohexylcarbodiimide, pyridine, and imidazole.

[0012] In some embodiments, the protective atmosphere is N2 atmosphere.

[0013] In some embodiments, the reaction solution is filtered to obtain a filtrate, and then the filtrate is subjected to rotary evaporation to remove the organic solvent to obtain the functional monomer XS.

[0014] In some embodiments, under the action of an initiator and a chain transfer agent, the ethylene glycol monovinyl polyethylene glycol ether, the first unsaturated carboxylic acid, the unsaturated phosphate ester, and the functional monomer XS are copolymerized to obtain a sulfate-resistant polycarboxylic acid water-reducing agent; wherein the copolymerization reaction temperature is 15 to 35° C.; the weight ratio of the ethylene glycol monovinyl polyethylene glycol ether, the first unsaturated carboxylic acid, the unsaturated phosphate ester, and the functional monomer XS is 200: (5 to 10): (4 to 8): (8 to 14).

[0015] In some embodiments, the initiator is composed of a reducing agent and an oxidizing agent; the copolymerization reaction process is: dissolving the ethylene glycol monovinyl polyethylene glycol ether in a certain amount of water; controlling the temperature of the reaction system at 15 to 35°C, and then adding an oxidizing agent and stirring evenly; then maintaining the temperature of the reaction system at 15 to 35°C, adding liquid A and liquid B for constant temperature reaction; after the addition is completed, keeping the reaction system at a temperature of 15 to 35°C for 0.5 to 1h; finally, adding a neutralizing agent to adjust the pH to 5.5 to 6.5 to obtain the sulfate-resistant polycarboxylic acid water-reducing agent; wherein, the functional monomer XS, the first unsaturated carboxylic acid, the unsaturated phosphate and a portion of water are evenly mixed to obtain the liquid A; the chain transfer agent, the reducing agent and a portion of water are evenly mixed to obtain the liquid B.

[0016] In some embodiments, the liquid A and the liquid B are added dropwise for 0.5 to 2.5 hours. The raw material formula of the copolymerization reaction is as follows, by weight: 200 parts of ethylene glycol monovinyl polyethylene glycol ether, 8 to 14 parts of functional monomer XS, 5 to 10 parts of the first unsaturated carboxylic acid, 4 to 8 parts of unsaturated phosphate, 1.0 to 2.5 parts of oxidant, 0.2 to 0.6 parts of reducing agent, 0.5 to 1.6 parts of chain transfer agent, and 200 to 230 parts of water in total.

[0017] In some embodiments, the molecular weight of the ethylene glycol monovinyl polyethylene glycol ether is 1500-3000.

[0018] In some embodiments, the first unsaturated carboxylic acid or unsaturated phosphate is at least one of acrylic acid, methacrylic acid, and maleic anhydride.

[0019] In some embodiments, the unsaturated phosphate ester is at least one of hydroxyethyl methacrylate phosphate, vinyl dimethyl phosphate, and allyl dimethyl phosphate.

[0020] In some embodiments, the oxidant is at least one of a 27.5% mass concentration hydrogen peroxide solution, ammonium persulfate, and sodium persulfate.

[0021] In some embodiments, the chain transfer agent is at least one of sodium hypophosphite, thioglycolic acid, and mercaptopropionic acid. In some embodiments, the reducing agent is at least one of ascorbic acid, Bruggolite FF6, and Bruggolite E01.

[0022] In some embodiments, the neutralizing agent is a sodium hydroxide solution with a mass concentration of 32%.

[0023] The present application also provides a method for preparing the sulfate-resistant polycarboxylate water-reducing agent as described above, wherein the initiator comprises an oxidant and a reducing agent; the preparation method comprises the following preparation steps: Dissolving the ethylene glycol monovinyl polyglycol ether in a certain amount of water, controlling the temperature of the reaction system at 15 to 35° C., and then adding an oxidant and stirring evenly to form a mixed solution; The functional monomer XS, the first unsaturated carboxylic acid, the unsaturated phosphate and a portion of water are uniformly mixed to obtain a liquid A; The chain transfer agent, the reducing agent and a portion of water are uniformly mixed to obtain liquid B; Then, the temperature of the reaction system is maintained at 15 to 35° C., and the solution A and the solution B are added dropwise to the mixed solution for constant temperature reaction, and the adding time is 0.5 to 2.5 hours; After the dropwise addition is completed, the reaction system is kept at a temperature of 15 to 35° C. for 0.5 to 1 hour, and finally a neutralizing agent is added to adjust the pH to 5.5 to 6.5 to obtain the sulfate-resistant polycarboxylate water-reducing agent.

[0024] The sulfate-resistant polycarboxylate water-reducing agent provided in this application has the following beneficial effects compared with the existing technology: The sulfate-resistant polycarboxylate water-reducing agent provided in the present application has both excellent sulfate resistance and good working performance. It is synthesized by free radical solution copolymerization synthesis technology at room temperature, and the preparation process does not require heating. The preparation steps are simple, the raw materials are easily available, and the equipment is conventional, which can meet the actual industrial application needs. DETAILED DESCRIPTION

[0025] In order to make the purpose, 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 clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] The present application also provides the following embodiments and comparative examples: Embodiment 1: Functional monomer XS preparation: (1) Add 132 parts by mass of 3-(3-aminophenoxy)propyltrimethoxysilane and 31 parts by mass of acrylic acid into a reactor; wherein the molar ratio of 3-(3-aminophenoxy)propyltrimethoxysilane to acrylic acid is 1.13:1; (2) Under N2 atmosphere, 500 mL of tetrahydrofuran was added, and the mixture was reacted at 50°C for 4 h under the catalysis of 4-dimethylaminopyridine (DMAP) to obtain a reaction solution; Wherein, the usage of catalyst 4-dimethylaminopyridine is 1.29 parts.

[0027] (3) The reaction solution is filtered and the obtained filtrate is subjected to rotary evaporation to remove the organic solvent, thereby obtaining the functional monomer XS.

[0028] Preparation of sulfate-resistant polycarboxylate water reducer: (1) Add 200 parts of ethylene glycol monovinyl polyglycol ether and 160 parts of water into a three-necked flask, maintain the temperature at 15-35°C, and stir to form a mixed solution; (2) 12.0 parts of functional monomer XS, 7.2 parts of acrylic acid, 5.4 parts of allyl dimethyl phosphate and 30 parts of water were mixed uniformly to prepare liquid A; (3) Mix 0.7 parts of mercaptopropionic acid, 0.35 parts of ascorbic acid and 34 parts of water to prepare solution B; (4) Add 1.5 parts of 27.5% hydrogen peroxide into the flask and stir evenly; (5) Add the above solution A and solution B dropwise into a three-necked flask for 1.5 hours and react at a constant temperature of 15-35°C; (6) After the addition is completed, the mixture is kept at 15 to 35° C. for 1 hour, and then a 32% sodium hydroxide solution is added to the three-necked flask to adjust the pH value of the mixed solution to 5.5 to 6.5, thereby obtaining the sulfate-resistant polycarboxylate water-reducing agent.

[0029] Embodiment 2: Functional monomer XS preparation: (1) 138 parts by mass of 3-(3-aminophenoxy)propyltrimethoxysilane and 37 parts by mass of methacrylic acid were added to a reactor; wherein the molar ratio of 3-(3-aminophenoxy)propyltrimethoxysilane to methacrylic acid was 1.18:1.

[0030] (2) Under N2 atmosphere, 500 mL of tetrahydrofuran was added, and the mixture was reacted at 54°C for 4 h under the catalysis of 4-dimethylaminopyridine (DMAP) to obtain a reaction solution; Wherein, the usage of catalyst 4-dimethylaminopyridine is 1.38 parts.

[0031] (3) The reaction solution is filtered and the obtained filtrate is subjected to rotary evaporation to remove the organic solvent, thereby obtaining the functional monomer XS.

[0032] Preparation of sulfate-resistant polycarboxylate water reducer: (1) Add 200 parts of ethylene glycol monovinyl polyglycol ether and 156 parts of water into a three-necked flask, maintain the temperature at 15-35°C, and stir to form a mixed solution; (2) 13.2 parts of functional monomer XS, 6.8 parts of acrylic acid, 6.00 parts of hydroxyethyl methacrylate phosphate and 32 parts of water were mixed uniformly to prepare liquid A; (3) Mix 1.2 parts of sodium hypophosphite, 0.28 parts of Bruggolite FF6 and 33 parts of water to prepare Liquid B; (4) Add 1.3 parts of 27.5% hydrogen peroxide into the flask and stir evenly; (5) Add the above solution A and solution B dropwise into a three-necked flask for 1.5 hours and react at a constant temperature of 15-35°C; (6) After the addition is completed, the mixture is kept at 15 to 35° C. for 1 hour, and then a 32% sodium hydroxide solution is added to the three-necked flask to adjust the pH value of the mixed solution to 5.5 to 6.5, thereby obtaining the sulfate-resistant polycarboxylate water-reducing agent.

[0033] Comparative Example 1: Commercially available polycarboxylate water reducer Point-S.

[0034] Comparative Example 2: (Functional monomer XS is replaced by acrylic acid) The only difference from the example is that the functional monomer XS in example 1 is replaced by acrylic acid, and the rest is the same as example 1.

[0035] Comparative Example 3: (Functional monomer XS is replaced by acrylamide) The only difference from the example is that the functional monomer XS in Example 1 is replaced by acrylamide, and the rest is the same as Example 1.

[0036] Comparative Example 4: (Functional monomer XS is replaced by vinyl trimethoxysilane) The only difference from the example is that the functional monomer XS in Example 1 is replaced by vinyltrimethoxysilane, and the rest is the same as Example 1.

[0037] Comparative Example 5: (Unsaturated phosphate ester replaced by acrylic acid) The only difference from the example is that the unsaturated phosphate in Example 1 is replaced by acrylic acid, and the rest is the same as Example 1.

[0038] Comparative Example 6: (the ratio of the first unsaturated carboxylic acid, the unsaturated phosphate and the functional monomer XS is out of range) The only difference from the example is that during the copolymerization reaction, 200 parts of ethylene glycol monovinyl polyethylene glycol ether, 14 parts of acrylic acid, 9 parts of allyl dimethyl phosphate, and 18 parts of functional monomer XS are used, and the rest is consistent with Example 1.

[0039] Performance test of embodiments and comparative examples: In order to further illustrate the performance effect of the sulfate-resistant polycarboxylate water-reducing agent provided in the present application, according to the standard GB8076-2008 "Concrete Admixtures", the above embodiments and comparative examples were subjected to cement paste fluidity tests under different sulfate concentrations; the water-reducing agent dosage was 0.12%, and the test results are shown in Table 1.

[0040] Table 1 Cement paste fluidity test results

[0041] In Table 1, the smaller the difference in the fluidity of the pure slurry under different sulfate concentrations, the better the adaptability of the polycarboxylate water-reducing agent to sulfate.

[0042] The experimental results show that: Under the condition of equal dosage, the adaptability, dispersion and dispersion retention performance of the polycarboxylate water-reducing agent of the embodiment of the present application to sulfate are better than those of comparative examples 1 to 6.

[0043] In Comparative Example 1, the existing polycarboxylate water-reducing agent Point-S has poor adaptability to sulfate concentration, dispersion and retention performance.

[0044] In Comparative Example 2, after the functional monomer was replaced with acrylic acid, the adaptability to sulfate concentration decreased significantly, and the dispersion and retention performance were poor.

[0045] In Comparative Example 3, after the functional monomer was replaced with acrylamide, the adaptability to sulfate concentration decreased significantly, and the dispersion performance decreased significantly.

[0046] In Comparative Example 4, after the functional monomer was replaced with vinyltrimethoxysilane, the adaptability to sulfate concentration decreased and the dispersion retention performance decreased significantly.

[0047] In Comparative Example 5, after the unsaturated phosphate was replaced by acrylic acid, the adaptability to sulfate concentration decreased and the dispersion performance was poor.

[0048] In Comparative Example 6, the dosage of the first unsaturated carboxylic acid, unsaturated phosphate and functional monomer XS exceeds the dosage recommended by the technical solution. The unbalanced monomer ratio is likely to affect the polymerization process, thereby causing changes in the molecular weight and distribution of the polymer. At the same time, the hydrophobicity and hydrophilicity of the polymer chain segment are unbalanced, affecting the stability and dispersibility of the polymer, which is not conducive to the free distribution of the water reducer molecules on the cement particles. In addition, the synergistic relationship between the phosphate monomer and the functional monomer XS is affected by the unbalanced monomer ratio. The phosphate monomer is not effective in promoting dispersion by providing negative charges. At the same time, the functional monomer XS does not significantly improve the adhesion and plasticity of cement particles, thereby affecting the fluidity and stability of the cement paste. Therefore, the adaptability of the polycarboxylic acid water reducer to sulfate concentration decreases, and the dispersion and dispersion retention performance decreases significantly.

[0049] In summary, the sulfate-resistant polycarboxylate water-reducing agent provided in the present application has at least the following design concepts and beneficial effects: 1. The sulfate-resistant polycarboxylate water reducer provided in the present application has excellent sulfate resistance. Siloxane in the water reducer molecule combines with the silanol group on the hydration product CSH gel to form a stable silicon-oxygen bond (Si-O-Si). These silicon-oxygen bonds have a good barrier effect on sulfate ions, improving its adsorption competition with sulfate on the surface of cement particles. Phosphate esters can form stable complexes with metal ions to prevent sulfate ions from reacting with water reducers or cement, thereby improving the sulfate resistance of water reducers.

[0050] 2. The sulfate-resistant polycarboxylate water-reducing agent provided by the present application has good working performance. The hydrolysis of the alkoxy groups of silane in the water-reducing agent molecules can reduce the interaction between cement particles, reduce the viscosity and yield stress of the cement paste, and at the same time, the good electron cloud stability of the benzene ring ensures that the amide group can be slowly hydrolyzed in the concrete environment, and the steric hindrance effect further prevents the aggregation and sedimentation of cement particles, and releases the encapsulated free water, ensuring the requirements of the concrete's fluidity over time.

[0051] 3. The sulfate-resistant polycarboxylate water-reducing agent provided in the present application is prepared by copolymerizing the functional monomer XS and unsaturated phosphate with ethylene glycol monovinyl polyethylene glycol ether and the first unsaturated carboxylic acid, wherein the copolymerized monomers act synergistically with each other, rather than simply superposing functions, and the structural selection and proportion design of each monomer will affect the structure of the final polycarboxylate water-reducing agent, thereby affecting its performance and effect.

[0052] The first unsaturated carboxylic acid, the functional monomer XS and the unsaturated phosphate have a synergistic relationship, and the monomer ratio is not within the scope of the present application. The unbalanced monomer ratio is likely to affect the polymerization process, thereby causing changes in the molecular weight and distribution of the polymer, and at the same time, the hydrophobicity and hydrophilicity of the polymer chain segments are unbalanced, affecting the stability and dispersibility of the polymer, which is not conducive to the free distribution of the water reducer molecules on the cement particles. In addition, the synergistic relationship between the phosphate monomer and the functional monomer XS is affected by the unbalanced monomer ratio. The phosphate monomer is not effective in promoting dispersion by providing a negative charge, and the functional monomer XS does not significantly improve the adhesion and plasticity of cement particles, thereby affecting the fluidity and stability of the cement paste. Therefore, the adaptability of the polycarboxylic acid water reducer to sulfate concentration decreases, and the dispersion and dispersion retention performance decreases significantly.

[0053] 4. The EPEG type polycarboxylic acid water reducer provided in the present application, by introducing functional monomer XS, introduces silane alkoxy, benzene ring, amide group and other groups that play a corresponding role in the water reducer. However, it is not possible to achieve the effect of the present application simply by introducing the corresponding silane alkoxy, benzene ring and amide group into the water reducer molecule. How to introduce silane alkoxy, benzene ring, amide group and other groups (whether different groups are introduced through copolymerization of different monomers, or multiple groups are integrated into a functional monomer to participate in the polymerization introduction, the two methods are different), and the specific structure of the functional monomer that integrates silane alkoxy, benzene ring, amide group and other groups for participating in the polymerization, will result in different side chain structures of the obtained polycarboxylic acid water reducer, thereby resulting in different structural molecules of the water reducer, which ultimately affects its performance and effect.

[0054] The present application adopts a functional monomer XS with integrated alkoxy, amide and other groups of a specific structure, and then introduces the functional monomer XS with a specific structure into the side chain of the polycarboxylic acid water reducer through a copolymerization reaction, so as to obtain the desired polycarboxylic acid water reducer structure and achieve the desired effect of the present application.

[0055] If an unsaturated amide monomer containing an amide group, an alkoxy-containing silane monomer, and a benzene ring-containing monomer are respectively used as comonomers to copolymerize with ethylene glycol monovinyl polyethylene glycol ether, an unsaturated carboxylic acid monomer, an unsaturated phosphate ester and other monomers, and the monomers with different groups cause competitive reactions due to differences in reaction activity and solubility, the side chain of the polycarboxylic acid has a structure in which the groups are unevenly distributed, which is different from the structure in which the groups are evenly distributed in the side chain of the present application, and the structure of the polycarboxylic acid water reducer obtained is different, and this solution cannot achieve the effect of the present application.

[0056] For example, the scheme disclosed in patent publication number CN104592457A is to prepare a terpolymer from 2-acrylamide-2-methylpropane sulfonic acid, vinyl aromatic compound monomer A and unsaturated amide monomer B under the action of sodium dodecyl sulfate and an initiator: then the terpolymer, polyoxyethylene polyoxypropylene ether copolymer monomer C, unsaturated carboxylic acid monomer D and silane coupling agent monomer E are subjected to an aqueous phase free radical polymerization reaction at 40°C to 45°C under the action of a redox system initiator and a chain transfer agent to obtain a sulfate-compatible polycarboxylate water reducer. This scheme does not provide a corresponding proof of effect in a high sulfate environment concentration (sulfate concentration greater than 70 mmol / L, sulfate content exceeding approximately 2% of the mass of cement). It can be seen from its test results that it has better cement paste fluidity and time loss in a low sulfate concentration environment (sulfate content of 0 to 1.0% of the mass of cement).

[0057] 5. The sulfate-resistant polycarboxylate water-reducing agent provided in this application has excellent compatibility with polycarboxylic acid molecules, supports independent use or compound application with conventional water-reducing agents, and has significant market potential.

[0058] 5. The sulfate-resistant polycarboxylate water-reducing agent provided in the present application can be prepared at room temperature, the process is simple and mild, no complicated temperature control steps are required, the energy consumption is low, and it has efficient production and practical value.

[0059] In summary, the present application introduces unsaturated amide phenyl silane functional monomers, and can cooperate with some common unsaturated carboxylic acids and unsaturated phosphates, adopts room temperature free radical solution copolymerization synthesis technology, and does not require heating to prepare a sulfate-resistant polycarboxylic acid water reducer with excellent sulfate resistance, good working performance and that can meet the needs of actual industrial applications.

[0060] It should be noted that: In this article, “~” is used to indicate a numerical range, and the range indicated by this expression includes two endpoint values.

[0061] In addition to the actual selections embodied in the above specific embodiments, the above formulation ranges may be used in the specific implementation of the present application, including but not limited to the above embodiment schemes.

[0062] The specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments of the present application, but are not intended to limit the present application. Those skilled in the art may make adaptive adjustments within the scope of the present application.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A sulfate-resistant polycarboxylate water-reducing agent, characterized in that: It is prepared by copolymerization of ethylene glycol monovinyl polyethylene glycol ether, a first unsaturated carboxylic acid, an unsaturated phosphate ester and a functional monomer XS under the action of an initiator and a chain transfer agent; The structural formula of the functional monomer XS is as follows: ； Wherein, R1 is H or CH3.

2. The sulfate-resistant polycarboxylate water-reducing agent according to claim 1, characterized in that: The preparation process of the functional monomer XS is as follows: Add 3-(3-aminophenoxy)propyltrimethoxysilane and a second unsaturated carboxylic acid into a reactor to form a mixture; wherein the molar ratio of 3-(3-aminophenoxy)propyltrimethoxysilane to the second unsaturated carboxylic acid is (1.0-1.2):1; An organic solvent and a catalyst are added to the mixture under a protective atmosphere; the mixture is heated to 40 to 60° C. and reacted for 3 to 6 hours under the action of the catalyst; and the reaction liquid is filtered and the organic solvent is removed in sequence to obtain the functional monomer XS.

3. The sulfate-resistant polycarboxylate water-reducing agent according to claim 2, characterized in that: The second unsaturated carboxylic acid is at least one of acrylic acid and methacrylic acid; The organic solvent is at least one of dichloromethane, chloroform, methyl acetate and tetrahydrofuran; The catalyst is at least one of 4-dimethylaminopyridine, dicyclohexylcarbodiimide, pyridine and imidazole.

4. The sulfate-resistant polycarboxylate water-reducing agent according to claim 2, characterized in that: The protective atmosphere is N2 atmosphere; The reaction solution is filtered to obtain a filtrate, and then the filtrate is subjected to rotary evaporation to remove the organic solvent to obtain the functional monomer XS.

5. The sulfate-resistant polycarboxylate water-reducing agent according to claim 1, characterized in that: Under the action of an initiator and a chain transfer agent, the ethylene glycol monovinyl polyethylene glycol ether, the first unsaturated carboxylic acid, the unsaturated phosphate ester, and the functional monomer XS are copolymerized to obtain a sulfate-resistant polycarboxylate water-reducing agent; Wherein, the copolymerization reaction temperature is 15-35°C; the weight ratio of ethylene glycol monovinyl polyethylene glycol ether, the first unsaturated carboxylic acid, the unsaturated phosphate ester, and the functional monomer XS is 200: (5-10): (4-8): (8-14).

6. The sulfate-resistant polycarboxylate water-reducing agent according to claim 1, characterized in that: The initiator is composed of a reducing agent and an oxidizing agent; the copolymerization process is: The ethylene glycol monovinyl polyglycol ether is dissolved in a certain amount of water; the temperature of the reaction system is controlled at 15 to 35° C., and then an oxidant is added and stirred evenly; then the temperature of the reaction system is maintained at 15 to 35° C., and liquid A and liquid B are added for constant temperature reaction; after the addition is completed, the reaction system is kept warm at 15 to 35° C. for 0.5 to 1 hour; finally, a neutralizer is added to adjust the pH to 5.5 to 6.5, to obtain the sulfate-resistant polycarboxylate water-reducing agent; The functional monomer XS, the first unsaturated carboxylic acid, the unsaturated phosphate and a portion of water are uniformly mixed to obtain the liquid A; the chain transfer agent, the reducing agent and a portion of water are uniformly mixed to obtain the liquid B.

7. The sulfate-resistant polycarboxylate water-reducing agent according to claim 6, characterized in that: The A solution and the B solution are added dropwise for 0.5 to 2.5 hours; The raw material formula of the copolymerization reaction is as follows by weight: 200 parts of ethylene glycol monovinyl polyethylene glycol ether, 8 to 14 parts of functional monomer XS, 5 to 10 parts of the first unsaturated carboxylic acid, 4 to 8 parts of unsaturated phosphate, 1.0 to 2.5 parts of oxidant, 0.2 to 0.6 parts of reducing agent, 0.5 to 1.6 parts of chain transfer agent, and 200 to 230 parts of water in total.

8. The sulfate-resistant polycarboxylate water-reducing agent according to claim 1, characterized in that: The molecular weight of the ethylene glycol monovinyl polyethylene glycol ether is 1500 to 3000; The first unsaturated carboxylic acid or unsaturated phosphate is at least one of acrylic acid, methacrylic acid, and maleic anhydride; The unsaturated phosphate ester is at least one of hydroxyethyl methacrylate phosphate, vinyl dimethyl phosphate, and allyl dimethyl phosphate.

9. The sulfate-resistant polycarboxylate water-reducing agent according to claim 6, characterized in that: The oxidant is at least one of a 27.5% mass concentration hydrogen peroxide solution, ammonium persulfate, and sodium persulfate; The chain transfer agent is at least one of sodium hypophosphite, thioglycolic acid, and mercaptopropionic acid; The reducing agent is at least one of ascorbic acid, Bruggolite FF6, and Bruggolite E01; The neutralizing agent is a sodium hydroxide solution with a mass concentration of 32%.

10. A method for preparing the sulfate-resistant polycarboxylate water-reducing agent according to any one of claims 1 to 9, characterized in that: The initiator comprises an oxidant and a reductant; and the preparation method comprises the following preparation steps: Dissolving the ethylene glycol monovinyl polyglycol ether in a certain amount of water, controlling the temperature of the reaction system at 15 to 35° C., and then adding an oxidant and stirring evenly to form a mixed solution; The functional monomer XS, the first unsaturated carboxylic acid, the unsaturated phosphate and a portion of water are uniformly mixed to obtain a liquid A; The chain transfer agent, the reducing agent and a portion of water are uniformly mixed to obtain liquid B; Then, the temperature of the reaction system is maintained at 15 to 35° C., and the solution A and the solution B are added dropwise to the mixed solution for constant temperature reaction, and the adding time is 0.5 to 2.5 hours; After the dropwise addition is completed, the reaction system is kept at a temperature of 15 to 35° C. for 0.5 to 1 hour, and finally a neutralizing agent is added to adjust the pH to 5.5 to 6.5 to obtain the sulfate-resistant polycarboxylate water-reducing agent.

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