Viscosity-reducing polycarboxylate water reducer and preparation method thereof

Abstract

The present application relates to a kind of viscosity-reducing polycarboxylic water-reducing agent and its preparation method, the viscosity-reducing polycarboxylic water-reducing agent includes by weight parts: allyl end-capped polyether monomer 180-300 parts;Crosslinking monomer 3-9 parts;Unsaturated acid monomer 20-32 parts;Unsaturated ester monomer 8-15 parts;Quaternary ammonium salt compound 4-8 parts;Oxidizing agent 1.5-3.0 parts;Reducing agent 0.2-0.4 parts and water;Wherein, allyl end-capped polyether monomer is prepared by the reaction of unsaturated end olefin monomer and allyl compound under the catalysis of alkaline catalyst.The present application introduces allyl end-capped polyether monomer in viscosity-reducing polycarboxylic water-reducing agent, enhances the steric hindrance effect of water-reducing agent while reducing the branch density of polycarboxylic water-reducing agent molecule, and the molecular chain is more flexible, which helps to maintain the fluidity of concrete, delays slump loss.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete admixtures, in particular to a viscosity-reducing polycarboxylate superplasticizer and a preparation method thereof. BACKGROUND

[0002] With the rapid development of China's construction industry, the demand for high-performance concrete in landmark buildings, super high-rise buildings, tunnels and cross-sea bridges and other projects is increasing. High-performance concrete has become an important material in the construction industry due to its strong load-bearing capacity, light weight, and good durability. However, due to its low water-binder ratio and the addition of a large amount of cementitious materials and mineral admixtures, the viscosity of the mixture is high, which can cause problems in the construction process such as mixing, transportation and pumping.

[0003] Currently, methods to solve the problem of concrete viscosity include increasing the dosage of admixtures or compounding additives (such as air entraining agents), optimizing the gradation of cementitious materials, etc. However, these methods have certain limitations, for example, increasing the dosage of admixtures can increase production costs and may cause concrete retardation, bleeding, etc.; optimizing the gradation of cementitious materials can partially improve viscosity and fluidity, but cannot fundamentally solve the problem.

[0004] Polycarboxylate superplasticizers have been widely used in modern concrete engineering due to their high water-reducing, good dispersing and environmental protection properties. However, traditional polycarboxylate superplasticizers still have the following problems in some application scenarios:

[0005] 1. Insufficient dispersing performance: The dispersing performance of polycarboxylate superplasticizers depends on the electrostatic repulsion and steric hindrance effects of the molecular chain. However, when the surface properties of cement particles are complex or the compatibility with admixtures is poor, these effects may be weakened, making it difficult for cement particles to be fully dispersed.

[0006] 2. High viscosity: The types and fineness of mineral admixtures and cementitious materials in concrete are high, which can easily increase the viscosity of the system. However, the lubricating effect and dispersing ability of traditional superplasticizers are limited, making it difficult to effectively reduce the overall viscosity.

[0007] 3. Strong sensitivity to raw materials and temperature: The chemical composition and physical properties of cement, aggregate and mineral admixtures in different regions vary significantly. Traditional superplasticizers are unstable in different material systems. In addition, under high or low temperature conditions, the adsorption and efficiency of the molecular chain of traditional superplasticizers may be affected, thereby reducing the water-reducing effect.

[0008] Therefore, given the characteristics of molecular structure design of polycarboxylate superplasticizers, by changing the molecular structure of polycarboxylate superplasticizers, a viscosity-reducing polycarboxylate superplasticizer with high dispersing performance is developed, which can effectively reduce the viscosity of concrete and improve the workability of concrete, which is of great significance to the development of the construction industry. SUMMARY

[0009] Therefore, it is necessary to provide a viscosity-reducing polycarboxylate superplasticizer with high dispersity.

[0010] To achieve the above object, the present application provides a technical solution:

[0011] A viscosity-reducing polycarboxylate superplasticizer, in terms of weight fraction, comprises:

[0012]

[0013] The allyl-terminated polyether monomer is prepared by reacting an unsaturated terminal olefin monomer and an allyl compound under the catalysis of an alkaline catalyst. Specifically, the unsaturated terminal olefin monomer includes at least one of ethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether, and the structural formulas thereof are as follows, respectively:

[0014]

[0015] Specifically, the crosslinking monomer includes at least one of trimethylammonium methyl methacrylate chloride, trimethylammonium methyl methacrylate chloride, trimethylammonium propyl methacrylate chloride, dimethylallyl chloride, and diethylallyl chloride.

[0016] The reducing agent includes at least one of ascorbic acid, sodium formaldehyde sulfoxylate, sodium sulfite, sodium sulfite, sodium bisulfite, and sodium hypophosphite, wherein the sodium hypophosphite can also act as a chain transfer agent.

[0017] The oxidizing agent includes at least one or a combination of hydrogen peroxide, sodium peroxide, potassium peroxide, magnesium peroxide, sodium persulfate, ammonium persulfate, sodium dichromate, potassium dichromate, and potassium permanganate; the chain transfer agent is one or a combination of thioglycolic acid, sodium hypophosphite, trisodium phosphate, mercaptopropionic acid, mercaptoethanol, and mercaptoacetic acid.

[0018] The unsaturated carboxylic acid monomer includes at least one of acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and itaconic acid.

[0019] The unsaturated ester includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and acetic acid ethyl acid.

[0020] Specifically, the allyl-terminated polyether monomer includes at least one of

[0021]

[0022] Specifically, the allyl compound includes at least one of allyl chloride and allyl bromide.​

[0023] Specifically, the basic catalyst comprises at least one of potassium hydroxide, sodium hydroxide and triethanolamine.

[0024] Specifically, the weight ratio of the unsaturated terminal enol monomer, the allyl compound and the basic catalyst is (10-15):(3-7):(5-10).

[0025] Specifically, the quaternary ammonium salt compound has the following structural formula:

[0026]

[0027]

[0028] one of the following.

[0029] Specifically, the preparation raw material of the viscosity-reducing polycarboxylate superplasticizer further comprises, in parts by weight:

[0030] 0.01-0.02 parts of ferrous sulfate.

[0031] More specifically, the chain transfer agent comprises sodium hypophosphite.

[0032] The application further provides a preparation method of the viscosity-reducing polycarboxylate superplasticizer, comprising the following steps:

[0033] The allyl-terminated polyether monomer, the oxidizing agent and water are stirred uniformly to completely dissolve them, to obtain a bottom liquid;

[0034] The A liquid and the B liquid are added dropwise into the bottom liquid, and after the dropwise addition is completed, the reaction is continued for 1-2 hours, to obtain the viscosity-reducing polycarboxylate superplasticizer.

[0035] The A liquid is an aqueous solution of the unsaturated acid monomer, the unsaturated ester monomer, the crosslinking monomer and the quaternary ammonium salt compound; the dropwise addition time of the A liquid is 50-70 minutes.

[0036] The B liquid is an aqueous solution of the reducing agent and the chain transfer agent.

[0037] Specifically, the preparation method of the allyl-terminated polyether monomer comprises the following steps:

[0038] The basic catalyst is added into the unsaturated terminal enol monomer, to obtain a first mixture;

[0039] The water bath is maintained at a temperature of 55-65 DEG C, the allyl compound is added dropwise into the first mixture, constant-temperature stirring is carried out for 4-6 hours, after the dropwise addition is completed, the reaction is continued for 1-2 hours, to obtain the allyl-terminated polyether monomer.

[0040] Specifically, the preparation method of the quaternary ammonium salt compound monomer comprises the steps of:

[0041] Dopamine is dissolved in an acidic solution to obtain a dopamine solution; specifically, the dopamine, aldehyde compound

[0042] The aldehyde compound is dissolved in an alcohol solution to obtain an aldehyde compound solution; specifically, the alcohol solution comprises anhydrous ethanol.

[0043] The aldehyde compound solution is added to the dopamine solution, stirred for 18-24 hours, and the pH value is adjusted to neutral to obtain compound A; the weight ratio of the dopamine, aldehyde compound and acidic solution is 1:(0.75-1.25):(50-62.5);

[0044] The compound A is dissolved in an alcohol solution in a water bath at 55-65 DEG C, a base is added, and after reaction for 3-5 hours, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride solution is added dropwise, and the reaction is continued for 4-5 hours to obtain the quaternary ammonium salt compound. More specifically, the quaternary ammonium salt compound can be washed with a washing solvent, and the washing solvent comprises at least one of acetone, ethanol and water; the alcohol solution comprises at least one of methanol, ethanol, isopropanol, n-butanol and ethylene glycol.

[0045] Specifically, the aldehyde compound comprises at least one of salicylaldehyde, o-vanillin, benzaldehyde, 4-bromo-2-hydroxybenzaldehyde and 2-hydroxy-1-naphthaldehyde;

[0046] The acidic solution comprises at least one of acetic acid, propionic acid, formic acid and dilute hydrochloric acid.

[0047] The beneficial effects of the present application are:

[0048] 1. The present application introduces an allyl-terminated polyether monomer into the viscosity-reducing polycarboxylic acid water reducer, which enhances the steric hindrance effect of the water reducer, reduces the branch density of the polycarboxylic acid water reducer molecules, and makes the molecular chain more flexible, which helps to maintain the fluidity of the concrete, delays the loss of slump, especially during long-distance transportation and pumping, effectively maintains the workability of the concrete, helps the water reducer to better adapt to the surface morphology of the cement particles, improves the dispersion effect, and at the same time reduces the viscosity of the concrete, further enhances the flowability of the polycarboxylic acid water reducer.

[0049] 2. The viscosity-reducing polycarboxylic acid water reducer of the present application is obtained by copolymerization of unsaturated ester monomer, unsaturated carboxylic acid monomer, quaternary ammonium salt compound, crosslinking monomer, oxidizing agent, reducing agent and water, which introduces a crosslinking monomer into the polymer molecular structure, and the hydrolysis of the macromolecular additive molecules in the crosslinking monomer in an alkaline environment releases macromolecules with dispersion effect, thereby achieving the effect of rapid dispersion, which can greatly reduce the phenomena of segregation or rapid loss of slump of concrete, and reduce the viscosity of the slurry.

[0050] The allyl-terminated polyether monomer in the side chain of the viscosity-reducing polycarboxylate superplasticizer is connected with oxygen and the superplasticizer main chain, so that the space resistance of the polyether macromonomer in the side chain of the viscosity-reducing polycarboxylate superplasticizer is reduced, the activity freedom of the polyether macromonomer in the side chain of the viscosity-reducing polycarboxylate superplasticizer is higher, and the wrapping and winding of the polyether macromonomer in the side chain of the viscosity-reducing polycarboxylate superplasticizer are improved, so that the viscosity-reducing polycarboxylate superplasticizer has strong adsorption capacity;

[0051] The carboxylate synergistic effect is beneficial to the wetting and adsorption of the viscosity-reducing polycarboxylate superplasticizer on cement, and improves the dispersibility and fluidity of concrete.

[0052] Meanwhile, the ester group is continuously hydrolyzed in the cement hydration process, continuously reacts with the cement hydration product, inhibits the growth of Ca(OH)2 and AFt crystal nucleus, slows down the hydration speed, and prolongs the cement hydration induction period, thereby improving the dispersion and retention.

[0053] 3. The viscosity-reducing polycarboxylate superplasticizer has the advantages of low dosage, high water-reducing rate, and good workability, can significantly reduce the viscosity of concrete, and improve the workability of concrete. DETAILED DESCRIPTION

[0054] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in combination with specific examples.

[0055] In the examples, the test methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0056] I. Preparation of allyl-terminated polyether monomer A

[0057] 1. Allyl-terminated polyether monomer A1:

[0058] 200 parts of ethylene glycol monovinyl ether were added to a four-necked flask, and 60 parts of potassium hydroxide were added to obtain a first mixture;

[0059] The temperature was maintained at 55 DEG C in a water bath under a nitrogen atmosphere, 100 parts of allyl chloride compound were slowly added to the first mixture, and constant temperature stirring was carried out at this temperature for 4 hours, after the addition was completed, constant temperature was continued at the same temperature for 2 hours, and finally 5 parts of phosphoric acid was added for neutralization treatment, to obtain the allyl-terminated polyether monomer A1.

[0060] 2. Allyl-terminated polyether monomer A2:

[0061] 200 parts of 4-hydroxybutyl vinyl ether were added to a four-necked flask, and 60 parts of sodium hydroxide were added to the first mixture to obtain a first mixture;

[0062] After maintaining the temperature at 55°C in a water bath under a nitrogen atmosphere, 100 parts of the allyl chloride compound was slowly added dropwise and stirred for 4 hours at the same temperature. After the addition was completed, the temperature was maintained at the same temperature for 2 hours. Finally, 5 parts of phosphoric acid was added for neutralization treatment, and an allyl-terminated polyether monomer A2 was obtained.

[0063] 3. Allyl-terminated polyether monomer A3:

[0064] 200 parts of diethylene glycol monovinyl ether was added to a four-necked flask, and 60 parts of sodium hydroxide was added to obtain a first mixture;

[0065] After maintaining the temperature at 55°C in a water bath under a nitrogen atmosphere, 100 parts of the allyl chloride compound was slowly added dropwise and stirred for 4 hours at the same temperature. After the addition was completed, the temperature was maintained at the same temperature for 2 hours. Finally, 5 parts of phosphoric acid was added for neutralization treatment, and an allyl-terminated polyether monomer A2 was obtained.

[0066] II. Preparation of quaternary ammonium salt compound B

[0067] 1. Preparation of quaternary ammonium salt compound B1:

[0068] 1.6 g of dopamine was dissolved in 80 mL of acetic acid, and then 1.2 g of salicylaldehyde was dissolved in 100 mL of anhydrous methanol and added to the dopamine solution, and stirred for 18 hours. The pH was adjusted to 7 using a sodium hydroxide solution, and then washed with a suitable washing solvent, and vacuum dried to obtain compound A.

[0069] 1.6 g of compound A was dissolved in 100 mL of isopropyl alcohol, and 10 mL of 40% sodium hydroxide was added, and reacted at 55°C in a water bath for 4 hours. Then, under the same water bath conditions, 30 mL of an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride (40 wt.%) was slowly added dropwise, and the temperature was controlled at 60°C, and the reaction was continued for 5 hours. Finally, the obtained product was washed with an alcohol solution, and dried under vacuum to obtain quaternary ammonium salt compound B1.

[0070] 2. Preparation of quaternary ammonium salt compound B2:

[0071] 1.6 g of dopamine was dissolved in 80 mL of acetic acid, and then 2.0 g of 4-bromo-2-hydroxybenzaldehyde was dissolved in 100 mL of anhydrous methanol and added to the dopamine solution, and stirred for 24 hours. The pH was adjusted to neutral using a sodium hydroxide solution, and then washed with a suitable washing solvent, and vacuum dried to obtain compound A.

[0072] Dissolve 1.6 g of compound A in 100 mL of isopropyl alcohol, add 10 mL of 40% sodium hydroxide, and react in a water bath at 55°C for 4 h. Then, slowly drop 30 mL of an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride (40 wt.%) under the same water bath condition, control the temperature at 60°C, and continue to react for 4-5 h. Finally, wash the obtained product with an alcohol solution, and dry under vacuum to obtain the quaternary ammonium salt compound B3.

[0073] 3. Preparation of quaternary ammonium salt compound B3:

[0074] Dissolve 1.6 g of dopamine in 80 mL of acetic acid, then dissolve 1.5 g of o-vanillin in 100 mL of anhydrous methanol and add the above dopamine solution, and stir for 20 h. Adjust the pH to neutral with a sodium hydroxide solution, then wash with a suitable washing solvent, and dry under vacuum to obtain compound A.

[0075] Then, dissolve 1.6 g of compound A in 100 mL of isopropyl alcohol, add 10 mL of 40% sodium hydroxide, and react in a water bath at 55°C for 4 h. Then, slowly drop 30 mL of an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride (40 wt.%) under the same water bath condition, control the temperature at 60°C, and continue to react for 4-5 h. Finally, wash the obtained product with an alcohol solution, and dry under vacuum to obtain the quaternary ammonium salt compound B3.

[0076] III. Preparation of viscosity-reducing polycarboxylic acid water-reducing agent

[0077] Example 1

[0078] Dissolve 180 g of allyl-terminated polyether monomer A1 and 300 g of water in a four-necked flask, stir to dissolve, then add 0.01 g of ferrous sulfate and 1.5 g of hydrogen peroxide, and adjust the reaction temperature to 35°C.

[0079] Simultaneously drop A and B liquids into the four-necked flask, continue to react for 1 h after the dropping is completed, then add liquid alkali to neutralize to obtain a viscosity-reducing polycarboxylic acid water-reducing agent.

[0080] The A liquid is a solution prepared from 22 g of acrylic acid, 8 g of hydroxyethyl acrylate, 3 g of methacryloyloxyethyltrimethylammonium chloride, 4 g of quaternary ammonium salt compound B1, and 10 g of water, and the dropping time of the A liquid is 70 min.

[0081] The B liquid is a solution prepared from 0.2 g of ascorbic acid, 0.22 g of mercaptoethanol, and 42 g of water, and the dropping time of the B liquid is 80 min.

[0082] Example 2

[0083] Into a four-necked flask, 180 g of allyl-terminated polyether monomer A2 and 300 g of water were stirred and dissolved, and then 0.01 g of ferrous sulfate and 1.5 g of hydrogen peroxide were added, and the reaction temperature was adjusted to 20°C.

[0084] Into a four-necked flask, 180 g of allyl-terminated polyether monomer A2 and 300 g of water were stirred and dissolved, and then 0.01 g of ferrous sulfate and 1.5 g of hydrogen peroxide were added, and the reaction temperature was adjusted to 20°C.

[0085] Example 3

[0086] Into a four-necked flask, 180 g of allyl-terminated polyether monomer A2 and 300 g of water were stirred and dissolved, and then 0.01 g of ferrous sulfate and 1.5 g of hydrogen peroxide were added, and the reaction temperature was adjusted to 20°C.

[0087] Comparative Example 1

[0088] The other steps were the same as in Example 1, and the difference between Comparative Example 1 and Example 1 was that:

[0089] The allyl-terminated polyether monomer A1 was replaced by ethylene glycol monovinyl polyethylene glycol ether.

[0090] Comparative Example 2

[0091] The other steps were the same as in Example 1, and the difference between Comparative Example 2 and Example 1 was that:

[0092] No quaternary ammonium salt compound was added, and the amount of water was adjusted so that the solid content of the viscosity-reducing polycarboxylate superplasticizer prepared was the same as that of Example 1.

[0093] Comparative Example 3

[0094] The other steps were the same as in Example 1, and the difference between Comparative Example 3 and Example 1 was that:

[0095] No crosslinking monomer was added, and the amount of water was adjusted so that the solid content of the viscosity-reducing polycarboxylate superplasticizer prepared was the same as that of Example 1.

[0096] Comparative Example 4

[0097] Commercially available water-reducing agent KZJ-Point 400S.

[0098] The polycarboxylic acid water-reducing agent samples synthesized in Examples 1-4 and Comparative Examples 1-4 and the commercially available polycarboxylic acid water-reducing agent were used to detect the initial slump and spread, slump and spread over time, and corresponding emptying time of concrete according to GB 8076-2008 "Concrete Admixtures" and GB 8077-2023 "Concrete Admixtures Homogeneity Test Method" using P·O 42.5R cement, machine-made sand, and crushed stone.

[0099] The concrete mix proportion was: cement 380 kg / m 3 , fly ash (II grade) 70 kg / m 3 , mineral powder 70 kg / m 3 , sand 7599 kg / m 3 , crushed stone (10-20 mm) 805 kg / m 3 , crushed stone (5-10 mm) 201 kg / m 3 The results are shown in Table 1.

[0100] Table 1: Concrete performance test results

[0101]

[0102] From the results in Table 1, it can be seen that the experimental results of Examples 1-4 and Comparative Examples 1-3 show that, compared with Comparative Example 3, the dosage and emptying time of the water-reducing agent prepared in the application are lower, and the dispersion and viscosity reduction effect are better.

[0103] Comparative Example 2 did not add a quaternary ammonium salt compound, and the concrete viscosity was higher, indicating that the introduction of a quaternary ammonium salt compound is beneficial to improving the viscosity of the slurry.

[0104] Comparative Example 3 did not add a crosslinking monomer, and the concrete viscosity was higher, and the emptying time was higher. The polycarboxylic acid water-reducing agent prepared in the application has good viscosity reduction performance, can improve the workability and flow rate of concrete, and has obvious improvement on the mechanical properties, has no adverse effects, is suitable for a wide range, is fast to prepare and has high efficiency.

[0105] It should be noted that the specific parameters or some reagents in the above examples are specific embodiments or preferred embodiments under the concept of the application, but are not limited thereto; those skilled in the art can make adaptive adjustments within the scope of the concept and protection of the application.

Claims

1. A viscosity-reducing polycarboxylate superplasticizer, characterized in that, The viscosity-reducing polycarboxylate superplasticizer comprises, by weight parts: The crosslinking monomer is methacryloyloxyethyltrimethylammonium chloride or acryloyloxyethyltrimethylammonium chloride; The allyl-terminated polyether monomer is allyl-terminated polyether monomer A1, allyl-terminated polyether monomer A2 or allyl-terminated polyether monomer A3; The preparation steps of allyl-terminated polyether monomer A1 are as follows: Add 200 parts of ethylene glycol monovinyl ether to a four-necked flask and add 60 parts of potassium hydroxide to obtain the first mixture; In a water bath maintained at 55°C under a nitrogen atmosphere, 100 parts of allyl chloride compound were slowly added dropwise to the first mixture and stirred at this temperature for 4 hours. After the addition was completed, the mixture was kept at the same temperature for 2 hours. Finally, 5 parts of phosphoric acid were added for neutralization to obtain allyl-terminated polyether monomer A1. The preparation steps of allyl-terminated polyether monomer A2 are as follows: 200 parts of 4-hydroxybutylvinyl ether were added to a four-necked flask, and 60 parts of sodium hydroxide were added to obtain the first mixture; After maintaining the temperature at 55°C in a water bath under a nitrogen atmosphere, 100 parts of allyl chloride compound were slowly added dropwise, and the mixture was stirred at this temperature for 4 hours. After the addition was complete, the mixture was kept at the same temperature for another 2 hours. Finally, 5 parts of phosphoric acid were added for neutralization to obtain allyl-terminated polyether monomer A2. The preparation steps of allyl-terminated polyether monomer A3 are as follows: Add 200 parts of diethylene glycol monovinyl ether to a four-necked flask and add 60 parts of sodium hydroxide to obtain the first mixture; In a water bath maintained at 55°C under a nitrogen atmosphere, 100 parts of allyl chloride compound were slowly added dropwise to the first mixture, and the mixture was stirred at this temperature for 4 hours. After the addition was complete, the mixture was kept at the same temperature for another 2 hours. Finally, 5 parts of phosphoric acid were added for neutralization to obtain allyl-terminated polyether monomer A3. The quaternary ammonium salt compound is quaternary ammonium salt compound B1, quaternary ammonium salt compound B2 or quaternary ammonium salt compound B3; The preparation steps of quaternary ammonium salt compound B1 are as follows: 1.6 g of dopamine was dissolved in 80 mL of acetic acid, and then 1.2 g of salicylaldehyde was dissolved in 100 mL of anhydrous methanol and added to the dopamine solution. The mixture was stirred for 18 hours. The pH was adjusted to 7 using sodium hydroxide solution, followed by washing with a suitable cleaning solvent and vacuum drying to obtain compound A. 1.6 g of compound A was dissolved in 100 mL of isopropanol, and 10 mL of 40% sodium hydroxide was added. The mixture was reacted in a water bath at 55 °C for 4 h. Subsequently, under the same water bath conditions, 30 mL of 40 wt.% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride was slowly added dropwise, and the temperature was controlled at 60 °C. The reaction was continued for 5 h. Finally, the product was washed with an alcohol solution and dried under vacuum to obtain quaternary ammonium salt compound B1. The preparation steps of quaternary ammonium salt compound B2 are as follows: 1.6 g of dopamine was dissolved in 80 mL of acetic acid, and then 2.0 g of 4-bromo-2-hydroxybenzaldehyde was dissolved in 100 mL of anhydrous methanol and added to the dopamine solution. The mixture was stirred for 24 hours. The pH was adjusted to neutral using sodium hydroxide solution, followed by washing with a suitable cleaning solvent and vacuum drying to obtain compound A. 1.6 g of compound A was dissolved in 100 mL of isopropanol, and 10 mL of 40% sodium hydroxide was added. The mixture was reacted in a water bath at 55 °C for 4 h. Subsequently, under the same water bath conditions, 30 mL of 40 wt.% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride was slowly added dropwise, and the temperature was controlled at 60 °C. The reaction was continued for another 4 h. Finally, the product was washed with an alcohol solution and dried under vacuum to obtain quaternary ammonium salt compound B2. The preparation steps of quaternary ammonium salt compound B3 are as follows: 1.6 g of dopamine was dissolved in 80 mL of acetic acid, and then 1.5 g of o-vanillin was dissolved in 100 mL of anhydrous methanol and added to the dopamine solution. The mixture was stirred for 20 hours. The pH was adjusted to neutral using sodium hydroxide solution, followed by washing with a suitable cleaning solvent and vacuum drying to obtain compound A. Next, 1.6 g of compound A was dissolved in 100 mL of isopropanol, and 10 mL of 40% sodium hydroxide was added. The mixture was reacted in a water bath at 55 °C for 4 h. Subsequently, under the same water bath conditions, 30 mL of 40 wt.% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride was slowly added dropwise, and the temperature was controlled at 60 °C. The reaction was continued for 4-5 h. Finally, the product was washed with an alcohol solution and dried under vacuum to obtain quaternary ammonium salt compound B3.

2. The viscosity-reducing polycarboxylate superplasticizer according to claim 1, characterized in that, The raw materials for preparing the viscosity-reducing polycarboxylate superplasticizer, by weight, also include: Ferrous sulfate 0.01-0.02 parts.

3. A method for preparing a viscosity-reducing polycarboxylate superplasticizer as described in any one of claims 1 to 2, characterized in that, Including the following steps: Allyl-terminated polyether monomer, oxidant and water are stirred until completely dissolved to obtain the base liquid; Add solution A and solution B dropwise to the base solution. After the addition is complete, continue the reaction at a constant temperature for 1 to 2 hours to obtain the viscosity-reducing polycarboxylate superplasticizer. Wherein, solution A is an aqueous solution of unsaturated acid monomers, unsaturated ester monomers, crosslinking monomers and quaternary ammonium salt compounds; Solution B is an aqueous solution of a reducing agent and a chain transfer agent.

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