Viscosity-reducing polycarboxylate-based water-reducing agent, preparation method and application thereof

Abstract

The application provides a viscosity-reducing polycarboxylic acid water-reducing agent, a preparation method and application thereof. The raw material of the viscosity-reducing polycarboxylic acid water-reducing agent comprises the following components in parts by weight: polycarboxylic acid 1000 parts, acrylic acid 150-750 parts, methacrylic acid 0-150 parts, ethylene glycol benzoate 100-500 parts, 98wt% concentrated sulfuric acid 3-10 parts, p-toluene sulfonic acid 0-5 parts, phenol 5-10 parts, 27.5wt% hydrogen peroxide 10-20 parts, reducing agent 1.2-2.4 parts, ferrous sulfate 0.003-0.03 parts, sodium hypophosphite 12-20 parts, 32wt% strong alkali solution 20-50 parts and water 1300-3000 parts. The polycarboxylic acid water-reducing agent contains a carboxyl group, a benzene group and a long side chain, has good dispersion and viscosity-reducing performance while ensuring the water-reducing effect, and can effectively improve the construction viscosity of concrete when added into high-strength and super-high-strength concrete.

Description

Technical Field

[0001] This invention belongs to the field of water-reducing agent technology, specifically relating to a viscosity-reducing polycarboxylate water-reducing agent, its preparation method, and its application. Background Technology

[0002] With the rapid development of the construction and materials industry, modern buildings are increasingly trending towards high-rise, lightweight, and large-span structures. High-strength concrete, with its high overall strength and light weight, is being increasingly used in national infrastructure projects. To achieve high or ultra-high strength concrete, a large amount of cementitious materials and a low water-cement ratio are required. This results in freshly mixed concrete having high viscosity and slow flow rate, making construction difficult and severely restricting the widespread application of high-strength concrete. The water-cement ratio, the type and dosage of admixtures, sand ratio, sand type and gradation, aggregate type and gradation, mud and powder content of sand and gravel, and the type and dosage of admixtures all affect the viscosity of concrete. Currently, methods to reduce the viscosity of high-strength concrete mainly involve increasing the dosage of superplasticizers, using high-quality mineral admixtures, and optimizing particle size distribution. However, increasing the dosage of superplasticizers to improve the initial fluidity of concrete can easily lead to segregation and bleeding in later stages. Therefore, developing a viscosity-reducing water-reducing agent to control the plastic viscosity of high-strength concrete during construction, ensuring suitable workability and reducing segregation and bleeding, would be highly beneficial for practical engineering construction. Summary of the Invention

[0003] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions:

[0004] One objective of this invention is to provide a viscosity-reducing polycarboxylate superplasticizer, wherein the raw materials of the superplasticizer include the following components in parts by weight: 1000 parts polyether, 150-750 parts acrylic acid, 0-150 parts methacrylic acid, 100-500 parts ethylene glycol phenyl ether, 3-10 parts 98wt% concentrated sulfuric acid, 0-5 parts p-toluenesulfonic acid, 5-10 parts phenthiazide, 10-20 parts 27.5wt% hydrogen peroxide, 1.2-2.4 parts reducing agent, 0.003-0.03 parts ferrous sulfate, 12-20 parts sodium hypophosphite, 20-50 parts 32wt% strong alkali solution, and 1300-3000 parts water.

[0005] It should be noted that the weight parts of the concentrated sulfuric acid, hydrogen peroxide, and sodium hydroxide are calculated based on their corresponding concentrations. Of course, in some embodiments, sulfuric acid, hydrogen peroxide, and sodium hydroxide of other concentrations can be used, and the weight parts added can be adjusted accordingly to change the concentration.

[0006] The present invention selects ethylene glycol phenyl ether for the reaction because the ethylene glycol group in its structure readily undergoes esterification with acrylic acid and methacrylic acid, and compared with other substances containing benzene ring groups such as phenol and hydroquinone, ethylene glycol phenyl ether is non-carcinogenic and has a high safety factor.

[0007] In the technical solution where the raw material of the water-reducing agent contains methacrylic acid, the presence of methyl groups in the methacrylic acid structure can improve the adsorption of the water-reducing agent in concrete, which is beneficial for reducing the viscosity of concrete.

[0008] In some embodiments, the polyether includes at least one of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether. Compared to other polyethers, methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether have comparable reactivity to ester monomers obtained by reacting ethylene glycol phenyl ether with acrylic acid and methacrylic acid, thus enabling them to undergo a more complete polymerization reaction at 40–70°C to improve the viscosity-reducing properties of the water-reducing agent.

[0009] In some embodiments, the number-average molecular weight of the polyether is 600–3000. If the molecular weight is low, the steric hindrance is insufficient, resulting in a low water reduction rate of the synthesized water-reducing agent. If the molecular weight is high, the synthesized water-reducing agent has an excessively large molecular weight, which can easily lead to segregation and bleeding in the concrete.

[0010] In some preferred embodiments, the raw materials of the water-reducing agent include: 1000 parts polyether, 300-600 parts acrylic acid, 50-100 parts methacrylic acid, 200-400 parts ethylene glycol phenyl ether, 5-8 parts 98wt% concentrated sulfuric acid, 1-4 parts p-toluenesulfonic acid, 6-9 parts phenthiazide, 12-18 parts 27.5wt% hydrogen peroxide, 1.5-2.1 parts reducing agent, 0.01-0.02 parts ferrous sulfate, 14-18 parts sodium hypophosphite, 30-40 parts 32wt% strong alkali solution, and 1400-2200 parts water.

[0011] In some embodiments, the reducing agent includes, but is not limited to, VC (vitamin C).

[0012] In some embodiments, the strong base includes, but is not limited to, at least one of sodium hydroxide and strong potassium oxide.

[0013] In some embodiments, the concentration of the effective active ingredient in the water-reducing agent is 40% to 60%.

[0014] In some embodiments, the water-reducing agent has a pH value of 4.0 to 6.0. Water-reducing agents with a pH value within this range are less likely to corrode equipment and will not cause alkali-aggregate reaction in concrete.

[0015] In some embodiments, the water-reducing agent has a weight-average molecular weight of 20,000–30,000, a PDI of 1.40–1.60, and a main peak content of 85%–95%. That is, the water-reducing agent prepared by the present invention has a small molecular weight, a wide distribution, and a high main peak content.

[0016] A second objective of this invention is to provide a method for preparing the viscosity-reducing polycarboxylate superplasticizer described above, the method comprising:

[0017] S1: Under inert atmosphere conditions, the first mixed reaction system containing 100-500 parts by weight of ethylene glycol phenyl ether, 6-9 parts by weight of phenthiazide, 150-750 parts by weight of acrylic acid, 0-150 parts by weight of methacrylic acid, 3-10 parts by weight of 98wt% concentrated sulfuric acid, and 0-5 parts by weight of p-toluenesulfonic acid is subjected to esterification reaction at a temperature of 80-120°C to obtain esterified monomers;

[0018] S2: A second mixed reaction system containing 1000 parts by weight of polyether, 12-20 parts by weight of sodium hypophosphite, 0.003-0.03 parts by weight of ferrous sulfate, 10-20 parts by weight of 27.5 wt% hydrogen peroxide, 408-1275 parts by weight of the esterified monomer, 1.2-2.4 parts by weight of reducing agent and 900-2400 parts by weight of water is subjected to a polymerization reaction at a temperature of 40-70℃, and then cured at a constant temperature of 40-70℃ for 30-90 minutes to obtain a viscosity-reducing polycarboxylate superplasticizer.

[0019] This invention utilizes the esterification reaction of ethylene glycol phenyl ether with acrylic acid and methacrylic acid to introduce a benzene ring, followed by polymerization with methyl allyl polyoxyethylene ether and / or isopentenyl polyoxyethylene ether under the aforementioned temperature conditions. The synthesized water-reducing agent contains carboxyl groups, phenyl groups, and long side chains. While ensuring water-reducing effect, the phenyl group has good hydrophobic properties and is not easily adsorbed onto the surface of cement particles, thus continuously playing a dispersing role. The water-reducing agent is suitable for application in high-strength and ultra-high-strength concrete. The introduction of phenyl groups can effectively improve the construction viscosity of concrete, for example, by adding water-reducing agents. When the amount is 0.25% wt of the cementitious material, the initial concrete spread is 550-600 mm with a backflow time of 4-8 s, and the 1-hour concrete spread is 520-550 mm with a backflow time of 6-10 s. Meanwhile, the esterified monomer obtained by esterification of ethylene glycol phenyl ether with acrylic acid and methacrylic acid has a similar reactivity to methyl allyl polyoxyethylene ether and / or isopentenyl polyoxyethylene ether. The water-reducing agent synthesized at 40-70℃ has a small molecular weight, wide distribution, and high effective content, which can effectively improve the viscosity reduction effect of the water-reducing agent.

[0020] In some embodiments, the preparation method specifically includes: in step S1, firstly, 100-500 parts by weight of ethylene glycol phenyl ether and 6-9 parts by weight of phenthiazide are mixed to obtain a first material, the vacuum degree is adjusted to -0.02 to -0.10 MPa, and the mixture is stirred, and the temperature of the first material is raised to 80-120°C within 30-60 minutes; then, under an inert atmosphere, a second material containing 150-750 parts by weight of acrylic acid, 0-150 parts by weight of methacrylic acid, 3-10 parts by weight of 98 wt% concentrated sulfuric acid and 0-5 parts by weight of p-toluenesulfonic acid is mixed with the first material, and an esterification reaction is carried out at a temperature of 80-120°C for 1-6 hours to obtain an esterified monomer.

[0021] In some preferred embodiments, in step S1, the vacuum degree is -0.04 to -0.08 MPa.

[0022] In some preferred embodiments, in step S1, the temperature of the first material is raised to 80-120°C within 40-50 minutes.

[0023] In some preferred embodiments, the temperature of the esterification reaction in S1 is 90–110°C.

[0024] In some preferred embodiments, in step S1, an inert atmosphere is introduced at a gas flow rate of 1 to 5 mL / min. More preferably, an inert atmosphere is introduced at a gas flow rate of 2 to 4 mL / min. The inert atmosphere includes, for example, nitrogen, but is not limited thereto.

[0025] In some preferred embodiments, the esterification reaction in step S1 takes 2 to 5 hours.

[0026] In some embodiments, S2 specifically includes: providing a third material containing a uniform mixture of 1000 parts by weight of polyether, 12-20 parts by weight of sodium hypophosphite, 500-1200 parts by weight of water, 0.003-0.03 parts by weight of ferrous sulfate and 10-20 parts by weight of 27.5 wt% hydrogen peroxide; and providing a fourth material containing a uniform mixture of 408-1275 parts by weight of esterifying monomer, 1.2-2.4 parts by weight of reducing agent and 400-1200 parts by weight of water. The fourth material is added in batches to the third material at a temperature of 40-70°C to carry out the polymerization reaction.

[0027] In some embodiments, the preparation method of the third material includes: first mixing 1000 parts by weight of polyether, 12-20 parts by weight of sodium hypophosphite and 500-1200 parts by weight of water, stirring, and raising the temperature of the third mixture to 40-70°C within 30 minutes, and then adding 0.003-0.03 parts by weight of ferrous sulfate and 10-20 parts by weight of 27.5 wt% hydrogen peroxide, stirring to mix them evenly, to obtain the third material.

[0028] Furthermore, in the preparation method of the third material, the temperature is raised to 40-70°C within 10-20 minutes, and then 0.003-0.03 parts by weight of ferrous sulfate and 10-2027.5 wt% by weight of hydrogen peroxide are added.

[0029] In some embodiments, in step S2, the polymerization reaction is carried out at a temperature of 50–60°C and then aged at a constant temperature of 50–60°C.

[0030] In some embodiments, step S2, adding the fourth material to the third material in batches, specifically includes adding the fourth material to the third material in batches at a uniform rate within 120 to 240 minutes.

[0031] Furthermore, the fourth material is added to the third material in batches at a uniform rate within 150–210 minutes.

[0032] In some embodiments, the preparation method further includes step S3: adjusting the pH value of the polymer to 4.0–6.0. ​​This is to prevent the water-reducing agent from corroding equipment and from causing alkali-aggregate reaction in the concrete.

[0033] Further, step S3 specifically includes: adding 20-50 parts by weight of a 32wt% strong alkali solution and 0-800 parts by weight of water to the polymer obtained in step S2, and stirring to adjust the pH value of the polymer to 4.0-6.0.

[0034] Furthermore, in step S3, the stirring time is 30–120 min, more preferably 60–90 min.

[0035] In some typical embodiments, the preparation method of the viscosity-reducing polycarboxylate superplasticizer includes:

[0036] 1) Add 100-500 parts by weight of ethylene glycol phenyl ether and 6-9 parts by weight of phenthiazide to a reaction vessel, evacuate to -0.02 to -0.10 MPa, and stir and heat, raising the temperature to 80-120℃ within 30-60 min; add 150-750 parts by weight of acrylic acid, 0-150 parts by weight of methacrylic acid, 3-10 parts by weight of concentrated sulfuric acid and 0-5 parts by weight of p-toluenesulfonic acid to the reaction vessel, while continuously purging with nitrogen gas for protection at a flow rate of 1-5 mL / min, and react at a constant temperature for 1-6 h before discharging to obtain the esterified monomer;

[0037] 2) Add 1000 parts by weight of polyether, 12-20 parts by weight of sodium hypophosphite and 500-1200 parts by weight of water to a reactor, stir and heat, and raise the temperature to 40-70°C within 30 minutes. Add 0.003-0.03 parts by weight of ferrous sulfate and 10-20 parts by weight of hydrogen peroxide to the reactor. After stirring for 5 minutes, add 408-1275 parts by weight of the esterified monomer, 1.2-2.4 parts by weight of reducing agent and 400-1200 parts by weight of water to the reactor at a uniform rate within 120-240 minutes. Continue to mature at a constant temperature for 30-90 minutes to obtain the polymer.

[0038] 3) Add 20-50 parts by weight of sodium hydroxide and 0-800 parts by weight of water to the polymer obtained in step 2), stir for 30-120 minutes, and adjust the pH value of the polymer to 4.0-6.0 to obtain a viscosity-reducing polycarboxylate superplasticizer with a concentration of 40%-60%.

[0039] The third objective of this invention is to provide the application of the viscosity-reducing polycarboxylate superplasticizer described in any of the above-mentioned claims in high-strength concrete.

[0040] The fourth objective of this invention is to provide a high-strength concrete, which includes cement, sand, stone and a water-reducing agent, wherein the water-reducing agent includes the viscosity-reducing polycarboxylate water-reducing agent described in any of the above technical solutions.

[0041] In some embodiments, the content of the viscosity-reducing polycarboxylate superplasticizer is 0.20% wt to 0.30% wt of the cementitious material. The cementitious material includes cement, mineral powder, and fly ash.

[0042] In some embodiments, the method for preparing high-strength concrete includes: introducing an appropriate amount of fine, uniform, and stable air bubbles into the concrete using a viscosity-reducing polycarboxylate superplasticizer to improve the workability of the concrete, thereby further reducing the viscosity of the concrete.

[0043] The fifth objective of this invention is to provide a method for controlling the plastic viscosity of high-strength concrete, the method comprising: adding the viscosity-reducing polycarboxylate superplasticizer described in any of the above technical solutions to the high-strength concrete.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects:

[0045] (1) The present invention obtains a polycarboxylic acid water-reducing agent by esterifying ethylene glycol phenyl ether with acrylic acid and methacrylic acid, and then further polymerizing it with methyl allyl polyoxyethylene ether and / or isopentenyl polyoxyethylene ether. The resulting agent contains carboxyl groups, phenyl groups, and long side chains, which can effectively reduce the viscosity of concrete while having a good water-reducing effect.

[0046] (2) The preparation method of the viscosity-reducing polycarboxylate superplasticizer provided by the present invention is simple and has the characteristics of being green and environmentally friendly;

[0047] (3) The viscosity-reducing polycarboxylate superplasticizer of the present invention can be widely used in high-strength and ultra-high-strength concrete. When the amount of superplasticizer added is 0.20-0.30%wt of the weight of cementitious material, the initial concrete spread is 550-600mm and the backflow time is 4-8s. The concrete spread after 1 hour is 520-550mm and the backflow time is 6-10s. Detailed Implementation

[0048] The technical solutions of the present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention. The specific functional details disclosed herein should not be construed as limiting, but are merely intended to form the basis of the claims and to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0049] Unless otherwise specified, all raw materials and reagents used in the embodiments of this invention are commercially available.

[0050] Example 1

[0051] This embodiment provides a viscosity-reducing polycarboxylate superplasticizer and its preparation method, including the following steps:

[0052] Step 1: Add 100 parts of ethylene glycol phenyl ether and 5 parts of phenothiazine to the reaction vessel, evacuate to -0.02 MPa, start stirring and heating, and raise the temperature to 80℃ within 30 min; weigh 150 parts of acrylic acid, 150 parts of methacrylic acid, 3 parts of concentrated sulfuric acid and 0 parts of p-toluenesulfonic acid, add them to the reaction vessel, and continuously purge with nitrogen gas for protection at a flow rate of 1 mL / min. After reacting at a constant temperature for 1 h, discharge the material to obtain the esterified monomer;

[0053] Step 2: Add 1000 parts of isopentenyl polyoxyethylene ether with a molecular weight of 3000, 20 parts of sodium hypophosphite, and 600 parts of water (bottom water) to the reactor. Start stirring and heating, and raise the temperature to 40°C in 5 minutes. Add 0.003 parts of ferrous sulfate and 10 parts of hydrogen peroxide to the reactor. After stirring for 5 minutes, add a solution of the esterified monomer obtained from S1, 2.4 parts of reducing agent VC, and 600 parts of water (dropped water) to the reactor at a uniform rate over 120 minutes. Continue to mature at a constant temperature for 60 minutes to obtain the polymer.

[0054] Step 3: Add 35 parts sodium hydroxide and 200 parts water (added later) to the polymer obtained from S2, stir for 60 minutes, and adjust the pH of the polymer to 6.0 to obtain a viscosity-reducing polycarboxylate superplasticizer with a solid content of 50%. The superplasticizer prepared in this example has a weight-average molecular weight of 29873, a PDI of 1.32, and a main peak content of 94.86%.

[0055] The water-reducing agent prepared in this embodiment was tested for performance in accordance with GB / T 8076-2008 "Concrete Admixtures". The test results showed that when 0.25%wt of the viscosity-reducing polycarboxylate water-reducing agent was added to the concrete, the initial spread of the concrete was 550mm and the backflow time was 8.03s. After 60min, the spread of the concrete was 530mm and the backflow time was 10.0s.

[0056] Examples 2-5

[0057] Examples 2-5 describe the preparation of polycarboxylate superplasticizers according to the methods and steps of Example 1, and the formulations and operating parameters in Table 1. The relevant performance indicators of the obtained polycarboxylate superplasticizers are shown in Table 2.

[0058] Table 1. Relevant raw material ratios and operating parameters in polycarboxylate superplasticizers in Examples 1-5

[0059]

[0060]

[0061] Table 2 shows the relevant properties of the polycarboxylate superplasticizers prepared in Examples 1-5.

[0062] Performance indicators Example 1 Example 2 Example 3 Example 4 Example 5 Solid content / % 50 55 45 40 60 Weight-average molecular weight 29873 27540 23418 25796 20125 Main peak content / % 94.86 90.35 92.08 88.97 85.13 PDI 1.32 1.45 1.39 1.36 1.50

[0063] Comparative Example 1

[0064] This comparative example uses ordinary polycarboxylate superplasticizer WH306, purchased from Ningbo Weihong New Materials Co., Ltd. High-strength concrete was prepared using ordinary polycarboxylate superplasticizer WH306 according to the methods shown in Table 3, and its properties are shown in Table 4.

[0065] Comparative Example 2

[0066] Comparative Example 2 uses commercially available viscosity-reducing polycarboxylate superplasticizer SBT808, purchased from Jiangsu Subote New Material Co., Ltd. High-strength concrete was prepared using superplasticizer SBT808 according to the results shown in Table 3, and its properties are shown in Table 4.

[0067] Comparative Example 3

[0068] The difference between Comparative Example 3 and Example 1 is that ethylene glycol phenyl ether in step (1) was replaced with phenol, while the rest of the process was the same as in Example 1. A water-reducing agent was obtained, and high-strength concrete was prepared according to Table 3, with its properties shown in Table 4.

[0069] The water-reducing agents of Examples 1-5 and Comparative Examples 1-3 were applied to high-strength concrete, and the mix proportions of the high-strength concrete are shown in Table 3. The corresponding properties of the high-strength concrete were tested, and the test results are shown in Table 4.

[0070] Table 3 Mix Proportions for High-Strength Concrete

[0071] cement / kg Mineral powder / kg fly ash / kg Manufactured sand / kg stone / kg Water / kg Water-reducing agent / kg 360 80 80 830 900 165 1.3

[0072] Table 4 shows the relevant properties of high-strength concrete containing water-reducing agents from Examples 1-5 and Comparative Examples 1-2.

[0073] Performance indicators Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Initial expansion / mm 550 560 565 600 585 600 570 500 Initial backflow time / s 8.03 6.15 4.06 7.12 5.24 15.87 12.39 15.87 1h expansion / mm 530 520 550 520 545 520 535 400 1 hour reverse flow time / s 10.0 9.25 6.01 8.36 7.55 30.76 18.93 23.08

[0074] As can be seen from Table 4, the viscosity-reducing polycarboxylate superplasticizer of the present invention has comparable effects to ordinary polycarboxylate superplasticizer and commercially available viscosity-reducing polycarboxylate superplasticizer in terms of initial expansion and 1-hour expansion. However, the initial and 1-hour backflow times are much shorter than those of the comparative example, indicating that the viscosity-reducing polycarboxylate superplasticizer prepared by the present invention has good performance in high-strength concrete and is superior to commercially available superplasticizers.

[0075] All aspects, embodiments, features, and examples of this invention are to be regarded as illustrative in all respects and are not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0076] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0077] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method for reducing the plastic viscosity of high-strength concrete, the high-strength concrete comprising cement, sand, stone, mineral powder, and fly ash, characterized in that, The method includes adding a viscosity-reducing polycarboxylate superplasticizer to the high-strength concrete. The content of the viscosity-reducing polycarboxylate superplasticizer is 0.20wt%~0.30wt% of the cementitious materials in the high-strength concrete. The cementitious materials include cement, mineral powder and fly ash. The raw materials of the viscosity-reducing polycarboxylate superplasticizer include the following components by weight: 1000 parts polyether, 150-750 parts acrylic acid, 0-150 parts methacrylic acid, 100-500 parts ethylene glycol phenyl ether, 3-10 parts 98wt% concentrated sulfuric acid, 0-5 parts p-toluenesulfonic acid, 6-9 parts phenthiazide, 10-20 parts 27.5wt% hydrogen peroxide, 1.2-2.4 parts reducing agent, 0.003-0.03 parts ferrous sulfate, 12-20 parts sodium hypophosphite, 20-50 parts 32wt% strong alkali solution, and 1300-3000 parts water; wherein the polyether is at least one of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether. The preparation method of the viscosity-reducing polycarboxylate superplasticizer includes: S1: Under an inert atmosphere, the first mixed reaction system containing 100-500 parts of ethylene glycol phenyl ether, 6-9 parts of phenothiazine, 150-750 parts of acrylic acid, 0-150 parts of methacrylic acid, 3-10 parts of 98wt% concentrated sulfuric acid, and 0-5 parts of p-toluenesulfonic acid is subjected to an esterification reaction at 80-120°C to obtain the esterified monomer. S2: A second mixed reaction system containing 1000 parts polyether, 12-20 parts sodium hypophosphite, 0.003-0.03 parts ferrous sulfate, 10-20 parts 27.5 wt% hydrogen peroxide, 408-1275 parts of the esterified monomer, 1.2-2.4 parts reducing agent and 900-2400 parts water is subjected to a polymerization reaction at 40-70°C, and then cured at a constant temperature of 40-70°C for 30-90 min to obtain a viscosity-reducing polycarboxylate superplasticizer; S3: Adjust the pH value of the viscosity-reducing polycarboxylate superplasticizer obtained in step S2 to 4.0-6.0 using 20-50 parts by weight of 32wt% strong alkali solution and 0-800 parts by weight of water.

2. The method according to claim 1, characterized in that, The number average molecular weight of the polyether is 600-3000.

3. The method according to claim 1, characterized in that, The raw materials of the viscosity-reducing polycarboxylate superplasticizer include: 1000 parts polyether, 300-600 parts acrylic acid, 50-100 parts methacrylic acid, 200-400 parts ethylene glycol phenyl ether, 5-8 parts 98wt% concentrated sulfuric acid, 1-4 parts p-toluenesulfonic acid, 6-9 parts phenthiazide, 12-18 parts 27.5wt% hydrogen peroxide, 1.5-2.1 parts reducing agent, 0.01-0.02 parts ferrous sulfate, 14-18 parts sodium hypophosphite, 30-40 parts 32wt% strong alkali solution, and 1400-2200 parts water.

4. The method according to claim 1, characterized in that, The reducing agent includes vitamin C.

5. The method according to claim 1, characterized in that, The strong base includes at least one of sodium hydroxide and potassium hydroxide.

6. The method according to claim 1, characterized in that, The concentration of the effective active ingredient in the viscosity-reducing polycarboxylate superplasticizer is 40%~60%; the PDI of the superplasticizer is 1.40~1.60, and the main peak content is 85%~95%.

7. The method according to claim 1, characterized in that: In step S1, 100-500 parts by weight of ethylene glycol phenyl ether and 6-9 parts by weight of phenthiazide are first mixed to obtain a first material. The vacuum degree is adjusted to -0.02 to -0.10 MPa, and the mixture is stirred. The temperature of the first material is raised to 80-120°C within 30-60 minutes. Then, under an inert atmosphere, a second material containing 150-750 parts by weight of acrylic acid, 0-150 parts by weight of methacrylic acid, 3-10 parts by weight of 98 wt% concentrated sulfuric acid, and 0-5 parts by weight of p-toluenesulfonic acid is mixed with the first material, and an esterification reaction is carried out at 80-120°C for 1-6 hours to obtain an esterified monomer.

8. The method according to claim 7, characterized in that: In S1, the vacuum degree is -0.04 to -0.08 MPa.

9. The method according to claim 7, characterized in that: In step S1, the temperature of the first material is raised to 80-120°C within 40-50 minutes.

10. The method according to claim 1, characterized in that: In S1, the temperature of the esterification reaction is 90~110℃.

11. The method according to claim 1, characterized in that: In step S1, an inert atmosphere is introduced at a gas flow rate of 1~5 mL / min.

12. The method according to claim 1, characterized in that: The esterification reaction in S1 takes 2-5 hours.

13. The method according to claim 1, characterized in that, S2 specifically includes: providing a third material containing a uniform mixture of 1000 parts by weight of polyether, 12-20 parts by weight of sodium hypophosphite, 500-1200 parts by weight of water, 0.003-0.03 parts by weight of ferrous sulfate and 10-20 parts by weight of 27.5 wt% hydrogen peroxide; and providing a fourth material containing a uniform mixture of 408-1275 parts by weight of esterifying monomer, 1.2-2.4 parts by weight of reducing agent and 400-1200 parts by weight of water. The fourth material is added to the third material in batches at a temperature of 40-70°C to carry out the polymerization reaction.

14. The method according to claim 13, characterized in that: The preparation method of the third material includes: first, mixing 1000 parts by weight of polyether, 12-20 parts by weight of sodium hypophosphite and 500-1200 parts by weight of water, stirring, and raising the temperature to 40-70°C within 30 minutes; then adding 0.003-0.03 parts by weight of ferrous sulfate and 10-20 parts by weight of 27.5 wt% hydrogen peroxide, stirring to mix them evenly, and obtaining the third material.

15. The method according to claim 1, characterized in that, In step S2, the polymerization reaction is carried out at 50~60℃ and then aged at a constant temperature of 50~60℃.

16. The method according to claim 13, characterized in that, In step S2, the fourth material is added to the third material in batches at a uniform rate within 120-240 minutes.

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