Viscosity-reducing polycarboxylate water reducer and preparation method thereof

Abstract

This invention relates to the field of building materials technology, and particularly to a viscosity-reducing polycarboxylate superplasticizer and its preparation method. The viscosity-reducing polycarboxylate superplasticizer uses polyethylene glycol dicyclopentenyl ether methacrylate as the macromonomer, combined with 2-methacryloyloxyethyl phosphocholine, 4-vinylphenylboronic acid, and polyethylene glycol phenyl ether methacrylate as small monomers, prepared via free radical polymerization. Finally, it undergoes freeze-drying and grinding to obtain the target powder product. When the prepared superplasticizer is added to concrete mixtures, it swells and unfolds into a comb-shaped polymer under mechanical stirring and alkaline conditions. Through PEG long side-chain lubrication and steric hindrance, the regulation of surface tension / interfacial energy by phosphocholine groups, and the selective adsorption of borate groups, the initial viscosity is significantly reduced, the viscosity increase over time is controlled, and segregation and bleeding are effectively suppressed, making it suitable for various cementitious systems.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a viscosity-reducing polycarboxylate superplasticizer and its preparation method. Background Technology

[0002] As an irreplaceable core structural material in modern engineering construction, concrete's performance development has always been deeply intertwined with the demands of industrialized construction, high-rise buildings, and green and low-carbon development. Currently, concrete materials are rapidly evolving towards high strength, ultra-high strength, high fluidity, and high durability. However, these development trends inevitably lead to the core technical challenge of excessively high viscosity in concrete systems. Excessive concrete viscosity has become a key bottleneck restricting project quality and construction efficiency, with consequences that permeate the entire construction process and extend to the long-term performance of the structure. Polycarboxylate superplasticizers, as the mainstream concrete admixtures, achieve dispersion by forming a steric hindrance effect on the surface of cement particles. However, conventional products often struggle to balance fluidity and viscosity reduction in complex systems with low water-cement ratios and high cementitious material content. This is because simply increasing the superplasticizer dosage can improve fluidity but easily leads to excessively low apparent viscosity, causing segregation and stratification. Furthermore, it lacks compatibility with systems with high mud content or containing fine-particle solid waste.

[0003] To fully utilize the viscosity-reducing properties of polycarboxylate superplasticizers, improve their dispersibility, and solve the problems of difficult concrete construction and performance degradation caused by high viscosity of concrete mixtures, numerous researchers have conducted related exploratory work. Chinese patent CN111748060A significantly reduced the HLB value of polycarboxylate superplasticizer molecules by introducing two ester monomers, trifluoroethanol acrylate and maleic anhydride diol ester, into the main chain, thereby reducing the viscosity of concrete mixtures. Chinese patent CN120483572A discloses a viscosity-reducing polycarboxylate superplasticizer suitable for high-strength concrete and its preparation method. This patented technology achieves hydrophobic modification of the polyether macromonomer by controlling the amounts of ethylene oxide and propylene oxide, followed by copolymerization with phosphate ester monomers to obtain the target polycarboxylate superplasticizer. This polycarboxylate superplasticizer provides greater steric hindrance and lower liquid surface tension, thus achieving a viscosity-reducing effect. Chinese patent CN120535230A discloses a method for preparing a viscosity-reducing concrete water-reducing agent. By introducing phosphate groups into the molecular structure of the polycarboxylate superplasticizer, it effectively reduces the HLB value of the cement paste surface, improves the fluidity of concrete, and achieves a viscosity-reducing effect. Generally speaking, existing patent technologies focus on introducing functional monomers into the polycarboxylate backbone to adjust the adsorption characteristics of the polycarboxylate backbone and the HLB value of the paste. However, existing patent technologies neglect the influence of the cement hydration process on the time-dependent evolution of concrete viscosity. In actual production, we often require the mixture to maintain a low viscosity throughout the construction process. On the one hand, lower viscosity can effectively reduce pumping friction resistance and improve construction efficiency. On the other hand, lower viscosity is more conducive to compaction during pouring, resulting in better durability and higher appearance quality.

[0004] Therefore, developing a polycarboxylate superplasticizer that can precisely control the viscosity of concrete, and optimizing the molecular structure design to effectively reduce the yield stress of the system and release free water while maintaining a suitable apparent viscosity to ensure the stability of the system over time, has become the core breakthrough in solving the construction problems of high-strength, high-flowability concrete. Summary of the Invention

[0005] To address the problems in related technologies, this invention proposes a viscosity-reducing polycarboxylate superplasticizer and its preparation method to overcome the aforementioned technical problems in existing related technologies. The viscosity-reducing carboxylate superplasticizer prepared in this invention, when added to concrete mixtures, swells and unfolds into a comb-shaped polymer under mechanical stirring and alkaline conditions. Through PEG long side chain lubrication and steric hindrance, the regulation of surface tension / interfacial energy by phosphocholine groups, and the selective adsorption of borate groups, the initial viscosity is significantly reduced, the viscosity increase over time is controlled, and segregation and bleeding are effectively suppressed. It is suitable for various cementitious systems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a viscosity-reducing polycarboxylate superplasticizer, wherein the molecular structural formula of the viscosity-reducing polycarboxylate superplasticizer is shown in Formula I: Formula I The viscosity-reducing polycarboxylate superplasticizer uses polyethylene glycol dicyclopentenyl ether methacrylate as the macromonomer, combined with small monomers, and is prepared by free radical polymerization to obtain a controllable release molecular structure; wherein, n is an integer from 1 to 4, m is an integer from 10 to 45; a:d=1 to 3, b:d=1 to 5, c:d=2 to 4.

[0007] Preferably, the number average molecular weight of the viscosity-reducing polycarboxylate superplasticizer is 10,000 to 100,000.

[0008] Preferably, the small monomers include polyethylene glycol phenyl ether methacrylate, 4-vinylphenylboronic acid, and 2-methacryloyloxyethyl phosphocholine.

[0009] To achieve the above objectives, the present invention also provides the following technical solution: A method for preparing a viscosity-reducing polycarboxylate superplasticizer includes the following steps: Step 1: Dissolve 0.1-0.3 mol of polyethylene glycol phenyl ether methacrylate, 0.1-0.5 mol of 4-vinylphenylboronic acid, and 0.2-0.4 mol of 2-methacryloyloxyethyl phosphocholine in 5-10 mol of deionized water as additive A; dissolve 0.01-0.02 mol of initiator in 1.5-2.0 mol of deionized water as additive B. Step 2: Add 0.1 mol of polyethylene glycol dicyclopentenyl ether methacrylate and 10-15 mol of deionized water to a reaction vessel equipped with heating and stirring. Then add 0.002-0.01 mol of chain transfer agent, 0.005-0.008 mol of reducing agent and 0.0003-0.0005 mol of catalyst to the reaction vessel and stir for 30 minutes to fully dissolve and mix the materials to obtain the reaction base. Step 3: Add 0.005~0.006 mol of pH buffer to the reaction substrate obtained in Step 2. After it is fully dissolved, add dropwise A and dropwise B prepared in Step 1 to the reaction substrate prepared in Step 2 simultaneously using a constant flow pump. Adjust the flow rate to ensure that dropwise A and dropwise B start and stop dropping at the same time. The dropping time is 100~300 min. After the dropping is completed, keep it warm and mature for 120 min to obtain a polymer aqueous solution. Freeze-dry and grind to obtain a powdered target viscosity-reducing polycarboxylate superplasticizer.

[0010] Preferably, in step one, the initiator is one or more combinations of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, azobisisobutyramidine hydrochloride, and azobisisobutyramidine hydrochloride.

[0011] Preferably, in step two, the chain transfer agent is one or more combinations of mercaptoethanol, mercaptoacetic acid, 3-mercaptopropionic acid, sodium 2-mercaptoethanesulfonate, sodium 3-mercaptopropanesulfonate, and dithiodiethanol.

[0012] Preferably, in step two, the reducing agent is one or more combinations of sodium bisulfite-formaldehyde sodium bisulfite, ascorbic acid, sodium sulfite, sodium hypophosphite, and sodium bisulfite.

[0013] Preferably, in step two, the catalyst is one or a combination of ferrous sulfate, ferrous chloride, copper chloride, copper sulfate, cobalt chloride, and manganese sulfate.

[0014] Preferably, in step three, the pH buffer is one or more combinations of potassium dihydrogen phosphate, sodium dihydrogen phosphate, citric acid, and acetic acid.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention is a viscosity-reducing polycarboxylate superplasticizer and its preparation method. Polyethylene glycol phenyl ether methacrylate with benzene ring and 4-vinylphenylboronic acid are used as small monomers for polymerization. After polymerization, due to hydrophobic association, the molecular structure is microsphere-shaped and the adsorption groups are wrapped inside the molecular structure. Therefore, a gradient release mechanism is presented. Under mechanical stirring and as the pH of cement paste increases, the spherical structure begins to swell and spread slowly, achieving a slow release effect throughout the process. (2) The present invention is a viscosity-reducing polycarboxylate superplasticizer and its preparation method. The proportion of hydrophobic and hydrophilic functional groups in the molecular structure of the viscosity-reducing polycarboxylate superplasticizer is appropriate, which can effectively reduce the surface tension of the pore solution and increase the rigidity of the liquid film of the bubble. As the hydration process evolves, when the ion solubility of the solution increases sharply, it can achieve excellent bubble stabilization effect, thereby greatly reducing the viscosity of the concrete mixture by utilizing the buffering and ball effect of the bubble. (3) The present invention is a viscosity-reducing polycarboxylate superplasticizer and its preparation method. The 2-methacryloyloxyethyl phosphocholine introduced into the molecular structure of the viscosity-reducing polycarboxylate superplasticizer is a typical amphoteric group, which significantly improves the adsorption adaptability of different viscosity-reducing material systems (with different charge characteristics). In addition, it better matches the surface charge sites of the mineral phase (usually positive and negative charges are alternately distributed), thus improving the adsorption stability. (4) This invention is a viscosity-reducing polycarboxylate superplasticizer and its preparation method. The 4-vinylphenylboronic acid introduced into the molecular structure of the viscosity-reducing polycarboxylate superplasticizer has pH-responsive characteristics. As the pH increases, the uncharged boric acid gradually transforms into a charged tetrahedral borate structure, thereby playing an adsorption and dispersion role to resist the viscosity increase effect brought about by the evolution of the hydration process (accompanied by the increase of pH). The borate group will undergo a cyclization reaction with o-silicondiol to generate a stable chemical bond adsorption, further improving the affinity of the superplasticizer on the surface of minerals with high silicon content. (5) The present invention is a viscosity-reducing polycarboxylate superplasticizer and its preparation method. The polyethylene glycol dicyclopentenyl ether methacrylate introduced into the molecular structure of the viscosity-reducing polycarboxylate superplasticizer uses hydrophobic dicyclopentene as the end group, which enhances the hydrophobic association, delays the dissolution and swelling process of polyethylene glycol segments, achieves a longer release time, and prolongs the viscosity reduction time of concrete mixture. In addition, as the end group, due to the directional arrangement of the hydrophobic end, the steric hindrance effect is enhanced, and the diffusion of water molecules is inhibited, achieving a strong hydration inhibition effect, which can significantly reduce the viscosity increase caused by the hydration process. Attached Figure Description

[0016] Figure 1 This refers to the change in concrete spread over time. Figure 2 The changes in concrete mixture T500 over time; Figure 3 The change in leakage time (V) of the concrete mixture over time; Figure 4 The results of the proton nuclear magnetic resonance spectroscopy analysis of Example 1 are shown below; Figure 5 The results of infrared spectral analysis are shown in Example 1; Figure 6 The results are from the gel permeation chromatography analysis of Example 1. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0018] Example 1 Add 0.10 mol polyethylene glycol dicyclopentenyl ether methacrylate (molecular weight 1099 g / mol) and 11.0 mol deionized water to the reaction vessel, then add 0.010 mol sodium 3-mercaptopropane sulfonate, 0.008 mol sodium hypophosphite, and 0.0004 mol copper chloride. Stir for 30 min and then heat to 60 °C. Prepare dropper A: dissolve 0.10 mol polyethylene glycol phenyl ether methacrylate (molecular weight 236 g / mol), 0.25 mol 4-vinylphenylboronic acid, and 0.25 mol 2-methacryloyloxyethyl phosphocholine in 7.0 mol deionized water. Prepare dropper B: dissolve 0.010 mol azobisisobutyramidine hydrochloride in 1.6 mol deionized water. Add 0.0052... Acetic acid was used as a pH buffer. Additive A and Additive B were simultaneously added dropwise over 300 min using a constant flow pump. After the addition was complete, the mixture was aged at 60 °C for 120 min, freeze-dried, and ground into a powder. The structural formula is shown in Formula I. Formula I Where a:b:c:d=1:2.5:2.5:1.

[0019] Example 2 Add 0.10 mol polyethylene glycol dicyclopentenyl ether methacrylate (molecular weight 2199 g / mol) and 10.0 mol deionized water to the reaction vessel, along with 0.008 mol mercaptoethanol, 0.007 mol ascorbic acid, and 0.0003 mol copper sulfate. Stir for 30 min and then heat to 55 °C and maintain a constant temperature. Prepare dropper A: dissolve 0.20 mol polyethylene glycol phenyl ether methacrylate (molecular weight 324 g / mol), 0.20 mol 4-vinylphenylboronic acid, and 0.40 mol 2-methacryloyloxyethyl phosphocholine in 6.0 mol deionized water. Prepare dropper B: dissolve 0.020 mol ammonium persulfate in 1.5 mol deionized water. Add 0.0060 mol citric acid to the substrate as a pH buffer. Simultaneously add A and B using a constant flow pump for 240 min. After the addition is complete, allow to mature at 55 °C for 120 minutes. The target polymer powder was obtained by freeze-drying and grinding, with the structural formula shown in Formula I: Formula I Where a:b:c:d=2:2:4:1.

[0020] Example 3 Add 0.10 mol polyethylene glycol dicyclopentenyl ether methacrylate (molecular weight 879 g / mol) and 15.0 mol deionized water to the reactor, along with 0.004 mol sodium 2-mercaptoethanesulfonate, 0.005 mol sodium bisulfite, and 0.0005 mol ferrous chloride. Stir for 30 min and then maintain a constant temperature of 45 °C. Droplet A was prepared by dissolving 0.10 mol polyethylene glycol phenyl ether methacrylate (molecular weight 324 g / mol), 0.40 mol 4-vinylphenylboronic acid, and 0.20 mol 2-methacryloyloxyethyl phosphocholine in 5.5 mol deionized water. Droplet B was prepared by dissolving 0.012 mol potassium persulfate in 2.0 mol deionized water. After adding 0.0050 mol sodium dihydrogen phosphate as a pH buffer to the substrate, A and B were simultaneously added dropwise using two constant flow pumps for 150 min, followed by a 45 °C temperature control. The product is aged at ℃ for 120 min, freeze-dried, and ground to obtain a powder product with the structural formula shown in Formula I: Formula I Where a:b:c:d=1:4:2:1.

[0021] Example 4 In a heated and stirred reaction vessel, add 0.10 mol of polyethylene glycol dicyclopentenyl ether methacrylate (molecular weight 659 g / mol) and 12.0 mol of deionized water, then add 0.006 mol of 3-mercaptopropionic acid, 0.006 mol of sodium bisulfite-formaldehyde sodium bisulfite, and 0.0004 mol of ferrous sulfate. Stir for 30 min to ensure complete dissolution and heat to 50 °C. Prepare dropwise addition A: dissolve 0.10 mol of ethylene glycol phenyl ether methacrylate (molecular weight 192 g / mol), 0.30 mol of 4-vinylphenylboronic acid, and 0.30 mol of 2-methacryloyloxyethyl phosphocholine in 8.0 mol of deionized water. Prepare dropwise addition B: dissolve 0.015 mol of hydrogen peroxide in 1.8 mol of deionized water. Add 0.0055 mol of ferrous sulfate to the reaction mixture. After using potassium dihydrogen phosphate as a pH buffer, A and B were simultaneously added dropwise for 180 min using two constant flow pumps. After the addition was completed, the mixture was kept at 50 ℃ for 120 min to mature, then freeze-dried and ground to obtain a powdered viscosity-reducing polycarboxylate superplasticizer, with the structural formula shown in Formula I: Formula I Where a:b:c:d=1:3:3:1.

[0022] Example 5 0.10 mol of polyethylene glycol dicyclopentenyl ether methacrylate (molecular weight 1759 g / mol) and 10.5 mol of deionized water were added to the reactor. Then, 0.002 mol of mercaptoacetic acid, 0.007 mol of ascorbic acid, and 0.0003 mol of manganese sulfate were added. After stirring for 30 min, the mixture was kept at a constant temperature of 50 °C. Separately, dropwise additive A was prepared: 0.20 mol of polyethylene glycol phenyl ether methacrylate (molecular weight 236 g / mol), 0.35 mol of 4-vinylphenylboronic acid, and 0.30 mol of 2-methacryloyloxyethyl phosphocholine were dissolved in 9.0 mol of deionized water. Dropwise additive B was prepared: 0.018 mol of sodium persulfate was dissolved in 1.7 mol of deionized water. A mixed buffer of potassium dihydrogen phosphate and citric acid in a 1:1 ratio, totaling 0.0060 mol, was added to the substrate. Subsequently, A and B were simultaneously added dropwise using two constant flow pumps. After the addition of the product was completed, it was aged at 50 °C for 120 min, freeze-dried, and ground to obtain a powdered product with the structural formula shown in Formula I: Formula I Where a:b:c:d=2:3.5:3:1.

[0023] Concrete mix proportion To investigate the viscosity-reducing effects of different water-reducing agents, relevant tests were conducted on high-strength concrete with a design strength of C80. The concrete mix design is shown in Table 1 below.

[0024] Table 1. Mix proportions of C80 concrete (kg / m³) 3 ) Concrete mixture dispersion performance test The performance of concrete mixtures was tested according to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". During mixture preparation, the initial slump of each test group was controlled to be 220±5 mm and the spread to be 550±10 mm by adjusting the dosage of water-reducing agent, ensuring that the test samples were in a similar initial slurry dispersion and suspension state. The initial (5 min) T500 and V-funnel time were then tested to evaluate the viscosity of the concrete mixture. Subsequently, the spread, T500, and V-funnel time of the concrete mixture were tested every 30 min. After 150 min, the concrete mixture was poured into molds to make 150 mm x 150 mm x 150 mm cube specimens. After 1 day, the specimens were demolded and placed in a standard curing laboratory for curing. The mechanical properties of the hardened concrete were tested after 28 days. Control groups 1, 2, and 3 used commercially available viscosity-reducing polycarboxylate superplasticizers. The dispersion performance of the concrete mixtures is shown in Table 2 below.

[0025] Table 2. Dispersion performance test of concrete mixture As shown in Table 2, the viscosity-reducing polycarboxylate superplasticizer prepared by the present invention has high water-reducing performance and can achieve a relatively excellent initial dispersion state under low dosage conditions. In addition, the T500 time and V leakage time can be significantly shortened by the viscosity-reducing polycarboxylate superplasticizer prepared by the present invention, which indicates that it has excellent viscosity-reducing effect.

[0026] Furthermore, we examined the changes in the state of the concrete over time, and the test results are as follows: Figure 1 As shown, the concrete mixtures in Examples 1-5 exhibited excellent slump retention stability, maintaining a spread of 510-560 mm within 150 minutes. The spread fluctuated steadily in the early stages and gradually decreased in the later stages, with an overall decrease of only 30-45 mm. In contrast, the spread of the control groups 1-3 showed an abnormally rapid increase in the early stages, followed by a sharp decrease, eventually dropping to 430-485 mm. In summary, the viscosity-reducing polycarboxylate superplasticizer of this invention significantly outperforms the control group in terms of concrete flowability stability and long-term slump retention.

[0027] Figure 2 , Figure 3 The curves showing the changes in T500 time and V-leakage time of the concrete mixture over time are presented. The T500 value curve shows that the T500 values ​​of Examples 1-5 remained within the 5-10s range over 150 minutes, exhibiting a slow linear increase, demonstrating excellent fluidity stability. In contrast, the T500 values ​​of Control Groups 1-3 first decreased and then surged, indicating insufficient cohesion in the early stages leading to the risk of bleeding and segregation, followed by a rapid loss of fluidity in the later stages. This demonstrates the significant advantage of the Examples 1-5 in terms of concrete fluidity stability. The V-leakage time curve shows that the V-leakage time of Examples 1-5 remained within the 20-40s range over 150 minutes, exhibiting a slow linear increase, demonstrating excellent anti-bleeding stability. In contrast, the V-leakage time of Control Groups 1-3 spiked dramatically, significantly impacting the pumping efficiency of the concrete. In summary, based on the T500 and V-leakage results, the viscosity-reducing polycarboxylate superplasticizer prepared by this patented technology achieves a significant reduction in initial viscosity, controlled viscosity growth over time, and effective suppression of segregation and bleeding.

[0028] like Figure 4As shown, to verify the successful synthesis of the target product, it was characterized by ^1H NMR. The aromatic signal at δ 7.409–7.643 ppm can be attributed to protons on the arylboronic acid-substituted aromatic ring, while another set of aromatic peaks at δ 6.655–6.727 ppm corresponds to protons on the left-side aryloxy-substituted benzene ring, indicating that both types of aromatic units with different electronic environments have been successfully introduced into the molecule. The characteristic peaks at δ 6.315–6.358 and 5.238–5.266 ppm belong to double bond protons in the right-side bridged cyclic alkene structure, proving that the unsaturated bridged ring unit is retained. Multiple signals in the range of δ 4.036–4.259 ppm can be attributed to methylene / methylene protons of adjacent ester groups, phosphate esters, and ether oxygens, indicating that polyesterification and polyoxygen-bridged linkage structures have been formed. The signals in the δ 3.709–3.771 ppm region are mainly attributed to the methylene protons of the repeating –OCH2CH2O– unit in the polyethylene glycol segment, indicating that the PEG segment has been successfully integrated into the target backbone. The signals in the δ 3.083–3.400 ppm region primarily originate from the –CH2CH2N⁺(CH3)3 fragment in the phosphocholine head group, where the presence of the quaternary ammonium methyl group and its adjacent methylene group further confirms the successful introduction of the choline head group. Meanwhile, a series of aliphatic signals in the δ 1.195–2.682 ppm region correspond to the bridging and adjacent double bond protons in the intermediate rigid polycyclic backbone and the right-side bridging ring structure. It should be noted that the extremely strong peak near 4.7 ppm mainly originates from residual water and is not involved in structure assignment.

[0029] like Figure 5 As shown, FTIR characterization was performed on the target product to further verify its structural composition. In the spectrum, 3370 cm⁻¹... -1 The broad peak at 2879 cm⁻¹ can be attributed to the stretching vibration of B–OH in the boric acid group; -1 The absorption peak at 1719 cm⁻¹ corresponds to the aliphatic C–H stretching vibration. -1 The presence of a distinct strong peak at 1629, 1607, 1552, and 1512 cm⁻¹ indicates that an ester carbonyl group (C=O) has been successfully introduced into the molecule. -1 The multiple absorption peaks at 1297, 1192, 1086, and 1014 cm⁻¹ can be attributed to aromatic ring skeletal vibrations, and may include contributions from the C=C vibrations in the right-side bridged cyclic alkene unit, indicating the presence of both aromatic structures and unsaturated bridged ring units in the molecule. -1 The strong absorption peaks at these locations correspond to the stretching vibrations of the ester C–O, phosphate P–O–C, and polyethylene glycol C–O–C segments, respectively, with the peak at 1086 cm⁻¹ being the most significant. -1The nearby characteristic peaks particularly indicate that the PEG segments have been successfully introduced into the target backbone. Meanwhile, the peaks at 992, 948, and 909 cm⁻¹... -1 The absorption peaks at 841, 811, 757, and 727 cm⁻¹ can be attributed to unsaturated vibrations related to the bridged cyclic alkene structure. -1 This corresponds to the out-of-plane bending vibration of the C–H substituted aromatic ring. Low wavenumber region: 664–429 cm⁻¹ -1 Multiple absorption sequences further support the presence of B–O, P–O, and related skeletal vibrations. Overall, the FTIR results are in good agreement with the structural features of the arylboronic acid, PEG segment, phosphocholine head group, esterification linkage, and bridged cyclic olefin unit in the target molecule, further confirming the successful synthesis of the target product.

[0030] like Figure 6 As shown, GPC results indicate that the sample is dominated by a main peak with an apparent molecular weight of approximately 34037 g / mol, indicating that the target polymer has been successfully formed. Simultaneously, a secondary peak with an apparent molecular weight of approximately 1100 g / mol is present at a longer retention time, suggesting that the sample still contains a small amount of low molecular weight components, possibly originating from oligomers or incompletely removed small molecule byproducts. Overall, the target polymer is the main component of the sample, and the polymerization reaction was generally successful.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A viscosity-reducing polycarboxylate superplasticizer, characterized in that, The molecular structure of the viscosity-reducing polycarboxylate superplasticizer is shown in Formula I: Formula I The viscosity-reducing polycarboxylate superplasticizer uses polyethylene glycol dicyclopentenyl ether methacrylate as the macromonomer, combined with small monomers, and is prepared by free radical polymerization to obtain a controllable release molecular structure; wherein, n is an integer from 1 to 4, m is an integer from 10 to 45; a:d=1 to 3, b:d=1 to 5, c:d=2 to 4.

2. The viscosity-reducing polycarboxylate superplasticizer according to claim 1, characterized in that, The number average molecular weight of the viscosity-reducing polycarboxylate superplasticizer is 10,000 to 100,000.

3. The viscosity-reducing polycarboxylate superplasticizer according to claim 1, characterized in that, The monomers include polyethylene glycol phenyl ether methacrylate, 4-vinylphenylboronic acid, and 2-methacryloyloxyethyl phosphocholine.

4. A method for preparing a viscosity-reducing polycarboxylate superplasticizer as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Dissolve 0.1-0.3 mol of polyethylene glycol phenyl ether methacrylate, 0.1-0.5 mol of 4-vinylphenylboronic acid, and 0.2-0.4 mol of 2-methacryloyloxyethyl phosphocholine in 5-10 mol of deionized water as additive A; dissolve 0.01-0.02 mol of initiator in 1.5-2.0 mol of deionized water as additive B. Step 2: Add 0.1 mol of polyethylene glycol dicyclopentenyl ether methacrylate and 10-15 mol of deionized water to a reaction vessel equipped with heating and stirring. Then add 0.002-0.01 mol of chain transfer agent, 0.005-0.008 mol of reducing agent and 0.0003-0.0005 mol of catalyst to the reaction vessel and stir for 30 minutes to fully dissolve and mix the materials to obtain the reaction base. Step 3: Add 0.005~0.006 mol of pH buffer to the reaction substrate obtained in Step 2. After it is fully dissolved, add dropwise A and dropwise B prepared in Step 1 to the reaction substrate prepared in Step 2 simultaneously using a constant flow pump. Adjust the flow rate to ensure that dropwise A and dropwise B start and stop dropping at the same time. The dropping time is 100~300 min. After the dropping is completed, keep it warm and mature for 120 min to obtain a polymer aqueous solution. Freeze-dry and grind to obtain a powdered target viscosity-reducing polycarboxylate superplasticizer.

5. The method for preparing a viscosity-reducing polycarboxylate superplasticizer according to claim 4, characterized in that, In step one, the initiator is one or more combinations of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, azobisisobutyramidine hydrochloride, and azobisisobutyramidine hydrochloride.

6. The method for preparing a viscosity-reducing polycarboxylate superplasticizer according to claim 4, characterized in that, In step two, the chain transfer agent is one or more combinations of mercaptoethanol, mercaptoacetic acid, 3-mercaptopropionic acid, sodium 2-mercaptoethanesulfonate, sodium 3-mercaptopropanesulfonate, and dithiodiethanol.

7. The method for preparing a viscosity-reducing polycarboxylate superplasticizer according to claim 4, characterized in that, In step two, the reducing agent is one or more combinations of sodium bisulfite-formaldehyde sodium bisulfite, ascorbic acid, sodium sulfite, sodium hypophosphite, and sodium bisulfite.

8. The method for preparing a viscosity-reducing polycarboxylate superplasticizer according to claim 4, characterized in that, In step two, the catalyst is one or a combination of ferrous sulfate, ferrous chloride, copper chloride, copper sulfate, cobalt chloride, and manganese sulfate.

9. The preparation method of a viscosity-reducing polycarboxylate superplasticizer according to claim 4, characterized in that, In step three, the pH buffer is one or more combinations of potassium dihydrogen phosphate, sodium dihydrogen phosphate, citric acid, and acetic acid.

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