A polycarboxylate-based high-performance water-reducing agent

Abstract

This invention belongs to the field of water-reducing agent technology, specifically relating to a polycarboxylate-based high-performance water-reducing agent, which is prepared from polyether, acrylic acid, hydrogen peroxide, iron-copper gluconate bisulfite catalyst, mercaptopropionic acid, liquid alkali, and deionized water as raw materials. In the preparation process, deionized water, polyether, and liquid alkali are first mixed to form a polyether base. Then, acrylic acid solution and mercaptopropionic acid conditioning solution are prepared separately. Subsequently, a portion of the acrylic acid solution, catalyst, and hydrogen peroxide are added to the polyether base, and the remaining solution is added dropwise to initiate the reaction. The catalyst is prepared by complexing, conditioning, aging, and filtering a solution of sodium gluconate, citric acid monohydrate, ferrous sulfate heptahydrate, copper sulfate pentahydrate, and sodium bisulfite. This invention features a simple preparation process, readily available raw materials, good reaction stability, and the resulting water-reducing agent exhibits excellent dispersibility and industrial applicability.

Description

Technical Field

[0001] This invention belongs to the field of water-reducing agent technology, and specifically relates to a polycarboxylate-based high-performance water-reducing agent. Background Technology

[0002] Polycarboxylate-based high-performance water-reducing agents are widely used dispersion and regulation materials in the field of concrete admixtures. Their molecular structure is usually composed of a main chain containing polyether side chains and carboxylic acid groups. They can improve the dispersion state of cementitious material particles through adsorption, electrostatic repulsion, and steric hindrance, thereby reducing the amount of mixing water and improving the fluidity of the paste. With the development of ready-mixed concrete, high-performance concrete, pumped concrete, and prefabricated building concrete, the engineering field has placed higher demands on the dispersion efficiency, adaptability, stability, and production controllability of water-reducing agents. Traditional water-reducing agents are prone to problems such as insufficient dispersion retention, appearance fluctuations, incomplete reaction conversion, and poor batch stability in complex cement systems, making it difficult to meet the continuous production needs under different raw material conditions.

[0003] Existing polycarboxylate-based high-performance water-reducing agents are mostly prepared by free radical polymerization of polyether macromonomers and acrylic monomers in an aqueous phase, with the polymerization process controlled by hydrogen peroxide, thiol-based chain transfer agents, and alkaline regulators. While this process offers relatively abundant raw material sources and mild operating conditions, it still suffers from a mismatch between initiation efficiency and chain transfer process in actual production. Particularly under ambient temperature reaction conditions, insufficient catalytic activity can lead to slow polymerization initiation and high monomer residue; conversely, excessively active catalytic activity can cause localized heat concentration, broadened molecular weight distribution, darker product color, or performance fluctuations. Therefore, achieving a mild, stable, and controllable polymerization reaction at ambient temperature is crucial for improving the stability of industrial-scale production of polycarboxylate-based high-performance water-reducing agents. Furthermore, existing catalytic or initiation-aided systems often suffer from high raw material costs, insufficient component stability, and poor compatibility with polyether and acrylic systems, affecting their practicality in large-scale production. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a polycarboxylate-based high-performance water-reducing agent, which is prepared from the following raw materials in parts by weight:

[0005] Polyether 4300-4700 parts, acrylic acid 260-310 parts, hydrogen peroxide 20-30 parts, iron-copper gluconate bisulfite catalyst 3-8 parts, 3-mercaptopropionic acid 15-28 parts, liquid alkali 45-65 parts, deionized water 4500-5200 parts.

[0006] According to a preferred embodiment of the present invention, the preparation steps of the polycarboxylate-based high-performance water-reducing agent include:

[0007] S1. Under stirring, deionized water, polyether and liquid alkali are added to the reaction vessel in sequence and stirred at room temperature to obtain polyether base material;

[0008] S2. Mix deionized water and acrylic acid to obtain solution A; mix deionized water and liquid alkali and add 3-mercaptopropionic acid to obtain solution B;

[0009] S3. Add solution A to the polyether substrate, followed by iron-copper gluconate bisulfite catalyst and hydrogen peroxide, stir, add solution A and solution B dropwise, and continue stirring.

[0010] In this invention, the preparation reaction of the polycarboxylate-based high-performance water-reducing agent mainly involves the free radical copolymerization of polyether and acrylic acid in an aqueous phase. The polyether is a GPEG-3000 polyether macromonomer, which is first introduced into the reactor with deionized water and liquid alkali. The polyether is wetted and dispersed in the deionized water, and the liquid alkali adjusts the acid-base environment of the system to reduce the influence of excessively high local acidity on the dispersion state and polymerization process of the polyether when acrylic acid is added later. Acrylic acid is mixed with deionized water to obtain solution A, which allows the acrylic acid to enter the reaction system in a more uniform state. After mixing deionized water and liquid alkali, 3-mercaptopropionic acid is added to obtain solution B, which makes the 3-mercaptopropionic acid more uniformly dispersed in the aqueous phase. Solution A is first added to the polyether substrate to pre-contact the acrylic acid with the polyether substrate. Then, an iron-copper gluconate bisulfite catalyst and hydrogen peroxide are added. The iron-copper complex centers in the iron-copper gluconate bisulfite catalyst promote the generation of free radicals with initiating ability in hydrogen peroxide at room temperature, initiating the copolymerization reaction between polyether and acrylic acid. When solutions A and B are added dropwise, acrylic acid continuously replenishes the unsaturated monomers containing carboxyl groups, polyether provides long side chain structures, 3-mercaptopropionic acid regulates the chain length of the growing chain through chain transfer, and liquid alkali buffers the acidity changes caused by acrylic acid, keeping the reaction system in a relatively stable aqueous polymerization state. As the reaction proceeds, acrylic acid units are gradually incorporated into the polymer backbone, and polyether side chains are distributed in the polymer molecules, forming a comb-shaped polymer structure containing carboxylic acid groups and polyether side chains. The carboxylic acid groups in this structure are beneficial for adsorption on the surface of cement particles, and the polyether side chains provide steric hindrance, making the cement particles more fully dispersed. Hydrogen peroxide and iron-copper gluconate bisulfite catalyst provide initiation conditions, 3-mercaptopropionic acid controls chain growth, and liquid alkali stabilizes the aqueous environment. The combined effect of all components gives the resulting polycarboxylic acid-based high-performance water-reducing agent good dispersibility and preparation stability.

[0011] According to a preferred embodiment of the present invention, in step S1, the polyether is a GPEG-3000 polyether macromonomer; and the liquid alkali is an aqueous solution of sodium hydroxide.

[0012] According to a preferred embodiment of the present invention, in step S2, the liquid alkali is an aqueous solution of sodium hydroxide.

[0013] According to a preferred embodiment of the present invention, in step S3, the mass fraction of the hydrogen peroxide is 27.5%.

[0014] According to a preferred embodiment of the present invention, the preparation method of the iron-copper gluconate bisulfite catalyst includes:

[0015] A1. By weight, add 40-70 parts sodium gluconate and 5-15 parts citric acid monohydrate to 1000-1500 parts deionized water, stir, adjust the pH, and obtain a complexing stabilized solution.

[0016] A2. Add 8-18 parts of ferrous sulfate heptahydrate and 1-4 parts of copper sulfate pentahydrate to 80-150 parts of deionized water, stir, and obtain a mixed solution of iron and copper salts; add the mixed solution of iron and copper salts to the complexing stabilizing solution, adjust the pH, stir, and obtain a complex solution of iron and copper gluconate.

[0017] A3. Add 10-20 parts of sodium bisulfite solution to 80-120 parts of deionized water and stir to obtain a bisulfite conditioning solution; add the bisulfite conditioning solution to the iron-copper gluconate complex solution, stir, add 5-10 parts of sodium gluconate, adjust the pH to obtain an iron-copper gluconate bisulfite catalytic solution.

[0018] A4. Let the iron-copper gluconate bisulfite catalytic solution stand and mature, filter, add deionized water, and stir.

[0019] In this invention, the formation of the iron-copper gluconate bisulfite catalyst is based on aqueous phase complexation, acid-base adjustment, and redox synergy. After sodium gluconate is added to deionized water, its carboxylate and hydroxyl structures provide coordination conditions for metal ions. Citric acid monohydrate possesses carboxyl coordination ability and acid-base adjustment ability; together, they form a complex stable liquid, preventing the subsequent addition of ferrous sulfate heptahydrate and copper sulfate pentahydrate from directly undergoing hydrolysis and precipitation due to local pH changes. Ferrous sulfate heptahydrate and copper sulfate pentahydrate form an iron-copper salt mixture in deionized water. After entering the complex stable liquid, ferrous and copper ions are gradually protected by the complexation of sodium gluconate and citric acid monohydrate, resulting in an iron-copper gluconate complex liquid. In this process, sodium gluconate improves the stability of ferrous ions in the aqueous phase, citric acid monohydrate assists in the dispersion of copper ions, and reduces the tendency for hydrolysis caused by excessively high local alkalinity when adjusting pH. After mixing sodium bisulfite solution with deionized water to form a bisulfite conditioning solution, an iron-copper gluconate complex solution is added. The bisulfite conditioning solution participates in the redox balance of the system, reducing the possibility of excessively rapid oxidation of ferrous ions and maintaining a relatively mild catalytic state for the iron-copper complex centers. Upon further addition of sodium gluconate, the metal complex centers are further stabilized. The iron-copper gluconate bisulfite catalyst solution gradually becomes homogenized during static aging. After filtration, deionized water is added and stirred to obtain the iron-copper gluconate bisulfite catalyst. This catalyst is not a direct mixture of single metal salts, but rather a composite aqueous catalytic system formed by introducing ferrous sulfate heptahydrate, copper sulfate pentahydrate, and sodium bisulfite solution into a complex environment composed of sodium gluconate and citric acid monohydrate. Its function is to stabilize the iron-copper complex centers and, in conjunction with hydrogen peroxide, provide a stable initiation effect in the subsequent polymerization system, reducing polymerization fluctuations caused by excessively rapid local reactions.

[0020] According to a preferred embodiment of the present invention, in A1, the pH is adjusted to 5.5-6.5.

[0021] According to a preferred embodiment of the present invention, in A2, the pH is adjusted to 4.5-5.5.

[0022] According to a preferred embodiment of the present invention, in A3, the pH is adjusted to 4.0-5.0.

[0023] According to a preferred embodiment of the present invention, in A4, the temperature for static curing is 20-30°C, and the time for static curing is 6-12 hours.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) This invention uses polyether, acrylic acid, hydrogen peroxide, iron-copper gluconate bisulfite catalyst, 3-mercaptopropionic acid, liquid alkali, and deionized water as raw materials to prepare a polycarboxylic acid-based high-performance water-reducing agent. Each raw material has a clear role in the preparation process. Polyether is beneficial for forming the long-chain structure required for dispersion, acrylic acid is beneficial for providing the carboxyl structure required for adsorption, and hydrogen peroxide, when combined with iron-copper gluconate bisulfite catalyst, can improve the initiation stability under room temperature conditions and reduce product performance fluctuations caused by insufficient polymerization initiation or excessively rapid local reactions.

[0026] (2) The iron-copper gluconate bisulfite catalyst was prepared from sodium gluconate, citric acid monohydrate, ferrous sulfate heptahydrate, copper sulfate pentahydrate, sodium bisulfite solution, and deionized water. Sodium gluconate and citric acid monohydrate can improve the stability of ferrous sulfate heptahydrate and copper sulfate pentahydrate in the aqueous phase, reducing the risk of precipitation when adjusting pH; sodium bisulfite solution can participate in the redox equilibrium, making the initiation process of the iron-copper gluconate bisulfite catalyst in combination with hydrogen peroxide more stable, thereby improving the continuity and batch stability of the polymerization reaction.

[0027] (3) In the preparation process of polycarboxylate-based high-performance water-reducing agents, liquid alkali can buffer the acidity changes caused by the introduction of acrylic acid, and 3-mercaptopropionic acid can regulate the growth of polymer chains and reduce performance fluctuations caused by excessively rapid molecular chain growth. The resulting polycarboxylate-based high-performance water-reducing agent contains an adsorption structure formed by acrylic acid and a dispersion structure formed by polyether, which can improve the dispersion state between cement particles and enhance the fluidity and retention capacity of the slurry. The raw materials used in this method are readily available, the preparation process is simple, and it is suitable for industrial production. Detailed Implementation

[0028] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0029] Example 1

[0030] This embodiment provides a method for preparing a polycarboxylate-based high-performance water-reducing agent, the steps of which include:

[0031] S1. Under stirring, 3500g of deionized water, 4500g of polyether and 35g of liquid alkali are added to the reaction vessel in sequence. The liquid alkali is a sodium hydroxide aqueous solution with a mass fraction of 32%. Stir at 25°C for 80 minutes to fully wet and disperse the polyether in the deionized water to obtain the polyether base material. The polyether is a GPEG-3000 polyether macromonomer.

[0032] S2. Add 400g of deionized water and 285g of acrylic acid to a mixing container and stir at 25°C for 10 minutes to obtain solution A, wherein the mass fraction of acrylic acid in solution A is 41.61%; add 950g of deionized water and 20g of liquid alkali to another mixing container, wherein the liquid alkali is a 32% sodium hydroxide aqueous solution, stir at 25°C for 10 minutes, then add 21.5g of 3-mercaptopropionic acid, and continue stirring for 10 minutes to obtain solution B;

[0033] S3. Add 62g of solution A to the polyether substrate obtained in S1, stir for 5 min, then add 5.5g of iron-copper gluconate bisulfite catalyst, continue stirring for 5 min, then add 25g of hydrogen peroxide with a mass fraction of 27.5%, and continue stirring for 3 min; then add solution B dropwise first, and after 2 min of solution B dropwise addition, start adding the remaining solution A dropwise. The dropwise addition time of the remaining solution A is 50 min, and the total dropwise addition time of solution B is 60 min. During the dropwise addition, keep stirring and control the temperature of the reaction system to not exceed 35℃. After the dropwise addition is completed, continue stirring for 60 min to obtain a polycarboxylate-based high-performance water-reducing agent.

[0034] Iron-copper gluconate bisulfite catalyst:

[0035] A1. Add 55g sodium gluconate and 10g citric acid monohydrate to 1250g deionized water and stir at 25℃ for 30min to fully dissolve sodium gluconate and citric acid monohydrate and form a homogeneous solution. Adjust the pH to 6.0 with a 32% sodium hydroxide aqueous solution. After adjustment, continue stirring for 20min to obtain a complexed stable solution.

[0036] A2. Add 13g of ferrous sulfate heptahydrate and 2.5g of copper sulfate pentahydrate to 115g of deionized water and stir at 25℃ for 20min to fully dissolve the ferrous sulfate heptahydrate and copper sulfate pentahydrate, obtaining a mixed solution of iron and copper salts; while stirring, slowly add the mixed solution of iron and copper salts to the complex stabilized solution obtained in A1 over a period of 30min. After the addition is complete, adjust the pH to 5.0 with a 32% sodium hydroxide aqueous solution and continue stirring for 40min to obtain an iron-copper gluconate complex solution.

[0037] A3. Add 15g of 30% sodium bisulfite solution to 100g of deionized water and stir at 25℃ for 10min to obtain a bisulfite conditioning solution. While stirring, add the bisulfite conditioning solution to the iron-copper gluconate complex solution obtained in A2 over a period of 20min. After the addition is complete, continue stirring for another 20min. Then add 7.5g of sodium gluconate and continue stirring for another 30min. Adjust the pH to 4.5 using a 32% sodium hydroxide aqueous solution to obtain an iron-copper gluconate bisulfite catalytic solution.

[0038] A4. The iron-copper gluconate bisulfite catalyst solution obtained in A3 was allowed to stand and mature at 25°C for 9 hours. After maturation, it was filtered through a 5μm pore size filter membrane. 100g of deionized water was added to the filtrate, and the mixture was stirred at 25°C for 10 minutes to obtain the iron-copper gluconate bisulfite catalyst.

[0039] Example 2

[0040] This embodiment provides a method for preparing a polycarboxylate-based high-performance water-reducing agent, the steps of which include:

[0041] S1. Under stirring, 3200g of deionized water, 4300g of polyether and 30g of liquid alkali are added to the reactor in sequence. Stirring at room temperature allows the polyether to be fully wetted and evenly dispersed in the deionized water to obtain the polyether base material, wherein the polyether is GPEG-3000 polyether macromonomer and the liquid alkali is sodium hydroxide aqueous solution.

[0042] S2. Add 350g of deionized water and 260g of acrylic acid to a mixing container and stir until homogeneous to obtain solution A; add 950g of deionized water and 15g of liquid alkali to another mixing container and stir until homogeneous, then add 15g of 3-mercaptopropionic acid and continue stirring until homogeneous to obtain solution B.

[0043] S3. Add 50g of solution A to the polyether substrate obtained in S1, stir evenly, then add 3g of iron-copper gluconate bisulfite catalyst and 20g of hydrogen peroxide. The mass fraction of the hydrogen peroxide is 27.5%. Continue stirring to evenly disperse the iron-copper gluconate bisulfite catalyst and hydrogen peroxide in the polyether substrate. Then add the remaining solution A and all of solution B dropwise, keeping the stirring constant during the dropwise addition. After the dropwise addition is complete, continue stirring until the system is homogeneous to obtain a polycarboxylate-based high-performance water-reducing agent.

[0044] Iron-copper gluconate bisulfite catalyst:

[0045] A1. Add 40g sodium gluconate and 5g citric acid monohydrate to 1000g deionized water. Stir to fully disperse and dissolve sodium gluconate and citric acid monohydrate. Adjust the pH to 5.5 and continue stirring until there is no visible insoluble matter in the system to obtain a complexed stable solution.

[0046] A2. Add 8g of ferrous sulfate heptahydrate and 1g of copper sulfate pentahydrate to 80g of deionized water and stir until the ferrous sulfate heptahydrate and copper sulfate pentahydrate are completely dispersed to obtain a ferric-copper salt mixture. Slowly add the ferric-copper salt mixture to the complex stabilized solution obtained in A1 while stirring. After the addition is complete, adjust the pH to 4.5 and continue stirring until the system is homogeneous to obtain a ferric-copper gluconate complex solution.

[0047] A3. Add 10g of sodium bisulfite solution to 80g of deionized water and stir until homogeneous to obtain a bisulfite conditioning solution; add the bisulfite conditioning solution to the iron-copper gluconate complex solution obtained in A2, stir until the system is homogeneous, add 5g of sodium gluconate, continue stirring, and adjust the pH to 4.0 to obtain an iron-copper gluconate bisulfite catalytic solution.

[0048] A4. The iron-copper gluconate bisulfite catalyst solution obtained in A3 was allowed to stand at 20°C for 6 hours to mature. After maturation, it was filtered, and 80g of deionized water was added to the filtrate. The mixture was stirred evenly to obtain the iron-copper gluconate bisulfite catalyst.

[0049] Example 3

[0050] The difference between this embodiment and Embodiment 1 is that this embodiment provides a polycarboxylate-based high-performance water-reducing agent, the steps of which include:

[0051] S1. Under stirring, 3800g of deionized water, 4700g of polyether and 40g of liquid alkali are added to the reactor in sequence. Stirring at room temperature allows the polyether to be fully wetted and evenly dispersed in the deionized water to obtain polyether base material, wherein the polyether is GPEG-3000 polyether macromonomer and the liquid alkali is sodium hydroxide aqueous solution.

[0052] S2. Add 410g of deionized water and 310g of acrylic acid to a mixing container and stir until homogeneous to obtain solution A; add 990g of deionized water and 25g of liquid alkali to another mixing container and stir until homogeneous, then add 28g of 3-mercaptopropionic acid and continue stirring until homogeneous to obtain solution B.

[0053] S3. Add 75g of solution A to the polyether substrate obtained in S1, stir evenly, then add 8g of iron-copper gluconate bisulfite catalyst and 30g of hydrogen peroxide. The mass fraction of the hydrogen peroxide is 27.5%. Continue stirring to evenly disperse the iron-copper gluconate bisulfite catalyst and hydrogen peroxide in the polyether substrate. Then add the remaining solution A and all of solution B dropwise, keeping the stirring constant during the dropwise addition. After the dropwise addition is complete, continue stirring until the system is homogeneous to obtain a polycarboxylate-based high-performance water-reducing agent.

[0054] Iron-copper gluconate bisulfite catalyst:

[0055] A1. Add 70g sodium gluconate and 15g citric acid monohydrate to 1500g deionized water. Stir to fully disperse and dissolve sodium gluconate and citric acid monohydrate. Adjust the pH to 6.5 and continue stirring until there is no visible insoluble matter in the system to obtain a complexed stable solution.

[0056] A2. Add 18g of ferrous sulfate heptahydrate and 4g of copper sulfate pentahydrate to 150g of deionized water and stir until the ferrous sulfate heptahydrate and copper sulfate pentahydrate are completely dispersed to obtain a ferric-copper salt mixture. Slowly add the ferric-copper salt mixture to the complex stabilized solution obtained in A1 while stirring. After the addition is complete, adjust the pH to 5.5 and continue stirring until the system is homogeneous to obtain a ferric-copper gluconate complex solution.

[0057] A3. Add 20g of sodium bisulfite solution to 120g of deionized water and stir until homogeneous to obtain a bisulfite conditioning solution; add the bisulfite conditioning solution to the iron-copper gluconate complex solution obtained in A2, stir until the system is homogeneous, add 10g of sodium gluconate, continue stirring, and adjust the pH to 5.0 to obtain an iron-copper gluconate bisulfite catalytic solution.

[0058] A4. The iron-copper gluconate bisulfite catalyst solution obtained in A3 was allowed to stand at 30°C for 12 hours to mature. After maturation, it was filtered, and 120g of deionized water was added to the filtrate. The mixture was stirred evenly to obtain the iron-copper gluconate bisulfite catalyst.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 1 is that 5.5g of iron-copper gluconate bisulfite catalyst is not added in S3, and 5.5g of deionized water is used instead of iron-copper gluconate bisulfite catalyst. The rest is the same as in Example 1.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that the iron-copper gluconate complex solution prepared in steps A1-A2 is used to replace the iron-copper gluconate bisulfite catalyst of equal mass; otherwise, it is the same as Example 1.

[0063] Comparative Example 3

[0064] The difference between this comparative example and Example 1 is that a catalyst prepared without the addition of sodium gluconate and citric acid monohydrate is used instead of an equal mass of iron-copper gluconate bisulfite catalyst; otherwise, it is the same as Example 1.

[0065] The performance of the polycarboxylate-based high-performance water-reducing agents provided in the above embodiments and comparative examples was tested using the following methods:

[0066] The polycarboxylate superplasticizers obtained in Examples 1, 2, 3, 1, 2, and 3 were taken as test samples. Before the test, each test sample was sealed and placed at 25°C for 2 hours and stirred evenly to avoid uneven sampling and test deviation.

[0067] For the solid content test, first place a clean weighing dish in a 105℃ oven to dry for 30 minutes. After removing it, place it in a desiccator to cool to 25℃ and weigh it, recording it as m0. Then weigh 2.000g of the sample to be tested and place it in a weighing dish, recording it as m1. Place the weighing dish and the sample in a 105℃ oven to dry until the difference between the two weighings is no greater than 0.002g. After removing it, place it in a desiccator to cool to 25℃ and weigh it, recording it as m2. Calculate the solid content according to (m2-m0) / (m1-m0)×100%. Each sample to be tested is tested in parallel 3 times, and the average value is taken as the solid content result.

[0068] During pH testing, the sample to be tested is placed in a constant temperature environment of 25℃ for 30 minutes to equilibrate. A calibrated pH meter is used for direct measurement, with the electrode inserted about 20 mm below the sample liquid surface. After the reading stabilizes, the result is recorded. Each sample is tested in parallel 3 times, and the average value is taken as the pH result.

[0069] For the 20℃ density test, the sample to be tested is placed in a 20℃ constant temperature water bath for 30 minutes to equilibrate. A clean and dry density bottle is used for the test. First, the mass of the empty density bottle is weighed, then it is filled with 20℃ deionized water and weighed to calibrate the volume of the density bottle. Then, the sample to be tested at 20℃ is filled and weighed. The density at 20℃ is calculated based on the mass of the sample to be tested and the volume of the density bottle. Each sample to be tested is tested in parallel 3 times, and the average value is taken as the density result at 20℃.

[0070] For the initial neat cement paste fluidity test, weigh 300g of cement and 87g of deionized water. Add 0.20% of the cement mass of the sample to be tested into the deionized water and stir evenly as mixing water. Add the cement and mixing water to the mixing pot, stir at low speed for 120s, stop for 15s and scrape off the paste on the mixing pot wall and blades, then stir at high speed for 120s. Immediately after stirring, pour the neat cement paste into a truncated conical mold placed in the center of a glass plate, smooth the top opening and lift the mold vertically to allow the neat cement paste to expand naturally. After the expansion stops, measure two mutually perpendicular diameters and take the average value as the initial neat cement paste fluidity.

[0071] For the 60-minute paste fluidity test, the same batch of paste after the initial paste fluidity test is placed in a sealed container and allowed to stand at 25°C for 60 minutes. After standing, it is stirred again for 60 seconds. Then, the two mutually perpendicular expansion diameters are measured according to the initial paste fluidity test method, and the average value is taken as the 60-minute paste fluidity.

[0072] During the water reduction rate test, concrete was prepared using the same batch of cement, sand, aggregate, deionized water, and the sample to be tested. First, blank concrete without the sample to be tested was prepared, and the water consumption when the target slump was reached was recorded. Then, the sample to be tested was added to the mixing water at 0.20% of the mass of cementitious materials. Under the same cementitious material dosage, sand ratio, aggregate gradation, and mixing conditions, the water consumption was adjusted so that the mixed concrete reached the same target slump range as the blank concrete. The water reduction rate was calculated as the percentage of the difference between the water consumption of the blank concrete and the water consumption of the mixed concrete to the water consumption of the blank concrete. Each sample to be tested was tested in parallel three times, and the average value was taken as the water reduction rate result.

[0073] The performance test data above are shown in Table 1.

[0074] Table 1 Performance Test Results

[0075]

[0076] As can be seen from the above, the solid content of Examples 1-3 is 50.1%, 49.9% and 50.2% respectively, all of which are stable at around 50.0%, while the solid content of Comparative Examples 1-3 is 48.6%, 49.1% and 48.9% respectively. This indicates that after using the iron-copper gluconate bisulfite catalyst, the polymerization reaction between polyether and acrylic acid is more complete, the effective solid content of the system is more stable, and the problems of insufficient reaction conversion and low solid content when no catalyst is used or the catalyst structure is incomplete are solved.

[0077] The pH values ​​of Examples 1-3 were 4.1, 3.9, and 4.3, respectively, all within a relatively stable range. Although the pH differences between Comparative Examples 1-3 were not significant, their solid content, density, and flow properties were significantly worse. This indicates that simply maintaining the pH value cannot guarantee the performance of the water-reducing agent. The key lies in the stable regulation of the initiation and chain growth process by the iron-copper gluconate bisulfite catalyst.

[0078] The densities of Examples 1-3 at 20°C were 1.112 g / cm³. 3 1.108 g / cm 3 and 1.116 g / cm 3 The concentration was higher than 1.096 g / cm³ in comparative examples 1-3. 3 1.102 g / cm 3 and 1.099 g / cm 3 This indicates that the concentration of the polymer product and the formation of the molecular structure in the example system are more stable.

[0079] Regarding dispersion performance, the initial slurry flowability of Examples 1-3 reached 286 mm, 274 mm, and 279 mm, respectively, which were significantly higher than 221 mm for Comparative Example 1, 245 mm for Comparative Example 2, and 238 mm for Comparative Example 3. This indicates that the complete iron-copper gluconate bisulfite catalyst can improve the initial dispersion ability of polycarboxylate-based high-performance water-reducing agents on cement particles. Comparative Example 1 did not add iron-copper gluconate bisulfite catalyst, and hydrogen peroxide could not form a stable and effective initiation effect, resulting in insufficient polymer structure and the lowest initial dispersion performance. Comparative Example 2 did not introduce sodium bisulfite solution, and the iron-copper gluconate complex solution lacked the regulation effect of bisulfite, which reduced the stability of the initiation process and resulted in the initial slurry flowability being lower than that of Examples 1-3. Comparative Example 3 did not add sodium gluconate and citric acid monohydrate, and the metal components lacked complexation protection, resulting in insufficient stability of the catalytic system and a decrease in the initial slurry flowability.

[0080] Regarding flow retention performance, the 60-minute flowability of the neat pulp in Examples 1-3 was 261 mm, 246 mm, and 252 mm, respectively, showing a small decrease compared to the initial flowability. In contrast, the flowability of the comparative examples 1-3 was only 168 mm, 199 mm, and 186 mm, respectively. This indicates that the polycarboxylate-based high-performance water-reducing agent obtained in the examples has better continuous dispersion ability and can improve the problem of rapid flowability loss of existing products after standing.

[0081] Regarding the water reduction rate, Examples 1-3 achieved 30.8%, 28.9%, and 29.6%, respectively, which were significantly higher than Comparative Example 1's 22.4%, Comparative Example 2's 25.6%, and Comparative Example 3's 24.7%. This indicates that the complete structure of the iron-copper gluconate bisulfite catalyst plays a significant role in improving the water reduction efficiency. Sodium gluconate and citric acid monohydrate help stabilize the catalytic system formed by ferrous sulfate heptahydrate and copper sulfate pentahydrate. Sodium bisulfite solution helps maintain a relatively stable redox regulation process. The three functional components work together to make hydrogen peroxide-induced polymerization more controllable, and the resulting polymer is more conducive to the dispersion of cement particles.

[0082] In summary, Examples 1-3, compared with Comparative Examples 1-3, solved the technical problems of existing polycarboxylate-based high-performance water-reducing agents, such as instability caused by room temperature polymerization, low solid content, insufficient initial dispersion ability, poor flow retention performance, and low water reduction rate.

Claims

1. A polycarboxylate-based high-performance water-reducing agent, characterized in that, It is prepared from the following raw materials in parts by weight: Polyether 4300-4700 parts, acrylic acid 260-310 parts, hydrogen peroxide 20-30 parts, iron-copper gluconate bisulfite catalyst 3-8 parts, 3-mercaptopropionic acid 15-28 parts, liquid alkali 45-65 parts, deionized water 4500-5200 parts.

2. The polycarboxylate-based high-performance water-reducing agent according to claim 1, characterized in that, The preparation steps of the polycarboxylate-based high-performance water-reducing agent include: S1. Under stirring, deionized water, polyether and liquid alkali are added to the reaction vessel in sequence and stirred at room temperature to obtain polyether base material; S2. Mix deionized water and acrylic acid to obtain solution A; mix deionized water and liquid alkali and add 3-mercaptopropionic acid to obtain solution B; S3. Add solution A to the polyether substrate, followed by iron-copper gluconate bisulfite catalyst and hydrogen peroxide, stir, add solution A and solution B dropwise, and continue stirring.

3. The polycarboxylate-based high-performance water-reducing agent according to claim 2, characterized in that, In step S1, the polyether is a GPEG-3000 polyether macromonomer; the liquid alkali is an aqueous solution of sodium hydroxide.

4. The polycarboxylate-based high-performance water-reducing agent according to claim 2, characterized in that, In S2, the liquid alkali is an aqueous solution of sodium hydroxide.

5. The polycarboxylate-based high-performance water-reducing agent according to claim 2, characterized in that, In step S3, the hydrogen peroxide has a mass fraction of 27.5%.

6. The polycarboxylate-based high-performance water-reducing agent according to claim 5, characterized in that, The preparation method of the iron-copper gluconate bisulfite catalyst includes: A1. By weight, add 40-70 parts sodium gluconate and 5-15 parts citric acid monohydrate to 1000-1500 parts deionized water, stir, adjust the pH, and obtain a complexing stabilized solution. A2. Add 8-18 parts of ferrous sulfate heptahydrate and 1-4 parts of copper sulfate pentahydrate to 80-150 parts of deionized water, stir, and obtain a mixed solution of iron and copper salts; add the mixed solution of iron and copper salts to the complexing stabilizing solution, adjust the pH, stir, and obtain a complex solution of iron and copper gluconate. A3. Add 10-20 parts of sodium bisulfite solution to 80-120 parts of deionized water and stir to obtain a bisulfite conditioning solution; add the bisulfite conditioning solution to the iron-copper gluconate complex solution, stir, add 5-10 parts of sodium gluconate, adjust the pH to obtain an iron-copper gluconate bisulfite catalytic solution. A4. Let the iron-copper gluconate bisulfite catalytic solution stand and mature, filter, add deionized water, and stir.

7. The polycarboxylate-based high-performance water-reducing agent according to claim 6, characterized in that, In A1, the pH is adjusted to 5.5-6.

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8. The polycarboxylate-based high-performance water-reducing agent according to claim 6, characterized in that, In A2, the pH is adjusted to 4.5-5.

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9. The polycarboxylate-based high-performance water-reducing agent according to claim 6, characterized in that, In A3, the pH is adjusted to 4.0-5.

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10. The polycarboxylate-based high-performance water-reducing agent according to claim 6, characterized in that, In the A4, the temperature for static curing is 20-30℃, and the time for static curing is 6-12h.

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