A low-sensitivity viscosity-reducing polycarboxylate water reducer and its preparation method and application

Abstract

The invention discloses a low-sensitivity viscosity-reducing polycarboxylate water reducer and a preparation method and application thereof, belonging to the technical field of concrete admixtures. The polycarboxylate water reducer is prepared by free radical copolymerization of an unsaturated acid monomer, an unsaturated sulfonate monomer, an unsaturated phosphated polyoxyethylene ether monomer, and a functional monomer in a molar ratio of a:b:c:d=(3-6):(0.5-2):1:(0.06-1.2). By designing the molecular structure of the water reducer, the molecular weight and the degree of polymerization of the main chain can be controlled, thereby changing the side chain density and generating different steric hindrance effects. By selectively introducing monomers containing functional groups with different surface activities for polymerization reaction, the hydrophilic-lipophilic balance value of the water reducer is changed, so that the adsorption capacity, dispersibility, and viscosity-reducing performance of the water reducer can be designed in a gradient performance manner, thereby realizing the functionalization of the polycarboxylate water reducer and significantly improving the comprehensive application effect in concrete.

Description

Technical Field

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

[0002] Polycarboxylate superplasticizers, as third-generation high-performance water reducers, have a comb-like molecular structure. Through the electrostatic repulsion provided by carboxyl and sulfonic acid groups on the main chain and the steric hindrance provided by grafted side chains, they release free water from the cement flocculation structure, achieving a dispersing and water-reducing effect. In recent years, amidst the surge in infrastructure construction in my country, polycarboxylate superplasticizers have become the most widely used water reducer in the construction industry, thanks to their low dosage, excellent dispersibility, designable functionality, and environmental friendliness.

[0003] With the widespread use of concrete resulting in significant natural resource consumption and the near-depletion of high-quality sand and stone resources, the incorporation of low-quality aggregates such as recycled aggregate, industrial waste residue, and machine-made sand into concrete has become an inevitable trend. During construction, even small changes in the polycarboxylate superplasticizer dosage at the appropriate dosage point can lead to insufficient or rapid fluidity loss in fresh concrete, or cause sensitive issues such as segregation and bleeding, making concrete production control more difficult and posing significant risks to concrete quality control.

[0004] Currently, the main method to improve concrete strength is to reduce the water-cement ratio. However, increasing concrete strength by reducing the water-cement ratio will increase the viscosity of the concrete, resulting in slow initial dispersion of high-strength concrete and difficulty in controlling stable fluidity. During the construction process, there are problems such as high pump pressure and pipe blockage, which will cause high-grade concrete to easily have quality problems during use, limiting the development of high-strength concrete.

[0005] To address these issues, some researchers have exploited the designability of high-performance polycarboxylate water-reducing agents (PCAs) by grafting molecular groups with slump-retention and viscosity-reducing properties to create low-sensitivity or viscosity-reducing PCAs, addressing current difficulties in concrete construction. Chinese patent document CN114195953B discloses "A Low-Sensitivity, High-Water-Retention Polycarboxylate Water-Reducing Agent and Its Preparation Method." This method introduces caffeic acid gamma-cyclodextrin unsaturated monomers, along with the crosslinker trimethylolpropane triacrylate, into a PCA water-reducing agent, effectively reducing free water release and imparting excellent water retention and low sensitivity. However, this method suffers from long reaction times, complex control processes, and undoubtedly reduces the dispersibility of the PCA. Chinese patent document CN116478343B discloses a "viscosity-reducing polycarboxylate water-reducing agent and its preparation method." First, an unsaturated phosphorus-nitrogen derivative is prepared using a phosphorus oxychloride derivative and an unsaturated amine as raw materials. This derivative is then copolymerized with polyethylene glycol monomethyl ether acrylate, an unsaturated carboxylic acid, and an unsaturated carboxylic acid ester to produce a polycarboxylate water-reducing agent containing highly polar phosphoramide groups that are not easily hydrolyzed. This water-reducing agent exhibits low dosage, high water-reducing efficiency, good dispersibility in cement, and low water bleeding, excellent dispersion retention, and strong operability. However, this method requires harsh reaction conditions, requiring some reactions to be carried out at low temperatures, making it difficult to scale up. The reaction solvent involves an organic solvent, which also involves hazardous substances such as polymerization inhibitors, placing significant environmental pressure on the production process. In summary, existing polycarboxylate water-reducers lack the comprehensive properties of high dispersibility, low sensitivity, and viscosity reduction. Furthermore, most polycarboxylate water-reducers require harsh and complex preparation processes, long reaction times, and use hazardous solvents. Summary of the Invention

[0006] Technical problem to be solved: In response to the problems existing in the application process of the background technology polycarboxylate water-reducing agent, the present invention provides a low-sensitivity and viscosity-reducing polycarboxylate water-reducing agent and its preparation method and application. The polycarboxylate water-reducing agent has the advantages of low sensitivity and viscosity reduction while having a water reduction rate superior to conventional products. It effectively solves the problems of poor fluidity, high viscosity, and poor robustness of high-strength concrete caused by the reduction of water-cement ratio, meets the application adaptability of various admixtures and machine-made sand of different qualities, increases the dispersion effect, provides better construction performance, and has broad application prospects.

[0007] Technical solution: The low-sensitivity viscosity-reducing polycarboxylate water-reducing agent described in the present invention has a structural formula as shown in Formula I:

[0008] Formula I;

[0009] In formula I: R1 is -H or -COOH, R2 is -H, -CH3 or -CH2COOH, R3 is -H or -CH3, M1 is Na, R4 is H or CH3, R5 is -CH2-, -CH2CH2-, -CH2CH2CH2CH2- or -OCH2CH2-, R6 is -H or CH3, R7 is C1 or C3 alkyl, R8, R9, R 10 is any one of -CH3, -CH3O, and -CH2CH3O; a, b, c, d, and n represent the molar number of each repeating unit; and the molecular weight of the polycarboxylate water reducer is 20,000 to 60,000 Da.

[0010] Preferably, the polycarboxylate water-reducing agent is prepared by free radical copolymerization of unsaturated acid monomers, unsaturated sulfonate monomers, unsaturated phosphated polyoxyethylene ether monomers and functional monomers in a molar ratio of a:b:c:d=(3-6):(0.5-2):1:(0.06-1.2).

[0011] Preferably, the unsaturated acid monomer has a structural formula as shown in Formula II:

[0012] Formula II;

[0013] In formula II: R1 is -H or -COOH, R2 is -H, -CH3 or -CH2COOH; wherein, if R1 is -COOH, R2 is -H; if R2 is -CH2COOH, R1 is -H;

[0014] The unsaturated acid monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid in any proportion.

[0015] Preferably, the unsaturated sulfonic acid or its salt monomer has a structural formula as shown in Formula III:

[0016] Formula III;

[0017] In formula III: R3 is -H or -CH3, M1 is Na;

[0018] The unsaturated sulfonate monomer is one of sodium allyl sulfonate and sodium methallyl sulfonate or a combination of the two in any proportion.

[0019] Preferably, the unsaturated phosphated polyoxyethylene ether monomer is a macromolecular monomer having a long polyether chain structure and a terminal that is glycosylated and then phosphorylated, and its terminal group contains an unsaturated carbon-carbon double bond, and its structural formula is shown in Formula IV:

[0020] Formula IV;

[0021] In formula IV: R4 is -H or -CH3, R5 is -CH2-, -CH2CH2-, -CH2CH2CH2CH2- or -OCH2CH2-, n is the number of structural units, n=38~152; the molecular weight of the unsaturated phosphated polyoxyethylene ether monomer is 2000~7000.

[0022] Preferably, the functional monomer structure is as shown in Formula V:

[0023] Formula V;

[0024] In formula V: R6 is -H or C1~C3 alkyl, R7 is C1 or C3 alkyl, R8, R9, R 10 Any one of -CH3, -CH3O, -CH2CH3O;

[0025] The functional monomer is one or more of 3-(methacryloyloxy)propyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, methacryloxypropyltriethoxysilane, methacryloxypropylmethyldiethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, (3-acryloyloxy)dimethylmethoxysilane, methacryloxymethyltriethoxysilane, and methacryloxypropyltriethoxysilane.

[0026] The present invention discloses a preparation method of a low-sensitivity viscosity-reducing polycarboxylate water-reducing agent, which comprises the following steps:

[0027] Step 1: preparing an unsaturated phosphated polyoxyethylene ether monomer: adding an unsaturated polyoxyethylene ether monomer and glucose into a reaction vessel and mixing evenly, adding a polymerization inhibitor, heating to 60-80°C, adding a catalyst and heating to 95-110°C under vacuum, keeping the temperature for 3-8 hours, cooling to 25-30°C, adjusting the pH value to 7-8, and obtaining a terminal glucose-glycosylated unsaturated polyoxyethylene ether monomer; then, under a protective atmosphere, heating to 50-70°C, adding polyphosphoric acid or P2O5 in batches into the reaction vessel and stirring to mix evenly, heating to 80-100°C, carrying out a phosphating reaction for 4-8 hours, and cooling to obtain an unsaturated phosphated polyoxyethylene ether monomer;

[0028] Step 2: adding an oxidant, a catalyst, a functional monomer and water to the prepared unsaturated phosphated polyoxyethylene ether monomer and mixing them evenly to form a primer solution, heating the mixture to 25-55° C. and stirring for 5-10 minutes; mixing the unsaturated acid monomer, a reducing agent, a chain transfer agent and water evenly to prepare a dropping solution A; mixing the unsaturated sulfonic acid or its salt monomer with water evenly to prepare a dropping solution B; dropping solution A and dropping solution B are gradually added dropwise into the primer solution by a peristaltic pump for reaction, the dropping time is 0.5-2 hours, and the dropping temperature is controlled at 25-55° C.; wherein the solid content of the primer solution and the dropping solution is 15-60%; then, after keeping the reaction warm for 1-2 hours, an alkaline neutralizer is added to adjust the pH value of the reaction solution to 6-8 to prepare the polycarboxylate water reducer.

[0029] Preferably, in step 1, the molar ratio of the unsaturated polyoxyethylene ether monomer, glucose, and polyphosphoric acid is 1:(1-1.1):(1-1.2), or the molar ratio of the unsaturated polyoxyethylene ether monomer, glucose, and P2O5 is 1:(1-1.1):(0.5-0.6);

[0030] The polymerization inhibitor is hydroquinone, and the amount of hydroquinone used is 0.001-0.004% of the weight of the unsaturated polyoxyethylene ether monomer;

[0031] The catalyst is benzenesulfonic acid or p-toluenesulfonic acid, and the amount of the catalyst is 0.15-0.4% of the weight of glucose;

[0032] The vacuum degree of the vacuum state is -0.080~-0.096MPa;

[0033] The alkali solution for adjusting pH is 30% by mass sodium hydroxide solution;

[0034] The polyphosphoric acid is one or more of tripolyphosphoric acid, tetrapolyphosphoric acid, pentapolyphosphoric acid, and hexapolyphosphoric acid, and its industrial grade content is 105-118% based on the mass fraction of phosphoric acid;

[0035] The unsaturated polyoxyethylene ether monomer is one or more of methyl allyl polyoxyethylene ether with a molecular weight of 2000-4000, isopentanol polyoxyethylene ether with a molecular weight of 3000-4000, 4-hydroxybutyl vinyl polyoxyethylene ether with a molecular weight of 3000-5000, and ethylene glycol monovinyl polyethylene glycol ether with a molecular weight of 3000-6000.

[0036] Preferably, in step 2, the oxidant is one or more of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate, and the amount thereof is 1-4% of the total molar amount of all unsaturated polymerizable monomers;

[0037] The reducing agent is one or more of L-ascorbic acid, sodium hypophosphite, sodium bisulfite, and sodium metabisulfite, and its amount is 0.2-1% of the total molar amount of the unsaturated polymerization monomer;

[0038] The chain transfer agent is one or more of mercaptoethanol, thioglycolic acid, and mercaptopropionic acid, and its usage is 1.6-4.8% of the total molar amount of the unsaturated polymerization monomer;

[0039] The catalyst used in the polymerization reaction is one of ferrous sulfate, ferrous chloride, and cupric chloride, and its amount is 0.006-0.01% of the total molar amount of the unsaturated polymerization monomer;

[0040] The alkaline neutralizing agent is a sodium hydroxide solution with a mass fraction of 30%.

[0041] The present invention also discloses an application of a low-sensitivity viscosity-reducing polycarboxylate water-reducing agent in a gel material. The polycarboxylate water-reducing agent is added in an amount of 0.05-0.5% by mass of the total gelling material, and the amount is a pure solid amount.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The polycarboxylate water-reducing agent of the present invention has the advantages of low sensitivity and viscosity reduction while having a water-reduction rate that is higher than conventional products. It effectively solves the problems of poor fluidity, high viscosity, and poor robustness caused by the low water-binder ratio in high-strength concrete. It meets the application adaptability of various admixtures and machine-made sand of different qualities, increases the dispersion effect, provides better construction performance, and has broad application prospects.

[0044] 2. The polycarboxylate water reducer is made by phosphorylating the terminal of the unsaturated polyoxyethylene ether monomer. The phosphate group has stronger electronegativity and chelating ability, has higher affinity on the surface of cement and different types of inert powder particles, and can quickly achieve a higher adsorption capacity. At the same time, the phosphate group can react with the Ca in cement. 2+ It forms a stable complex, delays the hydration process of cement, effectively improves the fluidity and slump resistance of concrete, and significantly enhances the dispersibility and viscosity reduction performance of polycarboxylate water-reducing agent.

[0045] 3. The polycarboxylate superplasticizer introduces sulfonic acid groups and siloxane groups. The released sulfonate ions give the polycarboxylate superplasticizer greater adsorption selectivity. The sulfonate ions compete with the polycarboxylate superplasticizer for adsorption on the clay surface, thereby reducing the clay's adsorption of the polycarboxylate superplasticizer, achieving better water reduction and retardation and slump retention effects. The introduction of siloxane groups can adjust the ratio of hydrophilic and hydrophobic groups, optimize the bubble structure of the concrete system, and significantly improve the homogeneity of the concrete. In addition, the siloxane groups significantly enhance the anchoring ability of the superplasticizer on the surfaces of cement and mineral admixture particles, effectively enhancing the slump retention effect and significantly improving the overall performance of the concrete.

[0046] 4. The polycarboxylate water reducer is modified with glucosidated ends to increase the steric hindrance effect of the polyether side chain, hindering the intercalation adsorption of clay on the polyether side chain, reducing the water reducer's sensitivity to clay and improving the material adaptability. At the same time, the introduced glucose molecules have a good retarding effect, which helps maintain the workability of concrete at high temperatures and for a long time, and improves the weathering adaptability of the water reducer.

[0047] 5. During the synthesis of this polycarboxylate superplasticizer, the molecular weight and the degree of polymerization of the main chain can be controlled by designing the superplasticizer's molecular structure, thereby changing the side chain density and producing different steric hindrance effects. By selectively introducing monomers containing functional groups with different surface activities for polymerization, the hydrophilic-lipophilic balance (HLB) of the superplasticizer is changed, allowing for gradient performance design of the superplasticizer's adsorption capacity, dispersibility, and viscosity reduction properties. Ultimately, the functionalization of the polycarboxylate superplasticizer is achieved, significantly improving the overall effect of its application in concrete.

[0048] 6. This polycarboxylate water reducer combines the advantages of high water reduction, long-term slump retention, low sensitivity, and reduced concrete viscosity. It can effectively solve application problems such as fluctuations in fluidity and state caused by unstable concrete quality, as well as difficulties in construction due to high viscosity of high-grade concrete. The unsaturated polyoxyethylene ether required for its synthesis includes common polyether types and has a wide range of adaptability.

[0049] 7. The preparation method of the present invention has the advantages of simple preparation process, greatly shortened reaction time, high production efficiency, and environmental protection, which is of great significance for promoting the research of polycarboxylic acid water reducers and improving the level of concrete application technology.

[0050] The present invention also has other beneficial effects which are described in the embodiment section of the specification and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The present invention is a flow chart of the preparation method of the low-sensitivity viscosity-reducing polycarboxylate water-reducing agent. DETAILED DESCRIPTION

[0052] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the following Figure 1 The technical solutions of the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present invention.

[0053] The present invention discloses a low-sensitivity viscosity-reducing polycarboxylate water reducer, the structural formula of the polycarboxylate water reducer is shown in Formula I:

[0054] Formula I;

[0055] In formula I: R1 is -H or -COOH, R2 is -H, -CH3 or -CH2COOH, R3 is -H or -CH3, M1 is Na, R4 is H or CH3, R5 is -CH2-, -CH2CH2-, -CH2CH2CH2CH2- or -OCH2CH2-, R6 is -H or CH3, R7 is C1 or C3 alkyl, R8, R9, R 10 is any one of -CH3, -CH3O, -CH2CH3O; a, b, c, d, n represent the molar number of each repeating unit; the molecular weight of the polycarboxylate water-reducer is 20000~60000Da. The polycarboxylate water-reducer is prepared by free radical copolymerization of unsaturated acid monomer, unsaturated sulfonate monomer, unsaturated phosphated polyoxyethylene ether monomer and functional monomer according to the molar ratio of a:b:c:d=(3~6):(0.5~2):1:(0.06~1.2). The polycarboxylate water-reducer of the present invention has the advantages of low sensitivity and viscosity reduction while having a leading water reduction rate of conventional products. It effectively solves the problems of poor fluidity, high viscosity, and poor robustness caused by the low water-binder ratio of high-strength concrete, meets the application adaptability of various admixtures and machine-made sand of different qualities, increases the dispersion effect, provides better construction performance, and has broad application prospects.

[0056] Wherein, the structural formula of the unsaturated acid monomer is as shown in Formula II:

[0057] Formula II;

[0058] In formula II: R1 is -H or -COOH, R2 is -H, -CH3 or -CH2COOH; wherein, if R1 is -COOH, R2 is -H; if R2 is -CH2COOH, R1 is -H; the unsaturated acid monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid in any proportion.

[0059] Wherein, the structural formula of the unsaturated sulfonic acid or its salt monomer is as shown in Formula III:

[0060] Formula III;

[0061] In Formula III, R3 is -H or -CH3, M1 is Na, and the unsaturated sulfonate monomer is one or a combination of sodium allyl sulfonate and sodium methallyl sulfonate in any proportion. This polycarboxylate superplasticizer incorporates a sulfonic acid group. The released sulfonate ions impart greater adsorption selectivity to the polycarboxylate superplasticizer. The sulfonate ions compete with the polycarboxylate superplasticizer for adsorption on the clay surface, thereby reducing the clay's adsorption of the polycarboxylate superplasticizer and achieving enhanced water reduction and slump-retarding properties.

[0062] The unsaturated phosphated polyoxyethylene ether monomer is a macromolecular monomer having a long polyether chain structure and a terminal that is glycosylated and then phosphorylated, and its terminal group contains an unsaturated carbon-carbon double bond, and its structural formula is shown in Formula IV:

[0063] Formula IV;

[0064] In formula IV, R4 is -H or -CH3, R5 is -CH2-, -CH2CH2-, -CH2CH2CH2CH2-, or -OCH2CH2-, and n is the number of structural units, n=38-152. The molecular weight of the unsaturated phosphated polyoxyethylene ether monomer is 2000-7000, and its molecular weight significantly affects the performance of the polycarboxylate water reducer. Controlling its molecular weight can regulate the steric hindrance effect of different capacities. The polycarboxylate water reducer is obtained by phosphorylating the terminal of the unsaturated polyoxyethylene ether monomer. The phosphate group has stronger electronegativity and chelating ability, has higher affinity on the surface of cement and different types of inert powder particles, and can quickly achieve a high adsorption capacity. At the same time, the phosphate group can react with the Ca in the cement. 2+ The formation of a stable complex delays the hydration process of cement, effectively improves the fluidity and slump retention of concrete, and significantly enhances the dispersibility and viscosity-reducing properties of the polycarboxylate water-reducing agent. The end modification with glucoside increases the steric hindrance effect of the polyether side chain, hinders the intercalation adsorption of the polyether side chain by clay, reduces the sensitivity of the water-reducing agent to clay, and improves the adaptability of the material. At the same time, the introduced glucose molecules have a good retarding effect, which is beneficial to maintaining the workability of concrete at high temperatures and for a long time, and improves the weathering adaptability of the water-reducing agent.

[0065] Wherein, the functional monomer structural formula is shown in Formula V:

[0066] Formula V;

[0067] In formula V: R6 is -H or C1~C3 alkyl, R7 is C1 or C3 alkyl, R8, R9, R 10 The functional monomer is any one of -CH3, -CH3O, and -CH2CH3O; the functional monomer is one or more of 3-(methacryloyloxy)propyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, methacryloxypropyltriethoxysilane, methacryloxypropylmethyldiethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, (3-acryloyloxy)dimethylmethoxysilane, methacryloxymethyltriethoxysilane, and methacryloxypropyltriethoxysilane. The polycarboxylic acid water reducer introduces siloxane groups to adjust the ratio of hydrophilic groups to hydrophobic groups, optimizes the bubble structure of the concrete system, and significantly improves the homogeneity of the concrete; in addition, the siloxane groups significantly improve the anchoring ability of the water reducer on the surface of cement and mineral admixture particles, effectively enhances the collapse protection effect, and significantly improves the comprehensive performance of the concrete.

[0068] In the synthesis of the polycarboxylate water-reducer of the present invention, the molecular weight and the degree of polymerization of the main chain can be controlled by designing the water-reducer molecular structure, thereby changing the side chain density and generating different steric hindrance effects. By selectively introducing monomers containing functional groups with different surface activities for polymerization reaction, the hydrophilic-lipophilic balance (HLB) value of the water-reducer is changed, so that the adsorption capacity, dispersibility and viscosity reduction performance of the water-reducer can be designed with gradient performance, ultimately achieving the functionalization of the polycarboxylate water-reducer and significantly improving the overall effect of its application in concrete. The polycarboxylate water-reducer has the advantages of high water reduction, long slump retention, low sensitivity and reduced concrete viscosity, and can effectively solve application problems such as fluctuations in fluidity and state caused by unstable quality of concrete materials and unfavorable construction conditions caused by high-grade concrete due to high viscosity. The unsaturated polyoxyethylene ether required for the synthesis includes common polyether types and has wide adaptability.

[0069] like Figure 1 As shown, the present invention discloses a method for preparing a low-sensitivity, viscosity-reducing polycarboxylate water-reducing agent. The method comprises two steps: first, synthesizing an unsaturated phosphated polyoxyethylene ether monomer; then, synthesizing the low-sensitivity, viscosity-reducing polycarboxylate water-reducing agent via a free radical copolymerization method. The unsaturated polyoxyethylene ether and other raw materials used in the examples of the present invention are all commercially available, chemically pure reagents. The preparation method comprises the following specific steps:

[0070] (1) Preparation of unsaturated phosphated polyoxyethylene ether monomer:

[0071] An unsaturated polyoxyethylene ether monomer and glucose are added to a reaction vessel and mixed uniformly. The unsaturated polyoxyethylene ether monomer is one or more of methyl allyl polyoxyethylene ether with a molecular weight of 2000-4000, isopentanol polyoxyethylene ether with a molecular weight of 3000-4000, 4-hydroxybutyl vinyl polyoxyethylene ether with a molecular weight of 3000-5000, and ethylene glycol monovinyl polyethylene glycol ether with a molecular weight of 3000-6000. A polymerization inhibitor is added, wherein the amount of hydroquinone is 0.001-0.004% by weight of the unsaturated polyoxyethylene ether monomer. The temperature is then raised to 60-80°C, and a catalyst is added, wherein the amount of benzenesulfonic acid or p-toluenesulfonic acid is 0.15-0.4% by weight of the glucose. The temperature is then raised to 95-110°C under a vacuum state of -0.080-0.096 MPa, maintained for 3-8 hours, and then cooled to 25-30°C. The pH value is adjusted to 7-8 with a 30% by mass sodium hydroxide solution to obtain a terminally glucoside unsaturated polyoxyethylene ether monomer. Next, under a protective atmosphere, the temperature is raised to 50-70°C, polyphosphoric acid or P2O5 is added to the reaction vessel in batches, stirred and mixed, and the temperature is raised to 80-100°C for phosphating reaction for 4-8 hours. After cooling, the unsaturated phosphated polyoxyethylene ether monomer is obtained. The polyphosphoric acid is one or more of tripolyphosphoric acid, tetrapolyphosphoric acid, pentapolyphosphoric acid, and hexapolyphosphoric acid, and its industrial grade content is 105-118% by mass of phosphoric acid. In this step, the molar ratio of the unsaturated polyoxyethylene ether monomer, glucose, and polyphosphoric acid is 1:(1-1.1):(1-1.2), or the molar ratio of the unsaturated polyoxyethylene ether monomer, glucose, and P2O5 is 1:(1-1.1):(0.5-0.6).

[0072] (2) Synthesis of polycarboxylate water reducer by free radical copolymerization:

[0073] An oxidizing agent, catalyst, functional monomer, and water are added to the prepared unsaturated phosphated polyoxyethylene ether monomer and mixed evenly to form a primer. The oxidizing agent is one or more of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate, and the amount thereof is 1-4% of the total molar amount of the unsaturated polymerized monomers. The catalyst is one of ferrous sulfate, ferrous chloride, and cupric chloride, and the amount thereof is 0.006-0.01% of the total molar amount of the unsaturated polymerized monomers. The temperature is then raised to 25-55°C and stirred for 5-10 minutes. The unsaturated acid monomer, reducing agent, and chain transfer agent are mixed evenly with water to form a dropwise addition solution A. The reducing agent is one or more of L-ascorbic acid, sodium hypophosphite, sodium bisulfite, and sodium metabisulfite, and the amount thereof is 0.2-1% of the total molar amount of the unsaturated polymerized monomers. The chain transfer agent is one or more of mercaptoethanol, thioglycolic acid, and mercaptopropionic acid, and the amount thereof is 1.6-4.8% of the total molar amount of the unsaturated polymerized monomers. Unsaturated sulfonic acid or its salt monomer is uniformly mixed with water to form a droplet solution B. Droplet solutions A and B are then added simultaneously and gradually to the primer solution via a peristaltic pump for a reaction over a period of 0.5 to 2 hours at a temperature of 25 to 55°C. The solids content of the primer solution and the droplet solution is 15 to 60%. After incubating the reaction for 1 to 2 hours, a 30% by mass sodium hydroxide solution is added to adjust the pH of the reaction solution to 6 to 8, thereby producing a polycarboxylate superplasticizer.

[0074] The preparation method of the present invention has the advantages of simple preparation process, greatly shortened reaction time, high production efficiency, and environmental protection, and is of great significance for promoting the research of polycarboxylate water reducers and improving the level of concrete application technology.

[0075] The present invention also discloses the use of a low-sensitivity, viscosity-reducing polycarboxylate water-reducing agent in a gel material. The polycarboxylate water-reducing agent is added in an amount of 0.05 to 0.5% by mass of the total gelling material, and the amount is a pure solid amount. If the amount of the polycarboxylate water-reducing agent added in the preparation of the gelling material is too low, its performance will deteriorate, while if the amount is too high, it will cause economic waste and fail to improve the performance.

[0076] The following are specific examples of the present invention, which are used to further illustrate the technical solutions and effects of the present invention. The unsaturated polyoxyethylene ether and other raw materials used were commercially available ordinary chemically pure reagents. The molecular weight of the polymers in the examples of the present invention was determined using a miniDAWN Tristar aqueous gel permeation chromatograph (GPC, Wyatt Technologies) equipped with a TSK-GELSW (Tosoh Biotechnology Co., Ltd.) column. The mobile phase was a 0.1 M NaNO3 aqueous solution at a flow rate of 1.0 mL / min and the sample mass percentage concentration was 0.50%.

[0077] Example 1: The preparation method of the polycarboxylate water-reducing agent of this embodiment comprises the following specific steps:

[0078] (1) Preparation of unsaturated phosphated polyoxyethylene ether monomer:

[0079] 0.2 mol of methyl allyl polyoxyethylene ether (molecular weight, 2400) and 0.21 mol of glucose were added to a four-necked flask equipped with a stirrer and thermometer and mixed thoroughly. Hydroquinone (0.002% by weight of methyl allyl polyoxyethylene ether (molecular weight, 2400)) was added. The temperature was then raised to 80°C, followed by the addition of p-toluenesulfonic acid (0.2% by weight of glucose). The mixture was then heated to 105°C under a vacuum of -0.080 to -0.096 MPa, maintained for 5 hours, and cooled to room temperature. The pH was then adjusted to 7 with a 30% by weight sodium hydroxide solution to obtain a terminally glucoside unsaturated polyoxyethylene ether monomer. Then, under a nitrogen protective atmosphere, the oil bath was heated to 60°C and maintained at a constant temperature. 0.22 mol of 115% polyphosphoric acid (CAS No.: 8017-16-1, molecular formula: Hn+2PnO3n+1, product No. P102919, ≥85% phosphate (as P205) basis, purchased from Aladdin Reagent (Shanghai) Co., Ltd.) was added to the reaction vessel in three equal portions and stirred to mix. The temperature was raised to 100°C and the phosphating reaction was carried out for 5.5 hours. After cooling, an unsaturated phosphated polyoxyethylene ether monomer was obtained, and Mw = 2712 was measured by GPC.

[0080] (2) Synthesis of polycarboxylate water reducer by free radical copolymerization:

[0081] 0.1 mol of unsaturated phosphated polyoxyethylene ether monomer (Mw molecular weight 2712) was added to a three-necked flask equipped with a stirrer. 0.01 mol of 3-methacryloyloxypropylmethyldimethoxysilane, 0.01 mol of hydrogen peroxide, 0.004 g of ferrous sulfate, and 271 g of water were added and mixed thoroughly to form a primer. The mixture was then heated to 35°C and stirred for 5-10 minutes. Dropping Solution A was prepared by mixing 0.3 mol of acrylic acid, 0.0047 mol of L-ascorbic acid, 0.013 mol of mercaptoethanol, and 32 g of water. Dropping Solution B was prepared by mixing 0.06 mol of sodium allyl sulfonate and 28 g of water. Dropping Solution A and Dropping Solution B were then added simultaneously and gradually to the primer via a peristaltic pump for 1.5 hours at a controlled temperature of 35°C. After the reaction was kept warm for 1 hour, a 30% by mass sodium hydroxide solution was added to adjust the pH value of the reaction solution to 7, thereby obtaining a polycarboxylate water reducer. The Mw measured by GPC was 26289.

[0082] Example 2: The preparation method of the polycarboxylate water-reducing agent of this embodiment comprises the following specific steps:

[0083] (1) Preparation of unsaturated phosphated polyoxyethylene ether monomer:

[0084] 0.2 mol of 4-hydroxybutyl vinyl polyoxyethylene ether (molecular weight, 3000) and 0.22 mol of glucose were added to a four-necked flask equipped with a stirrer and a thermometer and mixed thoroughly. Hydroquinone (0.003% by weight of 4-hydroxybutyl vinyl polyoxyethylene ether (molecular weight, 3000)) was then added. The mixture was then heated to 70°C and then benzenesulfonic acid (0.25% by weight of glucose) was added. The mixture was then heated to 105°C under a vacuum of -0.080 to -0.096 MPa, maintained for 4.5 hours, and cooled to room temperature. The pH was then adjusted to 7 with a 30% by weight sodium hydroxide solution to obtain a terminally glucoside unsaturated polyoxyethylene ether monomer. Then, under a nitrogen protective atmosphere, the oil bath was heated to 70°C and kept at a constant temperature. 0.24 mol of 115% polyphosphoric acid (CAS No.: 8017-16-1, molecular formula: Hn+2PnO3n+1, product No. P102919, ≥85% phosphate (as P205) basis, purchased from Aladdin Reagent (Shanghai) Co., Ltd.) was added to the reaction vessel in three equal portions, stirred and mixed. The temperature was raised to 90°C, and the phosphating reaction was carried out for 6.5 hours. After cooling, an unsaturated phosphated polyoxyethylene ether monomer was obtained, and Mw = 3347 was measured by GPC.

[0085] (2) Synthesis of polycarboxylate water reducer by free radical copolymerization:

[0086] 0.1 mol of unsaturated phosphated polyoxyethylene ether monomer (Mw molecular weight 3347) was added to a three-necked flask equipped with a stirrer. 0.1 mol of methacryloyloxypropylmethyldiethoxysilane, 0.015 mol of ammonium persulfate, 0.003 g of ferrous chloride, and 335 g of water were added and mixed uniformly to form a primer. The mixture was then heated to 25°C and stirred for 5-10 minutes. Dropping solution A was then prepared by mixing 0.45 mol of methacrylic acid, 0.0025 mol of sodium bisulfite, 0.015 mol of mercaptoethanol, and 32 g of water. Dropping solution B was prepared by mixing 0.1 mol of sodium methyl allyl sulfonate and 28 g of water. Dropping solutions A and B were then added simultaneously and gradually to the primer via a peristaltic pump for 2.0 hours at a temperature of 25°C. After the reaction was kept warm for 2 hours, a 30% by mass sodium hydroxide solution was added to adjust the pH value of the reaction solution to 7, thereby obtaining a polycarboxylate water reducer. The Mw measured by GPC was 39276.

[0087] Example 3: The preparation method of the polycarboxylate water-reducing agent of this embodiment comprises the following specific steps:

[0088] (1) Preparation of unsaturated phosphated polyoxyethylene ether monomer:

[0089] 0.2 mol of 4-hydroxybutyl vinyl polyoxyethylene ether (molecular weight, 4000) and 0.21 mol of glucose were added to a four-necked flask equipped with a stirrer and a thermometer and mixed thoroughly. Hydroquinone (0.0025% by weight of 4-hydroxybutyl vinyl polyoxyethylene ether (molecular weight, 4000)) was added, and the mixture was heated to 60°C. Then, p-toluenesulfonic acid (0.3% by weight of glucose) was added. The mixture was then heated to 110°C under a vacuum of -0.080 to -0.096 MPa, maintained for 4 hours, and cooled to room temperature. The pH was adjusted to 7 with a 30% by weight sodium hydroxide solution to obtain a terminally glucosidated unsaturated polyoxyethylene ether monomer. Then, under a nitrogen protective atmosphere, the oil bath was heated to 50°C and kept at a constant temperature. 0.22 mol of polyphosphoric acid (CAS No.: 8017-16-1, molecular formula: Hn+2PnO3n+1, product No. P102919, ≥85% phosphate (as P205) basis, purchased from Aladdin Reagent (Shanghai) Co., Ltd.) with a content of 115% was added to the reaction vessel in three equal portions and stirred to mix. The temperature was raised to 80°C, and the phosphating reaction was carried out for 7.5 hours. After cooling, an unsaturated phosphated polyoxyethylene ether monomer was obtained, and Mw = 4417 was measured by GPC.

[0090] (2) Synthesis of polycarboxylate water reducer by free radical copolymerization:

[0091] 0.1 mol of unsaturated phosphated polyoxyethylene ether monomer (Mw molecular weight 4417) was added to a three-necked flask equipped with a stirrer. 0.12 mol of 3-(methacryloyloxy)propyltrimethoxysilane, 0.038 mol of potassium persulfate, 0.005 g of copper chloride, and 440 g of water were added and mixed uniformly to form a primer. The mixture was then heated to 30°C and stirred for 5-10 minutes. Dropping Solution A was prepared by mixing 0.5 mol of acrylic acid, 0.1 mol of maleic acid, 0.0077 mol of sodium bisulfite, 0.045 mol of mercaptopropionic acid, and 32 g of water. Dropping Solution B was prepared by mixing 0.15 mol of sodium allyl sulfonate and 28 g of water. Dropping Solution A and Dropping Solution B were then added simultaneously and gradually to the primer via a peristaltic pump for 0.5 h at a controlled temperature of 30°C. After the reaction was kept warm for 1 hour, a 30% by mass sodium hydroxide solution was added to adjust the pH value of the reaction solution to 7, thereby obtaining a polycarboxylate water reducer. The Mw measured by GPC was 48695.

[0092] Example 4: The preparation method of the polycarboxylate water-reducing agent of this embodiment comprises the following specific steps:

[0093] (1) Preparation of unsaturated phosphated polyoxyethylene ether monomer:

[0094] 0.2 mol of prenol polyoxyethylene ether (molecular weight, 3000) and 0.21 mol of glucose were added to a four-necked flask equipped with a stirrer and thermometer and mixed thoroughly. Hydroquinone (0.003% by weight of prenol polyoxyethylene ether, 3000) was added, and the temperature was raised to 65°C. Then, p-toluenesulfonic acid (0.35% by weight of glucose) was added. The temperature was then raised to 100°C under a vacuum of -0.080 to -0.096 MPa, maintained for 6 hours, and then cooled to room temperature. The pH was adjusted to 7 with a 30% by weight sodium hydroxide solution to obtain a terminally glucoside unsaturated polyoxyethylene ether monomer. Then, under a nitrogen protective atmosphere, the oil bath was heated to 65°C and kept at a constant temperature. 0.1 mol of P2O5 was added to the reaction vessel in three equal portions and stirred to mix. The temperature was raised to 100°C and the phosphating reaction was carried out for 7 hours. After cooling, an unsaturated phosphated polyoxyethylene ether monomer was obtained. GPC measured Mw = 3324.

[0095] (2) Synthesis of polycarboxylate water reducer by free radical copolymerization:

[0096] 0.1 mol of unsaturated phosphated polyoxyethylene ether monomer (Mw molecular weight 3324) was added to a three-necked flask equipped with a stirrer. 0.08 mol of γ-methacryloyloxypropylmethyldimethoxysilane, 0.02 mol of ammonium persulfate, 0.006 g of ferrous sulfate, and 270 g of water were added and mixed uniformly to form a primer. The mixture was then heated to 40°C and stirred for 5-10 minutes. Dropping solution A was then prepared by mixing 0.35 mol of acrylic acid, 0.0047 mol of L-ascorbic acid, 0.02 mol of thioglycolic acid, and 43 g of water. Dropping solution B was prepared by mixing 0.14 mol of sodium methyl allyl sulfonate and 37 g of water. Dropping solutions A and B were then added simultaneously and gradually to the primer via a peristaltic pump for 2.0 hours at a temperature of 45°C. After the reaction was kept warm for 1.5 hours, a 30% by mass sodium hydroxide solution was added to adjust the pH value of the reaction solution to 7, thereby obtaining a polycarboxylate water reducer. The Mw measured by GPC was 36375.

[0097] Example 5: The preparation method of the polycarboxylate water-reducing agent of this embodiment comprises the following specific steps:

[0098] (1) Preparation of unsaturated phosphated polyoxyethylene ether monomer:

[0099] 0.2 mol of ethylene glycol monovinyl polyethylene glycol ether (molecular weight, 4000) and 0.22 mol of glucose were added to a four-necked flask equipped with a stirrer and thermometer and mixed thoroughly. Hydroquinone (0.0035% by weight of ethylene glycol monovinyl polyethylene glycol ether (molecular weight, 4000)) was added. The temperature was then raised to 65°C, and benzenesulfonic acid (0.25% by weight of glucose) was added. The temperature was then raised to 110°C under a vacuum of -0.080 to -0.096 MPa, maintained for 7.5 hours, and cooled to room temperature. The pH was then adjusted to 7 with a 30% by mass sodium hydroxide solution to obtain a terminally glucoside unsaturated polyoxyethylene ether monomer. Then, under a nitrogen protective atmosphere, the oil bath was heated to 50°C and kept at a constant temperature. 0.24 mol of 115% polyphosphoric acid (CAS No.: 8017-16-1, molecular formula: Hn+2PnO3n+1, product No. P102919, ≥85% phosphate (as P205) basis, purchased from Aladdin Reagent (Shanghai) Co., Ltd.) was added to the reaction vessel in three equal portions and stirred to mix. The temperature was raised to 100°C and the phosphating reaction was carried out for 6 hours. After cooling, an unsaturated phosphated polyoxyethylene ether monomer was obtained. GPC measured Mw = 4412.

[0100] (2) Synthesis of polycarboxylate water reducer by free radical copolymerization:

[0101] 0.1 mol of unsaturated phosphated polyoxyethylene ether monomer (Mw molecular weight 4412) was added to a three-necked flask equipped with a stirrer. 0.1 mol of methacryloxymethyltriethoxysilane, 0.014 mol of sodium persulfate, 0.0048 g of ferrous chloride, and 340 g of water were added and mixed uniformly to form a primer. The mixture was then heated to 45°C and stirred for 5-10 minutes. 0.4 mol of itaconic acid, 0.0036 mol of sodium metabisulfite, 0.017 mol of thioglycolic acid, and 45 g of water were mixed uniformly to form Dropping Solution A. 0.15 mol of sodium allyl sulfonate and 32 g of water were mixed uniformly to form Dropping Solution B. Dropping Solution A and Dropping Solution B were then added simultaneously and gradually to the primer via a peristaltic pump for reaction. The addition time was 1.5 hours, and the addition temperature was controlled at 45°C. After the reaction was kept warm for 1 hour, a 30% by mass sodium hydroxide solution was added to adjust the pH value of the reaction solution to 7, thereby obtaining a polycarboxylate water reducer. The Mw measured by GPC was 45478.

[0102] Example 6: The preparation method of the polycarboxylate water-reducing agent of this embodiment comprises the following specific steps:

[0103] (1) Preparation of unsaturated phosphated polyoxyethylene ether monomer:

[0104] 0.2 mol of ethylene glycol monovinyl polyethylene glycol ether (molecular weight 6000) and 0.2 mol of glucose were added to a four-necked flask equipped with a stirrer and a thermometer and mixed uniformly. Hydroquinone (0.003% by weight of ethylene glycol monovinyl polyethylene glycol ether (molecular weight 6000)) was added, and the temperature was raised to 60°C. Then, p-toluenesulfonic acid (0.35% by weight of glucose) was added. The temperature was then raised to 100°C under a vacuum of -0.080 to -0.096 MPa, maintained for 5.5 hours, and then cooled to room temperature. The pH was adjusted to 7 with a 30% by mass sodium hydroxide solution to obtain a terminally glucoside unsaturated polyoxyethylene ether monomer. Then, under a nitrogen protective atmosphere, the oil bath was heated to 50°C and kept at a constant temperature. 0.12 mol of P2O5 was added to the reaction vessel in three equal portions and stirred to mix. The temperature was raised to 90°C and the phosphating reaction was carried out for 8 hours. After cooling, an unsaturated phosphated polyoxyethylene ether monomer was obtained. GPC measured Mw = 6327.

[0105] (2) Synthesis of polycarboxylate water reducer by free radical copolymerization:

[0106] 0.1 mol of unsaturated phosphated polyoxyethylene ether monomer (Mw molecular weight 4327) was added to a three-necked flask equipped with a stirrer. 0.06 mol of methacryloyloxypropyltriethoxysilane, 0.02 mol of hydrogen peroxide, 0.006 g of ferrous sulfate, and 400 g of water were added and mixed uniformly to form a primer. The mixture was then heated to 55°C and stirred for 5-10 minutes. Dropping solution A was prepared by mixing 0.4 mol of fumaric acid, 0.003 mol of sodium hypophosphite, 0.027 mol of mercaptoethanol, and 40 g of water. Dropping solution B was prepared by mixing 0.16 mol of sodium allyl sulfonate and 35 g of water. Dropping solutions A and B were then added simultaneously and gradually to the primer via a peristaltic pump for 0.5 h at a temperature of 55°C. After the reaction was kept warm for 1 hour, a 30% by mass sodium hydroxide solution was added to adjust the pH value of the reaction solution to 7, thereby obtaining a polycarboxylate water reducer. The Mw measured by GPC was 57845.

[0107] Example 7: The preparation method of the polycarboxylate water-reducing agent of this embodiment comprises the following specific steps:

[0108] (1) Preparation of unsaturated phosphated polyoxyethylene ether monomer:

[0109] 0.2 mol of methyl allyl polyoxyethylene ether (molecular weight, 3000) and 0.21 mol of glucose were added to a four-necked flask equipped with a stirrer and thermometer and mixed thoroughly. Hydroquinone (0.004% by weight of methyl allyl polyoxyethylene ether (molecular weight, 3000)) was added. The temperature was then raised to 65°C, followed by the addition of p-toluenesulfonic acid (0.25% by weight of glucose). The temperature was then raised to 110°C under a vacuum of -0.080 to -0.096 MPa, maintained for 6 hours, and then cooled to room temperature. The pH was then adjusted to 7 with a 30% by weight sodium hydroxide solution to obtain a terminally glucoside unsaturated polyoxyethylene ether monomer. Then, under a nitrogen protective atmosphere, the oil bath was heated to 60°C and maintained at a constant temperature. 0.21 mol of 115% polyphosphoric acid (CAS No.: 8017-16-1, molecular formula: Hn+2PnO3n+1, product No. P102919, ≥85% phosphate (as P205) basis, purchased from Aladdin Reagent (Shanghai) Co., Ltd.) was added to the reaction vessel in three equal portions and stirred to mix. The temperature was raised to 85°C and the phosphating reaction was carried out for 8 hours. After cooling, an unsaturated phosphated polyoxyethylene ether monomer was obtained, and Mw = 3378 was measured by GPC.

[0110] (2) Synthesis of polycarboxylate water reducer by free radical copolymerization:

[0111] 0.1 mol of unsaturated phosphated polyoxyethylene ether monomer (Mw molecular weight 3378) was added to a three-necked flask equipped with a stirrer. 0.006 mol of (3-acryloyloxy)dimethylmethoxysilane, 0.027 mol of hydrogen peroxide, 0.005 g of copper chloride, and 330 g of water were added and mixed thoroughly to form a primer. The mixture was then heated to 35°C and stirred for 5-10 minutes. Dropping Solution A was then prepared by mixing 0.6 mol of acrylic acid, 0.007 mol of L-ascorbic acid, 0.029 mol of mercaptopropionic acid, and 40 g of water. Dropping Solution B was prepared by mixing 0.2 mol of sodium methyl allyl sulfonate and 30 g of water. Dropping Solution A and Dropping Solution B were then added simultaneously and gradually to the primer via a peristaltic pump for 2 hours at a controlled temperature of 35°C. After the reaction was kept warm for 1.5 hours, a 30% by mass sodium hydroxide solution was added to adjust the pH value of the reaction solution to 7, thereby obtaining a polycarboxylate water reducer. The Mw measured by GPC was 42785.

[0112] Example 8: The preparation method of the polycarboxylate water-reducing agent of this embodiment comprises the following specific steps:

[0113] (1) Preparation of unsaturated phosphated polyoxyethylene ether monomer:

[0114] 0.2 mol of prenol polyoxyethylene ether (molecular weight, 3000) and 0.21 mol of glucose were added to a four-necked flask equipped with a stirrer and a thermometer and mixed thoroughly. Hydroquinone (0.003% by weight of prenol polyoxyethylene ether, 3000) was added, and the temperature was raised to 70°C. Then, p-toluenesulfonic acid (0.35% by weight of glucose) was added. The temperature was then raised to 105°C under a vacuum of -0.080 to -0.096 MPa, maintained for 6.5 hours, and cooled to room temperature. The pH was adjusted to 7 with a 30% by mass sodium hydroxide solution to obtain a terminally glucoside unsaturated polyoxyethylene ether monomer. Then, under a nitrogen protective atmosphere, the oil bath was heated to 55°C and maintained at a constant temperature. 0.24 mol of 115% polyphosphoric acid (CAS No.: 8017-16-1, molecular formula: Hn+2PnO3n+1, product No. P102919, ≥85% phosphate (as P205) basis, purchased from Aladdin Reagent (Shanghai) Co., Ltd.) was added to the reaction vessel in three equal portions and stirred to mix. The temperature was raised to 90°C and the phosphating reaction was carried out for 7 hours. After cooling, an unsaturated phosphated polyoxyethylene ether monomer was obtained, and Mw = 3386 was measured by GPC.

[0115] (2) Synthesis of polycarboxylate water reducer by free radical copolymerization:

[0116] 0.1 mol of unsaturated phosphated polyoxyethylene ether monomer (Mw molecular weight 3386) was added to a three-necked flask equipped with a stirrer. 0.08 mol of 3-(methacryloyloxy)propyltrimethoxysilane, 0.02 mol of hydrogen peroxide, 0.004 g of ferrous sulfate, and 340 g of water were added and mixed uniformly to form a primer. The mixture was then heated to 25°C and stirred for 5-10 minutes. Dropping Solution A was then prepared by mixing 0.3 mol of acrylic acid, 0.15 mol of maleic acid, 0.0027 mol of L-ascorbic acid, 0.022 mol of mercaptoethanol, and 30 g of water. Dropping Solution B was prepared by mixing 0.12 mol of sodium allyl sulfonate and 25 g of water. Dropping Solution A and Dropping Solution B were then added simultaneously and gradually to the primer via a peristaltic pump for 1.5 hours at a controlled temperature of 25°C. After the reaction was kept warm for 1.5 hours, a 30% by mass sodium hydroxide solution was added to adjust the pH value of the reaction solution to 7, thereby obtaining a polycarboxylate water reducer. The Mw measured by GPC was 52435.

[0117] Comparative Example 1: Comparative Example 1 uses a commercially available high-performance polycarboxylate water-reducing agent, and the Mw measured by GPC is 30635.

[0118] Comparative Example 2: 0.1 mol of methyl allyl polyoxyethylene ether (Mw molecular weight of 2400), 0.005 mol of hydrogen peroxide and 240 g of water were added to a three-necked flask equipped with a stirrer and mixed evenly, then heated to 40°C and stirred for 5-10 minutes; 0.45 mol of acrylic acid, 0.0011 mol of L-ascorbic acid, 0.017 mol of mercaptoethanol and 60 g of water were mixed to form a dropping solution, which was added dropwise into the three-necked flask under continuous stirring at a constant temperature of 40°C for 2 hours. After the addition was completed, the mixture was kept warm for 1 hour, and a 30% by mass fraction of sodium hydroxide solution was added to adjust the pH value of the reaction solution to 7. A common polycarboxylate water reducer was prepared in the laboratory, and the Mw measured by GPC was 27864.

[0119] The polycarboxylate water-reducing agent samples obtained in Examples 1 to 8 of the present invention and Comparative Examples 1 to 2 are used to prepare concrete cementitious materials, wherein the cement used can be selected from Helin PO42.5, Helin PO52.5, Conch PO42.5, and benchmark PO42.5 cements; the mineral powder is S95 mineral powder produced by a factory in Jiangnan; the fly ash is Class I fly ash produced by a factory in Jiangsu; the sand is medium sand with a fineness modulus M=2.6; and the gravel is basalt with a continuously graded particle size of 5 to 20 mm.

[0120] Application Example 1: Concrete air content, slump, and spread were measured according to the methods specified in GB / T 50080-2016, "Standard for Test Methods of Performance of Ordinary Concrete Mixtures." The water reduction rate of the samples was determined according to GB 8076-2008, "Concrete Admixtures." The polycarboxylate superplasticizer samples obtained in Examples 1-8 and Comparative Examples 1-2 were added to the corresponding concrete cementitious materials at a dosage of 0.13%. The water consumption was adjusted to maintain the initial slump of the concrete at 22±1 cm. The concrete mix ratio by weight was: 250 parts by weight of Helin PO42.5 cement, 50 parts by weight of mineral powder, 60 parts by weight of fly ash, 770 parts by weight of sand, 440 parts by weight of large stone, 495 parts by weight of medium stone, 165 parts by weight of small stone, and 160 parts by weight of water. The concrete performance test results are shown in Table 1.

[0121] Table 1 Test results of concrete properties obtained from Examples 1 to 8 of the present invention and Comparative Examples 1 to 2:

[0122] .

[0123] As shown in Table 1, Examples 1-8 of the present invention, with the same polycarboxylate superplasticizer dosage and air content as Comparative Examples 1-2, achieved an average water reduction rate of 43.6%, while the water reduction rate of the comparative example was only approximately 35.8%. The water reduction rate of the examples was 7.8% higher than that of the comparative example, indicating that the low-sensitivity, viscosity-reducing polycarboxylate superplasticizers of the present invention improve water-reducing performance by more than 20% compared to existing polycarboxylate superplasticizers. Furthermore, the slump and spread of concrete incorporating the low-sensitivity, viscosity-reducing polycarboxylate superplasticizers of the present invention after 60 minutes showed little change compared to the initial slump and spread, and both the initial slump and spread after 60 minutes were superior to those of concrete incorporating existing polycarboxylate products. The air content results for the concrete in the examples of the present invention and the comparative example show that the difference between the two is not significant, indicating that the increased water reduction and slump retention capabilities are not due to excessive gas introduction, demonstrating that the low-sensitivity, viscosity-reducing polycarboxylate superplasticizers of the present invention have excellent water-reducing and slump retention properties.

[0124] Application Example 2: Referring to GB / T 8077-2023 "Test Method for Homogeneity of Concrete Admixtures", the fluidity of the polycarboxylate water-reducer was measured for different cements and at different temperatures. In order to study the adaptability sensitivity of the low-sensitivity viscosity-reducing polycarboxylate water-reducers of Examples 1 to 8 of the present invention and the conventional polycarboxylate water-reducers of Comparative Examples 1 to 2 to different cements, Portland cement produced by different manufacturers was selected for slurry testing at different temperatures. The polycarboxylate water-reducer dosage was fixed at 0.12%, and the water-cement ratio was fixed at 0.29. The test results of the sensitivity of the polycarboxylate water-reducer samples of Examples 1 to 8 of the present invention and Comparative Examples 1 to 2 to cement and temperature are shown in Table 2.

[0125] Table 2 Test results of sensitivity of polycarboxylate water-reducing agent samples of Examples 1 to 8 of the present invention and Comparative Examples 1 to 2 to cement and temperature:

[0126] .

[0127] As can be seen from Table 2, although there are differences between different cements, the overall change trend is the same, and the low-sensitivity viscosity-reducing polycarboxylate water-reducing agent of the embodiment of the present invention has little difference in fluidity in different cements. The fluctuation of the fluidity of the slurry of the embodiment of the present invention at different ambient temperatures is significantly smaller than that of the comparative example, indicating that the low-sensitivity viscosity-reducing polycarboxylate water-reducing agent of the embodiment of the present invention has good adaptability and lower sensitivity to different cements compared with the existing polycarboxylate product water-reducing agent.

[0128] Application Example 3: Montmorillonite is a typical clay with a much greater adsorption capacity for polycarboxylate superplasticizers than cement. In this experiment, montmorillonite was added to cement to simulate the mud content in sandstone materials. The tolerance of the polycarboxylate superplasticizers of Examples 1-8 and Comparative Examples 1-2 to mud was tested. The fluidity of the paste was measured according to GB / T 8077-2023, "Test Method for Homogeneity of Concrete Admixtures." Different masses of montmorillonite were substituted for the corresponding masses of cement, the water-cement ratio was fixed at 0.29, and the superplasticizer dosage was adjusted to achieve an initial fluidity of 260 mm. The results of the clay resistance test of the polycarboxylate superplasticizer samples of Examples 1-8 and Comparative Examples 1-2 are shown in Table 3.

[0129] Table 3 Anti-clay performance test results of polycarboxylate water-reducing agent samples of Examples 1 to 8 of the present invention and Comparative Examples 1 to 2:

[0130] ;

[0131] Note: “--” means no fluidity.

[0132] As can be seen from Table 3, when montmorillonite is added at a content of 0.5% and 1%, the fluidity of the cement pastes of Examples 1 to 8 of the present invention decreases by approximately 5.7% and 17.1%, respectively, while the fluidity of the cement pastes of Comparative Examples 1 to 2 decreases by more than 32% until the fluidity is lost. This indicates that the low-sensitivity viscosity-reducing polycarboxylate water-reducing agents of Examples 1 to 8 of the present invention have good tolerance to montmorillonite, and this product has a significant competitive advantage in some applications where the mud content of sand and gravel aggregates is relatively high.

[0133] Application Example 4: Mineral powder and fly ash are both commonly used admixtures in concrete. The sensitivity and adaptability of different polycarboxylate water-reducers to mineral fine powders significantly impacts concrete performance. The methods specified in GB 8076-2008, "Concrete Admixtures," were used to examine the effects of the polycarboxylate water-reducers of Examples 1-8 and Comparative Examples 1-2 on concrete performance at varying admixture dosages (mineral powder and fly ash). Concrete mix ratio 1: 226 parts by weight of cement, 84 parts by weight of mineral powder, 75 parts by weight of fly ash, 760 parts by weight of sand, 1090 parts by weight of stone, and 165 parts by weight of water; Concrete mix ratio 2: 152 parts by weight of cement, 128 parts by weight of mineral powder, 105 parts by weight of fly ash, 760 parts by weight of sand, 1090 parts by weight of stone, and 165 parts by weight of water. The slump and spread of concrete were measured according to the method specified in GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The test results of concrete performance of different mix ratios of the polycarboxylate water-reducing agent samples of Examples 1 to 8 of the present invention and Comparative Examples 1 and 2 are shown in Table 4.

[0134] Table 4 Concrete performance test results of different mix ratios of polycarboxylate water-reducing agent samples of Examples 1 to 8 of the present invention and Comparative Examples 1 to 2:

[0135] .

[0136] As can be seen from Table 4, under the conditions of two different concrete mix ratios, the dosage of the polycarboxylate water-reducing agent in the two tests is kept unchanged. The fluctuations in the expansion and slump of the concrete in Examples 1 to 8 of the present invention are significantly smaller than those in Comparative Examples 1 to 2 under two different mix ratios. Moreover, under the concrete mass mix ratio 2 (high slag and fly ash dosage), the initial dispersion of the concrete in Comparative Examples 1 to 2 is slow and the slump increases after 30 minutes. The state of Examples 1 to 8 of the present invention is stable and no slump occurs, indicating that the low-sensitivity viscosity-reducing polycarboxylate water-reducing agent in Examples 1 to 8 of the present invention has lower sensitivity and excellent adaptability to changes in the dosage of admixtures (slag and fly ash).

[0137] Application Example 5: The effects of the polycarboxylate water-reducing agents of Examples 1 to 8 and Comparative Examples 1 to 2 on high-strength concrete were tested according to the method specified in GB 8076-2008 "Concrete Admixtures." The polycarboxylate water-reducing agent dosage was adjusted to ensure an initial slump of the concrete of 24 ± 1 cm. The concrete mix ratio was as follows: 380 parts by weight of cement, 105 parts by weight of mineral powder, 82 parts by weight of fly ash, 17 parts by weight of silica fume, 745 parts by weight of sand, 1130 parts by weight of stone, and 145 parts by weight of water. The mixture performance was tested with reference to GB / T50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures". The emptying time of fresh concrete was tested using an inverted slump cone. The concrete viscosity was quantified by measuring the initial emptying time using an inverted slump cone. The specific method was as follows: the slump cone was inverted, the bottom was sealed, the concrete was filled and smoothed (generally, the inverted slump cone was fixed on a bracket with the bottom 50 cm off the ground), the bottom cover was quickly slid open, and the concrete emptying time was measured using a stopwatch. The performance test results of the high-strength concrete of Examples 1 to 8 of the present invention and Comparative Examples 1 to 2 are shown in Table 5.

[0138] Table 5 Performance test results of high-strength concrete of Examples 1 to 8 of the present invention and Comparative Examples 1 to 2:

[0139] .

[0140] As shown in Table 5, even when the polycarboxylate water-reducing agent dosage of Examples 1-8 of the present invention is approximately 22% lower than that of Comparative Examples 1-2, the initial slump / spread of the concrete of the Examples of the present invention is similar to that of the Comparative Examples, and the slump and spread after 60 minutes are both better than those of the Comparative Examples. This demonstrates that the low-sensitivity, viscosity-reducing polycarboxylate water-reducing agent of the present invention has excellent performance in terms of high water reduction and high slump retention. When the air content of Examples 1-8 of the present invention and Comparative Examples 1-2 is similar, the initial flow-free time of the high-strength concrete of Examples 1-8 of the present invention is close to 10 seconds, which is significantly less than the 28-32 seconds of Comparative Examples 1-2. This demonstrates that the low-sensitivity, viscosity-reducing polycarboxylate water-reducing agent of the present invention can effectively reduce the viscosity of high-strength concrete, improve the workability of concrete, and facilitate the pumping of concrete during construction. This polycarboxylate water-reducing agent product has broad application prospects in the high-strength concrete market.

[0141] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low-sensitivity viscosity-reducing polycarboxylate water-reducing agent, characterized in that: The structural formula of the polycarboxylate water reducer is shown in Formula I: Formula I; In formula I: R1 is -H or -COOH, R2 is -H, -CH3 or -CH2COOH, R3 is -H or -CH3, M1 is Na, R4 is H or CH3, R5 is -CH2-, -CH2CH2-, -CH2CH2CH2CH2- or -OCH2CH2-, R6 is -H or CH3, R7 is C1 or C3 alkylene, R8, R9, R 10 is any one of -CH3, CH3O-, and CH2CH3O-; a, b, c, d, and n represent the molar number of each repeating unit; the polycarboxylate water-reducing agent is prepared by free radical copolymerization of an unsaturated acid monomer, an unsaturated sulfonate monomer, an unsaturated phosphated polyoxyethylene ether monomer, and a functional monomer in a molar ratio of a:b:c:d=(3-6):(0.5-2):1:(0.06-1.2), and has a molecular weight of 20,000-60,000 Da; Wherein, the functional monomer is one or more of 3-(methacryloyloxy)propyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, methacryloxypropyltriethoxysilane, methacryloxypropylmethyldiethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, (3-acryloyloxy)dimethylmethoxysilane, methacryloxymethyltriethoxysilane, and methacryloxypropyltriethoxysilane.

2. The low-sensitivity viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The structural formula of the unsaturated acid monomer is shown in Formula II: Formula II; In formula II: R1 is -H or -COOH, R2 is -H, -CH3 or -CH2COOH; wherein, if R1 is -COOH, R2 is -H; if R2 is -CH2COOH, R1 is -H; The unsaturated acid monomer is one or more of acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid in any proportion.

3. The low-sensitivity viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The structural formula of the unsaturated sulfonic acid or its salt monomer is shown in Formula III: Formula III; In formula III: R3 is -H or -CH3, M1 is Na; The unsaturated sulfonate monomer is one of sodium allyl sulfonate and sodium methallyl sulfonate, or a combination of the two in any proportion.

4. The low-sensitivity viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The unsaturated phosphated polyoxyethylene ether monomer is a macromolecular monomer having a long polyether chain structure and a terminal that is glycosylated and then phosphorylated. Its terminal group contains an unsaturated carbon-carbon double bond, and its structural formula is shown in Formula IV: Formula IV; In formula IV: R4 is -H or -CH3, R5 is -CH2-, -CH2CH2-, -CH2CH2CH2CH2- or -OCH2CH2-, n is the number of structural units, n=38~152; the molecular weight of the unsaturated phosphated polyoxyethylene ether monomer is 2000~7000.

5. The low-sensitivity viscosity-reducing polycarboxylate water-reducing agent according to claim 1, characterized in that: The functional monomer structural formula is shown in Formula V: Formula V; In formula V: R6 is -H or C1~C3 alkyl, R7 is C1 or C3 alkylene, R8, R9, R 10 It is any one of -CH3, CH3O-, and CH2CH3O-.

6. A method for preparing the low-sensitivity viscosity-reducing polycarboxylate water-reducing agent according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: Step 1: preparing an unsaturated phosphated polyoxyethylene ether monomer: adding an unsaturated polyoxyethylene ether monomer and glucose into a reaction vessel and mixing evenly, adding a polymerization inhibitor, heating to 60-80°C, adding a catalyst and heating to 95-110°C under vacuum, keeping the temperature for 3-8 hours, cooling to 25-30°C, adjusting the pH value to 7-8, and obtaining a terminal glucose-glycosylated unsaturated polyoxyethylene ether monomer; then, under a protective atmosphere, heating to 50-70°C, adding polyphosphoric acid or P2O5 in batches into the reaction vessel and stirring to mix evenly, heating to 80-100°C, carrying out a phosphating reaction for 4-8 hours, and cooling to obtain an unsaturated phosphated polyoxyethylene ether monomer; Step 2: adding an oxidant, a catalyst, a functional monomer and water to the prepared unsaturated phosphated polyoxyethylene ether monomer and mixing them evenly to form a primer solution, heating the mixture to 25-55° C. and stirring for 5-10 minutes; mixing the unsaturated acid monomer, a reducing agent, a chain transfer agent and water evenly to prepare a dropping solution A; mixing the unsaturated sulfonic acid or its salt monomer with water evenly to prepare a dropping solution B; dropping solution A and dropping solution B are gradually added dropwise into the primer solution by a peristaltic pump for reaction, the dropping time is 0.5-2 hours, and the dropping temperature is controlled at 25-55° C.; wherein the solid content of the primer solution and the dropping solution is 15-60%; then, after keeping the reaction warm for 1-2 hours, an alkaline neutralizer is added to adjust the pH value of the reaction solution to 6-8 to prepare the polycarboxylate water reducer.

7. The method for preparing the low-sensitivity viscosity-reducing polycarboxylate water-reducing agent according to claim 6, characterized in that: In step 1, the molar ratio of the unsaturated polyoxyethylene ether monomer, glucose, and polyphosphoric acid is 1:(1-1.1):(1-1.2), or the molar ratio of the unsaturated polyoxyethylene ether monomer, glucose, and P2O5 is 1:(1-1.1):(0.5-0.6); The polymerization inhibitor is hydroquinone, and the amount of hydroquinone used is 0.001-0.004% of the weight of the unsaturated polyoxyethylene ether monomer; The catalyst is benzenesulfonic acid or p-toluenesulfonic acid, and the amount of the catalyst is 0.15-0.4% of the weight of glucose; The vacuum degree of the vacuum state is -0.080~-0.096MPa; The alkali solution for adjusting pH is 30% by mass sodium hydroxide solution; The polyphosphoric acid is one or more of tripolyphosphoric acid, tetrapolyphosphoric acid, pentapolyphosphoric acid and hexapolyphosphoric acid, and its industrial-grade product has a content of 105-118% based on the mass fraction of P2O5; The unsaturated polyoxyethylene ether monomer is one or more of methyl allyl polyoxyethylene ether with a molecular weight of 2000-4000, isopentanol polyoxyethylene ether with a molecular weight of 3000-4000, 4-hydroxybutyl vinyl polyoxyethylene ether with a molecular weight of 3000-5000, and ethylene glycol monovinyl polyethylene glycol ether with a molecular weight of 3000-6000.

8. The method for preparing the low-sensitivity viscosity-reducing polycarboxylate water-reducing agent according to claim 6, wherein: In step 2, the oxidant is one or more of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate, and the amount thereof is 1-4% of the total molar amount of all unsaturated polymerizable monomers; The reducing agent is one or more of L-ascorbic acid, sodium hypophosphite, sodium bisulfite, and sodium metabisulfite, and its amount is 0.2-1% of the total molar amount of the unsaturated polymerization monomer; The chain transfer agent is one or more of mercaptoethanol, thioglycolic acid, and mercaptopropionic acid, and its usage is 1.6-4.8% of the total molar amount of the unsaturated polymer monomer; The catalyst used in the polymerization reaction is one of ferrous sulfate, ferrous chloride, and cupric chloride, and its amount is 0.006-0.01% of the total molar amount of the unsaturated polymerization monomer; The alkaline neutralizing agent is a sodium hydroxide solution with a mass fraction of 30%.

9. Use of the low-sensitivity viscosity-reducing polycarboxylate water-reducing agent according to any one of claims 1 to 5 in a gel material, characterized in that: The polycarboxylate water-reducing agent is added in an amount of 0.05-0.5% by mass of the total cementitious material, and the amount is pure solid amount.

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