Polycarboxylate-type water reducing agent synthesized at normal temperature and preparation method of polycarboxylic-type water reducing agent

Abstract

The invention relates to the field of preparation of concrete admixtures, in particular to a normal-temperature synthesized polycarboxylate-type water reducer and a preparation method thereof.The polycarboxylate-type water reducer is prepared by reacting raw materials including a bottoming solution and a dropwise adding solution, the bottoming solution comprises vinyl ether macromonomers, esterified macromonomers, a buffer reagent, an oxidizing agent and water, and the dropwise adding solution is prepared by reacting the raw materials including the bottoming solution and the dropwise adding solution. The dropping liquid comprises unsaturated carboxylic acid, an activity regulator, a chain transfer agent, a reducing agent and water; the pH value of the base solution is 7-10; the esterified macromonomer comprises at least one of methoxy polyethylene glycol acrylate and methoxy polyethylene glycol methacrylate, the initial dropwise adding temperature of the polymerization reaction can be increased to 20-40 DEG C, the temperature in the reaction process can be controlled to be lower than or equal to 50 DEG C, and the finally prepared polycarboxylic acid type water reducing agent has the advantages of high water reducing rate, good workability and the like.

Description

Technical Field

[0001] The present application relates to the field of concrete admixture preparation, and more specifically, to a room-temperature synthesized polycarboxylic acid-based water reducer and a preparation method thereof. Background Art

[0002] Since the first generation of conventional water reducers, represented by lignin sulfonates, was introduced in concrete in 1930, they have undergone three major iterations and upgrades, culminating in the development of the third generation of high-performance polycarboxylate-based water reducers, currently the most widely used type of water reducer in commercial concrete. Their comb-shaped molecular structure, with adjustable adsorption groups and polyether side chains, offers advantages such as high molecular structure designability, low dosage, high water reduction rates, and excellent performance. They can significantly reduce cement usage in commercial concrete or improve concrete strength, playing a significant role in promoting green production of commercial concrete and reducing carbon emissions.

[0003] Polyether macromonomers are the main raw materials for polycarboxylic acid-based water reducers, with an annual domestic demand of about 2 million tons. They include allyl polyethylene glycol ether (APEG), 2-methylprop-2-enyl polyethylene glycol ether (HPEG), 3-methylbut-3-enyl polyethylene glycol ether (IPEG), and other polyether macromonomers. Currently, they have developed into the latest generation of polyether macromonomers - vinyl ether macromonomers, including ethyleneoxy polyethylene glycol (EPEG) and ethyleneoxybutyl polyethylene glycol (VPEG), which account for more than 60% of the domestic polyether macromonomer market share.

[0004] Liu Guanjie et al. found that the polymerization activity of vinyl ether macromonomers is higher than that of HPEG and IPEG (Liu Guanjie et al., Study on the conditions and properties of vinyl ether macromonomer EPEG synthesis of polycarboxylic acid water reducer [J]. Concrete, 2021, (5), 61-66). Chinese patent CN 112708045 A reported that VPEG polyether macromonomers were polymerized with unsaturated carboxylic acids, allylamine, acrylamide, etc. to synthesize a low-sensitivity ultra-early-strength polycarboxylic acid water reducer. VPEG macromonomers and cationic groups were introduced into the molecular structure of the water reducer to improve the anti-mud performance and low-sensitivity adaptability of the water reducer. Chinese patent CN 111777725 A reported that EPEG polyether macromonomers were polymerized with unsaturated carboxylic acids, etc. to synthesize a polycarboxylic acid water reducer with excellent dispersion and slump retention properties. Chinese patent CN112480330A reported that EPEG polyether macromonomers were polymerized with unsaturated acids to synthesize a viscosity-reducing polycarboxylic acid water reducer. Patent CN 111808239 A reported that polyether macromonomers such as EPEG-4800A and VPEG-4800 were polymerized with monomers such as acrylic acid to prepare a water reducer with excellent early strength properties.

[0005] The aforementioned patents and literature report the synthesis of polycarboxylic acid-based water-reducing agents (PCAs) by aqueous free radical polymerization of vinyl ether macromonomers (EPEG or VPEG) with monomers such as unsaturated carboxylic acids. These agents exhibit various performance advantages, including anti-mud resistance, low sensitivity, viscosity reduction, early strength, water reduction, and slump retention. However, the application of PCAs also faces the following urgent challenges: First, the polymerization reaction generally begins at low temperatures, around 5-15°C. Second, the short addition time of the unsaturated acid results in a high exotherm during the polymerization reaction, requiring specialized cooling methods to control the temperature. Third, the polymerization reaction equipment cannot be large, requiring auxiliary facilities such as specialized refrigeration units, which limits the promotion and application of these polyether macromonomers among small and medium-sized water-reducing agent manufacturers.

[0006] Based on this, the present application provides a room-temperature synthesis method for a polycarboxylic acid-based water reducer that is technologically advanced, economically feasible, and convenient for industrial mass production. Summary of the Invention

[0007] The present application provides a room-temperature synthesized polycarboxylic acid-based water reducer and a preparation method thereof. The initial dropwise addition temperature of the polymerization reaction described in the present application can be increased to 20-40°C, and the temperature during the reaction process can be controlled to ≤50°C. Conventional circulating water can be used to meet the cooling requirements during the water reducer synthesis process. The polycarboxylic acid-based water reducer finally prepared has performance advantages such as a high water reduction rate and good workability.

[0008] In the first aspect, the present application provides a polycarboxylic acid-based water reducer, which adopts the following technical solution:

[0009] A polycarboxylic acid-based water reducer is prepared by reacting raw materials including a primer and a dropper, wherein the primer comprises a vinyl ether macromonomer, an esterified macromonomer, a buffering agent, an oxidant, and water, and the dropper comprises an unsaturated carboxylic acid, an activity regulator, a chain transfer agent, a reducing agent, and water. The pH value of the primer is 7-10; the esterified macromonomer comprises at least one of methoxy polyethylene glycol acrylate and methoxy polyethylene glycol methacrylate, and the amount of the esterified macromonomer is 1%-5% of the mass of the vinyl ether macromonomer; and the mass ratio of the unsaturated carboxylic acid to the vinyl ether macromonomer is 1:(10-15).

[0010] By adopting the above technical solution, the addition of the activity regulator reduces the polymerization activity of the unsaturated carboxylic acid, while the appropriate pH value can reduce the polymerization activity of the unsaturated carboxylic acid, reduce the activity difference between the unsaturated carboxylic acid and the vinyl ether macromonomer, reduce the effect of the pH value on the double bond of the vinyl ether macromonomer, and improve the conversion rate of the vinyl ether macromonomer; and the introduction of the esterified macromonomer as the third monomer has a good polymerization match with the double bond of the vinyl ether macromonomer, which can improve the conversion rate of the vinyl ether macromonomer and also greatly improve the workability of the water reducer.

[0011] Furthermore, the amount of the oxidizing agent is 0.3% to 1.0% of the total mass of the unsaturated carboxylic acid and the vinyl ether macromonomer; the amount of the activity regulator is 2% to 10% of the mass of the unsaturated carboxylic acid; the amount of the chain transfer agent is 0.2% to 0.8% of the total mass of the unsaturated carboxylic acid and the vinyl ether macromonomer; and the amount of the reducing agent is 0.1% to 0.3% of the total mass of the unsaturated carboxylic acid and the vinyl ether macromonomer.

[0012] Furthermore, the vinyl ether macromonomer includes at least one of EPEG1500, EPEG2500, EPEG3000, EPEG4000, EPEG5000, VPEG1500, VPEG2500, VPEG3000, VPEG4000, and VPEG5000.

[0013] Furthermore, the number average molecular weight of the esterified macromonomer is 200-1000.

[0014] Furthermore, the buffering agent is a sodium salt of a polycarboxylic acid water reducer with a pH value between 8 and 10. Still further, the solid content of the sodium salt of the polycarboxylic acid water reducer is 40%, and the amount used is 5% to 10% of the mass of the vinyl ether macromonomer.

[0015] By adopting the above technical solution, the sodium salt of the polycarboxylic acid-based water-reducing agent with a pH value between 8 and 10 not only has the function of neutralizing unsaturated carboxylic acids, but also has water-reducing properties itself, which can avoid or reduce the adverse effects of liquid alkali neutralization on the performance of the water-reducing agent, thereby making the water-reducing agent have good water-reducing properties.

[0016] Furthermore, the oxidant includes at least one of ammonium persulfate, potassium persulfate, sodium persulfate, and 27.5% hydrogen peroxide.

[0017] Furthermore, the unsaturated carboxylic acid includes at least one of acrylic acid, methacrylic acid, itaconic acid, and itaconic anhydride.

[0018] Furthermore, the activity regulator includes at least one of hydroxymethyl acrylamide, acrylamide, N,N-dimethyl acrylamide, N,N-diethyl acrylamide, dimethylaminopropyl acrylamide, N-phenyl acrylamide, N-benzyl acrylamide, sodium acrylate, sodium methacrylate, and itaconic acid.

[0019] Furthermore, the chain transfer agent includes at least one of thioglycolic acid, mercaptopropionic acid, and mercaptoethanol.

[0020] Furthermore, the reducing agent includes at least one of L-ascorbic acid, bleaching powder, and E51.

[0021] Furthermore, the weight average molecular weight of the water reducer is 20,000 to 60,000.

[0022] By adopting the above technical solution, the water reducer has better water reduction and slump retention effects. If the molecular weight is too large or too small, the conversion rate of the polyether macromonomer or the performance of the water reducer produced will be adversely affected.

[0023] In a second aspect, the present application provides a method for preparing a polycarboxylic acid-based water reducer, which adopts the following technical solution:

[0024] A method for preparing a polycarboxylic acid-based water reducer comprises the following steps:

[0025] Preparation of dropping solution: unsaturated carboxylic acid, activity regulator, water, etc. are prepared in a certain mass ratio to prepare dropping solution A; chain transfer agent, water, etc. are prepared in a certain mass ratio to prepare dropping solution B; reducing agent, water, etc. are prepared in a certain mass ratio to prepare dropping solution C;

[0026] Preparation of primer: Add vinyl ether macromonomer, esterification macromonomer, buffer reagent, oxidant and water according to a certain mass into the reaction device and stir for a certain time to prepare the primer;

[0027] Preparation of water reducer: Solution A, solution B, and solution C are added dropwise to the primer solution of the reaction device within a certain period of time. After the addition is completed, the reaction is continued for 30 to 60 minutes, and the pH value is adjusted to neutral to obtain the finished polycarboxylic acid water reducer.

[0028] Furthermore, in the water reducing agent preparation step, the initial dropwise addition temperature is 20-40° C., and the maximum temperature in the reactor during the dropwise addition and insulation process is ≤50° C. Specifically, the reactor temperature can be controlled using the coils in the reactor and the jacket circulating water.

[0029] Furthermore, in the water reducing agent preparation step, the dropping time of the dropping liquid A is 50 min to 70 min, the dropping time of the dropping liquid B is 50 min to 70 min, and the dropping time of the dropping liquid C is 60 min to 80 min.

[0030] In summary, this application has the following beneficial effects:

[0031] 1. The preparation process of the water-reducing agent of the present application does not require modification of existing synthesis equipment or addition of a refrigeration unit. Traditional circulating water temperature control measures are still used, without increasing the equipment and cooling costs of the polycarboxylic acid-based water-reducing agent synthesized from vinyl ether macromonomers. By introducing an activity regulator into the unsaturated carboxylic acid droplet, the acidity of the unsaturated carboxylic acid is reduced, thereby lowering the polymerization activity of the unsaturated carboxylic acid salt compared to before neutralization. This helps to reduce the problem of self-polymerization of the unsaturated carboxylic acid under conditions of high initial temperatures.

[0032] 2. The water-reducing agent of the present application incorporates an alkaline sodium salt of a polycarboxylate water-reducing agent as a buffering agent into the primer solution, further neutralizing the unsaturated carboxylic acid added dropwise to the reactor to form a salt, thereby reducing the acidity and polymerization activity of the unsaturated carboxylate salt and preventing self-polymerization of the unsaturated carboxylic acid. Furthermore, the use of an alkaline sodium salt of a polycarboxylate water-reducing agent, a buffering agent with water-reducing properties, can avoid the problem of reduced performance of the final water-reducing agent caused by the solid content being occupied by other inorganic bases.

[0033] 3. The present application introduces an esterified macromonomer into the primer. The double bond polymerization activity of the esterified macromonomer is between that of the unsaturated carboxylic acid and the vinyl ether macromonomer, which is more compatible with the double bond polymerization activity of the vinyl ether macromonomer, and helps to improve the monomer conversion rate of the vinyl ether macromonomer. At the same time, the molecular weight of the esterified macromonomer is relatively small, which has a significant effect on improving workability, and can improve the workability of the final prepared polycarboxylic acid water reducer. DETAILED DESCRIPTION

[0034] The present application is further described in detail below with reference to the embodiments.

[0035] In the examples of this application, the molecular weight and molecular weight distribution of the polycarboxylate superplasticizer were determined using a Wyatt Technology Corporation gel permeation chromatography instrument. (Gel column: Shodex SB806 + SB803 columns connected in series; eluent: tetrahydrofuran; mobile phase rate: 1 ml / min; injection volume: 20 μl; sample preparation concentration: 0.5% (g sample / g mobile phase); detector: Shodex RI-71 differential refractive index detector; standard: polyethylene glycol GPC standard (Sigma-Aldrich, molecular weights: 1,010,000, 478,000, 263,000, 118,000, 44,700, 18,600, 6,690, 1,960, 628, 232).

[0036] In the application examples of the present application, unless otherwise specified, the parts described in the examples are specifically parts by mass, and the addition amounts of other materials are converted into parts by mass.

[0037] Example

[0038] The present invention provides a polycarboxylate-based water reducer prepared by reacting a primer containing a vinyl ether macromonomer, an esterified macromonomer, a buffer, an oxidant, and water, and a droplet containing an unsaturated carboxylic acid, an activity regulator, a chain transfer agent, a reducing agent, and water. The primer has a pH of 7 to 10. The water reducer has a weight-average molecular weight of 20,000 to 60,000.

[0039] In the primer, the vinyl ether macromonomer includes at least one of EPEG1500, EPEG2500, EPEG3000, EPEG4000, EPEG5000, VPEG1500, VPEG2500, VPEG3000, VPEG4000, and VPEG5000.

[0040] The esterified macromonomer includes at least one of methoxy polyethylene glycol acrylate and methoxy polyethylene glycol methacrylate. The amount of the esterified macromonomer is 1%-5% of the mass of the vinyl ether macromonomer. The number average molecular weight of the esterified macromonomer is 200-1000.

[0041] The buffering agent is a sodium salt of a polycarboxylic acid water reducer with a pH value between 8 and 10. Furthermore, the solid content of the sodium salt of the polycarboxylic acid water reducer is 40%, and the amount used is 5% to 10% of the mass of the vinyl ether macromonomer.

[0042] The oxidant comprises at least one of ammonium persulfate, potassium persulfate, sodium persulfate, and 27.5% hydrogen peroxide. The amount of the oxidant used is 0.3% to 1.0% of the total mass of the unsaturated carboxylic acid and the vinyl ether macromonomer.

[0043] In the dropwise addition liquid, the unsaturated carboxylic acid includes at least one of acrylic acid, methacrylic acid, itaconic acid, and itaconic anhydride. The mass ratio of the unsaturated carboxylic acid to the vinyl ether macromonomer is 1:(10-15).

[0044] The activity regulator includes at least one of hydroxymethyl acrylamide, acrylamide, N,N-dimethyl acrylamide, N,N-diethyl acrylamide, dimethylaminopropyl acrylamide, N-phenyl acrylamide, N-benzylacrylamide, sodium acrylate, sodium methacrylate, and itaconic acid. The amount of the activity regulator is 2% to 10% by weight of the unsaturated carboxylic acid.

[0045] The chain transfer agent comprises at least one of mercaptoacetic acid, mercaptopropionic acid and mercaptoethanol, and the amount of the chain transfer agent is 0.2% to 0.8% of the total mass of the unsaturated carboxylic acid and the vinyl ether macromonomer.

[0046] The reducing agent comprises at least one of L-ascorbic acid, bleaching agent and E51. The amount of the reducing agent is 0.1% to 0.3% of the total mass of the unsaturated carboxylic acid and the vinyl ether macromonomer.

[0047] In a second aspect, the present application provides a method for preparing a polycarboxylic acid-based water reducer, which adopts the following technical solution:

[0048] A method for preparing a polycarboxylic acid-based water reducer comprises the following steps:

[0049] Preparation of dropping solution: unsaturated carboxylic acid, activity regulator, water, etc. are prepared in a certain mass ratio to prepare dropping solution A; chain transfer agent, water, etc. are prepared in a certain mass ratio to prepare dropping solution B; reducing agent, water, etc. are prepared in a certain mass ratio to prepare dropping solution C;

[0050] Preparation of primer: Add vinyl ether macromonomer, esterification macromonomer, buffer reagent, oxidant and water according to a certain mass into the reaction device and stir for a certain time to prepare the primer;

[0051] Preparation of water reducer: Solution A, solution B, and solution C are added dropwise to the primer solution of the reaction device within a certain period of time. After the addition is completed, the reaction is continued for 30 to 60 minutes, and the pH value is adjusted to neutral to obtain the finished polycarboxylic acid water reducer.

[0052] Specifically, after mixing the unsaturated carboxylic acid and the activity regulator, water is added to dilute the mixture to a 40-60% aqueous solution, preferably 50% in this embodiment. The chain transfer agent is diluted with water to a 20-30% aqueous solution. The reducing agent is diluted with water to a 2-5% aqueous solution. The vinyl ether macromonomer is diluted with deionized water to a 40-60% aqueous solution.

[0053] Furthermore, in the primer preparation step of this application, a stainless steel reactor equipped with mechanical stirring, internal coils, and jacketed heat exchange can be used. The single reactor can produce between 10 tons and 30 tons of water-reducing agent mother liquor. The raw materials are added to the reactor according to the set mass concentration, and the mechanical stirring is turned on and stirred for 30 minutes to ensure that the polyether macromonomer and water are fully mixed and dissolved.

[0054] Furthermore, in the water reducing agent preparation step, the initial dropwise addition temperature is 20-40° C., and the maximum temperature in the reactor during the dropwise addition and insulation process is ≤50° C. Specifically, the reactor temperature can be controlled using the coil inside the reactor and the jacket circulating water.

[0055] Furthermore, in the water reducing agent preparation step, the dropping time of the dropping liquid A is 50 min to 70 min, the dropping time of the dropping liquid B is 50 min to 70 min, and the dropping time of the dropping liquid C is 60 min to 80 min.

[0056] Furthermore, after the addition of dropwise liquids A, B and C is completed, the reaction is continued for 50 to 60 minutes, and liquid alkali with a solid content of 32% is added to neutralize the reaction system to a pH of about 7 to obtain a colorless or light brown polycarboxylate water-reducing agent product.

[0057] The following is an explanation through specific examples.

[0058] Example 1

[0059] Preparation of the dropping solution: Weigh 10.0 parts of acrylic acid and 0.2 parts of hydroxymethyl acrylamide, add water to dilute to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.22 parts of thioglycolic acid, add water to dilute to a 20% aqueous solution, referred to as Dropping Solution B; weigh 0.11 parts of L-ascorbic acid, add water to dilute to a 2% aqueous solution, referred to as Dropping Solution C;

[0060] Weigh 100 parts of EPEG-5000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 40% aqueous solution. Then, weigh 10.0 parts of sodium salt of a polycarboxylic acid-based water reducer (pH = 8), 5.0 parts of methoxy polyethylene glycol acrylate (Mn = 200), and 0.33 parts of hydrogen peroxide (27.5%) into the reaction apparatus, achieving a final pH of 7.5. Turn on the mechanical agitator and circulating water in the reaction apparatus, maintain the reaction temperature at 20°C, set the addition time for solutions A and B to 50 minutes, and set the addition time for solution C to 60 minutes. Maintain the reaction temperature at ≤40°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-1. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 93.15%, the weight average molecular weight (Mw) was 58760, and the molecular weight distribution (PDI) was 1.55.

[0061] Example 2

[0062] Preparation of dropping solution: Weigh 6.7 parts of acrylic acid and 0.67 parts of acrylamide, add water to dilute to a 50% aqueous solution, called dropping solution A; weigh 0.85 parts of mercaptopropionic acid, add water to dilute to a 30% aqueous solution, called dropping solution B; weigh 0.32 parts of bleaching powder, add water to dilute to a 5% aqueous solution, called dropping solution C;

[0063] Weigh 100 parts of EPEG-1500 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 55% aqueous solution. Sequentially weigh 5.0 parts of polycarboxylic acid-based water reducer sodium salt (pH = 10), 1.0 part of methoxy polyethylene glycol acrylate (Mn = 1000), and 1.07 parts of ammonium persulfate and add them to the reaction apparatus. The final pH of the primer solution is 9.5. Turn on the mechanical stirring device and circulating water of the reaction apparatus. Control the reaction system temperature at 40°C. Set the addition time of dropwise addition solutions A and B to 60 minutes, and the addition time of dropwise addition solution C to 70 minutes. Maintain the reaction temperature ≤ 50°C during the addition process. After the addition was completed, the reaction was continued by keeping warm for 60 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-2. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 94.28%, the weight average molecular weight (Mw) was 20760, and the molecular weight distribution (PDI) was 1.75.

[0064] Example 3

[0065] Preparation of the dropping solution: Weigh 6.0 parts of acrylic acid, 3.0 parts of methacrylic acid, and 0.67 parts of N,N-dimethylacrylamide, and dilute with water to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.55 parts of mercaptoethanol, and dilute with water to a 25% aqueous solution, referred to as Dropping Solution B; weigh 0.22 parts of E51, and dilute with water to a 3% aqueous solution, referred to as Dropping Solution C;

[0066] Weigh 100 parts of VPEG-3000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 45% aqueous solution. Then, weigh 8.0 parts of sodium salt of a polycarboxylic acid-based water reducer (pH = 9), 3.5 parts of methoxy polyethylene glycol acrylate (Mn = 800), and 0.78 parts of sodium persulfate. The final pH of the primer solution was 8. Turn on the mechanical agitator and circulating water in the reaction apparatus. Maintain the reaction temperature at 30°C. Set the addition time for solutions A and B to 70 minutes, and the addition time for solution C to 80 minutes. Maintain the reaction temperature at ≤40°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-3. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 92.75%, the weight average molecular weight (Mw) was 32492, and the molecular weight distribution (PDI) was 1.63.

[0067] Example 4

[0068] Preparation of the dropping solution: Weigh 5.0 parts of acrylic acid, 2.5 parts of itaconic acid, and 0.61 parts of N-phenylacrylamide, and dilute with water to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.55 parts of mercaptoethanol, and dilute with water to a 25% aqueous solution, referred to as Dropping Solution B; weigh 0.28 parts of L-ascorbic acid, and dilute with water to a 4% aqueous solution, referred to as Dropping Solution C;

[0069] Weigh 100 parts of VPEG-2500 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 60% aqueous solution. Then, weigh 6.0 parts of sodium salt of a polycarboxylic acid-based water reducer (pH = 8), 2.5 parts of methoxy polyethylene glycol acrylate (Mn = 600), and 0.45 parts of potassium persulfate and add them to the reaction apparatus. The final pH of the primer solution is 7.5. Turn on the mechanical stirring device and circulating water in the reaction apparatus. The reaction system temperature is controlled at 25°C. Set the addition time of dropwise addition solutions A and B to 55 minutes, and the addition time of dropwise addition solution C to 65 minutes. During the addition, the reaction temperature is maintained at ≤40°C. After the addition was completed, the reaction was continued by keeping warm for 60 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-4. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 93.95%, the weight average molecular weight (Mw) was 38182, and the molecular weight distribution (PDI) was 1.67.

[0070] Example 5

[0071] Preparation of the dropping solution: Weigh 4.0 parts of acrylic acid, 2.0 parts of methacrylic acid, 3.0 parts of itaconic anhydride, and 0.48 parts of sodium acrylate, and dilute with water to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.44 parts of mercaptopropionic acid, and dilute with water to a 20% aqueous solution, referred to as Dropping Solution B; weigh 0.17 parts of L-ascorbic acid, and dilute with water to a 3% aqueous solution, referred to as Dropping Solution C;

[0072] Weigh 100 parts of EPEG-4000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 50% aqueous solution. Then, weigh 8.0 parts of polycarboxylic acid-based water reducer sodium salt (pH = 10), 1.5 parts of methoxy polyethylene glycol acrylate (Mn = 400), and 0.72 parts of ammonium persulfate and add them to the reaction apparatus, achieving a final pH of 9. Turn on the mechanical agitator and circulating water in the reaction apparatus. Maintain the reaction temperature at 20°C. Set the addition time for solutions A and B to 60 minutes, and the addition time for solution C to 70 minutes. Maintain the reaction temperature at ≤40°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-5. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 95.19%, the weight average molecular weight (Mw) was 45739, and the molecular weight distribution (PDI) was 1.59.

[0073] Example 6

[0074] Preparation of the dropping solution: Weigh 4.0 parts of acrylic acid, 4.0 parts of methacrylic acid, and 0.73 parts of sodium itaconate, and dilute with water to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.75 parts of mercaptopropionic acid, and dilute with water to a 25% aqueous solution, referred to as Dropping Solution B; weigh 0.23 parts of L-ascorbic acid, and dilute with water to a 2% aqueous solution, referred to as Dropping Solution C;

[0075] Weigh 100 parts of VPEG-5000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 45% aqueous solution. Then, weigh 6.0 parts of sodium salt of a polycarboxylic acid-based water reducer (pH = 10), 4.0 parts of methoxy polyethylene glycol acrylate (Mn = 500), and 0.60 parts of hydrogen peroxide (27.5%) into the reaction apparatus, achieving a final pH of 8.5. Turn on the mechanical agitator and circulating water in the reaction apparatus, maintain the reaction temperature at 35°C, set the addition time for solutions A and B to 55 minutes, and set the addition time for solution C to 65 minutes. Maintain the reaction temperature at ≤40°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-6. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 93.76%, the weight average molecular weight (Mw) was 27745, and the molecular weight distribution (PDI) was 1.61.

[0076] Comparative Example

[0077] Comparative Example 1

[0078] Preparation of the dropping solution: Weigh 7.5 parts of acrylic acid and dilute it with water to a 50% aqueous solution, referred to as Dropping Solution A; weigh 1.63 parts of thioglycolic acid and dilute it with water to a 25% aqueous solution, referred to as Dropping Solution B; weigh 0.2 parts of E51 and dilute it with water to a 4% aqueous solution, referred to as Dropping Solution C;

[0079] Weigh 100 parts of EPEG-6000 polyether macromonomer in a reaction apparatus, add 150 parts of water, and prepare an aqueous solution with a mass concentration of 30%. Weigh 0.75 parts of hydrogen peroxide (27.5%) and add it to the reaction apparatus. Turn on the mechanical stirring device and circulating water of the reaction apparatus, control the temperature of the reaction system at 25°C, set the dropping time of liquid A and B to 50min, set the dropping time of liquid C to 60min, and control the reaction temperature ≤40°C during the dropping process. After the addition is completed, continue to keep warm and react for 50min. After the reaction is completed, use 32% liquid alkali to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which is the finished product of the polycarboxylate water reducer, recorded as PCE-7. After GPC testing, the conversion rate of vinyl ether macromonomer is 88.54%, the weight average molecular weight (Mw) is 17374, and the molecular weight distribution (PDI) is 1.46.

[0080] Comparative Example 2

[0081] Preparation of the dropping solution: Weigh 12.5 parts of acrylic acid and 1.1 parts of 32% liquid caustic soda, add water to dilute to a 50% aqueous solution, called dropping solution A; weigh 0.56 parts of mercaptopropionic acid, add water to dilute to a 20% aqueous solution, called dropping solution B; weigh 0.21 parts of L-ascorbic acid, add water to dilute to a 5% aqueous solution, called dropping solution C;

[0082] Weigh 100 parts of VPEG-1000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 45% aqueous solution. Then, weigh 3.0 parts of 32% liquid caustic soda, 3.8 parts of methoxy polyethylene glycol acrylate (Mn=900), and 0.82 parts of 27.5% hydrogen peroxide solution and add them to the reaction apparatus. Turn on the mechanical agitator and circulating water in the reaction apparatus. Control the reaction temperature at 30°C. Set the addition time for solutions A and B to 30 minutes, and the addition time for solution C to 60 minutes. Maintain the reaction temperature at ≤45°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-8. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 86.91%, the weight average molecular weight (Mw) was 34942, and the molecular weight distribution (PDI) was 1.64.

[0083] Comparative Example 3

[0084] Preparation of the dropping solution: Weigh 7.5 parts of acrylic acid, 0.71 parts of acrylamide, and 2.8 parts of methoxy polyethylene glycol acrylate (Mn=700), and dilute with water to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.69 parts of mercaptoethanol, and dilute with water to a 30% aqueous solution, referred to as Dropping Solution B; weigh 0.19 parts of L-ascorbic acid, and dilute with water to a 5% aqueous solution, referred to as Dropping Solution C;

[0085] 100 parts of EPEG-2500 polyether macromonomer were weighed into a reaction apparatus and 150 parts of water were added to prepare an aqueous solution with a mass concentration of 45%. 6.5 parts of sodium salt of polycarboxylic acid water reducer (pH = 3) and 0.82 parts of hydrogen peroxide (27.5%) were weighed and added to the reaction apparatus in sequence. The mechanical stirring device and circulating water of the reaction apparatus were turned on, the temperature of the reaction system was controlled at 25°C, the addition time of dropwise addition liquids A and B was set to 90 minutes, and the addition time of dropwise addition liquid C was set to 90 minutes. During the addition process, the reaction temperature was controlled to ≤40°C. After the addition was completed, the reaction was continued to be kept warm for 60 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylic acid water reducer, recorded as PCE-9. GPC test showed that the conversion rate of vinyl ether macromonomer was 87.65%, the weight average molecular weight (Mw) was 28994, and the molecular weight distribution (PDI) was 1.68.

[0086] Comparative Example 4

[0087] Preparation of the dropping solution: Weigh 10.0 parts of acrylic acid and 0.88 parts of 32% liquid caustic soda, add water to dilute to a 50% aqueous solution, referred to as dropping solution A; weigh 0.22 parts of thioglycolic acid, add water to dilute to a 20% aqueous solution, referred to as dropping solution B; weigh 0.11 parts of L-ascorbic acid, add water to dilute to a 2% aqueous solution, referred to as dropping solution C;

[0088] Weigh 100 parts of EPEG-5000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 40% aqueous solution. Then, weigh 10.0 parts of sodium salt of a polycarboxylic acid-based water reducer (pH = 8), 5.0 parts of methoxy polyethylene glycol acrylate (Mn = 200), and 0.33 parts of hydrogen peroxide (27.5%) into the reaction apparatus. Turn on the mechanical agitator and circulating water in the reaction apparatus. Maintain the reaction temperature at 20°C. Set the addition time for solutions A and B to 50 minutes, and the addition time for solution C to 60 minutes. Maintain the reaction temperature at ≤40°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-10. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 91.15%, the weight average molecular weight (Mw) was 42640, and the molecular weight distribution (PDI) was 1.51.

[0089] Comparative Example 5

[0090] Preparation of the dropping solution: Weigh 10.0 parts of acrylic acid and 0.2 parts of hydroxymethyl acrylamide, add water to dilute to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.22 parts of thioglycolic acid, add water to dilute to a 20% aqueous solution, referred to as Dropping Solution B; weigh 0.11 parts of L-ascorbic acid, add water to dilute to a 2% aqueous solution, referred to as Dropping Solution C;

[0091] Weigh 100 parts of EPEG-5000 polyether macromonomer into a reaction apparatus, add 150 parts of water to prepare an aqueous solution with a mass concentration of 40%. Weigh 10.0 parts of sodium salt of polycarboxylic acid water reducer (pH = 8) and 0.33 parts of hydrogen peroxide (27.5%) and add them to the reaction apparatus in sequence. Turn on the mechanical stirring device and circulating water of the reaction apparatus, control the temperature of the reaction system at 20°C, set the dropwise addition time of liquids A and B to 50 minutes, set the dropwise addition time of liquid C to 60 minutes, and control the reaction temperature ≤40°C during the dropwise addition process. After the dropwise addition is completed, continue to keep warm and react for 50 minutes. After the reaction is completed, use 32% liquid caustic soda to adjust the polymerization system pH to 7 to obtain a light yellow liquid with a certain viscosity, which is the finished polycarboxylic acid water reducer, recorded as PCE-11. GPC test shows that the conversion rate of vinyl ether macromonomer is 92.12%, the weight average molecular weight (Mw) is 46620, and the molecular weight distribution (PDI) is 1.5.

[0092] Comparative Example 6

[0093] Preparation of the dropping solution: Weigh 10.0 parts of acrylic acid and 0.2 parts of hydroxymethyl acrylamide, add water to dilute to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.22 parts of thioglycolic acid, add water to dilute to a 20% aqueous solution, referred to as Dropping Solution B; weigh 0.11 parts of L-ascorbic acid, add water to dilute to a 2% aqueous solution, referred to as Dropping Solution C;

[0094] Weigh 100 parts of EPEG-5000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 40% aqueous solution. Then, weigh 10.0 parts of sodium salt of a polycarboxylic acid-based water reducer (pH = 8), 5.0 parts of methyl allyl alcohol polyoxyethylene ether (Mn = 1000), and 0.33 parts of hydrogen peroxide (27.5%) into the reaction apparatus. Turn on the mechanical agitator and circulating water in the reaction apparatus. Maintain the reaction temperature at 20°C. Set the addition time for solutions A and B to 50 minutes, and the addition time for solution C to 60 minutes. Maintain the reaction temperature at ≤40°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-12. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 92.65%, the weight average molecular weight (Mw) was 50760, and the molecular weight distribution (PDI) was 1.53.

[0095] Comparative Example 7

[0096] Preparation of the dropping solution: Weigh 10.0 parts of acrylic acid and 0.2 parts of hydroxymethyl acrylamide, add water to dilute to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.22 parts of thioglycolic acid, add water to dilute to a 20% aqueous solution, referred to as Dropping Solution B; weigh 0.11 parts of L-ascorbic acid, add water to dilute to a 2% aqueous solution, referred to as Dropping Solution C;

[0097] Weigh 100 parts of EPEG-5000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 40% aqueous solution. Then, weigh 10.0 parts of sodium salt of a polycarboxylic acid-based water reducer (pH = 8), 10.0 parts of methoxy polyethylene glycol acrylate (Mn = 200), and 0.33 parts of hydrogen peroxide (27.5%) into the reaction apparatus. Turn on the mechanical agitator and circulating water in the reaction apparatus. Maintain the reaction temperature at 20°C. Set the addition time for solutions A and B to 50 minutes, and the addition time for solution C to 60 minutes. Maintain the reaction temperature at ≤40°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-13. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 92.01%, the weight average molecular weight (Mw) was 62450, and the molecular weight distribution (PDI) was 1.67.

[0098] Comparative Example 8:

[0099] Preparation of the dropping solution: Weigh 10.0 parts of acrylic acid and 0.2 parts of hydroxymethyl acrylamide, add water to dilute to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.22 parts of thioglycolic acid, add water to dilute to a 20% aqueous solution, referred to as Dropping Solution B; weigh 0.11 parts of L-ascorbic acid, add water to dilute to a 2% aqueous solution, referred to as Dropping Solution C;

[0100] Weigh 100 parts of EPEG-5000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 40% aqueous solution. Then, weigh 10.0 parts of a polycarboxylic acid-based water reducer (pH = 3), 5.0 parts of methoxy polyethylene glycol acrylate (Mn = 200), and 0.33 parts of 27.5% hydrogen peroxide solution and add them to the reaction apparatus. Turn on the mechanical agitator and circulating water in the reaction apparatus. Maintain the reaction temperature at 20°C. Set the addition time for solutions A and B to 50 minutes, and the addition time for solution C to 60 minutes. Maintain the reaction temperature at ≤40°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-14. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 89.18%, the weight average molecular weight (Mw) was 39730, and the molecular weight distribution (PDI) was 1.44.

[0101] Comparative Example 9

[0102] Preparation of the dropping solution: Weigh 10.0 parts of acrylic acid and 0.2 parts of hydroxymethyl acrylamide, add water to dilute to a 50% aqueous solution, referred to as Dropping Solution A; weigh 0.22 parts of thioglycolic acid, add water to dilute to a 20% aqueous solution, referred to as Dropping Solution B; weigh 0.11 parts of L-ascorbic acid, add water to dilute to a 2% aqueous solution, referred to as Dropping Solution C;

[0103] Weigh 100 parts of EPEG-5000 polyether macromonomer into a reaction apparatus and add 150 parts of water to prepare a 40% aqueous solution. Then, weigh 10.0 parts of sodium salt of a polycarboxylic acid-based water reducer (pH = 8), 5.0 parts of methoxy polyethylene glycol acrylate (Mn = 200), and 0.33 parts of hydrogen peroxide (27.5%) into the reaction apparatus. Turn on the mechanical agitator and circulating water in the reaction apparatus. Control the reaction system temperature at 45°C. Set the addition time for solutions A and B to 50 minutes, and the addition time for solution C to 60 minutes. Maintain the reaction temperature at ≤60°C during the additions. After the addition was completed, the reaction was continued by keeping warm for 50 minutes. After the reaction was completed, 32% liquid caustic soda was used to adjust the pH of the polymerization system to 7 to obtain a light yellow liquid with a certain viscosity, which was the finished polycarboxylate water-reducing agent, recorded as PCE-15. GPC testing showed that the conversion rate of the vinyl ether macromonomer was 86.23%, the weight average molecular weight (Mw) was 29860, and the molecular weight distribution (PDI) was 1.45.

[0104] Application Examples

[0105] In the application examples, unless otherwise specified, the cement used is ordinary Portland cement (PO 42.5). Referring to GB / T8077-2000, the water reducer prepared in this application is added to the cement and stirred evenly.

[0106] Performance testing

[0107] The test temperature was controlled at 25±5°C. The cement paste fluidity test was conducted according to the method specified in GB / T8077-2000, "Test Method for Homogeneity of Concrete Admixtures." Comparative Examples 1-9 and PCE-6C, a commercially available polycarboxylate superplasticizer synthesized at low temperature using vinyl ether macromonomers, were used as comparison samples. The cement paste fluidity test was performed on a flat glass plate using 300g of cement and 87g of water. The fluidity of the cement paste was measured after 60 and 120 minutes. The test results are shown in Table 1.

[0108] Table 1 Cement paste fluidity test results

[0109]

[0110] The results in Table 1 show that, compared to Comparative Examples 1-3, the water-reducing agent samples PCE-1 to PCE-6 prepared by the room-temperature synthesis method of the polycarboxylate water-reducing agent of the present application exhibit better initial flow properties and slump retention. The neat slurry rotational viscosity is also significantly lower than that of Comparative Examples 1-3 and the commercially available PCE-6C, demonstrating a significant improvement in workability. These test results demonstrate that the room-temperature synthesis method of the polycarboxylate water-reducing agent of the present application effectively addresses the problem of requiring low-temperature control when synthesizing polycarboxylate water-reducing agents using vinyl ether macromonomers as raw materials. Both the initial dropwise addition temperature and the maximum temperature can be controlled directly using conventional circulating water, demonstrating significant technological advancement and innovation.

[0111] Furthermore, the performance of comparative examples 4 to 9 is analyzed. Among them, comparative example 4 does not use the active regulator of the present application, but uses liquid alkali instead; comparative example 5 does not use the esterified macromonomer; comparative example 6 uses methyl allyl alcohol polyoxyethylene ether (Mn=1000) instead of the esterified macromonomer of the present application; comparative example 7 increases the amount of the esterified macromonomer to 10 parts, and the esterified macromonomer is excessive; comparative example 8 adds a polycarboxylic acid water reducer with too low a pH value; comparative example 9 adds it at too high a temperature. Its slump retention performance has decreased to varying degrees, and its net slurry rotation viscosity is too large, and its workability has decreased. This shows that in the technical solution of the present application, the reason why an excellent performance water reducer can be obtained under normal temperature synthesis conditions is that each raw material component is very important. This is because the initial dropwise addition temperature of traditional C6 polyether synthetic water reducers is between 0-15°C, and the maximum reaction temperature is ≤25°C. The reasons for the stringent control of reaction temperature are: first, as the reaction temperature increases, the difference in the double bond polymerization activity of C6 polyether and the double bond polymerization activity of unsaturated carboxylic acid increases, and acrylic acid homopolymerization causes the C6 polyether conversion rate to decrease; second, under acidic conditions, the double bond of C6 polyether is unstable and easily destroyed under acidic conditions above 30°C, causing the polyether monomer to lose its double bond and be unable to polymerize. The present application reduces the polymerization activity of unsaturated carboxylic acid by using an activity regulator, while also reducing the polymerization activity of unsaturated carboxylic acid, reducing the activity difference between unsaturated carboxylic acid and vinyl ether macromonomer, reducing the effect of pH on the double bond of vinyl ether macromonomer, and improving the conversion rate of vinyl ether macromonomer; and introducing an esterified macromonomer as the third monomer. The double bond of the esterified macromonomer has good polymerization compatibility with the double bond of the vinyl ether macromonomer, which can improve the conversion rate of the vinyl ether macromonomer and also greatly improve the workability of the water reducer.

[0112] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A polycarboxylic acid water reducer, characterized in that: The invention is prepared by reacting raw materials including a primer liquid and a dropping liquid, wherein the primer liquid includes a vinyl ether macromonomer, an esterification macromonomer, a buffering agent, an oxidant and water, and the dropping liquid includes an unsaturated carboxylic acid, an activity regulator, a chain transfer agent, a reducing agent and water; the pH value of the primer liquid is 7-10; the esterification macromonomer includes at least one of methoxy polyethylene glycol acrylate and methoxy polyethylene glycol methacrylate, and the amount of the esterification macromonomer is 1%-5% of the mass of the vinyl ether macromonomer; and the mass ratio of the unsaturated carboxylic acid to the vinyl ether macromonomer is 1:(10-15).

2. A polycarboxylate water reducer according to claim 1, characterized in that: The amount of the oxidizing agent is 0.3% to 1.0% of the total mass of the unsaturated carboxylic acid and the vinyl ether macromonomer; the amount of the activity regulator is 2% to 10% of the mass of the unsaturated carboxylic acid; the amount of the chain transfer agent is 0.2% to 0.8% of the total mass of the unsaturated carboxylic acid and the vinyl ether macromonomer; and the amount of the reducing agent is 0.1% to 0.3% of the total mass of the unsaturated carboxylic acid and the vinyl ether macromonomer.

3. A polycarboxylic acid water reducer according to claim 1, characterized in that: The vinyl ether macromonomer includes at least one of EPEG1500, EPEG2500, EPEG3000, EPEG4000, EPEG5000, VPEG1500, VPEG2500, VPEG3000, VPEG4000, and VPEG5000.

4. A polycarboxylic acid water reducer according to claim 1, characterized in that: The number average molecular weight of the esterified macromonomer is 200-1000.

5. A polycarboxylate water reducer according to claim 1, characterized in that: The buffer agent is a sodium salt of a polycarboxylic acid water reducer with a pH value between 8 and 10.

6. A polycarboxylic acid water reducer according to claim 1, characterized in that: The unsaturated carboxylic acid includes at least one of acrylic acid, methacrylic acid, itaconic acid, and itaconic anhydride.

7. A polycarboxylic acid water reducer according to claim 1, characterized in that: The activity regulator includes at least one of hydroxymethyl acrylamide, acrylamide, N,N-dimethyl acrylamide, N,N-diethyl acrylamide, dimethylaminopropyl acrylamide, N-phenyl acrylamide, N-benzylacrylamide, sodium acrylate, sodium methacrylate, and itaconic acid.

8. The polycarboxylate water reducer according to claim 1, characterized in that: The weight average molecular weight of the water reducer is 20,000 to 60,000.

9. A method for preparing the polycarboxylic acid water reducer according to any one of claims 1 to 8, characterized in that: The following steps are involved: Preparation of dropping solution: unsaturated carboxylic acid, activity regulator, water, etc. are prepared in a certain mass ratio to prepare dropping solution A; chain transfer agent, water, etc. are prepared in a certain mass ratio to prepare dropping solution B; reducing agent, water, etc. are prepared in a certain mass ratio to prepare dropping solution C; Preparation of primer: Add vinyl ether macromonomer, esterification macromonomer, buffer reagent, oxidant and water according to a certain mass into the reaction device and stir for a certain time to prepare the primer; Preparation of water reducer: Solution A, solution B, and solution C are added dropwise to the primer solution of the reaction device within a certain period of time. The initial dropping temperature is 20-40°C. The maximum temperature in the reactor during the dropping process and the insulation process is ≤50°C. After the dropping is completed, the reaction is continued for 30-60 minutes. The pH value is adjusted to neutral to obtain the finished polycarboxylic acid water reducer.

10. The method for preparing the polycarboxylic acid water reducer according to claim 9, characterized in that: In the water reducing agent preparation step, the dropping time of the dropping liquid A is 50 min to 70 min, the dropping time of the dropping liquid B is 50 min to 70 min, and the dropping time of the dropping liquid C is 60 min to 80 min.

Images