A quick-adsorbing water-resisting hydration product covering type water reducing agent and a preparation method thereof

Abstract

This invention proposes a fast-adsorption, hydration-product-resistant water-reducing agent and its preparation method, belonging to the field of concrete admixture preparation technology. This invention uses a polyether macromonomer, acrylic acid, long-branched functional monomer a, and long-branched functional monomer b to prepare a copolymer via free radical polymerization. Long-branched functional monomer a is modified allyl epoxy ether sodium phosphate with a weight-average molecular weight of 10,000-14,000 g / mol; its phosphate groups preferentially adsorb onto the surface of cement particles, and the long branching delays the covering of hydration products. Long-branched functional monomer b is a copolymer of hydroxyethyl acrylate, hydroxypropyl acrylate, and allyl mercaptoacetate with a weight-average molecular weight of 8,000-12,000 g / mol, providing a large number of ester groups, which hydrolyze under alkaline conditions to produce secondary dispersion. The water-reducing agent of this invention can be rapidly adsorbed, with no loss of slump within 2 hours and no significant increase, significantly improving the workability of concrete, reducing the dosage of water-reducing agent, and improving early and late strength. It is suitable for general-purpose silicate cement with high fineness and high admixture content.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture preparation technology, and particularly relates to a fast-adsorption, water-resistant product-covering water-reducing agent and its preparation method. Background Technology

[0002] Polycarboxylate superplasticizers are widely used in concrete due to their high water reduction rate, high adjustability, and environmental friendliness. However, their compatibility with raw materials has long been a challenge for industry professionals. Cement is a crucial component of concrete and the most significant factor affecting the water-reducing and dispersing properties of polycarboxylate superplasticizers. Ordinary Portland cement is a hydraulic cementitious material mainly composed of raw materials containing CaO, SiO2, Al2O3, and Fe2O3 in a specific ratio, produced through a process of "two grindings and one firing." Its chemical composition, specific surface area, and particle morphology all influence its compatibility with polycarboxylate superplasticizers. On June 1, 2024, with the formal implementation of the mandatory national standard GB175-2023 "General Portland Cement", limestone powder can be used as a main admixture and alternative admixture in cement products. The proportion of cement clinker made primarily from industrial solid wastes such as blast furnace slag and fly ash is increasing. Furthermore, the cement industry is accelerating its transformation towards low-carbon and environmentally friendly practices. Under cost pressures, cement plants typically increase the fineness of cement to improve its early strength, allowing for the incorporation of more admixtures and significantly reducing raw material and overall production costs. However, excessively fine cement leads to abnormally rapid hydration in the early stages. Conventional polycarboxylate superplasticizers cannot adsorb onto the surface of cement particles in time before being covered by cement hydration products, resulting in poor early water-reducing effects, increased dosage, and rapid slump loss. However, as cement hydration progresses, the admixtures used in cement cannot consume the free polycarboxylate superplasticizer in time during the later stages of hydration, which can lead to excessive bleeding and segregation in the concrete, seriously affecting the normal pouring of concrete and the quality of the project.

[0003] To address the aforementioned contradictions, existing technologies have attempted to improve adsorption rates by introducing phosphate groups or to achieve sustained-release dispersion by adding ester functional monomers. However, these approaches often suffer from trade-offs: if adsorption is too rapid and ester hydrolysis is insufficient, subsequent dispersion compensation is inadequate, resulting in slump loss (e.g., patent CN114478939A); if there are too many ester groups or the branches are too short, early adsorption may be hindered or excessive hydrolysis may occur later, leading to adverse reactions (e.g., patent CN114478939A). Furthermore, most conventional functional monomers have relatively small molecular weights (typically hundreds to thousands), providing limited steric hindrance, making it difficult to effectively delay the coverage of adsorbed water-reducing agent molecules by hydration products (e.g., patent CN114989367A). Therefore, there is an urgent need to develop a water-reducing agent that can quickly anchor to the surface of cement particles, delay the coverage of hydration products, and continuously provide appropriate dispersion compensation in the mid-to-late stages, to meet the application requirements of high-fineness cement with high blended content under the new national standard.

[0004] Therefore, the preparation of a fast-adsorption, water-resistant, product-resistant, and coating-type water-reducing agent to adapt to the changes in the composition of cement under the new national standard is of great significance for the application and development of polycarboxylate water-reducing agents in concrete. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a fast-adsorption, water-resistant product-covering water-reducing agent and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a fast-adsorbing, water-resistant, product-coating water-reducing agent, wherein the water-reducing agent is a copolymer prepared by free radical polymerization of raw materials containing the following monomers: Polyether macromonomer, acrylic acid, long-branched functional monomer a and long-branched functional monomer b; The long-branched functional monomer a is modified allyl epoxy ether sodium phosphate, with a weight-average molecular weight of 10,000 to 14,000 g / mol. The long-branched functional monomer b is a copolymer obtained by copolymerizing hydroxyethyl acrylate, hydroxypropyl acrylate and allyl mercaptoacetate, with a weight-average molecular weight of 8000~12000 g / mol.

[0007] Furthermore, the polyether macromonomer is isopentenyl alcohol polyoxyethylene ether.

[0008] Furthermore, the amounts of each raw material, by weight, are as follows: 300-400 parts of polyether macromonomer 65 parts acrylic acid 40-60 parts of long-branched functional monomer a 30-50 parts of long-branched functional monomer b.

[0009] Furthermore, the preparation method of the long-branched functional monomer a includes the following steps: By weight, 800-1000 parts of allyl glycidyl ether, 2-5 parts of hydroquinone and 2-4 parts of toluene were added to the reactor, heated to 50-70°C, and phosphoric acid aqueous solution was slowly added dropwise with stirring. After the addition was completed, the temperature was maintained for 60 minutes. After cooling, the pH was adjusted to 7-8, the solvent was removed, and the mixture was filtered to obtain the long-branched functional monomer a.

[0010] Furthermore, the preparation method of the long-branched functional monomer b includes the following steps: By weight, 280-320 parts of hydroxyethyl acrylate, 200-250 parts of hydroxypropyl acrylate, 400-500 parts of dioxane, 20-40 parts of 4-cyano-4-(thiobenzoyl)valerate and 3-5 parts of azobisisobutyronitrile are added to a reactor, and the reaction is carried out under nitrogen protection. Then, 6-10 parts of allyl mercaptoacetate are added to continue the reaction. After cooling, the long-branched functional monomer b is obtained.

[0011] This invention also proposes a method for preparing the above-mentioned fast-adsorption, water-resistant product-covered water-reducing agent, comprising the following steps: The polyether macromonomer, long-branched functional monomer a, and long-branched functional monomer b are mixed with water and heated to react at 35-45°C. Then, an initiator is added, and simultaneously, an aqueous solution of acrylic acid and a reducing agent are added dropwise. After the addition is complete, the reaction continues. After the reaction is completed, the temperature is lowered, and the pH is neutralized to 6-7 with alkali solution. The concentration is then adjusted to obtain the fast-adsorption, water-resistant product-covered water-reducing agent.

[0012] Furthermore, the initiator is hydrogen peroxide and ferrous sulfate, and the mass ratio of the initiator to the polyether macromonomer is 2:(75~100).

[0013] Furthermore, the reducing agent aqueous solution comprises ascorbic acid, mercaptopropionic acid and water, and the mass ratio of the reducing agent aqueous solution to the polyether macromonomer is 41:(60~80).

[0014] Furthermore, the acrylic acid aqueous solution and reducing agent aqueous solution are added dropwise over 2 to 3 hours, and the reaction continues for 60 to 120 minutes after the addition is complete.

[0015] Furthermore, the alkaline solution is a 30 wt.% NaOH solution.

[0016] Polycarboxylate superplasticizers are typically produced by free radical polymerization of polyether macromonomers, acrylic acid, and functional monomers. Their molecular structure is a comb-like structure composed of a main chain and side chains. The carboxyl groups (-COO⁻) on the main chain adsorb onto the positively charged surface of cement particles. After adsorbing the anions, the cement particles acquire a charge of the same sign, generating electrostatic repulsion between the particles and preventing flocculation due to attraction between opposite charges. Simultaneously, when the superplasticizer molecules adsorb onto the surface of the cement particles, these long side chains extend into the liquid phase like brushes, forming a steric hindrance layer of a certain thickness and density around the cement particles, further preventing agglomeration. Compared with existing technologies, this invention has the following advantages and technical effects: (1) The fast-adsorption hydration product-resistant water-reducing agent prepared in this invention is made by free radical polymerization of polyether macromonomer, acrylic acid, and long-branched functional monomers a and b. Compared with conventional polycarboxylate water-reducing agents, the long-branched functional monomer a is modified allyl epoxy ether sodium phosphate with a molecular weight of about 12000 g / mol. The branched chain is longer than that of conventional functional monomers and has a strong phosphate group. It will preferentially "occupy" the surface of cement particles and adsorb C3A and early positively charged hydration products, which will greatly improve the adsorption rate of water-reducing agent. Moreover, its long branched chain characteristics can delay the coverage of hydration products on water-reducing agent molecules. It can achieve a high water reduction and dispersion effect in the early stage of concrete mixing (within 2 minutes), avoiding the large bleeding and separation of concrete in the later stage due to excessive dosage of water-reducing agent. The analysis focuses on the following: The long-branched functional monomer b is polymerized from hydroxyethyl acrylate, hydroxypropyl acrylate, and allyl mercaptoacetate. Compared to conventional ester functional monomers, this branch has a longer branch length and a molecular weight of approximately 10,000 g / mol. In the final free radical polymerization molecular structure, it can provide a large number of ester groups with fewer side chains, reducing the impact on the main chain -COO⁻ and promoting the adsorption of carboxyl groups on the main chain onto cement particles. Simultaneously, the ester groups hydrolyze under alkaline conditions, and the resulting carboxyl groups can be re-adsorbed onto cement hydration products, forming a secondary dispersion. This avoids the problem of rapid concrete loss caused by the complete coverage of polycarboxylic acid molecules that were initially rapidly adsorbed onto cement particles by hydration products. Furthermore, it can continuously release and maintain effective adsorption, ensuring that the concrete still has good flow properties in the later stages.

[0017] (2) The present invention prepares a fast-adsorption hydration product-resistant water-reducing agent that can be quickly adsorbed on cement surface particles, delaying the polycarboxylate water-reducing agent from being covered by excessively fine cement hydration products. This avoids the problem of poor water reduction effect, increased dosage, and rapid slump loss in concrete due to slow adsorption of polycarboxylate water-reducing agent in the early stage. At the same time, it avoids the phenomenon of excessive bleeding and segregation in concrete in the later stage of concrete due to the inability of the admixtures used in cement to consume the free polycarboxylate water-reducing agent in time during the later stage of hydration. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 XRD pattern of cement used for performance testing. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0020] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] This invention provides a fast-adsorption, water-resistant, product-coated water-reducing agent, which is a copolymer prepared by free radical polymerization of raw materials containing the following monomers: Polyether macromonomer, acrylic acid, long-branched functional monomer a and long-branched functional monomer b; Among them, the long-branched functional monomer a is modified allyl epoxy ether sodium phosphate, with a weight-average molecular weight (Mw) of 10000~14000 g / mol. The long-branched functional monomer b is a copolymer obtained by copolymerizing hydroxyethyl acrylate, hydroxypropyl acrylate and allyl mercaptoacetate, with a weight-average molecular weight of 8000~12000 g / mol.

[0025] The phosphate groups on the main chain of the water-reducing agent copolymer of this invention (derived from long-branched functional monomer a) have a strong coordination effect on the surface of cement particles (especially C3A and early positively charged hydration products), enabling preferential and rapid adsorption. The long branches of long-branched functional monomer a (Mw=10000~14000 g / mol) form a steric barrier on the surface of cement particles, delaying the physical coverage of hydration products. At the same time, long-branched functional monomer b (Mw=8000~12000 g / mol) carries a large number of ester groups, which gradually hydrolyze to generate carboxyl groups in the alkaline environment of cement hydration, providing secondary dispersion adsorption and compensating for the loss of dispersion caused by the initial coverage.

[0026] In some embodiments of the present invention, the weight-average molecular weight of the fast-adsorption water-resistant product-covered water-reducing agent is 23,000~27,000 g / mol.

[0027] In some embodiments of the present invention, the polyether macromonomer is isopentenyl alcohol polyoxyethylene ether; more specifically, the polyether macromonomer is isopentenyl alcohol polyoxyethylene ether (TPEG2400) with a molecular weight of 2400. Isopentenyl alcohol polyoxyethylene ether has high polymerization activity and adjustable side chain density. Its polyether side chains fully extend in water, providing stable steric repulsion forces. This, combined with the electrostatic adsorption of phosphate groups, enhances the rapid adsorption and long-term dispersion stability of the water-reducing agent on the surface of cement particles.

[0028] In this embodiment of the invention, the amount of each raw material in the fast-adsorption, water-resistant product-covering water-reducing agent, by weight, is as follows: 300-400 parts of polyether macromonomer, 65 parts of acrylic acid, 40-60 parts of long-branched functional monomer a, and 30-50 parts of long-branched functional monomer b.

[0029] In some embodiments of the present invention, the preparation method of the long-branched functional monomer a includes the following steps: By weight, 800-1000 parts of allyl glycidyl ether, 2-5 parts of hydroquinone, and 2-4 parts of toluene were added to a reactor. The mixture was heated to 50-70°C, and an aqueous phosphoric acid solution was slowly added dropwise with stirring. After the addition was complete, the mixture was kept at this temperature for 60 minutes. After cooling, the pH was adjusted to 7-8, the solvent was removed, and the mixture was filtered to obtain the long-branched functional monomer a. During the preparation process, the epoxy group of allyl glycidyl ether undergoes ring-opening esterification under the action of phosphoric acid to generate a long-chain allyl ether structure with phosphate ester groups. Hydroquinone inhibits polymerization side reactions, and toluene acts as a dehydrating agent to promote complete reaction. Neutralization to pH 7-8 converts the phosphate groups into sodium salt form, improving water solubility, and finally, a phosphate-functionalized long-branched monomer with controllable molecular weight is obtained.

[0030] For example, in an embodiment of the present invention, the preparation method of the long-branched functional monomer a specifically includes the following steps: In a reactor equipped with a stirrer, a dropping device, a reflux condenser, and a heating device, 800-1000 parts of allyl glycidyl ether, 2-5 parts of hydroquinone, and 2-4 parts of toluene were added. The mixture was then heated in a water bath to 50-70°C at a rotation speed of 250-300 r / min. A phosphoric acid aqueous solution (composed of 40-50 parts of phosphoric acid (85 wt.%) and 100 parts of deionized water) was slowly added dropwise under stirring over a period of 2-4 h. After the addition was complete, the mixture was kept at this temperature for 60 min. The reaction system was then cooled to room temperature, and a NaOH solution (30 wt.%) was slowly added dropwise under stirring to adjust the pH to 7-8. The residual solvent was removed using a rotary evaporator, and the inorganic salts were removed by filtration to obtain the product, a brown viscous liquid long-chain functional monomer a (modified allyl epoxy ether sodium phosphate). The weight-average molecular weight was determined to be 10000-14000 g / mol by gel permeation chromatography.

[0031] Furthermore, the preparation method of the long-branched functional monomer b includes the following steps: By weight, 280-320 parts of hydroxyethyl acrylate, 200-250 parts of hydroxypropyl acrylate, 400-500 parts of dioxane, 20-40 parts of 4-cyano-4-(thiobenzoyl)valerate, and 3-5 parts of azobisisobutyronitrile were added to a reactor. The reaction was carried out under nitrogen protection and heated. Then, 6-10 parts of allyl mercaptoacetate were added to continue the reaction. After cooling, long-branched functional monomer b was obtained. The preparation process used 4-cyano-4-(thiobenzoyl)valerate as a chain transfer agent and azobisisobutyronitrile as an initiator. The molecular weight of the copolymer was controlled at 8000-12000 g / mol by reversible addition-fragmentation chain transfer (RAFT) living polymerization. Hydroxyethyl acrylate and hydroxypropyl acrylate provided hydroxyl and ester groups, respectively. Allyl mercaptoacetate introduced polymerizable double bonds in the later stage of polymerization, so that monomer b had unsaturated groups that could participate in subsequent free radical polymerization, which facilitated grafting onto the main chain of the water-reducing agent.

[0032] For example, in an embodiment of the present invention, the preparation method of the long-branched functional monomer b specifically includes the following steps: In a reactor equipped with a stirrer, a dropping device, a heating device, and a nitrogen protection device, 280-320 parts of hydroxyethyl acrylate, 200-250 parts of hydroxypropyl acrylate, 400-500 parts of dioxane, 20-40 parts of 4-cyano-4-(thiobenzoyl)valerate, and 3-5 parts of azobisisobutyronitrile were added. Nitrogen gas was bubbled through for 60 minutes to remove oxygen, and the nitrogen pressure was maintained continuously. The mixture was heated in a water bath to 60-70°C at a speed of 250-300 r / min for 1.5-2.5 hours. Then, 6-10 parts of allyl mercaptoacetate were rapidly injected into the reaction system using a degassing syringe, and the reaction was continued for 2-4 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a transparent, viscous long-branched functional monomer b. The weight-average molecular weight was determined to be 8000-12000 g / mol by gel permeation chromatography.

[0033] This invention also proposes a method for preparing the above-mentioned fast-adsorption, water-resistant product-covered water-reducing agent, comprising the following steps: Polyether macromonomer, long-branched functional monomer a, long-branched functional monomer b are mixed with water and heated to react at 35~45℃. Then an initiator is added, and simultaneously, an aqueous solution of acrylic acid and a reducing agent are added dropwise. After the addition is complete, the reaction continues. After the reaction is completed, the temperature is lowered, and the pH is neutralized to 6~7 with alkali solution. The concentration is adjusted to obtain a fast-adsorption, water-resistant product-covering water-reducing agent.

[0034] In the preparation process of the water-reducing agent in this embodiment of the invention, a polyether macromonomer and two long-branched functional monomers are first blended and pre-activated at 35-45°C. Then, an initiator is added, and acrylic acid and a reducing agent are added dropwise simultaneously to achieve copolymerization of acrylic acid with each monomer. The dropwise addition method controls the reaction rate to prevent localized explosive polymerization. Finally, the mixture is neutralized to pH 6-7 to convert the carboxyl groups into sodium carboxylate, improving water solubility and stabilizing the product.

[0035] In some embodiments of the present invention, the initiator is hydrogen peroxide and ferrous sulfate, and the mass ratio of hydrogen peroxide to ferrous sulfate is 5:3; the mass ratio of initiator to polyether macromonomer is 2:(75~100), that is, in the embodiments, 300~400 parts of polyether macromonomer are added to 8 parts of initiator (including 5 parts of hydrogen peroxide and 3 parts of ferrous sulfate).

[0036] In some embodiments of the present invention, the reducing agent aqueous solution comprises ascorbic acid, mercaptopropionic acid, and water, and the mass ratio of the reducing agent aqueous solution to the polyether macromonomer is 41:(60~80), that is, in the embodiments, 300~400 parts of polyether macromonomer are added to 205 parts of the reducing agent aqueous solution (composed of 2 parts ascorbic acid, 3 parts mercaptopropionic acid, and 200 parts deionized water). Hydrogen peroxide and ferrous sulfate constitute a redox initiation system, which can generate free radicals at a relatively low temperature (35~45°C), avoiding premature hydrolysis of the ester group in monomer b or decomposition of the phosphate ester group in monomer a due to high temperature, while ensuring the stable progress of the polymerization reaction.

[0037] In some embodiments of the present invention, the acrylic acid aqueous solution and the reducing agent aqueous solution are added dropwise over 2-3 hours, and the reaction continues for 60-120 minutes after the addition is complete. Ascorbic acid is used as a reducing agent to activate the initiation system, and mercaptopropionic acid is used as a chain transfer agent to adjust the polymer molecular weight. The two work synergistically to control the chain length and molecular weight distribution of the copolymer, ensuring that the product has suitable overall properties. The mass ratio of the reducing agent aqueous solution to the polyether macromonomer is designed to ensure a moderate reaction rate.

[0038] In some embodiments of the present invention, the alkaline solution is a 30 wt.% NaOH solution.

[0039] For example, in an embodiment of the present invention, the preparation method of the fast-adsorption water-resistant product-covered water-reducing agent specifically includes the following steps: In a reactor equipped with a stirrer, a dropping device, and a heating device, add 300-400 parts of TPEG2400, 40-60 parts of long-branched functional monomer a, 30-50 parts of long-branched functional monomer b, and 200-300 parts of deionized water. Heat to 35-45°C at a rotation speed of 250-300 r / min. Then add an initiator (including 5 parts of hydrogen peroxide and 3 parts of ferrous sulfate (1 wt.%)), and simultaneously add solutions a and b dropwise. Solution A is composed of 65 parts acrylic acid and 150 parts deionized water; Solution B is composed of 2 parts ascorbic acid, 3 parts mercaptopropionic acid and 200 parts deionized water. The addition time is 2-3 hours. After the addition is complete, the reaction continues for 60-120 minutes. After the reaction is completed, the temperature of the system is lowered to room temperature. The solution is neutralized to pH 6-7 with NaOH solution (30 wt.%) and deionized water to obtain a 40% concentration of adsorbed and water-resistant product-covered water-reducing agent.

[0040] The water-reducing agent with adsorption and water-resistant product covering obtained by this invention is added to concrete in the form of a compound water-reducing agent, wherein the ratio of each ton of compound water-reducing agent is: fast adsorption and water-resistant product covering water-reducing agent : retarder (sodium gluconate) : air-entraining agent (triterpenoid saponins) : water = 350 : 20 : 3 : 627.

[0041] In the embodiments of this invention, unless otherwise specified, "parts" refers to "number of parts by weight".

[0042] In the embodiments of this invention, "room temperature" refers to "25±2℃".

[0043] All raw materials used in the embodiments of this invention were purchased commercially.

[0044] The technical solution of the present invention will be further illustrated by the following embodiments.

[0045] Example 1 (1) Preparation of long-branched functional monomer a In a reactor equipped with a stirrer, a dropping device, a reflux condenser, and a heating device, 800 parts of allyl glycidyl ether, 2 parts of hydroquinone, and 2 parts of toluene were added. The mixture was then heated to 50°C in a water bath at a speed of 250 r / min. Phosphoric acid aqueous solution (composed of 40 parts of phosphoric acid (85 wt.%) and 100 parts of deionized water) was then slowly added dropwise over a period of 2 h. After the addition was complete, the mixture was kept at this temperature for 60 min. The reaction system was then cooled to room temperature, and NaOH solution (30 wt.%) was slowly added dropwise over a stirring period to adjust the pH to 7-8. The residual solvent was removed using a rotary evaporator, and the generated inorganic salts were removed by filtration to obtain the product, a brown viscous liquid long-branched functional monomer a. The weight-average molecular weight was determined to be 10875 g / mol by gel permeation chromatography.

[0046] (2) Preparation of long-branched functional monomer b In a reactor equipped with a stirrer, a dropping device, a heating device, and a nitrogen protection device, 280 parts of hydroxyethyl acrylate, 200 parts of hydroxypropyl acrylate, 400 parts of dioxane, 20 parts of 4-cyano-4-(thiobenzoyl)valerate, and 3 parts of azobisisobutyronitrile were added. Nitrogen gas was bubbled through the reactor for 60 min to remove oxygen, and the nitrogen pressure was maintained continuously. The reactor was heated to 60°C in a water bath at a speed of 250 r / min for 1.5 hours. Then, 6 parts of allyl mercaptoacetate were rapidly injected into the reaction system using a degassing syringe, and the reaction was continued for 2 hours. After the reaction was completed, the reactor was cooled to room temperature to obtain a transparent, viscous long-branched functional monomer b, which was found to have a weight-average molecular weight of 8358 g / mol by gel permeation chromatography.

[0047] (3) Preparation of fast-adsorption water-resistant product-covered water-reducing agent In a reactor equipped with a stirrer, a dropping device, and a heating device, 300 parts of TPEG2400, 40 parts of long-branched functional monomer a, 30 parts of long-branched functional monomer b, and 200 parts of deionized water were added. The temperature was raised to 35°C, and the stirring speed was set to 250 r / min. Then, an initiator (including 5 parts of hydrogen peroxide and 3 parts of ferrous sulfate (1 wt.%)) was added, and solutions a and b were added dropwise simultaneously (solution a was a mixture of 65 parts of acrylic acid and 150 parts of deionized water; solution b was a mixture of 2 parts of ascorbic acid, 3 parts of mercaptopropionic acid, and 200 parts of deionized water). The dropping time was 2 h, and the reaction continued for 60 min after the addition was completed. After the reaction was completed, the temperature of the system was lowered to room temperature, and the solution was neutralized to pH 6-7 with NaOH solution (30 wt.%) and deionized water to obtain a 40% concentration of adsorbed and water-resistant product-covered water-reducing agent. The weight-average molecular weight was 23573 g / mol, and the conversion rate was 92%, as determined by gel permeation chromatography.

[0048] Example 2 (1) Preparation of long-branched functional monomer a In a reactor equipped with a stirrer, a dropping device, a reflux condenser, and a heating device, 1000 parts of allyl glycidyl ether, 5 parts of hydroquinone, and 2 parts of toluene were added. The mixture was then heated to 50°C in a water bath at a speed of 300 r / min. A phosphoric acid aqueous solution (composed of 50 parts of phosphoric acid (85 wt.%) and 100 parts of deionized water) was then slowly added dropwise over a period of 4 h. After the addition was complete, the mixture was kept at this temperature for 60 min. The reaction system was then cooled to room temperature, and a NaOH solution (30 wt.%) was slowly added dropwise over a stirring period to adjust the pH to 7-8. The residual solvent was removed using a rotary evaporator, and the generated inorganic salts were removed by filtration to obtain the product, a brown viscous liquid long-branched functional monomer a. The weight-average molecular weight was determined to be 13817 g / mol by gel permeation chromatography.

[0049] (2) Preparation of long-branched functional monomer b In a reactor equipped with a stirrer, a dropping device, a heating device, and a nitrogen protection device, 320 parts of hydroxyethyl acrylate, 250 parts of hydroxypropyl acrylate, 500 parts of dioxane, 40 parts of 4-cyano-4-(thiobenzoyl)valerate, and 5 parts of azobisisobutyronitrile were added. Nitrogen gas was bubbled through for 60 min to remove oxygen, and the nitrogen pressure was maintained continuously. The reactor was heated to 70°C in a water bath at a speed of 300 r / min for 2.5 hours. Then, 10 parts of allyl mercaptoacetate were rapidly injected into the reaction system using a degassing syringe, and the reaction was continued for 4 hours. After the reaction was completed, the reactor was cooled to room temperature to obtain a transparent, viscous long-branched functional monomer b, which was found to have a weight-average molecular weight of 11859 g / mol by gel permeation chromatography.

[0050] (3) Preparation of fast-adsorption water-resistant product-covered water-reducing agent In a reactor equipped with a stirrer, a dropping device, and a heating device, 400 parts of TPEG2400, 60 parts of long-branched functional monomer a, 50 parts of long-branched functional monomer b, and 300 parts of deionized water were added. The temperature was raised to 45°C, and the stirring speed was set to 300 r / min. Then, an initiator (including 5 parts of hydrogen peroxide and 3 parts of ferrous sulfate (1 wt.%)) was added, and solutions a and b were added dropwise simultaneously (solution a was a mixture of 65 parts of acrylic acid and 150 parts of deionized water; solution b was a mixture of 2 parts of ascorbic acid, 3 parts of mercaptopropionic acid, and 200 parts of deionized water). The dropping time was 3 h, and the reaction continued for 120 min after the dropping was completed. After the reaction was completed, the temperature of the system was lowered to room temperature, and the solution was neutralized to pH 6-7 with NaOH solution (30 wt.%) and deionized water to obtain a 40% concentration of adsorbed and water-resistant product-covered water-reducing agent. The weight-average molecular weight was 26787 g / mol, and the conversion rate was 93%, as determined by gel permeation chromatography.

[0051] Example 3 (1) Preparation of long-branched functional monomer a In a reactor equipped with a stirrer, a dropping device, a reflux condenser, and a heating device, 900 parts of allyl glycidyl ether, 3 parts of hydroquinone, and 3 parts of toluene were added. The mixture was then heated to 60°C in a water bath at a speed of 280 r / min. A phosphoric acid aqueous solution (composed of 45 parts of phosphoric acid (85 wt.%) and 100 parts of deionized water) was then slowly added dropwise over a period of 3 h. After the addition was complete, the mixture was kept at this temperature for 60 min. The reaction system was then cooled to room temperature, and a NaOH solution (30 wt.%) was slowly added dropwise over a stirring period to adjust the pH to 7-8. The residual solvent was removed using a rotary evaporator, and the generated inorganic salts were removed by filtration to obtain the product, a brown viscous liquid long-branched functional monomer a. The weight-average molecular weight was determined to be 12543 g / mol by gel permeation chromatography.

[0052] (2) Preparation of long-branched functional monomer b In a reactor equipped with a stirrer, a dropping device, a heating device, and a nitrogen protection device, 300 parts of hydroxyethyl acrylate, 220 parts of hydroxypropyl acrylate, 450 parts of dioxane, 30 parts of 4-cyano-4-(thiobenzoyl)valerate, and 4 parts of azobisisobutyronitrile were added. Nitrogen gas was bubbled through for 60 minutes to remove oxygen, and the nitrogen pressure was maintained continuously. The reactor was heated to 65°C in a water bath at a speed of 280 r / min for 2 hours. Then, 8 parts of allyl mercaptoacetate were rapidly injected into the reaction system using a degassing syringe, and the reaction was continued for 3 hours. After the reaction was completed, the reactor was cooled to room temperature to obtain a transparent, viscous long-branched functional monomer b. The weight-average molecular weight was determined to be 10746 g / mol by gel permeation chromatography.

[0053] (3) Preparation of fast-adsorption water-resistant product-covered water-reducing agent In a reactor equipped with a stirrer, a dropping device, and a heating device, 350 parts of TPEG2400, 50 parts of long-branched functional monomer a, 40 parts of long-branched functional monomer b, and 250 parts of deionized water were added. The temperature was raised to 40°C, and the stirring speed was set to 280 r / min. Then, an initiator (including 5 parts of hydrogen peroxide and 3 parts of ferrous sulfate (1 wt.%)) was added, and solutions a and b were added dropwise simultaneously (solution a was a mixture of 65 parts of acrylic acid and 150 parts of deionized water; solution b was a mixture of 2 parts of ascorbic acid, 3 parts of mercaptopropionic acid, and 200 parts of deionized water). The dropping time was 2.5 h. After the dropping was completed, the reaction continued for 90 min. After the reaction was completed, the temperature of the system was lowered to room temperature, and the solution was neutralized to pH 6-7 with NaOH solution (30 wt.%) and deionized water to obtain a 40% concentration of adsorbed and water-resistant product-covered water-reducing agent. The weight-average molecular weight was 25759 g / mol, and the conversion rate was 96%, as determined by gel permeation chromatography.

[0054] Example 4 (1) Preparation of long-branched functional monomer a In a reactor equipped with a stirrer, a dropping device, a reflux condenser, and a heating device, 900 parts of allyl glycidyl ether, 3 parts of hydroquinone, and 3 parts of toluene were added. The mixture was then heated to 60°C in a water bath at a speed of 280 r / min. A phosphoric acid aqueous solution (composed of 45 parts of phosphoric acid (85 wt.%) and 100 parts of deionized water) was then slowly added dropwise over a period of 3 h. After the addition was complete, the mixture was kept at this temperature for 60 min. The reaction system was then cooled to room temperature, and a NaOH solution (30 wt.%) was slowly added dropwise over a stirring period to adjust the pH to 7-8. The residual solvent was removed using a rotary evaporator, and the generated inorganic salts were removed by filtration to obtain the product, a brown viscous liquid long-branched functional monomer a. The weight-average molecular weight was determined to be 12543 g / mol by gel permeation chromatography.

[0055] (2) Preparation of long-branched functional monomer b In a reactor equipped with a stirrer, a dropping device, a heating device, and a nitrogen protection device, 300 parts of hydroxyethyl acrylate, 220 parts of hydroxypropyl acrylate, 450 parts of dioxane, 30 parts of 4-cyano-4-(thiobenzoyl)valerate, and 4 parts of azobisisobutyronitrile were added. Nitrogen gas was bubbled through for 60 minutes to remove oxygen, and the nitrogen pressure was maintained continuously. The reactor was heated to 65°C in a water bath at a speed of 280 r / min for 2 hours. Then, 8 parts of allyl mercaptoacetate were rapidly injected into the reaction system using a degassing syringe, and the reaction was continued for 3 hours. After the reaction was completed, the reactor was cooled to room temperature to obtain a transparent, viscous long-branched functional monomer b. The weight-average molecular weight was determined to be 10746 g / mol by gel permeation chromatography.

[0056] (3) Preparation of fast-adsorption water-resistant product-covered water-reducing agent In a reactor equipped with a stirrer, a dropping device, and a heating device, 400 parts of TPEG2400, 60 parts of long-branched functional monomer a, 50 parts of long-branched functional monomer b, and 300 parts of deionized water were added. The temperature was raised to 45°C, and the stirring speed was set to 300 r / min. Then, an initiator (including 5 parts of hydrogen peroxide and 3 parts of ferrous sulfate (1 wt.%)) was added, and solutions a and b were added dropwise simultaneously (solution a was a mixture of 65 parts of acrylic acid and 150 parts of deionized water; solution b was a mixture of 2 parts of ascorbic acid, 3 parts of mercaptopropionic acid, and 200 parts of deionized water). The dropping time was 3 h, and the reaction continued for 120 min after the addition was completed. After the reaction was completed, the temperature of the system was lowered to room temperature, and the solution was neutralized to pH 6-7 with NaOH solution (30 wt.%) and deionized water to obtain a 40% concentration of adsorbed and water-resistant product-covered water-reducing agent. The weight-average molecular weight was 26545 g / mol, and the conversion rate was 94%, as determined by gel permeation chromatography.

[0057] Comparative Example 1 Same as Example 3, except that phosphoric acid (85 wt.%) in the preparation process of long-branched functional monomer a is replaced with concentrated sulfuric acid of equal solids (equivalent amount calculated based on 100% pure substance), and the rest of the steps are the same as in Example 3.

[0058] Comparative Example 2 Same as Example 3, except that the hydroxypropyl acrylate in the preparation process of the long-branched functional monomer b is replaced with hydroxyethyl acrylate of equal folded solids, and the rest of the steps are the same as in Example 3.

[0059] Comparative Example 3 Same as Example 3, except that TPEG2400 is replaced with the same amount of HPEG2400 (methyl allyl polyoxyethylene ether with a molecular weight of 2400), and the rest of the steps are the same as in Example 3.

[0060] Comparative Example 4 Same as Example 3, except that the addition of phosphoric acid aqueous solution is omitted in the preparation of long branched functional monomer a. Step (1) is as follows: 900 parts of allyl glycidyl ether, 3 parts of hydroquinone and 3 parts of toluene are added to a reactor equipped with a stirrer, a dropping device, a reflux condenser and a heating device. Then, the mixture is heated to 60°C in a water bath and the rotation speed is set to 280 r / min. After that, the reaction system is cooled to room temperature. NaOH solution (concentration of 30 wt.%) is slowly added dropwise under stirring to adjust the pH of the system to 7-8. The residual solvent is removed by a rotary cold evaporator and the generated inorganic salt is removed by filtration to obtain monomer a.

[0061] The remaining steps are consistent with those in Example 3.

[0062] Comparative Example 5 Same as Example 3, except that the long-branched functional monomer b is replaced with an equal mass fraction of polyethylene glycol monomethyl ether methacrylate (a conventional ester macromonomer), and the rest of the steps are the same as in Example 3.

[0063] Comparative Example 6 Same as Example 3, except that in the preparation of long-branched functional monomer a, an aqueous solution of phosphoric acid (composed of 10 parts of phosphoric acid (85 wt.%) and 100 parts of deionized water) was slowly added dropwise under stirring to obtain long-branched functional monomer a, and the weight-average molecular weight was 15036 g / mol as determined by gel permeation chromatography.

[0064] The remaining steps are consistent with those in Example 3.

[0065] Comparative Example 7 Same as Example 3, except that in the preparation of long-branched functional monomer b, the water bath heating temperature is raised to 45°C, and step (2) is specifically as follows: In a reactor equipped with a stirrer, a dropping device, a heating device, and a nitrogen protection device, 300 parts of hydroxyethyl acrylate, 220 parts of hydroxypropyl acrylate, 450 parts of dioxane, 30 parts of 4-cyano-4-(thiobenzoyl)valerate, and 4 parts of azobisisobutyronitrile were added. Nitrogen gas was bubbled through for 60 minutes to remove oxygen, and the nitrogen pressure was maintained continuously. The reactor was heated to 45°C in a water bath at a speed of 280 r / min for 2 hours. Then, 8 parts of allyl mercaptoacetate were rapidly injected into the reaction system using a degassing syringe, and the reaction was continued for 3 hours. After the reaction was completed, the reactor was cooled to room temperature to obtain a transparent, viscous long-branched functional monomer b. The weight-average molecular weight was determined to be 6519 g / mol by gel permeation chromatography.

[0066] The remaining steps are consistent with those in Example 3.

[0067] Performance testing The concrete test was conducted to assess the performance of the fast-adsorption, water-resistant, product-resistant, covered water-reducing agent. Specifically: The performance of the admixtures obtained in the examples and comparative examples was tested through concrete tests. The cement used was Huaxin P·O 42.5 cement. Concrete mixed with this cement exhibited rapid water loss within the first 30 minutes at the construction site, followed by significant bleeding after 1 hour. The mineral composition of the cement was analyzed, and the cement XRD pattern is shown below. Figure 1 As shown in Table 1, the XRF of cement is shown in Table 2, and the particle size distribution of cement is shown in Table 2.

[0068] Table 1. Cement XRF Test Results (%) Table 2. Particle size distribution of cement particles (%) The manufactured sand has a fineness modulus of 2.8, a stone powder content of 6%, a methylene blue MB value of 1.0, and the aggregate is continuously graded crushed stone ranging from 5mm to 31.5mm. The concrete mix design is shown in Table 3, where the amount of compound water-reducing agent is the amount required to achieve a concrete slump of 220mm.

[0069] Concrete slump, spread, specimen molding, preparation, and curing were performed according to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". Concrete strength was measured according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". In the blank control, each ton of compound water-reducing agent contained conventional six-carbon polycarboxylate water-reducing agent (six-carbon P6). The ratio of compound water-reducing agent per ton was: polycarboxylate water-reducing agent (six-carbon P6): retarder (sodium gluconate): air-entraining agent (triterpenoid saponins): water = 350: 20: 3: 627. In each example and comparative example, the water-reducing agent used per ton of compound water-reducing agent was the prepared water-reducing agent. The ratio of each ton of compound water-reducing agent was: fast-adsorption water-resistant product-covering water-reducing agent : retarder (sodium gluconate) : air-entraining agent (triterpenoid saponins) : water = 350 : 20 : 3 : 627. All test groups maintained the same slump of 220 mm at the concrete discharge point by adjusting the dosage of water-reducing agent. Then, the changes in slump and spread of the concrete were observed at 30 min, 1 h, and 2 h. The test results are shown in Table 4 (the dosage of compound water-reducing agent in Table 3 is the dosage required to achieve a slump of 220 mm, so the dosage of compound water-reducing agent in each group in Table 4 will be different).

[0070] Table 3 Concrete mix proportions (kg / m³) 3 ) Table 4 Concrete Test Results As shown in Table 4, the fast-adsorption, water-resistant product-coated water-reducing agent prepared in the embodiments of the present invention, compared with the blank control group, showed that the concrete of the embodiments had a lower dosage of compound water-reducing agent at the same slump. The slump and spread of the concrete did not show any loss or increase at 0.5h, 1h, and 2h, indicating better workability and no surface bleeding. The compressive strength of the embodiments at 3d, 7d, and 28d after molding was significantly improved compared to the blank control group. (The text repeats itself here.)

[0071] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A fast-adsorbing, water-resistant, product-coating water-reducing agent, characterized in that, The water-reducing agent is a copolymer prepared by free radical polymerization of raw materials containing the following monomers: Polyether macromonomer, acrylic acid, long-branched functional monomer a and long-branched functional monomer b; The long-branched functional monomer a is modified allyl epoxy ether sodium phosphate, with a weight-average molecular weight of 10,000 to 14,000 g / mol. The long-branched functional monomer b is a copolymer obtained by copolymerizing hydroxyethyl acrylate, hydroxypropyl acrylate and allyl mercaptoacetate, with a weight-average molecular weight of 8000~12000 g / mol.

2. The fast-adsorption, water-resistant, product-resistant, and coating-type water-reducing agent according to claim 1, characterized in that, The polyether macromonomer is isopentenyl alcohol polyoxyethylene ether.

3. The fast-adsorption, water-resistant, product-resistant, coating-type water-reducing agent according to claim 1, characterized in that, The amounts of each raw material, by weight, are as follows: 300-400 parts of polyether macromonomer; 65 parts acrylic acid; 40-60 parts of long-branched functional monomer a; 30-50 parts of long-branched functional monomer b.

4. The fast-adsorption, water-resistant, product-resistant, and coating-type water-reducing agent according to claim 1, characterized in that, The preparation method of the long-branched functional monomer a includes the following steps: By weight, 800-1000 parts of allyl glycidyl ether, 2-5 parts of hydroquinone and 2-4 parts of toluene were added to the reactor, heated to 50-70°C, and phosphoric acid aqueous solution was added dropwise with stirring. After the addition was completed, the temperature was maintained for 60 minutes. After cooling, the pH was adjusted to 7-8, the solvent was removed, and the mixture was filtered to obtain the long-branched functional monomer a.

5. The fast-adsorption, water-resistant, product-resistant, and coating-type water-reducing agent according to claim 1, characterized in that, The preparation method of the long-branched functional monomer b includes the following steps: By weight, 280-320 parts of hydroxyethyl acrylate, 200-250 parts of hydroxypropyl acrylate, 400-500 parts of dioxane, 20-40 parts of 4-cyano-4-(thiobenzoyl)valerate and 3-5 parts of azobisisobutyronitrile are added to a reactor, and the reaction is carried out under nitrogen protection. Then, 6-10 parts of allyl mercaptoacetate are added to continue the reaction. After cooling, the long-branched functional monomer b is obtained.

6. A method for preparing a fast-adsorption, water-resistant, product-coated water-reducing agent according to any one of claims 1 to 5, characterized in that, Includes the following steps: The polyether macromonomer, long-branched functional monomer a, and long-branched functional monomer b are mixed with water and heated to react at 35-45°C. Then, an initiator is added, and simultaneously, an aqueous solution of acrylic acid and a reducing agent are added dropwise. After the addition is complete, the reaction continues. After the reaction is completed, the temperature is lowered, and the pH is neutralized to 6-7 with alkali solution. The concentration is then adjusted to obtain the fast-adsorption, water-resistant product-covered water-reducing agent.

7. The preparation method of the fast-adsorption, water-resistant, product-coated water-reducing agent according to claim 6, characterized in that, The initiator is hydrogen peroxide and ferrous sulfate, and the mass ratio of the initiator to the polyether macromonomer is 2:(75~100).

8. The preparation method of the fast-adsorption, water-resistant, product-coated water-reducing agent according to claim 6, characterized in that, The reducing agent aqueous solution contains ascorbic acid, mercaptopropionic acid and water, and the mass ratio of the reducing agent aqueous solution to the polyether macromonomer is 41:(60~80).

9. The preparation method of the fast-adsorption, water-resistant, product-coated water-reducing agent according to claim 6, characterized in that, The acrylic acid aqueous solution and reducing agent aqueous solution are added dropwise over 2 to 3 hours, and the reaction continues for 60 to 120 minutes after the addition is complete.

10. The preparation method of the fast-adsorption, water-resistant, product-covering water-reducing agent according to claim 6, characterized in that, The alkaline solution is a 30 wt.% NaOH solution.

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