A rust-resistant polycarboxylate superplasticizer, a preparation method and application thereof

Abstract

This invention proposes a corrosion-inhibiting polycarboxylate superplasticizer, its preparation method, and its application. The corrosion-inhibiting polycarboxylate superplasticizer is prepared by a ring-opening grafting reaction between an epoxy-containing polycarboxylate superplasticizer and triethanolamine borate. A functionalized framework is constructed using epoxy-containing monomers, and then corrosion-inhibiting groups are stably anchored to the molecular side chains through a nucleophilic ring-opening reaction, achieving molecular-level integration of water-reducing and corrosion-inhibiting functions. Through the directional adsorption of amino groups onto the surface of reinforcing steel to form a film, combined with the anodic passivation inhibition induced by borate, corrosive media are effectively isolated. Simultaneously, the released borate ions react with calcium ions in the pore fluid to form micro-precipitates in situ, filling capillary pores and significantly optimizing pore size distribution. This invention solves the problems of poor component compatibility and performance interference, significantly reducing the chloride ion permeability coefficient even at low dosages, and significantly improving the mechanical strength and durability of concrete. The process of this invention is simple, the reaction conditions are mild, and it is suitable for the protection of reinforced concrete structures in marine engineering and harsh environments.

Description

Technical Field

[0001] This invention relates to the field of concrete admixtures, and particularly to a rust-inhibiting polycarboxylate superplasticizer, its preparation method, and its application. Background Technology

[0002] In marine engineering, such as wharves, seawalls, cross-sea bridges, and tunnels, reinforced concrete is the most commonly used civil engineering material. However, the marine environment contains a large number of corrosive ions, and the tidal action and long-term erosion by waves pose severe external factors that can seriously damage reinforced concrete structures, significantly shortening their service life. Among these factors, chloride ion corrosion of the reinforcing steel is one of the core factors inducing premature structural damage and failure. The corrosion products of the steel produce volume expansion and internal stress, leading to the peeling, detachment, and even failure of the concrete protective layer, seriously affecting structural safety and causing significant economic losses. Therefore, corrosion protection of reinforced concrete in marine environments has important theoretical research significance and practical engineering application value.

[0003] To delay steel corrosion and extend the service life of concrete structures, the industry has proposed various corrosion protection technologies, including concrete matrix performance optimization technology, surface coating technology, electrochemical protection technology, and rust inhibitor technology. Rust inhibitors, either directly incorporated into the concrete structure or sprayed onto its surface, can slow down the migration of chloride ions to the steel reinforcement surface, postpone corrosion initiation time, and improve the corrosion resistance of the steel. Traditional inorganic rust inhibitors, primarily based on nitrites, while possessing high rust-inhibiting efficiency, have been banned in many countries due to their side effects on concrete and significant biotoxicity. In contrast, organic rust inhibitors, represented by alkanolamines and carboxylic acids, have gained wider application due to their greener, more environmentally friendly, and more efficient advantages.

[0004] Currently, rust inhibitors are often used in engineering sites in physical compound form with water-reducing agents. However, the mixture is prone to stratification, which not only weakens their respective core performance, leading to a decrease in water reduction rate and rust inhibition effect, but also increases material management and labor input at the construction site. To solve the compatibility problem of physical compounding, the development of chemically modified polycarboxylate superplasticizers with both water-reducing and rust-inhibiting functions has become an industry trend. However, existing synthesis technologies still face many bottlenecks in terms of process complexity and production stability.

[0005] Patent CN116554414B discloses a method for preparing a rust-inhibiting polycarboxylate superplasticizer and its application. This method employs a three-step process, and the synthesis of the key component, p-isopropylene phenol polyalkoxy ether, requires high temperature and high pressure conditions, resulting in stringent reaction conditions, cumbersome production steps, and complex synthesis processes. Patent CN112708069A discloses an ester-based polycarboxylate superplasticizer with rust-inhibiting properties and its preparation method. This method involves first esterifying a rust-inhibiting monomer A with dihydroxyl groups and an unsaturated acid to obtain an esterification intermediate, which is then copolymerized with other components. Because this esterification product is a multifunctional crosslinking monomer, it is highly susceptible to uncontrollable crosslinking reactions during polymerization, posing a significant risk of gelation and severely impacting the quality controllability and product stability of industrial production.

[0006] Therefore, developing a novel multifunctional polycarboxylate high-performance water-reducing agent through molecular design that can avoid the defects of physical compound incompatibility and has mild preparation conditions and high production stability has important practical value and application prospects for solving the hidden danger of steel corrosion in seawater and sea sand environments, improving engineering construction efficiency and structural durability. Summary of the Invention

[0007] To address the aforementioned technical problems, this application provides a rust-inhibiting polycarboxylate superplasticizer, its preparation method, and its application.

[0008] In a first aspect, the present invention proposes a rust-inhibiting polycarboxylate superplasticizer, which is prepared by a ring-opening grafting reaction between an epoxy-containing polycarboxylate superplasticizer and triethanolamine borate.

[0009] The above technical solution overcomes the technical defects of traditional physical compound rust inhibitors, such as easy precipitation and poor compatibility. It achieves the stable introduction of rust-inhibiting groups into the molecular skeleton of water-reducing agents through chemical bonding, thus endowing the polymer with long-lasting anti-corrosion and rust-inhibiting functions.

[0010] Furthermore, the polymer raw materials for preparing the epoxy-containing polycarboxylic acid water-reducing agent include, by weight: 185–205 parts unsaturated polyether, 2.0–21.0 parts unsaturated sulfonate, 15.0–20.0 parts unsaturated carboxylic acid, and 0.8–8.0 parts glycidyl methacrylate. This limits the core monomer combination for synthesizing the precursor polymer backbone with active epoxy side chains, ensuring that the main chain possesses excellent steric hindrance effect to achieve water reduction and slump retention, while providing sufficient reaction sites for subsequent nucleophilic grafting reactions.

[0011] Furthermore, the polymer raw materials for preparing epoxy-containing polycarboxylic acid water-reducing agents also include, by weight: 0.8–2.5 parts oxidant, 0.2–0.6 parts reducing agent, 0.6–3.1 parts chain transfer agent, 1.2–1.4 parts liquid alkali and 211–280 parts water.

[0012] The above technical solution provides a redox system that can initiate polymerization at room temperature and a regulator that controls the distribution of polymer chain length, which effectively ensures the stable conversion of the copolymerization reaction under mild conditions and avoids cross-linking and gelation of macromolecules.

[0013] Furthermore, the unsaturated polyether includes ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000; the unsaturated sulfonate is sodium methacrylate sulfonate; and the unsaturated carboxylic acid is selected from at least one of acrylic acid or methacrylic acid.

[0014] Furthermore, the oxidant is selected from at least one of potassium persulfate or ammonium persulfate; the reducing agent is selected from at least one of ascorbic acid, sodium bisulfite, or organic sulfinate derivatives; the chain transfer agent is selected from at least one of mercaptoacetic acid, mercaptopropionic acid, and mercaptoethanol; and the liquid alkali is selected from at least one of sodium hydroxide solution or potassium hydroxide solution.

[0015] In the above technical solution, the preferred large monomer with suitable steric hindrance, highly active functional monomer, and specific room temperature catalytic system ensure that the molecular weight distribution of the copolymer is concentrated and that efficient copolymerization is achieved without damaging the sensitive epoxy groups.

[0016] Furthermore, the reaction raw materials for preparing the rust-inhibiting polycarboxylate superplasticizer, by weight, include: 200 parts of epoxy-containing polycarboxylate superplasticizer with a solid content of 50%, 2.5–3.5 parts of liquid alkali, 0.05–0.1 parts of catalyst, 4.0–4.5 parts of triethanolamine borate ester, and 35.0–40.0 parts of water. This ensures that the core raw material ratio for the ring-opening grafting reaction stage is locked in, guaranteeing that the rust inhibitor molecules can be fully grafted under suitable alkaline and catalytic conditions, preventing the residue of unreacted byproducts and performance degradation.

[0017] Secondly, the present invention provides a method for preparing a rust-inhibiting polycarboxylate superplasticizer as described in the first aspect, the method comprising:

[0018] S1, unsaturated polyether, unsaturated sulfonate, and water are mixed and dissolved, and unsaturated carboxylic acid, liquid alkali, and oxidant are added sequentially and mixed evenly to obtain a base solution; at room temperature, a first solution and a second solution are simultaneously added dropwise to the base solution. The first solution includes unsaturated carboxylic acid, glycidyl methacrylate, and water, and the second solution includes a chain transfer agent, a reducing agent, and water; after the addition is complete, the reaction is kept at a constant temperature to obtain an epoxy-containing polycarboxylic acid water-reducing agent; S2, add liquid alkali to the epoxy-containing polycarboxylate superplasticizer to adjust the pH of the system to 9.0-9.5, add catalyst and mix evenly; add an aqueous solution containing triethanolamine borate dropwise at room temperature, and keep the reaction at the temperature after the addition is complete to obtain the rust-inhibiting polycarboxylate superplasticizer.

[0019] The above technical solution establishes a technical framework of "stepwise acid addition to prevent gelation" and "room temperature double drop addition", which not only achieves efficient retention of side chain epoxy groups, but also greatly reduces the energy consumption and danger of traditional high-temperature synthesis processes.

[0020] Furthermore, in step S1, the specific steps for preparing the epoxy-containing polycarboxylate superplasticizer, by weight, include: S11, mix and dissolve 185-205 parts of unsaturated polyether, 2.0-21.0 parts of unsaturated sulfonate and 184-225 parts of water, add 2.4-2.8 parts of unsaturated carboxylic acid, stir evenly, then add 1.2-1.4 parts of liquid alkali, stir evenly; add 0.8-2.5 parts of oxidant, stir evenly to obtain the base liquid; S12, a first solution is prepared by uniformly mixing 13.5–17.0 parts of unsaturated carboxylic acid, 0.8–8.0 parts of glycidyl methacrylate, and 12.0–20.0 parts of water; a second solution is prepared by uniformly mixing 0.6–3.1 parts of chain transfer agent, 0.2–0.6 parts of reducing agent, and 15.0–62.0 parts of water. S13, at room temperature, the first solution and the second solution are simultaneously added dropwise to the base liquid for 1 to 3 hours. After the addition is completed, the reaction time is kept at the temperature for 0.5 to 1.2 hours to obtain an epoxy-containing polycarboxylate superplasticizer with a solid content of 50%.

[0021] The above technical solution refines the precise feeding sequence and dropping kinetic parameters for precursor synthesis. Through scientific material distribution, it completely eliminates the risk of explosive polymerization caused by strong exothermic reactions, ensuring the uniformity and stability of the polymer molecular skeleton structure.

[0022] Furthermore, step S2 includes: S21, mix 200 parts of epoxy-containing polycarboxylate superplasticizer with a solid content of 50% with 2.5 to 3.5 parts of liquid alkali, adjust the pH of the system to 9.0 to 9.5, then add 0.05 to 0.1 parts of catalyst and stir evenly; S22, mix 4.0 to 4.5 parts of triethanolamine borate with 35.0 to 40.0 parts of water to prepare an aqueous solution containing triethanolamine borate; S23, at room temperature, an aqueous solution containing triethanolamine borate is added dropwise to the mixed system obtained in S21 for 1 to 1.5 hours, and the reaction time after the addition is 0.5 to 1 hour to obtain a rust-inhibiting polycarboxylate superplasticizer.

[0023] The above technical solution clarifies the alkaline catalytic window and kinetic time for the nucleophilic grafting reaction, ensuring a high conversion rate for the ring-opening reaction while avoiding the hydrolysis and breakage of the main chain caused by excessively vigorous reaction.

[0024] Furthermore, the ambient temperature in both steps S1 and S2 is 10℃~30℃.

[0025] Thirdly, the present invention proposes the application of the rust-inhibiting polycarboxylate superplasticizer described in the first aspect and the preparation method of the rust-inhibiting polycarboxylate superplasticizer described in the second aspect in the preparation of building materials or concrete.

[0026] In the above technical solution, this invention achieves a molecular-level uniform distribution of rust-inhibiting groups in the microstructure of concrete by limiting the application of rust-inhibiting polycarboxylate superplasticizers in building materials and concrete. Compared with traditional external admixtures of rust inhibitors, this invention guides the rust-inhibiting components to migrate directionally to the surface of reinforcing steel bars through the adsorption and dispersion of superplasticizer molecules. Without altering the concrete construction process, this significantly improves the structural durability and service life of large-scale civil engineering projects, especially those in high-chlorine environments.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes chemical grafting technology to stably anchor triethanolamine borate ester onto the side chains of a polycarboxylate backbone, fundamentally overcoming technical bottlenecks such as poor compatibility, easy precipitation, and mutual interference between different components in the compound system. Because the rust-inhibiting functional groups and the water-reducing agent's active groups are located in the same macromolecular chain segment, the rust-inhibiting components achieve uniform molecular-level dispersion at the microscopic level during concrete mixing, synergistically exerting the steric hindrance water-reducing effect and electrochemical protection function, thus achieving an ideal superposition and multiplication of "water-reducing and rust-inhibiting" performance.

[0028] 2. On one hand, this invention utilizes the extremely strong polar adsorption capacity of the amino groups in the grafted structure to preferentially and directionally align the polymer chain segments on the surface of the reinforcing steel, forming a dense and robust hydrophobic molecular protective film that effectively isolates the reinforcing steel matrix from corrosive media such as chloride ions and oxygen. On the other hand, the borate ions in the molecular structure can react with the ferrous ions on the surface of the reinforcing steel to generate a poorly soluble iron-boron composite oxide passivation layer. By effectively inhibiting the anodic electrochemical reaction process, this significantly increases the pitting potential of the reinforcing steel in strongly alkaline and high-chloride environments, endowing the reinforcing steel with excellent long-term corrosion resistance.

[0029] 3. This invention significantly improves the overall density and structural durability of concrete materials. The borate ions released from the molecular chains can chemically react with calcium ions in the concrete pore fluid, generating in-situ insoluble calcium borate micro-precipitates. These fine precipitates effectively fill and block the capillary pores and micro-cracks inside the concrete, significantly optimizing the pore size distribution. This physical sealing effect, combined with the water-reducing and densifying effect of the water-reducing agent, greatly increases the diffusion resistance of corrosive media migrating to the surface of the reinforcing steel, macroscopically manifested as a significant reduction in the chloride ion permeability coefficient, thereby significantly extending the service life of reinforced concrete structures in marine engineering and harsh environments.

[0030] 4. This invention employs an innovative two-step synthesis process of "copolymerization followed by grafting," with the entire production process conducted at room temperature. The reaction conditions are extremely mild and do not require energy-intensive thermal initiation. Through scientific monomer allocation and dropwise timing control, the self-polymerization and gelation problems of highly reactive epoxy monomers during polymerization are effectively solved. The process route is simple and easy to scale up for industrial production. This method not only significantly reduces production energy consumption and safety risks but also does not generate harmful byproducts during synthesis, aligning with the sustainable development direction of green chemistry and building energy conservation and emission reduction. It possesses extremely high engineering application value and market prospects. Attached Figure Description

[0031] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of the invention. Many anticipated advantages of the embodiments and other embodiments of the invention will be readily recognized as they become better understood through reference to the following detailed description. Elements in the drawings are not necessarily to scale. The same reference numerals refer to corresponding similar parts.

[0032] Figure 1 This is a flowchart of a method for preparing a rust-inhibiting polycarboxylate superplasticizer according to an embodiment of the present invention. Detailed Implementation

[0033] In the following detailed description, reference is made to the accompanying drawings, which form part of the detailed description and are illustrated by way of illustrative specific embodiments in which the invention may be practiced. In this regard, directional terms such as “top,” “bottom,” “left,” “right,” “up,” “down,” etc., are used with reference to the orientation of the described figures. Because components of the embodiments may be positioned in several different orientations, directional terms are used for illustrative purposes and are by no means limiting.

[0034] It should be understood that other embodiments or logical changes may be made without departing from the scope of the invention. Therefore, the following detailed description should not be taken in a limiting sense, and the scope of the invention is defined by the appended claims.

[0035] Figure 1 A flowchart illustrating a method for preparing a rust-inhibiting polycarboxylate superplasticizer according to an embodiment of this application is shown. Figure 1 As shown, the method includes the following steps: S1, unsaturated polyether, unsaturated sulfonate and water are mixed and dissolved, and unsaturated carboxylic acid, liquid alkali and oxidant are added in sequence and mixed evenly to obtain a base liquid; at room temperature, a first solution and a second solution are added dropwise to the base liquid simultaneously. The first solution includes unsaturated carboxylic acid, glycidyl methacrylate and water, and the second solution includes chain transfer agent, reducing agent and water; after the addition is completed, the reaction is kept at a constant temperature to obtain epoxy-containing polycarboxylic acid water-reducing agent.

[0036] In some specific embodiments, by weight, 185-205 parts of unsaturated polyether, 2.0-21.0 parts of unsaturated sulfonate, and 184-225 parts of water are mixed and, after complete dissolution, 2.4-2.8 parts of unsaturated carboxylic acid are added and stirred evenly; then 1.2-1.4 parts of liquid alkali are added and stirred evenly; then 0.8-2.5 parts of oxidant are added and stirred evenly to obtain the base solution; at room temperature, a first solution and a second solution are added dropwise simultaneously. The first solution includes 13.5-17.0 parts of unsaturated carboxylic acid, 0.8-8.0 parts of glycidyl methacrylate, and 12.0-20.0 parts of water, and the second solution includes 0.6-3.1 parts of chain transfer agent, 0.2-0.6 parts of reducing agent, and 15.0-62.0 parts of water; after the dropwise addition is complete, the reaction is maintained at a constant temperature to obtain an epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50%.

[0037] Specifically, by weight, 185–205 parts of ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000, 2.0–21.0 parts of sodium methacrylate sulfonate, and 184–225 parts of water are added to a four-necked flask and stirred until completely dissolved. Then, 2.4–2.8 parts of acrylic acid or methacrylic acid are added and stirred for 10 minutes. Next, 1.2–1.4 parts of liquid alkali are added and stirred for 10 minutes. Finally, 0.8–2.5 parts of potassium persulfate or ammonium persulfate are added and stirred for 8–12 minutes to obtain the base solution. A first solution is obtained by uniformly mixing 13.5–17.0 parts of acrylic acid or methacrylic acid, 0.8–8.0 parts of glycidyl methacrylate, and 12.0–20.0 parts of water. A second solution is obtained by uniformly mixing 0.6–3.1 parts of mercaptoacetic acid, mercaptopropionic acid, or mercaptoethanol, 0.2–0.6 parts of ascorbic acid, sodium bisulfite, or an organic sulfinate derivative, and 15.0–62.0 parts of water. At room temperature, the first and second solutions are added dropwise to a four-necked flask simultaneously for 1–3 hours, and then kept at the temperature for 0.5–1.2 hours to obtain an epoxy-containing polycarboxylate superplasticizer with a solid content of 50%.

[0038] S2, add liquid alkali to the epoxy-containing polycarboxylate superplasticizer to adjust the pH of the system to 9.0-9.5, add catalyst and mix evenly; add an aqueous solution containing triethanolamine borate dropwise at room temperature, and keep the reaction at the temperature after the addition is complete to obtain the rust-inhibiting polycarboxylate superplasticizer.

[0039] In some specific embodiments, 200 parts of epoxy-containing polycarboxylate superplasticizer and 2.5-3.5 parts of liquid alkali were added to a three-necked flask, followed by 0.05-0.1 parts of tetrabutylammonium bromide, and stirred for 10 minutes. Then, 4.0-4.5 parts of triethanolamine borate and 35.0-40.0 parts of water were uniformly mixed and added dropwise over 1.0-1.5 hours, followed by maintaining the temperature for 0.5-1 hour to obtain a rust-inhibiting polycarboxylate superplasticizer.

[0040] In some specific embodiments, the liquid alkali includes at least one of sodium hydroxide solution or potassium hydroxide solution.

[0041] The core synthetic mechanism of this invention employs a molecular structure design strategy of "copolymerization followed by grafting." Because the target rust-inhibiting functional molecule, triethanolamine borate, lacks unsaturated double bonds capable of participating in free radical polymerization, it cannot be directly introduced into the polycarboxylic acid macromolecular backbone via conventional one-step copolymerization. However, triethanolamine borate is rich in free hydroxyl groups, which possess strong nucleophilicity and can, under the activation of specific catalysts, act as nucleophiles to undergo efficient nucleophilic ring-opening reactions with epoxy groups. Based on these chemical characteristics, this invention creatively introduces a bifunctional monomer possessing both polymerizable unsaturated double bonds and highly reactive epoxy groups in the first polymerization step. By free radical copolymerizing this bifunctional monomer with unsaturated monomers such as ethylene glycol monovinyl polyvinyl alcohol ether and acrylic acid, a polycarboxylic acid polymer precursor with numerous pendant epoxy groups on its side chains is synthesized first. Subsequently, in the second grafting reaction stage, under the catalysis of a catalyst, the free hydroxyl groups in triethanolamine borate ester undergo nucleophilic attack on the epoxy groups on the side chains of the polycarboxylic acid precursor, initiating an epoxy ring-opening esterification or etherification reaction. Through this ingenious reaction pathway, this invention successfully anchors triethanolamine borate ester to the polycarboxylic acid backbone in a stable covalent bond form. This allows the final synthesized single-component polymer to perfectly integrate the steric hindrance effect of the comb-shaped water-reducing agent molecule and the electrochemical protective function of the rust-inhibiting group at the microscopic level, thus possessing both excellent water-reducing and slump-preserving properties and long-lasting rust-inhibiting performance for steel reinforcement.

[0042] In actual production, the reaction system is insensitive to ambient temperature and does not require complex heating mantles or condensation circulation equipment. It can spontaneously complete the free radical polymerization and nucleophilic ring-opening grafting process under normal room temperature conditions. This "no heating, no cooling" process not only simplifies the operation process and reduces the impact of manual temperature control errors on product quality, but also enables the stable preparation of high-performance rust-inhibiting water-reducing agents even under rudimentary temporary production conditions such as marine engineering sites.

[0043] The rust-inhibiting polycarboxylate superplasticizer finally obtained through the above preparation method is prepared by a ring-opening grafting reaction between an epoxy-containing polycarboxylate superplasticizer and triethanolamine borate.

[0044] In some specific embodiments, the polymer raw materials for preparing the epoxy-containing polycarboxylic acid water-reducing agent include, by weight: 185-205 parts of unsaturated polyether, 2.0-21.0 parts of unsaturated sulfonate, 15.0-20.0 parts of unsaturated carboxylic acid, and 0.8-8.0 parts of glycidyl methacrylate. The unsaturated polyether includes ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000; the unsaturated sulfonate is sodium methacrylate; and the unsaturated carboxylic acid is selected from at least one of acrylic acid or methacrylic acid.

[0045] In some specific embodiments, the polymer raw materials for preparing the epoxy-containing polycarboxylic acid water-reducing agent further include, by weight: 0.8–2.5 parts of oxidant, 0.2–0.6 parts of reducing agent, 0.6–3.1 parts of chain transfer agent, 1.2–1.4 parts of liquid alkali, and 211–280 parts of water. The oxidant is selected from at least one of potassium persulfate or ammonium persulfate; the reducing agent is selected from at least one of ascorbic acid, sodium bisulfite, or organic sulfinate derivatives; the chain transfer agent is selected from at least one of mercaptoacetic acid, mercaptopropionic acid, and mercaptoethanol; and the liquid alkali is selected from at least one of sodium hydroxide solution or potassium hydroxide solution.

[0046] In some specific embodiments, the reaction raw materials for preparing the rust-inhibiting polycarboxylate superplasticizer include, by weight: 200 parts of epoxy-containing polycarboxylate superplasticizer with a solid content of 50%, 2.5 to 3.5 parts of liquid alkali, 0.05 to 0.1 parts of catalyst, 4.0 to 4.5 parts of triethanolamine borate ester and 35.0 to 40.0 parts of water.

[0047] In some specific embodiments, the pH value of the rust-inhibiting polycarboxylate superplasticizer is 6 to 7.

[0048] Example 1 (1) Preparation of epoxy-containing polycarboxylate superplasticizer: By weight, 185 parts of ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000, 2.01 parts of sodium methacrylate sulfonate and 184 parts of water were added to a four-necked flask and stirred until completely dissolved; then 2.46 parts of acrylic acid were added and stirred for 10 min; then 1.23 parts of liquid alkali were added and stirred for 10 min; then 1 part of potassium persulfate was added and stirred for 10 min to obtain the base solution.

[0049] Mix 13.55 parts acrylic acid, 6.57 parts glycidyl methacrylate and 16.5 parts water evenly to prepare the first solution; mix 0.69 parts mercaptoethanol, 0.33 parts ascorbic acid and 17.7 parts water evenly to prepare the second solution.

[0050] At room temperature, the first solution and the second solution are simultaneously and uniformly added dropwise to a four-necked flask containing the above-mentioned base liquid. The addition time is 2 hours. After the addition is completed, the reaction is continued at the temperature for 1 hour to obtain an epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50%.

[0051] (2) Preparation of rust-inhibiting polycarboxylate superplasticizer: Add 200 parts of the epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50% prepared above and 3 parts of liquid alkali to a three-necked flask, then add 0.08 parts of tetrabutylammonium bromide as a catalyst, and stir for 10 minutes to mix evenly.

[0052] 4.15 parts of triethanolamine borate and 37.35 parts of water were mixed evenly to prepare an aqueous solution of rust inhibitor (i.e., an aqueous solution containing triethanolamine borate); at room temperature, the aqueous solution of rust inhibitor was added dropwise to the above three-necked flask over a period of 1 hour. After the addition was completed, the reaction was continued at the temperature for another 0.5 hours to obtain a rust-inhibiting polycarboxylate superplasticizer.

[0053] Example 2 (1) Preparation of epoxy-containing polycarboxylate superplasticizer: By weight, 185 parts of ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000, 8.02 parts of sodium methacrylate sulfonate, and 190 parts of water were added to a four-necked flask and stirred until completely dissolved; then 2.46 parts of methacrylic acid were added and stirred for 10 min; next, 1.23 parts of liquid alkali were added and stirred for 10 min; then 2.21 parts of ammonium persulfate were added and stirred for 10 min to obtain the base solution.

[0054] Mix 13.54 parts methacrylic acid, 0.88 parts glycidyl methacrylate, and 12.02 parts water evenly to prepare the first solution; mix 3.06 parts mercaptopropionic acid, 0.43 parts sodium bisulfite, and 60.54 parts water evenly to prepare the second solution.

[0055] At room temperature, the first solution and the second solution were simultaneously and uniformly added dropwise to a four-necked flask containing the above-mentioned base liquid for 1 hour. After the addition was completed, the reaction was continued at the temperature for 0.8 hours to obtain an epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50%.

[0056] (2) Preparation of rust-inhibiting polycarboxylate superplasticizer: Add 200 parts of the epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50% prepared above and 3 parts of liquid alkali to a three-necked flask, then add 0.08 parts of tetrabutylammonium bromide as a catalyst, and stir for 10 minutes to mix evenly.

[0057] Mix 4.15 parts of triethanolamine borate with 37.35 parts of water to prepare an aqueous solution of rust inhibitor; at room temperature, add the aqueous solution of rust inhibitor dropwise to the above three-necked flask at a uniform rate for 1 hour. After the addition is complete, continue to keep the temperature for 1 hour to obtain the rust-inhibiting polycarboxylate superplasticizer.

[0058] Example 3 (1) Preparation of epoxy-containing polycarboxylate superplasticizer: By weight, 195 parts of ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000, 16.82 parts of sodium methacrylate sulfonate, and 208.5 parts of water were added to a four-necked flask and stirred until completely dissolved. Then, 2.6 parts of methacrylic acid were added and stirred for 10 minutes. Next, 1.3 parts of liquid alkali were added and stirred for 10 minutes. Finally, 1.68 parts of potassium persulfate were added and stirred for 10 minutes to obtain the base solution.

[0059] Mix 15.6 parts methacrylic acid, 4.62 parts glycidyl methacrylate, and 16.9 parts water evenly to prepare the first solution; mix 2.3 parts mercaptopropionic acid, 0.55 parts ascorbic acid, and 49.4 parts water evenly to prepare the second solution.

[0060] At room temperature, the first solution and the second solution are simultaneously and uniformly added dropwise to a four-necked flask containing the above-mentioned base liquid for 1 hour. After the addition is completed, the reaction is continued at the temperature for another 1 hour to obtain an epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50%.

[0061] (2) Preparation of rust-inhibiting polycarboxylate superplasticizer: Add 200 parts of the epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50% prepared above and 3 parts of liquid alkali to a three-necked flask, then add 0.08 parts of tetrabutylammonium bromide as a catalyst, and stir for 10 minutes to mix evenly.

[0062] Mix 4.15 parts of triethanolamine borate with 37.35 parts of water to prepare an aqueous solution of rust inhibitor; at room temperature, add the aqueous solution of rust inhibitor dropwise to the three-necked flask at a uniform rate over a period of 1.5 hours. After the addition is complete, continue to keep the mixture warm for another 0.5 hours to obtain a rust-inhibiting polycarboxylate superplasticizer.

[0063] Example 4 (1) Preparation of epoxy-containing polycarboxylate superplasticizer: By weight, 200 parts of ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000, 2.13 parts of sodium methacrylate sulfonate and 199 parts of water were added to a four-necked flask and stirred until completely dissolved; then 2.67 parts of acrylic acid were added and stirred for 10 min; then 1.33 parts of liquid alkali were added and stirred for 10 min; then 0.87 parts of ammonium persulfate were added and stirred for 10 min to obtain the base solution.

[0064] Mix 16.59 parts acrylic acid, 7.11 parts glycidyl methacrylate and 19.78 parts water evenly to prepare the first solution; mix 0.6 parts mercaptoethanol, 0.28 parts ascorbic acid and 15.42 parts water evenly to prepare the second solution.

[0065] At room temperature, the first solution and the second solution are simultaneously and uniformly added dropwise to a four-necked flask containing the above-mentioned base liquid for 1 hour. After the addition is completed, the reaction is continued at the temperature for another 1 hour to obtain an epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50%.

[0066] (2) Preparation of rust-inhibiting polycarboxylate superplasticizer: Add 200 parts of the epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50% prepared above and 3 parts of liquid alkali to a three-necked flask, then add 0.08 parts of tetrabutylammonium bromide as a catalyst, and stir for 10 minutes to mix evenly.

[0067] Mix 4.15 parts of triethanolamine borate with 37.35 parts of water to prepare an aqueous solution of rust inhibitor; at room temperature, add the aqueous solution of rust inhibitor dropwise to the above three-necked flask at a uniform rate for 1 hour. After the addition is complete, continue to keep the temperature for 0.5 hours to obtain the rust-inhibiting polycarboxylate superplasticizer.

[0068] Example 5 (1) Preparation of epoxy-containing polycarboxylate superplasticizer: By weight, 205 parts of ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000, 20.5 parts of sodium methacrylate sulfonate and 222 parts of water were added to a four-necked flask and stirred until completely dissolved; then 2.73 parts of acrylic acid were added and stirred for 10 min; then 1.36 parts of liquid alkali were added and stirred for 10 min; then 1.1 parts of ammonium persulfate were added and stirred for 10 min to obtain the base solution.

[0069] Mix 15 parts acrylic acid, 7.77 parts glycidyl methacrylate and 19 parts water evenly to prepare the first solution; mix 0.76 parts mercaptoethanol, 0.21 parts sodium bisulfite and 16.8 parts water evenly to prepare the second solution.

[0070] At room temperature, the first solution and the second solution are simultaneously and uniformly added dropwise to a four-necked flask containing the above-mentioned base liquid for 1 hour. After the addition is completed, the reaction is continued at the temperature for another 1 hour to obtain an epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50%.

[0071] (2) Preparation of rust-inhibiting polycarboxylate superplasticizer: Add 200 parts of the epoxy-containing polycarboxylic acid water-reducing agent with a solid content of 50% prepared above and 3 parts of liquid alkali to a three-necked flask, then add 0.08 parts of tetrabutylammonium bromide as a catalyst, and stir for 10 minutes to mix evenly.

[0072] Mix 4.15 parts of triethanolamine borate with 37.35 parts of water to prepare an aqueous solution of rust inhibitor; at room temperature, add the aqueous solution of rust inhibitor dropwise to the above three-necked flask at a uniform rate for 1 hour. After the addition is complete, continue to keep the temperature for 0.5 hours to obtain the rust-inhibiting polycarboxylate superplasticizer.

[0073] Example 6 This embodiment provides a rust-inhibiting polycarboxylate superplasticizer, the preparation method of which is basically the same as that of Example 4, except that: in the preparation process of epoxy-containing polycarboxylate superplasticizer in step (1), 0.28 parts of ascorbic acid in the second solution are replaced with 0.28 parts of organic sulfinate derivative; the composition, ratio and process steps of the remaining raw materials are consistent with those of Example 1.

[0074] Example 7 This embodiment provides a rust-inhibiting polycarboxylate superplasticizer, the preparation method of which is basically the same as that of Example 4, except that: in the preparation process of epoxy-containing polycarboxylate superplasticizer in step (1), 0.6 parts of mercaptoethanol in the second solution are replaced with 0.6 parts of mercaptoacetic acid; the composition, ratio and process steps of the remaining raw materials are consistent with those of Example 4.

[0075] Comparative Example 1 Preparation of polycarboxylate superplasticizer (ungrafted rust inhibitor): By weight, 200 parts of ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000, 2.13 parts of sodium methacrylate sulfonate, and 199 parts of water were added to a four-necked flask and stirred until completely dissolved. Then, 2.67 parts of acrylic acid were added and stirred for 10 minutes. Next, 1.33 parts of liquid alkali were added and stirred for 10 minutes. Finally, 0.87 parts of ammonium persulfate were added and stirred for 10 minutes to obtain the base solution. 16.59 parts of acrylic acid, 7.11 parts of glycidyl methacrylate, and 13.82 parts of water were mixed evenly to prepare the first solution. 0.6 parts of mercaptoethanol, 0.28 parts of ascorbic acid, and 15.42 parts of water were mixed evenly to prepare the second solution. At room temperature, the first and second solutions were simultaneously and uniformly added dropwise to the four-necked flask containing the base solution over a period of 1 hour. After the addition was complete, the reaction was continued at the same temperature for another 1 hour to obtain a polycarboxylate superplasticizer with a solid content of 50%.

[0076] Comparative Example 2 Control group of commercially available physical compound rust inhibitors: Commercially available Subote SBT-ZX(V) type reinforced concrete corrosion inhibitor was selected as the control sample. In subsequent concrete performance verification, to ensure consistent benchmark fluidity, the admixture used was still the ungrafted polycarboxylate superplasticizer prepared in Comparative Example 1 (dosage was 3.56 kg / m³ as shown in Table 2). 3 Meanwhile, an additional 4% of the total mass of the commercially available rust inhibitor was added as physical additives to conduct composite verification.

[0077] The samples prepared in Examples 1-5 and Comparative Examples 1-2 of this invention were subjected to tests on the corrosion resistance of reinforcing steel and the application performance of concrete. The test results are detailed in Tables 1 to 3. Table 1 Potential Test Results / mV

[0078] The corrosion inhibition performance test of the reinforcing steel bars was conducted in accordance with the national standard GB / T33803-2015 "Test Method for Corrosion Resistance Performance of Corrosion Inhibitors for Reinforcing Steel Bars". Specific potential test results and macroscopic observations are shown in Table 1. After 7 days of continuous testing in a corrosive solution environment: Comparative Example 1 (conventional polycarboxylate superplasticizer without grafted corrosion inhibitor) showed obvious rust marks on the surface of the reinforcing steel bars, and the immersion solution changed color; its spontaneous potential shifted sharply negatively over time, dropping significantly to -332mV by the 7th day, indicating that the passivation film on the surface of the reinforcing steel bars had been destroyed, resulting in severe active corrosion. This demonstrates that the basic polymer superplasticizer skeleton itself does not possess any corrosion inhibition or anti-corrosion capabilities. Examples 1-5 (the corrosion-inhibiting polycarboxylate superplasticizer of this invention): The surface of the reinforcing steel bars was smooth and rust-free, and the solution remained clear and undiscolored. Its potential remained within a relatively positive range (between -189mV and -238mV) and fluctuated smoothly from 1 to 7 days. This strongly demonstrates that by introducing triethanolamine borate into the polymer chain segments through room-temperature copolymerization and ring-opening grafting technology, this single-component water-reducing agent can effectively form a dense protective film on the surface of reinforcing steel, significantly inhibiting electrochemical corrosion. Compared with Comparative Example 2 (physical admixture of commercially available rust inhibitor), Examples 1-5, in their low-dosage, single-component form, achieved or even partially outperformed Comparative Example 2 (where the potential remained at -210mV on day 7 in Example 4) which contained up to 4% of commercially available compounded rust inhibitor in the total amount of cementitious materials. This not only significantly reduces material costs but also completely solves the technical defects of traditional physical compounding methods, such as uneven distribution, late-stage precipitation, and poor compatibility.

[0079] In the concrete application performance test, referring to GB / T8076-2008 "Concrete Admixtures" and GB / T31296-2014 "Concrete Corrosion Inhibitors", the slump, compressive strength, and chloride ion permeability ratio of the rust-inhibiting polycarboxylate superplasticizer prepared in the embodiments of this invention and the comparative sample were tested. The mix proportion of the reference concrete is shown in Table 2, and the experimental results are shown in Table 3. Among them, for comparative example 2, the "admixture" mentioned in Table 2 is the ungrafted polycarboxylate superplasticizer prepared in comparative example 1; in addition, comparative example 2 also requires additional physical admixture of commercially available SBT-ZX(V) type rust inhibitor, the dosage of which is 4% of the total mass of cementitious materials (cement, fly ash and slag powder) in Table 2, that is, the actual additional amount of the commercially available rust inhibitor is 13.56 kg / m³. 3 Examples 1-5 and Comparative Example 1 of this invention only added single-component additives in the amounts specified in Table 2, without any additional physical compounding.

[0080] Table 2. Experimental mix proportions (unit: kg / m³) 3 )

[0081] Table 3 Concrete Performance Data

[0082] As can be seen from the test results in Tables 2 and 3, the rust-inhibiting polycarboxylate superplasticizer prepared by this invention has excellent comprehensive application performance.

[0083] Regarding workability and water-reducing performance, under the same mix proportions and admixture dosages, the initial slump of Examples 1-5 remained between 200 and 210 mm, achieving the same excellent level as the comparative examples. Furthermore, the workability of the concrete in Examples 1-5 was rated as "good," significantly better than the "average" of Comparative Examples 1 and 2. This indicates that the triethanolamine borate introduced through copolymerization and grafting not only did not disrupt the water-reducing and slump-retaining functions of the polycarboxylic acid macromolecular backbone, but also further improved the cohesiveness and encapsulation of the concrete through optimization of the molecular chain structure.

[0084] In terms of mechanical properties, the 7-day compressive strength (27.4–29.6 MPa) and 28-day compressive strength (45.3–47.1 MPa) of Examples 1–5 were slightly higher than those of the ungrafted Comparative Example 1 and the physically compounded Comparative Example 2 (Example 4 showed the best performance). This overcomes the technical bias that the addition of commercially available alkanolamine rust inhibitors often leads to a decrease in the early strength of concrete, proving that the chemically grafted single-molecule structure of the present invention has a good positive promoting effect on the cement hydration process, and achieves a steady increase in the compressive strength of concrete.

[0085] Furthermore, this invention exhibits exceptionally high resistance to chloride ion penetration and durability. As a key indicator of the durability of marine engineering concrete, Comparative Example 1, without grafted rust-inhibiting groups, showed a penetration coefficient as high as 92%, indicating poor durability; Comparative Example 2, with physical admixture of commercially available rust inhibitors, reduced this to 83%; while the penetration coefficients of Examples 1-5 of this invention were significantly reduced to 75%-84% (with Example 4 reaching as low as 75%). This strongly demonstrates that grafting rust-inhibiting functional groups onto the polymer backbone of water-reducing agents via chemical bonds can achieve molecular-level uniform dispersion of rust-inhibiting components at the microscopic pore level of concrete; this dispersion effect is far superior to traditional physical admixtures, effectively sealing capillary pores and blocking the penetration channels of free chloride ions, thereby endowing concrete with excellent resistance to seawater erosion and corrosion prevention.

[0086] Analysis of the test data in Tables 1 and 3 shows that, while maintaining excellent workability of fresh concrete, Examples 1-5 of this invention exhibit a significant positive shift in self-corrosion potential compared to Comparative Example 1 without grafting modification, and the chloride ion permeability coefficient can be reduced to as low as 75%. This result fully demonstrates from an experimental perspective that the amino and borate functional groups introduced by the present invention through chemical grafting successfully construct a multi-synergistic anti-corrosion mechanism of "physical adsorption film formation, electrochemical passivation inhibition, and micropore sealing" in the microstructure of the concrete on the surface of the reinforcing steel and its vicinity.

[0087] Furthermore, based on the in-depth data analysis in Table 3, the chloride ion penetration performance of this embodiment is not only far superior to Comparative Example 1 (the blank control), but also significantly outperforms Comparative Example 2 (the physical compounding process). This strongly confirms that borate ions, uniformly released with the molecular-level dispersion of the water-reducing agent, can interact with the pore fluid in concrete. A highly efficient in-situ chemical deposition reaction occurs. The resulting fine, insoluble calcium borate crystals synergistically enhance the water-reducing and densifying effect of the polycarboxylate superplasticizer. By effectively filling and blocking the capillary pores and microcracks inside the concrete, the pore size distribution is optimized, achieving a significant improvement in the resistance to penetration and diffusion. This fundamentally strengthens the durability and service safety of reinforced concrete structures under harsh environments.

[0088] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A rust-inhibiting polycarboxylate superplasticizer, characterized in that, The rust-inhibiting polycarboxylate superplasticizer is prepared by a ring-opening grafting reaction between an epoxy-containing polycarboxylate superplasticizer and triethanolamine borate.

2. The rust-inhibiting polycarboxylate superplasticizer according to claim 1, characterized in that, The polymer raw materials for preparing the epoxy-containing polycarboxylic acid water-reducing agent include, by weight: 185-205 parts of unsaturated polyether, 2.0-21.0 parts of unsaturated sulfonate, 15.0-20.0 parts of unsaturated carboxylic acid and 0.8-8.0 parts of glycidyl methacrylate.

3. The rust-inhibiting polycarboxylate superplasticizer according to claim 2, characterized in that, The polymer raw materials for preparing the epoxy-containing polycarboxylic acid water-reducing agent further include, by weight: 0.8-2.5 parts oxidant, 0.2-0.6 parts reducing agent, 0.6-3.1 parts chain transfer agent, 1.2-1.4 parts liquid alkali and 211-280 parts water.

4. The rust-inhibiting polycarboxylate superplasticizer according to claim 2, characterized in that, The unsaturated polyether includes ethylene glycol monovinyl polyvinyl alcohol ether with a molecular weight of 3000; the unsaturated sulfonate is sodium methacrylate sulfonate; and the unsaturated carboxylic acid is selected from at least one of acrylic acid or methacrylic acid.

5. The rust-inhibiting polycarboxylate superplasticizer according to claim 3, characterized in that, The oxidizing agent is selected from at least one of potassium persulfate or ammonium persulfate; the reducing agent is selected from at least one of ascorbic acid, sodium bisulfite, or organic sulfinate derivatives; the chain transfer agent is selected from at least one of mercaptoacetic acid, mercaptopropionic acid, and mercaptoethanol; and the liquid alkali is selected from at least one of sodium hydroxide solution or potassium hydroxide solution.

6. The rust-inhibiting polycarboxylate superplasticizer according to claim 1, characterized in that, The reaction raw materials for preparing the rust-inhibiting polycarboxylate superplasticizer include, by weight: 200 parts of the epoxy-containing polycarboxylate superplasticizer with a solid content of 50%, 2.5 to 3.5 parts of liquid alkali, 0.05 to 0.1 parts of catalyst, 4.0 to 4.5 parts of triethanolamine borate ester and 35.0 to 40.0 parts of water.

7. A method for preparing a rust-inhibiting polycarboxylate superplasticizer as described in any one of claims 1 to 6, characterized in that, The method includes: S1, unsaturated polyether, unsaturated sulfonate, and water are mixed and dissolved, and unsaturated carboxylic acid, liquid alkali, and oxidant are added sequentially and mixed evenly to obtain a base solution; at room temperature, a first solution and a second solution are simultaneously added dropwise to the base solution, the first solution comprising unsaturated carboxylic acid, glycidyl methacrylate, and water, and the second solution comprising a chain transfer agent, a reducing agent, and water; after the addition is complete, the reaction is maintained at a certain temperature to obtain the epoxy-containing polycarboxylic acid water-reducing agent; S2, add liquid alkali to the epoxy-containing polycarboxylate superplasticizer to adjust the pH of the system to 9.0-9.5, add catalyst and mix evenly; add an aqueous solution containing triethanolamine borate dropwise at room temperature, and keep the reaction at the temperature after the addition is complete to obtain the rust-inhibiting polycarboxylate superplasticizer.

8. The preparation method of the rust-inhibiting polycarboxylate superplasticizer according to claim 7, characterized in that, In step S1, the specific steps for preparing the epoxy-containing polycarboxylate superplasticizer, by weight, include: S11, 185-205 parts of unsaturated polyether, 2.0-21.0 parts of unsaturated sulfonate and 184-225 parts of water are mixed and dissolved, 2.4-2.8 parts of unsaturated carboxylic acid are added, and the mixture is stirred evenly. Then 1.2-1.4 parts of liquid alkali are added and stirred evenly. Finally, 0.8-2.5 parts of oxidant are added and stirred evenly to obtain the base liquid. S12, 13.5–17.0 parts of unsaturated carboxylic acid, 0.8–8.0 parts of glycidyl methacrylate, and 12.0–20.0 parts of water are mixed evenly to obtain the first solution; 0.6–3.1 parts of chain transfer agent, 0.2–0.6 parts of reducing agent, and 15.0–62.0 parts of water are mixed evenly to obtain the second solution; S13, the first solution and the second solution are simultaneously added dropwise to the base liquid at room temperature for 1 to 3 hours. After the addition is completed, the reaction time is kept warm for 0.5 to 1.2 hours to obtain the epoxy-containing polycarboxylate superplasticizer with a solid content of 50%.

9. The preparation method of the rust-inhibiting polycarboxylate superplasticizer according to claim 7, characterized in that, Step S2 includes: S21, mix 200 parts of the epoxy-containing polycarboxylate superplasticizer with a solid content of 50% with 2.5 to 3.5 parts of liquid alkali, adjust the pH of the system to 9.0 to 9.5, then add 0.05 to 0.1 parts of the catalyst and stir evenly; S22, mix 4.0 to 4.5 parts of triethanolamine borate with 35.0 to 40.0 parts of water to prepare the aqueous solution containing triethanolamine borate; S23, at room temperature, the aqueous solution containing triethanolamine borate is added dropwise to the mixed system obtained in S21 for 1 to 1.5 hours, and the reaction time after the addition is 0.5 to 1 hour to obtain the rust-inhibiting polycarboxylate superplasticizer.

10. The application of a rust-inhibiting polycarboxylate superplasticizer as described in any one of claims 1 to 6 in the preparation of building materials or concrete.

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