High-stability water-reducing agent and preparation method thereof

Abstract

The application discloses a high-stability water-reducing agent and a preparation method thereof. The water-reducing agent comprises the following raw materials in parts by weight: 100-150 parts of an amino silane oligomer, 80-120 parts of an epoxy-terminated allyl polyether, 0.5-3 parts of a Lewis acid catalyst, and 5-10 parts of a sodium hydroxide solution. The water-reducing agent comprises a main chain and polyethylene glycol side chains, the main chain further comprises a silicon-oxygen structure (Si-O-Si) and Si-OH active groups, and thus the chemical stability of concrete can be improved and the water consumption of the concrete can be reduced.

Description

Technical Field

[0001] This invention relates to the field of concrete additives, and in particular to a highly stable water-reducing agent and its preparation method. Background Technology

[0002] Polycarboxylate superplasticizers, as a core component of high-performance concrete additives, directly affect the workability and long-term durability of concrete due to their molecular structure and chemical stability. Traditional polycarboxylate superplasticizers use C / C single bonds as the backbone, introducing polyoxyethylene ether side chains to enhance steric hindrance and achieve dispersion in concrete. However, these superplasticizers exhibit significant drawbacks in strongly alkaline environments: when the pH of the concrete system exceeds 12, the C / C backbone is prone to chain breakage and hydrolysis, resulting in a half-life of less than 30 days. This leads to exacerbated slump loss in the concrete, severely impacting construction quality.

[0003] To improve slump performance, researchers have made numerous attempts. For example, patent CN102993432A discloses a method of introducing functional side chains through intermediate modification. While this improves the slump retention of water-reducing agents to some extent, it does not optimize the structure of the main chain and cannot fundamentally solve the problem of chain breakage and hydrolysis of the main chain under strong alkaline conditions. Furthermore, researchers have introduced silane modification technology into the field of water-reducing agents. However, existing technologies, such as patent CN117844347A, are mostly limited to modifying the side chains, optimizing material properties only by adjusting the side chain length or functional group type. They do not consider introducing the silicon-oxygen bond structure into the molecular main chain, failing to fully utilize the high-temperature and acid-alkali skeletal advantages of the silicon-oxygen bond. This results in poor chemical stability of the water-reducing agent under strong alkaline conditions, making it difficult to meet the stringent chemical stability requirements of high-performance concrete.

[0004] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art. Summary of the Invention

[0005] The purpose of this invention is to synthesize a water-reducing agent containing a main chain and polyethylene glycol side chains. The main chain contains a silicon-oxygen structure (Si-O-Si) and Si-OH active groups, which can improve the chemical stability of concrete and reduce the water consumption of concrete.

[0006] To achieve the above objectives, the present invention provides a highly stable water-reducing agent comprising the following raw materials in the indicated weight ratios:

[0007] 100-150 parts of aminosilane oligomer

[0008] 80-120 parts of terminal epoxy allyl polyether

[0009] Lewis acid catalyst 0.5-3 parts

[0010] 5-10 parts of sodium hydroxide solution.

[0011] Optionally, the raw materials include the following parts by weight: 120 parts of aminosilane oligomer, 100 parts of terminal epoxy allyl polyether, 1.5 parts of Lewis acid catalyst, and 5 parts of sodium hydroxide solution.

[0012] Optionally, the molar ratio of the terminal epoxy allyl polyether to the aminosilane oligomer is 1:(1.2-1.5), and the mass fraction of the sodium hydroxide solution is 30%-35%.

[0013] Optionally, the Lewis acid catalyst is either boron trifluoride diethyl ether or aluminum chloride.

[0014] Optionally, the molecular weight of the aminosilane oligomer is 500-2000, and the molecular weight of the terminal epoxy allyl polyether is 500-1500.

[0015] The present invention also provides a method for preparing the above-mentioned highly stable water-reducing agent, the method comprising:

[0016] Step 1: Mix the aminosilane oligomer with the terminal epoxy allyl polyether and heat it to undergo an amidation reaction under the action of a Lewis acid catalyst to obtain the prepolymer;

[0017] Step 2: Add sodium hydroxide solution to the prepolymer to allow for hydrolysis and obtain a highly stable water-reducing agent.

[0018] Optionally, in step 1, the heating temperature is 60℃-80℃, and the amidation reaction time is 4h-6h.

[0019] Optionally, in step 2, the hydrolysis temperature is 40℃-60℃, the hydrolysis reaction time is 2h-3h, and the pH is ≥13.

[0020] Optionally, after step 2, the process further includes: filtering the highly stable water-reducing agent.

[0021] Optionally, the pH of the highly stable water-reducing agent is adjusted to 7-8, resulting in a highly stable water-reducing agent with a solid content of 40%-50%.

[0022] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0023] Under alkaline conditions, a water-reducing agent containing a main chain and polyethylene glycol side chains was synthesized. The main chain contains a silicon-oxygen structure (Si-O-Si) and Si-OH active groups. On the one hand, the Si-O bond energy is relatively large and is not prone to chain scission hydrolysis, which significantly improves the chemical stability of the water-reducing agent and thus the chemical stability of concrete. On the other hand, the Si-O bond angle has a high degree of freedom, and adjacent chemical bonds can be rotated through single bonds, so that the bond angle can be flexibly changed between 140° and 180°, which has high flexibility and can more easily encapsulate cement particles. Furthermore, the Ca-O-Si bond formed by the reaction of the Si-OH active groups with the cement hydration product Ca(OH)2 has a large binding energy. The presence of Si-O bonds and Ca-O-Si bonds can enable the water-reducing agent to be firmly adsorbed on the surface of cement particles, thereby increasing the water reduction rate of the water-reducing agent and thus reducing the water consumption of concrete. Attached Figure Description

[0024] Figure 1 This is a flowchart of the preparation method of the high-stability water-reducing agent of the present invention.

[0025] Figure 2 This is a schematic diagram of the chemical equation for the amidation reaction of the present invention.

[0026] Figure 3 This is a schematic diagram of the chemical equation for the hydrolysis reaction of the present invention. Detailed Implementation

[0027] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the highly stable water-reducing agent and its preparation method proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions, intended only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the accompanying drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes and to enable those skilled in the art to understand and read them, and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0028] As described in the background section, existing technologies do not consider introducing the silicon-oxygen bond structure into the molecular backbone of water-reducing agents. This fails to fully utilize the high-temperature resistance and acid / alkali resistance of the silicon-oxygen bond framework, resulting in poor chemical stability of the water-reducing agent in strongly alkaline environments, making it difficult to meet the stringent chemical stability requirements of high-performance concrete. Therefore, this invention introduces the silicon-oxygen bond structure into the molecular backbone of the water-reducing agent. The Si-O bond energy is relatively large and less prone to chain scission and hydrolysis, significantly improving the chemical stability of the water-reducing agent and consequently improving the chemical stability of concrete. Furthermore, the high degree of freedom of the Si-O bond angle provides greater flexibility, allowing for easier encapsulation of cement particles, thereby increasing the water-reducing rate of the water-reducing agent and reducing the water consumption of concrete.

[0029] Specifically, the present invention provides a highly stable water-reducing agent comprising the following raw materials in the following weight ratios: 100-150 parts of aminosilane oligomer; 80-120 parts of terminal epoxy allyl polyether; 0.5-3 parts of Lewis acid catalyst; and 5-10 parts of sodium hydroxide solution.

[0030] Preferably, the raw materials comprise the following parts by weight: 120 parts of aminosilane oligomer; 100 parts of terminal epoxy allyl polyether; 1.5 parts of Lewis acid catalyst; and 5 parts of sodium hydroxide solution. The structural formula of the aminosilane oligomer is: In the structural formula, n takes a positive integer between 150 and 300. The structural formula of the terminal epoxy allyl polyether is: In the structural formula, x takes a positive integer from 10 to 15, and y takes a positive integer from 2 to 17.

[0031] In some embodiments, the molar ratio of terminal epoxy allyl polyether to aminosilane oligomer is 1:(1.2-1.5), the mass fraction of sodium hydroxide solution is 30%-35%, the Lewis acid catalyst is any one of boron trifluoride ether and aluminum chloride, the molecular weight of aminosilane oligomer is 500-2000, and the molecular weight of terminal epoxy allyl polyether is 500-1500.

[0032] like Figure 1 As shown, the present invention also provides a method for preparing the above-mentioned highly stable water-reducing agent, the method comprising:

[0033] Step 1: Mix the aminosilane oligomer with the terminal epoxy allyl polyether and heat it to undergo an amidation reaction under the action of a Lewis acid catalyst to obtain the prepolymer.

[0034] Under the above weight ratio, the Lewis acid catalyst catalyzes the amidation reaction between the aminosilane oligomer and the terminal epoxy allyl polyether to obtain a prepolymer with amide bonds (-CONH-) and polyethylene glycol side chains. The structural formula of the prepolymer is as follows: In the structural formula, x takes a positive integer from 10 to 15, y takes a positive integer from 2 to 17, p + q = n, the value of q is related to the added terminal epoxy allyl polyether, and n takes a positive integer from 150 to 300 (see [link to structural formula]). Figure 2 ).

[0035] In some embodiments, the heating temperature is 60℃-80℃, and the amidation reaction time is 4h-6h. The higher the heating temperature and the longer the reaction time, the more complete the amidation reaction and the higher the content of the prepolymer obtained. Since the amide bonds in the prepolymer are beneficial to improving alkali resistance, the higher the prepolymer content, the stronger the alkali resistance.

[0036] Step 2: Add sodium hydroxide solution to the prepolymer to allow for hydrolysis and obtain a highly stable water-reducing agent.

[0037] Add a 30%-35% sodium hydroxide solution to the prepolymer obtained above, controlling the pH to ≥13, to induce a hydrolysis reaction, yielding a highly stable water-reducing agent containing a main chain and side chains. The main chain contains silicon-oxygen structures (Si-O-Si) and Si-OH active groups, and the side chains are polyethylene glycol. The main chain and side chains are connected by amide bonds (see [link to product]). Figure 3 The Si-O bond has a large energy and is not prone to chain scission and hydrolysis, which significantly improves the chemical stability of water-reducing agents and concrete. The Si-O bond angle has a high degree of freedom, and adjacent chemical bonds can be rotated through single bonds, so that the bond angle can be flexibly changed between 140° and 180°, which has high flexibility and can more easily encapsulate cement particles. At the same time, the Ca-O-Si bond formed by the reaction of Si-OH active groups with cement hydration product Ca(OH)2 has a large binding energy. The presence of Si-O bonds and Ca-O-Si bonds can enable water-reducing agents to be firmly adsorbed on the surface of cement particles, improve the water reduction rate of water-reducing agents, and thus reduce the water consumption of concrete.

[0038] In some embodiments, the hydrolysis temperature is 40℃-60℃ and the hydrolysis reaction time is 2h-3h.

[0039] Following step 2, the process further includes: filtering the highly stable water-reducing agent.

[0040] The water-reducing agent solution was diluted with water to adjust the pH to 7-8, and then filtered to remove impurities, ultimately yielding a highly stable water-reducing agent with a solid content of 40%-50%. Under pH conditions of 7-8, the highly stable water-reducing agent exhibits better stability and a longer shelf life.

[0041] The preparation method of the high-stability water-reducing agent of the present invention is described in detail below with reference to the embodiments. The aminosilane oligomer used in the embodiments was purchased from USI (United Silicon) Nanjing Co., Ltd., the terminal epoxy allyl polyether was purchased from Liaoning Kelon Fine Chemical Co., Ltd., and the boron trifluoride ether and sodium hydroxide solution were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0042] Example

[0043] Step 1: Under the catalysis of 1.5 parts boron trifluoride diethyl ether, 120 parts of aminosilane oligomer with a molecular weight of 1200 and 100 parts of terminal epoxy allyl polyether with a molecular weight of 1000 are heated at 60°C and amidated for 4 hours to obtain a prepolymer with amide bonds and polyethylene glycol side chains.

[0044] Step 2: Add 5 parts of 30% sodium hydroxide solution to the prepolymer obtained in Step 1, control the pH to 13, heat at 40°C, and hydrolyze for 2 hours to obtain a highly stable water-reducing agent.

[0045] Step 3: Adjust the pH of the high-stability water-reducing agent solution obtained in Step 2 to 7, and filter the water-reducing agent to finally obtain a high-stability water-reducing agent with a solid content of 40%.

[0046] The highly stable water-reducing agent prepared in the examples was added to concrete, and the chemical stability, water consumption, and compressive strength of the concrete were tested simultaneously. Test results showed that under strongly alkaline conditions (pH=13), the viscosity of the concrete remained above 90% for 30 days (tested using the method in GB / T 8077-2012), indicating strong chemical stability. The adsorption capacity of the water-reducing agent on the surface of cement particles reached 8.2 mg / g (tested using XPS), increasing the cement coverage by 30%, thereby increasing the water reduction rate of the water-reducing agent by 23% (water-cement ratio of 0.29, tested using the method in GB 8076-2008), significantly reducing the water consumption of the concrete. Compared with C30 concrete, the 7-day compressive strength of the concrete with the added highly stable water-reducing agent increased by 18%.

[0047] In summary, this invention synthesizes a water-reducing agent comprising a main chain and polyethylene glycol side chains. The main chain contains a silicon-oxygen structure (Si-O-Si) and Si-OH active groups. The Si-O bond energy is relatively large and is not prone to chain scission hydrolysis, significantly improving the chemical stability of the water-reducing agent and concrete. At the same time, the Si-O bond angle has a high degree of freedom and high flexibility, making it easier to encapsulate cement particles. Furthermore, the Ca-O-Si bond formed by the reaction of the Si-OH active groups with the cement hydration product Ca(OH)2 has a large binding energy. The presence of Si-O and Ca-O-Si bonds enables the water-reducing agent to be firmly adsorbed on the surface of cement particles, increasing the water reduction rate of the water-reducing agent and thus reducing the water consumption of concrete.

[0048] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0049] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a highly stable water-reducing agent, characterized in that, The method includes: Step 1: Mix the aminosilane polymer with the terminal epoxy allyl polyether and heat it to undergo an amidation reaction under the action of a Lewis acid catalyst to obtain the prepolymer; Step 2: Add sodium hydroxide solution to the prepolymer to allow a hydrolysis reaction to occur, thereby obtaining a highly stable water-reducing agent; The weight ratio of the raw materials is as follows: 100-150 parts of aminosilane polymer 80-120 parts of terminal epoxy allyl polyether Lewis acid catalyst 0.5-3 parts 5-10 parts sodium hydroxide solution; The main chain of the high-stability water-reducing agent contains a Si-O-Si silicon-oxygen structure and a Si-OH active group; The structural formula of the aminosilane polymer is as follows: n takes a positive integer between 150 and 300.

2. The preparation method of the high-stability water-reducing agent as described in claim 1, characterized in that, The raw materials contain the following parts by weight: 120 parts aminosilane polymer, 100 parts terminal epoxy allyl polyether, 1.5 parts Lewis acid catalyst, and 5 parts sodium hydroxide solution.

3. The preparation method of the high-stability water-reducing agent as described in claim 1, characterized in that, The molar ratio of the terminal epoxy allyl polyether to the aminosilane polymer is 1:(1.2-1.5), and the mass fraction of the sodium hydroxide solution is 30%-35%.

4. The preparation method of the high-stability water-reducing agent as described in claim 1, characterized in that, The Lewis acid catalyst is either boron trifluoride diethyl ether or aluminum chloride.

5. The preparation method of the high-stability water-reducing agent as described in claim 1, characterized in that, In step 1, the heating temperature is 60℃-80℃, and the amidation reaction time is 4h-6h.

6. The method for preparing the high-stability water-reducing agent as described in claim 1, characterized in that, In step 2, the hydrolysis temperature is 40℃-60℃, the hydrolysis reaction time is 2h-3h, and the pH is ≥13.

7. The preparation method of the high-stability water-reducing agent as described in claim 1, characterized in that, Following step 2, the process further includes: filtering the highly stable water-reducing agent.

8. The preparation method of the high-stability water-reducing agent as described in claim 7, characterized in that, The pH of the highly stable water-reducing agent is adjusted to 7-8, and the solid content of the resulting highly stable water-reducing agent is 40%-50%.

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