Anti-freezing agent based on sodium formate as well as preparation method and application of anti-freezing agent

Abstract

The invention provides an anti-freezing agent based on sodium formate and a preparation method and application thereof.The preparation method of the anti-freezing agent comprises the following steps that S1, zirconium-based metal salt and organic ligands are dissolved in an organic solvent, zirconium ions and the organic ligands form a frame structure through solvothermal reaction, and an MOF material is obtained; wherein the organic ligand comprises at least one of 2-amino terephthalic acid and 2, 5-diamino terephthalic acid; s2, activating carboxyl on a polycarboxylic acid water reducing agent, and reacting with amino on the MOF material to obtain a polycarboxylic acid modified MOF material; s3, the polycarboxylic acid modified MOF material is soaked in a sodium salt aqueous solution, so that sodium salt is adsorbed and loaded on the polycarboxylic acid modified MOF material, and an anti-freezing agent is obtained; wherein the sodium salt comprises sodium formate. The anti-freezing agent obtained by the method has good long-acting anti-freezing and water-reducing effects, and can be used for preparing a novel wall material with relatively good anti-freezing capability.

Description

Technical Field

[0001] This application belongs to the technical field of antifreeze production, and specifically relates to a formate-based antifreeze and its preparation method and application. Background Art

[0002] With the development of construction engineering technology, the construction of concrete projects in cold regions has received increasing attention. Under low-temperature environments, the hydration reaction of concrete is slow, and the early strength development is insufficient. It is extremely vulnerable to external factors such as freeze-thaw cycles, thus reducing the durability of the project. Therefore, it is of great significance to develop efficient, environmentally friendly, and economical concrete antifreezes.

[0003] Existing antifreezes mainly include chloride salts (such as calcium chloride) and organic antifreezes. Although calcium chloride has good antifreeze performance, its high corrosiveness poses a threat to the durability of steel bars and concrete structures; while some organic antifreezes are limited due to high costs and environmental pollution problems. In addition, some traditional antifreezes may also affect the concrete hydration process in low-temperature environments, resulting in unsatisfactory early strength development, thereby affecting the project progress and quality.

[0004] In recent years, formate has gradually attracted attention due to its low corrosiveness, good environmental friendliness, and certain hydration promotion effect. Formate can decompose into Na + and formate ions (HCOO - ) in the cement paste. These ions can regulate the surface charge of cement particles and promote the dispersion between particles, thus playing a water-reducing role to a certain extent. At the same time, formate has an antifreeze effect in low-temperature environments, which helps to improve the construction conditions in winter. However, currently, the mainstream method of using formate as a concrete antifreeze is to add it as an antifreeze component to the concrete. However, formate is easily soluble in water and is released too quickly in the concrete system, easily lost and unable to effectively play a long-term antifreeze and water-reducing effect. Therefore, it is necessary to optimize the preparation process of formate-based antifreezes to improve the above problems.

[0005] Patent CN110423038A discloses a water-reducing agent and its preparation method, an antifreeze and its uses, and concrete. The antifreeze is formed by blending a water-reducing agent and a non-oxidizing salt. The water-reducing agent includes: isopentenyl alcohol polyoxyethylene ether and allyl alcohol polyoxyethylene ether, and at least one of acrylic acid and maleic anhydride. The molar ratio of the isopentenyl alcohol polyoxyethylene ether to the allyl alcohol polyoxyethylene ether is 1:0.8, and the non-oxidizing salt includes formate and sodium thiocyanate. Blending formate with the water-reducing agent and other additives in this antifreeze cannot effectively solve the problem of rapid release and easy loss of formate.

[0006] Based on this, it is necessary to provide a formate-based antifreeze with good long-term antifreeze and water-reducing effects. Summary of the Invention

[0007] In view of this, the present application provides an antifreeze based on sodium formate, its preparation method and application. Through the slow release of sodium formate and the optimization of its structure, the antifreeze can achieve good long-term antifreeze and water-reducing effects.

[0008] In the first aspect, the present application provides a method for preparing an antifreeze based on sodium formate, including the following steps:

[0009] Step S1: Dissolve a zirconium-based metal salt and an organic ligand in an organic solvent, and through a solvothermal reaction, make zirconium ions and the organic ligand form a framework structure to obtain a MOF material; wherein, the organic ligand includes at least one of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid;

[0010] Step S2: After activating the carboxyl groups on the polycarboxylate water reducer, react with the amino groups on the MOF material to obtain a polycarboxylate-modified MOF material;

[0011] Step S3: Immerse the polycarboxylate-modified MOF material in a sodium salt aqueous solution to adsorb and load the sodium salt on the polycarboxylate-modified MOF material to obtain an antifreeze; wherein the sodium salt includes sodium formate.

[0012] Based on the present application, in order to overcome the problem in the related art that sodium formate is released too quickly and easily lost during the concrete preparation process, the inventor prepared an amino-functionalized zirconium-based MOF material. The zirconium-based MOF material has a good specific surface area, which can provide a large number of adsorption sites for the adsorption of sodium formate, thereby effectively loading sodium formate. At the same time, the zirconium-based MOF material has high chemical stability and can maintain a stable structure in the high-pH environment of concrete, reducing the premature release of sodium formate caused by the disintegration of the MOF material. The pore structure of the zirconium-based MOF material can also limit the diffusion rate of sodium formate, achieving a slow-release effect on sodium formate. Further, the organic ligand uses terephthalic acid with an amino group, and the obtained zirconium-based MOF material has active amino groups. By activating the carboxyl groups on the polycarboxylate superplasticizer and reacting with the amino groups on the MOF material, the polycarboxylate superplasticizer is grafted onto the surface of the MOF material. There are still unreacted carboxyl groups on the polycarboxylate superplasticizer on the surface of the MOF material, which are adsorbed on the surface of cement particles during the cement hydration process, making the MOF material itself have a certain water-reducing effect. Cooperating with the released sodium formate, it can continuously improve the dispersibility of the cement paste, thereby effectively increasing the water reduction rate. On the other hand, the polycarboxylate superplasticizer grafted on the surface of the MOF is equivalent to forming a "flexible protective layer" on the surface, which can promote the dispersion of the MOF material in the concrete slurry and can also adjust the release rate of sodium formate, reducing the decrease in fluidity caused by excessive treatment of sodium formate. At the same time, since this antifreeze can slowly release sodium formate for a long time, cooperating with the polycarboxylate superplasticizer on the surface of the MOF material, it can make the cement particles disperse more evenly, reduce the internal porosity and capillary pore volume of the concrete, and cooperate with sodium formate to lower the freezing point of water, effectively reducing the damage to the internal structure of the concrete caused by freeze-thaw cycles. Therefore, the antifreeze obtained by this method has good long-term antifreeze and water-reducing effects.

[0013] In some embodiments, the step S1 specifically includes: dissolving 5 parts of zirconium metal salt, 7 - 15 parts of organic ligand, and 20 - 50 parts of glacial acetic acid in 300 - 600 parts of N,N-dimethylformamide, and reacting in a high-pressure reactor at 115 - 130 °C for 18 - 30 h to obtain the MOF material.

[0014] In the above-mentioned some embodiments, the MOF material prepared under the above conditions has a more uniform pore structure, which can further increase the loading amount of sodium formate in the MOF material, thereby making the antifreeze have better long-term antifreeze and water-reducing effects.

[0015] In some embodiments, the zirconium metal salt includes ZrOCl2·8H2O.

[0016] In some of the above embodiments, ZrOCl2·8H2O is used as the zirconium-based metal salt. Compared with using ZrCl4 as the zirconium-based metal salt, the content of chloride ions in the MOF material can be reduced, thereby reducing the chlorine content in the antifreeze and decreasing its impact on the performance of concrete.

[0017] In some embodiments, the organic ligand includes 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid, and the mass ratio of 2-aminoterephthalic acid to 2,5-diaminoterephthalic acid is 1:0.2 - 0.5.

[0018] Based on the above embodiments, the inventors found that the selection of the organic ligand will affect the long-term anti-freezing and water-reducing effects of the antifreeze. When 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid with a mass ratio of 1:0.2 - 0.5 are used as the organic ligand, the antifreeze has better long-term anti-freezing and water-reducing effects; the possible reason is that different mass ratios of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid will affect the content of amino groups on the surface of the MOF material, and the content of amino groups on its surface will affect the crosslinking density with the polycarboxylate water reducer, thereby affecting the release rate of sodium formate, and thus affecting the performance of the antifreeze; on the other hand, different organic ligands will also affect the coordination environment of zirconium ions, thereby affecting the pore structure of the MOF material, and will also have a certain impact on the performance of the antifreeze.

[0019] In some embodiments, step S2 specifically includes: dissolving 1 - 3 parts of polycarboxylate water reducer, 0.1 - 0.3 parts of EDC and 0.1 - 0.3 parts of NHS in 300 - 600 parts of buffer solution with a pH of 5 - 6.5, and then adding 5 parts of MOF material and reacting for 4 - 8 h to obtain polycarboxylate-modified MOF material.

[0020] In some of the above embodiments, by activating the polycarboxylate water reducer with EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) and NHS (N-hydroxysuccinimide), the carboxyl groups on the surface of the polycarboxylate water reducer can have good reaction activity and can undergo amidation reaction with the amino groups on the surface of the MOF material at room temperature, thereby grafting the polycarboxylate water reducer onto the MOF material to obtain polycarboxylate-modified MOF material.

[0021] It can be understood that on the one hand, polycarboxylate promotes the dispersion of the MOF material and regulates the release rate of sodium formate by forming a "flexible protective layer" on the MOF material. On the other hand, polycarboxylate can also provide more sites (through electrostatic, hydrogen bond and other forces) on the MOF material for sodium formate to adsorb and bind, increasing the loading amount of sodium formate in the antifreeze.

[0022] It should be noted that the loading amount of sodium formate in the antifreeze can be roughly measured by thermogravimetric analysis. The specific method is to perform thermogravimetric analysis on the polycarboxylic acid-modified MOF material without adsorption to obtain the grafting content of the polycarboxylic acid water reducer in the antifreeze; then perform thermogravimetric analysis on the antifreeze adsorbed with sodium formate to obtain the total mass of the polycarboxylic acid water reducer and sodium formate in the antifreeze. Subtracting the two gives the loading amount of sodium formate in the antifreeze. As an example, the loading amount of sodium formate in the antifreeze of an embodiment of the present application is 25.8 wt%.

[0023] In some embodiments, step S3 specifically includes: soaking 5 parts of the polycarboxylic acid-modified MOF material in 300 - 600 parts of the sodium salt aqueous solution, soaking and adsorbing for 24 - 36 h to obtain the antifreeze; wherein, the mass fraction of sodium formate in the sodium salt aqueous solution is 20% - 40%.

[0024] In the above-mentioned some embodiments, under the above conditions, the polycarboxylic acid-modified MOF material can be fully loaded with sodium formate, improving the loading amount of sodium formate in the antifreeze, so that the antifreeze has better long-term anti-freezing and water-reducing effects.

[0025] In some embodiments, the sodium salt aqueous solution further includes sodium phosphate, and the mass fraction of sodium phosphate in the sodium salt aqueous solution is 2% - 5%.

[0026] In the above-mentioned some embodiments, the inventors found that during the process of loading sodium formate, loading an appropriate amount of sodium phosphate in the antifreeze can further improve the performance of the antifreeze; the reason may be that when an appropriate amount of sodium phosphate is loaded in the antifreeze, the sodium ions can slow down the dissolution of sodium formate through the ion competition effect, and the dissolved phosphate can form a weak complex with sodium formate, which can increase the residence time of sodium formate in the antifreeze, thereby controlling the release rate of sodium formate in the antifreeze and making the antifreeze have better long-term anti-freezing and water-reducing effects.

[0027] In a second aspect, the present application provides an antifreeze based on sodium formate, which is prepared by the method according to any one of the embodiments of the first aspect.

[0028] According to the present application, since this antifreeze is obtained by the method according to any one of the embodiments of the first aspect, it has the beneficial effects of the first aspect.

[0029] In a third aspect, the present application provides a concrete building material, including the antifreeze according to any one of the embodiments of the second aspect.

[0030] According to the present application, it includes an antifreeze agent according to any embodiment of the second aspect. This antifreeze agent has good long-term antifreeze and water-reducing effects, enabling concrete building materials to have higher strength and antifreeze ability. Therefore, this concrete building material can be used as a new wall material with better antifreeze ability.

[0031] In some embodiments, the dosage of the antifreeze agent is 0.5% - 2.5% of the cement dosage. Based on the above embodiments, when the dosage of the antifreeze agent is within the above range, its water-reducing and long-term antifreeze effects can be better exerted, enabling the concrete building material to have better strength and antifreeze ability. Specific Embodiments

[0032] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0033] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0034] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" can explicitly or implicitly include at least one of these features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0035] In the present application, unless otherwise specified, "parts" all refer to "parts by mass".

[0036] The solutions of the present application will be described below in conjunction with the following specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments are all from ordinary commercially available products, and the devices or equipment used are all purchased from conventional market sales channels.

[0037] Polycarboxylate water reducer, the polycarboxylate superplasticizer SPC-100 purchased from Kelong Refinement.

[0038] Example 1

[0039] Preparation of the antifreeze agent based on sodium formate:

[0040] Dissolve 5 parts of ZrOCl2·8H2O in 500 parts of N,N-dimethylformamide, then add 8 parts of organic ligand and 40 parts of glacial acetic acid. After mixing evenly, transfer it to a high-pressure reactor and react at 120 °C for 24 h. Centrifuge and separate, wash 3 times with N,N-dimethylformamide, then wash 3 times with ethanol, and dry in vacuum at 80 °C for 7 h to obtain the MOF material; the organic ligand is 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid with a mass ratio of 1:0.2.

[0041] Dissolve 2 parts of polycarboxylate superplasticizer in 450 parts of MES buffer solution with a pH of 5.5, then add 0.15 parts of EDC and 0.15 parts of NHS, and stir and activate at room temperature for 30 min; then ultrasonically disperse 5 parts of MOF material in 50 parts of MES buffer solution with a pH of 5.5, mix it with the activated polycarboxylate superplasticizer solution, react at room temperature for 6 h, centrifuge and separate, wash 3 times with water, then wash 3 times with ethanol, and dry in vacuum at 60 °C for 12 h to obtain the polycarboxylate-modified MOF material.

[0042] Soak 5 parts of polycarboxylate-modified MOF material in 400 parts of sodium salt aqueous solution, soak and adsorb for 30 h, centrifuge and separate, wash twice with ethanol, and dry in vacuum at 60 °C for 12 h to obtain the antifreeze; among them, the mass fraction of sodium formate in the sodium salt aqueous solution is 35%, and the mass fraction of sodium phosphate is 3.5%.

[0043] Example 2

[0044] Preparation of formate-based antifreeze:

[0045] Dissolve 5 parts of ZrOCl2·8H2O in 500 parts of N,N-dimethylformamide, then add 8 parts of organic ligand and 40 parts of glacial acetic acid. After mixing evenly, transfer it to a high-pressure reactor and react at 120 °C for 24 h. Centrifuge and separate, wash 3 times with N,N-dimethylformamide, then wash 3 times with ethanol, and dry in vacuum at 80 °C for 7 h to obtain the MOF material; the organic ligand is 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid with a mass ratio of 1:0.5.

[0046] Dissolve 2 parts of polycarboxylate superplasticizer in 450 parts of MES buffer solution with a pH of 5.5, then add 0.15 parts of EDC and 0.15 parts of NHS, and stir and activate at room temperature for 30 min; then ultrasonically disperse 5 parts of MOF material in 50 parts of MES buffer solution with a pH of 5.5, mix it with the activated polycarboxylate superplasticizer solution, react at room temperature for 6 h, centrifuge and separate, wash 3 times with water, then wash 3 times with ethanol, and dry in vacuum at 60 °C for 12 h to obtain the polycarboxylate-modified MOF material.

[0047] Soak 5 parts of the polycarboxylic acid-modified MOF material in 400 parts of the sodium salt aqueous solution, soak and adsorb for 30 h, centrifuge and separate, wash twice with ethanol, and vacuum dry at 60 °C for 12 h to obtain the antifreeze agent; among them, the mass fraction of sodium formate in the sodium salt aqueous solution is 35%, and the mass fraction of sodium phosphate is 3.5%.

[0048] Example 3

[0049] Preparation of the antifreeze agent based on sodium formate:

[0050] Dissolve 5 parts of ZrOCl₂·8H₂O in 500 parts of N,N-dimethylformamide, add 8 parts of the organic ligand and 40 parts of glacial acetic acid, mix well and transfer to a high-pressure reactor to react at 120 °C for 24 h, centrifuge and separate, wash 3 times with N,N-dimethylformamide, then wash 3 times with ethanol, and vacuum dry at 80 °C for 7 h to obtain the MOF material; the organic ligand is 2-aminoterephthalic acid;

[0051] Dissolve 2 parts of the polycarboxylic acid water reducer in 450 parts of the MES buffer solution with a pH of 5.5, add 0.15 parts of EDC and 0.15 parts of NHS, and stir and activate at room temperature for 30 min; then ultrasonically disperse 5 parts of the MOF material in 50 parts of the MES buffer solution with a pH of 5.5, mix with the activated polycarboxylic acid water reducer solution, react at room temperature for 6 h, centrifuge and separate, wash 3 times with water, then wash 3 times with ethanol, and vacuum dry at 60 °C for 12 h to obtain the polycarboxylic acid-modified MOF material;

[0052] Soak 5 parts of the polycarboxylic acid-modified MOF material in 400 parts of the sodium salt aqueous solution, soak and adsorb for 30 h, centrifuge and separate, wash twice with ethanol, and vacuum dry at 60 °C for 12 h to obtain the antifreeze agent; among them, the mass fraction of sodium formate in the sodium salt aqueous solution is 35%, and the mass fraction of sodium phosphate is 3.5%.

[0053] Example 4

[0054] Preparation of the antifreeze agent based on sodium formate:

[0055] Dissolve 5 parts of ZrOCl₂·8H₂O in 500 parts of N,N-dimethylformamide, add 8 parts of the organic ligand and 40 parts of glacial acetic acid, mix well and transfer to a high-pressure reactor to react at 120 °C for 24 h, centrifuge and separate, wash 3 times with N,N-dimethylformamide, then wash 3 times with ethanol, and vacuum dry at 80 °C for 7 h to obtain the MOF material; the organic ligand is a 1:1 mass ratio of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid;

[0056] Dissolve 2 parts of polycarboxylate superplasticizer in 450 parts of MES buffer solution with a pH of 5.5, then add 0.15 parts of EDC and 0.15 parts of NHS, and stir and activate at room temperature for 30 min; then ultrasonically disperse 5 parts of MOF material in 50 parts of MES buffer solution with a pH of 5.5, mix it with the activated polycarboxylate superplasticizer solution, react at room temperature for 6 h, centrifuge and separate, wash 3 times with water, then wash 3 times with ethanol, and vacuum dry at 60 °C for 12 h to obtain polycarboxylate-modified MOF material;

[0057] Soak 5 parts of polycarboxylate-modified MOF material in 400 parts of sodium salt aqueous solution, soak and adsorb for 30 h, centrifuge and separate, wash twice with ethanol, and vacuum dry at 60 °C for 12 h to obtain an antifreeze agent; among them, the mass fraction of sodium formate in the sodium salt aqueous solution is 35%, and the mass fraction of sodium phosphate is 3.5%.

[0058] Example 5

[0059] Preparation of formate-based antifreeze agent:

[0060] Dissolve 5 parts of ZrOCl2·8H2O in 500 parts of N,N-dimethylformamide, then add 8 parts of organic ligand and 40 parts of glacial acetic acid, mix well and transfer to a high-pressure reaction kettle to react at 120 °C for 24 h, centrifuge and separate, wash 3 times with N,N-dimethylformamide, then wash 3 times with ethanol, and vacuum dry at 80 °C for 7 h to obtain MOF material; the organic ligand is 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid with a mass ratio of 1:0.2;

[0061] Dissolve 2 parts of polycarboxylate superplasticizer in 450 parts of MES buffer solution with a pH of 5.5, then add 0.15 parts of EDC and 0.15 parts of NHS, and stir and activate at room temperature for 30 min; then ultrasonically disperse 5 parts of MOF material in 50 parts of MES buffer solution with a pH of 5.5, mix it with the activated polycarboxylate superplasticizer solution, react at room temperature for 6 h, centrifuge and separate, wash 3 times with water, then wash 3 times with ethanol, and vacuum dry at 60 °C for 12 h to obtain polycarboxylate-modified MOF material;

[0062] Soak 5 parts of polycarboxylate-modified MOF material in 400 parts of sodium formate aqueous solution with a mass fraction of 35%, soak and adsorb for 30 h, centrifuge and separate, wash twice with ethanol, and vacuum dry at 60 °C for 12 h to obtain an antifreeze agent.

[0063] Comparative Example 1

[0064] Preparation of formate-based antifreeze agent:

[0065] Dissolve 5 parts of ZrOCl2·8H2O in 500 parts of N,N-dimethylformamide, then add 8 parts of organic ligand and 40 parts of glacial acetic acid. After mixing evenly, transfer it to a high-pressure reactor and react at 120 °C for 24 h. Centrifuge and separate, wash 3 times with N,N-dimethylformamide, and then wash 3 times with ethanol. Dry in vacuum at 80 °C for 7 h to obtain the MOF material; the organic ligand is 2-aminoterephthalic acid;

[0066] Soak 5 parts of the MOF material in 400 parts of an aqueous solution of sodium formate with a mass fraction of 35%, soak and adsorb for 30 h, centrifuge and separate, wash twice with ethanol, and dry in vacuum at 60 °C for 12 h to obtain the antifreeze agent.

[0067] Testing Part

[0068] Refer to GB / T 8076-2008 "Concrete Admixtures" for the antifreeze agents obtained in each example and comparative example. The dosage of the antifreeze agent is 1.5 wt% of the cement dosage, and test its water reduction rate and 1 h slump retention rate;

[0069] Refer to JGJ 55-2000 "Code for Mix Proportion Design of Ordinary Concrete", with the dosage of the antifreeze agent being 1.5 wt% of the cement dosage, prepare concrete cube specimens with dimensions of 100 mm×100 mm×100 mm (water-binder ratio is 0.4). Refer to the rapid freezing method in "Standard Test Method for Long-Term Performance and Durability of Ordinary Concrete". After curing for 7 days, place them at -15 °C for 4 h, and then at 20 °C for 4 h, cycle 100 times, and record their mass loss rate.

[0070] Table 1

[0071] Water reducing rate (%) 1h slump retention rate (%) Mass loss rate (%) Example 1 35.6 86.3 1.12 Example 2 34.9 87.6 1.08 Example 3 30.5 79.6 2.26 Example 4 29.5 85.3 1.69 Example 5 31.2 78.3 2.01 Comparative Example 1 18.6 56.8 4.69

[0072] As can be seen from Table 1, the antifreeze agents obtained in each example have higher water reduction rate, 1 h slump retention rate and lower mass loss rate compared with the comparative examples, indicating that the antifreeze agents obtained in each example have good water reduction and long-term antifreeze effects. The reason may be that in Comparative Example 1, the MOF material was directly used to load sodium formate, and the water reduction effect of relying solely on the released sodium formate was poor. The polycarboxylate water reducer on the surface of the MOF in each example can play a better water reduction effect. The loaded sodium formate is more likely to be lost compared with each example, resulting in poor slump retention rate and long-term antifreeze performance.

[0073] As can be seen from Examples 1 to 4, using different organic ligands to prepare the MOF material has a certain influence on the water reduction and antifreeze properties of the antifreeze agent; when the organic ligand is 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid with a mass ratio of 1:0.2 - 0.5, the obtained antifreeze agent has better water reduction and long-term antifreeze effects.

[0074] According to Embodiments 1 and 5, it can be seen that by loading a small amount of sodium phosphate in the antifreeze, it can cooperate with sodium formate to make the antifreeze have better water-reducing and long-term anti-freezing effects.

[0075] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing an antifreeze agent based on sodium formate, characterized in that The following steps are involved: Step S1: dissolving a zirconium-based metal salt and an organic ligand in an organic solvent, and forming a framework structure between zirconium ions and the organic ligand through a solvothermal reaction to obtain a MOF material; wherein the organic ligand comprises at least one of 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid; Step S2: activating the carboxyl group on the polycarboxylate water-reducing agent and reacting it with the amino group on the MOF material to obtain a polycarboxylate modified MOF material; Step S3: soaking the polycarboxylic acid modified MOF material in a sodium salt aqueous solution, so that the sodium salt is adsorbed and loaded on the polycarboxylic acid modified MOF material to obtain an antifreeze agent; wherein the sodium salt includes sodium formate.

2. The method according to claim 1, characterized in that The step S1 specifically includes: 5 parts of zirconium-based metal salt, 7 to 15 parts of organic ligand and 20 to 50 parts of glacial acetic acid are dissolved in 300 to 600 parts of N,N-dimethylformamide, and reacted at 115 to 130° C. for 18 to 30 hours in a high-pressure reactor to obtain a MOF material.

3. The method according to claim 1 or 2, characterized in that: The zirconium-based metal salt includes ZrOCl2·8H2O.

4. The method according to claim 1 or 2, characterized in that: The organic ligand comprises 2-aminoterephthalic acid and 2,5-diaminoterephthalic acid, and the mass ratio of the 2-aminoterephthalic acid to the 2,5-diaminoterephthalic acid is 1:0.2-0.

5.

5. The method according to claim 1, characterized in that: The step S2 specifically includes: 1 to 3 parts of polycarboxylic acid water reducer, 0.1 to 0.3 parts of EDC and 0.1 to 0.3 parts of NHS are dissolved in 300 to 600 parts of a buffer solution with a pH of 5 to 6.5, and then 5 parts of MOF material are added and reacted for 4 to 8 hours to obtain a polycarboxylic acid modified MOF material.

6. The method according to claim 1, characterized in that The step S3 specifically includes: Five parts of polycarboxylic acid modified MOF material are immersed in 300-600 parts of sodium salt aqueous solution for immersion and adsorption for 24-36 hours to obtain an antifreeze agent; wherein the mass fraction of sodium formate in the sodium salt aqueous solution is 20%-40%.

7. The method according to claim 6, characterized in that The sodium salt aqueous solution also includes sodium phosphate, and the mass fraction of the sodium phosphate in the sodium salt aqueous solution is 2% to 5%.

8. An antifreeze agent based on sodium formate, characterized in that Prepared according to the method according to any one of claims 1 to 7.

9. A concrete building material, characterized in that: The antifreeze agent according to claim 8.

10. The concrete building material according to claim 9, characterized in that: The dosage of the antifreeze agent is 0.5% to 2.5% of the cement dosage.