Green-synthesized stone protection material and preparation method thereof

Abstract

The application relates to the technical field of stone protection materials, in particular to a green-synthesized stone protection material and a preparation method thereof. A metal zinc salt and a polyhydroxy terephthalic acid are added into a mixed solution of deionized water and anhydrous ethanol to be stirred and dissolved to obtain a solution A, a fluorosilane coupling agent is added dropwise into the solution A, and ultrasonic dispersion is carried out to obtain a solution B. Then, the solution B is transferred into an ultrasonic microwave extraction instrument to be reacted, and after the reaction is completed, a solution C is obtained. A dispersing agent is added dropwise into the solution C, and stirring and ultrasonic dispersion are carried out to obtain the stone protection material. The stone protection material is applied to a stone surface, so that the hydrophobicity, air permeability and durability of the stone can be effectively improved, and the protection effect can be achieved. The preparation method can not only realize efficient synthesis and surface hydrophobic modification of MOF materials, but also has the advantages of simple one-pot microwave ultrasonic synthesis technology, short reaction period and strong applicability, and can provide important research ideas and technical routes for development of a new stone protection material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of stone protection materials, and particularly relates to a green-synthesized stone protection material and a preparation method thereof. BACKGROUND

[0002] As one of the most widely used materials in historical relics and modern engineering, stone is not only an important part of cultural heritage, but also bears important decorative and bearing functions in civil engineering and building structure engineering. However, due to long-term exposure to the natural environment, stone is inevitably affected by multiple factors such as acid rain erosion, biological invasion and human damage, resulting in surface weathering, salt corrosion crystallization, crack expansion and strength reduction. Not only does it affect the authenticity and integrity of cultural relics, but it also threatens the durability and safety of engineering structures. Especially under the background of intensified industrial pollution and changing climate conditions, stone protection is facing greater challenges, and there is an urgent need to develop new protective materials and technologies that are green, environmentally friendly, long-lasting and highly adaptable to the environment.

[0003] Although the current commonly used inorganic or organic polymer protective materials can improve the anti-deterioration performance of stone to some extent, they generally have poor adhesion, high brittleness, fast aging and easy discoloration, and it is difficult to simultaneously consider protection, weather resistance and stone compatibility.

[0004] Metal-organic framework materials (MOFs) are a class of porous crystalline materials with adjustable structure, high-ordered pore system, excellent specific surface area and good functional modification ability. In recent years, they have received extensive attention and application in the fields of gas adsorption and catalysis. Through surface functionalization modification, MOFs are expected to realize the hydrophobicity, antifouling and air permeability regulation of stone surface, and are extremely potential new protective materials. However, traditional synthesis of MOFs generally relies on toxic solvents such as N, N-dimethylformamide (DMF), N, N-diethylformamide (DEF), and often needs complex post-treatment, which has the problems of poor environmental friendliness and low efficiency. SUMMARY

[0005] To solve the above problems, the purpose of the present application is to provide a green-synthesized stone protection material and a preparation method thereof. Based on a microwave-ultrasonic wave synergistic reaction device, a metal source, an organic ligand and a fluorosilane coupling agent are introduced into the system, and the synthesis and surface modification of the material are realized simultaneously. The use of toxic organic solvents and the complex post-treatment process can be effectively avoided, the greenness and efficiency of material synthesis can be significantly improved, and the prepared material has excellent performance, good adaptability and practicality.

[0006] The application introduces fluorosilane coupling agent, metal ions and organic ligand in alcohol-water system, forms stable low surface energy hydrophobic layer on the surface of Zn-MOF crystal framework while constructing the framework. The prepared material has regular nanopore structure, can provide excellent hydrophobicity, stone adaptability and durability, and has green and efficient synthesis process, simple operation, provides new ideas and technology for long-term stable protection of stone and development of functional materials.

[0007] The application provides a preparation method of green-synthesized stone protection material, and specifically comprises the following steps.

[0008] (1) A metal zinc salt and a polyhydroxy terephthalic acid are respectively added to a mixed solution of deionized water and anhydrous ethanol, and after stirring and dissolving, a solution A is obtained, then a fluorosilane coupling agent is added dropwise to the solution A, and after the addition is completed, ultrasonic dispersion is performed to obtain a solution B;

[0009] (2) The solution B obtained in step (1) is placed in a sample tank of an ultrasonic microwave extraction instrument, a condenser tube is screwed, ultrasonic wave power and frequency, microwave power and temperature are sequentially set, after the setting is completed, heating reaction is performed to obtain a solution C;

[0010] (3) A dispersing agent is added dropwise to the solution C, and after the addition is completed, ultrasonic stirring is performed to form a transparent sol, and the transparent sol is the stone protection material, which is denoted as Zn-MOF@FS.

[0011] Further, in step (1), the metal zinc salt is selected from one of zinc nitrate hexahydrate, zinc acetate dihydrate or zinc hydroxide.

[0012] Further, in step (1), the polyhydroxy terephthalic acid is selected from one of 2-hydroxy terephthalic acid, 2,3-dihydroxy terephthalic acid and 2,3,5,6-tetrahydroxy terephthalic acid.

[0013] Further, in step (1), the molar ratio of the polyhydroxy terephthalic acid to the metal zinc salt is 1:1.5-2.

[0014] Further, in step (1), in the mixed solution of deionized water and anhydrous ethanol, the volume ratio of deionized water to anhydrous ethanol is 1:6-8, and the amount of deionized water is 2-5 mL.

[0015] Further, in step (1), the volume of the added fluorosilane coupling agent accounts for 2-5% of the sum of the volume of the solution A and the volume of the fluorosilane coupling agent.

[0016] Further, in step (1), the fluorosilane coupling agent is selected from one of perfluorohexyltriethoxysilane, perfluorooctyltriethoxysilane, dodecafluoroheptylpropylmethyldimethoxysilane, tridecafluorooctyltrimethoxysilane and heptadecafluorodecyltrimethoxysilane.

[0017] Further, the ultrasonic dispersion in step (1) is 10-15 min.

[0018] Further, the solution B obtained in step (1) is transferred to a triangular flask in step (2), and the triangular flask is placed in a sample tank of an ultrasonic microwave synergistic extraction instrument.

[0019] Further, the ultrasonic power is set to 50 W and the frequency is 40 Hz in step (2).

[0020] Further, the microwave power is 100-300 W and the temperature is 100-120 DEG C in step (2).

[0021] Further, the heating reaction is 15-25 min in step (2).

[0022] Further, the mass of the dispersant accounts for 1-3% of the total system mass in step (3), and the total system mass refers to the sum of the mass of the dispersant and the mass of the solution C.

[0023] Further, the dispersant in step (3) is one of polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, polyacrylamide, polyacrylic acid sodium, and poly (methyl methacrylate) dodecafluoroheptyl ester.

[0024] Further, the ultrasonic and stirring are 15-30 min in step (3).

[0025] The application also provides a stone protection material prepared by the above preparation method.

[0026] Further, the stone protection material mainly comprises flaky crystals, and the whole is a quasi-triangle structure with a side length of about 105-330 nm, and the surface is coated with a dense layer with a thickness of about 30-50 nm.

[0027] The application realizes the integrated treatment from the preparation and synthesis of MOFs precursor to the surface modification by means of an ultrasonic microwave synergistic reaction device through a one-pot method, improves the process efficiency and simplifies the operation process. The stone protection material of the application can effectively improve the hydrophobicity, air permeability and durability of the stone when applied to the surface of the stone, and achieves the protection effect. Through the preparation method of the application, not only the efficient synthesis and surface hydrophobic modification of the MOFs material are realized, but also the one-pot microwave ultrasonic synthesis technology is simple in process, short in reaction period and strong in applicability, which can provide an important research idea and technical route for the development of new stone protection materials.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] (1) The present invention adopts microwave-ultrasound synergistic "one-pot" synthesis technology, which introduces metal source, organic ligand and fluorosilane coupling agent in the same reaction system simultaneously, so as to realize the synthesis and surface modification of Zn-MOF materials at the same time, which significantly simplifies the multi-step process of traditional MOFs that requires synthesis and modification, greatly reduces energy consumption and reagent consumption, and is more green and environmentally friendly.

[0030] (2) Combining microwave rapid and uniform heating with ultrasonic cavitation to promote nucleation significantly improves the crystallinity and reaction efficiency of the material, while achieving precise introduction of functional groups. The reaction conditions are easy to control, and the synthesis process has good repeatability and consistency.

[0031] (3) MOF-5, as a typical zinc-based metal-organic framework material, has a regular structure, unobstructed pores, and a large specific surface area. Through the preparation method of the present invention, a hydrophobic interface layer can be effectively constructed while maintaining its original pore structure, which significantly improves its applicability and functional diversity in stone protection;

[0032] (4) The material prepared by the present invention has both the structural stability of inorganic MOFs and the protective properties of organic hydrophobic groups. It can effectively overcome the defects of traditional organic coatings such as easy aging, easy yellowing and poor permeability. It can also maintain stable protective performance in complex environments such as high temperature and humidity. It can be widely used for long-term protection of different types of stone and has significant engineering application potential and cultural heritage protection value. Attached Figure Description

[0033] Figure 1 This is a comparison of the hydrophobic properties of the Zn-MOF@FS stone samples prepared in Example 1, with and without coating (left) and coating (right).

[0034] Figure 2 This is a water contact angle test diagram of the Zn-MOF@FS prepared in Example 1;

[0035] Figure 3 This is the X-ray diffraction pattern of the Zn-MOF@FS prepared in Example 1;

[0036] Figure 4 This is the Fourier transform infrared spectrum of the Zn-MOF@FS prepared in Example 1;

[0037] Figure 5 This is a transmission electron microscope image of the Zn-MOF@FS prepared in Example 1. Detailed Implementation

[0038] To better understand the content of this invention, it will be further described below with reference to specific embodiments and accompanying drawings. The following embodiments are based on the technology of this invention and provide detailed implementation methods and operating steps, but the scope of protection of this invention is not limited to the following embodiments.

[0039] Example 1:

[0040] (1) After mixing deionized water and anhydrous ethanol, a mixed solution of the two is obtained. The amount of deionized water is 2 mL and the volume ratio of deionized water to anhydrous ethanol is 1:6. Then, 1.5 mmol of zinc nitrate hexahydrate and 1 mmol of 2,3,5,6-tetrahydroxyterephthalic acid are added to the above mixed solution and stirred to dissolve, resulting in solution A. Then, perfluorohexyltriethoxysilane is added dropwise to solution A. The volume fraction of perfluorohexyltriethoxysilane is 3% of the sum of the volumes of solution A and perfluorohexyltriethoxysilane. After the addition is completed, the solution is ultrasonically dispersed for 10 min to obtain solution B.

[0041] (2) Transfer the solution B obtained in step (1) to an Erlenmeyer flask, place the Erlenmeyer flask into the sample slot of the ultrasonic-microwave co-extraction instrument, tighten the condenser tube, set the ultrasonic power to 50W, frequency to 40KHz, microwave power to 100W, and temperature to 100℃, and heat the reaction at 100℃ for 15min to obtain solution C.

[0042] (3) Add polyvinyl alcohol dropwise to solution C. The mass fraction of polyvinyl alcohol is 1% of the total mass of the system (i.e., the sum of the mass of solution C and polyvinyl alcohol). After the addition is completed, sonicate and stir for 15 minutes to form a transparent sol. The above transparent sol is the stone protection material, denoted as Zn-MOF@FS.

[0043] Performance testing:

[0044] The hydrophobic properties of stone samples with and without the Zn-MOF@FS coating are compared, for example... Figure 1 As shown, the left side represents the untreated sample, and the right side represents the sample coated with Zn-MOF@FS. It can be seen that the water droplets on the treated sample surface are evenly distributed and have intact morphology, significantly better than the untreated sample, indicating a significant improvement in its hydrophobic properties.

[0045] The water contact angle of the Zn-MOF@FS prepared in Example 1 was tested, as follows: Figure 2 As shown, the water contact angle was measured to be 126.25°, indicating that the prepared material is a hydrophobic MOF.

[0046] Figure 3The XRD pattern of Zn-MOF@FS prepared in Example 1 shows that there are multiple obvious diffraction peaks near 8.7°, 15.4°, 17.6°, 28.2° and 32.4°, indicating that the material has good crystallinity and maintains the basic crystal structure of MOF-5.

[0047] The Fourier transform infrared spectrum of the Zn-MOF@FS prepared in Example 1 is shown below. Figure 4 As shown. The modified sample measured 1240–1140 cm⁻¹. -1 Characteristic peaks of -CF2 / -CF3 stretching vibrations appeared within the range, and at approximately 1056 cm⁻¹... -1 The strong absorption peak at 1650-1400 cm⁻¹ corresponds to the symmetric stretching vibration of Si–O, indicating that fluorosilyl groups have been successfully grafted onto the material surface and formed a silicon-oxygen network structure. -1 The characteristic peaks within the range correspond to carboxylate ions (-COO). - The presence of both symmetrical and asymmetrical stretching vibrations indicates that the modification process did not disrupt the material's coordination structure.

[0048] Figure 5 The image shows a transmission electron microscope (TEM) image of the Zn-MOF@FS material prepared in Example 1. It can be seen that Zn-MOF@FS is mainly composed of thin-film crystals with an overall quasi-triangular structure, with sides approximately 105-330 nm in length, and its surface is covered by a dense layer approximately 30-50 nm thick. This thin-film quasi-triangular structure gives it unique advantages in stone protection applications. Its layered structure makes it easier to spread on the stone surface, forming a more continuous and flat protective film, thereby effectively reducing porosity and penetration channels. Furthermore, multiple layers can be overlapped during deposition, further enhancing the density and overall uniformity of the film. Compared to traditional materials, it is more suitable for constructing dense, robust, and durable protective barriers, and has greater application potential in improving the weathering resistance of stone.

[0049] The activation index H of Zn-MOF@FS is calculated using the following formula:

[0050]

[0051] A higher activation index indicates a better activation effect and better hydrophobic properties. The activation index of the Zn-MOF@FS prepared in Example 1 was calculated to be 78.51%, indicating that the material prepared in Example 1 has good hydrophobic properties.

[0052] The Zn-MOF@FS prepared in Example 1 was uniformly coated onto the surface of a cylindrical limestone sample with a diameter of 50 mm and a height of 100 mm. After coating, the sample was dried in an oven at 120°C for 2 hours and designated as Sample B. The limestone sample without coating was designated as Sample A. Samples A and B were immersed in a NaCl solution with pH=4 for 45 days. Then, uniaxial compression tests were performed on them using an RMT-301 rock and concrete compression testing machine. The displacement-controlled rate was used in the test, with a rate of 0.002 mm / s. The results showed that compared with Sample A without protective material, Sample B exhibited a 5.31% reduction in peak strength after erosion (as shown in Table 1), indicating that the prepared Zn-MOF@FS material has a good protective effect on the stone sample and can effectively reduce the erosion of acidic solutions.

[0053] Example 2:

[0054] (1) After mixing deionized water and anhydrous ethanol, a mixed solution of the two is obtained. The amount of deionized water is 3 mL and the volume ratio of deionized water to anhydrous ethanol is 1:7. Then take 1.7 mmol of zinc acetate dihydrate and 1 mmol of 2,3-dihydroxyterephthalic acid and add them to the above mixed solution respectively. Stir to dissolve them to obtain solution A. Then add perfluorooctyltriethoxysilane dropwise to solution A. The volume fraction of perfluorooctyltriethoxysilane is 4% of the sum of the volumes of solution A and perfluorooctyltriethoxysilane. After the addition is completed, sonicate for 12 min to obtain solution B.

[0055] (2) Transfer the solution B obtained in step (1) to an Erlenmeyer flask, place the Erlenmeyer flask into the sample slot of the ultrasonic-microwave co-extraction instrument, tighten the condenser tube, set the ultrasonic power to 50W, the frequency to 40KHz, the microwave power to 200W, and the temperature to 110℃, and heat the reaction at 110℃ for 20min to obtain solution C.

[0056] (3) Add polyacrylamide dropwise to solution C. The mass fraction of polyacrylamide in the whole system (i.e., the sum of the mass of solution C and polyacrylamide) is 2%. After the addition is completed, sonicate and stir for 20 minutes to form a transparent sol. The above transparent sol is the stone protection material, denoted as Zn-MOF@FS.

[0057] Performance testing:

[0058] The Zn-MOF@FS prepared in Example 2 was subjected to a water contact angle test, and the measured water contact angle was 135.78°, indicating that hydrophobic MOFs were successfully synthesized.

[0059] The activation index of the Zn-MOF@FS prepared in Example 2 was calculated to be 83.89%, indicating that the material prepared in Example 2 has good hydrophobic properties.

[0060] The Zn-MOF@FS prepared in Example 2 was uniformly coated onto the surface of a cylindrical limestone sample with a diameter of 50 mm and a height of 100 mm. After coating, the sample was dried in an oven at 120°C for 2 hours and was designated as sample C. The limestone sample without coating was designated as sample A. Samples A and C were immersed in a NaCl solution with pH=4 for 45 days. Then, uniaxial compression tests were performed on them using an RMT-301 rock and concrete compression testing machine. The displacement-controlled rate was used in the test, with a rate of 0.002 mm / s. The results showed that compared with sample A without protective material, sample C exhibited a 7.84% reduction in peak strength after erosion (as shown in Table 1), indicating that the prepared Zn-MOF@FS material has a good protective effect on the stone sample and can effectively reduce the erosion of acidic solutions.

[0061] Example 3:

[0062] (1) After mixing deionized water and anhydrous ethanol, a mixed solution of the two is obtained. The amount of deionized water is 5 mL and the volume ratio of deionized water to anhydrous ethanol is 1:8. Then take 2 mmol of zinc hydroxide and 1 mmol of 2-hydroxyterephthalic acid and add them to the above mixed solution respectively. Stir to dissolve them to obtain solution A. Then add dodecylfluoroheptylpropylmethyldimethoxysilane dropwise to solution A. The volume fraction of dodecylfluoroheptylpropylmethyldimethoxysilane is 5% of the sum of the volumes of solution A and dodecylfluoroheptylpropylmethyldimethoxysilane. After the addition is completed, sonicate for 15 min to obtain solution B.

[0063] (2) Transfer the solution B obtained in step (1) to an Erlenmeyer flask, place the Erlenmeyer flask into the sample slot of the ultrasonic-microwave co-extraction instrument, tighten the condenser tube, set the ultrasonic power to 50W, the frequency to 40KHz, the microwave power to 300W, and the temperature to 120℃, and heat the reaction at 120℃ for 25min to obtain solution C.

[0064] (3) Add poly(dodecyl fluoroheptyl methacrylate) dropwise to solution C. The mass fraction of poly(dodecyl fluoroheptyl methacrylate) in the whole system (i.e., the sum of the mass of solution C and poly(dodecyl fluoroheptyl methacrylate)) is 3%. After the addition is completed, sonicate and stir for 30 minutes to form a transparent sol. The above transparent sol is the stone protection material, denoted as Zn-MOF@FS.

[0065] Performance testing:

[0066] The Zn-MOF@FS prepared in Example 3 was tested for water contact angle. The measured water contact angle was 151.26° and the hydrophobic angle was >140°, indicating that superhydrophobic MOFs were successfully synthesized.

[0067] The activation index of the Zn-MOF@FS prepared in Example 3 was calculated to be 89.52%, indicating that the material prepared in Example 3 has good hydrophobic properties.

[0068] The Zn-MOF@FS prepared in Example 3 was uniformly coated onto the surface of a cylindrical limestone sample with a diameter of 50 mm and a height of 100 mm. After coating, the sample was dried in an oven at 120°C for 2 hours and was designated as sample D. The limestone sample without coating was designated as sample A. Samples A and D were immersed in a NaCl solution with pH=4 for 45 days. Then, uniaxial compression tests were performed on them using an RMT-301 rock and concrete compression testing machine with a displacement-controlled rate of 0.002 mm / s. The results showed that compared with sample A without protective material, sample D exhibited an 8.38% reduction in peak strength after erosion (as shown in Table 1), indicating that the prepared Zn-MOF@FS material has a good protective effect on the stone sample and can effectively reduce the erosion of acidic solutions.

[0069] Table 1. Changes in peak intensity after erosion in Examples 1-3 and Sample A without protective material.

[0070]

[0071] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a green synthetic stone protection material, characterized in that, Specifically, the following steps are included: (1) Take zinc salt and polyhydroxy terephthalic acid and add them to a mixed solution of deionized water and anhydrous ethanol. The volume ratio of deionized water to anhydrous ethanol is 1:6-8. After stirring and dissolving, solution A is obtained. The molar ratio of polyhydroxy terephthalic acid to zinc salt is 1:1.5-2. Then, fluorosilane coupling agent is added dropwise to solution A. After the addition is completed, the solution is ultrasonically dispersed to obtain solution B. (2) Place the solution B obtained in step (1) into the sample tank of the ultrasonic-microwave synergistic extraction instrument, tighten the condenser tube, and set the ultrasonic power and frequency, microwave power and temperature in sequence. After setting, heat the reaction to obtain solution C. (3) Add the dispersant dropwise to solution C, and after the addition is complete, sonicate and stir to form a transparent sol. The above transparent sol is the stone protection material.

2. The preparation method of the green synthetic stone protection material as described in claim 1, characterized in that, In step (1), the zinc salt is selected from zinc nitrate hexahydrate, zinc acetate dihydrate, or zinc hydroxide; the polyhydroxy terephthalic acid is selected from 2-hydroxy terephthalic acid, 2,3-dihydroxy terephthalic acid, or 2,3,5,6-tetrahydroxy terephthalic acid; in the mixed solution of deionized water and anhydrous ethanol, the amount of deionized water used is 2-5 mL.

3. The preparation method of the green synthetic stone protection material as described in claim 1, characterized in that, In step (1), the fluorosilane coupling agent is selected from one of perfluorohexyltriethoxysilane, perfluorooctyltriethoxysilane, dodecafluoroheptylpropylmethyldimethoxysilane, tridecafluorooctyltrimethoxysilane, and heptadecafluorodecyltrimethoxysilane.

4. The preparation method of the green synthetic stone protective material as described in claim 1, characterized in that, The volume of the fluorosilane coupling agent added in step (1) is 2-5% of the sum of the volumes of solution A and the fluorosilane coupling agent; after adding the fluorosilane coupling agent, ultrasonically disperse for 10-15 minutes.

5. The method for preparing the green synthetic stone protective material as described in claim 1, characterized in that, In step (2), the solution B obtained in step (1) is transferred to an Erlenmeyer flask, and the Erlenmeyer flask is placed in the sample chamber of the ultrasonic microwave co-extraction instrument; after setting, the reaction is heated for 15-25 minutes.

6. The method for preparing the green synthetic stone protective material as described in claim 1, characterized in that, In step (2), the ultrasonic power is set to 50W and the frequency to 40Hz; the microwave power is 100-300W and the temperature is 100-120℃.

7. The method for preparing the green synthetic stone protective material as described in claim 1, characterized in that, In step (3), the mass of the dispersant accounts for 1-3% of the total mass of the system; after adding the dispersant, sonicate and stir for 15-30 minutes.

8. The method for preparing the green synthetic stone protective material as described in claim 1, characterized in that, In step (3), the dispersant is one of polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, polyacrylamide, sodium polyacrylate, and polydodecylfluoroheptyl methacrylate.

9. The stone protection material obtained by any one of the preparation methods described in claims 1 to 8.

10. The stone protection material as described in claim 9, characterized in that, The stone protection material is mainly composed of thin-film crystals, with an overall quasi-triangular structure. The quasi-triangle has a side length of 105-330nm, and its surface is covered by a dense layer with a thickness of 30-50nm.

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