Antique building brick and tile freeze-thaw-resistant protective material as well as preparation method and application thereof

Abstract

The invention relates to a freeze-thaw-resistant protective material for ancient building tiles, and a preparation method and application of the freeze-thaw-resistant protective material. The protection material is prepared through a sol-gel method, raw materials comprise tetraethyl orthosilicate and hydroxyl-terminated polydimethylsiloxane, a solvent is ethyl alcohol, a hydrolytic agent is deionized water, and a catalyst is oxalic acid dihydrate. Wherein the molar ratio of the tetraethyl orthosilicate to the deionized water to the oxalic acid dihydrate is 1: 4: 0.17, and the hydroxyl-terminated polydimethylsiloxane accounts for 1-4wt% of the total solid content in the protective material. According to the protective material obtained by the invention, through the introduction of the hydroxyl-terminated polydimethylsiloxane and the hydrophobic gas-phase nano silicon dioxide particles, the cracking of a tetraethyl orthosilicate gel network is effectively reduced, and the stability of the material in cold climate is enhanced. The good permeability and hydrophobicity of the material effectively improve the freeze-thaw resistance of ancient building tiles, keep the permeability and structural integrity of cultural relics, and are suitable for long-acting protection in cold regions.

Description

Technical Field

[0001] The invention belongs to the technical field of cultural relics protection materials and relates to an anti-freezing and thawing protection material for ancient building bricks and tiles and a preparation method and application thereof. Background Art

[0002] my country has a large number of precious ancient buildings, among which bricks and tiles are commonly used as building materials because of their low cost and easy production. However, in the cold northern regions, the bricks and tiles of ancient buildings have been affected by severe cold weather for a long time, and water has repeatedly frozen and thawed inside the bricks and tiles, resulting in increased porosity, more cracks and fissures, and reduced strength, which seriously shortens their service life and poses a huge threat to the preservation of ancient buildings.

[0003] Traditional restoration methods often use direct replacement of antique bricks and tiles, but this will lead to the loss of historical information and is costly. Therefore, it is particularly important to find an anti-freeze-thaw protective material that can effectively protect the bricks and tiles of ancient buildings from freeze-thaw damage while maintaining their historical style and value. Although there are many anti-freeze-thaw protective materials on the market, they all have certain defects. Polymer protective materials have poor durability. When used outdoors for a long time, such as acrylic-based coatings, they are easily affected by photooxidation, and the protective effect decreases significantly over time; inorganic protective materials have poor fluidity and insufficient permeability in the brick and tile matrix, making it difficult to fully exert their protective effect, and are prone to form a passivation layer on the surface of the matrix, hindering water and gas exchange and causing salt damage; although organic-inorganic composite materials have good overall performance, they often face problems such as uneven dispersion of nanoparticles during the preparation process, which affects the material performance.

[0004] Patent CN114657789A discloses a kind of organosilicon super hydrophobic coating, made of tetraethyl orthosilicate, terminal hydroxyl sealing agent, silicon dioxide particles and catalyst, can be used for surface modification. However, the coating has many deficiencies in the application process. First, it is necessary to prepare dispersion A and solution B respectively during preparation, and the substrate is reacted into a super hydrophobic coating by immersion or spraying, and its application mode adopts two-step operation, and the process is complicated and easily causes the coating to penetrate unevenly inside the brick and tile, affecting reinforcement and anti-freeze-thaw effect. Secondly, the coating cannot be fully infiltrated inside the brick and tile by a simple immersion method, and is prone to cracking and poor film-forming property during drying. And the coating is not optimized for the freeze-thaw damage problem of ancient building bricks and tiles in cold areas, and it is difficult to meet actual needs.

[0005] Therefore, it is of great practical significance to develop an anti-freeze-thaw protective material for ancient building bricks and tiles that has excellent performance, is easy to prepare, and can effectively solve existing problems. Summary of the invention

[0006] The purpose of the present invention is to provide an anti-freeze-thaw protective material for ancient building bricks and tiles and its preparation method and application in order to overcome the common defects of the above-mentioned existing silicon-based protective materials such as cracking. The protective material should have the advantages of good fluidity, stability, permeability and anti-freeze-thaw performance, and can effectively protect the bricks and tiles of ancient buildings and extend their service life.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] Disclosed is an anti-freezing and thawing protective material for ancient building bricks and tiles. The protective material is prepared by a sol-gel method, and the raw materials include tetraethyl orthosilicate and terminal hydroxyl polydimethylsiloxane, the solvent is ethanol, the hydrolyzing agent is deionized water, and the catalyst is oxalic acid dihydrate; wherein the molar ratio of tetraethyl orthosilicate:deionized water:oxalic acid dihydrate is 1:4:0.17, and the terminal hydroxyl polydimethylsiloxane accounts for 1-4wt% of the total solid content in the protective material.

[0009] Furthermore, the raw materials also include hydrophobic fumed nano-silica particles, and the molar ratio of tetraethyl orthosilicate: deionized water: hydrophobic fumed nano-silica particles: oxalic acid dihydrate is 1:4:0.17:0.17. Adding hydrophobic fumed nano-silica particles can further improve the film-forming property of the ancient building brick and tile anti-freeze-thaw protection material.

[0010] Preferably, the particle size of the hydrophobic fumed nano-silica particles is 7-14 nm.

[0011] Preferably, the viscosity of the hydroxy-terminated polydimethylsiloxane is 40 ost.

[0012] Preferably, the total solid content of the protective material is 25 wt %.

[0013] The present invention also provides a method for preparing the aforementioned ancient building brick and tile anti-freezing and thawing protective material, comprising the following steps:

[0014] (1) ultrasonically homogenously dispersing hydrophobic fumed nano-silica particles and hydroxyl-terminated polydimethylsiloxane in ethanol to obtain dispersion A;

[0015] (2) Under high-speed magnetic stirring, weighed tetraethyl orthosilicate is added dropwise to dispersion A. After the addition is complete, dispersion B is homogenized by ultrasonication to obtain dispersion B;

[0016] (3) Add a solution of oxalic acid dihydrate dissolved in deionized water dropwise to dispersion B. After the addition is complete, seal the container at room temperature and stir at high speed magnetically to perform a sol-gel process, thereby finally obtaining a transparent sol.

[0017] The dispersion temperature in step (1) is room temperature, and the dispersion is dispersed by ultrasonic homogenization until the dispersion A is clear and transparent without precipitation.

[0018] According to a specific embodiment of the present invention, the ultrasonic homogenization dispersion time in step (1) is 120 min; the ultrasonic homogenization dispersion time in step (2) is 30 min; and the high-speed magnetic stirring time in step (3) is 360 min.

[0019] According to a specific embodiment of the present invention, in step (4), a plastic wrap is used for sealing.

[0020] The present invention also provides the use of the aforementioned anti-freeze-thaw protective material for ancient building bricks and tiles in the protection of ancient building bricks and tiles, wherein the anti-freeze-thaw protective material for ancient building bricks and tiles is infiltrated into the interior of the bricks and tiles by soaking, and after soaking, the bricks and tiles are taken out and the excess liquid is absorbed by filter paper for maintenance. The anti-freeze-thaw protective material for ancient building bricks and tiles of the present invention can conveniently modify the bricks and tiles by soaking, thereby improving the anti-freeze-thaw performance of the bricks and tiles, and the modified bricks and tiles have reduced water absorption, enhanced mechanical properties, and small color changes on the basis of basically not changing the appearance and overall pore structure.

[0021] The working principle of the present invention includes the following aspects:

[0022] (1) The tetraethyl orthosilicate used in the present invention forms a silicon-oxygen network structure in the hydrolysis and condensation reaction, and the hydrophobic fumed silica nanoparticles are used as fillers to further enhance the rigid skeleton of the material, thereby improving the compression resistance and freeze-thaw resistance. The terminal hydroxyl polydimethylsiloxane is used as a flexible segment, so that the overall material has moderate flexibility and can resist the stress generated in the freeze-thaw cycle, thereby reducing the cracking phenomenon of the material.

[0023] (2) The organic groups of the terminal hydroxyl polydimethylsiloxane used in the present invention endow the material with good hydrophobicity, so that the material forms a hydrophobic coating on the surface of bricks and tiles, preventing excessive penetration of water into the interior of the brick and tile structure, thereby effectively reducing the water content in the bricks and tiles and reducing structural damage caused by the expansion of water freezing.

[0024] (3) This material is designed to have excellent fluidity and permeability, which enables it to penetrate into the pores of bricks and tiles and evenly cover the pore walls, which not only improves the bonding strength between the material and the bricks and tiles, but also enhances its internal anti-freeze and thaw ability.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention uses tetraethyl orthosilicate as the main silicon-based precursor, and introduces terminal hydroxyl polydimethylsiloxane and selectively introduces hydrophobic gas-phase nano-silica particles to form a composite material. Tetraethyl orthosilicate is used as the skeleton material of the curing framework, and together with terminal hydroxyl polydimethylsiloxane, it participates in forming a cross-linked structure, which solves the problem that traditional silicon-based protective materials are easy to crack and have poor film-forming properties during the drying process. The formula of the present invention is specially designed for the freeze-thaw protection of bricks and tiles in ancient buildings. The method of directly soaking bricks and tiles is simple and efficient, and can make the material penetrate evenly into the interior. By introducing specific raw materials to form special structures and functional groups, the cracking of the gel network is effectively reduced, the freeze-thaw resistance is enhanced, and the air permeability and structural integrity of the cultural relics can be maintained.

[0027] (2) The present invention can still maintain high mechanical properties and structural integrity after multiple freeze-thaw cycles. By introducing hydroxy-terminated polydimethylsiloxane, a hydrophobic protective layer is formed on the surface of the material, which can effectively prevent water from penetrating, reduce the freeze-thaw cycles caused by temperature changes, and thus improve the freeze-thaw resistance of the brick and tile material.

[0028] (3) The present invention can ensure permeability and adhesion without affecting the overall air permeability of bricks and tiles. The fluidity and low viscosity of the material allow it to penetrate into the micropores of bricks and tiles, which can enhance the strength of the internal structure without hindering the normal gas exchange between bricks and tiles and the environment.

[0029] (4) After curing, the protective material of the present invention forms a Si-O-Si main chain skeleton, has good stability, and can resist erosion by environmental factors such as ultraviolet light and humidity.

[0030] (5) The protective material of the present invention is a transparent amorphous gel containing functional groups such as -OH, -CH and Si-C, which is hydrophobic and has good fluidity and stability. The protective material can be allowed to penetrate into the interior of bricks and tiles by immersion to modify the bricks and tiles and improve their anti-freeze-thaw performance. The modified bricks and tiles have reduced water absorption, enhanced mechanical properties and little color change without substantially changing their appearance and overall pore structure.

[0031] (6) The preparation process of the present invention is simple and easy, the required raw materials are relatively cheap, and it can be operated at room temperature, which reduces the cost of use and is suitable for large-scale application in the anti-freeze-thaw protection of bricks and tiles in ancient buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a scanning electron microscope image of the brick and tile sample after being reinforced with the silicon-based three-component composite material in Example 1 of the present invention;

[0033] Figure 2The FTIR spectra of Example 1, Example 2, Example 3, Example 4, Comparative Example 1, Comparative Example 2, tetraethyl orthosilicate and hydroxy-terminated polydimethylsiloxane are shown in the figure. It can be clearly seen from the figure that the CH bond stretching vibration peak at 2950 cm-1 and the -CH bond stretching vibration peak at 1261 cm-1 and 850 cm-1 corresponding to the hydroxy-terminated polydimethylsiloxane raw material are shown in the figure. 3 Characteristic peaks such as bond stretching vibration peaks and bending vibration peaks prove the existence of various functional groups in the material, indicating that a specific chemical structure is formed after the material is cured. DETAILED DESCRIPTION

[0034] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] Unless otherwise specified, the equipment used in the following examples are all conventional equipment in the art; the reagents used are all commercially available products or prepared by conventional methods in the art unless otherwise specified. Anything not described in detail in the following examples can be achieved by conventional experimental means in the art.

[0036] Embodiment 1:

[0037] A method for preparing an anti-freeze-thaw protective material for ancient building bricks and tiles, comprising the following steps:

[0038] (1) 7-14 nm hydrophobic fumed nano-silica particles and hydroxyl-terminated polydimethylsiloxane are ultrasonically homogenized and dispersed in ethanol to obtain dispersion A. The ultrasonic homogenization dispersion time is 120 min and the temperature is room temperature. Dispersion A is clear and transparent without precipitation.

[0039] (2) Under high-speed magnetic stirring, weighed tetraethyl orthosilicate was added dropwise to dispersion A. After the addition was completed, dispersion B was homogenized by ultrasonication at room temperature for 30 min.

[0040] (3) Add a solution of oxalic acid dihydrate dissolved in deionized water dropwise to dispersion B. After the addition is complete, seal the mixture with plastic wrap at room temperature and stir at high speed for 360 min to perform a sol-gel process, thereby obtaining a transparent sol.

[0041] The molar ratio of tetraethyl orthosilicate: deionized water: hydrophobic fumed nano-silica particles: oxalic acid dihydrate is 1:4:0.17:0.17; and the viscosity of the hydroxy-terminated polydimethylsiloxane is 40ost.

[0042] The total solid content of the finally prepared ancient building brick and tile anti-freezing and thawing protective material is 25wt%, and the terminal hydroxyl polydimethylsiloxane accounts for 4wt% of the total solid content (ie, SP4 group).

[0043] The above-mentioned ancient building brick and tile anti-freeze-thaw protection material introduces terminal hydroxyl polydimethylsiloxane and nano-silica hydrophobic units into the rigid silicon oxygen network formed by tetraethyl orthosilicate, so that the material skeleton is connected by Si-O-Si while giving the material a certain hydrophobicity. Therefore, the ancient building brick and tile anti-freeze-thaw protection material has both hydrophobicity and high weather resistance of traditional polysiloxane, so that it can produce certain structural adjustments during the curing process to prevent the occurrence of cracking problems.

[0044] The above-mentioned ancient building brick and tile anti-freeze-thaw protection material is used as a reinforcement protective agent for the anti-freeze-thaw protection of ancient building bricks and tiles, and the specific steps are as follows:

[0045] The purchased antique bricks and tiles (mainly composed of sandstone) were cleaned and dried, and then immersed in the anti-freeze-thaw protective material for ancient building bricks and tiles. The liquid level of the anti-freeze-thaw protective material for ancient building bricks and tiles was always maintained at 2 cm higher than the antique bricks and tiles. The immersion time was 4 hours. After completion, the bricks and tiles were taken out and the excess liquid was absorbed with filter paper. The curing was completed in 3 weeks at a temperature of 25°C and 50% Rh.

[0046] like Figure 1 As shown, it can be seen that the anti-freeze-thaw protective material for ancient building bricks and tiles of this embodiment 1 is evenly covered on the sandstone surface without any cracks, which has a good reinforcement effect.

[0047] The color difference and compressive strength of the antique bricks and tiles before and after protection were tested using a 3nh YS3060 spectrophotometer and a CTM 9200 200KN microcomputer-controlled electronic universal mechanical testing machine, and the air permeability was tested using the cup method. The results are shown in Table 1.

[0048] The color difference test shows that the color difference ΔE of the brick sample after being protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 1 and the brick sample before protection is 3.71, which has good color fidelity.

[0049] The color difference test shows that the color difference ΔE between the tile sample after being protected by the ancient building brick and tile anti-freeze-thaw protection material of Example 1 and the tile sample before protection is 4.56, which has general color fidelity.

[0050] The air permeability test shows that the water vapor permeability of the brick sample of Example 1 before protection is 63.7g / m 2 / 24h, the water vapor permeability of the brick sample after protection is 49g / m 2 / 24h, a decrease of 23%, indicating that the brick samples protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 1 still have good air permeability.

[0051] The compressive strength test shows that the compressive strength of the brick sample in Example 1 before protection is 12.25 MPa, and the compressive strength of the brick sample after protection is increased to 16.36 MPa, indicating that the ancient building brick and tile anti-freeze-thaw protection material in Example 1 has a good reinforcement and protection effect on the brick samples.

[0052] The compressive strength test shows that the compressive strength of the tile sample in Example 1 before protection is 18 MPa, and the compressive strength of the tile sample after protection is increased to 20.16 MPa, indicating that the ancient building brick and tile anti-freeze-thaw protection material in Example 1 has a good reinforcement and protection effect on the tile sample.

[0053] The protective material of Example 1 has good film-forming properties and no cracking was found; the color difference change ΔE of the brick samples was 3.71 and the air permeability was reduced by 23%, both within the acceptable range, and the compressive strength was increased by 33.6%; the color difference change of the tile samples was general, and the compressive strength was increased by 12%.

[0054] Embodiment 2:

[0055] A preparation method and application of an anti-freeze-thaw protective material for ancient building bricks and tiles is basically the same as Example 1, except that the terminal hydroxyl polydimethylsiloxane accounts for 2% of the total solid content (ie, SP2 group).

[0056] The color difference and compressive strength of the antique bricks and tiles before and after protection were tested using a 3nh YS3060 spectrophotometer and a CTM 9200 200KN microcomputer-controlled electronic universal mechanical testing machine, and the air permeability was tested using the cup method. The results are shown in Table 1.

[0057] The color difference test shows that the color difference ΔE of the brick sample after being protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 2 and the brick sample before protection is 3.18, which has good color fidelity.

[0058] The color difference test shows that the color difference ΔE between the tile sample after being protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 2 and the tile sample before protection is 3.04, which has good color fidelity.

[0059] The air permeability test shows that the water vapor permeability of the brick sample of Example 2 before protection is 63.6 g / m 2 / 24h, the water vapor permeability of the brick sample after protection is 54.8g / m 2 / 24h, only reduced by 13.8%, indicating that the brick samples protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 2 still have good air permeability.

[0060] The compressive strength test shows that the compressive strength of the brick sample in Example 2 before protection is 12.25 MPa, and the compressive strength of the brick sample after protection is increased to 14.37 MPa, indicating that the ancient building brick and tile anti-freeze-thaw protection material in Example 2 has a good reinforcement and protection effect on bricks.

[0061] The compressive strength test shows that the compressive strength of the tile sample before protection is 18 MPa, and the compressive strength of the tile sample after protection is increased to 21.98 MPa, indicating that the ancient building brick and tile anti-freeze-thaw protection material in Example 2 has a good reinforcement and protection effect on the tile sample.

[0062] The protective material of Example 2 has good film-forming properties and no cracking was found; the color difference change and air permeability are within an acceptable range; the compressive strength index of the tile sample is significantly improved by 22.1%; the compressive strength of the brick sample is improved by 17%.

[0063] Embodiment 3:

[0064] A preparation method and application of an anti-freeze-thaw protective material for ancient building bricks and tiles is basically the same as Example 1, except that the terminal hydroxyl polydimethylsiloxane accounts for 1% of the total solid content (ie, SP1 group).

[0065] The color difference and compressive strength of the antique bricks and tiles before and after protection were tested using a 3nh YS3060 spectrophotometer and a CTM 9200 200KN microcomputer-controlled electronic universal mechanical testing machine, and the air permeability was tested using the cup method. The results are shown in Table 1.

[0066] The color difference test shows that the color difference ΔE between the brick samples protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 3 and the brick samples before protection is 2.01, which has good color fidelity.

[0067] The color difference test shows that the color difference ΔE between the tile samples protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 3 and the tile samples before protection is 1.52, which has good color fidelity.

[0068] The air permeability test shows that the water vapor permeability of the brick sample of Example 3 before protection is 63.6 g / m 2 / 24h, the water vapor permeability of the brick sample after protection is 56.1g / m 2 / 24h, a decrease of 11.8%, indicating that the brick samples protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 3 still have good air permeability.

[0069] The compressive strength test shows that the compressive strength of the brick sample in Example 3 before protection is 12.25 MPa, and the compressive strength of the brick sample after protection is increased to 14.06 MPa, indicating that the ancient building brick and tile anti-freeze-thaw protection material in Example 3 has a good reinforcement and protection effect on the brick samples.

[0070] The compressive strength test shows that the compressive strength of the tile sample in Example 3 before protection is 18 MPa, and the compressive strength of the tile sample after protection is increased to 20.87 MPa, indicating that the ancient building brick and tile anti-freeze-thaw protection material in Example 3 has a good reinforcement and protection effect on the tile sample.

[0071] The protective material of Example 3 has good film-forming properties and no cracking is found; the color difference and air permeability changes are within an acceptable range, and the parameters such as compressive strength are improved, with the compressive strength of brick samples increased by 14.8% and that of tile samples increased by 15.9%.

[0072] Embodiment 4:

[0073] A preparation method and application of an anti-freeze-thaw protective material for ancient building bricks and tiles is basically the same as Example 1, except that the terminal hydroxyl polydimethylsiloxane accounts for 1% of the total solid content and no hydrophobic gas-phase nano-silica particles (i.e., Group P1) are added.

[0074] The color difference and compressive strength of the antique bricks and tiles before and after protection were tested using a 3nh YS3060 spectrophotometer and a CTM 9200 200KN microcomputer-controlled electronic universal mechanical testing machine, and the air permeability was tested using the cup method. The results are shown in Table 1.

[0075] The color difference test shows that the color difference ΔE of the brick sample after being protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 4 and the brick sample before protection is 3.78, which has good color fidelity.

[0076] The color difference test shows that the color difference ΔE between the tile samples protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 4 and the tile samples before protection is 3.41, which has good color fidelity.

[0077] The air permeability test shows that the water vapor permeability of the brick sample of Example 4 before protection is 63.6 g / m 2 / 24h, the water vapor permeability of the brick sample after protection is 56g / m 2 / 24h, only reduced by 11.95%, indicating that the brick samples protected by the ancient building brick and tile anti-freeze-thaw protection material in Example 4 still have good air permeability.

[0078] The compressive strength test shows that the compressive strength of the brick sample in Example 4 before protection is 12.25 MPa, and the compressive strength of the brick sample after protection is increased to 15.25 MPa, indicating that the ancient building brick and tile anti-freeze-thaw protection material in Example 4 has a good reinforcement and protection effect on the brick samples.

[0079] The compressive strength test shows that the compressive strength of the tile sample in Example 4 before protection is 18 MPa, and the compressive strength of the tile sample after protection is increased to 21.71 MPa, indicating that the ancient building brick and tile anti-freeze-thaw protection material in Example 4 has a good reinforcement and protection effect on the tile sample.

[0080] The protective material of Example 4 has good film-forming property and no cracking is found. The color difference change and air permeability are within the acceptable range. The compressive strength of the brick sample is increased by 24.5%, and the compressive strength of the tile sample is increased by 20.6%.

[0081] Comparative Example:

[0082] Antique bricks and tiles (i.e. Group C) manufactured by Daixian Brick and Tile Factory, Xinzhou City, Shanxi Province.

[0083] Table 1

[0084]

[0085]

[0086] The brick and tile samples reinforced with the anti-freeze-thaw protection materials of the ancient building bricks and tiles in Examples 1-4 and the brick and tile samples in the comparative example were subjected to FTIR spectral analysis. The results are as follows: Figure 2 As shown. Figure 2 It can be clearly seen that the C-H bond stretching vibration peaks of the SP1 group, SP2 group, SP4 group and P1 group are located at 2950 cm-1, and the -CH bond stretching vibration peaks corresponding to the terminal hydroxyl polydimethylsiloxane raw materials at 1261 cm-1 and 850 cm-1 are 3 The characteristic peaks such as the bond stretching vibration peak and the bending vibration peak prove the existence of various functional groups in the material, indicating that the anti-freeze-thaw protection materials for ancient building bricks and tiles in Examples 1-4 form a specific chemical structure after curing. -1 850cm -1 There are obvious -CH 3 The stretching vibration peak and bending vibration peak of the bond are located at 806cm -1 The infrared absorption peak at is the bending vibration peak of Si-C bond, which is derived from the Si-CH 3 , proving the introduction of hydrophobic units of SP1, SP2, SP4 and P1. -1 850cm -1 There is no corresponding -CH 3 The stretching vibration peaks and bending vibration peaks of the bonds.

[0087] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A material for protecting ancient building bricks and tiles from freezing and thawing, characterized in that: The protective material is prepared by a sol-gel method, and the raw materials include tetraethyl orthosilicate and terminal hydroxyl polydimethylsiloxane, the solvent is ethanol, the hydrolyzing agent is deionized water, and the catalyst is oxalic acid dihydrate; wherein the molar ratio of tetraethyl orthosilicate:deionized water:oxalic acid dihydrate is 1:4:0.17, and the terminal hydroxyl polydimethylsiloxane accounts for 1-4wt% of the total solid content in the protective material.

2. The anti-freezing and thawing protective material for ancient building bricks and tiles according to claim 1 is characterized in that: The raw materials also include hydrophobic fumed nano-silica particles, and the molar ratio of tetraethyl orthosilicate: deionized water: hydrophobic fumed nano-silica particles: oxalic acid dihydrate is 1:4:0.17:0.

17.

3. The anti-freeze-thaw protective material for ancient building bricks and tiles according to claim 2, characterized in that: The particle size of the hydrophobic fumed nano-silicon dioxide particles is 7-14 nm.

4. The anti-freezing and thawing protective material for ancient building bricks and tiles according to claim 1, characterized in that: The viscosity of the terminal hydroxyl polydimethylsiloxane is 40 ost.

5. The anti-freezing and thawing protective material for ancient building bricks and tiles according to claim 1, characterized in that: The total solid content of the protective material is 25 wt %.

6. A method for preparing the anti-freezing and thawing protective material for ancient building bricks and tiles according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) ultrasonically homogenously dispersing the raw materials except tetraethyl orthosilicate in ethanol to obtain dispersion A; (2) Under high-speed magnetic stirring, weighed tetraethyl orthosilicate is added dropwise to dispersion A. After the addition is complete, dispersion B is homogenized by ultrasonication to obtain dispersion B; (3) Add a solution of oxalic acid dihydrate dissolved in deionized water dropwise to dispersion B. After the addition is complete, seal the container at room temperature and stir at high speed magnetically to perform a sol-gel process, thereby finally obtaining a transparent sol.

7. The preparation method according to claim 6, characterized in that: The ultrasonic homogenization dispersion time in step (1) is 120 min; the ultrasonic homogenization dispersion time in step (2) is 30 min; and the high-speed magnetic stirring time in step (3) is 360 min.

8. The preparation method according to claim 6 or 7, characterized in that: In step (4), plastic wrap is used for sealing.

9. An application of the anti-freezing and thawing protective material for ancient building bricks and tiles as claimed in any one of claims 1 to 5 in the protection of ancient building bricks and tiles, characterized in that: The anti-freeze-thaw protective material for ancient building bricks and tiles is allowed to penetrate into the interior of the bricks and tiles by soaking. After the soaking is completed, the bricks and tiles are taken out and the excess liquid is absorbed by filter paper before maintenance.

Images