CN103224408A - Reinforcement material for preservation of cultural relics, and preparation method and application thereof - Google Patents

Abstract

The invention relates to a reinforcement material for cultural relics protection and its preparation method and application. The cultural relics protection material is based on tetraethyl orthosilicate and modified with silicon dioxide nanoparticles and hydroxyl-terminated polydimethylsiloxane. The organosilicon composite material prepared by sol-gel reaction, wherein the mass ratio of tetraethyl orthosilicate, nano-silicon oxide and polydimethylsiloxane is 100: (0-25): (0-6 ).

Description

Reinforcement material for cultural relics protection and its preparation method and application

technical field

The invention belongs to the technical field of cultural relics protection, and relates to a non-cracking organic silicon protective agent for reinforcement and protection of cultural relics and its performance, especially suitable for the protection and reinforcement of stone cultural relics.

Background technique

Stone cultural relics are an important part of cultural heritage. Due to their loose and porous structure, they are easily affected by water, salt, and wind in the environment. Therefore, protective materials with excellent performance are urgently needed for reinforcement and protection. Generally speaking, stone cultural relics protection materials are required to have low viscosity, good permeability, good weather resistance, good cohesion, adhesion and compatibility with the cultural relics substrate, certain reversibility, non-toxic, environmental Friendly, do not change the appearance of cultural heritage, consider possible property changes during the deterioration process, and should not produce new substances that will damage cultural relics after aging. Organosilicon materials stand out from all kinds of protective materials due to their advantages of high permeability, good compatibility with stone and stability to ultraviolet radiation, and have been widely researched and applied in the protection of stone cultural relics. Tetraethyl silicate (TEOS) and its oligomers are the most widely used among the commercial protective agents.

However, due to the existence of capillary action, etc., after the silicone protective material penetrates into the stone matrix, it is easy to crack during the gelation and drying process, and the cracked fragments will form a secondary capillary network in the stone matrix, making the water absorption of the stone The increase may accelerate various deteriorations caused by the action of water. Aiming at the problem of brittle cracking of silicone materials, there have been many researches in the world. The typical one is PMC (Particle Modified Consolidant) protective agent, which introduces metal nanoparticles into silicone to reduce capillary action; introduces elastic segments such as polydimethylsiloxane Oxane, enhances flexibility. Although they have all obtained remarkable anti-cracking effects, there are also many defects. The more prominent problems that actually limit the application are: PMC protective agent has a great influence on the appearance and color of the stone matrix; the introduction of elastic chain segments reduces the ability of the stone to resist salt damage and causes deterioration.

Chinese patent application 201110208130.0 discloses a nano-material for stone protective film and its preparation method. The material in this application uses PEO polyoxyethylene as a surfactant, hydrochloric acid or ammonia as a catalyst to prepare silica colloidal balls through solvent evaporation-induced self-assembly method (EISA ) preparation, the purpose of protection is achieved by forming a film on the surface of the stone, but it does not involve making the protective material enter the interior of the stone matrix to fill the pores to form a continuous gel network structure for reinforcement, nor does it mention the cracking modification and salt resistance of the material In addition, the materials prepared by this method need to use surfactants, and the catalysts used are hydrochloric acid or ammonia water, which have a certain corrosive effect on the cultural relics themselves.

Contents of the invention

Therefore, the object of the present invention is to provide a novel nano-silica-hydroxyl-terminated polydimethylsiloxane-tetraethyl orthosilicate ternary composite protection material and a preparation method thereof, so as to meet the protection requirements of stone cultural relics.

Here, on the one hand, the present invention provides a reinforcement material for the protection of cultural relics. The material for the protection of cultural relics is based on tetraethyl orthosilicate and modified with silicon dioxide nanoparticles and hydroxyl-terminated polydimethylsiloxane. The organosilicon composite material prepared by sol-gel reaction, wherein the mass ratio of tetraethyl orthosilicate, nano-silicon oxide and polydimethylsiloxane is 100: (0-25): (0-6 ).

The protective solution mainly composed of tetraethyl orthosilicate of the present invention has a low viscosity and is easy to penetrate into porous stone cultural relics. It acts on the stone and reacts and polymerizes with environmental water vapor, and the colloidal silicon produced is in the rock pores. Deposit in the structure, or react with the hydroxyl group in the hydrophilic stone to form a stable Si-O-Si bond, play the role of the original cement in the sandstone, and enhance the force between mineral particles, thereby significantly enhancing the strength of the original deteriorated stone. It plays a very good role of reinforcement and protection. Selecting nanoparticles and elastic chain segments to modify tetraethyl orthosilicate at the same time achieves the purpose of anti-cracking and obtains excellent weather resistance. The silica network generated by tetraethyl orthosilicate in the ternary composite material mainly provides reinforcement performance; nanoparticles can improve the problem of silicone cracking, improve the salt aging resistance of cultural relics, and make up for the limitation of elastomer PDMS on salt aging resistance. Damage; elastomeric PDMS further improves the problem of silicone cracking, and at the same time improves the change of chromatic aberration caused by nanoparticles. Through the synergistic effect of the three, the material with the best comprehensive performance can be obtained.

On the other hand, the present invention provides a method for preparing the above-mentioned reinforcement material for cultural relics protection, comprising mixing ethyl orthosilicate, isopropanol sol of nano silicon oxide, catalyst and water for preliminary hydrolysis, wherein the ethyl orthosilicate The mass ratio of ester to nano silicon oxide is 100:(0-25), the molar ratio of tetraethyl orthosilicate to water is (0.1-10):1; and polydimethylsiloxane is added and stirred at room temperature for 2 The reinforcement material for protection of cultural relics is prepared in ~10 hours, wherein the mass ratio of tetraethyl orthosilicate to polydimethylsiloxane is 100: (0-6).

The method of the present invention uses silica nanoparticles, hydroxyl-terminated polydimethylsiloxane (PDMS) and tetraethyl orthosilicate to carry out sol-gel reaction together, and can prepare a ternary composite cultural relic protection with no cracking and excellent performance The process method of the material. The material is prepared by adding a small amount of silicon dioxide nanoparticles and elastic PDMS to ethyl orthosilicate, using a sol-gel method, and is a translucent liquid with good fluidity.

Preferably, the mass percent concentration of nano-silicon oxide in the isopropanol sol of nano-silicon oxide is 0.5-5%.

Preferably, the particle size of the silica nanoparticles is 5-50 nm, more preferably 10-20 nm.

Preferably, the molecular weight of the hydroxyl-terminated polydimethylsiloxane is 400-5000, the mass fraction of hydroxyl groups is 4-6%, and the viscosity is 5-500cp.

Preferably, the catalyst is dibutyltin dilaurate, and the mass ratio of ethyl orthosilicate to the catalyst is 100: (1-5). The catalyst used is a neutral catalyst, which is more in line with the requirements of cultural relics protection materials compared with the use of acidic or basic catalysts in the prior art.

Preferably, the preliminary hydrolysis is carried out at 40-70°C with stirring for 4-8 hours.

In yet another aspect, the present invention provides an application of the above-mentioned protection and reinforcement material for cultural relics, including: applying the protective material to cultural relics by dipping, spraying, or brushing for infiltration treatment, and placing the infiltrated cultural relics in Curing in the air at normal temperature and pressure or in a constant temperature and humidity box.

Preferably, the cultural relics are stone cultural relics.

Beneficial effects of the present invention:

1) The protective agent does not crack in the natural environment;

2) Good compatibility with stone;

3) Excellent resistance to salt damage;

4) Little effect on stone appearance;

5) The reinforcement effect is obvious;

6) Significantly improve the hydrophobic performance of stone.

7) The method of preparation and use is simple and easy to operate.

Description of drawings

Fig. 1 is the SEM photograph of the cultural relic reinforced by the reinforcement protection material of the present invention;

Fig. 2 is the physical picture of the cultural relics reinforced by the reinforcement protection material of the present invention before and after the dry salt cycle.

Detailed ways

The present invention will be further described below in conjunction with the drawings and the following embodiments. It should be understood that the following embodiments of the drawings are only used to illustrate the present invention, not to limit the present invention.

The novel non-cracking organosilicon cultural relics protection material of the present invention mainly comprises tetraethyl orthosilicate, silicon dioxide nanoparticles and hydroxyl-terminated polydimethylsiloxane. Using the sol-gel process to prepare ternary composite cultural relics protection materials with no cracking and superior performance, firstly, the tetraethyl orthosilicate added with silica isopropanol solution is prehydrolyzed under a catalyst and a certain temperature, and then other components are added. point.

The preparation method and use method of the present invention comprise the following steps:

(1) Preparation of protective materials: Add nano-silica isopropanol sol, catalyst and water to an appropriate amount of tetraethyl orthosilicate for preliminary hydrolysis, then add polydimethylsiloxane, and stir magnetically at room temperature for 2-10 hours.

(2) Reinforcement process: Apply protective materials to stone cultural relics by dipping, spraying, brushing, etc., which can be performed multiple times depending on the actual situation. Place the finished stone samples in the air at normal temperature and pressure or in a constant temperature and humidity box for curing.

Firstly, the silicon dioxide nanoparticles are dispersed with isopropanol to form a uniform sol by ultrasonic dispersion. The size of the silicon dioxide nanoparticles can be 5-50 nanometers, preferably 10-20nm. The mass fraction of nano-silicon in the propanol sol is 0.5-5%.

Mix the isopropanol sol of silica nanoparticles prepared above and tetraethyl orthosilicate, the amount of the two can be determined according to the mass ratio of tetraethyl orthosilicate and nano-silica as 100: (0-25), ultrasonic Disperse for about 10 minutes, add water and catalyst for preliminary hydrolysis. The present invention controls the hydrolysis and polycondensation process of organic silicon by controlling the amount of water used, and the molar ratio of water to tetraethyl orthosilicate can be 0.1:1-10:1. The catalyst used in the present invention is preferably a neutral catalyst, which will not cause acid-base corrosion to stone cultural relics, such as dibutyltin dilaurate (DBTL), and the amount of the catalyst can be 1-5% of the mass of ethyl orthosilicate. The preliminary hydrolysis can be carried out by stirring at 40-70° C. for 4-8 hours, and magnetic stirring can be used for stirring.

Then add, for example dropwise, hydroxyl-terminated polydimethylsiloxane, and stir at room temperature for 2 to 10 hours to obtain a translucent and uniform protective material system with good fluidity. The molecular weight of the hydroxyl-terminated polydimethylsiloxane used is 400-5000, the mass fraction of hydroxyl groups is 4-6%, and the viscosity is 5-500cp. The amount of hydroxyl-terminated polydimethylsiloxane can be 0-6% of the mass of orthosilicate

The amount of the above-mentioned components of the present invention is determined after repeated experiments. In the entire protective agent system, the mass ratio of tetraethyl orthosilicate, nano-silicon oxide and polydimethylsiloxane is 100: (0-25): ( 0~6).

The protective material prepared above can be applied to cultural relics, especially stone cultural relics, for example, dipping, spraying, brushing and other methods are used for infiltration operations, and multiple operations can be performed depending on the actual situation. Place the finished stone samples in the air at normal temperature and pressure or in a constant temperature and humidity box for curing.

Through microscopic observation, surface hydrophobicity test, water absorption rate and porosity test, air permeability test, compressive strength test, appearance color difference test and salt damage test, it is shown that the reinforcement material invented above has good permeability of organic silicon materials, and In addition to the general characteristics of good stone compatibility, it also has obvious advantages compared with the existing modified silicone materials. 1) The strengthening material does not crack after acting on the stone matrix, the capillary pressure is reduced and the existence of the elastic segment effectively improves the shortcomings of silicone; 2) The applied protective material has little effect on the appearance of cultural relics, basically solving the problem of PMC reinforcement. Disadvantages of causing large color difference; 3) Excellent resistance to salt damage, it may be that the existence of nanoparticles hinders the transport process of soluble salts; 4) The reinforcement effect is obvious, and the silicon-oxygen-silicon skeleton formed by the hydrolysis and polycondensation of tetraethyl silicate plays a role Reinforcement and protection; 5) The hydrophobicity of the stone is improved, and the outer methyl group provided by polydimethylsiloxane plays a hydrophobic role on the surface of the stone.

Microscopic observation: SEM (S-4800, Hitachi) observes cultural relic samples, referring to Fig. 1, which shows the SEM photo of cultural relics reinforced by the reinforcement protection material of the present invention, from which it can be seen that the surface of the protected cultural relics has generated continuous, dense , no cracks, visible microstructure of nanoparticle clusters.

Surface hydrophobicity test: Using a static contact angle measuring instrument (JC2000C, Shanghai Zhongchen), the average contact angle of the reinforced sample to deionized water is 100-120°, while the blank stone is almost completely hydrophilic, indicating that the hydrophobicity is greatly improved. improve.

Water absorption and porosity detection: use a ceramic water absorption tester (Hunan Xiangke) to test, the water absorption rate of the stone without protection material treatment is 11.97%, and the porosity is 24.18%. Reduced to 10-10.5%, with a porosity of 21-21.5%. This is related to the above-mentioned increase in hydrophobicity, and it shows that the protection treatment has not changed the stone microstructure to a large extent.

Gas permeability test: According to the German Industrial Standard 52615, the water vapor transmission resistance of the stone is tested. The water vapor transmission resistance coefficient of the blank stone is 1.356, and the water vapor transmission resistance coefficient of the reinforced sample is 1.77-1.79. The reduction is not much, that is, the original air permeability of the cultural relics can be better maintained.

Compressive strength test: Carry out a mechanical test on the block sample (5592 material universal testing machine, Instron), the average strength value of the blank sample is 12.8MPa, and the average strength value of the reinforced sample is 14.2-15.5MPa, and the reinforcement strength is moderate.

Appearance color difference test: record the color value of the same point before and after the stone protection treatment (CM2600d spectrophotometer, Konica), the measured color difference ΔE is 3-13, which can meet the color difference value requirements allowed by the protection of cultural relics under better conditions (ΔE<5).

Salt damage resistance test: Soak the reinforced sample in a 16% sodium sulfate solution for 7 hours, take it out and put it in a 60°C oven (DHG-9075A, Shanghai Yiheng), and keep it for 15 hours, which is a cycle. After 5 cycles, the appearance of the sample is basically complete, and the mass loss is less than 13%. Referring to Fig. 2, it shows the physical picture of the cultural relics reinforced by the reinforcement protection material of the present invention before and after the dry salt cycle, from which it can be seen that the appearance of the sample is basically complete after 5 dry and wet salt cycles.

Examples are given below to describe the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention, and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the above contents of the present invention all belong to the present invention scope of protection. The specific temperature, time, feeding amount, etc. of the following examples are only an example of a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific numerical values exemplified below .

Example 1

5g of silica nanoparticles (nano-SiO _{2 ) with a particle size of 15nm (nano-SiO 2} ) and 95g of isopropanol were formulated into a homogeneous sol, and 40g of the sol was mixed with 9g of tetraethyl orthosilicate (TEOS), and ultrasonically dispersed for 10 minutes. Add 3 g of water and 0.09 g of DBTL dropwise, stir magnetically at 40°C for 4 h, add dropwise 0.45 g of hydroxyl-terminated polydimethylsiloxane (PDMS) and continue stirring for 1 h to obtain a translucent homogeneous solution. The mass ratio of TEOS, nano silicon oxide, and PDMS added is 100:22.2:5; the amount of water added is 3g, and the ratio of water to silicon (the molar ratio of tetraethylorthosilicate to water) is 4:1.

Use the red sandstone near the Dafo Temple in Shaanxi, cut and process it into two specifications of 2*2*2cm block and 4*4*1cm flake, ultrasonically clean with ethanol, and dry naturally. Immerse with the above protective agent, take it out and place it in a constant temperature and humidity box (SETH-Z-022R, ESPEC) to cure for one month.

Microscopic observation: SEM (S-4800, Hitachi) observation of stone samples shows that a continuous dense microstructure with no cracks and visible nanoparticle clusters is formed on the surface of the sandstone.

Surface hydrophobicity test: Using a static contact angle measuring instrument (JC2000C, Shanghai Zhongchen), the average contact angle of the reinforced sample to deionized water is 128.8 degrees, while the blank stone is almost completely hydrophilic, indicating that the hydrophobicity is greatly improved.

Water absorption and porosity detection: use a ceramic water absorption tester (Hunan Xiangke) to test, the water absorption rate of the stone without protection material treatment is 11.97%, and the porosity is 24.18%. reduced to 10.32%, and the porosity was 21.43%. It is related to the above-mentioned increase in hydrophobicity, and it shows that the protection treatment has not changed the stone microstructure to a large extent.

Gas permeability test: According to the German Industrial Standard 52615, the water vapor transmission resistance of the stone is tested. The water vapor transmission resistance coefficient of the blank stone is 1.356, and the water vapor transmission resistance coefficient of the reinforced sample is 1.781. The air permeability is reduced but not reduced. many.

Compressive strength test: Carry out a mechanical test on the block sample (5592 material universal testing machine, Instron), the average strength value of the blank sample is 12.8MPa, and the average strength value of the reinforced sample is 14.2MPa, and the reinforcement strength is moderate.

Appearance color difference test: record the color value of the same point before and after the stone protection treatment (CM2600d spectrophotometer, Konica), and the measured color difference ΔE is 6.8. Slightly higher than the range of color difference allowed by cultural relics protection (ΔE<5).

Salt damage resistance test: Soak the reinforced sample in a 16% sodium sulfate solution for 7 hours, take it out and put it in a 60°C oven (DHG-9075A, Shanghai Yiheng), and keep it for 15 hours, which is a cycle. After 5 cycles, the appearance of the sample is basically complete, and the mass loss is less than 13%.

Experimental example 2

Example 1 was basically repeated, except that the amount of silicon dioxide nanoparticles in the component was 10% of that of tetraethyl orthosilicate. Microscopic observation shows that the surface of the sample is continuous without cracking, and nano-clusters are visible; the color difference value ΔE is 6.12, with a slight color change, showing a little whitening; the appearance of the sample changes little during the salt damage cycle, and the mass loss after 5 dry and wet salt cycles About 16%.

Experimental example 3

Example 1 was basically repeated, except that the amount of silicon dioxide nanoparticles in the component was 5% of tetraethyl orthosilicate. Microscopic observation shows that the surface of the sample is continuous without cracking, and nano-clusters are visible; the color difference value ΔE is 5.47, and the color change is weak; the appearance of the sample changes little during the salt damage cycle, and the mass loss is about 18% after 5 dry and wet salt cycles.

Experimental example 4

Example 1 was basically repeated, except that the amount of hydroxyl-terminated polydimethylsiloxane in the component was 3% of tetraethyl orthosilicate. Microscopically observe that the surface of the sample is continuous without cracking, and nano-clusters are visible. The color difference value ΔE is about 8.8, and the color changes greatly. The appearance of the sample changed little during the salt damage cycle, and the mass loss was about 11% after 5 dry and wet salt cycles.

Experimental example 5

Example 1 was basically repeated, except that the amount of hydroxyl-terminated polydimethylsiloxane in the component was 1% of tetraethyl orthosilicate. Microscopic observation shows that the surface of the sample is continuous without cracking, and nano-clusters are visible; the color difference value ΔE is about 12.6, and the color changes greatly; the appearance of the sample changes little during the salt damage cycle, and the mass loss after 5 dry and wet salt cycles is about 9% .

Experimental example 6

Basically repeat Example 1, except that the water-to-silicon ratio is 0.1:1, and the protection material with no cracks, water repellency, good air permeability, certain reinforcement strength, small change in appearance color difference, and good salt resistance is also obtained.

Experimental example 7

Basically repeat Example 1, except that the water-to-silicon ratio is 10:1, and the protective material with no cracks, water repellency, good air permeability, certain reinforcement strength, small change in appearance color difference, and good salt resistance is also obtained.

Experimental example 8

Example 1 was basically repeated, except that silica nanoparticles with a particle size of 5nm were used to obtain a protective material with no cracks, water repellency, good air permeability, certain reinforcement strength, small change in appearance color difference, and good salt resistance.

Experimental example 9

Example 1 was basically repeated, except that silica nanoparticles with a particle size of 50nm were used to obtain a protective material with no cracks, water repellency, good air permeability, certain reinforcement strength, small change in appearance color difference, and good salt resistance.

Experiment 10

Basically repeat embodiment 1, only stone sample processing technology is spraying, institute's protective effect is the same as embodiment 1.

Experiment 11

Basically repeat embodiment 1, only stone sample processing technology is brushing, institute's protective effect is the same as embodiment 1.

Industrial applicability

The cultural relics reinforcement material of the present invention has good compatibility with stone materials, good fluidity, and can be used for cultural relics protection by conventional methods such as penetration and coating, and can be gelled under normal temperature and pressure to play a good role in reinforcement and protection, and the reinforcement effect is obvious , can significantly improve the water-repellent performance of stone, and has superior salt damage resistance, and the reinforcement has little effect on the appearance of cultural relics, and it is expected to be widely used in the reinforcement and protection of cultural relics, especially stone cultural relics.

Claims (10)

1. A reinforcement material for cultural relics protection, characterized in that, the cultural relics protection material is based on tetraethyl orthosilicate, with silicon dioxide nanoparticles and hydroxyl-terminated polydimethylsiloxane as a modifier through The organosilicon composite material prepared by sol-gel reaction, wherein the mass ratio of tetraethylorthosilicate, nano silicon oxide and polydimethylsiloxane is 100:(0-25):(0-6). 2. A method for preparing the cultural relics protection reinforcement material according to claim 1, characterized in that, comprising: mixing ethyl orthosilicate, isopropanol sol of nano silicon oxide, catalyst and water for preliminary hydrolysis, wherein the mass ratio of ethyl ortho silicate and nano silicon oxide is 100: (0-25), the The molar ratio of tetraethyl orthosilicate to water is (0.1-10):1; polydimethylsiloxane is added and stirred at room temperature for 2-10 hours to prepare the reinforcement material for cultural relics protection, wherein the tetraethyl orthosilicate The mass ratio to polydimethylsiloxane is 100: (0-6). 3. The method according to claim 2, characterized in that the mass percent concentration of nano-silicon oxide in the isopropanol sol of nano-silicon oxide is 0.5-5%. 4. The method according to claim 2 or 3, characterized in that the particle diameter of the silica nanoparticles is 5-50 nm. 5. The method according to claim 4, characterized in that the particle diameter of the silica nanoparticles is 10-20 nm. 6. The method according to any one of claims 2 to 5, wherein the molecular weight of the hydroxyl-terminated polydimethylsiloxane is 400 to 5000, the mass fraction of hydroxyl is 4 to 6%, and the viscosity is 5~500cp. 7. according to the method described in any one in claim 2 to 6, it is characterized in that, described catalyzer is dibutyltin dilaurate, and the mass ratio of described ethyl orthosilicate and catalyzer is 100: (1～5 ). 8. The method according to any one of claims 2-7, characterized in that the preliminary hydrolysis is carried out at 40-70°C with stirring for 4-8 hours. 9. The application of the cultural relics protection reinforcement material according to claim 1, characterized in that it comprises: applying the protection material to cultural relics by dipping, spraying or brushing for infiltration treatment, and applying the infiltration treatment The cultural relics should be cured in the air at normal temperature and pressure or in a constant temperature and humidity box. 10. The application according to claim 9, wherein the cultural relics are stone cultural relics.

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