Sericin cross-linked calcium carbonate oligomer for ancient mural reinforcement, preparation method and application method

Abstract

The present invention relates to a sericin-crosslinked calcium carbonate oligomer for reinforcing ancient murals, and its preparation and application methods. Sericin is dissolved in absolute ethanol containing calcium chloride, then triethylamine is added, and then urea is added to the mixed solution and heated to generate a sericin-crosslinked calcium carbonate oligomer. This method is simple and easy to operate. More importantly, after being applied to ancient murals, it is found that under normal temperature and common use, the sericin-crosslinked calcium carbonate oligomer prepared by the present invention obtains a continuous structure through the synergistic effect of the protein in sericin during the crystallization process, thereby realizing high-strength reinforcement of the murals, which is 3-5 times that of nano-calcium hydroxide and 6-8 times that of the reported calcium carbonate oligomers at present. The complete crystallization time of calcium carbonate in this material is about 0.5-1 hour, which is much better than that of nano-calcium hydroxide for 9-14 days. This material is a breakthrough in the application of inorganic materials in cultural relics protection and has good popularization prospects.

Description

Technical Field

[0001] The present invention belongs to the field of cultural relics protection materials, and relates to a sericin cross-linked calcium carbonate oligomer for ancient mural reinforcement, and its preparation and application methods. Background Art

[0002] Mural reinforcement materials are mainly divided into two categories: organic and inorganic. Organic materials (such as polyacrylic resin) have high bonding strength and short onset time, and have been widely used. However, such materials are prone to aging and have poor compatibility with the mural body. Inorganic materials have good aging resistance and good compatibility with the mural body, and are currently the mainstream direction of research on cultural relics protection materials (J.Colloid Interface Sci.2013,392,42 - 49.). Inorganic mural protection materials are mainly alkaline earth metal nano-hydroxides, such as nano-calcium hydroxide, nano-magnesium hydroxide, etc. Among them, nano-calcium hydroxide is the most studied and has the best compatibility with murals among inorganic cultural relics protection materials. The main principle of nano-calcium hydroxide for mural reinforcement is that calcium hydroxide nanoparticles are dispersed in an alcohol solution, and then the alcohol solution of nano-calcium hydroxide is applied to the mural surface. The calcium hydroxide nanoparticles enter the mural pores with the alcohol solution. After the liquid evaporates, the calcium hydroxide nanoparticles react with carbon dioxide in the air to form a calcium carbonate network, thereby reinforcing the mural. During the transformation of calcium hydroxide to calcium carbonate, amorphous calcium carbonate (ACC) must be generated first, and then gradually and slowly transformed into crystalline calcium carbonate (such as calcite), so as to finally achieve effective reinforcement of the mural (J.Cult.Herit.2021,50,25 - 42.), and the process is slow (usually takes 1 to two weeks). In addition, even if it is completely transformed into crystalline calcium carbonate, its reinforcement strength is still insufficient.

[0003] Calcium carbonate oligomer is a high molecular compound with a small molecular weight composed of calcium carbonate units, and has excellent plasticity similar to that of high molecular polymers, which is different from traditional amorphous calcium carbonate. However, there is no report on its use for mural reinforcement at present. In addition, from the crystallization mechanism, this material forms a powder without strength at normal temperature and pressure. It can form a blocky high-strength continuous structure only at high temperature (320°C) (Nature,2019,574,396). However, high temperature is unacceptable in mural protection. Summary of the Invention

[0004] Technical Problems to be Solved

[0005] In order to avoid the deficiencies of the prior art, the present invention provides a sericin cross-linked calcium carbonate oligomer for ancient mural reinforcement, and its preparation and application methods.

[0006] Technical Solutions

[0007] A preparation method of sericin cross-linked calcium carbonate oligomer for ancient mural reinforcement, characterized by the following steps:

[0008] Step 1: Preparation of calcium chloride ethanol solution containing sericin: Dissolve sericin in ethanol to obtain an ethanol solution containing sericin, add calcium chloride dihydrate to the ethanol solution containing sericin, and stir and sonicate until calcium chloride dihydrate is completely dissolved to obtain a calcium chloride ethanol solution containing sericin;

[0009] Step 2: Preparation of calcium carbonate oligomer: Add triethylamine to the calcium chloride ethanol solution containing sericin, stir evenly, then add urea to the above solution and heat to 80 - 90 °C, keep warm for 5 - 10 min and then cool naturally to room temperature, and then centrifuge and wash with ethanol for multiple times to obtain calcium carbonate oligomer.

[0010] In the calcium chloride ethanol solution containing sericin and the mixture of triethylamine and urea, the proportion of each component is: add 8 - 10 mL of triethylamine and 3 - 5 g of urea to one portion of the calcium chloride ethanol solution containing sericin.

[0011] For the calcium chloride ethanol solution containing sericin, the proportion of each component is: 0.5 - 1.5 g of sericin, 50 - 100 mL of ethanol and 2.2 - 4.4 g of calcium chloride dihydrate.

[0012] The calcium carbonate oligomer obtained by washing with ethanol for multiple times is washed 2 - 3 times to obtain calcium carbonate oligomer.

[0013] A sericin cross-linked calcium carbonate oligomer for ancient mural reinforcement obtained by the above preparation method, characterized in that sericin is added to the calcium carbonate oligomer, and at high temperature, urea releases carbon dioxide and reacts with Ca 2+ to react, and under the action of triethylamine and sericin, a sericin cross-linked calcium carbonate oligomer is generated.

[0014] Under normal temperature and common use, the sericin cross-linked calcium carbonate oligomer obtains a continuous structure through the synergistic effect with the protein in sericin during the crystallization process, achieving high-strength reinforcement of the mural, which is 3 - 5 times that of nano-calcium hydroxide and 6 - 8 times that of the reported calcium carbonate oligomer at present.

[0015] A reinforcement method for ancient murals using sericin cross-linked calcium carbonate oligomer for ancient mural reinforcement, characterized in that: ultrasonically disperse the calcium carbonate oligomer in ethanol, spray the solution on the surface of the mural until it is no longer absorbed, then remove the excess solution on the surface, and spray a small amount of water on the surface of the mural after the solution evaporates; repeat the above steps multiple times after the water dries, and finally place the reinforced mural in an environment with a room temperature of 50% - 75% humidity for 1 - 3 days after the last water dries.

[0016] The concentration of the ethanol solution of the calcium carbonate oligomer is 5 - 10 mg / mL.

[0017] Cotton balls are used to remove the excess solution on the surface.

[0018] After the water dries, the above steps are repeated for more than 2 times.

[0019] Beneficial effects

[0020] A sericin - crosslinked calcium carbonate oligomer for ancient mural reinforcement, its preparation method and application method are proposed in the present invention. First, sericin is dissolved in absolute ethanol containing calcium chloride, then triethylamine is added, and then urea is added to the mixed solution and heated to 80 - 90 °C. At high temperature, urea releases carbon dioxide and reacts with Ca 2+ to generate a sericin - crosslinked calcium carbonate oligomer under the action of triethylamine and sericin. This method is simple and easy to operate. More importantly, after being applied to ancient murals, it is found that under normal temperature and common use, the sericin - crosslinked calcium carbonate oligomer prepared in the present invention obtains a continuous structure through the synergistic action with the protein in sericin during the crystallization process, thus realizing high - strength reinforcement of the murals, which is 3 - 5 times that of nano - calcium hydroxide and 6 - 8 times that of the reported calcium carbonate oligomers at present. The complete crystallization time of calcium carbonate in this material is about 0.5 - 1 hour, far better than 9 - 14 days of nano - calcium hydroxide. This material is a breakthrough in the application of inorganic materials in cultural relic protection and has good popularization prospects.

[0021] Compared with the prior art, the preparation method of the sericin - crosslinked calcium carbonate oligomer provided by the present invention is simple. Under normal temperature and pressure, after being applied to murals, the sericin - crosslinked calcium carbonate oligomer prepared in the present invention obtains a continuous structure through the synergistic action with the protein in sericin during the crystallization process, and can realize high - strength reinforcement of the murals. The reinforcement strength is 3 - 5 times that of nano - calcium hydroxide and 6 - 8 times that of the reported calcium carbonate oligomers at present. More importantly, the test results show that the calcium carbonate in the sericin - crosslinked calcium carbonate oligomer prepared in the present invention can be completely transformed into crystalline calcium carbonate in 0.5 - 1 hour, while nano - calcium hydroxide needs 9 - 14 days to become crystalline calcium carbonate. This material has great application prospects in cultural relics. Specific embodiments

[0022] The present invention will be further described in combination with embodiments:

[0023] The present invention provides a sericin - crosslinked calcium carbonate oligomer for ancient mural reinforcement and its preparation method.

[0024] It is mainly prepared by the following steps:

[0025] Step 1: Preparation of calcium chloride ethanol solution containing sericin protein: First, dissolve 0.5 - 1.5 grams of sericin protein in 50 - 100 mL of ethanol to obtain an ethanol solution containing sericin protein. Then, add 2.2 - 4.4 grams of calcium chloride dihydrate to the ethanol solution containing sericin protein, and stir and sonicate until the calcium chloride dihydrate is completely dissolved to obtain a calcium chloride ethanol solution containing sericin protein.

[0026] Step 2: Preparation of sericin protein cross-linked calcium carbonate oligomer: Add 8 - 10 mL of triethylamine to the calcium chloride ethanol solution containing sericin protein prepared in Step 1. After stirring evenly, add 3 - 5 grams of urea to the above solution and heat to 80 - 90 °C. Keep warm for 5 - 10 minutes and then cool naturally to room temperature. Then, centrifuge and wash with ethanol 2 - 3 times to obtain sericin protein cross-linked calcium carbonate oligomer.

[0027] Mural reinforcement method: Redisperse the prepared sericin protein cross-linked calcium carbonate oligomer in ethanol by ultrasonic treatment to obtain an ethanol solution of calcium carbonate oligomer with a concentration of 5 - 10 mg / mL. Spray this solution onto the surface of the mural until it is no longer absorbed, and then wipe off the excess solution on the surface with absorbent cotton. After the solution evaporates, spray a small amount of water onto the surface of the mural. After the water dries, repeat the above steps 2 times. After the last time the water dries, place the reinforced mural in an environment with a room temperature of 50% - 75% humidity for 1 - 3 days.

[0028] Example 1:

[0029] First, dissolve 0.5 grams of sericin protein in 50 mL of ethanol to obtain an ethanol solution containing sericin protein. Then, add 2.2 grams of calcium chloride dihydrate to the ethanol solution containing sericin protein, and stir and sonicate until the calcium chloride dihydrate is completely dissolved to obtain a calcium chloride ethanol solution containing sericin protein. Add triethylamine to the calcium chloride ethanol solution containing sericin protein. After stirring evenly, add 3 grams of urea to the above solution and heat to 80 °C. Keep warm for 5 minutes and then cool naturally to room temperature. Then, centrifuge and wash with ethanol 2 times to obtain sericin protein cross-linked calcium carbonate oligomer.

[0030] Mural reinforcement method: Redisperse the prepared sericin protein cross-linked calcium carbonate oligomer in ethanol by ultrasonic treatment to obtain an ethanol solution of sericin protein cross-linked calcium carbonate oligomer with a concentration of 5 mg / mL. Spray this solution onto the surface of the mural until it is no longer absorbed, and then wipe off the excess solution on the surface with absorbent cotton. After the solution evaporates, spray a small amount of water onto the surface of the mural. After the water dries, repeat the above steps 2 times. After the last time the water dries, place the reinforced mural in an environment with a room temperature of 50% humidity for 1 day.

[0031] The test results show that the sericin-crosslinked calcium carbonate oligomer can be completely transformed into crystalline calcium carbonate in 0.5 hours, while nano-calcium hydroxide requires 9 days respectively. In addition, the sericin-crosslinked calcium carbonate oligomer prepared in the present invention has a mural reinforcement strength 3 times that of nano-calcium hydroxide and 6 times that of the reported calcium carbonate oligomers.

[0032] Example 2:

[0033] First, dissolve 0.8 g of sericin in 80 mL of ethanol to obtain an ethanol solution containing sericin. Then, add 3.3 g of calcium chloride dihydrate to the ethanol solution containing sericin, and stir and ultrasonically treat until the calcium chloride dihydrate is completely dissolved to obtain a calcium chloride ethanol solution containing sericin. Add triethylamine to the calcium chloride ethanol solution containing sericin, stir evenly, then add 4 g of urea to the above solution and heat to 85 °C, keep warm for 6 min, then naturally cool to room temperature, and then centrifuge and wash with ethanol 3 times to obtain the sericin-crosslinked calcium carbonate oligomer.

[0034] Mural reinforcement method: Redisperse the prepared sericin-crosslinked calcium carbonate oligomer in ethanol by ultrasonic treatment to obtain an ethanol solution of sericin-crosslinked calcium carbonate oligomer with a concentration of 6 mg / mL. Spray this solution on the surface of the mural until it is no longer absorbed, then wipe off the excess solution on the surface with absorbent cotton. After the solution evaporates, spray a small amount of water on the surface of the mural again. Repeat the above steps 2 times after the water dries. After the last time the water dries, place the reinforced mural in an environment with a room temperature of 60% humidity for 2 days.

[0035] The test results show that the sericin-crosslinked calcium carbonate oligomer can be completely transformed into crystalline calcium carbonate in 0.6 hours, while nano-calcium hydroxide takes 10 days. In addition, the sericin-crosslinked calcium carbonate oligomer prepared in the present invention has a mural reinforcement strength 3 times that of nano-calcium hydroxide and 7 times that of the reported calcium carbonate oligomers.

[0036] Example 3:

[0037] First, dissolve 0.9 g of sericin in 90 mL of ethanol to obtain an ethanol solution containing sericin. Then, add 4.4 g of calcium chloride dihydrate to the ethanol solution containing sericin, and stir and ultrasonically treat until the calcium chloride dihydrate is completely dissolved to obtain a calcium chloride ethanol solution containing sericin. Add triethylamine to the calcium chloride ethanol solution containing sericin, stir evenly, then add 4 g of urea to the above solution and heat to 88 °C, keep warm for 7 min, then naturally cool to room temperature, and then centrifuge and wash with ethanol 3 times to obtain the sericin-crosslinked calcium carbonate oligomer.

[0038] Mural reinforcement method: The prepared sericin-crosslinked calcium carbonate oligomer is redispersed in ethanol by ultrasonic wave to obtain an ethanol solution of sericin-crosslinked calcium carbonate oligomer with a concentration of 8 mg / mL. Sprinkle this solution on the surface of the mural until it is no longer absorbed, then wipe off the excess solution on the surface with absorbent cotton. After the solution evaporates, spray a small amount of water on the surface of the mural. Repeat the above steps 2 times after the water dries. After the last time the water dries, place the reinforced mural in an environment with a room temperature of 65% humidity for 2 days.

[0039] The test results show that the sericin-crosslinked calcium carbonate oligomer can be completely transformed into crystalline calcium carbonate in 0.8 hours, while it takes 12 days for nano-calcium hydroxide. In addition, the sericin-crosslinked calcium carbonate oligomer prepared by the present invention has a mural reinforcement strength 4 times that of nano-calcium hydroxide and 7 times that of the reported calcium carbonate oligomer.

[0040] Example 4:

[0041] First, dissolve 1 g of sericin in 100 mL of ethanol to obtain an ethanol solution containing sericin. Then add 4.4 g of calcium chloride dihydrate to the ethanol solution containing sericin, and stir and ultrasonic until the calcium chloride dihydrate is completely dissolved to obtain a calcium chloride ethanol solution containing sericin. Add triethylamine to the calcium chloride ethanol solution containing sericin, stir evenly, then add 5 g of urea to the above solution and heat to 90 °C, keep warm for 10 min and then cool to room temperature naturally, and then centrifuge and wash 3 times with ethanol to obtain sericin-crosslinked calcium carbonate oligomer.

[0042] Mural reinforcement method: The prepared sericin-crosslinked calcium carbonate oligomer is redispersed in ethanol by ultrasonic wave to obtain an ethanol solution of sericin-crosslinked calcium carbonate oligomer with a concentration of 10 mg / mL. Sprinkle this solution on the surface of the mural until it is no longer absorbed, then wipe off the excess solution on the surface with absorbent cotton. After the solution evaporates, spray a small amount of water on the surface of the mural. Repeat the above steps 2 times after the water dries. After the last time the water dries, place the reinforced mural in an environment with a room temperature of 75% humidity for 3 days.

[0043] The test results show that the sericin-crosslinked calcium carbonate oligomer can be completely transformed into crystalline calcium carbonate in 1 hour, while it takes 14 days for nano-calcium hydroxide. In addition, the sericin-crosslinked calcium carbonate oligomer prepared by the present invention has a mural reinforcement strength 4 times that of nano-calcium hydroxide and 8 times that of the reported calcium carbonate oligomer.

[0044] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be understood that the above description should not be construed as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and substitutions of the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A preparation method of sericin cross-linked calcium carbonate oligomer for ancient mural reinforcement, characterized in that The steps are as follows: Step 1: Preparation of calcium chloride ethanol solution containing sericin protein: Dissolve sericin protein in ethanol to obtain an ethanol solution containing sericin protein, add calcium chloride dihydrate to the ethanol solution containing sericin protein, and stir and sonicate until calcium chloride dihydrate is completely dissolved to obtain a calcium chloride ethanol solution containing sericin protein; For the calcium chloride ethanol solution containing sericin protein, the proportion of each component is: 0.5 - 1.5 grams of sericin protein, 50 - 100 mL of ethanol, and 2.2 - 4.4 grams of calcium chloride dihydrate; Step 2: Preparation of calcium carbonate oligomer: Add triethylamine to the calcium chloride ethanol solution containing sericin protein prepared in Step 1, stir evenly, then add urea to the above solution and heat to 80 - 90 °C, keep warm for 5 - 10 min and then cool naturally to room temperature, and then centrifuge and wash with ethanol multiple times to obtain calcium carbonate oligomer; In the mixture of the calcium chloride ethanol solution containing sericin protein, triethylamine and urea, the proportion of each component is: add 8 - 10 mL of triethylamine and 3 - 5 grams of urea to one portion of the calcium chloride ethanol solution containing sericin protein.

2. The preparation method of the sericin cross-linked calcium carbonate oligomer for ancient mural reinforcement according to claim 1, characterized in that: The calcium carbonate oligomer obtained by washing with ethanol multiple times is washed 2 - 3 times to obtain the calcium carbonate oligomer.

3. The sericin protein cross-linked calcium carbonate oligomer for ancient mural reinforcement obtained by the preparation method according to claim 1 or 2, characterized in that Sericin is added to the calcium carbonate oligomer. At high temperature, urea releases carbon dioxide to react with Ca 2+ and, under the action of triethylamine and sericin, a calcium carbonate oligomer crosslinked with sericin is formed.

4. The sericin cross-linked calcium carbonate oligomer for ancient mural reinforcement according to claim 3, characterized in that: Under normal temperature and pressure, the calcium carbonate oligomer crosslinked with sericin protein obtains a continuous structure through the synergistic effect with the protein in sericin protein during the crystallization process, realizing the high-strength reinforcement of the mural.

5. A method for strengthening ancient murals using sericin cross-linked calcium carbonate oligomers prepared by the method of any one of claims 1 or 2, characterized in that: Ultrasonically disperse the calcium carbonate oligomer in ethanol, spray this solution on the surface of the mural until it is no longer absorbed, then remove the excess solution on the surface, and spray a small amount of water on the surface of the mural after the solution evaporates; Repeat the above steps multiple times after the water dries. After the last time the water dries, place the reinforced mural in an environment with a room temperature of 50% - 75% humidity for 1 - 3 days.

6. The method according to claim 5, characterized in that: The concentration of the ethanol solution of the calcium carbonate oligomer is 5 - 10 mg / mL.

7. The method according to claim 5, characterized in that: The excess solution on the surface is removed using absorbent cotton.

8. The method according to claim 5, wherein: Repeating the above steps multiple times after the water dries is more than 2 times.