Hydrogel for cleaning insoluble calcium salt on surface of marine effluent ceramic cultural relic and preparation method of hydrogel

Abstract

The invention discloses hydrogel for cleaning insoluble calcium salt on the surface of a marine effluent ceramic cultural relic and a preparation method of the hydrogel. Comprising the following steps: adding bentonite and citric acid into a polyvinyl alcohol aqueous solution, and stirring to obtain A; adding citric acid and chitosan into the polyacrylic acid aqueous solution, and stirring to obtain B; and adding B into A, magnetically stirring at a certain temperature to form a homogeneous composite solution, and carrying out multiple freezing-unfreezing cycles to obtain the hydrogel for cleaning the insoluble calcium salt on the surface of the marine effluent ceramic cultural relic. The preparation method is simple and low in cost. The cleaning agent citric acid is loaded in a gel network formed by polyvinyl alcohol and polyacrylic acid so as to limit the flowability and penetration depth of the cleaning agent citric acid, the glaze layer is protected while the insoluble calcium salt on the surface of the ceramic cultural relic is cleaned, and the damage of the body glaze caused by excessive cleaning is prevented. In the preparation process, citric acid and hydroxyl in a polymer network can form a hydrogen bond through carboxyl of citric acid, physical crosslinking is assisted, and use of a toxic crosslinking agent is avoided. The prepared cleaning gel is high in porosity, good in water-retaining property and good in flexibility, and has stimulation responsiveness and peelable characteristics, and pores of the cleaning gel are communicated with one another. Experiments for cleaning the insoluble calcium salt on the surface of the ceramic cultural relic show that the gel can be attached to the uneven porcelain surface, the cleaning agent is slowly released, the hard and compact insoluble calcium salt is selectively removed, the gel is effective and safe, and the gel is easy to peel and free of residues after being cleaned.

Description

Technical Field

[0001] The present invention relates to the cleaning of marine-excavated ceramic cultural relics, belonging to the technical field of cultural relics protection, and particularly relates to a hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics and a preparation method thereof. Background Art

[0002] Ceramics were important commodities traded on the ancient Maritime Silk Road in China and accounted for more than 90% of marine-excavated cultural relics. Ancient sunken ships unearthed in China, such as "Huaguangjiao I", "Wanjiao I", "Nanhai I", "Nan'ao I", the Yuan Dynasty sunken ship in Shengbaiyu, Fujian, and the Ming Dynasty sunken ships No. 1 and No. 2 on the deep-sea continental slope in the South China Sea, etc., have unearthed tens of millions of ceramic shipborne cultural relics. These cultural relics are of great value for studying the history of ancient maritime trade and exchanges. However, due to long-term erosion by seawater, seabed sediment, marine organisms, other ship cargo, and corrosion products, marine-excavated ceramic cultural relics will be corroded to varying degrees. In particular, the surfaces of porcelain exposed on the seabed are attached with marine benthic organisms such as barnacles, oysters, mussels, corals, worms, and spiral tube worms. After salvage, the remains of these marine organisms are firmly fixed on the surface of ceramic cultural relics, forming calcium-insoluble salts mainly composed of calcium carbonate, which are hard in texture and seriously cover archaeological information such as the shape, decoration, pattern, and color of the porcelain. In addition, after being salvaged ashore, ceramic cultural relics are transferred from a long-term stable marine environment to an atmospheric environment and are easily affected by fluctuations in environmental temperature and humidity, resulting in an accelerated corrosion and damage process. Therefore, once ceramic cultural relics are salvaged, it is necessary to promptly clean the calcium-insoluble salts on the surface.

[0003] The current cleaning methods mainly include the following: (1) Physical cleaning, including mechanical peeling, ultrasonic cleaning, laser cleaning, micro-nano bubble cleaning, etc. The first two cleaning methods have problems of low efficiency, and the cleaning is not delicate and thorough. Laser cleaning and micro-nano bubble cleaning technologies have higher output energy and higher efficiency. However, laser cleaning is greatly affected by laser parameters, incident angles, the degree of porcelain corrosion, the distribution of surface sediments, and the interaction mechanism, and there is a risk of damaging the ceramic body. Micro-nano bubbles have micro-bursting force and can weaken the binding force between the salvaged ceramics and surface sediments, but there are still problems of damaging the ceramic body and being difficult to clean locally and controllably. (2) Wet chemical cleaning, that is, solution cleaning, including water washing and cleaning with cleaning agents such as acids, surfactants, enzymes, chelating agents, etc. Chemical cleaning agents can effectively remove surface sediments on ceramics, but the better the cleaning ability of the reagent, the stronger the damage to the porcelain, which will cause the dissolution of the components of the ceramic body and glaze. In addition, it is difficult to control the diffusion, penetration, and volatilization processes of the cleaning solution, resulting in over-cleaning and damaging the cultural relics. Summary of the Invention

[0004] To avoid the deficiencies of the prior art, the present invention provides a hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics and a preparation method thereof. The hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics provided by the present invention uses citric acid as the effective cleaning ingredient in the gel system and water as the solvent; the interpenetrating polymer network of polyvinyl alcohol and polyacrylic acid serves as the three-dimensional framework of the gel carrier, forming a high-density hydrogen bond network and physical entanglement crosslinking between the two. Among them, polyvinyl alcohol dominates the strength and stability of the gel network, and polyacrylic acid endows the gel with pH sensitivity to slowly control the release of citric acid; chitosan plays a role in adjusting the pH and regulating the pore structure of the gel network, and bentonite is used as a mechanical strengthening filler to improve the crosslinking degree and flexibility of the hydrogel network, aiming to enable the gel to closely adhere to the rough ceramic surface. This hydrogel has a high porosity with interconnected pores, a wide pore size distribution range, good water retention, good flexibility, pH-stimuli responsiveness, and peelable characteristics. More importantly, the cleaning agent citric acid is confined in the gel carrier to control its fluidity and penetration in the cracks of the glaze layer of ceramic cultural relics, thereby improving the controllability and safety of the cleaning process.

[0005] According to the first aspect of the technical solution of the present invention, a preparation method of a hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics is provided, including:

[0006] S1: Add bentonite and citric acid to an aqueous solution of polyvinyl alcohol, and stir to obtain A;

[0007] S2: Add citric acid and chitosan to an aqueous solution of polyacrylic acid, and stir to obtain B;

[0008] S3: Add B to A, and magnetically stir at a certain temperature until a homogeneous composite solution is formed. After multiple freeze-thaw cycles, a hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics is obtained.

[0009] Further, in S1, the mass of polyvinyl alcohol is 3.2 g, which is dissolved in pure water at 90 °C to obtain an aqueous solution of polyvinyl alcohol; the mass of bentonite is 0.48 g, the mass of the citric acid powder is 4 g, the mass of the chitosan powder is 0.24 g, and the mass of the citric acid powder is 4 g.

[0010] Further, in S1, the mass of polyvinyl alcohol is 4 g, which is dissolved in pure water at 90 °C to obtain an aqueous solution of polyvinyl alcohol; the mass of bentonite is 0.48 g, the mass of the citric acid powder is 5 g, the mass of the chitosan powder is 0.24 g, and the mass of the citric acid powder is 5 g.

[0011] Further, in the step S1, 4 g of polyvinyl alcohol is dissolved in pure water at 90 °C to obtain an aqueous polyvinyl alcohol solution; 3 g of bentonite, 3 g of citric acid powder, and 0.24 g of chitosan powder are used, and the mass of the citric acid powder is 3 g.

[0012] Further, in the step S1, the stirring time is 30 min.

[0013] Further, in the step S2, the stirring time is 30 min.

[0014] Further, in the step S3, B is added to A, and magnetic stirring is carried out at 60 °C until a homogeneous composite solution is formed.

[0015] Further, in the step S3, the number of freeze-thaw cycles is 3 times.

[0016] Further, during the freeze-thaw cycle, it is frozen at -18 °C for 10 h and thawed at room temperature for 2 h, and this is repeated 3 times.

[0017] According to the second aspect of the technical solution of the present invention, a hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics is provided, wherein the hydrogel is prepared by using the preparation method described in any of the above aspects.

[0018] Among them, the mass fraction of the components of the hydrogel is 9.2% - 10% of polyvinyl alcohol, 3% - 3.4% of polyacrylic acid, 17.2% - 25.1% of citric acid, 0.7% - 1.2% of bentonite, 0.6% - 0.7% of chitosan, and 60.1% - 68.8% of water.

[0019] Advantages of the present invention:

[0020] In the technical solution of the present invention, bentonite, citric acid and chitosan are respectively added to aqueous solutions of polyvinyl alcohol and polyacrylic acid, and after 3 freeze-thaw cycles, a hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics is prepared. The preparation method is simple, convenient and low-cost. The cleaning agent citric acid is loaded in the three-dimensional network gel formed by polyvinyl alcohol and polyacrylic acid to limit its fluidity and penetration depth, effectively protecting the glaze layer while cleaning the calcium-insoluble salts on the surface of ceramic cultural relics and preventing damage to the body and glaze caused by over-cleaning. During the preparation process, citric acid can also form hydrogen bonds through its carboxyl groups with the hydroxyl groups in the polymer network to assist physical crosslinking, avoiding the use of toxic crosslinking agents. The prepared cleaning gel has a high porosity, interconnected pores, good water retention, good flexibility, stimulus responsiveness and peelable characteristics. Experiments on cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics show that the gel can adhere to the uneven surface of porcelain. As a slow-release medium for the cleaning agent, it can effectively and selectively remove hard and dense calcium-insoluble salts, avoiding uncontrolled diffusion of the cleaning agent and over-infiltration of the glaze layer. After cleaning, the gel can be easily peeled off and removed without residue, showing good cleaning performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the structures shown in these drawings.

[0022] Figure 1 It is a flow chart of the preparation method of the hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics according to the technical solution of the present invention.

[0023] Figure 2 It is an electron micrograph of the hydrogel prepared in Example 1 of the present invention.

[0024] Figure 3 It is the effect of cleaning calcium-insoluble salts on the surface of the Longquan celadon wares excavated from the Yuan Dynasty sunken ship at Shengbeiyu, Fujian in Example 1 of the present invention. Figure a is a microscopic photograph of the surface of the celadon ware before cleaning, Figure b is a microscopic photograph of the surface of the celadon ware after cleaning, Figure c is the microscopic Raman surface scanning analysis area of the surface of the celadon ware at a larger optical microscope magnification, Figure d is a pseudo-color map (two-dimensional) of the microscopic Raman surface scan result, Figure e is the microscopic infrared surface scanning analysis spectra during the three processes of before, during and after cleaning, and Figure f is the microscopic Raman surface scanning analysis spectrum after cleaning.

[0025] The realization, functional characteristics and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0027] The terms "first", "second", etc. in the specification and claims of the present disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present disclosure described herein can be implemented, for example, in an order different from those illustrated or described herein.

[0028] In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0029] "Plurality" includes two or more.

[0030] And / or, it should be understood that for the term "and / or" used in the present disclosure, it is merely an association relationship describing associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Reducing labor input and facilitating business automation, with the characteristics of generality, high efficiency, and high precision.

[0031] The technical solution of the present invention first provides a preparation method of a hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics, as Figure 1 shown, including:

[0032] S101: Add bentonite and citric acid to an aqueous solution of polyvinyl alcohol, and stir for 30 min to obtain A;

[0033] S102: Add citric acid and chitosan to an aqueous solution of polyacrylic acid, and stir for 30 min to obtain B;

[0034] S103: Add B to A, magnetically stir at 60 °C until a homogeneous composite solution is formed, and after 3 freeze-thaw cycles, the hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics is obtained.

[0035] The technical solution of the present invention also provides a hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics. Among them, the hydrogel is prepared by the preparation method described above.

[0036] Among them, the mass fractions of the components of the hydrogel are 9.2%-10% of polyvinyl alcohol, 3%-3.4% of polyacrylic acid, 17.2%-25.1% of citric acid, 0.7%-1.2% of bentonite, 0.6%-0.7% of chitosan, and 60.1%-68.8% of water.

[0037] Example 1

[0038] Dissolve 3.2 g of polyvinyl alcohol in pure water at 90°C, add 0.48 g of bentonite and 4 g of citric acid powder, and stir for 30 min to obtain solution A; add 0.24 g of chitosan powder and 4 g of citric acid powder to the aqueous solution of polyacrylic acid and stir evenly to obtain solution B. Add B to A and stir magnetically at 60°C until a homogeneous composite solution is formed to obtain a pre-gel solution. Then freeze it at -18°C for 10 h and thaw it at room temperature for 2 h, and repeat the freeze-thaw cycle 3 times to obtain the hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics, as Figure 2 shown. Apply the prepared hydrogel to the Longquan celadon bowl excavated from the Yuan Dynasty shipwreck in Shengbeiyu, Zhangzhou, Fujian, keep the applied area moist, remove the hydrogel after 5-6 h, and it can be observed that as Figure 3 shown in figures a-f in. Under an optical microscope, most of the calcium-insoluble salts on the surface of the excavated porcelain are significantly disappeared, the roughness of the porcelain glaze is reduced, and it is flatter than before cleaning. The results of micro-Raman and micro-infrared analysis show that the characteristic peaks attributed to calcium carbonate (Raman: 1085 cm -1 ; IR: 1430 cm -1 ± and 880 cm -1 ±) have significantly reduced intensities or even disappeared.

[0039] Example 2

[0040] Dissolve 4 g of polyvinyl alcohol in pure water at 90°C, add 0.48 g of bentonite and 5 g of citric acid powder, and stir for 30 min to obtain solution A; add 0.24 g of chitosan powder and 5 g of citric acid powder to the aqueous solution of polyacrylic acid and stir evenly to obtain solution B. Add B to A and stir magnetically at 60°C until a homogeneous composite solution is formed to obtain a pre-gel solution. Then freeze it at -18°C for 10 h and thaw it at room temperature for 2 h, and repeat the freeze-thaw cycle 3 times to obtain the hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics.

[0041] Example 3

[0042] Dissolve 4 g of polyvinyl alcohol in pure water at 90 °C, add 3 g of bentonite and 3 g of citric acid powder, and stir for 30 min to obtain solution A; add 0.24 g of chitosan powder and 3 g of citric acid powder to an aqueous solution of polyacrylic acid and stir evenly to obtain solution B. Add B to A and magnetically stir at 60 °C until a homogeneous composite solution is formed. The obtained pre-gel solution is then frozen at -18 °C for 10 h and thawed at room temperature for 2 h. Repeat the freeze-thaw cycle 3 times to obtain the hydrogel for cleaning the calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics.

[0043] In summary, the technical solution of the present invention provides a hydrogel for cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics and its preparation method. The preparation method is simple and low-cost. The cleaning agent citric acid is loaded in the gel network formed by polyvinyl alcohol and polyacrylic acid to limit its fluidity and penetration depth, protect the glaze layer while cleaning the calcium-insoluble salts on the surface of ceramic cultural relics, and prevent damage to the body and glaze caused by over-cleaning. During the preparation process, citric acid can also form hydrogen bonds through its own carboxyl group and the hydroxyl group in the polymer network to assist physical cross-linking, avoiding the use of toxic cross-linking agents. The prepared cleaning gel has a high porosity, interconnected pores, good water retention, good flexibility, stimulus responsiveness, and peelable characteristics. Experiments on cleaning calcium-insoluble salts on the surface of marine-excavated ceramic cultural relics show that the gel can adhere to the uneven surface of porcelain, slowly release the cleaning agent, selectively remove hard and dense calcium-insoluble salts, effectively and safely, and the gel is easy to peel off and has no residue after cleaning.

[0044] Specifically, the cleaning results show that the hydrogel exhibits extremely strong control ability for the diffusion and release of the cleaning agent, has high adaptability and adhesion to the rough surface of marine-excavated porcelain cultural relics with sediments attached, can specifically clean calcium-insoluble salts, and the gel body can be peeled off after cleaning. The above properties are related to five factors: ① the occurrence of phase separation during the freeze-thaw cycle induces gel formation; ② polyvinyl alcohol plays a templating role; ③ hydrogen bond formation occurs within and between polymer chain molecules and with the hydroxyl groups on the porcelain surface; ④ the pH stimulus responsiveness of polyacrylic acid; ⑤ the coupled action of chemical dissolution, physical adsorption, and complexation adsorption mechanisms.

[0045] At the same time, the non-toxic and environmentally friendly citric acid can also act as a cross-linking agent to promote the formation of the gel network. The carboxyl group in its molecular chain can form hydrogen bonds with the hydroxyl group in the polymer network, restricting the movement of polymer molecular chains, thereby stabilizing the gel network structure and assisting physical cross-linking, avoiding the use of toxic chemical cross-linking agents such as glutaraldehyde.

[0046] At the same time, the content of the cleaning agent citric acid can be flexibly adjusted according to the thickness of the calcium-insoluble salts on the surface of the marine-excavated ceramic cultural relics, and the method of multiple applications can be adopted to obtain the best cleaning effect.

[0047] It should be noted that in this text, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or device comprising that element.

[0048] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0049] Through the description of the above embodiments, those skilled in the art can clearly understand that the above implementation methods can be realized by means of software plus a necessary general hardware platform. Of course, it can also be realized by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to enable a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in various embodiments of the present invention.

[0050] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific implementation manners. The above specific implementation manners are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the purpose of the present invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. A preparation method of a hydrogel for cleaning calcium-insoluble salts on the surface of marine water-exposed ceramic cultural relics, characterized in that, The preparation method includes: S1: Add bentonite and citric acid into an aqueous solution of polyvinyl alcohol, and obtain A after stirring; S2: Add citric acid and chitosan into an aqueous solution of polyacrylic acid, and obtain B after stirring; S3: Add B into A, magnetically stir at a certain temperature until a homogeneous composite solution is formed, and obtain the hydrogel for cleaning calcium-insoluble salts on the surface of marine water-exposed ceramic cultural relics after multiple freeze-thaw cycles.

2. The preparation method according to claim 1, characterized in that, In the above S1, the mass of polyvinyl alcohol is 3.2 g, which is dissolved in pure water at 90 °C to obtain an aqueous solution of polyvinyl alcohol; the mass of bentonite is 0.48 g, the mass of citric acid powder is 4 g, the mass of chitosan powder is 0.24 g, and the mass of citric acid powder is 4 g.

3. The preparation method according to claim 1, characterized in that, In the above S1, the mass of polyvinyl alcohol is 4 g, which is dissolved in pure water at 90 °C to obtain an aqueous solution of polyvinyl alcohol; the mass of bentonite is 0.48 g, the mass of citric acid powder is 5 g, the mass of chitosan powder is 0.24 g, and the mass of citric acid powder is 5 g.

4. The preparation method according to claim 1, wherein, In the above S1, the mass of polyvinyl alcohol is 4 g, which is dissolved in pure water at 90 °C to obtain an aqueous solution of polyvinyl alcohol; the mass of bentonite is 3 g, the mass of citric acid powder is 3 g, the mass of chitosan powder is 0.24 g, and the mass of citric acid powder is 3 g.

5. The preparation method according to claim 1, characterized in that, In the above S1, the stirring time is 30 min.

6. The preparation method according to claim 1, characterized in that, In the above S2, the stirring time is 30 min.

7. The preparation method according to claim 1, characterized in that, In the above S3, add B into A, and magnetically stir at 60 °C until a homogeneous composite solution is formed.

8. The preparation method according to claim 1, characterized in that, In the above S3, the number of freeze-thaw cycles is 3 times.

9. The preparation method according to claim 8, characterized in that, During the above freeze-thaw cycle, freeze at -18 °C for 10 h and thaw at room temperature for 2 h, and repeat 3 times.

10. A hydrogel for cleaning calcium-insoluble salts on the surface of marine water-emerged ceramic cultural relics, characterized in that, The hydrogel is prepared by using the preparation method according to any one of claims 1 to 9, wherein, the mass fraction of the components of the hydrogel is 9.2%-10% of polyvinyl alcohol, 3%-3.4% of polyacrylic acid, 17.2%-25.1% of citric acid, 0.7%-1.2% of bentonite, 0.6%-0.7% of chitosan, and 60.1%-68.8% of water.

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