A cardanol emulsion, a preparation method thereof and a method for using the same in archaeological paint film reinforcement

Abstract

The present invention discloses a cardanol emulsion, a preparation method thereof and a method for using the same in reinforcing archaeological paint films, belonging to the technical field of cultural relics protection. The preparation method of the cardanol emulsion includes: a cardanol monomer dispersion step: taking 1-4 parts of cardanol, 1-3 parts of a solvent, 1-3 parts of an emulsifier, and 4-6 parts of water, mixing the cardanol and the solvent in an appropriate ratio to form a dispersion; an emulsification step: sequentially adding the emulsifier and water to the dispersion, and fully mixing evenly to form a cardanol emulsion. In the present invention, cardanol penetrates into the damaged archaeological paint film, and through the catalysis of fungal laccase, cardanol reacts with the broken urushiol polymer fragments in the paint film to in-situ generate oligomers similar to raw paint films, playing a role in repairing the holes in the paint film, promoting the healing of the cracks in the paint film, and improving the strength of the paint film. The present invention simulates the film-forming process of raw lacquer, ensures the maximum compatibility between the reinforcing material and the cultural relic body, and at the same time has the remarkable advantages of environmental friendliness.

Description

Technical Field

[0001] The present invention relates to the protection and restoration of archaeological paint films, belonging to the technical field of cultural relics protection, and particularly relates to a cardanol emulsion, a preparation method thereof, and a method for using the same to reinforce archaeological paint films. Background Art

[0002] Lacquerware cultural relics are artistic treasures with unique oriental characteristics and precious cultural heritages in China. Before being excavated or salvaged, archaeological lacquerware has been buried underground or soaked in water for a long time, and has been eroded by acids, alkalis, salts and microorganisms in the burial environment. The paint film has undergone serious degradation, with molecular chain breakage and cross-linking reactions, making the paint film brittle and losing elasticity, increasing pores, and thus causing the paint film to absorb water and expand. After the lacquerware is unearthed / removed from water, due to sudden changes in environmental temperature and humidity, water loss and other reasons, the paint film will become brittle, warp and fall off. Therefore, it is necessary to carry out toughening and strengthening reinforcement treatment on the archaeological paint film.

[0003] The main raw material of the ancient lacquer layer of lacquerware is Chinese raw lacquer. Raw lacquer is the only water-based natural polymer composite coating in the world that comes from green plants and can dry naturally at room temperature under the catalysis of biological enzymes. It is mainly composed of urushiol, laccase, glycoprotein, gum, water and other substances. The film-forming process of raw lacquer is driven by laccase. Under aerobic conditions, urushiol is catalyzed into free radicals, and then non-enzymatic free radical polymerization reactions occur to generate dimers, trimers, polymers, etc. Eventually, they interact with other components of raw lacquer to assemble and form a continuous paint film. The paint film has a highly cross-linked and irregular three-dimensional network structure, with excellent properties such as water resistance, antioxidant property and corrosion resistance, but it has poor alkali resistance and ultraviolet resistance. In the archaeological lacquer film, the phenolic hydroxyl groups, ether bonds and unsaturated bonds in the side chains of urushiol polymers are oxidized into aldehydes, ketones, acids and esters. These carbonyl compounds generate free radicals after absorbing light, further accelerating the degradation reaction of the paint film. When the cracking speed of the paint film macromolecules is greater than the cross-linking speed, it will lead to the cracking and even pulverization of the raw lacquer film. The main steps for the protection and restoration of the decayed and rotten paint film unearthed from archaeology are softening and reinforcement and reattachment. The softening of the paint film includes physical methods and chemical methods. The physical method utilizes the thermoplasticity of the paint film and makes it soft through heating or aqueous solution heating method. The chemical method uses polyols and polyethylene glycol (PEG) as softening agents. For reinforcement and reattachment, synthetic polymer resin reinforcing agents such as epoxy resin, acrylic resin, ethyl silicate, polyvinyl acetate emulsion, etc. are used. The common problems of these chemical materials are that they are quite different from the main components and properties of the paint film body, have poor compatibility, poor weather resistance, and use a lot of organic solvents, which are not environmentally friendly. Some researchers invented a paint film adhesive by compounding transparent lacquer, raw lacquer, rice paste, lead monoxide and Rocima342, which can ensure the long-term preservation of the paint film without falling off in the natural environment. However, lead monoxide in the raw materials is toxic, and raw lacquer also has a certain sensitization effect, which is harmful to human health. Another researcher invented a method for repairing the loose and dry-shrunk and deformed lacquerware. Although it can restore the shape of the wooden carcass that has shrunk and deformed, it does not repair and reinforce the paint film. In addition, the loose materials and repair materials used in this method are all alkaline materials, which will further corrode the paint film. Summary of the Invention

[0004] To solve the above problems, the present invention provides a cardanol emulsion, a preparation method thereof and a method for using the same for reinforcing archaeological paint films. In the present invention, cardanol is infiltrated into the damaged archaeological paint film, and through the catalysis of fungal laccase, cardanol reacts with the broken urushiol polymer fragments in the paint film to in-situ generate oligomers similar to the raw lacquer film, which plays a role in repairing the holes in the paint film, promoting the healing of the cracks in the paint film, and improving the strength of the paint film. The present invention simulates the film-forming process of raw lacquer, ensures the maximum compatibility between the reinforcing material and the cultural relic body, and at the same time has the significant advantage of being green and environmentally friendly.

[0005] To achieve the above object, the present invention is realized through the following technical solutions:

[0006] According to the first aspect of the technical solution of the present invention, a preparation method of a cardanol emulsion is provided. The raw materials used in the cardanol emulsion include: cardanol, a solvent, an emulsifier, and water;

[0007] Among them, the preparation method includes the following steps:

[0008] (1) Cardanol monomer dispersion step: Take 1 - 4 parts of cardanol, 1 - 3 parts of a solvent, 1 - 3 parts of an emulsifier, and 4 - 6 parts of water. Mix the cardanol and the solvent evenly in an appropriate proportion to form a dispersion;

[0009] (2) Emulsification step: Add the emulsifier and water to the dispersion in sequence, and mix well until a cardanol emulsion is formed.

[0010] Further, the solvent is one or more of the following materials: ethanol, methanol, acetone, dimethyl sulfoxide, and diethylene glycol monobutyl ether.

[0011] Further, the emulsifier is one or more of the following materials: alkyl polyoxyethylene ether, polyoxyethylene hydrogenated castor oil RH40, nonylphenol polyoxyethylene ether, phenethylphenol polyoxyethylene ether, phenethylphenol polyoxyethylene polyoxypropylene ether, alkylbenzene sulfonate, alkylnaphthalene sulfonate, nonylphenol polyoxyethylene (4) ether, octylphenol polyoxyethylene (10) ether.

[0012] Further, the water is: tap water, pure water, or deionized water.

[0013] Further, in the cardanol emulsion, the mass fraction of cardanol is 10% - 40%, the mass fraction of the solvent is 10% - 30%, the mass fraction of the emulsifier is 10% - 30%, and the remaining component is water.

[0014] According to the second aspect of the technical solution of the present invention, a cardanol emulsion is provided, wherein the cardanol emulsion is prepared by using the preparation method described in any of the above aspects.

[0015] According to the third aspect of the technical solution of the present invention, a method for strengthening an archaeological paint film with the cardanol emulsion described in the above aspects is provided, which includes the following steps:

[0016] (1) Paint film softening: Soak the paint film with a softening agent to make it soft again;

[0017] (2) Reinforcing agent penetration: Fully penetrate the cardanol emulsion into the paint film;

[0018] (3) Catalytic reinforcement agent polymerization: Add a buffer solution with a certain pH value to the laccase, mix evenly to prepare a laccase solution with a certain enzyme activity. Take out the paint film from the cardanol solution and apply the laccase solution, and then catalyze the polymerization of cardanol by water bath heating;

[0019] (4) Drying: Slowly dry the reinforced paint film while controlling the temperature and humidity.

[0020] Further, the softening agent in the step (1) is one or a mixture of polyethylene glycol, glycerol, propylene glycol, and ethylene glycol.

[0021] Further, the auxiliary processes for fully infiltrating the cardanol emulsion into the paint film in the step (2) include dipping, spraying, and brushing.

[0022] Further, the buffer solution in the step (3) is acetic acid - ammonium acetate or acetic acid - sodium acetate buffer solution, and the pH is 4.0 - 5.5.

[0023] Further, the laccase used in the laccase solution in the step (3) is fungal laccase, including Aspergillus niger laccase, Trametes versicolor laccase, and Aspergillus oryzae laccase, and the enzyme activity of the fungal laccase is 50U / ml - 200U / ml.

[0024] Further, the application method of the laccase solution in the step (3) includes dipping, spraying, and brushing, and it is applied 2 - 5 times in total, with an interval of 5 - 24h, and the water bath reaction temperature is from room temperature to 45°C.

[0025] Further, the drying conditions in the step (4) are 10 - 40°C and the humidity is 50% - 80%.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1) Compared with the filling mechanism of common synthetic polymer reinforcement agents, the present invention is significantly different. By using the urushiol polymer fragments remaining in the archaeological paint film and catalyzing the in-situ polymerization of cardanol by laccase to repair and reinforce the damaged paint film, the whole repair process simulates the biochemical reaction process of raw lacquer film formation, and the generated product has good compatibility with the paint film body, meeting the principle of raw material repair in cultural relics protection.

[0028] 2) The cardanol structure contains a benzene ring structure, which has high temperature resistance and anti-mildew and antibacterial properties; the 15-carbon long straight chain can provide good toughness, which is beneficial to the long-term preservation of lacquerware.

[0029] 3) It has strong controllability. By regulating the content of cardanol emulsion and the enzyme-catalyzed reaction conditions, archaeological paint films with different degrees of damage can be repaired.

[0030] 4) Easy to operate, with mild reaction conditions. The entire strengthening operation is carried out at normal temperature and pressure, and only water is released as a reaction product during the process, which is green and environmentally friendly.

[0031] 5) Cardanol is a biological resource with wide sources, low price, non-toxic and harmless. As a substitute for raw lacquer, it has good application prospects in the restoration of archaeological lacquerware. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of the operation process for preparing the cardanol emulsion and strengthening the archaeological paint film described in the present invention.

[0033] Figure 2 are photos of cardanol emulsion reinforcing agents with different concentrations.

[0034] Figure 3 are the appearances of the archaeological paint film sample strengthened according to Example 1 of the present invention before (a) and after (b) being treated by the method described in the present invention.

[0035] Figure 4 are electron microscope photos of the archaeological paint film sample strengthened according to Example 2 of the present invention before (a) and after (b) being treated by the method described in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] In order to better understand the preparation and use effects of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The following embodiments completed based on the above technical solutions are part of the embodiments of the present invention, but are not limited to these embodiments.

[0037] The following will make a detailed description of the specific embodiments of the present invention with reference to the accompanying drawings.

[0038] Cardanol is a light yellow slightly transparent oily liquid refined from natural cashew nut shell oil. Its structure is similar to that of urushiol in raw lacquer. It is a phenolic compound with an unsaturated long side chain and has high reaction activity. Cardanol is rich in sources, low in price, safe and non-toxic. The present invention provides a cardanol emulsion, a preparation method thereof and a method for strengthening an archaeological paint film, including steps such as the preparation of a cardanol emulsion reinforcing agent, film softening, penetration of the reinforcing agent, catalyzing the polymerization of the reinforcing agent and drying.

[0039] The preparation method of the cardanol emulsion includes the following steps:

[0040] (1) Cardanol monomer dispersion step: 1 - 4 parts of cardanol, 1 - 3 parts of solvent, 1 - 3 parts of emulsifier, 4 - 6 parts of water. Mix cardanol and the solvent in an appropriate ratio evenly to form a transparent dispersion liquid.

[0041] (2) Emulsification step: Add an emulsifier and water to the dispersion liquid in sequence, and mix them thoroughly by methods such as mechanical stirring or ultrasonic oscillation until a uniform, transparent, and stable emulsion is formed.

[0042] Further, the solvent selected in the step (1) is one or more of the following materials: ethanol, methanol, acetone, dimethyl sulfoxide, diethylene glycol monobutyl ether, and the total mass fraction is 10% - 30%. Among them, diethylene glycol monobutyl ether is preferably selected, which can not only reduce the oil-water interfacial tension, but also its low evaporation rate makes the emulsion stable without instability caused by evaporation.

[0043] Further, the emulsifier selected in the step (1) is one or more of the following materials: alkyl polyoxyethylene ether, polyoxyethylene hydrogenated castor oil RH40, nonylphenol polyoxyethylene ether, phenethylphenol polyoxyethylene ether, phenethylphenol polyoxyethylene polyoxypropylene ether, alkyl benzene sulfonate, alkyl naphthalene sulfonate, nonylphenol polyoxyethylene (4) ether, octylphenol polyoxyethylene (10) ether, and the total mass fraction is 10% - 30%. The selected emulsifiers are all non-ionic surfactants, with less toxicity and irritation, and will not damage cultural relics; they are less affected by external factors such as pH, which is beneficial to maintaining the stability of the emulsion.

[0044] Further, the mass fraction of cardanol in the step (1) is 10% - 40%. Preferably 30%, which can keep the emulsion with low viscosity while maximizing the content of active ingredients in the microemulsion.

[0045] Further, the water selected in the step (1) is: tap water, pure water or deionized water.

[0046] The present invention also relates to a cardanol emulsion prepared by the above method, and a method for strengthening archaeological paint films using the cardanol emulsion, including the following steps:

[0047] (1) Paint film softening: Soak the paint film with a chemical softener to make it soft again.

[0048] (2) Penetration of the reinforcing agent: Fully penetrate the cardanol emulsion into the paint film.

[0049] (3) Catalytic polymerization of the reinforcing agent: Add laccase to a buffer solution with an appropriate pH, mix it evenly to prepare an enzyme solution with moderate enzyme activity. Transfer the paint film from the cardanol solution to the laccase solution for impregnation, or spray the paint film with the laccase solution multiple times, and heat it in a water bath to catalyze the polymerization of cardanol.

[0050] (4) Drying: Slowly dry the strengthened paint film while controlling the temperature and humidity.

[0051] Furthermore, the chemical softener used in step (1) is a mixture of one or more of polyethylene glycol, glycerol, propylene glycol, and ethylene glycol. The polyol material can be filled in the micropores of the paint film by immersion, and the hydroxyl group can be connected with the lacquer phenol by intermolecular hydrogen bonds, which weakens the intermolecular forces of the lacquer, increases the distance between molecular chains, swells the paint film, disperses stress, and softens.

[0052] Furthermore, the auxiliary processes of emulsion penetration in step (2) include dipping, spraying, brushing, etc., which can be flexibly selected according to the size and preservation condition of the archaeological lacquerware. For smaller paint films, dipping is preferred, while for larger paint films, spraying or multiple brushing methods can be used.

[0053] Furthermore, the buffer used in the enzyme solution in step (3) is acetic acid-ammonium acetate or acetic acid-sodium acetate buffer, with a pH of 4.0 to 5.5. Acetic acid-sodium acetate is preferred because it has less irritation.

[0054] Furthermore, the laccase used in the enzyme solution in step (3) is fungal laccase, including Aspergillus niger laccase, Versicolor laccase, and Aspergillus oryzae laccase, and the enzyme activity of the laccase is about 50U / ml to 200U / ml. Fungal laccase has the advantages of high activity, small molecule, adaptability to temperature of 25-50°C, and can still react at room temperature, and is an ideal enzyme catalyst.

[0055] Furthermore, the application method of the enzyme solution in step (3) includes dipping, spraying, brushing, etc., and according to the actual application scenario, it is applied 2-5 times in total, with an interval of 5-24 hours, and the water bath reaction temperature is about room temperature to 45° C. Preferably, 45° C. is the optimal temperature for fungal laccase.

[0056] Furthermore, the drying conditions controlled in step (4) are 10-40° C. and 50%-80% humidity.

[0057] Specifically, Figure 1 As shown, the archaeological paint film reinforcement method provided by the technical solution of the present invention includes:

[0058] Step S101: mixing cardanol, solvent, emulsifier and water in an appropriate proportion and fully dispersing them to form a uniform and stable emulsion;

[0059] Step S102: using chemical reagents to soften the paint film;

[0060] Step S103: allowing the cardanol emulsion to fully penetrate into the paint film;

[0061] Step S104: preparing a laccase solution, and applying the enzyme solution to the paint film to promote the polymerization of cardanol;

[0062] Step S105: Control the temperature and humidity to dry slowly.

[0063] The prepared microemulsion is shown in Figure (2), and it is a light yellow, clear, transparent and stable liquid with good fluidity.

[0064] Example 1:

[0065] The emulsion used in this example contains: 10 wt% of cardanol, 10 wt% of ethanol, 10 wt% of phenethylphenol polyoxyethylene polyoxypropylene ether, and 70 wt% of deionized water. Powdered Aspergillus niger laccase with an activity of 5000 U / g and acetic acid - ammonium acetate buffer solution with a pH of 5.0 were selected, and the enzyme activity in the laccase solution was 100 U / mL.

[0066] Cardanol, ethanol, phenethylphenol polyoxyethylene polyoxypropylene ether, and water were thoroughly mixed by ultrasonic waves to form a free - dispersed, homogeneous, transparent and stable light yellow liquid. The archaeological paint film was soaked in polyethylene glycol 400 with concentrations of 40 wt% and 60 wt% for 6 h in sequence to make it soft. The archaeological paint film was from the scattered paint films unearthed from the Western Zhou Dynasty tombs in Liujiawa, Shaanxi. The prepared cardanol emulsion was used to soak the paint film for 12 h. The acetic acid - ammonium acetate solution with a pH of 5.0 was heated in a water bath to 45 °C, and then the laccase was dissolved in the acetic acid - ammonium acetate solution and stirred until the system was mixed evenly. The paint film was transferred from the cardanol emulsion to the laccase solution and heated in a water bath at 45 °C to catalyze the polymerization of cardanol for 8 h. Finally, the strengthened paint film was dried in an environmental test chamber with a humidity of 75%.

[0067] Most of the holes and cracks in the archaeological paint film strengthened in Example 1 could be filled and repaired, as Figure 3 shown in (a) and (b). Before treatment, there were many cracks and holes on the surface of the paint film, and if it was allowed to dry freely, shrinkage and warping would occur rapidly; after treatment, most of the holes and cracks on the surface of the paint film were filled and repaired, and the surface of the dried paint film was flat. The flexural strength of the paint film before and after strengthening was tested using a thermomechanical analyzer, and the stress and strain of the treated paint film were significantly improved compared with those before strengthening.

[0068] Example 2:

[0069] The emulsion used in this example contains: 20 wt% of cardanol, 15 wt% of acetone, a total of 20 wt% of polyoxyethylene hydrogenated castor oil RH40 and phenethylphenol polyoxyethylene polyoxypropylene ether, and 45 wt% of pure water. Powdered Trametes versicolor laccase with an activity of 5000 U / g and acetic acid - sodium acetate buffer solution with a pH of 4.5 were selected, and the enzyme activity in the laccase solution was 200 U / mL.

[0070] Cardanol, acetone, polyoxyethylene hydrogenated castor oil RH40, polyoxyethylene polyoxypropylene phenyl ethyl phenol ether, and pure water were thoroughly mixed by mechanical stirring to form a free-dispersed, homogeneous, transparent, and stable light yellow liquid. The archaeological paint film was successively immersed in a mixed solution of ethanol and glycerol for 12 h to soften it. The archaeological paint film was from the scattered paint films unearthed from the Zhongshan State Tomb in Guxun, Xingtang, Hebei. The prepared cardanol emulsion was sprayed on the paint film 3 times. The pH 4.5 acetic acid-sodium acetate solution was heated in a water bath to 40 °C, and then laccase was dissolved in the acetic acid-sodium acetate solution and stirred until the system was uniformly mixed. The paint film treated with the cardanol emulsion was transferred to the laccase solution, and the polymerization of cardanol was catalyzed by heating in a water bath at 40 °C for 12 h. Finally, the strengthened paint film was placed in a petri dish, sealed with a plastic film, and dried at room temperature.

[0071] As described in (1)-(2), in the strengthened archaeological paint film, cardanol can be observed to fill the small holes and cracks inside the paint film under an electron microscope, as shown in Figure 4 (a) and (b) shown below. Before treatment, the inside of the paint film was filled with holes of different sizes, which not only further increased the speed of water absorption and loss but also severely reduced the toughness of the paint film and increased its rigidity. After treatment, a polymer film was formed on the surface of the paint film, and the formed polymer molecules played a supporting role and effectively filled the holes.

[0072] Example 3:

[0073] The emulsion used in this example contained: 30 wt% cardanol, 25 wt% dimethyl sulfoxide, 30 wt% of the mixture of nonylphenol polyoxyethylene (4) ether and octylphenol polyoxyethylene (10) ether, and 15 wt% tap water. Powdered Aspergillus oryzae laccase with an activity of 10000 U / g and acetic acid-sodium acetate buffer solution with a pH of 4.5 were selected, and the enzyme activity in the laccase solution was 200 U / mL.

[0074] Cardanol, dimethyl sulfoxide, nonylphenol polyoxyethylene (4) ether, octylphenol polyoxyethylene (10) ether, and tap water were thoroughly mixed to form a free-dispersed, homogeneous, transparent, and stable light yellow liquid. The archaeological paint film was immersed in a mixed solution of polyethylene glycol and ethanol for 12 h to soften it. The archaeological paint film was from the painted paint film unearthed from the Western Zhou Tomb in Liujiawa, Shaanxi. The prepared cardanol emulsion was sprayed on the paint film 5 times. Laccase with a pH of 4.5 was dissolved in the acetic acid-sodium acetate solution and stirred until the system was uniformly mixed. The laccase solution was sprayed on the paint film 5 times, and the polymerization of cardanol was catalyzed by heating in a water bath for 18 h. Finally, the strengthened paint film was dried in an environmental test chamber with a humidity of 75%.

[0075] As described in (1)-(2), the holes and cracks in the strengthened archaeological paint film can be significantly repaired without affecting the painted colors.

[0076] Example 4:

[0077] The emulsion used in this example contains: 20 wt% cardanol, 15 wt% diethylene glycol monobutyl ether, 20 wt% of nonylphenol polyoxyethylene (4) ether and octylphenol polyoxyethylene (10) ether in total, and deionized water is added to make up 45 wt%. Powdered Aspergillus niger laccase with an activity of 1000 U / g and acetic acid-sodium acetate buffer solution with a pH of 4.0 are selected, and the enzyme activity in the laccase solution is 50 U / mL.

[0078] Cardanol, diethylene glycol monobutyl ether, nonylphenol polyoxyethylene (4) ether, octylphenol polyoxyethylene (10) ether and deionized water are fully mixed to form a free-dispersing, homogeneous, transparent and stable light yellow liquid. A mixed solution of polyethylene glycol and glycerol is used to repeatedly brush and soften the paint film. The softening agent solution on the surface of the paint film is wiped dry, and the cardanol emulsion is repeatedly brushed on the surface of the paint film with a brush every half an hour for a total of 10 h until the reinforcing agent completely penetrates. The laccase is dissolved in acetic acid-sodium acetate solution with a pH of 4.0 and stirred until the system is uniformly mixed. The excess cardanol emulsion on the surface of the paint film is wiped dry, and the laccase solution is sprayed with a small sprayer and reapplied every 1 h, and the reaction time is 1 d. Finally, the reinforced paint film is dried in an environmental test chamber with a humidity of 60%.

[0079] For the archaeological lacquerware samples reinforced as described in (1)-(2), no secondary warping or hollowing phenomena occurred after long-term observation.

[0080] In summary, the present invention discloses a cardanol emulsion, a preparation method thereof and a method for reinforcing archaeological paint films. This method makes a water-in-oil emulsion from cardanol, penetrates it into the damaged archaeological paint film, and catalyzes the reaction of cardanol with the broken urushiol polymer fragments in the paint film by fungal laccase to in-situ generate oligomers similar to the raw paint film, which plays a role in repairing the holes in the paint film, promoting the healing of the cracks in the paint film and improving the strength of the paint film. The method of the present invention has the remarkable advantages of good compatibility with archaeological paint films, green safety, low cost, mild reaction conditions and wide application range.

[0081] The above examples and the description in the specification are only the principles and the best embodiments of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A method for strengthening archaeological paint films using cardanol emulsion, characterized in that, It includes the following steps: (1) Film softening: Soak the paint film with a softening agent to make it soft again; (2) Reinforcing agent penetration: Fully penetrate the cardanol emulsion into the paint film; (3) Catalyze the polymerization of the reinforcing agent: Add a buffer solution with a certain pH value to laccase, mix evenly to prepare a laccase solution with a certain enzyme activity, take out the paint film from the cardanol solution and apply the laccase solution, and then heat it in a water bath to catalyze the polymerization of cardanol. Among them, the pH of the buffer solution is 4.0 - 5.5; the laccase used in the laccase solution is fungal laccase, and the enzyme activity of the fungal laccase is 50 U / ml - 200 U / ml; (4) Drying: Slowly dry the reinforced paint film by controlling the temperature and humidity to obtain a reinforced archaeological paint film. Among them, the preparation method of the cardanol emulsion includes the following steps: (1) Cardanol monomer dispersion step: Take 1 - 4 parts of cardanol, 1 - 3 parts of solvent, 1 - 3 parts of emulsifier, and 4 - 6 parts of water. Mix the cardanol and the solvent evenly in an appropriate ratio to form a dispersion; (2) Emulsification step: Add the emulsifier and water to the dispersion in sequence, and mix well until a cardanol emulsion is formed.

2. The method for strengthening archaeological paint films using cardanol emulsion according to claim 1, characterized in that, The softening agent in the step (1) of film softening is one or a mixture of polyethylene glycol, glycerol, propylene glycol, and ethylene glycol.

3. The method for strengthening archaeological paint films using cardanol emulsion according to claim 1, characterized in that, The auxiliary process of fully penetrating the cardanol emulsion into the paint film in the step (2) of reinforcing agent penetration is impregnation, spraying, or brushing.

4. The method for strengthening archaeological paint films using cardanol emulsion according to claim 1, characterized in that, In the step (3) of catalyzing the polymerization of the reinforcing agent, the buffer solution is acetic acid - ammonium acetate or acetic acid - sodium acetate buffer solution; the fungal laccase is Aspergillus niger laccase, Coriolus versicolor laccase, or Aspergillus oryzae laccase; the application method of the laccase solution is impregnation, spraying, or brushing, and it is applied 2 - 5 times with an interval of 5 - 24 h, and the water bath reaction temperature is from room temperature to 45°C.

5. The method for strengthening archaeological paint films using cardanol emulsion according to claim 1, characterized in that, The drying conditions in the step (4) of drying are 10 - 40 °C and a humidity of 50% - 80%.

6. The method for strengthening archaeological paint films using cardanol emulsion according to claim 1, characterized in that, The solvent is one or more of the following materials: ethanol, methanol, acetone, dimethyl sulfoxide, and diethylene glycol monobutyl ether.

7. The method for strengthening archaeological paint films using cardanol emulsion according to claim 1, characterized in that, The emulsifier is one or more of the following materials: polyoxyethylene hydrogenated castor oil RH40, phenethylphenol polyoxyethylene ether, phenethylphenol polyoxyethylene polyoxypropylene ether, alkylbenzene sulfonate, alkylnaphthalene sulfonate, nonylphenol polyoxyethylene (4) ether, and octylphenol polyoxyethylene (10) ether.

8. The method for strengthening archaeological paint films using cardanol emulsion according to claim 1, characterized in that, The mass fraction of cardanol in the cardanol emulsion is 10% - 40%, the mass fraction of the solvent is 10% - 30%, the mass fraction of the emulsifier is 10% - 30%, and the remaining component is water.

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