Microemulsion-loaded hydrogel for cleaning smoked murals as well as preparation method and application thereof

Abstract

The invention discloses a micro-emulsion-loaded hydrogel for cleaning smoked murals and a preparation method and application thereof, and belongs to the technical field of cultural relic preservation, the method comprises the following steps: mixing a polyoxyethylene ether nonionic surfactant, an anionic surfactant, saturated monohydric alcohol and liquid petroleum hydrocarbon, dissolving in water, and uniformly stirring at room temperature to obtain a micro-emulsion; the preparation method comprises the following steps: dissolving polyvinyl alcohol and polyacrylic acid in dimethyl sulfoxide, heating in a water bath, and gelatinizing to obtain a PVA-PAA hydrogel precursor; and putting the PVA-PAA hydrogel precursor into the micro-emulsion, and reacting at room temperature to obtain the micro-emulsion loaded hydrogel for cleaning the smoked mural. The microemulsion is stably fixed in a PVA-PAA gel network, so that the controllable release and localization effects of the cleaning agent are realized, and the permeation out-of-control of the traditional liquid cleaning agent is avoided. The cleaning agent has the advantages of simple preparation process, good mechanical properties and water retention, mild and efficient removal of smoked deposition, higher safety and protectiveness to a mural pigment layer and a substrate, and improvement of the cleaning efficiency and the operation stability.

Description

Technical Field

[0001] This invention belongs to the field of cultural relic protection technology, specifically relating to a loaded microemulsion hydrogel for cleaning smoked murals, its preparation method, and its application. Background Technology

[0002] Ancient murals, as treasures in the human art treasury, carry profound historical accumulation and unique cultural memories. Their painting techniques and artistic styles showcase the aesthetic pursuits and social landscapes of different periods. From Buddhist themes in the Mogao Grottoes of Dunhuang to decorative scenes in temples, monasteries, and tombs across the country, these murals not only possess extremely high artistic value but also provide invaluable material for the study of ancient society, religion, folklore, and pigment technology. However, because murals are mostly located in semi-open or open environments, they are subject to long-term exposure to natural factors such as light, humidity, temperature fluctuations, and air pollution. Coupled with damage caused by historical human activities, various diseases have appeared on the surface of the murals. Among them, smoke pollution is one of the most common types of damage in religious and residential places such as temples and grottoes. The smoke mainly comes from the burning of incense, candles, and oil lamps during religious ceremonies, as well as the mixture of soot and grease accumulated from activities such as heating and cooking in the space where the murals were located. These pollutants form a dense, highly adhesive black covering on the surface of the murals, severely obscuring the colors and lines of the painting, affecting its artistic expression and viewing effect. At the same time, its chemical components may also accelerate the aging and peeling of the pigment layer. Therefore, effectively and safely removing smoke pollutants has become an important and urgent task in the protection and restoration of murals.

[0003] Currently, various technologies and materials have been tried and applied in the field of cultural relic conservation to clean murals stained with smoke and other surface contaminants. These mainly include chemical cleaning, mechanical cleaning, and laser cleaning technology. Chemical cleaning often uses organic solvents, surfactant solutions, or alkaline cleaning agents to remove stains through dissolution or emulsification. Mechanical cleaning relies on physical means such as scalpels, soft brushes, and sponges for surface cleaning and is suitable for loosely attached contaminants. Laser cleaning technology, as a more advanced method, uses lasers of specific wavelengths to vibrate or vaporize contaminants, thereby achieving precise removal. In addition, gel-based materials have gradually gained attention in cultural relic conservation cleaning in recent years. For example, polyacrylic acid and polyvinyl alcohol hydrogels are used as carriers to load cleaning agents for targeted cleaning, reducing excessive solvent penetration into the porous structure of murals. These methods have achieved certain results in the treatment of different types of murals and contaminants, and some research results have been tested and applied in several mural conservation projects both domestically and internationally.

[0004] While existing cleaning technologies can remove some smoke contaminants under certain conditions, they still have many limitations and risks. Chemical solvent cleaning, although possessing some cleaning ability, easily penetrates the pigment layer or ground layer of murals, causing pigment dissolution, smudging, or aging of the bonding materials. Furthermore, some volatile solvents may pose health hazards to operators and the environment. Laser cleaning, despite its high precision, may cause discoloration or structural damage to certain mineral pigments due to its thermal and photochemical effects, especially for murals with fragile underlying surfaces. Traditional mechanical cleaning methods rely on operator experience and are prone to scratching or abrasion of the mural surface due to improper force control. In addition, most liquid cleaning agents cannot remain on vertical or inclined walls for extended periods, resulting in insufficient cleaning time, affecting the overall cleaning effect, and potentially causing contamination of surrounding areas due to cleaning agent spillage. Therefore, there is an urgent need to develop new cleaning materials and technologies that balance cleaning efficiency, controllable action, material safety, and minimal intervention on the mural substrate to meet the increasingly stringent requirements for cultural relic protection and restoration. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a loaded microemulsion hydrogel for cleaning smoked murals, its preparation method and application, so as to solve the technical problems of uncontrolled penetration, low cleaning efficiency and potential damage in existing cleaning methods when removing smoked layers from murals.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing a loaded microemulsion hydrogel for cleaning smoked murals, comprising: A microemulsion was obtained by mixing and dissolving polyoxyethylene ether nonionic surfactants, anionic surfactants, saturated monohydric alcohols and liquid petroleum hydrocarbons in water and stirring at room temperature until homogeneous. Polyvinyl alcohol and polyacrylic acid were dissolved in dimethyl sulfoxide, heated in a water bath, and gelled to obtain a PVA-PAA hydrogel precursor. The PVA-PAA hydrogel precursor was placed in a microemulsion and reacted at room temperature to displace the dimethyl sulfoxide in the hydrogel precursor, resulting in a loaded microemulsion hydrogel for cleaning smoked murals.

[0007] Preferably, the microemulsion comprises, by mass percentage: 12.8%-14% of polyoxyethylene ether nonionic surfactant, 1.6%-1.75% of anionic surfactant, 1.6%-1.75% of saturated monohydric alcohol and 4%-4.375% of liquid petroleum hydrocarbon, with the balance being deionized water.

[0008] Preferably, the polyoxyethylene ether nonionic surfactant includes: fatty alcohol polyoxyethylene ether, polyoxyethylene lauryl ether, polyoxyethylene sorbitan monolaurate, or octylphenoxy polyoxyethylene ether.

[0009] Preferably, the anionic surfactant includes: sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, α-olefin sulfonate, or linear alkylbenzenesulfonate.

[0010] Preferably, the saturated monohydric alcohol includes: n-pentanol, n-butanol, isopropanol, or n-hexanol.

[0011] Preferably, the liquid petroleum hydrocarbons include: liquid paraffin, octane, decane, or mineral oil.

[0012] Preferably, the stirring time at room temperature is 1-1.5 hours; the water bath heating conditions include: water bath heating at 90-95°C for 1.5-2 hours.

[0013] Preferably, the gelation temperature is -15 to 20°C; the mass percentage of polyvinyl alcohol to polyacrylic acid is (50%-90%): (10%-50%); and the reaction time at room temperature is 24-36 hours.

[0014] The present invention also discloses a loaded microemulsion hydrogel for cleaning smoked murals, which is prepared by the above-described preparation method of the loaded microemulsion hydrogel for cleaning smoked murals.

[0015] The present invention also discloses the application of the loaded microemulsion hydrogel for cleaning smoked murals prepared by the above-mentioned method for cleaning smoked murals in cleaning smoked stains on mural surfaces.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing a loaded microemulsion hydrogel for cleaning smoked murals. The method involves mixing and dissolving a polyoxyethylene ether nonionic surfactant, an anionic surfactant, a saturated monohydric alcohol, and liquid petroleum hydrocarbon in water, stirring at room temperature to obtain a microemulsion. The polyoxyethylene ether nonionic surfactant provides emulsification and reduces interfacial tension; the anionic surfactant enhances the stripping ability of oily contaminants; the saturated monohydric alcohol acts as a co-surfactant to optimize the stability of the microemulsion; the liquid petroleum hydrocarbon dissolves the oily components in smoked stains; polyvinyl alcohol and polyacrylic acid are dissolved in dimethyl sulfoxide, heated in a water bath, and gelled to obtain a PVA-PAA hydrogel precursor, forming a gel carrier with high water retention. Utilizing the high water retention of polyvinyl alcohol and the ionic crosslinking properties of polyacrylic acid, and using dimethyl sulfoxide as a solvent to promote full molecular chain extension, water bath heating induces the formation of a dense network structure, thereby obtaining a precursor with excellent mechanical properties and controllable swelling, providing a stable carrier for subsequent loading and preventing detergent loss on vertical surfaces. A PVA-PAA hydrogel precursor was placed in a microemulsion and reacted at room temperature to displace dimethyl sulfoxide from the precursor, resulting in a loaded microemulsion hydrogel for cleaning smoked murals. Utilizing the difference in affinity between water molecules and dimethyl sulfoxide in the microemulsion, uniform penetration and fixation of the microemulsion into the hydrogel network were achieved, ensuring the slow release and prolonged retention of cleaning components in the stained area, thus achieving uniform loading of the microemulsion within the gel network. The hydrophilic network structure of the loaded microemulsion hydrogel can adsorb and carry dirt, reducing secondary pollution during the cleaning process and avoiding the rapid evaporation or excessive penetration problems of traditional liquid cleaners. By stably integrating the microemulsion into the hydrogel network, controlled release and localization of cleaning components were achieved, effectively avoiding the runaway penetration problems of traditional cleaning methods on mural surfaces and improving the stability and safety of the cleaning process. The resulting hydrogel exhibits good mechanical properties and water retention, gently and efficiently removing smoke deposits while providing greater safety and protection for the mural pigment layer and substrate, significantly improving cleaning efficiency and operational stability.

[0017] Furthermore, polyoxyethylene ether nonionic surfactants can form a stable interfacial film structure, effectively encapsulating the oil phase components to dissolve the grease in smoke stains. Simultaneously, their hydrophilic-lipophilic balance is moderate, preventing the microemulsion from easily breaking due to excessively low proportions or excessive penetration due to excessively high proportions. Anionic and nonionic surfactants work synergistically to enhance the microemulsion's emulsification ability for smoke stains without damaging the electrochemical stability of the pigment layer, avoiding pigment peeling due to electrostatic repulsion from excessively high concentrations or reduced cleaning efficiency due to excessively low concentrations. Saturated monohydric alcohols act as co-surfactants to regulate interfacial tension, promoting the spontaneous formation and long-term stability of the microemulsion at room temperature, ensuring that the microemulsion structure is not easily affected by temperature fluctuations during cleaning. Liquid petroleum hydrocarbons, as the oil phase, provide the ability to dissolve carbonaceous deposits in smoke, while proportion control prevents residual oil phase from softening the mural surface or insufficient proportions from leading to incomplete cleaning. Deionized water maintains the aqueous environment of the microemulsion, supporting surfactant function and reducing drying stress on the porous structure of the mural. It effectively avoids phase separation and uneven release during the loading process, reducing the risk of penetration and damage to the mural pigment layer; at the same time, the precise balance of the proportions of each component optimizes the cleaning ability, which can efficiently dissolve grease and carbon deposits in smoke stains, while preventing excessive action on the mural surface, thus ensuring the safety of the mural pigment layer and substrate structure while ensuring cleaning efficiency.

[0018] Furthermore, by limiting the specific types of nonionic surfactants such as polyoxyethylene ethers, fatty alcohol polyoxyethylene ethers form a stable oil-in-water microemulsion structure to gently encapsulate the oil components in smoke stains. Polyoxyethylene lauryl ethers maintain the long-term stability of the microemulsion while reducing the amount of surfactant used. Polyoxyethylene sorbitan monolaurate utilizes polyhydroxy groups to enhance compatibility with the hydrogel network to avoid excessively high local concentrations. Octylphenoxy polyoxyethylene ethers regulate the microemulsion particle size through the length of hydrophobic segments to control the release rate of cleaning components, ensuring that the microemulsion maintains structural integrity during the PVA-PAA hydrogel precursor replacement process. This effectively prevents pigment layer smudging or structural damage caused by microemulsion demulsification or premature release of cleaning agents.

[0019] Furthermore, by limiting the specific types of anionic surfactants, the microemulsion system forms a selective interfacial film structure on the mural surface. The benzene ring structure of sodium dodecylbenzenesulfonate enhances the directional adsorption of smoke greases, the short-chain characteristics of sodium dodecyl sulfate control the penetration depth of the microemulsion into the porous structure of the mural, the straight-chain olefin skeleton of α-olefin sulfonate ensures low reactivity during the process, and the uniform alkyl chain distribution of linear alkylbenzenesulfonate provides stable interfacial tension regulation. This constructs a precise dissolution mechanism for smoke stains, ensuring that the cleaning effect is limited to the surface of the contaminants without penetrating the pigment layer or ground layer of the mural. This effectively avoids the problem of fluctuating cleaning effects caused by inappropriate selection of anionic surfactants, significantly reduces the risk of chemical erosion of the mural pigment layer, and prevents secondary pollution caused by surfactant residue, thereby improving the safety and reliability of the smoke-stained mural cleaning process.

[0020] Furthermore, by limiting the specific types of saturated monohydric alcohols, the oil-water interfacial tension in the microemulsion system can be precisely controlled. n-Pentanol, n-Butanol, Isopropanol, or n-Hexanol, as co-surfactants, utilize their differences in carbon chain length and molecular configuration to synergistically construct a stable microemulsion structure. Linear-chain alcohols, through the balance between their hydrophobic and hydrophilic heads, reduce interfacial energy and form curved interfaces, while branched-chain alcohols enhance the microemulsion's resistance to demulsification through steric hindrance. This allows the microemulsion to form uniformly dispersed nano-droplets on the mural surface, ensuring both highly efficient dissolution of smoke stains and, through molecular-scale interfacial control, a gentle and controllable cleaning process. This achieves a balance between cleaning efficiency and safety while minimizing interference with the cultural relics.

[0021] Furthermore, by selecting the specific type of liquid petroleum hydrocarbon and matching it with the physicochemical properties of other components in the microemulsion system, a microemulsion structure with optimized performance is formed. The saturated molecular structure of liquid paraffin effectively inhibits volatilization, ensuring continuous stability during the cleaning process; octane's moderate lipophilicity promotes stain emulsification while limiting the penetration of the microemulsion onto the mural surface; decane's long carbon chain structure increases the viscosity of the oil phase, extending the dissolution time; and the refined components of mineral oil provide a mild chemical environment. This enables the microemulsion to achieve a slow-release and controlled-release function, ensuring efficient removal of smoke stains while preventing excessive penetration of the cleaning agent into the mural. It controls the penetration depth of the cleaning agent on the mural surface, avoiding the risk of pigment layer damage caused by improper selection of liquid petroleum hydrocarbons, and reducing volatile hazards and environmental health risks during operation.

[0022] Furthermore, the stirring time at room temperature is 1-1.5 hours to ensure that the components of the microemulsion are fully mixed kinetically, avoiding phase separation caused by insufficient stirring. The water bath heating conditions include heating at 90-95℃ for 1.5-2 hours, ensuring that the crosslinking reaction of polyvinyl alcohol and polyacrylic acid in dimethyl sulfoxide avoids both excessively slow reaction rates due to low temperatures and polymer chain degradation caused by high temperatures, thus forming a dense and uniform gel network. This allows the hydrogel precursor to efficiently displace dimethyl sulfoxide during subsequent replacement processes, enabling the microemulsion to stably embed into the gel network, ultimately achieving the controlled release of cleaning components on the mural surface.

[0023] Furthermore, the gelation temperature is -15 to 20°C, effectively suppressing the thermal motion of polymer chain segments and promoting the formation of a dense and uniform three-dimensional network structure between polyvinyl alcohol and polyacrylic acid. This structure provides a stable physical framework for subsequent microemulsion loading. The mass percentage of polyvinyl alcohol to polyacrylic acid is (50%-90%):(10%-50%), enabling the hydroxyl groups of polyvinyl alcohol and the carboxyl groups of polyacrylic acid to complement each other at the molecular scale, ensuring both the mechanical strength of the hydrogel and enhancing its hydrophilic swelling properties. The reaction time at room temperature is 24-36 hours, during which the surfactants, alcohols, and petroleum hydrocarbon components in the microemulsion gradually replace the dimethyl sulfoxide solvent in the hydrogel precursor, achieving uniform distribution and stable embedding of the microemulsion in the gel network. This ensures that the hydrogel possesses long-lasting structural stability and controllable sustained-release properties during mural cleaning, thereby effectively solving the technical problems of insufficient residue and uncontrolled penetration depth of vertical wall cleaners.

[0024] The present invention discloses a loaded microemulsion hydrogel for cleaning smoked murals. By integrating the microemulsion system into a PVA-PAA hydrogel carrier, the controlled release and localization of the cleaning agent are achieved, effectively solving the problems of uncontrolled penetration, low cleaning efficiency and potential damage in the cleaning of smoked murals. It achieves the effect of gently and efficiently removing smoke stains while protecting the structure of the mural.

[0025] This invention discloses the application of a loaded microemulsion hydrogel for cleaning smoked murals. By stably fixing the microemulsion system within a PVA-PAA hydrogel network, it achieves controlled release and localization of cleaning components, avoiding excessive penetration and loss of traditional liquid cleaning agents in porous structures. Simultaneously, the hydrogel's water-retention properties allow it to remain stably on vertical or inclined surfaces for extended periods, prolonging the cleaning time and ensuring thorough dissolution of smoked stains. Furthermore, the mild surfactants and alcohols in the microemulsion selectively dissolve the mixture of grease and soot in the smoked stains without damaging the mural's pigment layer and substrate structure, reducing the risk of chemical damage. The hydrophilic network structure of the hydrogel also adsorbs and carries dissolved dirt, reducing secondary pollution, thus achieving a safe, efficient, and environmentally friendly mural cleaning effect. Attached Figure Description

[0026] Figure 1 Infrared images of the loaded microemulsion hydrogels for cleaning smoked murals prepared in Examples 1-5 of this invention and the PVA hydrogels of the loaded microemulsions for cleaning smoked murals prepared in the comparative examples. Figure 2 SEM images of the loaded microemulsion hydrogels for cleaning smoked murals prepared in Examples 1-5 of this invention and the PVA hydrogels of the loaded microemulsions for cleaning smoked murals prepared in the comparative examples; wherein the mass ratios of PVA and PAA are: (a) 10:0; (b) 9:1; (c) 8:2; (d) 7:3; (e) 6:4; (f) 5:5; Figure 3 The stretching curves are shown for the loaded microemulsion hydrogels for cleaning smoked murals prepared in Examples 1-5 of this invention and the PVA hydrogels of loaded microemulsions for cleaning smoked murals prepared in the comparative examples. Figure 4 The images show the cleaning effect of a smoked simulated mural using a hydrogel loaded with a microemulsion for cleaning smoked murals, prepared in Example 3 of this invention. (a) is an original simulated mural image; (a1) is a super-depth-of-field image of the ultramarine surface of the original simulated mural; (a2) is a super-depth-of-field image of the iron oxide surface of the original simulated mural; (a3) ​​is a super-depth-of-field image of the iron yellow surface of the original simulated mural; (b) is an image of a smoked simulated mural; (b1) is a super-depth-of-field image of the ultramarine surface of the smoked simulated mural; (b2) is a super-depth-of-field image of the iron oxide surface of the smoked simulated mural; (b3) is a super-depth-of-field image of the iron yellow surface of the smoked simulated mural; (c) is an image of a smoked simulated mural after hydrogel cleaning; (c1) is a super-depth-of-field image of the ultramarine surface of the smoked simulated mural after hydrogel cleaning; (c2) is a super-depth-of-field image of the iron oxide surface of the smoked simulated mural after hydrogel cleaning; (c3) is a super-depth-of-field image of the iron yellow surface of the smoked simulated mural after hydrogel cleaning. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0029] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0030] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0031] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0032] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.

[0033] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0034] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0035] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0036] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0037] This invention provides a method for preparing a loaded microemulsion hydrogel for cleaning smoked murals, comprising the following steps: 1) Microemulsion preparation: Dissolve a mixed solution of polyoxyethylene ether nonionic surfactant, anionic surfactant, saturated monohydric alcohol and liquid petroleum hydrocarbon in water and stir at room temperature for 1-1.5 h to obtain a transparent microemulsion; the microemulsion composition by mass percentage is: 12.8%-14% polyoxyethylene ether nonionic surfactant, 1.6%-1.75% anionic surfactant, 1.6%-1.75% saturated monohydric alcohol and 4%-4.375% liquid petroleum hydrocarbon, with the balance being deionized water.

[0038] Among them, polyoxyethylene ether nonionic surfactants include: fatty alcohol polyoxyethylene ether, polyoxyethylene lauryl ether, polyoxyethylene sorbitan monolaurate or octylphenoxy polyoxyethylene ether.

[0039] Anionic surfactants include sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, α-olefin sulfonate, or linear alkylbenzenesulfonate.

[0040] Saturated monohydric alcohols include: n-pentanol, n-butanol, isopropanol, or n-hexanol.

[0041] Liquid petroleum hydrocarbons include: liquid paraffin, octane, decane, or mineral oil.

[0042] 2) Hydrogel preparation: PVA and PAA are dissolved in DMSO and heated in a water bath at 90-95℃ for 1.5-2h to obtain a mixed solution. The solution is then placed in a petri dish and gelled at -15--20℃ to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor composition, by mass percentage, is 50%-90% PVA and 10%-50% PAA.

[0043] 3) Solvent replacement: The hydrogel precursor prepared in step 2) is placed in the transparent microemulsion prepared in step 1) and reacted for 24-36 hours to replace the DMSO in the hydrogel precursor, thereby obtaining a loaded microemulsion hydrogel for cleaning smoked murals.

[0044] The microemulsion hydrogel prepared in this invention for cleaning smoked murals possesses gentle yet highly effective cleaning capabilities, avoiding damage to the mural's surface. Using PVA-PAA hydrogel as a carrier, it loads a microemulsion system composed of AEO-9, SDBS, n-pentanol, liquid paraffin, and water, enabling it to penetrate deep into the mural surface and efficiently dissolve smoke stains. Compared to traditional organic solvents or strong acid / alkali cleaning methods, this system selectively removes stains without damaging the mural's pigment layer, substrate structure, or adhesives, ensuring the integrity of the artifact. Furthermore, the hydrogel provides a buffering effect during the cleaning process, preventing mechanical damage caused by excessive friction.

[0045] This invention provides a loaded microemulsion hydrogel for cleaning smoked murals, featuring a sustained-release mechanism for precise and controllable cleaning. Due to the excellent swelling and sustained-release properties of PVA-PAA hydrogel, this invention enables the slow release of cleaning ingredients, allowing the microemulsion to act on the mural surface for an extended period, thereby improving cleaning efficiency. Compared to the problems of traditional liquid cleaners' easy evaporation or rapid loss, the hydrogel of this invention ensures the stable residence of the cleaning agent in the stained area, allowing the stains to be fully dissolved and removed. Simultaneously, the hydrophilic network structure of the hydrogel can adsorb and carry away dirt, reducing secondary pollution during the cleaning process.

[0046] The microemulsion hydrogel prepared by this invention for cleaning smoked murals is environmentally friendly and safe, reducing the impact on cultural relics and the environment. Traditional mural cleaning methods may involve the use of corrosive and toxic chemical reagents such as organic solvents, strong alkalis, or strong acids. In contrast, the microemulsion system used in this invention is mainly composed of mild surfactants, alcohols, and liquid paraffin, avoiding adverse effects on human health and the environment. Furthermore, the PVA-PAA hydrogel itself is non-toxic and harmless, and its swelling degree can be precisely controlled, reducing cleaning agent waste and further lowering the risk of environmental pollution.

[0047] The environmentally friendly characteristics of this invention make it particularly suitable for the protection and restoration of cultural heritage, and it has broad application value in practical applications.

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0049] Example 1 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of fatty alcohol polyoxyethylene ether, sodium dodecylbenzenesulfonate, n-pentanol, and liquid paraffin was dissolved in water and stirred evenly at room temperature to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 12.8% fatty alcohol polyoxyethylene ether, 1.6% sodium dodecylbenzenesulfonate, 1.6% n-pentanol, 4% liquid paraffin, and the balance being deionized water.

[0050] 2) Dissolve PVA and PAA in DMSO and heat in a 95°C water bath for 2 hours to obtain a mixed solution. Place the solution in a petri dish and gel at -20°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor composition by mass percentage is: 50% PVA and 50% PAA.

[0051] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 24 hours to replace the DMSO in the gel precursor, thus obtaining a loaded microemulsion hydrogel for cleaning smoked murals.

[0052] Example 2 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of fatty alcohol polyoxyethylene ether, sodium dodecylbenzenesulfonate, and liquid paraffin was dissolved in water and stirred evenly at room temperature to obtain a transparent microemulsion. The mass percentages of each component in the microemulsion were: 13% fatty alcohol polyoxyethylene ether, 1.625% sodium dodecylbenzenesulfonate, 1.625% n-pentanol, 4.0625% liquid paraffin, and the balance being deionized water.

[0053] 2) Dissolve PVA and PAA in DMSO and heat in a 95°C water bath for 2 hours to obtain a mixed solution. Place the solution in a petri dish and gel at -20°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor composition by mass percentage is: 60% PVA and 40% PAA.

[0054] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 24 hours to replace the DMSO in the gel precursor, thus obtaining a loaded microemulsion hydrogel for cleaning smoked murals.

[0055] Example 3 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of fatty alcohol polyoxyethylene ether, sodium dodecylbenzenesulfonate, n-pentanol, and liquid paraffin was dissolved in water and stirred evenly at room temperature to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 13.2% fatty alcohol polyoxyethylene ether, 1.65% sodium dodecylbenzenesulfonate, 1.65% n-pentanol, 4.125% liquid paraffin, and the balance being deionized water.

[0056] 2) Dissolve PVA and PAA in DMSO and heat in a 95°C water bath for 2 hours to obtain a mixed solution. Place the solution in a petri dish and gel at -20°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor composition by mass percentage is: 70% PVA and 30% PAA.

[0057] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 24 hours to replace the DMSO in the gel precursor, thus obtaining a loaded microemulsion hydrogel for cleaning smoked murals.

[0058] Example 4 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of fatty alcohol polyoxyethylene ether, sodium dodecylbenzenesulfonate, n-pentanol, and liquid paraffin was dissolved in water and stirred evenly at room temperature to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 13.6% fatty alcohol polyoxyethylene ether, 1.7% sodium dodecylbenzenesulfonate, 1.7% n-pentanol, 4.25% liquid paraffin, and the balance being deionized water.

[0059] 2) Dissolve PVA and PAA in DMSO and heat in a 95°C water bath for 2 hours to obtain a mixed solution. Place the solution in a petri dish and gel at -20°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor consists of 80% PVA and 20% PAA by mass percentage.

[0060] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 24 hours to replace the DMSO in the gel precursor, thus obtaining a loaded microemulsion hydrogel for cleaning smoked murals.

[0061] Example 5 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of fatty alcohol polyoxyethylene ether, sodium dodecylbenzenesulfonate, n-pentanol, and liquid paraffin was dissolved in water and stirred evenly at room temperature to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 13.8% fatty alcohol polyoxyethylene ether, 1.725% sodium dodecylbenzenesulfonate, 1.725% n-pentanol, 4.3% liquid paraffin, and the balance being deionized water.

[0062] 2) Dissolve PVA and PAA in DMSO and heat in a 95°C water bath for 2 hours to obtain a mixed solution. Place the solution in a petri dish and gel at -20°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor consists of 90% PVA and 10% PAA by mass percentage.

[0063] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 24 hours to replace the DMSO in the gel precursor, thus obtaining a loaded microemulsion hydrogel for cleaning smoked murals.

[0064] Example 6 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of polyoxyethylene lauryl ether, sodium dodecyl sulfate, n-pentanol, and liquid paraffin was dissolved in water and stirred at room temperature for 1 hour to obtain a transparent microemulsion. The mass percentages of each component in the microemulsion were: 14% polyoxyethylene lauryl ether, 1.75% sodium dodecyl sulfate, 1.75% n-pentanol, 4.375% liquid paraffin, and the balance being deionized water.

[0065] 2) Dissolve PVA and PAA in DMSO and heat in a 90°C water bath for 1.5 h to obtain a mixed solution. Place the solution in a petri dish and gel at -15°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor composition by mass percentage is: 70% PVA and 30% PAA.

[0066] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 36 hours to replace the DMSO in the hydrogel precursor, thus obtaining a loaded microemulsion hydrogel.

[0067] Example 7 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of polyoxyethylene sorbitan monolaurate, α-olefin sulfonate, n-butanol, and octane was dissolved in water and stirred at room temperature for 1.2 h to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 13.5% polyoxyethylene sorbitan monolaurate, 1.68% α-olefin sulfonate, 1.68% n-butanol, 4.2% octane, and the balance being deionized water.

[0068] 2) Dissolve PVA and PAA in DMSO and heat in a 92°C water bath for 1.8 h to obtain a mixed solution. Place the solution in a petri dish and gel at -18°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor composition by mass percentage is: 60% PVA and 40% PAA.

[0069] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 30 h to replace the DMSO in the hydrogel precursor, thus obtaining a loaded microemulsion hydrogel.

[0070] Example 8 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of octylphenoxy polyoxyethylene ether, sodium linear alkylbenzene sulfonate, isopropanol, and decane was dissolved in water and stirred at room temperature for 1.5 h to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 13.1% octylphenoxy polyoxyethylene ether, 1.7% sodium linear alkylbenzene sulfonate, 1.7% isopropanol, 4.1% decane, and the balance being deionized water.

[0071] 2) Dissolve PVA and PAA in DMSO and heat in a 93°C water bath for 1.6 h to obtain a mixed solution. Place the solution in a petri dish and gel at -17°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor composition by mass percentage is: 80% PVA and 20% PAA.

[0072] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 32 h to replace the DMSO in the hydrogel precursor, thus obtaining a loaded microemulsion hydrogel.

[0073] Example 9 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of fatty alcohol polyoxyethylene ether, sodium dodecylbenzenesulfonate, n-hexanol, and mineral oil was dissolved in water and stirred at room temperature for 1.3 hours to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 13.3% fatty alcohol polyoxyethylene ether, 1.65% sodium dodecylbenzenesulfonate, 1.65% n-hexanol, 4.3% mineral oil, and the balance being deionized water.

[0074] 2) Dissolve PVA and PAA in DMSO and heat in a 94°C water bath for 1.7 h to obtain a mixed solution. Place the solution in a petri dish and gel at -19°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor composition by mass percentage is: 50% PVA and 50% PAA.

[0075] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 28 hours to replace the DMSO in the gel precursor, thus obtaining a loaded microemulsion hydrogel.

[0076] Example 10 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of polyoxyethylene lauryl ether, sodium dodecyl sulfate, n-butanol, and octane was dissolved in water and stirred at room temperature for 1 hour to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 12.8% polyoxyethylene lauryl ether, 1.6% sodium dodecyl sulfate, 1.6% n-butanol, 4% octane, and the balance being deionized water.

[0077] 2) Dissolve PVA and PAA in DMSO and heat in a 95°C water bath for 2 hours to obtain a mixed solution. Place the solution in a petri dish and gel at -20°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor consists of 90% PVA and 10% PAA by mass percentage.

[0078] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 36 hours to replace the DMSO in the hydrogel precursor, thus obtaining a loaded microemulsion hydrogel.

[0079] Example 11 A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals includes the following steps: 1) A mixed solution of polyoxyethylene sorbitan monolaurate, α-olefin sulfonate, isopropanol, and decane was dissolved in water and stirred at room temperature for 1.5 h to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 14% polyoxyethylene sorbitan monolaurate, 1.75% α-olefin sulfonate, 1.75% isopropanol, 4.375% decane, and the balance being deionized water.

[0080] 2) Dissolve PVA and PAA in DMSO and heat in a 90°C water bath for 1.5 h to obtain a mixed solution. Place the solution in a petri dish and gel at -15°C to obtain the PVA-PAA hydrogel precursor. The hydrogel precursor composition by mass percentage is: 70% PVA and 30% PAA.

[0081] 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 24 hours to replace the DMSO in the hydrogel precursor, thus obtaining a loaded microemulsion hydrogel.

[0082] Comparative Example A method for preparing a PVA hydrogel loaded with a microemulsion for cleaning smoked murals includes the following steps: 1) A mixed solution of fatty alcohol polyoxyethylene ether, sodium dodecylbenzenesulfonate, n-pentanol, and liquid paraffin was dissolved in water and stirred evenly at room temperature to obtain a transparent microemulsion. The mass percentage of each component in the microemulsion was: 12.8% fatty alcohol polyoxyethylene ether, 1.6% sodium dodecylbenzenesulfonate, 1.6% n-pentanol, 4% liquid paraffin, and the balance being deionized water.

[0083] 2) Dissolve PVA in DMSO and heat in a 95°C water bath for 2 hours to obtain a mixed solution. Place the solution in a petri dish and gel at -20°C to obtain the PVA hydrogel precursor. 3) The prepared hydrogel precursor was placed in a transparent microemulsion and reacted for 24 hours to replace the DMSO in the hydrogel precursor, thus obtaining a PVA hydrogel loaded with microemulsion for cleaning smoked murals.

[0084] Figure 1 The images show infrared spectroscopy of the microemulsion-loaded hydrogels for cleaning smoked murals prepared in Examples 1-5 of this invention and the PVA hydrogels for cleaning smoked murals prepared in the comparative example. It can be seen that PAA and microemulsion were successfully loaded in the hydrogels.

[0085] Figure 2The images show SEM images of the loaded microemulsion hydrogels for cleaning smoked murals prepared in Examples 1-5 of this invention and the PVA hydrogels for cleaning smoked murals prepared in the comparative example. The mass ratios of PVA and PAA are: (a) 10:0; (b) 9:1; (c) 8:2; (d) 7:3; (e) 6:4; (f) 5:5. It can be seen that the PVA-PAA hydrogels exhibit a dense and uniform porous structure, which is beneficial for the adsorption of pollutants.

[0086] Figure 3 The tensile curves of the loaded microemulsion hydrogels for cleaning smoked murals prepared in Examples 1-5 of this invention and the PVA hydrogels of loaded microemulsions for cleaning smoked murals prepared in the comparative example are shown. It can be seen that the hydrogels have excellent mechanical properties, with the highest stress reaching 0.66 MPa and the strain reaching 700%.

[0087] Figure 4 The images show the cleaning effect of a smoked simulated mural using a hydrogel loaded with a microemulsion for cleaning smoked murals, prepared in Example 3 of this invention. (a) is an original simulated mural image; (a1) is a super-depth-of-field image of the ultramarine surface of the original simulated mural; (a2) is a super-depth-of-field image of the iron oxide surface of the original simulated mural; (a3) ​​is a super-depth-of-field image of the iron yellow surface of the original simulated mural; (b) is an image of a smoked simulated mural; (b1) is a super-depth-of-field image of the ultramarine surface of the smoked simulated mural; (b2) is a super-depth-of-field image of the iron oxide surface of the smoked simulated mural; (b3) is a super-depth-of-field image of the iron yellow surface of the smoked simulated mural; (c) is an image of a smoked simulated mural after hydrogel cleaning; (c1) is a super-depth-of-field image of the ultramarine surface of the smoked simulated mural after hydrogel cleaning; (c2) is a super-depth-of-field image of the iron oxide surface of the smoked simulated mural after hydrogel cleaning; (c3) is a super-depth-of-field image of the iron yellow surface of the smoked simulated mural after hydrogel cleaning. It can be seen that the contaminants are effectively cleaned.

[0088] In summary, this invention provides a method for preparing a loaded microemulsion hydrogel for cleaning smoked murals, along with its preparation and application. It employs more environmentally friendly and effective raw material formulations and processes, and offers a method for preparing a loaded microemulsion hydrogel for cleaning smoked stains on mural surfaces, thus expanding the potential of hydrogel cleaning materials in cultural heritage preservation.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a loaded microemulsion hydrogel for cleaning smoked murals, characterized in that, include: A microemulsion was obtained by mixing and dissolving polyoxyethylene ether nonionic surfactants, anionic surfactants, saturated monohydric alcohols and liquid petroleum hydrocarbons in water and stirring at room temperature until homogeneous. Polyvinyl alcohol and polyacrylic acid were dissolved in dimethyl sulfoxide, heated in a water bath, and gelled to obtain a PVA-PAA hydrogel precursor. The PVA-PAA hydrogel precursor was placed in a microemulsion and reacted at room temperature to displace the dimethyl sulfoxide in the hydrogel precursor, resulting in a loaded microemulsion hydrogel for cleaning smoked murals.

2. The method for preparing the loaded microemulsion hydrogel for cleaning smoked murals according to claim 1, characterized in that, The microemulsion comprises, by mass percentage: 12.8%-14% of polyoxyethylene ether nonionic surfactant, 1.6%-1.75% of anionic surfactant, 1.6%-1.75% of saturated monohydric alcohol and 4%-4.375% of liquid petroleum hydrocarbon, with the balance being deionized water.

3. The method for preparing the loaded microemulsion hydrogel for cleaning smoked murals according to claim 1, characterized in that, The polyoxyethylene ether nonionic surfactants include: fatty alcohol polyoxyethylene ether, polyoxyethylene lauryl ether, polyoxyethylene sorbitan monolaurate, or octylphenoxy polyoxyethylene ether.

4. The method for preparing the loaded microemulsion hydrogel for cleaning smoked murals according to claim 1, characterized in that, The anionic surfactant includes: sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, α-olefin sulfonate, or linear alkylbenzenesulfonate.

5. The method for preparing the loaded microemulsion hydrogel for cleaning smoked murals according to claim 1, characterized in that, The saturated monohydric alcohols include: n-pentanol, n-butanol, isopropanol, or n-hexanol.

6. The method for preparing the loaded microemulsion hydrogel for cleaning smoked murals according to claim 1, characterized in that, The liquid petroleum hydrocarbons include: liquid paraffin, octane, decane, or mineral oil.

7. The method for preparing the loaded microemulsion hydrogel for cleaning smoked murals according to claim 1, characterized in that, The stirring time at room temperature is 1-1.5 hours; the water bath heating conditions include: water bath heating at 90-95℃ for 1.5-2 hours.

8. The method for preparing the loaded microemulsion hydrogel for cleaning smoked murals according to claim 1, characterized in that, The gelation temperature is -15 to 20°C; the mass percentage of polyvinyl alcohol to polyacrylic acid is (50%-90%):(10%-50%); the reaction time at room temperature is 24-36 hours.

9. A loaded microemulsion hydrogel for cleaning smoked murals, characterized in that, The loaded microemulsion hydrogel for cleaning smoked murals was prepared using the method described in any one of claims 1-8.

10. The application of the loaded microemulsion hydrogel for cleaning smoked murals prepared by the method of any one of claims 1-8 in cleaning smoked mural stains.

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