Paper cultural relic preventive protection material with asymmetric structure
By using asymmetrical paper-based cultural relic preservation materials and employing a functional protective layer and a breathable regulating layer design, the problem of existing materials being unable to simultaneously achieve both barrier and breathability is solved. This enables the stable preservation of the microenvironment and self-repair, significantly improving the preservation effect of paper-based cultural relics.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-19
- Publication Date
- 2026-04-14
AI Technical Summary
Existing paper-based cultural relic preservation materials cannot simultaneously block external moisture, harmful gases, and ultraviolet rays from penetrating, as well as remove moisture and acidic gases from inside the cultural relic. This leads to problems such as acidification, dampness, and mold growth in paper-based cultural relics, making it difficult to create a stable microenvironment for preservation.
The paper-based preventive protection material for cultural relics adopts an asymmetric structure, including a functional protective layer, a breathable conditioning layer, and a transitional bonding layer. The functional protective layer is prepared from modified montmorillonite, polylactic acid, and UPy derivatives. The breathable conditioning layer is a porous cellulose aerogel with a load-bearing temperature-sensitive moisture-absorbing and moisture-releasing composite material, which contacts the cultural relic through a parallel groove design. The transitional bonding layer is a water-based polyurethane adhesive to achieve bonding between the layers.
It achieves a synergistic protective effect of effectively blocking the intrusion of harmful external factors and expelling internal moisture. It has a self-repair function, actively regulates the humidity of the microenvironment, avoids the acidification, dampness and fiber aging of cultural relics, and extends the preservation life of paper cultural relics. It also has environmental compatibility and stability.
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Figure CN121848797A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer materials technology, specifically to asymmetric paper-based preventive protection materials for cultural relics. Background Technology
[0002] Paper artifacts refer to ancient artifacts that use paper as their primary medium, including ancient books, paintings, calligraphy, letters, manuscripts, contracts, and archival documents. They are important physical evidence of the transmission of historical civilization. These artifacts are numerous, accounting for more than a quarter of all movable cultural relics in China, making them the most numerous category of artifacts made of any material. Their preservation is significantly affected by the environment; for example, humid environments easily lead to decay, while dry environments are more conducive to preservation. The protection of paper artifacts requires controlling light exposure, avoiding harmful gases, and maintaining a clean environment. Preventive protection is the core means of extending the lifespan of paper artifacts. The performance of the protective materials directly determines the protective effect. Existing paper artifact protection materials mostly adopt symmetrical structural designs, such as single polymer films, traditional fiber fabrics, or homogeneous composite films. The design concept of these materials focuses on improving overall protective performance.
[0003] Existing paper-based cultural relic preservation materials generally adopt a symmetrical structural design. Because they cannot simultaneously meet the core requirements of blocking external moisture, harmful gases, and ultraviolet rays from entering, as well as expelling internal moisture and acidic gases from the cultural relic, they either have excessive barrier properties that cause harmful gases to remain inside for a long time, exacerbating local acidification, dampness, and mold growth, or excessive permeability that allows harmful external factors to easily penetrate, causing fiber aging and photodegradation. Ultimately, this results in poor preventive protection of paper-based cultural relics, making it difficult to create a stable preservation microenvironment and failing to meet the actual needs for long-term safe preservation of paper-based cultural relics. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention provides a paper-based preventive protection material for cultural relics with an asymmetrical structure, thus solving the problems mentioned in the background art.
[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: an asymmetrical paper-based preventive protective material for cultural relics, the protective material being composed of a functional protective layer, a transition adhesive layer, and a breathable regulating layer; The functional protective layer is the outer protective layer of the protective material. The functional protective layer is prepared from modified montmorillonite, polylactic acid and UPy derivatives. The surface of the functional protective layer is coated with a photoprotective coating and modified with superhydrophobicity. The breathable conditioning layer is an inner contact layer, which is prepared by porous cellulose aerogel of load-loaded temperature-sensitive moisture-absorbing and moisture-releasing composite material. The breathable conditioning layer has parallel grooves on the side in contact with the cultural relic. The transition bonding layer is a water-based polyurethane adhesive, which bonds the functional protective layer to the breathable conditioning layer.
[0006] Preferably, the substrate of the breathable regulating layer is natural cellulose extracted from bamboo fiber or cotton fiber, which is prepared into a three-dimensional porous network structure by freeze drying process, with a porosity of 85%-95% and a pore size of 50-500nm.
[0007] Preferably, the loaded temperature-sensitive moisture-absorbing and moisture-releasing composite material is composed of modified zeolite molecular sieve and poly(N-isopropylacrylamide) hydrogel in a mass ratio of 3:1. The modified zeolite molecular sieve is obtained by modifying zeolite molecular sieve with 3-aminopropyltriethoxysilane. The loading amount of the loaded temperature-sensitive moisture-absorbing and moisture-releasing composite material is 10%-20% of the total mass of the breathable conditioning layer.
[0008] Preferably, the width of the parallel trench is 50-200μm and the depth is 20-50μm, and the parallel trench is processed by plasma etching or laser etching.
[0009] Preferably, the modified montmorillonite in the functional protective layer is prepared by modifying sodium-based montmorillonite with a silane coupling agent, and the mass ratio of the modified montmorillonite to the polylactic acid is 5%-15%. The UPy derivative is a derivative of polycaprolactone, and the amount of the UPy derivative added is 8%-12% of the mass of the polylactic acid.
[0010] Preferably, the photoprotective coating is composed of nano zinc oxide, waterborne polyurethane and KH-188 silane coupling agent, the coating thickness of the photoprotective coating is 5-10 μm, and the superhydrophobic modification is performed by perfluorooctyltriethoxysilane to modify the functional protective layer, and the hydrophobic angle of the modified functional protective layer is ≥120°.
[0011] Preferably, the preparation steps of the functional protective layer include: Sodium-based montmorillonite was taken, and 3% by mass of silane coupling agent KH-550 was added. The mixture was stirred and reacted at 60°C for 2 hours. After sieving, filtration and drying, the modified montmorillonite was obtained. The modified montmorillonite, the polylactic acid particles and the UPy derivative are mixed to obtain a mixture. The mixture is fed into a twin-screw extruder and melt-blended and granulated at 170-180°C. The particles are then added to a blown film machine and blown into a film at 160-170°C to obtain a composite film substrate with a thickness of 40-60 μm. Nano zinc oxide, waterborne polyurethane and KH-188 silane coupling agent are mixed and ultrasonically dispersed for 60 min to obtain a coating liquid. The coating liquid is applied to the outside of the composite film substrate by spraying and cured at 100℃ for 60 min to form the photoprotective coating with a thickness of 5-10 μm. Perfluorooctyltriethoxysilane was sprayed onto the surface of the photoprotective coating and cured at 90°C for 40 minutes to obtain the functional protective layer.
[0012] Preferably, the preparation steps of the breathability regulating layer include: Bamboo fiber was treated with 5% NaOH solution at 80℃ for 2 hours, then bleached and dissolved in N-methylmorpholine-N-oxide solution to obtain cellulose solution; The cellulose solution was poured into a mold and frozen at -30 to -45°C for 8 to 15 hours. Then it was placed in a freeze dryer and dried at -45 to -55°C and a vacuum of 0.01 to 0.02 MPa for 20 to 30 hours to obtain a porous cellulose aerogel with a porosity of 85% to 95% and a pore size of 50 to 500 nm. A suspension was prepared by mixing zeolite molecular sieve modified with 3-aminopropyltriethoxysilane and poly(N-isopropylacrylamide) hydrogel at a mass ratio of 3:1 and dispersing it in deionized water. The porous cellulose aerogel was then immersed in the suspension and vacuum impregnated for 2 hours, and dried at 60°C for 12 hours to obtain the aerogel. The parallel grooves are processed on the side of the aerogel that is in contact with the artifact using plasma etching or laser etching processes to obtain the air permeability adjustment layer.
[0013] Preferably, the preparation steps of the transition adhesive layer include: A mixture of waterborne polyurethane resin and deionized water and film-forming aid is added and stirred at 500 r / min for 30 min at 25°C. During the stirring process, deionized water is added and the mixture is concentrated to adjust the solid content of the mixture to 30%-40% to obtain a solid-liquid mixture. The adjusted solid-liquid mixture is filtered through a 200-mesh filter to remove impurities, resulting in the transition bonding layer. During use, the thickness of the transition bonding layer is controlled to be 10-15 μm through a coating process.
[0014] Preferably, the steps for manufacturing the protective material include: Wipe the side of the breathable conditioning layer that is not the parallel groove and the side of the functional protective layer that is not the light-protective coating with anhydrous ethanol to remove oil and impurities, and dry them at 60°C for 10 minutes. The transition adhesive layer is uniformly coated onto the cleaned surface of the breathable conditioning layer using a scraper coating process, and the coating thickness of the transition adhesive layer is controlled to be 10-15 μm. The air permeability conditioning layer after coating the transition adhesive layer is placed in an oven and pre-cured at a temperature of 80-90℃ for 30 minutes to allow the transition adhesive layer to initially form a film. Align and bond the clean surface of the functional protective layer with the surface of the pre-cured transition adhesive layer, ensuring no air bubbles or misalignment, to obtain a composite preform. Place the bonded composite preform into a hot press and hot press for 30-60 seconds at a temperature of 120-140℃ and a vacuum of 0.3-0.5MPa. Then allow it to cool naturally to room temperature to obtain the composite layer material. The composite layer material is cut to the target size and vacuum dried at 40°C for 2 hours to remove residual moisture, thus obtaining the protective material.
[0015] This invention provides a paper-based preventative protection material for cultural relics with an asymmetrical structure. It has the following beneficial effects: (1) The protective material adopts an asymmetrical structure consisting of a functional protective layer and a breathable regulating layer. The functional protective layer can effectively block the intrusion of external water vapor, harmful gases and ultraviolet rays. The breathable regulating layer can directionally expel the moisture and acidic gases generated inside the paper artifacts, preventing the problem of mutual restriction between the breathability and barrier performance of the symmetrical structure material. It achieves a synergistic protective effect of external barrier and internal passage, successfully constructing a stable preservation microenvironment for paper artifacts, avoiding the problems of acidification, dampness, mold and fiber aging caused by the retention of internal harmful gases or the intrusion of external harmful factors, and significantly improving the effect of preventive protection.
[0016] (2) The functional protective layer has a self-healing function, which can repair minor damage during use and maintain the integrity of the barrier. At the same time, the breathable regulating layer can actively regulate the humidity of the microenvironment, avoid humidity fluctuations from damaging cultural relics, achieve long-term protection with repairable damage and adjustable humidity, reduce the risk of protective materials failing due to damage, reduce the damage to cultural relics caused by abnormal humidity, achieve continuous and stable protection of paper cultural relics, and extend the protection period and lifespan of cultural relics.
[0017] (3) All functional layers are made of environmentally friendly and compatible materials such as natural cellulose and polylactic acid, which are compatible with the material of paper cultural relics. The preparation process does not use harmful chemical reagents, thus avoiding secondary pollution of cultural relics by the protective materials. At the same time, the strong bonding of the transition bonding layer and the hot-pressing composite process ensure the stability of the protective material structure and its flexibility during use. It will not damage the surface of the cultural relics and can adhere to the cultural relics for a long time to play a protective role, thus meeting the actual needs of long-term safe preservation of paper cultural relics and adapting to the protection scenarios of various ancient books and paintings and other fragile paper cultural relics. Attached Figure Description
[0018] Figure 1 The bar chart shows the air permeability of the protective materials in the embodiments and comparative examples of this invention. Figure 2 The bar chart shows the water vapor barrier efficiency of the protective materials in the embodiments and comparative examples of this invention. Figure 3 The above is a bar chart showing the sulfur dioxide blocking rate of the protective materials in the embodiments and comparative examples of this invention. Figure 4 The above are bar charts showing the ultraviolet blocking efficiency of the protective materials in the embodiments and comparative examples of this invention. Figure 5 The bar chart shows the self-healing efficiency of the protective materials in the embodiments and comparative examples of this invention. Figure 6 A bar chart showing the pH value of Xuan paper preserved for 30 days in the embodiments and comparative examples of this invention. Detailed Implementation
[0019] 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 embodiments of the present invention, and 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.
[0020] Please see Figure 1 This invention provides a paper-based preventive protective material with an asymmetrical structure. To achieve the above objectives, this invention is implemented through the following technical solution: the protective material consists of a functional protective layer, a transition adhesive layer, and a breathable regulating layer. The functional protective layer is the outer protective layer of the protective material. The functional protective layer is prepared from modified montmorillonite, polylactic acid and UPy derivatives. The surface of the functional protective layer is coated with a photoprotective coating and modified with superhydrophobicity. The breathable conditioning layer is the inner contact layer, which is made of porous cellulose aerogel with load-loaded temperature-sensitive moisture-absorbing and moisture-releasing composite material. Parallel grooves are provided on the side of the breathable conditioning layer that contacts the cultural relic. The transition bonding layer is a water-based polyurethane adhesive, which bonds the functional protective layer and the breathable conditioning layer together.
[0021] The substrate of the breathable regulating layer is natural cellulose extracted from bamboo fiber or cotton fiber, which is prepared into a three-dimensional porous network structure through freeze drying process, with a porosity of 85%-95% and a pore size of 50-500nm.
[0022] The load-bearing temperature-sensitive moisture-absorbing and moisture-releasing composite material is composed of modified zeolite molecular sieve and poly(N-isopropylacrylamide) hydrogel in a mass ratio of 3:1. The modified zeolite molecular sieve is prepared by modifying zeolite molecular sieve with 3-aminopropyltriethoxysilane. The load of the load-bearing temperature-sensitive moisture-absorbing and moisture-releasing composite material is 10%-20% of the total mass of the breathable conditioning layer.
[0023] The parallel trenches have a width of 50-200μm and a depth of 20-50μm. The parallel trenches are processed using plasma etching or laser etching processes.
[0024] The modified montmorillonite in the functional protective layer is prepared by modifying sodium-based montmorillonite with a silane coupling agent, and the mass ratio of modified montmorillonite to polylactic acid is 5%–15%. UPy derivatives are derivatives of polycaprolactone, and the amount of UPy derivatives added is 8%-12% of the mass of polylactic acid.
[0025] The photoprotective coating is composed of nano zinc oxide, waterborne polyurethane and KH-188 silane coupling agent. The coating thickness is 5-10 μm. The superhydrophobic modification is performed by perfluorooctyltriethoxysilane to modify the functional protective layer. After modification, the hydrophobic angle of the functional protective layer is ≥120°.
[0026] The preparation steps of the functional protective layer include: Sodium-based montmorillonite was mixed with 3% by mass of silane coupling agent KH-550 and stirred at 60℃ for 2 hours. After sieving, filtration and drying, modified montmorillonite was obtained. Modified montmorillonite, polylactic acid particles and UPy derivatives are mixed to obtain a mixture. The mixture is fed into a twin-screw extruder and melt-blended and granulated at 170-180℃. The particles are then added to a blown film machine and blown at 160-170℃ to obtain a composite film substrate with a thickness of 40-60μm. Nano zinc oxide, waterborne polyurethane and KH-188 silane coupling agent were mixed and ultrasonically dispersed for 60 min to prepare a coating liquid. The coating liquid was applied to the outside of the composite film substrate by spraying and cured at 100℃ for 60 min to form a photoprotective coating with a thickness of 5-10 μm. Perfluorooctyltriethoxysilane was sprayed onto the surface of the photoprotective coating and cured at 90°C for 40 minutes to obtain a functional protective layer.
[0027] The preparation steps of the breathable conditioning layer include: Bamboo fiber was treated with 5% NaOH solution at 80℃ for 2 hours, then bleached and dissolved in N-methylmorpholine-N-oxide solution to obtain cellulose solution; The cellulose solution was poured into a mold and frozen at -30 to -45°C for 8 to 15 hours. Then it was placed in a freeze dryer and dried at -45 to -55°C and a vacuum of 0.01 to 0.02 MPa for 20 to 30 hours to obtain a porous cellulose aerogel with a porosity of 85% to 95% and a pore size of 50 to 500 nm. A suspension was prepared by mixing zeolite molecular sieve modified with 3-aminopropyltriethoxysilane with poly(N-isopropylacrylamide) hydrogel at a mass ratio of 3:1 and dispersing it in deionized water. The porous cellulose aerogel was then immersed in the suspension and vacuum impregnated for 2 hours, and dried at 60°C for 12 hours to obtain the aerogel. Parallel grooves are fabricated on the side of the aerogel that is in contact with the artifact using plasma etching or laser etching processes to obtain an air permeability regulating layer.
[0028] The preparation steps of the transition bonding layer include: A mixture of waterborne polyurethane resin, deionized water, and film-forming aid was added and stirred at 500 r / min for 30 min at 25°C. During the stirring process, deionized water was added and the mixture was concentrated to adjust the solid content of the mixture to 30%–40%, thus obtaining a solid-liquid mixture. The adjusted solid-liquid mixture is filtered through a 200-mesh filter to remove impurities, resulting in a transitional bonding layer. During use, the thickness of the transitional bonding layer is controlled to be 10-15 μm through a coating process.
[0029] The steps involved in making protective materials include: Wipe the non-parallel groove side of the breathable conditioning layer and the non-photoprotective coating side of the functional protective layer with anhydrous ethanol to remove oil and impurities, and dry them at 60°C for 10 minutes. The transition adhesive layer is uniformly coated onto the cleaned surface of the breathable conditioning layer using a scraper coating process, and the coating thickness of the transition adhesive layer is controlled to be 10-15μm. After coating the transition adhesive layer, the breathable conditioning layer is placed in an oven and pre-cured at a temperature of 80-90℃ for 30 minutes to allow the transition adhesive layer to initially form a film. Align and bond the clean surface of the functional protective layer with the surface of the pre-cured transition adhesive layer, ensuring no air bubbles or misalignment, to obtain a composite preform. Place the bonded composite preform into a hot press and hot press for 30-60 seconds at a temperature of 120-140℃ and a vacuum of 0.3-0.5MPa. Then allow it to cool naturally to room temperature to obtain the composite layer material. The composite layer material was cut to the target size and vacuum dried at 40°C for 2 hours to remove residual moisture, thus obtaining the protective material.
[0030] Example Preparation of functional protective layer Take 10 kg of sodium-based montmorillonite, add 3% (w / w) of silane coupling agent KH-550 aqueous solution, stir and react at 300 r / min for 2 h at 60℃, filter through a 100-mesh sieve, and dry in an oven at 80℃ for 4 h to obtain modified montmorillonite. Take 8 kg of modified montmorillonite, 80 kg of polylactic acid granules and 8 kg of polycaprolactone-UPy derivative and mix them evenly to obtain a mixture. Put the mixture into a twin-screw extruder and melt-blend and granulate at 175°C. Then add the granules into a blown film machine and blown film at 165°C to obtain a composite film substrate with a thickness of 50 μm. Mix 1.2 kg of nano zinc oxide, 6.8 kg of waterborne polyurethane and 1.0 kg of KH-188 silane coupling agent, add deionized water to prepare a coating liquid, ultrasonically disperse for 60 min, apply to the outside of the composite film substrate using an air spraying process (pressure 0.3 MPa), and cure in a 100℃ oven for 60 min to form a photoprotective coating with a thickness of 8 μm. Perfluorooctyltriethoxysilane was uniformly sprayed onto the surface of the photoprotective coating and cured in an oven at 90°C for 40 minutes. The hydrophobic angle was measured to be 125°, thus obtaining the functional protective layer.
[0031] Preparation of breathable conditioning layer Take 5 kg of bamboo fiber, add 5% NaOH solution, keep it at 80℃ for 2 hours, wash it with deionized water until neutral, then bleach it with 3% hydrogen peroxide solution for 30 minutes, wash and dry it, then dissolve it in 60% N-methylmorpholine-N-oxide solution and stir until completely dissolved to obtain cellulose solution. The cellulose solution was poured into a flat mold and frozen in a -40℃ freezer for 12 hours. Then it was placed in a freeze dryer and dried for 24 hours at -50℃ and a vacuum of 0.015MPa to obtain a porous cellulose aerogel with a porosity of 90% and a pore size of 200nm. 3 kg of zeolite molecular sieve modified with 3-aminopropyltriethoxysilane was mixed with 1 kg of poly(N-isopropylacrylamide) hydrogel and dispersed in 10 kg of deionized water. The mixture was sonicated for 30 min to obtain a suspension. Porous cellulose aerogel was then immersed in the suspension and vacuum impregnated at 0.05 MPa for 2 h. After removal, the aerogel was dried in a 60 °C forced-air dryer for 12 h. The loading was measured to be 15%. Using plasma etching technology (power 100W, gas flow rate 20sccm), parallel grooves were processed on the side of the aerogel that was in contact with the artifact. The grooves were 100μm wide and 30μm deep, thus obtaining a breathable adjustment layer.
[0032] Preparation of transition adhesive layer Take 10 kg of waterborne polyurethane resin, add 5 kg of deionized water and 0.7 kg of film-forming aid propylene glycol methyl ether acetate, and stir at 500 r / min for 30 min at 25℃. During the stirring process, add 2 kg of deionized water to adjust the solid content of the mixture to 35% to obtain a solid-liquid mixture. Filter the adjusted solid-liquid mixture through a 200-mesh filter to remove mechanical impurities and air bubbles to obtain a transitional adhesive layer.
[0033] Production of protective materials Wipe the non-groove side of the breathable conditioning layer and the non-light-protective coating side of the functional protective layer with anhydrous ethanol to remove oil and impurities, and dry them in an oven at 60°C for 10 minutes. A doctor blade coating process is used to uniformly coat the transition adhesive layer onto the cleaned surface of the breathable conditioning layer, controlling the coating thickness to 12μm; After coating the transition adhesive layer, the breathable conditioning layer is placed in an oven and pre-cured at 85°C for 30 minutes to allow the transition adhesive layer to initially form a film. Align and bond the clean surface of the functional protective layer with the surface of the pre-cured transition adhesive layer, ensuring no bubbles or misalignment, to obtain a composite preform. Place the bonded composite preform into a hot press and hot press for 45 seconds at a temperature of 130℃ and a pressure of 0.4MPa, then allow it to cool naturally to room temperature to obtain the composite layer material. The composite layer material is cut to the target size of the cultural relic and vacuum dried at 40°C for 2 hours to remove residual moisture, resulting in an asymmetric paper-based preventive protective material for cultural relics.
[0034] Comparative Example The existing symmetrical structure protective material is used, specifically: a single polylactic acid membrane (50 μm thick) and an unmodified porous cellulose aerogel (100 μm thick) are made by hot pressing (130℃, 0.4 MPa, 45s). The polylactic acid membrane is not modified in any way, and the cellulose aerogel is not loaded with moisture-absorbing and moisture-releasing materials and has no groove structure.
[0035] Test case Gas permeability test: Tested according to GB / T 1038-2000 "Test methods for gas permeability of plastic films and sheets - Part 1: Differential pressure method"; Water vapor barrier test: Tested according to GB / T 1037-1988 "Test method for water vapor permeability of plastic films and sheets - cup method"; Sulfur dioxide barrier rate test: The amount of sulfur dioxide gas passing through at a concentration of 100 ppm was tested using a gas permeability tester. UV blocking rate test: Using a UV-Vis spectrophotometer, at 25℃ and 50%RH, the transmittance of the material in the 200-400nm UV band was tested, and the UV blocking rate was calculated based on the transmittance. Self-healing efficiency test: A 50μm wide scratch was made on the material surface with a blade. After 24 hours, the healing of the scratch was observed under a microscope, and the repair area ratio was calculated. Humidity regulation range test: Place the material in an environment with a temperature of 25℃ and an initial humidity of 30%RH, and record the humidity rise to a stable value; then place it in an environment with a temperature of 25℃ and an initial humidity of 80%RH, and record the humidity drop to a stable value. Cultural relic compatibility test: The material was bonded to a blank Xuan paper sample and placed in an environment of 50℃ and 60%RH for 30 days. The pH value change and surface morphology of the Xuan paper were then detected.
[0036] The protective materials of the embodiments and comparative examples were compared and tested according to the above test content. The test results are shown in the table below:
[0037] As can be seen from the table, the asymmetric structure paper cultural relic preventive protection material prepared in the example has been tested and verified to have a comprehensive performance that far exceeds that of the existing symmetric structure protection material in the comparative example. The air permeability of the example reached 5800 mL / (m²). 2 • 24h • 0.1MPa), compared to a control of 3200mL / (m 2 • 24h • 0.1MPa) increased by 81.25%, achieving efficient removal of moisture and acidic gases from inside paper artifacts while protecting them, with a water vapor barrier rate as low as 1.2g / (m³). 2 • 24h), the sulfur dioxide blocking rate reaches 98.2%, which is 85.88% lower and 50.38% higher than the control ratio, respectively, effectively blocking the intrusion of harmful substances from the outside world and achieving the effect of both breathability and barrier. In terms of functional expansion, the embodiment uses a photoprotective coating design with an ultraviolet blocking rate of 98.5%, which can effectively prevent the photodegradation of cultural relics. With the help of the dynamic hydrogen bonding of UPy derivatives, the self-repair efficiency of 50μm scratches reaches 92.3% in 24 hours, which solves the problem of protection failure after existing materials are damaged. By using a load-bearing temperature-sensitive moisture-absorbing and moisture-releasing composite material, the appropriate humidity regulation of cultural relics can be achieved at 48%–63% RH, while the comparative model has no humidity control capability at all. Regarding the compatibility with cultural relics, the pH value of the example material changed by only 0.12 after being bonded to Xuan paper for 30 days, with no surface damage or adhesion. This is far superior to the pH value change and slight adhesion of the comparative example (0.35), thus avoiding secondary pollution. In summary, this protective material performs excellently in key indicators such as breathability, barrier properties, light protection, self-healing, humidity regulation, and compatibility with cultural relics, fully meeting the preventive protection needs for the long-term stable preservation of paper cultural relics.
[0038] By using asymmetrical protective materials, a synergistic protective effect of external barrier and internal permeability is achieved. Through the differentiated design of the functional protective layer and the breathable regulating layer, the functional protective layer is enhanced with modified montmorillonite to improve barrier properties and superhydrophobic modification to improve impermeability, effectively blocking external water vapor, harmful gases and ultraviolet rays. The porous cellulose aerogel of the breathable regulating layer works synergistically with the parallel groove structure to ensure the directional and efficient outflow of internal gases. This solves the problem of mutual restriction between breathability and barrier properties in symmetrical structural materials, avoiding acidification and dampness caused by the retention of internal harmful gases or aging caused by the intrusion of external harmful factors, thus building a stable isolation barrier for cultural relics. The UPy derivative of the functional protective layer endows the material with self-healing capabilities, enabling it to repair minor damage during use, maintain the integrity of the barrier, and reduce maintenance costs. The photoprotective coating reduces the risk of photodegradation of cultural relics through the ultraviolet shielding effect of nano zinc oxide. The temperature-sensitive moisture-absorbing and moisture-releasing composite material of the breathable regulating layer can actively adapt to changes in environmental humidity, stabilize the microenvironment within the suitable range for cultural relics, and avoid mold and fiber hydrolysis caused by humidity fluctuations. It achieves comprehensive and long-lasting protection with repairable minor damage, controllable preservation environment, and protection against damage, significantly extending the preservation life of paper cultural relics. Each layer is made of environmentally friendly materials such as natural cellulose, polylactic acid, and modified zeolite. The preparation process leaves no harmful chemical residues, and the water-based polyurethane adhesive in the transition bonding layer has good compatibility with the material of the cultural relics. Tests have shown no risk of secondary pollution, thus avoiding damage to fragile paper cultural relics by the protective material. At the same time, the material is formed into a whole through a gradient hot-pressing composite process, which combines structural stability and flexibility. It can fit paper cultural relics of different forms such as ancient books and calligraphy and paintings, and is suitable for diverse protection scenarios such as museum display, packaging and transportation. This lays the foundation for its industrialization and promotion in the field of cultural relic protection, and has significant practical value and market prospects.
[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.
Claims
1. A paper-based preventive conservation material for cultural relics with an asymmetrical structure, characterized in that: The protective material consists of a functional protective layer, a transition adhesive layer, and a breathable conditioning layer; The functional protective layer is the outer protective layer of the protective material. The functional protective layer is prepared from modified montmorillonite, polylactic acid and UPy derivatives. The surface of the functional protective layer is coated with a photoprotective coating and modified with superhydrophobicity. The breathable conditioning layer is an inner contact layer, which is prepared by porous cellulose aerogel of load-loaded temperature-sensitive moisture-absorbing and moisture-releasing composite material. The breathable conditioning layer has parallel grooves on the side in contact with the cultural relic. The transition bonding layer is a water-based polyurethane adhesive, which bonds the functional protective layer to the breathable conditioning layer.
2. The asymmetric structure paper-based preventive conservation material for cultural relics according to claim 1, characterized in that: The substrate of the breathable regulating layer is natural cellulose extracted from bamboo fiber or cotton fiber, which is prepared into a three-dimensional porous network structure by freeze drying process, with a porosity of 85%-95% and a pore size of 50-500nm.
3. The asymmetric structure paper-based preventive conservation material for cultural relics according to claim 1, characterized in that: The loaded temperature-sensitive moisture-absorbing and moisture-releasing composite material is composed of modified zeolite molecular sieve and poly(N-isopropylacrylamide) hydrogel in a mass ratio of 3:
1. The modified zeolite molecular sieve is obtained by modifying zeolite molecular sieve with 3-aminopropyltriethoxysilane. The loading amount of the loaded temperature-sensitive moisture-absorbing and moisture-releasing composite material is 10%-20% of the total mass of the breathable conditioning layer.
4. The asymmetric structure paper-based preventive protective material for cultural relics according to claim 1, characterized in that: The parallel trenches have a width of 50-200μm and a depth of 20-50μm, and are processed using plasma etching or laser etching processes.
5. The asymmetric structure paper-based preventive protective material for cultural relics according to claim 1, characterized in that: The modified montmorillonite in the functional protective layer is prepared by modifying sodium-based montmorillonite with a silane coupling agent, and the mass ratio of the modified montmorillonite to the polylactic acid is 5%-15%. The UPy derivative is a derivative of polycaprolactone, and the amount of the UPy derivative added is 8%-12% of the mass of the polylactic acid.
6. The asymmetric structure paper-based preventive protective material for cultural relics according to claim 1, characterized in that: The photoprotective coating is composed of nano zinc oxide, waterborne polyurethane and KH-188 silane coupling agent. The coating thickness of the photoprotective coating is 5-10 μm. The superhydrophobic modification is performed by modifying the functional protective layer with perfluorooctyltriethoxysilane. After modification, the hydrophobic angle of the functional protective layer is ≥120°.
7. The asymmetric structure paper-based preventive conservation material for cultural relics according to claim 1, characterized in that: The preparation steps of the functional protective layer include: Sodium-based montmorillonite was taken, and 3% by mass of silane coupling agent KH-550 was added. The mixture was stirred and reacted at 60°C for 2 hours. After sieving, filtration and drying, the modified montmorillonite was obtained. The modified montmorillonite, the polylactic acid particles and the UPy derivative are mixed to obtain a mixture. The mixture is fed into a twin-screw extruder and melt-blended and granulated at 170-180°C. The particles are then added to a blown film machine and blown into a film at 160-170°C to obtain a composite film substrate with a thickness of 40-60 μm. Nano zinc oxide, waterborne polyurethane and KH-188 silane coupling agent are mixed and ultrasonically dispersed for 60 min to obtain a coating liquid. The coating liquid is applied to the outside of the composite film substrate by spraying and cured at 100℃ for 60 min to form the photoprotective coating with a thickness of 5-10 μm. Perfluorooctyltriethoxysilane was sprayed onto the surface of the photoprotective coating and cured at 90°C for 40 minutes to obtain the functional protective layer.
8. The asymmetric structure paper-based preventive protective material for cultural relics according to claim 1, characterized in that: The preparation steps of the breathability regulating layer include: Bamboo fiber was treated with 5% NaOH solution at 80℃ for 2 hours, then bleached and dissolved in N-methylmorpholine-N-oxide solution to obtain cellulose solution; The cellulose solution was poured into a mold and frozen at -30 to -45°C for 8 to 15 hours. Then it was placed in a freeze dryer and dried at -45 to -55°C and a vacuum of 0.01 to 0.02 MPa for 20 to 30 hours to obtain a porous cellulose aerogel with a porosity of 85% to 95% and a pore size of 50 to 500 nm. A suspension was prepared by mixing zeolite molecular sieve modified with 3-aminopropyltriethoxysilane and poly(N-isopropylacrylamide) hydrogel at a mass ratio of 3:1 and dispersing it in deionized water. The porous cellulose aerogel was then immersed in the suspension and vacuum impregnated for 2 hours, and dried at 60°C for 12 hours to obtain the aerogel. The parallel grooves are processed on the side of the aerogel that is in contact with the artifact using plasma etching or laser etching processes to obtain the air permeability adjustment layer.
9. The asymmetric structure paper-based preventive protective material for cultural relics according to claim 1, characterized in that: The preparation steps of the transition bonding layer include: A mixture of waterborne polyurethane resin and deionized water and film-forming aid is added and stirred at 500 r / min for 30 min at 25°C. During the stirring process, deionized water is added and the mixture is concentrated to adjust the solid content of the mixture to 30%-40% to obtain a solid-liquid mixture. The adjusted solid-liquid mixture is filtered through a 200-mesh filter to remove impurities, resulting in the transition bonding layer. During use, the thickness of the transition bonding layer is controlled to be 10-15 μm through a coating process.
10. The asymmetric structure paper-based preventive conservation material for cultural relics according to claim 1, characterized in that: The steps for manufacturing the protective material include: Wipe the side of the breathable conditioning layer that is not the parallel groove and the side of the functional protective layer that is not the light-protective coating with anhydrous ethanol to remove oil and impurities, and dry them at 60°C for 10 minutes. The transition adhesive layer is uniformly coated onto the cleaned surface of the breathable conditioning layer using a scraper coating process, and the coating thickness of the transition adhesive layer is controlled to be 10-15 μm. The air permeability conditioning layer after coating the transition adhesive layer is placed in an oven and pre-cured at a temperature of 80-90℃ for 30 minutes to allow the transition adhesive layer to initially form a film. Align and bond the clean surface of the functional protective layer with the surface of the pre-cured transition adhesive layer, ensuring no air bubbles or misalignment, to obtain a composite preform. Place the bonded composite preform into a hot press and hot press for 30-60 seconds at a temperature of 120-140℃ and a vacuum of 0.3-0.5MPa. Then allow it to cool naturally to room temperature to obtain the composite layer material. The composite layer material is cut to the target size and vacuum dried at 40°C for 2 hours to remove residual moisture, thus obtaining the protective material.