Method for preparing multifunctional protective nanometer paper loaded with magnesium compound and application thereof
By preparing multifunctional protective nanopaper loaded with magnesium compounds, the problems of fiber swelling and insufficient alkali reserve during the deacidification process of paper cultural relics were solved, achieving safe and long-lasting protection of paper cultural relics. It also has flame-retardant and antibacterial properties, and maintains the original structure of the cultural relics.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SH INST OF QUALITY INSPECTION & TECHNICAL RESEARCH
- Filing Date
- 2024-05-29
- Publication Date
- 2026-07-24
AI Technical Summary
Existing methods for deacidifying paper artifacts suffer from problems such as fiber swelling, pigment fading, and insufficient alkali reserves. Furthermore, some gaseous deacidifying agents pose a risk of combustion and explosion, making it difficult to achieve safe and long-lasting preservation of paper artifacts.
A multifunctional protective nanopaper loaded with magnesium compounds was prepared by modifying the carboxyl groups of bacterial cellulose membranes and treating them with magnesium salt precursors, combined with a dynamic circulating flow reaction. This nanopaper, with uniformly distributed high alkalinity particles, is used for deacidification, flame retardancy, and antibacterial protection of paper cultural relics.
It achieves long-lasting alkaline neutralization, maintains the slightly alkaline state of the paper's microenvironment, possesses excellent flame-retardant properties, and does not damage the original structure of paper artifacts, thus conforming to the principle of minimal intervention in cultural relic protection.
Smart Images
Figure CN118547528B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of deacidification technology for the preservation of paper cultural relics, specifically relating to a method for preparing multifunctional protective nanopaper loaded with magnesium compounds and its application in the deacidification and preservation of paper cultural relics. Background Technology
[0002] Ancient books, archives, documents, and other paper artifacts possess significant cultural and historical value. However, during long-term preservation, these artifacts are susceptible to irreversible deterioration due to both internal and external environmental factors. Paper fibers are prone to acidification and yellowing, decay and breakage, powdery aging, insect infestation, and mold growth. Acidification occurs when cellulose undergoes hydrolysis under acidic conditions, leading to the breakage of β-glycosidic bonds and a decrease in the degree of cellulose polymerization, resulting in a decline in the paper's mechanical properties. Currently, the primary method for addressing paper acidification is deacidification.
[0003] Paper deacidification refers to the introduction of alkaline substances into paper artifacts to neutralize acidic substances in the paper, while retaining a certain amount of alkaline substances (commonly known as alkali retention) to neutralize any acidic substances that may be generated later. However, most current deacidification methods involve liquid-phase or gas-phase processes. Liquid-phase deacidification (e.g., patent documents CN117661370A, CN117306309A, CN116791398A, CN116463885A, CN115748295A) typically requires mixing alkaline substances with solvents, but the use of solvents can cause fiber swelling and pigment fading in liquid-sensitive paper artifacts. Gas-phase deacidification (e.g., patent documents CN117306309A, CN115216997A, CN113073495A) often faces the challenge of insufficient alkali reserves, and some gaseous deacidifying agents may also pose a risk of combustion and explosion. Therefore, further development is needed to ensure the safety and long-term effectiveness of deacidification methods for paper artifacts.
[0004] Patent document CN115928495A discloses a multifunctional protective backing paper made of mineralized bacterial cellulose for preventive protection of paper cultural relics, its preparation method, and its application. It loads alkaline inorganic materials such as calcium carbonate, magnesium carbonate, and hydroxyapatite onto a bacterial fiber membrane with a three-dimensional nano-network structure to create a multifunctional protective backing paper. This paper serves as a sandwich or surface paper in contact with paper cultural relics, exhibiting good deacidification and flame-retardant protection. However, different charged groups have varying abilities to induce mineralization; groups with lower electronegativity have weaker mineralization capabilities. The hydroxyl groups on the surface of the bacterial cellulose in CN115928495A have relatively weak electronegativity, which is unfavorable for the distribution and growth of inorganic particles, resulting in slow mineralization speed, poor inorganic binding force and crystal growth stability, and uneven distribution of alkaline particles. Furthermore, the preparation method in this document results in insufficient alkaline reserves of inorganic particles within the cellulose, making it difficult to continuously neutralize acids generated in paper cultural relics over a long period. Summary of the Invention
[0005] To overcome the aforementioned deficiencies in the prior art, this invention provides a method for preparing a multifunctional protective nanopaper loaded with magnesium compounds and its application in the deacidification and protection of paper cultural relics. This nanopaper can continuously neutralize acids in paper cultural relics and maintain the paper's microenvironment in a weakly alkaline state for a long time, while also endowing paper cultural relics with multifunctional protective functions of deacidification and flame retardancy.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows.
[0007] The present invention discloses a method for preparing a multifunctional protective nanopaper loaded with magnesium compounds, characterized by comprising the following steps:
[0008] (1) Carboxyl modification of bacterial cellulose membranes:
[0009] The bacterial cellulose membrane was washed with distilled water, placed on gauze, and squeezed to remove excess water. Then it was added to a tetramethylpiperidine nitride TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification to obtain a carboxyl-modified bacterial cellulose membrane.
[0010] (2) Preparation of precursor-loaded bacterial cellulose scaffolds
[0011] The carboxyl-modified bacterial cellulose membrane was placed in a magnesium salt precursor solution and allowed to stand for 0.5–2 hours, then frozen at -20–-80°C for 1–12 hours; then transferred to a vacuum freeze dryer and dried for 12–36 hours to obtain a bacterial cellulose scaffold loaded with the precursor.
[0012] (3) Preparation of multifunctional protective nanopaper loaded with magnesium compounds
[0013] The bacterial cellulose scaffold was placed in a microreactor, and an alkaline reaction solution was dynamically circulated in the microreactor and reacted with the bacterial cellulose scaffold. The reaction temperature was 30–70°C, and the reaction time was 0.5–24 h. After the reaction was completed, the paper was washed with deionized water and dried to obtain the multifunctional protective nanopaper loaded with magnesium compounds.
[0014] Preferably, in step (1), the washed bacterial cellulose membrane is a semi-transparent wet film with a thickness of 20-100 μm.
[0015] Preferably, in step (1), the carboxyl modification process is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution at a mass ratio of 1:(2-20), and the bacterial cellulose membrane is immersed in the TEMPO / NaBr aqueous solution for 30-60 minutes, wherein the mass ratio of TEMPO to the bacterial cellulose membrane is 1:(20-200); then, a NaClO solution with a concentration of 5-10 wt% is added, the pH of the system is controlled to be 9.5-10.5, and the immersion is continued for 0.5-2 hours under mechanical stirring, wherein the mass ratio of TEMPO to NaClO is 1:(20-200).
[0016] Preferably, in step (2), the precursor solution is magnesium chloride MgCl2, magnesium sulfate MgSO3 or magnesium nitrate Mg(NO3)2, with a concentration of 0.1 to 5 mol / L.
[0017] Preferably, in step (2), the freeze-drying temperature of the vacuum freeze dryer is -30 to -80°C, and the vacuum degree is 1 to 10 Pa.
[0018] Preferably, in step (3), the magnesium salt is magnesium hydroxide or magnesium carbonate.
[0019] Preferably, in step (3), the alkaline reaction solution refers to a mixture prepared by placing a 0.1-10 mol / L NH3 water or NaOH solution, or a 0.5-5 mol / L Na2CO3, K2CO3 or NH4HCO3 solution, in a constant pressure dropping funnel and adding it dropwise at a rate of 2-10 ml / min to a flask containing a substrate solution and stirring; the substrate solution is a 0.05-2 mol / L NaCl solution.
[0020] Preferably, in step (3), the drying method is freeze-drying under vacuum conditions of -80 to -30°C or hot-press drying at 30 to 80°C.
[0021] Preferably, in step (3), the structure of the microreactor is as follows: one end of the reactor tank is connected to the heating bottle through a pipe, the other end of the reactor tank is connected to the peristaltic pump through a pipe, and the outlet of the peristaltic pump is connected to the heating bottle, thereby forming a circulation system of reactor tank, peristaltic pump and reaction bottle; a constant pressure dripping funnel is inserted into the heating bottle from the top.
[0022] A second objective of this invention is to provide a multifunctional protective nanopaper loaded with magnesium compounds prepared using the aforementioned method for preparing a multifunctional protective nanopaper loaded with magnesium compounds.
[0023] A third objective of this invention is to provide the application of the aforementioned magnesium compound-loaded multifunctional protective nanopaper as a multifunctional protective material for paper artifacts, offering deacidification, flame retardancy, and antibacterial properties. The protection involves the multifunctional protective nanopaper directly or indirectly contacting the paper artifact. Specifically, the liner paper can be used as a layer or surface paper in contact with the paper artifact; or it can be used as liner paper and cardboard for artifact boxes, cardboard for artifact cartons, cardboard for artifact pouches, outer decorative paper and inner liner paper for boxes, paper bags and envelopes for preserving artifacts, backing paper for displaying artifacts, or padding paper for exhibiting artifacts, etc.
[0024] This invention utilizes bacterial cellulose nanofibers as templates and employs a dynamic circulating flow environment to slowly introduce the reaction solution into the flow system. This allows magnesium compound nuclei to grow uniformly and slowly within the three-dimensional network of bacterial cellulose, dispersing microparticles evenly and at a high loading rate within the bacterial cellulose nanofiber network. This improves the uniformity and loading rate of alkaline particles, resulting in a nanopaper with strong alkalinity and a large alkali reserve. This facilitates the long-term, sustained release of alkaline substances, neutralizing acidic substances in the microenvironment of paper artifacts. The morphology and loading rate of inorganic substances can be controlled through the regulation of reaction conditions. Simultaneously, the highly loaded organic-inorganic composite structure of this nanopaper endows it with excellent flame retardancy. Furthermore, inorganic particles do not remain on the surface of the paper artifact or penetrate its interior, avoiding irreversible damage. This method effectively preserves the original structure and fiber morphology of the paper. This protective approach adheres to the principles of minimal intervention and reversibility in artifact preservation, causing no damage to the paper and effectively preserving its original structure and fiber morphology. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the preparation method of the multifunctional protective nanopaper of the present invention. Detailed implementation method:
[0026] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0027] Example 1
[0028] (1) Carboxyl modification of bacterial cellulose membranes:
[0029] The bacterial cellulose membrane was washed with distilled water, placed on gauze, and squeezed for 10 minutes to remove excess free water. Then it was added to a tetramethylpiperidine nitride oxychloride TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification to obtain a carboxyl modified bacterial cellulose membrane.
[0030] The carboxyl modification process is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution at a mass ratio of 1:6. The bacterial cellulose membrane is then immersed in the TEMPO / NaBr aqueous solution for 30 minutes, with a mass ratio of TEMPO to bacterial cellulose membrane of 1:50. Subsequently, a 5 wt% NaClO solution is added, and the pH of the system is controlled at 10. The membrane is then immersed for another 2 hours under mechanical stirring, with a mass ratio of TEMPO to NaClO of 1:100.
[0031] (2) Preparation of MgCl2-loaded bacterial cellulose scaffolds
[0032] The carboxyl-modified bacterial cellulose membrane was placed in a 3 mol / L MgCl2 precursor solution and allowed to stand for 0.5 h, then frozen at -20 °C for 12 h; then transferred to a vacuum freeze dryer and dried at -50 °C and 8 Pa for 24 h to obtain a MgCl2-loaded bacterial cellulose scaffold.
[0033] (3) Preparation of multifunctional protective nanopaper loaded with Mg(OH)2
[0034] A bacterial cellulose scaffold was placed in a microreactor. The microreactor was structured as follows: one end of the reactor tank was connected to a heating flask via a pipe, and the other end of the reactor tank was connected to a peristaltic pump via a pipe. The outlet of the peristaltic pump was then connected to the heating flask, thus forming a circulation system of the reactor tank, peristaltic pump, and reaction flask. A constant-pressure dropping funnel was inserted into the heating flask from the top. The reaction flask contained a 0.05 mol / L NaCl solution, and the temperature was maintained at 40°C using a water bath outside the reaction flask. A 2 mol / L NH3 solution was placed in the constant-pressure dropping funnel and added dropwise to the reaction flask at a rate of 5 ml / min, and stirred evenly to form an alkaline reaction solution. The alkaline reaction solution in the reaction flask was dynamically circulated in the microreactor and reacted with the bacterial cellulose scaffold for 10 hours. After the reaction, the scaffold was washed with deionized water and dried by hot pressing at 50°C to obtain a multifunctional protective nanopaper loaded with Mg(OH)2.
[0035] (4) Application of multifunctional protective nanopaper loaded with Mg(OH)2
[0036] Multifunctional protective nanopaper loaded with Mg(OH)2 was used as the inner lining of the apparatus. The paper sample to be protected (Whatman 1001 model paper) was placed in the middle of the inner lining, while the control group was set as a blank paper sample without any treatment. The two groups of paper samples were placed in an oven at 80°C and 65% relative humidity (refer to ISO 5630-3) for 10 days to accelerate aging, simulating the aging and degradation process of paper cultural relics under long-term preservation.
[0037] Degree of polymerization: The degree of polymerization of paper is measured using the copper ethylenediamine solution viscosity method according to ISO 5351. Specifically, an appropriate amount of the paper sample to be tested is weighed into a certain amount of copper ethylenediamine solution, shaken thoroughly to dissolve, and then its viscosity is measured using a viscometer under standard temperature conditions. The degree of polymerization is then calculated according to the method specified in ISO 5351. Each group of samples is tested three times, and the final degree of polymerization result is the average value.
[0038] pH: The pH value of the paper was determined using a HANNA pH meter (HI9125) in accordance with the method of GB / T13528-2015.
[0039] Colorimetry: The colorimetry of the paper was measured using a colorimeter (NR10QC) according to CIE-L*,a*,b* methods.
[0040] Table 1. Color difference, degree of polymerization, and pH of the nanopaper in the protected and unprotected groups in Example 1.
[0041]
[0042] The results of the accelerated aging test after 10 days in Example 1 are shown in Table 1. The paper samples in the protected group showed no significant color change, the degree of polymerization only decreased from 935 to 881, and the paper pH increased from the initial 7.05 to 7.74. In contrast, the paper in the unprotected group turned yellow, and after 10 days, the degree of polymerization dropped sharply from 935 to 792, and the paper pH decreased from the initial 7.05 to 6.23. This demonstrates that the multifunctional protective nanopaper liner loaded with Mg(OH)2 in Example 1 can effectively slow down the aging process of paper.
[0043] Example 2
[0044] (1) Carboxyl modification of bacterial cellulose membranes:
[0045] The bacterial cellulose membrane was washed with distilled water, placed on gauze, and squeezed for 10 minutes to remove excess free water. Then it was added to a tetramethylpiperidine nitride oxychloride TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification to obtain a carboxyl modified bacterial cellulose membrane.
[0046] The carboxyl modification process is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution at a mass ratio of 1:10. The bacterial cellulose membrane is then immersed in the TEMPO / NaBr aqueous solution for 30 minutes, with a mass ratio of TEMPO to bacterial cellulose membrane of 1:80. Subsequently, a 5 wt% NaClO solution is added, and the pH of the system is controlled at 10. The membrane is then immersed for another 2 hours under mechanical stirring, with a mass ratio of TEMPO to NaClO of 1:100.
[0047] (2) Preparation of precursor-loaded bacterial cellulose scaffolds
[0048] The carboxyl-modified bacterial cellulose membrane was placed in a 2 mol / L Mg(NO3)2 precursor solution and allowed to stand for 0.5 h, then frozen at -20°C for 12 h; then transferred to a vacuum freeze dryer and dried at -50°C and 8 Pa for 24 h to obtain a Mg(NO3)2-loaded bacterial cellulose scaffold.
[0049] (3) Preparation of multifunctional protective nanopaper loaded with MgCO3
[0050] A bacterial cellulose scaffold was placed in a microreactor with the same structure as in Example 1. The reaction flask contained a 0.05 mol / L NaCl solution, and the temperature was maintained at 35°C using a water bath outside the flask. A 3 mol / L NH4HCO3 solution was placed in a constant-pressure dropping funnel and added dropwise to the reaction flask at a rate of 3 ml / min. The solution was stirred evenly to form an alkaline reaction solution. The alkaline reaction solution in the reaction flask was dynamically circulated in the microreactor and reacted with the bacterial cellulose scaffold for 10 h. After the reaction, the scaffold was washed with deionized water and dried by hot pressing at 50°C to obtain a multifunctional protective nanopaper loaded with MgCO3.
[0051] (4) Application of multifunctional protective nanopaper loaded with MgCO3
[0052] Multifunctional protective nanopaper loaded with MgCO3 was used as the inner lining of the apparatus. The paper sample to be protected (Whatman1001 model paper) was placed in the middle of the inner lining, while the control group was set as a blank paper sample without any treatment. The two groups of paper samples were placed in an oven at 80℃ and 65% relative humidity (refer to ISO 5630-3) for 10 days to accelerate aging, simulating the aging and degradation process of paper cultural relics under long-term preservation.
[0053] Degree of polymerization: The degree of polymerization of paper is measured using the copper ethylenediamine solution viscosity method according to ISO 5351. Specifically, an appropriate amount of the paper sample to be tested is weighed into a certain amount of copper ethylenediamine solution, shaken thoroughly to dissolve, and then its viscosity is measured using a viscometer under standard temperature conditions. The degree of polymerization is then calculated according to the method specified in ISO 5351. Each group of samples is tested three times, and the final degree of polymerization result is the average value.
[0054] pH: The pH value of the paper was determined using a HANNA pH meter (HI9125) in accordance with the method of GB / T13528-2015.
[0055] Colorimetry: The colorimetry of the paper was measured using a colorimeter (NR10QC) according to CIE-L*,a*,b* methods.
[0056] Limiting Oxygen Index (LOI): The limiting oxygen index (LOI) of the sample is analyzed using a limiting oxygen index tester. A 100mm*15mm sample is placed in the combustion chamber, and the oxygen content in the atmosphere is adjusted to find the lowest oxygen concentration that supports continuous combustion.
[0057] Table 2 shows the color difference, degree of polymerization, and pH of the multifunctional protective nanopaper with MgCO3 in Example 2, comparing the protected and unprotected groups.
[0058]
[0059] The results of the accelerated aging test after 10 days in Example 2 are shown in Table 2. The paper samples in the protected group showed no significant color change, the degree of polymerization only decreased from 928 to 878, and the paper pH increased from the initial 7.14 to 7.86. In contrast, the paper in the unprotected group turned yellow, and after 10 days, the degree of polymerization dropped sharply from 928 to 786, and the paper pH decreased from the initial 7.14 to 6.13. This demonstrates that the MgCO3-loaded multifunctional protective nanopaper liner in Example 2 can effectively slow down the aging process of paper.
[0060] The limiting oxygen index of the multifunctional protective nanopaper loaded with MgCO3 was tested, and the results showed that the limiting oxygen index of the nanopaper was greater than 40, making it difficult to burn and thus exhibiting excellent flame retardant properties.
[0061] Example 3
[0062] (1) Carboxyl modification of bacterial cellulose membranes:
[0063] The bacterial cellulose membrane was washed with distilled water, placed on gauze, and squeezed for 10 minutes to remove excess free water. Then it was added to a tetramethylpiperidine nitride oxychloride TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification to obtain a carboxyl modified bacterial cellulose membrane.
[0064] The carboxyl modification process is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution at a mass ratio of 1:10. The bacterial cellulose membrane is then immersed in the TEMPO / NaBr aqueous solution for 50 min, with a mass ratio of TEMPO to bacterial cellulose membrane of 1:80. Subsequently, a 5 wt% NaClO solution is added, and the pH of the system is controlled at 10. The membrane is then immersed for another 2 h under mechanical stirring, with a mass ratio of TEMPO to NaClO of 1:100.
[0065] (2) Preparation of precursor-loaded bacterial cellulose scaffolds
[0066] The carboxyl-modified bacterial cellulose membrane was placed in a 1 mol / L MgSO4 precursor solution and allowed to stand for 0.5 h, then frozen at -20°C for 12 h; then transferred to a vacuum freeze dryer and dried at -50°C and 8 Pa for 24 h to obtain a MgSO4-loaded bacterial cellulose scaffold.
[0067] (3) Preparation of multifunctional protective nanopaper loaded with MgCO3
[0068] The bacterial cellulose scaffold was placed in a microreactor with the same structure as in Example 1. The reaction flask contained a 0.05 mol / L NaCl solution, and the temperature was maintained at 40°C using a water bath outside the flask. A 2 mol / L Na2CO3 solution was placed in a constant-pressure dropping funnel and added dropwise to the reaction flask at a rate of 7 ml / min. The solution was stirred evenly to form an alkaline reaction solution. The alkaline reaction solution in the reaction flask was dynamically circulated in the microreactor and reacted with the bacterial cellulose scaffold for 10 h. After the reaction, the scaffold was washed with deionized water and dried by hot pressing at 50°C to obtain the multifunctional protective nanopaper loaded with MgCO3.
[0069] (4) Application of multifunctional protective nanopaper loaded with MgCO3
[0070] Multifunctional protective nanopaper loaded with MgCO3 was used as the inner lining of the apparatus. The paper sample to be protected (Whatman1001 model paper) was placed in the middle of the inner lining, while the control group was set as a blank paper sample without any treatment. The two groups of paper samples were placed in an oven at 80℃ and 65% relative humidity (refer to ISO 5630-3) for 10 days to accelerate aging, simulating the aging and degradation process of paper cultural relics under long-term preservation.
[0071] Degree of polymerization: The degree of polymerization of paper is measured using the copper ethylenediamine solution viscosity method according to ISO 5351. Specifically, an appropriate amount of the paper sample to be tested is weighed into a certain amount of copper ethylenediamine solution, shaken thoroughly to dissolve, and then its viscosity is measured using a viscometer under standard temperature conditions. The degree of polymerization is then calculated according to the method specified in ISO 5351. Each group of samples is tested three times, and the final degree of polymerization result is the average value.
[0072] pH: The pH value of the paper was determined using a HANNA pH meter (HI9125) in accordance with the method of GB / T13528-2015.
[0073] Colorimetry: The colorimetry of the paper was measured using a colorimeter (NR10QC) according to CIE-L*,a*,b* methods.
[0074] Limiting Oxygen Index (LOI): The limiting oxygen index (LOI) of the sample is analyzed using a limiting oxygen index tester. A 100mm*15mm sample is placed in the combustion chamber, and the oxygen content in the atmosphere is adjusted to find the lowest oxygen concentration that supports continuous combustion.
[0075] Table 3. Color difference, degree of polymerization, and pH of the multifunctional protective nanopaper loaded with MgCO3 in Example 3 between the protected and unprotected groups.
[0076]
[0077] The results of the accelerated aging test after 10 days in Example 3 are shown in Table 3. The paper samples in the protected group showed no significant color change, the degree of polymerization only decreased from 922 to 892, and the paper pH increased from the initial 7.07 to 7.95. In contrast, the paper in the unprotected group turned yellow, and after 10 days, the degree of polymerization dropped sharply from 922 to 762, and the paper pH decreased from the initial 7.07 to 6.14. This demonstrates that the multifunctional protective nanopaper liner loaded with MgCO3 in Example 3 can effectively slow down the aging process of paper.
[0078] The limiting oxygen index of the multifunctional protective nanopaper loaded with MgCO3 was tested, and the results showed that the limiting oxygen index of the nanopaper was greater than 40, making it difficult to burn and thus exhibiting excellent flame retardant properties.
[0079] Example 4
[0080] (1) Carboxyl modification of bacterial cellulose membranes:
[0081] The bacterial cellulose membrane was washed with distilled water, placed on gauze, and squeezed for 10 minutes to remove excess free water. Then it was added to a tetramethylpiperidine nitride oxychloride TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification to obtain a carboxyl modified bacterial cellulose membrane.
[0082] The carboxyl modification process is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution at a mass ratio of 1:10. The bacterial cellulose membrane is then immersed in the TEMPO / NaBr aqueous solution for 50 min, with a mass ratio of TEMPO to bacterial cellulose membrane of 1:80. Subsequently, a 5 wt% NaClO solution is added, and the pH of the system is controlled at 10. The membrane is then immersed for another 2 h under mechanical stirring, with a mass ratio of TEMPO to NaClO of 1:100.
[0083] (2) Preparation of precursor-loaded bacterial cellulose scaffolds
[0084] The carboxyl-modified bacterial cellulose membrane was placed in a 2 mol / L Mg(NO3)2 precursor solution and allowed to stand for 0.5 h, then frozen at -20°C for 12 h; then transferred to a vacuum freeze dryer and dried at -50°C and 8 Pa for 24 h to obtain a Mg(NO3)2-loaded bacterial cellulose scaffold.
[0085] (3) Preparation of multifunctional protective nanopaper loaded with Mg(OH)2
[0086] The bacterial cellulose scaffold was placed in a microreactor with the same structure as in Example 1. The reaction flask contained a 0.05 mol / L NaCl solution, and the temperature was maintained at 40°C using a water bath outside the flask. A 2 mol / L NaOH solution was placed in a constant-pressure dropping funnel and added dropwise to the reaction flask at a rate of 8 ml / min. The solution was stirred evenly to form an alkaline reaction solution. The alkaline reaction solution in the reaction flask was dynamically circulated in the microreactor and reacted with the bacterial cellulose scaffold for 10 h. After the reaction, the scaffold was washed with deionized water and dried by hot pressing at 50°C to obtain the multifunctional protective nanopaper loaded with Mg(OH)2.
[0087] (4) Application of multifunctional protective nanopaper loaded with Mg(OH)2
[0088] Multifunctional protective nanopaper loaded with Mg(OH)2 was used as the inner lining of the apparatus. The paper sample to be protected (Whatman 1001 model paper) was placed in the middle of the lining, while a control group consisting of a blank paper sample without any treatment was set up. To illustrate the technical superiority of the nanopaper prepared by this technology compared with the bio-enzyme-induced mineralization film prepared by patent document CN115928495A, protection group A (nanopaper prepared by this invention) and protection group B (bio-enzyme-induced mineralization film prepared by patent document CN115928495A) were set up for comparison. The three groups of paper samples were placed in an oven at 80°C and 65% relative humidity (refer to ISO 5630-3) for accelerated aging for 10 days to simulate the aging and degradation process of paper cultural relics under long-term preservation.
[0089] Degree of polymerization: The degree of polymerization of paper is measured using the copper ethylenediamine solution viscosity method according to ISO 5351. Specifically, an appropriate amount of the paper sample to be tested is weighed into a certain amount of copper ethylenediamine solution, shaken thoroughly to dissolve, and then its viscosity is measured using a viscometer under standard temperature conditions. The degree of polymerization is then calculated according to the method specified in ISO 5351. Each group of samples is tested three times, and the final degree of polymerization result is the average value.
[0090] pH: The pH value of the paper was determined using a HANNA pH meter (HI9125) in accordance with the method of GB / T13528-2015.
[0091] Colorimetry: The colorimetry of the paper was measured using a colorimeter (NR10QC) according to CIE-L*,a*,b* methods.
[0092] Table 4. Color difference, degree of polymerization, and pH of the multifunctional protective nanopaper loaded with Mg(OH)2 in Example 4 between the protected and unprotected groups.
[0093]
[0094] The results of the accelerated aging experiment after 10 days in Example 4 are shown in Table 3. The paper samples in the protected group showed no significant color change, the degree of polymerization only decreased from 936 to 892, and the paper pH increased from the initial 7.13 to 7.92. In contrast, the paper in the unprotected group turned yellow, and after 10 days, the degree of polymerization dropped sharply from 936 to 765, and the paper pH decreased from the initial 7.13 to 6.25. This indicates that the multifunctional protective nanopaper liner loaded with Mg(OH)2 in Example 4 can effectively slow down the aging process of paper. The comparison between protected group A and protected group B shows that the nanopaper prepared by this technology has a more significant protective effect on paper.
[0095] Example 5
[0096] (1) Carboxyl modification of bacterial cellulose membranes:
[0097] The bacterial cellulose membrane was washed with distilled water, placed on gauze, and squeezed for 10 minutes to remove excess free water. Then it was added to a tetramethylpiperidine nitride oxychloride TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification to obtain a carboxyl modified bacterial cellulose membrane.
[0098] The carboxyl modification process is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution at a mass ratio of 1:10. The bacterial cellulose membrane is then immersed in the TEMPO / NaBr aqueous solution for 50 min, with a mass ratio of TEMPO to bacterial cellulose membrane of 1:80. Subsequently, a 5 wt% NaClO solution is added, and the pH of the system is controlled at 10. The membrane is then immersed for another 2 h under mechanical stirring, with a mass ratio of TEMPO to NaClO of 1:100.
[0099] (2) Preparation of MgSO4-loaded bacterial cellulose scaffolds
[0100] The carboxyl-modified bacterial cellulose membrane was placed in a 2 mol / L MgSO4 precursor solution and allowed to stand for 0.5 h, then frozen at -20 °C for 12 h; then transferred to a vacuum freeze dryer and dried at -50 °C and 8 Pa for 24 h to obtain a MgSO4-loaded bacterial cellulose scaffold.
[0101] (3) Preparation of multifunctional protective nanopaper loaded with Mg(OH)2
[0102] The bacterial cellulose scaffold was placed in a microreactor with the same structure as in Example 1. The reaction flask contained a 0.05 mol / L NaCl solution, and the temperature was maintained at 30°C using a water bath outside the flask. A 3 mol / L NH3 solution was placed in a constant-pressure dropping funnel and added dropwise to the reaction flask at a rate of 8 ml / min. The solution was stirred evenly to form an alkaline reaction solution. The alkaline reaction solution in the reaction flask was dynamically circulated in the microreactor and reacted with the bacterial cellulose scaffold for 10 h. After the reaction, the scaffold was washed with deionized water and dried by hot pressing at 50°C to obtain the multifunctional protective nanopaper loaded with Mg(OH)2.
[0103] (4) Application of multifunctional protective nanopaper loaded with Mg(OH)2
[0104] Multifunctional protective nanopaper loaded with Mg(OH)2 was used as the inner lining of the apparatus. The paper sample to be protected (Whatman 1001 model paper) was placed in the middle of the lining, while a control group consisting of an untreated blank paper sample was set up. To illustrate the technical superiority of the nanopaper prepared by this technology compared with the bio-enzyme-induced mineralization film prepared by patent document CN115928495A, protection group A (nanopaper prepared by this technology) and protection group B (bio-enzyme-induced mineralization film prepared by patent document CN115928495A) were set up for comparison. The three groups of paper samples were placed in an oven at 80°C and 65% relative humidity (refer to ISO 5630-3) for accelerated aging for 10 days to simulate the aging and degradation process of paper artifacts under long-term preservation.
[0105] Degree of polymerization: The degree of polymerization of paper is measured using the copper ethylenediamine solution viscosity method according to ISO 5351. Specifically, an appropriate amount of the paper sample to be tested is weighed into a certain amount of copper ethylenediamine solution, shaken thoroughly to dissolve, and then its viscosity is measured using a viscometer under standard temperature conditions. The degree of polymerization is then calculated according to the method specified in ISO 5351. Each group of samples is tested three times, and the final degree of polymerization result is the average value.
[0106] pH: The pH value of the paper was determined using a HANNA pH meter (HI9125) in accordance with the method of GB / T13528-2015.
[0107] Colorimetry: The colorimetry of the paper was measured using a colorimeter (NR10QC) according to CIE-L*,a*,b* methods.
[0108] Limiting Oxygen Index (LOI): The limiting oxygen index (LOI) of the sample is analyzed using a limiting oxygen index tester. A 100mm*15mm sample is placed in the combustion chamber, and the oxygen content in the atmosphere is adjusted to find the lowest oxygen concentration that supports continuous combustion.
[0109] Table 5. Color difference, degree of polymerization, and pH of the multifunctional protective nanopaper loaded with Mg(OH)2 in Example 5 between the protected and unprotected groups.
[0110]
[0111] The results of the accelerated aging experiment after 10 days in Example 5 are shown in Table 5. The paper samples in the protected group showed no significant color change, the degree of polymerization only decreased from 926 to 875, and the paper pH increased from the initial 7.16 to 7.86. In contrast, the paper in the unprotected group turned yellow, and after 10 days, the degree of polymerization dropped sharply from 926 to 718, and the paper pH decreased from the initial 7.16 to 6.04. This indicates that the multifunctional protective nanopaper liner loaded with Mg(OH)2 in Example 5 can effectively slow down the aging process of paper. The comparison between protected group A and protected group B shows that the nanopaper prepared by this technology has a more significant protective effect on paper.
[0112] The limiting oxygen index of the multifunctional protective nanopaper loaded with Mg(OH)2 was tested. The results showed that the limiting oxygen index of the nanopaper was greater than 40, making it difficult to burn and thus exhibiting excellent flame retardant properties.
Claims
1. A method for preparing a multifunctional protective nanopaper loaded with magnesium compounds, characterized in that, Includes the following steps: (1) Carboxyl modification of bacterial cellulose membrane: The bacterial cellulose membrane was washed with distilled water, placed on gauze, and squeezed to remove excess water; It was then added to a tetramethylpiperidine nitride TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification to obtain a carboxyl-modified bacterial cellulose membrane; (2) Preparation of precursor-loaded bacterial cellulose scaffold: The carboxyl-modified bacterial cellulose membrane was placed in a magnesium salt precursor solution and allowed to stand for 0.5 to 2 hours, then frozen at -20 to -80°C for 1 to 12 hours; then transferred to a vacuum freeze dryer and dried for 12 to 36 hours to obtain the precursor-loaded bacterial cellulose scaffold. (3) Preparation of multifunctional protective nanopaper loaded with magnesium compounds: The bacterial cellulose scaffold is placed in a microreactor, and the alkaline reaction solution is dynamically circulated in the microreactor and reacted with the bacterial cellulose scaffold. The reaction temperature is 30-70℃ and the reaction time is 0.5-24h. After the reaction is completed, the nanopaper is washed with deionized water and dried to obtain the multifunctional protective nanopaper loaded with magnesium compounds. The structure of the microreactor in step (3) is as follows: one end of the reactor tank is connected to the heating bottle through a pipe, the other end of the reactor tank is connected to the peristaltic pump through a pipe, and the outlet of the peristaltic pump is connected to the heating bottle, thereby forming a circulation system of reactor tank, peristaltic pump and reaction bottle; a constant pressure dripping funnel is inserted into the heating bottle from the top.
2. The method for preparing multifunctional protective nanopaper according to claim 1, characterized in that, In step (1), the washed bacterial cellulose membrane is a semi-transparent wet film with a thickness of 20-100µm.
3. The method for preparing multifunctional protective nanopaper according to claim 1, characterized in that, In step (1), the carboxyl modification process is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution at a mass ratio of 1:(2-20), and the bacterial cellulose membrane is immersed in the TEMPO / NaBr aqueous solution for 30-60 minutes, wherein the mass ratio of TEMPO to the bacterial cellulose membrane is 1:(20-200); then, a NaClO solution with a concentration of 5-10wt% is added, the pH value of the system is controlled to be 9.5-10.5, and the immersion is continued for 0.5-2 hours under mechanical stirring, wherein the mass ratio of TEMPO to NaClO is 1:(20-200).
4. The method for preparing multifunctional protective nanopaper according to claim 1, characterized in that, In step (2), the precursor solution is magnesium chloride, magnesium sulfate or magnesium nitrate, with a concentration of 0.1 to 5 mol / L.
5. The method for preparing multifunctional protective nanopaper according to claim 1, characterized in that, In step (2), the freeze-drying temperature of the vacuum freeze dryer is -30 to -80°C, and the vacuum degree is 1 to 10 Pa.
6. The method for preparing multifunctional protective nanopaper according to claim 1, characterized in that, In step (3), the magnesium salt is magnesium hydroxide or magnesium carbonate.
7. The method for preparing multifunctional protective nanopaper according to claim 1, characterized in that, In step (3), the alkaline reaction solution refers to a mixture prepared by placing a 0.1-10 mol / L NH3 water or NaOH solution, or a 0.5-5 mol / L Na2CO3, K2CO3 or NH4HCO3 solution, in a constant pressure dropping funnel and adding it dropwise at a rate of 2-10 ml / min to a flask containing a substrate solution and stirring; the substrate solution is a 0.05-2 mol / L NaCl solution.
8. The method for preparing multifunctional protective nanopaper according to claim 1, characterized in that, In step (3), the drying method is freeze drying under vacuum conditions of -80 to -30°C or hot pressing drying at 30 to 80°C.
9. The multifunctional protective nanopaper loaded with magnesium compounds prepared by the method for preparing a multifunctional protective nanopaper loaded with magnesium compounds according to any one of claims 1 to 8.
10. The application of the multifunctional protective nanopaper loaded with magnesium compounds according to claim 9, characterized in that, It serves as a multifunctional protective material for paper cultural relics, offering deacidification, flame retardancy, and antibacterial properties.