Preparation and application of zinc-doped magnesium mineralized nanometer paper

Abstract

The application discloses a preparation method of zinc-doped magnesium mineralized nano paper, which comprises the following steps: soaking a bacterial cellulose membrane in a lithium chloride dimethylacetamide solution, and standing at room temperature for 4-10 hours to make the bacterial cellulose membrane fully swell; then adding the bacterial cellulose membrane into a tetramethylpiperidine N-oxide (TEMPO) / NaBr / NaClO aqueous solution system to perform carboxyl modification treatment; placing the bacterial cellulose membrane into a zinc nitrate solution, and stirring and reacting at a temperature of 40-60 DEG C to obtain a bacterial cellulose membrane loaded with nano ZnO; then placing the bacterial cellulose membrane into a magnesium nitrate solution for 0.5-2 hours; taking out the bacterial cellulose membrane and placing it into a micro reactor, and making an ammonium bicarbonate reaction solution flow dynamically and circulate to react with the bacterial cellulose membrane; and cleaning and drying. The application makes the nano fiber more easily combine with magnesium ions, improves the binding force and growth stability of the mineralized crystal, and improves the uniformity and loading of the alkaline particles, which is beneficial to the long-term and sustained release of alkaline substances.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of paper cultural relic protection and deacidification, and particularly relates to a preparation method of zinc-doped magnesium mineralized nano paper and application thereof in paper cultural relic protection. BACKGROUND

[0002] Paper cultural relics such as ancient books, archives and documents have important cultural and historical value. However, during the long-term protection of paper cultural relics, they are affected by the external environment and their own factors, and the paper fibers are prone to yellowing, decay, breakage, powdery aging, insect damage and mildew, etc., thereby leading to irreversible deterioration of paper cultural relics. The acidification of paper is a hydrolysis reaction of cellulose under acidic conditions, which leads to the breakage of β-glycosidic bonds, thereby reducing the degree of polymerization of cellulose and the mechanical properties of paper. At present, the acidification of paper is mainly solved by deacidification.

[0003] Paper deacidification refers to introducing alkaline substances into paper cultural relics to neutralize the acidic substances in the paper, while retaining a certain amount of alkaline substances (commonly known as alkali retention) in the paper to neutralize the acidic substances that may be generated thereafter. However, most of the current deacidification methods are through liquid or gas phase means to deacidify paper cultural relics. Liquid deacidification (for example, patent documents CN117661370A, CN117306309A, CN116791398A, CN116463885A and CN115748295A) usually needs to mix alkaline substances with solvents, but the use of solvents will cause problems such as fiber swelling and pigment fading to paper cultural relics that are sensitive to liquids. Gas deacidification (for example, patent documents CN117306309A, CN115216997A and CN113073495A) usually faces the dilemma of insufficient alkali reserve, and some gas deacidifiers may also cause the danger of combustion and explosion. Therefore, safe and durable deacidification methods for paper cultural relics still need to be further developed.

[0004] In addition, when mold or bacteria appear on the paper, they will rapidly reproduce on the paper using the fibers, starch paste, glue and other substances in the paper as nutrients, which will reduce the mechanical strength of the paper and cause perforation and other phenomena, greatly reducing the service life of the paper. In addition, the organic acids decomposed by mold or bacteria in the process of absorbing nutrients will increase the acidity of the paper and cause the hydrolysis of the paper fibers.

[0005] Patent document CN115928495A discloses a mineralized bacterial cellulose multifunctional protective lining paper for preventive protection of paper cultural relics and a preparation method and application thereof. Alkaline inorganic substances such as calcium carbonate, magnesium carbonate and hydroxyapatite are loaded on a bacterial fiber membrane with a three-dimensional nanometer network structure to form a multifunctional protective lining paper, which is used as a sandwich paper or a surface paper in contact with paper cultural relics, and has good paper deacidification and flame retardation protection effect. However, different charge groups have different mineralization abilities, and groups with lower electronegativity have weaker mineralization ability. The hydroxyl groups on the surface of the bacterial cellulose in CN115928495A have weak electronegativity, which is not conducive to the distribution and growth of inorganic particles, and has the disadvantages of slow mineralization speed, poor stability of inorganic particle combination and crystal growth, and uneven distribution of alkaline particles. In addition, the preparation method in the document cannot cope with paper degradation induced by mold or bacteria. SUMMARY

[0006] In order to overcome the above-mentioned defects of the prior art, the present application provides a preparation method of zinc-doped magnesium mineralized nanometer paper and its application in the protection of paper cultural relics, which can continuously neutralize the acid in the paper cultural relics and maintain the weak alkaline state of the paper microenvironment for a long time, and also endows the paper with antibacterial properties against common mold on the paper, thereby achieving the multifunctional protection of deacidification, flame retardation and antibacterial properties of paper cultural relics.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows.

[0008] The preparation method of the zinc-doped magnesium mineralized nanometer paper of the present application comprises the following steps:

[0009] (1) Swelling and carboxyl modification of bacterial cellulose membrane:

[0010] The bacterial cellulose membrane is washed with distilled water; it is soaked in a lithium chloride (LiCl) dimethylacetamide (DMAC) solution, and is left to swell at room temperature for 4-10 hours to obtain a transparent bacterial cellulose membrane; then it is added to a tetramethylpiperidinooxy (TEMPO) / NaBr / NaClO aqueous solution system for carboxyl modification treatment to obtain a carboxyl-modified bacterial cellulose membrane;

[0011] (2) Loading of nanometer zinc oxide (ZnO) on the bacterial cellulose membrane

[0012] immersing the carboxyl-modified bacterial cellulose membrane into a zinc nitrate solution, stirring and reacting at a temperature of 40-60°C for 0.5-2h, then adding an aqueous NaOH solution, and continuing to react at 40-60°C for 0.5-2h; after washing with deionized water, vacuum drying at a temperature of 110-130°C for 0.5-3h; to obtain a bacterial cellulose membrane loaded with nano-ZnO;

[0013] (3) preparing a zinc-doped magnesium mineralized nanometer paper

[0014] immersing the bacterial cellulose membrane loaded with nano-ZnO into a magnesium nitrate solution for 0.5-2h; then taking it out and placing it into a micro-reactor, and making an ammonium bicarbonate reaction solution flow dynamically in the micro-reactor and react with the bacterial cellulose membrane loaded with nano-ZnO, at a reaction temperature of 30-70°C for 0.5-24h; after the reaction, washing with deionized water and drying, the zinc-doped magnesium mineralized nanometer paper is obtained.

[0015] Preferably, in the step (1), the washed bacterial cellulose membrane is a semi-transparent wet film with a thickness of 20-100μm.

[0016] Preferably, in the step (1), the concentration of the lithium chloride dimethylacetamide solution is 3-5wt / v.

[0017] Preferably, in the step (1), the carboxyl-modification process is as follows: TEMPO and NaBr are mixed in a mass ratio of 1:(2-20) to prepare a TEMPO / NaBr aqueous solution, and then the bacterial cellulose membrane is immersed in the TEMPO / NaBr aqueous solution for 30-60min, with a mass ratio of TEMPO to bacterial cellulose membrane of 1:(20-200); then a NaClO solution with a concentration of 5-10wt% is added, the pH value of the system is controlled at 10-10.5, and the immersion is continued for 0.5-2h under mechanical stirring, with a mass ratio of TEMPO to NaClO of 1:(20-200).

[0018] Preferably, in the step (2), the zinc nitrate solution is an ethanol solution of zinc nitrate (Zn(NO3)2) with a concentration of 0.01-2mol / L; and the concentration of the aqueous NaOH solution is 0.01-1mol / L.

[0019] Preferably, in the step (3), the magnesium nitrate solution is an aqueous solution of Mg(NO3)2 with a concentration of 0.1-5 mol / L; the ammonium bicarbonate reaction solution refers to an aqueous solution of NH4HCO3 with a concentration of 0.1-10 mol / L, which is added dropwise into a flask containing a substrate solution at a rate of 2-10 ml / min to form a mixture by stirring; the substrate solution is an aqueous solution of NaCl or polyethylene glycol (PEG) with a concentration of 0.01-0.5 mol / L.

[0020] Preferably, in the step (3), the drying includes freeze-drying under vacuum at-80-30℃ or hot-press drying at 30-80℃.

[0021] Preferably, in the step (3), the micro-reactor has the structure that one end of a reactor tank is connected to a heating flask through a pipeline, the other end of the reactor tank is connected to a peristaltic pump through a pipeline, and the outlet of the peristaltic pump is connected to the heating flask, thereby forming a circulation system of the reactor tank, the peristaltic pump and the heating flask; a constant-pressure dropping funnel is inserted into the top of the heating flask.

[0022] A second object of the present application is to provide a zinc-doped magnesium mineralized nanometer paper prepared by the preparation method of the zinc-doped magnesium mineralized nanometer paper.

[0023] A third object of the present application is to provide an application of the zinc-doped magnesium mineralized nanometer paper as a paper-based cultural relic deacidification, flame-retardant, antibacterial multifunctional protective material. The protection mode includes that the mineralized nanometer paper is directly or indirectly contacted with the paper-based cultural relic. Specifically, the nanometer paper is contacted with the paper-based cultural relic as a sandwich paper or a surface paper; or can be used as a paperboard for a cultural relic box and a lining paper, a paperboard for a paper box of a cultural relic, a paperboard for a bag of a cultural relic, a back paper for a display of a cultural relic, or a lining paper for an exhibition of a cultural relic.

[0024] The present application utilizes bacterial cellulose nanofibers as a template, loads zinc oxide nanoparticles for in-situ growth, and controls the loading amount of nanoparticles by adjusting the reaction conditions; utilizes a dynamic circulation flow environment to make the crystal nuclei of zinc oxide and magnesium carbonate uniformly and slowly precipitate and mineralize in the three-dimensional network of bacterial cellulose, and evenly and highly disperses the small particles in the network of bacterial cellulose nanofibers, thereby improving the uniformity and loading amount of the alkaline particles, making the nanometer paper have strong alkalinity and large alkaline storage, and being beneficial to long-term and sustained release of alkaline substances to neutralize acidic substances in the microenvironment of a paper-based cultural relic; meanwhile, the high-loading organic-inorganic composite structure of the nanometer paper endows it with excellent flame retardancy, and the nanometer zinc oxide loaded by the nanometer paper also has an antibacterial effect on some common molds in paper.

[0025] Therefore, the zinc-doped magnesium mineralized nanometer paper is simple to prepare and convenient to apply, can be used as a protective material such as a cultural relic box lining paper, and realizes the multifunctional protection of paper cultural relics such as deacidification, flame retardation and antibiosis. The inorganic particles cannot be left on the surface or enter the inside of the paper cultural relics, avoid irreversible damage to the paper cultural relics, can well preserve the original structure and fiber morphology of the paper, and follow the principle of minimal intervention and reversibility of cultural relic protection. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A schematic diagram of a preparation method of the zinc-doped magnesium mineralized nanometer paper of the present application. DETAILED DESCRIPTION

[0027] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not used to limit the scope of the present application. In addition, it should be understood that those skilled in the art can make various modifications or changes to the present application after reading the content taught by the present application, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

[0028] Example 1

[0029] (1) Swelling and carboxyl modification of bacterial cellulose membrane:

[0030] The bacterial cellulose membrane is washed with distilled water; it is immersed in a 4%wt / v LiCl DMAC solution, and is placed at room temperature for 8h to make it swell sufficiently, and a transparent bacterial cellulose membrane is obtained; then it is added to a TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification treatment, and a carboxyl modified bacterial cellulose membrane is obtained.

[0031] The process of carboxyl modification treatment is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution with a mass ratio of 1:6, and then the bacterial cellulose membrane is immersed in the TEMPO / NaBr aqueous solution for 30min, and the mass ratio of TEMPO to the bacterial cellulose membrane is 1:50; then a 5wt% NaClO solution is added, the pH value of the system is controlled to be 10, and the immersion is continued for 2h under mechanical stirring, and the mass ratio of TEMPO to NaClO is 1:100.

[0032] (2) Loading of nano-ZnO on the bacterial cellulose membrane

[0033] The carboxyl-modified bacterial cellulose membrane was placed in a zinc nitrate ethanol solution with a concentration of 0.2 mol / L, and stirred at 50°C for 1 h, then a 0.4 mol / L NaOH aqueous solution was added, and stirring was continued at 50°C for 0.5 h. After the reaction was completed, the bacterial cellulose membrane was removed, washed with deionized water, and then placed in a 120°C oven for vacuum drying for 1 h. A bacterial cellulose membrane loaded with nano-ZnO was obtained.

[0034] (3) Preparation of zinc-doped magnesium mineralized nanometer paper

[0035] The bacterial cellulose membrane loaded with nano-ZnO was immersed in a magnesium nitrate solution with a concentration of 3 mol / L for 1 h. Then it was taken out and placed in a micro-reactor. The micro-reactor had the following structure: one end of the reactor tank was connected to a heating bottle through a pipeline, the other end of the reactor tank was connected to a peristaltic pump through a pipeline, and the outlet of the peristaltic pump was connected to the heating bottle, thereby forming a circulating system of a reactor tank, a peristaltic pump, and a reaction bottle. A constant-pressure dropping funnel was inserted into the top of the heating bottle. A 0.01 mol / L NaCl solution was added to the reaction bottle, and a water bath was used to maintain the temperature at 40°C. A 2 mol / L NH4HCO3 aqueous solution was placed in the constant-pressure dropping funnel and added to the reaction bottle at a rate of 5 ml / min to form an alkaline reaction solution under uniform stirring. The alkaline reaction solution in the reaction bottle was circulated dynamically in the micro-reactor and reacted with the bacterial cellulose membrane loaded with nano-ZnO for 2 h. After the reaction was completed, the bacterial cellulose membrane was washed with deionized water and then dried by hot pressing at 50°C to obtain zinc-doped magnesium mineralized nanometer paper.

[0036] (4) Application of zinc-doped magnesium mineralized nanometer paper

[0037] The zinc-doped magnesium mineralized nanometer paper was used as a lining for a container, and paper samples (Whatman 1001 model paper) that needed to be protected were placed in the middle of the lining. A control group was set up with untreated blank paper samples. The two groups of paper samples were placed in an oven at 80°C and 65% relative humidity (according to ISO 5630-3) for accelerated aging for 7 days to fully simulate the aging and degradation process of paper cultural relics during long-term storage.

[0038] Degree of polymerization: The degree of polymerization of the paper was measured according to ISO 5351 using the copper ethylenediamine solution viscosity method. Specifically, an appropriate amount of paper sample to be tested was weighed into a certain amount of copper ethylenediamine solution, shaken and dissolved, and then the viscosity was measured under standard temperature conditions using a viscometer. The degree of polymerization was then calculated according to the method specified in ISO 5351. Each sample was tested 3 times, and the final degree of polymerization result was taken as the average value.

[0039] pH: The pH of the paper was measured by a HANNA pH meter (HI9125) according to the method of GB / T 13528-2015.

[0040] Color: The color of the paper was measured by a color difference meter (NR10QC) according to the method of CIE-L*, a*, b*.

[0041] Limiting oxygen index: The limiting oxygen index (LOI) of the sample was analyzed by a limiting oxygen index tester, and the sample with a size of 100 mm*15 mm was placed in a combustion chamber, the oxygen content in the atmosphere was adjusted, and the lowest oxygen concentration supporting continuous combustion was found.

[0042] Inhibition zone: the well cultured E. coli and S. aureus were diluted to 108CFU / mL with sterile water, 50 μL of each was spread on the nutrient agar solid medium, the composite film cut into a 15.0 mm circle was placed in the middle of the medium, and the medium was placed in a 37°C microbial incubator for 24h. The size of the inhibition zone was measured, and each sample was tested in triplicate.

[0043] Table 1 Color difference, degree of polymerization and pH of the zinc-doped magnesium mineralized nanometer paper protection group and the unprotected group of paper of Example 1

[0044]

[0045] Table 2 Antibacterial properties of zinc-doped magnesium mineralized nanometer paper of Example 1

[0046]

[0047] The results of the paper samples after 7-day accelerated aging test in Example 1 are shown in Table 1, the paper samples of the protection group have no obvious color change, the degree of polymerization decreases from 950 to 932 only, and the pH of the paper increases from the initial 7.07 to 7.85. The color of the paper of the unprotected group turns yellow, and the degree of polymerization of the paper decreases sharply from 950 to 732 after 7 days, and the pH of the paper decreases from the initial 7.07 to 6.02. The diameter of the antibacterial circle of the zinc-doped magnesium mineralized nanometer paper (Table 1 and Table 2) indicates that it has good antibacterial effect. Therefore, the zinc-doped magnesium-loaded nanometer paper lining provided in the embodiment can effectively slow down the aging process of the paper.

[0048] The zinc-doped magnesium-loaded multifunctional protective nanometer paper was tested for limiting oxygen index, and the results showed that the limiting oxygen index of the nanometer paper was greater than 40, which was difficult to burn, and therefore had excellent flame retardant properties.

[0049] Example 2

[0050] (1) Swelling and carboxyl modification of bacterial cellulose film:

[0051] The bacterial cellulose membrane is washed with distilled water; it is immersed in a 3%wt / v LiCl DMAC solution, and is left to stand at room temperature for 8h to make it fully swollen, to obtain a transparent bacterial cellulose membrane; then it is added to a TEMPO / NaBr / NaClO aqueous solution system to perform carboxyl modification treatment, to obtain a carboxyl-modified bacterial cellulose membrane;

[0052] The carboxyl modification treatment process is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution in a mass ratio of 1:6, then the bacterial cellulose membrane is immersed in the TEMPO / NaBr aqueous solution for 30min, and the mass ratio of TEMPO to the bacterial cellulose membrane is 1:50; then a 5wt% NaClO solution is added, the pH value of the system is controlled to be 10, and the immersion is continued for 2h under mechanical stirring, and the mass ratio of TEMPO to NaClO is 1:100.

[0053] (2) Loading of nano-ZnO on the bacterial cellulose membrane

[0054] The carboxyl-modified bacterial cellulose membrane is immersed in a 0.3mol / L zinc nitrate ethanol solution, and is stirred at 50℃ for 1h, then a 0.6mol / L NaOH aqueous solution is added, and the stirring is continued at 50℃ for 0.5h; after the reaction is completed, the bacterial cellulose membrane is taken out, washed with deionized water, and then transferred to a 120℃ oven for vacuum drying for 1h; thus a bacterial cellulose membrane loaded with nano-ZnO is obtained.

[0055] (3) Preparation of zinc-doped magnesium mineralized nanometer paper

[0056] The bacterial cellulose membrane loaded with nano-ZnO is immersed in a 2mol / L magnesium nitrate solution for 1h; then it is taken out and placed in a microreactor, which has the same structure as that in Example 1, and a 0.05mol / L NaCl solution is added to the reaction bottle, and a water bath is used to keep the temperature at 40℃; a 3mol / L NH4HCO3 aqueous solution is placed in a constant-pressure dropping funnel, and is added to the reaction bottle at a rate of 5ml / min, to form an alkaline reaction solution under uniform stirring; the alkaline reaction solution in the reaction bottle is made to flow dynamically in the microreactor and react with the bacterial cellulose membrane loaded with nano-ZnO for 2h; after the reaction is completed, the bacterial cellulose membrane is washed with deionized water, and is dried by hot pressing at 50℃, to obtain zinc-doped magnesium mineralized nanometer paper.

[0057] (4) Application of zinc-doped magnesium mineralized nanometer paper

[0058] The zinc-doped magnesium mineralized nanopaper was used as the lining of the holder, and the paper samples (Whatman 1001 model paper) to be protected were placed in the middle of the lining, while the control group was the blank paper sample without any treatment. The two groups of paper samples were placed in an oven at 80°C and 65% relative humidity (referring to ISO 5630-3) for accelerated aging for 7 days to fully simulate the aging degradation process of paper cultural relics under long-term preservation.

[0059] The degree of polymerization, pH value, color, limiting oxygen index and antibacterial circle test were the same as in Example 1.

[0060] Table 3 Color difference, degree of polymerization and pH of the zinc-doped magnesium mineralized nanopaper protected group and the unprotected group of paper in Example 2

[0061]

[0062] Table 4 Antibacterial performance of the zinc-doped magnesium mineralized nanopaper in Example 2

[0063]

[0064] The results of the paper samples after 7 days of accelerated aging in Example 2 are shown in Table 3. The paper samples in the protected group had no obvious color change, the degree of polymerization decreased from 948 to only 898, and the pH of the paper increased from the initial 7.05 to 7.60. The paper in the unprotected group turned yellow, and the degree of polymerization of the paper decreased sharply from 948 to 746 after 7 days, and the pH of the paper decreased from the initial 7.05 to 6.10. The diameter of the antibacterial circle of the zinc-doped magnesium mineralized nanopaper (Tables 3 and 4) indicates that it has good antibacterial effect. It is shown that the zinc-doped magnesium mineralized nanopaper lining provided in this example can effectively slow down the aging process of the paper.

[0065] The zinc-doped magnesium mineralized multifunctional protective nanopaper was tested for limiting oxygen index, and the results showed that the limiting oxygen index of the nanopaper was greater than 40, and it was difficult to burn, thus having excellent flame retardant performance.

[0066] Example 3

[0067] (1) Swelling and carboxyl modification of bacterial cellulose membrane:

[0068] The bacterial cellulose membrane was washed clean with distilled water; it was soaked in a 4% wt / v LiCl DMAC solution, and was left to stand at room temperature for 8h to fully swell, obtaining a transparent bacterial cellulose membrane; then it was added to a TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification treatment, obtaining a carboxyl-modified bacterial cellulose membrane;

[0069] The process of carboxyl modification treatment is as follows: TEMPO and NaBr are prepared into a TEMPO / NaBr aqueous solution with a mass ratio of 1:6, and then the bacterial cellulose membrane is soaked in the TEMPO / NaBr aqueous solution for 30 min, with a mass ratio of TEMPO to bacterial cellulose membrane of 1:50; then a 5wt% NaClO solution is added, the pH value of the system is controlled at 10, and the soaking is continued for 2 h under mechanical stirring, with a mass ratio of TEMPO to NaClO of 1:100.

[0070] (2) Loading of nano-ZnO on the bacterial cellulose membrane

[0071] The carboxyl-modified bacterial cellulose membrane is placed in a 0.2 mol / L zinc nitrate ethanol solution, stirred at 50°C for 1.5 h, and then a 0.4 mol / L NaOH aqueous solution is added, and the stirring is continued at 50°C for 0.5 h; after the reaction is completed, the bacterial cellulose membrane is transferred out, washed with deionized water, and then transferred to a 120°C oven for vacuum drying for 1 h; thus a bacterial cellulose membrane loaded with nano-ZnO is obtained.

[0072] (3) Preparation of zinc-doped magnesium mineralized nanometer paper

[0073] The bacterial cellulose membrane loaded with nano-ZnO is placed in a 2.5 mol / L magnesium nitrate solution for 1 h; then it is taken out and placed in a micro-reactor with the same structure as in Example 1, a 0.3 mol / L NaCl solution is added to the reaction bottle, and a water bath is used to maintain the temperature at 40°C; a 4 mol / L NH4HCO3 aqueous solution is placed in a constant-pressure dropping funnel, and is added to the reaction bottle at a rate of 5 ml / min to form an alkaline reaction solution under uniform stirring; the alkaline reaction solution in the reaction bottle is circulated and flows dynamically in the micro-reactor to react with the bacterial cellulose membrane loaded with nano-ZnO for 2 h; after the reaction is completed, the bacterial cellulose membrane is washed with deionized water, and then dried by hot pressing at 50°C; thus a zinc-doped magnesium mineralized nanometer paper is obtained.

[0074] (4) Application of zinc-doped magnesium mineralized nanometer paper

[0075] The zinc-doped magnesium mineralized nanometer paper is used as a lining of a container, and paper samples (Whatman 1001 model paper) to be protected are placed in the lining, and a control group of untreated blank paper samples is set up. The two groups of paper samples are placed in an oven at 80°C and 65% relative humidity (referring to ISO 5630-3) for accelerated aging for 7 days to fully simulate the aging and degradation process of paper cultural relics under long-term preservation.

[0076] The degree of polymerization, pH value, color and inhibition zone test are the same as in Example 1.

[0077] Table 5 Color difference, degree of polymerization and pH of the zinc-doped magnesium mineralized nanometer paper of Example 3

[0078]

[0079] Table 6 Antibacterial performance of the zinc-doped magnesium mineralized nanometer paper of Example 3

[0080]

[0081] The results of the paper samples after the 7-day accelerated aging test in Example 3 are shown in Table 5. The paper samples in the protected group had no obvious color change, the degree of polymerization decreased from 938 to 897 only, and the pH of the paper increased from the initial 7.24 to 7.94. The paper samples in the unprotected group turned yellow, the degree of polymerization of the paper decreased sharply from 938 to 752 after 7 days, and the pH of the paper decreased from the initial 7.24 to 6.45. The diameter of the antibacterial circle of the zinc-doped magnesium mineralized nanometer paper (Table 5 and Table 6) indicates that it has good antibacterial effect. It is shown that the zinc-doped magnesium-loaded nanometer paper lining provided in the present embodiment can effectively slow down the aging process of the paper.

[0082] Example 4

[0083] (1) Swelling and carboxyl modification of bacterial cellulose film:

[0084] The bacterial cellulose film was washed with distilled water; it was immersed in a 4% wt / v LiCl DMAC solution, and was allowed to swell at room temperature for 8 h to obtain a transparent bacterial cellulose film; then it was added to a TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification treatment to obtain a carboxyl-modified bacterial cellulose film.

[0085] The carboxyl modification process was as follows: TEMPO and NaBr were prepared into a TEMPO / NaBr aqueous solution at a mass ratio of 1:6, and then the bacterial cellulose film was immersed in the TEMPO / NaBr aqueous solution for 30 min, with a mass ratio of TEMPO to bacterial cellulose film of 1:50; then a 5wt% NaClO solution was added, the pH value of the system was controlled at 10, and the immersion was continued for 2 h under mechanical stirring, with a mass ratio of TEMPO to NaClO of 1:100.

[0086] (2) Loading of nanometer ZnO on the bacterial cellulose film

[0087] The carboxyl-modified bacterial cellulose membrane was put into a zinc nitrate ethanol solution with a concentration of 0.2 mol / L, and stirred at 60°C for 1 h, then a 0.5 mol / L NaOH aqueous solution was added, and the stirring reaction was continued at 60°C for 1 h; after the reaction was completed, the bacterial cellulose membrane was transferred out, washed with deionized water, and then vacuum dried in an oven at 120°C for 1 h; a bacterial cellulose membrane loaded with nano-ZnO was obtained.

[0088] (3) Preparation of zinc-doped magnesium mineralized nanometer paper

[0089] The bacterial cellulose membrane loaded with nano-ZnO was immersed in a magnesium nitrate solution with a concentration of 4 mol / L for 1 h; then it was taken out and put into a micro-reactor with the same structure as in Example 1, a 0.3 mol / L NaCl solution was added to the reaction bottle, and a water bath was used to maintain the temperature at 40°C; a 6 mol / L NH4HCO3 aqueous solution was placed in a constant-pressure dropping funnel, and was added to the reaction bottle at a rate of 5 ml / min to form an alkaline reaction solution under uniform stirring; the alkaline reaction solution in the reaction bottle was circulated and flowed dynamically in the micro-reactor and reacted with the bacterial cellulose membrane loaded with nano-ZnO for 2 h; after the reaction was completed, the bacterial cellulose membrane was washed with deionized water, and then dried by hot pressing at 50°C to obtain zinc-doped magnesium mineralized nanometer paper.

[0090] (4) Application of zinc-doped magnesium mineralized nanometer paper

[0091] The zinc-doped magnesium mineralized nanometer paper was used as a lining in a container, and paper samples (Whatman 1001 model paper) that needed to be protected were placed in the middle of the lining, and a control group of untreated blank paper samples was set up. The two groups of paper samples were placed in an oven at 80°C and 65% relative humidity (according to ISO 5630-3) for accelerated aging for 7 days to fully simulate the aging and degradation process of paper cultural relics during long-term storage.

[0092] The degree of polymerization, pH value, color and inhibition zone test were the same as in Example 1.

[0093] Table 7 Color difference, degree of polymerization and pH of the zinc-doped magnesium mineralized nanometer paper of Example 4

[0094]

[0095] Table 8 Inhibition performance of the zinc-doped magnesium mineralized nanometer paper of Example 4

[0096]

[0097] The results of the paper samples after 7-day accelerated aging test in Example 4 are shown in Table 7. The paper samples in the protection group had no obvious color change, the degree of polymerization decreased from 974 to 932 only, and the paper pH increased from the initial 7.24 to 8.02. The paper samples in the non-protection group turned yellow, the degree of polymerization decreased sharply from 974 to 798 after 7 days, and the paper pH decreased from the initial 7.24 to 6.31. The diameter of the bacteriostatic circle (Tables 7 and 8) of the zinc-doped magnesium mineralized nano-paper showed that it had good bacteriostatic effect. It is shown that the zinc-doped magnesium nano-paper liner provided in the embodiment can effectively slow down the aging process of the paper.

[0098] Example 5

[0099] (1) Swelling and carboxyl modification of bacterial cellulose membrane

[0100] The bacterial cellulose membrane was washed with distilled water; it was immersed in a 3% wt / v LiCl DMAC solution, and was left to swell at room temperature for 8 h to obtain a transparent bacterial cellulose membrane; then it was added to a TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification treatment to obtain a carboxyl-modified bacterial cellulose membrane.

[0101] The carboxyl modification process was as follows: TEMPO and NaBr were prepared into a TEMPO / NaBr aqueous solution at a mass ratio of 1:6, and then the bacterial cellulose membrane was immersed in the TEMPO / NaBr aqueous solution for 30 min, with a mass ratio of TEMPO to bacterial cellulose membrane of 1:50; then a 5wt% NaClO solution was added, the pH value of the system was controlled at 10, and the immersion was continued for 2 h under mechanical stirring, with a mass ratio of TEMPO to NaClO of 1:100.

[0102] (2) Loading of nano-ZnO on the bacterial cellulose membrane

[0103] The carboxyl-modified bacterial cellulose membrane was placed in a 0.1 mol / L zinc nitrate ethanol solution, and was stirred at 60°C for 1 h, and then a 0.5 mol / L NaOH aqueous solution was added, and the stirring was continued at 60°C for 1 h; after the reaction was completed, the bacterial cellulose membrane was transferred out, washed with deionized water, and then transferred to a 120°C oven for vacuum drying for 1 h; and a bacterial cellulose membrane loaded with nano-ZnO was obtained.

[0104] (3) Preparation of zinc-doped magnesium mineralized nano-paper

[0105] The ZnO-loaded bacterial cellulose membrane was immersed in a magnesium nitrate solution with a concentration of 3 mol / L for 1 h. Then, it was taken out and placed in a microreactor with the same structure as that of Example 1. A NaCl solution with a concentration of 0.3 mol / L was injected into the reaction bottle, and a water bath was used to maintain the temperature at 40°C. An aqueous NH4HCO3 solution with a concentration of 5 mol / L was placed in a constant-pressure dropping funnel and added to the reaction bottle at a rate of 8 ml / min to form an alkaline reaction solution. The alkaline reaction solution in the reaction bottle was circulated and flowed dynamically in the microreactor to react with the ZnO-loaded bacterial cellulose membrane for 2 h. After the reaction, the product was washed with deionized water and dried by hot pressing at 50°C to obtain the zinc-doped magnesium mineralized nanometer paper.

[0106] (4) Application of zinc-doped magnesium mineralized nanometer paper

[0107] The zinc-doped magnesium mineralized nanometer paper was used as a lining in a device, and paper samples (Whatman 1001 model paper) that needed to be protected were placed in the middle of the lining. A control group of untreated blank paper samples was also set up. In order to demonstrate the technical superiority of the nanometer paper prepared by the present technology compared to the biologically enzyme-induced mineralized membrane prepared by the patent document CN115928495A, a protection group A (nanometer paper prepared by the present technology) and a protection group B (biologically enzyme-induced mineralized membrane prepared by the patent document CN115928495A) were set up. The three groups of paper samples were placed in an oven at 80°C and 65% relative humidity (refer to ISO 5630-3) to accelerate aging for 7 days, in order to fully simulate the aging and degradation process of paper cultural relics during long-term preservation.

[0108] The degree of polymerization, pH value, color and inhibition zone test were the same as in Example 1.

[0109] Table 9 Color difference, degree of polymerization and pH of the zinc-doped magnesium mineralized nanometer paper protection group and the unprotected group of paper in Example 3

[0110]

[0111] Table 10 Inhibition performance of the zinc-doped magnesium mineralized nanometer paper in Example 3

[0112]

[0113] The results of the paper samples after 7 days of accelerated aging experiment in Example 3 are shown in Table 5. The paper samples in the protected group had no obvious color change, the degree of polymerization decreased from 954 to 902 only, and the pH of the paper increased from the initial 7.35 to 7.97. The paper samples in the unprotected group turned yellow, the degree of polymerization of the paper decreased sharply from 954 to 748 after 7 days, and the pH of the paper decreased from the initial 7.35 to 6.43. The diameter of the bacteriostatic circle (Tables 9 and 10) of the zinc-doped magnesium mineralized nanometer paper showed that it had good bacteriostatic effect. It is shown that the zinc-doped magnesium-loaded nanometer paper lining provided in the embodiment can effectively slow down the aging process of the paper.

Claims

1. A method for preparing zinc-doped magnesium mineralized nanopaper, characterized in that, Includes the following steps: (1) Swelling and carboxyl modification of bacterial cellulose membranes: Wash the bacterial cellulose membrane with distilled water. The bacterial cellulose membrane was soaked in a lithium chloride dimethylacetamide solution and allowed to swell fully at room temperature for 4–10 hours to obtain a transparent bacterial cellulose membrane. Then, it was added to a tetramethylpiperidine nitride oxychloride TEMPO / NaBr / NaClO aqueous solution system for carboxyl modification treatment to obtain a carboxyl modified bacterial cellulose membrane. (2) Loading of nano zinc oxide on bacterial cellulose membranes The carboxyl-modified bacterial cellulose membrane was placed in a zinc nitrate solution and stirred at 40–60°C for 0.5–2 h. Then, an aqueous NaOH solution was added, and the reaction was continued at 40–60°C for another 0.5–2 h. After washing with deionized water, the membrane was vacuum dried at 110–130°C for 0.5–3 h to obtain a bacterial cellulose membrane loaded with nano-ZnO. (3) Preparation of zinc-doped magnesium mineralized nanopaper The bacterial cellulose membrane loaded with nano-ZnO was immersed in a magnesium nitrate solution for 0.5–2 hours; then it was removed and placed in a microreactor, where an ammonium bicarbonate reaction solution was dynamically circulated and reacted with the bacterial cellulose membrane loaded with nano-ZnO. The reaction temperature was 30–70°C and the reaction time was 0.5–24 hours. After the reaction was completed, the membrane was washed with deionized water and dried to obtain the zinc-doped magnesium mineralized nanopaper.

2. The method for preparing zinc-doped magnesium mineralized 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 zinc-doped magnesium mineralized nanopaper according to claim 1, characterized in that, In step (1), the concentration of the lithium chloride dimethylacetamide solution is 3-5% wt / v.

4. The method for preparing zinc-doped magnesium mineralized 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 10-10.5, 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).

5. The method for preparing zinc-doped magnesium mineralized nanopaper according to claim 1, characterized in that, In step (2), the zinc nitrate solution is an ethanolic solution of zinc nitrate with a concentration of 0.01 to 2 mol / L; the NaOH aqueous solution has a concentration of 0.01 to 1 mol / L.

6. The method for preparing zinc-doped magnesium mineralized nanopaper according to claim 1, characterized in that, In step (3), the magnesium nitrate solution is an aqueous solution of 0.1-5 mol / L Mg(NO3)2; the ammonium bicarbonate reaction solution is a mixture prepared by placing an aqueous solution of 0.1-10 mol / L NH4HCO3 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 an aqueous solution of 0.01-0.5 mol / L NaCl or a aqueous solution of polyethylene glycol (PEG).

7. The method for preparing zinc-doped magnesium mineralized nanopaper according to claim 1, characterized in that, In step (3), the drying includes freeze drying at -80 to 30°C under vacuum or hot pressing at 30 to 80°C.

8. The method for preparing zinc-doped magnesium mineralized nanopaper according to claim 1, characterized in that, The reactor tank is connected to a heating flask via a pipe, and the other end of the reactor tank is connected to a peristaltic pump via a pipe. The outlet of the peristaltic pump is 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 is inserted into the heating flask from the top.

9. Zinc-doped magnesium mineralized nanopaper prepared by the method for preparing zinc-doped magnesium mineralized nanopaper according to any one of claims 1 to 8.

10. The application of the zinc-doped magnesium mineralized nanopaper 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.

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