Paper protectant with enhanced, antibacterial mildew and ultraviolet aging resistance and application

Abstract

The application belongs to the field of paper protection, and particularly relates to a paper protection agent with the functions of strengthening, antibacterial and antifungal and anti-UV aging and application. The protection agent is composed of nanocellulose and N-doped carbon quantum dots. 2 The amount of nanocellulose is 0.1-1 mg / cm 2 The amount of N-doped carbon quantum dots is 0.5-4 mg / cm The dispersant is an isopropanol aqueous solution with a volume ratio of 80 / 20. The combination of nanocellulose and N-doped carbon quantum dots in the application has the effects of strengthening, antibacterial and antifungal and anti-UV aging on the aging paper, and has no obvious influence on the color difference and whiteness of the treated paper. The protection agent has remarkable effects, is green and environment-friendly, and has a simple protection method, short treatment time and easy implementation, and has important significance for promoting the protection process of the aging paper.

Description

Technical Field

[0001] This invention belongs to the field of paper protection, specifically relating to a paper protectant and its application with strengthening, antibacterial, antifungal, and anti-UV aging functions. Background Technology

[0002] Paper artifacts, as carriers of civilization, bear witness to the rise and fall of a nation and possess immeasurable historical value. my country has conducted relatively in-depth research on the preservation of paper artifacts. However, due to various adverse effects such as intentional damage, production methods, and microbial contamination, these paper items have long suffered severe acidification, aging, yellowing, and brittleness; some documents have even turned to powder. Many paper artifacts have suffered irreparable damage due to microbial erosion. Therefore, strengthening, antibacterial, antifungal, and anti-aging properties of aged paper have become important research directions for many researchers.

[0003] When microorganisms proliferate on paper, their metabolic waste lowers the paper's pH value, accelerates aging, and ultimately causes the paper to yellow and become brittle. Extracellular enzymes secreted by mold degrade organic matter such as cellulose, not only damaging the paper's structure and reducing its mechanical properties, but also causing the paper to clump together, making it impossible to read. Furthermore, the colored pigments secreted by these molds leave mold spots on the paper, severely damaging the original appearance of the artifact. This not only obscures ink marks but also affects its aesthetic appeal; if not completely removed, it can diminish the artifact's inherent value. Moreover, mold products are mostly organic acids, which further reduce the paper's mechanical properties, causing yellowing and brittleness. Therefore, antibacterial and anti-mold protection for paper artifacts is particularly important.

[0004] Currently, antibacterial treatment of paper can be divided into two aspects: antibacterial treatment of the paper itself and antibacterial treatment of the storage space. Among these, chemical fumigation is the most widely used method for antibacterial treatment of paper, using chemical reagents such as polyoxymethylene and phosphine. However, the toxicity of these reagents can seriously harm the skin and respiratory system of archive managers and readers.

[0005] Polymers used for reinforcement include polyvinyl acetate, polyacrylic acid, and polyvinyl alcohol, but these synthetic materials suffer from poor polymer stability and poor compatibility with paper fibers. Some natural polymers, such as gelatin, chitosan, and cellulose, have also been used for paper reinforcement. Among these, nanocellulose, with its optical transparency, high specific surface area, high crystallinity, high strength, biodegradability, and colloidal dispersion stability, has become one of the most promising and widely researched solutions for paper reinforcement.

[0006] In existing technologies, the enhancement, antibacterial and antifungal properties, and protection against ultraviolet aging of paper cultural relics are mostly carried out separately. The increase in reagents and operating procedures not only increases costs but also harms the surrounding environment. More importantly, with the increase in the use of chemical agents, the damage to paper cultural relics also increases. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a multifunctional protective agent that is green, natural, safe, and integrates reinforcement, antibacterial, antifungal, and UV-resistant properties for paper artifacts. This multifunctional protective agent is composed of nanocellulose and nitrogen-doped carbon quantum dots. Nanocellulose strengthens and reinforces the paper, while the nitrogen-doped carbon quantum dots provide antibacterial, antifungal, and UV-resistant protection. In this invention, the nanocellulose is prepared using the peracetic acid method, retaining most of the hemicellulose and having a low carboxyl content, which helps improve the paper's reinforcement effect. The nitrogen-doped carbon quantum dots in the protective agent have carbon sources derived from apigenin and nitrogen sources derived from 3-aminopropyltriethoxysilane, exhibiting excellent antibacterial and antifungal effects.

[0008] The method for preparing nanocellulose provided by this invention includes the following steps:

[0009] (1) Cut the 5g dry pulp board into pieces, place it in a beaker, add 800mL of 0.1M hydrochloric acid solution and soak for 24h, then use a household blender to crush it to obtain pulp and filter it.

[0010] (2) Add 1 g of filtered pulp with an oven-dry weight to 50 mL of 4 wt% peracetic acid solution and homogenize at 16000 rpm for 5 min.

[0011] (3) After adjusting the pH of the solution to 4.8, the pulp was added to a three-necked flask and reacted at 85°C for 45 min. After filtration, 4 wt% peracetic acid solution was added again. This step was repeated 4 times. The pulp was then washed with deionized water until the pH was neutral. Nanocellulose was obtained by processing with a high-pressure homogenizer (500 bar) for 30 min.

[0012] The method for preparing N-doped carbon quantum dots provided by the present invention is as follows: 30 mg of apigenin and 2-5 mL of 3-aminopropyltriethoxysilane (the molar ratio of apigenin and 3-aminopropyltriethoxysilane is 1:80-200) are added to 30 mL of ethanol and dissolved. Then, the solution is transferred to a 50 mL high-pressure reactor and reacted at 210 °C for 10 h. After the reaction, the solution is filtered through a 0.22 μM microporous membrane to obtain an N-doped carbon quantum dot dispersion.

[0013] The protective agent of this invention is used for strengthening, antibacterial and antifungal properties, and UV aging protection of aged paper. The specific application method is as follows: Nanocellulose and N-doped carbon quantum dots are prepared into an isopropanol suspension. The protective agent suspension is then coated onto 26cm × 18cm paper in multiple applications using a glass rod, and then placed in a vacuum drying oven at 30°C for vacuum drying. The amount of nanocellulose used is 0.1-1 mg / cm³. 2 In paper, the amount of nitrogen-doped carbon quantum dots used is 1-4 mg / cm³. 2 Paper.

[0014] The isopropanol solution is an aqueous solution of isopropanol with a volume ratio of 80 / 20.

[0015] The lignin content of the prepared nanocellulose was determined according to GB / T 47-1989.

[0016] The hemicellulose content of the prepared nanocellulose was determined according to GB / T 2677.9-1994.

[0017] The treated and aged paper was left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH). The tensile strength, folding endurance and tear strength of the aged paper before and after treatment were determined according to GB / T 12914-2018, GB / T 457-2008 and GB / T 455-2002, respectively.

[0018] The paper deacidification, antibacterial, antifungal, and UV-resistant aging protection agents used in the above-mentioned paper application employed paper from the 1980 issue of "Popular Cinema" magazine, with a basis weight of 53.0 ± 1.0 g / m³. 2 The pH value is 4.6-4.7.

[0019] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0020] (1) The nanocellulose prepared by the peracetic acid method in this protective agent removes lignin while retaining most of the hemicellulose. The retention of hemicellulose has a certain effect on improving the paper strength.

[0021] (2) The N-doped carbon quantum dots synthesized in this protective agent can play an obvious antibacterial and anti-mildew effect when applied to paper, and the application of N-doped carbon quantum dots can enable paper to have a certain ability to resist ultraviolet aging.

[0022] (3) This protective agent has the functions of paper strengthening, antibacterial and mildew prevention, and UV aging prevention. It is not only green and safe, but also reduces the damage to paper cultural relics caused by repeated use of drugs. Attached Figure Description

[0023] Figure 1 The fluorescence emission spectrum of the N-doped carbon quantum dots prepared in Example 1 (in the figure, EX represents the excitation wavelength);

[0024] Figure 2 TEM image of the nanocellulose prepared in Example 1;

[0025] Figure 3 The effect of nanocellulose dosage on the folding endurance of paper samples before and after dry heat aging;

[0026] Figure 4The effect of nanocellulose dosage on the tear strength of paper samples before and after dry heat aging;

[0027] Figure 5 The effect of nanocellulose dosage on the tensile strength of paper samples before and after dry heat aging;

[0028] Figure 6 The effect of N-CQDs dosage on the folding endurance of paper samples before and after UV aging;

[0029] Figure 7 The effect of N-CQDs dosage on the tear strength of paper samples before and after UV aging;

[0030] Figure 8 The effect of N-CQDs dosage on the tensile strength of paper samples before and after UV aging;

[0031] Figure 9 The inhibitory effect of N-CQDs on Aspergillus niger after being applied to paper samples;

[0032] Figure 10 The inhibitory effect of N-CQDs on Staphylococcus aureus after being applied to paper samples;

[0033] Figure 11 The inhibitory effect of N-CQDs on Escherichia coli after being applied to paper samples;

[0034] Figure 12 The effect of CQDs on the inhibition of Aspergillus niger after being applied to the paper sample in Comparative Example 1 is shown. Detailed Implementation

[0035] The present invention will be described in further detail below with reference to specific embodiments. These embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention in any way.

[0036] Example 1

[0037] A 5g oven-dry pulp board was cut into small pieces, placed in a beaker, and soaked in 800mL of 0.1M hydrochloric acid solution for 24 hours. The pulp was then blended using a household high-speed blender to obtain paper pulp. A 1g oven-dry pulp was added to 50mL of 4wt% peracetic acid solution and homogenized at 16000rpm for 5 minutes. After adjusting the pH to 4.8, the pulp was added to a three-necked flask and reacted at 85℃ for 45 minutes. The mixture was then filtered, and 4wt% peracetic acid was added again. This process was repeated four times. The pulp was then washed with deionized water until the pH was neutral. Finally, it was homogenized using a high-pressure homogenizer (500bar) for 30 minutes to obtain nanocellulose. The test results of hemicellulose and lignin in the prepared nanocellulose are shown in Table 1 below.

[0038] Table 1

[0039] Raw pulp (%) 3.45 16.28 Nanocellulose (%) 0.6 8.28

[0040] 30 mg of apigenin and 3 mL of 3-aminopropyltriethoxysilane were dissolved in 30 mL of ethanol, then transferred to a 50 mL high-pressure reactor and reacted at 210 °C for 10 h. After the reaction, the N-doped carbon quantum dot dispersion was obtained by filtration through a 0.22 μM microporous membrane.

[0041] The above-mentioned nanocellulose and N-doped carbon quantum dots were added to an isopropanol aqueous solution with a volume ratio of 80 / 20 to prepare a 20 mL suspension. This suspension was then coated onto aged paper measuring approximately 26 cm × 18 cm using a glass rod in multiple applications. The treated paper samples were placed in a vacuum drying oven and dried at 30°C. The amount of nanocellulose used was 0.6 mg / cm³. 2 The amount of nitrogen-doped carbon quantum dots used in the paper is 0.5 mg / cm³. 2 Paper.

[0042] The experimental paper was from the 1981 issue of "Popular Cinema" magazine. After drying, the paper samples were left to stand for 24 hours at 23±1℃ and 50±2%RH. The tensile index, tear strength, folding endurance, color difference, and whiteness (before aging) of the treated paper samples were then measured. At the same time, some of the paper samples that had been left to stand for 24 hours were subjected to dry heat aging at 105℃±2℃ for 72 hours and then irradiated with 340nm ultraviolet light for 72 hours. The relevant properties of the paper were then tested (after aging).

[0043] Example 2

[0044] 30 mg of apigenin was dissolved in 30 mL of ethanol, along with 2 mL and 5 mL of 3-aminopropyltriethoxysilane. The solution was then transferred to a 50 mL high-pressure reactor and reacted at 210 °C for 10 h. After the reaction, the solution was filtered through a 0.22 μM microporous membrane to obtain an N-doped carbon quantum dot dispersion. The N-doped carbon quantum dot stock solution was characterized using a fluorescence spectrophotometer. It was found that with the addition of 2 mL of 3-aminopropyltriethoxysilane (to provide an alkaline environment), apigenin could not be completely dissolved, and the resulting N-doped carbon quantum dots showed no fluorescence. With the addition of 5 mL of 3-aminopropyltriethoxysilane, the fluorescence intensity of the resulting N-doped carbon quantum dot stock solution significantly weakened.

[0045] Example 3

[0046] The nanocellulose and N-doped carbon quantum dots prepared in Example 1 were added to an isopropanol aqueous solution with a volume ratio of 80 / 20 to prepare a 20 mL suspension. This suspension was then coated onto aged paper measuring approximately 26 cm × 18 cm using a glass rod in multiple applications. The paper was then placed in a vacuum drying oven and dried at 30°C. The amounts of nanocellulose used were 0.1, 0.2, and 1 mg / cm³, respectively. 2 The amount of nitrogen-doped carbon quantum dots on the paper sample was fixed at 0.5 mg / cm³. 2Paper. After drying, the paper samples were left to stand for 24 hours at 23±1℃ and 50±2%RH. The tensile index, tear strength, folding endurance, color difference, and whiteness of the treated paper samples were then measured (before dry heat aging). At the same time, some of the paper samples that had been left to stand for 24 hours were subjected to dry heat aging treatment at 105℃±2℃ for 72 hours, and the relevant properties of the paper samples were tested (after dry heat aging).

[0047] The fixed N-CQD dosage is 0.5 mg / cm³. 2 The whiteness and color difference properties of paper samples were tested by varying the amount of nanocellulose (CNF). The results are shown in Table 2.

[0048] Table 2

[0049]

[0050] Example 4

[0051] The nanocellulose and N-doped carbon quantum dots prepared in Example 1 were added to an isopropanol aqueous solution with a volume ratio of 80 / 20 to prepare a 20 mL suspension. The suspension was then coated in portions using a glass rod onto a surface approximately 480 cm². 2 The aged paper (26cm × 18cm) was placed in a vacuum drying oven and dried at 30℃. The amount of nanocellulose used was fixed at 0.6mg / cm³. 2 Paper, with N-doped carbon quantum dots added at concentrations of 0.25, 1, and 2 mg / cm³. 2 Paper samples, after drying, were left to stand at 23±1℃ and 50±2%RH for 24 hours. The tensile index, tear strength, folding endurance, color difference, and whiteness (before aging) of the treated paper were then measured. Simultaneously, some of the paper samples after 24 hours of standing were irradiated under 340nm ultraviolet light for 72 hours. The tensile index, tear strength, folding endurance, color difference, and whiteness (after ultraviolet aging) of the paper samples before and after ultraviolet aging were then measured. The amount of nanocellulose was fixed at 0.6 mg / cm³. 2 The whiteness and color difference performance of the paper samples were tested by varying the amount of N-CQD used. The results are shown in Table 3.

[0052] Table 3

[0053]

[0054] Example 5

[0055] The nanocellulose and N-doped carbon quantum dots prepared in Example 1 were added to an isopropanol aqueous solution with a volume ratio of 80 / 20 to prepare a 20 mL suspension. The suspension was then coated in portions using a glass rod onto a surface approximately 480 cm². 2 The aged paper (26cm × 18cm) was placed in a vacuum drying oven and dried at 30℃. The amount of nanocellulose used was fixed at 0.6mg / cm³. 2Paper with N-doped carbon quantum dots at concentrations of 0.5, 1, 2, and 4 mg / cm³. 2 The dried paper samples were used to measure the antibacterial and antifungal effects against Escherichia coli, Staphylococcus aureus, and Aspergillus niger.

[0056] Comparative Example 1

[0057] 30 mg of apigenin was dissolved in 30 mL of ethanol and then transferred to a 50 mL high-pressure reactor. The reaction was carried out at 210 °C for 10 h. After the reaction, the carbon quantum dot dispersion was obtained by filtration through a 0.22 μM microporous membrane.

[0058] The nanocellulose and carbon quantum dots obtained in Example 1 were added to an isopropanol aqueous solution with a volume ratio of 80 / 20 to prepare a 20 mL suspension, wherein the amount of nanocellulose was fixed at 0.6 mg / cm³. 2 Paper, with carbon quantum dots used at concentrations of 0.5, 1, 2, and 4 mg / cm³. 2 The paper is coated with a coating method and then placed in a vacuum drying oven at 30°C for vacuum drying.

[0059] Antibacterial experiments were conducted on paper coated with carbon quantum dots and nanocellulose, and it was found that the paper had no significant inhibitory effect on Aspergillus niger.

[0060] Comparative Example 2

[0061] Cut 5g of oven-dry cardboard into small pieces, place them in a beaker, add 800mL of 0.1M hydrochloric acid solution and soak for 24h. Then, use a household high-speed blender to grind the pulp for later use. Add 1g of oven-dry pulp to 50mL of 8M hydrochloric acid solution and homogenize at 16000rpm for 5min. Add the pulp to a three-necked flask under mechanical stirring (600rpm) and reflux at 110℃ for 4h. After the reaction, centrifuge at 6000r / min for 6min, remove the supernatant, disperse the precipitate with deionized water and place it in a dialysis bag with a molecular weight cutoff of 12000-14000. Dialyze with deionized water until neutral. Remove the dialyzed nanocellulose dispersion from the dialysis bag and treat it in an ice bath with a cell disruptor for 30min to ensure uniform dispersion, thus obtaining a nanocellulose dispersion.

[0062] A comparison of the tensile strength of paper coated with the two types of nanocellulose revealed that the nanocellulose prepared by the 4wt% peracetic acid method in Example 1 increased the tensile strength of the paper by 34.5%, while the nanocellulose prepared by the 8M hydrochloric acid solution acid degradation method in Comparative Example 2 increased the tensile strength of the paper by 26.2%.

Claims

1. A paper protectant with reinforcing, antibacterial, antifungal, and UV-resistant properties, characterized in that, The paper protectant is composed of nanocellulose and N-doped carbon quantum dots; wherein the mass ratio of nanocellulose to N-doped carbon quantum dots is 0.1-1:0.5-4. The method for preparing the N-doped carbon quantum dots is as follows: apigenin and 3-aminopropyltriethoxysilane are added to ethanol, dissolved, and then transferred to a 50mL high-pressure reactor. The mixture is then subjected to a solvothermal reaction at 210℃ for 10h, and the N-doped carbon quantum dot dispersion is obtained by filtration through a 0.22μM microporous membrane.

2. The paper protectant with reinforcing, antibacterial, antifungal, and anti-UV aging functions according to claim 1, characterized in that, The preparation method of the nanocellulose is as follows: (1) Cut the 5g dry pulp board into pieces, place it in a beaker, add 800mL of 0.1M hydrochloric acid solution and soak for 24h. Then, use a household blender to crush the pulp and filter it. (2) Add peracetic acid solution to the filtered pulp and homogenize it at 16000 rpm for 5 min; After adjusting the pH to 4.8, the pulp was added to a three-necked flask and reacted at 85°C for 45 minutes, then filtered. (3) After filtering, the pulp is re-added with peracetic acid solution and the above step (2) is repeated 4 times. The pulp is then washed with deionized water until the pH is neutral and then treated with a high-pressure homogenizer for 30 minutes to obtain nanocellulose.

3. The paper protectant with reinforcing, antibacterial, antifungal, and anti-UV aging functions according to claim 2, characterized in that, The peracetic acid solution has a mass fraction of 4%, the solid-liquid ratio of the dry weight of the pulp to 4 wt% peracetic acid is 1 g: 50 ml, and the pressure of the high-pressure homogenizer is 500 bar.

4. The paper protectant with reinforcing, antibacterial, antifungal, and anti-UV aging functions according to claim 1, characterized in that, The molar ratio of apigenin to 3-aminopropyltriethoxysilane is 1:80-200.

5. The application of a paper protectant with reinforcing, antibacterial, antifungal, and anti-UV aging functions according to any one of claims 1-4, characterized in that, The paper protectant is used to strengthen aged paper, provide antibacterial and antifungal properties, and protect against UV aging.

6. The application of the paper protectant with reinforcing, antibacterial, antifungal, and anti-UV aging functions according to claim 5, characterized in that, The application method is as follows: nanocellulose and N-doped carbon quantum dots are prepared into a suspension of isopropanol, and then the suspension is coated onto a 26cm×18cm paper in several batches using a glass rod, and then placed in a vacuum drying oven at 30°C for vacuum drying.

7. The application of the paper protectant with reinforcing, antibacterial, antifungal, and anti-UV aging functions according to claim 6, characterized in that, The isopropanol solution is an aqueous solution of isopropanol with a volume ratio of 80 / 20.

8. The application of the paper protectant with reinforcing, antibacterial, antifungal, and anti-UV aging functions according to claim 6, characterized in that, The dosage of nanocellulose is 0.1-1 mg / cm³. 2 In paper, the amount of nitrogen-doped carbon quantum dots used is 0.5-4 mg / cm³. 2 Paper.

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