A method for deacidification and reinforcement of paper with a vaterite-type calcium carbonate and modified nanocellulose

Abstract

The present application belongs to the technical field of paper deacidification, and particularly relates to a method for deacidifying and reinforcing paper by using nanocellulose and vaterite calcium carbonate. The method uses vaterite calcium carbonate as a deacidifying agent and γ-aminopropyl triethoxysilane modified nanocellulose as a reinforcing agent to achieve deacidification and reinforcement of paper. The concentration of the vaterite calcium carbonate dispersion is 5-20 g / L, the concentration of the modified nanocellulose dispersion is 0.5-5 g / L, and the dispersing agents for both are ethanol. The method has good deacidification, reinforcement and anti-aging effects on paper.

Description

Technical Field

[0001] This invention belongs to the field of paper deacidification technology, specifically relating to a method for deacidifying and reinforcing paper using aragonite-type calcium carbonate and modified nanocellulose. Background Technology

[0002] Paper artifacts are traces and authentic records of historical development, playing an irreplaceable and vital role in the recording, accumulation, protection, and dissemination of human history and culture. However, with the passage of time, a large number of old archives and documents are experiencing accelerated damage. Due to acidification, paper often shows varying degrees of aging, yellowing, and even fragmentation into paper scraps. This problem has long plagued collection institutions such as libraries, archives, and museums at all levels.

[0003] Paper acidification is a significant factor affecting the preservation time of paper archives. Cellulose is an important component of paper. Under acidic conditions, cellulose degrades, causing its molecular chains to break, resulting in shorter fiber lengths and reduced interlocking forces, thus decreasing paper strength (Wang Zhen. Archival Science Communications, 2021). Currently, the generally accepted effective means to solve the problem of acidification in paper documents is deacidification treatment. The principle is to penetrate alkaline substances into the paper through different media, and interact with the paper fibers through adhesion and bonding to neutralize the free acid and maintain a certain alkali reserve, thereby achieving the purpose of continuous deacidification (Zhang Cui. Inner Mongolia Science and Technology and Economy, 2023).

[0004] Literature reports indicate that materials used for deacidification are mostly alkaline, including metal bicarbonates (calcium bicarbonate, magnesium bicarbonate, etc.), metal hydroxides (calcium hydroxide, magnesium hydroxide), amine salts, and other molecular compounds (Giorgi R, Dei L, Ceccato M, et al., Langmuir, 2002). Among these, calcium carbonate, as a papermaking raw material, has the advantages of moderate alkalinity and low toxicity, thus attracting researchers' attention. In 2019, Researchers prepared deacidifying agents with a concentration of 20 g / L by dispersing calcium carbonate in ethanol and isopropanol solvents, respectively. After deacidification by both solvents, the pH value of the paper increased from 4.8 to between 8 and 9. J, Kadivec M, Kunaver M, et al. Heritage Science, 2019. Palladino et al. used 20 g / L calcium carbonate supplemented with nanocellulose to deacidify textiles. After treatment, the pH value of the paper reached 7.3, and the mechanical properties were significantly improved. Artificial aging revealed that calcium carbonate slowed down the degradation of cotton products (Palladino N, Hacke M, Poggi G, et al. Nanomaterials, 2020.). This demonstrates that the use of calcium carbonate can significantly improve paper acidification. However, the high concentration used can easily cause secondary damage to the treated paper. This is because the calcium carbonate used above is calcite-type calcium carbonate, which has low reactivity and requires a high concentration to achieve the deacidification requirements.

[0005] In paper reinforcement, polymers, starches, and chitosans are commonly chosen as reinforcing materials (Yang D, Stimpson TC, Soucy J, et al. Cellulose, 2019; Watcharakitti J, Nimnuan J, Krusong K, et al. Polymers, 2023; Ni S, Liu N, Fu Y, et al. Progress in Organic Coatings, 2021). However, these materials also present some problems, such as starch's susceptibility to mold growth and polymers' low film strength at low concentrations. Furthermore, due to their significant differences in properties compared to paper, they can easily cause secondary damage. Therefore, nanocellulose has gained attention due to its closer similarity to paper fiber structure and properties, along with its high strength and high specific surface area. Cellulose nanofibers prepared using the TEMPO oxidation method are particularly popular due to their high yield and minimal fiber damage (Zeng J, Zeng Z, Cheng Z, et al. Sci. (Rep, 2021.), but this method will produce carboxyl groups on cellulose molecules, affecting the deacidification effect, and water is present in both the preparation and dispersion process, which will cause the treated paper to wrinkle when it is air-dried. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a safe and effective deacidifying agent and a reinforcing agent with good deacidification and reinforcement effects, as well as a method for deacidifying and reinforcing paper.

[0007] The method for deacidifying and reinforcing paper using aragonite-type calcium carbonate and modified nanocellulose is as follows: Aragonite-type calcium carbonate, used as a deacidifying agent, is prepared into an ethanol dispersion, and modified nanocellulose, used as a reinforcing agent, is also prepared into an ethanol dispersion. The dispersions are then sprayed onto aged paper using a vacuum spray bottle.

[0008] Aragonite-type calcium carbonate was chosen as a deacidifying agent to improve the pH value and alkali resistance of the paper, reducing the amount of raw materials used. Aragonite-type calcium carbonate differs from calcite; it is extremely rare in nature and unlike the single crystals of calcite, it is typically a polycrystalline spherical aragonite composed of multiple nano-sized spheroids. As a metastable phase of calcium carbonate, aragonite has high solubility and surface free energy, reducing secondary damage to the paper during processing. Modified nanocellulose was chosen as a reinforcing agent to improve paper strength. The amino groups in nanocellulose can neutralize the carboxyl groups on the cellulose chains, mitigating the adverse effects of deacidification, while also improving the dispersion stability of nanocellulose in ethanol.

[0009] The preparation method of aragonite-type calcium carbonate is as follows: Sodium carbonate is weighed and dissolved in 25% ethanol solution, calcium nitrate and hexadecyltrimethylammonium bromide (CTAB) are weighed and dissolved in 25% ethanol solution, sodium carbonate solution is added to calcium nitrate solution at a rate of 80 mL / min using a peristaltic pump, and the reaction is carried out at 10℃ with a stirring rate of 1250 rpm for 10 min, and finally filtered to obtain aragonite-type calcium carbonate.

[0010] The mass ratio of sodium carbonate, calcium nitrate, and hexadecyltrimethylammonium bromide is 1:3.1:0.024.

[0011] The preparation method of modified nanocellulose is as follows:

[0012] (1) The pulp soaked in hydrochloric acid and then dissolved was placed in a three-necked flask, distilled water was added, and after sonication for 20 minutes, oxidized cellulose fibers were obtained by TEMPO oxidation.

[0013] (2) Disperse oxidized cellulose fibers in water and sonicate for 30 min to obtain nanocellulose (CNFs). Adjust the pH of the dispersion to 4 with acetic acid and stir at 1000 rpm for 10 min at room temperature to obtain nanocellulose dispersion.

[0014] (3) Mix γ-aminopropyltriethoxysilane (APTES) with ethanol, adjust the pH of the mixture to 4 using acetic acid, and then add it to the nanocellulose dispersion in step (2) and stir at room temperature for 24 hours.

[0015] The mass ratio of γ-aminopropyltriethoxysilane, ethanol, and nanocellulose is 1:3:0.2.

[0016] (4) After the reaction, the dispersion was microwaved for 5 minutes using a microwave oven with a power of 700W, and finally filtered to obtain modified nanocellulose (NH2-CNFs).

[0017] The specific treatment methods for deacidification and reinforcement are as follows:

[0018] (1) Weigh out the granules of aragonite-type calcium carbonate and place them in a beaker. Add ethanol and sonicate for 5 minutes to prepare a dispersion of deacidifying agent with a concentration of 5-20 g / L. Put this deacidifying agent dispersion into a vacuum spray bottle and spray it evenly on the aged paper in four batches. Place it in a fume hood to air dry naturally.

[0019] (2) Weigh the modified nanocellulose and place it in a beaker. Add ethanol and sonicate for 5 minutes to prepare a dispersion of 0.5-5 g / L of reinforcing agent. Put this reinforcing agent dispersion into a vacuum spray bottle and spray it evenly on the aged paper that has been deacidified in four batches. Place it in a fume hood and let it air dry naturally.

[0020] The treated aged paper was left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH), and the pH value was determined according to GB / T1545—2008 "Determination of acidity or alkalinity of water extracts from paper, paperboard and pulp".

[0021] Alkali reserves were determined according to GB / T 24998—2010 "Determination of Alkali Reserves in Paperboard and Paperboard".

[0022] The tensile strength was determined according to GB / T 12914—2018 "Determination of tensile strength of paper and paperboard - constant rate tensile test".

[0023] Folding endurance was determined according to GB / T 457—2008 "Determination of folding endurance of paper and paperboard";

[0024] Tear strength was determined according to GB / T 455—2002 "Determination of tear strength of paper and paperboard";

[0025] The aforementioned method for deacidifying and reinforcing paper uses aged paper from the 1980 issue of "Popular Cinema" magazine, with a basis weight of 50.0 ± 1.0 g / m³. 2 pH is 4.6, alkaline storage is

[0026] 0.0131 mol / kg.

[0027] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0028] 1. This invention uses aragonite-type calcium carbonate as a paper deacidifying agent, which expands the application range of this crystal form. This crystal form of calcium carbonate is easy to prepare, has high reactivity, and can achieve good deacidification effect with a lower concentration.

[0029] 2. This invention uses modified nanocellulose as a paper strengthening agent. The stability of modified nanocellulose in ethanol is greatly improved, and the amino groups on the APTES molecular chain can significantly reduce the carboxyl group content on cellulose, so that no additional acidic substances are added while strengthening the paper. At the same time, due to the interaction between APTES and nanocellulose, the strengthened paper has better anti-aging effect and hydrophobic properties.

[0030] 3. This invention utilizes the deacidifying effect of aragonite-type calcium carbonate to improve the acidity and alkaline storage of paper, slow down the corrosion of paper by acid, and extend the life of paper; it utilizes the reinforcing effect of modified nanocellulose to improve the mechanical properties of paper, enhance its anti-aging ability, and help extend the shelf life of paper. Attached image description:

[0031] Figure 1 Fourier transform infrared spectrum of the aragonite-type calcium carbonate prepared in Example 1.

[0032] Figure 2 The XRD pattern of the aragonite-type calcium carbonate prepared in Example 1 is shown.

[0033] Figure 3 The image shows the SEM spectrum of the aragonite-type calcium carbonate prepared in Example 1.

[0034] Figure 4 This is a TEM image of the modified nanocellulose prepared in Example 1.

[0035] Figure 5 This is a SEM image of aged paper after deacidification and reinforcement in Example 1.

[0036] Figure 6 The relationship between the amount of aragonite-type calcium carbonate used and the pH value of deacidified paper and alkali storage.

[0037] Figure 7 The relationship between the amount of modified nanocellulose and the tensile strength of the reinforced paper.

[0038] Figure 8 The relationship between the amount of modified nanocellulose and the folding endurance of the reinforced paper.

[0039] Figure 9 The relationship between the amount of modified nanocellulose and the tear strength of the reinforced paper. Detailed Implementation

[0040] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the reagents used are commercially available unless otherwise specified.

[0041] Example 1

[0042] 2.65 g of sodium carbonate was dissolved in 100 mL of 25% ethanol solution. 8.2 g of calcium nitrate and 0.0625 g of hexadecyltrimethylammonium bromide (CTAB) were dissolved in 100 mL of 25% ethanol solution. The sodium carbonate solution was added to the calcium nitrate solution using a peristaltic pump at a rate of 80 mL / min. The mixture was reacted at 1250 rpm for 10 min at 10 °C. Finally, the mixture was filtered to obtain aragonite-type calcium carbonate. The Fourier transform infrared spectroscopy (FTIR) was used to analyze the calcium carbonate. Figure 1 As shown), XRD (as shown) Figure 2 (as shown) and SEM (such as Figure 3 Characterization methods (as shown) have demonstrated that spheroidal calcium carbonate was obtained.

[0043] Place 0.2g of the above-mentioned aragonite-type calcium carbonate into a beaker, add 20mL of ethanol, and sonicate for 5min to prepare deacidifying agent A.

[0044] Take 5g (octane-dry weight) of bleached coniferous sulfate pulp board, cut it into small pieces and place it in a beaker. Add 800mL of 0.1M hydrochloric acid, let it stand for 24 hours, and then grind it with a high-speed blender to obtain pulp. Weigh 1g (octane-dry weight) of the obtained pulp and place it in a three-necked flask. Add 100mL of water, sonicate for 20 minutes, and then add 0.15g of sodium bromide, 0.024g of TEMPO (tetramethylpiperidine oxide), and 3.75mL of sodium hypochlorite. After reacting for 1 hour, add another 3.75mL of sodium hypochlorite and continue reacting for 1 hour. This reaction is carried out at room temperature and with stirring at 1000r / min. During the reaction, 0.1M sodium hydroxide or 0.1M hydrochloric acid was added to control the pH of the reaction system to be stable at 10.0. After the reaction was completed, the oxidized cellulose fibers were obtained by filtration. 0.5g of the above oxidized cellulose fibers (dry weight) was weighed and dispersed in 50mL of deionized water. The dispersion of nanocellulose (CNFs) was prepared by ultrasonic disruption for 30min. The pH of the nanocellulose dispersion was adjusted to 4 using acetic acid. The dispersion was stirred at 1000rpm for 10min at room temperature to obtain the nanocellulose dispersion.

[0045] 2.5 mL of γ-aminopropyltriethoxysilane (APTES) and 7.5 mL of ethanol were measured into a beaker, and the pH of the mixture was adjusted to 4 using acetic acid. Then, it was added to the nanocellulose dispersion. After reacting for 24 h, the dispersion was microwave-heated for 5 min. Finally, the modified nanocellulose (NH2-CNFs) was obtained by filtration. After modification, the carboxyl content decreased from 1.68 mmol / g to 0.66 mmol / g.

[0046] Weigh 0.06 g (dry weight) of the above modified nanocellulose and place it in a beaker. Add 20 mL of ethanol and sonicate for 5 min to prepare reinforcement agent A.

[0047] A full page (26cm x 18cm) of the 1980 issue of the magazine "Popular Cinema" weighs approximately 2.5g, with a basis weight of approximately 50.0g / m³. 2 The above-mentioned deacidifying and reinforcing agents are sequentially sprayed onto the aged paper, and the specific process is as follows:

[0048] Deacidifying agent A is placed in a vacuum spray bottle and sprayed evenly on the aged paper in four applications. The paper is then placed in a fume hood to air dry naturally. Then, reinforcing agent A is placed in the same vacuum spray bottle and sprayed evenly on the deacidified aged paper in four applications. The paper is then placed in a fume hood to air dry naturally.

[0049] After natural drying, the paper was left to stand in a constant temperature and humidity environment (23±1℃, 50±2%RH) for 24 hours. The pH value, alkali resistance, tensile strength, folding endurance, tear strength, color difference, and whiteness of the treated paper were then measured (referred to as "after treatment" in the table). The results were analyzed using SEM images. Figure 5 It can be observed that aragonite-type calcium carbonate is distributed on the surface of the paper. At the same time, a portion of the paper that has been left to stand for 24 hours is subjected to dry heat aging treatment at 105±2℃ for 72 hours, and the relevant properties of the paper sample are tested (referred to as aged in the table).

[0050] The results are shown in Table 1 below:

[0051] Table 1

[0052]

[0053] After protective treatment, the water contact angle of aged paper increased from 50° to 83°.

[0054] Example 2

[0055] Weigh 0.1g of aragonite-type calcium carbonate and place it in a beaker. Add 20mL of ethanol and sonicate for 5min to prepare deacidifying agent B.

[0056] The reinforcing agent dispersion is the same as in Example 1.

[0057] A full page (26cm × 18cm) of the 1980 issue of the magazine "Popular Cinema" was cut. Deacidifying agent B was sprayed onto the aged paper, and it was allowed to air dry naturally. Then, reinforcing agent A was sprayed onto the deacidified aged paper, following the same process as in Example 1. The paper was then left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH) before measuring its pH value, alkali storage, color difference, and whiteness. Simultaneously, a portion of the paper that had been left to stand for 24 hours was subjected to dry heat aging treatment at 105±2℃ for 72 hours, and the relevant properties of the paper samples were tested.

[0058] The results are shown in Table 2 below:

[0059] Table 2

[0060]

[0061] Example 3

[0062] Weigh 0.3g of aragonite-type calcium carbonate and place it in a beaker. Add 20mL of ethanol and sonicate for 5min to prepare deacidifying agent C.

[0063] The reinforcing agent dispersion is the same as in Example 1.

[0064] A full page (26cm × 18cm) of the 1980 magazine "Popular Cinema" was cut off. Deacidifying agent C was sprayed onto the aged paper and allowed to air dry naturally. Then, reinforcing agent A was sprayed onto the deacidified aged paper. The specific process was the same as in Example 1. After completion, the paper was left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH) and the pH value, alkali storage, color difference value and whiteness were measured. At the same time, a portion of the paper that had been left to stand for 24 hours was subjected to dry heat aging treatment at 105±2℃ for 72 hours and the relevant properties of the paper samples were tested.

[0065] The results are shown in Table 3 below:

[0066] Table 3

[0067]

[0068]

[0069] Example 4

[0070] Weigh 0.4g of aragonite-type calcium carbonate and place it in a beaker. Add 20mL of ethanol and sonicate for 5min to prepare deacidifying agent D.

[0071] The reinforcing agent dispersion is the same as in Example 1.

[0072] A full page (26cm × 18cm) of the 1980 magazine "Popular Cinema" was cut off. Deacidifying agent D was sprayed onto the aged paper and allowed to air dry naturally. Then, reinforcing agent A was sprayed onto the deacidified aged paper. The specific process was the same as in Example 1. After completion, the paper was left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH) and the pH value, alkali storage, color difference value and whiteness were measured. At the same time, a portion of the paper that had been left to stand for 24 hours was subjected to dry heat aging treatment at 105±2℃ for 72 hours and the relevant properties of the paper samples were tested.

[0073] The results are shown in Table 4 below:

[0074] Table 4

[0075]

[0076] Example 5

[0077] Weigh 0.01 g (dry weight) of the above modified nanocellulose and place it in a beaker. Add 20 mL of ethanol and sonicate for 5 min to prepare reinforcement agent B.

[0078] The deacidifying agent dispersion is the same as in Example 1.

[0079] A full page (26cm × 18cm) of the 1980 magazine "Popular Cinema" was cut off. Deacidifying agent A was sprayed onto the aged paper, and it was allowed to air dry naturally. Then, reinforcing agent B was sprayed onto the aged paper, following the same process as in Example 1. After completion, the paper was left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH) and then the tensile strength, folding endurance, tear strength, color difference value, and whiteness were measured. At the same time, a portion of the paper that had been left to stand for 24 hours was subjected to dry heat aging treatment at 105±2℃ for 72 hours, and the relevant properties of the paper samples were tested.

[0080] The results are shown in Table 5 below:

[0081] Table 5

[0082]

[0083] Example 6

[0084] Weigh 0.02 g (dry weight) of the above modified nanocellulose and place it in a beaker. Add 20 mL of ethanol and sonicate for 5 min to prepare the reinforcing agent C.

[0085] The deacidifying agent dispersion is the same as in Example 1.

[0086] A full page (26cm × 18cm) of the 1980 magazine "Popular Cinema" was cut off. Deacidifying agent A was sprayed onto the aged paper, and it was allowed to air dry naturally. Then, reinforcing agent C was sprayed onto the aged paper, following the same process as in Example 1. After completion, the paper was left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH) and then the tensile strength, folding endurance, tear strength, color difference value, and whiteness were measured. At the same time, a portion of the paper that had been left to stand for 24 hours was subjected to dry heat aging treatment at 105±2℃ for 72 hours, and the relevant properties of the paper samples were tested.

[0087] The results are shown in Table 6 below:

[0088] Table 6

[0089]

[0090] Example 7

[0091] Weigh 0.1g (dry weight) of the above modified nanocellulose and place it in a beaker. Add 20mL of ethanol and sonicate for 5min to prepare the reinforcing agent D.

[0092] The deacidifying agent dispersion is the same as in Example 1.

[0093] Approximately 2.5g of a full page of the 1980 magazine "Popular Cinema" was cut off. Deacidifying agent A was sprayed onto the aged paper, and it was allowed to air dry naturally. Then, reinforcing agent D was sprayed onto the aged paper, following the same process as in Example 1. After completion, the paper was left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH) before its tensile strength, folding endurance, tear strength, color difference value, and whiteness were measured. At the same time, a portion of the paper that had been left to stand for 24 hours was subjected to dry heat aging treatment at 105±2℃ for 72 hours, and the relevant properties of the paper samples were tested.

[0094] The results are shown in Table 7 below:

[0095] Table 7

[0096]

[0097] Comparative Example 1

[0098] Weigh 0.2g of commercially available calcite-type calcium carbonate and place it in a beaker. Add 20mL of ethanol and sonicate for 5 minutes to prepare deacidifying agent E.

[0099] The reinforcing agent dispersion is the same as in Example 1;

[0100] A full page (26cm × 18cm) of the 1980 issue of the magazine "Popular Cinema" was cut off. Deacidifying agent E was sprayed onto the paper and allowed to dry naturally. Then, the reinforcing agent A was sprayed onto the paper and allowed to dry naturally. After drying, the paper was left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH). The pH value, alkali storage, tensile strength, folding endurance, tear strength, color difference value, and whiteness were measured.

[0101] The results are shown in Table 8 below:

[0102] Table 8

[0103]

[0104]

[0105] By analyzing and comparing Example 1 and Comparative Example 1, it can be seen that, at the same concentration, the pH value and alkali storage of paper treated with aragonite-type calcium carbonate are significantly higher than those of calcite-type calcium carbonate.

[0106] Comparative Example 2

[0107] Weigh 0.01g (dry weight) of nanocellulose and place it in a beaker. Add 12mL of ethanol and 8mL of water, and sonicate for 5min to prepare reinforcement agent E.

[0108] Approximately 2.5g of a full page of the 1980 magazine "Popular Cinema" was cut off, and deacidifying agent A and reinforcing agent E were sprayed onto the paper respectively (same as in Example 5). After completion, the paper was left to stand for 24 hours in a constant temperature and humidity environment (23±1℃, 50±2%RH) and then the tensile strength, folding endurance and tear strength were measured. At the same time, a portion of the paper that had been left to stand for 24 hours was subjected to dry heat aging treatment at 105±2℃ for 72 hours, and the relevant properties of the paper sample were tested (after aging).

[0109] The results are shown in Table 9 below:

[0110] Table 9

[0111]

[0112] Comparative analysis of Example 5 and Comparative Example 2 shows that, at the same concentration, although the modification weakens the ability of nanocellulose to improve paper strength, it improves its anti-aging ability. After aging, the tensile strength, folding endurance, and tear strength of the sprayed nanocellulose paper sample decreased by 6.4%, 41.7%, and 20.9%, respectively. However, after the modified nanocellulose paper was reinforced, the decreases were 4.4%, 30.4%, and 8.0%, respectively. All three values ​​were significantly reduced.

[0113] Therefore, the paper deacidifying agent and paper strengthening agent prepared by the present invention use calcium carbonate and pulp as raw materials, which improves the pH value, alkali storage and tensile strength of paper and can maintain them after aging.

[0114] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for deacidifying and reinforcing paper using aragonite-type calcium carbonate and modified nanocellulose, characterized in that, The method is as follows: aragonite-type calcium carbonate, used as a deacidifying agent, and modified nanocellulose, used as a reinforcing agent, are respectively prepared into ethanol dispersions, and then sprayed onto aged paper through a vacuum spray bottle. The method for preparing the aragonite-type calcium carbonate is as follows: Sodium carbonate is weighed and dissolved in a 25% ethanol solution, calcium nitrate and hexadecyltrimethylammonium bromide are weighed and dissolved in a 25% ethanol solution, the sodium carbonate solution is added to the calcium nitrate solution at a rate of 80 mL / min using a peristaltic pump, the mixture is stirred and reacted at 10℃ and 1250 rpm for 10 min, and the mixture is filtered to obtain the aragonite-type calcium carbonate. The preparation method of the modified nanocellulose is as follows: (1) The pulp that has been soaked in hydrochloric acid and loosened was placed in a three-necked flask, distilled water was added, and after sonication for 20 minutes, oxidized cellulose fibers were obtained by TEMPO oxidation. (2) Nanocellulose CNFs were prepared by dispersing oxidized cellulose fibers in water and ultrasonically breaking them for 30 min. The pH of the dispersion was adjusted to 4 using acetic acid and stirred at 1000 rpm at room temperature to obtain a nanocellulose dispersion. (3) Mix γ-aminopropyltriethoxysilane with ethanol, adjust the pH of the mixture to 4 with acetic acid, and then add it to the nanocellulose dispersion in step (2) and stir at room temperature for 24 hours. (4) After the reaction, the dispersion was heated by microwave and filtered to obtain modified nanocellulose NH2-CNFs.

2. The method for deacidifying and reinforcing paper using aragonite-type calcium carbonate and modified nanocellulose according to claim 1, characterized in that, The mass ratio of sodium carbonate, calcium nitrate, and hexadecyltrimethylammonium bromide is 1:3.1:0.

024.

3. The method for deacidifying and reinforcing paper using aragonite-type calcium carbonate and modified nanocellulose according to claim 1, characterized in that, In step (3), the mass ratio of γ-aminopropyltriethoxysilane, ethanol and nanocellulose is 1:3:0.

2.

4. The method for deacidifying and reinforcing paper using aragonite-type calcium carbonate and modified nanocellulose according to claim 1, characterized in that, Step (4) Microwave heating: The microwave oven power is 700W and the microwave heating time is 5min.

5. The method for deacidifying and reinforcing paper using aragonite-type calcium carbonate and modified nanocellulose according to claim 1, characterized in that, The concentration of the aragonite-type calcium carbonate ethanol dispersion is 5-20 g / L.

6. The method for deacidifying and reinforcing paper using aragonite-type calcium carbonate and modified nanocellulose according to claim 1, characterized in that, The concentration of the modified nanocellulose ethanol dispersion is 0.5-5 g / L.

7. The method for deacidifying and reinforcing paper using aragonite-type calcium carbonate and modified nanocellulose according to claim 1, characterized in that, The spraying method is as follows: First, spray the ethanol dispersion of aragonite-type calcium carbonate evenly in four coats. After the paper is air-dried naturally, spray the ethanol dispersion of modified nanocellulose evenly in four coats and let it air-dry naturally.

Images