A cellulose-based multifunctional composite material capable of reinforcing paper and enhancing hydrophobicity of paper after deacidification of the paper

Abstract

This application discloses a cellulose-based multifunctional composite material that strengthens and enhances the hydrophobicity of paper after deacidification, belonging to the technical field of historical ancient paper artifact preservation and composite multifunctional materials. This application first prepares a cellulose-based grafted fluorinated copolymer, then mixes and reacts it with a metal hydroxide precursor to obtain the cellulose-based multifunctional composite material. This application utilizes the similarity between the fluorinated cellulose fragments in the multifunctional composite material and the composition and structure of paper to promote the penetration of the multifunctional composite material into the gaps between paper fibers and its binding with the paper cellulose during the paper deacidification process, thus achieving excellent strengthening and hydrophobic effects. Therefore, after deacidification, the paper possesses excellent mechanical strength and hydrophobicity, while also exhibiting weak alkalinity and high alkali reserve. Furthermore, the multifunctional composite material of this application also exhibits good dispersibility in fluorocarbon media and will be widely used in paper deacidification.

Description

Technical Field

[0001] This application belongs to the technical field of historical ancient paper cultural relics protection and composite multifunctional materials, and more specifically, it relates to a cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after paper is deacidified. Background Technology

[0002] The key cause of aging in paper artifacts is acidification and deliquescence. This is because the β-1,4 glycosidic bonds connecting glucose monomers in the paper's cellulose undergo gradual hydrolysis under acid catalysis, leading to a decrease in the degree of cellulose polymerization and a decline in the paper's mechanical strength, until the paper completely weathers into powder, losing all mechanical strength and its value for storage and preservation (Cultural Relics Conservation and Archaeological Science, 2008, 20: 85-94). Therefore, deacidification, consolidation, and hydrophobic treatments are particularly important for acidic paper artifacts.

[0003] Currently, significant progress has been made in the research and development of paper deacidification materials and processes both domestically and internationally. Some deacidification materials and processes have been successfully applied to the preventive preservation of paper archives and cultural relics (Acta Chimica Sinica, 2023, 81:309-318). Among them, the Bookkeeper deacidification process has been adopted by numerous libraries and archives, accounting for approximately 75% of the paper deacidification market. In recent years, while deacidifying paper, attention has also been paid to enhancing its mechanical strength and hydrophobicity, i.e., efforts have been made to develop multifunctional composite materials. For example, cellulose and its derivatives, which are similar to paper in composition and easy to bind, are introduced into multifunctional composite materials to strengthen paper strength; hydrophobic materials containing alkyl groups and their derivatives are introduced to improve the hydrophobicity of paper. For example, Amornkitbamrung et al. (RSC Advances, 2015, 5:32950-32961) used trimethylsilyl cellulose (TMSC) as a dispersing and reinforcing agent to uniformly disperse magnesium hydroxide (Mg(OH)2) in hexamethyldisiloxane (HMDSO). After deacidification treatment of paper, acidic paper became weakly alkaline, and the mechanical strength of acidic paper was significantly improved while exhibiting excellent hydrophobicity. However, this method is only a simple mechanical mixing of alkaline materials and reinforcing hydrophobic materials, which makes it difficult to ensure that the deacidification and reinforcing hydrophobic materials are uniformly embedded in the paper fibers. Huang et al. (Journal of Cultural Heritage, 2018, 34: 61-68) dispersed oleic acid-modified magnesium oxide in cyclohexane and soaked acidic paper. Not only did the pH value of the three types of acidic paper increase to about 8.0, but its 20s static water contact angle also increased from the original 50° to about 120°, showing excellent hydrophobicity. However, the drawback is that the composite material lacks compatibility with paper, and the paper strength is only slightly improved. Ma et al. (International Journal of Biologic Macromolecules, 2022, 207: 232-241) first uniformly coated cellulose (CNCS) onto acidic paper, then sprayed calcium carbonate (CaCO3) and polydimethylsiloxane (PDMS) dispersed in tetrahydrofuran solution onto the CNCS-coated acidic paper, and finally deposited methyltrimethoxysilane (MTMS) onto the acidic paper in the vapor phase. After treatment, the pH value of the acidic paper became 7.70. Due to the stepwise cellulose (CNCS) coating and vapor phase deposition, the mechanical strength and hydrophobicity of the paper were significantly improved. The tear strength of the paper increased by 26.51% compared with the untreated paper, and the static water contact angle reached 155.7°. Although this method may allow the deacidifying, reinforcing and hydrophobic materials to be uniformly dispersed in the gaps between the paper fibers, its multi-step treatment is not only cumbersome but also causes a certain degree of damage to the already fragile paper.Therefore, there is an urgent need to develop a multifunctional composite material that combines deacidification with reinforcement and hydrophobic properties.

[0004] Compared to common organic solvents such as methanol and ethanol, fluorocarbons (FCCs) are non-flammable, have low toxicity, and do not damage the ink, making them the mainstream solvent used in liquid-phase deacidification processes for paper (Journal of Cultural Heritage, 2019, 37: 137-147). However, the low surface activity of FCCs makes it difficult to stably disperse many inorganic and organic materials in FCC media, causing inconvenience to the deacidification operation and seriously affecting the paper deacidification efficiency. Among the three patents previously disclosed by the applicant's research group, patent CN108589411A (An attapulgite composite material and its application) effectively solved the problem of paper deacidification technology and could maintain the alkalinity of paper for a long time; patent CN114753186A (A paper deacidification composite material with high stability suspension dispersion in fluorocarbon medium and its preparation method and application) effectively solved the problem of high stability suspension dispersion of deacidification materials in fluorocarbon medium; and patent CN117107548A (A method for preparing and applying a composite deacidification material that gives paper high alkali content and hydrophobicity after deacidification treatment) effectively solved the problems of high alkali content and hydrophobicity after paper deacidification. The solutions to these problems have given existing deacidification materials a certain application prospect in paper treatment. However, with the continuous promotion of applications, the applicant has found that existing paper deacidification materials have problems such as almost no reinforcement performance or insufficient paper reinforcement performance after deacidification, and ineffective combination of paper deacidification materials and reinforcing hydrophobic materials. Therefore, further innovation of existing paper deacidification materials is needed to meet the application requirements.

[0005] Application content

[0006] To address the aforementioned problems in the existing technology, the technical problem to be solved by this application is to provide a cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after deacidification. This material, while possessing high dispersibility and high alkali content, should also strengthen paper and enhance its hydrophobicity after deacidification. Another technical problem to be solved by this application is to provide a method for preparing the aforementioned cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after deacidification. This method is characterized by its simplicity, safety, and environmental friendliness. A further technical problem to be solved by this application is to provide the application of the aforementioned cellulose-based multifunctional composite material in the functions of paper deacidification, strengthening, and hydrophobicity.

[0007] To solve the above-mentioned technical problems, the technical solution adopted in this application is as follows:

[0008] A method for preparing a cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after deacidification involves polymerizing a fluorinated monomer and a cellulose macromolecular initiator to obtain a cellulose-based grafted fluorinated copolymer, and then mixing the obtained cellulose-based grafted fluorinated copolymer with a metal hydroxide precursor and reacting the mixture to obtain the cellulose-based multifunctional composite material.

[0009] Preferably, the preparation process of the cellulose macromolecular initiator is as follows: cellulose, lithium chloride, N-bromosuccinimide (NBS) and 2-bromoisobutyryl bromide are added to N,N-dimethylacetamide for reaction. After the reaction is completed, the mixture is cooled to room temperature, filtered, washed, and vacuum dried to obtain the cellulose macromolecular initiator.

[0010] Preferably, the preparation process of the cellulose-based grafted fluorinated copolymer is as follows: under nitrogen protection, cellulose macromolecular initiator, fluorinated monomer, N,N,N',N”,N”-pentamethyldiethylenetriamine (PMDET A), CuBr catalyst and N,N-dimethylformamide solvent are taken and reacted. After the reaction is completed, the copolymer is separated, washed and dried to obtain the cellulose-based grafted fluorinated copolymer.

[0011] Preferably, the fluorinated monomer is 2-(perfluorooctyl)ethyl methacrylate, and the preparation process and the preparation process of the obtained cellulose-based grafted polymer 2-(perfluorooctyl)ethyl methacrylate are shown in the reaction formula in the specific embodiment.

[0012] Preferably, the reaction temperature is 40–60°C and the reaction time is 2–8 h.

[0013] Preferably, the cellulose is selected from any one or more of α-cellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, cyanoethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose. More preferably, the cellulose is selected from any one or more of α-cellulose, methylcellulose, and ethylcellulose.

[0014] Preferably, the fluorinated monomer is selected from one or more of perfluoroalkyl ethyl methacrylate and perfluorocycloalkyl ethyl methacrylate. More preferably, the fluorinated monomer is selected from one or more of 2-(perfluorooctyl)ethyl methacrylate, dodecafluoroheptyl methacrylate, perfluorohexyl ethyl methacrylate, perfluorobutyl ethyl methacrylate, and perfluorocyclohexyl methacrylate.

[0015] Preferably, the metal hydroxide accounts for 30-80% of the mass fraction of the metal hydroxide / cellulose-based grafted fluorinated copolymer multifunctional composite material, and the metal hydroxide is selected from either magnesium hydroxide or calcium hydroxide.

[0016] Preferably, the metal hydroxide is magnesium hydroxide, and the structural formula of the prepared magnesium hydroxide / cellulose-based grafted polymerized 2-(perfluorooctyl)ethyl methacrylate multifunctional composite material is shown in the specific embodiment.

[0017] The method for preparing the cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after deacidification specifically includes the following steps:

[0018] 1) Preparation of cellulose-based grafted fluorinated copolymers;

[0019] 2) Prepare an ethanol solution containing calcium and magnesium ions and cellulose-based grafted fluorinated copolymer;

[0020] 3) Slowly add a precipitant solution containing sodium hydroxide and hydrazine hydrate to the solution in step 2), and mix and stir.

[0021] 4) The mixture obtained in step 3) is placed in a reaction vessel and reacted under controlled temperature. The mixture after reaction is separated, washed and vacuum dried to obtain a multifunctional composite material of metal hydroxide / cellulose-based grafted fluorinated copolymer.

[0022] Preferably, in step 2), the calcium ions are selected from one or more calcium salts, and the magnesium ions are selected from one or more magnesium salts. More preferably, the calcium salts and magnesium salts are selected from any one or more acetates, sulfates, nitrates, chlorides, and bicarbonates.

[0023] The method for preparing a cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after deacidification, and the resulting cellulose-based multifunctional composite material.

[0024] The aforementioned cellulose-based multifunctional composite material is used in paper deacidification, reinforcement, and hydrophobicity applications.

[0025] The specific steps for the application are as follows:

[0026] 1) A multifunctional composite material of metal hydroxide / cellulose-based grafted fluorinated copolymer is dispersed in a fluorocarbon medium and ultrasonically treated for 30 min to obtain a stable suspension, which is then used for paper deacidification; the fluorocarbon medium is selected from any one or more of perfluorooctane, perfluoroheptane, perfluorononane, perfluorobutyltetrahydrofuran, perfluorocyclic ether, perfluorocyclohexane, perfluoromethylcyclohexane, perfluorotoluene, and perfluoro-2,7-dimethyloctane; the concentration of the multifunctional composite material in the paper deacidification suspension is 3-7 g / L;

[0027] 2) The paper to be deacidified is soaked in the paper deacidification suspension for 30 minutes, and then air-dried at room temperature to complete the paper protection treatment.

[0028] To address the technical challenge of achieving high dispersibility, weak alkalinity, and high alkali reserve in paper deacidification materials, while simultaneously strengthening the paper and enhancing its hydrophobicity after deacidification, the applicant, building upon previous work, employed graft polymerization technology to tightly bind cellulose and fluorinated copolymers through covalent bonds, resulting in cellulose-based grafted fluorinated copolymers. This ensures that the modified cellulose can be stably suspended and dispersed in a fluorocarbon medium, exhibiting excellent dispersibility. Then, using the cellulose-based grafted fluorinated copolymer as a carrier, it is compounded with an alkaline deacidification material via a solvothermal method to prepare a multifunctional composite material. In this multifunctional composite material, a specific amount of alkaline component has a deacidifying effect on acidic paper, ensuring that the deacidified paper possesses both weak alkalinity and high alkali reserve. Utilizing the similarity in composition and structure between the fluorinated cellulose fragments in the multifunctional composite material and paper, the composite material penetrates into the gaps between paper fibers and binds with the paper cellulose, providing reinforcement and hydrophobicity. This ensures that the multifunctional composite material achieves high dispersibility, weak alkalinity, and high alkali reserve, while simultaneously strengthening the paper and enhancing its hydrophobicity after deacidification treatment.

[0029] Compared to existing technologies, the beneficial effects of this application are as follows:

[0030] (1) The cellulose-based multifunctional composite material prepared in this application is first made by combining cellulose with a fluorinated copolymer through covalent bonds, and then loading metal hydroxide onto the cellulose-based grafted fluorinated copolymer through hydrogen bonds. This multifunctional composite material can ensure that deacidifying, reinforcing and hydrophobic materials can be evenly distributed and embedded in the gaps of paper fibers.

[0031] (2) The cellulose in the cellulose-based multifunctional composite material prepared in this application has many hydroxyl groups and contains a large number of hydrogen bond sites, which has good compatibility with paper and excellent mechanical properties, so that the multifunctional composite material has excellent paper strengthening performance; while the fluorinated polymer in the cellulose-based multifunctional composite material not only makes the composite deacidification material stably suspended and dispersed in the fluorocarbon medium, but also has hydrophobicity, so that the deacidified paper exhibits strong hydrophobicity, which is conducive to its long-term preservation; in addition, since the inorganic metal hydroxide grows on the cellulose-based grafted fluorinated copolymer, it avoids direct contact with the paper, so that the deacidified paper is still weakly alkaline even with a high alkali content.

[0032] (3) The cellulose-based multifunctional composite material prepared in this application can be used to obtain a paper deacidifying agent that is highly stable and dispersed in a fluorocarbon medium by simple ultrasonic treatment. The acidified paper is then soaked in the deacidifying agent for deacidification. The method is simple and the steps are easy.

[0033] (4) The results of the embodiments of this application confirm that after the cellulose-based multifunctional composite material is deacidified, the surface pH value of the paper increases from the original 4.73 to 7.43, and the alkali reserve is 310.88 mmol / kg. Compared with the untreated paper, the folding endurance, tensile strength, tear strength and water contact angle of the treated paper are increased by 94.6%, 29.9%, 20.4% and 134.7% respectively, which solves the existing problem of embrittlement of acidified paper and has good application value in the deacidification and protection of paper cultural relics. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the preparation of cellulose-based multifunctional composite materials according to this application;

[0035] Figure 2 The infrared spectra of cellulose (a), cellulose macromolecular initiator (b), cellulose-based multifunctional composite material Mg(OH)2 / Cellulose-g-PFOEMA (c), Mg(OH)2 (d) and PFOEMA monomer (e) prepared in Example 1 are shown.

[0036] Figure 3 This is a scanning electron microscope image of the cellulose-based multifunctional composite material Mg(OH)2 / Cellulose-g-PFOE MA sample prepared in Example 1;

[0037] Figure 4 The images show optical images of the paper deacidifying agent prepared in Example 6; in the images, A is an optical image of the paper deacidifying agent prepared in Example 1, B is an optical image of the paper deacidifying agent prepared in Comparative Example 1, and C is an optical image of the paper deacidifying agent prepared in Comparative Example 2.

[0038] Figure 5 The graph shows the mechanical strength of the paper before and after deacidification and after aging in Example 6; in the graph, A is the folding endurance, B is the tensile strength, and C is the tear strength.

[0039] Figure 6 The images shown are scanning electron microscope (SEM) images of the paper before and after deacidification in Example 6; where A is the paper without deacidification treatment and B is the paper after deacidification treatment.

[0040] Figure 7 This is a diagram showing the stable contact angle between paper and water before and after deacidification treatment and after aging in Application Example 6. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the application is further described below with reference to specific embodiments. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0042] The present application provides a method for preparing a cellulose-based multifunctional composite material that strengthens paper and enhances its hydrophobicity after deacidification, using 2-(perfluorooctyl)ethyl methacrylate (PFOEMA) as a fluorinated monomer and a cellulose-grafted fluoropolymer carrier. The reaction formula is as follows:

[0043]

[0044] Process flow as follows Figure 1 As shown, the specific steps include:

[0045] 1) Preparation of cellulose macromolecular initiator: Cellulose, lithium chloride, N-bromosuccinimide, 2-bromoisobutyryl bromide and N,N-dimethylacetamide solvent are reacted to prepare cellulose macromolecular initiator;

[0046] 2) Preparation of cellulose-based grafted fluorinated copolymer: Under nitrogen protection, the cellulose macromolecular initiator prepared in step 1), fluorinated monomer, N,N,N',N”,N”-pentamethyldiethylenetriamine, CuBr catalyst and N,N-dimethylformamide solvent were reacted. After the reaction was completed, the cellulose-based grafted fluorinated copolymer was obtained by separation, washing and drying.

[0047] 3) Preparation of cellulose-based multifunctional composite materials: Magnesium or calcium salts are dissolved in anhydrous ethanol, cellulose-based grafted fluorinated copolymers are added, and then the mixture is slowly titrated with a precipitate containing sodium hydroxide and hydrazine hydrate to obtain a mixed solution. The cellulose-based multifunctional composite material is then obtained after a temperature-controlled reaction. A typical structural formula of the cellulose-based multifunctional composite material is as follows:

[0048]

[0049] The following specific embodiments are all carried out according to the above process, wherein the average length of the selected α-cellulose is 25 μm.

[0050] Example 1

[0051] A method for preparing a cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after deacidification includes the following steps:

[0052] (1) Preparation of cellulose macromolecular initiators:

[0053] 3.24 g of α-cellulose was added to 90 mL of N,N-dimethylacetamide and stirred at 120 °C for 2 h. After the reaction was completed, the temperature was lowered to 100 °C, 7.2 g of lithium chloride was added, and the reaction was carried out at 100 °C for 5 h. After the reaction was completed, the temperature was lowered to 50 °C, 0.72 g of N-bromosuccinimide was added, and after reacting for 10 min, 23.0 g of 2-bromoisobutyryl bromide was added. Finally, the resulting reaction solution was reacted at 50 °C for 48 h. After cooling to room temperature, the solution was filtered, washed to remove impurities, and dried under vacuum at 50 °C to obtain the cellulose macromolecular initiator, denoted as Cellulose-Br.

[0054] (2) Preparation of cellulose-based grafted fluorinated copolymer (cellulose grafted polymer of 2-(perfluorooctyl)ethyl methacrylate):

[0055] Weigh 0.5g of Cellulose-Br prepared in step (1) and dissolve it in 85mL of N,N-dimethylformamide. Then add 0.1733g of N,N,N',N”,N”-pentamethyldiethylenetriamine and 2.0g of 2-(perfluorooctyl)ethyl methacrylate. Inject the resulting reaction solution into a three-necked flask that has been pre-vacuumed and purged with nitrogen (circulated three times) using a syringe and react at 50℃ for 30min. Dissolve 0.0718g of cuprous bromide in 15mL of N,N-dimethylformamide to prepare a catalyst. Add the prepared catalyst into the three-necked flask using a syringe and react at 50℃ for 4h. After cooling to room temperature, filter, separate, and wash to remove impurities. Dry under vacuum at 50℃ to obtain cellulose grafted polymer 2-(perfluorooctyl)ethyl methacrylate, denoted as Cellulose-g-PF OEMA.

[0056] (3) Preparation of cellulose-based multifunctional composite materials:

[0057] 0.429 g of magnesium acetate tetrahydrate was dissolved in 20 mL of anhydrous ethanol under ultrasonic treatment (70 W power, 40 kHz frequency), and 0.464 g of Cellulose-g-PFOEMA carrier prepared in step (2) was added. The mixture was stirred ultrasonically (70 W power, 40 kHz frequency) at room temperature and then set aside. 0.16 g of sodium hydroxide was dissolved in 20 mL of aqueous solution, and 4.0 mL of 80% hydrazine hydrate was added to prepare a precipitate. The precipitate was slowly added dropwise to the above-mentioned prepared solution and stirred at room temperature for 30 min. The mixed solution was then transferred to a 100 mL reactor lined with polytetrafluoroethylene and reacted at 150 °C for 12 h. After cooling to room temperature, the mixture was centrifuged and washed to remove impurities, thus obtaining a cellulose-based multifunctional composite material, denoted as Mg(OH)2 / Cellulose-g-PFOEMA, in which the mass fraction of magnesium hydroxide in the cellulose-based multifunctional composite material was 55-60%.

[0058] Depend on Figure 2 It can be seen that 3334cm in the figure -1 1056cm -1 and 1029cm -1 The absorption peaks are the vibrational absorption peaks of -OH on cellulose (a) and CO, respectively; 3700 cm⁻¹ -1 The absorption peak is the vibrational absorption peak of the -OH group of magnesium hydroxide (d); 1241 cm⁻¹ -1 1205cm -1 1149cm -1 1725cm -1 and 1639cm -1 The absorption peaks at 664 cm⁻¹ are characteristic absorption peaks of the CF group, -C=O group, and C=C group of the 2-(perfluorooctyl)ethyl methacrylate monomer (e), respectively. -1 The C-Br group of the cellulose macromolecular initiator (b) indicates that the cellulose has been brominated; the Mg(OH)2 / Cellulose-g-PFOEM A composite deacidifying material (c) at 3334 cm⁻¹ -1 The weakening peak intensity at 1735 cm⁻¹ indicates that the cellulose -OH groups have been partially substituted; -1 A sharp peak appears at 1241 cm⁻¹, which is the absorption peak of the -C=O vibration of the ester bond in the Mg(OH)₂ / Cellulose-g-PFOEMA composite deacidification material; while at 1241 cm⁻¹... -1 1205cm -1 1149cm -1 The appearance of the characteristic peak of the CF group indicates that the grafting of monomer 2-(perfluorooctyl)ethyl methacrylate was successful; while the peak at 1639 cm⁻¹... -1The disappearance of the characteristic absorption peak indicates that the 2-(perfluorooctyl)ethyl methacrylate monomer has polymerized. Furthermore, compared to the original Mg(OH)₂, the 3700 cm⁻¹ peak... -1 The decrease in the hydroxyl peak indicates that Mg(OH)2 undergoes hydrogen bonding with Cellulose-g-PFOEMA.

[0059] Depend on Figure 3 It can be seen that the synthesized regular hexagonal nanosheets of magnesium hydroxide are uniformly dispersed on the Cellulos eg-PFOEMA support.

[0060] Example 2

[0061] The preparation method of cellulose-based grafted fluorinated copolymers is the same as step 2) in Example 1, except that the fluorinated monomers used are replaced with dodecylfluoroheptyl methacrylate (DFMA), perfluorohexyl ethyl acrylate (PFHEA), perfluorobutyl ethyl methacrylate (PFBEMA), and perfluorocyclohexyl methacrylate (PFCHMA), respectively. The prepared cellulose-based grafted fluorinated copolymers are labeled as Cellulose-g-DFMA, Cellulose-g-PFHEA, Cellulose-g-PFBEMA, and Cellulose-g-PFCHMA, respectively.

[0062] Example 3

[0063] The preparation of the cellulose-based multifunctional composite material is the same as step 3) in Example 1, except that the mass of the Cellulose-g-PFOEMA carrier prepared in step 2) is different, as detailed below:

[0064] 1) By adding 0.116g of Cellulose-g-PFOEMA carrier, the mass fraction of magnesium hydroxide in the prepared composite deacidification material Mg(OH)2 / Cellulose-g-PFOEMA is 85-90%.

[0065] 2) By adding 0.232g of Cellulose-g-PFOEMA carrier, the mass fraction of magnesium hydroxide in the prepared composite deacidification material Mg(OH)2 / Cellulose-g-PFOEMA is 75-80%.

[0066] 3) Adding 0.348g of Cellulose-g-PFOEMA carrier, the mass fraction of magnesium hydroxide in the prepared composite deacidification material Mg(OH)2 / Cellulose-g-PFOEMA is 65-70%.

[0067] 4) Add 0.58g of Cellulose-g-PFOEMA carrier to prepare the composite deacidification material Mg(OH)2 / Cellulose-g-PFOEMA, in which the mass fraction of magnesium hydroxide is 45-50%.

[0068] Example 4

[0069] The preparation method of the cellulose-based multifunctional composite material is the same as in Example 1, except that in step 3), 0.464g of the Cellulose-g-DFMA carrier, Cellulose-g-PFHEA carrier, Cellulose-g-PFBEMA carrier, and Cellulose-g-PFCHMA carrier prepared in Example 2 are added respectively. The mass fraction of magnesium hydroxide in the resulting composite deacidification materials (Mg(OH)2 / Cellulose-g-DFMA, Mg(OH)2 / Cellulose-g-PFHEA, Mg(OH)2 / Cellulose-g-PFBEMA, and Mg(OH)2 / Cellulose-g-PFCHMA, respectively) is 55-60%.

[0070] Example 5

[0071] The preparation method of the cellulose-based multifunctional composite material is the same as in Example 1, except that in step 3), 0.316g of calcium acetate is used to replace 0.429g of magnesium acetate tetrahydrate, and the target product is obtained as follows:

[0072] 1) After adding 0.116g of Cellulose-g-PFOEMA carrier, the mass fraction of calcium hydroxide in the obtained composite deacidification material Ca(OH)2 / Cellulose-g-PFOEMA is 85-90%.

[0073] 2) After adding 0.232g of Cellulose-g-PFOEMA carrier, the mass fraction of calcium hydroxide in the obtained composite deacidification material Ca(OH)2 / Cellulose-g-PFOEMA is 75-80%.

[0074] 3) Adding 0.348g of Cellulose-g-PFOEMA carrier, the mass fraction of calcium hydroxide in the obtained composite deacidification material Ca(OH)2 / Cellulose-g-PFOEMA is 65-70%.

[0075] 4) Adding 0.464g of Cellulose-g-PFOEMA carrier, the mass fraction of calcium hydroxide in the obtained composite deacidification material Ca(OH)2 / Cellulose-g-PFOEMA is 55-60%.

[0076] 5) Adding 0.58g of Cellulose-g-PFOEMA carrier, the mass fraction of calcium hydroxide in the obtained composite deacidification material Ca(OH)2 / Cellulose-g-PFOEMA is 45-50%.

[0077] Comparative Example 1

[0078] 0.429 g of magnesium acetate tetrahydrate was dissolved in 20 mL of anhydrous ethanol under ultrasonic treatment (70 W, 40 kHz) and stirred at room temperature under ultrasonic treatment (70 W, 40 kHz). 0.16 g of sodium hydroxide was dissolved in 20 mL of aqueous solution, and 4.0 mL of 80% hydrazine hydrate was added to prepare a precipitate. The precipitate was slowly added dropwise to the prepared solution and stirred at room temperature for 30 min. The mixture was then transferred to a 100 mL reaction vessel lined with polytetrafluoroethylene and reacted at 150 °C for 12 h. After cooling to room temperature, the mixture was centrifuged and washed to remove impurities, yielding pure Mg(OH)₂.

[0079] Comparative Example 2

[0080] In the preparation of cellulose-grafted polymerized octadecyl methacrylate, the monomer used was octadecyl methacrylate (SMA), and the remaining preparation methods and parameters were the same as in step 2) of Example 1, labeled as Cellulose-g-SMA; in the preparation of the metal hydroxide / cellulose-based grafted non-fluorinated copolymer multifunctional composite material, 0.464g of the prepared Cellulose-g-SMA carrier was added, and the remaining preparation methods and parameters were the same as in step 3) of Example 1, to obtain the composite deacidification material Mg(OH)2 / Cellulose-g-SMA.

[0081] Application Example 6

[0082] 1. Comparison of dispersion performance

[0083] 1.4g of deacidifying material was uniformly dispersed in 200mL of perfluorooctane mixed solution, and ultrasonically dispersed (70W power, 40kHz frequency) for 30min. The dispersion performance of the product was observed after standing. The results are as follows: Figure 4 As shown.

[0084] Figure 4 A is Mg(OH)2 / Cellulose-g-PFOEMA prepared in Example 1. This composite deacidifying material can be suspended and dispersed stably in a perfluorooctane mixed solvent, and its stable suspension and dispersion time is not less than 120 min.

[0085] Figure 4B is the Mg(OH)2 material prepared in Comparative Example 1. After standing for 30 minutes, the Mg(OH)2 showed obvious sedimentation.

[0086] Figure 4 C is the composite deacidification material Mg(OH)2 / Cellulose-g-SMA prepared in Comparative Example 2. After standing for 10 minutes, the solid particles showed obvious sedimentation, indicating that the non-fluorine-containing carrier suspension was very poor.

[0087] 2. Comparison of deacidification performance

[0088] Acidic paper with an average pH of 4.73 was immersed in the above-mentioned Mg(OH)2 / Cellulose-g-PFOEMA perfluorooctane mixed solution using a paper immersion deacidification method. During the process, the paper was gently shaken with tweezers and turned over every 5 minutes. The immersion time was 30 minutes. After deacidification, the paper was allowed to air dry at room temperature for 24 hours. The surface pH of the paper treated with the multifunctional composite material Mg(OH)2 / Cellulose-g-PFOEMA increased from 4.73 to 7.43, and the alkali reserve was 310.88 mmol / kg (see Table 1), showing both weak alkalinity and high alkali reserve.

[0089] The deacidified paper was placed in an oven and aged at 105℃ for 72 hours. Tested according to the national standard GB / T1545.2-2003, the average pH value of the paper surface treated with the multifunctional composite material was 7.35, and the alkali reserve was 289.44 mmol / kg, while the average pH value of the untreated paper surface after aging was 4.35. This indicates that the paper treated with the multifunctional composite material Mg(OH)2 / Cellulose-g-PFOEMA has anti-aging properties.

[0090] The mechanical strength (folding endurance, tensile strength, and tear strength), microstructure, and hydrophobicity (water contact angle) of the paper before and after deacidification, as well as the paper after dry heat aging before and after deacidification, were measured. The results are as follows: Figure 5-7 As shown in Table 1.

[0091] Table 1 Performance results of paper samples

[0092]

[0093] Depend on Figure 5As shown in Table 1, the mechanical strength of paper treated with the multifunctional composite material Mg(OH)2 / Cellulose-g-PFOEMA is significantly improved. Compared with untreated paper, the folding endurance, tensile strength, and tear strength of the treated paper are increased by 94.6%, 29.9%, and 20.4%, respectively. Even after dry heat aging treatment, it still exhibits excellent mechanical strength compared with untreated paper, with folding endurance, tensile strength, and tear strength increased by 67.4%, 23.4%, and 14.1%, respectively. This indicates that the paper treated with the multifunctional composite material Mg(OH)2 / Cellulose-g-PFOEMA has good anti-aging properties and excellent mechanical strength.

[0094] Depend on Figure 6 It can be seen that, compared to untreated paper ( Figure 6 A) Multifunctional composite materials can be uniformly embedded inside paper fibers. Figure 6 B), thereby improving the mechanical strength of the paper.

[0095] Depend on Figure 7 It can be seen that the water contact angle of the untreated acidic paper was 52.5° after 20 minutes of water contact angle test, while the water contact angles of the paper treated with multifunctional composite material before and after aging were 123.2° and 127.5°, respectively, indicating that the paper treated with multifunctional composite material exhibits excellent hydrophobicity.

[0096] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for preparing a cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after deacidification, characterized in that, Specifically, the following steps are included: 1) A cellulose macromolecular initiator was prepared by reacting cellulose, lithium chloride, N-bromosuccinimide, 2-bromoisobutyryl bromide, and N,N-dimethylacetamide solvent; the mass ratio of cellulose, lithium chloride, N-bromosuccinimide, 2-bromoisobutyryl bromide, and N,N-dimethylacetamide solvent was 3~3.5 : 7~7.5 : 0.5~1 : 23 : 80~90. 2) Under nitrogen protection, the cellulose macromolecular initiator prepared in step 1) is reacted with a fluorinated monomer, N,N,N',N”,N”-pentamethyldiethylenetriamine, CuBr catalyst, and N,N-dimethylformamide solvent. After the reaction, the mixture is separated, washed, and dried to obtain a cellulose-based grafted fluorinated copolymer. The mass ratio of the cellulose macromolecular initiator, fluorinated monomer, N,N,N',N”,N”-pentamethyldiethylenetriamine, CuBr catalyst, and N,N-dimethylformamide solvent is 0.5 : 2 : 0.15 ~ 0.2 : 0.05 ~ 0.1 : 95 ~ 100. The fluorinated monomer is selected from any one of 2-(perfluorooctyl)ethyl methacrylate, dodecafluoroheptyl methacrylate, perfluorohexyl ethyl acrylate, perfluorobutyl ethyl methacrylate, and perfluorocyclohexyl methacrylate. 3) Prepare an ethanol solution containing calcium and magnesium ions and cellulose-based grafted fluorine copolymer. Dissolve magnesium or calcium salts in anhydrous ethanol, add cellulose-based grafted fluorine copolymer, and then slowly add a precipitant solution containing sodium hydroxide and hydrazine hydrate. Mix and stir, transfer the mixture to a reaction vessel for temperature-controlled reaction, and separate, wash and vacuum dry the product to obtain a multifunctional composite material of metal hydroxide / cellulose-based grafted fluorine copolymer, which is the cellulose-based multifunctional composite material. The calcium salt and magnesium salt are selected from any one or more of acetate, sulfate, nitrate, chloride, and bicarbonate; the metal hydroxide accounts for 30-80% of the mass fraction of the metal hydroxide / cellulose-based grafted fluorinated copolymer multifunctional composite material.

2. The method for preparing a cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after deacidification, as described in claim 1, is characterized in that... In step 1), the cellulose is selected from any one or more of α-cellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, cyanoethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose.

3. The method for preparing a cellulose-based multifunctional composite material that can strengthen paper and enhance its hydrophobicity after deacidification, as described in claim 1, is characterized in that... In step 2), the reaction temperature is 40 ~ 60 ℃ and the reaction time is 2 ~ 8 h.

4. The cellulose-based multifunctional composite material prepared by the method of any one of claims 1-3, which enables paper to be strengthened and its hydrophobicity to be enhanced after deacidification.

5. The application of the cellulose-based multifunctional composite material according to claim 4 in the deacidification, reinforcement, and hydrophobicity of paper.

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