Modified bacterial cellulose stabilizes akd sizing agent emulsion and preparation method thereof

Abstract

The application belongs to the technical field of papermaking, and provides a modified bacterial cellulose stable AKD sizing agent emulsion.TEMPO oxidized bacterial cellulose nanofiber suspension and silver amide solution are heated and reacted to obtain TBC@Ag; TEOS is added dropwise into the ethanol dispersion of TBC@Ag and stirred and reacted to obtain TBC@Ag@SiO2; the water dispersion of TBC@Ag@SiO2 and molten AKD are sheared and emulsified under insulation, and then an ice water bath is used to obtain the AKD sizing agent emulsion.The prepared AKD sizing agent is suitable for surface coating and sizing, has the advantages of no need to add a surfactant, green environmental protection, high storage stability, uniform and small emulsion particles, simplified preparation process, low cost, good adaptability to pH and temperature fluctuations, safe and reliable operation, and is suitable for popularization and application in the production of packaging paper and high-performance paper.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking and relates to the preparation of an AKD sizing agent emulsion. Background Art

[0002] The disclosure of this background information is intended to enhance understanding of the general background of the invention and should not necessarily be regarded as an acknowledgment or any form of suggestion that this information constitutes the prior art already known to a person skilled in the art.

[0003] With the continuous advancement of papermaking technology, paper performance requirements in terms of water resistance, moisture resistance, and strength are increasingly demanding. To meet these high standards, AKD (olefin dianhydride) sizing agents, as a key sizing material, are widely used to improve paper's water and moisture resistance. AKD sizing agents react with hydroxyl groups in pulp fibers to form water-insoluble compounds, significantly reducing paper's water absorption and improving its moisture resistance. Despite the importance of AKD sizing agents in practice, traditional AKD emulsification processes still have limitations. Key issues include poor solubility, poor dispersibility, and insufficient reactivity, which directly impact the stability and efficiency of sizing. Traditional emulsification processes, in particular, often rely on surfactants as emulsifiers, but these chemical emulsifiers can pose environmental and safety concerns. The use of surfactants not only complicates the production process but can also emit hazardous substances such as volatile organic compounds (VOCs), increasing production costs and causing significant environmental pollution. Therefore, there is an urgent need for an efficient, environmentally friendly and stable emulsification technology to overcome existing problems, improve sizing effects, and meet the modern papermaking industry's growing demand for paper performance.

[0004] To overcome the shortcomings of traditional emulsification processes, solid particle emulsification technology (i.e., Pickering emulsions) has recently attracted widespread attention as an innovative alternative. Unlike traditional emulsion systems that rely on surfactants, Pickering emulsions utilize solid particles (such as silica, titanium dioxide, and silicon dioxide) to stabilize the water-oil interface. These solid particles have high surface energy and can self-assemble into highly stable structures, effectively avoiding the stability issues associated with traditional emulsifiers and ensuring the stability of the emulsion during long-term storage and use. Furthermore, Pickering emulsions offer significant environmental advantages: the use of solid particles significantly reduces or completely replaces surfactants, reducing production costs and significantly reducing the generation of harmful substances, thus complying with modern environmental standards. This makes Pickering emulsions an ideal alternative emulsification technology, overcoming the environmental pollution issues associated with traditional emulsification processes while demonstrating superior performance. Compared to traditional emulsions, Pickering emulsions offer significant improvements in emulsification efficiency, stability, and environmental friendliness, making them particularly suitable for demanding production processes with significant environmental impacts.

[0005] In this context, the use of nanocellulose as an emulsifier not only enhances emulsion stability but also significantly improves sizing effectiveness. Nanocellulose is a novel renewable biomaterial that has gained widespread application and attention in recent years due to its excellent mechanical properties, surface characteristics, and good biodegradability. Nanocellulose can be extracted from plants, animals, and bacteria, and is typically produced through physical, chemical, or enzymatic treatments. Due to its rich hydroxyl groups and large surface area, nanocellulose interacts strongly with other molecules or particles, significantly improving the dispersion and stability of the emulsion. During the AKD emulsification process, nanocellulose improves the emulsion's rheological properties and enhances the stability of the water-oil interface, thereby improving the water resistance, moisture resistance, and strength of the paper. Furthermore, the introduction of nanocellulose reduces the use of traditional surfactants, reducing production costs and environmental pollution. The use of nanocellulose as an emulsifier aligns with environmental and sustainable development requirements and excels in improving sizing effectiveness and enhancing paper properties. By using nanocellulose to emulsify AKD, the papermaking industry can achieve more efficient, environmentally friendly, and high-performance sizing technology, thereby promoting the development of green and sustainable paper production. Bacterial cellulose (BC) is a natural polysaccharide produced by bacteria. It possesses a highly crystalline nanofiber structure and a rich surface area with hydroxyl groups, resulting in strong hydrophilicity and high mechanical strength. This gives BC excellent application potential in various fields, particularly in emulsification technology. As a natural, renewable material, BC can partially or completely replace surfactants, providing greener and more environmentally friendly emulsification solutions. Summary of the Invention

[0006] In order to prepare a more stable and environmentally friendly AKD emulsion emulsification system, the present invention provides an AKD emulsion stabilizer, which does not require other surfactants during the emulsion preparation process, simplifies the process and effectively improves the emulsion stability, and significantly enhances the sizing agent.

[0007] Another object of the present invention is to provide a use of the above stabilizer in the preparation of AKD emulsion.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions.

[0009] A method for preparing a papermaking sizing agent emulsion stabilizer comprises the following steps:

[0010] (1) The suspension of TEMPO-oxidized bacterial cellulose nanofibers (TBC) and silver ammonia solution were heated to react, and then centrifuged to wash and remove impurities to obtain oxidized bacterial cellulose loaded with nanosilver particles (TBC@Ag);

[0011] (2) Ethyl silicate (TEOS) was added dropwise to the ethanol dispersion of TBC@Ag, stirred for reaction, and then centrifuged for washing to remove impurities, thereby obtaining oxidized bacterial cellulose loaded with nanosilver particles and nanosilicon dioxide particles (TBC@Ag@SiO2).

[0012] In step (1), the average length of the TEMPO-oxidized bacterial cellulose nanofibers is 20 μm and the diameter is 50 nm to 100 nm.

[0013] In step (1), the TEMPO-oxidized bacterial cellulose nanofibers can be purchased commercially or obtained using methods in the prior art, such as catalytic oxidation of bacterial cellulose nanofibers using a TEMPO / NaBr / NaClO system in an aqueous solution at a pH of about 10. In order to increase the reaction rate and oxidation degree, ultrasonic treatment can also be assisted during the reaction. Specifically, the steps are: adding NaBr and TEMPO to the bacterial cellulose nanofiber suspension, then adding a NaClO solution, adjusting the pH to 10-10.5 for reaction, terminating the reaction, adjusting the pH of the system to neutral, filtering and washing to remove impurities, and obtaining TEMPO-oxidized bacterial cellulose nanofibers. The addition ratio of the bacterial cellulose nanofibers, NaBr, TEMPO and NaClO is 1 g: 0.1 mmol: 9.72 mmol: (20-60.4) mmol.

[0014] In step (1), the silver ammonia solution is prepared by adding 4% (v / v) of 25 wt% ammonia water to 0.5 wt% silver nitrate solution and mixing.

[0015] In step (1), TBC and silver ammonia solution are mixed by adding 1% (w / w)-20% (w / w) silver ammonia solution to a 1 wt% TBC suspension; preferably, 10% (w / w) silver ammonia solution is added to a 1 wt% TBC suspension and mixed.

[0016] In step (1), the reaction temperature is 70°C-90°C; and the reaction time is 0.5 h-2 h.

[0017] In step (2), the mass ratio of TBC@Ag to TEOS is 1:(4.65-13.95).

[0018] In step (2), the reaction time is 6 h-18 h.

[0019] The present invention also provides TBC@Ag@SiO2 obtained by the above method; wherein nanosilver particles with a particle size of 30 nm to 90 nm are covalently or coordinately bonded to the hydroxyl groups on the surface of bacterial cellulose, and nanosilicon dioxide particles with a particle size of 20 nm to 40 nm are covalently bonded to the hydroxyl groups. After coating on a surface such as paper, this TBC@Ag@SiO2 can release silver ions. When in contact with bacteria, the silver ions are released from the surface. At the contact interface, the silver ions are electrostatically attracted by their positive charge and the negative charge on the bacterial cell membrane surface. They then bind to sulfur- and phosphorus-containing groups (such as phospholipids) on the cell membrane, disrupting the integrity of the cell membrane and achieving a good bactericidal effect.

[0020] The papermaking sizing agent emulsion stabilizer can be used to prepare a papermaking sizing agent emulsion, wherein the sizing agent comprises AKD or ASA, and is obtained by mixing a sizing agent solution and a stabilizer solution and then emulsifying the mixture.

[0021] An AKD sizing agent, the preparation method of which is as follows:

[0022] The TBC@Ag@SiO2 aqueous dispersion and molten alkyl ketene dimer (AKD) were shear-emulsified under heat preservation conditions and then placed in an ice-water bath.

[0023] The concentration of TBC@Ag@SiO2 aqueous dispersion is 0.2 wt%-1.0 wt%.

[0024] The volume ratio of AKD to the aqueous dispersion is 1:5-1:20, more preferably 1:9.

[0025] The shear emulsification rate is 12000 rpm-20000 rpm; more preferably 15000 rpm-18000 rpm.

[0026] The shear emulsification time is 4 min-8 min; more preferably 6 min-7 min.

[0027] The insulation temperature is 65℃-90℃.

[0028] Nanosilver (Ag) and nanosilica are attached to the surface of bacterial cellulose. Due to their high surface activity, they can be adsorbed at the oil-water interface, reducing surface tension. The steric hindrance effect generated by their combination with bacterial cellulose can prevent oil droplets from coalescing and promote emulsification.

[0029] An AKD sizing agent obtained by the above preparation method; the average particle size of the droplets in the emulsion is 2 μm-5 μm.

[0030] The AKD sizing agent can be used for sizing hydrophobic food-grade packaging paper.

[0031] A paper prepared using the TBC@Ag@SiO2 or AKD sizing agent.

[0032] The present invention has the following advantages:

[0033] The AKD sizing agent prepared by the present invention, which uses modified bacterial cellulose as an emulsifier, is suitable for surface coating and sizing, has the advantages of not requiring the addition of surfactants, being environmentally friendly, and having high storage stability; its emulsion particles are uniform and fine, and can effectively enhance the water resistance, surface strength, and smoothness of paper, thereby improving printability; and its preparation process is simplified, the cost is low, and it has good adaptability to pH and temperature fluctuations, and the operation is safe and reliable, making it suitable for promotion and application in the production of packaging paper and high-performance paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The scanning electron microscope image (A) and infrared spectrum (B) of TBC@Ag@SiO2;

[0035] Figure 2 The appearance (left) and micrograph (right) of AKD sizing agent emulsion stabilized with TBC@Ag@SiO2;

[0036] Figure 3 This is a scanning electron microscope image of the surface-coated sized paper using AKD sizing emulsion stabilized with TBC@Ag@SiO2;

[0037] Figure 4 The liquid-repellent effect of AKD sizing emulsion coated on the surface of sized paper with TBC@Ag@SiO2 as stabilizer;

[0038] Figure 5 It is the water contact angle of paper coated with AKD sizing emulsion stabilized by TBC@Ag@SiO2. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the embodiments and drawings, but the present invention is not limited to the following embodiments.

[0040] Example 1 Preparation of TBC@Ag@SiO2 and AKD emulsion

[0041] 1. Preparation of TBC@Ag@SiO2

[0042] (1) NaBr and TEMPO were added to a 1 wt% suspension of bacterial cellulose nanofibers (average length 20 μm, diameter 50 nm-100 nm) to dissolve the suspension. 5% NaClO solution was then added to adjust the ratio of bacterial cellulose nanofibers, NaBr, TEMPO, and NaClO to 1 g:0.1 mmol:9.72 mmol:20 mmol. The pH was adjusted to 10-10.5 and stirred for 1 h. After terminating the reaction by adding 10 mL of anhydrous ethanol, the pH of the system was adjusted to about 7. The precipitate was filtered and washed several times to remove impurities to obtain TEMPO-oxidized bacterial cellulose nanofibers (TBC).

[0043] (2) About 4% (v / v) of 25 wt% ammonia water was added to a 0.5 wt% silver nitrate solution to obtain a silver ammonia solution; TBC was prepared into a 1 wt% aqueous suspension; 10% (w / w) of the aqueous suspension was added to the silver ammonia solution, and the mixture was reacted in an 80°C water bath for 1 h to obtain TBC loaded with silver particles (TBC@Ag);

[0044] (3) 100 mL of 1% TBC@Ag suspension was dispersed in 300 mL of anhydrous ethanol and reacted with 4.65 g of TEOS for 12 h. The precipitate was obtained by centrifugation and washed several times to obtain oxidized bacterial cellulose loaded with nanosilver particles and nanosilica particles (TBC@Ag@SiO2). The scanning electron microscope and infrared spectrum of the precipitate are shown in Figure 2. Figure 1 As shown, nano-silicon dioxide particles with a particle size of 20 nm-40 nm are combined with the hydroxyl groups of oxidized bacterial cellulose through silicon-oxygen bonds (Si-OC); nano-silver particles with a particle size of 30 nm-90 nm are combined with the hydroxyl groups of oxidized bacterial cellulose through coordination bonds.

[0045] In the above steps, the surface of bacterial cellulose (TBC) after TEMPO oxidation treatment is negatively charged and can react with silver ammonium ions ([Ag(NH3)2] + ) undergoes ion exchange, replacing the sodium ions. During this process, on the one hand, silver ammonium ions stably adhere to the TBC surface through electrostatic interactions; on the other hand, the silver ammonium ions tightly adhere to the cellulose surface and promote the reduction of silver ions to metallic silver (Ag), thereby forming silver nanoparticles (AgNPs).

[0046] 2. Preparation of AKD Emulsion

[0047] (1) heating alkyl ketene dimer (AKD) to 70°C to obtain molten AKD as the oil phase;

[0048] (2) Dispersing TBC@Ag@SiO2 in water to obtain a 0.8 wt% dispersion as the aqueous phase;

[0049] (3) The oil phase and the water phase were mixed in a volume ratio of 1:9, heated at 70°C, stirred at a shear rate of 12,000 rpm for 5 min, and then quickly cooled in an ice bath to obtain an oil-in-water AKD Pickering emulsion, i.e., an AKD sizing agent;

[0050] AKD sizing agent appearance and emulsion micrograph Figure 2 As shown: the average particle size of the emulsion droplets is 3.7 μm, and the emulsion droplets are evenly distributed. After diluting the emulsion 10 times, it is used for paper surface coating and sizing, and the coating amount is 6 g / m 2 , the scanning electron microscope of the paper after sizing is as follows Figure 3 As shown: AKD emulsion forms a uniform and complete adhesion layer on the surface of paper fibers. This coverage helps to improve the hydrophobicity and water resistance of paper. When water is dripped on the paper after sizing, it shows a significant liquid-repellent effect ( Figure 4 The water contact angle was measured by contact angle meter to be 111° ( Figure 5 ), showing good water resistance and sizing effect.

[0051] 3. Temperature adaptability

[0052] The AKD emulsion prepared above was stored at 4°C, 25°C, 37°C, 60°C and 95°C for 2 days, and the changes in particle size and emulsion volume fraction were observed.

[0053] Table 1 Emulsion stability at different temperatures

[0054]

[0055] The results are shown in Table 1. After 2 days of storage at 4°C, 25°C, 37°C, and 60°C, the emulsion particle size increased only slightly, and the emulsion volume fraction remained almost at 100%, with no obvious demulsification. However, at 95°C, the emulsion particle size increased significantly to approximately 7.7 nm, more than twice that at 25°C, indicating that small oil droplets aggregated into large droplets. In addition, the emulsion volume fraction decreased to 85%, reflecting that some emulsion demulsification occurred. In contrast, the commercial AKD emulsion completely demulsified at 95°C. The emulsion prepared in this patent exhibited only slight demulsification, fully demonstrating its excellent thermal stability.

[0056] 4. pH adaptability

[0057] The pH values ​​of the AKD emulsions prepared above were adjusted to 7.5, 6.5, 5.5 and 4.5, respectively, and then stored for 10 days. The changes in the emulsion particle size and emulsion volume fraction were observed to evaluate their stability.

[0058] Table 2 Emulsion stability at different pH

[0059]

[0060] The results are shown in Table 2. After the emulsion was adjusted to pH 7.5, 6.5, 5.5, and 4.5 and stored for 10 days, the particle size increased to some extent, with the largest increase being 1.3 μm at pH 4.5 (from 3.7 μm to 5.0 μm). The emulsion volume fraction remained at 100% at pH 7.5, 6.5, and 5.5, with no significant demulsification. It only decreased slightly to 96% at pH 4.5. This demonstrates that the emulsion exhibits good resistance to demulsification over a wide pH range and maintains high application stability under long-term storage conditions.

[0061] Example 2 Preparation of TBC@Ag@SiO2 and AKD emulsion

[0062] 1. Preparation of TBC@Ag@SiO2

[0063] (1) NaBr and TEMPO were added to a 1 wt% suspension of bacterial cellulose nanofibers (average length 20 μm, diameter 50 nm-100 nm) to dissolve the suspension. 10% NaClO solution was then added to adjust the ratio of bacterial cellulose nanofibers, NaBr, TEMPO, and NaClO to 1 g:0.1 mmol:9.72 mmol:40 mmol. The pH was adjusted to 10-10.5 and stirred for 1 h. After terminating the reaction by adding 10 mL of anhydrous ethanol, the pH of the system was adjusted to about 7. The precipitate was filtered and washed several times to remove impurities to obtain TEMPO-oxidized bacterial cellulose nanofibers (TBC).

[0064] (2) About 4% (v / v) of 25 wt% ammonia water was added to a 0.5 wt% silver nitrate solution to obtain a silver ammonia solution; TBC was prepared into a 1 wt% aqueous suspension; 1% (w / w) of the aqueous suspension was added to the silver ammonia solution, and the mixture was reacted in an 80°C water bath for 1 h to obtain TBC loaded with silver particles (TBC@Ag);

[0065] (3) 100 mL of 1% TBC@Ag suspension was dispersed in 300 mL of anhydrous ethanol and reacted with 9.3 g of TEOS solution for 12 h. The precipitate was obtained by centrifugation and washed several times to obtain oxidized bacterial cellulose loaded with nanosilver particles and nanosilica particles (TBC@Ag@SiO2).

[0066] 2. Preparation of AKD Emulsion

[0067] (1) heating alkyl ketene dimer (AKD) to 65°C to obtain molten AKD as the oil phase;

[0068] (2) Dispersing TBC@Ag@SiO2 in water to obtain a 0.5 wt% dispersion as the aqueous phase;

[0069] (3) The oil phase and the water phase were mixed in a volume ratio of 1:15, heated at 70 °C, stirred at a shear rate of 15,000 rpm for 5 min, and then quickly cooled in an ice bath to obtain an oil-in-water AKD Pickering emulsion, i.e., an AKD sizing agent; the average particle size of the emulsion droplets was 5.2 μm; after the emulsion was diluted 10 times, it was coated on the paper surface with a coating amount of 4 g / m 2 The water contact angle of the paper after sizing reaches 102°.

[0070] Example 3 Preparation of TBC@Ag@SiO2 and AKD emulsion

[0071] 1. Preparation of TBC@Ag@SiO2

[0072] (1) NaBr and TEMPO were added to a 1 wt% suspension of bacterial cellulose nanofibers (average length 20 μm, diameter 50 nm-100 nm) to dissolve the suspension. 10% NaClO solution was then added to adjust the ratio of bacterial cellulose nanofibers, NaBr, TEMPO, and NaClO to 1 g:0.1 mmol:9.72 mmol:60.4 mmol. The pH was adjusted to 10-10.5 and stirred for 1 h. After terminating the reaction by adding 10 mL of anhydrous ethanol, the pH of the system was adjusted to about 7. The precipitate was filtered and washed several times to remove impurities to obtain TEMPO-oxidized bacterial cellulose nanofibers (TBC).

[0073] (2) About 4% (v / v) of 25 wt% ammonia water was added to a 0.5 wt% silver nitrate solution to obtain a silver ammonia solution; TBC was prepared into a 1 wt% aqueous suspension; 10% (w / w) of the aqueous suspension was added to the silver ammonia solution, and the mixture was reacted in an 80°C water bath for 1 h to obtain TBC loaded with silver particles (TBC@Ag);

[0074] (3) 100 mL of 1% TBC@Ag suspension was dispersed in 300 mL of anhydrous ethanol and reacted with 13.95 g of TEOS for 12 h. The precipitate was obtained by centrifugation and washed several times to obtain oxidized bacterial cellulose loaded with nanosilver particles and nanosilica particles (TBC@Ag@SiO2).

[0075] 2. Preparation of AKD Emulsion

[0076] (1) heating alkyl ketene dimer (AKD) to 85°C to obtain molten AKD as the oil phase;

[0077] (2) Dispersing TBC@Ag@SiO2 in water to obtain a 1.0 wt% dispersion as the aqueous phase;

[0078] (3) The oil phase and the water phase were mixed in a volume ratio of 1:20, heated at 85°C, stirred at a shear rate of 18,000 rpm for 5 min, and then quickly cooled in an ice bath to obtain an oil-in-water AKD Pickering emulsion, i.e., an AKD sizing agent; the average particle size of the emulsion droplets was 4.3 μm; after the emulsion was diluted 10 times, it was coated on the paper surface with a coating amount of 8 g / m 2 The water contact angle of the paper after sizing reaches 105°.

[0079] Comparative Example 1 Preparation of BC-dispersed AKD emulsion

[0080] (1) heating alkyl ketene dimer (AKD) to 80°C to obtain molten AKD as the oil phase;

[0081] (2) dispersing bacterial cellulose (BC) in water to obtain a 0.5 wt% dispersion as the aqueous phase;

[0082] (3) The oil phase and the water phase were mixed in a volume ratio of 1:10, heated at 75°C, stirred at a shear rate of 18,000 rpm for 5 min, and then rapidly cooled in an ice bath to obtain an oil-in-water AKD Pickering emulsion, i.e., an AKD sizing agent. The average particle size of the emulsion droplets was 6.4 μm. After the emulsion was diluted 10 times, it was applied to the paper surface at a coating amount of 6 g / m². The water contact angle of the paper after sizing reached 82°.

[0083] Application Example 1: AKD sizing agent sizing effect

[0084] The AKD sizing agent of Example 1-3 was diluted 10 times and then applied to the surface of paper to apply sizing and measure the sizing degree according to the following method:

[0085] The paper to be sized was placed on a nanocellulose coating / coating machine (CUF5-200, Sumet, Germany). The diluted AKD sizing emulsion was added to the coating material box. The coating speed was adjusted to 1.5 cm / s, the coating pressure was 10 N / m, the coating drying temperature was 105°C, and the drying time was 30 min.

[0086] Sizing performance is evaluated by measuring the sizing degree of paper (GB / T5405-2002). Before measurement, the paper is cut into 30×30 mm squares and equilibrated at 25°C and 50% humidity for 24 hours. The paper is folded to form a boat-shaped structure with a base area of ​​approximately 20×20 mm. The structure is then floated in a 2% dilute ammonium thiocyanate solution. A dropper with a plastic tip is used to place a 0.5 μL drop of 1% ferric chloride solution on top of the boat-shaped paper. A stopwatch is used to measure the sizing degree of the paper sample. The measurement ends when a red spot appears in the middle of the ferric chloride droplet. The time is determined by the appearance of a red spot in the middle of the ferric chloride droplet. The measurement is repeated 10 times on both the front and back sides of the test sample, and the average value is calculated.

[0087] Table 3 Effects of different storage times on the properties and sizing degree of different AKD sizing agent emulsions

[0088]

[0089] The data in the table show significant differences in emulsion stability, particle size distribution, and sizing performance among the AKD sizing agents in different examples. Overall, smaller emulsion particle size (e.g., 3.7 μm in Example 1) increases stability and improves sizing performance (initial sizing efficiency and long-term water resistance). Coating weight also significantly affects sizing efficiency. A higher coating weight (e.g., 8 g / m² in Example 3) can partially compensate for the larger emulsion particle size, but a too low coating weight (e.g., 4 g / m² in Example 2) may result in insufficient sizing performance. Furthermore, both emulsion stability and sizing performance decrease with extended storage time. However, sizing agents with smaller particle size and a moderate coating weight (e.g., Example 1) exhibit superior overall performance, making them suitable for long-term storage and efficient sizing.

[0090] Bacterial cellulose is a natural polymer synthesized by bacteria and exhibits excellent biocompatibility. Attaching nanosilver and nanosilica to the surface of bacterial cellulose not only imparts antibacterial properties but also enhances its emulsifying effect. AKD emulsions emulsified with bacterial cellulose effectively disperse AKD in water and ensure uniform coating on the paper surface. This emulsification method avoids the use of chemical solvents in traditional AKD emulsions, reducing potential harm to the environment and human health. Compared to the harmful ingredients that may be present in traditional emulsions, such as chemical solvents and surfactants, bacterial cellulose emulsions are more environmentally friendly and safer.

[0091] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A method for preparing a papermaking sizing agent emulsion stabilizer, characterized in that: The following steps are involved: (1) The suspension of TEMPO-oxidized bacterial cellulose nanofibers and silver ammonia solution were heated to react, and then centrifuged to wash and remove impurities to obtain TBC@Ag; (2) Ethyl silicate was added dropwise to the ethanol dispersion of TBC@Ag, stirred for reaction, and then centrifuged for washing to remove impurities, thereby obtaining oxidized bacterial cellulose TBC@Ag@SiO2 loaded with nanosilver particles and nanosilicon dioxide particles; In step (1), the TEMPO-oxidized bacterial cellulose nanofibers have an average length of 20 μm and a diameter of 50 nm-100 nm; In step (1), the silver ammonia solution is prepared by adding 4% (v / v) of 25wt% ammonia water to 0.5wt% silver nitrate solution; In step (1), the TEMPO-oxidized bacterial cellulose nanofiber suspension and the silver ammonia solution are mixed by adding 1% (w / w)-20% (w / w) silver ammonia solution to 1 wt% of the TEMPO-oxidized bacterial cellulose nanofiber suspension; In step (1), the reaction temperature is 70°C-90°C; the reaction time is 0.5 h-2 h; In step (2), the mass ratio of TBC@Ag to TEOS is 1:(4.65-13.95); In step (2), the reaction time is 6 h-18 h; In step (1), the preparation method of the TEMPO-oxidized bacterial cellulose nanofibers is as follows: adding NaBr and TEMPO to a bacterial cellulose nanofiber suspension, then adding a NaClO solution, adjusting the pH to 10-10.5 for reaction, terminating the reaction, adjusting the pH of the system to neutral, filtering and washing to remove impurities, and obtaining TEMPO-oxidized bacterial cellulose nanofibers; the addition ratio of the bacterial cellulose nanofibers, NaBr, TEMPO and NaClO is 1 g:0.1 mmol:9.72 mmol:(20-60.4) mmol; In the papermaking sizing agent emulsion stabilizer, nano silver particles with a particle size of 30 nm to 90 nm are bonded to the hydroxyl groups on the surface of bacterial cellulose through covalent bonds or coordination bonds; and nano silicon dioxide with a particle size of 20 nm to 40 nm is bonded to the hydroxyl groups on the surface of bacterial cellulose through covalent bonds.

2. The preparation method according to claim 1, characterized in that In step (1), 10% (w / w) silver ammonia solution is added to a 1 wt% TEMPO-oxidized bacterial cellulose nanofiber suspension and mixed.

3. A papermaking sizing agent emulsion stabilizer obtained by the preparation method according to claim 1 or 2, characterized in that: Nanosilver particles with a particle size of 30 nm-90 nm are bound to the hydroxyl groups on the surface of bacterial cellulose through covalent bonds or coordination bonds; nanosilica particles with a particle size of 20 nm-40 nm are bound to the hydroxyl groups on the surface of bacterial cellulose through covalent bonds.

4. Use of the paper sizing agent emulsion stabilizer according to claim 3 in preparing a paper sizing agent emulsion, characterized in that: The sizing agent comprises AKD or ASA.

5. A method for preparing an AKD sizing agent emulsion, characterized in that: The following steps are involved: The aqueous dispersion of the papermaking sizing agent emulsion stabilizer according to claim 3 and molten AKD are shear-emulsified under heat preservation conditions and then placed in an ice-water bath; The concentration of TBC@Ag@SiO2 aqueous dispersion is 0.2 wt%-1.0 wt%; The volume ratio of AKD to aqueous dispersion is 1:5-1:20; The shear emulsification rate is 12000 rpm-20000 rpm; The shear emulsification time is 4 min-8 min; The insulation temperature is 65℃-90℃.

6. The preparation method according to claim 5, characterized in that The volume ratio of AKD to water dispersion is 1:9; the shear emulsification rate is 15000 rpm-18000 rpm; and the shear emulsification time is 6 min-7 min.

7. An AKD sizing agent emulsion obtained by the preparation method according to claim 5 or 6, characterized in that: The average particle size of the droplets in the emulsion is 2 μm-5 μm.

8. Use of the AKD sizing agent emulsion according to claim 7 in preparing hydrophobic food-grade packaging paper.

9. A paper prepared from the papermaking sizing agent emulsion stabilizer according to claim 3 or the AKD sizing agent emulsion according to claim 7.

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