Modified bacterial cellulose stabilizes asa sizing agent emulsion and preparation method and application thereof

Abstract

The application belongs to the technical field of papermaking, and provides a modified bacterial cellulose stabilized ASA 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 solution of TBC@Ag and stirred and reacted to obtain TBC@Ag@SiO2; ASA is added into the water dispersion solution of TBC@Ag@SiO2 and sheared and emulsified, so that the modified bacterial cellulose stabilized ASA sizing agent emulsion can be obtained.The ASA emulsion prepared by the application can effectively block the influence of environmental factors on the emulsion, significantly improve the interface stability of the emulsion, does not need to add additional surfactants, makes the sizing process more simple, effectively improves the long-term stability of the ASA emulsion, prevents the water phase and the oil phase from separating, and improves the water resistance, antibacterial property and ultraviolet resistance of paper.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking sizing agent preparation and relates to the preparation of an ASA 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] Currently, ASA sizing agents are typically emulsified on-site using cationic starch and low-molecular-weight surfactants and require immediate use. However, the cationic starch process is complex, requiring gelatinization and cooling before addition. This complicates the emulsification process, makes precise control difficult, and can lead to sedimentation and felt clogging. Furthermore, the surfactants used can negatively impact sizing effectiveness and the environment. In recent years, research on ASA emulsification preparation has made significant progress, resulting in a growing body of technological achievements, providing new solutions for the application of ASA in the papermaking industry.

[0004] In research to enhance the stability and sizing performance of ASA (alkenyl succinic anhydride) emulsions, both inorganic particles and organic emulsifiers have been widely used to improve their performance. However, these approaches still have significant limitations in practical application. For example, Chinese Patent No. CN102268839B discloses a Pickering emulsion-based ASA sizing agent using quaternary ammonium salt-intercalated nano-cationic modified montmorillonite as an emulsifier. By combining with magnesium salt to form an aqueous phase, ASA can be emulsified without the need for surfactants. However, while the use of inorganic particles provides initial stability, their low emulsion concentration and poor storage stability limit high-concentration applications, making it difficult to maintain good performance under long-term storage conditions. Similarly, Chinese Patent No. CN102493272A uses hectorite and nano-titanium dioxide as emulsifiers, forming a stable emulsion through appropriate pH adjustment and mechanical shearing. Although this approach reduces the use of surfactants to a certain extent, emulsion systems relying on inorganic particles still face the problem of hydrolysis, and the ASA sizing activity decreases during long-term storage. In terms of organic emulsifiers, Chinese patent CN104746388A improves the sizing effect of ASA by adding papermaking filler particles modified with hydroxyl-containing natural hydrocarbon high molecular weight polysaccharide compounds to the pulp. This method enhances the retention rate of ASA on the fiber surface and reduces the deposition problem caused by hydrolysis. However, this technology still requires a high amount of emulsifier to maintain stability, which increases production costs and environmental burden. In addition, Chinese patent CN109989293A proposes using a specific proportion of emulsifiers and a strong shear force emulsification pump in the ASA emulsion to control the emulsion particle size to improve its stability and sizing effect. Although this method enhances the uniformity and durability of the emulsion, the limitations of relying on surfactants are still significant. Summary of the Invention

[0005] To overcome the problems existing in existing ASA emulsion emulsification systems, the present invention provides a method for preparing an ASA Pickering emulsion stabilized by modified bacterial cellulose and its application in internal sizing. The emulsion can stably form an ASA Pickering emulsion without the need for the addition of a surfactant.

[0006] Another objective of the present invention is to provide a process for internal sizing of paper pulp using the aforementioned ASA sizing agent. The resulting sized paper not only exhibits excellent water resistance but also possesses antibacterial and UV-blocking properties, further expanding its value in specialty paper applications.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions.

[0008] A method for preparing an ASA sizing agent comprises the following steps:

[0009] (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);

[0010] (2) Ethyl ethyl silicate (TEOS) was added dropwise to the TBC@Ag ethanol dispersion, 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);

[0011] (3) ASA was added to the TBC@Ag@SiO2 dispersion and the ASA Pickering sizing emulsion was obtained after shearing and emulsification.

[0012] In step (1), the TEMPO-oxidized bacterial cellulose nanofibers can be obtained by methods in the prior art, such as catalytic oxidation of the bacterial cellulose nanofibers in an aqueous solution with a pH of about 10 using a TEMPO / NaBr / NaClO system. 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.

[0013] In step (1), the silver ammonia solution is prepared by dissolving 0.1 g of silver nitrate in 20 mL of deionized water to form a 0.5 wt% silver nitrate solution, then adding 1 mL of a 20% ammonia solution and stirring thoroughly to form a silver ammonia solution; at this time, the silver ammonia concentration of the solution is 0.396 wt%.

[0014] In step (1), the mass ratio of silver ammonia to TBC is not limited; preferably, the mass ratio of silver ammonia to TBC is 0.069:0.82.

[0015] In step (1), the reaction temperature is 70°C-90°C; and the reaction time is 0.5 h-2 h.

[0016] In step (2), the mass ratio of TBC@Ag to TEOS is 1:4.64-13.95.

[0017] In step (2), the reaction time is 6 h-18 h.

[0018] In the TBC@Ag@SiO2, silica particles with a particle size of 20 nm-40 nm are bonded to the hydroxyl groups of oxidized bacterial cellulose through silicon-oxygen bonds (Si-OC); silver particles with a particle size of 30 nm-90 nm are bonded to the hydroxyl groups of oxidized bacterial cellulose through coordination bonds.

[0019] In step (3), the concentration of the TBC@Ag@SiO2 dispersion is 0.2wt%-1wt%.

[0020] In step (3), the mass ratio of ASA to TBC@Ag@SiO2 is (125-25):1, more preferably 50:1.

[0021] In step (3), the shear emulsification rate is 5000 rpm-20000 rpm; more preferably 10000 rpm-12000 rpm.

[0022] In step (3), the shear emulsification time is 1 min to 8 min; more preferably 3 min to 4 min.

[0023] In step (3), the concentration of ASA in the ASA Pickering sizing emulsion is 10 wt%-40 wt%.

[0024] An ASA emulsion obtained by the above preparation method; the average particle size of the droplets in the emulsion is 5-10 μm.

[0025] A paper prepared from the above ASA emulsion.

[0026] The present invention has the following advantages:

[0027] The TBC@Ag@SiO2 used in this invention is a bacterial cellulose-based granular material with antibacterial and UV resistance properties, with nanosilver (Ag) and silicon dioxide (SiO2) loaded on its surface, thus endowing the material with broad-spectrum antibacterial and UV resistance. As a stabilizer for Pickering emulsions, TBC@Ag@SiO2 forms a dense and stable fiber film at both the ASA-water and oil-water interfaces, effectively blocking the effects of environmental factors on the emulsion and significantly improving the interfacial stability of the emulsion. In ASA emulsion sizing, TBC@Ag@SiO2 not only reduces the amount of emulsion stabilizer used, but also avoids the addition of additional surfactants, making the sizing process simpler, effectively improving the long-term stability of the ASA emulsion, preventing the separation of the aqueous and oil phases, and enhancing the water resistance, antibacterial properties, and UV resistance of the paper, providing an innovative solution for green and environmentally friendly paper sizing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1is the infrared spectra of TBC@Ag@SiO2, TBC and bacterial cellulose nanofibers (BC);

[0029] Figure 2 is the scanning electron microscope image of TBC@Ag@SiO2;

[0030] Figure 3 This is a microscopic image of the ASA sizing agent emulsion stabilized with TBC@Ag@SiO2;

[0031] Figure 4 The comparison of the lyophobic effect of ASA sizing emulsion stabilized by TBC@Ag@SiO2 on paper sized in pulp and unsized paper;

[0032] Figure 5 is the dynamic three-phase contact angle between BC and TBC@Ag@SiO2;

[0033] Figure 6 The figure is a comparison of the weight loss of unsized paper and sized paper during the preservation of strawberries. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the following examples and accompanying drawings, but the present invention is not limited to the following examples. Unless otherwise specified, the sizing method, sizing degree measurement, contact angle measurement, and paper UV transmittance measurement methods in each example are as follows:

[0035] (1) Gluing method

[0036] Before sizing, the ASA sizing emulsion was diluted to 0.2%, and the pulp concentration was adjusted to 1%. 1% aluminum sulfate (mass percentage relative to the absolute dry pulp) was added to the pulp at a stirring rate of 500 rpm. The pH of the pulp was then adjusted to 7.5-8.5 with a 1 mol / L sodium hydroxide solution. ASA emulsion and 0.03% CPAM were then added in sequence. The mixture was stirred at 500 rpm for 2 min and allowed to stand for 30 s. A PTI paper sheet maker (RK3AKWT, Austria) was then used to make hand sheets with a basis weight of 60 g / m 2 (T205 om-88, TAPPI) papermaking was performed using the Kaiser method (manual papermaking) in accordance with ISO 5289 / 2 and DIN 54358. The handsheets were dried at 105°C and then equilibrated at room temperature for 24 hours at an ambient humidity of 50%.

[0037] (2) Determination of sizing degree

[0038] Sizing performance was evaluated by measuring the sizing degree of paper (GB / T5405-2002). Before measurement, the paper was cut into 30 × 30 mm squares and equilibrated at 25°C and 50% humidity for 24 hours. The paper was folded to form a boat-shaped structure with a base area of ​​approximately 20 × 20 mm. The structure was then floated in a 2% dilute ammonium thiocyanate solution. A 0.5 μL drop of 1% ferric chloride solution was placed on top of the boat-shaped paper using a plastic dropper. A stopwatch was used to measure the sizing degree of the paper sample. The measurement was stopped when a red spot appeared in the middle of the ferric chloride droplet. The time was determined by the appearance of a red spot in the middle of the ferric chloride droplet. The measurement was performed 10 times on both the front and back sides of the sample, and the average value was calculated.

[0039] (3) Contact angle measurement

[0040] The contact angle of paper was measured using a fully automatic video optical contact angle meter. First, ensure that the sample surface is clean and flat, and fix the paper sample horizontally on the measurement platform. Use a 5 μL droplet volume and deionized water as the test liquid. Use an automatic injection system to accurately add a droplet of constant volume to the paper surface, start the measurement program to automatically collect the side view image of the droplet, and the system automatically identifies the droplet contour and calculates the contact angle. To ensure the accuracy and representativeness of the measurement results, 10 different measurement positions were selected on the front and back of the paper, the contact angle data were recorded, and the average value of the front and back measurements was taken.

[0041] (4) Paper UV transmittance

[0042] Place the paper sample on the fixture to ensure that the light passes through the sample vertically; scan it with a UV-visible spectrophotometer at a UV wavelength of 200-400 nm to measure the sample transmittance.

[0043] Example 1 Preparation of ASA emulsion

[0044] (1) NaBr and TEMPO were added to a 1 wt% bacterial cellulose nanofiber suspension to dissolve it, and then NaClO solution was added to make the ratio of bacterial cellulose nanofiber, NaBr, TEMPO and NaClO 1 g:0.1 mmol:9.72 mmol:20 mmol; the pH was adjusted to 10-10.5 and stirred for 1 h. After adding 10 mL of anhydrous ethanol to terminate the reaction, the pH of the system was adjusted to about 7, and the precipitate was filtered to obtain the precipitate. The precipitate was washed several times to remove impurities to obtain TEMPO-oxidized bacterial cellulose nanofiber (TBC);

[0045] (2) Dissolve 0.1 g of silver nitrate in 20 mL of deionized water to prepare a 0.5 wt% silver nitrate solution; add 1 mL of 20% ammonia solution and stir thoroughly to form a silver ammonia solution with a concentration of 0.396 wt%;

[0046] Add all 21 mL of the silver-ammonia solution to 100 mL of 1% TBC suspension to obtain a mixed solution with a silver-ammonia concentration of 0.069 wt% and a TBC concentration of 0.82 wt%.

[0047] The mixture was reacted in a water bath at 80°C for 1 h to obtain TBC loaded with silver particles (TBC@Ag).

[0048] (3) 100 mL of 1% TBC@Ag solution was dispersed in 300 mL of anhydrous ethanol, and then TEOS was added to make the mass ratio of TBC@Ag and TEOS 1:5. The reaction was carried out for 12 h, and the precipitate was obtained by centrifugation. After repeated centrifugation and washing, oxidized bacterial cellulose loaded with nanosilver particles and nanosilica particles (TBC@Ag@SiO2) was obtained. Its infrared spectrum is shown in FIG. Figure 1 Shown: Bacterial cellulose (BC) at 3400-3500 cm -1 The hydroxyl stretching vibration peak at 2900 cm indicates that it contains a large number of hydroxyl groups, while the peak at 2900 cm -1 The CH stretching vibration peak at 1100-1200 cm -1 The COC stretching vibration peaks reveal the presence of methyl, methylene groups and glycosidic bonds in the cellulose molecules. After conversion to TEMPO-oxidized bacterial cellulose (TBC), the hydroxyl peaks weakened, while the peaks at 1720-1750 cm -1 The carboxyl stretching vibration peak appeared at 1100 cm, which indicated that TEMPO oxidation successfully converted part of the hydroxyl groups into carboxyl groups. Furthermore, when nanosilver and nanosilica were attached to the surface of oxidized bacterial cellulose to form TBC@Ag@SiO2, the hydroxyl peak was further weakened, and the Si-O-Si stretching vibration peak was at 1100 cm -1 Appears near and is between 500-600 cm -1 The appearance of Ag-O or Si-OC related vibration peaks at , confirms the successful attachment of nano-silver and nano-silicon dioxide;

[0049] 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).

[0050] Scanning electron microscopy Figure 2As shown: bacterial cellulose is about 20 μm long and 50-100 nm in diameter, nanosilver particles are 30-90 nm in size, and nanosilica particles are 20-40 nm in size;

[0051] (4) 0.2 parts by weight of TBC@Ag@SiO2 was dispersed in 100 parts of water, 25 parts by weight of ASA was added, and shear emulsification was carried out at a speed of 8000 rpm for 2 minutes to prepare an ASA sizing emulsion with an internal phase volume fraction of 20%. The obtained ASA sizing agent had a uniform appearance, and the emulsion micrograph ( Figure 3 ) showed that the average droplet size was 8.6 μm, and there was no phase separation or demulsification after 72 hours, indicating that the emulsion had excellent stability.

[0052] After the newly prepared ASA emulsion was left for 1 hour, it was diluted to 0.1% with deionized water and used for internal sizing of pulp. The ASA dosage was 0.5%. The sizing degree of the obtained sized paper was 623 seconds, and the UV transmittance of the paper at 365 nm was only 16.38%. Figure 4 and Figure 5 Comparisons of the lyophobic effect and dynamic three-phase contact angle of base paper and sized paper show that the paper sized with the ASA emulsion exhibits superior water repellency. The water contact angle of the sized paper reaches 121°. After the ASA emulsion was left for 72 hours, the emulsion volume fraction of the sizing agent remained unchanged. Repeating the sizing steps yielded a sizing degree of 534 seconds, sufficient to ensure the quality of the sizing during transportation and use. The paper also exhibited excellent optical shielding properties through its UV transmittance. Even after 30 days, the emulsion volume fraction of the ASA emulsion still reached 99%, and the sizing degree remained at 397 seconds, maintaining good sizing performance, demonstrating the excellent storage stability of this ASA sizing emulsion.

[0053] Example 2 Preparation of TBC@Ag@SiO2 and AKD emulsion

[0054] 1. Preparation of TBC@Ag@SiO2

[0055] (1) NaBr and TEMPO were added to a 1 wt% bacterial cellulose nanofiber suspension to dissolve it, and then 10% NaClO solution was added to make the ratio of bacterial cellulose nanofiber, NaBr, TEMPO and NaClO be 1 g:0.1 mmol:9.72 mmol:40 mmol; the pH was adjusted to 10-10.5 and stirred for 1 h. After adding 10 mL of anhydrous ethanol to terminate the reaction, the pH of the system was adjusted to about 7, and the precipitate was obtained by filtration. The precipitate was washed several times to remove impurities to obtain TEMPO-oxidized bacterial cellulose nanofiber (TBC);

[0056] (2) Dissolve 0.1 g of silver nitrate in 20 mL of deionized water to prepare a 0.5 wt% silver nitrate solution; add 1 mL of 20% ammonia solution and stir thoroughly to form a silver ammonia solution with a concentration of 0.396 wt%;

[0057] Add all 21 mL of the silver-ammonia solution to 100 mL of 1% TBC suspension to obtain a mixed solution with a silver-ammonia concentration of 0.069 wt% and a TBC concentration of 0.82 wt%.

[0058] The mixture was reacted in a water bath at 80°C for 1 h to obtain TBC loaded with silver particles (TBC@Ag).

[0059] (3) Disperse 100 mL of 1% TBC@Ag solution in 300 mL of anhydrous ethanol, then add TEOS to make the mass ratio of TBC@Ag to TEOS 1:10. React for 12 h, centrifuge to obtain a precipitate, and centrifuge and wash multiple times to obtain oxidized bacterial cellulose loaded with nanosilver particles and nanosilica particles (TBC@Ag@SiO2);

[0060] (4) 0.5 parts by weight of TBC@Ag@SiO2 was dispersed in 100 parts by weight of water, 50 parts by weight of ASA was added, and shear emulsification was performed at a speed of 10,000 rpm for 3 min to prepare an ASA sizing emulsion with an internal phase volume fraction of 33%.

[0061] The average droplet size of the emulsion was 5.2 μm. After 72 hours of aging, no phase separation or demulsification occurred, indicating good emulsion stability. The freshly prepared ASA sizing emulsion (aged for 1 hour) was diluted to 0.2% with deionized water for internal sizing of paper pulp with an ASA dosage of 0.5%. The resulting sized paper had a sizing degree of 977 s. After aging the ASA sizing emulsion for 72 hours and repeating the above steps, the resulting sized paper had a sizing degree of 793 s, sufficient for transportation and use. The paper had a transmittance of only 7.47% at 365 nm. The water contact angle of the sized paper reached 118°. Even after 30 days of aging, the emulsion volume fraction of the sizing agent remained at 100%. Repeating the above steps resulted in a sizing degree of 522 s, maintaining good sizing performance, demonstrating the excellent storage stability of the prepared ASA sizing emulsion.

[0062] Example 3 Preparation of TBC@Ag@SiO2 and AKD emulsion

[0063] 1. Preparation of TBC@Ag@SiO2

[0064] (1) NaBr and TEMPO were added to a 1 wt% bacterial cellulose nanofiber suspension to dissolve it, and then 10% NaClO solution was added to make the ratio of bacterial cellulose nanofiber, NaBr, TEMPO and NaClO be 1 g:0.1 mmol:9.72mmol:60.4 mmol; the pH was adjusted to 10-10.5 and stirred for 1 h. After adding 10 mL of anhydrous ethanol to terminate the reaction, the pH of the system was adjusted to about 7, and the precipitate was obtained by filtration. The precipitate was washed several times to remove impurities to obtain TEMPO-oxidized bacterial cellulose nanofiber (TBC);

[0065] (2) Dissolve 0.1 g of silver nitrate in 20 mL of deionized water to prepare a 0.5 wt% silver nitrate solution; add 1 mL of 20% ammonia solution and stir thoroughly to form a silver ammonia solution with a concentration of 0.396 wt%;

[0066] Add all 21 mL of the silver-ammonia solution to 100 mL of 1% TBC suspension to obtain a mixed solution with a silver-ammonia concentration of 0.069 wt% and a TBC concentration of 0.82 wt%.

[0067] The mixture was reacted in a water bath at 80°C for 1 h to obtain TBC loaded with silver particles (TBC@Ag).

[0068] (3) Disperse 100 mL of 1% TBC@Ag solution in 300 mL of anhydrous ethanol, then add TEOS to make the mass ratio of TBC@Ag to TEOS 1:10. React for 12 h, centrifuge to obtain a precipitate, and centrifuge and wash multiple times to obtain oxidized bacterial cellulose loaded with nanosilver particles and nanosilica particles (TBC@Ag@SiO2);

[0069] (4) 1 part by weight of TBC@Ag@SiO2 was dispersed in 100 parts by weight of water, 100 parts by weight of ASA was added, and shear emulsification was carried out at a speed of 15,000 rpm for 4 min to prepare an ASA sizing emulsion with an internal phase volume fraction of 50%. The average particle size of the emulsion droplets was 6.5 μm. After being placed for 72 hours, there was no phase precipitation and no demulsification phenomenon, and the emulsion had good stability.

[0070] The prepared ASA sizing emulsion (standing for 1 hour) was diluted to 0.2% with deionized water for internal sizing of paper pulp. The sizing performance of the paper obtained with an ASA dosage of 0.5% was 782 s. After the prepared ASA sizing emulsion was allowed to stand for 72 hours and the above steps were repeated, the resulting sizing performance was 584 s, sufficient for transportation and use. The transmittance of the paper at 365 nm was only 3.86%. The water contact angle of the sized paper reached 127°. After the prepared ASA emulsion was allowed to stand for 30 days, the emulsion volume fraction still reached 99%. Repeating the above steps resulted in a sizing performance of 467 s, maintaining good sizing performance, demonstrating the good storage stability of the prepared ASA sizing emulsion.

[0071] Comparative Example 1 Preparation of BC-stabilized ASA emulsion

[0072] 0.2 parts by weight of bacterial cellulose nanofibers were dispersed in 100 parts of water, 25 parts by weight of ASA were added, and shear emulsification was carried out at a speed of 10,000 rpm for 2 min to prepare an ASA sizing emulsion with an internal phase volume fraction of 20% and an average particle size of 14.7 μm.

[0073] Application Example 1 Preparation of sized paper

[0074] Before sizing, the ASA sizing emulsion obtained in Example 1 and Comparative Example 1 was diluted to 0.2%, the pulp concentration was adjusted to 1%, and 1% aluminum sulfate (mass percentage relative to the absolute dry pulp) was added to the pulp at a stirring rate of 500 rpm. Then, the slurry pH was adjusted to 7.5-8.5 with a 1 mol / L sodium hydroxide solution. Then, the ASA emulsion and 0.03% CPAM were added in sequence. After stirring at 500 rpm for 2 minutes, the mixture was allowed to stand for 30 seconds. Then, a PTI paper sheet machine (RK3AKWT, Austria) was used to make hand sheets. The basis weight of the hand sheets was 60 g / m 2 (T205 om-88, TAPPI) papermaking was performed using the Kaiser hand-sheeting method according to ISO 5289 / 2 and DIN 54358 standards. The handsheets were dried at 105°C and then equilibrated for 24 hours at room temperature and 50% humidity to produce BC ASA sizing paper (Comparative Example 1) and TBC@Ag@SiO2 ASA sizing paper (Example 1).

[0075] Application Example 2: Freshness-keeping effect of paper after sizing

[0076] Strawberries were placed in a transparent glass fresh-keeping box, sealed with the different sizing papers prepared in Application Example 1. Unsizing paper served as a control. The boxes were then stored at room temperature and observed for nine days. During the observation period, the strawberries were regularly weighed using a digital balance to obtain and quantify water loss. Changes in the color and morphology of the strawberries were also recorded by regularly taking photographs.

[0077] Weight loss rate = ,

[0078] Among them, m1 is the initial weight and m2 is the weight during testing on a certain day.

[0079] The control sample had the highest weight loss, reaching nearly 6% by day 7. In contrast, strawberry wrappers treated with ASA emulsion prepared with TBC@Ag@SiO2 showed minimal weight loss during storage, remaining below 2%, significantly outperforming the ASA emulsion-treated wrappers prepared with BC.

[0080] 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 modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for preparing an ASA Pickering sizing emulsion, 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 and impurity removal to obtain TBC@Ag@SiO2; (3) ASA was added to the TBC@Ag@SiO2 dispersion and the ASA Pickering sizing emulsion was obtained after shearing and emulsification; 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 step (1), the mass ratio of silver ammonia to TEMPO-oxidized bacterial cellulose nanofibers is 0.069:0.82; 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 ethyl silicate is 1:(4.64-13.95); In step (2), the reaction time is 6 h-18 h; In step (3), the concentration of TBC@Ag@SiO2 dispersion is 0.2wt%-1wt%; In step (3), the mass ratio of ASA to TBC@Ag@SiO2 is (25-125):1; In step (3), the shear emulsification rate is 5000 rpm-20000 rpm; In step (3), the shear emulsification time is 1 min to 8 min; In step (3), the concentration of ASA in the ASA Pickering sizing emulsion is 10 wt%-40 wt%.

2. The preparation method according to claim 1, characterized in that In step (3), the mass ratio of ASA to TBC@Ag@SiO2 is 50:1; In step (3), the shear emulsification rate is 10000 rpm-12000 rpm; In step (3), the shear emulsification time is 3 min-4 min.

3. The preparation method according to claim 1, characterized in that In step (1), the silver ammonia solution is prepared by dissolving 0.1 g of silver nitrate in 20 mL of deionized water to prepare a 0.5 wt% silver nitrate solution, then adding 1 mL of 20% ammonia solution and stirring thoroughly to form a silver ammonia solution.

4. An ASA Pickering sizing emulsion obtained by the preparation method according to any one of claims 1 to 3.

5. The ASA Pickering sizing emulsion according to claim 4, characterized in that The average particle size of the droplets in the ASA Pickering sizing emulsion is 5-10 μm.

6. A paper prepared from the ASA Pickering sizing emulsion according to claim 4 or 5.

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